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https://oercommons.org/courseware/lesson/66607/overview
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Future Value of an Annuity Lab
PMT Formula Lab
Present Value Lab
Present Value of an Annuity Lab
Time Value of Money
Overview
This lesson covers the topic of Time Value of Money and prepares students for lessons on simple interest loans (operating notes and lines of credit) and amortized loans. It introduces the ideas of present and future values, compounding and discounting, payements and time periods. It uses Microsoft Excel extensively as an aid for problem calculations.
Time Value of Money
Time Value of Money
When it comes to money, the bottom line is that a dollar today is preferred to a dollar in the future. Why you ask? Here are four reasons:
- If that dollar is spent on consumption, we would prefer to receive that enjoyment now. That is simply human nature. I don’t want to buy new clothes next month or next year, I want them now.
- That dollar could be invested with someone that needs that dollar now, where it would then earn interest. While I may not need to spend the money now, either for business or for consumption, someone else does, and they are willing to pay you rent on your money. So by delaying your satisfaction of spending that dollar, you are actually receiving a benefit in earning interest when you are paid back.
- Risk is a factor, in that unforeseen circumstances could prevent us from receiving the dollar in the future. Risk here is many places. As grim as it seems, you may be unable to spend the money in the future due to death or injury. Or it could come from investing the money with someone else, yes you are entitled to an interest payment, but that only happens if they are able to pay you back.
- Inflation may diminish the value of that dollar over time. The definition of inflation is too many dollars chasing too few assets. When this occurs, the dollar is the same, it simply purchases less stuff as a result. So inflation doesn’t change the dollar (it is still worth $1) as much as it changes the values of everything that dollar buys.
There are two types of values that we look at when examining the time value of money. The first is Present Value (PV) (I will always abbreviate teems with the syntax that Excel uses) which is simply the number of dollars available or invested at the current time or the current value of some amount to be received in the future. The second is Future Value (FV) which is the amount to be received at some point in the future or the amount a present value will be worth at some future date when invested at a given interest rate.
Other terms that are important to know and understand are as follows:
Payment (PMT) – The number of dollars to be paid or received in a time period.
Interest Rate (rate) – The interest rate used to find present and future values. It is quoted in percent and represents the value of return for renting your money out to someone else, or what you have to pay to rent money from someone else. Often when we are finding present values of a future income the interest rate is refereed to as a discount rate.
Time Periods (nper) – The number of time periods used to compute present and future values.
Annuity – A term used to describe a series of periodic payments.
A quick note about interest rates. The interest rate is a return on the amount of money, but it has to have a time period associated with it. You cannot have a 5% interest rate, unless you state how long you expect it to take to return to you 5% of the original value. In other words, an interest rate, always needs to have a time component to it. For this section, we will always assume the rates are APR – annual percentage rates (unless you are explicitly told otherwise). Meaning that a 5% APR, will return 5% of its initial value at the end of exactly 1 year:
- A woman loans her neighbor $1000 at an APR of 5%. She is expecting to receive the $1000 she initially loaned her, plus 5% of the value back at the end of the year. 5% * $1000 = $50. So she intends to receive the $50 interest payment as well as the original $1000 back at the end of the year.
- Rates can also me be monthly rates. If the woman in the previous example wanted to loan $1000 at an MPR (monthly percentage rate) of 5%, then she expects to receive the $50 interest payment and the $1000 original amount back at the end of 1 month. A 5% MPR Is equivalent to a 60% APR, since 5% MPR * 12 months = 60% APR (we even use unit cancelling in finance!).
- Rates can also be weekly rates, daily rates, or any variation of the calendar that you can think of. The key is always this – the rate and the time always need to be in the same unit. In other words, if the time period is in years, the rate must be in years. If the rate is in days, the time period must be in days.
It is also important to understand that the direction we are heading from a present value to a future value or from a future value to a present value dictates whether we are compounding or discounting. In short, when we are moving from a present value (what we have today) to a future value (what it will be worth in a year) we are compounding the present value to arrive at the future value. When we know what we will have in the future and want to know what it is worth today, we are discounting back to the present. The image below helps to explain:
Future Value
Future Value Calculations
The image below represents the visual of what it means to go from a PV to an FV. Over time, because of the time value of money, the present value grows into a larger future value. In the section that follows you will learn the math, as well as tools that can be used to do these calculations.
When we work on FV problems, we know what the present value is. Essentially, we know what we have today, what we need to calculate is what that present amount will be worth in the future. Imagine we currently have $1000 and we want to know what that $1000 will be worth if it were to earn 8% APR for 1 year, 2 years and 3 years? There are actually multiple methods for answering these, so we will go through each one individually.
Table:
First we can create a table that calculates the interest earned each year – year by year. It is somewhat tedious and time consuming, but it is important to understand what is going on before learning to use the tools that easier and faster. The key here is that every year is just a simple interest problem. Simple interest means that you are only calculating the interest earned for 1 time period. In this case 1 year. See the table below:
| Year | Value at beginning of year ($) | Interest rate (%) | Interest earned ($) | Value at end of year ($) |
| 1 | 1000.00 | 8 | 80.00 | 1080.00 |
| 2 | 1080.00 | 8 | 86.40 | 1166.40 |
| 3 | 1166.40 | 8 | 93.31 | 1259.71 |
If we break down the table above, you will se that it is pretty simple math. In year 1 we start with $1000 and it earns 8% APR interest. Since this is a simple interest problem, you only need to take $1000 * 8% = $80. That is why the interest earned is $80. So at the end of the 1st year, the value is now $1080, since the original $1000 + $80 (interest earned) = $1080. Since $1080 is the value at the end of the 1st year, it stands to reason that $1080 will be the value at the start of the 2nd year, so the process starts all over again, only this time the formula for interest earned in year 2 is $1080 * 8% = $86.40. That interest earned is added to the value that you started with of $1080 + $86.40 = $1166.40.
That right there is what is known as compound interest. Compound interest is the act of earning interest on an investment and then having the interest earned start earning interest itself. We only ever invested $1000, but since we left the original $80 of interest earned in the investment, the next year we start earning even more interest. If we would have taken the initial interest payment out (in other words pocketed the $80 interest payment, in year 2 we would have only had $1000 earning 8% interest.
The tables are good, and they are important to understand for the remainder of the section on finance, however, for most cases of determining the future values and present values, they are lengthy, cumbersome and take too much time. Lucky for us, there are 2 other ways that are easier to use and much faster.
Formula:
The mathematical formula for computing the future value of an investment is as follows:
FV = PV (1 + i)ⁿ
where FV = future value, PV = present value, i = interest rate and n = time periods or nper
To calculate our problem from earlier, e plug in our information into the formula to get:
FV = $1000 (1 + 0.08)3 => FV = $1000 (1.08)3 => FV = $1000 * 1.25971
FV = $1259.71
As you can see, we get the same answer for the final year three future value in the table as we do when use the mathematical formula. And lets be honest, given the calcualtors that we have available today, working math problems to powers is not that difficult. The problem above is easily calculated on a simple calculator on your computer by using the xy button on your calculator. First you type in the value for x, in our case 1.08, then you hit the xy button on your calculator and then finally hit the number of years, in our case 3. Once you get your answer of 1.257912 (to be exact) multiply that by the present value which was $1000.
Excel:
The last and simplest method for calculating the future value of an investment, is to use excel, which is essentially a really powerful calculator that also organizes data as well as whole host of other things! Utilizing excel is quite simple, but you do have to familiarize yourself with what it is and does. In this class, you have already done several tasks within excel and have utilized it to help answer other problems. The key is to create a table and LABEL things as you type them in. Essentially what we will be doing is creating a calculator, but it is important to label what you are entering and what you are calculating. The screenshots below will walk you through the process:
In the screenshot above, I have entered all of the information into an excel table, also notice that I labeled what type of an interest rate I am working with, as well as labeled what unit time was in. This is an important part that oftentimes people forget. Remember that the unit of time must be the same for the rate as it is for the time period. That is why it is good to get into the habit of checking through labeling. The only part left is to enter a formula to do the calculating for us:
Once you select the “Financial” drop down menu scroll down until you find the FV formula and select it:
I prefer to utilize cell referencing when creating these calculators. This means rather than typing in the information that I want use as the input data, I will link the input to existing cells:
For the rate instead of entering 8%, I referenced cell B3 which contains 8%. For the Nper instead of entering 3 years, I referenced cell B4 which contains 3. We will use this same formula for calculating annuities, but we are not there yet, so as a result we leave the Pmt section empty and ignore it. For Pv it is important to understand a simple concept here, I actually entered cell -B2. That is right I actually entered the negative symbol first, then the cell. The reason for this is another learning moment. In order to make money by investing it or loaning it to someone else, I must give the money away for a time. It is a necessary part of investing. You must allow someone else to use your money in exchange for a “promise” to repay. You do NOT have to enter the Pv as a negative, however, notice that in the screenshot above the answer is given in the “Function Arguments” box, I have it circled in red = 1259.712. Notice what happens when I do NOT enter the Pv as a negative:
The answer is returned in the negative. Excel is very literal in how it calculates. In this case it assumes that you received $1000, and will now have to pay someone $1259.71. It is not a big deal, but it can cause issues if you use the answer to calculate further problems. The end result of the FV formula:
The reason this method of calculating future value problems is generally preferred once students get the hang of using excel is that it can easily be manipulated. Say you want to know how much the FV would be worth if you invested the $1000 today for 10 years at 5%. All you need to do is adjust the Rate and the NPER:
For a quick practice calculate the following Future Value Problems:
- PV = $2500, I = 5.05%, n = 10 years
- PV = $20,550, I = 4.45%, n = 15 years
- PV = $40,000, I = 3.23%, n = 4 years
- PV = $10,223, I = 2.5%, n = 12 years
Future Value of an Annuity
Future Value of an Annuity
Annuities are a popular method of investing. The essential idea is that you pay a lump sum amount of money today, and receive a series of payments over time, great for retirement lifestyle. Or you make a stream of payments (say $500 per month) over time and receive a lump-sum payment in the future. The latter is an example of a future value of an annuity problem. The idea is that we will save a certain amount every time period (can be weeks, months or years), that investment will earn interest, as well as continue to grow as we continue to add additional dollars to the investment each time period. The streams of investment are known as payments (PMT) which we skipped over in the Future Value section when learning how to work these problems on excel. Below is a visual representation of a FV of an annuity:
When we work on FV of annuity problems, we know what the PMT is. What we are wanting to know is, at a given interest rate and a set series of payments, how much will the investment be worth at a certain time in the future? Imagine we have decided to start saving $1000 annually at 8% APR. We want to know what it will be worth at the end of 3 years. Again, there are multiple methods for solving these problems, and we will go through each one individually. One last note before we go and start calculating the answers to these problems, we skipped over another item on the excel problems in the previous unit – type. The type is looking at when the compounding takes place – the beginning of the time period or the end. Typically, the compounding takes place at the end of the time period. Which makes sense. If you are the one paying an interest for the use of someone else’s money, you wouldn’t want to pay them until the end of the period. Most of the problems will be assumed to have the compounding take place at the end, which is why on excel, we left that section blank (see screenshot below):
Notice on the function arguments when you are in the “Type” section, the definition shows up below:
Type is a value representing the timing of payment; payment at the beginning of the period = 1; payment at the end of the period = 0 or omitted.
Since most often, the payment occurs at the end of the period, the default is if you leave that section blank it assumes that the payment and thus the compounding occurs at the end. Bottom-line, assume that the payment occurs at the end of the period, unless you are specifically told that it occurs at the beginning.
Table
Just like a Future Value problem, we can calculate the answer by using a table format going on a year by year basis. It is still time consuming and tedious, but it is also a good way to learn what is actually going on during the compounding. See the table below:
| Year | Value at beginning of the year | Interest rate (%) | Interest earned ($) | Payment ($) | Value at end of year ($) |
| 1 | $0 | 8 | 0.00 | 1000.00 | 1000.00 |
| 2 | $1000 | 8 | 80.00 | 1000.00 | 2080.00 |
| 3 | $2080 | 8 | 166.40 | 1000.00 | 3246.40 |
The table illustrates how the money grows as we add it to the investment. There isn’t any interest earned in the first time period since the payment is not made until the end of year.
Formula:
The mathematical formula for computing the future value of an investment is as follows:
FV = PMT x
where FV = future value, PMT = payment, i = interest rate and n = time periods or nper
To calculate our problem from earlier, e plug in our information into the formula to get:
FV = $1000 x => FV = $1000 x => FV = $1000 x => FV = $1000 x 3.2464
FV = $3246.40
Let’s be honest. That is not a fun equation to have to work through every time. So I highly recommend learning how to use excel in the following section!
Excel:
The formula for the FV of an annuity is the same as the FV. Remember how we ignored the PMT section in the formula before? That is what we will be using now:
Once again, we entered the PMT as a negative since we must give up $1000 each year, in order to get back the $3246.40 at the end of year 3. If we would have entered the PMT as a positive we would get this for the answer:
This is NOT the end of the world, but it does cause some issues when using the answers in further problems. That is why I always recommend entering all of the input data so that it shows up as a positive answer.
For a quick practice calculate the following Future Value Problems:
- PMT = $15,000, I = 5.65%, n = 10 years
- PMT = $500, I = 4.45%, n = 25 years
- PMT = $1000, I = 3.23%, n = 4 years
- PMT = $1000, I = 2.5%, n = 15 years
It is possible to make a lump-sum payment (a PV) today and then continue to contribute with periodic installments or payments. In that case, you would enter both a PV and a PMT, all other fields remain the same:
Assume you save $25,000 today from an inheritance, and then continue to invest $2500 at the end of each year for the next 30 years at 5% APR. What will be the FV?
What if the payment was made at the beginning of the period?
Present Value
Present Value Calculations
Present value refers to the value today of a sum of money to be received or paid in the future. Present values are found by discounting. And the interest rate is referred to as a discount rate. The image below represents the visual of what it means to go from a FV to an PV. The goal in these problems is to figure out what a certain amount of money that you know you will have, or want to have in the future is worth right now, given the current discount rate. In the section that follows you will learn the math, as well as tools that can be used to do these calculations.
When we work on PV problems, we know what the future value is. This is sometimes a little bit difficult for people to grasp. How do we NOT know what something is worth today? Think of this in two different ways. We are either going to receive a set amount of money at some time in the future and we want to know what it is worth today, or we want to have a certain amount of money saved up by a date later in the future and we want to know how much we need to save today in order to get that amount saved up. Tables are difficult and cumbersome to use when discounting and so are formulas, there is essentially one way to calculate PV problems, excel (that isn’t necessarily true, but now that you have a good grasp on how to use excel, it is pointless to work through the other methods!).
Formula:
We are NOT going to work through the formula, but I did want to at the very least show it to you:
Excel
As in the previous units, labeling is very important. Assume we are trying to find out what $8000 to be paid out at the end of 3 years is worth today given an 11% discount rate?
For this problem, we will use the PV formula:
Just as in the FV problems, we leave the PMT field blank, and since you are NOT told anything about when the discounting will occur (beginning or the end of the period) the default is that it will occur at the end of the time period, thus we leave the Type field blank as well (or enter 0). Again to make things simple and not end up with a negative answer, we also enter the Fv field as a negative.
For a quick practice calculate the following Present Value Problems:
- FV = $2500, I = 5.05%, n = 10 years
- FV = $20,550, I = 4.45%, n = 15 years
- FV = $40,000, I = 3.23%, n = 4 years
- FV = $10,223, I = 2.5%, n = 12 years
Present Value of an Annuity
Present Value of an Annuity
When we look at the present value of an annuity, we are now looking at how much money we will need to invest today, in order to guarantee a certain level of payments in the future. This is a classic question for a retiree, or someone nearing retirement. In retirement, you do not have a job, which means no stream of income (except for social security). So many retirees will take their savings and retirement accounts, take the lump sum and place them into an annuity that makes a periodic payment for a certain amount of time. How much money is placed into the annuity is dependent on how much they have access to, as well as what the periodic payment needs to be. In this section, we will again jump right to the use of excel for calculating these problems for simplicity. We will also add in another issue that we often run into, when the rate and the time period do not match (i.e. the rate is an APR, but the pmts are made monthly). The image below is an illustration of what the PV of an annuity looks like:
Formula:
We are NOT going to work through the formula, but I did want to at the very least show it to you:
PV = PMT x
Excel
As in the previous units, labeling is very important. Assume we are trying to find out what annual payments of $1000 to be paid out at the end of each year, for the next 3 years is worth today given an 8% discount rate?
In other words, if I want to receive payments of $1000 at the end of each year, for the next three years, given a discount rate of 8%, I would need to place $2577.10 into an annuity today. Again, there isn’t much difference in the present value problems and the present value of an annuity, with the exception that we are entering the Pmt and not the Fv. Also, again notice that we enter the Pmt in as a negative so that answer is returned to us as a positive. Technically though, in order to receive the $1000 payments at the end of each year for the next three years, you would need to give up $2577.10 today.
Rate and nper not in the same unit
I mentioned earlier, that sometimes the rate and the time period aren’t in the same units. I also mentioned at the beginning of the Time Value of Money unit, that the two must be in the same unit of time in order to work the calculations. This really isn’t a problem; we just need to make an adjustment at some point. Take the following example:
You are planning on retiring and would like to place some of your life savings into an annuity that makes monthly payments over the next 20 years. There are 12 months in a year, so you would be looking at 20 years * 12 months/year = 240 months or 240 payments. Assuming an APR of 5%, how much money would you need to invest in the annuity today in order to receive a monthly payment of $2000 at the end of each month?
The problem here is that the pmt and the nper are in monthly units, but the rate is in annual units. We must do a calculation to the rate. Since there will be a total of 240 pmts, the nper must be in months, and since the nper must be in months, so to does the rate. To adjust an APR to a MPR (monthly percentage rate) you simply take the APR and divide it by 12 - %5/12 = 0.417% MPR. This is a lot easier to do in excel, than with a computer:
This problem is incorrect, because the rate and the nper are in different units of time. We need to convert the rate into an MPR, to do this simply enter the following formula in the rate cell:
Notice that I started with an “=” in cell C3, that tells excel that you want it to do a mathematical equation. I also adjust the label to an MPR so that I know that I have made the adjustment. The final answer looks like:
Again, since the payment is made at the end of the time period, we leave the Type field blank. On occasion you will be told that the payment is made at the beginning of the time period, at that point you will need to enter a “1” into the Type field.
For a quick practice calculate the following Present Value Problems:
- PMT = $15,000, I = 5.65%, n = 120 months
- PMT = $500, I = 4.45%, n = 25 years
- PMT = $1000, I = 3.23%, n = 48 months
- PMT = $1000, I = 0.5% MPR, n = 15 years
In problem #1 since the Nper is in months, that means that the payment will be made every month and therefore the rate needs to be converted to an MPR (divide the APR by 12). The same occurs in #3 but notice I did NOT change my label to MPR. That is why it is so important to label things and make sure you adjust your labels! In problem #4, since the payment is made annually, the rate needs to be adjusted from an MPR to an APR. In order to accomplish this simply multiply the MPR of 0.50% * 12 months/year = 6.00% APR.
One last note on adjusting rates. When you do it, just use excel to make the adjustment. Here is why:
If you use your calculator to adjust 5% APR to an MPR you will get this:
When you type your answer into the excel sheet you will most likely just type in 0.42%, which in fairness is what would show up:
The problem is that when you dig deeper in excel and expand the decimal:
We are working with this as the rate: And Notice the difference in the answer:
Granted the difference is small, but it is a difference, nonetheless. I cannot urge you enough to stop using your calculator or your phone to do these calculations and start using excel for all of them!
PMT Formula
The PMT Function
This last section covers the idea of the payment or PMT. It is handy when you have a sum of money that you are looking at investing into some type of an annuity to use the PMT formula in excel so that you will know how much your payment will be. Or when you know how much money you want to have in the future, how much your periodic payment will need to be.
The PMT formula can also be used to calculate loan payments for vehicles, houses, etc. when loans are taken out. We will be using that function more in the upcoming units – simple interest loans and amortized loans.
The classic example of this is if you were in a car accident caused by the other driver. Their insurance company might offer to settle with you over the claim. Oftentimes they will offer you a structured settlement. Which is a fancy way of saying that they are going to make periodic payments to you, each time period for a set amount of time – a payment! How much will that payment be? Again, that depends on the present or future value, the rate, the time period and the type (payment made at the ending or the beginning of the time period).
For example, you are in a car accident. The insurance company for the other driver offers you a settlement of $65,000 received today, or you can receive the payment in a structured settlement (an annuity). If they will pay out over the next five years making monthly payments at a 4.5% APR interest rate, making the payments at the end of the period, how much will the monthly payment be for?
Excel is the simplest method to solve this problem. You will again enter the following information:
Present value = $65,000, nper = 60 months, rate = 4.5%/12, type = 0 or omit
Select the PMT formula from the Formula ribbon > Financial > PMT
In other words, if I took the settlement offer from the insurance company in the form of a structured settlement, rather than receiving $65,000 today, I would instead receive $1211.80 at the end of each month for the next 5 years. Again a couple key points; we adjusted the APR of 4.5% to an MPR of 0.38% and we did the calculation in excel by entering =4.5%/12 directly into cell B3 (this eliminates any rounding errors, and we entered the time period as 5 years * 12 months/year = 60 months. One thing to note is that since the option was to take the $65,000 today, the $65,000 is a PV. There is also a place to enter the FV in the PMT function which we will look at next.
Assume you would like to have $1,000,000 saved up in a retirement account by the time you turn 65. You are currently 20 years old and you want to know how much you would need to save each month in order to have $1,000,000 by the time you turn 65 given a compounding rate of 3% APR. The information for excel looks like this:
We must modify the rate like this: We must modify the nper like this:
First, we have to determine how many years we will be saving for, then multiply those years by 12 to get the correct number of months.
Loan Payment Calculations
The PMT function can also be used to calculate the payment amount on an Equal Total Payments (ETP) loan (we will learn more about those in the Amortized Loans Unit). Imagine that you borrow $45,000 from the bank to purchase a new truck. The bank quotes you a 5% APR, making annual payments at the end of the year for 5 years. What will be your annual payment?
Enter the following information into excel:
PV = $45,000, rate = 5.00% APR, nper = 5 years:
In other words, you will make 5 annual payments at the end of each year for $10,393.87. One huge advantage to knowing how to do these calculations is the ease of changing the terms of the loan. Say another bank offer the same loan but at a 4% APR, you can quickly check the result by simply changing the rate:
A 1% reduction in the rate lowers the annual payment by $285.65. Using excel allows for simplicity in recalculating loan payments given different loan terms.
For a quick practice calculate the following PMT Problems:
- PV = $85,000, I = 5.65% APR, n = 5 years – structured settlement
- FV = $500,000, I = 4.45%, n = 25 years - savings calculator
- PV = $40,000, I = 3.23% APR, n = 48 months – car loan
- FV = $10,000, I = 0.4% MPR, n = 60 months - savings calculator
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oercommons
|
2025-03-18T00:37:09.267670
|
Activity/Lab
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/66607/overview",
"title": "Time Value of Money",
"author": "Functions"
}
|
https://oercommons.org/courseware/lesson/97338/overview
|
Critical thinking listening sheet
How to get along with others
Overview
This lesson plan is adopted from the website
https://dohadebates.com/course/better-conversations/#01-prepare and the video of Dr. Clayton
The writer has added some ideas and stages but Dr. Clayton is the original author of the ideas and the video. He has inspired the author and made her choose the plan to teach the theme.
The lesson is designed to teach Civil communication, discussion skills at college, students will be able to use essential skills to have better conversations.
It is made up of five different classroom stages with various activities for teachers to run with pupils, with detailed notes for the staff member delivering the activities.
|
oercommons
|
2025-03-18T00:37:09.289610
|
09/20/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/97338/overview",
"title": "How to get along with others",
"author": "Dung Lê Thị Kim"
}
|
https://oercommons.org/courseware/lesson/86061/overview
|
ION EXCHANGE CHROMATOGRAPHY
Overview
The topic of illstration is Ion Exchange Chromatography which contain two application of it one is softening hardness of water and other is determination of organic acid from cosmetics. The illustration is made in "Miro" app.
ION EXCHANGE CHROMATOGRAPHY
Application of Ion Exchange Chromatography:
|
oercommons
|
2025-03-18T00:37:09.302310
|
09/21/2021
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/86061/overview",
"title": "ION EXCHANGE CHROMATOGRAPHY",
"author": "Bhagyashri Kowarkar"
}
|
https://oercommons.org/courseware/lesson/115919/overview
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HIST 0700: World History - Dr. Warsh 2014
Overview
This course approaches the idea and practice of World History through the lens of commodities and consumption. Over the course of the semester it will consider the last 1000 years of world history by examining the global production, circulation, and consumption of goods. In addition to its focus on the role of commodities in shaping local and global histories, the class will focus on several central themes: mass migrations of people; colonialism and imperialism; the global formation of capitalist economies and industrialization; the emergence of modern states; nationalism; and the rise of consumer societies.
Attachments
The attachment for this resource is a sample syllabus for a world history course that was taught in 2014.
About This Resource
This resource was contributed by Dr. Molly Warsh, Associate Professor, Department of History, Associate Director of the World History Center and Head of Educational Outreach, the University of Pittsburgh.
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oercommons
|
2025-03-18T00:37:09.319926
|
Alliance for Learning in World History
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{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/115919/overview",
"title": "HIST 0700: World History - Dr. Warsh 2014",
"author": "Syllabus"
}
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https://oercommons.org/courseware/lesson/94608/overview
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PSYC-1030 Discussion Prompt: Covid-19 Pandemic
Overview
The Covid-19 pandemic has disrupted the lives of individuals across the globe. For this discussion, please conduct an internet search to explore the psychological concepts of Covid. Then, in your own words, explain what Covid-19 is, and how the Covid-19 pandemic has effected your community from a psychological perspective. Make sure that your responses are based on your research of this topic.
Discussion board topics provide you with the opportunity to strengthen your ability to communicate effectively in writing. After reading the appropriate chapter, answer the discussion question and then comment on responses made by at least 2 of your peers. You are expected to post contributions that are well thought out, well written, and that apply to the principles of effective communication.
The Covid-19 pandemic has disrupted the lives of individuals across the globe. For this discussion, please conduct an internet search to explore the psychological concepts of Covid. Then, in your own words, explain what Covid-19 is, and how the Covid-19 pandemic has effected your community from a psychological perspective. Make sure that your responses are based on your research of this topic.
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oercommons
|
2025-03-18T00:37:09.331872
|
06/27/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/94608/overview",
"title": "PSYC-1030 Discussion Prompt: Covid-19 Pandemic",
"author": "Sherria King"
}
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https://oercommons.org/courseware/lesson/90538/overview
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assessments-games1
Why Alternative Assessments are NICE!
Overview
Shares why diverse assessments are nice for students!
Why Alternative Assessments are NICE
This shares some reasons why diverse assessments are nice!
CC-BY Licensing
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oercommons
|
2025-03-18T00:37:09.348891
|
03/01/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/90538/overview",
"title": "Why Alternative Assessments are NICE!",
"author": "Andrea Bearman"
}
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https://oercommons.org/courseware/lesson/99349/overview
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ENG101 College Composition I
Overview
Composing expository and argumentative essays for specific audiences. Emphasis on the processes of writing, reading and critical thinking. Introduction to research and documentation.
Course Content:
- Essay content
- Organization and structure
- Purpose and audience
- Language
- Grammar and punctuation
- Research
Learning Outcomes:
- Write thesis statements. (1)
- Select content and details. (1)
- Use organizational strategies. (2)
- Apply reasoned development strategies reflecting knowledge about a topic. (2)
- Use persuasive reasoning. (3)
- Select and apply voice. (3)
- Apply sentence structure strategies. (4)
- Incorporate purposeful, varied and appropriate vocabulary. (4)
- Apply conventions of standard written English. (5)
- Locate and evaluate information. (6)
- Analyze and interpret information. (6)
- Integrate and document information. (6)
Required Assessment:
- A minimum of 4,500 words of student writing with 2,700 of this formal writing, reviewed by the instructor.
Required Assessment:
- A minimum of 4,500 words of student writing with 2,700 of this formal writing, reviewed by the instructor
ENG101 College Composition I
Material Description
Composing expository and argumentative essays for specific audiences. Emphasis on the processes of writing, reading and critical thinking. Introduction to research and documentation.
Course Content:
- Essay content
- Organization and structure
- Purpose and audience
- Language
- Grammar and punctuation
- Research
Learning Outcomes:
- Write thesis statements.
- Select content and details.
- Use organizational strategies.
- Apply reasoned development strategies reflecting knowledge about a topic.
- Use persuasive reasoning.
- Select and apply voice.
- Apply sentence structure strategies.
- Incorporate purposeful, varied and appropriate vocabulary.
- Apply conventions of standard written English
- Locate and evaluate information.
- Analyze and interpret information.
- Integrate and document information.
Required Assessment:
- A minimum of 4,500 words of student writing with 2,700 of this formal writing, reviewed by the instructor.
Required Assessment:
- A minimum of 4,500 words of student writing with 2,700 of this formal writing, reviewed by the instructor
Context for sharing:
Adding to the available body of OER composition courses.
Course link: Canvas Commons
Course download: Common Cartridge
This file can be downloaded and used in most LMS platforms
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oercommons
|
2025-03-18T00:37:09.372944
|
12/10/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/99349/overview",
"title": "ENG101 College Composition I",
"author": "Sandi Van Lieu"
}
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https://oercommons.org/courseware/lesson/96875/overview
|
Tic Tac Toe Version2 Part 1 how it works
Tic Tac Toe Version 2 Part 2 Let's Run It Again
7- Tic Tac Toe Game In Java Ver. 2
Overview
Let's review what we learned about Java
7- Tic Tac Toe Game In Java Ver. 2 (Lecture Videos)
let's review the concepts we learned in Java.
Java Source File
The source code of the second version of the Tic Tac Toe game in Java
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oercommons
|
2025-03-18T00:37:09.391301
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08/30/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/96875/overview",
"title": "7- Tic Tac Toe Game In Java Ver. 2",
"author": "Saeid Samadidana"
}
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https://oercommons.org/courseware/lesson/84247/overview
|
English 1A Sample Reading List
English 1A Syllabus
English 1A: College Reading and Composition
Overview
Reading, analyzing, and writing college-level prose with emphasis on the expository; studying writing as a process; exploring different writing strategies; summarizing; editing, and critiquing; conducting research (gathering, organizing, evaluating, integrating and documenting information).
Syllabus, Sample Assignment, and Readings
Reading, analyzing, and writing college-level prose with emphasis on the expository; studying writing as a process; exploring different writing strategies; summarizing; editing, and critiquing; conducting research (gathering, organizing, evaluating, integrating and documenting information).
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oercommons
|
2025-03-18T00:37:09.411082
|
Open for Antiracism Program (OFAR)
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{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/84247/overview",
"title": "English 1A: College Reading and Composition",
"author": "Syllabus"
}
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https://oercommons.org/courseware/lesson/112803/overview
|
Calibration of glassware procedure
Calibration of Glassware and a Micropipette
Overview
This is Experiment #1 in the Analytical Chemistry Lab sequence at MSU Denver. It walks students through the calibration of three pieces of glassware and a micropipette. The Excel template is populated with prior student data so that calculations can be completed before lab and then updated with new data during lab. This allows for a mastery approach to the calibration, where students are able to repeat the calibration until the required tolerance is met.
Calibration of Glassware and a Micropipette
This is Experiment #1 in the Analytical Chemistry Lab sequence at MSU Denver. It walks students through the calibration of three pieces of glassware and a micropipette. The Excel template is populated with prior student data so that calculations can be completed before lab and then updated with new data during lab. This allows for a mastery approach to the calibration, where students are able to repeat the calibration until the required tolerance is met.
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oercommons
|
2025-03-18T00:37:09.428590
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Alycia Palmer
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{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/112803/overview",
"title": "Calibration of Glassware and a Micropipette",
"author": "Assessment"
}
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https://oercommons.org/courseware/lesson/64939/overview
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Education Standards
Expanding Vocabulary: Adverbs
Overview
This Worksheet gives students practice on finding new words to express the same idea. It focuses on expanding the use of adverbs in English.
Expanding Vocabulary: Adverbs
Here is a worksheet to help students expand their vocabulary, in this case, this practice is mainly to work on learning new adverbs.
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oercommons
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2025-03-18T00:37:09.449595
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04/05/2020
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/64939/overview",
"title": "Expanding Vocabulary: Adverbs",
"author": "Carolina Retana"
}
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https://oercommons.org/courseware/lesson/56712/overview
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Standard: Develop a model based on evidence to illustrate the life span of the sun and the role of nuclear fusion in the sun’s core to release energy in the form of radiation. [Clarification Statement: Emphasis is on the energy transfer mechanisms that allow energy from nuclear fusion in the sun’s core to reach Earth. Examples of evidence for the model include observations of the masses and lifetimes of other stars, as well as the ways that the sun’s radiation varies due to sudden solar flares (“space weather”), the 11-year sunspot cycle, and non-cyclic variations over centuries.] [Assessment Boundary: Assessment does not include details of the atomic and sub-atomic processes involved with the sun’s nuclear fusion.]
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oercommons
|
2025-03-18T00:37:09.476329
|
08/06/2019
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/56712/overview",
"title": "12.2 Mendelian Genetics (dominance / recessive traits)",
"author": "Urbi Ghosh"
}
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https://oercommons.org/courseware/lesson/91311/overview
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Purpose and Function of Adjective Clauses
Overview
Overview of the Modules
Introduction: Purpose and Function of Adjective Clauses
- Why should I care about adjective clauses?
- What do adjective clauses do?
- What do adjective clauses look like?
- Adjective clauses vs. Noun clauses vs. Adverb clauses
- Authentic English Analysis
About Relative Pronouns
- Combining Two Sentences with an Adjective Clause
- List of Relative Pronouns
- Relative Pronouns: Subject or Object of the Adjective Clause?
- Identifying vs. Non-Identifying Adjective Clauses
- Relative Pronouns: Object of a Preposition
- Who vs. Whom?
Less Common Relative Pronouns
- Whose vs. Who's
- When, Where, and Why as Relative Pronouns
Common Problems with Adjective Clauses
Purpose and Function of Adjective Clauses
Below is a Power Point presentation that introduces the purpose and function of adjective clauses for CEFR B1 learners.
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oercommons
|
2025-03-18T00:37:09.494436
|
Lesson
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91311/overview",
"title": "Purpose and Function of Adjective Clauses",
"author": "Language, Grammar and Vocabulary"
}
|
https://oercommons.org/courseware/lesson/96840/overview
|
https://www.youtube.com/watch?v=PQptY2meU9c
The Galapagos Islands
Overview
The Galapagos Islands are famed for their unique animal species found nowhere else on Earth. What intrigues you the most about this archipelago?
reading
Read about Island
говориння
переказати текст
письмо
написати про власну мандпівку
слухання
прослухати доповідача, та викласти власну думку
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oercommons
|
2025-03-18T00:37:09.515407
|
08/29/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/96840/overview",
"title": "The Galapagos Islands",
"author": "Oksana Bohdanova"
}
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https://oercommons.org/courseware/lesson/80382/overview
|
Course Resource Pages for Online Materials
CS 116 Syllabus_OER
Introduction to Computer Science I
Overview
This syllabus contains information, websites, and resources that are freely available to students as an alternative to a single textbook that is purchased. The semester course focuses on two major sections: 1) Learning Microsoft Office 2019 and 2) Computer Concepts. Students should develop a comfortable understanding of working in Microsoft Office 2019 as well as gain knowledge of computer concepts after taking this course.
Course Information
Texas Southern University
Department of Computer Science
Course ID: CS 116 - 3 hours
Course Title: Introduction to Computer Science I
Instructor Name: Dr. June Claiborne
Instructor Title: Adjunct Professor
Instructor Contact Information:
Location: Hannah Hall, Rm. 320H
Email: june.claiborne@tsu.edu
Phone: 713-313-4853
Course Description
Study of computers as a tool for information processing, content creation and communication. Topics include: basics of computer systems; productivity tools (word processing, spreadsheets, and presentation generation); multimedia; and information retrieval and sharing. Certain sections may cover topics related to specific fields of study.
Pre-requisites: None (This course is a core-course requirement)
Student Learning Outcomes / Objectives
Resource page contains list of required website links for completing weekly assignments.
1. Critical Thinking Skills – Develop custom design project applications
2. Communication Skills – Create projects by assessing the needs of scores
3. Group Participation – Develop teamwork skills
4. Personal Responsibilities – Each week assignments are due
Course Materials:
Textbook: Open Educational Resources (OER) will be used for this course. These resources are free and have been approved for use by the Instructor. Sources may vary from semester to semester.
Required Software: Microsoft Office 365 & Office 2019
Online Materials:
Online materials and links will be available throughout your Blackboard course that contain the software for reading and information as well as assignments for each week.
Course Support and Assistance
Teaching Assistant:
A Teaching Assistant will be available if you are having trouble. Your instructor will provide TA information so that you can contact them if needed. He/she will select the method of contact to use, either phone or email. The Teaching Assistant will also be in our class every Friday after Week 2.
Blackboard Information & Support:
All students must have access to TSU email and Blackboard.
Blackboard Login Information: Username = student’s complete TSU email Password = MyTSUWeb portal password.
For help with Blackboard:
- Phone – 713-313-7242 (8am-5pm) or 713-313-4357 (24/7)
- Email – tsuonline@tsu.edu
- In Person – Hannah Hall – Suite 320
OIT Support:
For help with MyTSUWeb portal or Blackboard Account Password Resets:
- Phone – 713-313-4357 (24/7)
- Toll Free Phone – 1-866-749-8237 (24/7)
- Service Requests - itservicecenter.tsu.edu
Your Computer Lab Account:
Access to Computer Lab: Any student can enter any classroom on the third floor in the where a lecture is not being held. You are welcome to work in the lab from: 8am – 8pm every day. Open labs are also available in the TSU Library Learning Center (LLC).
Your instructor will provide you with a letter during the first week of the semester that contains information on how to access your login account in the computer lab.
Also a desktop version of Office 365 has been installed on all computer lab computers. Simply click on the office application to open Word, PowerPoint, Excel, etc.
Class Participation
Requirements:
- You must Login to Blackboard and access TSU-EMAIL regularly to be successful in this course.
- You must access the OER materials (which serve as your textbook), readings, instructions, step-by-step videos, and complete the assignments, quizzes and exams throughout the semester
- You must read your TSU emails and Blackboard Announcements in the course regularly.
- Students that “FAIL” to participate in the activities and attendance will be reported to the office. Failing to complete assignments within the first 4 weeks of school can be a reason to report a student to main campus offices, due to LACK of participation or missing assignments.
- This course provides the student with more skills for MS-OFFICE & COMPUTER CONCEPTS. Therefore, it is STRONGLY RECOMMENDED that you read and do the assignments that are due each week. Do not wait until the last minute to complete the lab assignments or you may run out of time.
- Follow the instructions for each assignment, which will be found in your Blackboard course for each Module.
- Assignments are due every Sunday at 11:59 pm for full credit. Late assignments are accepted, but 10 points will be deducted.
Attendance Policies:
Absences that result in your missing a quiz, lab assignment, or project must be accompanied by a valid excuse before any makeup work will be accepted. (signed by your degree advisor or athletic advisor).
Students who have missed up to 4 consecutive classes and/or up to 4 assignments/quizzes will be administratively dropped from the course.
*Note: Attendance will be checked each class period, starting with Week 1 roll call so that instructor can learn your names. Starting in Week 2 or Week 3, an attendance sign-in sheet will be used. Make sure you sign the attendance sheet every class period to acknowledge that you have attended class for that day.
Academic Misconduct Policy & Scholastic Dishonesty
At Texas Southern University we are strongly committed to upholding standards of academic integrity. All forms of academic dishonesty should be avoided, especially the following:
- Copying from another student’s homework, quiz, or test.
- Possessing or using materials, during an exam or test that are not authorized.
- Using, buying, stealing, transporting, or soliciting a test, draft, facsimile, or answer key.
- Permitting someone to take a test for you or taking a test for someone else.
- Cheating during an exam or quiz.
All students need to credit the person working in the lab by name: graduate or classmates.
Course Grading
Weighted Scale is based on:
80% The total assignments for the semester including: quizzes and exams, attendance,
Class work/homework.
20% Final exam or project
Grading Scale:
98% - 100%: A+ 88% - 89%: B+ 78% - 79%: C+ 68% - 68%: D+ 0% - 59%: F
93% - 97%: A 83% - 87%: B 73% - 77%: C 63% - 67%: D
90% - 92%: A- 80% - 82%: B- 70% - 72%: C- 60% - 62% D-
Student Resources
Welcome Desk: 713-313-7402
Research & Instructional Support: 713-313-7402
Circulation, ILL & Course Reserves: 713-313-1082
Computer Lab Support: 713-313-7150 (Labs with print stations are in room 319, 419 and 519)
University Student Services:
Student Services: 713-313-1038
Health Center, Counseling, etc.:
http://students.tsu.edu/departments/health-services/
Clinic Hours: 8am-5pm – 713-313-7173
Student Accessibility Services:
Students needing academic accommodations should contact:
Student Accessibility Services Office (SASO):
Phone: 713-313-7691 or 713-313-4210
Location: Fairchild Building, Room 147, 8am - 5pm, Monday – Friday
ADA Policy:
Texas Southern University maintains a policy for students with disabilities in accordance with the American with Disabilities Act of 1990, and Section 504 of the Rehabilitation Act of 1973. Under these federal guidelines, the University is obligated to:
- Protect the civil rights of students and disabilities
- Protect the confidentiality and privacy of students with disabilities
- Provide reasonable accommodations and services to students with known disabilities, who are qualified to meet the requirements of the academic program, apart from the handicapping condition.
- The burden of proof is on the student to demonstrate the need for requested accommodations. If you are qualified to receive services, please contact the Student Accessibility Services Office (SASO).
Students with documented disabilities should visit SASO and request a letter for the instructor so our department can set accommodations for the computer lab or mentoring by one of the graduate students.
Course Schedule and Assignments
Week 1
- Familiarize yourself with the syllabus and assignment due dates.
- Send your instructor a note using your TSU student email, confirming that your TSU email is working and that you are able to login to Blackboard. *Note: This exercise is worth 10 points toward your final grade.
- In your Blackboard course: Discussion Board,
- Briefly introduce yourself to the class
- Visit the Q & A section if you have a question or information to share with your classmates
If Microsoft 365 Office Suites is not available on your computer, obtain TSU free access to Microsoft 365 Office Suites. Simply login with your regular TSU student email and password.
____________________________________________________________________________
Week 2 & 3: Course Content – Microsoft WORD: Open Educational Resources (free resources) are hyperlinked
- Creating a Flyer
- Assignment: Create a flyer using example in your Blackboard course. Be as creative as possible (10 pts.)
- Creating a Research Paper (Resources found in Purdue Owl Writing – Purdue University and OER Commons)
- Resource: Purdue Owl Writing Lab
- APA Style Using MS Word
- Choosing the Right Words – PPT
- Formatting Title Pages/APA Style
- The Basics of Quoting – YouTube video
- Assignment: Write 5-page Research Paper, including cover page, citations, and reference page on your future career. You will need to search for information on your major for this project. Research Paper due in Week 6 (100 pts.)
- Creating a Business Letter (Resources found in OER Commons)
- Written Communications for Writing Letters
- Written Communications – Emails and Letters PPT
- Communications and Editing 2
- Options for Starting a letter
- Assignment: You are in your senior year, preparing to graduate in your major, and applying for jobs to start your career. Write a Resume and include a Business cover letter in correct format (100 pts.)
Supplemental free book available: Microsoft Word 2019 , by Shelley Fishel
____________________________________________________________________________
Week 4 & 5: Microsoft POWERPOINT
Digital Textbook Required (free to students): PowerPoint 2019 (professional ebook – Bookboon), by Shelley Fishel.
In this book, you will learn how to build a presentation, including how to modify the Slide Master, change the Theme and Rehearse the presentation. Learn about adding Tables, Charts, Pictures and SmartArt to your slide deck. Find out how to create a template and save the Slide Master for future use.
Read following chapters:
- Chapter 9 – Creating a Presentation
- Chapter 28 – Adding and formatting shapes
- Chapter 30 – Working with Slide Content
- Chapter 31 – Working with Pictures and Images
- Assignment: Create a PowerPoint presentation with information on your major and your career goals once you graduate. Be as creative as possible using text, images, etc. Presentation should include a cover slide and at least 4 content slides. (100 pts.)
____________________________________________________________________________
Week 6 & 7: Microsoft EXCEL
Digital Textbook Required: Beginning Excel 2019 , by Noreen Brown, Barbara Lave, Hallie Puncochar, Julie Romey, Mary Schatz, Art Schneider, & Diane Shingledecker
This textbook was written for a community college introductory course in spreadsheets utilizing Microsoft Excel. While the figures shown utilize Excel 2019, the textbook was written to be applicable to other versions of Excel as well. The book introduces new users to the basics of spreadsheets and is appropriate for students in any major who have not used Excel before. This textbook includes instructions for Excel for Mac also.
- Creating a Worksheet and a Chart
- Read Chapter 1 – Fundamental Skills
- Formulas, Functions, and Formatting
- Read Chapter 2 – Mathematical Computations
- Read Chapter 4 - Presenting Data with Charts
- Assignment: Create a Personal Budget Spreadsheet, Yearly projections of your personal budget, expenses, and calculations. Include a 3D pie chart, and line chart with monthly expenses per month and each expense legend. (100pts.)
- Working with Large Worksheets, Charting, and What-if Analysis
- Read Chapter 3 – Formulas, Functions, Logical and Lookup Functions
- Assignment: Create a Vacation Package Analysis Workbook (100 pts.)
____________________________________________________________________________
Week 8 – Midterm Week: Midterm Exam or group project (100 pts.)
____________________________________________________________________________
Week 9 – Computer Concepts
Module 1: Impact of Digital Technology
- Read the following (Found in OER Commons):
- How Computers Work
- Artificial Intelligence
- Robotics
- Disability Assistance
- Read Virtual Reality – PPT in the course
- Technology in The Workplace – Word document found in the course
- Using Microsoft Teams
1. Assignment: Discussion Activity 1 - “Technology in The Workplace”. Discuss how you might use technology in your future career. Make sure you post to your instructor and respond to at least 2 of your classmates. (10 pts.)
- Quiz (10 pts.)
____________________________________________________________________________
Week 10 – Computer Concepts
Module 2: The Web
- Read: The Internet of Things (Found in OER Commons):
- Assignment: Discussion Activity 2 – “Working in Your Internet Browser”. Discuss your views about working on the internet in your daily life for school and work. Is it a personal distraction to receive constant advertisements or are they helpful? Why or why not? Make sure you post to your instructor and respond to at least 2 of your classmates. (10 pts.)
- Quiz (10 pts.)
____________________________________________________________________________
Week 11 – Computer Concepts
Module 3: Computer Hardware
- Read PPT file in course: Computer Components (Hardware)
- Assignment: Pretend you are buying a computer, visit this website link for information on buying a computer and the process: https://www.oercommons.org/search?f.search=computers
- Assignment: Discussion Activity 3 – “Types of Computers to Purchase”. Discuss the pros and cons to purchasing the most expensive computer available and why it may not be the most effective for someone. Make sure you post to your instructor and respond to at least 2 of your classmates. (10 pts.)
- Quiz (10 pts.)
____________________________________________________________________________
Week 12 – Computer Concepts
Module 4: Operating Systems & File Management
- Read information on Operating Systems and File Management (Found in OER Commons):
- Operating Systems & File Management
- Operating Systems course
- File Systems and management – Word Document found in the course
- File System Management – PDF document found in the course
- Assignment: Discussion Activity 4 – “Types of Operating Systems”. Name some of the operating systems available for a PC and or Mac. If you were a computer consultant, which operating system would you recommend to a client purchasing a computer and why? Make sure you post to your instructor and respond to at least 2 of your classmates. (10 pts.)
- Quiz (10 pts.)
____________________________________________________________________________
Week 13 – Computer Concepts
Module 5: Software and Apps
- Watch video on Designing an App (Found in OER Commons):
- Read PPT file in course: What is a Program (Software)
- Assignment: Discussion Activity 5 – Discuss how apps are created. How has using apps made your life more convenient for home, school, and work uses. Make sure you post to your instructor and respond to at least 2 of your classmates. (10 pts.)
- Quiz (10 pts.)
____________________________________________________________________________
Week 14 & 15 – Computer Concepts
Module 6: Security and Safety
- Watch the video: The Internet: Cybersecurity and Crime – YouTube video
- Watch the video: Data Protection and Security on the Web - MERLOT Video Lecture
- Read and Review the PowerPoint file on Cybersecurity in your course
- Cybersecurity – PPT found in the course
- Assignment: Discussion Activity 6 – “Identifying Spam Emails and Suspicious Web Links”. Discuss some of the ways that you might distinguish spam email from a safe one. What should you do when receiving a compromised email? Make sure you post to your instructor and respond to at least 2 of your classmates. (10 pts.)
- Quiz (10 pts.)
**Note: Also use these last 2 weeks to complete any missing assignments and activities.
____________________________________________________________________________
Week 16: Final Exam Week: Final Exam or Group Project (100 pts.)
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oercommons
|
2025-03-18T00:37:09.611031
|
Homework/Assignment
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/80382/overview",
"title": "Introduction to Computer Science I",
"author": "Information Science"
}
|
https://oercommons.org/courseware/lesson/122333/overview
|
MNT 110 Final Exam
MNT-110, Intro to Maintenance Procedures
MNT 110 Mid Term Exam
MNT 110 Questions and Answers
MNT-110 Intro to Maintenance Procedures
Overview
This course covers basic maintenance fundamentals for power transmission equipment. Topics include equipment inspection, lubrication, alignment, and other scheduled maintenance procedures. Upon completion, students should be able to demonstrate knowledge of accepted maintenance procedures and practices according to current industry standards.
Materials include full course layout and quiz questions and answers uploaded seperately.
MNT-110 Intro to Maintenance Procedures
This course covers basic maintenance fundamentals for power transmission equipment. Topics include equipment inspection, lubrication, alignment, and other scheduled maintenance procedures. Upon completion, students should be able to demonstrate knowledge of accepted maintenance procedures and practices according to current industry standards.
This product was funded by a grant awarded by the U.S. Department of Labor's Employment and Training Administration. The product was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor. The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership.
|
oercommons
|
2025-03-18T00:37:09.632375
|
12/02/2024
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/122333/overview",
"title": "MNT-110 Intro to Maintenance Procedures",
"author": "Bo Bunn"
}
|
https://oercommons.org/courseware/lesson/89744/overview
|
Abraham Lincoln and Dan Stone - Illinois House of Representatives Journal Entry, March 3, 1837
Overview
Statement by Abraham Lincoln and Dan Stone on the Subject of Domestic Slavery March 3, 1837
Abraham Lincoln and Dan Stone - Illinois House of Representatives Journal Entry, March 3, 1837
Representatives Abraham Lincoln (R-IL) and Dan Stone (R-IL), statement in the Illinois House of Representatives Journal regarding Domestic Slavery
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oercommons
|
2025-03-18T00:37:09.649807
|
Christopher Gilliland
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/89744/overview",
"title": "Abraham Lincoln and Dan Stone - Illinois House of Representatives Journal Entry, March 3, 1837",
"author": "Susan Jennings"
}
|
https://oercommons.org/courseware/lesson/56911/overview
|
Education Standards
Chapter 1 Lecture Notes
Lab Syllabus
Course Syllabus
Chapter 1: What Is Chemistry?
Assignment 1 Questions
Introduction to Chemistry
Overview
This module seeks to answer the question, what is chemistry? To answer this question, topics such as the scientific method, physical state of matter, law of conservation of matter, classification of matter, physical and chemical properties, measurements etc. are addressed. This module is designed primarily for students with no previous chemistry courses.
CHE 121(30)
Learning Outcomes of MODULE ONE:
Chapter 1: Chemistry in Context
By the end of this module, you will be able to:
1.1 Chemistry in Context
- Outline the historical development of chemistry
- Provide examples of the importance of chemistry in everyday life
- Describe the scientific method
- Differentiate among hypotheses, theories, and laws
- Provide examples illustrating macroscopic, microscopic, and symbolic domains
1.2 Phases and Classification of Matter
- Describe the basic properties of each physical state of matter: solid, liquid, and gas
- Distinguish between mass and weight
- Apply the law of conservation of matter
- Classify matter as an element, compound, homogeneous mixture, or heterogeneous mixture with regard to its physical state and composition
- Define and give examples of atoms and molecules
1.3 Physical and Chemical Properties
- Identify properties of and changes in matter as physical or chemical
- Identify properties of matter as extensive or intensive
1.4 Measurements
- Explain the process of measurement
- Identify the three basic parts of a quantity
- Describe the properties and units of length, mass, volume, density, temperature, and time
- Perform basic unit calculations and conversions in the metric and other unit systems
1.5 Measurement Uncertainty, Accuracy, and Precision
- Define accuracy and precision
- Distinguish exact and uncertain numbers
- Correctly represent uncertainty in quantities using significant figures
- Apply proper rounding rules to computed quantities
1.6 Mathematical Treatment of Measurement Results
- Explain the dimensional analysis (factor label) approach to mathematical calculations involving quantities
- Use dimensional analysis to carry out unit conversions for a given property and computations involving two or more properties
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oercommons
|
2025-03-18T00:37:09.687222
|
08/14/2019
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/56911/overview",
"title": "Introduction to Chemistry",
"author": "Sherryllene Pinnock"
}
|
https://oercommons.org/courseware/lesson/82127/overview
|
Teacher & Student Grade Tracking Spreadsheet
Overview
This resource is a Google Sheet Template that aids students and teachers in tracking individual student grades based on the number of points they've earned in the course compared to the total number of points available.
Teacher Instructions
This resources is a Google Spreadsheet Template that teachers and students can use to track their grade and progress in a course based on the number of points they have earned compared to the total number of points available.
The calculations on this spreadsheet are based on a grading system that DOES NOT include differing weights for categories. The calculations will only work if you calculate grades in your class with no weighted items.
This spreadsheet also calculates grades based on the following grade distribution:
Teachers who are familiar with Google Sheets and inputting calculations could easily adjust this grading scale if needed by adjusting the calculation in the "Earn at least this many points" column of the spreadsheet template.
Here are a few tips for using this spreadsheet successfully with your students:
1) The teacher should fill in the "Assignment #", "Assignment Name", "Priority Level", "Points Possible", and "Assignment Type" columns with the indicated information for their course. Do not trust students to input this correctly. They may make mistakes and assume they've earned a grade that they actually haven't due to their error.
2) Double check all the calculations to make sure they are calculating correctly for your course.
3) This grade tracking sheet can be useful for both the teacher and the student:
Teachers - this sheet is especially helpful when students ask you what they need to do to earn the grade they desire. It's also helpful when students have a lot of work to catch-up on and need a plan for getting on track.
Students - this sheet is helpful for students to see if they are on track for the grade they desire. It also helps them prioritize what work is most important to work on first.
4) Once all the information is filled in for your course, you can choose to let students make a copy of this spreadsheet for themselves to track their own grade. OR (my preferred method) you could make individual copies for the students who need it and share the sheet with them using the sheet's "Share" settings. This allows you, the teacher, to have oversight over the sheet and make sure it is being used correctly.
5) Consider using the grade tracking sheet during parent teacher conferences to help parents understand their student's progress in the class.
6) Keep a close eye on your tracking spreadsheets to make sure they are correct throughout the year. You don't want students making copies of incorrect information and basing their grade on it.
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oercommons
|
2025-03-18T00:37:09.706803
|
Sara Scholes
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/82127/overview",
"title": "Teacher & Student Grade Tracking Spreadsheet",
"author": "Student Guide"
}
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https://oercommons.org/courseware/lesson/67225/overview
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Introduction to Computing Reading & Learning Objectives
Overview
Welcome to Computers/Networking 101
Hopefully with videos and PPT I can teach you the basic of Computers
Introduction to Computing Reading & Learning Objectives
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oercommons
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2025-03-18T00:37:09.724004
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Juan Rodriguez
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/67225/overview",
"title": "Introduction to Computing Reading & Learning Objectives",
"author": "Lecture Notes"
}
|
https://oercommons.org/courseware/lesson/101080/overview
|
Arabic Level 1, Activity 14: "مُرَاجَعَة مَا سَبَق / Review" (Face-to-Face/Online)
Overview
In this activity, students will practice three main lessons they took in previous chapters, which are the Subject Pronouns, the Demonstrative Pronouns, and the Nisba Adjective.
Can-Do Statements:
- I can use call someone according to their pronouns.
- I can use this and that in a conversation for either feminine or masculine forms.
- I can say someone's nationality from the country name.
About The Pathways Project
Please Note: Many of the activities on the Pathways Project OER Repository were created by upper-division students at Boise State University and serve as a foundation that our community of practice can build upon and refine. While they are polished, we welcome and encourage collaboration from language instructors to help modify grammar, syntax, and content where needed. Kindly contact amberhoye@boisestate.edu with any suggestions and we will update the content in a timely manner. — The Pathways Project
Looking for the English Version of this activity to adapt for your language? CLICK HERE
About the Boise State World Languages Resource Center (WLRC) Language Activity Repository
The activities provided by the Boise State World Languages Resource Center (WLRC) serve as foundational activities which can be adapted by any language and scaled up or down on the proficiency scale. Many of these activities offer an English Version that is “language-agnostic” to provide language instructors from around the country a platform to remix these instructional materials, infusing them with their target language and culture! The activities within the Pathways Project OER Repository seek to help students solidify their interpersonal speaking and interpretive skills through task-based situations or communicative activities. These activities should be facilitated in the target language for approximately 90% (or more), per the recommendation of the American Council on the Teaching of Foreign Languages.
How to use the WLRC Repository’s Activities:
1. Use the Activity as is:
Before you begin:
- Most activities are 30 minutes in duration, unless otherwise specified.
- Be sure to read through the activity description, and review the list of required materials. You will notice that the activity materials are also highlighted in yellow throughout the activity instructions.
If you have any suggestions about grammar, syntax, and content, please kindly contact amberhoye@boisestate.edu.
2. Remix for Your Language Classroom:
When you are ready to begin remixing the activity, in order to adapt it for the needs of your language classroom, simply click the blue “Remix This Resource” button at the top of your screen. This will then take you to a screen with a NEW, editable version of this activity. The text provided in purple is a suggestion of what you might say to your students in the target language, and may be altered for different levels and age groups. All activities have “NCSSFL-ACTFL Can-Do” statements, a warm-up, a main activity, and a wrap-up.
Many of the activities include printable cards and other instructional materials such as Google Slideshows. If you would like to make changes to these materials in Spanish, follow the instructions below:
- Google Slideshows:
- To begin, go to File -> Copy to create an editable version of the slideshow.
- Once finished with your changes, please complete the following steps to share:
- Click on Share
- Who Has Access
- Ensure link sharing is on and allow external access.
- Materials Saved as PDF: Please email WLRCLAR@gmail.com and we will provide you with an editable copy. Please allow up to two business days for a response. For YouTube videos and other websites, hyperlinks are provided.
3. Adapt for Another Language:
- See the linked English Version at the top of the activity (English Version may not be available for all activities)
Activity Instructions
مُرَاجَعَة مَا سَبَق / Review
Description:
In this activity, students will practice three main lessons they took in previous chapters, which are the Subject Pronouns, the Demonstrative Pronouns, and the Nisba Adjective.
Semantic Topics:
انا - انت - هو - هي - هذا - ذاك - امريكي - امريكية, this, that, she, he
Grammatical Topics:
Subject Pronouns, Demonstrative Pronouns, and Nisba Adjectives.
NCSSFL-ACTFL World-Readiness Standards:
- Standard 1.1: Students engage in conversations or correspondence in Arabic to provide and obtain information, express feelings and emotions, and exchange opinions.
- Standard 1.2: Students understand and interpret spoken and written Arabic on a variety of topics.
- Standard 4.1: Students demonstrate an understanding of the nature of language through comparisons of Arabic and their own languages.
Idaho Content Standards for World Languages:
- COMM 1.1: Interact and negotiate meaning (spoken, signed, written conversation) to share information, reactions, feelings, and opinions.
- COMM 2.1: Understand, interpret, and analyze what is heard, read, or viewed on a variety of topics.
- COMP 1.1: Observe formal and informal forms of language.
- COMP 1.2: Identify patterns and explain discrepancies in the sounds and the writing system in the target language.
NCSSFL-ACTFL Can-Do Statements:
- I can use call someone according to their pronouns.
- I can use this and that in a conversation for either feminine or masculine forms.
- I can say someone's nationality from the country name.
Materials Needed:
Warm-Up
- Greet students in Arabic السلام عليكم and then share your screen with students and pull up the presentation. And don’t forget to press Slideshow.
رحب بالطلاب باللغة العربية السلام عليكم ثم شارك شاشتك مع الطلاب وافتح العرض التقديمي. ولا تنس الضغط على زر العرض.. - Move to the next slide with the “Can-Do Statements” and read each Can-Do statement in English.
انتقل إلى الشريحة التالية "عبارات Can-Do" واقرأ كل عبارة Can-Do باللغة الإنجليزية. - Next, move to slide #3. You will just read through slides #3, #4, #5, and #6 and review with students the Subject Pronouns, the Demonstrative Pronouns, and the Nisba Adjective.
بعد ذلك ، انتقل إلى الشريحة 3. سوف تقرأ فقط خلال الشرائح 3 و 4 و 5 و 6 وتراجع مع الطلاب ضمائر الموضوع والضمائر التوضيحية وصفة النسبا. - You may ask students to read the Arabic example for each slide to make them engage with you!
يمكنك أن تطلب من الطلاب قراءة المثال العربي لكل شريحة لجعلهم يتفاعلون معك!
Main Activity
- Students will review the questions starting on slide 9. They will choose the correct answer from the multiple-subject pronouns choices.
سيقوم الطلاب بمراجعة الأسئلة بدءًا من الشريحة 9. وسيختارون الإجابة الصحيحة من اختيارات الضمائر متعددة الموضوعات. - Then, they will translate the English sentence to Arabic using the correct Demonstrative Pronouns.
بعد ذلك ، سيترجمون الجملة الإنجليزية إلى العربية باستخدام الضمائر التوضيحية الصحيحة.
Last, students will practice the Nisba Adjective by finding the correct nationality for each question.
أخيرًا ، سيتدرب الطلاب على صفة النسبة من خلال إيجاد الجنسية الصحيحة لكل سؤال.
Wrap-Up
Ask students if they have any questions.
اسألهم اذا كان لديهم اي سؤال؟
End of Activity
- Read Can-Do statements once more and have students evaluate
their confidence.
(Use thumbs up/thumbs down or download our student cards.) - Encourage students to be honest in their self-evaluation.
- Pay attention, and try to use feedback for future activities!
NCSSFL-ACTFL Can-Do Statements:
- I can use call someone according to their pronouns.
- I can use this and that in a conversation for either feminine or masculine forms.
- I can say someone's nationality from the country name.
|
oercommons
|
2025-03-18T00:37:09.752725
|
World Cultures
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/101080/overview",
"title": "Arabic Level 1, Activity 14: \"مُرَاجَعَة مَا سَبَق / Review\" (Face-to-Face/Online)",
"author": "Languages"
}
|
https://oercommons.org/courseware/lesson/110952/overview
|
READING: Taxonomy
Overview
This is a Reading for my Canvas-based BIO100 course.
Module 1
This is a Canvas page associated with content for my BIO100 course.
1.4 READING: Taxonomy
Biology is all about studying life on Earth. There's an amazing variety of living things out there! This diversity comes from a process called evolution, which is when new species develop from older ones over time. Scientists who study evolution look at all kinds of living things, from tiny cells to whole environments.
The branch of Biology that studies the classification of living things is called Taxonomy, which comes from the Ancient Greek words "taxis" (arrangement) and "nomia" (method). Based on this system, living things are grouped according to their similarities into taxa (singular: taxon). Taxa are ranked hierarchically to create smaller taxa within larger taxa. There are dynamic developments within the science of taxonomy, and different branches of biology may use slightly different systems. In this course, we will use the most widely accepted ranking system, which consists of the ranks named:
The hierarchy of biological classification's eight major taxonomic ranks. A Family contains one or more genera. Intermediate minor rankings are not shown.
This image has been released into the public domain by Pengo at English Wikipedia. The artwork is from Peter Halasz.
Modern taxonomy has a much more complex classification system than the one we are learning here. The modern system is still largely based on the work of Carl Linnaeus, who published it in the 18th century but takes into account all the knowledge derived from genetics and the study of DNA.
Before Linnaeus, it was difficult to name and identify organisms because different regions had different names for the same thing. Linnaeus devised a new way to name organisms using two names, called the Binomial Naming System. This system uses a unique name for each organism that includes two parts - the first part is capitalized and represents the Genus, and the second part is all lowercase and represents the Species. For example, the blue jay is known as Cyanocitta cristata, and modern humans are known as Homo sapiens. This system helps scientists from all over the world to identify and refer to the same organism using the same name.
Here is an interesting 13-minute video lecture from Khan Academy (Khan Salman) that looks at the science of Taxonomy and where humans fit into the tree of life: https://www.khanacademy.org/science/biology/her/tree-of-life/v/taxonomy-and-the-tree-of-life
This diagram shows the levels of taxonomic hierarchy for a dog,
from the broadest category—Domain—to the most specific—Species.
What kind of features do biologists look at to decide how to classify a particular form of life? There are many aspects. For example, the general external morphology (i.e., what an organism looks like and how similar it is to another), what special structures are present, what the internal organs look like, how it develops from egg to adult, the structure of their cells, their specific chemistry including the substances their body secretes, and, nowadays, more and more, the code encrypted into their DNA, which determines which proteins the organism can build and how similar those proteins are to another organism.
Other clues include their behaviors, such as special courtship rituals, dances, or calls, and their habits, such as where they live, what food they eat, how they approach the seasons, and what kind of parasites inhabit their bodies.
Attribution: CC BY 4.0 DEED - https://creativecommons.org/licenses/by/4.0/
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oercommons
|
2025-03-18T00:37:09.768260
|
12/10/2023
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/110952/overview",
"title": "READING: Taxonomy",
"author": "Daniela Maldini"
}
|
https://oercommons.org/courseware/lesson/28781/overview
|
Introduction to Demand and Supply
Why Can We Not Get Enough of Organic?
Organic food is increasingly popular, not just in the United States, but worldwide. At one time, consumers had to go to specialty stores or farmers' markets to find organic produce. Now it is available in most grocery stores. In short, organic is part of the mainstream.
Ever wonder why organic food costs more than conventional food? Why, say, does an organic Fuji apple cost $1.99 a pound, while its conventional counterpart costs $1.49 a pound? The same price relationship is true for just about every organic product on the market. If many organic foods are locally grown, would they not take less time to get to market and therefore be cheaper? What are the forces that keep those prices from coming down? Turns out those forces have quite a bit to do with this chapter’s topic: demand and supply.
Introduction to Demand and Supply
In this chapter, you will learn about:
- Demand, Supply, and Equilibrium in Markets for Goods and Services
- Shifts in Demand and Supply for Goods and Services
- Changes in Equilibrium Price and Quantity: The Four-Step Process
- Price Ceilings and Price Floors
An auction bidder pays thousands of dollars for a dress Whitney Houston wore. A collector spends a small fortune for a few drawings by John Lennon. People usually react to purchases like these in two ways: their jaw drops because they think these are high prices to pay for such goods or they think these are rare, desirable items and the amount paid seems right.
Visit this website to read a list of bizarre items that have been purchased for their ties to celebrities. These examples represent an interesting facet of demand and supply.
When economists talk about prices, they are less interested in making judgments than in gaining a practical understanding of what determines prices and why prices change. Consider a price most of us contend with weekly: that of a gallon of gas. Why was the average price of gasoline in the United States $3.71 per gallon in June 2014? Why did the price for gasoline fall sharply to $1.96 per gallon by January 2016? To explain these price movements, economists focus on the determinants of what gasoline buyers are willing to pay and what gasoline sellers are willing to accept.
As it turns out, the price of gasoline in June of any given year is nearly always higher than the price in January of that same year. Over recent decades, gasoline prices in midsummer have averaged about 10 cents per gallon more than their midwinter low. The likely reason is that people drive more in the summer, and are also willing to pay more for gas, but that does not explain how steeply gas prices fell. Other factors were at work during those 18 months, such as increases in supply and decreases in the demand for crude oil.
This chapter introduces the economic model of demand and supply—one of the most powerful models in all of economics. The discussion here begins by examining how demand and supply determine the price and the quantity sold in markets for goods and services, and how changes in demand and supply lead to changes in prices and quantities.
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oercommons
|
2025-03-18T00:37:09.784466
| null |
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/28781/overview",
"title": "Principles of Macroeconomics 2e, Demand and Supply",
"author": null
}
|
https://oercommons.org/courseware/lesson/28782/overview
|
Demand, Supply, and Equilibrium in Markets for Goods and Services
Overview
By the end of this section, you will be able to:
- Explain demand, quantity demanded, and the law of demand
- Identify a demand curve and a supply curve
- Explain supply, quantity supplied, and the law of supply
- Explain equilibrium, equilibrium price, and equilibrium quantity
First let’s first focus on what economists mean by demand, what they mean by supply, and then how demand and supply interact in a market.
Demand for Goods and Services
Economists use the term demand to refer to the amount of some good or service consumers are willing and able to purchase at each price. Demand is fundamentally based on needs and wants—if you have no need or want for something, you won't buy it. While a consumer may be able to differentiate between a need and a want, but from an economist’s perspective they are the same thing. Demand is also based on ability to pay. If you cannot pay for it, you have no effective demand. By this definition, a homeless person probably has no effective demand for shelter.
What a buyer pays for a unit of the specific good or service is called price. The total number of units that consumers would purchase at that price is called the quantity demanded. A rise in price of a good or service almost always decreases the quantity demanded of that good or service. Conversely, a fall in price will increase the quantity demanded. When the price of a gallon of gasoline increases, for example, people look for ways to reduce their consumption by combining several errands, commuting by carpool or mass transit, or taking weekend or vacation trips closer to home. Economists call this inverse relationship between price and quantity demanded the law of demand. The law of demand assumes that all other variables that affect demand (which we explain in the next module) are held constant.
We can show an example from the market for gasoline in a table or a graph. Economist call a table that shows the quantity demanded at each price, such as Table, a demand schedule. In this case we measure price in dollars per gallon of gasoline. We measure the quantity demanded in millions of gallons over some time period (for example, per day or per year) and over some geographic area (like a state or a country). A demand curve shows the relationship between price and quantity demanded on a graph like Figure, with quantity on the horizontal axis and the price per gallon on the vertical axis. (Note that this is an exception to the normal rule in mathematics that the independent variable (x) goes on the horizontal axis and the dependent variable (y) goes on the vertical. Economics is not math.)
Table shows the demand schedule and the graph in Figure shows the demand curve. These are two ways to describe the same relationship between price and quantity demanded.
| Price (per gallon) | Quantity Demanded (millions of gallons) |
|---|---|
| $1.00 | 800 |
| $1.20 | 700 |
| $1.40 | 600 |
| $1.60 | 550 |
| $1.80 | 500 |
| $2.00 | 460 |
| $2.20 | 420 |
Demand curves will appear somewhat different for each product. They may appear relatively steep or flat, or they may be straight or curved. Nearly all demand curves share the fundamental similarity that they slope down from left to right. Demand curves embody the law of demand: As the price increases, the quantity demanded decreases, and conversely, as the price decreases, the quantity demanded increases.
Confused about these different types of demand? Read the next Clear It Up feature.
Is demand the same as quantity demanded?
In economic terminology, demand is not the same as quantity demanded. When economists talk about demand, they mean the relationship between a range of prices and the quantities demanded at those prices, as illustrated by a demand curve or a demand schedule. When economists talk about quantity demanded, they mean only a certain point on the demand curve, or one quantity on the demand schedule. In short, demand refers to the curve and quantity demanded refers to the (specific) point on the curve.
Supply of Goods and Services
When economists talk about supply, they mean the amount of some good or service a producer is willing to supply at each price. Price is what the producer receives for selling one unit of a good or service. A rise in price almost always leads to an increase in the quantity supplied of that good or service, while a fall in price will decrease the quantity supplied. When the price of gasoline rises, for example, it encourages profit-seeking firms to take several actions: expand exploration for oil reserves; drill for more oil; invest in more pipelines and oil tankers to bring the oil to plants for refining into gasoline; build new oil refineries; purchase additional pipelines and trucks to ship the gasoline to gas stations; and open more gas stations or keep existing gas stations open longer hours. Economists call this positive relationship between price and quantity supplied—that a higher price leads to a higher quantity supplied and a lower price leads to a lower quantity supplied—the law of supply. The law of supply assumes that all other variables that affect supply (to be explained in the next module) are held constant.
Still unsure about the different types of supply? See the following Clear It Up feature.
Is supply the same as quantity supplied?
In economic terminology, supply is not the same as quantity supplied. When economists refer to supply, they mean the relationship between a range of prices and the quantities supplied at those prices, a relationship that we can illustrate with a supply curve or a supply schedule. When economists refer to quantity supplied, they mean only a certain point on the supply curve, or one quantity on the supply schedule. In short, supply refers to the curve and quantity supplied refers to the (specific) point on the curve.
Figure illustrates the law of supply, again using the market for gasoline as an example. Like demand, we can illustrate supply using a table or a graph. A supply schedule is a table, like Table, that shows the quantity supplied at a range of different prices. Again, we measure price in dollars per gallon of gasoline and we measure quantity supplied in millions of gallons. A supply curve is a graphic illustration of the relationship between price, shown on the vertical axis, and quantity, shown on the horizontal axis. The supply schedule and the supply curve are just two different ways of showing the same information. Notice that the horizontal and vertical axes on the graph for the supply curve are the same as for the demand curve.
| Price (per gallon) | Quantity Supplied (millions of gallons) |
|---|---|
| $1.00 | 500 |
| $1.20 | 550 |
| $1.40 | 600 |
| $1.60 | 640 |
| $1.80 | 680 |
| $2.00 | 700 |
| $2.20 | 720 |
The shape of supply curves will vary somewhat according to the product: steeper, flatter, straighter, or curved. Nearly all supply curves, however, share a basic similarity: they slope up from left to right and illustrate the law of supply: as the price rises, say, from $1.00 per gallon to $2.20 per gallon, the quantity supplied increases from 500 gallons to 720 gallons. Conversely, as the price falls, the quantity supplied decreases.
Equilibrium—Where Demand and Supply Intersect
Because the graphs for demand and supply curves both have price on the vertical axis and quantity on the horizontal axis, the demand curve and supply curve for a particular good or service can appear on the same graph. Together, demand and supply determine the price and the quantity that will be bought and sold in a market.
Figure illustrates the interaction of demand and supply in the market for gasoline. The demand curve (D) is identical to Figure. The supply curve (S) is identical to Figure. Table contains the same information in tabular form.
| Price (per gallon) | Quantity demanded (millions of gallons) | Quantity supplied (millions of gallons) |
|---|---|---|
| $1.00 | 800 | 500 |
| $1.20 | 700 | 550 |
| $1.40 | 600 | 600 |
| $1.60 | 550 | 640 |
| $1.80 | 500 | 680 |
| $2.00 | 460 | 700 |
| $2.20 | 420 | 720 |
Remember this: When two lines on a diagram cross, this intersection usually means something. The point where the supply curve (S) and the demand curve (D) cross, designated by point E in Figure, is called the equilibrium. The equilibrium price is the only price where the plans of consumers and the plans of producers agree—that is, where the amount of the product consumers want to buy (quantity demanded) is equal to the amount producers want to sell (quantity supplied). Economists call this common quantity the equilibrium quantity. At any other price, the quantity demanded does not equal the quantity supplied, so the market is not in equilibrium at that price.
In Figure, the equilibrium price is $1.40 per gallon of gasoline and the equilibrium quantity is 600 million gallons. If you had only the demand and supply schedules, and not the graph, you could find the equilibrium by looking for the price level on the tables where the quantity demanded and the quantity supplied are equal.
The word “equilibrium” means “balance.” If a market is at its equilibrium price and quantity, then it has no reason to move away from that point. However, if a market is not at equilibrium, then economic pressures arise to move the market toward the equilibrium price and the equilibrium quantity.
Imagine, for example, that the price of a gallon of gasoline was above the equilibrium price—that is, instead of $1.40 per gallon, the price is $1.80 per gallon. The dashed horizontal line at the price of $1.80 in Figure illustrates this above equilibrium price. At this higher price, the quantity demanded drops from 600 to 500. This decline in quantity reflects how consumers react to the higher price by finding ways to use less gasoline.
Moreover, at this higher price of $1.80, the quantity of gasoline supplied rises from the 600 to 680, as the higher price makes it more profitable for gasoline producers to expand their output. Now, consider how quantity demanded and quantity supplied are related at this above-equilibrium price. Quantity demanded has fallen to 500 gallons, while quantity supplied has risen to 680 gallons. In fact, at any above-equilibrium price, the quantity supplied exceeds the quantity demanded. We call this an excess supply or a surplus.
With a surplus, gasoline accumulates at gas stations, in tanker trucks, in pipelines, and at oil refineries. This accumulation puts pressure on gasoline sellers. If a surplus remains unsold, those firms involved in making and selling gasoline are not receiving enough cash to pay their workers and to cover their expenses. In this situation, some producers and sellers will want to cut prices, because it is better to sell at a lower price than not to sell at all. Once some sellers start cutting prices, others will follow to avoid losing sales. These price reductions in turn will stimulate a higher quantity demanded. Therefore, if the price is above the equilibrium level, incentives built into the structure of demand and supply will create pressures for the price to fall toward the equilibrium.
Now suppose that the price is below its equilibrium level at $1.20 per gallon, as the dashed horizontal line at this price in Figure shows. At this lower price, the quantity demanded increases from 600 to 700 as drivers take longer trips, spend more minutes warming up the car in the driveway in wintertime, stop sharing rides to work, and buy larger cars that get fewer miles to the gallon. However, the below-equilibrium price reduces gasoline producers’ incentives to produce and sell gasoline, and the quantity supplied falls from 600 to 550.
When the price is below equilibrium, there is excess demand, or a shortage—that is, at the given price the quantity demanded, which has been stimulated by the lower price, now exceeds the quantity supplied, which had been depressed by the lower price. In this situation, eager gasoline buyers mob the gas stations, only to find many stations running short of fuel. Oil companies and gas stations recognize that they have an opportunity to make higher profits by selling what gasoline they have at a higher price. As a result, the price rises toward the equilibrium level. Read Demand, Supply, and Efficiency for more discussion on the importance of the demand and supply model.
Key Concepts and Summary
A demand schedule is a table that shows the quantity demanded at different prices in the market. A demand curve shows the relationship between quantity demanded and price in a given market on a graph. The law of demand states that a higher price typically leads to a lower quantity demanded.
A supply schedule is a table that shows the quantity supplied at different prices in the market. A supply curve shows the relationship between quantity supplied and price on a graph. The law of supply says that a higher price typically leads to a higher quantity supplied.
The equilibrium price and equilibrium quantity occur where the supply and demand curves cross. The equilibrium occurs where the quantity demanded is equal to the quantity supplied. If the price is below the equilibrium level, then the quantity demanded will exceed the quantity supplied. Excess demand or a shortage will exist. If the price is above the equilibrium level, then the quantity supplied will exceed the quantity demanded. Excess supply or a surplus will exist. In either case, economic pressures will push the price toward the equilibrium level.
Self-Check Question
Review Figure. Suppose the price of gasoline is $1.60 per gallon. Is the quantity demanded higher or lower than at the equilibrium price of $1.40 per gallon? What about the quantity supplied? Is there a shortage or a surplus in the market? If so, how much?
Hint:
Since $1.60 per gallon is above the equilibrium price, the quantity demanded would be lower at 550 gallons and the quantity supplied would be higher at 640 gallons. (These results are due to the laws of demand and supply, respectively.) The outcome of lower Qd and higher Qs would be a surplus in the gasoline market of 640 – 550 = 90 gallons.
Review Questions
What determines the level of prices in a market?
What does a downward-sloping demand curve mean about how buyers in a market will react to a higher price?
Will demand curves have the same exact shape in all markets? If not, how will they differ?
Will supply curves have the same shape in all markets? If not, how will they differ?
What is the relationship between quantity demanded and quantity supplied at equilibrium? What is the relationship when there is a shortage? What is the relationship when there is a surplus?
How can you locate the equilibrium point on a demand and supply graph?
If the price is above the equilibrium level, would you predict a surplus or a shortage? If the price is below the equilibrium level, would you predict a surplus or a shortage? Why?
When the price is above the equilibrium, explain how market forces move the market price to equilibrium. Do the same when the price is below the equilibrium.
What is the difference between the demand and the quantity demanded of a product, say milk? Explain in words and show the difference on a graph with a demand curve for milk.
What is the difference between the supply and the quantity supplied of a product, say milk? Explain in words and show the difference on a graph with the supply curve for milk.
Critical Thinking Questions
Review Figure. Suppose the government decided that, since gasoline is a necessity, its price should be legally capped at $1.30 per gallon. What do you anticipate would be the outcome in the gasoline market?
Explain why the following statement is false: “In the goods market, no buyer would be willing to pay more than the equilibrium price.”
Explain why the following statement is false: “In the goods market, no seller would be willing to sell for less than the equilibrium price.”
Problems
Review Figure again. Suppose the price of gasoline is $1.00. Will the quantity demanded be lower or higher than at the equilibrium price of $1.40 per gallon? Will the quantity supplied be lower or higher? Is there a shortage or a surplus in the market? If so, of how much?
References
Costanza, Robert, and Lisa Wainger. “No Accounting For Nature: How Conventional Economics Distorts the Value of Things.” The Washington Post. September 2, 1990.
European Commission: Agriculture and Rural Development. 2013. "Overview of the CAP Reform: 2014-2024." Accessed April 13, 205. http://ec.europa.eu/agriculture/cap-post-2013/.
Radford, R. A. “The Economic Organisation of a P.O.W. Camp.” Economica. no. 48 (1945): 189-201. http://www.jstor.org/stable/2550133.
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"title": "Principles of Macroeconomics 2e, Demand and Supply",
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https://oercommons.org/courseware/lesson/28783/overview
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Shifts in Demand and Supply for Goods and Services
Overview
By the end of this section, you will be able to:
- Identify factors that affect demand
- Graph demand curves and demand shifts
- Identify factors that affect supply
- Graph supply curves and supply shifts
The previous module explored how price affects the quantity demanded and the quantity supplied. The result was the demand curve and the supply curve. Price, however, is not the only factor that influences demand, nor is it the only thing that influences supply. For example, how is demand for vegetarian food affected if, say, health concerns cause more consumers to avoid eating meat? How is the supply of diamonds affected if diamond producers discover several new diamond mines? What are the major factors, in addition to the price, that influence demand or supply?
Visit this website to read a brief note on how marketing strategies can influence supply and demand of products.
What Factors Affect Demand?
We defined demand as the amount of some product a consumer is willing and able to purchase at each price. That suggests at least two factors in addition to price that affect demand. Willingness to purchase suggests a desire, based on what economists call tastes and preferences. If you neither need nor want something, you will not buy it. Ability to purchase suggests that income is important. Professors are usually able to afford better housing and transportation than students, because they have more income. Prices of related goods can affect demand also. If you need a new car, the price of a Honda may affect your demand for a Ford. Finally, the size or composition of the population can affect demand. The more children a family has, the greater their demand for clothing. The more driving-age children a family has, the greater their demand for car insurance, and the less for diapers and baby formula.
These factors matter for both individual and market demand as a whole. Exactly how do these various factors affect demand, and how do we show the effects graphically? To answer those questions, we need the ceteris paribus assumption.
The Ceteris Paribus Assumption
A demand curve or a supply curve is a relationship between two, and only two, variables: quantity on the horizontal axis and price on the vertical axis. The assumption behind a demand curve or a supply curve is that no relevant economic factors, other than the product’s price, are changing. Economists call this assumption ceteris paribus, a Latin phrase meaning “other things being equal.” Any given demand or supply curve is based on the ceteris paribus assumption that all else is held equal. A demand curve or a supply curve is a relationship between two, and only two, variables when all other variables are kept constant. If all else is not held equal, then the laws of supply and demand will not necessarily hold, as the following Clear It Up feature shows.
When does ceteris paribus apply?
We typically apply ceteris paribus when we observe how changes in price affect demand or supply, but we can apply ceteris paribus more generally. In the real world, demand and supply depend on more factors than just price. For example, a consumer’s demand depends on income and a producer’s supply depends on the cost of producing the product. How can we analyze the effect on demand or supply if multiple factors are changing at the same time—say price rises and income falls? The answer is that we examine the changes one at a time, assuming the other factors are held constant.
For example, we can say that an increase in the price reduces the amount consumers will buy (assuming income, and anything else that affects demand, is unchanged). Additionally, a decrease in income reduces the amount consumers can afford to buy (assuming price, and anything else that affects demand, is unchanged). This is what the ceteris paribus assumption really means. In this particular case, after we analyze each factor separately, we can combine the results. The amount consumers buy falls for two reasons: first because of the higher price and second because of the lower income.
How Does Income Affect Demand?
Let’s use income as an example of how factors other than price affect demand. Figure shows the initial demand for automobiles as D0. At point Q, for example, if the price is $20,000 per car, the quantity of cars demanded is 18 million. D0 also shows how the quantity of cars demanded would change as a result of a higher or lower price. For example, if the price of a car rose to $22,000, the quantity demanded would decrease to 17 million, at point R.
The original demand curve D0, like every demand curve, is based on the ceteris paribus assumption that no other economically relevant factors change. Now imagine that the economy expands in a way that raises the incomes of many people, making cars more affordable. How will this affect demand? How can we show this graphically?
Return to Figure. The price of cars is still $20,000, but with higher incomes, the quantity demanded has now increased to 20 million cars, shown at point S. As a result of the higher income levels, the demand curve shifts to the right to the new demand curve D1, indicating an increase in demand. Table shows clearly that this increased demand would occur at every price, not just the original one.
| Price | Decrease to D2 | Original Quantity Demanded D0 | Increase to D1 |
|---|---|---|---|
| $16,000 | 17.6 million | 22.0 million | 24.0 million |
| $18,000 | 16.0 million | 20.0 million | 22.0 million |
| $20,000 | 14.4 million | 18.0 million | 20.0 million |
| $22,000 | 13.6 million | 17.0 million | 19.0 million |
| $24,000 | 13.2 million | 16.5 million | 18.5 million |
| $26,000 | 12.8 million | 16.0 million | 18.0 million |
Now, imagine that the economy slows down so that many people lose their jobs or work fewer hours, reducing their incomes. In this case, the decrease in income would lead to a lower quantity of cars demanded at every given price, and the original demand curve D0 would shift left to D2. The shift from D0 to D2 represents such a decrease in demand: At any given price level, the quantity demanded is now lower. In this example, a price of $20,000 means 18 million cars sold along the original demand curve, but only 14.4 million sold after demand fell.
When a demand curve shifts, it does not mean that the quantity demanded by every individual buyer changes by the same amount. In this example, not everyone would have higher or lower income and not everyone would buy or not buy an additional car. Instead, a shift in a demand curve captures a pattern for the market as a whole.
In the previous section, we argued that higher income causes greater demand at every price. This is true for most goods and services. For some—luxury cars, vacations in Europe, and fine jewelry—the effect of a rise in income can be especially pronounced. A product whose demand rises when income rises, and vice versa, is called a normal good. A few exceptions to this pattern do exist. As incomes rise, many people will buy fewer generic brand groceries and more name brand groceries. They are less likely to buy used cars and more likely to buy new cars. They will be less likely to rent an apartment and more likely to own a home. A product whose demand falls when income rises, and vice versa, is called an inferior good. In other words, when income increases, the demand curve shifts to the left.
Other Factors That Shift Demand Curves
Income is not the only factor that causes a shift in demand. Other factors that change demand include tastes and preferences, the composition or size of the population, the prices of related goods, and even expectations. A change in any one of the underlying factors that determine what quantity people are willing to buy at a given price will cause a shift in demand. Graphically, the new demand curve lies either to the right (an increase) or to the left (a decrease) of the original demand curve. Let’s look at these factors.
Changing Tastes or Preferences
From 1980 to 2014, the per-person consumption of chicken by Americans rose from 48 pounds per year to 85 pounds per year, and consumption of beef fell from 77 pounds per year to 54 pounds per year, according to the U.S. Department of Agriculture (USDA). Changes like these are largely due to movements in taste, which change the quantity of a good demanded at every price: that is, they shift the demand curve for that good, rightward for chicken and leftward for beef.
Changes in the Composition of the Population
The proportion of elderly citizens in the United States population is rising. It rose from 9.8% in 1970 to 12.6% in 2000, and will be a projected (by the U.S. Census Bureau) 20% of the population by 2030. A society with relatively more children, like the United States in the 1960s, will have greater demand for goods and services like tricycles and day care facilities. A society with relatively more elderly persons, as the United States is projected to have by 2030, has a higher demand for nursing homes and hearing aids. Similarly, changes in the size of the population can affect the demand for housing and many other goods. Each of these changes in demand will be shown as a shift in the demand curve.
Changes in the prices of related goods such as substitutes or complements also can affect the demand for a product. A substitute is a good or service that we can use in place of another good or service. As electronic books, like this one, become more available, you would expect to see a decrease in demand for traditional printed books. A lower price for a substitute decreases demand for the other product. For example, in recent years as the price of tablet computers has fallen, the quantity demanded has increased (because of the law of demand). Since people are purchasing tablets, there has been a decrease in demand for laptops, which we can show graphically as a leftward shift in the demand curve for laptops. A higher price for a substitute good has the reverse effect.
Other goods are complements for each other, meaning we often use the goods together, because consumption of one good tends to enhance consumption of the other. Examples include breakfast cereal and milk; notebooks and pens or pencils, golf balls and golf clubs; gasoline and sport utility vehicles; and the five-way combination of bacon, lettuce, tomato, mayonnaise, and bread. If the price of golf clubs rises, since the quantity demanded of golf clubs falls (because of the law of demand), demand for a complement good like golf balls decreases, too. Similarly, a higher price for skis would shift the demand curve for a complement good like ski resort trips to the left, while a lower price for a complement has the reverse effect.
Changes in Expectations about Future Prices or Other Factors that Affect Demand
While it is clear that the price of a good affects the quantity demanded, it is also true that expectations about the future price (or expectations about tastes and preferences, income, and so on) can affect demand. For example, if people hear that a hurricane is coming, they may rush to the store to buy flashlight batteries and bottled water. If people learn that the price of a good like coffee is likely to rise in the future, they may head for the store to stock up on coffee now. We show these changes in demand as shifts in the curve. Therefore, a shift in demand happens when a change in some economic factor (other than price) causes a different quantity to be demanded at every price. The following Work It Out feature shows how this happens.
Shift in Demand
A shift in demand means that at any price (and at every price), the quantity demanded will be different than it was before. Following is an example of a shift in demand due to an income increase.
Step 1. Draw the graph of a demand curve for a normal good like pizza. Pick a price (like P0). Identify the corresponding Q0. See an example in Figure.
Step 2. Suppose income increases. As a result of the change, are consumers going to buy more or less pizza? The answer is more. Draw a dotted horizontal line from the chosen price, through the original quantity demanded, to the new point with the new Q1. Draw a dotted vertical line down to the horizontal axis and label the new Q1. Figure provides an example.
Step 3. Now, shift the curve through the new point. You will see that an increase in income causes an upward (or rightward) shift in the demand curve, so that at any price the quantities demanded will be higher, as Figure illustrates.
Summing Up Factors That Change Demand
Figure summarizes six factors that can shift demand curves. The direction of the arrows indicates whether the demand curve shifts represent an increase in demand or a decrease in demand. Notice that a change in the price of the good or service itself is not listed among the factors that can shift a demand curve. A change in the price of a good or service causes a movement along a specific demand curve, and it typically leads to some change in the quantity demanded, but it does not shift the demand curve.
When a demand curve shifts, it will then intersect with a given supply curve at a different equilibrium price and quantity. We are, however, getting ahead of our story. Before discussing how changes in demand can affect equilibrium price and quantity, we first need to discuss shifts in supply curves.
How Production Costs Affect Supply
A supply curve shows how quantity supplied will change as the price rises and falls, assuming ceteris paribus so that no other economically relevant factors are changing. If other factors relevant to supply do change, then the entire supply curve will shift. Just as we described a shift in demand as a change in the quantity demanded at every price, a shift in supply means a change in the quantity supplied at every price.
In thinking about the factors that affect supply, remember what motivates firms: profits, which are the difference between revenues and costs. A firm produces goods and services using combinations of labor, materials, and machinery, or what we call inputs or factors of production. If a firm faces lower costs of production, while the prices for the good or service the firm produces remain unchanged, a firm’s profits go up. When a firm’s profits increase, it is more motivated to produce output, since the more it produces the more profit it will earn. When costs of production fall, a firm will tend to supply a larger quantity at any given price for its output. We can show this by the supply curve shifting to the right.
Take, for example, a messenger company that delivers packages around a city. The company may find that buying gasoline is one of its main costs. If the price of gasoline falls, then the company will find it can deliver messages more cheaply than before. Since lower costs correspond to higher profits, the messenger company may now supply more of its services at any given price. For example, given the lower gasoline prices, the company can now serve a greater area, and increase its supply.
Conversely, if a firm faces higher costs of production, then it will earn lower profits at any given selling price for its products. As a result, a higher cost of production typically causes a firm to supply a smaller quantity at any given price. In this case, the supply curve shifts to the left.
Consider the supply for cars, shown by curve S0 in Figure. Point J indicates that if the price is $20,000, the quantity supplied will be 18 million cars. If the price rises to $22,000 per car, ceteris paribus, the quantity supplied will rise to 20 million cars, as point K on the S0 curve shows. We can show the same information in table form, as in Table.
| Price | Decrease to S1 | Original Quantity Supplied S0 | Increase to S2 |
|---|---|---|---|
| $16,000 | 10.5 million | 12.0 million | 13.2 million |
| $18,000 | 13.5 million | 15.0 million | 16.5 million |
| $20,000 | 16.5 million | 18.0 million | 19.8 million |
| $22,000 | 18.5 million | 20.0 million | 22.0 million |
| $24,000 | 19.5 million | 21.0 million | 23.1 million |
| $26,000 | 20.5 million | 22.0 million | 24.2 million |
Now, imagine that the price of steel, an important ingredient in manufacturing cars, rises, so that producing a car has become more expensive. At any given price for selling cars, car manufacturers will react by supplying a lower quantity. We can show this graphically as a leftward shift of supply, from S0 to S1, which indicates that at any given price, the quantity supplied decreases. In this example, at a price of $20,000, the quantity supplied decreases from 18 million on the original supply curve (S0) to 16.5 million on the supply curve S1, which is labeled as point L.
Conversely, if the price of steel decreases, producing a car becomes less expensive. At any given price for selling cars, car manufacturers can now expect to earn higher profits, so they will supply a higher quantity. The shift of supply to the right, from S0 to S2, means that at all prices, the quantity supplied has increased. In this example, at a price of $20,000, the quantity supplied increases from 18 million on the original supply curve (S0) to 19.8 million on the supply curve S2, which is labeled M.
Other Factors That Affect Supply
In the example above, we saw that changes in the prices of inputs in the production process will affect the cost of production and thus the supply. Several other things affect the cost of production, too, such as changes in weather or other natural conditions, new technologies for production, and some government policies.
Changes in weather and climate will affect the cost of production for many agricultural products. For example, in 2014 the Manchurian Plain in Northeastern China, which produces most of the country's wheat, corn, and soybeans, experienced its most severe drought in 50 years. A drought decreases the supply of agricultural products, which means that at any given price, a lower quantity will be supplied. Conversely, especially good weather would shift the supply curve to the right.
When a firm discovers a new technology that allows the firm to produce at a lower cost, the supply curve will shift to the right, as well. For instance, in the 1960s a major scientific effort nicknamed the Green Revolution focused on breeding improved seeds for basic crops like wheat and rice. By the early 1990s, more than two-thirds of the wheat and rice in low-income countries around the world used these Green Revolution seeds—and the harvest was twice as high per acre. A technological improvement that reduces costs of production will shift supply to the right, so that a greater quantity will be produced at any given price.
Government policies can affect the cost of production and the supply curve through taxes, regulations, and subsidies. For example, the U.S. government imposes a tax on alcoholic beverages that collects about $8 billion per year from producers. Businesses treat taxes as costs. Higher costs decrease supply for the reasons we discussed above. Other examples of policy that can affect cost are the wide array of government regulations that require firms to spend money to provide a cleaner environment or a safer workplace. Complying with regulations increases costs.
A government subsidy, on the other hand, is the opposite of a tax. A subsidy occurs when the government pays a firm directly or reduces the firm’s taxes if the firm carries out certain actions. From the firm’s perspective, taxes or regulations are an additional cost of production that shifts supply to the left, leading the firm to produce a lower quantity at every given price. Government subsidies reduce the cost of production and increase supply at every given price, shifting supply to the right. The following Work It Out feature shows how this shift happens.
Shift in Supply
We know that a supply curve shows the minimum price a firm will accept to produce a given quantity of output. What happens to the supply curve when the cost of production goes up? Following is an example of a shift in supply due to a production cost increase.
Step 1. Draw a graph of a supply curve for pizza. Pick a quantity (like Q0). If you draw a vertical line up from Q0 to the supply curve, you will see the price the firm chooses. Figure provides an example.
Step 2. Why did the firm choose that price and not some other? One way to think about this is that the price is composed of two parts. The first part is the cost of producing pizzas at the margin; in this case, the cost of producing the pizza, including cost of ingredients (e.g., dough, sauce, cheese, and pepperoni), the cost of the pizza oven, the shop rent, and the workers' wages. The second part is the firm’s desired profit, which is determined, among other factors, by the profit margins in that particular business. If you add these two parts together, you get the price the firm wishes to charge. The quantity Q0 and associated price P0 give you one point on the firm’s supply curve, as Figure illustrates.
Step 3. Now, suppose that the cost of production increases. Perhaps cheese has become more expensive by $0.75 per pizza. If that is true, the firm will want to raise its price by the amount of the increase in cost ($0.75). Draw this point on the supply curve directly above the initial point on the curve, but $0.75 higher, as Figure shows.
Step 4. Shift the supply curve through this point. You will see that an increase in cost causes an upward (or a leftward) shift of the supply curve so that at any price, the quantities supplied will be smaller, as Figure illustrates.
Summing Up Factors That Change Supply
Changes in the cost of inputs, natural disasters, new technologies, and the impact of government decisions all affect the cost of production. In turn, these factors affect how much firms are willing to supply at any given price.
Figure summarizes factors that change the supply of goods and services. Notice that a change in the price of the product itself is not among the factors that shift the supply curve. Although a change in price of a good or service typically causes a change in quantity supplied or a movement along the supply curve for that specific good or service, it does not cause the supply curve itself to shift.
Because demand and supply curves appear on a two-dimensional diagram with only price and quantity on the axes, an unwary visitor to the land of economics might be fooled into believing that economics is about only four topics: demand, supply, price, and quantity. However, demand and supply are really “umbrella” concepts: demand covers all the factors that affect demand, and supply covers all the factors that affect supply. We include factors other than price that affect demand and supply are included by using shifts in the demand or the supply curve. In this way, the two-dimensional demand and supply model becomes a powerful tool for analyzing a wide range of economic circumstances.
Key Concepts and Summary
Economists often use the ceteris paribus or “other things being equal” assumption: while examining the economic impact of one event, all other factors remain unchanged for analysis purposes. Factors that can shift the demand curve for goods and services, causing a different quantity to be demanded at any given price, include changes in tastes, population, income, prices of substitute or complement goods, and expectations about future conditions and prices. Factors that can shift the supply curve for goods and services, causing a different quantity to be supplied at any given price, include input prices, natural conditions, changes in technology, and government taxes, regulations, or subsidies.
Self-Check Questions
Why do economists use the ceteris paribus assumption?
Hint:
To make it easier to analyze complex problems. Ceteris paribus allows you to look at the effect of one factor at a time on what it is you are trying to analyze. When you have analyzed all the factors individually, you add the results together to get the final answer.
In an analysis of the market for paint, an economist discovers the facts listed below. State whether each of these changes will affect supply or demand, and in what direction.
- There have recently been some important cost-saving inventions in the technology for making paint.
- Paint is lasting longer, so that property owners need not repaint as often.
- Because of severe hailstorms, many people need to repaint now.
- The hailstorms damaged several factories that make paint, forcing them to close down for several months.
Hint:
- An improvement in technology that reduces the cost of production will cause an increase in supply. Alternatively, you can think of this as a reduction in price necessary for firms to supply any quantity. Either way, this can be shown as a rightward (or downward) shift in the supply curve.
- An improvement in product quality is treated as an increase in tastes or preferences, meaning consumers demand more paint at any price level, so demand increases or shifts to the right. If this seems counterintuitive, note that demand in the future for the longer-lasting paint will fall, since consumers are essentially shifting demand from the future to the present.
- An increase in need causes an increase in demand or a rightward shift in the demand curve.
- Factory damage means that firms are unable to supply as much in the present. Technically, this is an increase in the cost of production. Either way you look at it, the supply curve shifts to the left.
Many changes are affecting the market for oil. Predict how each of the following events will affect the equilibrium price and quantity in the market for oil. In each case, state how the event will affect the supply and demand diagram. Create a sketch of the diagram if necessary.
- Cars are becoming more fuel efficient, and therefore get more miles to the gallon.
- The winter is exceptionally cold.
- A major discovery of new oil is made off the coast of Norway.
- The economies of some major oil-using nations, like Japan, slow down.
- A war in the Middle East disrupts oil-pumping schedules.
- Landlords install additional insulation in buildings.
- The price of solar energy falls dramatically.
- Chemical companies invent a new, popular kind of plastic made from oil.
Hint:
- More fuel-efficient cars means there is less need for gasoline. This causes a leftward shift in the demand for gasoline and thus oil. Since the demand curve is shifting down the supply curve, the equilibrium price and quantity both fall.
- Cold weather increases the need for heating oil. This causes a rightward shift in the demand for heating oil and thus oil. Since the demand curve is shifting up the supply curve, the equilibrium price and quantity both rise.
- A discovery of new oil will make oil more abundant. This can be shown as a rightward shift in the supply curve, which will cause a decrease in the equilibrium price along with an increase in the equilibrium quantity. (The supply curve shifts down the demand curve so price and quantity follow the law of demand. If price goes down, then the quantity goes up.)
- When an economy slows down, it produces less output and demands less input, including energy, which is used in the production of virtually everything. A decrease in demand for energy will be reflected as a decrease in the demand for oil, or a leftward shift in demand for oil. Since the demand curve is shifting down the supply curve, both the equilibrium price and quantity of oil will fall.
- Disruption of oil pumping will reduce the supply of oil. This leftward shift in the supply curve will show a movement up the demand curve, resulting in an increase in the equilibrium price of oil and a decrease in the equilibrium quantity.
- Increased insulation will decrease the demand for heating. This leftward shift in the demand for oil causes a movement down the supply curve, resulting in a decrease in the equilibrium price and quantity of oil.
- Solar energy is a substitute for oil-based energy. So if solar energy becomes cheaper, the demand for oil will decrease as consumers switch from oil to solar. The decrease in demand for oil will be shown as a leftward shift in the demand curve. As the demand curve shifts down the supply curve, both equilibrium price and quantity for oil will fall.
- A new, popular kind of plastic will increase the demand for oil. The increase in demand will be shown as a rightward shift in demand, raising the equilibrium price and quantity of oil.
Review Questions
When analyzing a market, how do economists deal with the problem that many factors that affect the market are changing at the same time?
Name some factors that can cause a shift in the demand curve in markets for goods and services.
Name some factors that can cause a shift in the supply curve in markets for goods and services.
Critical Thinking Questions
Consider the demand for hamburgers. If the price of a substitute good (for example, hot dogs) increases and the price of a complement good (for example, hamburger buns) increases, can you tell for sure what will happen to the demand for hamburgers? Why or why not? Illustrate your answer with a graph.
How do you suppose the demographics of an aging population of “Baby Boomers” in the United States will affect the demand for milk? Justify your answer.
We know that a change in the price of a product causes a movement along the demand curve. Suppose consumers believe that prices will be rising in the future. How will that affect demand for the product in the present? Can you show this graphically?
Suppose there is a soda tax to curb obesity. What should a reduction in the soda tax do to the supply of sodas and to the equilibrium price and quantity? Can you show this graphically? Hint: Assume that the soda tax is collected from the sellers.
Problems
Table shows information on the demand and supply for bicycles, where the quantities of bicycles are measured in thousands.
| Price | Qd | Qs |
|---|---|---|
| $120 | 50 | 36 |
| $150 | 40 | 40 |
| $180 | 32 | 48 |
| $210 | 28 | 56 |
| $240 | 24 | 70 |
- What is the quantity demanded and the quantity supplied at a price of $210?
- At what price is the quantity supplied equal to 48,000?
- Graph the demand and supply curve for bicycles. How can you determine the equilibrium price and quantity from the graph? How can you determine the equilibrium price and quantity from the table? What are the equilibrium price and equilibrium quantity?
- If the price was $120, what would the quantities demanded and supplied be? Would a shortage or surplus exist? If so, how large would the shortage or surplus be?
The computer market in recent years has seen many more computers sell at much lower prices. What shift in demand or supply is most likely to explain this outcome? Sketch a demand and supply diagram and explain your reasoning for each.
- A rise in demand
- A fall in demand
- A rise in supply
- A fall in supply
References
Landsburg, Steven E. The Armchair Economist: Economics and Everyday Life. New York: The Free Press. 2012. specifically Section IV: How Markets Work.
National Chicken Council. 2015. "Per Capita Consumption of Poultry and Livestock, 1965 to Estimated 2015, in Pounds." Accessed April 13, 2015. http://www.nationalchickencouncil.org/about-the-industry/statistics/per-capita-consumption-of-poultry-and-livestock-1965-to-estimated-2012-in-pounds/.
Wessel, David. “Saudi Arabia Fears $40-a-Barrel Oil, Too.” The Wall Street Journal. May 27, 2004, p. 42. http://online.wsj.com/news/articles/SB108561000087822300.
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Changes in Equilibrium Price and Quantity: The Four-Step Process
Overview
By the end of this section, you will be able to:
- Identify equilibrium price and quantity through the four-step process
- Graph equilibrium price and quantity
- Contrast shifts of demand or supply and movements along a demand or supply curve
- Graph demand and supply curves, including equilibrium price and quantity, based on real-world examples
Let’s begin this discussion with a single economic event. It might be an event that affects demand, like a change in income, population, tastes, prices of substitutes or complements, or expectations about future prices. It might be an event that affects supply, like a change in natural conditions, input prices, or technology, or government policies that affect production. How does this economic event affect equilibrium price and quantity? We will analyze this question using a four-step process.
Step 1. Draw a demand and supply model before the economic change took place. To establish the model requires four standard pieces of information: The law of demand, which tells us the slope of the demand curve; the law of supply, which gives us the slope of the supply curve; the shift variables for demand; and the shift variables for supply. From this model, find the initial equilibrium values for price and quantity.
Step 2. Decide whether the economic change you are analyzing affects demand or supply. In other words, does the event refer to something in the list of demand factors or supply factors?
Step 3. Decide whether the effect on demand or supply causes the curve to shift to the right or to the left, and sketch the new demand or supply curve on the diagram. In other words, does the event increase or decrease the amount consumers want to buy or producers want to sell?
Step 4. Identify the new equilibrium and then compare the original equilibrium price and quantity to the new equilibrium price and quantity.
Let’s consider one example that involves a shift in supply and one that involves a shift in demand. Then we will consider an example where both supply and demand shift.
Good Weather for Salmon Fishing
Supposed that during the summer of 2015, weather conditions were excellent for commercial salmon fishing off the California coast. Heavy rains meant higher than normal levels of water in the rivers, which helps the salmon to breed. Slightly cooler ocean temperatures stimulated the growth of plankton, the microscopic organisms at the bottom of the ocean food chain, providing everything in the ocean with a hearty food supply. The ocean stayed calm during fishing season, so commercial fishing operations did not lose many days to bad weather. How did these climate conditions affect the quantity and price of salmon? Figure illustrates the four-step approach, which we explain below, to work through this problem. Table also provides the information to work the problem.
| Price per Pound | Quantity Supplied in 2014 | Quantity Supplied in 2015 | Quantity Demanded |
|---|---|---|---|
| $2.00 | 80 | 400 | 840 |
| $2.25 | 120 | 480 | 680 |
| $2.50 | 160 | 550 | 550 |
| $2.75 | 200 | 600 | 450 |
| $3.00 | 230 | 640 | 350 |
| $3.25 | 250 | 670 | 250 |
| $3.50 | 270 | 700 | 200 |
Step 1. Draw a demand and supply model to illustrate the market for salmon in the year before the good weather conditions began. The demand curve D0 and the supply curve S0 show that the original equilibrium price is $3.25 per pound and the original equilibrium quantity is 250,000 fish. (This price per pound is what commercial buyers pay at the fishing docks. What consumers pay at the grocery is higher.)
Step 2. Did the economic event affect supply or demand? Good weather is an example of a natural condition that affects supply.
Step 3. Was the effect on supply an increase or a decrease? Good weather is a change in natural conditions that increases the quantity supplied at any given price. The supply curve shifts to the right, moving from the original supply curve S0 to the new supply curve S1, which Figure and Table show.
Step 4. Compare the new equilibrium price and quantity to the original equilibrium. At the new equilibrium E1, the equilibrium price falls from $3.25 to $2.50, but the equilibrium quantity increases from 250,000 to 550,000 salmon. Notice that the equilibrium quantity demanded increased, even though the demand curve did not move.
In short, good weather conditions increased supply of the California commercial salmon. The result was a higher equilibrium quantity of salmon bought and sold in the market at a lower price.
Newspapers and the Internet
According to the Pew Research Center for People and the Press, increasingly more people, especially younger people, are obtaining their news from online and digital sources. The majority of U.S. adults now own smartphones or tablets, and most of those Americans say they use them in part to access the news. From 2004 to 2012, the share of Americans who reported obtaining their news from digital sources increased from 24% to 39%. How has this affected consumption of print news media, and radio and television news? Figure and the text below illustrates using the four-step analysis to answer this question.
Step 1. Develop a demand and supply model to think about what the market looked like before the event. The demand curve D0 and the supply curve S0 show the original relationships. In this case, we perform the analysis without specific numbers on the price and quantity axis.
Step 2. Did the described change affect supply or demand? A change in tastes, from traditional news sources (print, radio, and television) to digital sources, caused a change in demand for the former.
Step 3. Was the effect on demand positive or negative? A shift to digital news sources will tend to mean a lower quantity demanded of traditional news sources at every given price, causing the demand curve for print and other traditional news sources to shift to the left, from D0 to D1.
Step 4. Compare the new equilibrium price and quantity to the original equilibrium price. The new equilibrium (E1) occurs at a lower quantity and a lower price than the original equilibrium (E0).
The decline in print news reading predates 2004. Print newspaper circulation peaked in 1973 and has declined since then due to competition from television and radio news. In 1991, 55% of Americans indicated they received their news from print sources, while only 29% did so in 2012. Radio news has followed a similar path in recent decades, with the share of Americans obtaining their news from radio declining from 54% in 1991 to 33% in 2012. Television news has held its own over the last 15 years, with a market share staying in the mid to upper fifties. What does this suggest for the future, given that two-thirds of Americans under 30 years old say they do not obtain their news from television at all?
The Interconnections and Speed of Adjustment in Real Markets
In the real world, many factors that affect demand and supply can change all at once. For example, the demand for cars might increase because of rising incomes and population, and it might decrease because of rising gasoline prices (a complementary good). Likewise, the supply of cars might increase because of innovative new technologies that reduce the cost of car production, and it might decrease as a result of new government regulations requiring the installation of costly pollution-control technology.
Moreover, rising incomes and population or changes in gasoline prices will affect many markets, not just cars. How can an economist sort out all these interconnected events? The answer lies in the ceteris paribus assumption. Look at how each economic event affects each market, one event at a time, holding all else constant. Then combine the analyses to see the net effect.
A Combined Example
The U.S. Postal Service is facing difficult challenges. Compensation for postal workers tends to increase most years due to cost-of-living increases. At the same time, increasingly more people are using email, text, and other digital message forms such as Facebook and Twitter to communicate with friends and others. What does this suggest about the continued viability of the Postal Service? Figure and the text below illustrate this using the four-step analysis to answer this question.
Since this problem involves two disturbances, we need two four-step analyses, the first to analyze the effects of higher compensation for postal workers, the second to analyze the effects of many people switching from “snail mail” to email and other digital messages.
Figure (a) shows the shift in supply discussed in the following steps.
Step 1. Draw a demand and supply model to illustrate what the market for the U.S. Postal Service looked like before this scenario starts. The demand curve D0 and the supply curve S0 show the original relationships.
Step 2. Did the described change affect supply or demand? Labor compensation is a cost of production. A change in production costs caused a change in supply for the Postal Service.
Step 3. Was the effect on supply positive or negative? Higher labor compensation leads to a lower quantity supplied of postal services at every given price, causing the supply curve for postal services to shift to the left, from S0 to S1.
Step 4. Compare the new equilibrium price and quantity to the original equilibrium price. The new equilibrium (E1) occurs at a lower quantity and a higher price than the original equilibrium (E0).
Figure (b) shows the shift in demand in the following steps.
Step 1. Draw a demand and supply model to illustrate what the market for U.S. Postal Services looked like before this scenario starts. The demand curve D0 and the supply curve S0 show the original relationships. Note that this diagram is independent from the diagram in panel (a).
Step 2. Did the change described affect supply or demand? A change in tastes away from snail mail toward digital messages will cause a change in demand for the Postal Service.
Step 3. Was the effect on demand positive or negative? A change in tastes away from snailmail toward digital messages causes lower quantity demanded of postal services at every given price, causing the demand curve for postal services to shift to the left, from D0 to D1.
Step 4. Compare the new equilibrium price and quantity to the original equilibrium price. The new equilibrium (E2) occurs at a lower quantity and a lower price than the original equilibrium (E0).
The final step in a scenario where both supply and demand shift is to combine the two individual analyses to determine what happens to the equilibrium quantity and price. Graphically, we superimpose the previous two diagrams one on top of the other, as in Figure.
Following are the results:
Effect on Quantity: The effect of higher labor compensation on Postal Services because it raises the cost of production is to decrease the equilibrium quantity. The effect of a change in tastes away from snail mail is to decrease the equilibrium quantity. Since both shifts are to the left, the overall impact is a decrease in the equilibrium quantity of Postal Services (Q3). This is easy to see graphically, since Q3 is to the left of Q0.
Effect on Price: The overall effect on price is more complicated. The effect of higher labor compensation on Postal Services, because it raises the cost of production, is to increase the equilibrium price. The effect of a change in tastes away from snail mail is to decrease the equilibrium price. Since the two effects are in opposite directions, unless we know the magnitudes of the two effects, the overall effect is unclear. This is not unusual. When both curves shift, typically we can determine the overall effect on price or on quantity, but not on both. In this case, we determined the overall effect on the equilibrium quantity, but not on the equilibrium price. In other cases, it might be the opposite.
The next Clear It Up feature focuses on the difference between shifts of supply or demand and movements along a curve.
What is the difference between shifts of demand or supply versus movements along a demand or supply curve?
One common mistake in applying the demand and supply framework is to confuse the shift of a demand or a supply curve with movement along a demand or supply curve. As an example, consider a problem that asks whether a drought will increase or decrease the equilibrium quantity and equilibrium price of wheat. Lee, a student in an introductory economics class, might reason:
“Well, it is clear that a drought reduces supply, so I will shift back the supply curve, as in the shift from the original supply curve S0 to S1 on the diagram (Shift 1). The equilibrium moves from E0 to E1, the equilibrium quantity is lower and the equilibrium price is higher. Then, a higher price makes farmers more likely to supply the good, so the supply curve shifts right, as shows the shift from S1 to S2, shows on the diagram (Shift 2), so that the equilibrium now moves from E1 to E2. The higher price, however, also reduces demand and so causes demand to shift back, like the shift from the original demand curve, D0 to D1 on the diagram (labeled Shift 3), and the equilibrium moves from E2 to E3.”
At about this point, Lee suspects that this answer is headed down the wrong path. Think about what might be wrong with Lee’s logic, and then read the answer that follows.
Answer: Lee’s first step is correct: that is, a drought shifts back the supply curve of wheat and leads to a prediction of a lower equilibrium quantity and a higher equilibrium price. This corresponds to a movement along the original demand curve (D0), from E0 to E1. The rest of Lee’s argument is wrong, because it mixes up shifts in supply with quantity supplied, and shifts in demand with quantity demanded. A higher or lower price never shifts the supply curve, as suggested by the shift in supply from S1 to S2. Instead, a price change leads to a movement along a given supply curve. Similarly, a higher or lower price never shifts a demand curve, as suggested in the shift from D0 to D1. Instead, a price change leads to a movement along a given demand curve. Remember, a change in the price of a good never causes the demand or supply curve for that good to shift.
Think carefully about the timeline of events: What happens first, what happens next? What is cause, what is effect? If you keep the order right, you are more likely to get the analysis correct.
In the four-step analysis of how economic events affect equilibrium price and quantity, the movement from the old to the new equilibrium seems immediate. As a practical matter, however, prices and quantities often do not zoom straight to equilibrium. More realistically, when an economic event causes demand or supply to shift, prices and quantities set off in the general direction of equilibrium. Even as they are moving toward one new equilibrium, a subsequent change in demand or supply often pushes prices toward another equilibrium.
Key Concepts and Summary
When using the supply and demand framework to think about how an event will affect the equilibrium price and quantity, proceed through four steps: (1) sketch a supply and demand diagram to think about what the market looked like before the event; (2) decide whether the event will affect supply or demand; (3) decide whether the effect on supply or demand is negative or positive, and draw the appropriate shifted supply or demand curve; (4) compare the new equilibrium price and quantity to the original ones.
Self-Check Questions
Let’s think about the market for air travel. From August 2014 to January 2015, the price of jet fuel increased roughly 47%. Using the four-step analysis, how do you think this fuel price increase affected the equilibrium price and quantity of air travel?
Hint:
Step 1. Draw the graph with the initial supply and demand curves. Label the initial equilibrium price and quantity.
Step 2. Did the economic event affect supply or demand? Jet fuel is a cost of producing air travel, so an increase in jet fuel price affects supply.
Step 3. An increase in the price of jet fuel caused a decrease in the cost of air travel. We show this as a downward or rightward shift in supply.
Step 4. A rightward shift in supply causes a movement down the demand curve, lowering the equilibrium price of air travel and increasing the equilibrium quantity.
A tariff is a tax on imported goods. Suppose the U.S. government cuts the tariff on imported flat screen televisions. Using the four-step analysis, how do you think the tariff reduction will affect the equilibrium price and quantity of flat screen TVs?
Hint:
Step 1. Draw the graph with the initial supply and demand curves. Label the initial equilibrium price and quantity.
Step 2. Did the economic event affect supply or demand? A tariff is treated like a cost of production, so this affects supply.
Step 3. A tariff reduction is equivalent to a decrease in the cost of production, which we can show as a rightward (or downward) shift in supply.
Step 4. A rightward shift in supply causes a movement down the demand curve, lowering the equilibrium price and raising the equilibrium quantity.
Review Questions
How does one analyze a market where both demand and supply shift?
What causes a movement along the demand curve? What causes a movement along the supply curve?
Critical Thinking Questions
Use the four-step process to analyze the impact of the advent of the iPod (or other portable digital music players) on the equilibrium price and quantity of the Sony Walkman (or other portable audio cassette players).
Use the four-step process to analyze the impact of a reduction in tariffs on imports of iPods on the equilibrium price and quantity of Sony Walkman-type products.
Suppose both of these events took place at the same time. Combine your analyses of the impacts of the iPod and the tariff reduction to determine the likely impact on the equilibrium price and quantity of Sony Walkman-type products. Show your answer graphically.
Problems
Table illustrates the market's demand and supply for cheddar cheese. Graph the data and find the equilibrium. Next, create a table showing the change in quantity demanded or quantity supplied, and a graph of the new equilibrium, in each of the following situations:
- The price of milk, a key input for cheese production, rises, so that the supply decreases by 80 pounds at every price.
- A new study says that eating cheese is good for your health, so that demand increases by 20% at every price.
| Price per Pound | Qd | Qs |
|---|---|---|
| $3.00 | 750 | 540 |
| $3.20 | 700 | 600 |
| $3.40 | 650 | 650 |
| $3.60 | 620 | 700 |
| $3.80 | 600 | 720 |
| $4.00 | 590 | 730 |
Table shows the supply and demand for movie tickets in a city. Graph demand and supply and identify the equilibrium. Then calculate in a table and graph the effect of the following two changes.
- Three new nightclubs open. They offer decent bands and have no cover charge, but make their money by selling food and drink. As a result, demand for movie tickets falls by six units at every price.
- The city eliminates a tax that it placed on all local entertainment businesses. The result is that the quantity supplied of movies at any given price increases by 10%.
| Price per Pound | Qd | Qs |
|---|---|---|
| $5.00 | 26 | 16 |
| $6.00 | 24 | 18 |
| $7.00 | 22 | 20 |
| $8.00 | 21 | 21 |
| $9.00 | 20 | 22 |
References
Pew Research Center. “Pew Research: Center for the People & the Press.” http://www.people-press.org/.
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https://oercommons.org/courseware/lesson/28785/overview
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Price Ceilings and Price Floors
Overview
By the end of this section, you will be able to:
- Explain price controls, price ceilings, and price floors
- Analyze demand and supply as a social adjustment mechanism
To this point in the chapter, we have been assuming that markets are free, that is, they operate with no government intervention. In this section, we will explore the outcomes, both anticipated and otherwise, when government does intervene in a market either to prevent the price of some good or service from rising “too high” or to prevent the price of some good or service from falling “too low”.
Economists believe there are a small number of fundamental principles that explain how economic agents respond in different situations. Two of these principles, which we have already introduced, are the laws of demand and supply.
Governments can pass laws affecting market outcomes, but no law can negate these economic principles. Rather, the principles will become apparent in sometimes unexpected ways, which may undermine the intent of the government policy. This is one of the major conclusions of this section.
Controversy sometimes surrounds the prices and quantities established by demand and supply, especially for products that are considered necessities. In some cases, discontent over prices turns into public pressure on politicians, who may then pass legislation to prevent a certain price from climbing “too high” or falling “too low.”
The demand and supply model shows how people and firms will react to the incentives that these laws provide to control prices, in ways that will often lead to undesirable consequences. Alternative policy tools can often achieve the desired goals of price control laws, while avoiding at least some of their costs and tradeoffs.
Price Ceilings
Laws that government enact to regulate prices are called price controls. Price controls come in two flavors. A price ceiling keeps a price from rising above a certain level (the “ceiling”), while a price floor keeps a price from falling below a given level (the “floor”). This section uses the demand and supply framework to analyze price ceilings. The next section discusses price floors.
A price ceiling is a legal maximum price that one pays for some good or service. A government imposes price ceilings in order to keep the price of some necessary good or service affordable. For example, in 2005 during Hurricane Katrina, the price of bottled water increased above $5 per gallon. As a result, many people called for price controls on bottled water to prevent the price from rising so high. In this particular case, the government did not impose a price ceiling, but there are other examples of where price ceilings did occur.
In many markets for goods and services, demanders outnumber suppliers. Consumers, who are also potential voters, sometimes unite behind a political proposal to hold down a certain price. In some cities, such as Albany, renters have pressed political leaders to pass rent control laws, a price ceiling that usually works by stating that landlords can raise rents by only a certain maximum percentage each year. Some of the best examples of rent control occur in urban areas such as New York, Washington D.C., or San Francisco.
Rent control becomes a politically hot topic when rents begin to rise rapidly. Everyone needs an affordable place to live. Perhaps a change in tastes makes a certain suburb or town a more popular place to live. Perhaps locally-based businesses expand, bringing higher incomes and more people into the area. Such changes can cause a change in the demand for rental housing, as Figure illustrates. The original equilibrium (E0) lies at the intersection of supply curve S0 and demand curve D0, corresponding to an equilibrium price of $500 and an equilibrium quantity of 15,000 units of rental housing. The effect of greater income or a change in tastes is to shift the demand curve for rental housing to the right, as the data in Table shows and the shift from D0 to D1 on the graph. In this market, at the new equilibrium E1, the price of a rental unit would rise to $600 and the equilibrium quantity would increase to 17,000 units.
| Price | Original Quantity Supplied | Original Quantity Demanded | New Quantity Demanded |
|---|---|---|---|
| $400 | 12,000 | 18,000 | 23,000 |
| $500 | 15,000 | 15,000 | 19,000 |
| $600 | 17,000 | 13,000 | 17,000 |
| $700 | 19,000 | 11,000 | 15,000 |
| $800 | 20,000 | 10,000 | 14,000 |
Suppose that a city government passes a rent control law to keep the price at the original equilibrium of $500 for a typical apartment. In Figure, the horizontal line at the price of $500 shows the legally fixed maximum price set by the rent control law. However, the underlying forces that shifted the demand curve to the right are still there. At that price ($500), the quantity supplied remains at the same 15,000 rental units, but the quantity demanded is 19,000 rental units. In other words, the quantity demanded exceeds the quantity supplied, so there is a shortage of rental housing. One of the ironies of price ceilings is that while the price ceiling was intended to help renters, there are actually fewer apartments rented out under the price ceiling (15,000 rental units) than would be the case at the market rent of $600 (17,000 rental units).
Price ceilings do not simply benefit renters at the expense of landlords. Rather, some renters (or potential renters) lose their housing as landlords convert apartments to co-ops and condos. Even when the housing remains in the rental market, landlords tend to spend less on maintenance and on essentials like heating, cooling, hot water, and lighting. The first rule of economics is you do not get something for nothing—everything has an opportunity cost. Thus, if renters obtain “cheaper” housing than the market requires, they tend to also end up with lower quality housing.
Price ceilings are enacted in an attempt to keep prices low for those who need the product. However, when the market price is not allowed to rise to the equilibrium level, quantity demanded exceeds quantity supplied, and thus a shortage occurs. Those who manage to purchase the product at the lower price given by the price ceiling will benefit, but sellers of the product will suffer, along with those who are not able to purchase the product at all. Quality is also likely to deteriorate.
Price Floors
A price floor is the lowest price that one can legally pay for some good or service. Perhaps the best-known example of a price floor is the minimum wage, which is based on the view that someone working full time should be able to afford a basic standard of living. The federal minimum wage in 2016 was $7.25 per hour, although some states and localities have a higher minimum wage. The federal minimum wage yields an annual income for a single person of $15,080, which is slightly higher than the Federal poverty line of $11,880. As the cost of living rises over time, the Congress periodically raises the federal minimum wage.
Price floors are sometimes called “price supports,” because they support a price by preventing it from falling below a certain level. Around the world, many countries have passed laws to create agricultural price supports. Farm prices and thus farm incomes fluctuate, sometimes widely. Even if, on average, farm incomes are adequate, some years they can be quite low. The purpose of price supports is to prevent these swings.
The most common way price supports work is that the government enters the market and buys up the product, adding to demand to keep prices higher than they otherwise would be. According to the Common Agricultural Policy reform passed in 2013, the European Union (EU) will spend about 60 billion euros per year, or 67 billion dollars per year (with the November 2016 exchange rate), or roughly 38% of the EU budget, on price supports for Europe’s farmers from 2014 to 2020.
Figure illustrates the effects of a government program that assures a price above the equilibrium by focusing on the market for wheat in Europe. In the absence of government intervention, the price would adjust so that the quantity supplied would equal the quantity demanded at the equilibrium point E0, with price P0 and quantity Q0. However, policies to keep prices high for farmers keeps the price above what would have been the market equilibrium level—the price Pf shown by the dashed horizontal line in the diagram. The result is a quantity supplied in excess of the quantity demanded (Qd). When quantity supplied exceeds quantity demanded, a surplus exists.
Economists estimate that the high-income areas of the world, including the United States, Europe, and Japan, spend roughly $1 billion per day in supporting their farmers. If the government is willing to purchase the excess supply (or to provide payments for others to purchase it), then farmers will benefit from the price floor, but taxpayers and consumers of food will pay the costs. Agricultural economists and policy makers have offered numerous proposals for reducing farm subsidies. In many countries, however, political support for subsidies for farmers remains strong. This is either because the population views this as supporting the traditional rural way of life or because of industry's lobbying power of the agro-business.
Key Concepts and Summary
Price ceilings prevent a price from rising above a certain level. When a price ceiling is set below the equilibrium price, quantity demanded will exceed quantity supplied, and excess demand or shortages will result. Price floors prevent a price from falling below a certain level. When a price floor is set above the equilibrium price, quantity supplied will exceed quantity demanded, and excess supply or surpluses will result. Price floors and price ceilings often lead to unintended consequences.
Self-Check Questions
What is the effect of a price ceiling on the quantity demanded of the product? What is the effect of a price ceiling on the quantity supplied? Why exactly does a price ceiling cause a shortage?
Hint:
A price ceiling (which is below the equilibrium price) will cause the quantity demanded to rise and the quantity supplied to fall. This is why a price ceiling creates a shortage.
Does a price ceiling change the equilibrium price?
Hint:
A price ceiling is just a legal restriction. Equilibrium is an economic condition. People may or may not obey the price ceiling, so the actual price may be at or above the price ceiling, but the price ceiling does not change the equilibrium price.
What would be the impact of imposing a price floor below the equilibrium price?
Hint:
A price ceiling is a legal maximum price, but a price floor is a legal minimum price and, consequently, it would leave room for the price to rise to its equilibrium level. In other words, a price floor below equilibrium will not be binding and will have no effect.
Review Questions
Does a price ceiling attempt to make a price higher or lower?
How does a price ceiling set below the equilibrium level affect quantity demanded and quantity supplied?
Does a price floor attempt to make a price higher or lower?
How does a price floor set above the equilibrium level affect quantity demanded and quantity supplied?
Critical Thinking Questions
Most government policy decisions have winners and losers. What are the effects of raising the minimum wage? It is more complex than simply producers lose and workers gain. Who are the winners and who are the losers, and what exactly do they win and lose? To what extent does the policy change achieve its goals?
Agricultural price supports result in governments holding large inventories of agricultural products. Why do you think the government cannot simply give the products away to poor people?
Can you propose a policy that would induce the market to supply more rental housing units?
Problems
A low-income country decides to set a price ceiling on bread so it can make sure that bread is affordable to the poor.Table provides the conditions of demand and supply. What are the equilibrium price and equilibrium quantity before the price ceiling? What will the excess demand or the shortage (that is, quantity demanded minus quantity supplied) be if the price ceiling is set at $2.40? At $2.00? At $3.60?
| Price | Qd | Qs |
|---|---|---|
| $1.60 | 9,000 | 5,000 |
| $2.00 | 8,500 | 5,500 |
| $2.40 | 8,000 | 6,400 |
| $2.80 | 7,500 | 7,500 |
| $3.20 | 7,000 | 9,000 |
| $3.60 | 6,500 | 11,000 |
| $4.00 | 6,000 | 15,000 |
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Demand, Supply, and Efficiency
Overview
- Contrast consumer surplus, producer surplus, and social surplus
- Explain why price floors and price ceilings can be inefficient
- Analyze demand and supply as a social adjustment mechanism
The familiar demand and supply diagram holds within it the concept of economic efficiency. One typical way that economists define efficiency is when it is impossible to improve the situation of one party without imposing a cost on another. Conversely, if a situation is inefficient, it becomes possible to benefit at least one party without imposing costs on others.
Efficiency in the demand and supply model has the same basic meaning: The economy is getting as much benefit as possible from its scarce resources and all the possible gains from trade have been achieved. In other words, the optimal amount of each good and service is produced and consumed.
Consumer Surplus, Producer Surplus, Social Surplus
Consider a market for tablet computers, as Figure shows. The equilibrium price is $80 and the equilibrium quantity is 28 million. To see the benefits to consumers, look at the segment of the demand curve above the equilibrium point and to the left. This portion of the demand curve shows that at least some demanders would have been willing to pay more than $80 for a tablet.
For example, point J shows that if the price were $90, 20 million tablets would be sold. Those consumers who would have been willing to pay $90 for a tablet based on the utility they expect to receive from it, but who were able to pay the equilibrium price of $80, clearly received a benefit beyond what they had to pay. Remember, the demand curve traces consumers’ willingness to pay for different quantities. The amount that individuals would have been willing to pay, minus the amount that they actually paid, is called consumer surplus. Consumer surplus is the area labeled F—that is, the area above the market price and below the demand curve.
The supply curve shows the quantity that firms are willing to supply at each price. For example, point K in Figure illustrates that, at $45, firms would still have been willing to supply a quantity of 14 million. Those producers who would have been willing to supply the tablets at $45, but who were instead able to charge the equilibrium price of $80, clearly received an extra benefit beyond what they required to supply the product. The amount that a seller is paid for a good minus the seller’s actual cost is called producer surplus. In Figure, producer surplus is the area labeled G—that is, the area between the market price and the segment of the supply curve below the equilibrium.
The sum of consumer surplus and producer surplus is social surplus, also referred to as economic surplus or total surplus. In Figure we show social surplus as the area F + G. Social surplus is larger at equilibrium quantity and price than it would be at any other quantity. This demonstrates the economic efficiency of the market equilibrium. In addition, at the efficient level of output, it is impossible to produce greater consumer surplus without reducing producer surplus, and it is impossible to produce greater producer surplus without reducing consumer surplus.
Inefficiency of Price Floors and Price Ceilings
The imposition of a price floor or a price ceiling will prevent a market from adjusting to its equilibrium price and quantity, and thus will create an inefficient outcome. However, there is an additional twist here. Along with creating inefficiency, price floors and ceilings will also transfer some consumer surplus to producers, or some producer surplus to consumers.
Imagine that several firms develop a promising but expensive new drug for treating back pain. If this therapy is left to the market, the equilibrium price will be $600 per month and 20,000 people will use the drug, as shown in Figure (a). The original level of consumer surplus is T + U and producer surplus is V + W + X. However, the government decides to impose a price ceiling of $400 to make the drug more affordable. At this price ceiling, firms in the market now produce only 15,000.
As a result, two changes occur. First, an inefficient outcome occurs and the total surplus of society is reduced. The loss in social surplus that occurs when the economy produces at an inefficient quantity is called deadweight loss. In a very real sense, it is like money thrown away that benefits no one. In Figure (a), the deadweight loss is the area U + W. When deadweight loss exists, it is possible for both consumer and producer surplus to be higher, in this case because the price control is blocking some suppliers and demanders from transactions they would both be willing to make.
A second change from the price ceiling is that some of the producer surplus is transferred to consumers. After the price ceiling is imposed, the new consumer surplus is T + V, while the new producer surplus is X. In other words, the price ceiling transfers the area of surplus (V) from producers to consumers. Note that the gain to consumers is less than the loss to producers, which is just another way of seeing the deadweight loss.
Figure (b) shows a price floor example using a string of struggling movie theaters, all in the same city. The current equilibrium is $8 per movie ticket, with 1,800 people attending movies. The original consumer surplus is G + H + J, and producer surplus is I + K. The city government is worried that movie theaters will go out of business, reducing the entertainment options available to citizens, so it decides to impose a price floor of $12 per ticket. As a result, the quantity demanded of movie tickets falls to 1,400. The new consumer surplus is G, and the new producer surplus is H + I. In effect, the price floor causes the area H to be transferred from consumer to producer surplus, but also causes a deadweight loss of J + K.
This analysis shows that a price ceiling, like a law establishing rent controls, will transfer some producer surplus to consumers—which helps to explain why consumers often favor them. Conversely, a price floor like a guarantee that farmers will receive a certain price for their crops will transfer some consumer surplus to producers, which explains why producers often favor them. However, both price floors and price ceilings block some transactions that buyers and sellers would have been willing to make, and creates deadweight loss. Removing such barriers, so that prices and quantities can adjust to their equilibrium level, will increase the economy’s social surplus.
Demand and Supply as a Social Adjustment Mechanism
The demand and supply model emphasizes that prices are not set only by demand or only by supply, but by the interaction between the two. In 1890, the famous economist Alfred Marshall wrote that asking whether supply or demand determined a price was like arguing “whether it is the upper or the under blade of a pair of scissors that cuts a piece of paper.” The answer is that both blades of the demand and supply scissors are always involved.
The adjustments of equilibrium price and quantity in a market-oriented economy often occur without much government direction or oversight. If the coffee crop in Brazil suffers a terrible frost, then the supply curve of coffee shifts to the left and the price of coffee rises. Some people—call them the coffee addicts—continue to drink coffee and pay the higher price. Others switch to tea or soft drinks. No government commission is needed to figure out how to adjust coffee prices, which companies will be allowed to process the remaining supply, which supermarkets in which cities will get how much coffee to sell, or which consumers will ultimately be allowed to drink the brew. Such adjustments in response to price changes happen all the time in a market economy, often so smoothly and rapidly that we barely notice them.
Think for a moment of all the seasonal foods that are available and inexpensive at certain times of the year, like fresh corn in midsummer, but more expensive at other times of the year. People alter their diets and restaurants alter their menus in response to these fluctuations in prices without fuss or fanfare. For both the U.S. economy and the world economy as a whole, markets—that is, demand and supply—are the primary social mechanism for answering the basic questions about what is produced, how it is produced, and for whom it is produced.
Why Can We Not Get Enough of Organic?
Organic food is grown without synthetic pesticides, chemical fertilizers or genetically modified seeds. In recent decades, the demand for organic products has increased dramatically. The Organic Trade Association reported sales increased from $1 billion in 1990 to $35.1 billion in 2013, more than 90% of which were sales of food products.
Why, then, are organic foods more expensive than their conventional counterparts? The answer is a clear application of the theories of supply and demand. As people have learned more about the harmful effects of chemical fertilizers, growth hormones, pesticides and the like from large-scale factory farming, our tastes and preferences for safer, organic foods have increased. This change in tastes has been reinforced by increases in income, which allow people to purchase pricier products, and has made organic foods more mainstream. This has led to an increased demand for organic foods. Graphically, the demand curve has shifted right, and we have moved up the supply curve as producers have responded to the higher prices by supplying a greater quantity.
In addition to the movement along the supply curve, we have also had an increase in the number of farmers converting to organic farming over time. This is represented by a shift to the right of the supply curve. Since both demand and supply have shifted to the right, the resulting equilibrium quantity of organic foods is definitely higher, but the price will only fall when the increase in supply is larger than the increase in demand. We may need more time before we see lower prices in organic foods. Since the production costs of these foods may remain higher than conventional farming, because organic fertilizers and pest management techniques are more expensive, they may never fully catch up with the lower prices of non-organic foods.
As a final, specific example: The Environmental Working Group’s “Dirty Dozen” list of fruits and vegetables, which test high for pesticide residue even after washing, was released in April 2013. The inclusion of strawberries on the list has led to an increase in demand for organic strawberries, resulting in both a higher equilibrium price and quantity of sales.
Consumer surplus is the gap between the price that consumers are willing to pay, based on their preferences, and the market equilibrium price. Producer surplus is the gap between the price for which producers are willing to sell a product, based on their costs, and the market equilibrium price. Social surplus is the sum of consumer surplus and producer surplus. Total surplus is larger at the equilibrium quantity and price than it will be at any other quantity and price. Deadweight loss is loss in total surplus that occurs when the economy produces at an inefficient quantity.
Does a price ceiling increase or decrease the number of transactions in a market? Why? What about a price floor?
Hint:
Assuming that people obey the price ceiling, the market price will be below equilibrium, which means that Qd will be more than Qs. Buyers can only buy what is offered for sale, so the number of transactions will fall to Qs. This is easy to see graphically. By analogous reasoning, with a price floor the market price will be above the equilibrium price, so Qd will be less than Qs. Since the limit on transactions here is demand, the number of transactions will fall to Qd. Note that because both price floors and price ceilings reduce the number of transactions, social surplus is less.
If a price floor benefits producers, why does a price floor reduce social surplus?
Hint:
Because the losses to consumers are greater than the benefits to producers, so the net effect is negative. Since the lost consumer surplus is greater than the additional producer surplus, social surplus falls.
What is consumer surplus? How is it illustrated on a demand and supply diagram?
What is producer surplus? How is it illustrated on a demand and supply diagram?
What is total surplus? How is it illustrated on a demand and supply diagram?
What is the relationship between total surplus and economic efficiency?
What is deadweight loss?
What term would an economist use to describe what happens when a shopper gets a “good deal” on a product?
Explain why voluntary transactions improve social welfare.
Why would a free market never operate at a quantity greater than the equilibrium quantity? Hint: What would be required for a transaction to occur at that quantity?
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Chapter 6: Theories of Learning
Overview
Learning Framework: Effective Strategies for College Success
Chapter 6: Theories of Learning
Learning Objectives
By the end of this chapter, you will be able to:
- Define thinking and thought
- Describe metacognition and how it applies to your learning
- Identify the stages of the learning process
- Define learning objectives
- Use Bloom’s taxonomy to interpret learning objectives and adjust your expectations accordingly
- Explain the model of strategic learning
Theories of Learning
Theories of Learning
What Is Thought?
“Cogito ergo sum.” This famous Latin phrase comes from French philosopher René Descartes in the early 1600s. Translated into English, it means “I think, therefore I am.” It’s actually a profound philosophical idea, and people have argued about it for centuries: we exist, and we are aware that we exist, because we think. Without thought or the ability to think, we don’t exist. Do you agree? Even if you think Descartes got it wrong, most would say that thought is intimately connected to being human and that, as humans, we are all thinking beings.
What, then, are thinking and thought? Below are some basic working definitions:
- Thinking is the mental process you use to form associations and models of the world. When you think, you manipulate information to form concepts, to engage in problem-solving, to reason, and to make decisions.
- Thought can be described as the act of thinking that produces thoughts, which arise as ideas, images, sounds, or even emotions.
Metacognition
Metacognition is one of the distinctive characteristics of the human mind that enables us to reflect on our own mental states. It is defined as “cognition about cognitive phenomena,” or “thinking about thinking.” Metacognition is reflected in many day-to-day activities, such as when you realize that one strategy is better than another for solving a particular type of problem, or when you are able to recognize how your own experiences and perspectives may impact how you understand, react to, or judge certain situations.
Metacognition includes two clusters of activities: knowledge about cognition and regulation of cognition. Metacognitive knowledge refers to a person’s knowledge or understanding of cognitive processes. In other words, it is the ability to think about what you know and how you know it. This includes knowledge about your own strengths and limitations as well as factors that may interact to help or hinder your learning. Metacognitive regulation builds on this knowledge and refers to a person’s ability to regulate cognitive processes during problem-solving. You use metacognitive knowledge to make decisions about how to approach new problems or how to effectively learn new information and skills. This involves using various self-regulatory mechanisms like planning ahead, monitoring your progress, and evaluating your own efficiency and effectiveness in learning a task.
To give a concrete example of these metacognitive activities, let’s apply them to how you study for an exam. Knowing that your cell phone’s notifications tend to distract you from studying is an example of metacognitive knowledge: you are aware of your phone’s potential to hinder your learning. Metacognitive regulation requires you to take action based on this knowledge and would involve you making the conscious decision to put your cell phone where you cannot see or hear it or to turn it off completely, while you study. In doing so, you regulate your use of your phone to help yourself be more successful in preparing for your exam.
Watch this supplemental video where Dr. Stephen Chew from Samford University explains how to use metacognition to help you get the most out of studying.
Stages of the Learning Process
We said earlier that metacognitive knowledge involves thinking about the cognitive process, about what you know and how you know it. An important first step in developing metacognitive knowledge about yourself as a learner is to develop an awareness of how we learn new things. Consider the experiences you’ve had with learning something new, such as learning to tie your shoes or drive a car. You probably began by showing interest in the process, and after some struggling, it became second nature. These experiences were all part of the learning process, which can be described in four stages:
- Unconscious incompetence: This will likely be the easiest learning stage—you don’t know what you don’t know yet. During this stage, a learner mainly shows interest in something or prepares for learning. For example, if you wanted to learn how to dance, you might watch a video, talk to an instructor, or sign up for a future class. Stage 1 might not take long.
- Conscious incompetence: This stage can be the most difficult for learners because you begin to register how much you need to learn—you know what you don’t know. This is metacognition at work! Think about the saying “It’s easier said than done.” In stage 1 the learner only has to discuss or show interest in a new experience, but in stage 2, they begin to apply new skills that contribute to reaching the learning goal. In the dance example above, you would now be learning basic dance steps. Successful completion of this stage relies on practice.
- Conscious competence: You are beginning to master some parts of the learning goal and are feeling some confidence about what you do know. For example, you might now be able to complete basic dance steps with few mistakes and without your instructor reminding you how to do them. Stage 3 requires skill repetition, and metacognition helps you identify where to focus your efforts.
- Unconscious competence: This is the final stage in which learners have successfully practiced and repeated the process they learned so many times that they can do it almost without thinking. At this point in your dancing, you might be able to apply your dance skills to a freestyle dance routine that you create yourself. However, to feel you are a “master” of a particular skill by the time you reach stage 4, you still need to practice constantly and reevaluate which stage you are in so you can keep learning. For example, if you now felt confident in basic dance skills and could perform your own dance routine, perhaps you’d want to explore other kinds of dance, such as tango or swing. That would return you to stage 1 or 2, but you might progress through the stages more quickly this time since you have already acquired some basic dance skills.
Take a moment to watch the following video by Kristos called The Process of Learning. As you watch, consider how painful it can be—literally!—to learn something new, but also how much joy can be experienced after it’s learned. Note that the video has no audio.
You can see that the skater, through repeated practice, must identify where he is going wrong, what he is doing that prevents him from landing the skill. Over time, he is able to isolate the problems and gradually correct them, until he is ultimately successful in mastering the new trick.
The Power of Thought
As a result of many amazing and potent research discoveries, the scientific community is learning a great deal about how plastic, malleable, and constantly changing the brain is. For example, the act of thinking—just thinking—can affect not only the way your brain works but also its physical shape and structure. While thinking is not a substitute for practice, you might be surprised to find how far it can get you. The following video explores some of these discoveries, which relate to all the thinking and thoughts involved in college success.
The following sections will help you to think more deeply and critically about your own thinking and learning. They will introduce you to some theories that help explain how people learn and how we can improve our learning. You will be able to think about your own learning in the context of these theories to identify your own strengths and areas where you can work to improve your learning process.
What Are Learning Objectives?
What exactly are learning objectives? You may have already noticed them—like the ones at the top of this page—throughout this course. Learning objectives specify what someone will know, care about, or be able to do as a result of a learning experience. When your professor states a learning objective, it describes what you can expect to get out of a particular class, assignment, or reading.
Paying attention to learning objectives can help focus your attention on the most critical aspects of a learning experience. If you read the objectives closely, it can also help you determine how deeply you are expected to engage with the material. We will now look at Bloom’s taxonomy, which provides a framework for interpreting learning objectives.
Bloom’s Taxonomy
In 1956, Dr. Benjamin Bloom, an American educational psychologist who was particularly interested how people learn, chaired a committee of educators that developed and classified a set of learning objectives, which came to be known as Bloom’s taxonomy. This classification system has been updated a little since it was first developed, but it remains important for both students and teachers in helping to understand the skills and structures involved in learning.
Bloom’s taxonomy divides the cognitive domain of learning into six main learning-skill levels, or learning-skill stages, which are arranged hierarchically—moving from the simplest of functions like remembering and understanding, to more complex learning skills, like applying and analyzing, to the most complex skills—evaluating and creating. The lower levels are more straightforward and fundamental, and the higher levels are more sophisticated. See Figure 1, below.
Figure 1
The following table describes the six main skillsets within the cognitive domain and gives you information on the level of learning expected for each. Read each description closely for details of what college-level work looks like in each domain (note that the table begins with remembering, the lowest level of the taxonomy).
| MAIN SKILL LEVELS WITHIN THE COGNITIVE DOMAIN | DESCRIPTION | EXAMPLES OF RELATED LEARNING SKILLS (specific actions related to the skillset) |
| Remembering | When you are skilled in remembering, you can recognize or recall knowledge you’ve already gained, and you can use it to produce or retrieve definitions, facts, and lists. Remembering may be how you studied in grade school or high school, but college will require you to do more with the information. | identify · relate · list · define · recall · memorize · repeat · record · name |
| Understanding | Understanding is the ability to grasp or construct meaning from oral, written, and graphic messages. Each college course will introduce you to new concepts, terms, processes, and functions. Once you gain a firm understanding of new information, you’ll find it easier to comprehend how or why something works. | restate · locate · report · recognize · explain · express · identify · discuss · describe · review · infer · illustrate · interpret · draw · represent · differentiate · conclude |
| Applying | When you apply, you use or implement learned material in new and concrete situations. In college, you will be tested or assessed on what you’ve learned in the previous levels. You will be asked to solve problems in new situations by applying knowledge and skills in new ways. You may need to relate abstract ideas to practical situations. | apply · relate · develop · translate · use · operate · organize · employ · restructure · interpret · demonstrate · illustrate · practice · calculate · show · exhibit · dramatize |
| Analyzing | When you analyze, you have the ability to break down or distinguish the parts of material into its components, so that its organizational structure may be better understood. At this level, you will have a clearer sense that you comprehend the content well. You will be able to answer questions such as what if, or why, or how something would work. | analyze · compare · probe · inquire · examine · contrast · categorize · differentiate · contrast · investigate · detect · survey · classify · deduce · experiment · scrutinize · discover · inspect · dissect · discriminate · separate |
| Evaluating | With skills in evaluating, you are able to judge, check, and even critique the value of material for a given purpose. At this level in college, you will be able to think critically, Your understanding of a concept or discipline will be profound. You may need to present and defend opinions. | judge · assess · compare · evaluate · conclude · measure · deduce · argue · decide · choose · rate · select · estimate · validate · consider · appraise · value · criticize · infer |
| Creating | With skills in creating, you are able to put parts together to form a coherent or unique new whole. You can reorganize elements into a new pattern or structure through generating, planning, or producing. Creating requires originality and inventiveness. It brings together all levels of learning to theorize, design, and test new products, concepts, or functions. | compose · produce · design · assemble · create · prepare · predict · modify · plan · invent · formulate · collect · generalize · document combine · relate · propose · develop · arrange · construct · organize · originate · derive · write |
Reading and interpreting learning objectives is a metacognitive act, as the information can help you determine the level of learning expected of you and give you clues as to how you can prepare for assessment. For example, if your objective is to identify the parts of an atom, you should first recognize that being able to “identify” information falls within the domain of “remembering”; you will need to memorize the parts and be able to correctly label them. Flashcards, labeling a diagram, or drawing one yourself should be sufficient ways to prepare for your test. If, however, your objective is to calculate atomic mass, you will need to know not only the parts of the atom but also how to account for those parts to come up with the atomic mass; “calculate” falls within the domain of “applying,” which requires you to take information and use it to solve a problem in a new context.
You can explore these cognitive domains further in the two videos, below. The first is from the Center for Learning Success at the Louisiana State University. It discusses Bloom’s taxonomy of learning levels with regard to student success in college.
This next video, Bloom’s Taxonomy Featuring Harry Potter Movies, is a culturally-based way of understanding and applying Bloom’s taxonomy. You can download a transcript of the video here.
Model of Strategic Learning
Thinking comes naturally. You don’t have to make it happen—it just does. But you can make it happen in different ways. For example, you can think positively or negatively. You can think with “heart” and you can think with rational judgment. You can also think strategically and analytically, and mathematically and scientifically. These are a few of the multiple ways in which the mind can process thought. To exercise metacognition is to think about your own thinking and cognitive processes. What are some forms of thinking you use? When do you use them, and why?
The Model of Strategic Learning presented here will provide a framework to help you make sense of all this thinking and act on it in ways that most effectively support your learning.
The word “strategic” suggests the execution of a carefully planned strategy with the intent of achieving a specific goal. The model of strategic learning, as outlined by Claire Ellen Weinstein, provides a comprehensive framework for developing appropriate strategies for learning given the unique conditions of each learner for any given learning experience. The model incorporates the learner’s skill, will, and self-regulation, as well as the academic environment they operate in.
- Skill refers to the learner’s content knowledge, self-awareness of strengths and weaknesses, and ability to employ effective skills such as goal-setting, active listening and reading, and note-taking.
- Will refers to the learner’s state of mind. This includes motivation, how you feel about learning (ranging from fear and anxiety to excitement and joy), beliefs about your abilities, and your level of commitment to personal goals.
- Self-regulation is how the learner recognizes and manages each of these factors. To be strategic about learning, you may exert self-control in the form of time-management, emotional control, seeking assistance, and/or monitoring progress; a learner who does so is more likely to be successful than one who fails to self-regulate.
- The academic environment encompasses factors that are external to the individual learner but still impact the learning process. Examples include access to academic support resources, the requirements of particular classes or assignments, teacher expectations, and the social context in which the learner lives.
Within this model, the learner is always at the center. Each learner is uniquely situated in terms of skill, will, and academic environment; it is also up to each learner to exercise self-regulation where possible to minimize or work around factors that interfere with learning and maximize those that support it.
This is an important model to understand, as it serves as the framework for this textbook and our course. You can watch this supplemental video, by Dr. Taylor Acee from Texas State University, for a good explanation and overview of The Model of Strategic Learning.
KEY TAKEAWAYS
- Thinking is the mental process you use to take in information and make sense of the world. Thought is the act of thinking that produces ideas, emotions, etc.
- Metacognition is thinking about thinking. It involves metacognitive knowledge (what do you know and how do you know it?) as well as metacognitive regulation (how do you use what you know to approach different types of problems?).
- In the stages of the learning process, you move from unconscious incompetence to unconscious competence; metacognition helps you advance through the 4 stages.
- Learning objectives state what you should know or be able to do as the result of a learning experience.
- Bloom’s taxonomy divides the cognitive domain into six levels, based on the level of complexity.
- Interpreting learning objectives can help you understand the extent to which you are expected to learn and be able to use the material.
- The model of strategic learning takes into account a learner’s skill, will, academic environment, and their ability to self-regulate given these conditions.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Theories of Learning. Authored by: Laura Lucas and Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Image. Authored by: Tamarcus Brown. Located at: https://unsplash.com/photos/T3uKisfmABY. License: CC0: No Rights Reserved
- Meta-Cognition in Mindfulness: A Conceptual Analysis. Authored by: Dilwar Hussain. Provided by: Psychological Thought. Located at: http://psyct.psychopen.eu/article/view/139/html. License: CC BY 4.0
- Patterns of Thought in College Success. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/patterns-of-thought/. License: CC BY 4.0
- The Learning Process in College Success. Authored by: Jolene Carr. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/the-learning-process/. License: CC BY 4.0
ALL RIGHTS RESERVED CONTENT
- Metacognition. Authored by: Lizzie Kittleman. Located at: https://www.youtube.com/watch?v=J_pUNQoB9ds. License: All Rights Reserved. License Terms: Standard YouTube License
- The Process of Learning. Authored by: Brendan Hayword. Located at: https://youtu.be/Ip7Dv8oopb8. License: All Rights Reserved. License Terms: Standard YouTube
- LicenseScientific Power of Thought. Authored by: Asap Science. Located at: https://youtu.be/-v-IMSKOtoE. License: All Rights Reserved. License Terms: Standard YouTube License
- How to Get the Most Out of Studying - Part 1. Authored by: Stephen Chew. Provided by: Samford University. Located at: https://www.youtube.com/watch?v=RH95h36NChI. License: Public Domain: No Known Copyright. License Terms: Standard YouTube License
- Bloom's Taxonomy Authored by: LSU Center for Academic Success. Located at: https://youtu.be/Qfp3x_qx5IM License: All Rights Reserved. License Terms: Standard YouTube License
- Bloom's Taxonomy featuring Harry Potter Authored by: Amanda Rusco. Located at: https://youtu.be/TI4kZb0vLiY. License: All Rights Reserved. License Terms: Standard YouTube License
- The Model of Strategic Learning Authored by: Dr. Taylor Acee. Located at: https://youtu.be/XeR33C4gzXQ. License: All Rights Reserved. License Terms: Standard YouTube License
REFERENCES
Cross, D. R., & Paris, S. G. (1988). Developmental and instructional analyses of children’s metacognition and reading comprehension. Journal of Educational Psychology, 80(2), 2131-142. Flavell, J. H. (1979). Metacognition and cognitive monitoring: A new area of cognitive-developmental inquiry. American Psychologist, 34(10), 10906-911. ↵
Cross, D. R., & Paris, S. G. (1988). Developmental and instructional analyses of children’s metacognition and reading comprehension. Journal of Educational Psychology, 80(2), 2131-142. Schraw, G., Crippen, K. J., & Hartley, K. (2006). Promoting self-regulation in science education: Metacognition as part of a broader perspective on learning. Research in Science Education, 36(1-2), 1-2111-139.
Flavell, J. H. (1979). Metacognition and cognitive monitoring: A new area of cognitive-developmental inquiry. American Psychologist, 34(10), 10906-911.
Hussain, D. (2015). Meta-Cognition in Mindfulness: A Conceptual Analysis. Psychological Thought, 8(2), 132-141. doi:http://dx.doi.org/10.5964/psyct.v8i2.139
Mansaray, David. "The Four Stages of Learning: The Path to Becoming an Expert." DavidMansaray.com. 2011. Web. 10 Feb 2016.
Wilson, Leslie Owen. "Anderson and Krathwohl - Bloom's Taxonomy Revised." The Second Principle. 2013. Web. 10 Feb 2016.
Weinstein, C.E. , Dierking, D., Husman, J., Roska, L., & Powdrill, L. (1998). "The impact of a course in strategic learning on the long-term retention of college students." Developmental education: Preparing successful college students. Monograph ser. #24 (pp. 85-96). Columbia, SC: National Research Center for the First-Year Experience and Students in Transition, U of South Carolina.
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Chapter 7: Critical and Creative Thinking
Overview
Learning Framework: Effective Strategies for College Success
Chapter 7: Critical and Creative Thinking
Learning Objectives
By the end of this section, you will be able to:
- Define critical thinking
- Describe the role that logic plays in critical thinking
- Describe how critical thinking skills can be used to evaluate information
- Perform fact-checking in the form of lateral reading to evaluate sources of information
- Identify strategies for developing yourself as a critical thinker
- Explore key elements and stages in the creative process
- Apply specific skills for stimulating creative perspectives and innovative options
- Integrate critical and creative thinking in the process of problem-solving
Critical and Creative Thinking
Critical Thinking
As a college student, you are tasked with engaging and expanding your thinking skills. One of the most important of these skills is critical thinking because it relates to nearly all tasks, situations, topics, careers, environments, challenges, and opportunities. It is a “domain-general” thinking skill, not one that is specific to a particular subject area.
What Is Critical Thinking?
Critical thinking is clear, reasonable, reflective thinking focused on deciding what to believe or do (Robert Ennis.) It means asking probing questions like “How do we know?” or “Is this true in every case or just in this instance?” It involves being skeptical and challenging assumptions rather than simply memorizing facts or blindly accepting what you hear or read.
Imagine, for example, that you’re reading a history textbook. You wonder who wrote it and why, because you detect certain biases in the writing. You find that the author has a limited scope of research focused only on a particular group within a population. In this case, your critical thinking reveals that there are “other sides to the story.”
Who are critical thinkers, and what characteristics do they have in common? Critical thinkers are usually curious and reflective people. They like to explore and probe new areas and seek knowledge, clarification, and new solutions. They ask pertinent questions, evaluate statements and arguments, and they distinguish between facts and opinion. They are also willing to examine their own beliefs, possessing a manner of humility that allows them to admit lack of knowledge or understanding when needed. They are open to changing their mind. Perhaps most of all, they actively enjoy learning, and seeking new knowledge is a lifelong pursuit. This may well be you!
No matter where you are on the road to being a critical thinker, you can always more fully develop and finely tune your skills. Doing so will help you develop more balanced arguments, express yourself clearly, read critically, and glean important information efficiently. Critical thinking skills will help you in any profession or any circumstance of life, from science to art to business to teaching. With critical thinking, you become a clearer thinker and problem solver.
| Critical Thining IS... | Critical Thinking IS NOT... |
| Questioning | Passively accepting |
| Skepticisim | Memorizing |
| Challenging reasoning | Group thinking |
| Examining Assumptions | Blind acceptance of authority |
| Uncovering biases | Following conventional thinking |
The following video, from Lawrence Bland, presents the major concepts and benefits of critical thinking.
Critical Thinking and Logic
Critical thinking is fundamentally a process of questioning information and data and then reflecting on and assessing what you discover to arrive at a reasonable conclusion. You may question the information you read in a textbook, or you may question what a politician or a professor or a classmate says.
You can also question a commonly held belief or a new idea. It is equally important (and even more challenging) to question your own thinking and beliefs! With critical thinking, anything and everything is subject to question and examination for the purpose of logically constructing reasoned perspectives.
What Is Logic?
The word logic comes from the Ancient Greek logike, referring to the science or art of reasoning. Using logic, a person evaluates arguments and reasoning and strives to distinguish between good and bad reasoning, or between truth and falsehood. Using logic, you can evaluate the ideas and claims of others, make good decisions, and form sound beliefs about the world.
Questions of Logic in Critical Thinking
Let’s use a simple example of applying logic to a critical-thinking situation. In this hypothetical scenario, a man has a Ph.D. in political science, and he works as a professor at a local college. His wife works at the college, too. They have three young children in the local school system, and their family is well known in the community. The man is now running for political office. Are his credentials and experience sufficient for entering public office? Will he be effective in the political office? Some voters might believe that his personal life and current job, on the surface, suggest he will do well in the position, and they will vote for him. In truth, the characteristics described don’t guarantee that the man will do a good job. The information is somewhat irrelevant. What else might you want to know? How about whether the man had previously held a political office and done a good job? In this case, we want to think critically about how much information is adequate in order to make a decision based on logic instead of assumptions.
The following questions, presented in Figure 1, below, are ones you may apply to formulate a logical, reasoned perspective in the above scenario or any other situation:
- What’s happening? Gather the basic information and begin to think of questions.
- Why is it important? Ask yourself why it’s significant and whether or not you agree.
- What don’t I see? Is there anything important missing?
- How do I know? Ask yourself where the information came from and how it was constructed.
- Who is saying it? What’s the position of the speaker and what is influencing them?
- What else? What if? What other ideas exist and are there other possibilities?
Figure 1
Problem-Solving with Critical Thinking
For most people, a typical day is filled with critical thinking and problem-solving challenges. In fact, critical thinking and problem-solving go hand-in-hand. They both refer to using knowledge, facts, and data to solve problems effectively. But with problem-solving, you are specifically identifying, selecting, and defending your solution. Below are some examples of using critical thinking to problem-solve:
- Your friend was upset and said some unkind words to you, which put a crimp in the relationship. You try to see through the angry behaviors to determine how you might best support your friend and help bring the relationship back to a comfortable spot.
- Your final art class project challenges you to conceptualize form in new ways. On the last day of class when students present their projects, you describe the techniques you used to fulfill the assignment. You explain why and how you selected that approach.
- You have a job interview for a position that you feel you are only partially qualified for, although you really want the job and are excited about the prospects. You analyze how you will explain your skills and experiences in a way to show that you are a good match for the prospective employer.
- You are doing well in college, and most of your college and living expenses are covered. But there are some gaps between what you want and what you feel you can afford. You analyze your income, savings, and budget to better calculate what you will need to stay in college and maintain your desired level of spending.
Evaluating Information with Critical Thinking
In 2010, a textbook used in fourth-grade classrooms in Virginia became big news for all the wrong reasons. The book, Our Virginia by Joy Masoff, caught the attention of a parent who was helping her child do her homework, according to an article in The Washington Post. Carol Sheriff was a historian for the College of William and Mary and as she worked with her daughter, she began to notice some glaring historical errors, not the least of which was a passage that described how thousands of African Americans fought for the South during the Civil War.
Further investigation into the book revealed that, although the author had written textbooks on a variety of subjects, she was not a trained historian. The research she had done to write Our Virginia, and in particular the information she included about Black Confederate soldiers, was done through the Internet and included sources created by groups like the Sons of Confederate Veterans, an organization that promotes views of history that de-emphasize the role of slavery in the Civil War.
There’s no question that evaluating sources is an important part of the research process and doesn’t just apply to Internet sources. Using inaccurate, irrelevant, or poorly researched sources can affect the quality of your own work. Being able to understand and apply the concepts that follow is crucial to becoming a more savvy user and creator of information.
Fact-Checking With Lateral Reading
When you find a source of information, how do you know if it’s true? How can you be sure that it is a reliable, trustworthy, and effective piece of evidence for your research? This section will introduce you to a set of strategies to quickly and effectively verify your sources, based on the approach taken by professional fact-checkers. Fact-checking is a form of information hygiene, the “metaphorical handwashing you engage in to prevent the spread of misinformation” (Caulfield). It can minimize your own susceptibility to misinformation and disinformation, and help you to avoid spreading it to others.
In 2017, the Stanford History Education Group conducted a study, “Lateral Reading: Reading Less and Learning More When Evaluating Digital Information.” Here, they assessed the internet evaluation skills of presumed experts: Stanford undergraduates, History professors, and professional fact-checkers. This fascinating study confirmed that even Stanford students and professors with PhDs in History struggled to identify credible sources on the internet.
For example, in one task, the participants were presented with two websites that provided information on bullying, and they were given up to ten minutes to determine which was the more reliable site. One of the websites (American Academy of Pediatrics) was from the largest professional organization of pediatricians in the world, while the other site (American College of Pediatricians) had been labeled a hate group because of its virulently anti-gay stance. The result?
- Only 50% of the historians identified the reliable website
- Only 20% of the undergrads identified the reliable website
- 100% of the fact-checkers were able to quickly identify the reliable website
Watch this supplemental video that gives an overview of The Stanford Experiment.
The SIFT Method
Mike Caulfield, Washington State University digital literacy expert, has helpfully condensed key fact-checking strategies into a short list of four moves, or things to do to quickly make a decision about whether or not a source is worthy of your attention. It is referred to as the “SIFT” method:
Stop
When you initially encounter a source of information and start to read it—stop. Ask yourself whether you know and trust the author, publisher, publication, or website. If you don’t, use the other fact-checking moves that follow, to get a better sense of what you’re looking at. In other words, don’t read, share, or use the source in your research until you know what it is, and you can verify it is reliable.
This is a particularly important step, considering what we know about the attention economy—social media, news organizations, and other digital platforms purposely promote sensational, divisive, and outrage-inducing content that emotionally hijacks our attention in order to keep us “engaged” with their sites (clicking, liking, commenting, sharing). Stop and check your emotions before engaging!
Investigate the Source
You don’t have to do a three-hour investigation into a source before you engage with it. But if you’re reading a piece on economics, and the author is a Nobel prize-winning economist, that would be useful information. Likewise, if you’re watching a video on the many benefits of milk consumption, you would want to be aware if the video was produced by the dairy industry. This doesn’t mean the Nobel economist will always be right and that the dairy industry can’t ever be trusted. But knowing the expertise and agenda of the person who created the source is crucial to your interpretation of the information provided.
When investigating a source, fact-checkers read “laterally” across many websites, rather than digging deep (reading “vertically”) into the one source they are evaluating. That is, they don’t spend much time on the source itself, but instead they quickly get off the page and see what others have said about the source. They open up many tabs in their browser, piecing together different bits of information from across the web to get a better picture of the source they’re investigating.
Watch the following short video for a demonstration of this strategy. Pay particular attention to how Wikipedia can be used to quickly get useful information about publications, organizations, and authors.
Find Better Coverage
What if the source you find is low-quality, or you can’t determine if it is reliable or not? Perhaps you don’t really care about the source—you care about the claim that source is making. You want to know if it is true or false. You want to know if it represents a consensus viewpoint, or if it is the subject of much disagreement. A common example of this is a meme you might encounter on social media. The random person or group who posted the meme may be less important than the quote or claim the meme makes.
Your best strategy in this case might be to find a better source altogether, to look for other coverage that includes trusted reporting or analysis on that same claim. Rather than relying on the source that you initially found, you can trade up for a higher quality source.
The point is that you’re not wedded to using that initial source. We have the internet! You can go out and find a better source, and invest your time there. Watch the followng video that demonstrates this strategy and notes how fact-checkers build a library of trusted sources they can rely on to provide better coverage.
Trace Claims, Quotes, and Media to the Original Context
Much of what we find on the internet has been stripped of context. Maybe there’s a video of a fight between two people with Person A as the aggressor. But what happened before that? What was clipped out of the video and what stayed in? Maybe there’s a picture that seems real but the caption could be misleading. Maybe a claim is made about a new medical treatment based on a research finding, but you’re not certain if the cited research paper actually said that. The people who re-report these stories either get things wrong by mistake, or, in some cases, they are intentionally misleading us.
In these cases you will want to trace the claim, quote, or media back to the source, so you can see it in its original context and get a sense of whether the version you saw was accurately presented. Watch the following video that discusses re-reporting vs. original reporting and demonstrates a quick tip: going “upstream” to find the original reporting source.
Developing Yourself As a Critical Thinker
Critical thinking is a fundamental skill for college students, but it should also be a lifelong pursuit. Below are additional strategies to develop yourself as a critical thinker in college and in everyday life:
- Reflect and practice: Always reflect on what you’ve learned. Is it true all the time? How did you arrive at your conclusions?
- Use wasted time: It’s certainly important to make time for relaxing, but if you find you are indulging in too much of a good thing, think about using your time more constructively. Determine when you do your best thinking and try to learn something new during that part of the day.
- Redefine the way you see things: It can be very uninteresting to always think the same way. Challenge yourself to see familiar things in new ways. Put yourself in someone else’s shoes and consider things from a different angle or perspective. If you’re trying to solve a problem, list all your concerns: what you need in order to solve it, who can help, what some possible barriers might be, etc. It’s often possible to reframe a problem as an opportunity. Try to find a solution where there seems to be none.
- Analyze the influences on your thinking and in your life: Why do you think or feel the way you do? Analyze your influences. Think about who in your life influences you. Do you feel or react a certain way because of social convention, or because you believe it is what is expected of you? Try to break out of any molds that may be constricting you.
- Express yourself: Critical thinking also involves being able to express yourself clearly. Most important in expressing yourself clearly is stating one point at a time. You might be inclined to argue every thought, but you might have greater impact if you focus just on your main arguments. This will help others to follow your thinking clearly. For more abstract ideas, assume that your audience may not understand. Provide examples, analogies, or metaphors where you can.
- Enhance your wellness: It’s easier to think critically when you take care of your mental and physical health. Try taking activity breaks throughout the day to reach 30 to 60 minutes of physical activity each day. Scheduling physical activity into your day can help lower stress and increase mental alertness. Also, do your most difficult work when you have the most energy. Think about the time of day you are most effective and have the most energy. Plan to do your most difficult work during these times. And be sure to reach out for help if you feel you need assistance with your mental or physical health (see Maintaining Your Mental (and Physical) Health for more information).
Creative Thinking
Creative thinking is an invaluable skill for college students because it helps you look at problems and situations from a fresh perspective. Creative thinking is a way to develop novel or unorthodox solutions that do not depend wholly on past or current solutions. It’s a way of employing strategies to clear your mind so that your thoughts and ideas can transcend what appears to be the limitations of a problem. Creative thinking is a way of moving beyond barriers and it can be understood as a skill, as opposed to an inborn talent or natural “gift”, that can be taught as well as learned.
However, the ability to think and act in creative ways is a natural ability that we all exhibited as children. The curiosity, wonder, imagination, playfulness, and persistence in obtaining new skills are what transformed us into the powerful learners that we became well before we entered school. As a creative thinker now, you are curious, optimistic, and imaginative. You see problems as interesting opportunities, and you challenge assumptions and suspend judgment. You don’t give up easily. You work hard. Is this you? Even if you don’t yet see yourself as a competent creative thinker or problem-solver yet, you can learn solid skills and techniques to help you become one.
How to Stimulate Creative Thinking
The following video, How to Stimulate the Creative Process, identifies six strategies to stimulate your creative thinking.
- Sleep on it. Over the years, researchers have found that the REM sleep cycle boosts our creativity and problem-solving abilities, providing us with innovative ideas or answers to vexing dilemmas when we awaken. Keep a pen and paper by the bed so you can write down your nocturnal insights if they wake you up.
- Go for a run or hit the gym. Studies indicate that exercise stimulates creative thinking, and the brainpower boost lasts for a few hours.
- Allow your mind to wander a few times every day. Far from being a waste of time, daydreaming has been found to be an essential part of generating new ideas. If you’re stuck on a problem or creatively blocked, think about something else for a while.
- Keep learning. Studying something far removed from your area of expertise is especially effective in helping you think in new ways.
- Put yourself in nerve-racking situations once in a while to fire up your brain. Fear and frustration can trigger innovative thinking.
- Keep a notebook with you, or create a file for ideas on your smartphone or laptop, so you always have a place to record fleeting thoughts. They’re sometimes the best ideas of all.
The following video, Where Good Ideas Come From by Steven Johnson, reinforces the idea that time allows creativity to flourish.
Watch this supplemental video by PBS Digital Studies: How To Be Creative | Off Book | PBS Digital Studio for a more in-depth look on how to become a “powerful creative person.”
Problem Solving with Creative Thinking
Creative problem-solving is a type of problem-solving that involves searching for new and novel solutions to problems. It’s a way to think “outside of the box.” Unlike critical thinking, which scrutinizes assumptions and uses reasoning, creative thinking is about generating alternative ideas— practices and solutions that are unique and effective. It’s about facing sometimes muddy and unclear problems and seeing how things can be done differently.
As you continue to develop your creative thinking skills, be alert to perceptions about creative thinking that could slow down progress. Remember that creative thinking and problem-solving are ways to transcend the limitations of a problem and see past barriers.
| FICTION | FACTS |
1 | Every problem has only one solution (or one right answer) | The goal of problem-solving is to solve the problem, and most problems can be solved in any number of ways. If you discover a solution that works, it’s a good solution. Other people may think up solutions that differ from yours, but that doesn’t make your solution wrong or unimportant. What is the solution to “putting words on paper?” Fountain pen, ballpoint, pencil, marker, typewriter, printer, printing press, word-processing… all are valid solutions! |
2 | The best answer, solution, or method has already been discovered | Look at the history of any solution and you’ll see that improvements, new solutions, and new right answers are always being found. What is the solution to human transportation? The ox or horse, the cart, the wagon, the train, the car, the airplane, the jet, the space shuttle? What is the best and last? |
3 | Creative answers are technologically complex | Only a few problems require complex technological solutions. Most problems you’ll encounter need only a thoughtful solution involving personal action and perhaps a few simple tools. Even many problems that seem to require technology can be addressed in other ways. |
4 | Ideas either come or they don’t. Nothing will help— certainly not structure. | There are many successful techniques for generating ideas. One important technique is to include structure. Create guidelines, limiting parameters, and concrete goals for yourself that stimulate and shape your creativity. This strategy can help you get past the intimidation of “the blank page.” For example, if you want to write a story about a person who gained insight through experience, you can stoke your creativity by limiting or narrowing your theme to “a young girl in Cambodia who escaped the Khmer Rouge to find a new life as a nurse in France.” Apply this specificity and structure to any creative endeavor. |
Critical and creative thinking complement each other when it comes to problem-solving. The process of alternatively focusing and expanding your thinking can generate more creative, innovative, and effective outcomes.
Problem-Solving Action Checklist
Problem-solving can be an efficient and rewarding process, especially if you are organized and mindful of critical steps and strategies. Remember to assume the attributes of a good critical thinker: if you are curious, reflective, knowledge-seeking, open to change, probing, organized, and ethical, your challenge or problem will be less of a hurdle, and you’ll be in a good position to find intelligent solutions. The steps outlined in this checklist will help you adhere to these qualities in your approach to any problem:
| STRATEGIES | ACTION CHECKLIST |
| 1. Define the problem |
|
| 2. Identify available solutions |
|
| 3. Select your solution |
|
KEY TAKEAWAYS
- Critical thinking is logical and reflective thinking focused on deciding what to believe or do.
- Critical thinking involves questioning and evaluating information.
- Evaluating information is a complex, but essential, process. You can use the SIFT method to help determine if sources and information are reliable.
- Creative thinking is both a natural aspect of childhood and a re-learnable skill as an adult.
- Creative thinking is as essential a skill as critical thinking and integrating them can contribute to innovative and rewarding experiences in life.
- Critical and creative thinking both contribute to our ability to solve problems in a variety of contexts.
- You can take specific actions to develop and strengthen your critical and creative thinking skills.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Critical and Creative Thinking Authored by: Laura Lucas, Tobin Quereau, and Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Chapter cover image. Authored by: Hans-Peter Gauster. Provided by: Unsplash. Located at: https://unsplash.com/photos/3y1zF4hIPCg. License: CC0: No Rights Reserved
- Creative Thinking Skills in College Success. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/creative-thinking-skills/. License: CC BY 4.0
- Critical Thinking Skills in College Success. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/critical-thinking-skills/. License: CC BY 4.0
- Evaluate: Assessing Your Research Process and Findings in Information Literacy. Authored by: Bernnard, Bobish, Hecker, Holden, Hosier, Jacobsen, Loney, Bullis. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/informationliteracy/chapter/evaluate-assessing-your-research-process-and-findings/. License: CC BY-NC-SA-4.0
- The SIFT Method in Introduction to College Research. Authored by: Walter D. Butler; Aloha Sargent; and Kelsey Smith. Provided by: Pressbooks. Located at: https://oer.pressbooks.pub/collegeresearch/chapter/the-sift-method/. License: CC BY 4.0
- Why Fact-Checking in Introduction to College Research. Authored by: Walter D. Butler; Aloha Sargent; and Kelsey Smith. Provided by: Pressbooks. Located at: https://oer.pressbooks.pub/collegeresearch/chapter/why-fact-checking/. License: CC BY 4.0
ALL RIGHTS RESERVED CONTENT
Where Good Ideas Come From. Authored by: Steven Johnson. Provided by: Riverhead Books. Located at: https://www.youtube.com/watch?v=NugRZGDbPFU. License: All Rights Reserved. License Terms: Standard YouTube License
How to Stimulate the Creative Process. Provided by: Howcast. Located at: https://youtu.be/kPC8e-Jk5uw. License: All Rights Reserved. License Terms: Standard YouTube License
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oercommons
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https://oercommons.org/courseware/lesson/25865/overview
|
Chapter 8: Ways of Knowing
Overview
Learning Framework: Effective Strategies for College Success
Chapter 8: Ways of Knowing
Learning Objectives
By the end of this chapter, you will be able to:
Describe the theory of multiple intelligences and identify your preferred intelligences
Describe the relationship between emotional intelligence and self-regulation
Identify the types of thinking that contribute to successful intelligence
Define multimodal learning
Apply multimodal approaches and a growth mindset to learning tasks
Ways of Knowing
Ways of Knowing
Introduction
Lee was excited to take a beginning Spanish class to prepare for a semester abroad in Spain. Before their first vocabulary quiz, they reviewed their notes many times. Lee took the quiz, but when they got the results, they were surprised to see that they had earned a B-, despite having studied so much.
Lee’s professor suggested that they experiment with different ways of studying. For example, in addition to studying their written notes, they might also try listening to audio recordings of the vocabulary words and repeating them out loud.
Many of us, like Lee, are accustomed to very traditional learning as a result of our experience as K–12 students. For instance, we can all remember listening to a teacher talk and copying notes off the chalkboard. However, when it comes to learning, one size doesn’t fit all. People have different learning strengths and preferences, and these can vary from subject to subject. For example, while Lee might prefer listening to recordings to help them learn Spanish, they might prefer hands-on activities like labs to master the concepts in their biology course. This chapter will explore some theories that take into account these different approaches to learning.
Multiple Intelligences
For nearly a century, educators and psychologists have debated the nature of intelligence, and more specifically whether intelligence is just one broad ability or can take more than one form. Many classical definitions of the concept have tended to define intelligence as a single broad ability that allows a person to solve or complete many sorts of tasks, or at least many academic tasks like reading, knowledge of vocabulary, and the solving of logical problems.
One of the most prominent of these models to portray intelligence as having multiple forms is Howard Gardner’s theory of multiple intelligences. Gardner proposes that there are eight different forms of intelligence, each of which functions independently of the others. Each person has a mix of all eight abilities—more of some and less of others—that helps to constitute that person’s individual cognitive profile. These eight intelligences are summarized in Table 1 below.
Since most tasks—including most tasks in classrooms—require several forms of intelligence and can be completed in more than one way, it is possible for people with various profiles of talents to succeed on a task equally well. In writing an essay, for example, a student with high interpersonal intelligence but rather average verbal intelligence might use her interpersonal strength to get a lot of help and advice from classmates and the teacher. A student with the opposite profile might work well on their own but without the benefit of help from others. Both students might end up with essays that are good, but good for different reasons.
Complete the Multiple Intelligences inventory and find your strengths. Multiple Intelligences Assessment
| Table 1: Multiple Intelligences According to Howard Gardner | |
|---|---|
| Form of intelligence | Examples of activities using the intelligence |
| Linguistic: Verbal skill; ability to use language well |
|
| Musical: Ability to create and understand music |
|
| Logical-Mathematical: logical skill; ability to reason, often using mathematics |
|
| Spatial: Ability to imagine and manipulate the arrangement of objects in the environment |
|
| Bodily-Kinesthetic: a sense of balance; coordination in use of one’s body |
|
| Interpersonal: Ability to discern others’ nonverbal feelings and thoughts |
|
| Intrapersonal: Sensitivity to one’s own thoughts and feelings |
|
| Naturalist: Sensitivity to subtle differences and patterns found in the natural environment |
|
This model can be useful as a way for students to think about how you approach your learning. Multiple intelligences suggest that there is (or may be) more than one way to be “smart,” and that you can benefit from identifying your personal strengths and preferences.
Watch this video for an explanation of the eight different types of Multiple Intelligences.
Emotional Intelligence
Emotional intelligence is an important element of self-regulation. It can be defined as the ability of individuals to recognize their own and other people’s emotions, discern between different feelings and label them appropriately, use emotional information to guide thinking and behavior, and manage and/or adjust emotions to adapt to environments or achieve one’s goal(s). Those with high levels of emotional intelligence are able to recognize and reflect on their own emotions (intrapersonal intelligence) and those of the people around them (interpersonal intelligence); they are also able to respond to those emotions in ways that minimize negative consequences and support the achievement of intended goals.
The following video provides a deeper look at emotional intelligence in the words of Daniel Goleman, a psychologist who has researched and written extensively on the topic:
One aspect of emotional intelligence is emotion regulation. Emotion regulation (self-regulation) refers to the capacity to manage and productively use one’s emotions. Emotional regulation is important in delaying gratification and self-control as demonstrated in Walter Mischel’s “Marshmallow Test” (1972). You can see the “Marshmallow Test” experiment here. As you read in Chapter 4 delaying gratification is one of the most important aspects in combating procrastination. Research has found that people who are better able to self-regulate and delay gratification, are less impulsive and have higher cognitive and social intelligence. They have better SAT scores, are rated by their friends as more socially adept, and cope with frustration and stress better than those with less skill at emotion regulation (Ayduk et al., 2000; Eigsti et al., 2006; Mischel & Ayduk, 2004). As you read in Chapter 6, self -regulation is a very important part of the Model of Strategic Learning.
Successful Intelligence
While the model of strategic learning focuses on the interaction between individual knowledge, abilities, and environment, other theories place greater emphasis on rounding out one’s cognitive abilities to be able to approach and solve problems in different ways. In his theory of successful intelligence, for example, Robert Sternberg proposes that to be successfully intelligent is to think well in three different ways: analytically, creatively, and practically. Typically, only analytical intelligence is valued on tests and in the classroom. Yet the style of intelligence that schools most readily recognize may well be less useful to many students in their adult lives than creative and practical intelligence.
- Analytical thinking encompasses the ability to think abstractly and process information effectively. People high on this dimension are able to think critically and analytically. Analytical thinking emphasizes effectiveness in information processing and is characterized by high test scores and high I.Q. scores.
- Creative thinking includes the ability to formulate new ideas, to combine seemingly unrelated facts or information. It emphasizes insight and the ability to invent new solutions and is overlooked by test scores.
- Practical thinking covers the ability to adapt to changing environmental conditions and to shape the environment so as to maximize one’s strengths and compensate for one’s weaknesses. It emphasizes intelligence in a practical sense. People high on this dimension quickly recognize what factors influence success on various tasks and are adept at both adapting to and shaping their environment so that they can accomplish various goals. Practical intelligence is not reflected in test scores.
Successful intelligence is most effective when it balances all three of its analytical, creative, and practical aspects. It is more important to know when and how to use these aspects of successful intelligence than just to have them. Successfully intelligent people don’t just have abilities, they reflect on when and how to use these abilities effectively.
Multimodal Learning
In the college setting, you’ll probably discover that instructors teach their course materials according to the method they think will be most effective for all students. Students are capable and have to learn in a variety of ways. Learning is not dependent on your learning style. The belief in learning styles has been largely debunked. Research shows that learning styles don't actually exist! (Cofield et al., 2004; Pashler, H. et al., 2008; Riener, C et al, 2010). The deleterious impact of believing in a debunked theory is students can shut down or lose interest when a professor isn’t teaching in a way that is consistent with your “preferred learning style”. It is important to understand that learning styles do not exist, as this will help you maintain a growth mindset as you learn new material in different subjects.
Students can identify and apply the learning benefits of a growth mindset, and make informed and effective learning choices in regards to personal engagement and motivation. In the example at the beginning of the chapter, Lee is better suited to incorporate different modalities to learn Spanish. Information in our brain is stored in terms of meaning, thus the more engaged a person is in their learning the more meaningful the material becomes. As you will learn in Chapter 9, the more engaged a person is in learning new material the more elaborate the encoding process becomes, therefore; making it easier to retrieve the new information.
KEY TAKEAWAYS
The theory of multiple intelligences proposes that intelligence is multi-faceted
Each learner has a unique set of strengths, and that there are many ways to be “smart.”
Emotional intelligence is an important factor in self-regulation
Successful Intelligence involves a combination of analytical, creative, and practical thinking
Learners can incorporate a variety of intelligences and a growth mindset to different learning tasks through multimodal learning
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Personal Learning Preferences. Authored by: Edgar Granillo, Laura Lucas, and Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Chapter cover image. Authored by: Lauren Mancke. Provided by: Unsplash. Located at: https://unsplash.com/photos/aOC7TSLb1o8. License: CC0: No Rights Reserved
- Emotional Intelligence. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Emotional_intelligence. License: CC BY-SA 3.0
- Multiple Intelligences in Educational Psychology. Authored by: Kelvin Seifert and Rosemary Sutton. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/educationalpsychology/chapter/multiple-intelligences/. License: CC BY 4.0
- The Learning Process in College Success. Authored by: Jolene Carr. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/the-learning-process/. License: CC BY 4.0
- Three Aspects of Successful Intelligence. Authored by: Mary Frangie. Provided by: Critical and Creative Thinking Graduate Program, University of Massachusetts Boston. Located at: http://cct.wikispaces.umb.edu/Three+Aspects+of+Successful+Intelligence. License: CC BY 4.0
ALL RIGHTS RESERVED CONTENT
- 8 Intelligences - Theory of Multiple Intelligences Explained - Dr. Howard Gardner. Authored by: Practical Psychology. License: All Rights Reserved. License Terms: Standard YouTube License
- Daniel Goleman Introduces Emotional Intelligence. Authored by: Big Think. Located at: https://youtu.be/Y7m9eNoB3NU. License: All Rights Reserved. License Terms: Standard YouTube License
REFERENCES
Ayduk, O., Mendoza-Denton, R., Mischel, W., Downey, G., Peake, P. K., & Rodriguez, M. (2000). Regulating the interpersonal self: Strategic self-regulation for coping with rejection sensitivity. Journal of Personality and Social Psychology, 79(5), 776–792
Coffield, F., Ecclestone, K., Moseley, D., & Hall, E. (2004). Learning styles and pedagogy in post 16 education: a critical and systematic review.Eigsti, I.-M., Zayas, V., Mischel, W., Shoda, Y., Ayduk, O., Dadlani, M. B., Casey, B. J. (2006). Predicting cognitive control from preschool to late adolescence and young adulthood. Psychological Science, 17(6), 478–484
Mischel, W., & Ayduk, O. (Eds.). (2004). Willpower in a cognitive-affective processing system: The dynamics of delay of gratification. New York, NY: Guilford Press.
Mischel, W., Ebbesen, E.B. (1970). Attention in delaying of gratification. Journal of Personality and Social Psychology, 16(2), 329-337.
Pashler, H., McDaniel, M., Rohrer, D., & Bjork, R. (2008). Learning Styles: Concepts and Evidence. Psychological Science in the Public Interest, 9(3), 105–119.
Riener, Cedar & Willingham, Daniel. (2010). The Myth of Learning Styles. Change: The Magazine of Higher Learning. 42. 32-35.
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https://oercommons.org/courseware/lesson/25866/overview
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Chapter 9: Memory and Information Processing
Overview
Learning Framework: Effective Strategies for College Success
Chapter 9: Memory and Information Processing
Learning Objectives
- By the end of this chapter, you will be able to:
- Identify and describe the three basic functions of memory
- Differentiate between sensory, short-term, and long-term memory
- Identify and describe methods for information retrieval
- Describe the forgetting curve and its implications for learning
- Describe strategies for deciding which course content to learn and retain
- Recognize and apply strategies for strengthening your memory
Memory and Information Processing
Memory and Information Processing
Memory
Memory is an information processing system that we often compare to a computer. Memory is the set of processes used to encode, store, and retrieve information over different periods of time.
Encoding involves the input of information into the memory system. Storage is the retention of the encoded information. Retrieval, or getting the information out of memory and back into awareness, is the third function.
ENCODING
We get information into our brains through a process called encoding, which is the input of information into the memory system. Once we receive sensory information from the environment, our brains label or code it. We organize the information with other similar information and connect new concepts to existing concepts. Encoding information occurs through both automatic processing and effortful processing.
If someone asks you what you ate for lunch today, more than likely you could recall this information quite easily. This is known as automatic processing, or the encoding of details like time, space, frequency, and the meaning of words. Automatic processing is usually done without any conscious awareness. Recalling the last time you studied for a test is another example of automatic processing. But what about the actual test material you studied? It probably required a lot of work and attention on your part in order to encode that information. This is known as effortful processing.
When you first learn new skills such as driving a car, you have to put forth effort and attention to encode information about how to start a car, how to brake, how to handle a turn, and so on. Once you know how to drive, you can encode additional information about this skill automatically.
What are the most effective ways to ensure that important memories are well encoded? Even a simple sentence is easier to recall when it is meaningful (Anderson, 1984). Read the following sentences (Bransford & McCarrell, 1974), then look away and count backwards from 30 by threes to zero, and then try to write down the sentences (no peeking back at this page!).
- The notes were sour because the seams split.
- The voyage wasn’t delayed because the bottle shattered.
- The haystack was important because the cloth ripped.
How well did you do? By themselves, the statements that you wrote down were most likely confusing and difficult for you to recall. Now, try writing them again, using the following prompts: bagpipe, ship christening, and parachutist. Next count backwards from 40 by fours, then check yourself to see how well you recalled the sentences this time. You can see that the sentences are now much more memorable because each of the sentences was placed in context. Material is far better encoded when you make it meaningful.
There are three types of encoding. The encoding of words and their meaning is known as semantic encoding. It was first demonstrated by William Bousfield (1935) in an experiment in which he asked people to memorize words. The 60 words were actually divided into 4 categories of meaning, although the participants did not know this because the words were randomly presented. When they were asked to remember the words, they tended to recall them in categories, showing that they paid attention to the meanings of the words as they learned them.
Visual encoding is the encoding of images, and acoustic encoding is the encoding of sounds, words in particular. To see how visual encoding works, read over this list of words: car, level, dog, truth, book, value. If you were asked later to recall the words from this list, which ones do you think you’d most likely remember? You would probably have an easier time recalling the words car, dog, and book, and a more difficult time recalling the words level, truth, and value. Why? Because you can recall images (mental pictures) more easily than words alone. When you read the words car, dog, and book you created images of these things in your mind. These are concrete, high-imagery words. On the other hand, abstract words like level, truth, and value are low-imagery words. High-imagery words are encoded both visually and semantically (Paivio, 1986), thus building a stronger memory.
Now let’s turn our attention to acoustic encoding. You are driving in your car and a song comes on the radio that you haven’t heard in at least 10 years, but you sing along, recalling every word. In the United States, children often learn the alphabet through song, and they learn the number of days in each month through rhyme: “Thirty days hath September, / April, June, and November; / All the rest have thirty-one, / Save February, with twenty-eight days clear, / And twenty-nine each leap year.” These lessons are easy to remember because of acoustic encoding. We encode the sounds the words make. This is one of the reasons why much of what we teach young children is done through song, rhyme, and rhythm.
Which of the three types of encoding do you think would give you the best memory of verbal information? Some years ago, psychologists Fergus Craik and Endel Tulving (1975) conducted a series of experiments to find out. Participants were given words along with questions about them. The questions required the participants to process the words at one of the three levels. The visual processing questions included such things as asking the participants about the font of the letters. The acoustic processing questions asked the participants about the sound or rhyming of the words, and the semantic processing questions asked the participants about the meaning of the words. After participants were presented with the words and questions, they were given an unexpected recall or recognition task.
Words that had been encoded semantically were better remembered than those encoded visually or acoustically. Semantic encoding involves a deeper level of processing than the shallower visual or acoustic encoding. Craik and Tulving concluded that we process verbal information best through semantic encoding, especially if we apply what is called the self-reference effect. The self-reference effect is the tendency for an individual to have better memory for information that relates to oneself in comparison to material that has less personal relevance (Rogers, Kuiper & Kirker, 1977). Could semantic encoding be beneficial to you as you attempt to memorize the concepts in this chapter?
STORAGE
Once the information has been encoded, we have to retain it. Our brains take the encoded information and place it in storage. Storage is the creation of a permanent record of information.
In order for a memory to go into storage (i.e., long-term memory), it has to pass through three distinct stages: Sensory Memory, Short-Term Memory, and finally Long-Term Memory. These stages were first proposed by Richard Atkinson and Richard Shiffrin (1968). Their model of human memory, called Atkinson-Shiffrin (A-S), is based on the belief that we process memories in the same way that a computer processes information.
According to the Atkinson-Shiffrin model of memory, information passes through three distinct stages in order for it to be stored in long-term memory.
Sensory Memory
In the Atkinson-Shiffrin model, stimuli from the environment are processed first in sensory memory: storage of brief sensory events, such as sights, sounds, and tastes. It is very brief storage—up to a couple of seconds. We are constantly bombarded with sensory information. We cannot absorb all of it, or even most of it. And most of it has no impact on our lives. For example, what was your professor wearing the last class period? As long as the professor was dressed appropriately, it does not really matter what she was wearing. Sensory information about sights, sounds, smells, and even textures, which we do not view as valuable information, we discard. If we view something as valuable, the information will move into our short-term memory system.
One study of sensory memory researched the significance of valuable information on short-term memory storage. J. R. Stroop discovered a memory phenomenon in the 1930s: you will name a color more easily if it appears printed in that color, which is called the Stroop effect. Try an experiment: name the colors of the words presented in the image below. Do not read the words, but say the color the word is printed in. For example, upon seeing the word “yellow” in green print, you should say “green,” not “yellow.” This experiment is fun, but it’s not as easy as it seems.
The Stroop effect describes why it is difficult for us to name a color when the word and the color of the word are different.
Short-Term Memory
Short-term memory is a temporary storage system that processes incoming sensory memory; sometimes it is called working memory. Short-term memory takes information from sensory memory and sometimes connects that memory to something already in long-term memory. Short-term memory storage lasts about 20 seconds. Think of short-term memory as the information you have displayed on your computer screen—a document, a spreadsheet, or a web page. Information in short-term memory either goes to long-term memory (when you save it to your hard drive) or it is discarded (when you delete a document or close a web browser).
You may find yourself asking, “How much information can our memory handle at once?” George Miller (1956), in his research on the capacity of memory, found that most people can retain about 7 items in short-term memory. Some remember 5, some 9, so he called the capacity of short-term memory the range of 7 items plus or minus 2. To explore the capacity and duration of your short-term memory, have a partner read the strings of random numbers below out loud to you, beginning each string by saying, “Ready?” and ending each by saying, “Recall,” at which point you should try to write down the string of numbers from memory.
Work through this series of numbers using the recall exercise explained above to determine the longest string of digits that you can store.
Note the longest string at which you got the series correct. For most people, this will be close to 7, Miller’s famous 7 plus or minus 2. Recall is somewhat better for random numbers than for random letters (Jacobs, 1887), and also often slightly better for information we hear (acoustic encoding) rather than see (visual encoding) (Anderson, 1969).
Long-term Memory
Long-term memory is the continuous storage of information. Unlike short-term memory, the storage capacity of long-term memory has no limits. It encompasses all the things you can remember that happened more than just a few minutes ago to all of the things that you can remember that happened days, weeks, and years ago. In keeping with the computer analogy, the information in your long-term memory would be like the information you have saved on the hard drive. It isn’t there on your desktop (your short-term memory), but you can pull up this information when you want it, at least most of the time. Not all long-term memories are strong memories. Some memories can only be recalled through prompts. For example, you might easily recall a fact— “What is the capital of the United States?”—or a procedure—“How do you ride a bike?”—but you might struggle to recall the name of the restaurant you had dinner when you were on vacation in France last summer. A prompt, such as that the restaurant was named after its owner, who spoke to you about your shared interest in soccer, may help you recall the name of the restaurant.
RETRIEVAL
So you have worked hard to encode (via effortful processing) and store some important information for your upcoming final exam. How do you get that information back out of storage when you need it? The act of getting information out of memory storage and back into conscious awareness is known as retrieval. This would be similar to finding and opening a paper you had previously saved on your computer’s hard drive. Now it’s back on your desktop, and you can work with it again. Our ability to retrieve information from long-term memory is vital to our everyday functioning. You must be able to retrieve information from memory in order to do everything from knowing how to brush your hair and teeth, to driving to work, to knowing how to perform your job once you get there.
There are three ways you can retrieve information out of your long-term memory storage system: recall, recognition, and relearning. Recall is what we most often think about when we talk about memory retrieval: it means you can access information without cues. For example, you would use recall for an essay test. Recognition happens when you identify information that you have previously learned after encountering it again. It involves a process of comparison. When you take a multiple-choice test, you are relying on recognition to help you choose the correct answer. Here is another example. Let’s say you graduated from high school 10 years ago, and you have returned to your hometown for your 10-year reunion. You may not be able to recall all of your classmates, but you recognize many of them based on their yearbook photos.
The third form of retrieval is relearning, and it’s just what it sounds like. It involves learning information that you previously learned. Whitney took Spanish in high school, but after high school, she did not have the opportunity to speak Spanish. Whitney is now 31, and her company has offered her an opportunity to work in their Mexico City office. In order to prepare herself, she enrolls in a Spanish course at the local community center. She’s surprised at how quickly she’s able to pick up the language after not speaking it for 13 years; this is an example of relearning.
This video explores these functions of memory and provides additional examples of how they work:
Forgetting
As we just learned, your brain must do some work (effortful processing) to encode information and move it into short-term, and ultimately long-term memory. This has strong implications for you as a student, as it can impact your learning – if you do not do the work to encode and store information, you are likely to forget it altogether.
The forgetting curve hypothesizes the decline of memory retention over time. This curve shows how information is lost over time when there is no attempt to retain it.
In 1885, German psychologist Hermann Ebbinghaus hypothesized that the rate of forgetting is exponential. Using himself as the sole subject in his experiment, he memorized lists of three-letter nonsense syllable words—two consonants and one vowel in the middle. He then measured his own capacity to relearn a given list of words after a variety of given time period. He found that forgetting occurs in a systematic manner, beginning rapidly and then leveling off, represented graphically in the Ebbinghaus forgetting curve. From this research, Ebbinghaus concluded that much of what we forget is lost soon after it is originally learned, but that the amount of forgetting eventually levels off.
Research indicates that people forget 80 percent of what they learn only a day later.[1] This statistic may not sound very encouraging, given all that you’re expected to learn and remember as a college student. Really, though, it points to the importance of a study strategy other than waiting until the night before a final exam to review a semester’s worth of readings and notes. When you learn something new, the goal is to “lock it in” sooner rather than later and move it from short-term memory to long-term memory, where it can be accessed when you need it (like at the end of the semester for your final exam or maybe years from now).
The next section will explore a variety of strategies you can use to process information more deeply and help improve recall.
Knowledge Acquisition Strategies
Mei felt anxious about an upcoming history exam. This would be her first test in a college class, and she wanted to do well. Meitook lots of notes during class and while reading the textbook. In preparation for the exam, she tried to review all five textbook chapters along with all of her notes.
The morning of the exam, Mei felt nervous and unprepared. After so much studying and review, why wasn’t she more confident?
Knowing What to Know
Mei’s situation shows that there really is such a thing as studying too much. Her mistake was in trying to master all of the course material. Whether you take one or more than one class, it’s simply impossible to retain every single particle of information you encounter in a textbook or lecture. And, instructors don’t generally give open-book exams or allow their students to preview the quizzes or tests ahead of time. So, how can you decide what to study and “know what to know”? The answer is to prioritize what you’re trying to learn and memorize, rather than trying to tackle all of it. Below are some strategies to help you do this.
- Think about concepts rather than facts: From time to time, you’ll need to memorize cold, hard facts—like a list of math equations or a vocabulary list in a Spanish class. Most of the time, though, instructors will care much more that you are learning about the key concepts in a subject or course—such as how photosynthesis works, how to write a thesis statement, the causes of the French Revolution, and so on. Mei, from the scenario above, might have been more successful with her studying—and felt better about it—if she had focused on the important historical developments (the “big ideas”) discussed in class, as opposed to trying to memorize a long list of dates and facts.
- Take cues from your instructor: Pay attention to what your instructor writes on the board or includes in study guides and handouts. Although these may be short—perhaps just a list of words and phrases—they are likely core concepts that you’ll want to focus on. Also, instructors tend to refer to important concepts repeatedly during class, and they may even tell you what’s important to know before an exam or other assessment.
- Look for key terms: Textbooks will often put key terms in bold or italics. These terms and their definitions are usually important and can help you remember larger concepts.
- Use summaries: Textbooks often have summaries or study guides at the end of each chapter. These summaries are a good way to check-in and see whether you grasp the main elements of the reading (each chapter of this text, for example, ends with a set of “key takeaways” that reiterate the most important concepts). If no summary is available, try to write your own—you’ll learn much more by writing about what you read than by reading alone.
Transferring Information to Long-Term Memory
In the previous discussion of how memory works, the importance of making intentional efforts to transfer information from short-term to long-term memory was noted. Below are some strategies to facilitate this process:
- Start reviewing new material immediately: Remember that people typically forget a significant amount of new information within 24 hours of learning it. As a student, you can benefit from starting to study new material right away. If you’re introduced to new concepts in class, for example, don’t wait a few days, or until the test is coming up, to start reviewing your notes and doing the related reading assignment. The sooner the better! Studying notes and writing questions or comments about what you learned right after class can help keep new information fresh in your mind.
- Study frequently for shorter periods of time: Once information becomes a part of long-term memory, you’re more likely to remember it. If you want to improve the odds of recalling course material by the time of an exam or a in future class, try reviewing it a little bit every day. Building up your knowledge and recall this way can also help you avoid needing to “cram” and feeling overwhelmed by everything you may have forgotten.
Strengthening Your Memory
We’ve discussed the importance of zeroing in on the main concepts you learn in class and of transferring them from short-term to long-term memory. But how can you work to strengthen your overall memory? Some people have stronger memories than others, but memorizing new information takes work for anyone. Below are some strategies that can aid memory.
Rehearsal
One strategy is rehearsal, or the conscious repetition of information to be remembered (Craik & Watkins, 1973). This strategy is linked to studying material frequently for shorter periods of time. You may not remember when or how you learned skills like riding a bike or tying your shoes. Mastery came with practice, and at some point, the skills became second nature. Academic learning is no different: if you spend enough time with important course concepts and practice them often, you will know them in the same way you know how to ride a bike, almost without thinking about them. For example, think about how you learned your multiplication tables. You may recall that 6 x 6 = 36, 6 x 7 = 42, and 6 x 8 = 48. Memorizing these facts is rehearsal.
Incorporate visuals
Visual aids like note cards, concept maps, and highlighted text are ways of making information stand out. Because they are shorter and more concise, they have the advantage of making the information to be memorized seem more manageable and less daunting (than an entire textbook chapter, for example). Some students write key terms on note cards and hang them around their desk or mirror so that they routinely see them and study them without even trying.
Create mnemonics
Memory devices known as mnemonics can help you retain information while only needing to remember a unique phrase or letter pattern that stands out. Mnemonic devices are memory aids that help us organize information for encoding. They are especially useful when we want to recall larger bits of information such as steps, stages, phases, and parts of a system (Bellezza, 1981).
There are different types of mnemonic devices, such as the acronym. An acronym is a word formed by the first letter of each of the words you want to remember. For example, even if you live near one, you might have difficulty recalling the names of all five Great Lakes. What if I told you to think of the word Homes? HOMES is an acronym that represents Huron, Ontario, Michigan, Erie, and Superior: the five Great Lakes.
Another type of mnemonic device is an acrostic: you make a phrase of all the first letters of the words. For example, if you are taking a math test and you are having difficulty remembering the order of operations, recalling the sentence “Please Excuse My Dear Aunt Sally” will help you, because the order of mathematical operations is Parentheses, Exponents, Multiplication, Division, Addition, Subtraction. There also are jingles, which are rhyming tunes that contain keywords related to the concept, such as “i before e, except after c.”
You might use a mnemonic device to help you remember someone’s name, a mathematical formula, or the six levels of Bloom’s taxonomy.
This is a knuckle mnemonic to help you remember the number of days in each month. Months with 31 days are represented by the protruding knuckles and shorter months fall in the spots between knuckles. (credit: modification of work by Cory Zanker)
Chunking
Another strategy is chunking, where you organize information into manageable bits or chunks (Bodie, Powers, & Fitch-Hauser, 2006). Chunking is useful when trying to remember information like dates and phone numbers. Instead of trying to remember 5205550467, you remember the number as 520-555-0467. So, if you met an interesting person at a party and you wanted to remember his phone number, you would naturally chunk it, and you could repeat the number over and over, combining the strategies of chunking and rehearsal.
Connect new information to old information
Take stock of what you already know—information that’s already stored in long-term memory—and use it as a foundation for learning newer information. It’s easier to remember new information if you can connect it to old information or to a familiar frame of reference. For example, if you are taking a sociology class and are learning about different types of social groups, you may be able to think of examples from your own experiences that relate to the different types.
Get quality sleep
Although some people require more or less sleep than the recommended amount, most people should aim for six–eight hours every night. School puts a lot of demands on the brain, and, like tired muscles after a long workout, your brain needs to rest after being exercised and taking in all sorts of new information during the day. Plus, while you are sleeping, your brain is still at work. During sleep the brain organizes and consolidates information to be stored in long-term memory (Abel & Bäuml, 2013). A good night’s rest can help you remember more and feel prepared for learning the next day.
Memory also relies on effective studying behaviors, like choosing where you study, how you study, and with whom you study. The following video provides specific studying strategies that can improve your memory.
KEY TAKEAWAYS
Memory involves encoding, storing, and retrieving information.
The three distinct stages of memory are sensory, short-term, and long-term.
Access information in long-term memory through recall, recognition, and relearning.
Without exerting any effort, we forget most of what we learn within 24 hours.
Learning requires the ability to prioritize information, focus on the most important concepts, and question/evaluate information.
Experiment with various strategies to strengthen your memory and identify what works best for you.
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Memory and Information Processing. Authored by: Laura Lucas. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Chapter cover image. Authored by: Jesse Orrico. Provided by: Unsplash. Located at: https://unsplash.com/photos/rmWtVQN5RzU. License: CC0: No Rights Reserved
- Image. Authored by: Cory Bouthillette. Provided by: Unsplash. Located at: https://unsplash.com/photos/3N7fqeT_ffw. License: CC0: No Rights Reserved
- Forgetting Curve. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Forgetting_curve. License: CC BY-SA 3.0
- How Memory Functions in Introduction to Psychology. Authored by: OpenStax. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/intropsychmaster/chapter/how-memory-functions/. License: CC BY 4.0
- The Role of Memory in College Success. Authored by: Jolene Carr. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/the-role-of-memory/. License: CC BY 4.0
- Ways to Enhance Memory in Introduction to Psychology. Authored by: OpenStax. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/intropsychmaster/chapter/how-memory-functions/. License: CC BY 4.0
ALL RIGHTS RESERVED CONTENT
- How We Make Memories - Crash Course Psychology #13. Authored by: CrashCourse. Located at: https://www.youtube.com/watch?v=bSycdIx-C48&feature=youtu.be. License: All Rights Reserved. License Terms: Standard YouTube License
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Chapter 1: Manage the Transition to College
Overview
Learning Framework: Effective Strategies for College Success
Chapter 1: Manage the Transition to College
Learning Objectives
By the end of this chapter, you will be able to:
- Identify the risks and rewards of college.
- Describe the responsibilities of college student life and how they differ from high school or early career life.
- Identify differences in class delivery and compare strategies for success in each type.
- Identify different categories of students who might share the same classroom as you.
- Identify similarities and differences between different types of students compared to yourself.
Manage the Transition To College
Welcome
Welcome to Austin Community College and Learning Framework: Effective Strategies for College Success. The purpose of the Learning Framework courses at ACC is to provide students with an opportunity to learn and adopt the knowledge, skills, motivation, and behaviors that will enhance their success in learning and in life. The course is the study of 1) research and theory in the psychology of learning, cognition, and motivation, 2) factors that impact learning, and 3) application of learning strategies. Theoretical models of strategic learning, cognition, and motivation serve as the conceptual basis for the introduction of college-level student academic strategies. Students use assessment instruments (e.g., learning inventories) to help them identify their own strengths and weaknesses as strategic learners. Students are ultimately expected to integrate and apply the learning skills discussed across their own academic programs and become effective and efficient learners. Students developing these skills should be able to continually draw from the theoretical models they have learned.
EDUC 1300/1200/1100 is structured according to the Model of Strategic Learning developed by C.E. Weinstein, covered in Chapter 6: Theories of Learning. Upon successfully completing this course, students will have explored the relationship between their own skill, will, self-regulation, and academic environment and the interconnected impact of these elements on academic achievement and learning.
Throughout the course, you will engage in self-reflection, self-assessments, and various activities and assignments designed to help you think about and apply the concepts. Many topics include videos and other media materials that provide a contextual understanding of the information.
The Risks And Rewards Of College
The cost of a four-year college education has risen roughly 135% since 1980, adjusting for inflation. For this and other reasons, more and more students must take out student loans to finance their education. Upon graduation, many find they have accrued a sizable debt. Given the significant expense, some question the value of earning a college degree. However, along with the rising cost, the lifetime earnings difference between college and high school graduates has widened. The increased earnings potential for a bachelor’s degree allows a college graduate to recover the cost of college over time and eventually surpass the earnings of those with only a high school diploma.
According to the National Center for Education Statistics, attending a four-year public college costs 57% more than it did 20 years ago, adjusting for inflation. In 2021-2022 dollars, one year's college tuition in 1963 cost just over $4,600. In 2021, it cost more than $14,000. Across all types of schools, the cost of college has increased more than 135%, or about 2.3 times, between 1963 and 2021. Compared to other school types, four-year public colleges saw the steepest price hikes from 2000-2021, jumping from roughly $14,000 a year to just under $22,000 annually.
According to Federal Student Aid, more than half of students leave college with debt, with the average student owing $28,950. In 2010, 34.3 million students received some sort of federal loan. By 2024, that number has risen to 42.8 million. That does not include private loans or loans taken by parents on behalf of their student.
For college to be a good investment, the benefits of a degree (e.g., higher pay) must outweigh the opportunity cost of attending. In this case, the opportunity cost is the sum of tuition, fees, and housing costs plus the wages that would have been earned from working directly after graduating from high school. Recent data from the Bureau of Labor Statistics show that while the cost of college increased, the labor-market value of a bachelor’s degree climbed to an all-time high. In 2023, college graduates with a bachelor’s degree earned on average almost $1,500 per week, while those with a high school diploma earned an average of $900 per week, 67% more than high school graduates. This increased earnings potential allows college graduates to “catch up” relatively quickly in terms of net lifetime earnings.
According to the College Board, recent college graduates who completely financed their education with student loans will earn enough by age 33 to cover the cost of those loans. They will also match the to-date lifetime earnings of those the same age with only a high school diploma. Thus, the opportunity cost of attending college is recovered over time.
A college degree also lowers the probability of unemployment. In 2023, the unemployment rate for those with a bachelor’s degree was 2.2%, while it was almost 4% for high school graduates. Furthermore, according to the Bureau of Labor Statistics, people who started jobs between the ages of 18 and 24 saw 61% of those jobs end in less than a year. In contrast, those who began working between the ages of 25 and 36 had only 34% of their jobs end within a year. Additionally, for the older age group, having more education significantly increased job duration. Despite the rising costs of college, a college degree still remains a wise investment.
What about Certificate Programs?
Since 2006, the number of people completing certificates – a credential that typically requires less time to finish than a two-year degree – has risen substantially at many schools. Institutions across the U.S. awarded more than one million certificates in 2021-2022, 38% more than in 2006-07, according to the National Center for Education Statistics. According to the Bureau of Labor Statistics, the 2023 median weekly earnings for those with a certificate is $1364, 51% higher than those with a high school degree. You can learn more about certificates from the Bureau of Labor Statistics Certificates: A fast track to careers.
Why the Gender Pay Gap?
As you likely noticed in the above chart, there is a difference in pay by gender, at all levels of education. This is a complicated issue with several contributing factors. You can learn more about the gender pay gap from "The Simple Truth about the Gender Pay Gap" from the AAUW. This 2021 updated version discusses the impact of Covid-19 on women and the work force.
The Community College Environment
Student Responsibilities
Now that you have transitioned into college, you will have new responsibilities. Research has shown that students who get involved in career-planning activities stay in college longer, graduate on time, improve their academic performance, tend to be more goal focused and motivated, and have a more satisfying and fulfilling college experience. This is why an important first step in college is examining your personal identity and values. By examining your values first, you begin the process of defining your educational goals and ultimately planning your career. You will explore your values in Chapter 3.
Secondary to the critical nature of assessing your values is the importance of committing to your responsibilities as a student. What are your new student responsibilities? Are they financial? Course-specific? Social? Health-related? Ethical? What exactly is expected of you?
Expectations for student behavior vary from campus to campus. A Web search for “college student responsibilities” reveals the breadth of expectations deemed important at any given institution.
Broadly, though, students are expected to at least act consistently with the values of the institution and to obey local, state, and federal laws. It may also be expected that you actively participate in your career decision-making process, respond to advising, and plan to graduate.
Institutions invariably provide additional details about student responsibilities. ACC's Student Rights and Responsibilities provides information on Student Standards of Conduct, Academic Integrity, and Student Complaint Procedures. Details may be formal or informal. The University of South Carolina site “What Every Student Needs to Know,” for example, outlines a formula of responsibilities for student success.
Overall, you demonstrate that you are a responsible student when you do the following:
- Uphold the values of honesty and academic integrity.
- Arrive on time and prepared for all classes, meetings, academic activities, and special events.
- Give attention to quality and excellence in completing assignments.
- Allow sufficient time to fulfill responsibilities outside of class.
- Observe etiquette in all communications, giving respect to instructors, fellow students, staff and the larger college community.
- Take full advantage of college resources available to you.
- Respect diversity in people, ideas, and opinions.
- Achieve educational goals in an organized, committed, and proactive manner.
- Take full responsibility for personal behavior.
- Comply with all college policies.
By allowing these overarching principles to guide you, you embrace responsibility and make choices that lead to college success.
College vs. High School
If you know others who attend or have attended college, then you have a head start on knowing what to expect during this odyssey. Still, the transition from high school to college is striking. Even for those that have not been in high school for a while, high school is often their last experience in a traditional educational setting. College life differs in many ways from high school. The following supplemental video clip is an overview of the challenges you may face as a student and provides examples of issues students face in transitioning from high school to college. Click on the “cc” box underneath the video to activate the closed captioning.
For more information about high school vs. college, refer to this detailed set of comparisons from Southern Methodist University: “High School vs. College”The site provides an extensive list of contrasts, such as the following:
- Following the rules in high school vs. choosing responsibly in college
- Going to high school classes vs. succeeding in college classes
- Understanding high school teachers vs. college professors
- Preparing for tests in high school vs. tests in college
- Interpreting grades in high school vs. grades in college
Watch this supplemental video from the UNLV Academic Success Center on the High School to College Transition.
Types Of Courses
Course Delivery Formats
Choices. And more choices. If college success is about anything, it’s about the choices you need to make in order to succeed. What do you want to learn? How do you want to learn it? Who do you want to learn it with and where? When do you learn best?
As part of the many choices you will make in college, you will often be able to select the format in which your college classes are offered. The list below illustrates some of the main formats you may choose. Some formats lend themselves more readily to certain subjects. Others are based on how instructors believe the content can most effectively be delivered. Knowing a bit about your options can help you select your best environments for learning.
Lecture
Lecture-style courses are likely the most common course format, at least historically. In lecture courses, the professor’s main goal is to share a large amount of information, ideas, principles, and/or resources. Lecture-style courses often include discussions and other interactions with your fellow students.
Tip: Students can best succeed in this environment with dedicated study habits, time-management skills, note-taking skills, reading skills, and active listening skills. If you have questions, be sure to ask them during class. Meet with your instructor during office hours to get help on what you don’t understand, and ensure that you’re prepared for exams or other graded projects.
Laboratory
Lab courses take place in a controlled environment with specialized equipment, typically in a special facility. Students participating in labs can expect to engage fully with the material—to learn by doing. In a lab, you get first-hand experience in developing, practicing, translating, testing, and applying principles.
Tip: To best succeed as a student in a lab course, be sure to find out in advance what the course goals are, and make sure they fit your needs as a student. Expect to practice and master precise technical skills, like using a microscope or measuring a chemical reaction. Be comfortable with working as part of a team of fellow students. Enjoy the personal touches that are inherent in lab format courses.
Seminar
Seminar-style courses are geared toward a small group of students who have achieved an advanced level of knowledge or skill in a certain area or subject. In a seminar, you will likely do a good deal of reading, writing, and discussing. You might also conduct original research. You will invariably explore a topic in great depth. The course may involve a final project such as a presentation, term paper, or demonstration.
Tip: To best succeed in a seminar-style course, you must be prepared to participate actively, which includes listening actively. You will need to be well prepared, too. As a seminar class size is ordinarily small, it will be important to feel comfortable in relating to fellow students; mutual respect is key. Initiative and responsiveness are also vital.
Studio
Studio-style courses, similar to seminars, are also very active, but an emphasis is placed mainly on developing concrete skills, such as fine arts or theater arts. Studio courses generally require you to use specific materials, instruments, equipment, and/or tools. Your course may culminate in a public display or performance.
Tip: To succeed in a studio-style course, you need good time-management skills, because you will likely put in more time than in a standard class. Coming to class is critical, as is being well prepared. You can expect your instructors to help you start on projects and to provide you with resources, but much of your work will be self-paced. Your fellow students will be additional learning resources.
Workshop
Workshop-style courses are generally short in length but intensive in scope and interaction. Workshops generally have a lower student-to-teacher ratio than other courses. Often the goal of a workshop is the acquisition of information and/or skills that you can immediately apply.
Tip: To succeed as a learner in a workshop, you will need to apply yourself and participate fully for a limited time. A workshop may last a shorter amount of time than a full term.
Independent Study
Independent Study courses may be less common than other course formats. They allow you to pursue special interests not met in your formal curriculum and often involve working closely with a particular faculty person or adviser. Independent studies usually involve significant reading and writing and often end in a research project or paper. Your special, perhaps unique, area of interest will be studied thoroughly.
Tip: To succeed in an independent-study course, be prepared to work independently but cooperatively with an adviser or faculty member. Adopt high standards for your work, as you can plan for the possibility that your project or culminating research will be of interest to a prospective employer. Assume full responsibility for your learning outcomes, and be sure to pick a topic that deeply interests you.
Study Abroad
Study-abroad courses and programs give students opportunities to learn certain subjects in a country other than their own. For most U.S. students, a typical time frame for studying abroad is one or two academic terms. For many students, study-abroad experiences are life-changing.
Tip: To succeed in studying abroad, it may be most important to communicate openly before, during, and after your experience. Learn as much about the culture in advance as possible. Keep up with studies, but take advantage of opportunities to socialize. Use social networking to connect with others who have traveled where you plan to go.
Technology-Enhanced Formats
Most, if not all, college course formats can be delivered with technology enhancements. For example, lecture-style courses are often delivered fully online, and lab courses often have Web enhancements. Online teaching and learning are commonplace at most colleges and universities. In fact, the most recent data (2012) about the number of students taking online courses shows that roughly one out of every three U.S. college students take at least one online course.
Technology-enhanced delivery methods may be synchronous (meaning in real-time, through some kind of live interaction tool) as well as asynchronous (meaning in delayed time; they may include online discussion boards that students visit at different times within a certain time frame).
The following table describes the attributes of four main “modes” of delivery relative to the technology enhancements involved.
| CONTENT DELIVERED ONLINE | FORMAT | DESCRIPTION |
|---|---|---|
| 0% | Face-to-Face / Traditional | A face-to-face course is delivered fully on-site with real-time, face-to-face interaction between the instructor and student. A face-to-face course may make use of computers, the Internet, or other electronic media in the classroom, but it does not use the institution’s learning management system for instruction. A learning management system, like Blackboard, Moodle, Canvas, or others, is an online teaching and learning environment that allows students and teachers to engage with one another and with course content. |
| 1% to 29% | Web-Enhanced | A Web-enhanced course takes place primarily in a traditional, face-to-face classroom, with some course materials being accessible online (generally in the learning management system), like digital readings to support learning objectives. All Web-enhanced classes regularly meet face-to-face. |
| 30% to 79% | Hybrid/ Blended | Hybrid courses (also called blended courses) strategically blend online and face-to-face delivery. “Flipped classrooms” are an example of hybrid delivery. In a flipped classroom, your instructor reverses the traditional order of in-class and out-of-class activity, such that you may be asked to view lectures at home before coming to class. You may then be asked to use class time for activities that enable you to engage dynamically with your instructor and fellow students. Blended courses have fewer in-person sessions than face-to-face or Web-enhanced courses. |
| 80+% | Online | An online course is delivered almost entirely through the institution’s learning management system or other online means, such as synchronous conferencing. Generally, very few or no on-site face-to-face class meetings are required. |
Online Courses
Most colleges now offer some online courses or regular courses with an online component. During Covid-19, almost all college courses are offered online. You experience an online course via a computer rather than a classroom. Many different variations exist, but all online courses share certain characteristics, such as working independently and communicating with the instructor (and sometimes other students) primarily through written computer messages.
Your online course may be Synchronous, which means it has scheduled virtual meeting times and attendance is usually required. At ACC, these courses are labeled as DLS DIL. Asynchronous means there are no live components to the class and all instruction is online. Asynchronous does not meet the class is self-paced; it will still have set due dates throughout the course. At ACC, asynchronous courses are labeled as ONL DIL. It is important to know the difference before registering. You should also find out what technology is required. Some classes require webcams for virtual meetings or proctored exams, some require you to have access to a printer, and almost all require that you have the ability to create, open, and edit word processing files.
- You need to own or have frequent access to a recent model of a computer with a high-speed, reliable Internet connection.
- For an asynchronous section, without set class meeting times, you need to self-motivate to schedule your time to participate regularly.
- Without an instructor or other students in the room, you need to be able to pay attention effectively to the computer screen. Learning on a computer is not as simple as passively watching television! Take notes.
- Without reminders in class and peer pressure from other students, you’ll need to take responsibility to complete all assignments and papers on time.
- Since your instructor will evaluate you primarily through your writing, you need good writing skills for an online course. If you believe you need to improve your writing skills, put off taking an online course until you feel better prepared.
- You must take the initiative to ask questions if you don’t understand something.
- You may need to be creative to find other ways to interact with other students in the course. You could form a study group and get together regularly in person with other students in the same course.
Watch this supplemental video, Online Classes Tips and Tricks, by Sarah Jane Lamberth, for some strategies to help you succeed in online classes.
Types of Classes in Your Degree Plan
Just as you have choices about the delivery format of your courses, you also have choices about where specific courses fit academically into your chosen degree program. For example, you can choose to take various combinations of required courses and elective courses in a given term. Typical college degree programs include both required and elective courses.
- A core course is a course required by your institution, and every student must take it in order to obtain a degree. It’s sometimes also called a general education course. Collectively, core courses are part of a core curriculum. Core courses are always essential to an academic degree, but they are not necessarily foundational to your major.
- A course required in your major, on the other hand, is essential to your specific field of study. For example, as an accounting student, you would probably have to take classes like organizational theory and principles of marketing. Your academic adviser can help you learn which courses within your major are required.
- An elective course, in contrast to both core courses and required courses in your major, is a variable component of your curriculum. You choose your electives from a number of optional subjects. Elective courses tend to be more specialized than required courses. They may also have fewer students than required courses.
Most educational programs prefer that students take a combination of elective and required courses during the same term. This is a good way to meet the demands of your program and take interesting courses outside your focus area at the same time.
Since your required courses will be clearly specified, you may not have any questions about which ones to take or when to take them. But since you get to choose which elective courses you take, some interesting questions may arise.
It’s important to track and plan your required and elective courses from the outset. Take advantage of a guidance counselor or another adviser to help you make sure you are on the best trajectory to graduation. Reassess your plan as needed.
Types Of College Students
Who Are You As a Student?
Imagine for a moment that you live in the ancient city of Athens, Greece. You are a student at Plato’s University of Athens, considered in modern times to be the first institution of higher learning in the Western world. The campus sits just outside Athens’s city walls, a mile from your home. You walk to class and take your seat in the gymnasium, where all classes are held. Gatherings are small, just a handful of fellow students, most of whom are males born and raised in Athens. When your class is finished, you walk back to the city. Your daily work awaits you—hurry.
Now return to the present time. How does your college environment compare to the university in ancient Athens? Where do you live now, relative to campus? Do you report to a job site before or after class? Who are your fellow students, and where do they live in relationship to you and campus? What city or country are they from?
If you indulge these imaginative comparisons, you may find many similarities in the past and the present. You may find many differences, too. Perhaps the most striking difference will be the makeup of each student body. Consider the following facts:
- In fall 2015, 20.2 million students attended American colleges and universities. That was almost 5 million more students than enrolled in the fall of 2000.
- Of the 20.2 million U.S. college students, about 17.3 million are undergraduates; about 3.0 million are in graduate programs.
- Almost half of all undergraduates (46 percent) are community college students.
- During the 2015–16 school year, colleges and universities are expected to award 952,000 associate’s degrees, 1.8 million bachelor’s degrees, 802,000 master’s degrees, and 179,000 doctor’s degrees.
- Females are expected to account for the majority of college students: about 11.5 million females attend in fall 2015, compared with 8.7 million males.
- More students attend full time than part-time (an estimated 12.6 million, compared with about 7.6 million).
- Nearly 4 out of 5 college students work part-time while studying for their degrees, averaging 19 hours a week.
- International students now make up about 4 percent of all university students in the U.S., which hosts more of the world’s 4.5 million international students than any other country.
These brief statistics point to the scope of university life in America and the diversity of the student body. Clearly, there is no “one size fits all” description of a college student. However, each student bears a responsibility to understand the diverse terrain of his or her peers. Who are the students you may share class with? How have they come to share the college experience with you?
In this section, we look at several main categories of students and at some of the needs of students in those categories. We also take a brief look at how all students, regardless of background, can make a plan to be successful in college.
Categories of Students
You may take classes with students from many walks of life. Which of these categories best describes you?
Traditional Students
Traditional undergraduate students typically enroll in college immediately after graduating from high school, and they attend classes on a continuous full-time basis at least during the fall and spring semesters (or fall, winter, and spring quarters). They complete a bachelor’s degree program in four or five years by the age of twenty-two or twenty-three. Traditional students are also typically financially dependent on others (such as their parents), do not have children, and consider their college career to be their primary responsibility. They may be employed only on a part-time basis, if at all, during the academic year.
Nontraditional Students
Nontraditional students do not enter college in the same calendar year that they finish high school. They typically attend classes part-time due to full-time work obligations. They are more likely to be financially independent, to have children, and/or to be caregivers of sick or elderly family members. Some nontraditional students may not have a high school diploma, or they may have received a general educational development degree (GED).
The following video features several nontraditional students from the College of William and Mary in Williamsburg, Virginia. Students discuss their status as nontraditional students and how they feel about it. Note that the differences are not just with age but also experience. Click on the “cc” box underneath the video to activate the closed captioning.
International Students and/or Non-native Speakers of English
International students are those who travel to a country different from their own for the purpose of studying in college. English is likely their second language. Non-native speakers of English, like international students, come from a different culture, too. For both of these groups, college may pose special challenges. For example, classes may at first, or for a time, pose hardships due to cultural and language barriers.
First-Generation College Students
First-generation students do not have a parent who graduated from college with a baccalaureate degree. College life may be less familiar to them, and the preparation for entering college may not have been stressed as a priority at home. Some time and support may be needed to become accustomed to the college environment. These students may experience a culture shift between school life and home life.
For an in-depth look at the experiences of four first-generation college students, you can watch this supplemental documentary called First Generation. This is a long documentary, over an hour, but is an engaging and relevant look at the experience of being a First Generation College Student.
For a shorter video, watch this supplemental video from PBS News Hour called Why First-Generation College Students Need Mentors Who Get Them.
Students with Disabilities
Students with disabilities include those who have attention-deficit/hyperactivity disorders, blindness or low vision, brain injuries, deafness/hard-of-hearing, learning disabilities, medical disabilities, physical disabilities, psychiatric disabilities, and speech and language disabilities. Students with disabilities are legally accorded reasonable accommodations that give them an equal opportunity to attain the same level of performance as students without a disability. Even with these accommodations, however, physical and electronic campus facilities and practices can pose special challenges. Time, energy, and added resources may be needed.
At Austin Community College, students with disabilities can get assistance from Student Accessibility Services.
Veterans and Military Affiliated Students
Austin Community College is home to many veterans and military-affiliated students, and this population is expected to increase as more veterans complete their service and seek higher education opportunities. Colleges play a large role in the transition veterans make when they return to civilian life and also benefit from veterans’ presence on their campuses.
While all students experience challenges when transitioning to college, veterans have unique challenges. As students, they have to interact with a civilian population and be responsible for their daily activities without having a direct chain of command to follow. Being a veteran also has its advantages. The skills and abilities that veterans bring to college can be an asset in many ways. Their service experience may make them more self-sufficient than other students, and their leadership skills are invaluable inside and outside the classroom. Veterans shared experiences lend a unique perspective that can enhance the learning experience for all students. The following is a list of characteristics that may apply to veteran students.
- Many veterans are older and may be more mature than traditional college-age students.
- Some veterans have more responsibilities, such as married life, children, and continuing military duties compared to traditional college-age students.
- Some veterans have seen overseas combat, but not all veteran students have been in combat situations or have been overseas.
- Some veterans have experienced war, death, horror, shock, fear, etc., and some may still be experiencing the physical and/or mental after-effects of deployment.
- Veterans are, in general, very motivated and self-disciplined students, and can contribute to the classroom and campus life.
Many veterans and military-affiliated students attend college using one of the GI Bills. GI Bill benefits help veterans and their families pay for college, graduate school, and training programs, but also come with specific stipulations and rules. ACC's Veterans Services helps veterans manage their benefits and get connected to a network of support and service. ACC’s Veterans Resource Center, located at the ACC Highland Campus, offers the college's military and veteran students a central, one-stop location for obtaining essential support services such as VA certification and advising for VA benefits. The 4,000-square-foot center also features a lounge area where students can connect with peers and participate in veteran-specific activities. ACC also offers VetSuccess on Campus, which provides a counselor to help veterans, active-duty military, and eligible family members obtain college and community services through hands-on assistance and referrals.
Early College High School and Dual Credit Students
Austin Community College offers programs for high school students that allow them to earn college credit while still enrolled in high school. The Early College High School Program offers qualified, motivated high school students to earn an associate degree (or up to 60 college credits) while earning their high school diplomas. Austin Community College and the partnering School District cover the cost of tuition, textbooks, transportation, and other fees. ECHS students save an average of $12,000 on tuition and fees. All ECHS classes are taught by ACC faculty and are offered at ACC campuses, online, and in partnering high schools.
ACC’s High School Programs offers college classes to qualified high school students in the ACC service area. Classes are taught by college faculty at an ACC campus, online, or at a high school campus. Tuition and fees are waived for in tax district students for up to 12 eligible classes. Out of tax district students are assessed a $150 per course fee for up to 12 eligible classes. Types of eligible courses include core curriculum, workforce, and foreign language. ECHS and Dual Credit students are often in classes with traditional ACC students.
The Office of High School and College Relations at ACC provides a variety of support services to assist students in their transition of beginning college while in high school. More than 8,300 high school students are enrolled at Austin Community College, earning college credits while completing high school.
Working Students
Many students are employed in either a part-time or full-time capacity. Balancing college life with work-life may be a challenge. Time management skills and good organization can help. These students typically have two jobs—being a student and an employee. It can be a lot to balance.
ACC's College Work-Study Program is a type of financial aid that provides eligible ACC students with the opportunity to work part-time with an ACC employer or an external community service partner. Work-study employees work up to 19 hours per week, receive a semi-monthly paycheck, and are paid $22.00 to $23 per hour depending on their position.
KEY TAKEAWAYS
- College can bring great benefits such as increased income and lower unemployment but comes with the risk of time and money.
- College brings new responsibilities and the expectations of college are very different from high school.
- There are several different types of course delivery formats in college including lectures, labs, seminars, and independent study.
- Many classes use technology to enhance the classroom experience, are taught solely online, or are a hybrid of classroom and online instruction.
- There are different types of classes, including those required for your degree plan such as core courses and major required courses as well as electives.
- There are many different kinds of college students and you will experience a diverse environment at a community college.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Manage the Transition to College. Authored by: Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Introduction to College Success. Authored by: Lumen Learning. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/introduction-to-college-success/. License: CC BY-NC-SA-4.0
- College Overview in College Success. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/college-overview/. License: CC BY 4.0
- Earnings and unemployment rate by educational attainment, 2021. Provided by: US Bureau of Labor Statistics. Located at: https://www.bls.gov/emp/chart-unemployment-earnings-education.htm License: Public Domain.
- Is a College Cap and Gown a Financial Ball and Chain? August 2011. Authored by: Lowell R. Ricketts, Research Associate. Provided by: Prepared by the Economic Education Group of the Federal Reserve Bank of St. Louis. Located at: https://files.stlouisfed.org/files/htdocs/pageone-economics/uploads/newsletter/2011/Lib0811ClassrmEdition.pdf. License: CC BY-NC 4.0
- Median weekly earnings by educational attainment and sex (annual). Provided by: Women's Bureau, An agency within the U.S. Department of Labor. Located at: https://www.dol.gov/agencies/wb/data/earnings/Median-weekly-earnings-educational-sex License: Public Domain.
- Personal Identity in College Success. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/personal-identity/. License: CC BY 4.0
- The Big Picture in San Jacinto EDUC 1300. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/the-big-picture/ License: CC BY 4.0Types of Students in College Success. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/types-of-students/. License: CC BY 4.0
- Veterans in the Classroom in Instructional Guide for University Faculty and Teaching Assistants. Provided by: Northern Illinois University. Located at: https://www.niu.edu/citl/resources/guides/instructional-guide/veterans-in-the-classroom.shtml License: CC BY-NC-SA-4.0
ALL RIGHTS RESERVED CONTENT
- First Generation. Authored by: FirstGenFilm. Located at: https://youtu.be/pfDx4duheHk v=EzSdSjsfT0A. License: All Rights Reserved. License Terms: Standard YouTube License
- Online Classes Tips and Tricks. Authored by: heyy its sj. Located at: https://youtu.be/2WuuTJSBk8w License: All Rights Reserved. License Terms: Standard YouTube License
- Student Development Courses. Provided by: Austin Community College. Located at: https://instruction.austincc.edu/student-development/our-courses/. License: All Rights Reserved.Transitioning from High School to College. Authored by: Samantha Noll. Located at: https://www.youtube.com/watch?v=EzSdSjsfT0A. License: All Rights Reserved. License Terms: Standard YouTube License
- Why first-generation students need mentors who get them. Authored by: PBS NewsHour. Located at: https://youtu.be/B1O9Lvv8lv4. License: All Rights Reserved. License Terms: Standard YouTube License
REFERENCES
"Fast Facts." National Center for Educational Statistics. Institute of Education Sciences, n.d. Web. 16 Feb 2016.
"Fast Facts from Our Fact Sheet." American Association of Community Colleges. 2016. Web. 16 Feb 2016.
"Table 318.10." National Center for Educational Statistics. Institute of Education Sciences, n.d. Web. 16 Feb. 2016.
"Table 105.20." National Center for Educational Statistics. Institute of Education Sciences, n.d. Web. 16 Feb. 2016.
Kingkade, Tyler. "Most College Students Work Part-Time Jobs, But Few Pay Their Way Through School: Poll." Huffpost Business. Huffington Post, 7 Aug 2013. Web. 16 Feb 2016.
"Open Doors." Institute of International Education. 2016. Web. 16 Feb 2016.
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Chapter 2: Set Yourself Up for Success
Overview
Learning Framework: Effective Strategies for College Success
Chapter 2: Set Yourself Up for Success
Learning Objectives
By the end of this chapter, you will be able to:
- Define what success means to you.
- Describe the qualities of a successful college student.
- Compare and contrast a Growth Mindset vs. a Fixed Mindset.
- Understand the concept of Self-Efficacy and how to apply it to your college success.
- Identify campus resources to support your success.
Set Yourself Up for Success
What Is Success?
Personal Responsibility for Success
A college education is aligned with greater success in many areas of life. While enrolled in college, most students are closely focused on making it through the next class or passing the next test. It can be easy to lose sight of the overall role that education plays in life. But sometimes it helps to recall what a truly great step forward you are taking!
It’s also important to recognize, though, that some students do not succeed in college and drop out within the first year. Sometimes this is due to financial problems or a personal or family crisis. But most of the time students drop out because they’re having trouble passing their courses.
In this section, we examine the elements of college success. Are there patterns of success you strive for but aren’t yet reaching? Where might you shore up your support? What strategies can you use to achieve success in your college endeavors?
Defining Success in College
How do you define college success? The definition really depends on you. You might think that “success” is earning an associate’s degree or attending classes in a four-year college. Maybe success is a bachelor’s or master’s degree or a Ph.D. Maybe success means receiving a certificate of completion or finishing skill-based training.
You might be thinking of other measures of college success, too, like grades. For instance, you might be unhappy with anything less than an A in a course, although maybe this depends on the difficulty of the subject. As long as you pass with a C, you might be perfectly content. But no matter how you define success personally, you probably wouldn’t think it means earning a D or lower grade in a class.
If most students believe that passing a class is the minimum requirement for “success,” and if most students want to be successful in their courses, why aren’t more college students consistently successful in the classroom?
Perhaps some common misconceptions are at play. For example, we often hear students say, “I just can’t do it!” or “I’m not good at math,” or “I guess college isn’t for me.” But, these explanations for success or failure aren’t necessarily accurate. Considerable research into college success reveals that having difficulty in or failing in college courses usually has nothing to do with intellect. More often success depends on how fully a student embraces and masters the following seven strategies:
- Learn how to listen actively in class and take effective notes (Chapters 10 and 11).
- Review the text and your reading notes prior to class (Chapter 12).
- Participate in class discussion and maybe even join a study group (Chapter 10.)
- Go to office hours and ask your instructor questions.
- Give yourself enough time to research, write, and edit your essays in manageable stages (Chapter 14).
- Take advantage of online or on-campus academic support resources (Chapter 2).
- Spend sufficient time studying (Chapter 5).
So if you feel you are not smart enough for college, ask yourself if you can implement some of these skills. Overall, students struggle in college, not because of natural intellect or smarts, but because of time management, organization, and lack of quality study time. The good news is that there are ways to combat this, and this course and textbook will help you do just that.
How Grades Play a Role in Shaping Success
In a recent online discussion at a student-support Web site, a college freshman posted the following concern about how serious they should be about getting good grades:
As a first semester freshman, I really have taken my education seriously. I’ve studied and done my homework nightly and have read all of the assignments. So far, I have all A’s in my classes, including calculus and programming. Now, with a month left to go in the semester, I feel myself slipping a bit on my studies. I blow off readings and homework more to go out at night during the week and I’ve even skipped a few classes to attend major sporting events. I also travel most weekends to visit my girlfriend. Still, I’ve gotten A’s on the exams even with these less extensive study habits, although not as high as before. So, my question really is this. Should I just be content with low A’s and B’s and enjoy myself during college, or should I strive to achieve all A’s?
How would you answer this student’s question, given what you know and sense about college life? Grades do matter to your success, right? Or . . . do they? The answer depends on who you ask and what your college and career goals are. Consider these additional factors:
- Undergraduate grades have been shown to have a positive impact on getting full-time employment in your career in a position appropriate to your degree.
- Grades also have been shown to have a positive net impact on your occupational status and earnings.
- Getting good grades, particularly in the first year of college, is important to your academic success throughout your college years.
- Grades are probably the best predictors of your persistence, your ability to graduate, and your prospects for enrolling in graduate school.
You stand to gain immeasurably when you get good grades.
Understanding Your Grade-Point Average (GPA)
Grades may not be the be-all and end-all in college life but, you should pay close attention to the GPA as it may be important to achieving your future goals. GPA is often an important criterion when applying for scholarships, specialized academic programs, internships, and transferring to a college or university.
A grade point average is a number representing the average value of the accumulated final grades earned in courses over time. More commonly called a GPA, a student’s grade point average is calculated by adding up all accumulated final grades and dividing that figure by the number of credit hours awarded. This calculation results in a mathematical mean—or average—of all final grades. The most common form of GPA is based on a 0 to 4.0 scale (A = 4.0, B = 3.0, C = 2.0, D = 1.0, and F = 0), with a 4.0 representing a “perfect” GPA—or a student having earned straight As in every course.
Austin Community College uses a standard letter grade system. When you finish your course, your instructor submits a letter grade of A, B, C, D or F that will then appear on your transcript. You can use this online GPA calculator to determine your GPA based on your grades and the number of credit hours for each course. You can check your official grades in MyACC by viewing your Unofficial Transcript.
The following are two examples of semester GPAs at ACC. Please note how the number of credit hours of a course affects the points earned. For example, the first student has two classes that are each three credit hours (EDUC 1300 and ENGL 1301) and two classes that are four credit hours (BIOL 1408 and MATH 1414), for a total of 14 credit hours. The second student is also taking four classes but they are all three credit hour courses, for a total of 12 credit hours.
Each instructor has their own grading criteria for what constitutes an A, B, C, etc. Check your syllabus carefully to find this information. Some instructors issue an A for a grade average of 90% or higher while others will issue an A for an 88% or a 92% or higher. Other instructors may use a point system to determine final grades. For example, 450 out of 500 points is an A, etc. Be sure to read each syllabus carefully so you understand how your final grade for each course is determined.
In addition to letter grades, there are also Incompletes. Withdrawals, and Pass/Fail. Students may request an Incomplete (I) due to extenuating circumstances that prevented them from completing the course work per the schedule. It is at the discretion of the instructor to determine whether to approve or deny the request. As a general rule, students must have been in good academic standing in the course prior to the request of an Incomplete. Students who receive an Incomplete will need to fulfill the requirements of the Incomplete contract as determined by agreement between the instructor and the student. If an Incomplete is not completed and resolved with a letter grade by the deadline, the I will automatically convert to an F.
Students have the option of a Course Withdrawal, resulting in a W on their transcript. Students should always check with an advisor before withdrawing as there are potential consequences that may affect academic standing, financial aid, military benefits, etc. Instructors may also withdraw a student from a course due to poor attendance, missing assignments, etc. This also results in a W on the transcript.
Lastly, some courses offer a Pass/Fail grading option. This is only available for a course if the college catalog specifies this option. If a given course permits two options of a letter grade or pass/fail grade, the student must declare the pass/fail option by the last day allowed for add/drop. Students may not change the pass/fail to a grade after the add/drop date. A passing grade is defined as the equivalent of a "C" grade or better and is not used when calculating GPA. However, An "F" (Failing) received in a course taken under a pass/fail option will be used in calculating GPA. Check with your advisor for specific information.
Words of Wisdom
It is important to know that college success is a responsibility shared with your institution. Above all, your college must provide you with stimulating learning experiences that encourage you to devote more time and effort to your learning. Additional institutional factors in your success include the following:
- High standards and expectations for your performance
- Assessment and timely feedback
- Peer support
- Encouragement and support for you to explore human differences
- Emphasis on your first college year
- Respect for diverse ways of knowing
- Integrating prior learning and experience
- Academic support programs tailored to your needs
- Ongoing application of learned skills
- Out-of-class contact with faculty[1]
Ideally, you and your college collaborate to create success in every way possible. The cooperative nature of college life is echoed in the following practical advice from a college graduate, recounted in The Student Experience by Kristen Mruk in Foundations of Academic Success: Words of Wisdom:
Professors do care about how you are doing in their class; they genuinely want you to succeed, but they will give you the grade you earn. There are people and resources on campus for you to utilize so you can earn the grade you want. Your professors are one of those resources, and are perhaps the most important. Go see them during office hours, ask them questions about the material and get extra help if you need it . . . Another resource to utilize can be found in the campus learning center . . . The first time I took a paper there, I recall standing outside the door for about ten minutes thinking of an excuse not to go in. Thankfully I saw a classmate walk in and I followed suit . . . Thanks to that first visit, I received an A- on the paper!
Characteristics Of Successful Students
Please take the following short quiz.
Read a text-only version of the activity here.
As you can see from the above quiz, it takes several qualities and habits to be successful in college.
When we think about going to college, we think about learning a subject deeply, getting prepared for a profession. We tend to associate colleges and universities with knowledge, and we’re not wrong in that regard.
But going to college, and doing well once we’re there, also relies heavily on our behaviors while we’re there. Professors and college administrators will expect you to behave in certain ways, without any explicit instructions on their part. For instance, professors will expect you to spend several hours a week working on class concepts (homework, writing, preparing for exams) on your own time. They will not tell you WHEN to spend those hours, but leave it up to you to recognize the need to put in the effort and schedule the time accordingly.
Consider this short video from Richard St. John, who spent years interviewing people who reached the top of their fields, across a wide range of careers. He traces the core behaviors that were common to all of these successful people and distill them down into 8 key traits.
To recap, those eight traits are: Passion, Work, Good Focus, Push, Serve, Ideas, and Persist
All eight traits are things that you can put into practice immediately. With them, you’ll see improvement in your school successes, as well as what lies beyond.
Keys to Success
According to Tobin Quereau, a long-time professor of student success courses at Austin Community College, there are Seven Keys to College Success. You can build a strong foundation for college success by implementing the following seven behaviors:
1. Show Up
- Be present mentally and physically for EVERY class.
- Pay attention to your attention so that you stay focused during class and while studying rather than becoming distracted or daydreaming.
- Establish a consistent, regular study schedule that takes priority over other activities.
2. Be Prepared
- Develop an accurate, realistic picture of your academic strengths, weaknesses, skills and behaviors so that you know where to put your attention and how to do your best work.
- Make a personal commitment to have ALL of your reading and studying done prior to each class and turn ALL of your assignments in ON TIME.
- Look ahead prior to each class to see what will be covered and skim relevant chapters of the textbook so that you can take more effective notes during class.
3. Manage Your Time, Your Life, and Your Stress Levels Effectively
- Make school a priority and keep a good balance between school, work, friends, and family.
- Don’t let immediate pleasures get in the way of important long-term tasks.
- Have back-up plans in place in case the unexpected happens.
4. Put in the Effort
- Learning, like life, is not easy or automatic, you will need to work hard to get ahead. Plan on several hours of reading and study for each class each week to do well.
- Be an active learner by studying regularly and learning as you go instead of putting it off until right before the exam.
- Use effective strategies for deeper, more lasting learning rather than just memorization.
5. Stay Motivated
- Be clear about the reasons you are here and what you can gain from continuing your education now and throughout your life.
- Set some realistic academic goals for each day and week and monitor your progress on them.
- Make a personal commitment to stay on course even when the going gets tough.
6. Seek Assistance Whenever Needed
- You are here to learn, but you don’t need to do it alone. Make use of all the available resources: your instructors, the Learning Lab tutors, study groups, advising, etc.
- When crisis strikes and life feels overwhelming, stay in touch with your instructor and get support from the free counseling services rather than just giving up and disappearing.
7. Finally, Learn from Everything!
- When you succeed in learning and getting good grades, pay attention to what helped and keep doing those things.
- And when things don’t turn out as you would like, figure out what went wrong or got in the way and make appropriate changes.
- You are responsible for your successes in life and you can improve your performance with committed effort and persistence, so give it your best and keep on learning!
Growth Mindset Vs. Fixed Mindset
What is the difference between a student with a growth mindset versus a student with a fixed mindset? Students with a growth mindset believe that intelligence can be developed. These students focus on learning over just looking smart, see effort as the key to success, and thrive in the face of a challenge. On the other side, students with a fixed mindset believe that people are born with a certain amount of intelligence, and they can’t do much to change that. These students focus on looking smart over learning, see effort as a sign of low ability, and wilt in the face of a challenge.
Carol Dweck, author of the 2006 book Mindset: The New Psychology of Success, defined both fixed and growth mindsets:
“In a fixed mindset students believe their basic abilities, their intelligence, their talents, are just fixed traits. They have a certain amount and that’s that, and then their goal becomes to look smart all the time and never look dumb. In a growth mindset students understand that their talents and abilities can be developed through effort, good teaching and persistence. They don’t necessarily think everyone’s the same or anyone can be Einstein, but they believe everyone can get smarter if they work at it.”
Before you read more about Growth Mindset, take a minute to take this Growth Mindset Assessment.
Which student do you think has more success in college? Think about this statement: You can learn new things, but you can’t really change your basic intelligence. People who really agree with this statement have a fixed mindset. People who really disagree with this statement have a growth mindset, and, of course, people might be somewhere in the middle.
It turns out that the more students disagree with statements like these, the more they have a growth mindset, the better they do in school. This is because students with a growth mindset approach school differently than students with a fixed mindset. They have different goals in school. The main goal for students with a fixed mindset is to show how smart they are or to hide how unintelligent they are. This makes sense if you think that intelligence is something you either have or you don’t have.
Students with a fixed mindset will avoid asking questions when they don’t understand something because they want to preserve the image that they are smart or hide that they’re not smart. But the main goal for students with a growth mindset is to learn. This also makes a lot of sense. If you think that intelligence is something that you can develop, the way you develop your intelligence is by learning new things. So students with a growth mindset will ask questions when they don’t understand something because that’s how they’ll learn. Similarly, students with a fixed mindset view effort negatively. They think, if I have to try, I must not be very smart at this. While students with a growth mindset view effort as the way that you learn, the way that you get smarter.
Where you’ll really see a difference in students with fixed and growth mindsets is when they are faced with a challenge or setback. Students with a fixed mindset will give up because they think their setback means they’re not smart, but students with a growth mindset actually like challenges. If they already knew how to do something, it wouldn’t be an opportunity to learn, to develop their intelligence.
Given that students with a growth mindset try harder in school, especially in the face of a challenge, it’s no surprise that they do better in school.
Students with a growth mindset view mistakes as a challenge rather than a wall. Many students shy away from challenging schoolwork and get discouraged quickly when they make mistakes. These students are at a significant disadvantage in school—and in life more generally—because they end up avoiding the most difficult work. Making mistakes is one of the most useful ways to learn. Our brains develop when we make a mistake and think about the mistake. This brain activity doesn’t happen when we get the answers correct on the first try.
What’s wrong with easy? According to Dweck, “it means you’re not learning as much as you could. If it was easy, well, you probably already knew how to do it.”
Watch this supplemental video, Developing a Growth Mindset with Carol Dweck, to understand more about how you can develop your own Growth Mindset.
And, remember, You Can Learn Anything!
Self-Efficacy
A concept that was first introduced by Albert Bandura in 1977, Self-efficacy is the belief that you are capable of carrying out a specific task or of reaching a specific goal (Bandura, 1977). Note that the belief and the action or goal are specific. Self-efficacy is a belief that you can write an acceptable term paper, for example, or repair an automobile, or make friends with a new student in the class. These are relatively specific beliefs and tasks. Self-efficacy is not about whether you believe that you are intelligent in general, whether you always like working with mechanical things, or think that you are generally a likable person. Self-efficacy is not a trait—there are not certain types of people with high self-efficacies and others with low self-efficacies (Stajkovic & Luthans, 1998). Rather, people have self-efficacy beliefs about specific goals and life domains. For example, if you believe that you have the skills necessary to do well in school and believe you can use those skills to excel, then you have high academic self-efficacy.
Self-efficacy may sound similar to a concept you may be familiar with already—self-esteem—but these are very different notions. Self-esteem refers to how much you like or “esteem” yourself—to what extent you believe you are a good and worthwhile person. Self-efficacy, however, refers to your self-confidence to perform well and to achieve in specific areas of life such as school, work, and relationships. Self-efficacy does influence self-esteem because how you feel about yourself overall is greatly influenced by your confidence in your ability to perform well in areas that are important to you and to achieve valued goals. For example, if performing well in athletics is very important to you, then your self-efficacy for athletics will greatly influence your self-esteem; however, if performing well in athletics is not at all important to you, then your self-efficacy for athletics will probably have little impact on your self-esteem.
Self-efficacy beliefs are not the same as “true” or documented skill or ability. They are self-constructed, meaning that they are personally developed perceptions. There can sometimes be discrepancies between a person’s self-efficacy beliefs and the person’s abilities. You can believe that you can write a good term paper, for example, without actually being able to do so, and vice versa: you can believe yourself incapable of writing a paper, but discover that you are in fact able to do so. In this way, self-efficacy is like the everyday idea of confidence, except that it is defined more precisely. And as with confidence, it is possible to have either too much or too little self-efficacy. The optimum level seems to be either at or slightly above true capacity (Bandura, 1997).
Self-efficacy beliefs are influenced in five different ways (Bandura, 1997), which are summarized below.
Influence | Definition |
Performance Experiences | When you do well and succeed at a particular task to attain a valued goal, you usually believe that you will succeed again at this task. When you fail, you often expect that you will fail again in the future if you try that task. |
Vicarious Performances | If someone who seems similar to you succeeds, then you may believe that you will succeed as well. |
Verbal Persuasion | This involves people telling you what they believe you are and are not capable of doing. Not all people will be equally persuasive. |
Imaginal Performances | What you imagine yourself doing and how well or poorly you imagine yourself doing it. |
Affective States and Physical Sensations | When you associate negative moods and negative physical sensations with failure, and positive moods and sensations with success. |
These five primary influencers of self-efficacy take many real-world forms that almost everyone has experienced. You may have had previous performance experiences affect your academic self-efficacy when you did well on a test and believed that you would do well on the next test. A vicarious performance may have affected your athletic self-efficacy when you saw your best friend skateboard for the first time and thought that you could skateboard well, too. Verbal persuasion could have affected your academic self-efficacy when a professor that you respect told you that you could get into the college of your choice if you worked hard at community college. It’s important to know that not all people are equally likely to influence your self-efficacy through verbal persuasion. People who you trust and respect are more likely to influence your self-efficacy than those you do not. Imaginal performances are an effective way to increase your self-efficacy. For example, imagine yourself doing well on a job interview may actually lead to more effective interviewing. Affective states and physical sensations abound when you think about the times you have given presentations in class. For example, you may have felt your heart racing while giving a presentation. If you believe your heart was racing because you had just had a lot of caffeine, it likely would not affect your performance. If you believe your heart was racing because you were doing a poor job, you might believe that you cannot give the presentation well. This is because you associate the feeling of anxiety with failure and expect to fail when you are feeling anxious.
Consider academic self-efficacy in your own life. Do you think your own self-efficacy has ever affected your academic ability? Do you think you have ever studied more or less intensely because you did or did not believe in your abilities to do well? Did you skip math homework or not turn in a paper because you thought you weren't going to do well on it? Students who believe in their ability to do well academically tend to be more motivated in school (Schunk, 1991). When students attain their goals, they continue to set even more challenging goals, which can lead to better performance in school in terms of higher grades and taking more challenging classes. For example, students with high academic self-efficacies might study harder because they believe that they are able to use their abilities to study effectively. Because they studied hard, they receive an A on their next test.
One question you might have about self-efficacy and academic performance is how a student’s actual academic ability interacts with self-efficacy to influence academic performance. The answer is that a student’s actual ability does play a role, but it is also influenced by self-efficacy. Students with greater ability perform better than those with lesser ability. But, among a group of students with the same exact level of academic ability, those with stronger academic self-efficacies outperform those with weaker self-efficacies.
Campus Resources For Success
There are many resources available at Austin Community College committed to helping you succeed during your time here and beyond. Being familiar with these resources, and be committed to using them when needed, is essential to your success. You may not need them right away; some you may not need at all. But you will at least find several to be vital. Be familiar with your options. Know where to find the services. Have contact information. Be prepared to visit for help. Use the following links to learn more about the services available at ACC to support your success.
Academic Resources
Academic Coaching
"Academic Coaching is a free service to ACC students where you can receive individualized support to help you stay focused, organized, and successful in your classes! Academic Coaches can help with learning style strategies such as time management, organization, motivation, note taking, test taking, reading comprehension, setting up study plans, and helping you to achieve your academic goals!"
Areas of Study Advising
Area of study advisors will help you select your classes, stay on track for your degree program, and make decisions about your educational and career goals. They can help you:
- Review your degree progress before each registration period.
- Prepare to meet with your area of study advisor throughout the semester to make sure you stay on track!
- Explore ACC areas of study and programs, as well as transfer and career options.
- Review your Program Map for your degree.
Ascender
Form friendships and celebrate culture with Ascender. This free program is open to all first-year Austin Community College students wanting to earn a bachelor’s degree. You’ll prepare for university transfer alongside a group of peers, receive one-on-one mentoring, attend family-friendly events, and much more!
BRASS
BRASS (Bold Representation of Achievement through Student Support) is a holistic support network for students at Austin Community College. Members prepare to become corporate and community leaders by participating in learning groups, specialized workshops, mentorship opportunities, and more.
Career Services
Get personalized career coaching with ACC’s Career Services and Career Counselors. Explore your options and create a plan of action to meet your goals. Explore majors & careers, get resume assistance.
International Student Services
International Student Services is eager to guide international students toward a rewarding college experience. They offer support from the time you apply to ACC until you earn an associate degree and/or transfer to a university.
Library Services
ACC Library Services offer a variety of support and services to students. They have the resources you need to excel in your coursework. We offer books, e-books, research guides, and 24/7 Expert Librarian chat. Everything you need is right at your fingertips.
Student Accessibility Services
There is a Student Accessibility Services (SAS) office at each campus. If you have a disability, contact Accessibility Services at the campus that’s most convenient for you.
Once you qualify for services, Accessibility Services staff meets with you to determine reasonable, appropriate, and effective accommodations based on the courses in which are enrolled and your disability.
Transfer Services
ACC Transfer Services is available to help you determine the best path to complete your associate degree, transfer successfully and meet your career goals. Advisors can help you select the right courses that transfer and satisfy your ACC and university degree requirements. You can also get help completing your university transfer application or researching transfer destinations.
Tutoring
At ACC, tutoring is FREE and available both online and in-person to all currently enrolled students. Our goal is to provide free, confidential, and convenient academic support for all ACC students.
Veteran Services
Austin Community College wants Veterans to achieve the college and career goals they have set for themselves. Our Veteran Affairs specialists will help you navigate the college enrollment process and enjoy the full value of your active duty or veteran’s educational benefits.
Writing Center
Whether you need help with academic writing, creative writing, screenplays, poetry, technical writing, or group writing projects, the Writing Center is here to help you strengthen your writing abilities!
Financial Resources
Financial Aid
Most students and families are eligible for some type of financial aid – from grants, scholarships, loans, or work-study. Learn more about applying for aid, watch helpful financial aid videos, or ask questions via our chatbot.
Scholarships
Submit just one ACC scholarship application to auto-match with hundreds of scholarship opportunities for college and semester-to-semester expenses!
Student Emergency Fund
ACC’S Student Emergency Fund (SEF) will help you stay on track to reach your academic and career goals should you experience unexpected expenses or a reduction or loss of income.
Student Money Management
ACC’s Student Money Management Office is here to help you take control of your money from financial coaching sessions to free online financial resources and more.
Personal Resources
Child Care
Finding affordable child care in Central Texas can be tough. Austin Community College is here to help.
Free Groceries
You and your family can receive groceries at no cost through ACC’s partnerships with Central Texas Food Bank’s (CTFB) mobile food distributions and other community partner food access opportunities.
Mental Health Counseling
ACC Mental Counselors are licensed professionals with Master's or Doctoral degrees who have been trained to provide guidance and potential solutions to emotional and psychological difficulties. They offer services and programs across the district to foster life balance, develop personal and academic growth, and help maintain a safe and healthy learning environment. ACC District Clinical Counseling Services provides virtual tele-mental health and in-person mental health counseling for enrolled ACC students.
Student Advocacy Center
The Student Advocacy Center (formerly the Support Center) provides specialized assistance and referrals to help you overcome personal and family challenges to completing your education. ACC’s Student Advocacy Center provides case management, financial assistance, and community referrals for students to remove barriers to success and help students complete their education.
Student Care Center
The Student Care Center is your hub for life support whether that’s access to food or a connection to community resources, including housing, transportation, legal aid, family support, and more.
Student Experience and Community
African American Cultural Center
The African-American Cultural Center at the Eastview Campus strives to increase understanding in the ACC and Central Texas communities of the culture, history, and contributions of African-Americans.
Asian American and Pacific Islander Cultural Center
The mission of othe Asian American and Pacifc Islander Cultural Center is to support students in their academic journey at ACC and create opportunities for the community throughout the district to learn about and engage with the AAPI heritage and cultures.
El Centro
The Latin American Cultural Center (formerly known as Latino/Latin American Studies Center, also known as “El Centro”) is ACC’s inter-disciplinary center supporting Latine/x and Mexican American studies. It strives to increase knowledge of the culture, history, and contribution of the Latine/x community in Austin and Central Texas.
Recreational Sports and Athletics (Intramurals)
If you’re looking for a little friendly competition, ACC Rec Sports provides several chances to compete in leagues and tournaments each semester.
Student Government Association
The Student Government Association (SGA) is the official voice of the ACC student body, advocating on behalf of students to the college administration. SGA members serve on college councils and committees and help drive many of the events, policies, and procedures that shape students’ college experience.
Student Life
The Student Life Office is the center for out-of-classroom activities on every Austin Community College campus and throughout the ACC District. Participating in co-curricular activities helps you gain valuable leadership skills that complement your academic work and enrich your college experience. Visit any campus Student Life Office to get started.
Truth, Racial Healing & Transformation Center
(TRHT) at ACC is a partnership with our community to build cross-racial relationships that lead to racial healing and an exploration of ways to transform the college and community for greater inclusion, belonging and success for all persons.
KEY TAKEAWAYS
- You determine your success and everyone’s definition of success is personal.
- Successful students have certain traits, characteristics, and habits, all of which can be learned and developed.
- Having a Growth Mindset, believing that intelligence and skills are gained, is a key to success.
- Self-efficacy, the belief that one is capable of reaching a goal, is another predictor of success.
- There are several campus resources available to support your success.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Set Yourself Up for Success. Authored by: Heather Syrett. Provided by: Austin Community College. License: License: CC BY-NC-SA 4.0
- Seven Keys to College Success. Authored by: Tobin Quereau. Provided by: Austin Community College. License: CC BY-NC-SA 4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Academic Honesty in EDUC 1300. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/academic-honesty/. License: CC BY 4.0
- Carol Dweck. Provided by: Wikipedia Located at: https://en.wikipedia.org/wiki/Carol_Dweck. License: CC BY 3.0
- Defining Success in EDUC 1300. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/defining-success/ License: CC BY 4.0
- Fixed or Growth Mindset: Which are you? Which are your students?. Provided by: ESU 8 Wednesday Webinars Located at: https://www.youtube.com/watch?v=d2YWh10_pzo. License: CC BY-NC-SA 4.0
- Grade Point Average. Provided by: The Glossary of Education Reform. Located at: https://www.edglossary.org/grade-point-average/ License: CC BY-NC-SA 4.0
- Introduction to Success Skills in Basic Reading and Writing. Provided by: Lumen Learning. at: https://courses.lumenlearning.com/basicreadingandwriting/chapter/why-it-matters-college-success/. License: CC BY 4.0
- Motivation as self-efficacy in Educational Psychology. Authored by: By Kelvin Seifert and Rosemary Sutton. Provided by: Lumen Learning Located at: https://courses.lumenlearning.com/educationalpsychology/chapter/motivation-as-self-efficacy/ License: CC BY 4.0
- Self-Efficacy. Authored by: By James E Maddux and Evan Kleiman at George Mason University.
Provided by: Noba. Located at: https://nobaproject.com/modules/self-efficacy License: CC BY-NC-SA 4.0 - Self-Fulfilling Prophecy. Provided by: Columbus State University. Located at: https://educationtrendsandissues.wikispaces.com/Self-Fulfilling+Prophecy. License: CC BY-NC-SA 4.0
- Types of Students in College Success. Authored by: Linda Bruce. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/types-of-students/. License: CC BY 4.0
- The Student Experience in Foundations of Academic Success: Words of Wisdom. Authored by: Thomas Priester. Provided by: SUNY Genesee Community College. Located at: https://milnepublishing.geneseo.edu/foundations-of-academic-success/. License: CC BY 4.0
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- ACC Students. Provided by: Austin Community College. Located at: https://www.austincc.edu/students License: All Rights Reserved.
- Developing a Growth Mindset with Carol Dweck. Provided by: Standford Alumni. Located at: https://youtu.be/hiiEeMN7vbQ. License: All Rights Reserved. License Terms: Standard YouTube License
- You Can Learn Anything. Provided by: Khan Academy Located at: https://youtu.be/JC82Il2cjqA. License: All Rights Reserved. License Terms: Standard YouTube License
REFERENCES
- Bandura, A. (1977). Self-efficacy: Toward a unifying theory of behavioral change. Psychological Review, 84(2), 191–215. doi:10.1037/0033-295X.84.2.191
- Bandura, A. (1997). Self-efficacy: The exercise of control. New York: Worth Publishers.
- Dweck, Carol S (2006). Mindset: The New Psychology of Success. New York: Random House.
- Schunk, D. H. (1991). Self-efficacy and academic motivation. Educational Psychologist, 26(3–4), 207–231. doi:10.1080/00461520.1991.9653133
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Introduction to Labor and Financial Markets
Baby Boomers Come of Age
The Census Bureau reports that as of 2013, 20% of the U.S. population was over 60 years old, which means that almost 63 million people are reaching an age when they will need increased medical care.
The baby boomer population, the group born between 1946 and 1964, is comprised of approximately 74 million people who have just reached retirement age. As this population grows older, they will be faced with common healthcare issues such as heart conditions, arthritis, and Alzheimer’s that may require hospitalization, long-term, or at-home nursing care. Aging baby boomers and advances in life-saving and life-extending technologies will increase the demand for healthcare and nursing. Additionally, the Affordable Care Act, which expands access to healthcare for millions of Americans, has further increase the demand, although with the election of Donald J. Trump, this increase may not be sustained.
According to the Bureau of Labor Statistics, registered nursing jobs are expected to increase by 16% between 2014 and 2024. The median annual wage of $67,490 (in 2015) is also expected to increase. The BLS forecasts that 439,000 new nurses will be in demand by 2022.
These data tell us, as economists, that the market for healthcare professionals, and nurses in particular, will face several challenges. Our study of supply and demand will help us to analyze what might happen in the labor market for nursing and other healthcare professionals, as we will discuss in the second half of this case at the end of the chapter.
Introduction to Labor and Financial Markets
In this chapter, you will learn about:
- Demand and Supply at Work in Labor Markets
- Demand and Supply in Financial Markets
- The Market System as an Efficient Mechanism for Information
The theories of supply and demand do not apply just to markets for goods. They apply to any market, even markets for things we may not think of as goods and services like labor and financial services. Labor markets are markets for employees or jobs. Financial services markets are markets for saving or borrowing.
When we think about demand and supply curves in goods and services markets, it is easy to picture the demanders and suppliers: businesses produce the products and households buy them. Who are the demanders and suppliers in labor and financial service markets? In labor markets job seekers (individuals) are the suppliers of labor, while firms and other employers who hire labor are the demanders for labor. In financial markets, any individual or firm who saves contributes to the supply of money, and any who borrows (person, firm, or government) contributes to the demand for money.
As a college student, you most likely participate in both labor and financial markets. Employment is a fact of life for most college students: According to the National Center for Educational Statistics, in 2013 40% of full-time college students and 76% of part-time college students were employed. Most college students are also heavily involved in financial markets, primarily as borrowers. Among full-time students, about half take out a loan to help finance their education each year, and those loans average about $6,000 per year. Many students also borrow for other expenses, like purchasing a car. As this chapter will illustrate, we can analyze labor markets and financial markets with the same tools we use to analyze demand and supply in the goods markets.
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Demand and Supply at Work in Labor Markets
Overview
By the end of this section, you will be able to:
- Predict shifts in the demand and supply curves of the labor market
- Explain the impact of new technology on the demand and supply curves of the labor market
- Explain price floors in the labor market such as minimum wage or a living wage
Markets for labor have demand and supply curves, just like markets for goods. The law of demand applies in labor markets this way: A higher salary or wage—that is, a higher price in the labor market—leads to a decrease in the quantity of labor demanded by employers, while a lower salary or wage leads to an increase in the quantity of labor demanded. The law of supply functions in labor markets, too: A higher price for labor leads to a higher quantity of labor supplied; a lower price leads to a lower quantity supplied.
Equilibrium in the Labor Market
In 2015, about 35,000 registered nurses worked in the Minneapolis-St. Paul-Bloomington, Minnesota-Wisconsin metropolitan area, according to the BLS. They worked for a variety of employers: hospitals, doctors’ offices, schools, health clinics, and nursing homes. Figure illustrates how demand and supply determine equilibrium in this labor market. The demand and supply schedules in Table list the quantity supplied and quantity demanded of nurses at different salaries.
| Annual Salary | Quantity Demanded | Quantity Supplied |
|---|---|---|
| $55,000 | 45,000 | 20,000 |
| $60,000 | 40,000 | 27,000 |
| $65,000 | 37,000 | 31,000 |
| $70,000 | 34,000 | 34,000 |
| $75,000 | 33,000 | 38,000 |
| $80,000 | 32,000 | 41,000 |
The horizontal axis shows the quantity of nurses hired. In this example we measure labor by number of workers, but another common way to measure the quantity of labor is by the number of hours worked. The vertical axis shows the price for nurses’ labor—that is, how much they are paid. In the real world, this “price” would be total labor compensation: salary plus benefits. It is not obvious, but benefits are a significant part (as high as 30 percent) of labor compensation. In this example we measure the price of labor by salary on an annual basis, although in other cases we could measure the price of labor by monthly or weekly pay, or even the wage paid per hour. As the salary for nurses rises, the quantity demanded will fall. Some hospitals and nursing homes may reduce the number of nurses they hire, or they may lay off some of their existing nurses, rather than pay them higher salaries. Employers who face higher nurses’ salaries may also try to replace some nursing functions by investing in physical equipment, like computer monitoring and diagnostic systems to monitor patients, or by using lower-paid health care aides to reduce the number of nurses they need.
As the salary for nurses rises, the quantity supplied will rise. If nurses’ salaries in Minneapolis-St. Paul-Bloomington are higher than in other cities, more nurses will move to Minneapolis-St. Paul-Bloomington to find jobs, more people will be willing to train as nurses, and those currently trained as nurses will be more likely to pursue nursing as a full-time job. In other words, there will be more nurses looking for jobs in the area.
At equilibrium, the quantity supplied and the quantity demanded are equal. Thus, every employer who wants to hire a nurse at this equilibrium wage can find a willing worker, and every nurse who wants to work at this equilibrium salary can find a job. In Figure, the supply curve (S) and demand curve (D) intersect at the equilibrium point (E). The equilibrium quantity of nurses in the Minneapolis-St. Paul-Bloomington area is 34,000, and the equilibrium salary is $70,000 per year. This example simplifies the nursing market by focusing on the “average” nurse. In reality, of course, the market for nurses actually comprises many smaller markets, like markets for nurses with varying degrees of experience and credentials. Many markets contain closely related products that differ in quality. For instance, even a simple product like gasoline comes in regular, premium, and super-premium, each with a different price. Even in such cases, discussing the average price of gasoline, like the average salary for nurses, can still be useful because it reflects what is happening in most of the submarkets.
When the price of labor is not at the equilibrium, economic incentives tend to move salaries toward the equilibrium. For example, if salaries for nurses in Minneapolis-St. Paul-Bloomington were above the equilibrium at $75,000 per year, then 38,000 people want to work as nurses, but employers want to hire only 33,000 nurses. At that above-equilibrium salary, excess supply or a surplus results. In a situation of excess supply in the labor market, with many applicants for every job opening, employers will have an incentive to offer lower wages than they otherwise would have. Nurses’ salary will move down toward equilibrium.
In contrast, if the salary is below the equilibrium at, say, $60,000 per year, then a situation of excess demand or a shortage arises. In this case, employers encouraged by the relatively lower wage want to hire 40,000 nurses, but only 27,000 individuals want to work as nurses at that salary in Minneapolis-St. Paul-Bloomington. In response to the shortage, some employers will offer higher pay to attract the nurses. Other employers will have to match the higher pay to keep their own employees. The higher salaries will encourage more nurses to train or work in Minneapolis-St. Paul-Bloomington. Again, price and quantity in the labor market will move toward equilibrium.
Shifts in Labor Demand
The demand curve for labor shows the quantity of labor employers wish to hire at any given salary or wage rate, under the ceteris paribus assumption. A change in the wage or salary will result in a change in the quantity demanded of labor. If the wage rate increases, employers will want to hire fewer employees. The quantity of labor demanded will decrease, and there will be a movement upward along the demand curve. If the wages and salaries decrease, employers are more likely to hire a greater number of workers. The quantity of labor demanded will increase, resulting in a downward movement along the demand curve.
Shifts in the demand curve for labor occur for many reasons. One key reason is that the demand for labor is based on the demand for the good or service that is produced. For example, the more new automobiles consumers demand, the greater the number of workers automakers will need to hire. Therefore the demand for labor is called a “derived demand.” Here are some examples of derived demand for labor:
- The demand for chefs is dependent on the demand for restaurant meals.
- The demand for pharmacists is dependent on the demand for prescription drugs.
- The demand for attorneys is dependent on the demand for legal services.
As the demand for the goods and services increases, the demand for labor will increase, or shift to the right, to meet employers’ production requirements. As the demand for the goods and services decreases, the demand for labor will decrease, or shift to the left. Table shows that in addition to the derived demand for labor, demand can also increase or decrease (shift) in response to several factors.
| Factors | Results |
|---|---|
| Demand for Output | When the demand for the good produced (output) increases, both the output price and profitability increase. As a result, producers demand more labor to ramp up production. |
| Education and Training | A well-trained and educated workforce causes an increase in the demand for that labor by employers. Increased levels of productivity within the workforce will cause the demand for labor to shift to the right. If the workforce is not well-trained or educated, employers will not hire from within that labor pool, since they will need to spend a significant amount of time and money training that workforce. Demand for such will shift to the left. |
| Technology | Technology changes can act as either substitutes for or complements to labor. When technology acts as a substitute, it replaces the need for the number of workers an employer needs to hire. For example, word processing decreased the number of typists needed in the workplace. This shifted the demand curve for typists left. An increase in the availability of certain technologies may increase the demand for labor. Technology that acts as a complement to labor will increase the demand for certain types of labor, resulting in a rightward shift of the demand curve. For example, the increased use of word processing and other software has increased the demand for information technology professionals who can resolve software and hardware issues related to a firm’s network. More and better technology will increase demand for skilled workers who know how to use technology to enhance workplace productivity. Those workers who do not adapt to changes in technology will experience a decrease in demand. |
| Number of Companies | An increase in the number of companies producing a given product will increase the demand for labor resulting in a shift to the right. A decrease in the number of companies producing a given product will decrease the demand for labor resulting in a shift to the left. |
| Government Regulations | Complying with government regulations can increase or decrease the demand for labor at any given wage. In the healthcare industry, government rules may require that nurses be hired to carry out certain medical procedures. This will increase the demand for nurses. Less-trained healthcare workers would be prohibited from carrying out these procedures, and the demand for these workers will shift to the left. |
| Price and Availability of Other Inputs | Labor is not the only input into the production process. For example, a salesperson at a call center needs a telephone and a computer terminal to enter data and record sales. If prices of other inputs fall, production will become more profitable and suppliers will demand more labor to increase production. This will cause a rightward shift in the demand curve for labor. The opposite is also true. Higher prices for other inputs lower demand for labor. |
Click here to read more about “Trends and Challenges for Work in the 21st Century.”
Shifts in Labor Supply
The supply of labor is upward-sloping and adheres to the law of supply: The higher the price, the greater the quantity supplied and the lower the price, the less quantity supplied. The supply curve models the tradeoff between supplying labor into the market or using time in leisure activities at every given price level. The higher the wage, the more labor is willing to work and forego leisure activities. Table lists some of the factors that will cause the supply to increase or decrease.
| Factors | Results |
|---|---|
| Number of Workers | An increased number of workers will cause the supply curve to shift to the right. An increased number of workers can be due to several factors, such as immigration, increasing population, an aging population, and changing demographics. Policies that encourage immigration will increase the supply of labor, and vice versa. Population grows when birth rates exceed death rates. This eventually increases supply of labor when the former reach working age. An aging and therefore retiring population will decrease the supply of labor. Another example of changing demographics is more women working outside of the home, which increases the supply of labor. |
| Required Education | The more required education, the lower the supply. There is a lower supply of PhD mathematicians than of high school mathematics teachers; there is a lower supply of cardiologists than of primary care physicians; and there is a lower supply of physicians than of nurses. |
| Government Policies | Government policies can also affect the supply of labor for jobs. Alternatively, the government may support rules that set high qualifications for certain jobs: academic training, certificates or licenses, or experience. When these qualifications are made tougher, the number of qualified workers will decrease at any given wage. On the other hand, the government may also subsidize training or even reduce the required level of qualifications. For example, government might offer subsidies for nursing schools or nursing students. Such provisions would shift the supply curve of nurses to the right. In addition, government policies that change the relative desirability of working versus not working also affect the labor supply. These include unemployment benefits, maternity leave, child care benefits, and welfare policy. For example, child care benefits may increase the labor supply of working mothers. Long term unemployment benefits may discourage job searching for unemployed workers. All these policies must therefore be carefully designed to minimize any negative labor supply effects. |
A change in salary will lead to a movement along labor demand or labor supply curves, but it will not shift those curves. However, other events like those we have outlined here will cause either the demand or the supply of labor to shift, and thus will move the labor market to a new equilibrium salary and quantity.
Technology and Wage Inequality: The Four-Step Process
Economic events can change the equilibrium salary (or wage) and quantity of labor. Consider how the wave of new information technologies, like computer and telecommunications networks, has affected low-skill and high-skill workers in the U.S. economy. From the perspective of employers who demand labor, these new technologies are often a substitute for low-skill laborers like file clerks who used to keep file cabinets full of paper records of transactions. However, the same new technologies are a complement to high-skill workers like managers, who benefit from the technological advances by having the ability to monitor more information, communicate more easily, and juggle a wider array of responsibilities. How will the new technologies affect the wages of high-skill and low-skill workers? For this question, the four-step process of analyzing how shifts in supply or demand affect a market (introduced in Demand and Supply) works in this way:
Step 1. What did the markets for low-skill labor and high-skill labor look like before the arrival of the new technologies? In Figure (a) and Figure (b), S0 is the original supply curve for labor and D0 is the original demand curve for labor in each market. In each graph, the original point of equilibrium, E0, occurs at the price W0 and the quantity Q0.
Step 2. Does the new technology affect the supply of labor from households or the demand for labor from firms? The technology change described here affects demand for labor by firms that hire workers.
Step 3. Will the new technology increase or decrease demand? Based on the description earlier, as the substitute for low-skill labor becomes available, demand for low-skill labor will shift to the left, from D0 to D1. As the technology complement for high-skill labor becomes cheaper, demand for high-skill labor will shift to the right, from D0 to D1.
Step 4. The new equilibrium for low-skill labor, shown as point E1 with price W1 and quantity Q1, has a lower wage and quantity hired than the original equilibrium, E0. The new equilibrium for high-skill labor, shown as point E1 with price W1 and quantity Q1, has a higher wage and quantity hired than the original equilibrium (E0).
Thus, the demand and supply model predicts that the new computer and communications technologies will raise the pay of high-skill workers but reduce the pay of low-skill workers. From the 1970s to the mid-2000s, the wage gap widened between high-skill and low-skill labor. According to the National Center for Education Statistics, in 1980, for example, a college graduate earned about 30% more than a high school graduate with comparable job experience, but by 2014, a college graduate earned about 66% more than an otherwise comparable high school graduate. Many economists believe that the trend toward greater wage inequality across the U.S. economy is due to improvements in technology.
Visit this website to read about ten tech skills that have lost relevance in today’s workforce.
Price Floors in the Labor Market: Living Wages and Minimum Wages
In contrast to goods and services markets, price ceilings are rare in labor markets, because rules that prevent people from earning income are not politically popular. There is one exception: boards of trustees or stockholders, as an example, propose limits on the high incomes of top business executives.
The labor market, however, presents some prominent examples of price floors, which are an attempt to increase the wages of low-paid workers. The U.S. government sets a minimum wage, a price floor that makes it illegal for an employer to pay employees less than a certain hourly rate. In mid-2009, the U.S. minimum wage was raised to $7.25 per hour. Local political movements in a number of U.S. cities have pushed for a higher minimum wage, which they call a living wage. Promoters of living wage laws maintain that the minimum wage is too low to ensure a reasonable standard of living. They base this conclusion on the calculation that, if you work 40 hours a week at a minimum wage of $7.25 per hour for 50 weeks a year, your annual income is $14,500, which is less than the official U.S. government definition of what it means for a family to be in poverty. (A family with two adults earning minimum wage and two young children will find it more cost efficient for one parent to provide childcare while the other works for income. Thus the family income would be $14,500, which is significantly lower than the federal poverty line for a family of four, which was $24,250 in 2015.)
Supporters of the living wage argue that full-time workers should be assured a high enough wage so that they can afford the essentials of life: food, clothing, shelter, and healthcare. Since Baltimore passed the first living wage law in 1994, several dozen cities enacted similar laws in the late 1990s and the 2000s. The living wage ordinances do not apply to all employers, but they have specified that all employees of the city or employees of firms that the city hires be paid at least a certain wage that is usually a few dollars per hour above the U.S. minimum wage.
Figure illustrates the situation of a city considering a living wage law. For simplicity, we assume that there is no federal minimum wage. The wage appears on the vertical axis, because the wage is the price in the labor market. Before the passage of the living wage law, the equilibrium wage is $10 per hour and the city hires 1,200 workers at this wage. However, a group of concerned citizens persuades the city council to enact a living wage law requiring employers to pay no less than $12 per hour. In response to the higher wage, 1,600 workers look for jobs with the city. At this higher wage, the city, as an employer, is willing to hire only 700 workers. At the price floor, the quantity supplied exceeds the quantity demanded, and a surplus of labor exists in this market. For workers who continue to have a job at a higher salary, life has improved. For those who were willing to work at the old wage rate but lost their jobs with the wage increase, life has not improved. Table shows the differences in supply and demand at different wages.
| Wage | Quantity Labor Demanded | Quantity Labor Supplied |
|---|---|---|
| $8/hr | 1,900 | 500 |
| $9/hr | 1,500 | 900 |
| $10/hr | 1,200 | 1,200 |
| $11/hr | 900 | 1,400 |
| $12/hr | 700 | 1,600 |
| $13/hr | 500 | 1,800 |
| $14/hr | 400 | 1,900 |
The Minimum Wage as an Example of a Price Floor
The U.S. minimum wage is a price floor that is set either very close to the equilibrium wage or even slightly below it. About 1% of American workers are actually paid the minimum wage. In other words, the vast majority of the U.S. labor force has its wages determined in the labor market, not as a result of the government price floor. However, for workers with low skills and little experience, like those without a high school diploma or teenagers, the minimum wage is quite important. In many cities, the federal minimum wage is apparently below the market price for unskilled labor, because employers offer more than the minimum wage to checkout clerks and other low-skill workers without any government prodding.
Economists have attempted to estimate how much the minimum wage reduces the quantity demanded of low-skill labor. A typical result of such studies is that a 10% increase in the minimum wage would decrease the hiring of unskilled workers by 1 to 2%, which seems a relatively small reduction. In fact, some studies have even found no effect of a higher minimum wage on employment at certain times and places—although these studies are controversial.
Let’s suppose that the minimum wage lies just slightly below the equilibrium wage level. Wages could fluctuate according to market forces above this price floor, but they would not be allowed to move beneath the floor. In this situation, the price floor minimum wage is nonbinding —that is, the price floor is not determining the market outcome. Even if the minimum wage moves just a little higher, it will still have no effect on the quantity of employment in the economy, as long as it remains below the equilibrium wage. Even if the government increases minimum wage by enough so that it rises slightly above the equilibrium wage and becomes binding, there will be only a small excess supply gap between the quantity demanded and quantity supplied.
These insights help to explain why U.S. minimum wage laws have historically had only a small impact on employment. Since the minimum wage has typically been set close to the equilibrium wage for low-skill labor and sometimes even below it, it has not had a large effect in creating an excess supply of labor. However, if the minimum wage increased dramatically—say, if it doubled to match the living wages that some U.S. cities have considered—then its impact on reducing the quantity demanded of employment would be far greater. As of 2017, many U.S. states are set to increase their minimum wage to $15 per hour. We will see what happens. The following Clear It Up feature describes in greater detail some of the arguments for and against changes to minimum wage.
What’s the harm in raising the minimum wage?
Because of the law of demand, a higher required wage will reduce the amount of low-skill employment either in terms of employees or in terms of work hours. Although there is controversy over the numbers, let’s say for the sake of the argument that a 10% rise in the minimum wage will reduce the employment of low-skill workers by 2%. Does this outcome mean that raising the minimum wage by 10% is bad public policy? Not necessarily.
If 98% of those receiving the minimum wage have a pay increase of 10%, but 2% of those receiving the minimum wage lose their jobs, are the gains for society as a whole greater than the losses? The answer is not clear, because job losses, even for a small group, may cause more pain than modest income gains for others. For one thing, we need to consider which minimum wage workers are losing their jobs. If the 2% of minimum wage workers who lose their jobs are struggling to support families, that is one thing. If those who lose their job are high school students picking up spending money over summer vacation, that is something else.
Another complexity is that many minimum wage workers do not work full-time for an entire year. Imagine a minimum wage worker who holds different part-time jobs for a few months at a time, with bouts of unemployment in between. The worker in this situation receives the 10% raise in the minimum wage when working, but also ends up working 2% fewer hours during the year because the higher minimum wage reduces how much employers want people to work. Overall, this worker’s income would rise because the 10% pay raise would more than offset the 2% fewer hours worked.
Of course, these arguments do not prove that raising the minimum wage is necessarily a good idea either. There may well be other, better public policy options for helping low-wage workers. (The Poverty and Economic Inequality chapter discusses some possibilities.) The lesson from this maze of minimum wage arguments is that complex social problems rarely have simple answers. Even those who agree on how a proposed economic policy affects quantity demanded and quantity supplied may still disagree on whether the policy is a good idea.
Concepts and Summary
In the labor market, households are on the supply side of the market and firms are on the demand side. In the market for financial capital, households and firms can be on either side of the market: they are suppliers of financial capital when they save or make financial investments, and demanders of financial capital when they borrow or receive financial investments.
In the demand and supply analysis of labor markets, we can measure the price by the annual salary or hourly wage received. We can measure the quantity of labor various ways, like number of workers or the number of hours worked.
Factors that can shift the demand curve for labor include: a change in the quantity demanded of the product that the labor produces; a change in the production process that uses more or less labor; and a change in government policy that affects the quantity of labor that firms wish to hire at a given wage. Demand can also increase or decrease (shift) in response to: workers’ level of education and training, technology, the number of companies, and availability and price of other inputs.
The main factors that can shift the supply curve for labor are: how desirable a job appears to workers relative to the alternatives, government policy that either restricts or encourages the quantity of workers trained for the job, the number of workers in the economy, and required education.
Self-Check Questions
In the labor market, what causes a movement along the demand curve? What causes a shift in the demand curve?
Hint:
Changes in the wage rate (the price of labor) cause a movement along the demand curve. A change in anything else that affects demand for labor (e.g., changes in output, changes in the production process that use more or less labor, government regulation) causes a shift in the demand curve.
In the labor market, what causes a movement along the supply curve? What causes a shift in the supply curve?
Hint:
Changes in the wage rate (the price of labor) cause a movement along the supply curve. A change in anything else that affects supply of labor (e.g., changes in how desirable the job is perceived to be, government policy to promote training in the field) causes a shift in the supply curve.
Why is a living wage considered a price floor? Does imposing a living wage have the same outcome as a minimum wage?
Hint:
Since a living wage is a suggested minimum wage, it acts like a price floor (assuming, of course, that it is followed). If the living wage is binding, it will cause an excess supply of labor at that wage rate.
Review Questions
What is the “price” commonly called in the labor market?
Are households demanders or suppliers in the goods market? Are firms demanders or suppliers in the goods market? What about the labor market and the financial market?
Name some factors that can cause a shift in the demand curve in labor markets.
Name some factors that can cause a shift in the supply curve in labor markets.
Critical Thinking Questions
Other than the demand for labor, what would be another example of a “derived demand?”
Suppose that a 5% increase in the minimum wage causes a 5% reduction in employment. How would this affect employers and how would it affect workers? In your opinion, would this be a good policy?
Under what circumstances would a minimum wage be a nonbinding price floor? Under what circumstances would a living wage be a binding price floor?
Problems
Identify each of the following as involving either demand or supply. Draw a circular flow diagram and label the flows A through F. (Some choices can be on both sides of the goods market.)
- Households in the labor market
- Firms in the goods market
- Firms in the financial market
- Households in the goods market
- Firms in the labor market
- Households in the financial market
Predict how each of the following events will raise or lower the equilibrium wage and quantity of oil workers in Texas. In each case, sketch a demand and supply diagram to illustrate your answer.
- The price of oil rises.
- New oil-drilling equipment is invented that is cheap and requires few workers to run.
- Several major companies that do not drill oil open factories in Texas, offering many well-paid jobs outside the oil industry.
- Government imposes costly new regulations to make oil-drilling a safer job.
References
American Community Survey. 2012. "School Enrollment and Work Status: 2011." Accessed April 13, 2015. http://www.census.gov/prod/2013pubs/acsbr11-14.pdf.
National Center for Educational Statistics. “Digest of Education Statistics.” (2008 and 2010). Accessed December 11, 2013. nces.ed.gov.
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https://oercommons.org/courseware/lesson/28789/overview
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Demand and Supply in Financial Markets
Overview
By the end of this section, you will be able to:
- Identify the demanders and suppliers in a financial market
- Explain how interest rates can affect supply and demand
- Analyze the economic effects of U.S. debt in terms of domestic financial markets
- Explain the role of price ceilings and usury laws in the U.S.
United States' households, institutions, and domestic businesses saved almost $1.3 trillion in 2015. Where did that savings go and how was it used? Some of the savings ended up in banks, which in turn loaned the money to individuals or businesses that wanted to borrow money. Some was invested in private companies or loaned to government agencies that wanted to borrow money to raise funds for purposes like building roads or mass transit. Some firms reinvested their savings in their own businesses.
In this section, we will determine how the demand and supply model links those who wish to supply financial capital (i.e., savings) with those who demand financial capital (i.e., borrowing). Those who save money (or make financial investments, which is the same thing), whether individuals or businesses, are on the supply side of the financial market. Those who borrow money are on the demand side of the financial market. For a more detailed treatment of the different kinds of financial investments like bank accounts, stocks and bonds, see the Financial Markets chapter.
Who Demands and Who Supplies in Financial Markets?
In any market, the price is what suppliers receive and what demanders pay. In financial markets, those who supply financial capital through saving expect to receive a rate of return, while those who demand financial capital by receiving funds expect to pay a rate of return. This rate of return can come in a variety of forms, depending on the type of investment.
The simplest example of a rate of return is the interest rate. For example, when you supply money into a savings account at a bank, you receive interest on your deposit. The interest the bank pays you as a percent of your deposits is the interest rate. Similarly, if you demand a loan to buy a car or a computer, you will need to pay interest on the money you borrow.
Let’s consider the market for borrowing money with credit cards. In 2015, almost 200 million Americans were cardholders. Credit cards allow you to borrow money from the card's issuer, and pay back the borrowed amount plus interest, although most allow you a period of time in which you can repay the loan without paying interest. A typical credit card interest rate ranges from 12% to 18% per year. In May 2016, Americans had about $943 billion outstanding in credit card debts. About half of U.S. families with credit cards report that they almost always pay the full balance on time, but one-quarter of U.S. families with credit cards say that they “hardly ever” pay off the card in full. In fact, in 2014, 56% of consumers carried an unpaid balance in the last 12 months. Let’s say that, on average, the annual interest rate for credit card borrowing is 15% per year. Thus, Americans pay tens of billions of dollars every year in interest on their credit cards—plus basic fees for the credit card or fees for late payments.
Figure illustrates demand and supply in the financial market for credit cards. The horizontal axis of the financial market shows the quantity of money loaned or borrowed in this market. The vertical or price axis shows the rate of return, which in the case of credit card borrowing we can measure with an interest rate. Table shows the quantity of financial capital that consumers demand at various interest rates and the quantity that credit card firms (often banks) are willing to supply.
| Interest Rate (%) | Quantity of Financial Capital Demanded (Borrowing) ($ billions) | Quantity of Financial Capital Supplied (Lending) ($ billions) |
|---|---|---|
| 11 | $800 | $420 |
| 13 | $700 | $510 |
| 15 | $600 | $600 |
| 17 | $550 | $660 |
| 19 | $500 | $720 |
| 21 | $480 | $750 |
The laws of demand and supply continue to apply in the financial markets. According to the law of demand, a higher rate of return (that is, a higher price) will decrease the quantity demanded. As the interest rate rises, consumers will reduce the quantity that they borrow. According to the law of supply, a higher price increases the quantity supplied. Consequently, as the interest rate paid on credit card borrowing rises, more firms will be eager to issue credit cards and to encourage customers to use them. Conversely, if the interest rate on credit cards falls, the quantity of financial capital supplied in the credit card market will decrease and the quantity demanded will fall.
Equilibrium in Financial Markets
In the financial market for credit cards in Figure, the supply curve (S) and the demand curve (D) cross at the equilibrium point (E). The equilibrium occurs at an interest rate of 15%, where the quantity of funds demanded and the quantity supplied are equal at an equilibrium quantity of $600 billion.
If the interest rate (remember, this measures the “price” in the financial market) is above the equilibrium level, then an excess supply, or a surplus, of financial capital will arise in this market. For example, at an interest rate of 21%, the quantity of funds supplied increases to $750 billion, while the quantity demanded decreases to $480 billion. At this above-equilibrium interest rate, firms are eager to supply loans to credit card borrowers, but relatively few people or businesses wish to borrow. As a result, some credit card firms will lower the interest rates (or other fees) they charge to attract more business. This strategy will push the interest rate down toward the equilibrium level.
If the interest rate is below the equilibrium, then excess demand or a shortage of funds occurs in this market. At an interest rate of 13%, the quantity of funds credit card borrowers demand increases to $700 billion, but the quantity credit card firms are willing to supply is only $510 billion. In this situation, credit card firms will perceive that they are overloaded with eager borrowers and conclude that they have an opportunity to raise interest rates or fees. The interest rate will face economic pressures to creep up toward the equilibrium level.
The FRED database publishes some two dozen measures of interest rates, including interest rates on credit cards, automobile loans, personal loans, mortgage loans, and more. You can find these at the FRED website.
Shifts in Demand and Supply in Financial Markets
Those who supply financial capital face two broad decisions: how much to save, and how to divide up their savings among different forms of financial investments. We will discuss each of these in turn.
Participants in financial markets must decide when they prefer to consume goods: now or in the future. Economists call this intertemporal decision making because it involves decisions across time. Unlike a decision about what to buy from the grocery store, people make investment or savings decisions across a period of time, sometimes a long period.
Most workers save for retirement because their income in the present is greater than their needs, while the opposite will be true once they retire. Thus, they save today and supply financial markets. If their income increases, they save more. If their perceived situation in the future changes, they change the amount of their saving. For example, there is some evidence that Social Security, the program that workers pay into in order to qualify for government checks after retirement, has tended to reduce the quantity of financial capital that workers save. If this is true, Social Security has shifted the supply of financial capital at any interest rate to the left.
By contrast, many college students need money today when their income is low (or nonexistent) to pay their college expenses. As a result, they borrow today and demand from financial markets. Once they graduate and become employed, they will pay back the loans. Individuals borrow money to purchase homes or cars. A business seeks financial investment so that it has the funds to build a factory or invest in a research and development project that will not pay off for five years, ten years, or even more. Thus, when consumers and businesses have greater confidence that they will be able to repay in the future, the quantity demanded of financial capital at any given interest rate will shift to the right.
For example, in the technology boom of the late 1990s, many businesses became extremely confident that investments in new technology would have a high rate of return, and their demand for financial capital shifted to the right. Conversely, during the 2008 and 2009 Great Recession, their demand for financial capital at any given interest rate shifted to the left.
To this point, we have been looking at saving in total. Now let us consider what affects saving in different types of financial investments. In deciding between different forms of financial investments, suppliers of financial capital will have to consider the rates of return and the risks involved. Rate of return is a positive attribute of investments, but risk is a negative. If Investment A becomes more risky, or the return diminishes, then savers will shift their funds to Investment B—and the supply curve of financial capital for Investment A will shift back to the left while the supply curve of capital for Investment B shifts to the right.
The United States as a Global Borrower
In the global economy, trillions of dollars of financial investment cross national borders every year. In the early 2000s, financial investors from foreign countries were investing several hundred billion dollars per year more in the U.S. economy than U.S. financial investors were investing abroad. The following Work It Out deals with one of the macroeconomic concerns for the U.S. economy in recent years.
The Effect of Growing U.S. Debt
Imagine that foreign investors viewed the U.S. economy as a less desirable place to put their money because of fears about the growth of the U.S. public debt. Using the four-step process for analyzing how changes in supply and demand affect equilibrium outcomes, how would increased U.S. public debt affect the equilibrium price and quantity for capital in U.S. financial markets?
Step 1. Draw a diagram showing demand and supply for financial capital that represents the original scenario in which foreign investors are pouring money into the U.S. economy. Figure shows a demand curve, D, and a supply curve, S, where the supply of capital includes the funds arriving from foreign investors. The original equilibrium E0 occurs at interest rate R0 and quantity of financial investment Q0.
Step 2. Will the diminished confidence in the U.S. economy as a place to invest affect demand or supply of financial capital? Yes, it will affect supply. Many foreign investors look to the U.S. financial markets to store their money in safe financial vehicles with low risk and stable returns. Diminished confidence means U.S. financial assets will be seen as more risky.
Step 3. Will supply increase or decrease? When the enthusiasm of foreign investors’ for investing their money in the U.S. economy diminishes, the supply of financial capital shifts to the left. Figure shows the supply curve shift from S0 to S1.
Step 4. Thus, foreign investors’ diminished enthusiasm leads to a new equilibrium, E1, which occurs at the higher interest rate, R1, and the lower quantity of financial investment, Q1. In short, U.S. borrowers will have to pay more interest on their borrowing.
The economy has experienced an enormous inflow of foreign capital. According to the U.S. Bureau of Economic Analysis, by the third quarter of 2015, U.S. investors had accumulated $23.3 trillion of foreign assets, but foreign investors owned a total of $30.6 trillion of U.S. assets. If foreign investors were to pull their money out of the U.S. economy and invest elsewhere in the world, the result could be a significantly lower quantity of financial investment in the United States, available only at a higher interest rate. This reduced inflow of foreign financial investment could impose hardship on U.S. consumers and firms interested in borrowing.
In a modern, developed economy, financial capital often moves invisibly through electronic transfers between one bank account and another. Yet we can analyze these flows of funds with the same tools of demand and supply as markets for goods or labor.
Price Ceilings in Financial Markets: Usury Laws
As we noted earlier, about 200 million Americans own credit cards, and their interest payments and fees total tens of billions of dollars each year. It is little wonder that political pressures sometimes arise for setting limits on the interest rates or fees that credit card companies charge. The firms that issue credit cards, including banks, oil companies, phone companies, and retail stores, respond that the higher interest rates are necessary to cover the losses created by those who borrow on their credit cards and who do not repay on time or at all. These companies also point out that cardholders can avoid paying interest if they pay their bills on time.
Consider the credit card market as Figure illustrators. In this financial market, the vertical axis shows the interest rate (which is the price in the financial market). Demanders in the credit card market are households and businesses. Suppliers are the companies that issue credit cards. This figure does not use specific numbers, which would be hypothetical in any case, but instead focuses on the underlying economic relationships. Imagine a law imposes a price ceiling that holds the interest rate charged on credit cards at the rate Rc, which lies below the interest rate R0 that would otherwise have prevailed in the market. The horizontal dashed line at interest rate Rc in Figure shows the price ceiling. The demand and supply model predicts that at the lower price ceiling interest rate, the quantity demanded of credit card debt will increase from its original level of Q0 to Qd; however, the quantity supplied of credit card debt will decrease from the original Q0 to Qs. At the price ceiling (Rc), quantity demanded will exceed quantity supplied. Consequently, a number of people who want to have credit cards and are willing to pay the prevailing interest rate will find that companies are unwilling to issue cards to them. The result will be a credit shortage.
Many states do have usury laws, which impose an upper limit on the interest rate that lenders can charge. However, in many cases these upper limits are well above the market interest rate. For example, if the interest rate is not allowed to rise above 30% per year, it can still fluctuate below that level according to market forces. A price ceiling that is set at a relatively high level is nonbinding, and it will have no practical effect unless the equilibrium price soars high enough to exceed the price ceiling.
Key Concepts and Summary
In the demand and supply analysis of financial markets, the “price” is the rate of return or the interest rate received. We measure the quantity by the money that flows from those who supply financial capital to those who demand it.
Two factors can shift the supply of financial capital to a certain investment: if people want to alter their existing levels of consumption, and if the riskiness or return on one investment changes relative to other investments. Factors that can shift demand for capital include business confidence and consumer confidence in the future—since financial investments received in the present are typically repaid in the future.
Self-Check Questions
In the financial market, what causes a movement along the demand curve? What causes a shift in the demand curve?
Hint:
Changes in the interest rate (i.e., the price of financial capital) cause a movement along the demand curve. A change in anything else (non-price variable) that affects demand for financial capital (e.g., changes in confidence about the future, changes in needs for borrowing) would shift the demand curve.
In the financial market, what causes a movement along the supply curve? What causes a shift in the supply curve?
Hint:
Changes in the interest rate (i.e., the price of financial capital) cause a movement along the supply curve. A change in anything else that affects the supply of financial capital (a non-price variable) such as income or future needs would shift the supply curve.
If a usury law limits interest rates to no more than 35%, what would the likely impact be on the amount of loans made and interest rates paid?
Hint:
If market interest rates stay in their normal range, an interest rate limit of 35% would not be binding. If the equilibrium interest rate rose above 35%, the interest rate would be capped at that rate, and the quantity of loans would be lower than the equilibrium quantity, causing a shortage of loans.
Which of the following changes in the financial market will lead to a decline in interest rates:
- a rise in demand
- a fall in demand
- a rise in supply
- a fall in supply
Hint:
b and c will lead to a fall in interest rates. At a lower demand, lenders will not be able to charge as much, and with more available lenders, competition for borrowers will drive rates down.
Which of the following changes in the financial market will lead to an increase in the quantity of loans made and received:
- a rise in demand
- a fall in demand
- a rise in supply
- a fall in supply
Hint:
a and c will increase the quantity of loans. More people who want to borrow will result in more loans being given, as will more people who want to lend.
Review Questions
How do economists define equilibrium in financial markets?
What would be a sign of a shortage in financial markets?
Would usury laws help or hinder resolution of a shortage in financial markets?
Critical Thinking Questions
Suppose the U.S. economy began to grow more rapidly than other countries in the world. What would be the likely impact on U.S. financial markets as part of the global economy?
If the government imposed a federal interest rate ceiling of 20% on all loans, who would gain and who would lose?
Problems
Predict how each of the following economic changes will affect the equilibrium price and quantity in the financial market for home loans. Sketch a demand and supply diagram to support your answers.
- The number of people at the most common ages for home-buying increases.
- People gain confidence that the economy is growing and that their jobs are secure.
- Banks that have made home loans find that a larger number of people than they expected are not repaying those loans.
- Because of a threat of a war, people become uncertain about their economic future.
- The overall level of saving in the economy diminishes.
- The federal government changes its bank regulations in a way that makes it cheaper and easier for banks to make home loans.
Table shows the amount of savings and borrowing in a market for loans to purchase homes, measured in millions of dollars, at various interest rates. What is the equilibrium interest rate and quantity in the capital financial market? How can you tell? Now, imagine that because of a shift in the perceptions of foreign investors, the supply curve shifts so that there will be $10 million less supplied at every interest rate. Calculate the new equilibrium interest rate and quantity, and explain why the direction of the interest rate shift makes intuitive sense.
| Interest Rate | Qs | Qd |
|---|---|---|
| 5% | 130 | 170 |
| 6% | 135 | 150 |
| 7% | 140 | 140 |
| 8% | 145 | 135 |
| 9% | 150 | 125 |
| 10% | 155 | 110 |
References
CreditCards.com. 2013. http://www.creditcards.com/credit-card-news/credit-card-industry-facts-personal-debt-statistics-1276.php.
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https://oercommons.org/courseware/lesson/28790/overview
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The Market System as an Efficient Mechanism for Information
Overview
By the end of this section, you will be able to:
- Apply demand and supply models to analyze prices and quantities
- Explain the effects of price controls on the equilibrium of prices and quantities
Prices exist in markets for goods and services, for labor, and for financial capital. In all of these markets, prices serve as a remarkable social mechanism for collecting, combining, and transmitting information that is relevant to the market—namely, the relationship between demand and supply—and then serving as messengers to convey that information to buyers and sellers. In a market-oriented economy, no government agency or guiding intelligence oversees the set of responses and interconnections that result from a change in price. Instead, each consumer reacts according to that person’s preferences and budget set, and each profit-seeking producer reacts to the impact on its expected profits. The following Clear It Up feature examines the demand and supply models.
Why are demand and supply curves important?
The demand and supply model is the second fundamental diagram for this course. (The opportunity set model that we introduced in the Choice in a World of Scarcity chapter was the first.) Just as it would be foolish to try to learn the arithmetic of long division by memorizing every possible combination of numbers that can be divided by each other, it would be foolish to try to memorize every specific example of demand and supply in this chapter, this textbook, or this course. Demand and supply is not primarily a list of examples. It is a model to analyze prices and quantities. Even though demand and supply diagrams have many labels, they are fundamentally the same in their logic. Your goal should be to understand the underlying model so you can use it to analyze any market.
Figure displays a generic demand and supply curve. The horizontal axis shows the different measures of quantity: a quantity of a good or service, or a quantity of labor for a given job, or a quantity of financial capital. The vertical axis shows a measure of price: the price of a good or service, the wage in the labor market, or the rate of return (like the interest rate) in the financial market.
The demand and supply model can explain the existing levels of prices, wages, and rates of return. To carry out such an analysis, think about the quantity that will be demanded at each price and the quantity that will be supplied at each price—that is, think about the shape of the demand and supply curves—and how these forces will combine to produce equilibrium.
We can also use demand and supply to explain how economic events will cause changes in prices, wages, and rates of return. There are only four possibilities: the change in any single event may cause the demand curve to shift right or to shift left, or it may cause the supply curve to shift right or to shift left. The key to analyzing the effect of an economic event on equilibrium prices and quantities is to determine which of these four possibilities occurred. The way to do this correctly is to think back to the list of factors that shift the demand and supply curves. Note that if more than one variable is changing at the same time, the overall impact will depend on the degree of the shifts. When there are multiple variables, economists isolate each change and analyze it independently.
An increase in the price of some product signals consumers that there is a shortage; therefore, they may want to economize on buying this product. For example, if you are thinking about taking a plane trip to Hawaii, but the ticket turns out to be expensive during the week you intend to go, you might consider other weeks when the ticket might be cheaper. The price could be high because you were planning to travel during a holiday when demand for traveling is high. Maybe the cost of an input like jet fuel increased or the airline has raised the price temporarily to see how many people are willing to pay it. Perhaps all of these factors are present at the same time. You do not need to analyze the market and break down the price change into its underlying factors. You just have to look at the ticket price and decide whether and when to fly.
In the same way, price changes provide useful information to producers. Imagine the situation of a farmer who grows oats and learns that the price of oats has risen. The higher price could be due to an increase in demand caused by a new scientific study proclaiming that eating oats is especially healthful. Perhaps the price of a substitute grain, like corn, has risen, and people have responded by buying more oats. The oat farmer does not need to know the details. The farmer only needs to know that the price of oats has risen and that it will be profitable to expand production as a result.
The actions of individual consumers and producers as they react to prices overlap and interlock in markets for goods, labor, and financial capital. A change in any single market is transmitted through these multiple interconnections to other markets. The vision of the role of flexible prices helping markets to reach equilibrium and linking different markets together helps to explain why price controls can be so counterproductive. Price controls are government laws that serve to regulate prices rather than allow the various markets to determine prices. There is an old proverb: “Don’t kill the messenger.” In ancient times, messengers carried information between distant cities and kingdoms. When they brought bad news, there was an emotional impulse to kill the messenger. However, killing the messenger did not kill the bad news. Moreover, killing the messenger had an undesirable side effect: Other messengers would refuse to bring news to that city or kingdom, depriving its citizens of vital information.
Those who seek price controls are trying to kill the messenger—or at least to stifle an unwelcome message that prices are bringing about the equilibrium level of price and quantity. However, price controls do nothing to affect the underlying forces of demand and supply, and this can have serious repercussions. During China’s “Great Leap Forward” in the late 1950s, the government kept food prices artificially low, with the result that 30 to 40 million people died of starvation because the low prices depressed farm production. This was communist party leader Mao Zedong's social and economic campaign to rapidly transform the country from an agrarian economy to a socialist society through rapid industrialization and collectivization. Changes in demand and supply will continue to reveal themselves through consumers’ and producers’ behavior. Immobilizing the price messenger through price controls will deprive everyone in the economy of critical information. Without this information, it becomes difficult for everyone—buyers and sellers alike—to react in a flexible and appropriate manner as changes occur throughout the economy.
Baby Boomers Come of Age
The theory of supply and demand can explain what happens in the labor markets and suggests that the demand for nurses will increase as healthcare needs of baby boomers increase, as Figure shows. The impact of that increase will result in an average salary higher than the $67,490 earned in 2015 referenced in the first part of this case. The new equilibrium (E1) will be at the new equilibrium price (Pe1).Equilibrium quantity will also increase from Qe0 to Qe1.
Suppose that as the demand for nurses increases, the supply shrinks due to an increasing number of nurses entering retirement and increases in the tuition of nursing degrees. The leftward shift of the supply curve in Figure captures the impact of a decreasing supply of nurses. The shifts in the two curves result in higher salaries for nurses, but the overall impact in the quantity of nurses is uncertain, as it depends on the relative shifts of supply and demand.
While we do not know if the number of nurses will increase or decrease relative to their initial employment, we know they will have higher salaries.
Key Concepts and Summary
The market price system provides a highly efficient mechanism for disseminating information about relative scarcities of goods, services, labor, and financial capital. Market participants do not need to know why prices have changed, only that the changes require them to revisit previous decisions they made about supply and demand. Price controls hide information about the true scarcity of products and thereby cause misallocation of resources.
Self-Check Questions
Identify the most accurate statement. A price floor will have the largest effect if it is set:
- substantially above the equilibrium price
- slightly above the equilibrium price
- slightly below the equilibrium price
- substantially below the equilibrium price
Sketch all four of these possibilities on a demand and supply diagram to illustrate your answer.
Hint:
A price floor prevents a price from falling below a certain level, but has no effect on prices above that level. It will have its biggest effect in creating excess supply (as measured by the entire area inside the dotted lines on the graph, from D to S) if it is substantially above the equilibrium price. This is illustrated in the following figure.
It will have a lesser effect if it is slightly above the equilibrium price. This is illustrated in the next figure.
It will have no effect if it is set either slightly or substantially below the equilibrium price, since an equilibrium price above a price floor will not be affected by that price floor. The following figure illustrates these situations.
A price ceiling will have the largest effect:
- substantially below the equilibrium price
- slightly below the equilibrium price
- substantially above the equilibrium price
- slightly above the equilibrium price
Sketch all four of these possibilities on a demand and supply diagram to illustrate your answer.
Hint:
A price ceiling prevents a price from rising above a certain level, but has no effect on prices below that level. It will have its biggest effect in creating excess demand if it is substantially below the equilibrium price. The following figure illustrates these situations.
When the price ceiling is set substantially or slightly above the equilibrium price, it will have no effect on creating excess demand. The following figure illustrates these situations.
Select the correct answer. A price floor will usually shift:
- demand
- supply
- both
- neither
Illustrate your answer with a diagram.
Hint:
Neither. A shift in demand or supply means that at every price, either a greater or a lower quantity is demanded or supplied. A price floor does not shift a demand curve or a supply curve. However, if the price floor is set above the equilibrium, it will cause the quantity supplied on the supply curve to be greater than the quantity demanded on the demand curve, leading to excess supply.
Select the correct answer. A price ceiling will usually shift:
- demand
- supply
- both
- neither
Hint:
Neither. A shift in demand or supply means that at every price, either a greater or a lower quantity is demanded or supplied. A price ceiling does not shift a demand curve or a supply curve. However, if the price ceiling is set below the equilibrium, it will cause the quantity demanded on the demand curve to be greater than the quantity supplied on the supply curve, leading to excess demand.
Review Question
Whether the product market or the labor market, what happens to the equilibrium price and quantity for each of the four possibilities: increase in demand, decrease in demand, increase in supply, and decrease in supply.
Critical Thinking Questions
Why are the factors that shift the demand for a product different from the factors that shift the demand for labor? Why are the factors that shift the supply of a product different from those that shift the supply of labor?
During a discussion several years ago on building a pipeline to Alaska to carry natural gas, the U.S. Senate passed a bill stipulating that there should be a guaranteed minimum price for the natural gas that would flow through the pipeline. The thinking behind the bill was that if private firms had a guaranteed price for their natural gas, they would be more willing to drill for gas and to pay to build the pipeline.
- Using the demand and supply framework, predict the effects of this price floor on the price, quantity demanded, and quantity supplied.
- With the enactment of this price floor for natural gas, what are some of the likely unintended consequences in the market?
- Suggest some policies other than the price floor that the government can pursue if it wishes to encourage drilling for natural gas and for a new pipeline in Alaska.
Problems
Imagine that to preserve the traditional way of life in small fishing villages, a government decides to impose a price floor that will guarantee all fishermen a certain price for their catch.
- Using the demand and supply framework, predict the effects on the price, quantity demanded, and quantity supplied.
- With the enactment of this price floor for fish, what are some of the likely unintended consequences in the market?
- Suggest some policies other than the price floor to make it possible for small fishing villages to continue.
What happens to the price and the quantity bought and sold in the cocoa market if countries producing cocoa experience a drought and a new study is released demonstrating the health benefits of cocoa? Illustrate your answer with a demand and supply graph.
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"url": "https://oercommons.org/courseware/lesson/28790/overview",
"title": "Principles of Macroeconomics 2e, Labor and Financial Markets",
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https://oercommons.org/courseware/lesson/25867/overview
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Chapter 10: Active Listening in the Classroom
Overview
Learning Framework: Effective Strategies for College Success
Chapter 10: Active Listening in the Classroom
Learning Objectives
By the end of this chapter, you will be able to:
- Explain why regular class attendance class is important.
- Understand the stages of the listening process.
- Identify effective listening strategies.
- Identify effective participation strategies.
- Identify strategies for obtaining content from a class you missed.
- Evaluate different teaching styles and how your personal learning style fit with each.
- Define active learning.
Active Listening in the Classroom
Active Listening in the Classroom
Why Go To Class?
Students don’t always want to go to class. They may have required classes that they find difficult or don’t enjoy, or they may feel overwhelmed by other commitments or feel tired if they have early morning classes. However, even if instructors allow a certain number of unexcused absences, you should aim to attend every class session. Class attendance enhances class performance in the following ways:
- Class participation: If you don’t attend class, you can’t participate in-class activities. Class activities are usually part of your final grade, and they can help you apply concepts you learn from lectures and reading assignments.
- Class interaction: If you rely on learning on your own (by doing the reading assignments outside of class, for example), you’ll miss out on class discussions with fellow students. Your classmates will often have the same questions as you, so going to class enables you to learn from them and ask your instructor about topics you all find difficult.
- Interaction with the instructor: There is a reason why classes are taught by instructors. Instructors specialize in the subjects they teach, and they can provide extra insight and perspective on the material you’re studying. Going to class gives you the chance to take notes and ask questions about the lectures. Also, the more you participate, the more your instructors will come to know you and be aware of any help or support you might need. This will make you feel more comfortable to approach them outside of class if you need advice or are struggling with the course material.
- Increased learning: Even though you will typically spend more time on coursework outside of the classroom, this makes class sessions even more valuable. Typically, in-class time will be devoted to the most challenging or key concepts covered in your textbooks. It’s important to know what these are so you can master them—also they’re likely to show up on exams.
Let’s compare students with different attitudes toward their classes:
Carlos wants to get through college, and he knows he needs the degree to get a decent job, but he’s just not that into it. He's never thought of himself as a good student, and that hasn’t changed much in college. He has trouble paying attention in those big lecture classes, which mostly seem pretty boring. He’s pretty sure he can pass all his courses as long as he takes the time to study before tests. It doesn’t bother him to skip classes when he’s studying for a test in a different class or finishing a reading assignment he didn’t get around to earlier. He does make it through his first year with a passing grade in every class, even those he didn’t go to very often. Then he fails the midterm exam in his first sophomore class. Depressed, he skips the next couple classes, then feels guilty and goes to the next. It’s even harder to stay awake because now he has no idea what they’re talking about. It’s too late to drop the course, and even a hard night of studying before the final isn’t enough to pass the course. In two other classes, he just barely passes. He has no idea what classes to take next term and is starting to think that maybe he’ll drop out for now.
Karen wants to have a good time in college and still do well enough to get a good job in business afterward. Her sorority keeps a file of class notes for her big lecture classes, and from talking to others and reviewing these notes, she’s discovered she can skip almost half of those big classes and still get a B or C on the tests. She stays focused on her grades, and because she has a good memory, she’s able to maintain OK grades. She doesn’t worry about talking to her instructors outside of class because she can always find out what she needs from another student. In her sophomore year, she has a quick conversation with her academic advisor and chooses her major. Those classes are smaller, and she goes to most of them, but she feels she’s pretty much figured out how it works and can usually still get the grade. In her senior year, she starts working on her résumé and asks other students in her major which instructors write the best letters of recommendation. She’s sure her college degree will land her a good job.
Logan enjoys their classes, even when they have to get up early after working or studying late the night before. They sometimes get so excited by something they learn in class that they rush up to the instructor after class to ask a question. In class discussions, they are not usually the first to speak out, but by the time another student has given an opinion, they have had time to organize their thoughts and enjoys arguing their ideas. Nearing the end of their sophomore year and unsure of what to major in given their many interests, they talk things over with one of their favorite instructors, whom they have gotten to know through office visits. The instructor gives Logan some insights into careers in that field and helps them explore their interests. Logan takes two more courses with this instructor over the next year, and they are comfortable in their senior year going to him to ask for a job reference. When they do, they're surprised and thrilled when he urges them to apply for a high-level paid internship with a company in the field—that happens to be run by a friend of his.
Think about the differences in the attitudes of these three students and how they approach their classes. One’s attitude toward learning, toward going to class, and toward the whole college experience is a huge factor in how successful a student will be. Make it your goal to attend every class; don’t even think about not going. Going to class is the first step in engaging in your education by interacting with the instructor and other students. Here are some reasons why it’s important to attend every class:
- Miss a class and you’ll miss something, even if you never know it. Even if a friend gives you notes for the class, they cannot contain everything said or shown by the instructor or written on the board for emphasis or questioned or commented on by other students. What you miss might affect your grade or your enthusiasm for the course. Why go to college at all if you’re not going to go to college?
- While some students may say that you don’t have to go to every class to do well on a test, that is very often a myth. Do you want to take that risk?
- Your final grade often reflects how you think about course concepts, and you will think more often and more clearly when engaged in class discussions and hearing the comments of other students. You can’t get this by borrowing class notes from a friend.
- Research shows there is a correlation between absences from class and lower grades. It may be that missing classes causes lower grades or that students with lower grades miss more classes. Either way, missing classes and lower grades can be intertwined in a downward spiral of achievement.
- Your instructor will note your absences, even in a large class. In addition to making a poor impression, you reduce your opportunities for future interactions. You might not ask a question the next class because of the potential embarrassment of the instructor saying that was covered in the last class, which you apparently missed. Nothing is more insulting to an instructor than when you skip a class and then show up to ask, “Did I miss anything important?”
- You might be tempted to skip a class because the instructor is “boring,” but it’s more likely that you found the class boring because you weren’t very attentive or didn’t appreciate how the instructor was teaching.
- You paid a lot of money for your tuition. Get your money’s worth!
Stages of the Listening Process
Listening is a skill of critical significance in all aspects of our lives, from maintaining our personal relationships, to getting our jobs done, to taking notes in class, to figuring out which bus to take to the airport. Regardless of how we’re engaged with listening, it’s important to understand that listening involves more than just hearing the words that are directed at us. Listening is an active process by which we make sense of, assess, and respond to what we hear.
The listening process involves five stages: receiving, understanding, evaluating, remembering, and responding. These stages will be discussed in more detail in later sections. An effective listener must hear and identify the speech sounds directed toward them, understand the message of those sounds, critically evaluate or assess that message, remember what’s been said, and respond (either verbally or nonverbally) to information they’ve received.
Effectively engaging in all five stages of the listening process lets us best gather the information we need from the world around us.
Active Listening
Active listening is a particular communication technique that requires the listener to provide feedback on what they hear to the speaker, by way of restating or paraphrasing what they have heard in their own words. The goal of this repetition is to confirm what the listener has heard and to confirm the understanding of both parties. The ability to actively listen demonstrates sincerity, and that nothing is being assumed or taken for granted. Active listening is most often used to improve personal relationships, reduce misunderstandings and conflicts, strengthen cooperation, and foster understanding.
When engaging with a particular speaker, a listener can use several degrees of active listening, each resulting in a different quality of communication with the speaker. This active listening chart shows three main degrees of listening: repeating, paraphrasing, and reflecting.
Active listening can also involve paying attention to the speaker’s behavior and body language. Having the ability to interpret a person’s body language lets the listener develop a more accurate understanding of the speaker’s message.
The Receiving Stage
The first stage of the listening process is the receiving stage, which involves hearing and attending.
Hearing is the physiological process of registering sound waves as they hit the eardrum. As obvious as it may seem, in order to effectively gather information through listening, we must first be able to physically hear what we’re listening to. The clearer the sound, the easier the listening process becomes.
Paired with hearing, attending is the other half of the receiving stage in the listening process. Attending is the process of accurately identifying and interpreting particular sounds we hear as words. The sounds we hear have no meaning until we give them their meaning in context. Listening is an active process that constructs meaning from both verbal and nonverbal messages.
The Challenges of Reception
Listeners are often bombarded with a variety of auditory stimuli all at once, so they must differentiate which of those stimuli are speech sounds and which are not. Effective listening involves being able to focus on speech sounds while disregarding other noise. For instance, a train passenger that hears the captain’s voice over the loudspeaker understands that the captain is speaking, then deciphers what the captain is saying despite other voices in the cabin. Another example is trying to listen to a friend tell a story while walking down a busy street. In order to best listen to what they're saying, the listener needs to ignore the ambient street sounds.
Attending also involves being able to discern human speech, also known as “speech segmentation. “ Identifying auditory stimuli as speech but not being able to break those speech sounds down into sentences and words would be a failure of the listening process. Discerning speech segmentation can be a more difficult activity when the listener is faced with an unfamiliar language.
The Understanding Stage
The second stage in the listening process is the understanding stage. Understanding or comprehension is “shared meaning between parties in a communication transaction” and constitutes the first step in the listening process. This is the stage during which the listener determines the context and meanings of the heard words. Determining the context and meaning of individual words, as well as assigning meaning in language, is essential to understanding sentences. This, in turn, is essential to understanding a speaker’s message.
Once the listener understands the speaker’s main point, they can begin to sort out the rest of the information they are hearing and decide where it belongs in their mental outline. For example, a political candidate listens to her opponent’s arguments to understand what policy decisions that opponent supports.
Before getting the big picture of a message, it can be difficult to focus on what the speaker is saying. Think about walking into a lecture class halfway through. You may immediately understand the words and sentences that you are hearing, but not immediately understand what the lecturer is proving or whether what you’re hearing at the moment is the main point, side note, or digression.
Understanding what we hear is a huge part of our everyday lives, particularly in terms of gathering basic information. In the office, people listen to their superiors for instructions about what they are to do. At school, students listen to teachers to learn new ideas. We listen to political candidates give policy speeches in order to determine who will get our vote. But without understanding what we hear, none of this everyday listening would relay any practical information to us.
One tactic for better understanding a speaker’s meaning is to ask questions. Asking questions allows the listener to fill in any holes they may have in the mental reconstruction of the speaker’s message.
The Evaluating Stage
This stage of the listening process is the one during which the listener assesses the information they received, both qualitatively and quantitatively. Evaluating allows the listener to form an opinion of what they heard and, if necessary, to begin developing a response.
During the evaluating stage, the listener determines whether or not the information they heard and understood from the speaker is well constructed or disorganized, biased or unbiased, true or false, significant or insignificant. They also ascertain how and why the speaker has come up with and conveyed the message that they delivered. This may involve considerations of a speaker’s personal or professional motivations and goals. For example, a listener may determine that a co-worker’s vehement condemnation of another for jamming the copier is factually correct, but may also understand that the co-worker’s child is sick and that may be putting them on edge. A voter who listens to and understands the points made in a political candidate’s stump speech can decide whether or not those points were convincing enough to earn their vote.
The evaluating stage occurs most effectively once the listener fully understands what the speaker is trying to say. While we can, and sometimes do, form opinions of information and ideas that we don’t fully understand—or even that we misunderstand—doing so is not often ideal in the long run. Having a clear understanding of a speaker’s message allows a listener to evaluate that message without getting bogged down in ambiguities or spending unnecessary time and energy addressing points that may be tangential or otherwise non-essential.
This stage of critical analysis is important for a listener in terms of how what they heard will affect their own ideas, decisions, actions, and/or beliefs.
The Remembering Stage
In the listening process, the remembering stage occurs as the listener categorizes and retains the information he’s gathered from the speaker for future access. The result–memory–allows the person to record information about people, objects, and events for later recall. This happens both during and after the speaker’s delivery.
Memory is essential throughout the listening process. We depend on our memory to fill in the blanks when we’re listening and to let us place what we’re hearing at the moment in the context of what we’ve heard before. If, for example, you forgot everything that you heard immediately after you heard it, you would not be able to follow along with what a speaker says, and conversations would be impossible. Moreover, a friend who expresses fear about a dog they see on the sidewalk ahead can help you recall that the friend began the conversation with her childhood memory of being attacked by a dog.
Remembering previous information is critical to moving forward. Similarly, making associations to past remembered information can help a listener understand what they are currently hearing in a wider context. In listening to a lecture about the symptoms of depression, for example, a listener might make a connection to the description of a character in a novel that they read years before.
Using information immediately after receiving it enhances information retention and lessens the forgetting curve or the rate at which we no longer retain information in our memory. Conversely, retention is lessened when we engage in mindless listening, and little effort is made to understand a speaker’s message.
Because everyone has different memories, the speaker and the listener may attach different meanings to the same statement. In this sense, establishing common ground in terms of context is extremely important, both for listeners and speakers.
The Responding Stage
The responding stage is the stage of the listening process wherein the listener provides verbal and/or nonverbal reactions based on short- or long-term memory. Following the remembering stage, a listener can respond to what they hear either verbally or non-verbally. Nonverbal signals can include gestures such as nodding, making eye contact, tapping a pen, fidgeting, scratching or cocking their head, smiling, rolling their eyes, grimacing, or any other body language. These kinds of responses can be displayed purposefully or involuntarily. Responding verbally might involve asking a question, requesting additional information, redirecting or changing the focus of a conversation, cutting off a speaker, or repeating what a speaker has said back to her in order to verify that the received message matches the intended message.
Nonverbal responses like nodding or eye contact allow the listener to communicate their level of interest without interrupting the speaker, thereby preserving the speaker/listener roles. When a listener responds verbally to what they hear and remember—for example, with a question or a comment—the speaker/listener roles are reversed, at least momentarily.
Responding adds action to the listening process, which would otherwise be an outwardly passive process. Oftentimes, the speaker looks for verbal and nonverbal responses from the listener to determine if and how their message is being understood and/or considered. Based on the listener’s responses, the speaker can choose to either adjust or continue with the delivery of her message. For example, if a listener’s brow is furrowed and their arms are crossed, the speaker may determine that they need to lighten their tone to better communicate their point. If a listener is smiling and nodding or asking questions, the speaker may feel that the listener is engaged and her message is being communicated effectively.
Effective Listening Strategies
Too many students try to get the grade just by going to class, maybe a little note-taking, and then cramming through the text right before an exam they feel unprepared for. Sound familiar? This approach may have worked for you in high school where tests and quizzes were more frequent and teachers prepared study guides for you, but colleges require you to take responsibility for your learning and to be better prepared.
Most students simply have not learned how to study and don’t understand how learning works. Learning is actually a cycle of four steps:
- Preparing
- Absorbing
- Capturing
- Reviewing
When you get in the habit of paying attention to this cycle, it becomes relatively easy to study well. But you must use all four steps.
This chapter focuses on listening, a key skill for learning new material. The next chapter focuses on note-taking, the most important skill in the capturing phase of the cycle. These skills are closely related. Good listening skills make you a better note-taker, and taking good notes can help you listen better. Both are key study skills to help you do better in your classes.
The Learning Cycle
Are you a good listener? Most of us like to think we are, but when we really think about it, we recognize that we are often only half-listening. We’re distracted, thinking about other things, or formulating what we are going to say in reaction to what we are hearing before the speaker has even finished. Effective listening is one of the most important learning tools you can have in college. And it is a skill that will benefit you on the job and help your relationships with others. Listening is nothing more than purposefully focusing on what a speaker is saying with the objective of understanding.
This definition is straightforward, but there are some important concepts that deserve a closer look. “Purposefully focusing” implies that you are actively processing what the speaker is saying, not just letting the sounds of their voice register in your senses. “With the objective of understanding” means that you will learn enough about what the speaker is saying to be able to form your own thoughts about the speaker’s message. Listening is an active process, as opposed to hearing, which is passive.
You listen to others in many situations: to interact with friends, to get instructions for a task, or to learn new material. There are two general types of listening situations: where you will be able to interact freely with the speaker (everyday conversations, small discussion classes, business meetings) and where interaction is limited (lectures and Webcasts).
In interactive situations, you should apply the basic principles of active listening. These are not hard to understand, but they are hard to implement and require practice to use them effectively.
Principles of Active Listening
- Focus on what is being said. Give the speaker your undivided attention. Clear your mind of anything else.
- Don’t prejudge or assume you already know the material. You want to understand what the person is saying; you don’t need to agree with it.
- Repeat what you just heard. Confirm with the speaker that what you heard is what they said.
- Ask the speaker to expand or clarify. If you are unsure you understand, ask questions; don’t assume.
- Listen for verbal cues and watch for nonverbal cues. Verbal cues are things your instructor says that communicate the importance. Examples are, “This is an important point” or “I want to make sure everyone understands this concept.” Your instructor is telling you what is most important. Nonverbal cues come from facial expressions, body positioning, arm gestures, and tone of voice. Examples include when the instructor repeats herself, gets louder, or starts using more hand gestures.
- Listen for requests. A speaker will often hide a request as a statement of a problem. If a friend says, “I hate math!” this may mean, “Can you help me figure out a solution to this problem?”
Listening in a classroom or lecture hall to learn can be challenging because you are limited by how, and how much, you can interact with an instructor during the class. The following strategies help make listening at lectures more effective and learning more fun.
- Get your mind in the right space. Prepare yourself mentally to receive the information the speaker is presenting by following the previous prep questions and by doing your assignments (instructors build upon work presented earlier).
- Get yourself in the right space. Sit toward the front of the room where you can make eye contact with the instructor easily. Most instructors read the body language of the students in the front rows to gauge how they are doing and if they are losing the class. Instructors also believe students who sit near the front of the room take their subject more seriously and are more willing to give them help when needed or to give them the benefit of the doubt when making a judgment call while assigning grades.
- Eliminate distractions. There are two types of distractions: internal and external distractions.
- Internal distractions are things like being hungry, tired, or distracted by other thoughts. Try to manage these by being well-rested and having a healthy meal before class.
- External distractions are things like a ringing cell phone or people talking in the hallway. To manage these distractions, turn your cell phone off and pack it away in your backpack. If you are using your laptop for notes, close all applications except the one that you use to take notes.
- Look for signals. Each instructor has a different way of telling you what is important. Some will repeat or paraphrase an idea; others will raise (or lower) their voices; others will write related words on the board. Learn what signals your instructors tend to use and be on the lookout for them. When they use that tactic, the idea they are presenting needs to go in your notes and in your mind—and don’t be surprised if it appears on a test or quiz!
- Listen for what is not being said. If an instructor doesn’t cover a subject or covers it only minimally, this signals that that material is not as important as other ideas covered in greater length.
- Sort the information. Decide what is important and what is not, what is clear and what is confusing, and what is new material and what is a review. This mental organizing will help you remember the information, take better notes, and ask better questions.
- Take notes. We cover taking notes in much greater detail later in the next chapter, but for now, think about how taking notes can help recall what your instructor said and how notes can help you organize your thoughts for asking questions.
- Ask questions. Asking questions is one of the most important things you can do in class. Most obviously it allows you to clear up any doubts you may have about the material, but it also helps you take ownership of (and therefore remember) the material. Good questions often help instructors expand upon their ideas and make the material more relevant to students. Thinking through the material critically in order to prepare your questions helps you organize your new knowledge and sort it into mental categories that will help you remember it.
What to Do If…
- Your instructor speaks too fast. Crank up your preparation. The more you know about the subject, the more you’ll be able to pick up from the instructor. Exchange class notes with other students to fill in gaps in notes. Visit the instructor during office hours to clarify areas you may have missed. You might ask the instructor—very politely, of course—to slow down, but habits like speaking fast are hard to break!
- Your instructor has a heavy accent. Sit as close to the instructor as possible. Make connections between what the instructor seems to be saying and what they are presenting on the board or screen. Ask questions when you don’t understand. Visit the instructor during office hours; the more you speak with the instructor the more likely you will learn to understand the accent.
- Your instructor speaks softly or mumbles. Sit as close to the instructor as possible and try to hold eye contact as much as possible. Check with other students if they are having problems listening, too; if so, you may want to bring the issue up with the instructor. It may be that the instructor is not used to the lecture hall your class is held in and can easily make adjustments.
Now That’s a Good Question…
Are you shy about asking questions? Do you think that others in the class will ridicule you for asking a dumb question? Students sometimes feel this way because they have never been taught how to ask questions. Practice these steps, and soon you will be on your way to customizing each course to meet your needs and letting the instructor know you value the course.
- Be prepared. Doing your assignments for a class or lecture will give you a good idea about the areas you are having trouble with and will help you frame some questions ahead of time.
- Position yourself for success. Sit near the front of the class. It will be easier for you to make eye contact with the instructor as you ask the question. Also, you won’t be intimidated by a class full of heads turning to stare at you as you ask your question.
- Don’t wait. Ask your questions as soon as the instructor has finished a thought. Being one of the first students to ask a question also will ensure that your question is given the time it deserves and won’t be cut short by the end of class.
- In a lecture class, write your questions down. Make sure you jot your questions down as they occur to you. Some may be answered in the course of the lecture, but if the instructor asks you to hold your questions until the end of class, you’ll be glad you have a list of the items you need the instructor to clarify or expand on.
- Ask specific questions. “I don’t understand” is a statement, not a question. Give the instructor guidance about what you are having trouble with. “Can you clarify the use of the formula for determining velocity?” is a better way of asking for help. If you ask your question at the end of class, give the instructor some context for your question by referring to the part of the lecture that triggered the question. For example, “Professor, you said the Union troops were emboldened by Lincoln’s leadership. Was this throughout the Civil War, or only after Gettysburg?”
- Don’t ask questions for the sake of asking questions. If your question is not thought out, or if it appears that you are asking the question to try to look smart, instructors will see right through you!
Effective Participation Strategies
Like listening, participating in class will help you get more out of class. It may also help you stand out as a student. Instructors notice the students who participate in class (and those who don’t), and participation is often a component of the final grade. “Participation” may include contributing to discussions, class activities, or projects. It means being actively involved. The following are some strategies for effective participation:
- Be a team player: Although most students have classmates they prefer to work with, they should be willing to collaborate in different types of groups. Teamwork demonstrates that a student can adapt to and learn in different situations.
- Share meaningful questions and comments: Some students speak up in class repeatedly if they know that participation is part of their grade. Although there isn’t necessarily anything wrong with this, it’s a good practice to focus on quality vs. quantity. For instance, a quieter student who raises her hand only twice during a discussion but provides thoughtful comments might be more noticeable to an instructor than a student who chimes in with everything that’s said.
- Be prepared: As with listening, effective participation relies on coming to class prepared. Students should complete all reading assignments beforehand and also review any notes from the previous meeting. This way they can come to class ready to discuss and engage. Be sure to write down any questions or comments you have—this is an especially good strategy for quieter students or those who need practice thinking on their feet.
The resource Class Participation: More Than Just Raising Your Hand can help you evaluate what you need to work on in order to participate in class more effectively.
Guidelines for Participating in Classes
Smaller classes generally favor discussion, but often instructors in large lecture classes also make some room for participation.
A concern or fear about speaking in public is one of the most common fears. If you feel afraid to speak out in class, take comfort from the fact that many others do as well—and that anyone can learn how to speak in class without much difficulty. Class participation is actually an impromptu, informal type of public speaking, and the same principles will get you through both: preparing and communicating.
- Set yourself up for success by coming to class fully prepared.
- Complete reading assignments.
- Review your notes on the reading and previous class to get yourself in the right mindset.
- If there is something you don’t understand well, start formulating your question now.
- Sit in the front with a good view of the instructor, board or screen, and other visual aids. In a lecture hall, this will help you hear better, pay better attention, and make a good impression on the instructor. Don’t sit with friends—socializing isn’t what you’re there for.
- Remember that your body language communicates as much as anything you say. Sit up and look alert, with a pleasant expression on your face, and make good eye contact with the instructor. Show some enthusiasm.
- Pay attention to the instructor’s body language, which can communicate much more than just words. How the instructor moves and gestures, and the looks on their face, will add meaning to the words—and will also cue you when it’s a good time to ask a question or stay silent.
- Take good notes, but don’t write obsessively—and never page through your textbook (or browse on a laptop).
- Don’t eat or play with your cell phone.
- Except when writing brief notes, keep your eyes on the instructor.
- Follow class protocol for making comments and asking questions.
- In a small class, the instructor may encourage students to ask questions at any time, while in some large lecture classes, the instructor may for ask questions at the end of the lecture. In this case, jot your questions in your notes so that you don’t forget them later.
- Don’t say or ask anything just to try to impress your instructor. Most instructors have been teaching long enough to immediately recognize insincere flattery—and the impression this makes is just the opposite of what you want.
- Pay attention to the instructor’s thinking style. Does this instructor emphasize theory more than facts, wide perspectives over specific ideas, abstractions more than concrete experience? Take a cue from your instructor’s approach and try to think in similar terms when participating in class.
- It’s fine to disagree with your instructor when you ask or answer a question. Many instructors invite challenges. Before speaking up, however, be sure you can explain why you disagree and give supporting evidence or reasons. Be respectful.
- Pay attention to your communication style. Use standard English when you ask or answer a question, not slang. Avoid sarcasm and joking around. Be assertive when you participate in class, showing confidence in your ideas while being respectful of the ideas of others. But avoid an aggressive style that attacks the ideas of others or is strongly emotional.
When your instructor asks a question to the class:
- Raise your hand and make eye contact, but don’t call out or wave your hand all around trying to catch their attention.
- Before speaking, take a moment to gather your thoughts and take a deep breath. Don’t just blurt it out—speak calmly and clearly.
When your instructor asks you a question directly:
- Be honest and admit it if you don’t know the answer or are not sure. Don’t try to fake it or make excuses. With a question that involves a reasoned opinion more than a fact, it’s fine to explain why you haven’t decided yet, such as when weighing two opposing ideas or actions; your comment may stimulate further discussion.
- Organize your thoughts to give a sufficient answer. Instructors seldom want a yes or no answer. Give your answer and provide reasons or evidence in support.
When you want to ask the instructor a question:
- Don’t ever feel a question is “stupid.” If you have been paying attention in class and have done the reading and you still don’t understand something, you have every right to ask.
- Ask at the appropriate time. Don’t interrupt the instructor or jump ahead and ask a question about something the instructor may be starting to explain. Wait for a natural pause and a good moment to ask. On the other hand, unless the instructor asks students to hold all questions until the end of class, don’t let too much time go by, or you may forget the question or its relevance to the topic.
- Don’t ask just because you weren’t paying attention. If you drift off during the first half of class and then realize in the second half that you don’t really understand what the instructor is talking about now, don’t ask a question about something that was already covered.
- Don’t ask a question that is really a complaint. You may be thinking, “Why would so-and-so believe that? That’s just crazy!” Take a moment to think about what you might gain from asking the question. It’s better to say, “I’m having some difficulty understanding what so-and-so is saying here. What evidence did they use to argue for that position?”
- Avoid dominating a discussion. It may be appropriate in some cases to make a follow-up comment after the instructor answers your question, but don’t try to turn the class into a one-on-one conversation between you and the instructor.
Lecture Hall Classes
Tom Woodward – Undercover – CC BY-NC 2.0.
While opportunities are fewer for student discussions in large lecture classes, participation is still important. The instructor almost always provides an opportunity to ask questions. Because time is limited, be ready with your question or comment when the opportunity arises, and don’t be shy about raising your hand first.
Being prepared is especially important in lecture classes. Have assigned readings done before class and review your notes. If you have a genuine question about something in the reading, ask about it. Jot down the question in your notes and be ready to ask if the lecture doesn’t clear it up for you.
Being prepared before asking a question also includes listening carefully to the lecture. You don’t want to ask a question whose answer was already given by the instructor in the lecture. Take a moment to organize your thoughts and choose your words carefully. Be as specific as you can. Don’t say something like, “I don’t understand the big deal about whether the earth revolves around the sun or the sun around the earth. So what?” Instead, you might ask, “When they discovered that the earth revolves around the sun, was that such a disturbing idea because people were upset to realize that maybe they weren’t the center of the universe?” The first question suggests you haven’t thought much about the topic, while the second shows that you are beginning to grasp the issue and want to understand it more fully.
Following are some additional guidelines for asking good questions:
- Ask a question or two early in the term, even on the first day of class. Once the instructor has “noticed” you as a class participant, you are more likely to be recognized again when you have a question. You won’t be lost in the crowd.
- Speak deliberately and professionally, not as you might when talking with a friend. Use standard English rather than slang.
- If you’re very shy about public speaking or worried you’ll say the wrong thing, write down your question before asking. Rehearse it in your mind.
- When you have the opportunity to ask questions in class, it’s better to ask right away rather than saving a question for after class. If you really find it difficult to speak up in a large class, this is an acceptable way to ask your question and participate. A private conversation with an instructor may also be more appropriate if the question involves a paper or other project you are working on for the course.
A note on technology in the lecture hall. Colleges are increasingly incorporating new technology in lecture halls. For example, each student in the lecture hall may have an electronic “clicker” with which the instructor can gain instant feedback on questions in class. Or the classroom may have wireless Internet and students are encouraged to use their laptops to communicate with the instructor in “real-time” during the lecture. In these cases, the most important thing is to take it seriously, even if you have anonymity. Most students appreciate the ability to give feedback and ask questions through such technology, but some abuse their anonymity by sending irrelevant, disruptive, or insulting messages.
If You Must Miss a Class…
- Plan in advance: Although nobody can plan to be sick, students should give their instructors advanced notice if they know they will need to miss class for something like a doctor’s appointment. This is not only respectful to the instructor, but they may be able to give you any handouts or assignments that you might otherwise miss. If you anticipate that class will be canceled on account of bad weather, etc., make sure you have all the materials, notes, etc. that you need to work at home. In college, “snow days” are rarely “free days”—i.e., expect that you will be responsible for all the work due on those days when school reopens.
- Talk to fellow students: Ask to borrow class notes from one or two classmates who are reliable note takers. Be sure to also ask them about any announcements or assignments the instructor made during the class you missed.
- Talk to your instructor: Even if you have already emailed or called your instructor, check in with him or her before or after the next class period to collect any missed handouts and ask if anything was assigned. While you can’t expect the instructor to repeat the lecture, you can ask what you should do to stay caught up. But remember the worst thing you can say to an instructor: “I missed class—did you talk about anything important?”
- Do the reading assignment(s) and any other homework. Take notes on any readings to be discussed in the class you missed. If you have questions on the reading or homework, seek help from your classmates. Completing the homework and coming prepared for the next session will demonstrate to your instructor that you are still dedicated to the class.
Teaching Style Versus Learning Preferences
As you learned in Unit 3, students have many different types of multiple intelligences and strenghts and weaknesses. Understanding your stengths and preferences can help you study more effectively. Most instructors tend to develop their own teaching style, however, and you will encounter different teaching styles in different courses. Students can benefit from having instructors who teach in different ways because it can help them become more versatile as learners and able to work and communicate with a variety of people. Variety can be a challenge for students who prefer to learn in specific settings. However, learning to recognize different teaching styles can help students adjust to them and still be successful. Below are descriptions of some main teaching styles and how they relate to different learning preferences:
- Authority style: Instructors with an authority style of teaching prefer to give lectures while standing in front of the class, often doing a combination of talking and writing information on the board. Students are expected to listen and take notes. While the authority style may work for active/reflective students who can take notes to review later, it may be difficult for kinesthetic learners. These students could take advantage of their learning preferences by drawing study guides in their notes and creating and playing review games when they study with friends.
- Demonstrator style: Instructors with a demonstrator style of teaching prefer to lecture, also, but they prefer to “show” students what they’re explaining, often by using visual aids such as Powerpoint presentations, handouts, and demos. While this teaching style may appeal to visual learners and auditory learners who can simultaneously hear and visualize the information, this approach may not be as appealing to kinesthetic learners. These students might offer to assist instructors during demonstrations, so they can be more active while learning.
- Facilitator style: Instructors with a facilitator style rely heavily on class discussion, asking students to participate a lot while they provide prompts and guiding questions. While this teaching style is effective for students who may prefer interaction, students may want to create concept maps in their notes, which they can review later, while those with kinesthetic or naturalistic preferences may want to write their notes on index cards to use for studying outside of class.
- Delegator style: Instructors with a delegator approach prefer to structure their classes around student-run projects and presentations—their own teaching takes a backseat to students teaching one another. While this teaching style may be beneficial for those tht prefer an interactive or hands-on environment, most students will need to take notes throughout the projects and presentations so that they have study guides they can use later.
- Hybrid style: Instructors with a hybrid teaching style use a combination of the teaching styles above. For example, during an hourlong class session, they might schedule twenty minutes for a lecture, twenty minutes for class discussion, and twenty minutes for a class activity. While this teaching style can potentially appeal to all learning preferences, some students may have trouble adjusting to the shifts in format or activities. Still, such classes—especially the group activities—provide opportunities for different learning preferences: some might take notes or record everyone’s ideas, others could facilitate their group’s conversation, and other learners could be responsible for creating any props or presentations to share the group work with the rest of the class.
When the instructor’s teaching style matches your learning preferences, you are usually more attentive in class and may seem to learn better. But what happens if your instructor has a style very different from your own? Let’s say, for example, that your instructor primarily lectures, speaks rapidly, and seldom uses visuals. This instructor also talks mostly on the level of large abstract ideas and almost never gives examples. Let’s say that you, in contrast, prefer more visual demonstrations, that you prefer visual aids and visualizing concrete examples of ideas. Therefore, perhaps you are having some difficulty paying attention in class and following the lectures. What can you do?
- Capitalize on your learning strengths. In this example, you could use a visual style of note-taking, such as concept maps, while listening to the lecture. If the instructor does not give examples for abstract ideas in the lecture, see if you can supply examples in your own thoughts as you listen.
- Form a study group with other students. A variety of students will likely involve a variety of learning preferences, and when going over course material with other students, such as when studying for a test, you can gain what they have learned through their styles while you contribute what you have learned through yours.
- Use ancillary study materials. Many textbooks point students to online resource centers or include a computer CD that offers additional learning materials. Such ancillary materials usually offer an opportunity to review course material in ways that may better fit your learning preferences.
- Communicate with your instructor to bridge the gap between their teaching style and your learning preferences. If the instructor is speaking in abstractions and general ideas you don’t understand, ask the instructor for an example.
- You can also communicate with the instructor privately during office hours. For example, you can explain that you are having difficulty understanding lectures because so many things are said so fast.
Active Learning
Megan is currently taking two classes: geology and American literature. In her geology class, the instructor lectures for the full class time and gives reading assignments. In Megan’s literature class, however, the instructor relies on class discussions, small group discussions, and occasionally even review games. Megan enjoys her literature class, but she struggles to feel engaged and interested in geology.What strategies can Megan use to stay motivated and involved in both of her courses?
Think about the college classes you’ve taken so far. Like Megan, you may feel like it’s a mixed bag: you probably enjoyed the courses with a variety of teaching styles and learning activities the most. Even if you’re a quieter, more reserved student who dislikes lots of group discussions, you probably prefer to have some class projects or writing assignments rather than lectures alone. Group projects, discussions, and writing are examples of active learning because they involve doing something. Active learning happens when students participate in their education through activities that enhance learning. Those activities may involve just thinking about what you’re learning. Active learning can take place both in and out of the classroom. The following are examples of activities that can facilitate active engagement in the classroom.
Class discussions: Class discussions can help students stay focused because they feature different voices besides that of the instructor. Students can also hear one another’s questions and comments and learn from one another. Such discussions may involve the entire class, or the instructor may organize smaller groups, giving quieter students a greater chance to talk. Another method is to create online discussion boards so that students have more time to develop their ideas and comments and keep the conversation going.
Writing assignments: Instructors may ask students to write short reaction papers or journal entries about lessons or reading assignments. Such assignments can help students review or reflect on what they just learned to help them understand and remember the material, and also provide a means of communicating questions and concerns to their instructors.
Student-led teaching: Many instructors believe that a true test of whether students understand concepts is being able to teach the material to others. For that reason, instructors will sometimes have students work in groups and research a topic or review assigned readings, and then prepare a mini-presentation and teach it to the rest of the class. This activity can help students feel more accountable for their learning and work harder since classmates will be relying on them.
Group discussions are examples of active learning that encourage students to participate in their education.
KEY TAKEAWAYS
- Regular classroom attendance and participation is an essential part of the learning process.
- There are five stages to Active Listening: receiving, understanding, evaluating, responding and remembering.
- Learning is a cycle of four steps: preparing, absorbing, capturing and reviewing.
- Active Listening requires more than just class attendance. There are strategies to help you become an active listener.
- Participating in class, including answering and asking questions, is a vital part of the classroom experience.
- If you must miss a class, be proactive by making plans to get the missed materials and information.
- Just like there are different learning preferences, there are different teaching styles that you need to work with and respond to.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Active Listening in the Classroom. Authored by: Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Class Attendance in EDUC 1300. Authored by: Jolene Carr. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/class-attendance/. License: CC BY 4.0
- Chapter 4: Listening, Taking Notes, and Remembering in College Success. Authored by: Anonymous. Provided by: University of Minnesota. Located at: http://www.oercommons.org/courses/college-success/view. License: CC BY-NC-SA-4.0
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oercommons
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2025-03-18T00:37:10.445970
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"url": "https://oercommons.org/courseware/lesson/25867/overview",
"title": "Learning Framework: Effective Strategies for College Success, Strategies for Academic Success",
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https://oercommons.org/courseware/lesson/25868/overview
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Chapter 11: Note-Taking Strategies
Overview
Learning Framework: Effective Strategies for College Success
Chapter 11: Note-Taking Strategies
Learning Objectives
By the end of this chapter, you will be able to:
- Explain why taking notes is important.
- Use the four primary methods of note taking: lists, outlines, concept maps, and the Cornell method.
- Apply strategies to make note-taking more effective.
- Organize your notes into effective study guides.
- Use teacher handouts to complement your notes.
- Determine what to do with your notes after the course is complete.
Note-Taking Strategies
Note-Taking Strategies
Note-Taking Strategies
Everybody takes notes, or at least everybody claims to. But if you take a close look, many who are claiming to take notes on their laptops are actually surfing the Web, and paper notebooks are filled with doodles interrupted by a couple of random words with an asterisk next to them reminding you that “This is important!” In college, these approaches will not work. In college, your instructors expect you to make connections between class lectures and reading assignments; they expect you to create an opinion about the material presented; they expect you to make connections between the material and life beyond college. Your notes are your roadmaps for these thoughts. Do you take good notes? After learning to listen, note taking is the most important skill to ensure your success in a class.
Effective note taking is important because it:
- Supports your listening efforts.
- Allows you to test your understanding of the material.
- Helps you remember the material better when you write key ideas down.
- Gives you a sense of what the instructor thinks is important.
- Creates your “ultimate study guide.”
Effective note-taking helps students retain what they learned in class so that they can use the material to study and build their knowledge and tackle more complex concepts later on. In fact, research indicates that there’s a 34 percent chance that students will remember key information if it’s present in their notes but only a 5 percent chance if it’s not. It doesn’t matter whether you prefer to write brief summaries or make visual guides and diagrams in your notes. The important thing is to find a note-taking strategy that works for you.
There are various forms of taking notes, and which one you choose depends on both your personal style and the instructor’s approach to the material. Each can be used in a notebook, index cards, or in a digital form on your laptop. No specific type is good for all students and all situations, so we recommend that you develop your own style, but you should also be ready to modify it to fit the needs of a specific class or instructor. To be effective, all of these methods require you to listen actively and to think; merely jotting down words the instructor is saying will be of little use to you.
The following are a few recommendations to try out:
- Stay organized: Keep your notes and handouts separate for each class. For example, you might have a different notebook and folder for each class or a large notebook with a different tab for each class. This will save you the time of trying to organize and locate your notes when studying for an exam.
- Use your paper: Many students try to fit all of a day’s class notes onto one page and are often left with many extra blank pages in their notebooks. Instead, every time your instructor changes topics, flip to a new page. This allows you to find the material easily and makes your notes much cleaner.
- Use visual cues: Try highlighting, underlining, or drawing arrows or exclamation points next to any main or difficult concepts. This will call attention to these sections and remind you to spend more time reviewing them.
- Group together similar concepts: Grouping or “chunking” material is a good way to make studying and memorization easier. You can try drawing the main concept and connecting it to smaller, related concepts or making an outline of the information. Either one can serve as an effective study guide.
- Make notes legible: Some people have messy handwriting. However, writing as clearly as possible when you take notes will make it easier to review them later. It’s also helpful if you’re asked to share your notes with another student who missed class. If laptop use is permitted during class, you can also type your notes.
The following video addresses other specific strategies for note-taking:
Note-Taking Systems
The following is a chart with a brief explanation of the main note-taking system. They are described in more depth later in the chapter.
| Method | Description | When to Use |
|---|---|---|
| Lists | A sequential listing of ideas as they are presented. Lists may be short phrases or complete paragraphs describing ideas in more detail. | This method is what most students use as a fallback if they haven’t learned other methods. This method typically requires a lot of writing, and you may find that you are not keeping up with the professor. It is not easy for students to prioritize ideas in this method. |
| Outlines | The outline method places the most important ideas along the left margin, which are numbered with Roman numerals. Supporting ideas to these main concepts are indented and are noted with capital letters. Under each of these ideas, further detail can be added, designated with an Arabic number, a lowercase letter, and so forth. | A good method to use when material presented by the instructor is well organized. Easy to use when taking notes on your computer. |
| Concept Maps | When designing a concept map, place a central idea in the center of the page and then add lines and new circles on the page for new ideas. Use arrows and lines to connect the various ideas. | A great method to show relationships among ideas. Also good if the instructor tends to hop from one idea to another and back. |
| Cornell Method | The Cornell method uses a two-column approach. The left column takes up no more than a third of the page and is often referred to as the “cue” or “recall” column. The right column (about two-thirds of the page) is used for taking notes using any of the methods described above or a combination of them. After class or completing the reading, review your notes and write the key ideas and concepts or questions in the left column. You may also include a summary box at the bottom of the page, in which to write a summary of the class or reading in your own words. | The Cornell method can include any of the methods above and provides a useful format for calling out key concepts, prioritizing ideas, and organizing review work. Most colleges recommend using some form of the Cornell method. |
The List Method
The list method is usually not the best choice because it is focused exclusively on capturing as much of what the instructor says as possible, not on processing the information. Most students who have not learned effective study skills use this method because it’s easy to think that this is what note taking is all about. Even if you are skilled in some form of shorthand, you should probably also learn one of the other methods described here, because they are all better at helping you process and remember the material. You may want to take notes in class using the list method, but transcribe your notes to an outline or concept map method after class as a part of your review process. It is always important to review your notes as soon as possible after class and write a summary of the class in your own words.
The Outline Method
The advantage of the outline method is that it allows you to prioritize the material. Key ideas are written to the left of the page, subordinate ideas are then indented, and details of the subordinate ideas can be indented further. To further organize your ideas, you can use the typical outlining numbering scheme (starting with Roman numerals for key ideas, moving to capital letters on the first subordinate level, Arabic numbers for the next level, and lowercase letters following.) At first, you may have trouble identifying when the instructor moves from one idea to another. This takes practice and experience with each instructor, so don’t give up! In the early stages, you should use your syllabus to determine what key ideas the instructor plans to present. Your reading assignments before class can also give you guidance in identifying the key ideas.
If you’re using your laptop computer for taking notes, a basic word processing application (like Microsoft Word or Works) is very effective. Format your document by selecting the outline format from the format bullets menu. Use the increase or decrease indent buttons to navigate the level of importance you want to give each item. The software will take care of the numbering for you!
After class, be sure to review your notes and then summarize the class in one or two short paragraphs using your own words. This summary will significantly affect your recall and will help you prepare for the next class.
The Concept Map Method
This is a very graphic method of note-taking that is especially good at capturing the relationships among ideas. Concept maps harness your visual sense to understand complex material “at a glance.” They also give you the flexibility to move from one idea to another and back easily (so they are helpful if your instructor moves freely through the material).
To develop a concept map, start by using your syllabus to rank the ideas you will listen to by level of detail (from high-level or abstract ideas to detailed facts). Select an overriding idea (high level or abstract) from the instructor’s lecture and place it in a circle in the middle of the page. Then create branches off that circle to record the more detailed information, creating additional limbs as you need them. Arrange the branches with others that interrelate closely. When a new high-level idea is presented, create a new circle with its own branches. Link together circles or concepts that are related. Use arrows and symbols to capture the relationship between the ideas. For example, an arrow may be used to illustrate cause or effect, a double-pointed arrow to illustrate dependence, or a dotted arrow to illustrate impact or effect.
As with all note-taking methods, you should summarize the chart in one or two paragraphs of your own words after class.
The Cornell Method
The Cornell method was developed in the 1950s by Professor Walter Pauk at Cornell University. It is recommended by most colleges because of its usefulness and flexibility. This method is simple to use for capturing notes, is helpful for defining priorities, and is a very helpful study tool.
The Cornell method follows a very specific format that consists of four boxes: a header, two columns, and a footer.
The header is a small box across the top of the page. In it, you write identification information like the course name and the date of the class. Underneath the header are two columns: a narrow one on the left (no more than one-third of the page) and a wide one on the right. The wide column, called the “notes” column, takes up most of the page and is used to capture your notes using any of the methods outlined earlier. The left column, known as the “cue” or “recall” column, is used to jot down main ideas, keywords, questions, clarifications, and other notes. It should be used both during the class and when reviewing your notes after class. Finally, use the box in the footer to write a summary of the class in your own words. This will help you make sense of your notes in the future and is a valuable tool to aid with recall and studying.
Using Index Cards with the Cornell Method
Some students like to use index cards to take notes. They actually lend themselves quite well to the Cornell method. Use the “back” or lined side of the card to write your notes in class. Use one card per key concept. The “front” unlined side of the card replaces the left hand “cue” column. Use it after class to write keywords, comments, or questions. When you study, the cards become flash cards with questions on one side and answers on the other. Write a summary of the class on a separate card and place it on the top of the deck as an introduction to what was covered in the class.
You will have noticed that all methods end with the same step: reviewing your notes as soon as possible after class. Any review of your notes is helpful (reading them, copying them into your computer, or even recasting them using another note-taking method). But THINK! Make your review of notes a thoughtful activity, not a mindless process. When you review your notes, think about questions you still have and determine how you will get the answers. (From the next class? Studying with a friend? Looking up material in your text or on the net?) Examine how the material applies to the course; make connections with notes from other class sessions, with the material in your text, and with concepts covered in class discussions. Finally, it’s fun to think about how the material in your notes applies to real life. Consider this both at the very strategic level (as in “What does this material mean to me in relation to what I want to do with my life?”) as well as at a very mundane level (as in “Is there anything cool here I can work into a conversation with my friends?”).
Instructor Handouts
Some instructors hand out or post their notes or their PowerPoint slides from their lectures. These handouts should never be considered a substitute for taking notes in class. They are a very useful complement and will help you confirm the accuracy of your notes, but they do not involve you in the process of learning as well as your own notes do. After class, review your notes with a highlighter in hand and mark keywords and ideas in your notes. This will help you write the summary of the class in your own words.
Watch this video from College Info Geek on How to Take Notes in Class.
General Tips on Note Taking
Regardless of what note-taking method you choose, there are some note-taking habits you should get into for all circumstances and all courses:
- Be prepared. Make sure you have the tools you need to do the job.
- If you are using a notebook, be sure you have it with you and that you have enough paper.
- Have a separate notebook or designated section for each class, so your notes from math aren’t mixed in with your Art History notes.
- Have a pen and perhaps a pen with different colored ink to use for emphasis.
- If you are taking notes on your laptop, make sure the battery is charged! Select the application that lends itself best to your style of note-taking. Microsoft Word works very well for outline notes, but you might find taking notes in Excel to work best if you are working within the Cornell method. (It’s easier to align your thoughts in the cue or recall column to your notes in the right column. Just be sure you keep one idea per row!) You can often find good note-taking templates online.
- Write on only one side of the paper. This will allow you to integrate your reading notes with your class notes. It will also keep your notes much cleaner.
- Label, number, and date all notes at the top of each page. This will help you keep organized.
- Leave space between topics. This will allow you to go back to a topic if the instructor re-visits it.
- Leaving space between topics keeps your notes much cleaner.
- Avoid writing cramped writing in the margins by turning to a blank page when your instructor switches topics.
- This makes it much easier to locate specific topics when you are reviewing.
- It is a nice visual representation of what topics your instructor spent the most time on.
- When using a laptop, position it such that you can see the instructor and whiteboard right over your screen. This will keep the instructor in your field of vision even if you have to glance at your screen or keyboard from time to time.
- Make sure your focus remains with the instructor and not on your laptop.
- A word of caution about laptops for note taking: use them if you are very adept at keyboarding, but remember that not all note-taking methods work well on laptops because they do not easily allow you to draw diagrams and use special notations (scientific and math formulas, for example).
- Ask your instructor before using a laptop for note-taking. Not all professors allow them.
- Don’t try to capture everything that is said. Listen for the big ideas and write them down.
- Make sure you can recognize the instructor’s emphasis cues and write down all ideas and keywords the instructor emphasizes.
- Listen for clues like “the four causes were…” or “to sum up.…”
- Copy anything the instructor writes on the board. It’s likely to be important.
- Use signals and abbreviations. Which ones you use is up to you, but be consistent so you will know exactly what you mean by “att.” when you review your notes.
- You may find it useful to keep a key to your abbreviations in all your notebooks.
- Use some method for identifying your own thoughts and questions to keep them separate from what the instructor or textbook author is saying. Some students use different color ink; others box or underline their own thoughts. Do whatever works for you.
- Create a symbol to use when you fall behind or get lost in your note-taking.
- Jot down the symbol, leave some space, and focus on what the instructor is covering now.
- Later you can ask a classmate or the professor to help you fill in what you missed, or you can find it in your textbook.
- Review your notes as soon after class as possible (the same day is best). This is the secret to making your notes work!
- Use the recall column to call out the key ideas and organize facts.
- Fill in any gaps in your notes and clean up or redraw hastily drawn diagrams.
- Write a summary of the main ideas of the class in your own words.
- This process is a great aid to recall.
- Be sure to include any conclusions from the lecture or discussion.
- Pretend you are writing the summary for someone else. This will make it clear and detailed.
Organizing Your Notes And Class Materials
The class is over, and you have a beautiful set of notes in your spiral notebook or saved on your laptop. You have written the summary of the class in your own words. Now what?
Start by organizing your notes. We recommend you use a three-ring binder for each of your subjects. Print your notes if you used a computer. If you used note cards, insert them in plastic photo holders for binders. Group all notes from a class or unit together in a section; this includes class notes, reading notes, and instructor handouts. You might also want to copy the instructor’s syllabus for the unit on the first page of the section.
Next, spend some time linking the information across the various notes. Use the recall column in your notes to link to related information in other notes (e.g., “See class notes date/page”).
If you have had a quiz or test on the unit, add it to your binder, too, but be sure to write out the correct answer for any item you missed. Link those corrections to your notes, too.
Use this opportunity to write “notes on your notes.” Review your summary to see if it still is valid in light of your notes on the reading and any handouts you may have added to your notes package.
You don’t need to become a pack rat with your notes. It is fairly safe to toss them after the end of a course except in the following cases:
- If the course you took is a prerequisite for another course, or when the course is part of a standard progression of courses that build upon each other (this is very common in math and science courses), you should keep them as a reference and review for the follow-up course.
- If the course may pertain to your future major, keep your notes. You may not realize it now that they may have future value when you study similar topics or even the same topics in more depth.
- If you are very interested in the course subject and would like to get into the material through a more advanced course, independent study, or even research, keep your notes as a prep tool for further work.
Watch this video from College Info Geek on how to organize your notes and school files.
KEY TAKEAWAYS
- After effective listening, good note taking is the most important skill for academic success.
- Choose among effective note-taking styles for what works best for you and modify it to meet the needs of a specific class or instructor.
- Outlines work well for taking notes on a laptop when the instructor is well organized.
- Concept map notes are good for showing the relationships among ideas.
- The Cornell method is effective for calling out key concepts and organizing notes for review.
- Instructor handouts and PowerPoint presentations help with, but do not replace, personal note taking.
- Keep your notes organized in a way that makes it easy to study for tests and other uses in the future.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Note-Taking Strategies. Authored by: Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Class Attendance in EDUC 1300. Authored by: Jolene Carr. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/class-attendance/. License: CC BY 4.0
- Chapter 4: Listening, Taking Notes, and Remembering in College Success. Authored by: Anonymous. Provided by: University of Minnesota. Located at: http://www.oercommons.org/courses/college-success/view. License: CC BY-NC-SA-4.0
ALL RIGHTS RESERVED CONTENT
- College Info Geek - How To Take Notes in Class. Authored by: Thomas Frank. Located at: https://www.youtube.com/watch?v=AffuwyJZTQQ. License: All Rights Reserved. License Terms: Standard YouTube License
- College Info Geek - How I Organize My Notes. Authored by: Thomas Frank. Located at: https://www.youtube.com/watch?v=yoheFZaYvLU. License: All Rights Reserved. License Terms: Standard YouTube License
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oercommons
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2025-03-18T00:37:10.484188
| null |
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"title": "Learning Framework: Effective Strategies for College Success, Strategies for Academic Success",
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https://oercommons.org/courseware/lesson/25869/overview
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Chapter 12: Active Reading Strategies
Overview
Learning Framework: Effective Strategies for College Success
Chapter 12: Active Reading Strategies
Learning Objectives
By the end of this chapter, you will be able to:
- Explain how reading in college is different from reading in high school.
- Identify common types of reading tasks assigned in a college class.
- Describe the purpose and instructor expectations of academic reading.
- Identify effective reading strategies for academic texts using the SQ3R System.
- Explore the Anatomy of a Textbook.
- Develop strategies to help you read effectively.
- Explore strategies for approaching specialized texts, such as math, sciences, and specialized platforms, such as online text.
- Identify vocabulary-building techniques to strengthen your reading comprehension.
Active Reading Strategies
Active Reading Strategies
Highschool Vs. College Reading Expectations
Think back to a high school history or literature class. Those were probably the classes in which you had the most reading. You would be assigned a chapter, or a few pages in a chapter, with the expectation that you would be discussing the reading assignment in class. In class, the teacher would guide you and your classmates through a review of your reading and ask questions to keep the discussion moving. The teacher usually was a key part of how you learned from your reading.
If you have been away from school for some time, it’s likely that your reading has been fairly casual. While time spent with a magazine or newspaper can be important, it’s not the sort of concentrated reading you will do in college. And no one will ask you to write in response to a magazine piece you’ve read or quiz you about a newspaper article.
In college, reading is much different. You will be expected to read much more. For each hour you spend in the classroom, you will be expected to spend two or more additional hours studying between classes, and most of that will be reading. Assignments will be longer (a couple of chapters is common, compared with perhaps only a few pages in high school) and much more difficult. College textbook authors write using many technical terms and include complex ideas. Many college authors include research, and some textbooks are written in a style you may find very dry. You will also have to read from a variety of sources: your textbook, ancillary materials, primary sources, academic journals, periodicals, and online postings. Your assignments in literature courses will be complete books, possibly with convoluted plots and unusual wording or dialects, and they may have so many characters you’ll feel like you need a scorecard to keep them straight.
In college, most instructors do not spend much time reviewing the reading assignment in class. Rather, they expect that you have done the assignment before coming to class and understand the material. The class lecture or discussion is often based on that expectation. Tests, too, are based on that expectation. This is why active reading is so important—it’s up to you to do the reading and comprehend what you read.
Types Of College Reading Materials
As a college student, you will eventually choose a major or focus of study. In your first year or so, though, you’ll probably have to complete “core” or required classes in different subjects. For example, even if you plan to major in English, you may still have to take at least one science, history, and math class. These different academic disciplines (and the instructors who teach them) can vary greatly in terms of the materials that students are assigned to read. Not all college reading is the same. So, what types can you expect to encounter?
Textbooks
Probably the most familiar reading material in college is the textbook. These are academic books, usually focused on one discipline, and their primary purpose is to educate readers on a particular subject—”Principles of Algebra,” for example, or “Introduction to Business.” It’s not uncommon for instructors to use one textbook as the primary text for an entire course. Instructors typically assign chapters as readings and may include any word problems or questions in the textbook, too.
Articles
Instructors may also assign academic articles or news articles. Academic articles are written by people who specialize in a particular field or subject, while news articles may be from recent newspapers and magazines. For example, in a science class, you may be asked to read an academic article on the benefits of rainforest preservation, whereas in a government class, you may be asked to read an article summarizing a recent presidential debate. Instructors may have you read the articles online or they may distribute copies in class or electronically.
The chief difference between news and academic articles is the intended audience of the publication. News articles are mass media: They are written for a broad audience, and they are published in magazines and newspapers that are generally available for purchase at grocery stores or bookstores. They may also be available online. Academic articles, on the other hand, are usually published in scholarly journals with fairly small circulations. While you won’t be able to purchase individual journal issues from Barnes and Noble, public and school libraries do make these journal issues and individual articles available. It’s common to access academic articles through online databases hosted by libraries.
Literature and Nonfiction Books
Instructors use literature and nonfiction books in their classes to teach students about different genres, events, time periods, and perspectives. For example, a history instructor might ask you to read the diary of a girl who lived during the Great Depression so you can learn what life was like back then. In an English class, your instructor might assign a series of short stories written during the 1960s by different American authors, so you can compare styles and thematic concerns.
Literature includes short stories, novels or novellas, graphic novels, drama, and poetry. Nonfiction works include creative nonfiction—narrative stories told from real life—as well as history, biography, and reference materials. Textbooks and scholarly articles are specific types of nonfiction; often their purpose is to instruct, whereas other forms of nonfiction are written to inform, to persuade, or to entertain.
Purpose Of Academic Reading
Casual reading across genres, from books and magazines to newspapers and blogs, is something students should be encouraged to do in their free time because it can be both educational and fun. In college, however, instructors generally expect students to read resources that have particular value in the context of a course. Why is academic reading beneficial?
- Information comes from reputable sources: Web sites and blogs can be a source of insight and information, but not all are useful as academic resources. They may be written by people or companies whose main purpose is to share an opinion or sell you something. Academic sources such as textbooks and scholarly journal articles, on the other hand, are usually written by experts in the field and have to pass stringent peer review requirements in order to get published.
- Learn how to form arguments: In most college classes except for creative writing, when instructors ask you to write a paper, they expect it to be argumentative in style. This means that the goal of the paper is to research a topic and develop an argument about it using evidence and facts to support your position. Since many college reading assignments (especially journal articles) are written in a similar style, you’ll gain experience studying their strategies and learning to emulate them.
- Exposure to different viewpoints: One purpose of assigned academic readings is to give students exposure to different viewpoints and ideas. For example, in an ethics class, you might be asked to read a series of articles written by medical professionals and religious leaders who are pro-life or pro-choice and consider the validity of their arguments. Such experience can help you wrestle with ideas and beliefs in new ways and develop a better understanding of how others’ views differ from your own.
Active Learning When Reading
Many instructors conduct their classes mainly through lectures. The lecture remains the most pervasive teaching format across the field of higher education. One reason is that the lecture is an efficient way for the instructor to control the content, organization, and pace of a presentation, particularly in a large group. However, there are drawbacks to this “information-transfer” approach, where the instructor does all the talking and the students quietly listen: students have a hard time paying attention from start to finish; the mind wanders. Also, current cognitive science research shows that adult learners need an opportunity to practice newfound skills and newly introduced content. Lectures can set the stage for that interaction or practice, but lectures alone don’t foster student mastery. While instructors typically speak 100–200 words per minute, students hear only 50–100 of them. Moreover, studies show that students retain 70 percent of what they hear during the first ten minutes of class and only 20 percent of what they hear during the last ten minutes of class.
Thus it is especially important for students in lecture-based courses to engage in active learning outside of the classroom. But it’s also true for other kinds of college courses—including the ones that have active learning opportunities in class. Why? Because college students spend more time working (and learning) independently and less time in the classroom with the instructor and peers. Also, much of one’s coursework consists of reading and writing assignments. How can these learning activities be active? The following are very effective strategies to help you be more engaged with, and get more out of, the learning you do outside the classroom:
- Write in your books: You can underline and circle key terms, or write questions and comments in the margins of their books. The writing serves as a visual aid for studying and makes it easier for you to remember what you’ve read or what you’d like to discuss in class. If you are borrowing a book or want to keep it unmarked so you can resell it later, try writing keywords and notes on Post-its and sticking them on the relevant pages. (Discussed more in Chapter 12)
- Annotate a text: Annotations typically mean writing a brief summary of a text and recording the works-cited information (title, author, publisher, etc.). This is a great way to “digest” and evaluate the sources you’re collecting for a research paper, but it’s also invaluable for shorter assignments and texts since it requires you to actively think and write about what you read. The activity, below, will give you practice annotating texts. (Discussed more in Chapter 12)
- Create mind maps: Mind maps are effective visuals tools for students, as they highlight the main points of readings or lessons. Think of a mind map as an outline with more graphics than words. For example, if a student were reading an article about America’s First Ladies, they might write, “First Ladies” in a large circle in the center of a piece of paper. Connected to the middle circle would be lines or arrows leading to smaller circles with visual representations of the women discussed in the article. Then, these circles might branch out to even smaller circles containing the attributes of each of these women. (Discussed more in Chapter 11)
The following video discusses the process of creating mind maps further and shows how they can be a helpful strategy for active engagement:
In addition to the strategies described above, the following are additional ways to engage in active reading and learning:
- Work when you are fully awake, and give yourself enough time to read a text more than once.
- Read with a pen or highlighter in hand, and underline or highlight significant ideas as you read.
- Interact with the ideas in the margins (summarize ideas; ask questions; paraphrase difficult sentences; make personal connections; answer questions asked earlier; challenge the author; etc.).
- As you read, keep the following in mind:
- What is the CONTEXT in which this text was written? (This writing contributes to what topic, discussion, or controversy? Context is bigger than this one written text.)
- Who is the intended AUDIENCE? (There’s often more than one intended audience.)
- What is the author’s PURPOSE? To entertain? To explain? To persuade? (There’s usually more than one purpose, and essays almost always have an element of persuasion.)
- How is this writing ORGANIZED? Compare and contrast? Classification? Chronological? Cause and effect? (There’s often more than one organizational form.)
- What is the author’s TONE? (What are the emotions behind the words? Are there places where the tone changes or shifts?)
- What TOOLS does the author use to accomplish her/his purpose? Facts and figures? Direct quotations? Fallacies in logic? Personal experience? Repetition? Sarcasm? Humor? Brevity?
- What is the author’s THESIS—the main argument or idea, condensed into one or two sentences?
- Foster an attitude of intellectual curiosity. You might not love all of the writing you’re asked to read and analyze, but you should have something interesting to say about it, even if that “something” is critical.
Reading Strategies For Academic Texts
Recall from the Active Learning section that effective reading requires more engagement than just reading the words on the page. In order to learn and retain what you read, it’s a good idea to do things like circling keywords, writing notes, and reflecting. Actively reading academic texts can be challenging for students who are used to reading for entertainment alone, but practicing the following steps will get you up to speed.
SQ3R
SQ3R is a reading comprehension method named for its five steps: Survey, Question, Read, Recite, and Review. The method was introduced by Francis Pleasant Robinson, an American education philosopher in his 1946 book Effective Study.
The method offers an efficient and active approach to reading textbook material. It was created for college students but is extremely useful in a variety of situations. Classrooms all over the world have begun using this method to better understand what they’re reading.
- Survey –You can gain insight from an academic text before you even begin the reading assignment. For example, if you are assigned a nonfiction book, read the title, the back of the book, and table of contents. Scanning this information can give you an initial idea of what you’ll be reading and some useful context for thinking about it. You can also start to make connections between the new reading and the knowledge you already have, which is another strategy for retaining information. Survey the document by scanning its contents, gathering the necessary information to focus on topics, and help set study goals.
- Read the title, introduction, summary, or a chapter’s first paragraph(s). This helps to orient yourself to how this chapter is organized and to understand the topic’s key points.
- Go through each boldface heading and subheading. This will help you to create a mental structure for the topic.
- Check all graphics and captions closely. They’re there to emphasize certain points and provide rich additional information.
- Check reading aids and any footnotes. Emphasized text (italics, bold font, etc.) is typically introduced to catch the reader’s attention or to provide clarification.
- Question – During this stage, you should note any questions on the subjects contained in the document. It is helpful to survey the textbook again, this time writing down the questions that you create while scanning each section. You can easily find what questions need to be answered by looking at the Learning Objectives at the beginning of a chapter, the headings, and sub-headings within the chapter and the Chapter Summary or Key Points at the end of a chapter. These questions become study goals and they will become information you’ll actively search later on while going through each section in detail.
- Write your questions down so you can fill in the answers as you read.
- Make sure to answer the questions in your own words, rather than copying directly from the text.
- Read – Read each section thoroughly, keeping your questions in mind. Try to find the answers and identify if you need additional ones. Mind Mapping can probably help to make sense of and correlate all the information.
- Recall/Recite – In the recall (or recite) stage, you should go through what you read and try to answer the questions you noted before. Check-in after every section, chapter, or topic to make sure you understand the material and can explain it, in your own words. It’s worth taking the time to write a short summary, even if your instructor doesn’t require it. The exercise of jotting down a few sentences or a short paragraph capturing the main ideas of the reading is enormously beneficial: it not only helps you understand and absorb what you read but gives you ready study and review materials for exams and other writing assignments. Pretend you are responsible for teaching this section to someone else. Can you do it? It’s at this stage that you consolidate knowledge, so refrain from moving on until you can recall the core information.
- Review – Reviewing all the collected information is the final step of the process. In this stage, you can review the collected information, go through any particular chapter, expand your own notes, or discuss the topics with colleagues and other experts. An excellent way to consolidate information is to present or teach it to someone else. It always helps to revisit what you’ve read for a quick refresher. Before class discussions or tests, it’s a good idea to review your questions, summaries, and any other notes you have taken.
The following video is an overview of the steps of the SQ3R System.
Anatomy of a Textbook
Good textbooks are designed to help you learn, not just to present information. They differ from other types of academic publications intended to present research findings, advance new ideas, or deeply examine a specific subject. Textbooks have many features worth exploring because they can help you understand your reading better and learn more effectively. In your textbooks, look for the elements listed in the table below.
| Textbook Feature | What It Is | Why You Might Find It Helpful |
|---|---|---|
Preface or Introduction | A section at the beginning of a book in which the author or editor outlines its purpose and scope, acknowledges individuals who helped prepare the book, and perhaps outlines the features of the book. | You will gain perspective on the author’s point of view, what the author considers important. If the preface is written with the student in mind, it will also give you guidance on how to “use” the textbook and its features. |
| Foreword | A section at the beginning of the book, often written by an expert in the subject matter (different from the author) endorsing the author’s work and explaining why the work is significant. | A foreword will give you an idea of what makes this book different from others in the field. It may provide hints as to why your instructor selected the book for your course. |
| Author Profile | A short biography of the author illustrating the author’s credibility in the subject matter. | This will help you understand the author’s perspective and what the author considers important. |
Table of Contents | A listing of all the chapters in the book and, in most cases, primary sections within chapters. | The table of contents is an outline of the entire book. It will be very helpful in establishing links among the text, the course objectives, and the syllabus. |
Chapter Preview or Learning Objectives | A section at the beginning of each chapter in which the author outlines what will be covered in the chapter and what the student should expect to know or be able to do at the end of the chapter. | These sections are invaluable for determining what you should pay special attention to. Be sure to compare these outcomes with the objectives stated in the course syllabus. |
| Introduction | The first paragraph(s) of a chapter, which states the chapter’s objectives and key themes. An introduction is also common at the beginning of primary chapter sections. | Introductions to chapters or sections are “must-reads” because they give you a road map to the material you are about to read, pointing you to what is truly important in the chapter or section. |
| Applied Practice Elements | Exercises, activities, or drills are designed to let students apply their knowledge gained from the reading. Some of these features may be presented via Web sites designed to supplement the text. | These features provide you with a great way to confirm your understanding of the material. If you have trouble with them, you should go back and reread the section. They also have the additional benefit of improving your recall of the material. |
| Chapter Summary | A section at the end of a chapter that confirms key ideas presented in the chapter. | It is a good idea to read this section before you read the body of the chapter. It will help you strategize about where you should invest your reading effort. |
| Review Material | A section at the end of the chapter which includes additional applied practice exercises, review questions, and suggestions for further reading. | The review questions will help you confirm your understanding of the material. |
| Endnotes and Bibliographies | Formal citations of sources used to prepare the text. | These will help you infer the author’s biases and are also valuable if doing further research on the subject for a paper. |
Strategies for Textbook Reading
The SQ3R system provides a proven approach to effective learning from texts. Following are some strategies you can use to enhance your reading even further:
- Pace yourself. Figure out how much time you have to complete the assignment. Divide the assignment into smaller blocks rather than trying to read the entire assignment in one sitting. If you have a week to do the assignment, for example, divide the work into five daily blocks, not seven; that way you won’t be behind if something comes up to prevent you from doing your work on a given day. If everything works out on schedule, you’ll end up with an extra day for review.
- Schedule your reading. Set aside blocks of time, preferably at the time of the day when you are most alert, to do your reading assignments. Don’t just leave them for the end of the day after completing written and other assignments.
- Get yourself in the right space. Choose to read in a quiet, well-lit space. Your chair should be comfortable but provide good support. Libraries were designed for reading—they should be your first option! Don’t use your bed for reading textbooks; since the time you were read bedtime stories, you have probably associated reading in bed with preparation for sleeping. The combination of the cozy bed, comforting memories, and dry text are sure to invite some shut-eye!
- Avoid distractions. Active reading takes place in your short-term memory. Every time you move from task to task, you have to “reboot” your short-term memory and you lose the continuity of active reading. Multitasking—listening to music or texting on your cell while you read—will cause you to lose your place and force you to start over again. Every time you lose focus, you cut your effectiveness and increase the amount of time you need to complete the assignment.
- Avoid reading fatigue. Work for about fifty minutes, and then give yourself a break for five to ten minutes. Put down the book, walk around, get a snack, stretch, or do some deep knee bends. Short physical activity will do wonders to help you feel refreshed.
- Read your most difficult assignments early in your reading time, when you are freshest.
- Make your reading interesting. Try connecting the material you are reading with your class lectures or with other chapters. Ask yourself where you disagree with the author. Approach finding answers to your questions like an investigative reporter. Carry on a mental conversation with the author.
- Highlight your reading material. Most readers tend to highlight too much, hiding key ideas in a sea of yellow lines, making it difficult to pick out the main points when it is time to review. When it comes to highlighting, less is more. Think critically before you highlight. Your choices will have a big impact on what you study and learn for the course. Make it your objective to highlight no more than 15-25% of what you read. Use highlighting after you have read a section to note the most important points, key terms, and concepts. You can’t know what the most important thing is unless you’ve read the whole section, so don’t highlight as you read.
- Annotate your reading material. Marking up your book may go against what you were told in high school when the school owned the books and expected to use them year after year. In college, you bought the book. Make it truly yours. Although some students may tell you that you can get more cash by selling a used book that is not marked up, this should not be a concern at this time—that’s not nearly as important as understanding the reading and doing well in the class!
The purpose of marking your textbook is to make it your personal studying assistant with the key ideas called out in the text. Use your pencil also to make annotations in the margin. Use a symbol like an exclamation mark (!) or an asterisk (*) to mark an idea that is particularly important. Use a question mark (?) to indicate something you don’t understand or are unclear about. Box new words, then write a short definition in the margin. Use “TQ” (for “test question”) or some other shorthand or symbol to signal key things that may appear in test or quiz questions. Write personal notes on items where you disagree with the author. Don’t feel you have to use the symbols listed here; create your own if you want, but be consistent. Your notes won’t help you if the first question you later have is “I wonder what I meant by that?”
Watch the following video on annotating texts:
- Get to Know the Conventions. Academic texts, like scientific studies and journal articles, may have sections that are new to you. If you’re not sure what an “abstract” is, research it online or ask your instructor. Understanding the meaning and purpose of such conventions is not only helpful for reading comprehension but for writing, too.
- Look up and Keep Track of Unfamiliar Terms and Phrases. Have a good college dictionary such as Merriam-Webster handy (or find it online) when you read complex academic texts, so you can look up the meaning of unfamiliar words and terms. Many textbooks also contain glossaries or “key terms” sections at the ends of chapters or the end of the book. If you can’t find the words you’re looking for in a standard dictionary, you may need one specially written for a particular discipline. For example, a medical dictionary would be a good resource for a course in anatomy and physiology. If you circle or underline terms and phrases that appear repeatedly, you’ll have a visual reminder to review and learn them. Repetition helps to lock in these new words and their meaning get them into long-term memory, so the more you review them the more you’ll understand and feel comfortable using them.
- Make Flashcards. If you are studying certain words for a test, or you know that certain phrases will be used frequently in a course or field, try making flashcards for review. For each key term, write the word on one side of an index card and the definition on the other. Drill yourself, and then ask your friends to help quiz you. Developing a strong vocabulary is similar to most hobbies and activities. Even experts in a field continue to encounter and adopt new words. The following video discusses more strategies for improving vocabulary.
Dealing With Special Texts
While the active reading process outlined earlier is very useful for most assignments, you should consider some additional strategies for reading assignments in other subjects.
Mathematics Texts
Mathematics presents unique challenges in that they typically contain a great number of formulas, charts, sample problems, and exercises. Follow these guidelines:
- Do not skip over these special elements as you work through the text.
- Read the formulas and make sure you understand the meaning of all the factors.
- Substitute actual numbers for the variables and work through the formula.
- Make formulas real by applying them to real-life situations.
- Do all exercises within the assigned text to make sure you understand the material.
- Since mathematical learning builds upon prior knowledge, do not go on to the next section until you have mastered the material in the current section.
- Seek help from the instructor or teaching assistant during office hours if need be.
Scientific Texts
Science occurs through the experimental process: posing hypotheses, and then using experimental data to prove or disprove them. When reading scientific texts, look for hypotheses and list them in the left column of your notes pages. Then make notes on the proof (or disproof) in the right column. In scientific studies, these are as important as the questions you ask for other texts. Think critically about the hypotheses and the experiments used to prove or disprove them. Think about questions like these:
- Can the experiment or observation be repeated? Would it reach the same results?
- Why did these results occur? What kinds of changes would affect the results?
- How could you change the experiment design or method of observation? How would you measure your results?
- What are the conclusions reached about the results? Could the same results be interpreted in a different way?
Social Sciences Texts
Social sciences texts, such as those for history, economics, and political science classes, often involve interpretation where the authors’ points of view and theories are as important as the facts they present. Put your critical thinking skills into overdrive when you are reading these texts. As you read, ask yourself questions such as the following:
- Why is the author using this argument?
- Is it consistent with what we’re learning in class?
- Do I agree with this argument?
- Would someone with a different point of view dispute this argument?
- What key ideas would be used to support a counterargument?
Record your reflections in the margins and in your notes.
Social science courses often require you to read primary source documents. Primary sources include documents, letters, diaries, newspaper reports, financial reports, lab reports, and records that provide firsthand accounts of the events, practices, or conditions you are studying. Start by understanding the author(s) of the document and his or her agenda. Infer their intended audience. What response did the authors hope to get from their audience? Do you consider this a bias? How does that bias affect your thinking about the subject? Do you recognize personal biases that affect how you might interpret the document?
Foreign Language Texts
Reading texts in a foreign language is particularly challenging, but it also provides you with invaluable practice and many new vocabulary words in your “new” language. It is an effort that really pays off. Start by analyzing a short portion of the text (a sentence or two) to see what you do know. Remember that all languages are built on idioms as much as on individual words. Do any of the phrase structures look familiar? Can you infer the meaning of the sentences? Do they make sense based on the context? If you still can’t make out the meaning, choose one or two words to look up in your dictionary and try again. Look for longer words, which generally are the nouns and verbs that will give you meaning sooner. Don’t rely on a dictionary (or an online translator); a word-for-word translation does not always yield good results. For example, the Spanish phrase “Entre y tome asiento” might correctly be translated (word for word) as “Between and drink a seat,” which means nothing, rather than its actual meaning, “Come in and take a seat.”
Reading in a foreign language is hard and tiring work. Make sure you schedule significantly more time than you would normally allocate for reading in your own language and reward yourself with more frequent breaks. But don’t shy away from doing this work; the best way to learn a new language is practice, practice, practice.
Note to English-language learners: You may feel that every book you are assigned is in a foreign language. If you do struggle with the high reading level required of college students, check for college resources that may be available to ESL (English as a second language) learners. Never feel that those resources are only for weak students. As a second-language learner, you possess a rich linguistic experience that many American-born students should envy. You simply need to account for the difficulties you’ll face and (like anyone learning a new language) practice, practice, practice.
Reading Graphics
You read earlier about noticing graphics in your text as a signal of important ideas. But it is equally important to understand what the graphics intend to convey. Textbooks contain tables, charts, maps, diagrams, illustrations, photographs, and the newest form of graphics, Internet URLs for accessing text and media material. Many students are tempted to skip over the graphic material and focus only on the reading. Don’t! Take the time to read and understand your textbook’s graphics. They will increase your understanding, and because they engage different comprehension processes, they will create different kinds of memory links to help you remember the material.
To get the most out of graphic material, use your critical thinking skills and question why each illustration is present and what it means. Don’t just glance at the graphics; take the time to read the title, caption, and any labeling in the illustration. In a chart, read the data labels to understand what is being shown or compared. Think about projecting the data points beyond the scope of the chart; what would happen next? Why?
The table below shows the most common graphic elements and notes what they do best. This knowledge may help guide your critical analysis of graphic elements.
TABLE Most often used to present raw data. Understand what is being measured. What data points stand out as very high or low?Why? Ask yourself what might cause these measurements to change. | |
BAR CHART Used to compare quantitative data or show changes in data over time. Also can be used to compare a limited number of data series over time. Often an illustration of data that can also be presented in a table. | |
LINE CHART Used to illustrate a trend in a series of data. May be used to compare different series over time. | |
PIE CHART Used to illustrate the distribution or share of elements as a part of a whole. Ask yourself what effect a change in the distribution of factors would have on the whole. | |
MAP Used to illustrate geographic distributions or movement across geographical space. In some cases can be used to show concentrations of populations or resources. When encountering a map, ask yourself if changes or comparisons are being illustrated. Understand how those changes or comparisons relate to the material in the text. | |
PHOTO Used to represent a person, a condition, or an idea discussed in the text. Sometimes photographs serve mainly to emphasize an important person or situation, but photographs can also be used to make a point. Ask yourself if the photograph reveals a biased point of view. | |
ILLUSTRATION Used to illustrate parts of an item. Invest time in these graphics. They are often used as parts of quizzes or exams. Look carefully at the labels. These are vocabulary words you should be able to define. | |
FLOWCHART or DIAGRAM Commonly used to illustrate processes. As you look at diagrams, ask yourself, “What happens first? What needs to happen to move to the next step?” |
Online Texts
Reading online texts presents unique challenges for some students. For one thing, you can’t readily circle or underline key terms or passages on the screen with a pencil. For another, there can be many tempting distractions while reading online – just a quick visit to social media sites or to check your email.
While there’s no substitute for old-fashioned self-discipline, you can take advantage of the following tips to make online reading more efficient and effective:
- Get a browser extension that allows you to highlight and annotate your online text.
- If possible, download the reading as a PDF, Word document, etc., so you can read it offline.
- Get an app or browser extension that disables your social media sites for specified periods of time.
- Adjust your screen to avoid glare and eye strain, and change the text font to be less distracting (for those essays written in Comic Sans).
- Follow the SQ3R system, taking notes and answering questions as you go. Since highlighting and annotating are more difficult with online texts, it is imperative that you take quality notes.
- Look for reputable online sources. Professors tend to assign reading from reputable print and online sources, so you can feel comfortable referencing such sources in class and for writing assignments. If you are looking for online sources independently, however, devote some time and energy to critically evaluating the quality of the source before spending time reading any resources you find there. Find out what you can about the author (if one is listed), the Website, and any affiliated sponsors it may have. Check that the information is current and accurate against similar information on other pages. Depending on what you are researching, sites that end in “.edu” (indicating an “education” site such as a college, university, or other academic institution) tend to be more reliable than “.com” sites. Check with a librarian for help in identifying reputable online sources.
Building Your Vocabulary
Gaining confidence with the unique terminology used in different disciplines can help you be more successful in your courses and in college generally. A good vocabulary is essential for success in any role that involves communication, and just about every role in life requires good communication skills. We include this section on vocabulary in this chapter on reading because of the connections between vocabulary building and reading. Building your vocabulary will make your reading easier, and reading is the best way to build your vocabulary.
Learning new words can be fun and does not need to involve tedious rote memorization of word lists. The first step, as with any other aspect of the learning cycle, is to prepare yourself to learn. Consciously decide that you want to improve your vocabulary; decide you want to be a student of words. Work to become more aware of the words around you: the words you hear, the words you read, the words you say, and those you write.
In addition to the suggestions described earlier, such as looking up unfamiliar words in dictionaries, the following are additional vocabulary-building techniques for you to try:
- Read everything and read often. Reading frequently both in and out of the classroom will help strengthen your vocabulary. Whenever you read a book, magazine, newspaper, blog, or any other resource, keep a running list of words you don’t know. Look up the words as you encounter them and try to incorporate them into your own speaking and writing.
- Be on the lookout for new words. Most will come to you as you read, but they may also appear in an instructor’s lecture, a class discussion, or a casual conversation with a friend. They may pop up in random places like billboards, menus, or even online ads!
- Write down the new words you encounter, along with the sentences in which they were used. Do this in your notes with new words from a class or reading assignment. If a new word does not come from a class, you can write it on just about anything, but make sure you write it. Many word lovers carry a small notepad or a stack of index cards specifically for this purpose.
- Infer the meaning of the word. The context in which the word is used may give you a good clue about its meaning. Do you recognize a common word root in the word? What do you think it means?
- Look up the word in a dictionary. Do this as soon as possible (but only after inferring the meaning). When you are reading, you should have a dictionary at hand for this purpose. In other situations, do this within a couple hours, definitely during the same day. How does the dictionary definition compare with what you inferred? Install a reliable dictionary app on your phone or computer. Look for ones that also pronounce the word.
- Make connections to words you already know. You may be familiar with the “looks like . . . sounds like” saying that applies to words. It means that you can sometimes look at a new word and guess the definition based on similar words whose meaning you know. For example, if you are reading a biology book on the human body and come across the word malignant, you might guess that this word means something negative or broken if you already know the word malfunction, which shares the “mal-” prefix.
- Write the word in a sentence, ideally one that is relevant to you. If the word has more than one definition, write a sentence for each.
- Say the word out loud and then say the definition and the sentence you wrote.
- Use the word. Find an occasion to use the word in speech or writing over the next two days.
- Schedule a weekly review with yourself to go over your new words and their meaning.
KEY TAKEAWAYS
- College reading is very different from high school reading.
- You must take personal responsibility for understanding what you read.
- Expect to spend about two or more hours on homework, most of it reading, for every hour you spend in class.
- Reading is a primary means for absorbing ideas in the learning cycle, but it is also very important for the other three aspects of the learning cycle.
- Understand how your textbook is put together and what features might help you with your reading.
- Plan your reading by scanning the reading assignment first, then create questions based on the section titles. Use the SQ3R system to help you focus and prioritize your reading.
- Don’t try to highlight your text as you read the first time through. At that point, it is hard to tell what is really important. Aim to highlight 15-25% of the text.
- End your reading time by reviewing your notes.
- Do all the exercises in math textbooks; apply the formulas to real-world situations.
- Each type of graphic material has its own strength; those strengths are usually clues about what the author wants to emphasize by using the graphic.
- Look for statements of hypotheses and experimental design when reading science texts.
- History, economics, and political science texts are heavily influenced by interpretation. Think critically about what you are reading.
- Working with foreign language texts requires more time and more frequent breaks. Don’t rely on word-for-word translations.
- The best way to build your vocabulary is to read, and a stronger vocabulary makes it easier and more fun to read.
- Look for new words everywhere, not just in class readings.
- Look up new words in the dictionary, write your own sentence using the new word. Say the word and definition out loud. Use the new word as soon as possible.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Active Reading Strategies. Authored by: Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- Active Learning in EDUC 1300. Authored by: Jolene Carr. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/active-engagement/. License: CC BY 4.0
- Chapter 5: Reading to Learn in College Success. Authored by: Anonymous. Provided by: University of Minnesota. Located at: http://www.oercommons.org/courses/college-success/view. License: CC BY-NC-SA-4.0
- Reading Strategies in EDUC 1300. Authored by: Jolene Carr. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/reading-strategies/. License: CC BY 4.0
- SQ3R. Provided by: Thousand Insights. Located at: https://thousandinsights.wordpress.com/2009/01/25/sq3r/. License: CC BY-SA 4.0
- SQ3R. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/SQ3R. License: CC BY-SA 3.0
- Understanding SQ3R Presentation. Authored by: Student Success Center OCtech. Located at: https://youtu.be/d0uVLSacIzA. License: CC BY 3.0
ALL RIGHTS RESERVED CONTENT
- How to Use a Mindmap. Provided by: Two-Point-Four. Located at: https://youtu.be/L0XzZCd2tPE. License: All Rights Reserved. License Terms: Standard YouTube License
- Annotate It: Provided by: Janene Davison. Located at: https://youtu.be/GkZtC3o0AjE. License: All Rights Reserved. License Terms: Standard YouTube License
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Chapter 13: Test Taking Strategies
Overview
Learning Framework: Effective Strategies for College Success
Chapter 13: Test Taking Strategies
Learning Objectives
By the end of this chapter, you will be able to:
- Understand the role of tests in the Learning Cycle.
- Define test anxiety, identify sources of test anxiety and techniques for preventing and controlling it.
- Identify long-term study strategies.
- Become familiar with different types of tests and test formats.
- Implement specific test strategies for before, during and after a test.
- Identify strategies for answering typical kinds of test questions (multiple choice, true/false, matching, short answer and essay).
- Understand the importance of academic integrity and the consequences of dishonesty.
- Effectively evaluate your test results and correct your mistakes.
- Use your test results as a study guide.
Test Taking Strategies
Test Taking Strategies
Testing As Part Of The Learning Cycle
Testing is a part of life. Have you ever participated in an athletic event? Completed a crossword puzzle? Acted in a play? Cooked dinner? Answered a child’s question? Prepared a cost estimate? All of these common life situations are forms of tests because they measure how much we know about a specific subject at a single point in time. They alone are not good measurements about how smart or gifted you are—they show only how much you know or can do at that moment. We can learn from how we have performed, and we can think about how to apply what we have learned to do even better next time. We can have fun measuring our progress.
Many of our daily activities are measurements of progress toward mastery of skills or knowledge. We welcome these opportunities for both work and fun. But when these opportunities are part of our academic life, we often dread them and rarely feel any sense of fun. In reality, however, academic tests are similar to real-life tests in the following ways:
- They help us measure our progress toward mastery of a particular skill.
- They are not a representation of how smart, talented, or skilled we are but rather are a measurement only of what we know about a specific subject at a specific point in time.
- They are extraordinary learning opportunities.
Academic tests in college are different from those you took in high school. College instructors expect to see much more of you in an exam: your thoughts, your interpretations, your thinking process, your conclusions. High school teachers usually look for your ability to repeat precisely what you read in your text or heard in your class. Success on high school tests relies much more on memorization than on understanding the material. This is why you need to modify your study habits and your strategies for taking exams in college.
Take a look at the learning cycle “The Learning Cycle: Review and Apply”. In this chapter, we cover reviewing and applying the material you learn; preparing for and taking exams is the practical application of this phase.
Let’s start at the top of the cycle. You have invested your time in preparing for class, you have been an active listener in class, and you have asked questions and taken notes. You have summarized what you learned and have looked for opportunities to apply the material. You have completed your reading assignments and compared your reading notes with your class notes. And now you hear your instructor say, “Remember the exam next week.”
A sense of dread takes over. You worry about the exam and what might be on it. You stay up for a couple of nights trying to work through the volumes of material the course has covered. Learning or remembering it all seems hopeless. You find yourself staring at the same paragraph in your text over and over again, but you just don’t seem to get it. As the exam looms closer, you feel your understanding of the material is slipping away. You show up for the exam and the first questions look familiar, but then you draw a blank—you’re suffering from test anxiety.
Test Anxiety And How To Control It
For many test-takers, preparing for a test and taking a test can easily cause worry and anxiety. In fact, most students report that they are more stressed by tests and schoolwork than by anything else in their lives, according to the American Test Anxiety Association. Most of us have experienced this. It is normal to feel stress before an exam, and in fact, that may be a good thing. Stress motivates you to study and review, generates adrenaline to help sharpen your reflexes and focus while taking the exam, and may even help you remember some of the material you need. But suffering too many stress symptoms or suffering any of them severely will impede your ability to show what you have learned. Test anxiety is a psychological condition in which a person feels distressed before, during, or after a test or exam to the point where stress causes poor performance. Anxiety during a test interferes with your ability to recall knowledge from memory as well as your ability to use higher-level thinking skills effectively.
- Roughly 16–20 percent of students have high test anxiety.
- Another 18 percent have moderately high test anxiety.
- Test anxiety is the most common academic impairment in grade school, high school, and college.
Below are some effects of moderate anxiety:
- Being distracted during a test
- Having difficulty comprehending relatively simple instructions
- Having trouble organizing or recalling relevant information
- Crying
- Illness
- Eating disturbance
- High blood pressure
- Acting out
- Toileting accidents
- Sleep disturbance
- Cheating
- Negative attitudes towards self, school, subjects
Below are some effects of extreme test anxiety:
- Overanxious disorder
- Social phobia
- Suicide
Poor test performance is also a significant outcome of test anxiety. Test-anxious students tend to have lower study skills and lower test-taking skills, but research also suggests that high levels of emotional distress correlate with reduced academic performance overall. Highly test-anxious students score about 12 percentile points below their low-anxiety peers. Students with test anxiety also have higher overall dropout rates. And test anxiety can negatively affect a student’s social, emotional, and behavioral development, as well as feelings about themselves and school.
Why does test anxiety occur? Inferior performance arises not because of intellectual problems or poor academic preparation. It occurs because testing situations create a sense of threat for those who experience test anxiety. The sense of threat then disrupts the learner’s attention and memory.
Other factors can influence test anxiety, too. Students with disabilities and students in gifted education classes tend to experience high rates of test anxiety.
If you experience test anxiety, have hope! Experiencing test anxiety doesn’t mean that there’s something wrong with you or that you aren’t capable of performing well in college. The trick is to keep stress and anxiety at a level where it can help you do your best rather than get in your way.
ACTIVITY: TESTING YOUR TEST ANXIETY
| T | F | I have a hard time starting to study for a test. |
| T | F | When studying for an exam, I feel desperate or lost. |
| T | F | When studying for an exam, I often feel bored and tired. |
| T | F | I don’t sleep well the night before an exam. |
| T | F | My appetite changes the day of the exam. (I’m not hungry and skip meals or I overeat—especially high-sugar items like candy or ice cream.) |
| T | F | When taking an exam, I am often confused or suffer mental blocks. |
| T | F | When taking an exam, I feel panicky and my palms get sweaty. |
| T | F | I’m usually in a bad mood after taking an exam. |
| T | F | I usually score lower on exams than on papers, assignments, and projects. |
| T | F | After an exam, I can remember things I couldn’t recall during the exam. |
Strategies for Preventing and Controlling Test Anxiety
There are steps you should take if you find that stress is getting in your way:
- Be prepared. A primary cause of test anxiety is not knowing the material. If you take good class and reading notes and review them regularly, this stressor should be greatly reduced if not eliminated. You should be confident going into your exam (but not overconfident).
- Practice! One of the best ways to prepare for an exam is to take practice tests. To overcome test-taking anxiety, practice test-taking in a test-like environment, like a study room in the library. Practice staying calm, relaxed, and confident. If you find yourself feeling overly anxious, stop and start again.
- Avoid negative thoughts. Your own negative thoughts—“I’ll never pass this exam” or “I can’t figure this out, I must be really stupid!”—may move you into a spiraling stress cycle that in itself causes enough anxiety to block your best efforts. When you feel you are brewing a storm of negative thoughts, stop what you are doing and clear your mind. Don’t practice having anxiety! Allow yourself to daydream a little; visualize yourself in pleasant surroundings with good friends. Don’t go back to work until you feel the tension release. Sometimes it helps to take a deep breath and shout “STOP!” and then proceed with clearing your mind. Once your mind is clear, repeat a reasonable affirmation to yourself—“I know this stuff”—before continuing your work.
- Visualize success. Picture what it will feel like to get that A. Translate that vision into specific, reasonable goals and work toward each individual goal. Take one step at a time and reward yourself for each goal you complete.
- It’s all about you! Don’t waste your time comparing yourself to other students in the class, especially during the exam. Keep focused on your own work and your own plan. Exams are not a race, so it doesn’t matter who turns in their paper first. Certainly, you have no idea how they did on their exam, so a thought like “Kristen is already done, she must have aced it, I wish I had her skills” is counterproductive and will only cause additional anxiety.
- Have a plan and follow it. As soon as you know that an exam is coming, you can develop a plan for studying. As soon as you get your exam paper, you should develop a plan for the exam itself. We’ll discuss this later in this chapter. Don’t wait to cram for an exam at the last minute; the pressure you put on yourself and the late-night will cause more anxiety, and you won’t learn or retain much.
- Make sure you eat well and get a good night’s sleep before the exam. Hunger, poor eating habits, energy drinks, and lack of sleep all contribute to test anxiety.
- Chill! You perform best when you are relaxed, so learn some relaxation exercises you can use during an exam. Before you begin your work, take a moment to listen to your body. Which muscles are tense? Move them slowly to relax them. Tense them and relax them. Exhale, then continue to exhale for a few more seconds until you feel that your lungs are empty. Inhale slowly through your nose and feel your ribcage expand as you do. This will help oxygenate your blood and reenergize your mind.
- Come early and prepared. Come to the exam with everything you need like your pencils, erasers, calculator, etc. Arrive to class early so you aren’t worried about time. Try to avoid the pre-exam chatter of your classmates, as this may contribute to your anxiety. Instead, pick your favorite chair and focus on relaxing.
- Put it in perspective. Take a minute to think about the three most important things in your life. They may be your family, your health, your friendships. Will you lose any of these important things as a result of the exam? An exam is not life or death and it needs to be put in perspective.
Health and wellness cannot be overstated as factors in test anxiety. Studying and preparing for exams can be easier when you take care of your mental and physical health. The following are a few tips for better health, better focus, and better grades:
- Try mini-meditation to reduce stress and improve focus. Breathe in deeply, count to five, and exhale slowly. Watch your lower abdomen expand and deflate. Repeat five times.
- Get sleep! Although some students may stay up until 4 a.m. studying, it’s not a healthy habit and is usually counter-productive. Your mind is more efficient when you get enough quality sleep, so make sure to schedule enough time for rest. If you practice a good study schedule, there is no need for all-night cramming. Stick to your study plan, review for about an hour, and get a good night’s sleep.
- Eat well. Have a healthy meal before your exam. Avoid energy drinks that will give you a temporary energy spurt, followed by a crash. Stay hydrated.
- Don’t try to be perfect. You’ll alleviate a lot of anxiety by learning that just “doing your best” is something to be proud of—it doesn’t have to be perfect.
- Reach out for help. If you feel you need assistance with your mental or physical health, talk to a counselor or visit a doctor.
Complete Section #2 Below: ACTIVITY: CONTROLLING NEGATIVE TALK
Watch this video from College Info Geek on Test Anxiety: How to Take On Your Exams Without Stress
Studying To Learn (Not Cram!)
You have truly learned material when you can readily recall it and actually use it, on tests or in real-life situations. Effective studying is your most important tool to combat test anxiety, but more importantly, effective studying helps you truly master the material and be able to apply it as you need to, in school and beyond.
In previous chapters, we set the foundation for effective learning. You learned how to listen and how to take notes. You learned how to read actively and how to capture information from written sources. Now we’ll follow up on some of those key ideas and take the learning cycle to its conclusion and a new beginning.
The reviewing and applying stage of the learning cycle involves studying and using the material you have been exposed to in your course. Recall that we emphasized the importance of reviewing your notes soon after the class or assignment. This review is largely what studying is all about.
Effective studying is an ongoing process of reviewing course material. The first and most important thing you should know is that studying is not something you do a few days before an exam. To be effective, studying is something you do as part of an ongoing learning process, throughout the duration of the term.
Studying Every Day
Studying begins after each class or assignment when you review your notes. Each study session should involve three steps:
- Gather your learning materials. Take time to merge your class notes with your reading notes. How do they complement each other? Stop and think. What do the notes tell you about your material? What aspects of the material are you unsure about? Do you need to reread a part of your text? Write down any questions you have for your instructor and pay a visit during office hours. It is better to clear up any misconceptions and get your questions answered soon after you are exposed to the material, rather than to wait, for two reasons: (1) the question or doubt is fresh in your mind and you won’t forget about it and (2) instructors usually build their lessons on material already presented. If you don’t take these steps now, you are setting yourself up for problems later in the course.
- Apply or visualize. What does this material mean to you? How will you use this new knowledge? Try to find a way to apply it in your own life or thoughts. If you can’t use the knowledge right away, visualize yourself using the knowledge to solve a problem or visualize yourself teaching the material to other students.
- Cement your knowledge. If you use the two-column note-taking method, cover up the right side of your notes with a piece of paper, leaving the questions in the left column exposed. Test yourself by trying to answer your questions without referring to your notes. How did you do? If you are unsure about anything, look up the answer and write it down right away. Don’t let a wrong answer be the last thing you wrote on a subject because you will most likely continue to remember the wrong answer.
Studying in Course Units
At the end of each unit, or at least every two weeks or so, use your notes and textbook to write an outline or summary of the material in your own words. (Remember the paragraphs you wrote to summarize each class or reading? They’ll be very helpful to you here.) After you have written the summary or outline, go back and reread your outline from the prior unit followed by the one you just wrote. Does the new one build on the earlier one? Do you feel confident you understand the material?
Studying before the Exam
At least a week before a major exam, ask yourself these questions: What has the instructor said about what is included in the exam? Has the instructor said anything about what types of questions will be included? If you were the instructor, what questions would you ask on an exam? Challenge yourself to come up with some really tough open-ended questions. Think about how you might answer them. Be sure to go to any review sessions the instructor or your section leader holds.
Now go back and review your outlines. Do they cover what the instructor has suggested might be on the exam? After reviewing your outlines, reread the sections of your notes that are most closely associated with expected exam questions. Pay special attention to those items the instructor emphasized during class. Read key points aloud and write them down on index cards. Make flashcards to review in downtimes, such as when you’re waiting for a bus or for a class to start.
More Tips for Success
- Schedule a consistent study and review time for each course at least once a week, in addition to your class and assignment time. Keep to that schedule as rigorously as you do your class schedule. Use your study time to go through the steps outlined earlier; this is not meant to be a substitute for your assignment time.
- Get yourself in the right space. Choose to study in a quiet, well-lit space. Your chair should be comfortable but provide good support. Remember that libraries were designed for reading and should be your first option.
- Minimize distractions. Turn off your cell phone and get away from Facebook, television, other nearby activities, and chatty friends or roommates. All of these can cut into the effectiveness of your study efforts. Multitasking and studying don’t mix.
- If you will be studying for a long time, take short breaks at least once an hour. Get up, stretch, breathe deeply, and then get back to work. (If you keep up with your daily assignments and schedule weekly review sessions for yourself—and keep them—there should be almost no need for long study sessions.)
Studying in Groups
Study groups are a great idea, as long as they are thoughtfully managed. A study group can give you new perspectives on course material and help you fill in gaps in your notes. Discussing course content will sharpen your critical thinking related to the subject, and being part of a group to which you are accountable will help you study consistently. In a study group, you will end up “teaching” each other the material, which is the strongest way to retain new material. But remember, being in a group working together doesn’t mean there will be less work for you as an individual; your work will just be much more effective.
Here are some tips for creating and managing effective study groups:
- Think small. Limit your study group to no more than three or four people. A larger group would limit each student’s participation and make scheduling of regular study sessions a real problem.
- Go for quality. Look for students who are doing well in the course, who ask questions, and who participate in class discussions. Don’t make friendship the primary consideration for who should be in your group. Meet up with your friends instead during “social time”—study time is all about learning.
- Look for complementary skills and learning styles. Complementary skills make for a good study group because your weaknesses will be countered by another student’s strengths. When a subject requires a combination of various skills, strengths in each of those skills are helpful (e.g., a group with one student who is really good at physics and another at math would be perfect for an engineering course). Finally, a variety of learning styles is helpful because each of you picks up differing signals and emphases from the instructor that you can share with each other, so you will not likely miss important points.
- Meet regularly. When you first set up a study group, agree to a regular meeting schedule and stick to it. Moving study session times around can result in nonparticipation, lack of preparation, and eventually the collapse of the study group. Equally important is keeping your sessions to the allotted times. If you waste time and regularly meet much longer than you agreed to, participants will not feel they are getting study value for their time invested.
- Define an agenda and objectives. Give your study sessions focus so that you don’t get sidetracked. Based on requests and comments from the group, the moderator should develop the agenda and start each session by summarizing what the group expects to cover and then keep the group to task.
- Include some of the following items on your agenda:
- Review and discuss class and assignment notes since your last meeting.
- Discuss assigned readings.
- Quiz each other on class material.
- “Reteach” aspects of the material team participants are unsure of.
- Brainstorm possible test questions and responses.
- Review quiz and test results and correct misunderstandings.
- Critique each other’s ideas for paper themes and approaches.
- Define questions to ask the instructor.
- Assign follow-up work. If there is any work that needs to be done between meetings, make sure that all team members know specifically what is expected of them and agree to do the work.
- Rotate the role of moderator or discussion leader. This helps ensure “ownership” of the group is spread equally across all members and ensures active participation and careful preparation.
Types of Tests
All tests are designed to determine how much you know about a particular subject at a particular point in time. There are many ways to understand how tests and exams fit into academia and college culture. One way is to ask what purpose the tests (also called assessments) serve. For example, what is your professor trying to achieve if they give you a survey-type test on the first day of class? How might the purpose of that test differ from that of, say, a practice quiz given before a midterm? And what is the purpose of a midterm?
Obviously, each survey, quiz, practice test, midterm, and final exam can serve different purposes. Depending upon the purpose, the assessment will fall into one of the following three categories:
- Pre-assessment
- Formative assessment
- Summative assessment
Pre-assessments: Tests in this category are used to measure the beliefs, assumptions, knowledge, and skills that you have when you begin a class or before you begin working on a new topic. With pre-assessments, your professor gathers baseline data to use at a later time to evaluate change—that is, by comparing former knowledge or skills against what you learn in class.
One approach to pre-assessment is for a professor to ask students at the start of the term to describe a term or concept that’s foundational to the course. Then, later in the course, the professor revisits that data to determine how the instruction changed your understanding of the same concept. Comparing what you know or believe before and after a course or lesson is a productive way to gauge how successful your learning was and how successful the teaching was.
Formative assessments: Tests in this category are typically quizzes, unit tests, pop quizzes, and review quizzes from a textbook or its Web site. Their main objective is to make sure you know the fundamental material before moving on to more challenging topics. Because these quizzes usually don’t count much toward your final grade, many students think they are not very important. In fact, these quizzes are very important, particularly to you; they can help you to identify what you know and what you still need to learn to be successful in the course and in applying the material. A poor result on a quiz may not negatively affect your final grade much, but learning from its results and correcting your mistakes will affect your final grade, on the positive side, when you take midterms and finals!
Summative assessments: Tests in this category are the assessments that students are most familiar with: midterms and finals. They are used by the instructor to determine if you are mastering a large portion of the material, and as such, they usually carry a heavyweight toward your final grade for the course. Because of this, summative assessments can be stressful, but they can also be an effective measurement tool.
Test Formats
Tests vary in style, rigor, and requirements. For example, in a closed book test, a test taker is typically required to rely upon memory to respond to specific items. In an open-book test, though, a test taker may use one or more supplementary resources such as a reference book or notes. Open-book testing may be used for subjects in which many technical terms or formulas are required to effectively answer questions, like in chemistry or physics.
In addition, tests may be administered formally or informally. In an informal test, you might simply respond in a class to questions posed by the instructor. In a formal test, you are usually expected to work alone, and the stakes are higher.
Below is a sampling of common test formats you may encounter. If you know what kind of test you’ll be taking, you can tailor your study approach to the format.
Common Test Types
There are three common test types: written tests, oral tests, and electronic tests. Let’s look at the kinds of things you’ll be expected to complete in each test type.
Written tests can be open book, closed book, or anywhere in between. Students are required to give written answers (as the name of this test type implies).
- Paper tests are still the most common type of test, requiring students to write answers on the test pages or in a separate test booklet or answer sheet. They are typically used for in-class tests. Neatness and good grammar count, even if it’s not an English exam. Remember that the instructor will be reading dozens of test papers and will not likely spend much time trying to figure out your hieroglyphics, arrows, and cross-outs.
- Open-book tests allow the student to consult their notes, textbook, or both while taking the exam. Instructors often give this type of test when they are more interested in seeing your thoughts and critical thinking than your memory power. Be prepared to expose and defend your own viewpoints. When preparing, know where key material is present in your book and notes; create an index for your notes and use sticky notes to flag key pages of your textbook before the exam. Be careful when copying information or formulas to your test answers, because nothing looks worse in an open-book exam than misusing the material at your disposal.
- Take-home tests are like open-book tests except you have the luxury of time on your side. Make sure you submit the exam on time. Know what the instructor’s expectations are about the content of your answers. The instructor will likely expect more detail and complete work because you are not under a strict time limit and because you have access to reference materials. Be clear about when the test is due. (Some instructors will ask you to e-mail your exam to them by a specific time.) Also, find out if the instructor allows or expects you to collaborate with classmates. Be sure to type your exam and don’t forget to spell-check!
Below you’ll find a table of the most common question types in written tests:
| Question Type | Description |
|---|---|
| Multiple choice (objective) | You are presented with a question and a set of answers for each question, and you must choose which answer or group of answers is correct. Multiple-choice questions usually require less time for test-takers to answer than other question types, and they are easy to score and grade. They also allow for a wide range of difficulty. |
| True False (objective) | You are presented with a statement, and you must determine whether it is true or false. True/false questions are generally not predominant on tests because instructors know that, statistically, random guesswork can yield a good score. But when used sparingly, true/false questions can be effective. |
| Matching (objective) | You are presented with a set of specific terms or ideas and a set of definitions or identifying characteristics. You must match each term with its correct definition or characteristics. |
| Fill-in-the-blank (objective) | You are presented with identifying characteristics, and you must recall and supply the correct associated term or idea. There are two types of fill-in-the-blank tests: 1) The easier version provides a word bank of possible words that will fill in the blanks. 2) The more difficult version has no word bank to choose from. Fill-in-the-blank tests with no word bank can be anxiety-producing. |
| Essay (subjective) | You are presented with a question or concept that you must explain in depth. Essay questions emphasize themes and broad ideas. Essay questions allow students to demonstrate critical thinking, creative thinking, and writing skills. |
Oral Tests or Presentations are a discussion type of test. They are also subjective: there isn’t just one correct answer to the test questions. The oral test is practiced in many schools and disciplines in which an examiner verbally poses questions to the student. The student must answer the question in such a way as to demonstrate sufficient knowledge of the subject. Usually, study guides or a syllabus are made available so that the students may prepare for the exam by reviewing practice questions and topics likely to be on the exam. The instructor can (and likely will) probe you on certain points, question your assumptions, or ask you to defend your point of view. Make sure you practice your presentation many times with and without an audience (your study group is good for this). Have a clear and concise point of view and keep to the allotted time. (You don’t want to miss delivering a killer close if your instructor cuts you off because you weren’t aware of the time!)
Electronic Tests or Online Tests are most commonly used for formative assessments, although they are starting to find their way into high-stakes exams, particularly in large lecture classes that fulfill a graduation requirement (like introductory psychology or history survey courses). The main advantage of online tests is that they can be computer-graded, providing fast feedback to the student (with formative tests) and allowing the instructor to grade hundreds of exams easily (with summative assessments). Since these tests are computer-graded, be aware that the instructor’s judgment is not involved in the grading. Your answers will be either right or wrong; there is no room for partially correct responses. With online tests, be sure you understand the testing software. Are there practice questions? If so, make sure you use them. Find out if you will be allowed to move freely between test sections to go back and check your work or to complete questions you might have skipped. Some testing software does not allow you to return to sections once they are “submitted.” Unless your exam needs to be taken at a specific time, don’t wait until the last minute to take the test. Should you have technical problems, you want to have time to resolve the issues. To avoid any conflicts with the testing software, close all other software applications before beginning the testing software. Electronic tests in the classroom are becoming more common as colleges install “smart classrooms” with technology such as wireless “clicker” technology that instructors may use to get a quick read of students’ understanding of a lecture. This testing method allows for only true-or-false and multiple-choice questions, so it is rarely used for summative assessments. When taking this kind of quick quiz, take notes on questions you miss so that you can focus on them when you do your own review.
Complete Section #3 Below: ACTIVITY: Test your Test Knowledge Crossword
Test-Taking Strategies
You have used all the study skills you learned in this course. You listen in class, take clear notes, read your textbook, compare your textbook and classroom notes, and review regularly. You have brought your test anxiety into control. Your upcoming test is now an opportunity for you to show what you have learned What else can you do to ensure success on a test?
Before the Test
- Use your study skills as you go.
- Research the test’s structure and scope.
- What is the test format?
- What chapters does it cover?
- How many questions are on it?
- What is the time limit?
- What materials are allowed?
- Is a study guide provided?
- Are practice tests available?
- What percentage of your final grade is the test?
- Collect and organize the resources you need to study.
- Classroom notes
- Textbook notes
- Master set of notes
- Study guides
- Practice tests
- Handouts
- Slides or presentations
- Study over several sessions
- Make a study plan for several days before the exam
- Have a clear goal for each study session
- Study in 45-60 minutes chunks and then take a break
- Make study aids
- Create flashcards
- Make a study guide
- Make a practice test
- Predict test questions
- Practice answering essay questions
- Get a good night’s sleep.
- Have a healthy breakfast
- Be sure you have all the necessary materials
- Pencils
- Erasers
- Pens
- Answer sheets/test booklets
- Calculators
- Arrive early and relax
During the Test
Scan the test first to see what it covers
- This often reduces anxiety and boosts confidence
- Identify the point value of each test section
- Write down what you know
- If you are trying to remember things like formulas, definitions, lists, etc., flip your test over and write down everything you are trying to remember. This will clear your brain, allowing you to focus 100% on the exam, rather than using part of your attention to remember specific information.
- Plan your time
- Now that you have scanned your test, how much time should you spend on each section?
- This can often reduce anxiety and keeps you from unnecessarily rushing
- Check on the time often to make sure you are on track. Slow down or speed up as necessary.
- Work on high point-value questions first
- Read the instructions carefully
- Don’t assume you know what the instructions are. Be sure!
- Answer the easy questions first and skip the harder ones.
- Go through the test and answer all of the ones you know first.
- Skip the ones you are unsure of. There are often clues later in the exam or another question that will spark your memory.
- Stay positive by not getting down about a question you don’t know. Skip it and return to it later.
- Read each question carefully!
- Answer everything. Don’t leave anything blank, even if you have to guess.
- Don’t rush! Use all the time available. There are no points for finishing first.
- Check your work for accuracy.
- Check to make sure you have answered all parts of a question.
- Check your answer sheet every 10 questions to make sure you aren’t mismarking.
- Only change an answer if you are SURE you made a mistake. Your first instinct is most likely correct.
After the Test
- Reward yourself for a job well done!
- Stick with your study schedule
- We have a tendency to take a break from our studies after an exam, often resulting in being behind the next week.
- Use the test as a learning tool
- What did you well?
- What can you do differently for the next test?
- What did you learn about this instructor’s testing style and how will that impact your study plan?
- What patterns do you notice about your test-taking?
- Did you lose points for not answering all parts of the essay?
- Did you not read questions or instructions carefully?
- Do you need to focus more on dates, vocabulary, formulas, etc.?
- Review your test carefully and fix all errors so you don’t make the same mistakes again.
- Apply the feedback to the next test
Strategies For Specific Question Types
You can gain even more confidence in your test-taking abilities by understanding the different kinds of questions an instructor may ask and apply the following proven strategies for answering them. Most instructors will likely use various conventional types of questions. Here are some tips for handling the most common types.
Multiple-Choice Questions
- Read the instructions carefully to determine if there may be more than one right answer.
- If there are multiple right answers, does the instructor expect you to choose just one, or do you need to mark all correct options?
- Read each question carefully and try to answer it in your head before reading the answer options.
- Then consider all the options.
- Eliminate first the options that are clearly incorrect.
- Compare the remaining answers with your own answer before choosing one and marking your paper.
- If you are stuck, treat the remaining answers as True/Fale statements. This often helps pick the correct answer.
- Look for clue words that hint that certain option answers might be correct or incorrect.
- Absolute words like “never,” “always,” “every,” or “none” are rarely found in a correct option.
- Less absolute words like “usually,” “often,” or “rarely” are regularly found in correct options.
- Be on the lookout for the word “not” in the stem phrase and in the answer choice options; it is an easy word to miss if you are reading too quickly, but it completely changes the meaning of the possible statements.
- Skip difficult questions.
- There are often clues in later questions. Or, you may recall information that you had forgotten
- Go back and answer all the questions.
- Do not leave any questions blank, unless there is a penalty for wrong answers (this is often on standardized tests like the SAT and LSAT but rarely on college tests.)
True-or-False Questions
- Most of the tips for multiple-choice questions apply here as well.
- Be particularly aware of the words “never,” “always,” “every,” “none,” and “not” because they can determine the correct answer.
- Answer the questions that are obvious to you first. Then go back to statements that require more thought.
- If the question is stated in the positive, restate it to yourself in the negative by adding the word “not” or “never.” Does the new statement sound truer or more false?
- If you still are unsure whether a statement is true or false and must guess, choose “true” because most tests include more true statements than false (but don’t guess if a wrong answer penalizes you more than one left blank).
Matching Columns
- Start by looking at the two columns to be matched. Is there an equal number of items in both columns? If they are not equal, do you have to match some items in the shorter column to two or more items in the longer column, or can you leave some items unmatched? Read the directions to be sure.
- If one column has a series of single words to be matched to phrases in the other column, read all the phrases first, then all the single words before trying to make any matches. Now go back and read each phrase and find the word that best suits the phrase.
- If both columns have single words to be matched, look to cut down the number of potential matches by grouping them by parts of speech (nouns with nouns, verbs with verbs, etc.).
- As always, start by making the matches that are obvious to you, and then work on the ones that require more thought. Mark off all items you have already used so you can easily see which words or phrases still remain to be matched.
Short Answer Questions
- Short answer questions are designed for you to recall and provide some very specific information (unlike essay questions, which also ask you to apply critical thinking to that information). When you read the question, ask yourself what exactly the instructor wants to know. Keep your answers short and specific.
Essay Questions
- Essay questions are used by instructors to evaluate your thinking and reasoning applied to the material covered in a course. Good essay answers are based on your thoughts, supported by examples from classes and reading assignments.
- Careful planning is critical to answering essay questions effectively. Note how many essay questions you have to answer and how difficult each question seems. Then allocate your time accordingly.
- Read the question carefully and underline or circle keywords.
- Watch for words that describe the instructor’s expectations for your response (see the table below.)
- Use other parts of the exam, like multiple choice, to help you recall vocabulary or specific information.
- If time allows, organize your thoughts by creating a quick outline for your essay. This helps ensure that you don’t leave out key points, and if you run out of time, it may pick up a few points for your grade.
- Jot down the specific information you might want to use, such as names, dates, and places.
- Introduce your essay answer, but get right to the point. Remember that the instructor will be grading dozens of papers and avoid “filler” text that does not add value to your answer.
- For example, rather than writing, “In our study of the Civil War, it is helpful to consider the many facets that lead to conflict, especially the economic factors that help explain this important turning point in our nation’s history,” write a more direct and concise statement like this: “Economic factors help explain the start of the Civil War.”
- Write neatly and watch your grammar and spelling.
- Allow time to proofread your essay. You want your instructor to want to read your essay, not dread it.
- Remember that grading essays is are largely subjective, and a favorable impression can lead to more favorable grading.
- Be sure to answer all parts of the question. Essay questions often have more than one part. Remember, too, that essay questions often have multiple acceptable answers.
Words to Watch for in Essay Questions
| Word | What It Means | What the Instructor Is Looking For |
|---|---|---|
| Analyze | Break concept into key parts | Don’t just list the parts; show how they work together and illustrate any patterns. |
| Compare | Show similarities (and sometimes differences) between two or more concepts or ideas | Define the similarities and clearly describe how the items or ideas are similar. Do these similarities lead to similar results or effects? Note that this word is often combined with “contrast.” If so, make sure you do both. |
| Contrast | Show differences between two or more concepts or ideas | Define the differences and clearly describe how the items or ideas are different. How do these differences result in different outcomes? Note that this word is often combined with “compare.” If so, make sure you do both. |
| Critique | Judge and analyze | Explain what is wrong—and right—about a concept. Include your own judgments, supported by evidence and quotes from experts that support your point of view. |
| Define | Describe the meaning of a word, phrase, or concept | Define the concept or idea as your instructor did in class—but use your own words. If your definition differs from what the instructor presented, support your difference with evidence. Keep this essay short. Examples can help illustrate a definition, but remember that examples alone are not a definition. |
| Discuss | Explain or review | Define the key questions around the issue to be discussed and then answer them. Another approach is to define the pros and cons on the issue and compare and contrast them. In either case, explore all relevant data and information. |
| Explain | Clarify, give reasons for something | Clarity is key for these questions. Outline your thoughts carefully. Proofread, edit, proofread, and proofread again! Good explanations are often lost in too many words. |
| Illustrate | Offer examples | Use examples from class material or reading assignments. Compare and contrast them to other examples you might come up with from additional reading or real life. |
| Prove | Provide evidence and arguments that something is true | Instructors who include this prompt in an exam question have often proven the hypothesis or other concepts in their class lectures. Think about the kind of evidence the instructor used and apply similar types of processes and data. |
| Summarize | Give a brief, precise description of an idea or concept | Keep it short, but cover all key points. This is one essay prompt where examples should not be included unless the instructions specifically ask for them. (For example, “Summarize the steps of the learning cycle and give examples of the main strategies you should apply in each one.”) |
Below is another video from College Info Geek called 10 Ways to Avoid Making Stupid Mistakes on Exams.
Practicing Academic Integrity On Exams
Throughout this book, we have focused on the active process of learning, not just on how to get good grades. The attitude of some students that grades are the end-all in academics has led many students to resort to academic dishonesty to try to get the best possible grades or handle the pressure of an academic program. Although you may be further tempted if you’ve heard people say, “Everybody does it,” or “It’s no big deal at my school,” you should be mindful of the consequences of cheating:
- You don’t learn as much. Cheating may get you the right answer on a particular exam question, but it won’t teach you how to apply knowledge in the world after school, nor will it give you a foundation of knowledge for learning the more advanced material. When you cheat, you cheat yourself out of opportunities.
- You risk failing the course or even expulsion from school. Each institution has its own definitions of and penalties for academic dishonesty, but most include cheating, plagiarism, and fabrication or falsification. The exact details of what is allowed or not allowed vary somewhat among different colleges and even instructors, so you should be sure to check your school’s Web site and your instructor’s guidelines to see what rules apply. Ignorance of the rules is seldom considered a valid defense.
- Cheating causes stress. Fear of getting caught will cause you stress and anxiety; this will get in the way of performing well with the information you do know.
- You’re throwing away your money and time. Getting a college education is a big investment of money and effort. You’re simply not getting your full value when you cheat because you don’t learn as much.
- You are trashing your integrity. Cheating once and getting away with it makes it easier to cheat again, and the more you cheat, the more comfortable you will feel with giving up your integrity in other areas of life—with perhaps even more serious consequences.
- Cheating lowers your self-esteem. If you cheat, you are telling yourself that you are simply not smart enough to handle learning. It also robs you of the feeling of satisfaction from genuine success.
Technology has made it easier to cheat. Your credit card and an Internet connection can procure a paper for you on just about any subject and length. You can copy and paste for free from various Web sites. Students have made creative use of texting and video on their cell phones to gain unauthorized access to material for exams. But be aware that technology has also created ways for instructors to easily detect these forms of academic dishonesty. Most colleges make these tools available to their instructors. Instructors are also modifying their testing approaches to reduce potential academic misconduct by using methods that are harder to cheat at (such as in-class essays that evaluate your thinking and oral presentations).
If you feel uneasy about doing something in your college work, trust your instincts. Confirm with the instructor that your intended form of research or use of the material is acceptable. Cheating just doesn’t pay.
Examples of Academic Dishonesty
Academic dishonesty can take many forms, and you should be careful to avoid them. The following list from Northwestern University is a clear and complete compilation of what most institutions will consider unacceptable academic behavior.
- Cheating: using unauthorized notes, study aids, or information on an examination; altering a graded work after it has been returned, then submitting the work for regrading; allowing another person to do one’s work and submitting that work under one’s own name; submitting identical or similar papers for credit in more than one course without prior permission from the course instructors.
- Plagiarism: submitting material that in part or whole is not entirely one’s own work without attributing those same portions to their correct source. You can read more about plagiarism in Chapters 2 and 14.
- Fabrication: falsifying or inventing any information, data, or citation; presenting data that were not gathered in accordance with standard guidelines defining the appropriate methods for collecting or generating data and failing to include an accurate account of the method by which the data were gathered or collected.
- Obtaining an Unfair Advantage: (a) stealing, reproducing, circulating, or otherwise gaining access to examination materials prior to the time authorized by the instructor; (b) stealing, destroying, defacing, or concealing library materials with the purpose of depriving others of their use; (c) unauthorized collaboration on an academic assignment; (d) retaining, possessing, using or circulating previously given examination materials, where those materials clearly indicate that they are to be returned to the instructor at the conclusion of the examination; (e) intentionally obstructing or interfering with another student’s academic work; or (f) otherwise undertaking an activity with the purpose of creating or obtaining an unfair academic advantage over other students’ academic work.
- Aiding and Abetting Academic Dishonesty: (a) providing material, information, or other assistance to another person with knowledge that such aid could be used in any of the violations stated above, or (b) providing false information in connection with any inquiry regarding academic integrity.
- Falsification of Records and Official Documents: altering documents affecting academic records; forging signatures of authorization or falsifying information on an official academic document, grade report, letter of permission, petition, drop/add form, ID card, or any other official University document.
- Unauthorized Access to computerized academic or administrative records or systems: viewing or altering computer records, modifying computer programs or systems, releasing or dispensing information gained via unauthorized access, or interfering with the use or availability of computer systems or information.
Using Test Results
So far, we have focused on how to study for and take tests effectively. This section discusses how to use test results to their greatest benefit. Some of your most important learning begins when your graded test paper is returned to you. Your first reaction, of course, is to see what grade you received and how you did compared with your classmates. This is a natural reaction.
Make sure you listen to the instructor as the papers are returned. What is the instructor saying about the test? Is there a particular point everyone had trouble with? Does the instructor generally think everyone did well? The instructor’s comments at this point may give you important information about what you should study more, about the value of review sessions, and even about possible questions for the next exam.
Although you may be tempted to throw away the exam, don’t. It is a very helpful tool for the next phase of preparing for learning. This is a three-step process, beginning with evaluating your results.
Evaluating Your Test Results
When you receive your test back, sit quietly and take a close look at it. What questions did you get wrong? What kind of mistakes were they? (See Table: “Exam Errors and How to Correct Them”.) Do you see a pattern? What questions did you get right? What were your strengths? What can you learn from the instructor’s comments?
Now think of the way in which you prepared for the exam and the extent to which you applied the exam strategies described earlier in this chapter. Were you prepared for the exam? Did you study the right material? What surprised you? Did you read the entire test before starting? Did your time allocation work well, or were you short of time on certain parts of the exam?
Table: Exam Errors and How to Correct Them
| Type of Error | Examples | Corrective Steps |
|---|---|---|
| Study and Preparation Errors | I did not study the material for that question (enough). | Practice predicting possible questions better. |
| I ran out of time. | Join a study group. | |
| I did not prepare enough. | Read the entire test before starting. Allocate your time. | |
| Focus Errors or Carelessness | I did not read the directions carefully. | Allocate exam time carefully. |
| I confused terms or concepts that I actually know well. | Give yourself time to read carefully and think before answering a question. | |
| I misread or misunderstood the question. | ||
| Content Errors | I studied the material but couldn’t make it work with the question | Seek additional help from the instructor. |
| I didn’t understand what the instructor wanted. | Go to all classes, labs, and review sessions. | |
| I confused terms or concepts. | Join a study group. | |
| Check and practice your active reading and listening skills. | ||
| Schedule regular study time for this course. | ||
| Mechanical Errors | The instructor misread my writing. | Slow down! Don’t rush through the exam. Take the time to do things right the first time. |
| I didn’t erase a wrong answer completely (on a computer-graded answer sheet). | ||
| I forgot to go back to a question I had skipped over. | ||
| I miscopied some calculations or facts from my worksheet. |
Based on your analysis of your test, identify the kind of corrective steps you should take to improve your learning and test performance. Implement those steps as you begin your preparation for your next class. If you don’t learn from your mistakes, you are doomed to repeat them; if you don’t learn from your successes, it will be harder to repeat them.
Correcting Your Mistakes
The second step in making your test work for you is to correct your wrong answers. The last time you wrote the information (when you took the test), you created a link to the wrong information in your memory, so that must be corrected.
- For multiple-choice questions, write out the question stem with the correct answer to form a single correct sentence or phrase.
- For true-or-false questions, write the full statement if it is true; if it is false, reword it in such a way that it is true (such as by inserting the word “not”). Then write the new statement.
- For math and science questions involving calculations, redo the entire solution with the calculations written out fully.
- You need not rewrite an entire essay question if you did not do well, but you should create a new outline for what would be a correct answer. Make sure you incorporate any ideas triggered by your instructor’s comments.
- When you have rewritten all your answers, read them all out loud before incorporating your new answers in your notes.
Integrating Your Test into Your Study Guide
Your corrected quizzes and midterm exams are important study tools for final exams. Make sure you file them with your notes for the study unit. Take the time to annotate your notes based on the exam. Pay particular attention to any gaps in your notes on topics that appeared in the quiz or exam. Research those points in your text or online and complete your notes. Review your exams throughout the term (not just before the final) to be sure you cement the course material into your memory.
When you prepare for the final exam, start by reviewing your quizzes and other tests to predict the kinds of questions the instructor may ask on the final. This will help focus your final studying when you have a large amount of coursework to cover.
If You Don’t Get Your Test Back
If your instructor chooses not to return tests to students, make an appointment to see the instructor soon after the test to review it and your performance. Take notes on what you had trouble with and the expected answers. Add these notes to your study guide. Make sure you don’t lose out on the opportunity to learn from your results.
KEY TAKEAWAYS
- Some stress before a test or exam is common and beneficial but test anxiety is stress that gets in the way of performing effectively.
- The most common causes of test anxiety are a lack of preparation and negative attitudes.
- The key to combating test anxiety is to try to reduce stressors to a manageable level rather than try to eliminate them totally.
- Effective studying happens over time, not just a few days before an exam. Consistent and regular review time helps you learn the material better and saves you time and anguish as exam time approaches.
- Study groups are a great idea, provided they are thoughtfully managed.
- In addition to studying, prepare for exams and quizzes by getting plenty of rest, eating well, and getting some exercise the day before the exam.
- Before the exam, learn as much as you can about the kinds of questions your instructor will be asking and the specific material that will be covered.
- The first step to the successful completion of an exam is to browse the entire exam and develop a plan (including a “time budget”) for completing the exam.
- Read questions carefully. Underline keywords in questions, particularly in essay questions and science questions.
- Being dishonest can have major consequences that can affect not only your college career but also your life beyond college.
- When you cheat, you are primarily cheating yourself.
- Working with exams does not end when your instructor hands back your graded test.
- Quizzes and midterms are reliable predictors of the kind of material that will be on the final exam.
- When evaluating your test performance, don’t look only at the content you missed. Identify the types of mistakes you commonly make and formulate plans to prevent these mistakes in future assessments.
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- Chapter 6: Preparing for and Taking Tests. in College Success. Authored by: Anonymous. Provided by: University of Minnesota. Located at: http://www.oercommons.org/courses/college-success/view. License: CC BY-NC-SA-4.0
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- Test Anxiety: How to Take On Your Exams Without Stress - College Info Geek. Authored by: Thomas Frank. Located at: https://www.youtube.com/watch?v=fHfHSq7PVDU. License: All Rights Reserved. License Terms: Standard YouTube
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Chapter 14: Effective Writing
Overview
Learning Framework: Effective Strategies for College Success
Chapter 14: Effective Writing
Learning Objectives
By the end of this chapter, you will be able to:
- Describe the importance of good writing skills.
- Define “academic writing" and explain the key aspects of academic writing.
- Define what instructors expect of a college student’s writing.
- Understand and utilize the five writing-process steps.
- Differentiate between revision and proofreading, and explain the value of each.
- Know where to get help with your writing.
- Understand the principles of academic integrity.
- Identify strategies for ethical use of sources in writing.
Effective Writing
The Importance Of Writing Skills
Writing is one of the key skills all successful students must acquire. You might think your main job in a history class is to learn facts about events. So you read your textbook and take notes on important dates, names, causes, etc. But however important these details are to your instructor, they don’t mean much if you can’t explain them in writing. Even if you remember the facts and believe you understand their meaning completely, if you can’t express your understanding by communicating it—in college that almost always means in writing—then as far as others may know, you don’t have an understanding. In a way, learning history is learning to write about history.
History is just one example. Consider a lab course—a class that’s as much hands-on as any in college. At some point, you’ll be asked to write a step-by-step report on an experiment you have run. The quality of your lab work will not show if you cannot describe that work and state your findings well in writing. Even though instructors in courses other than English classes may not comment directly on your writing, their judgment of your understanding will still be mostly based on what you write. This means that in all your courses, not just your English courses, instructors expect good writing.
In college courses, writing is how ideas are exchanged, from scholars to students and from students back to scholars. While the grade in some courses may be based mostly on class participation, oral reports, or multiple-choice exams, writing is by far the single most important form of instruction and assessment.
If you find that a scary thought, take heart! By paying attention to your writing and learning and practicing basic skills, even those who never thought of themselves as good writers can succeed in college writing. As with other college skills, getting off to a good start is mostly a matter of being motivated and developing a confident attitude that you can do it. Research shows that deliberate practice—that is, close focus on improving one’s skills—makes all the difference in how one performs.
A survey of employers conducted by the Association of American Colleges and Universities found that 89 percent of employers say that colleges and universities should place more emphasis on “the ability to effectively communicate orally and in writing.” In addition, several of the other valued skills are grounded in written communication: “Critical thinking and analytical reasoning skills” (81 percent); “The ability to analyze and solve complex problems” (75 percent); and “The ability to locate, organize, and evaluate information from multiple sources” (68 percent).
The payoff for improving your writing comes much sooner than graduation. Suppose you complete about 40 classes for a 120-credit bachelor's degree, and—averaging across writing-intensive and non-writing-intensive courses—you produce about 2,500 words of formal writing per class. Even with that low estimate, you’ll write 100,000 words during your college career. That’s roughly equivalent to a 330-page book.
Spending a few hours sharpening your writing skills will make those 100,000 words much easier and more rewarding to write. All of your professors care about good writing.
What is Academic Writing?
Writing in college is a fairly specialized writing situation, and it has developed its own codes and conventions that you need to have a keen awareness of if you are going to write successfully in college. Let’s break down the writing situation in college:
| Who’s your audience? | Primarily the professor and possibly your classmates (though you may be asked to include a secondary outside audience). |
| What’s the occasion or context? | An assignment given by the teacher within a learning context and designed to have you learn and demonstrate your learning. |
| What’s your message? | It will be your learning or the interpretation gained from your study of the subject matter. |
| What’s your purpose? | To show your learning and get a good grade (or to accomplish the goals of the writing assignment). |
| What documents/ genres are used? | The essay is the most frequent type of document used. |
Every form of writing has its conventions. How we write text messages to our friends is different from how we write a job application; the language used in a soap opera is different from the language used on the news. And the language of academic writing has its own set of characteristics.
As a basic rule, academic writing is more formal than the everyday language we tend to use for communication. But at the same time, academic writing isn't about impressing people with ‘big words’ or being overly formal. It needs to be clear, concise, and objective so that you can communicate your ideas effectively.
Compare these two sentences - they contain the same information, but the better style example is much shorter, simpler, and easier to understand.
Poor style: The primary ambition of expressing concepts in an academic fashion is to provide assistance for the audience of the piece in comprehending the information being conveyed in an expeditious and accessible manner.
Better style: Effective academic writing helps readers understand your points quickly and easily.
Instead of being formal, academic writing uses neutral words and avoids informal, conversational, or colloquial language. For example, 'many factors' is more academic than 'loads of things'. Also, avoid personal language - you're not the focus of the work (unless it's a reflective assignment like those often found in this EDUC course). You should also generally use objective language, for example, "it is really bad" is subjective, but "a key negative consequence" is objective.
Be Clear
Clarity is a key aspect of academic writing style. This helps the reader understand and follow your points easily.
- Break down long, complex sentences into shorter, clearer sentences.
- Don’t use formal or unusual words where you can use a ‘normal’ one.
- You won’t get points for being overly formal, or ‘sounding like an academic ’ - probably the opposite, as this makes your writing harder to follow.
Be concise
Academic writing also aims to be concise and use as few words as possible. Remove words and phrases that don’t add anything to your argument. This makes your writing clearer and means you’ll have more words to make your points with. After writing a paragraph, read it back and remove any unnecessary words. Be ruthless!
Avoid personal pronouns
Usually, you're not the focus of the writing, so using personal pronouns can make the important aspects of your writing harder to identify. We also know that you wrote the work, or that you did the research, so you don't need to tell us this.
Avoiding personal pronouns like "I" helps you focus on what's important:
- I will argue that... → This essay will argue that...
- I tested the samples → Samples were tested
The exception is reflective writing. In this case, you may use personal language to discuss your own experiences.
Be objective
Academic writing is based on objective arguments. Using personal or emotive language makes your writing subjective and more opinion-based, and so weakens these arguments.
- I think X is the best solution. → Based on this evidence, it seems X is the best solution.
- In my opinion, this happened because... → The reasons for this are...
- Many people believe that... → It is widely believed that...
- avoid emotive and subjective words like "unfortunately", "luckily" etc.
Use Structure
Academic writing has a clear, logical structure to communicate your points and show the connections between them; a well-structured assignment is easy for the reader to follow and understand.
These general principles apply to structuring most types of academic writing:
- Use a linear structure where points build on each other - don't jump backward and forwards.
- Start with more general and then move to the more specific ideas and points.
- Put more relevant/important information first.
- Everything is relevant to the main argument or point of the paragraph.
- Use cohesion to join ideas and points clearly - don't make the reader do the work.
- Follow any structural requirements for your assignment or type of writing.
The best way to write a well-structured assignment is to have a good plan before you start writing. What's your argument? What are the main points you want to include? What's a logical way to order these points? Don't just launch into writing with no idea of where you're going!
To make a general plan:
- Make a list of the information and points to include.
- Organize similar points into groups.
- Put the groups in a logical order.
- Within each group, organize the points logically.
- Check the plan to make sure it meets task requirements.
Paragraph Structure
A well-structured paragraph contains one main point or idea - all the information included is relevant to this point. If it's not related to the main point, it probably shouldn't be there!
There are many ways to structure a paragraph, but they generally all include:
- a topic sentence showing the main point
- the body of the paragraph, integrating:
- development of the point: more detail, examples, etc.
- evidence to support the point
- critical analysis showing how evidence relates to the main point
- a final wrap-up linking to the overall argument or the next paragraph
However, this is only a guide - there are many ways to structure a paragraph. Reading sources from your field will help you to get a feel of ways to organize paragraphs.
Be Cohesive
Cohesive words and phrases are used heavily in academic writing style to smoothly link points. They're generally small and fairly simple but are integral to communicating your argument. If the structure is the order of your points, cohesion is what ties them together and guides the reader through your argument.
Create cohesion using words and phrases that show the relationships between points. For example:
- basic connectives: and, or, but, so
- giving more detail: for example, to illustrate, an example of this is
- showing contrast: however, although, while, conversely, alternatively
- showing similarity: another, also, similarly, collectively, taken together
- cause/effect: leading to, the effect of this is, therefore, may stem from
- referencing words: this/that, who, which/that, the groups, these findings
- showing implications: this suggests that, these findings may mean that, based on this
Myths About College Writing
There are many misconceptions about college writing. Here are a few myths that can lead to problems in writing.
Myth #1: The “Paint by Numbers” myth
Some writers believe they must perform certain steps in a particular order to write “correctly.” Rather than being a lock-step linear process, writing is “recursive.” That means we cycle through and repeat the various activities of the writing process many times as we write.
Myth #2: Writers only start writing when they have everything figured out
Writing is not like sending a fax! Writers figure out much of what they want to write as they write it. Rather than waiting, get some writing on the page—even with gaps or problems. You can come back to patch up rough spots.
Myth #3: Perfect first drafts
We put unrealistic expectations on early drafts, either by focusing too much on the impossible task of making them perfect (which can put a cap on the development of our ideas), or by making too little effort because we don’t care or know about their inevitable problems. Nobody writes perfect first drafts; polished writing takes lots of revision.
Myth #4: Some got it; I don’t—the genius fallacy
When you see your writing ability as something fixed or out of your control (as if it were in your genetic code), then you won’t believe you can improve as a writer and are likely not to make any efforts in that direction. With effort and study, though, you can improve as a writer.
Myth #5: Good grammar is good writing
When people say “I can’t write,” what they often mean is they have problems with grammatical correctness. Writing, however, is about more than just grammatical correctness. Good writing is a matter of achieving your desired effect on an intended audience. Plus, as we saw in Myth #3, no one writes perfect first drafts.
Myth #6: The Five-Paragraph Essay
Some people say to avoid it at all costs, while others believe no other way to write exists. With an introduction, three supporting paragraphs, and a conclusion, the five-paragraph essay is a format you should know, but one which you will outgrow. You’ll have to gauge the particular writing assignment to see whether and how this format is useful for you.
Myth #7: Never use “I”
Adopting this formal stance of objectivity implies a distrust (almost fear) of informality and often leads to artificial, puffed-up prose. Although some writing situations will call on you to avoid using “I” (for example, a lab report), much college writing can be done in a middle, semi-formal style where it is ok to use “I.”
What Do Instructors Want?
Successful academic writing starts with recognizing what the instructor is requesting, or what you are required to do. So pay close attention to the assignment. Sometimes the essential information about an assignment is conveyed through class discussions, however, so be sure to listen for the keywords that will help you understand what the instructor expects. If you feel the assignment does not give you a sense of direction, seek clarification.
Some instructors may say they have no particular expectations for student papers. This is partly true. College instructors do not usually have one right answer in mind or one right approach to take when they assign a paper topic. They expect you to engage in critical thinking and decide for yourself what you are saying and how to say it. But in other ways, college instructors do have expectations, and it is important to understand them. Some expectations involve mastering the material or demonstrating critical thinking. Other expectations involve specific writing skills. Most college instructors expect certain characteristics in student writing. Here are general principles you should follow when writing essays or student “papers.” (Some may not be appropriate for specific formats such as lab reports.)
Title the paper to identify your topic. This may sound obvious, but it needs to be said. Some students think of a paper as an exercise and write something like “Assignment 2: History 101” on the title page. Such a title gives no idea about how you are approaching the assignment or your topic. Your title should prepare your reader for what your paper is about or what you will argue. (With essays, always consider your reader as an educated adult interested in your topic. An essay is not a letter written to your instructor.) Compare the following:
Incorrect: Assignment 2: History 101
Correct: Why the New World Was Not “New”
It is obvious which of these two titles begins to prepare your reader for the paper itself. Similarly, don’t make your title the same as the title of a work you are writing about. Instead, be sure your title signals an aspect of the work you are focusing on:
Incorrect: Catcher in the Rye
Correct: Family Relationships in Catcher in the Rye
Address the terms of the assignment. Again, pay particular attention to words in the assignment that signal a preferred approach. If the instructor asks you to “argue” a point, be sure to make a statement that expresses your idea about the topic. Then follow that statement with your reasons and evidence in support of the statement. Look for any signals that will help you focus or limit your approach. Since no paper can cover everything about a complex topic, what is it that your instructor wants you to cover?
Finally, pay attention to the little things. For example, if the assignment specifies “5 to 6 pages in length,” write a five- to six-page paper. Don’t try to stretch a short paper longer by enlarging the font (12 points is standard) or making your margins bigger than the normal one inch (or as specified by the instructor). If the assignment is due at the beginning of class on Monday, have it ready then or before. Do not assume you can negotiate a revised due date.
In your introduction, define your topic and establish your approach or sense of purpose. Think of your introduction as an extension of your title. Instructors (like all readers) appreciate being oriented by a clear opening. They appreciate knowing that you have a purpose for your topic—that you have a reason for writing the paper. If they feel they’ve just been dropped into the middle of a paper, they may miss important ideas. They may not make the connections you want them to make.
Build from a thesis or a clearly stated sense of purpose. Many college assignments require you to make some form of argument. To do that, you generally start with a statement that needs to be supported and build from there. Your thesis is that statement; it is a guiding assertion for the paper. Be clear in your mind about the difference between your topic and your thesis. The topic is what your paper is about; the thesis is what you argue about the topic. Some assignments do not require an explicit argument and thesis, but even then you should make clear at the beginning your main emphasis, your purpose, or your most important idea.
Develop ideas patiently. You might, like many students, worry about boring your reader with too much detail or information. However, college instructors will not be bored by carefully explained ideas, well-selected examples, and relevant details. College instructors, after all, are professionally devoted to their subjects. If your sociology instructor asks you to write about youth crime in rural areas, you can be sure they are interested in that subject.
Integrate—do not just “plug-in”—quotations, graphs, and illustrations. As you outline or sketch out your material, you will think things like “This quotation can go here” or “I can put that graph there.” Remember that a quotation, graph, or illustration does not make a point for you. You make the point first and then use such material to help back it up. Using a quotation, a graph, or an illustration involves more than simply sticking it into the paper. Always lead into such material. Make sure the reader understands why you are using it and how it fits in at that place in your presentation.
Build clear transitions at the beginning of every paragraph to link from one idea to another. A good paper is more than a list of good ideas. It should also show how the ideas fit together. As you write the first sentence of any paragraph, have a clear sense of what the prior paragraph was about. Think of the first sentence in any paragraph as a kind of bridge for the reader from what came before.
Document your sources appropriately. If your paper involves research of any kind, indicate the use you make of outside sources. If you have used those sources well, there is no reason to hide them. Careful research and the thoughtful application of the ideas and evidence of others are part of what college instructors value.
Carefully edit your paper. College instructors assume you will take the time to edit and proofread your essay. A misspelled word or an incomplete sentence may signal a lack of concern on your part. It may not seem fair to make a harsh judgment about your seriousness based on little errors, but in all writing, impressions count. Since it is often hard to find small errors in our own writing, ask a classmate or a friend to review it and mark any word or sentence that seems “off” in any way. Although you should certainly use a spell-checker, don’t assume it can catch everything.
Turn in a clean hard copy. Some instructors accept or even prefer digital papers, but do not assume this. Some instructors want a paper copy. Present your paper in a professional (and unfussy) way, using a staple or paper clip on the left top to hold the pages together (unless the instructor specifies otherwise). If submitting digitally, make sure the formatting you intended remains intact after you upload the file. Review the uploaded file carefully before pressing "submit." And, be sure you are uploading the file type requested by your instructor/
The Writing Process
The following video provides a thorough overview of the five steps of the writing process.
No writer, not even a professional, composes a perfect draft in her first attempt. Every writer fumbles and has to work through a series of steps to arrive at a high-quality finished project.
You may have encountered these steps as assignments in classes—draft a thesis statement, complete an outline, turn in a rough draft, and participate in a peer review. The further you get into higher education, the less often these steps will be completed as part of a class.
That’s not to say that you won’t still need to follow these steps on your own. It helps to recognize that these steps, commonly, referred to as the writing process, aren’t rigid and prescribed. Instead, it can be liberating to see them as flexible, allowing you to adapt them to your personal habits, preferences, and the topic at hand. You will probably find that your process changes, depending on the type of writing you’re doing and your comfort level with the subject matter.
Consider the following flowchart of the writing process:
The writing process can be summed up in five steps: pre-writing, planning and outlining, drafting, revising, and editing (proofreading.) Keep in mind that it isn’t always a linear process, though. It’s okay to loop back to earlier steps again if needed. For instance, after completing a draft, you may realize that a significant aspect of the topic is missing, which sends you back to researching. Or the process of research may lead you to an unexpected subtopic, which shifts your focus and leads you to revise your thesis. Embrace the circular path that writing often takes!
Because writing is sometimes hard, procrastination is easy. Don’t let yourself put off the task. Use the time management strategies described in Chapter 4. One good approach is to schedule shorter periods over a series of days, rather than trying to sit down for one long period to accomplish a lot. (Even professional writers can write only so much at a time.)
- Prewriting. This stage is for generating ideas, understanding the ideas of others, and collecting information (note-taking, free-writing, brainstorming, researching, etc.) This is where you will decide on the specific topic of your paper.
- Planning and Outlining. Here, you are organizing and focusing on ideas. You are making a plan for your writing, which can include an outline or a mind map.
- Drafting. In the drafting stage, you are writing initial drafts of a text focusing mainly on the development, organization, and elaboration of ideas.
- Revision. In the revision stage, let the work sit and come back to it later with a fresh set of eyes. You may cycle back between drafting and revision several times before moving on. This is also a good time to get feedback from others. In the revision stage, you are further developing and clarifying ideas and the structure of the text. If the work requires additional research or idea generation, return to the planning stage.
- Editing and Proofreading. Here the focus is on surface-level features of the text. This is where you correct grammar, spelling, and punctuation.
What’s the Difference Between Revision and Editing?
These last two stages of the writing process are often confused with each other, but they mean very different things and serve very different purposes.
Revision is literally “reseeing.” It asks a writer to step away from a piece of work for a significant amount of time and return later to see it with new eyes. This is why the process of producing multiple drafts of an essay is so important. It allows some space in between, to let thoughts mature, connections to arise, and gaps in content or an argument to appear. It’s also difficult to do, especially given that most college students face tight timelines to get big writing projects done. Still, there are some tricks to help you “re-see” a piece of writing when you’re short on time, such as reading a paper backward, sentence by sentence, and reading your work aloud. Both are ways of reconceptualizing your writing so you approach it from a fresh perspective. Whenever possible, build in at least a day or two to set a draft aside before returning to work on the final version.
Revising a draft usually involves significant changes including the following:
- Making organizational changes like the reordering of paragraphs (don’t forget that new transitions will be needed when you move paragraphs).
- Clarifying the thesis or adjustments between the thesis and supporting points that follow.
- Cutting material that is unnecessary or irrelevant.
- Adding new points to strengthen or clarify the presentation.
Editing and Proofreading are the last steps following revision. This is the point where spelling, grammar, punctuation, and formatting all take center stage.
Editing and proofreading are focused, late-stage activities for style and correctness. They are important final parts of the writing process, but they should not be confused with revision itself. Editing and proofreading a draft involve these steps:
- Careful spell-checking. This includes checking the spelling of names.
- Attention to sentence-level issues. Be especially attentive to sentence boundaries, subject-verb agreement, punctuation, and pronoun referents. You can also attend at this stage to matters of style.
A person can be the best writer in the world and still be a terrible proofreader. It’s okay not to memorize every rule out there, but to know where to turn for help. Utilizing the grammar-check feature of your word processor is a good start, but it won’t solve every issue. There are also programs you can use such as Grammarly.
Finding a trusted person to help you edit is perfectly ethical, as long as that person offers you advice and doesn’t do any of the writing for you. Professional writers rely on outside readers for the revision and editing process, and it’s good practice for you to do so, too.
Remember to get started on a writing assignment early so that you complete the first draft well before the due date, allowing you time for genuine revision and careful editing.
CHECKLISTS FOR REVISION AND EDITING
When you revise…
| Check the assignment: does your paper do what it’s supposed to do? | |
| Check the title: does it clearly identify the overall topic or position? | |
| Check the introduction: does it set the stage and establish the purpose? | |
| Check each paragraph in the body: does each begin with a transition from the preceding? | |
| Check the organization: does it make sense why each topic precedes or follows another? | |
| Check development: is each topic fully explained, detailed, supported, and exemplified? | |
| Check the conclusion: does it restate the thesis and pull key ideas together? |
When you edit…
| Read the paper aloud, listening for flow and natural word style. | |
| Check for any lapses into slang, colloquialisms, or nonstandard English phrasing. | |
| Check sentence-level mechanics: grammar and punctuation (pay special attention to past writing problems). | |
| When everything seems done, run the spell-checker again and do a final proofread. | |
| Check physical layout and mechanics against instructor’s expectations: Title page? Font and margins? Endnotes? |
Getting Help with Writing
Writing can be hard work. Most colleges provide resources that can help you from the early stages of an assignment through to the completion of an essay. Your first resource may be a writing class. Most students are encouraged or required to enroll in a writing class in their first term, and it’s a good idea for everyone. Use everything you learn there about drafting and revising in all your courses.
Most colleges have a tutoring service that focuses primarily on student writing. At ACC, you can request help from the Learning Lab Tutors, either virtually or in person at any of the campuses. You can also get assistance from The Writing Center.
Three points about writing tutors are crucial:
- Writing tutors are there for all student writers—not just for weak or inexperienced writers. Writing in college is supposed to be a challenge. Some students make writing even harder by thinking that good writers work in isolation. But writing is a social act. A good paper should engage others.
- Tutors are not there for you to “correct” sentence-level problems or polish your finished draft. They will help you identify and understand sentence-level problems so that you can achieve greater control over your writing. But, their more important goals often are to address larger concerns like the paper’s organization, the fullness of its development, and the clarity of its argument. So don’t make your first appointment the day before a paper is due, because you may need more time to revise after discussing the paper with a tutor.
- Tutors cannot help you if you do not do your part. Tutors respond only to what you say and write; they cannot enable you to magically jump past the thinking an assignment requires. So do some thinking about the assignment before your meeting and be sure to bring relevant materials with you. For example, bring the paper assignment. You might also bring the course syllabus and perhaps even the required textbook. Most importantly, bring any writing you’ve done in response to the assignment (an outline, a thesis statement, a draft, an introductory paragraph). If you want to get help from a tutor, you need to give the tutor something to work with.
The ACC Library is a great resource for writing papers. You can go to any ACC campus library, email them, call them, zoom them, and there is even a 24-hour live chat. They can help you find appropriate sources, show you how to use citation tools, and help you with citing sources,
Writing Websites and writing handbooks. Many writing websites and handbooks can help you along every step of the way, especially in the late stages of your work. You’ll find lessons on style as well as information about language conventions and “correctness.” Not only should you use the handbook your composition instructor assigns in a writing class, but you should not sell that book back at the end of the term. You will need it again for future writing. For more help, become familiar with a good Web site for student writers. There are many, but here are a few recommended ones:
Purdue Online Writing Lab (OWL)
Handouts from the Writing Center at UNC-Chapel Hill
Practicing Academic Integrity
At most educational institutions, “academic honesty” means demonstrating and upholding the highest integrity and honesty in all the academic work that you do. In short, it means doing your own work, not cheating, and not presenting the work of others as your own. ACC has a detailed Academic Integrity Process. ACC's Value Statement on Academic Integrity states:
"Acts of academic dishonesty/misconduct undermine the learning process, present a disadvantage to students who earn credit honestly, and subvert the academic mission of the institution. The potential consequences of fraudulent credentials raise additional concerns for individuals and communities beyond campus who rely on institutions of higher learning to certify students’ academic achievements, and expect to benefit from the claimed knowledge and skills of their graduates."
The following are some common forms of academic dishonesty prohibited by most academic institutions:
Cheating
Cheating can take the form of cheat sheets, looking over someone’s shoulder during an exam, or any forbidden sharing of information between students regarding an exam or exercise. Many elaborate methods of cheating have been developed over the years—storing information in graphing calculators, checking cell phones during bathroom breaks, using apps like Chegg to complete your homework or a take-home exam, using online solutions, using AI to write papers or answer exam questions, etc. Cheating differs from most other forms of academic dishonesty, in that people can engage in it without benefiting themselves academically. For example, a student who illicitly texted answers to a friend during a test would be cheating, even though the student’s own work is in no way affected.
Deception
Deception is providing false information to an instructor concerning an academic assignment. Examples of this include taking more time on a take-home test than is allowed, giving a dishonest excuse when asking for a deadline extension, or falsely claiming to have submitted work. Essentially, it's lying to your instructor.
Fabrication
Fabrication is the falsification of data, information, or citations in an academic assignment. This includes making up citations to back up arguments or inventing quotations. Fabrication is most common in the natural sciences, where students sometimes falsify data to make experiments “work” or false claims are made about the research performed.
Plagiarism
Plagiarism, as defined in the 1995 Random House Compact Unabridged Dictionary, is the “use or close imitation of the language and thoughts of another author and the representation of them as one’s own original work.” In an academic setting, it is seen as the adoption or reproduction of original intellectual creations (such as concepts, ideas, methods, pieces of information or expressions, etc.) of another author (whether an individual, group, or organization) without proper acknowledgment. This can range from borrowing a particular phrase or sentence to paraphrasing someone else’s original idea without citing it. Today, in our networked digital world, the most common form of plagiarism is copying and pasting online material without crediting the source. This includes copying AI generated text.
Common Forms of Plagiarism
According to “The Reality and Solution of College Plagiarism” created by the Health Informatics Department of the University of Illinois at Chicago, there are ten main forms of plagiarism that students commit:
- Submitting someone else’s work as their own (this includes AI-generated work).
- Taking passages from their own previous work without adding citations (submitting a paper you previously wrote for another class or another assignment).
- Rewriting someone’s work without properly citing sources (this includes AI-generated work).
- Using quotations, but not citing the source.
- Interweaving various sources together in the work without citing.
- Citing some, but not all passages that should be cited.
- Melding together cited and uncited sections of the piece.
- Providing proper citations, but failing to change the structure and wording of the borrowed ideas enough.
- Inaccurately citing the source.
- Relying too heavily on other people’s work. Failing to bring original thought into the text.
As a college student, you are now a member of a scholarly community that values other people’s ideas. You will routinely be asked to reference and discuss other people’s thoughts and writing in the course of producing your own work. That’s why it’s so important to understand what plagiarism is and the steps you can take to avoid it.
Avoiding Plagiarism
Below are some useful guidelines to help you avoid plagiarism and show academic honesty in your work:
- Quotes: If you quote another work directly, cite your source. This includes AI-generated work.
- Paraphrase: If you put someone else’s idea into your own words, you still need to cite the author.
- Visual Materials: If you cite statistics, graphs, or charts from a study, cite the source. Keep in mind that if you didn’t do the original research, then you need to credit the person(s) or institution, etc. that did.
The easiest way to make sure you don’t accidentally plagiarize someone else’s work is by taking careful notes as you research. If you are researching on the Web, be sure to copy and paste the links into your notes so you can keep track of the sites you’re visiting. Be sure to list all the sources you consult.
There are many handy online tools to help you create and track references as you go. For example, you can try using Son of Citation Machine. Library databases often have a citation generator. Keeping careful notes will not only help you avoid inadvertent plagiarism, but it will also help you if you need to return to a source later (to check or get more information). If you use citation tools like Son of Citation, be sure to check the accuracy of the citations before you submit your assignment.
Lastly, if you’re in doubt about whether something constitutes plagiarism, cite the source or leave the material out. Better still, ask for help. Most colleges have a writing center, a tutoring center, and a library where students can get help with their writing. Taking the time to seek advice is better than getting in trouble for not attributing your sources. Be honest about your ideas, and give credit where it’s due.
Consequences of Plagiarism
In the academic world, plagiarism is considered a serious offense that can result in punishments such as a failing grade on a particular assignment, the entire course, or even being expelled from the institution. Individual instructors and courses may have their own policies regarding academic honesty and plagiarism; statements of these can usually be found in the course syllabus or online course description.
Avoid Plagiarism: Cite Your Sources
College courses offer a few writing opportunities that won’t require using outside resources. Creative writing classes, applied lab classes, or field research classes will value what you create entirely from your own mind or from the work completed for the class. For most college writing, however, you will need to consult at least one outside source, and possibly more.
The following video provides a helpful overview of how sources are used most effectively and responsibly in academic writing.
Note that this video models MLA-style citations. This is one of several different styles you might be asked to practice in your classes. Your instructors should state which of the major styles they expect you to use in their courses.
Regardless of the style, the same principles are true any time a source is used: give credit to the source when it is used in the writing itself, as well as in a bibliography (or Works Cited page, or References page) at the end.
Plagiarism is the unacknowledged use of material from a source. At the most obvious level, plagiarism involves using someone else’s words and ideas as if they were your own. There’s not much to say about copying another person’s work: it’s cheating, pure and simple. But plagiarism is not always so simple. Notice that the definition of plagiarism involves “words and ideas.” Let’s break that down a little further.
Words. Copying the words of another is wrong. If you use another’s words, those words must be in quotation marks, and you must tell your reader where those words came from. But it is not enough to make a few surface changes in wording. You can’t just change some words and call the material yours; an extended paraphrase is not acceptable. For example, compare the two passages that follow. The first comes from Murder Most Foul, a book by Karen Halttunen on changing ideas about murder in nineteenth-century America; the second is a close paraphrase of the same passage:
The new murder narratives were overwhelmingly secular works, written by a diverse array of printers, hack writers, sentimental poets, lawyers, and even murderers themselves, who were displacing the clergy as the dominant interpreters of the crime.
The murder stories that were developing were almost always secular works that were written by many different sorts of people. Printers, hack writers, poets, attorneys, and sometimes even the criminals themselves were writing murder stories. They were the new interpreters of the crime, replacing religious leaders who had held that role before.
It is easy to see that the writer of the second version has closely followed the ideas and even used some of the same words as the original. This is a serious form of plagiarism. Even if this writer were to acknowledge the author, there would still be a problem. To simply cite the source at the end does not excuse using so much of the original source.
Ideas. Ideas are also a form of intellectual property. Consider this third version of the previous passage:
At one time, religious leaders shaped the way the public thought about murder. But in nineteenth-century America, this changed. Society’s attitudes were influenced more and more by secular writers.
This version summarizes the original. That is, it states the main idea in compressed form in language that does not come from the original. However, it could still be seen as plagiarism if the source is not cited. This example may make you wonder if you can write anything without citing a source. To help you sort out what ideas need to be cited and what does not, think about these principles:
Common knowledge. There is no need to cite common knowledge. Common knowledge does not mean knowledge everyone has. It means knowledge that everyone can easily access. For example, most people do not know the date of George Washington’s death, but everyone can easily find that information. If the information or idea can be found in multiple sources and the information or idea remains constant from source to source, it can be considered common knowledge. This is one reason so much research is usually done for college writing—the more sources you read, the more easily you can sort out what is common knowledge: if you see an uncited idea in multiple sources, then you can feel secure that idea is common knowledge.
Distinct contributions. One does need to cite ideas that are distinct contributions. A distinct contribution need not be a discovery from the work of one person. It need only be an insight that is not commonly expressed (not found in multiple sources) and not universally agreed upon.
Disputable figures. Always remember that numbers are only as good as the sources they come from. If you use numbers like attendance figures, unemployment rates, or demographic profiles—or any statistics at all—always cite your source of those numbers. If your instructor does not know the source you used, you will not get much credit for the information you have collected.
Everything said previously about using sources applies to all forms of sources. Some students mistakenly believe that material from the Web, for example, need not be cited. Or that an idea from an instructor’s lecture is automatically common property. You must evaluate all sources in the same way and cite them as necessary.
Forms of Citation. You should check with your instructors about their preferred form of citation when you write papers for courses. No one standard is used in all academic papers. You can learn about the three major forms or styles used in almost any college writing handbook and on many Websites for college writers:
- The Modern Language Association (MLA) system of citation is widely used but is most commonly adopted in humanities courses, particularly literature courses.
- The American Psychological Association (APA) system of citation is most common in the social sciences.
- The Turabian Documentation Style (or Chicago) is widely used but perhaps most commonly in history courses.
Many college departments have their own style guides, which may be based on one of the above. Your instructor should refer you to his or her preferred guide, but be sure to ask if you have not been given explicit direction.
KEY TAKEAWAYS
- Writing is crucial to college success because it is the most common means of evaluation.
- Writers in college must pay close attention to the terms of an assignment.
- Writing is a process that involves several steps; the product will not be good if one does not allow time for the process.
- Seek feedback from classmates, tutors, and instructors during the writing process.
- Revision is not the same thing as editing.
- Understanding and practicing Academic Integrity is a crucial component of college success.
- Words and ideas from sources must be properly cited.
LICENSES AND ATTRIBUTIONS
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Writing Effectively. Authored by: Heather Syrett. Provided by: Austin Community College. License: CC BY-NC-SA-4.0
CC LICENSED CONTENT, SHARED PREVIOUSLY
- Academic Writing: a Practical Guide in University Library. Provided by: University of York. Located at: https://subjectguides.york.ac.uk/academic-writing/academic-style. License: CC BY-NC-SA-4.0
- Chapter 8: Writing for Classes. in College Success. Authored by: Anonymous. Provided by: University of Minnesota. Located at: http://www.oercommons.org/courses/college-success/view. License: CC BY-NC-SA-4.0
- Editing. Authored by: Joseph M. Moxley. Provided by: Writing Commons. Located at: https://writingcommons.org/section/editing/ License: CC BY-NC-ND 4.0
- What is Academic Writing in Starting the Journey: An Intro to College Writing. Authored by: Lennie L. Irving Provided by: Pressbooks. Located at: https://fsw.pressbooks.pub/enc1101/chapter/thinking-deeper-title-of-article-here/. License: CC BY-NC-SA-4.0
- Writing Processes in Technical Writing Essentials. Authored by: Suzan Last Provided by: Pressbooks. Located at: https://pressbooks.bccampus.ca/technicalwriting/chapter/writing-processes/#retfig1.5.1 License: CC BY 4.0
- Writing Strategies in EDUC 1300. Provided by: Lumen Learning. Located at: https://courses.lumenlearning.com/sanjacinto-learningframework/chapter/writing-strategies/. License: CC BY 4.0
ALL RIGHTS RESERVED CONTENT
- UNC The Writing Center Handouts. Located at: http://writingcenter.unc.edu/handouts/. License: All Rights Reserved
- Purdue Online Writing Lab. Located at: https://owl.english.purdue.edu/owl/resource/747/01/. License: All Rights Reserved
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https://oercommons.org/courseware/lesson/15570/overview
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U.S. Political Map (credit: U.S. Department of the Interior, U.S. Geological Survey, The National Atlas of the United States of America/nationalatlas.gov)
(credit: U.S. Department of the Interior, U.S. Geological Survey, The National Atlas of the United States of America/nationalatlas.gov)
(credit: U.S. Department of the Interior, U.S. Geological Survey, The National Atlas of the United States of America/nationalatlas.gov)
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https://oercommons.org/courseware/lesson/28802/overview
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Introduction to Economic Growth
Calories and Economic Growth
On average, humans need about 2,500 calories a day to survive, depending on height, weight, and gender. The economist Brad DeLong estimates that the average worker in the early 1600s earned wages that could afford him 2,500 food calories. This worker lived in Western Europe. Two hundred years later, that same worker could afford 3,000 food calories. However, between 1800 and 1875, just a time span of just 75 years, economic growth was so rapid that western European workers could purchase 5,000 food calories a day. By 2012, a low skilled worker in an affluent Western European/North American country could afford to purchase 2.4 million food calories per day.
What caused such a rapid rise in living standards between 1800 and 1875 and thereafter? Why is it that many countries, especially those in Western Europe, North America, and parts of East Asia, can feed their populations more than adequately, while others cannot? We will look at these and other questions as we examine long-run economic growth.
Introduction to Economic Growth
In this chapter, you will learn about:
- The Relatively Recent Arrival of Economic Growth
- Labor Productivity and Economic Growth
- Components of Economic Growth
- Economic Convergence
Every country worries about economic growth. In the United States and other high-income countries, the question is whether economic growth continues to provide the same remarkable gains in our standard of living as it did during the twentieth century. Meanwhile, can middle-income countries like Brazil, Egypt, or Poland catch up to the higher-income countries, or must they remain in the second tier of per capita income? Of the world’s population of roughly 7.5 billion people, about 1.1 billion are scraping by on incomes that average less than $2 per day, not that different from the standard of living 2,000 years ago. Can the world’s poor be lifted from their fearful poverty? As the 1995 Nobel laureate in economics, Robert E. Lucas Jr., once noted: “The consequences for human welfare involved in questions like these are simply staggering: Once one starts to think about them, it is hard to think about anything else.”
Dramatic improvements in a nation’s standard of living are possible. After the Korean War in the late 1950s, the Republic of Korea, often called South Korea, was one of the poorest economies in the world. Most South Koreans worked in peasant agriculture. According to the British economist Angus Maddison, who devoted life’s work to measuring GDP and population in the world economy, GDP per capita in 1990 international dollars was $854 per year. From the 1960s to the early twenty-first century, a time period well within the lifetime and memory of many adults, the South Korean economy grew rapidly. Over these four decades, GDP per capita increased by more than 6% per year. According to the World Bank, GDP for South Korea now exceeds $30,000 in nominal terms, placing it firmly among high-income countries like Italy, New Zealand, and Israel. Measured by total GDP in 2015, South Korea is the eleventh-largest economy in the world. For a nation of 50 million people, this transformation is extraordinary.
South Korea is a standout example, but it is not the only case of rapid and sustained economic growth. Other East Asian nations, like Thailand and Indonesia, have seen very rapid growth as well. China has grown enormously since it enacted market-oriented economic reforms around 1980. GDP per capita in high-income economies like the United States also has grown dramatically albeit over a longer time frame. Since the Civil War, the U.S. economy has transformed from a primarily rural and agricultural economy to an economy based on services, manufacturing, and technology.
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https://oercommons.org/courseware/lesson/28803/overview
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The Relatively Recent Arrival of Economic Growth
Overview
By the end of this section, you will be able to:
- Explain the conditions that have allowed for modern economic growth in the last two centuries
- Analyze the influence of public policies on an economy's long-run economic growth
Let’s begin with a brief overview of spectacular economic growth patterns around the world in the last two centuries. We commonly refer to this as the period of modern economic growth. (Later in the chapter we will discuss lower economic growth rates and some key ingredients for economic progress.) Rapid and sustained economic growth is a relatively recent experience for the human race. Before the last two centuries, although rulers, nobles, and conquerors could afford some extravagances and although economies rose above the subsistence level, the average person’s standard of living had not changed much for centuries.
Progressive, powerful economic and institutional changes started to have a significant effect in the late eighteenth and early nineteenth centuries. According to the Dutch economic historian Jan Luiten van Zanden, slavery-based societies, favorable demographics, global trading routes, and standardized trading institutions that spread with different empires set the stage for the Industrial Revolution to succeed. The Industrial Revolution refers to the widespread use of power-driven machinery and the economic and social changes that resulted in the first half of the 1800s. Ingenious machines—the steam engine, the power loom, and the steam locomotive—performed tasks that otherwise would have taken vast numbers of workers to do. The Industrial Revolution began in Great Britain, and soon spread to the United States, Germany, and other countries.
The jobs for ordinary people working with these machines were often dirty and dangerous by modern standards, but the alternative jobs of that time in peasant agriculture and small-village industry were often dirty and dangerous, too. The new jobs of the Industrial Revolution typically offered higher pay and a chance for social mobility. A self-reinforcing cycle began: New inventions and investments generated profits, the profits provided funds for more new investment and inventions, and the investments and inventions provided opportunities for further profits. Slowly, a group of national economies in Europe and North America emerged from centuries of sluggishness into a period of rapid modern growth. During the last two centuries, the average GDP growth rate per capita in the leading industrialized countries has been about 2% per year. What were times like before then? Read the following Clear It Up feature for the answer.
What were economic conditions like before 1870?
Angus Maddison, a quantitative economic historian, led the most systematic inquiry into national incomes before 1870. Economists recently have refined and used his methods to compile GDP per capita estimates from year 1 C.E. to 1348. Table is an important counterpoint to most of the narrative in this chapter. It shows that nations can decline as well as rise. A wide array of forces, such as epidemics, natural and weather-related disasters, the inability to govern large empires, and the remarkably slow pace of technological and institutional progress explain declines in income. Institutions are the traditions and laws by which people in a community agree to behave and govern themselves. Such institutions include marriage, religion, education, and laws of governance. Institutional progress is the development and codification of these institutions to reinforce social order, and thus, economic growth.
One example of such an institution is the Magna Carta (Great Charter), which the English nobles forced King John to sign in 1215. The Magna Carta codified the principles of due process, whereby a free man could not be penalized unless his peers had made a lawful judgment against him. The United States in its own constitution later adopted this concept. This social order may have contributed to England’s GDP per capita in 1348, which was second to that of northern Italy.
In studying economic growth, a country’s institutional framework plays a critical role. Table also shows relative global equality for almost 1,300 years. After this, we begin to see significant divergence in income (not in the table).
| Year | Northern Italy | Spain | England | Holland | Byzantium | Iraq | Egypt | Japan |
|---|---|---|---|---|---|---|---|---|
| 1 | $800 | $600 | $600 | $600 | $700 | $700 | $700 | - |
| 730 | - | - | - | - | - | $920 | $730 | $402 |
| 1000 | - | - | - | - | $600 | $820 | $600 | - |
| 1150 | - | - | - | - | $580 | $680 | $660 | $520 |
| 1280 | - | - | - | - | - | - | $670 | $527 |
| 1300 | $1,588 | $864 | $892 | - | - | - | $610 | - |
| 1348 | $1,486 | $907 | $919 | - | - | - | - | - |
Another fascinating and underreported fact is the high levels of income, compared to others at that time, attained by the Islamic Empire Abbasid Caliphate—which was founded in present-day Iraq in 730 C.E. At its height, the empire spanned large regions of the Middle East, North Africa, and Spain until its gradual decline over 200 years.
The Industrial Revolution led to increasing inequality among nations. Some economies took off, whereas others, like many of those in Africa or Asia, remained close to a subsistence standard of living. General calculations show that the 17 countries of the world with the most-developed economies had, on average, 2.4 times the GDP per capita of the world’s poorest economies in 1870. By 1960, the most developed economies had 4.2 times the GDP per capita of the poorest economies.
However, by the middle of the twentieth century, some countries had shown that catching up was possible. Japan’s economic growth took off in the 1960s and 1970s, with a growth rate of real GDP per capita averaging 11% per year during those decades. Certain countries in Latin America experienced a boom in economic growth in the 1960s as well. In Brazil, for example, GDP per capita expanded by an average annual rate of 11.1% from 1968 to 1973. In the 1970s, some East Asian economies, including South Korea, Thailand, and Taiwan, saw rapid growth. In these countries, growth rates of 11% to 12% per year in GDP per capita were not uncommon. More recently, China, with its population of nearly 1.4 billion people, grew at a per capita rate 9% per year from 1984 into the 2000s. India, with a population of 1.3 billion, has shown promising signs of economic growth, with growth in GDP per capita of about 4% per year during the 1990s and climbing toward 7% to 8% per year in the 2000s.
Visit this website to read about the Asian Development Bank.
These waves of catch-up economic growth have not reached all shores. In certain African countries like Niger, Tanzania, and Sudan, for example, GDP per capita at the start of the 2000s was still less than $300, not much higher than it was in the nineteenth century and for centuries before that. In the context of the overall situation of low-income people around the world, the good economic news from China (population: 1.4 billion) and India (population: 1.3 billion) is, nonetheless, astounding and heartening.
Economic growth in the last two centuries has made a striking change in the human condition. Richard Easterlin, an economist at the University of Southern California, wrote in 2000:
By many measures, a revolution in the human condition is sweeping the world. Most people today are better fed, clothed, and housed than their predecessors two centuries ago. They are healthier, live longer, and are better educated. Women’s lives are less centered on reproduction and political democracy has gained a foothold. Although Western Europe and its offshoots have been the leaders of this advance, most of the less developed nations have joined in during the 20th century, with the newly emerging nations of sub-Saharan Africa the latest to participate. Although the picture is not one of universal progress, it is the greatest advance in the human condition of the world’s population ever achieved in such a brief span of time.
Rule of Law and Economic Growth
Economic growth depends on many factors. Key among those factors is adherence to the rule of law and protection of property rights and contractual rights by a country’s government so that markets can work effectively and efficiently. Laws must be clear, public, fair, enforced, and equally applicable to all members of society. Property rights, as you might recall from Environmental Protection and Negative Externalities are the rights of individuals and firms to own property and use it as they see fit. If you have $100, you have the right to use that money, whether you spend it, lend it, or keep it in a jar. It is your property. The definition of property includes physical property as well as the right to your training and experience, especially since your training is what determines your livelihood. Using this property includes the right to enter into contracts with other parties with your property. Individuals or firms must own the property to enter into a contract.
Contractual rights, then, are based on property rights and they allow individuals to enter into agreements with others regarding the use of their property providing recourse through the legal system in the event of noncompliance. One example is the employment agreement: a skilled surgeon operates on an ill person and expects payment. Failure to pay would constitute property theft by the patient. The theft is property the services that the surgeon provided. In a society with strong property rights and contractual rights, the terms of the patient–surgeon contract will be fulfilled, because the surgeon would have recourse through the court system to extract payment from that individual. Without a legal system that enforces contracts, people would not be likely to enter into contracts for current or future services because of the risk of non-payment. This would make it difficult to transact business and would slow economic growth.
The World Bank considers a country’s legal system effective if it upholds property rights and contractual rights. The World Bank has developed a ranking system for countries’ legal systems based on effective protection of property rights and rule-based governance using a scale from 1 to 6, with 1 being the lowest and 6 the highest rating. In 2013, the world average ranking was 2.9. The three countries with the lowest ranking of 1.5 were Afghanistan, the Central African Republic, and Zimbabwe. Their GDP per capita was $679, $333, and $1,007 respectively. The World Bank cites Afghanistan as having a low standard of living, weak government structure, and lack of adherence to the rule of law, which has stymied its economic growth. The landlocked Central African Republic has poor economic resources as well as political instability and is a source of children used in human trafficking. Zimbabwe has had declining and often negative growth for much of the period since 1998. Land redistribution and price controls have disrupted the economy, and corruption and violence have dominated the political process. Although global economic growth has increased, those countries lacking a clear system of property rights and an independent court system free from corruption have lagged far behind.
Key Concepts and Summary
Since the early nineteenth century, there has been a spectacular process of long-run economic growth during which the world’s leading economies—mostly those in Western Europe and North America—expanded GDP per capita at an average rate of about 2% per year. In the last half-century, countries like Japan, South Korea, and China have shown the potential to catch up. The Industrial Revolution facilitated the extensive process of economic growth, that economists often refer to as modern economic growth. This increased worker productivity and trade, as well as the development of governance and market institutions.
Self-Check Questions
Explain what the Industrial Revolution was and where it began.
Hint:
The Industrial Revolution refers to the widespread use of power-driven machinery and the economic and social changes that resulted in the first half of the 1800s. Ingenious machines—the steam engine, the power loom, and the steam locomotive—performed tasks that would have taken vast numbers of workers to do. The Industrial Revolution began in Great Britain, and soon spread to the United States, Germany, and other countries.
Explain the difference between property rights and contractual rights. Why do they matter to economic growth?
Hint:
Property rights are the rights of individuals and firms to own property and use it as they see fit. Contractual rights are based on property rights and they allow individuals to enter into agreements with others regarding the use of their property providing recourse through the legal system in the event of noncompliance. Economic growth occurs when the standard of living increases in an economy, which occurs when output is increasing and incomes are rising. For this to happen, societies must create a legal environment that gives individuals the ability to use their property to their fullest and highest use, including the right to trade or sell that property. Without a legal system that enforces contracts, people would not be likely to enter into contracts for current or future services because of the risk of non-payment. This would make it difficult to transact business and would slow economic growth.
Review Questions
How did the Industrial Revolution increase the economic growth rate and income levels in the United States?
How much should a nation be concerned if its rate of economic growth is just 2% slower than other nations?
Critical Thinking Question
Over the past 50 years, many countries have experienced an annual growth rate in real GDP per capita greater than that of the United States. Some examples are China, Japan, South Korea, and Taiwan. Does that mean the United States is regressing relative to other countries? Does that mean these countries will eventually overtake the United States in terms of the growth rate of real GDP per capita? Explain.
References
Bolt, Jutta, and Jan Luiten van Zanden. “The Maddison Project: The First Update of the Maddison Project Re-Estimating Growth Before 1820 (Maddison-Project Working Paper WP-4).” University of Groningen: Groningen Growth and Development Centre. Last modified January 2013. http://www.ggdc.net/maddison/publications/pdf/wp4.pdf.
Central Intelligence Agency. “The World Factbook: Country Comparison GDP (Purchasing Power Parity).” https://www.cia.gov/library/publications/the-world-factbook/rankorder/2001rank.html.
DeLong, Brad. “Lighting the Rocket of Growth and Lightening the Toil of Work: Another Outtake from My ‘Slouching Towards Utopia’ MS....” This is Brad DeLong's Grasping Reality (blog). September 3, 2013. http://delong.typepad.com/sdj/2013/09/lighting-the-rocket-of-growth-and-lightening-the-toil-of-work-another-outtake-from-my-slouching-towards-utopia-ms.html.
Easterlin, Richard A. “The Worldwide Standard of Living since 1800.” The Journal of Economic Perspectives. no. 1 (2000): 7–26. http://pubs.aeaweb.org/doi/pdfplus/10.1257/jep.14.1.7.
Maddison, Angus. Contours of the World Economy 1-2030 AD: Essays in Macro-Economic History. Oxford: Oxford University Press, 2007.
British Library. “Treasures in Full: Magna Carta.” http://www.bl.uk/treasures/magnacarta/.
Rothbard, Murray N. Ludwig von Mises Institute. “Property Rights and the Theory of Contracts.” The Ethics of Liberty. Last modified June 22, 2007. http://mises.org/daily/2580.
Salois, Matthew J., J. Richard Tiffin, and Kelvin George Balcombe. IDEAS: Research Division of the Federal Reserve Bank of St. Louis. “Impact of Income on Calorie and Nutrient Intakes: A Cross-Country Analysis.” Presention at the annual meeting of the Agricultural and Applied Economics Association, Pittsburg, PA, July 24–26, 2011. http://ideas.repec.org/p/ags/aaea11/103647.html.
van Zanden, Jan Luiten. The Long Road to the Industrial Revolution: The European Economy in a Global Perspective, 1000–1800 (Global Economic History Series). Boston: Brill, 2009.
The World Bank. “CPIA Property Rights and Rule-based Governance Rating (1=low to 6=high).” http://data.worldbank.org/indicator/IQ.CPA.PROP.XQ.
Rex A. Hudson, ed. Brazil: A Country Study. “Spectacular Growth, 1968–73.” Washington: GPO for the Library of Congress, 1997. http://countrystudies.us/brazil/64.htm.
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Labor Productivity and Economic Growth
Overview
By the end of this section, you will be able to:
- Identify the role of labor productivity in promoting economic growth
- Analyze the sources of economic growth using the aggregate production function
- Measure an economy’s rate of productivity growth
- Evaluate the power of sustained growth
Sustained long-term economic growth comes from increases in worker productivity, which essentially means how well we do things. In other words, how efficient is your nation with its time and workers? Labor productivity is the value that each employed person creates per unit of his or her input. The easiest way to comprehend labor productivity is to imagine a Canadian worker who can make 10 loaves of bread in an hour versus a U.S. worker who in the same hour can make only two loaves of bread. In this fictional example, the Canadians are more productive. More productivity essentially means you can do more in the same amount of time. This in turn frees up resources for workers to use elsewhere.
What determines how productive workers are? The answer is pretty intuitive. The first determinant of labor productivity is human capital. Human capital is the accumulated knowledge (from education and experience), skills, and expertise that the average worker in an economy possesses. Typically the higher the average level of education in an economy, the higher the accumulated human capital and the higher the labor productivity.
The second factor that determines labor productivity is technological change. Technological change is a combination of invention—advances in knowledge—and innovation, which is putting those advances to use in a new product or service. For example, the transistor was invented in 1947. It allowed us to miniaturize the footprint of electronic devices and use less power than the tube technology that came before it. Innovations since then have produced smaller and better transistors that are ubiquitous in products as varied as smart-phones, computers, and escalators. Developing the transistor has allowed workers to be anywhere with smaller devices. People can use these devices to communicate with other workers, measure product quality or do any other task in less time, improving worker productivity.
The third factor that determines labor productivity is economies of scale. Recall that economies of scale are the cost advantages that industries obtain due to size. (Read more about economies of scale in Production, Cost and Industry Structure.) Consider again the case of the fictional Canadian worker who could produce 10 loaves of bread in an hour. If this difference in productivity was due only to economies of scale, it could be that the Canadian worker had access to a large industrial-size oven while the U.S. worker was using a standard residential size oven.
Now that we have explored the determinants of worker productivity, let’s turn to how economists measure economic growth and productivity.
Sources of Economic Growth: The Aggregate Production Function
To analyze the sources of economic growth, it is useful to think about a production function, which is the technical relationship by which economic inputs like labor, machinery, and raw materials are turned into outputs like goods and services that consumers use. A microeconomic production function describes a firm's or perhaps an industry's inputs and outputs. In macroeconomics, we call the connection from inputs to outputs for the entire economy an aggregate production function.
Components of the Aggregate Production Function
Economists construct different production functions depending on the focus of their studies. Figure presents two examples of aggregate production functions. In the first production function in Figure (a), the output is GDP. The inputs in this example are workforce, human capital, physical capital, and technology. We discuss these inputs further in the module, Components of Economic Growth.
Measuring Productivity
An economy’s rate of productivity growth is closely linked to the growth rate of its GDP per capita, although the two are not identical. For example, if the percentage of the population who holds jobs in an economy increases, GDP per capita will increase but the productivity of individual workers may not be affected. Over the long term, the only way that GDP per capita can grow continually is if the productivity of the average worker rises or if there are complementary increases in capital.
A common measure of U.S. productivity per worker is dollar value per hour the worker contributes to the employer’s output. This measure excludes government workers, because their output is not sold in the market and so their productivity is hard to measure. It also excludes farming, which accounts for only a relatively small share of the U.S. economy. Figure shows an index of output per hour, with 2009 as the base year (when the index equals 100). The index equaled about 106 in 2014. In 1972, the index equaled 50, which shows that workers have more than doubled their productivity since then.
According to the Department of Labor, U.S. productivity growth was fairly strong in the 1950s but then declined in the 1970s and 1980s before rising again in the second half of the 1990s and the first half of the 2000s. In fact, the rate of productivity measured by the change in output per hour worked averaged 3.2% per year from 1950 to 1970; dropped to 1.9% per year from 1970 to 1990; and then climbed back to over 2.3% from 1991 to the present, with another modest slowdown after 2001. Figure shows average annual rates of productivity growth averaged over time since 1950.
The “New Economy” Controversy
In recent years a controversy has been brewing among economists about the resurgence of U.S. productivity in the second half of the 1990s. One school of thought argues that the United States had developed a “new economy” based on the extraordinary advances in communications and information technology of the 1990s. The most optimistic proponents argue that it would generate higher average productivity growth for decades to come. The pessimists, alternatively, argue that even five or ten years of stronger productivity growth does not prove that higher productivity will last for the long term. It is hard to infer anything about long-term productivity trends during the later part of the 2000s, because the steep 2008-2009 recession, with its sharp but not completely synchronized declines in output and employment, complicates any interpretation. While productivity growth was high in 2009 and 2010 (around 3%), it has slowed down since then.
Productivity growth is also closely linked to the average level of wages. Over time, the amount that firms are willing to pay workers will depend on the value of the output those workers produce. If a few employers tried to pay their workers less than what those workers produced, then those workers would receive offers of higher wages from other profit-seeking employers. If a few employers mistakenly paid their workers more than what those workers produced, those employers would soon end up with losses. In the long run, productivity per hour is the most important determinant of the average wage level in any economy. To learn how to compare economies in this regard, follow the steps in the following Work It Out feature.
Comparing the Economies of Two Countries
The Organization for Economic Co-operation and Development (OECD) tracks data on the annual growth rate of real GDP per hour worked. You can find these data on the OECD data webpage “Growth in GDP per capita, productivity and ULC” at this website.
Step 1. Visit the OECD website given above and select two countries to compare.
Step 2. On the drop-down menu “Subject,” select “ GDP per capita, constant prices,” and under “Measure,” select “Annual growth/change.” Then record the data for the countries you have chosen for the five most recent years.
Step 3. Go back to the drop-down “Subject” menu and select “GDP per hour worked, constant prices,” and under “Measure” again select “Annual growth/change.” Select data for the same years for which you selected GDP per capita data.
Step 4. Compare real GDP growth for both countries. Table provides an example of a comparison between Belgium and Canada.
| Australia | 2011 | 2012 | 2013 | 2014 | 2015 |
| Real GDP/Capita Growth (%) | 2.3% | 1.5% | 1.3% | 1.4 | 0.1% |
| Real GDP Growth/Hours Worked (%) | 1.7% | −0.1% | 1.4% | 2.2% | −0.2% |
| Belgium | 2011 | 2012 | 2013 | 2014 | 2015 |
| Real GDP/Capita Growth (%) | 0.9 | −0.6 | −0.5 | 1.2 | 1.0 |
| Real GDP Growth/Hours Worked (%) | −0.5 | −0.3 | 0.4 | 1.4 | 0.9 |
Step 5. For both measures, growth in Canada is greater than growth in Belgium for the first four years. In addition, there are year-to-year fluctuations. Many factors can affect growth. For example, one factor that may have contributed to Canada’s stronger growth may be its larger inflows of immigrants, who generally contribute to economic growth.
The Power of Sustained Economic Growth
Nothing is more important for people’s standard of living than sustained economic growth. Even small changes in the rate of growth, when sustained and compounded over long periods of time, make an enormous difference in the standard of living. Consider Table, in which the rows of the table show several different rates of growth in GDP per capita and the columns show different periods of time. Assume for simplicity that an economy starts with a GDP per capita of 100. The table then applies the following formula to calculate what GDP will be at the given growth rate in the future:
For example, an economy that starts with a GDP of 100 and grows at 3% per year will reach a GDP of 209 after 25 years; that is, 100 (1.03)25 = 209.
The slowest rate of GDP per capita growth in the table, just 1% per year, is similar to what the United States experienced during its weakest years of productivity growth. The second highest rate, 3% per year, is close to what the U.S. economy experienced during the strong economy of the late 1990s and into the 2000s. Higher rates of per capita growth, such as 5% or 8% per year, represent the experience of rapid growth in economies like Japan, Korea, and China.
Table shows that even a few percentage points of difference in economic growth rates will have a profound effect if sustained and compounded over time. For example, an economy growing at a 1% annual rate over 50 years will see its GDP per capita rise by a total of 64%, from 100 to 164 in this example. However, a country growing at a 5% annual rate will see (almost) the same amount of growth—from 100 to 163—over just 10 years. Rapid rates of economic growth can bring profound transformation. (See the following Clear It Up feature on the relationship between compound growth rates and compound interest rates.) If the rate of growth is 8%, young adults starting at age 20 will see the average standard of living in their country more than double by the time they reach age 30, and grow nearly sixfold by the time they reach age 45.
| Growth Rate | Value of an original 100 in 10 Years | Value of an original 100 in 25 Years | Value of an original 100 in 50 Years |
|---|---|---|---|
| 1% | 110 | 128 | 164 |
| 3% | 134 | 209 | 438 |
| 5% | 163 | 339 | 1,147 |
| 8% | 216 | 685 | 4,690 |
How are compound growth rates and compound interest rates related?
The formula for GDP growth rates over different periods of time, as Figure shows, is exactly the same as the formula for how a given amount of financial savings grows at a certain interest rate over time, as presented in Choice in a World of Scarcity. Both formulas have the same ingredients:
- an original starting amount, in one case GDP and in the other case an amount of financial saving;
- a percentage increase over time, in one case the GDP growth rate and in the other case an interest rate;
- and an amount of time over which this effect happens.
Recall that compound interest is interest that is earned on past interest. It causes the total amount of financial savings to grow dramatically over time. Similarly, compound rates of economic growth, or the compound growth rate, means that we multiply the rate of growth by a base that includes past GDP growth, with dramatic effects over time.
For example, in 2013, the Central Intelligence Agency's World Fact Book reported that South Korea had a GDP of $1.67 trillion with a growth rate of 2.8%. We can estimate that at that growth rate, South Korea’s GDP will be $1.92 trillion in five years. If we apply the growth rate to each year’s ending GDP for the next five years, we will calculate that at the end of year one, GDP is $1.72 trillion. In year two, we start with the end-of-year one value of $1.72 and increase it by 2.8%. Year three starts with the end-of-year two GDP, and we increase it by 2.8% and so on, as Table depicts.
| Year | Starting GDP | Growth Rate 2% | Year-End Amount |
|---|---|---|---|
| 1 | $1.67 Trillion × | (1+0.028) | $1.72 Trillion |
| 2 | $1.72 Trillion × | (1+0.028) | $1.76 Trillion |
| 3 | $1.76 Trillion × | (1+0.028) | $1.81 Trillion |
| 4 | $1.81 Trillion × | (1+0.028) | $1.87 Trillion |
| 5 | $1.87 Trillion × | (1+0.028) | $1.92 Trillion |
Another way to calculate the growth rate is to apply the following formula:
Where “future value” is the value of GDP five years hence, “present value” is the starting GDP amount of $1.67 trillion, “g” is the growth rate of 2.8%, and “n” is the number of periods for which we are calculating growth.
Key Concepts and Summary
We can measure productivity, the value of what is produced per worker, or per hour worked, as the level of GDP per worker or GDP per hour. The United States experienced a productivity slowdown between 1973 and 1989. Since then, U.S. productivity has rebounded for the most part, but annual growth in productivity in the nonfarm business sector has been less than one percent each year between 2011 and 2016. It is not clear what productivity growth will be in the coming years. The rate of productivity growth is the primary determinant of an economy’s rate of long-term economic growth and higher wages. Over decades and generations, seemingly small differences of a few percentage points in the annual rate of economic growth make an enormous difference in GDP per capita. An aggregate production function specifies how certain inputs in the economy, like human capital, physical capital, and technology, lead to the output measured as GDP per capita.
Compound interest and compound growth rates behave in the same way as productivity rates. Seemingly small changes in percentage points can have big impacts on income over time.
Self-Check Questions
Are there other ways in which we can measure productivity besides the amount produced per hour of work?
Hint:
Yes. Since productivity is output per unit of input, we can measure productivity using GDP (output) per worker (input).
Assume there are two countries: South Korea and the United States. South Korea grows at 4% and the United States grows at 1%. For the sake of simplicity, assume they both start from the same fictional income level, $10,000. What will the incomes of the United States and South Korea be in 20 years? By how many multiples will each country’s income grow in 20 years?
Hint:
In 20 years the United States will have an income of 10,000 × (1 + 0.01)20 = $12,201.90, and South Korea will have an income of 10,000 × (1 + 0.04)20 = $21,911.23. South Korea has grown by a multiple of 2.1 and the United States by a multiple of 1.2.
Review Questions
How is GDP per capita calculated differently from labor productivity?
How do gains in labor productivity lead to gains in GDP per capita?
Critical Thinking Questions
Labor Productivity and Economic Growth outlined the logic of how increased productivity is associated with increased wages. Detail a situation where this is not the case and explain why it is not.
Change in labor productivity is one of the most watched international statistics of growth. Visit the St. Louis Federal Reserve website and find the data section (http://research.stlouisfed.org). Find international comparisons of labor productivity, listed under the FRED Economic database (Growth Rate of Total Labor Productivity), and compare two countries in the recent past. State what you think the reasons for differences in labor productivity could be.
Refer back to the Work It Out about Comparing the Economies of Two Countries and examine the data for the two countries you chose. How are they similar? How are they different?
Problems
An economy starts off with a GDP per capita of $5,000. How large will the GDP per capita be if it grows at an annual rate of 2% for 20 years? 2% for 40 years? 4% for 40 years? 6% for 40 years?
An economy starts off with a GDP per capita of 12,000 euros. How large will the GDP per capita be if it grows at an annual rate of 3% for 10 years? 3% for 30 years? 6% for 30 years?
Say that the average worker in Canada has a productivity level of $30 per hour while the average worker in the United Kingdom has a productivity level of $25 per hour (both measured in U.S. dollars). Over the next five years, say that worker productivity in Canada grows at 1% per year while worker productivity in the UK grows 3% per year. After five years, who will have the higher productivity level, and by how much?
Say that the average worker in the U.S. economy is eight times as productive as an average worker in Mexico. If the productivity of U.S. workers grows at 2% for 25 years and the productivity of Mexico’s workers grows at 6% for 25 years, which country will have higher worker productivity at that point?
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2025-03-18T00:37:10.800902
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https://oercommons.org/courseware/lesson/28805/overview
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Components of Economic Growth
Overview
By the end of this section, you will be able to:
- Discuss the components of economic growth, including physical capital, human capital, and technology
- Explain capital deepening and its significance
- Analyze the methods employed in economic growth accounting studies
- Identify factors that contribute to a healthy climate for economic growth
Over decades and generations, seemingly small differences of a few percentage points in the annual rate of economic growth make an enormous difference in GDP per capita. In this module, we discuss some of the components of economic growth, including physical capital, human capital, and technology.
The category of physical capital includes the plant and equipment that firms use as well as things like roads (also called infrastructure). Again, greater physical capital implies more output. Physical capital can affect productivity in two ways: (1) an increase in the quantity of physical capital (for example, more computers of the same quality); and (2) an increase in the quality of physical capital (same number of computers but the computers are faster, and so on). Human capital refers to the skills and knowledge that make workers productive. Human capital and physical capital accumulation are similar: In both cases, investment now pays off in higher productivity in the future.
The category of technology is the “joker in the deck.” Earlier we described it as the combination of invention and innovation. When most people think of new technology, the invention of new products like the laser, the smartphone, or some new wonder drug come to mind. In food production, developing more drought-resistant seeds is another example of technology. Technology, as economists use the term, however, includes still more. It includes new ways of organizing work, like the invention of the assembly line, new methods for ensuring better quality of output in factories, and innovative institutions that facilitate the process of converting inputs into output. In short, technology comprises all the advances that make the existing machines and other inputs produce more, and at higher quality, as well as altogether new products.
It may not make sense to compare the GDPs of China and say, Benin, simply because of the great difference in population size. To understand economic growth, which is really concerned with the growth in living standards of an average person, it is often useful to focus on GDP per capita. Using GDP per capita also makes it easier to compare countries with smaller numbers of people, like Belgium, Uruguay, or Zimbabwe, with countries that have larger populations, like the United States, the Russian Federation, or Nigeria.
To obtain a per capita production function, divide each input in (a) by the population. This creates a second aggregate production function where the output is GDP per capita (that is, GDP divided by population). The inputs are the average level of human capital per person, the average level of physical capital per person, and the level of technology per person—see (b). The result of having population in the denominator is mathematically appealing. Increases in population lower per capita income. However, increasing population is important for the average person only if the rate of income growth exceeds population growth. A more important reason for constructing a per capita production function is to understand the contribution of human and physical capital.
Capital Deepening
When society increases the level of capital per person, we call the result capital deepening. The idea of capital deepening can apply both to additional human capital per worker and to additional physical capital per worker.
Recall that one way to measure human capital is to look at the average levels of education in an economy. Figure illustrates the human capital deepening for U.S. workers by showing that the proportion of the U.S. population with a high school and a college degree is rising. As recently as 1970, for example, only about half of U.S. adults had at least a high school diploma. By the start of the twenty-first century, more than 80% of adults had graduated from high school. The idea of human capital deepening also applies to the years of experience that workers have, but the average experience level of U.S. workers has not changed much in recent decades. Thus, the key dimension for deepening human capital in the U.S. economy focuses more on additional education and training than on a higher average level of work experience.
Figure shows physical capital deepening in the U.S. economy. The average U.S. worker in the late 2000s was working with physical capital worth almost three times as much as that of the average worker of the early 1950s.
Not only does the current U.S. economy have better-educated workers with more and improved physical capital than it did several decades ago, but these workers have access to more advanced technologies. Growth in technology is impossible to measure with a simple line on a graph, but evidence that we live in an age of technological marvels is all around us—discoveries in genetics and in the structure of particles, the wireless internet, and other inventions almost too numerous to count. The U.S. Patent and Trademark Office typically has issued more than 150,000 patents annually in recent years.
This recipe for economic growth—investing in labor productivity, with investments in human capital and technology, as well as increasing physical capital—also applies to other economies. South Korea, for example, already achieved universal enrollment in primary school (the equivalent of kindergarten through sixth grade in the United States) by 1965, when Korea’s GDP per capita was still near its rock bottom low. By the late 1980s, Korea had achieved almost universal secondary school education (the equivalent of a high school education in the United States). With regard to physical capital, Korea’s rates of investment had been about 15% of GDP at the start of the 1960s, but doubled to 30–35% of GDP by the late 1960s and early 1970s. With regard to technology, South Korean students went to universities and colleges around the world to obtain scientific and technical training, and South Korean firms reached out to study and form partnerships with firms that could offer them technological insights. These factors combined to foster South Korea’s high rate of economic growth.
Growth Accounting Studies
Since the late 1950s, economists have conducted growth accounting studies to determine the extent to which physical and human capital deepening and technology have contributed to growth. The usual approach uses an aggregate production function to estimate how much of per capita economic growth can be attributed to growth in physical capital and human capital. We can measure these two inputs at least roughly. The part of growth that is unexplained by measured inputs, called the residual, is then attributed to growth in technology. The exact numerical estimates differ from study to study and from country to country, depending on how researchers measured these three main factors and over what time horizons. For studies of the U.S. economy, three lessons commonly emerge from growth accounting studies.
First, technology is typically the most important contributor to U.S. economic growth. Growth in human capital and physical capital often explains only half or less than half of the economic growth that occurs. New ways of doing things are tremendously important.
Second, while investment in physical capital is essential to growth in labor productivity and GDP per capita, building human capital is at least as important. Economic growth is not just a matter of more machines and buildings. One vivid example of the power of human capital and technological knowledge occurred in Europe in the years after World War II (1939–1945). During the war, a large share of Europe’s physical capital, such as factories, roads, and vehicles, was destroyed. Europe also lost an overwhelming amount of human capital in the form of millions of men, women, and children who died during the war. However, the powerful combination of skilled workers and technological knowledge, working within a market-oriented economic framework, rebuilt Europe’s productive capacity to an even higher level within less than two decades.
A third lesson is that these three factors of human capital, physical capital, and technology work together. Workers with a higher level of education and skills are often better at coming up with new technological innovations. These technological innovations are often ideas that cannot increase production until they become a part of new investment in physical capital. New machines that embody technological innovations often require additional training, which builds worker skills further. If the recipe for economic growth is to succeed, an economy needs all the ingredients of the aggregate production function. See the following Clear It Up feature for an example of how human capital, physical capital, and technology can combine to significantly impact lives.
How do girls’ education and economic growth relate in low-income countries?
In the early 2000s, according to the World Bank, about 110 million children between the ages of 6 and 11 were not in school—and about two-thirds of them were girls. In Afghanistan, for example, the literacy rate for those aged 15-24 for the period 2005-2014 was 62% for males and only 32% for females. In Benin, in West Africa, it was 55% for males and 31% for females. In Nigeria, Africa’s most populous country, it was 76% for males and 58 percent for females.
Whenever any child does not receive a basic education, it is both a human and an economic loss. In low-income countries, wages typically increase by an average of 10 to 20% with each additional year of education. There is, however, some intriguing evidence that helping girls in low-income countries to close the education gap with boys may be especially important, because of the social role that many of the girls will play as mothers and homemakers.
Girls in low-income countries who receive more education tend to grow up to have fewer, healthier, better-educated children. Their children are more likely to be better nourished and to receive basic health care like immunizations. Economic research on women in low-income economies backs up these findings. When 20 women obtain one additional year of schooling, as a group they will, on average, have one less child. When 1,000 women obtain one additional year of schooling, on average one to two fewer women from that group will die in childbirth. When a woman stays in school an additional year, that factor alone means that, on average, each of her children will spend an additional half-year in school. Education for girls is a good investment because it is an investment in economic growth with benefits beyond the current generation.
A Healthy Climate for Economic Growth
While physical and human capital deepening and better technology are important, equally important to a nation’s well-being is the climate or system within which these inputs are cultivated. Both the type of market economy and a legal system that governs and sustains property rights and contractual rights are important contributors to a healthy economic climate.
A healthy economic climate usually involves some sort of market orientation at the microeconomic, individual, or firm decision-making level. Markets that allow personal and business rewards and incentives for increasing human and physical capital encourage overall macroeconomic growth. For example, when workers participate in a competitive and well-functioning labor market, they have an incentive to acquire additional human capital, because additional education and skills will pay off in higher wages. Firms have an incentive to invest in physical capital and in training workers, because they expect to earn higher profits for their shareholders. Both individuals and firms look for new technologies, because even small inventions can make work easier or lead to product improvement. Collectively, such individual and business decisions made within a market structure add up to macroeconomic growth. Much of the rapid growth since the late nineteenth century has come from harnessing the power of competitive markets to allocate resources. This market orientation typically reaches beyond national borders and includes openness to international trade.
A general orientation toward markets does not rule out important roles for government. There are times when markets fail to allocate capital or technology in a manner that provides the greatest benefit for society as a whole. The government's role is to correct these failures. In addition, government can guide or influence markets toward certain outcomes. The following examples highlight some important areas that governments around the world have chosen to invest in to facilitate capital deepening and technology:
- Education. The Danish government requires all children under 16 to attend school. They can choose to attend a public school (Folkeskole) or a private school. Students do not pay tuition to attend Folkeskole. Thirteen percent of primary/secondary (elementary/high) school is private, and the government supplies vouchers to citizens who choose private school.
- Savings and Investment. In the United States, as in other countries, the government taxes gains from private investment. Low capital gains taxes encourage investment and so also economic growth.
- Infrastructure. The Japanese government in the mid-1990s undertook significant infrastructure projects to improve roads and public works. This in turn increased the stock of physical capital and ultimately economic growth.
- Special Economic Zones. The island of Mauritius is one of the few African nations to encourage international trade in government-supported special economic zones (SEZ). These are areas of the country, usually with access to a port where, among other benefits, the government does not tax trade. As a result of its SEZ, Mauritius has enjoyed above-average economic growth since the 1980s. Free trade does not have to occur in an SEZ however. Governments can encourage international trade across the board, or surrender to protectionism.
- Scientific Research. The European Union has strong programs to invest in scientific research. The researchers Abraham García and Pierre Mohnen demonstrate that firms which received support from the Austrian government actually increased their research intensity and had more sales. Governments can support scientific research and technical training that helps to create and spread new technologies. Governments can also provide a legal environment that protects the ability of inventors to profit from their inventions.
There are many more ways in which the government can play an active role in promoting economic growth. We explore them in other chapters and in particular in Macroeconomic Policy Around the World. A healthy climate for growth in GDP per capita and labor productivity includes human capital deepening, physical capital deepening, and technological gains, operating in a market-oriented economy with supportive government policies.
Key Concepts and Summary
Over decades and generations, seemingly small differences of a few percentage points in the annual rate of economic growth make an enormous difference in GDP per capita. Capital deepening refers to an increase in the amount of capital per worker, either human capital per worker, in the form of higher education or skills, or physical capital per worker. Technology, in its economic meaning, refers broadly to all new methods of production, which includes major scientific inventions but also small inventions and even better forms of management or other types of institutions. A healthy climate for growth in GDP per capita consists of improvements in human capital, physical capital, and technology, in a market-oriented environment with supportive public policies and institutions.
Self-Check Questions
What do the growth accounting studies conclude are the determinants of growth? Which is more important, the determinants or how they are combined?
Hint:
Capital deepening and technology are important. What seems to be more important is how they are combined.
What policies can the government of a free-market economy implement to stimulate economic growth?
Hint:
Government can contribute to economic growth by investing in human capital through the education system, building a strong physical infrastructure for transportation and commerce, increasing investment by lowering capital gains taxes, creating special economic zones that allow for reduced tariffs, and investing in research and development.
List the areas where government policy can help economic growth.
Hint:
Public education, low investment taxes, funding for infrastructure projects, special economic zones
Review Questions
What is an aggregate production function?
What is capital deepening?
What do economists mean when they refer to improvements in technology?
Critical Thinking Questions
Education seems to be important for human capital deepening. As people become better educated and more knowledgeable, are there limits to how much additional benefit more education can provide? Why or why not?
Describe some of the political and social tradeoffs that might occur when a less developed country adopts a strategy to promote labor force participation and economic growth via investment in girls’ education.
Why is investing in girls’ education beneficial for growth?
How is the concept of technology, as defined with the aggregate production function, different from our everyday use of the word?
References
“Women and the World Economy: A Guide to Womenomics.” The Economist, April 12, 2006. http://www.economist.com/node/6802551.
Farole, Thomas, and Gokhan Akinci, eds. Special Economic Zones: Progress, Emerging Challenges, and Future Directions. Washington: The World Bank, 2011. http://publications.worldbank.org/index.php?main_page=product_info&products_id=24138.
Garcia, Abraham, and Pierre Mohnen. United Nations University, Maastricht Economic and Social Research and Training Centre on Innovation and Technology: UNU-MERIT. “Impact of Government Support on R&D and Innovation (Working Paper Series #2010-034).” http://www.merit.unu.edu/publications/wppdf/2010/wp2010-034.pdf.
Heston, Alan, Robert Summers, and Bettina Aten. “Penn World Table Version 7.1.” Center for International Comparisons of Production, Income and Prices at the University of Pennsylvania. Last modified July 2012. https://pwt.sas.upenn.edu/php_site/pwt71/pwt71_form.php.
United States Department of Labor: Bureau of Labor Statistics. “Women at Work: A Visual Essay.” Monthly Labor Review, October 2003, 45–50. http://www.bls.gov/opub/mlr/2003/10/ressum3.pdf.
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2025-03-18T00:37:10.832663
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Economic Convergence
Overview
By the end of this section, you will be able to:
- Explain economic convergence
- Analyze various arguments for and against economic convergence
- Evaluate the speed of economic convergence between high-income countries and the rest of the world
Some low-income and middle-income economies around the world have shown a pattern of convergence, in which their economies grow faster than those of high-income countries. GDP increased by an average rate of 2.7% per year in the 1990s and 2.3% per year from 2000 to 2008 in the high-income countries of the world, which include the United States, Canada, the European Union countries, Japan, Australia, and New Zealand.
Table lists 10 countries that belong to an informal “fast growth club.” These countries averaged GDP growth (after adjusting for inflation) of at least 5% per year in both the time periods from 1990 to 2000 and from 2000 to 2008. Since economic growth in these countries has exceeded the average of the world’s high-income economies, these countries may converge with the high-income countries. The second part of Table lists the “slow growth club,” which consists of countries that averaged GDP growth of 2% per year or less (after adjusting for inflation) during the same time periods. The final portion of Table shows GDP growth rates for the countries of the world divided by income.
| Country | Average Growth Rate of Real GDP 1990–2000 | Average Growth Rate of Real GDP 2000–2008 |
|---|---|---|
| Fast Growth Club (5% or more per year in both time periods) | ||
| Cambodia | 7.1% | 9.1% |
| China | 10.6% | 9.9% |
| India | 6.0% | 7.1% |
| Ireland | 7.5% | 5.1% |
| Jordan | 5.0% | 6.3% |
| Laos | 6.5% | 6.8 % |
| Mozambique | 6.4% | 7.3% |
| Sudan | 5.4% | 7.3% |
| Uganda | 7.1% | 7.3% |
| Vietnam | 7.9% | 7.3% |
| Slow Growth Club (2% or less per year in both time periods) | ||
| Central African Republic | 2.0% | 0.8% |
| France | 2.0% | 1.8% |
| Germany | 1.8% | 1.3% |
| Guinea-Bissau | 1.2% | 0.2% |
| Haiti | –1.5% | 0.3% |
| Italy | 1.6% | 1.2% |
| Jamaica | 0.9% | 1.4% |
| Japan | 1.3% | 1.3% |
| Switzerland | 1.0% | 2.0% |
| United States (for reference) | 3.2% | 2.2% |
| World Overview | ||
| High income | 2.7% | 2.3% |
| Low income | 3.8% | 5.6% |
| Middle income | 4.7% | 6.1% |
Each of the countries in Table has its own unique story of investments in human and physical capital, technological gains, market forces, government policies, and even lucky events, but an overall pattern of convergence is clear. The low-income countries have GDP growth that is faster than that of the middle-income countries, which in turn have GDP growth that is faster than that of the high-income countries. Two prominent members of the fast-growth club are China and India, which between them have nearly 40% of the world’s population. Some prominent members of the slow-growth club are high-income countries like France, Germany, Italy, and Japan.
Will this pattern of economic convergence persist into the future? This is a controversial question among economists that we will consider by looking at some of the main arguments on both sides.
Arguments Favoring Convergence
Several arguments suggest that low-income countries might have an advantage in achieving greater worker productivity and economic growth in the future.
A first argument is based on diminishing marginal returns. Even though deepening human and physical capital will tend to increase GDP per capita, the law of diminishing returns suggests that as an economy continues to increase its human and physical capital, the marginal gains to economic growth will diminish. For example, raising the average education level of the population by two years from a tenth-grade level to a high school diploma (while holding all other inputs constant) would produce a certain increase in output. An additional two-year increase, so that the average person had a two-year college degree, would increase output further, but the marginal gain would be smaller. Yet another additional two-year increase in the level of education, so that the average person would have a four-year-college bachelor’s degree, would increase output still further, but the marginal increase would again be smaller. A similar lesson holds for physical capital. If the quantity of physical capital available to the average worker increases, by, say, $5,000 to $10,000 (again, while holding all other inputs constant), it will increase the level of output. An additional increase from $10,000 to $15,000 will increase output further, but the marginal increase will be smaller.
Low-income countries like China and India tend to have lower levels of human capital and physical capital, so an investment in capital deepening should have a larger marginal effect in these countries than in high-income countries, where levels of human and physical capital are already relatively high. Diminishing returns implies that low-income economies could converge to the levels that the high-income countries achieve.
A second argument is that low-income countries may find it easier to improve their technologies than high-income countries. High-income countries must continually invent new technologies, whereas low-income countries can often find ways of applying technology that has already been invented and is well understood. The economist Alexander Gerschenkron (1904–1978) gave this phenomenon a memorable name: “the advantages of backwardness.” Of course, he did not literally mean that it is an advantage to have a lower standard of living. He was pointing out that a country that is behind has some extra potential for catching up.
Finally, optimists argue that many countries have observed the experience of those that have grown more quickly and have learned from it. Moreover, once the people of a country begin to enjoy the benefits of a higher standard of living, they may be more likely to build and support the market-friendly institutions that will help provide this standard of living.
View this video to learn about economic growth across the world.
Arguments That Convergence Is neither Inevitable nor Likely
If the economy's growth depended only on the deepening of human capital and physical capital, then we would expect that economy's growth rate to slow down over the long run because of diminishing marginal returns. However, there is another crucial factor in the aggregate production function: technology.
Developing new technology can provide a way for an economy to sidestep the diminishing marginal returns of capital deepening. Figure shows how. The figure's horizontal axis measures the amount of capital deepening, which on this figure is an overall measure that includes deepening of both physical and human capital. The amount of human and physical capital per worker increases as you move from left to right, from C1 to C2 to C3. The diagram's vertical axis measures per capita output. Start by considering the lowest line in this diagram, labeled Technology 1. Along this aggregate production function, the level of technology is held constant, so the line shows only the relationship between capital deepening and output. As capital deepens from C1 to C2 to C3 and the economy moves from R to U to W, per capita output does increase—but the way in which the line starts out steeper on the left but then flattens as it moves to the right shows the diminishing marginal returns, as additional marginal amounts of capital deepening increase output by ever-smaller amounts. The shape of the aggregate production line (Technology 1) shows that the ability of capital deepening, by itself, to generate sustained economic growth is limited, since diminishing returns will eventually set in.
Now, bring improvements in technology into the picture. Improved technology means that with a given set of inputs, more output is possible. The production function labeled Technology 1 in the figure is based on one level of technology, but Technology 2 is based on an improved level of technology, so for every level of capital deepening on the horizontal axis, it produces a higher level of output on the vertical axis. In turn, production function Technology 3 represents a still higher level of technology, so that for every level of inputs on the horizontal axis, it produces a higher level of output on the vertical axis than either of the other two aggregate production functions.
Most healthy, growing economies are deepening their human and physical capital and increasing technology at the same time. As a result, the economy can move from a choice like point R on the Technology 1 aggregate production line to a point like S on Technology 2 and a point like T on the still higher aggregate production line (Technology 3). With the combination of technology and capital deepening, the rise in GDP per capita in high-income countries does not need to fade away because of diminishing returns. The gains from technology can offset the diminishing returns involved with capital deepening.
Will technological improvements themselves run into diminishing returns over time? That is, will it become continually harder and more costly to discover new technological improvements? Perhaps someday, but, at least over the last two centuries since the beginning of the Industrial Revolution, improvements in technology have not run into diminishing marginal returns. Modern inventions, like the internet or discoveries in genetics or materials science, do not seem to provide smaller gains to output than earlier inventions like the steam engine or the railroad. One reason that technological ideas do not seem to run into diminishing returns is that we often can apply widely the ideas of new technology at a marginal cost that is very low or even zero. A specific worker or group of workers must use a specific additional machine, or an additional year of education. Many workers across the economy can use a new technology or invention at very low marginal cost.
The argument that it is easier for a low-income country to copy and adapt existing technology than it is for a high-income country to invent new technology is not necessarily true, either. When it comes to adapting and using new technology, a society’s performance is not necessarily guaranteed, but is the result of whether the country's economic, educational, and public policy institutions are supportive. In theory, perhaps, low-income countries have many opportunities to copy and adapt technology, but if they lack the appropriate supportive economic infrastructure and institutions, the theoretical possibility that backwardness might have certain advantages is of little practical relevance.
Visit this website to read more about economic growth in India.
The Slowness of Convergence
Although economic convergence between the high-income countries and the rest of the world seems possible and even likely, it will proceed slowly. Consider, for example, a country that starts off with a GDP per capita of $40,000, which would roughly represent a typical high-income country today, and another country that starts out at $4,000, which is roughly the level in low-income but not impoverished countries like Indonesia, Guatemala, or Egypt. Say that the rich country chugs along at a 2% annual growth rate of GDP per capita, while the poorer country grows at the aggressive rate of 7% per year. After 30 years, GDP per capita in the rich country will be $72,450 (that is, $40,000 (1 + 0.02)30) while in the poor country it will be $30,450 (that is, $4,000 (1 + 0.07)30). Convergence has occurred. The rich country used to be 10 times as wealthy as the poor one, and now it is only about 2.4 times as wealthy. Even after 30 consecutive years of very rapid growth, however, people in the low-income country are still likely to feel quite poor compared to people in the rich country. Moreover, as the poor country catches up, its opportunities for catch-up growth are reduced, and its growth rate may slow down somewhat.
The slowness of convergence illustrates again that small differences in annual rates of economic growth become huge differences over time. The high-income countries have been building up their advantage in standard of living over decades—more than a century in some cases. Even in an optimistic scenario, it will take decades for the low-income countries of the world to catch up significantly.
Calories and Economic Growth
We can tell the story of modern economic growth by looking at calorie consumption over time. The dramatic rise in incomes allowed the average person to eat better and consume more calories. How did these incomes increase? The neoclassical growth consensus uses the aggregate production function to suggest that the period of modern economic growth came about because of increases in inputs such as technology and physical and human capital. Also important was the way in which technological progress combined with physical and human capital deepening to create growth and convergence. The issue of distribution of income notwithstanding, it is clear that the average worker can afford more calories in 2017 than in 1875.
Aside from increases in income, there is another reason why the average person can afford more food. Modern agriculture has allowed many countries to produce more food than they need. Despite having more than enough food, however, many governments and multilateral agencies have not solved the food distribution problem. In fact, food shortages, famine, or general food insecurity are caused more often by the failure of government macroeconomic policy, according to the Nobel Prize-winning economist Amartya Sen. Sen has conducted extensive research into issues of inequality, poverty, and the role of government in improving standards of living. Macroeconomic policies that strive toward stable inflation, full employment, education of women, and preservation of property rights are more likely to eliminate starvation and provide for a more even distribution of food.
Because we have more food per capita, global food prices have decreased since 1875. The prices of some foods, however, have decreased more than the prices of others. For example, researchers from the University of Washington have shown that in the United States, calories from zucchini and lettuce are 100 times more expensive than calories from oil, butter, and sugar. Research from countries like India, China, and the United States suggests that as incomes rise, individuals want more calories from fats and protein and fewer from carbohydrates. This has very interesting implications for global food production, obesity, and environmental consequences. Affluent urban India has an obesity problem much like many parts of the United States. The forces of convergence are at work.
Key Concepts and Summary
When countries with lower GDP levels per capita catch up to countries with higher GDP levels per capita, we call the process convergence. Convergence can occur even when both high- and low-income countries increase investment in physical and human capital with the objective of growing GDP. This is because the impact of new investment in physical and human capital on a low-income country may result in huge gains as new skills or equipment combine with the labor force. In higher-income countries, however, a level of investment equal to that of the low income country is not likely to have as big an impact, because the more developed country most likely already has high levels of capital investment. Therefore, the marginal gain from this additional investment tends to be successively less and less. Higher income countries are more likely to have diminishing returns to their investments and must continually invent new technologies. This allows lower-income economies to have a chance for convergent growth. However, many high-income economies have developed economic and political institutions that provide a healthy economic climate for an ongoing stream of technological innovations. Continuous technological innovation can counterbalance diminishing returns to investments in human and physical capital.
Self-Check Questions
Use an example to explain why, after periods of rapid growth, a low-income country that has not caught up to a high-income country may feel poor.
Hint:
A good way to think about this is how a runner who has fallen behind in a race feels psychologically and physically as he catches up. Playing catch-up can be more taxing than maintaining one’s position at the head of the pack.
Would the following events usually lead to capital deepening? Why or why not?
- A weak economy in which businesses become reluctant to make long-term investments in physical capital.
- A rise in international trade.
- A trend in which many more adults participate in continuing education courses through their employers and at colleges and universities.
Hint:
- No. Capital deepening refers to an increase in the amount of capital per person in an economy. A decrease in investment by firms will actually cause the opposite of capital deepening (since the population will grow over time).
- There is no direct connection between an increase in international trade and capital deepening. One could imagine particular scenarios where trade could lead to capital deepening (for example, if international capital inflows—which are the counterpart to increasing the trade deficit—lead to an increase in physical capital investment), but in general, no.
- Yes. Capital deepening refers to an increase in either physical capital or human capital per person. Continuing education or any time of lifelong learning adds to human capital and thus creates capital deepening.
What are the “advantages of backwardness” for economic growth?
Hint:
The advantages of backwardness include faster growth rates because of the process of convergence, as well as the ability to adopt new technologies that were developed first in the “leader” countries. While being “backward” is not inherently a good thing, Gerschenkron stressed that there are certain advantages which aid countries trying to “catch up.”
Would you expect capital deepening to result in diminished returns? Why or why not? Would you expect improvements in technology to result in diminished returns? Why or why not?
Hint:
Capital deepening, by definition, should lead to diminished returns because you're investing more and more but using the same methods of production, leading to the marginal productivity declining. This is shown on a production function as a movement along the curve. Improvements in technology should not lead to diminished returns because you are finding new and more efficient ways of using the same amount of capital. This can be illustrated as a shift upward of the production function curve.
Why does productivity growth in high-income economies not slow down as it runs into diminishing returns from additional investments in physical capital and human capital? Does this show one area where the theory of diminishing returns fails to apply? Why or why not?
Hint:
Productivity growth from new advances in technology will not slow because the new methods of production will be adopted relatively quickly and easily, at very low marginal cost. Also, countries that are seeing technology growth usually have a vast and powerful set of institutions for training workers and building better machines, which allows the maximum amount of people to benefit from the new technology. These factors have the added effect of making additional technological advances even easier for these countries.
Review Questions
For a high-income economy like the United States, what aggregate production function elements are most important in bringing about growth in GDP per capita? What about a middle-income country such as Brazil? A low-income country such as Niger?
List some arguments for and against the likelihood of convergence.
Critical Thinking Questions
What sorts of policies can governments implement to encourage convergence?
As technological change makes us more sedentary and food costs increase, obesity is likely. What factors do you think may limit obesity?
References
Central Intelligence Agency. “The World Factbook: Country Comparison: GDP–Real Growth Rate.” https://www.cia.gov/library/publications/the-world-factbook/rankorder/2003rank.html.
Sen, Amartya. “Hunger in the Contemporary World (Discussion Paper DEDPS/8).” The Suntory Centre: London School of Economics and Political Science. Last modified November 1997. http://sticerd.lse.ac.uk/dps/de/dedps8.pdf.
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Introduction to Inflation
A $550 Million Loaf of Bread?
If you were born within the last three decades in the United States, Canada, or many other countries in the developed world, you probably have no real experience with a high rate of inflation. Inflation is when most prices in an entire economy are rising. However, there is an extreme form of inflation called hyperinflation. This occurred in Germany between 1921 and 1928, and more recently in Zimbabwe between 2008 and 2009. In November 2008, Zimbabwe had an inflation rate of 79.6 billion percent. In contrast, in 2014, the United States had an average annual rate of inflation of 1.6%.
Zimbabwe’s inflation rate was so high it is difficult to comprehend, so let’s put it into context. It is equivalent to price increases of 98% per day. This means that, from one day to the next, prices essentially double. What is life like in an economy afflicted with hyperinflation? Most of you reading this will have never experienced this phenomenon. The government adjusted prices for commodities in Zimbabwean dollars several times each day. There was no desire to hold on to currency since it lost value by the minute. The people there spent a great deal of time getting rid of any cash they acquired by purchasing whatever food or other commodities they could find. At one point, a loaf of bread cost 550 million Zimbabwean dollars. Teachers' salaries were in the trillions a month; however, this was equivalent to only one U.S. dollar a day. At its height, it took 621,984,228 Zimbabwean dollars to purchase one U.S. dollar.
Government agencies had no money to pay their workers so they started printing money to pay their bills rather than raising taxes. Rising prices caused the government to enact price controls on private businesses, which led to shortages and the emergence of black markets. In 2009, the country abandoned its currency and allowed people to use foreign currencies for purchases.
How does this happen? How can both government and the economy fail to function at the most basic level? Before we consider these extreme cases of hyperinflation, let’s first look at inflation itself.
Introduction to Inflation
In this chapter, you will learn about:
- Tracking Inflation
- How to Measure Changes in the Cost of Living
- How the U.S. and Other Countries Experience Inflation
- The Confusion Over Inflation
- Indexing and Its Limitations
Inflation is a general and ongoing rise in the level of prices in an entire economy. Inflation does not refer to a change in relative prices. A relative price change occurs when you see that the price of tuition has risen, but the price of laptops has fallen. Inflation, on the other hand, means that there is pressure for prices to rise in most markets in the economy. In addition, price increases in the supply-and-demand model were one-time events, representing a shift from a previous equilibrium to a new one. Inflation implies an ongoing rise in prices. If inflation happened for one year and then stopped, then it would not be inflation any more.
This chapter begins by showing how to combine prices of individual goods and services to create a measure of overall inflation. It discusses the historical and recent experience of inflation, both in the United States and in other countries around the world. Other chapters have sometimes included a note under an exhibit or a parenthetical reminder in the text saying that the numbers have been adjusted for inflation. In this chapter, it is time to show how to use inflation statistics to adjust other economic variables, so that you can tell how much of, for example, we can attribute the rise in GDP over different periods of time to an actual increase in the production of goods and services and how much we should attribute to the fact that prices for most items have risen.
Inflation has consequences for people and firms throughout the economy, in their roles as lenders and borrowers, wage-earners, taxpayers, and consumers. The chapter concludes with a discussion of some imperfections and biases in the inflation statistics, and a preview of policies for fighting inflation that we will discuss in other chapters.
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https://oercommons.org/courseware/lesson/28813/overview
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Tracking Inflation
Overview
By the end of this section, you will be able to:
- Calculate the annual rate of inflation
- Explain and use index numbers and base years when simplifying the total quantity spent over a year for products
- Calculate inflation rates using index numbers
Dinner table conversations where you might have heard about inflation usually entail reminiscing about when “everything seemed to cost so much less. You used to be able to buy three gallons of gasoline for a dollar and then go see an afternoon movie for another dollar.” Table compares some prices of common goods in 1970 and 2017. Of course, the average prices in this table may not reflect the prices where you live. The cost of living in New York City is much higher than in Houston, Texas, for example. In addition, certain products have evolved over recent decades. A new car in 2017, loaded with antipollution equipment, safety gear, computerized engine controls, and many other technological advances, is a more advanced machine (and more fuel efficient) than your typical 1970s car. However, put details like these to one side for the moment, and look at the overall pattern. The primary reason behind the price rises in Table—and all the price increases for the other products in the economy—is not specific to the market for housing or cars or gasoline or movie tickets. Instead, it is part of a general rise in the level of all prices. At the beginning of 2017, $1 had about the same purchasing power in overall terms of goods and services as 18 cents did in 1972, because of the amount of inflation that has occurred over that time period.
| Items | 1970 | 2017 |
|---|---|---|
| Pound of ground beef | $0.66 | $3.62 |
| Pound of butter | $0.87 | $2.03 |
| Movie ticket | $1.55 | $8.65 |
| Sales price of new home (median) | $22,000 | $312,900 |
| New car | $3,000 | $4,077 |
| Gallon of gasoline | $0.36 | $2.35 |
| Average hourly wage for a manufacturing worker | $3.23 | $20.65 |
| Per capita GDP | $5,069 | $57,294 |
Moreover, the power of inflation does not affect just goods and services, but wages and income levels, too. The second-to-last row of Table shows that the average hourly wage for a manufacturing worker increased nearly six-fold from 1970 to 2017. The average worker in 2017 is better educated and more productive than the average worker in 1970—but not six times more productive. Per capita GDP increased substantially from 1970 to 2017, but is the average person in the U.S. economy really more than eleven times better off in just 47 years? Not likely.
A modern economy has millions of goods and services whose prices are continually quivering in the breezes of supply and demand. How can all of these shifts in price attribute to a single inflation rate? As with many problems in economic measurement, the conceptual answer is reasonably straightforward: Economists combine prices of a variety of goods and services into a single price level. The inflation rate is simply the percentage change in the price level. Applying the concept, however, involves some practical difficulties.
The Price of a Basket of Goods
To calculate the price level, economists begin with the concept of a basket of goods and services, consisting of the different items individuals, businesses, or organizations typically buy. The next step is to look at how the prices of those items change over time. In thinking about how to combine individual prices into an overall price level, many people find that their first impulse is to calculate the average of the prices. Such a calculation, however, could easily be misleading because some products matter more than others.
Changes in the prices of goods for which people spend a larger share of their incomes will matter more than changes in the prices of goods for which people spend a smaller share of their incomes. For example, an increase of 10% in the rental rate on housing matters more to most people than whether the price of carrots rises by 10%. To construct an overall measure of the price level, economists compute a weighted average of the prices of the items in the basket, where the weights are based on the actual quantities of goods and services people buy. The following Work It Out feature walks you through the steps of calculating the annual rate of inflation based on a few products.
Calculating an Annual Rate of Inflation
Consider the simple basket of goods with only three items, represented in Table. Say that in any given month, a college student spends money on 20 hamburgers, one bottle of aspirin, and five movies. The table provides prices for these items over four years through each time period (Pd). Prices of some goods in the basket may rise while others fall. In this example, the price of aspirin does not change over the four years, while movies increase in price and hamburgers bounce up and down. The table shows the cost of buying the given basket of goods at the prices prevailing at that time.
| Items | Hamburger | Aspirin | Movies | Total | Inflation Rate |
|---|---|---|---|---|---|
| Qty | 20 | 1 bottle | 5 | - | - |
| (Pd 1) Price | $3.00 | $10.00 | $6.00 | - | - |
| (Pd 1) Amount Spent | $60.00 | $10.00 | $30.00 | $100.00 | - |
| (Pd 2) Price | $3.20 | $10.00 | $6.50 | - | - |
| (Pd 2) Amount Spent | $64.00 | $10.00 | $32.50 | $106.50 | 6.5% |
| (Pd 3) Price | $3.10 | $10.00 | $7.00 | - | - |
| (Pd 3) Amount Spent | $62.00 | $10.00 | $35.00 | $107.00 | 0.5% |
| (Pd 4) Price | $3.50 | $10.00 | $7.50 | - | - |
| (Pd 4) Amount Spent | $70.00 | $10.00 | $37.50 | $117.50 | 9.8% |
To calculate the annual rate of inflation in this example:
Step 1. Find the percentage change in the cost of purchasing the overall basket of goods between the time periods. The general equation for percentage changes between two years, whether in the context of inflation or in any other calculation, is:
Step 2. From period 1 to period 2, the total cost of purchasing the basket of goods in Table rises from $100 to $106.50. Therefore, the percentage change over this time—the inflation rate—is:
Step 3. From period 2 to period 3, the overall change in the cost of purchasing the basket rises from $106.50 to $107. Thus, the inflation rate over this time, again calculated by the percentage change, is approximately:
Step 4. From period 3 to period 4, the overall cost rises from $107 to $117.50. The inflation rate is thus:
This calculation of the change in the total cost of purchasing a basket of goods accounts for how much a student spends on each good. Hamburgers are the lowest-priced good in this example, and aspirin is the highest-priced. If an individual buys a greater quantity of a low-price good, then it makes sense that changes in the price of that good should have a larger impact on the buying power of that person’s money. The larger impact of hamburgers shows up in the “amount spent” row, where, in all time periods, hamburgers are the largest item within the amount spent row.
Index Numbers
The numerical results of a calculation based on a basket of goods can get a little messy. The simplified example in Table has only three goods and the prices are in even dollars, not numbers like 79 cents or $124.99. If the list of products were much longer, and we used more realistic prices, the total quantity spent over a year might be some messy-looking number like $17,147.51 or $27,654.92.
To simplify the task of interpreting the price levels for more realistic and complex baskets of goods, economists typically report the price level in each period as an index number, rather than as the dollar amount for buying the basket of goods. Economists create price indices to calculate an overall average change in relative prices over time. To convert the money spent on the basket to an index number, economists arbitrarily choose one year to be the base year, or starting point from which we measure changes in prices. The base year, by definition, has an index number equal to 100. This sounds complicated, but it is really a simple math trick. In the example above, say that we choose time period 3 as the base year. Since the total amount of spending in that year is $107, we divide that amount by itself ($107) and multiply by 100. Again, this is because the index number in the base year always has to have a value of 100. Then, to figure out the values of the index number for the other years, we divide the dollar amounts for the other years by 1.07 as well. Note also that the dollar signs cancel out so that index numbers have no units.
Table shows calculations for the other values of the index number, based on the example in Table. Because we calculate the index numbers so that they are in exactly the same proportion as the total dollar cost of purchasing the basket of goods, we can calculate the inflation rate based on the index numbers, using the percentage change formula. Thus, the inflation rate from period 1 to period 2 would be
This is the same answer that we derived when measuring inflation based on the dollar cost of the basket of goods for the same time period.
| Total Spending | Index Number | Inflation Rate Since Previous Period | |
|---|---|---|---|
| Period 1 | $100 | ||
| Period 2 | $106.50 | ||
| Period 3 | $107 | ||
| Period 4 | $117.50 |
If the inflation rate is the same whether it is based on dollar values or index numbers, then why bother with the index numbers? The advantage is that indexing allows easier eyeballing of the inflation numbers. If you glance at two index numbers like 107 and 110, you know automatically that the rate of inflation between the two years is about, but not quite exactly equal to, 3%. By contrast, imagine that we express the price levels in absolute dollars of a large basket of goods, so that when you looked at the data, the numbers were $19,493.62 and $20,040.17. Most people find it difficult to eyeball those kinds of numbers and say that it is a change of about 3%. However, the two numbers expressed in absolute dollars are exactly in the same proportion of 107 to 110 as the previous example. If you’re wondering why simple subtraction of the index numbers wouldn’t work, read the following Clear It Up feature.
Why do you not just subtract index numbers?
A word of warning: When a price index moves from, say, 107 to 110, the rate of inflation is not exactly 3%. Remember, the inflation rate is not derived by subtracting the index numbers, but rather through the percentage-change calculation. We calculate the precise inflation rate as the price index moves from 107 to 110 as 100 x (110 – 107) / 107 = 100 x 0.028 = 2.8%. When the base year is fairly close to 100, a quick subtraction is not a terrible shortcut to calculating the inflation rate—but when precision matters down to tenths of a percent, subtracting will not give the right answer.
Two final points about index numbers are worth remembering. First, index numbers have no dollar signs or other units attached to them. Although we can use index numbers to calculate a percentage inflation rate, the index numbers themselves do not have percentage signs. Index numbers just mirror the proportions that we find in other data. They transform the other data so that it is easier to work with the data.
Second, the choice of a base year for the index number—that is, the year that is automatically set equal to 100—is arbitrary. We choose it as a starting point from which we can track changes in prices. In the official inflation statistics, it is common to use one base year for a few years, and then to update it, so that the base year of 100 is relatively close to the present. However, any base year that we choose for the index numbers will result in exactly the same inflation rate. To see this in the previous example, imagine that period 1 is the base year when total spending was $100, and we assign it an index number of 100. At a glance, you can see that the index numbers would now exactly match the dollar figures, and the inflation rate in the first period would be 6.5%.
Now that we see how indexes work to track inflation, the next module will show us how economists measure the cost of living.
Watch this video from the cartoon Duck Tales to view a mini-lesson on inflation.
Key Concepts and Summary
Economists measure the price level by using a basket of goods and services and calculating how the total cost of buying that basket of goods will increase over time. Economists often express the price level in terms of index numbers, which transform the cost of buying the basket of goods and services into a series of numbers in the same proportion to each other, but with an arbitrary base year of 100. We measure the inflation rate as the percentage change between price levels or index numbers over time.
Self-Check Questions
Table shows the fruit prices that the typical college student purchased from 2001 to 2004. What is the amount spent each year on the “basket” of fruit with the quantities shown in column 2?
| Items | Qty | (2001) Price | (2001) Amount Spent | (2002) Price | (2002) Amount Spent | (2003) Price | (2003) Amount Spent | (2004) Price | (2004) Amount Spent |
|---|---|---|---|---|---|---|---|---|---|
| Apples | 10 | $0.50 | $0.75 | $0.85 | $0.88 | ||||
| Bananas | 12 | $0.20 | $0.25 | $0.25 | $0.29 | ||||
| Grapes | 2 | $0.65 | $0.70 | $0.90 | $0.95 | ||||
| Raspberries | 1 | $2.00 | $1.90 | $2.05 | $2.13 | $2.13 | |||
| Total |
Hint:
To compute the amount spent on each fruit in each year, you multiply the quantity of each fruit by the price.
- 10 apples × 50 cents each = $5.00 spent on apples in 2001.
- 12 bananas × 20 cents each = $2.40 spent on bananas in 2001.
- 2 bunches of grapes at 65 cents each = $1.30 spent on grapes in 2001.
- 1 pint of raspberries at $2 each = $2.00 spent on raspberries in 2001.
Adding up the amounts gives you the total cost of the fruit basket. The total cost of the fruit basket in 2001 was $5.00 + $2.40 + $1.30 + $2.00 = $10.70. The total costs for all the years are shown in the following table.
| 2001 | 2002 | 2003 | 2004 |
|---|---|---|---|
| $10.70 | $13.80 | $15.35 | $16.31 |
Construct the price index for a “fruit basket” in each year using 2003 as the base year.
Hint:
If 2003 is the base year, then the index number has a value of 100 in 2003. To transform the cost of a fruit basket each year, we divide each year’s value by $15.35, the value of the base year, and then multiply the result by 100. The price index is shown in the following table.
| 2001 | 2002 | 2003 | 2004 |
|---|---|---|---|
| 69.71 | 89.90 | 100.00 | 106.3 |
Note that the base year has a value of 100; years before the base year have values less than 100; and years after have values more than 100.
Compute the inflation rate for fruit prices from 2001 to 2004.
Hint:
The inflation rate is calculated as the percentage change in the price index from year to year. For example, the inflation rate between 2001 and 2002 is (84.61 – 69.71) / 69.71 = 0.2137 = 21.37%. The inflation rates for all the years are shown in the last row of the following table, which includes the two previous answers.
| Items | Qty | (2001) Price | (2001) Amount Spent | (2002) Price | (2002) Amount Spent | (2003) Price | (2003) Amount Spent | (2004) Price | (2004) Amount Spent |
|---|---|---|---|---|---|---|---|---|---|
| Apples | 10 | $0.50 | $5.00 | $0.75 | $7.50 | $0.85 | $8.50 | $0.88 | $8.80 |
| Bananas | 12 | $0.20 | $2.40 | $0.25 | $3.00 | $0.25 | $3.00 | $0.29 | $3.48 |
| Grapes | 2 | $0.65 | $1.30 | $0.70 | $1.40 | $0.90 | $1.80 | $0.95 | $1.90 |
| Raspberries | 1 | $2.00 | $2.00 | $1.90 | $1.90 | $2.05 | $2.05 | $2.13 | $2.13 |
| Total | $10.70 | $13.80 | $15.35 | $16.31 | |||||
| Price Index | 69.71 | 84.61 | 100.00 | 106.3 | |||||
| Inflation Rate | 21.37% | 18.19% | 6.3% |
Edna is living in a retirement home where most of her needs are taken care of, but she has some discretionary spending. Based on the basket of goods in Table, by what percentage does Edna’s cost of living increase between time 1 and time 2?
| Items | Quantity | (Time 1) Price | (Time 2) Price |
|---|---|---|---|
| Gifts for grandchildren | 12 | $50 | $60 |
| Pizza delivery | 24 | $15 | $16 |
| Blouses | 6 | $60 | $50 |
| Vacation trips | 2 | $400 | $420 |
Hint:
Begin by calculating the total cost of buying the basket in each time period, as shown in the following table.
| Items | Quantity | (Time 1) Price | (Time 1) Total Cost | (Time 2) Price | (Time 2) Total Cost |
|---|---|---|---|---|---|
| Gifts | 12 | $50 | $600 | $60 | $720 |
| Pizza | 24 | $15 | $360 | $16 | $384 |
| Blouses | 6 | $60 | $360 | $50 | $300 |
| Trips | 2 | $400 | $800 | $420 | $840 |
| Total Cost | $2,120 | $2,244 |
The rise in cost of living is calculated as the percentage increase:
(2244 – 2120) / 2120 = 0.0585 = 5.85%.
Review Questions
How do economists use a basket of goods and services to measure the price level?
Why do economists use index numbers to measure the price level rather than dollar value of goods?
What is the difference between the price level and the rate of inflation?
Critical Thinking Question
Inflation rates, like most statistics, are imperfect measures. Can you identify some ways that the inflation rate for fruit does not perfectly capture the rising price of fruit?
Problems
The index number representing the price level changes from 110 to 115 in one year, and then from 115 to 120 the next year. Since the index number increases by five each year, is five the inflation rate each year? Is the inflation rate the same each year? Explain your answer.
The total price of purchasing a basket of goods in the United Kingdom over four years is: year 1=£940, year 2=£970, year 3=£1000, and year 4=£1070. Calculate two price indices, one using year 1 as the base year (set equal to 100) and the other using year 4 as the base year (set equal to 100). Then, calculate the inflation rate based on the first price index. If you had used the other price index, would you get a different inflation rate? If you are unsure, do the calculation and find out.
References
Sources for Table:
http://www.eia.gov/dnav/pet/pet_pri_gnd_a_epmr_pte_dpgal_w.htm
http://data.bls.gov/cgi-bin/surveymost?ap
http://www.bls.gov/ro3/apmw.htm
http://www.autoblog.com/2014/03/12/who-can-afford-the-average-car-price-only-folks-in-washington/
https://www.census.gov/construction/nrs/pdf/uspricemon.pdf
http://www.bls.gov/news.release/empsit.t24.htm
http://variety.com/2015/film/news/movie-ticket-prices-increased-in-2014-1201409670/
US Inflation Calculator. "Historical Inflation Rates: 1914-2013." Accessed March 4, 2015. http://www.usinflationcalculator.com/inflation/historical-inflation-rates/.
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How to Measure Changes in the Cost of Living
Overview
By the end of this section, you will be able to:
- Use the Consumer Price Index (CPI) to calculate U.S. inflation rates
- Identify several ways the Bureau of Labor Statistics avoids biases in the Consumer Price Index (CPI)
- Differentiate among the Consumer Price Index (CPI), the Producer Price Index (PPI), the International Price Index, the Employment Cost Index, and the GDP deflator.
The most commonly cited measure of inflation in the United States is the Consumer Price Index (CPI). Government statisticians at the U.S. Bureau of Labor Statistics calculate the CPI based on the prices in a fixed basket of goods and services that represents the purchases of the average family of four. In recent years, the statisticians have paid considerable attention to a subtle problem: that the change in the total cost of buying a fixed basket of goods and services over time is conceptually not quite the same as the change in the cost of living, because the cost of living represents how much it costs for a person to feel that his or her consumption provides an equal level of satisfaction or utility.
To understand the distinction, imagine that over the past 10 years, the cost of purchasing a fixed basket of goods increased by 25% and your salary also increased by 25%. Has your personal standard of living held constant? If you do not necessarily purchase an identical fixed basket of goods every year, then an inflation calculation based on the cost of a fixed basket of goods may be a misleading measure of how your cost of living has changed. Two problems arise here: substitution bias and quality/new goods bias.
When the price of a good rises, consumers tend to purchase less of it and to seek out substitutes instead. Conversely, as the price of a good falls, people will tend to purchase more of it. This pattern implies that goods with generally rising prices should tend over time to become less important in the overall basket of goods used to calculate inflation, while goods with falling prices should tend to become more important. Consider, as an example, a rise in the price of peaches by $100 per pound. If consumers were utterly inflexible in their demand for peaches, this would lead to a big rise in the price of food for consumers. Alternatively, imagine that people are utterly indifferent to whether they have peaches or other types of fruit. Now, if peach prices rise, people completely switch to other fruit choices and the average price of food does not change at all. A fixed and unchanging basket of goods assumes that consumers are locked into buying exactly the same goods, regardless of price changes—not a very likely assumption. Thus, substitution bias—the rise in the price of a fixed basket of goods over time—tends to overstate the rise in a consumer’s true cost of living, because it does not take into account that the person can substitute away from goods whose relative prices have risen.
The other major problem in using a fixed basket of goods as the basis for calculating inflation is how to deal with the arrival of improved versions of older goods or altogether new goods. Consider the problem that arises if a cereal is improved by adding 12 essential vitamins and minerals—and also if a box of the cereal costs 5% more. It would clearly be misleading to count the entire resulting higher price as inflation, because the new price reflects a higher quality (or at least different) product. Ideally, one would like to know how much of the higher price is due to the quality change, and how much of it is just a higher price. The Bureau of Labor Statistics, which is responsible for computing the Consumer Price Index, must deal with these difficulties in adjusting for quality changes.
Visit this website to view a list of Ford car prices between 1909 and 1927. Consider how these prices compare to today’s models. Is the product today of a different quality?
We can think of a new product as an extreme improvement in quality—from something that did not exist to something that does. However, the basket of goods that was fixed in the past obviously does not include new goods created since then. The basket of goods and services in the Consumer Price Index (CPI) is revised and updated over time, and so new products are gradually included. However, the process takes some time. For example, room air conditioners were widely sold in the early 1950s, but were not introduced into the basket of goods behind the Consumer Price Index until 1964. The VCR and personal computer were available in the late 1970s and widely sold by the early 1980s, but did not enter the CPI basket of goods until 1987. By 1996, there were more than 40 million cellular phone subscribers in the United States—but cell phones were not yet part of the CPI basket of goods. The parade of inventions has continued, with the CPI inevitably lagging a few years behind.
The arrival of new goods creates problems with respect to the accuracy of measuring inflation. The reason people buy new goods, presumably, is that the new goods offer better value for money than existing goods. Thus, if the price index leaves out new goods, it overlooks one of the ways in which the cost of living is improving. In addition, the price of a new good is often higher when it is first introduced and then declines over time. If the new good is not included in the CPI for some years, until its price is already lower, the CPI may miss counting this price decline altogether. Taking these arguments together, the quality/new goods bias means that the rise in the price of a fixed basket of goods over time tends to overstate the rise in a consumer’s true cost of living, because it does not account for how improvements in the quality of existing goods or the invention of new goods improves the standard of living. The following Clear It Up feature is a must-read on how statisticians comprise and calculate the CPI.
How do U.S. government statisticians measure the Consumer Price Index?
When the U.S. Bureau of Labor Statistics (BLS) calculates the Consumer Price Index, the first task is to decide on a basket of goods that is representative of the purchases of the average household. We do this by using the Consumer Expenditure Survey, a national survey of about 7,000 households, which provides detailed information on spending habits. Statisticians divide consumer expenditures into eight major groups (seen below), which in turn they divide into more than 200 individual item categories. The BLS currently uses 1982–1984 as the base period.
For each of the 200 individual expenditure items, the BLS chooses several hundred very specific examples of that item and looks at the prices of those examples. In figuring out the “breakfast cereal” item under the overall category of “foods and beverages,” the BLS picks several hundred examples of breakfast cereal. One example might be the price of a 24-oz. box of a particular brand of cereal sold at a particular store. The BLS statistically selects specific products and sizes and stores to reflect what people buy and where they shop. The basket of goods in the Consumer Price Index thus consists of about 80,000 products; that is, several hundred specific products in over 200 broad-item categories. Statisticians rotate about one-quarter of these 80,000 specific products of the sample each year, and replace them with a different set of products.
The next step is to collect data on prices. Data collectors visit or call about 23,000 stores in 87 urban areas all over the United States every month to collect prices on these 80,000 specific products. The BLS also conducts a survey of 50,000 landlords or tenants to collect information about rents.
Statisticians then calculate the Consumer Price Index by taking the 80,000 prices of individual products and combining them, using weights (see Figure) determined by the quantities of these products that people buy and allowing for factors like substitution between goods and quality improvements, into price indices for the 200 or so overall items. Then, the statisticians combine the price indices for the 200 items into an overall Consumer Price Index. According the Consumer Price Index website, there are eight categories that data collectors use:
The Eight Major Categories in the Consumer Price Index
- Food and beverages (breakfast cereal, milk, coffee, chicken, wine, full-service meals, and snacks)
- Housing (renter’s cost of housing, homeowner’s cost of housing, fuel oil, bedroom furniture)
- Apparel (men’s shirts and sweaters, women’s dresses, jewelry)
- Transportation (new vehicles, airline fares, gasoline, motor vehicle insurance)
- Medical care (prescription drugs and medical supplies, physicians’ services, eyeglasses and eye care, hospital services)
- Recreation (televisions, cable television, pets and pet products, sports equipment, admissions)
- Education and communication (college tuition, postage, telephone services, computer software and accessories)
- Other goods and services (tobacco and smoking products, haircuts and other personal services, funeral expenses)
The CPI and Core Inflation Index
Imagine if you were driving a company truck across the country- you probably would care about things like the prices of available roadside food and motel rooms as well as the truck’s operating condition. However, the manager of the firm might have different priorities. He would care mostly about the truck’s on-time performance and much less so about the food you were eating and the places you were staying. In other words, the company manager would be paying attention to the firm's production, while ignoring transitory elements that impacted you, but did not affect the company’s bottom line.
In a sense, a similar situation occurs with regard to measures of inflation. As we’ve learned, CPI measures prices as they affect everyday household spending. Economists typically calculate a core inflation index by taking the CPI and excluding volatile economic variables. In this way, economists have a better sense of the underlying trends in prices that affect the cost of living.
Examples of excluded variables include energy and food prices, which can jump around from month to month because of the weather. According to an article by Kent Bernhard, during Hurricane Katrina in 2005, a key supply point for the nation’s gasoline was nearly knocked out. Gas prices quickly shot up across the nation, in some places by up to 40 cents a gallon in one day. This was not the cause of an economic policy but rather a short-lived event until the pumps were restored in the region. In this case, the CPI that month would register the change as a cost of living event to households, but the core inflation index would remain unchanged. As a result, the Federal Reserve’s decisions on interest rates would not be influenced. Similarly, droughts can cause world-wide spikes in food prices that, if temporary, do not affect the nation’s economic capability.
As former Chairman of the Federal Reserve Ben Bernanke noted in 1999 about the core inflation index, “It provide(s) a better guide to monetary policy than the other indices, since it measures the more persistent underlying inflation rather than transitory influences on the price level.” Bernanke also noted that it helps communicate that the Federal Reserve does not need to respond to every inflationary shock since some price changes are transitory and not part of a structural change in the economy.
In sum, both the CPI and the core inflation index are important, but serve different audiences. The CPI helps households understand their overall cost of living from month to month, while the core inflation index is a preferred gauge from which to make important government policy changes.
Practical Solutions for the Substitution and the Quality/New Goods Biases
By the early 2000s, the Bureau of Labor Statistics was using alternative mathematical methods for calculating the Consumer Price Index, more complicated than just adding up the cost of a fixed basket of goods, to allow for some substitution between goods. It was also updating the basket of goods behind the CPI more frequently, so that it could include new and improved goods more rapidly. For certain products, the BLS was carrying out studies to try to measure the quality improvement. For example, with computers, an economic study can try to adjust for changes in speed, memory, screen size, and other product characteristics, and then calculate the change in price after accounting for these product changes. However, these adjustments are inevitably imperfect, and exactly how to make these adjustments is often a source of controversy among professional economists.
By the early 2000s, the substitution bias and quality/new goods bias had been somewhat reduced, so that since then the rise in the CPI probably overstates the true rise in inflation by only about 0.5% per year. Over one or a few years, this is not much. Over a period of a decade or two, even half of a percent per year compounds to a more significant amount. In addition, the CPI tracks prices from physical locations, and not at online sites like Amazon, where prices can be lower.
When measuring inflation (and other economic statistics, too), a tradeoff arises between simplicity and interpretation. If we calculate the inflation rate with a basket of goods that is fixed and unchanging, then the calculation of an inflation rate is straightforward, but the problems of substitution bias and quality/new goods bias will arise. However, when the basket of goods is allowed to shift and evolve to reflect substitution toward lower relative prices, quality improvements, and new goods, the technical details of calculating the inflation rate grow more complex.
Additional Price Indices: PPI, GDP Deflator, and More
The basket of goods behind the Consumer Price Index represents an average hypothetical U.S. household's consumption, which is to say that it does not exactly capture anyone’s personal experience. When the task is to calculate an average level of inflation, this approach works fine. What if, however, you are concerned about inflation experienced by a certain group, like the elderly, or the poor, or single-parent families with children, or Hispanic-Americans? In specific situations, a price index based on the buying power of the average consumer may not feel quite right.
This problem has a straightforward solution. If the Consumer Price Index does not serve the desired purpose, then invent another index, based on a basket of goods appropriate for the group of interest. The Bureau of Labor Statistics publishes a number of experimental price indices: some for particular groups like the elderly or the poor, some for different geographic areas, and some for certain broad categories of goods like food or housing.
The BLS also calculates several price indices that are not based on baskets of consumer goods. For example, the Producer Price Index (PPI) is based on prices paid for supplies and inputs by producers of goods and services. We can break it down into price indices for different industries, commodities, and stages of processing (like finished goods, intermediate goods, or crude materials for further processing). There is an International Price Index based on the prices of merchandise that is exported or imported. An Employment Cost Index measures wage inflation in the labor market. The GDP deflator, which the Bureau of Economic Analysis measures, is a price index that includes all the GDP components (that is, consumption plus investment plus government plus exports minus imports). Unlike the CPI, its baskets are not fixed but re-calculate what that year’s GDP would have been worth using the base-year’s prices. MIT's Billion Prices Project is a more recent alternative attempt to measure prices: economists collect data online from retailers and then put them into an index that they compare to the CPI (Source: http://bpp.mit.edu/usa/).
What’s the best measure of inflation? If one is concerned with the most accurate measure of inflation, one should use the GDP deflator as it picks up the prices of goods and services produced. However, it is not a good measure of the cost of living as it includes prices of many products not purchased by households (for example, aircraft, fire engines, factory buildings, office complexes, and bulldozers). If one wants the most accurate measure of inflation as it impacts households, one should use the CPI, as it only picks up prices of products purchased by households. That is why economists sometimes refer to the CPI as the cost-of-living index. As the Bureau of Labor Statistics states on its website: “The ‘best’ measure of inflation for a given application depends on the intended use of the data.”
Key Concepts and Summary
Measuring price levels with a fixed basket of goods will always have two problems: the substitution bias, by which a fixed basket of goods does not allow for buying more of what becomes relatively less expensive and less of what becomes relatively more expensive; and the quality/new goods bias, by which a fixed basket cannot account for improvements in quality and the advent of new goods. These problems can be reduced in degree—for example, by allowing the basket of goods to evolve over time—but we cannot totally eliminate them. The most commonly cited measure of inflation is the Consumer Price Index (CPI), which is based on a basket of goods representing what the typical consumer buys. The Core Inflation Index further breaks down the CPI by excluding volatile economic commodities. Several price indices are not based on baskets of consumer goods. The GDP deflator is based on all GDP components. The Producer Price Index is based on prices of supplies and inputs bought by producers of goods and services. An Employment Cost Index measures wage inflation in the labor market. An International Price Index is based on the prices of merchandise that is exported or imported.
Self-Check Questions
How to Measure Changes in the Cost of Living introduced a number of different price indices. Which price index would be best to use to adjust your paycheck for inflation?
Hint:
Since the CPI measures the prices of the goods and services purchased by the typical urban consumer, it measures the prices of things that people buy with their paycheck. For that reason, the CPI would be the best price index to use for this purpose.
The Consumer Price Index is subject to the substitution bias and the quality/new goods bias. Are the Producer Price Index and the GDP Deflator also subject to these biases? Why or why not?
Hint:
The PPI is subject to those biases for essentially the same reasons as the CPI is. The GDP deflator picks up prices of what is actually purchased that year, so there are no biases. That is the advantage of using the GDP deflator over the CPI.
Review Questions
Why does “substitution bias” arise if we calculate the inflation rate based on a fixed basket of goods?
Why does the “quality/new goods bias” arise if we calculate the inflation rate based on a fixed basket of goods?
Critical Thinking Question
Given the federal budget deficit in recent years, some economists have argued that by adjusting Social Security payments for inflation using the CPI, Social Security is overpaying recipients. What is their argument, and do you agree or disagree with it?
Why is the GDP deflator not an accurate measure of inflation as it impacts a household?
Imagine that the government statisticians who calculate the inflation rate have been updating the basic basket of goods once every 10 years, but now they decide to update it every five years. How will this change affect the amount of substitution bias and quality/new goods bias?
Describe a situation, either a government policy situation, an economic problem, or a private sector situation, where using the CPI to convert from nominal to real would be more appropriate than using the GDP deflator.
Describe a situation, either a government policy situation, an economic problem, or a private sector situation, where using the GDP deflator to convert from nominal to real would be more appropriate than using the CPI.
References
Bernhard, Kent. “Pump Prices Jump Across U.S. after Katrina.” NBC News, September 1, 2005. http://www.nbcnews.com/id/9146363/ns/business-local_business/t/pump-prices-jump-across-us-after-katrina/#.U00kRfk7um4.
Wynne, Mark A. “Core Inflation, A Review of Some Conceptual Issues.” Federal Reserve Bank of St. Louis. p. 209. Accessed April 14, 2014. http://research.stlouisfed.org/publications/review/08/05/part2/Wynne.pdf
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How the U.S. and Other Countries Experience Inflation
Overview
By the end of this section, you will be able to:
- Identify patterns of inflation for the United States using data from the Consumer Price Index
- Identify patterns of inflation on an international level
In the last three decades, inflation has been relatively low in the U.S. economy, with the Consumer Price Index typically rising 2% to 4% per year. Looking back over the twentieth century, there have been several periods where inflation caused the price level to rise at double-digit rates, but nothing has come close to hyperinflation.
Historical Inflation in the U.S. Economy
Figure (a) shows the level of prices in the Consumer Price Index stretching back to 1913. In this case, the base years (when the CPI is defined as 100) are set for the average level of prices that existed from 1982 to 1984. Figure (b) shows the annual percentage changes in the CPI over time, which is the inflation rate.
The first two waves of inflation are easy to characterize in historical terms: they are right after World War I and World War II. However, there are also two periods of severe negative inflation—called deflation—in the early decades of the twentieth century: one following the deep 1920-21 recession of and the other during the 1930s Great Depression of the 1930s. (Since inflation is a time when the buying power of money in terms of goods and services is reduced, deflation will be a time when the buying power of money in terms of goods and services increases.) For the period from 1900 to about 1960, the major inflations and deflations nearly balanced each other out, so the average annual rate of inflation over these years was only about 1% per year. A third wave of more severe inflation arrived in the 1970s and departed in the early 1980s.
Visit this website to use an inflation calculator and discover how prices have changed in the last 100 years.
Times of recession or depression often seem to be times when the inflation rate is lower, as in the recession of 1920–1921, the Great Depression, the recession of 1980–1982, and the Great Recession in 2008–2009. There were a few months in 2009 that were deflationary, but not at an annual rate. High levels of unemployment typically accompany recessions, and the total demand for goods falls, pulling the price level down. Conversely, the rate of inflation often, but not always, seems to start moving up when the economy is growing very strongly, like right after wartime or during the 1960s. The frameworks for macroeconomic analysis, that we developed in other chapters, will explain why recession often accompanies higher unemployment and lower inflation, while rapid economic growth often brings lower unemployment but higher inflation.
Inflation around the World
Around the rest of the world, the pattern of inflation has been very mixed; Figure shows inflation rates over the last several decades. Many industrialized countries, not just the United States, had relatively high inflation rates in the 1970s. For example, in 1975, Japan’s inflation rate was over 8% and the inflation rate for the United Kingdom was almost 25%. In the 1980s, inflation rates came down in the United States and in Europe and have largely stayed down.
Countries with controlled economies in the 1970s, like the Soviet Union and China, historically had very low rates of measured inflation—because prices were forbidden to rise by law, except for the cases where the government deemed a price increase to be due to quality improvements. However, these countries also had perpetual shortages of goods, since forbidding prices to rise acts like a price ceiling and creates a situation where quantity demanded often exceeds quantity supplied. As Russia and China made a transition toward more market-oriented economies, they also experienced outbursts of inflation, although we should regard the statistics for these economies as somewhat shakier. Inflation in China averaged about 10% per year for much of the 1980s and early 1990s, although it has dropped off since then. Russia experienced hyperinflation—an outburst of high inflation—of 2,500% per year in the early 1990s, although by 2006 Russia’s consumer price inflation had dipped below 10% per year, as Figure shows. The closest the United States has ever reached hyperinflation was during the 1860–1865 Civil War, in the Confederate states.
Many countries in Latin America experienced raging inflation during the 1980s and early 1990s, with inflation rates often well above 100% per year. In 1990, for example, both Brazil and Argentina saw inflation climb above 2000%. Certain countries in Africa experienced extremely high rates of inflation, sometimes bordering on hyperinflation, in the 1990s. Nigeria, the most populous country in Africa, had an inflation rate of 75% in 1995.
In the early 2000s, the problem of inflation appears to have diminished for most countries, at least in comparison to the worst times of recent decades. As we noted in this earlier Bring it Home feature, in recent years, the world’s worst example of hyperinflation was in Zimbabwe, where at one point the government was issuing bills with a face value of $100 trillion (in Zimbabwean dollars)—that is, the bills had $100,000,000,000,000 written on the front, but were almost worthless. In many countries, the memory of double-digit, triple-digit, and even quadruple-digit inflation is not very far in the past.
Key Concepts and Summary
In the U.S. economy, the annual inflation rate in the last two decades has typically been around 2% to 4%. The periods of highest inflation in the United States in the twentieth century occurred during the years after World Wars I and II, and in the 1970s. The period of lowest inflation—actually, with deflation—was the 1930s Great Depression.
Self-Check Question
Go to this website for the Purchasing Power Calculator at MeasuringWorth.com. How much money would it take today to purchase what one dollar would have bought in the year of your birth?
Hint:
The calculator requires you to input three numbers:
- The first year, in this case the year of your birth
- The amount of money you would want to translate in terms of its purchasing power
- The last year—now or the most recent year the calculator will accept
My birth year is 1955. The amount is $1. The year 2012 is currently the latest year the calculator will accept. The simple purchasing power calculator shows that $1 of purchases in 1955 would cost $8.57 in 2012. The website also explains how the true answer is more complicated than that shown by the simple purchasing power calculator.
Review Questions
What has been a typical range of inflation in the U.S. economy in the last decade or so?
Over the last century, during what periods was the U.S. inflation rate highest and lowest?
What is deflation?
Critical Thinking Question
Why do you think the U.S. experience with inflation over the last 50 years has been so much milder than in many other countries?
Problems
Within 1 or 2 percentage points, what has the U.S. inflation rate been during the last 20 years? Draw a graph to show the data.
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The Confusion Over Inflation
Overview
By the end of this section, you will be able to:
- Explain how inflation can cause redistributions of purchasing power
- Identify ways inflation can blur the perception of supply and demand
- Explain the economic benefits and challenges of inflation
Economists usually oppose high inflation, but they oppose it in a milder way than many non-economists. Robert Shiller, one of 2013’s Nobel Prize winners in economics, carried out several surveys during the 1990s about attitudes toward inflation. One of his questions asked, “Do you agree that preventing high inflation is an important national priority, as important as preventing drug abuse or preventing deterioration in the quality of our schools?” Answers were on a scale of 1–5, where 1 meant “Fully agree” and 5 meant “Completely disagree.” For the U.S. population as a whole, 52% answered “Fully agree” that preventing high inflation was a highly important national priority and just 4% said “Completely disagree.” However, among professional economists, only 18% answered “Fully agree,” while the same percentage of 18% answered “Completely disagree.”
The Land of Funny Money
What are the economic problems caused by inflation, and why do economists often regard them with less concern than the general public? Consider a very short story: “The Land of Funny Money.”
One morning, everyone in the Land of Funny Money awakened to find that everything denominated in money had increased by 20%. The change was completely unexpected. Every price in every store was 20% higher. Paychecks were 20% higher. Interest rates were 20 % higher. The amount of money, everywhere from wallets to savings accounts, was 20% larger. This overnight inflation of prices made newspaper headlines everywhere in the Land of Funny Money. However, the headlines quickly disappeared, as people realized that in terms of what they could actually buy with their incomes, this inflation had no economic impact. Everyone’s pay could still buy exactly the same set of goods as it did before. Everyone’s savings were still sufficient to buy exactly the same car, vacation, or retirement that they could have bought before. Equal levels of inflation in all wages and prices ended up not mattering much at all.
When the people in Robert Shiller’s surveys explained their concern about inflation, one typical reason was that they feared that as prices rose, they would not be able to afford to buy as much. In other words, people were worried because they did not live in a place like the Land of Funny Money, where all prices and wages rose simultaneously. Instead, people live here on Planet Earth, where prices might rise while wages do not rise at all, or where wages rise more slowly than prices.
Economists note that over most periods, the inflation level in prices is roughly similar to the inflation level in wages, and so they reason that, on average, over time, people’s economic status is not greatly changed by inflation. If all prices, wages, and interest rates adjusted automatically and immediately with inflation, as in the Land of Funny Money, then no one’s purchasing power, profits, or real loan payments would change. However, if other economic variables do not move exactly in sync with inflation, or if they adjust for inflation only after a time lag, then inflation can cause three types of problems: unintended redistributions of purchasing power, blurred price signals, and difficulties in long-term planning.
Unintended Redistributions of Purchasing Power
Inflation can cause redistributions of purchasing power that hurt some and help others. People who are hurt by inflation include those who are holding considerable cash, whether it is in a safe deposit box or in a cardboard box under the bed. When inflation happens, the buying power of cash diminishes. However, cash is only an example of a more general problem: anyone who has financial assets invested in a way that the nominal return does not keep up with inflation will tend to suffer from inflation. For example, if a person has money in a bank account that pays 4% interest, but inflation rises to 5%, then the real rate of return for the money invested in that bank account is negative 1%.
The problem of a good-looking nominal interest rate transforming into an ugly-looking real interest rate can be worsened by taxes. The U.S. income tax is charged on the nominal interest received in dollar terms, without an adjustment for inflation. Thus, the government taxes a person who invests $10,000 and receives a 5% nominal rate of interest on the $500 received—no matter whether the inflation rate is 0%, 5%, or 10%. If inflation is 0%, then the real interest rate is 5% and all $500 is a gain in buying power. However, if inflation is 5%, then the real interest rate is zero and the person had no real gain—but owes income tax on the nominal gain anyway. If inflation is 10%, then the real interest rate is negative 5% and the person is actually falling behind in buying power, but would still owe taxes on the $500 in nominal gains.
Inflation can cause unintended redistributions for wage earners, too. Wages do typically creep up with inflation over time, eventually. The last row of at the start of this chapter showed that the average hourly wage in manufacturing in the U.S. economy increased from $3.23 in 1970 to $20.65 in 2017, which is an increase by a factor of more than six. Over that time period, the Consumer Price Index increased by an almost identical amount. However, increases in wages may lag behind inflation for a year or two, since wage adjustments are often somewhat sticky and occur only once or twice a year. Moreover, the extent to which wages keep up with inflation creates insecurity for workers and may involve painful, prolonged conflicts between employers and employees. If the government adjusts minimum wage for inflation only infrequently, minimum wage workers are losing purchasing power from their nominal wages, as Figure shows.
One sizable group of people has often received a large share of their income in a form that does not increase over time: retirees who receive a private company pension. Most pensions have traditionally been set as a fixed nominal dollar amount per year at retirement. For this reason, economists call pensions “defined benefits” plans. Even if inflation is low, the combination of inflation and a fixed income can create a substantial problem over time. A person who retires on a fixed income at age 65 will find that losing just 1% to 2% of buying power per year to inflation compounds to a considerable loss of buying power after a decade or two.
Fortunately, pensions and other defined benefits retirement plans are increasingly rare, replaced instead by “defined contribution” plans, such as 401(k)s and 403(b)s. In these plans, the employer contributes a fixed amount to the worker’s retirement account on a regular basis (usually every pay check). The employee often contributes as well. The worker invests these funds in a wide range of investment vehicles. These plans are tax deferred, and they are portable so that if the individual takes a job with a different employer, their 401(k) comes with them. To the extent that the investments made generate real rates of return, retirees do not suffer from the inflation costs of traditional pensioners.
However, ordinary people can sometimes benefit from the unintended redistributions of inflation. Consider someone who borrows $10,000 to buy a car at a fixed interest rate of 9%. If inflation is 3% at the time the loan is made, then he or she must repay the loan at a real interest rate of 6%. However, if inflation rises to 9%, then the real interest rate on the loan is zero. In this case, the borrower’s benefit from inflation is the lender’s loss. A borrower paying a fixed interest rate, who benefits from inflation, is just the flip side of an investor receiving a fixed interest rate, who suffers from inflation. The lesson is that when interest rates are fixed, rises in the rate of inflation tend to penalize suppliers of financial capital, who receive repayment in dollars that are worth less because of inflation, while demanders of financial capital end up better off, because they can repay their loans in dollars that are worth less than originally expected.
The unintended redistributions of buying power that inflation causes may have a broader effect on society. America’s widespread acceptance of market forces rests on a perception that people’s actions have a reasonable connection to market outcomes. When inflation causes a retiree who built up a pension or invested at a fixed interest rate to suffer, however, while someone who borrowed at a fixed interest rate benefits from inflation, it is hard to believe that this outcome was deserved in any way. Similarly, when homeowners benefit from inflation because the price of their homes rises, while renters suffer because they are paying higher rent, it is hard to see any useful incentive effects. One of the reasons that the general public dislikes inflation is a sense that it makes economic rewards and penalties more arbitrary—and therefore likely to be perceived as unfair – even dangerous, as the next Clear It Up feature shows.
Is there a connection between German hyperinflation and Hitler’s rise to power?
Germany suffered an intense hyperinflation of its currency, the Mark, in the years after World War I, when the Weimar Republic in Germany resorted to printing money to pay its bills and the onset of the Great Depression created the social turmoil that Adolf Hitler was able to take advantage of in his rise to power. Shiller described the connection this way in a National Bureau of Economic Research 1996 Working Paper:
A fact that is probably little known to young people today, even in Germany, is that the final collapse of the Mark in 1923, the time when the Mark’s inflation reached astronomical levels (inflation of 35,974.9% in November 1923 alone, for an annual rate that month of 4.69 × 1028%), came in the same month as did Hitler’s Beer Hall Putsch, his Nazi Party’s armed attempt to overthrow the German government. This failed putsch resulted in Hitler’s imprisonment, at which time he wrote his book Mein Kampf, setting forth an inspirational plan for Germany’s future, suggesting plans for world domination. . .
. . . Most people in Germany today probably do not clearly remember these events; this lack of attention to it may be because its memory is blurred by the more dramatic events that succeeded it (the Nazi seizure of power and World War II). However, to someone living through these historical events in sequence . . . [the putsch] may have been remembered as vivid evidence of the potential effects of inflation.
Blurred Price Signals
Prices are the messengers in a market economy, conveying information about conditions of demand and supply. Inflation blurs those price messages. Inflation means that we perceive price signals more vaguely, like a radio program received with considerable static. If the static becomes severe, it is hard to tell what is happening.
In Israel, when inflation accelerated to an annual rate of 500% in 1985, some stores stopped posting prices directly on items, since they would have had to put new labels on the items or shelves every few days to reflect inflation. Instead, a shopper just took items from a shelf and went up to the checkout register to find out the price for that day. Obviously, this situation makes comparing prices and shopping for the best deal rather difficult. When the levels and changes of prices become uncertain, businesses and individuals find it harder to react to economic signals. In a world where inflation is at a high rate, but bouncing up and down to some extent, does a higher price of a good mean that inflation has risen, or that supply of that good has decreased, or that demand for that good has increased? Should a buyer of the good take the higher prices as an economic hint to start substituting other products—or have the prices of the substitutes risen by an equal amount? Should a seller of the good take a higher price as a reason to increase production—or is the higher price only a sign of a general inflation in which the prices of all inputs to production are rising as well? The true story will presumably become clear over time, but at a given moment, who can say?
High and variable inflation means that the incentives in the economy to adjust in response to changes in prices are weaker. Markets will adjust toward their equilibrium prices and quantities more erratically and slowly, and many individual markets will experience a greater chance of surpluses and shortages.
Problems of Long-Term Planning
Inflation can make long-term planning difficult. In discussing unintended redistributions, we considered the case of someone trying to plan for retirement with a pension that is fixed in nominal terms and a high rate of inflation. Similar problems arise for all people trying to save for retirement, because they must consider what their money will really buy several decades in the future when we cannot know the rate of future inflation.
Inflation, especially at moderate or high levels, will pose substantial planning problems for businesses, too. A firm can make money from inflation—for example, by paying bills and wages as late as possible so that it can pay in inflated dollars, while collecting revenues as soon as possible. A firm can also suffer losses from inflation, as in the case of a retail business that gets stuck holding too much cash, only to see inflation eroding the value of that cash. However, when a business spends its time focusing on how to profit by inflation, or at least how to avoid suffering from it, an inevitable tradeoff strikes: less time is spent on improving products and services or on figuring out how to make existing products and services more cheaply. An economy with high inflation rewards businesses that have found clever ways of profiting from inflation, which are not necessarily the businesses that excel at productivity, innovation, or quality of service.
In the short term, low or moderate levels of inflation may not pose an overwhelming difficulty for business planning, because costs of doing business and sales revenues may rise at similar rates. If, however, inflation varies substantially over the short or medium term, then it may make sense for businesses to stick to shorter-term strategies. The evidence as to whether relatively low rates of inflation reduce productivity is controversial among economists. There is some evidence that if inflation can be held to moderate levels of less than 3% per year, it need not prevent a nation’s real economy from growing at a healthy pace. For some countries that have experienced hyperinflation of several thousand percent per year, an annual inflation rate of 20–30% may feel basically the same as zero. However, several economists have pointed to the suggestive fact that when U.S. inflation heated up in the early 1970s—to 10%—U.S. growth in productivity slowed down, and when inflation slowed down in the 1980s, productivity edged up again not long thereafter, as Figure shows.
Any Benefits of Inflation?
Although the economic effects of inflation are primarily negative, two countervailing points are worth noting. First, the impact of inflation will differ considerably according to whether it is creeping up slowly at 0% to 2% per year, galloping along at 10% to 20% per year, or racing to the point of hyperinflation at, say, 40% per month. Hyperinflation can rip an economy and a society apart. An annual inflation rate of 2%, 3%, or 4%, however, is a long way from a national crisis. Low inflation is also better than deflation which occurs with severe recessions.
Second, economists sometimes argue that moderate inflation may help the economy by making wages in labor markets more flexible. The discussion in Unemployment pointed out that wages tend to be sticky in their downward movements and that unemployment can result. A little inflation could nibble away at real wages, and thus help real wages to decline if necessary. In this way, even if a moderate or high rate of inflation may act as sand in the gears of the economy, perhaps a low rate of inflation serves as oil for the gears of the labor market. This argument is controversial. A full analysis would have to account for all the effects of inflation. It does, however, offer another reason to believe that, all things considered, very low rates of inflation may not be especially harmful.
Key Concepts and Summary
Unexpected inflation will tend to hurt those whose money received, in terms of wages and interest payments, does not rise with inflation. In contrast, inflation can help those who owe money that they can pay in less valuable, inflated dollars. Low rates of inflation have relatively little economic impact over the short term. Over the medium and the long term, even low rates of inflation can complicate future planning. High rates of inflation can muddle price signals in the short term and prevent market forces from operating efficiently, and can vastly complicate long-term savings and investment decisions.
Self-Check Question
If inflation rises unexpectedly by 5%, would a state government that had recently borrowed money to pay for a new highway benefit or lose?
Hint:
The state government would benefit because it would repay the loan in less valuable dollars than it borrowed. Plus, tax revenues for the state government would increase because of the inflation.
Review Question
Identify several parties likely to be helped and hurt by inflation.
Critical Thinking Questions
If, over time, wages and salaries on average rise at least as fast as inflation, why do people worry about how inflation affects incomes?
Who in an economy is the big winner from inflation?
References
Shiller, Robert. “Why Do People Dislike Inflation?” NBER Working Paper Series, National Bureau of Economic Research, p. 52. 1996.
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Indexing and Its Limitations
Overview
By the end of this section, you will be able to:
- Explain the relationship between indexing and inflation
- Identify three ways the government can control inflation through macroeconomic policy
When a price, wage, or interest rate is adjusted automatically with inflation, economists use the term indexed. An indexed payment increases according to the index number that measures inflation. Those in private markets and government programs observe a wide range of indexing arrangements. Since the negative effects of inflation depend in large part on having inflation unexpectedly affect one part of the economy but not another—say, increasing the prices that people pay but not the wages that workers receive—indexing will take some of the sting out of inflation.
Indexing in Private Markets
In the 1970s and 1980s, labor unions commonly negotiated wage contracts that had cost-of-living adjustments (COLAs) which guaranteed that their wages would keep up with inflation. These contracts were sometimes written as, for example, COLA plus 3%. Thus, if inflation was 5%, the wage increase would automatically be 8%, but if inflation rose to 9%, the wage increase would automatically be 12%. COLAs are a form of indexing applied to wages.
Loans often have built-in inflation adjustments, too, so that if the inflation rate rises by two percentage points, then the interest rate that a financial institution charges on the loan rises by two percentage points as well. An adjustable-rate mortgage (ARM) is a type of loan that one can use to purchase a home in which the interest rate varies with the rate of inflation. Often, a borrower will be able receive a lower interest rate if borrowing with an ARM, compared to a fixed-rate loan. The reason is that with an ARM, the lender is protected against the risk that higher inflation will reduce the real loan payments, and so the risk premium part of the interest rate can be correspondingly lower.
A number of ongoing or long-term business contracts also have provisions that prices will adjust automatically according to inflation. Sellers like such contracts because they are not locked into a low nominal selling price if inflation turns out higher than expected. Buyers like such contracts because they are not locked into a high buying price if inflation turns out to be lower than expected. A contract with automatic adjustments for inflation in effect agrees on a real price for the borrower to pay, rather than a nominal price.
Indexing in Government Programs
Many government programs are indexed to inflation. The U.S. income tax code is designed so that as a person’s income rises above certain levels, the tax rate on the marginal income earned rises as well. That is what the expression “move into a higher tax bracket” means. For example, according to the basic tax tables from the Internal Revenue Service, in 2017 a single person owed 10% of all taxable income from $0 to $9,325; 15% of all income from $9,326 to $37,950; 25% of all taxable income from $37,951 to $91,900; 28% of all taxable income from $91,901 to $191,650; 33% of all taxable income from $191,651 to $416,700; 35% of all taxable income from $416,701 to $418,400; and 39.6% of all income from $418,401 and above.
Because of the many complex provisions in the rest of the tax code, it is difficult to determine exactly the taxes an individual owes the government based on these numbers, but the numbers illustrate the basic theme that tax rates rise as the marginal dollar of income rises. Until the late 1970s, if nominal wages increased along with inflation, people were moved into higher tax brackets and owed a higher proportion of their income in taxes, even though their real income had not risen. In 1981, the government eliminated this “bracket creep”. Now, the income levels where higher tax rates kick in are indexed to rise automatically with inflation.
The Social Security program offers two examples of indexing. Since the passage of the Social Security Indexing Act of 1972, the level of Social Security benefits increases each year along with the Consumer Price Index. Also, Social Security is funded by payroll taxes, which the government imposes on the income earned up to a certain amount—$117,000 in 2014. The government adjusts this level of income upward each year according to the rate of inflation, so that an indexed increase in the Social Security tax base accompanies the indexed rise in the benefit level.
As yet another example of a government program affected by indexing, in 1996 the U.S., government began offering indexed bonds. Bonds are means by which the U.S. government (and many private-sector companies as well) borrows money; that is, investors buy the bonds, and then the government repays the money with interest. Traditionally, government bonds have paid a fixed rate of interest. This policy gave a government that had borrowed an incentive to encourage inflation, because it could then repay its past borrowing in inflated dollars at a lower real interest rate. However, indexed bonds promise to pay a certain real rate of interest above whatever inflation rate occurs. In the case of a retiree trying to plan for the long term and worried about the risk of inflation, for example, indexed bonds that guarantee a rate of return higher than inflation—no matter the level of inflation—can be a very comforting investment.
Might Indexing Reduce Concern over Inflation?
Indexing may seem like an obviously useful step. After all, when individuals, firms, and government programs are indexed against inflation, then people can worry less about arbitrary redistributions and other effects of inflation.
However, some of the fiercest opponents of inflation express grave concern about indexing. They point out that indexing is always partial. Not every employer will provide COLAs for workers. Not all companies can assume that costs and revenues will rise in lockstep with the general rates of inflation. Not all interest rates for borrowers and savers will change to match inflation exactly. However, as partial inflation indexing spreads, the political opposition to inflation may diminish. After all, older people whose Social Security benefits are protected against inflation, or banks that have loaned their money with adjustable-rate loans, no longer have as much reason to care whether inflation heats up. In a world where some people are indexed against inflation and some are not, financially savvy businesses and investors may seek out ways to be protected against inflation, while the financially unsophisticated and small businesses may suffer from it most.
A Preview of Policy Discussions of Inflation
This chapter has focused on how economists measure inflation, historical experience with inflation, how to adjust nominal variables into real ones, how inflation affects the economy, and how indexing works. We have barely hinted at the causes of inflation, and we have not addressed government policies to deal with inflation. We will examine these issues in depth in other chapters. However, it is useful to offer a preview here.
We can sum up the cause of inflation in one phrase: Too many dollars chasing too few goods. The great surges of inflation early in the twentieth century came after wars, which are a time when government spending is very high, but consumers have little to buy, because production is going to the war effort. Governments also commonly impose price controls during wartime. After the war, the price controls end and pent-up buying power surges forth, driving up inflation. Otherwise, if too few dollars are chasing too many goods, then inflation will decline or even turn into deflation. Therefore, we typically associate slowdowns in economic activity, as in major recessions and the Great Depression, with a reduction in inflation or even outright deflation.
The policy implications are clear. If we are to avoid inflation, the amount of purchasing power in the economy must grow at roughly the same rate as the production of goods. Macroeconomic policies that the government can use to affect the amount of purchasing power—through taxes, spending, and regulation of interest rates and credit—can thus cause inflation to rise or reduce inflation to lower levels.
A $550 Million Loaf of Bread?
As we will learn in Money and Banking, the existence of money provides enormous benefits to an economy. In a real sense, money is the lubrication that enhances the workings of markets. Money makes transactions easier. It allows people to find employment producing one product, then use the money earned to purchase the other products they need to live. However, too much money in circulation can lead to inflation. Extreme cases of governments recklessly printing money lead to hyperinflation. Inflation reduces the value of money. Hyperinflation, because money loses value so quickly, ultimately results in people no longer using money. The economy reverts to barter, or it adopts another country’s more stable currency, like U.S. dollars. In the meantime, the economy literally falls apart as people leave jobs and fend for themselves because it is not worth the time to work for money that will be worthless in a few days.
Only national governments have the power to cause hyperinflation. Hyperinflation typically happens when government faces extraordinary demands for spending, which it cannot finance by taxes or borrowing. The only option is to print money—more and more of it. With more money in circulation chasing the same amount (or even fewer) goods and services, the only result is increasingly higher prices until the economy and/or the government collapses. This is why economists are generally wary of letting inflation spiral out of control.
Key Concepts and Summary
A payment is indexed if it is automatically adjusted for inflation. Examples of indexing in the private sector include wage contracts with cost-of-living adjustments (COLAs) and loan agreements like adjustable-rate mortgages (ARMs). Examples of indexing in the public sector include tax brackets and Social Security payments.
Self-Check Questions
How should an increase in inflation affect the interest rate on an adjustable-rate mortgage?
Hint:
Higher inflation reduces real interest rates on fixed rate mortgages. Because ARMs can be adjusted, higher inflation leads to higher interest rates on ARMs.
A fixed-rate mortgage has the same interest rate over the life of the loan, whether the mortgage is for 15 or 30 years. By contrast, an adjustable-rate mortgage changes with market interest rates over the life of the mortgage. If inflation falls unexpectedly by 3%, what would likely happen to a homeowner with an adjustable-rate mortgage?
Hint:
Because the mortgage has an adjustable rate, the rate should fall by 3%, the same as inflation, to keep the real interest rate the same.
Review Questions
What is indexing?
Name several forms of indexing in the private and public sector.
Critical Thinking Questions
If a government gains from unexpected inflation when it borrows, why would it choose to offer indexed bonds?
Do you think perfect indexing is possible? Why or why not?
Problems
If inflation rises unexpectedly by 5%, indicate for each of the following whether the economic actor is helped, hurt, or unaffected:
- A union member with a COLA wage contract
- Someone with a large stash of cash in a safe deposit box
- A bank lending money at a fixed rate of interest
- A person who is not due to receive a pay raise for another 11 months
Rosalie the Retiree knows that when she retires in 16 years, her company will give her a one-time payment of $20,000. However, if the inflation rate is 6% per year, how much buying power will that $20,000 have when measured in today’s dollars? Hint: Start by calculating the rise in the price level over the 16 years.
References
Wines, Michael. “How Bad is Inflation in Zimbabwe?” The New York Times, May 2, 2006. http://www.nytimes.com/2006/05/02/world/africa/02zimbabwe.html?pagewanted=all&_r=0.
Hanke, Steve H. “R.I.P. Zimbabwe Dollar.” CATO Institute. Accessed December 31, 2013. http://www.cato.org/zimbabwe.
Massachusetts Institute of Technology. 2015. "Billion Prices Project." Accessed March 4, 2015. http://bpp.mit.edu/usa/.
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Introduction to Exchange Rates and International Capital Flows
Is a Stronger Dollar Good for the U.S. Economy?
From 2002 to 2008, the U.S. dollar lost more than a quarter of its value in foreign currency markets. On January 1, 2002, one dollar was worth 1.11 euros. On April 24, 2008 it hit its lowest point with a dollar being worth 0.64 euros. During this period, the trade deficit between the United States and the European Union grew from a yearly total of approximately –85.7 billion dollars in 2002 to 95.8 billion dollars in 2008. Was this a good thing or a bad thing for the U.S. economy?
We live in a global world. U.S. consumers buy trillions of dollars worth of imported goods and services each year, not just from the European Union, but from all over the world. U.S. businesses sell trillions of dollars’ worth of exports. U.S. citizens, businesses, and governments invest trillions of dollars abroad every year. Foreign investors, businesses, and governments invest trillions of dollars in the United States each year. Indeed, foreigners are a major buyer of U.S. federal debt.
Many people feel that a weaker dollar is bad for America, that it’s an indication of a weak economy, but is it? This chapter will help answer that question.
Introduction to Exchange Rates and International Capital Flows
In this chapter, you will learn about:
- How the Foreign Exchange Market Works
- Demand and Supply Shifts in Foreign Exchange Markets
- Macroeconomic Effects of Exchange Rates
- Exchange Rate Policies
The world has over 150 different currencies, from the Afghanistan afghani and the Albanian lek all the way through the alphabet to the Zambian kwacha and the Zimbabwean dollar. For international economic transactions, households or firms will wish to exchange one currency for another. Perhaps the need for exchanging currencies will come from a German firm that exports products to Russia, but then wishes to exchange the Russian rubles it has earned for euros, so that the firm can pay its workers and suppliers in Germany. Perhaps it will be a South African firm that wishes to purchase a mining operation in Angola, but to make the purchase it must convert South African rand to Angolan kwanza. Perhaps it will be an American tourist visiting China, who wishes to convert U.S. dollars to Chinese yuan to pay the hotel bill.
Exchange rates can sometimes change very swiftly. For example, in the United Kingdom the pound was worth about $1.50 just before the nation voted to leave the European Union (also known as the Brexit vote), but fell to $1.37 just after the vote and continued falling to reach 30-year lows a few months later. For firms engaged in international buying, selling, lending, and borrowing, these swings in exchange rates can have an enormous effect on profits.
This chapter discusses the international dimension of money, which involves conversions from one currency to another at an exchange rate. An exchange rate is nothing more than a price—that is, the price of one currency in terms of another currency—and so we can analyze it with the tools of supply and demand. The first module of this chapter begins with an overview of foreign exchange markets: their size, their main participants, and the vocabulary for discussing movements of exchange rates. The following module uses demand and supply graphs to analyze some of the main factors that cause shifts in exchange rates. A final module then brings the central bank and monetary policy back into the picture. Each country must decide whether to allow the market to determine its exchange rate, or have the central bank intervene. All the choices for exchange rate policy involve distinctive tradeoffs and risks.
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How the Foreign Exchange Market Works
Overview
By the end of this section, you will be able to:
- Define "foreign exchange market"
- Describe different types of investments like foreign direct investments (FDI), portfolio investments, and hedging
- Explain how appreciating or depreciating currency affects exchange rates
- Identify who benefits from a stronger currency and benefits from a weaker currency
Most countries have different currencies, but not all. Sometimes small economies use an economically larger neighbor's currency. For example, Ecuador, El Salvador, and Panama have decided to dollarize—that is, to use the U.S. dollar as their currency. Sometimes nations share a common currency. A large-scale example of a common currency is the decision by 17 European nations—including some very large economies such as France, Germany, and Italy—to replace their former currencies with the euro. With these exceptions, most of the international economy takes place in a situation of multiple national currencies in which both people and firms need to convert from one currency to another when selling, buying, hiring, borrowing, traveling, or investing across national borders. We call the market in which people or firms use one currency to purchase another currency the foreign exchange market.
You have encountered the basic concept of exchange rates in earlier chapters. In The International Trade and Capital Flows, for example, we discussed how economists use exchange rates to compare GDP statistics from countries where they measure GDP in different currencies. These earlier examples, however, took the actual exchange rate as given, as if it were a fact of nature. In reality, the exchange rate is a price—the price of one currency expressed in terms of units of another currency. The key framework for analyzing prices, whether in this course, any other economics course, in public policy, or business examples, is the operation of supply and demand in markets.
Visit this website for an exchange rate calculator.
The Extraordinary Size of the Foreign Exchange Markets
The quantities traded in foreign exchange markets are breathtaking. A 2013 Bank of International Settlements survey found that $5.3 trillion per day was traded on foreign exchange markets, which makes the foreign exchange market the largest market in the world economy. In contrast, 2013 U.S. real GDP was $15.8 trillion per year.
Table shows the currencies most commonly traded on foreign exchange markets. The U.S. dollar dominates the foreign exchange market, followed by the euro, the British pound, the Australian dollar, and the Japanese yen.
| Currency | % Daily Share |
|---|---|
| U.S. dollar | 87.6% |
| Euro | 31.3% |
| Japanese yen | 21.6% |
| British pound | 12.8% |
| Australian dollar | 6.9% |
| Canadian dollar | 5.1% |
| Swiss franc | 4.8% |
| Chinese yuan | 2.6% |
Demanders and Suppliers of Currency in Foreign Exchange Markets
In foreign exchange markets, demand and supply become closely interrelated, because a person or firm who demands one currency must at the same time supply another currency—and vice versa. To get a sense of this, it is useful to consider four groups of people or firms who participate in the market: (1) firms that are involved in international trade of goods and services; (2) tourists visiting other countries; (3) international investors buying ownership (or part-ownership) of a foreign firm; (4) international investors making financial investments that do not involve ownership. Let’s consider these categories in turn.
Firms that buy and sell on international markets find that their costs for workers, suppliers, and investors are measured in the currency of the nation where their production occurs, but their revenues from sales are measured in the currency of the different nation where their sales happened. Thus, a Chinese firm exporting abroad will earn some other currency—say, U.S. dollars—but will need Chinese yuan to pay the workers, suppliers, and investors who are based in China. In the foreign exchange markets, this firm will be a supplier of U.S. dollars and a demander of Chinese yuan.
International tourists will supply their home currency to receive the currency of the country they are visiting. For example, an American tourist who is visiting China will supply U.S. dollars into the foreign exchange market and demand Chinese yuan.
We often divide financial investments that cross international boundaries, and require exchanging currency into two categories. Foreign direct investment (FDI) refers to purchasing a firm (at least ten percent) in another country or starting up a new enterprise in a foreign country For example, in 2008 the Belgian beer-brewing company InBev bought the U.S. beer-maker Anheuser-Busch for $52 billion. To make this purchase, InBev would have to supply euros (the currency of Belgium) to the foreign exchange market and demand U.S. dollars.
The other kind of international financial investment, portfolio investment, involves a purely financial investment that does not entail any management responsibility. An example would be a U.S. financial investor who purchased U.K. government bonds, or deposited money in a British bank. To make such investments, the American investor would supply U.S. dollars in the foreign exchange market and demand British pounds.
Business people often link portfolio investment to expectations about how exchange rates will shift. Look at a U.S. financial investor who is considering purchasing U.K. issued bonds. For simplicity, ignore any bond interest payment (which will be small in the short run anyway) and focus on exchange rates. Say that a British pound is currently worth $1.50 in U.S. currency. However, the investor believes that in a month, the British pound will be worth $1.60 in U.S. currency. Thus, as Figure (a) shows, this investor would change $24,000 for 16,000 British pounds. In a month, if the pound is worth $1.60, then the portfolio investor can trade back to U.S. dollars at the new exchange rate, and have $25,600—a nice profit. A portfolio investor who believes that the foreign exchange rate for the pound will work in the opposite direction can also invest accordingly. Say that an investor expects that the pound, now worth $1.50 in U.S. currency, will decline to $1.40. Then, as Figure (b) shows, that investor could start off with £20,000 in British currency (borrowing the money if necessary), convert it to $30,000 in U.S. currency, wait a month, and then convert back to approximately £21,429 in British currency—again making a nice profit. Of course, this kind of investing comes without guarantees, and an investor will suffer losses if the exchange rates do not move as predicted.
Many portfolio investment decisions are not as simple as betting that the currency's value will change in one direction or the other. Instead, they involve firms trying to protect themselves from movements in exchange rates. Imagine you are running a U.S. firm that is exporting to France. You have signed a contract to deliver certain products and will receive 1 million euros a year from now. However, you do not know how much this contract will be worth in U.S. dollars, because the dollar/euro exchange rate can fluctuate in the next year. Let’s say you want to know for sure what the contract will be worth, and not take a risk that the euro will be worth less in U.S. dollars than it currently is. You can hedge, which means using a financial transaction to protect yourself against a risk from one of your investments (in this case, currency risk from the contract). Specifically, you can sign a financial contract and pay a fee that guarantees you a certain exchange rate one year from now—regardless of what the market exchange rate is at that time. Now, it is possible that the euro will be worth more in dollars a year from now, so your hedging contract will be unnecessary, and you will have paid a fee for nothing. However, if the value of the euro in dollars declines, then you are protected by the hedge. When parties wish to enter financial contracts like hedging, they normally rely on a financial institution or brokerage company to handle the hedging. These companies either take a fee or create a spread in the exchange rate in order to earn money through the service they provide.
Both foreign direct investment and portfolio investment involve an investor who supplies domestic currency and demands a foreign currency. With portfolio investment, the client purchases less than ten percent of a company. As such, business players often get involved with portfolio investment with a short term focus. With foreign direct investment the investor purchases more than ten percent of a company and the investor typically assumes some managerial responsibility. Thus, foreign direct investment tends to have a more long-run focus. As a practical matter, an investor can withdraw portfolio investments from a country much more quickly than foreign direct investments. A U.S. portfolio investor who wants to buy or sell U.K. government bonds can do so with a phone call or a few computer keyboard clicks. However, a U.S. firm that wants to buy or sell a company, such as one that manufactures automobile parts in the United Kingdom, will find that planning and carrying out the transaction takes a few weeks, even months. Table summarizes the main categories of currency demanders and suppliers.
| Demand for the U.S. Dollar Comes from… | Supply of the U.S. Dollar Comes from… |
|---|---|
| A U.S. exporting firm that earned foreign currency and is trying to pay U.S.-based expenses | A foreign firm that has sold imported goods in the United States, earned U.S. dollars, and is trying to pay expenses incurred in its home country |
| Foreign tourists visiting the United States | U.S. tourists leaving to visit other countries |
| Foreign investors who wish to make direct investments in the U.S. economy | U.S. investors who want to make foreign direct investments in other countries |
| Foreign investors who wish to make portfolio investments in the U.S. economy | U.S. investors who want to make portfolio investments in other countries |
Participants in the Exchange Rate Market
The foreign exchange market does not involve the ultimate suppliers and demanders of foreign exchange literally seeking each other. If Martina decides to leave her home in Venezuela and take a trip in the United States, she does not need to find a U.S. citizen who is planning to take a vacation in Venezuela and arrange a person-to-person currency trade. Instead, the foreign exchange market works through financial institutions, and it operates on several levels.
Most people and firms who are exchanging a substantial quantity of currency go to a bank, and most banks provide foreign exchange as a service to customers. These banks (and a few other firms), known as dealers, then trade the foreign exchange. This is called the interbank market.
In the world economy, roughly 2,000 firms are foreign exchange dealers. The U.S. economy has less than 100 foreign exchange dealers, but the largest 12 or so dealers carry out more than half the total transactions. The foreign exchange market has no central location, but the major dealers keep a close watch on each other at all times.
The foreign exchange market is huge not because of the demands of tourists, firms, or even foreign direct investment, but instead because of portfolio investment and the actions of interlocking foreign exchange dealers. International tourism is a very large industry, involving about $1 trillion per year. Global exports are about 23% of global GDP; which is about $18 trillion per year. Foreign direct investment totaled about $1.5 trillion in the end of 2013. These quantities are dwarfed, however, by the $5.3 trillion per day traded in foreign exchange markets. Most transactions in the foreign exchange market are for portfolio investment—relatively short-term movements of financial capital between currencies—and because of the large foreign exchange dealers' actions as they constantly buy and sell with each other.
Strengthening and Weakening Currency
When the prices of most goods and services change, the price "rises or "falls". For exchange rates, the terminology is different. When the exchange rate for a currency rises, so that the currency exchanges for more of other currencies, we refer to it as appreciating or “strengthening.” When the exchange rate for a currency falls, so that a currency trades for less of other currencies, we refer to it as depreciating or “weakening.”
To illustrate the use of these terms, consider the exchange rate between the U.S. dollar and the Canadian dollar since 1980, in Figure (a). The vertical axis in Figure (a) shows the price of $1 in U.S. currency, measured in terms of Canadian currency. Clearly, exchange rates can move up and down substantially. A U.S. dollar traded for $1.17 Canadian in 1980. The U.S. dollar appreciated or strengthened to $1.39 Canadian in 1986, depreciated or weakened to $1.15 Canadian in 1991, and then appreciated or strengthened to $1.60 Canadian by early in 2002, fell to roughly $1.20 Canadian in 2009, and then had a sharp spike up and decline in 2009 and 2010. In May of 2017, the U.S. dollar stood at $1.36 Canadian. The units in which we measure exchange rates can be confusing, because we measure the exchange rate of the U.S. dollar exchange using a different currency—the Canadian dollar. However, exchange rates always measure the price of one unit of currency by using a different currency.
In looking at the exchange rate between two currencies, the appreciation or strengthening of one currency must mean the depreciation or weakening of the other. Figure (b) shows the exchange rate for the Canadian dollar, measured in terms of U.S. dollars. The exchange rate of the U.S. dollar measured in Canadian dollars, in Figure (a), is a perfect mirror image with the Canadian dollar exchange rate measured in U.S. dollars, in Figure (b). A fall in the Canada $/U.S. $ ratio means a rise in the U.S. $/Canada $ ratio, and vice versa.
With the price of a typical good or service, it is clear that higher prices benefit sellers and hurt buyers, while lower prices benefit buyers and hurt sellers. In the case of exchange rates, where the buyers and sellers are not always intuitively obvious, it is useful to trace how a stronger or weaker currency will affect different market participants. Consider, for example, the impact of a stronger U.S. dollar on six different groups of economic actors, as Figure shows: (1) U.S. exporters selling abroad; (2) foreign exporters (that is, firms selling imports in the U.S. economy); (3) U.S. tourists abroad; (4) foreign tourists visiting the United States; (5) U.S. investors (either foreign direct investment or portfolio investment) considering opportunities in other countries; (6) and foreign investors considering opportunities in the U.S. economy.
For a U.S. firm selling abroad, a stronger U.S. dollar is a curse. A strong U.S. dollar means that foreign currencies are correspondingly weak. When this exporting firm earns foreign currencies through its export sales, and then converts them back to U.S. dollars to pay workers, suppliers, and investors, the stronger dollar means that the foreign currency buys fewer U.S. dollars than if the currency had not strengthened, and that the firm’s profits (as measured in dollars) fall. As a result, the firm may choose to reduce its exports, or it may raise its selling price, which will also tend to reduce its exports. In this way, a stronger currency reduces a country’s exports.
Conversely, for a foreign firm selling in the U.S. economy, a stronger dollar is a blessing. Each dollar earned through export sales, when traded back into the exporting firm's home currency, will now buy more home currency than expected before the dollar had strengthened. As a result, the stronger dollar means that the importing firm will earn higher profits than expected. The firm will seek to expand its sales in the U.S. economy, or it may reduce prices, which will also lead to expanded sales. In this way, a stronger U.S. dollar means that consumers will purchase more from foreign producers, expanding the country’s level of imports.
For a U.S. tourist abroad, who is exchanging U.S. dollars for foreign currency as necessary, a stronger U.S. dollar is a benefit. The tourist receives more foreign currency for each U.S. dollar, and consequently the cost of the trip in U.S. dollars is lower. When a country’s currency is strong, it is a good time for citizens of that country to tour abroad. Imagine a U.S. tourist who has saved up $5,000 for a trip to South Africa. In 2010, $1 bought 7.3 South African rand, so the tourist had 36,500 rand to spend. In 2012, $1 bought 8.2 rand, so the tourist had 41,000 rand to spend. By 2015, $1 bought nearly 13 rand. Clearly, more recent years have been better for U.S. tourists to visit South Africa. For foreign visitors to the United States, the opposite pattern holds true. A relatively stronger U.S. dollar means that their own currencies are relatively weaker, so that as they shift from their own currency to U.S. dollars, they have fewer U.S. dollars than previously. When a country’s currency is strong, it is not an especially good time for foreign tourists to visit.
A stronger dollar injures the prospects of a U.S. financial investor who has already invested money in another country. A U.S. financial investor abroad must first convert U.S. dollars to a foreign currency, invest in a foreign country, and then later convert that foreign currency back to U.S. dollars. If in the meantime the U.S. dollar becomes stronger and the foreign currency becomes weaker, then when the investor converts back to U.S. dollars, the rate of return on that investment will be less than originally expected at the time it was made.
However, a stronger U.S. dollar boosts the returns of a foreign investor putting money into a U.S. investment. That foreign investor converts from the home currency to U.S. dollars and seeks a U.S. investment, while later planning to switch back to the home currency. If, in the meantime, the dollar grows stronger, then when the time comes to convert from U.S. dollars back to the foreign currency, the investor will receive more foreign currency than expected at the time the original investment was made.
The preceding paragraphs all focus on the case where the U.S. dollar becomes stronger. The first column in Figure illustrates the corresponding happy or unhappy economic reactions. The following Work It Out feature centers the analysis on the opposite: a weaker dollar.
Effects of a Weaker Dollar
Let’s work through the effects of a weaker dollar on a U.S. exporter, a foreign exporter into the United States, a U.S. tourist going abroad, a foreign tourist coming to the United States, a U.S. investor abroad, and a foreign investor in the United States.
Step 1. Note that the demand for U.S. exports is a function of the price of those exports, which depends on the dollar price of those goods and the exchange rate of the dollar in terms of foreign currency. For example, a Ford pickup truck costs $25,000 in the United States. When it is sold in the United Kingdom, the price is $25,000 / $1.30 per British pound, or £19,231. The dollar affects the price foreigners face who may purchase U.S. exports.
Step 2. Consider that, if the dollar weakens, the pound rises in value. If the pound rises to $2.00 per pound, then the price of a Ford pickup is now $25,000 / $2.00 = £12,500. A weaker dollar means the foreign currency buys more dollars, which means that U.S. exports appear less expensive.
Step 3. Summarize that a weaker U.S. dollar leads to an increase in U.S. exports. For a foreign exporter, the outcome is just the opposite.
Step 4. Suppose a brewery in England is interested in selling its Bass Ale to a grocery store in the United States. If the price of a six pack of Bass Ale is £6.00 and the exchange rate is $1.30 per British pound, the price for the grocery store is 6.00 × $1.30 = $7.80 per six pack. If the dollar weakens to $2.00 per pound, the price of Bass Ale is now 6.00 × $2.00 = $12.
Step 5. Summarize that, from the perspective of U.S. purchasers, a weaker dollar means that foreign currency is more expensive, which means that foreign goods are more expensive also. This leads to a decrease in U.S. imports, which is bad for the foreign exporter.
Step 6. Consider U.S. tourists going abroad. They face the same situation as a U.S. importer—they are purchasing a foreign trip. A weaker dollar means that their trip will cost more, since a given expenditure of foreign currency (e.g., hotel bill) will take more dollars. The result is that the tourist may not stay as long abroad, and some may choose not to travel at all.
Step 7. Consider that, for the foreign tourist to the United States, a weaker dollar is a boon. It means their currency goes further, so the cost of a trip to the United States will be less. Foreigners may choose to take longer trips to the United States, and more foreign tourists may decide to take U.S. trips.
Step 8. Note that a U.S. investor abroad faces the same situation as a U.S. importer—they are purchasing a foreign asset. A U.S. investor will see a weaker dollar as an increase in the “price” of investment, since the same number of dollars will buy less foreign currency and thus less foreign assets. This should decrease the amount of U.S. investment abroad.
Step 9. Note also that foreign investors in the Unites States will have the opposite experience. Since foreign currency buys more dollars, they will likely invest in more U.S. assets.
At this point, you should have a good sense of the major players in the foreign exchange market: firms involved in international trade, tourists, international financial investors, banks, and foreign exchange dealers. The next module shows how players can use the tools of demand and supply in foreign exchange markets to explain the underlying causes of stronger and weaker currencies (we address “stronger” and “weaker” more in the following Clear It Up feature).
Why is a stronger currency not necessarily better?
One common misunderstanding about exchange rates is that a “stronger” or “appreciating” currency must be better than a “weaker” or “depreciating” currency. After all, is it not obvious that “strong” is better than “weak”? Do not let the terminology confuse you. When a currency becomes stronger, so that it purchases more of other currencies, it benefits some in the economy and injures others. Stronger currency is not necessarily better, it is just different.
Key Concepts and Summary
In the foreign exchange market, people and firms exchange one currency to purchase another currency. The demand for dollars comes from those U.S. export firms seeking to convert their earnings in foreign currency back into U.S. dollars; foreign tourists converting their earnings in a foreign currency back into U.S. dollars; and foreign investors seeking to make financial investments in the U.S. economy. On the supply side of the foreign exchange market for the trading of U.S. dollars are foreign firms that have sold imports in the U.S. economy and are seeking to convert their earnings back to their home currency; U.S. tourists abroad; and U.S. investors seeking to make financial investments in foreign economies. When currency A can buy more of currency B, then currency A has strengthened or appreciated relative to B. When currency A can buy less of currency B, then currency A has weakened or depreciated relative to B. If currency A strengthens or appreciates relative to currency B, then currency B must necessarily weaken or depreciate with regard to currency A. A stronger currency benefits those who are buying with that currency and injures those who are selling. A weaker currency injures those, like importers, who are buying with that currency and benefits those who are selling with it, like exporters.
Self-Check Questions
How will a stronger euro affect the following economic agents?
- A British exporter to Germany.
- A Dutch tourist visiting Chile.
- A Greek bank investing in a Canadian government bond.
- A French exporter to Germany.
Hint:
- The British use the pound sterling, while Germans use the euro, so a British exporter will receive euros from export sales, which will need to be exchanged for pounds. A stronger euro will mean more pounds per euro, so the exporter will be better off. In addition, the lower price for German imports will stimulate demand for British exports. For both these reasons, a stronger euro benefits the British exporter.
- The Dutch use euros while the Chileans use pesos, so the Dutch tourist needs to turn euros into Chilean pesos. An increase in the euro means that the tourist will get more pesos per euro. As a consequence, the Dutch tourist will have a less expensive vacation than he planned, so the tourist will be better off.
- The Greek use euros while the Canadians use dollars. An increase in the euro means it will buy more Canadian dollars. As a result, the Greek bank will see a decrease in the cost of the Canadian bonds, so it may purchase more bonds. Either way, the Greek bank benefits.
- Since both the French and Germans use the euro, an increase in the euro, in terms of other currencies, should have no impact on the French exporter.
Review Questions
What is the foreign exchange market?
Describe some buyers and some sellers in the market for U.S. dollars.
What is the difference between foreign direct investment and portfolio investment?
What does it mean to hedge a financial transaction?
What does it mean to say that a currency appreciates? Depreciates? Becomes stronger? Becomes weaker?
Critical Thinking Question
Why would a nation “dollarize”—that is, adopt another country’s currency instead of having its own?
Can you think of any major disadvantages to dollarization? How would a central bank work in a country that has dollarized?
Problems
A British pound cost $2.00 in U.S. dollars in 2008, but $1.27 in U.S. dollars in 2017. Was the pound weaker or stronger against the dollar? Did the dollar appreciate or depreciate versus the pound?
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https://oercommons.org/courseware/lesson/28854/overview
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Demand and Supply Shifts in Foreign Exchange Markets
Overview
By the end of this section, you will be able to:
- Explain supply and demand for exchange rates
- Define arbitrage
- Explain purchasing power parity's importance when comparing countries.
The foreign exchange market involves firms, households, and investors who demand and supply currencies coming together through their banks and the key foreign exchange dealers. Figure (a) offers an example for the exchange rate between the U.S. dollar and the Mexican peso. The vertical axis shows the exchange rate for U.S. dollars, which in this case is measured in pesos. The horizontal axis shows the quantity of U.S. dollars traded in the foreign exchange market each day. The demand curve (D) for U.S. dollars intersects with the supply curve (S) of U.S. dollars at the equilibrium point (E), which is an exchange rate of 10 pesos per dollar and a total volume of $8.5 billion.
Figure (b) presents the same demand and supply information from the perspective of the Mexican peso. The vertical axis shows the exchange rate for Mexican pesos, which is measured in U.S. dollars. The horizontal axis shows the quantity of Mexican pesos traded in the foreign exchange market. The demand curve (D) for Mexican pesos intersects with the supply curve (S) of Mexican pesos at the equilibrium point (E), which is an exchange rate of 10 cents in U.S. currency for each Mexican peso and a total volume of 85 billion pesos. Note that the two exchange rates are inverses: 10 pesos per dollar is the same as 10 cents per peso (or $0.10 per peso). In the actual foreign exchange market, almost all of the trading for Mexican pesos is for U.S. dollars. What factors would cause the demand or supply to shift, thus leading to a change in the equilibrium exchange rate? We discuss the answer to this question in the following section.
Expectations about Future Exchange Rates
One reason to demand a currency on the foreign exchange market is the belief that the currency's value is about to increase. One reason to supply a currency—that is, sell it on the foreign exchange market—is the expectation that the currency's value is about to decline. For example, imagine that a leading business newspaper, like the Wall Street Journal or the Financial Times, runs an article predicting that the Mexican peso will appreciate in value. Figure illustrates the likely effects of such an article. Demand for the Mexican peso shifts to the right, from D0 to D1, as investors become eager to purchase pesos. Conversely, the supply of pesos shifts to the left, from S0 to S1, because investors will be less willing to give them up. The result is that the equilibrium exchange rate rises from 10 cents/peso to 12 cents/peso and the equilibrium exchange rate rises from 85 billion to 90 billion pesos as the equilibrium moves from E0 to E1.
Figure also illustrates some peculiar traits of supply and demand diagrams in the foreign exchange market. In contrast to all the other cases of supply and demand you have considered, in the foreign exchange market, supply and demand typically both move at the same time. Groups of participants in the foreign exchange market like firms and investors include some who are buyers and some who are sellers. An expectation of a future shift in the exchange rate affects both buyers and sellers—that is, it affects both demand and supply for a currency.
The shifts in demand and supply curves both cause the exchange rate to shift in the same direction. In this example, they both make the peso exchange rate stronger. However, the shifts in demand and supply work in opposing directions on the quantity traded. In this example, the rising demand for pesos is causing the quantity to rise while the falling supply of pesos is causing quantity to fall. In this specific example, the result is a higher quantity. However, in other cases, the result could be that quantity remains unchanged or declines.
This example also helps to explain why exchange rates often move quite substantially in a short period of a few weeks or months. When investors expect a country’s currency to strengthen in the future, they buy the currency and cause it to appreciate immediately. The currency's appreciation can lead other investors to believe that future appreciation is likely—and thus lead to even further appreciation. Similarly, a fear that a currency might weaken quickly leads to an actual weakening of the currency, which often reinforces the belief that the currency will weaken further. Thus, beliefs about the future path of exchange rates can be self-reinforcing, at least for a time, and a large share of the trading in foreign exchange markets involves dealers trying to outguess each other on what direction exchange rates will move next.
Differences across Countries in Rates of Return
The motivation for investment, whether domestic or foreign, is to earn a return. If rates of return in a country look relatively high, then that country will tend to attract funds from abroad. Conversely, if rates of return in a country look relatively low, then funds will tend to flee to other economies. Changes in the expected rate of return will shift demand and supply for a currency. For example, imagine that interest rates rise in the United States as compared with Mexico. Thus, financial investments in the United States promise a higher return than previously. As a result, more investors will demand U.S. dollars so that they can buy interest-bearing assets and fewer investors will be willing to supply U.S. dollars to foreign exchange markets. Demand for the U.S. dollar will shift to the right, from D0 to D1, and supply will shift to the left, from S0 to S1, as Figure shows. The new equilibrium (E1), will occur at an exchange rate of nine pesos/dollar and the same quantity of $8.5 billion. Thus, a higher interest rate or rate of return relative to other countries leads a nation’s currency to appreciate or strengthen, and a lower interest rate relative to other countries leads a nation’s currency to depreciate or weaken. Since a nation’s central bank can use monetary policy to affect its interest rates, a central bank can also cause changes in exchange rates—a connection that we will discuss in more detail later in this chapter.
Relative Inflation
If a country experiences a relatively high inflation rate compared with other economies, then the buying power of its currency is eroding, which will tend to discourage anyone from wanting to acquire or to hold the currency. Figure shows an example based on an actual episode concerning the Mexican peso. In 1986–87, Mexico experienced an inflation rate of over 200%. Not surprisingly, as inflation dramatically decreased the peso's purchasing power in Mexico. The peso's exchange rate value declined as well. Figure shows that the demand for the peso on foreign exchange markets decreased from D0 to D1, while the peso's supply increased from S0 to S1. The equilibrium exchange rate fell from $2.50 per peso at the original equilibrium (E0) to $0.50 per peso at the new equilibrium (E1). In this example, the quantity of pesos traded on foreign exchange markets remained the same, even as the exchange rate shifted.
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Purchasing Power Parity
Over the long term, exchange rates must bear some relationship to the currency's buying power in terms of internationally traded goods. If at a certain exchange rate it was much cheaper to buy internationally traded goods—such as oil, steel, computers, and cars—in one country than in another country, businesses would start buying in the cheap country, selling in other countries, and pocketing the profits.
For example, if a U.S. dollar is worth $1.30 in Canadian currency, then a car that sells for $20,000 in the United States should sell for $26,000 in Canada. If the price of cars in Canada were much lower than $26,000, then at least some U.S. car-buyers would convert their U.S. dollars to Canadian dollars and buy their cars in Canada. If the price of cars were much higher than $26,000 in this example, then at least some Canadian buyers would convert their Canadian dollars to U.S. dollars and go to the United States to purchase their cars. This is known as arbitrage, the process of buying and selling goods or currencies across international borders at a profit. It may occur slowly, but over time, it will force prices and exchange rates to align so that the price of internationally traded goods is similar in all countries.
We call the exchange rate that equalizes the prices of internationally traded goods across countries the purchasing power parity (PPP) exchange rate. A group of economists at the International Comparison Program, run by the World Bank, have calculated the PPP exchange rate for all countries, based on detailed studies of the prices and quantities of internationally tradable goods.
The purchasing power parity exchange rate has two functions. First, economists often use PPP exchange rates for international comparison of GDP and other economic statistics. Imagine that you are preparing a table showing the size of GDP in many countries in several recent years, and for ease of comparison, you are converting all the values into U.S. dollars. When you insert the value for Japan, you need to use a yen/dollar exchange rate. However, should you use the market exchange rate or the PPP exchange rate? Market exchange rates bounce around. In 2014, the exchange rate was 105 yen/dollar, but in late 2015 the U.S. dollar exchange rate versus the yen was 121 yen/dollar. For simplicity, say that Japan’s GDP was ¥500 trillion in both 2014 and 2015. If you use the market exchange rates, then Japan’s GDP will be $4.8 trillion in 2014 (that is, ¥500 trillion /(¥105/dollar)) and $4.1 trillion in 2015 (that is, ¥500 trillion /(¥121/dollar)).
The misleading appearance of a changing Japanese economy occurs only because we used the market exchange rate, which often has short-run rises and falls. However, PPP exchange rates stay fairly constant and change only modestly, if at all, from year to year.
The second function of PPP is that exchanges rates will often get closer to it as time passes. It is true that in the short and medium run, as exchange rates adjust to relative inflation rates, rates of return, and to expectations about how interest rates and inflation will shift, the exchange rates will often move away from the PPP exchange rate for a time. However, knowing the PPP will allow you to track and predict exchange rate relationships.
Key Concepts and Summary
In the extreme short run, ranging from a few minutes to a few weeks, speculators who are trying to invest in currencies that will grow stronger, and to sell currencies that will grow weaker influence exchange rates. Such speculation can create a self-fulfilling prophecy, at least for a time, where an expected appreciation leads to a stronger currency and vice versa. In the relatively short run, differences in rates of return influence exchange rate markets. Countries with relatively high real rates of return (for example, high interest rates) will tend to experience stronger currencies as they attract money from abroad, while countries with relatively low rates of return will tend to experience weaker exchange rates as investors convert to other currencies.
In the medium run of a few months or a few years, inflation rates influence exchange rate markets. Countries with relatively high inflation will tend to experience less demand for their currency than countries with lower inflation, and thus currency depreciation. Over long periods of many years, exchange rates tend to adjust toward the purchasing power parity (PPP) rate, which is the exchange rate such that the prices of internationally tradable goods in different countries, when converted at the PPP exchange rate to a common currency, are similar in all economies.
Self-Check Questions
Suppose that political unrest in Egypt leads financial markets to anticipate a depreciation in the Egyptian pound. How will that affect the demand for pounds, supply of pounds, and exchange rate for pounds compared to, say, U.S. dollars?
Hint:
Expected depreciation in a currency will lead people to divest themselves of the currency. We should expect to see an increase in the supply of pounds and a decrease in demand for pounds. The result should be a decrease in the value of the pound vis à vis the dollar.
Suppose U.S. interest rates decline compared to the rest of the world. What would be the likely impact on the demand for dollars, supply of dollars, and exchange rate for dollars compared to, say, euros?
Hint:
Lower U.S. interest rates make U.S. assets less desirable compared to assets in the European Union. We should expect to see a decrease in demand for dollars and an increase in supply of dollars in foreign currency markets. As a result, we should expect to see the dollar depreciate compared to the euro.
Suppose Argentina gets inflation under control and the Argentine inflation rate decreases substantially. What would likely happen to the demand for Argentine pesos, the supply of Argentine pesos, and the peso/U.S. dollar exchange rate?
Hint:
A decrease in Argentine inflation relative to other countries should cause an increase in demand for pesos, a decrease in supply of pesos, and an appreciation of the peso in foreign currency markets.
Review Questions
Does an expectation of a stronger exchange rate in the future affect the exchange rate in the present? If so, how?
Does a higher rate of return in a nation’s economy, all other things being equal, affect the exchange rate of its currency? If so, how?
Does a higher inflation rate in an economy, other things being equal, affect the exchange rate of its currency? If so, how?
What is the purchasing power parity exchange rate?
Critical Thinking Questions
If a country’s currency is expected to appreciate in value, what would you think will be the impact of expected exchange rates on yields (e.g., the interest rate paid on government bonds) in that country? Hint: Think about how expected exchange rate changes and interest rates affect a currency's demand and supply.
Do you think that a country experiencing hyperinflation is more or less likely to have an exchange rate equal to its purchasing power parity value when compared to a country with a low inflation rate?
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2025-03-18T00:37:11.132846
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Macroeconomic Effects of Exchange Rates
Overview
By the end of this section you will be able to:
- Explain how exchange rate shifting influences aggregate demand and supply
- Explain how shifting exchange rates also can influence loans and banks
A central bank will be concerned about the exchange rate for multiple reasons: (1) Movements in the exchange rate will affect the quantity of aggregate demand in an economy; (2) frequent substantial fluctuations in the exchange rate can disrupt international trade and cause problems in a nation’s banking system–this may contribute to an unsustainable balance of trade and large inflows of international financial capital, which can set up the economy for a deep recession if international investors decide to move their money to another country. Let’s discuss these scenarios in turn.
Exchange Rates, Aggregate Demand, and Aggregate Supply
Foreign trade in goods and services typically involves incurring the costs of production in one currency while receiving revenues from sales in another currency. As a result, movements in exchange rates can have a powerful effect on incentives to export and import, and thus on aggregate demand in the economy as a whole.
For example, in 1999, when the euro first became a currency, its value measured in U.S. currency was $1.06/euro. By the end of 2013, the euro had risen (and the U.S. dollar had correspondingly weakened) to $1.37/euro. However, by the end of February, 2017, the exchange rate was once again $1.06/euro. Consider the situation of a French firm that each year incurs €10 million in costs, and sells its products in the United States for $10 million. In 1999, when this firm converted $10 million back to euros at the exchange rate of $1.06/euro (that is, $10 million × [€1/$1.06]), it received €9.4 million, and suffered a loss. In 2013, when this same firm converted $10 million back to euros at the exchange rate of $1.37/euro (that is, $10 million × [€1 euro/$1.37]), it received approximately €7.3 million and an even larger loss. In the beginning of 2017, with the exchange rate back at $1.06/euro the firm would suffer a loss once again. This example shows how a stronger euro discourages exports by the French firm, because it makes the costs of production in the domestic currency higher relative to the sales revenues earned in another country. From the point of view of the U.S. economy, the example also shows how a weaker U.S. dollar encourages exports.
Since an increase in exports results in more dollars flowing into the economy, and an increase in imports means more dollars are flowing out, it is easy to conclude that exports are “good” for the economy and imports are “bad,” but this overlooks the role of exchange rates. If an American consumer buys a Japanese car for $20,000 instead of an American car for $30,000, it may be tempting to argue that the American economy has lost out. However, the Japanese company will have to convert those dollars to yen to pay its workers and operate its factories. Whoever buys those dollars will have to use them to purchase American goods and services, so the money comes right back into the American economy. At the same time, the consumer saves money by buying a less expensive import, and can use the extra money for other purposes.
Fluctuations in Exchange Rates
Exchange rates can fluctuate a great deal in the short run. As yet one more example, the Indian rupee moved from 39 rupees/dollar in February 2008 to 51 rupees/dollar in March 2009, a decline of more than one-fourth in the value of the rupee on foreign exchange markets. Figure earlier showed that even two economically developed neighboring economies like the United States and Canada can see significant movements in exchange rates over a few years. For firms that depend on export sales, or firms that rely on imported inputs to production, or even purely domestic firms that compete with firms tied into international trade—which in many countries adds up to half or more of a nation’s GDP—sharp movements in exchange rates can lead to dramatic changes in profits and losses. A central bank may desire to keep exchange rates from moving too much as part of providing a stable business climate, where firms can focus on productivity and innovation, not on reacting to exchange rate fluctuations.
One of the most economically destructive effects of exchange rate fluctuations can happen through the banking system. Financial institutions measure most international loans are measured in a few large currencies, like U.S. dollars, European euros, and Japanese yen. In countries that do not use these currencies, banks often borrow funds in the currencies of other countries, like U.S. dollars, but then lend in their own domestic currency. The left-hand chain of events in Figure shows how this pattern of international borrowing can work. A bank in Thailand borrows one million in U.S. dollars. Then the bank converts the dollars to its domestic currency—in the case of Thailand, the currency is the baht—at a rate of 40 baht/dollar. The bank then lends the baht to a firm in Thailand. The business repays the loan in baht, and the bank converts it back to U.S. dollars to pay off its original U.S. dollar loan.
This process of borrowing in a foreign currency and lending in a domestic currency can work just fine, as long as the exchange rate does not shift. In the scenario outlined, if the dollar strengthens and the baht weakens, a problem arises. The right-hand chain of events in Figure illustrates what happens when the baht unexpectedly weakens from 40 baht/dollar to 50 baht/dollar. The Thai firm still repays the loan in full to the bank. However, because of the shift in the exchange rate, the bank cannot repay its loan in U.S. dollars. (Of course, if the exchange rate had changed in the other direction, making the Thai currency stronger, the bank could have realized an unexpectedly large profit.)
In 1997–1998, countries across eastern Asia, like Thailand, Korea, Malaysia, and Indonesia, experienced a sharp depreciation of their currencies, in some cases 50% or more. These countries had been experiencing substantial inflows of foreign investment capital, with bank lending increasing by 20% to 30% per year through the mid-1990s. When their exchange rates depreciated, the banking systems in these countries were bankrupt. Argentina experienced a similar chain of events in 2002. When the Argentine peso depreciated, Argentina’s banks found themselves unable to pay back what they had borrowed in U.S. dollars.
Banks play a vital role in any economy in facilitating transactions and in making loans to firms and consumers. When most of a country’s largest banks become bankrupt simultaneously, a sharp decline in aggregate demand and a deep recession results. Since the main responsibilities of a central bank are to control the money supply and to ensure that the banking system is stable, a central bank must be concerned about whether large and unexpected exchange rate depreciation will drive most of the country’s existing banks into bankruptcy. For more on this concern, return to the chapter on .
Summing Up Public Policy and Exchange Rates
Every nation would prefer a stable exchange rate to facilitate international trade and reduce the degree of risk and uncertainty in the economy. However, a nation may sometimes want a weaker exchange rate to stimulate aggregate demand and reduce a recession, or a stronger exchange rate to fight inflation. The country must also be concerned that rapid movements from a weak to a strong exchange rate may cripple its export industries, while rapid movements from a strong to a weak exchange rate can cripple its banking sector. In short, every choice of an exchange rate—whether it should be stronger or weaker, or fixed or changing—represents potential tradeoffs.
Key Concepts and Summary
A central bank will be concerned about the exchange rate for several reasons. Exchange rates will affect imports and exports, and thus affect aggregate demand in the economy. Fluctuations in exchange rates may cause difficulties for many firms, but especially banks. The exchange rate may accompany unsustainable flows of international financial capital.
Self-Check Questions
This chapter has explained that “one of the most economically destructive effects of exchange rate fluctuations can happen through the banking system,” if banks borrow from abroad to lend domestically. Why is this less likely to be a problem for the U.S. banking system?
Hint:
The problem occurs when banks borrow foreign currency but lend in domestic currency. Since banks’ assets (loans they made) are in domestic currency, while their debts (money they borrowed) are in foreign currency, when the domestic currency declines, their debts grow larger. If the domestic currency falls substantially in value, as happened during the Asian financial crisis, then the banking system could fail. This problem is unlikely to occur for U.S. banks because, even when they borrow from abroad, they tend to borrow dollars. Remember, there are trillions of dollars in circulation in the global economy. Since both assets and debts are in dollars, a change in the value of the dollar does not cause banking system failure the way it can when banks borrow in foreign currency.
A booming economy can attract financial capital inflows, which promote further growth. However, capital can just as easily flow out of the country, leading to economic recession. Is a country whose economy is booming because it decided to stimulate consumer spending more or less likely to experience capital flight than an economy whose boom is caused by economic investment expenditure?
Hint:
While capital flight is possible in either case, if a country borrows to invest in real capital it is more likely to be able to generate the income to pay back its debts than a country that borrows to finance consumption. As a result, an investment-stimulated economy is less likely to provoke capital flight and economic recession.
Review Questions
What are some of the reasons a central bank is likely to care, at least to some extent, about the exchange rate?
How can an unexpected fall in exchange rates injure the financial health of a nation’s banks?
Critical Thinking Questions
Suppose a country has an overall balance of trade so that exports of goods and services equal imports of goods and services. Does that imply that the country has balanced trade with each of its trading partners?
We learned that changes in exchange rates and the corresponding changes in the balance of trade amplify monetary policy. From the perspective of a nation’s central bank, is this a good thing or a bad thing?
If a developing country needs foreign capital inflows, management expertise, and technology, how can it encourage foreign investors while at the same time protect itself against capital flight and banking system collapse, as happened during the Asian financial crisis?
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Exchange Rate Policies
Overview
By the end of this section, you will be able to:
- Differentiate among a floating exchange rate, a soft peg, a hard peg, and a merged currency
- Identify the tradeoffs that come with a floating exchange rate, a soft peg, a hard peg, and a merged currency
Exchange rate policies come in a range of different forms listed in Figure: let the foreign exchange market determine the exchange rate; let the market set the value of the exchange rate most of the time, but have the central bank sometimes intervene to prevent fluctuations that seem too large; have the central bank guarantee a specific exchange rate; or share a currency with other countries. Let’s discuss each type of exchange rate policy and its tradeoffs.
Floating Exchange Rates
We refer to a policy which allows the foreign exchange market to set exchange rates as a floating exchange rate. The U.S. dollar is a floating exchange rate, as are the currencies of about 40% of the countries in the world economy. The major concern with this policy is that exchange rates can move a great deal in a short time.
Consider the U.S. exchange rate expressed in terms of another fairly stable currency, the Japanese yen, as Figure shows. On January 1, 2002, the exchange rate was 133 yen/dollar. On January 1, 2005, it was 103 yen/dollar. On June 1, 2007, it was 122 yen/dollar, on January 1, 2012, it was 77 yen per dollar, and on March 1, 2015, it was 120 yen per dollar. As investor sentiment swings back and forth, driving exchange rates up and down, exporters, importers, and banks involved in international lending are all affected. At worst, large movements in exchange rates can drive companies into bankruptcy or trigger a nationwide banking collapse. However, even in the moderate case of the yen/dollar exchange rate, these movements of roughly 30 percent back and forth impose stress on both economies as firms must alter their export and import plans to take the new exchange rates into account. Especially in smaller countries where international trade is a relatively large share of GDP, exchange rate movements can rattle their economies.
However, movements of floating exchange rates have advantages, too. After all, prices of goods and services rise and fall throughout a market economy, as demand and supply shift. If an economy experiences strong inflows or outflows of international financial capital, or has relatively high inflation, or if it experiences strong productivity growth so that purchasing power changes relative to other economies, then it makes economic sense for the exchange rate to shift as well.
Floating exchange rate advocates often argue that if government policies were more predictable and stable, then inflation rates and interest rates would be more predictable and stable. Exchange rates would bounce around less, too. The economist Milton Friedman (1912–2006), for example, wrote a defense of floating exchange rates in 1962 in his book Capitalism and Freedom:
Being in favor of floating exchange rates does not mean being in favor of unstable exchange rates. When we support a free price system [for goods and services] at home, this does not imply that we favor a system in which prices fluctuate wildly up and down. What we want is a system in which prices are free to fluctuate but in which the forces determining them are sufficiently stable so that in fact prices move within moderate ranges. This is equally true in a system of floating exchange rates. The ultimate objective is a world in which exchange rates, while free to vary, are, in fact, highly stable because basic economic policies and conditions are stable.
Advocates of floating exchange rates admit that, yes, exchange rates may sometimes fluctuate. They point out, however, that if a central bank focuses on preventing either high inflation or deep recession, with low and reasonably steady interest rates, then exchange rates will have less reason to vary.
Using Soft Pegs and Hard Pegs
When a government intervenes in the foreign exchange market so that the currency's exchange rate is different from what the market would have produced, it establishes a “peg” for its currency. A soft peg is the name for an exchange rate policy where the government usually allows the market to set exchange rate, but in some cases, especially if the exchange rate seems to be moving rapidly in one direction, the central bank will intervene in the market. With a hard peg exchange rate policy, the central bank sets a fixed and unchanging value for the exchange rate. A central bank can implement soft peg and hard peg policies.
Suppose the market exchange rate for the Brazilian currency, the real, would be 35 cents/real with a daily quantity of 15 billion real traded in the market, as the equilibrium E0 in Figure (a) and Figure (b) show. However, Brazil's government decides that the exchange rate should be 30 cents/real, as Figure (a) shows. Perhaps Brazil sets this lower exchange rate to benefit its export industries. Perhaps it is an attempt to stimulate aggregate demand by stimulating exports. Perhaps Brazil believes that the current market exchange rate is higher than the long-term purchasing power parity value of the real, so it is minimizing fluctuations in the real by keeping it at this lower rate. Perhaps the government set the target exchange rate sometime in the past, and it is now maintaining it for the sake of stability. Whatever the reason, if Brazil’s central bank wishes to keep the exchange rate below the market level, it must face the reality that at this weaker exchange rate of 30 cents/real, the quantity demanded of its currency at 17 billion reals is greater than the quantity supplied of 13 billion reals in the foreign exchange market.
The Brazilian central bank could weaken its exchange rate in two ways. One approach is to use an expansionary monetary policy that leads to lower interest rates. In foreign exchange markets, the lower interest rates will reduce demand and increase supply of the real and lead to depreciation. Central banks do not use this technique often because lowering interest rates to weaken the currency may be in conflict with the country’s monetary policy goals. Alternatively, Brazil’s central bank could trade directly in the foreign exchange market. The central bank can expand the money supply by creating reals, use the reals to purchase foreign currencies, and avoid selling any of its own currency. In this way, it can fill the gap between quantity demanded and quantity supplied of its currency.
Figure (b) shows the opposite situation. Here, the Brazilian government desires a stronger exchange rate of 40 cents/real than the market rate of 35 cents/real. Perhaps Brazil desires the stronger currency to reduce aggregate demand and to fight inflation, or perhaps Brazil believes that that current market exchange rate is temporarily lower than the long-term rate. Whatever the reason, at the higher desired exchange rate, the quantity supplied of 16 billion reals exceeds the quantity demanded of 14 billion reals.
Brazil’s central bank can use a contractionary monetary policy to raise interest rates, which will increase demand and reduce currency supply on foreign exchange markets, and lead to an appreciation. Alternatively, Brazil’s central bank can trade directly in the foreign exchange market. In this case, with an excess supply of its own currency in foreign exchange markets, the central bank must use reserves of foreign currency, like U.S. dollars, to demand its own currency and thus cause an appreciation of its exchange rate.
Both a soft peg and a hard peg policy require that the central bank intervene in the foreign exchange market. However, a hard peg policy attempts to preserve a fixed exchange rate at all times. A soft peg policy typically allows the exchange rate to move up and down by relatively small amounts in the short run of several months or a year, and to move by larger amounts over time, but seeks to avoid extreme short-term fluctuations.
Tradeoffs of Soft Pegs and Hard Pegs
When a country decides to alter the market exchange rate, it faces a number of tradeoffs. If it uses monetary policy to alter the exchange rate, it then cannot at the same time use monetary policy to address issues of inflation or recession. If it uses direct purchases and sales of foreign currencies in exchange rates, then it must face the issue of how it will handle its reserves of foreign currency. Finally, a pegged exchange rate can even create additional movements of the exchange rate. For example, even the possibility of government intervention in exchange rate markets will lead to rumors about whether and when the government will intervene, and dealers in the foreign exchange market will react to those rumors. Let’s consider these issues in turn.
One concern with pegged exchange rate policies is that they imply a country’s monetary policy is no longer focused on controlling inflation or shortening recessions, but now must also take the exchange rate into account. For example, when a country pegs its exchange rate, it will sometimes face economic situations where it would like to have an expansionary monetary policy to fight recession—but it cannot do so because that policy would depreciate its exchange rate and break its hard peg. With a soft peg exchange rate policy, the central bank can sometimes ignore the exchange rate and focus on domestic inflation or recession—but in other cases the central bank may ignore inflation or recession and instead focus on its soft peg exchange rate. With a hard peg policy, domestic monetary policy is effectively no longer determined by domestic inflation or unemployment, but only by what monetary policy is needed to keep the exchange rate at the hard peg.
Another issue arises when a central bank intervenes directly in the exchange rate market. If a central bank ends up in a situation where it is perpetually creating and selling its own currency on foreign exchange markets, it will be buying the currency of other countries, like U.S. dollars or euros, to hold as reserves. Holding large reserves of other currencies has an opportunity cost, and central banks will not wish to boost such reserves without limit.
In addition, a central bank that causes a large increase in the supply of money is also risking an inflationary surge in aggregate demand. Conversely, when a central bank wishes to buy its own currency, it can do so by using its reserves of international currency like the U.S. dollar or the euro. However, if the central bank runs out of such reserves, it can no longer use this method to strengthen its currency. Thus, buying foreign currencies in exchange rate markets can be expensive and inflationary, while selling foreign currencies can work only until a central bank runs out of reserves.
Yet another issue is that when a government pegs its exchange rate, it may unintentionally create another reason for additional fluctuation. With a soft peg policy, foreign exchange dealers and international investors react to every rumor about how or when the central bank is likely to intervene to influence the exchange rate, and as they react to rumors the exchange rate will shift up and down. Thus, even though the goal of a soft peg policy is to reduce short-term fluctuations of the exchange rate, the existence of the policy—when anticipated in the foreign exchange market—may sometimes increase short-term fluctuations as international investors try to anticipate how and when the central bank will act. The following Clear It Up feature discusses the effects of international capital flows—capital that flows across national boundaries as either portfolio investment or direct investment.
How do Tobin taxes control the flow of capital?
Some countries like Chile and Malaysia have sought to reduce movements in exchange rates by limiting international financial capital inflows and outflows. The government can enact this policy either through targeted taxes or by regulations.
Taxes on international capital flows are sometimes known as Tobin taxes, named after James Tobin, the 1981 Nobel laureate in economics who proposed such a tax in a 1972 lecture. For example, a government might tax all foreign exchange transactions, or attempt to tax short-term portfolio investment while exempting long-term foreign direct investment. Countries can also use regulation to forbid certain kinds of foreign investment in the first place or to make it difficult for international financial investors to withdraw their funds from a country.
The goal of such policies is to reduce international capital flows, especially short-term portfolio flows, in the hope that doing so will reduce the chance of large movements in exchange rates that can bring macroeconomic disaster.
However, proposals to limit international financial flows have severe practical difficulties. National governments impose taxes, not international ones. If one government imposes a Tobin tax on exchange rate transactions carried out within its territory, a firm based someplace like the Grand Caymans, an island nation in the Caribbean well-known for allowing some financial wheeling and dealing might easily operate the exchange rate market. In an interconnected global economy, if goods and services are allowed to flow across national borders, then payments need to flow across borders, too. It is very difficult—in fact close to impossible—for a nation to allow only the flows of payments that relate to goods and services, while clamping down or taxing other flows of financial capital. If a nation participates in international trade, it must also participate in international capital movements.
Finally, countries all over the world, especially low-income countries, are crying out for foreign investment to help develop their economies. Policies that discourage international financial investment may prevent some possible harm, but they rule out potentially substantial economic benefits as well.
A hard peg exchange rate policy will not allow short-term fluctuations in the exchange rate. If the government first announces a hard peg and then later changes its mind—perhaps the government becomes unwilling to keep interest rates high or to hold high levels of foreign exchange reserves—then the result of abandoning a hard peg could be a dramatic shift in the exchange rate.
In the mid-2000s, about one-third of the countries in the world used a soft peg approach and about one-quarter used a hard peg approach. The general trend in the 1990s was to shift away from a soft peg approach in favor of either floating rates or a hard peg. The concern is that a successful soft peg policy may, for a time, lead to very little variation in exchange rates, so that firms and banks in the economy begin to act as if a hard peg exists. When the exchange rate does move, the effects are especially painful because firms and banks have not planned and hedged against a possible change. Thus, the argument went, it is better either to be clear that the exchange rate is always flexible, or that it is fixed, but choosing an in-between soft peg option may end up being worst of all.
A Merged Currency
A final approach to exchange rate policy is for a nation to choose a common currency shared with one or more nations is also called a merged currency. A merged currency approach eliminates foreign exchange risk altogether. Just as no one worries about exchange rate movements when buying and selling between New York and California, Europeans know that the value of the euro will be the same in Germany and France and other European nations that have adopted the euro.
However, a merged currency also poses problems. Like a hard peg, a merged currency means that a nation has given up altogether on domestic monetary policy, and instead has put its interest rate policies in other hands. When Ecuador uses the U.S. dollar as its currency, it has no voice in whether the Federal Reserve raises or lowers interest rates. The European Central Bank that determines monetary policy for the euro has representatives from all the euro nations. However, from the standpoint of, say, Portugal, there will be times when the decisions of the European Central Bank about monetary policy do not match the decisions that a Portuguese central bank would have made.
The lines between these four different exchange rate policies can blend into each other. For example, a soft peg exchange rate policy in which the government almost never acts to intervene in the exchange rate market will look a great deal like a floating exchange rate. Conversely, a soft peg policy in which the government intervenes often to keep the exchange rate near a specific level will look a lot like a hard peg. A decision to merge currencies with another country is, in effect, a decision to have a permanently fixed exchange rate with those countries, which is like a very hard exchange rate peg. Table summarizes the range of exchange rates policy choices, with their advantages and disadvantages.
| Situation | Floating Exchange Rates | Soft Peg | Hard Peg | Merged Currency |
|---|---|---|---|---|
| Large short-run fluctuations in exchange rates? | Often considerable in the short term | Maybe less in the short run, but still large changes over time | None, unless a change in the fixed rate | None |
| Large long-term fluctuations in exchange rates? | Can often happen | Can often happen | Cannot happen unless hard peg changes, in which case substantial volatility can occur | Cannot happen |
| Power of central bank to conduct countercyclical monetary policy? | Flexible exchange rates make monetary policy stronger | Some power, although conflicts may arise between exchange rate policy and countercyclical policy | Very little; central bank must keep exchange rate fixed | None; nation does not have its own currency |
| Costs of holding foreign exchange reserves? | Do not need to hold reserves | Hold moderate reserves that rise and fall over time | Hold large reserves | No need to hold reserves |
| Risk of ending up with an exchange rate that causes a large trade imbalance and very high inflows or outflows of financial capital? | Adjusts often | Adjusts over the medium term, if not the short term | May end up over time either far above or below the market level | Cannot adjust |
Global macroeconomics would be easier if the whole world had one currency and one central bank. The exchange rates between different currencies complicate the picture. If financial markets solely set exchange rates, they fluctuate substantially as short-term portfolio investors try to anticipate tomorrow’s news. If the government attempts to intervene in exchange rate markets through soft pegs or hard pegs, it gives up at least some of the power to use monetary policy to focus on domestic inflations and recessions, and it risks causing even greater fluctuations in foreign exchange markets.
There is no consensus among economists about which exchange rate policies are best: floating, soft peg, hard peg, or merged currencies. The choice depends both on how well a nation’s central bank can implement a specific exchange rate policy and on how well a nation’s firms and banks can adapt to different exchange rate policies. A national economy that does a fairly good job at achieving the four main economic goals of growth, low inflation, low unemployment, and a sustainable balance of trade will probably do just fine most of the time with any exchange rate policy. Conversely, no exchange rate policy is likely to save an economy that consistently fails at achieving these goals. Alternatively, a merged currency applied across wide geographic and cultural areas carries with it its own set of problems, such as the ability for countries to conduct their own independent monetary policies.
Is a Stronger Dollar Good for the U.S. Economy?
The foreign exchange value of the dollar is a price and whether a higher price is good or bad depends on where you are standing: sellers benefit from higher prices and buyers are harmed. A stronger dollar is good for U.S. imports (and people working for U.S. importers) and U.S. investment abroad. It is also good for U.S. tourists going to other countries, since their dollar goes further. However, a stronger dollar is bad for U.S. exports (and people working in U.S. export industries); it is bad for foreign investment in the United States (leading, for example, to higher U.S. interest rates); and it is bad for foreign tourists (as well as U.S hotels, restaurants, and others in the tourist industry). In short, whether the U.S. dollar is good or bad is a more complex question than you may have thought. The economic answer is “it depends.”
Key Concepts and Summary
In a floating exchange rate policy, a government determines its country’s exchange rate in the foreign exchange market. In a soft peg exchange rate policy, the foreign exchange market usually determines a country's exchange rate, but the government sometimes intervenes to strengthen or weaken it. In a hard peg exchange rate policy, the government chooses an exchange rate. A central bank can intervene in exchange markets in two ways. It can raise or lower interest rates to make the currency stronger or weaker. It also can directly purchase or sell its currency in foreign exchange markets. All exchange rates policies face tradeoffs. A hard peg exchange rate policy will reduce exchange rate fluctuations, but means that a country must focus its monetary policy on the exchange rate, not on fighting recession or controlling inflation. When a nation merges its currency with another nation, it gives up on nationally oriented monetary policy altogether.
A soft peg exchange rate may create additional volatility as exchange rate markets try to anticipate when and how the government will intervene. A flexible exchange rate policy allows monetary policy to focus on inflation and unemployment, and allows the exchange rate to change with inflation and rates of return, but also raises a risk that exchange rates may sometimes make large and abrupt movements. The spectrum of exchange rate policies includes: (a) a floating exchange rate, (b) a pegged exchange rate, soft or hard, and (c) a merged currency. Monetary policy can focus on a variety of goals: (a) inflation; (b) inflation or unemployment, depending on which is the most dangerous obstacle; and (c) a long-term rule based policy designed to keep the money supply stable and predictable.
Self-Check Questions
How would a contractionary monetary policy affect the exchange rate, net exports, aggregate demand, and aggregate supply?
Hint:
A contractionary monetary policy, by driving up domestic interest rates, would cause the currency to appreciate. The higher value of the currency in foreign exchange markets would reduce exports, since from the perspective of foreign buyers, they are now more expensive. The higher value of the currency would similarly stimulate imports, since they would now be cheaper from the perspective of domestic buyers. Lower exports and higher imports cause net exports (EX – IM) to fall, which causes aggregate demand to fall. The result would be a decrease in GDP working through the exchange rate mechanism reinforcing the effect contractionary monetary policy has on domestic investment expenditure. However, cheaper imports would stimulate aggregate supply, bringing GDP back to potential, though at a lower price level.
A central bank can allow its currency to fall indefinitely, but it cannot allow its currency to rise indefinitely. Why not?
Hint:
For a currency to fall, a central bank need only supply more of its currency in foreign exchange markets. It can print as much domestic currency as it likes. For a currency to rise, a central bank needs to buy its currency in foreign exchange markets, paying with foreign currency. Since no central bank has an infinite amount of foreign currency reserves, it cannot buy its currency indefinitely.
Is a country for which imports and exports comprise a large fraction of the GDP more likely to adopt a flexible exchange rate or a fixed (hard peg) exchange rate?
Hint:
Variations in exchange rates, because they change import and export prices, disturb international trade flows. When trade is a large part of a nation’s economic activity, government will find it more advantageous to fix exchange rates to minimize disruptions of trade flows.
Review Questions
What is the difference between a floating exchange rate, a soft peg, a hard peg, and dollarization?
List some advantages and disadvantages of the different exchange rate policies.
Critical Thinking Questions
Many developing countries, like Mexico, have moderate to high rates of inflation. At the same time, international trade plays an important role in their economies. What type of exchange rate regime would be best for such a country’s currency vis à vis the U.S. dollar?
What would make a country decide to change from a common currency, like the euro, back to its own currency?
References
Friedman, Milton. Capitalism and Freedom. Chicago: University of Chicago Press, 1962.
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https://oercommons.org/courseware/lesson/28876/overview
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Introduction to International Trade
Just Whose iPhone Is It?
The iPhone is a global product. Apple does not manufacture the iPhone components, nor does it assemble them. The assembly is done by Foxconn Corporation, a Taiwanese company, at its factory in Sengzhen, China. But, Samsung, the electronics firm and competitor to Apple, actually supplies many of the parts that make up an iPhone—representing about 26% of the costs of production. That means, that Samsung is both the biggest supplier and biggest competitor for Apple. Why do these two firms work together to produce the iPhone? To understand the economic logic behind international trade, you have to accept, as these firms do, that trade is about mutually beneficial exchange. Samsung is one of the world’s largest electronics parts suppliers. Apple lets Samsung focus on making the best parts, which allows Apple to concentrate on its strength—designing elegant products that are easy to use. If each company (and by extension each country) focuses on what it does best, there will be gains for all through trade.
Introduction to International Trade
In this chapter, you will learn about:
- Absolute and Comparative Advantage
- What Happens When a Country Has an Absolute Advantage in All Goods
- Intra-industry Trade between Similar Economies
- The Benefits of Reducing Barriers to International Trade
We live in a global marketplace. The food on your table might include fresh fruit from Chile, cheese from France, and bottled water from Scotland. Your wireless phone might have been made in Taiwan or Korea. The clothes you wear might be designed in Italy and manufactured in China. The toys you give to a child might have come from India. The car you drive might come from Japan, Germany, or Korea. The gasoline in the tank might be refined from crude oil from Saudi Arabia, Mexico, or Nigeria. As a worker, if your job is involved with farming, machinery, airplanes, cars, scientific instruments, or many other technology-related industries, the odds are good that a hearty proportion of the sales of your employer—and hence the money that pays your salary—comes from export sales. We are all linked by international trade, and the volume of that trade has grown dramatically in the last few decades.
The first wave of globalization started in the nineteenth century and lasted up to the beginning of World War I. Over that time, global exports as a share of global GDP rose from less than 1% of GDP in 1820 to 9% of GDP in 1913. As the Nobel Prize-winning economist Paul Krugman of Princeton University wrote in 1995:
It is a late-twentieth-century conceit that we invented the global economy just yesterday. In fact, world markets achieved an impressive degree of integration during the second half of the nineteenth century. Indeed, if one wants a specific date for the beginning of a truly global economy, one might well choose 1869, the year in which both the Suez Canal and the Union Pacific railroad were completed. By the eve of the First World War steamships and railroads had created markets for standardized commodities, like wheat and wool, that were fully global in their reach. Even the global flow of information was better than modern observers, focused on electronic technology, tend to realize: the first submarine telegraph cable was laid under the Atlantic in 1858, and by 1900 all of the world’s major economic regions could effectively communicate instantaneously.
This first wave of globalization crashed to a halt early in the twentieth century. World War I severed many economic connections. During the Great Depression of the 1930s, many nations misguidedly tried to fix their own economies by reducing foreign trade with others. World War II further hindered international trade. Global flows of goods and financial capital were rebuilt only slowly after World War II. It was not until the early 1980s that global economic forces again became as important, relative to the size of the world economy, as they were before World War I.
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Absolute and Comparative Advantage
Overview
By the end of this section, you will be able to:
- Define absolute advantage, comparative advantage, and opportunity costs
- Explain the gains of trade created when a country specializes
The American statesman Benjamin Franklin (1706–1790) once wrote: “No nation was ever ruined by trade.” Many economists would express their attitudes toward international trade in an even more positive manner. The evidence that international trade confers overall benefits on economies is pretty strong. Trade has accompanied economic growth in the United States and around the world. Many of the national economies that have shown the most rapid growth in the last several decades—for example, Japan, South Korea, China, and India—have done so by dramatically orienting their economies toward international trade. There is no modern example of a country that has shut itself off from world trade and yet prospered. To understand the benefits of trade, or why we trade in the first place, we need to understand the concepts of comparative and absolute advantage.
In 1817, David Ricardo, a businessman, economist, and member of the British Parliament, wrote a treatise called On the Principles of Political Economy and Taxation. In this treatise, Ricardo argued that specialization and free trade benefit all trading partners, even those that may be relatively inefficient. To see what he meant, we must be able to distinguish between absolute and comparative advantage.
A country has an absolute advantage over another country in producing a good if it uses fewer resources to produce that good. Absolute advantage can be the result of a country’s natural endowment. For example, extracting oil in Saudi Arabia is pretty much just a matter of “drilling a hole.” Producing oil in other countries can require considerable exploration and costly technologies for drilling and extraction—if they have any oil at all. The United States has some of the richest farmland in the world, making it easier to grow corn and wheat than in many other countries. Guatemala and Colombia have climates especially suited for growing coffee. Chile and Zambia have some of the world’s richest copper mines. As some have argued, “geography is destiny.” Chile will provide copper and Guatemala will produce coffee, and they will trade. When each country has a product others need and it can produce it with fewer resources in one country than in another, then it is easy to imagine all parties benefitting from trade. However, thinking about trade just in terms of geography and absolute advantage is incomplete. Trade really occurs because of comparative advantage.
Recall from the chapter Choice in a World of Scarcity that a country has a comparative advantage when it can produce a good at a lower cost in terms of other goods. The question each country or company should be asking when it trades is this: “What do we give up to produce this good?” It should be no surprise that the concept of comparative advantage is based on this idea of opportunity cost from Choice in a World of Scarcity. For example, if Zambia focuses its resources on producing copper, it cannot use its labor, land and financial resources to produce other goods such as corn. As a result, Zambia gives up the opportunity to produce corn. How do we quantify the cost in terms of other goods? Simplify the problem and assume that Zambia just needs labor to produce copper and corn. The companies that produce either copper or corn tell you that it takes two hours to mine a ton of copper and one hour to harvest a bushel of corn. This means the opportunity cost of producing a ton of copper is two bushels of corn. The next section develops absolute and comparative advantage in greater detail and relates them to trade.
Visit this website for a list of articles and podcasts pertaining to international trade topics.
A Numerical Example of Absolute and Comparative Advantage
Consider a hypothetical world with two countries, Saudi Arabia and the United States, and two products, oil and corn. Further assume that consumers in both countries desire both these goods. These goods are homogeneous, meaning that consumers/producers cannot differentiate between corn or oil from either country. There is only one resource available in both countries, labor hours. Saudi Arabia can produce oil with fewer resources, while the United States can produce corn with fewer resources. Table illustrates the advantages of the two countries, expressed in terms of how many hours it takes to produce one unit of each good.
| Country | Oil (hours per barrel) | Corn (hours per bushel) |
|---|---|---|
| Saudi Arabia | 1 | 4 |
| United States | 2 | 1 |
In Table, Saudi Arabia has an absolute advantage in producing oil because it only takes an hour to produce a barrel of oil compared to two hours in the United States. The United States has an absolute advantage in producing corn.
To simplify, let’s say that Saudi Arabia and the United States each have 100 worker hours (see Table). Figure illustrates what each country is capable of producing on its own using a production possibility frontier (PPF) graph. Recall from Choice in a World of Scarcity that the production possibilities frontier shows the maximum amount that each country can produce given its limited resources, in this case workers, and its level of technology.
| Country | Oil Production using 100 worker hours (barrels) | Corn Production using 100 worker hours (bushels) | |
|---|---|---|---|
| Saudi Arabia | 100 | or | 25 |
| United States | 50 | or | 100 |
Arguably Saudi and U.S. consumers desire both oil and corn to live. Let’s say that before trade occurs, both countries produce and consume at point C or C'. Thus, before trade, the Saudi Arabian economy will devote 60 worker hours to produce oil, as Table shows. Given the information in Table, this choice implies that it produces/consumes 60 barrels of oil. With the remaining 40 worker hours, since it needs four hours to produce a bushel of corn, it can produce only 10 bushels. To be at point C', the U.S. economy devotes 40 worker hours to produce 20 barrels of oil and it can allocate the remaining worker hours to produce 60 bushels of corn.
| Country | Oil Production (barrels) | Corn Production (bushels) |
|---|---|---|
| Saudi Arabia (C) | 60 | 10 |
| United States (C') | 20 | 60 |
| Total World Production | 80 | 70 |
The slope of the production possibility frontier illustrates the opportunity cost of producing oil in terms of corn. Using all its resources, the United States can produce 50 barrels of oil or 100 bushels of corn; therefore, the opportunity cost of one barrel of oil is two bushels of corn—or the slope is 1/2. Thus, in the U.S. production possibility frontier graph, every increase in oil production of one barrel implies a decrease of two bushels of corn. Saudi Arabia can produce 100 barrels of oil or 25 bushels of corn. The opportunity cost of producing one barrel of oil is the loss of 1/4 of a bushel of corn that Saudi workers could otherwise have produced. In terms of corn, notice that Saudi Arabia gives up the least to produce a barrel of oil. Table summarizes these calculations.
| Country | Opportunity cost of one unit — Oil (in terms of corn) | Opportunity cost of one unit — Corn (in terms of oil) |
|---|---|---|
| Saudi Arabia | ¼ | 4 |
| United States | 2 | ½ |
Again recall that we defined comparative advantage as the opportunity cost of producing goods. Since Saudi Arabia gives up the least to produce a barrel of oil, ( < in Table) it has a comparative advantage in oil production. The United States gives up the least to produce a bushel of corn, so it has a comparative advantage in corn production.
In this example, there is symmetry between absolute and comparative advantage. Saudi Arabia needs fewer worker hours to produce oil (absolute advantage, see Table), and also gives up the least in terms of other goods to produce oil (comparative advantage, see Table). Such symmetry is not always the case, as we will show after we have discussed gains from trade fully, but first, read the following Clear It Up feature to make sure you understand why the PPF line in the graphs is straight.
Can a production possibility frontier be straight?
When you first met the production possibility frontier (PPF) in the chapter on Choice in a World of Scarcity we drew it with an outward-bending shape. This shape illustrated that as we transferred inputs from producing one good to another—like from education to health services—there were increasing opportunity costs. In the examples in this chapter, we draw the PPFs as straight lines, which means that opportunity costs are constant. When we transfer a marginal unit of labor away from growing corn and toward producing oil, the decline in the quantity of corn and the increase in the quantity of oil is always the same. In reality this is possible only if the contribution of additional workers to output did not change as the scale of production changed. The linear production possibilities frontier is a less realistic model, but a straight line simplifies calculations. It also illustrates economic themes like absolute and comparative advantage just as clearly.
Gains from Trade
Consider the trading positions of the United States and Saudi Arabia after they have specialized and traded. Before trade, Saudi Arabia produces/consumes 60 barrels of oil and 10 bushels of corn. The United States produces/consumes 20 barrels of oil and 60 bushels of corn. Given their current production levels, if the United States can trade an amount of corn fewer than 60 bushels and receives in exchange an amount of oil greater than 20 barrels, it will gain from trade. With trade, the United States can consume more of both goods than it did without specialization and trade. (Recall that the chapter Welcome to Economics! defined specialization as it applies to workers and firms. Economists also use specialization to describe the occurrence when a country shifts resources to focus on producing a good that offers comparative advantage.) Similarly, if Saudi Arabia can trade an amount of oil less than 60 barrels and receive in exchange an amount of corn greater than 10 bushels, it will have more of both goods than it did before specialization and trade. Table illustrates the range of trades that would benefit both sides.
| The U.S. economy, after specialization, will benefit if it: | The Saudi Arabian economy, after specialization, will benefit if it: |
|---|---|
| Exports no more than 60 bushels of corn | Imports at least 10 bushels of corn |
| Imports at least 20 barrels of oil | Exports less than 60 barrels of oil |
The underlying reason why trade benefits both sides is rooted in the concept of opportunity cost, as the following Clear It Up feature explains. If Saudi Arabia wishes to expand domestic production of corn in a world without international trade, then based on its opportunity costs it must give up four barrels of oil for every one additional bushel of corn. If Saudi Arabia could find a way to give up less than four barrels of oil for an additional bushel of corn (or equivalently, to receive more than one bushel of corn for four barrels of oil), it would be better off.
What are the opportunity costs and gains from trade?
The range of trades that will benefit each country is based on the country’s opportunity cost of producing each good. The United States can produce 100 bushels of corn or 50 barrels of oil. For the United States, the opportunity cost of producing one barrel of oil is two bushels of corn. If we divide the numbers above by 50, we get the same ratio: one barrel of oil is equivalent to two bushels of corn, or (100/50 = 2 and 50/50 = 1). In a trade with Saudi Arabia, if the United States is going to give up 100 bushels of corn in exports, it must import at least 50 barrels of oil to be just as well off. Clearly, to gain from trade it needs to be able to gain more than a half barrel of oil for its bushel of corn—or why trade at all?
Recall that David Ricardo argued that if each country specializes in its comparative advantage, it will benefit from trade, and total global output will increase. How can we show gains from trade as a result of comparative advantage and specialization? Table shows the output assuming that each country specializes in its comparative advantage and produces no other good. This is 100% specialization. Specialization leads to an increase in total world production. (Compare the total world production in Table to that in Table.)
| Country | Quantity produced after 100% specialization — Oil (barrels) | Quantity produced after 100% specialization — Corn (bushels) |
|---|---|---|
| Saudi Arabia | 100 | 0 |
| United States | 0 | 100 |
| Total World Production | 100 | 100 |
What if we did not have complete specialization, as in Table? Would there still be gains from trade? Consider another example, such as when the United States and Saudi Arabia start at C and C', respectively, as Figure shows. Consider what occurs when trade is allowed and the United States exports 20 bushels of corn to Saudi Arabia in exchange for 20 barrels of oil.
Starting at point C, which shows Saudi oil production of 60, reduce Saudi oil domestic oil consumption by 20, since 20 is exported to the United States and exchanged for 20 units of corn. This enables Saudi to reach point D, where oil consumption is now 40 barrels and corn consumption has increased to 30 (see Figure). Notice that even without 100% specialization, if the “trading price,” in this case 20 barrels of oil for 20 bushels of corn, is greater than the country’s opportunity cost, the Saudis will gain from trade. Since the post-trade consumption point D is beyond its production possibility frontier, Saudi Arabia has gained from trade.
Visit this website for trade-related data visualizations.
Key Concepts and Summary
A country has an absolute advantage in those products in which it has a productivity edge over other countries; it takes fewer resources to produce a product. A country has a comparative advantage when it can produce a good at a lower cost in terms of other goods. Countries that specialize based on comparative advantage gain from trade.
Self-Check Questions
True or False: The source of comparative advantage must be natural elements like climate and mineral deposits. Explain.
Hint:
False. Anything that leads to different levels of productivity between two economies can be a source of comparative advantage. For example, the education of workers, the knowledge base of engineers and scientists in a country, the part of a split-up value chain where they have their specialized learning, economies of scale, and other factors can all determine comparative advantage.
Brazil can produce 100 pounds of beef or 10 autos. In contrast the United States can produce 40 pounds of beef or 30 autos. Which country has the absolute advantage in beef? Which country has the absolute advantage in producing autos? What is the opportunity cost of producing one pound of beef in Brazil? What is the opportunity cost of producing one pound of beef in the United States?
Hint:
Brazil has the absolute advantage in producing beef and the United States has the absolute advantage in autos. The opportunity cost of producing one pound of beef is 1/10 of an auto; in the United States it is 3/4 of an auto.
In France it takes one worker to produce one sweater, and one worker to produce one bottle of wine. In Tunisia it takes two workers to produce one sweater, and three workers to produce one bottle of wine. Who has the absolute advantage in production of sweaters? Who has the absolute advantage in the production of wine? How can you tell?
Hint:
In answering questions like these, it is often helpful to begin by organizing the information in a table, such as in the following table. Notice that, in this case, the productivity of the countries is expressed in terms of how many workers it takes to produce a unit of a product.
| Country | One Sweater | One Bottle of wine |
|---|---|---|
| France | 1 worker | 1 worker |
| Tunisia | 2 workers | 3 workers |
In this example, France has an absolute advantage in the production of both sweaters and wine. You can tell because it takes France less labor to produce a unit of the good.
Review Questions
What is absolute advantage? What is comparative advantage?
Under what conditions does comparative advantage lead to gains from trade?
What factors does Paul Krugman identify that supported expanding international trade in the 1800s?
Critical Thinking Questions
Are differences in geography behind the differences in absolute advantages?
Why does the United States not have an absolute advantage in coffee?
Look at [link]. Compute the opportunity costs of producing sweaters and wine in both France and Tunisia. Who has the lowest opportunity cost of producing sweaters and who has the lowest opportunity cost of producing wine? Explain what it means to have a lower opportunity cost.
Problems
France and Tunisia both have Mediterranean climates that are excellent for producing/harvesting green beans and tomatoes. In France it takes two hours for each worker to harvest green beans and two hours to harvest a tomato. Tunisian workers need only one hour to harvest the tomatoes but four hours to harvest green beans. Assume there are only two workers, one in each country, and each works 40 hours a week.
- Draw a production possibilities frontier for each country. Hint: Remember the production possibility frontier is the maximum that all workers can produce at a unit of time which, in this problem, is a week.
- Identify which country has the absolute advantage in green beans and which country has the absolute advantage in tomatoes.
- Identify which country has the comparative advantage.
- How much would France have to give up in terms of tomatoes to gain from trade? How much would it have to give up in terms of green beans?
References
Krugman, Paul R. Pop Internationalism. The MIT Press, Cambridge. 1996.
Krugman, Paul R. “What Do Undergrads Need to Know about Trade?” American Economic Review 83, no. 2. 1993. 23-26.
Ricardo, David. On the Principles of Political Economy and Taxation. London: John Murray, 1817.
Ricardo, David. “On the Principles of Political Economy and Taxation.” Library of Economics and Liberty. http://www.econlib.org/library/Ricardo/ricP.html.
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What Happens When a Country Has an Absolute Advantage in All Goods
Overview
By the end of this section, you will be able to:
- Show the relationship between production costs and comparative advantage
- Identify situations of mutually beneficial trade
- Identify trade benefits by considering opportunity costs
What happens to the possibilities for trade if one country has an absolute advantage in everything? This is typical for high-income countries that often have well-educated workers, technologically advanced equipment, and the most up-to-date production processes. These high-income countries can produce all products with fewer resources than a low-income country. If the high-income country is more productive across the board, will there still be gains from trade? Good students of Ricardo understand that trade is about mutually beneficial exchange. Even when one country has an absolute advantage in all products, trade can still benefit both sides. This is because gains from trade come from specializing in one’s comparative advantage.
Production Possibilities and Comparative Advantage
Consider the example of trade between the United States and Mexico described in Table. In this example, it takes four U.S. workers to produce 1,000 pairs of shoes, but it takes five Mexican workers to do so. It takes one U.S. worker to produce 1,000 refrigerators, but it takes four Mexican workers to do so. The United States has an absolute advantage in productivity with regard to both shoes and refrigerators; that is, it takes fewer workers in the United States than in Mexico to produce both a given number of shoes and a given number of refrigerators.
| Country | Number of Workers needed to produce 1,000 units — Shoes | Number of Workers needed to produce 1,000 units — Refrigerators |
|---|---|---|
| United States | 4 workers | 1 worker |
| Mexico | 5 workers | 4 workers |
Absolute advantage simply compares the productivity of a worker between countries. It answers the question, “How many inputs do I need to produce shoes in Mexico?” Comparative advantage asks this same question slightly differently. Instead of comparing how many workers it takes to produce a good, it asks, “How much am I giving up to produce this good in this country?” Another way of looking at this is that comparative advantage identifies the good for which the producer’s absolute advantage is relatively larger, or where the producer’s absolute productivity disadvantage is relatively smaller. The United States can produce 1,000 shoes with four-fifths as many workers as Mexico (four versus five), but it can produce 1,000 refrigerators with only one-quarter as many workers (one versus four). So, the comparative advantage of the United States, where its absolute productivity advantage is relatively greatest, lies with refrigerators, and Mexico’s comparative advantage, where its absolute productivity disadvantage is least, is in the production of shoes.
Mutually Beneficial Trade with Comparative Advantage
When nations increase production in their area of comparative advantage and trade with each other, both countries can benefit. Again, the production possibility frontier is a useful tool to visualize this benefit.
Consider a situation where the United States and Mexico each have 40 workers. For example, as Table shows, if the United States divides its labor so that 40 workers are making shoes, then, since it takes four workers in the United States to make 1,000 shoes, a total of 10,000 shoes will be produced. (If four workers can make 1,000 shoes, then 40 workers will make 10,000 shoes). If the 40 workers in the United States are making refrigerators, and each worker can produce 1,000 refrigerators, then a total of 40,000 refrigerators will be produced.
| Country | Shoe Production — using 40 workers | Refrigerator Production — using 40 workers | |
|---|---|---|---|
| United States | 10,000 shoes | or | 40,000 refrigerators |
| Mexico | 8,000 shoes | or | 10,000 refrigerators |
As always, the slope of the production possibility frontier for each country is the opportunity cost of one refrigerator in terms of foregone shoe production–when labor is transferred from producing the latter to producing the former (see Figure).
Let’s say that, in the situation before trade, each nation prefers to produce a combination of shoes and refrigerators that is shown at point A. Table shows the output of each good for each country and the total output for the two countries.
| Country | Current Shoe Production | Current Refrigerator Production |
|---|---|---|
| United States | 5,000 | 20,000 |
| Mexico | 4,000 | 5,000 |
| Total | 9,000 | 25,000 |
Continuing with this scenario, suppose that each country transfers some amount of labor toward its area of comparative advantage. For example, the United States transfers six workers away from shoes and toward producing refrigerators. As a result, U.S. production of shoes decreases by 1,500 units (6/4 × 1,000), while its production of refrigerators increases by 6,000 (that is, 6/1 × 1,000). Mexico also moves production toward its area of comparative advantage, transferring 10 workers away from refrigerators and toward production of shoes. As a result, production of refrigerators in Mexico falls by 2,500 (10/4 × 1,000), but production of shoes increases by 2,000 pairs (10/5 × 1,000). Notice that when both countries shift production toward each of their comparative advantages (what they are relatively better at), their combined production of both goods rises, as shown in Table. The reduction of shoe production by 1,500 pairs in the United States is more than offset by the gain of 2,000 pairs of shoes in Mexico, while the reduction of 2,500 refrigerators in Mexico is more than offset by the additional 6,000 refrigerators produced in the United States.
| Country | Shoe Production | Refrigerator Production |
|---|---|---|
| United States | 3,500 | 26,000 |
| Mexico | 6,000 | 2,500 |
| Total | 9,500 | 28,500 |
This numerical example illustrates the remarkable insight of comparative advantage: even when one country has an absolute advantage in all goods and another country has an absolute disadvantage in all goods, both countries can still benefit from trade. Even though the United States has an absolute advantage in producing both refrigerators and shoes, it makes economic sense for it to specialize in the good for which it has a comparative advantage. The United States will export refrigerators and in return import shoes.
How Opportunity Cost Sets the Boundaries of Trade
This example shows that both parties can benefit from specializing in their comparative advantages and trading. By using the opportunity costs in this example, it is possible to identify the range of possible trades that would benefit each country.
Mexico started out, before specialization and trade, producing 4,000 pairs of shoes and 5,000 refrigerators (see Figure and Table). Then, in the numerical example given, Mexico shifted production toward its comparative advantage and produced 6,000 pairs of shoes but only 2,500 refrigerators. Thus, if Mexico can export no more than 2,000 pairs of shoes (giving up 2,000 pairs of shoes) in exchange for imports of at least 2,500 refrigerators (a gain of 2,500 refrigerators), it will be able to consume more of both goods than before trade. Mexico will be unambiguously better off. Conversely, the United States started off, before specialization and trade, producing 5,000 pairs of shoes and 20,000 refrigerators. In the example, it then shifted production toward its comparative advantage, producing only 3,500 shoes but 26,000 refrigerators. If the United States can export no more than 6,000 refrigerators in exchange for imports of at least 1,500 pairs of shoes, it will be able to consume more of both goods and will be unambiguously better off.
The range of trades that can benefit both nations is shown in Table. For example, a trade where the U.S. exports 4,000 refrigerators to Mexico in exchange for 1,800 pairs of shoes would benefit both sides, in the sense that both countries would be able to consume more of both goods than in a world without trade.
| The U.S. economy, after specialization, will benefit if it: | The Mexican economy, after specialization, will benefit if it: |
|---|---|
| Exports fewer than 6,000 refrigerators | Imports at least 2,500 refrigerators |
| Imports at least 1,500 pairs of shoes | Exports no more than 2,000 pairs of shoes |
Trade allows each country to take advantage of lower opportunity costs in the other country. If Mexico wants to produce more refrigerators without trade, it must face its domestic opportunity costs and reduce shoe production. If Mexico, instead, produces more shoes and then trades for refrigerators made in the United States, where the opportunity cost of producing refrigerators is lower, Mexico can in effect take advantage of the lower opportunity cost of refrigerators in the United States. Conversely, when the United States specializes in its comparative advantage of refrigerator production and trades for shoes produced in Mexico, international trade allows the United States to take advantage of the lower opportunity cost of shoe production in Mexico.
The theory of comparative advantage explains why countries trade: they have different comparative advantages. It shows that the gains from international trade result from pursuing comparative advantage and producing at a lower opportunity cost. The following Work It Out feature shows how to calculate absolute and comparative advantage and the way to apply them to a country’s production.
Calculating Absolute and Comparative Advantage
In Canada a worker can produce 20 barrels of oil or 40 tons of lumber. In Venezuela, a worker can produce 60 barrels of oil or 30 tons of lumber.
| Country | Oil (barrels) | Lumber (tons) | |
|---|---|---|---|
| Canada | 20 | or | 40 |
| Venezuela | 60 | or | 30 |
- Who has the absolute advantage in the production of oil or lumber? How can you tell?
- Which country has a comparative advantage in the production of oil?
- Which country has a comparative advantage in producing lumber?
- In this example, is absolute advantage the same as comparative advantage, or not?
- In what product should Canada specialize? In what product should Venezuela specialize?
Step 1. Make a table like Table.
Step 2. To calculate absolute advantage, look at the larger of the numbers for each product. One worker in Canada can produce more lumber (40 tons versus 30 tons), so Canada has the absolute advantage in lumber. One worker in Venezuela can produce 60 barrels of oil compared to a worker in Canada who can produce only 20.
Step 3. To calculate comparative advantage, find the opportunity cost of producing one barrel of oil in both countries. The country with the lowest opportunity cost has the comparative advantage. With the same labor time, Canada can produce either 20 barrels of oil or 40 tons of lumber. So in effect, 20 barrels of oil is equivalent to 40 tons of lumber: 20 oil = 40 lumber. Divide both sides of the equation by 20 to calculate the opportunity cost of one barrel of oil in Canada. 20/20 oil = 40/20 lumber. 1 oil = 2 lumber. To produce one additional barrel of oil in Canada has an opportunity cost of 2 lumber. Calculate the same way for Venezuela: 60 oil = 30 lumber. Divide both sides of the equation by 60. One oil in Venezuela has an opportunity cost of 1/2 lumber. Because 1/2 lumber < 2 lumber, Venezuela has the comparative advantage in producing oil.
Step 4. Calculate the opportunity cost of one lumber by reversing the numbers, with lumber on the left side of the equation. In Canada, 40 lumber is equivalent in labor time to 20 barrels of oil: 40 lumber = 20 oil. Divide each side of the equation by 40. The opportunity cost of one lumber is 1/2 oil. In Venezuela, the equivalent labor time will produce 30 lumber or 60 oil: 30 lumber = 60 oil. Divide each side by 30. One lumber has an opportunity cost of two oil. Canada has the lower opportunity cost in producing lumber.
Step 5. In this example, absolute advantage is the same as comparative advantage. Canada has the absolute and comparative advantage in lumber; Venezuela has the absolute and comparative advantage in oil.
Step 6. Canada should specialize in the commodity for which it has a relative lower opportunity cost, which is lumber, and Venezuela should specialize in oil. Canada will be exporting lumber and importing oil, and Venezuela will be exporting oil and importing lumber.
Comparative Advantage Goes Camping
To build an intuitive understanding of how comparative advantage can benefit all parties, set aside examples that involve national economies for a moment and consider the situation of a group of friends who decide to go camping together. The six friends have a wide range of skills and experiences, but one person in particular, Jethro, has done lots of camping before and is also a great athlete. Jethro has an absolute advantage in all aspects of camping: he is faster at carrying a backpack, gathering firewood, paddling a canoe, setting up tents, making a meal, and washing up. So here is the question: Because Jethro has an absolute productivity advantage in everything, should he do all the work?
Of course not! Even if Jethro is willing to work like a mule while everyone else sits around, he, like all mortals, only has 24 hours in a day. If everyone sits around and waits for Jethro to do everything, not only will Jethro be an unhappy camper, but there will not be much output for his group of six friends to consume. The theory of comparative advantage suggests that everyone will benefit if they figure out their areas of comparative advantage—that is, the area of camping where their productivity disadvantage is least, compared to Jethro. For example, it may be that Jethro is 80% faster at building fires and cooking meals than anyone else, but only 20% faster at gathering firewood and 10% faster at setting up tents. In that case, Jethro should focus on building fires and making meals, and others should attend to the other tasks, each according to where their productivity disadvantage is smallest. If the campers coordinate their efforts according to comparative advantage, they can all gain.
Key Concepts and Summary
Even when a country has high levels of productivity in all goods, it can still benefit from trade. Gains from trade come about as a result of comparative advantage. By specializing in a good that it gives up the least to produce, a country can produce more and offer that additional output for sale. If other countries specialize in the area of their comparative advantage as well and trade, the highly productive country is able to benefit from a lower opportunity cost of production in other countries.
Self-Check Question
In Germany it takes three workers to make one television and four workers to make one video camera. In Poland it takes six workers to make one television and 12 workers to make one video camera.
- Who has the absolute advantage in the production of televisions? Who has the absolute advantage in the production of video cameras? How can you tell?
- Calculate the opportunity cost of producing one additional television set in Germany and in Poland. (Your calculation may involve fractions, which is fine.) Which country has a comparative advantage in the production of televisions?
- Calculate the opportunity cost of producing one video camera in Germany and in Poland. Which country has a comparative advantage in the production of video cameras?
- In this example, is absolute advantage the same as comparative advantage, or not?
- In what product should Germany specialize? In what product should Poland specialize?
Hint:
- In Germany, it takes fewer workers to make either a television or a video camera. Germany has an absolute advantage in the production of both goods.
- Producing an additional television in Germany requires three workers. Shifting those three German workers will reduce video camera production by 3/4 of a camera. Producing an additional television set in Poland requires six workers, and shifting those workers from the other good reduces output of video cameras by 6/12 of a camera, or 1/2. Thus, the opportunity cost of producing televisions is lower in Poland, so Poland has the comparative advantage in the production of televisions. Note: Do not let the fractions like 3/4 of a camera or 1/2 of a video camera bother you. If either country was to expand television production by a significant amount—that is, lots more than one unit—then we will be talking about whole cameras and not fractional ones. You can also spot this conclusion by noticing that Poland’s absolute disadvantage is relatively lower in televisions, because Poland needs twice as many workers to produce a television but three times as many to produce a video camera, so the product with the relatively lower absolute disadvantage is Poland’s comparative advantage.
- Producing a video camera in Germany requires four workers, and shifting those four workers away from television production has an opportunity cost of 4/3 television sets. Producing a video camera in Poland requires 12 workers, and shifting those 12 workers away from television production has an opportunity cost of two television sets. Thus, the opportunity cost of producing video cameras is lower in Germany, and video cameras will be Germany’s comparative advantage.
- In this example, absolute advantage differs from comparative advantage. Germany has the absolute advantage in the production of both goods, but Poland has a comparative advantage in the production of televisions.
- Germany should specialize, at least to some extent, in the production of video cameras, export video cameras, and import televisions. Conversely, Poland should specialize, at least to some extent, in the production of televisions, export televisions, and import video cameras.
Review Questions
Is it possible to have a comparative advantage in the production of a good but not to have an absolute advantage? Explain.
How does comparative advantage lead to gains from trade?
Critical Thinking Questions
You just overheard your friend say the following: “Poor countries like Malawi have no absolute advantages. They have poor soil, low investments in formal education and hence low-skill workers, no capital, and no natural resources to speak of. Because they have no advantage, they cannot benefit from trade.” How would you respond?
Look at Table. Is there a range of trades for which there will be no gains?
You just got a job in Washington, D.C. You move into an apartment with some acquaintances. All your roommates, however, are slackers and do not clean up after themselves. You, on the other hand, can clean faster than each of them. You determine that you are 70% faster at dishes and 10% faster with vacuuming. All of these tasks have to be done daily. Which jobs should you assign to your roommates to get the most free time overall? Assume you have the same number of hours to devote to cleaning. Now, since you are faster, you seem to get done quicker than your roommate. What sorts of problems may this create? Can you imagine a trade-related analogy to this problem?
Problems
In Japan, one worker can make 5 tons of rubber or 80 radios. In Malaysia, one worker can make 10 tons of rubber or 40 radios.
- Who has the absolute advantage in the production of rubber or radios? How can you tell?
- Calculate the opportunity cost of producing 80 additional radios in Japan and in Malaysia. (Your calculation may involve fractions, which is fine.) Which country has a comparative advantage in the production of radios?
- Calculate the opportunity cost of producing 10 additional tons of rubber in Japan and in Malaysia. Which country has a comparative advantage in producing rubber?
- In this example, does each country have an absolute advantage and a comparative advantage in the same good?
- In what product should Japan specialize? In what product should Malaysia specialize?
Review the numbers for Canada and Venezuela from Table which describes how many barrels of oil and tons of lumber the workers can produce. Use these numbers to answer the rest of this question.
- Draw a production possibilities frontier for each country. Assume there are 100 workers in each country. Canadians and Venezuelans desire both oil and lumber. Canadians want at least 2,000 tons of lumber. Mark a point on their production possibilities where they can get at least 3,000 tons.
- Assume that the Canadians specialize completely because they figured out they have a comparative advantage in lumber. They are willing to give up 1,000 tons of lumber. How much oil should they ask for in return for this lumber to be as well off as they were with no trade? How much should they ask for if they want to gain from trading with Venezuela? Note: We can think of this “ask” as the relative price or trade price of lumber.
- Is the Canadian “ask” you identified in (b) also beneficial for Venezuelans? Use the production possibilities frontier graph for Venezuela to show that Venezuelans can gain from trade.
In [link], is there an “ask” where Venezuelans may say “no thank you” to trading with Canada?
References
Bernstein, William J. A Splendid Exchange: How Trade Shaped the World. Atlantic Monthly Press. New York. 2008.
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Intra-industry Trade between Similar Economies
Overview
By the end of this section, you will be able to:
- Identify at least two advantages of intra-industry trading
- Explain the relationship between economies of scale and intra-industry trade
Absolute and comparative advantages explain a great deal about global trading patterns. For example, they help to explain the patterns that we noted at the start of this chapter, like why you may be eating fresh fruit from Chile or Mexico, or why lower productivity regions like Africa and Latin America are able to sell a substantial proportion of their exports to higher productivity regions like the European Union and North America. Comparative advantage, however, at least at first glance, does not seem especially well-suited to explain other common patterns of international trade.
The Prevalence of Intra-industry Trade between Similar Economies
The theory of comparative advantage suggests that trade should happen between economies with large differences in opportunity costs of production. Roughly half of all world trade involves shipping goods between the fairly similar high-income economies of the United States, Canada, the European Union, Japan, Mexico, and China (see Table).
| Country | U.S. Exports Go to ... | U.S. Imports Come from ... |
|---|---|---|
| European Union | 19.0% | 21.0% |
| Canada | 22.0% | 14.0% |
| Japan | 4.0% | 6.0% |
| Mexico | 15.0% | 13.0% |
| China | 8.0% | 20.0% |
Moreover, the theory of comparative advantage suggests that each economy should specialize to a degree in certain products, and then exchange those products. A high proportion of trade, however, is intra-industry trade—that is, trade of goods within the same industry from one country to another. For example, the United States produces and exports autos and imports autos. Table shows some of the largest categories of U.S. exports and imports. In all of these categories, the United States is both a substantial exporter and a substantial importer of goods from the same industry. In 2014, according to the Bureau of Economic Analysis, the United States exported $146 billion worth of autos, and imported $327 billion worth of autos. About 60% of U.S. trade and 60% of European trade is intra-industry trade.
| Some U.S. Exports | Quantity of Exports ($ billions) | Quantity of Imports ($ billions) |
|---|---|---|
| Autos | $146 | $327 |
| Food and beverages | $144 | $126 |
| Capital goods | $550 | $551 |
| Consumer goods | $199 | $558 |
| Industrial supplies | $507 | $665 |
| Other transportation | $45 | $55 |
Why do similar high-income economies engage in intra-industry trade? What can be the economic benefit of having workers of fairly similar skills making cars, computers, machinery and other products which are then shipped across the oceans to and from the United States, the European Union, and Japan? There are two reasons: (1) The division of labor leads to learning, innovation, and unique skills; and (2) economies of scale.
Gains from Specialization and Learning
Consider the category of machinery, where the U.S. economy has considerable intra-industry trade. Machinery comes in many varieties, so the United States may be exporting machinery for manufacturing with wood, but importing machinery for photographic processing. The underlying reason why a country like the United States, Japan, or Germany produces one kind of machinery rather than another is usually not related to U.S., German, or Japanese firms and workers having generally higher or lower skills. It is just that, in working on very specific and particular products, firms in certain countries develop unique and different skills.
Specialization in the world economy can be very finely split. In fact, recent years have seen a trend in international trade, which economists call splitting up the value chain. The value chain describes how a good is produced in stages. As indicated in the beginning of the chapter, producing the iPhone involves designing and engineering the phone in the United States, supplying parts from Korea, assembling the parts in China, and advertising and marketing in the United States. Thanks in large part to improvements in communication technology, sharing information, and transportation, it has become easier to split up the value chain. Instead of production in a single large factory, different firms operating in various places and even different countries can divide the value chain. Because firms split up the value chain, international trade often does not involve nations trading whole finished products like automobiles or refrigerators. Instead, it involves shipping more specialized goods like, say, automobile dashboards or the shelving that fits inside refrigerators. Intra-industry trade between similar countries produces economic gains because it allows workers and firms to learn and innovate on particular products—and often to focus on very particular parts of the value chain.
Visit this website for some interesting information about the assembly of the iPhone.
Economies of Scale, Competition, Variety
A second broad reason that intra-industry trade between similar nations produces economic gains involves economies of scale. The concept of economies of scale, as we introduced in Production, Costs and Industry Structure, means that as the scale of output goes up, average costs of production decline—at least up to a point. Figure illustrates economies of scale for a plant producing toaster ovens. The horizontal axis of the figure shows the quantity of production by a certain firm or at a certain manufacturing plant. The vertical axis measures the average cost of production. Production plant S produces a small level of output at 30 units and has an average cost of production of $30 per toaster oven. Plant M produces at a medium level of output at 50 units, and has an average cost of production of $20 per toaster oven. Plant L produces 150 units of output with an average cost of production of only $10 per toaster oven. Although plant V can produce 200 units of output, it still has the same unit cost as Plant L.
In this example, a small or medium plant, like S or M, will not be able to compete in the market with a large or a very large plant like L or V, because the firm that operates L or V will be able to produce and sell its output at a lower price. In this example, economies of scale operate up to point L, but beyond point L to V, the additional scale of production does not continue to reduce average costs of production.
The concept of economies of scale becomes especially relevant to international trade when it enables one or two large producers to supply the entire country. For example, a single large automobile factory could probably supply all the cars consumers purchase in a smaller economy like the United Kingdom or Belgium in a given year. However, if a country has only one or two large factories producing cars, and no international trade, then consumers in that country would have relatively little choice between kinds of cars (other than the color of the paint and other nonessential options). Little or no competition will exist between different car manufacturers.
International trade provides a way to combine the lower average production costs that come from economies of scale and still have competition and variety for consumers. Large automobile factories in different countries can make and sell their products around the world. If General Motors, Ford, and Chrysler were the only players in the U.S. automobile market, the level of competition and consumer choice would be considerably lower than when U.S. carmakers must face competition from Toyota, Honda, Suzuki, Fiat, Mitsubishi, Nissan, Volkswagen, Kia, Hyundai, BMW, Subaru, and others. Greater competition brings with it innovation and responsiveness to what consumers want. America’s car producers make far better cars now than they did several decades ago, and much of the reason is competitive pressure, especially from East Asian and European carmakers.
Dynamic Comparative Advantage
The sources of gains from intra-industry trade between similar economies—namely, the learning that comes from a high degree of specialization and splitting up the value chain and from economies of scale—do not contradict the earlier theory of comparative advantage. Instead, they help to broaden the concept.
In intra-industry trade, climate or geography do not determine the level of worker productivity. Even the general level of education or skill does not determine it. Instead, how firms engage in specific learning about specialized products, including taking advantage of economies of scale determine the level of worker productivity. In this vision, comparative advantage can be dynamic—that is, it can evolve and change over time as one develops new skills and as manufacturers split the value chain in new ways. This line of thinking also suggests that countries are not destined to have the same comparative advantage forever, but must instead be flexible in response to ongoing changes in comparative advantage.
Key Concepts and Summary
A large share of global trade happens between high-income economies that are quite similar in having well-educated workers and advanced technology. These countries practice intra-industry trade, in which they import and export the same products at the same time, like cars, machinery, and computers. In the case of intra-industry trade between economies with similar income levels, the gains from trade come from specialized learning in very particular tasks and from economies of scale. Splitting up the value chain means that several stages of producing a good take place in different countries around the world.
Self-Check Questions
How can there be any economic gains for a country from both importing and exporting the same good, like cars?
Hint:
There are a number of possible advantages of intra-industry trade. Both nations can take advantage of extreme specialization and learning in certain kinds of cars with certain traits, like gas-efficient cars, luxury cars, sport-utility vehicles, higher- and lower-quality cars, and so on. Moreover, nations can take advantage of economies of scale, so that large companies will compete against each other across international borders, providing the benefits of competition and variety to customers. This same argument applies to trade between U.S. states, where people often buy products made by people of other states, even though a similar product is made within the boundaries of their own state. All states—and all countries—can benefit from this kind of competition and trade.
Table shows how the average costs of production for semiconductors (the “chips” in computer memories) change as the quantity of semiconductors built at that factory increases.
- Based on these data, sketch a curve with quantity produced on the horizontal axis and average cost of production on the vertical axis. How does the curve illustrate economies of scale?
- If the equilibrium quantity of semiconductors demanded is 90,000, can this economy take full advantage of economies of scale? What about if quantity demanded is 70,000 semiconductors? 50,000 semiconductors? 30,000 semiconductors?
- Explain how international trade could make it possible for even a small economy to take full advantage of economies of scale, while also benefiting from competition and the variety offered by several producers.
| Quantity of Semiconductors | Average Total Cost |
|---|---|
| 10,000 | $8 each |
| 20,000 | $5 each |
| 30,000 | $3 each |
| 40,000 | $2 each |
| 100,000 | $2 each |
Hint:
- Start by plotting the points on a sketch diagram and then drawing a line through them. The following figure illustrates the average costs of production of semiconductors. The curve illustrates economies of scale by showing that as the scale increases—that is, as production at this particular factory goes up—the average cost of production declines. The economies of scale exist up to an output of 40,000 semiconductors; at higher outputs, the average cost of production does not seem to decline any further.
- At any quantity demanded above 40,000, this economy can take full advantage of economies of scale; that is, it can produce at the lowest cost per unit. Indeed, if the quantity demanded was quite high, like 500,000, then there could be a number of different factories all taking full advantage of economies of scale and competing with each other. If the quantity demanded falls below 40,000, then the economy by itself, without foreign trade, cannot take full advantage of economies of scale.
- The simplest answer to this question is that the small country could have a large enough factory to take full advantage of economies of scale, but then export most of the output. For semiconductors, countries like Taiwan and Korea have recently fit this description. Moreover, this country could also import semiconductors from other countries which also have large factories, thus getting the benefits of competition and variety. A slightly more complex answer is that the country can get these benefits of economies of scale without producing semiconductors, but simply by buying semiconductors made at low cost around the world. An economy, especially a smaller country, may well end up specializing and producing a few items on a large scale, but then trading those items for other items produced on a large scale, and thus gaining the benefits of economies of scale by trade, as well as by direct production.
Review Questions
What is intra-industry trade?
What are the two main sources of economic gains from intra-industry trade?
What is splitting up the value chain?
Critical Thinking Questions
Does intra-industry trade contradict the theory of comparative advantage?
Do consumers benefit from intra-industry trade?
Why might intra-industry trade seem surprising from the point of view of comparative advantage?
Problems
From earlier chapters you will recall that technological change shifts the average cost curves. Draw a graph showing how technological change could influence intra-industry trade.
Consider two countries: South Korea and Taiwan. Taiwan can produce one million mobile phones per day at the cost of $10 per phone and South Korea can produce 50 million mobile phones at $5 per phone. Assume these phones are the same type and quality and there is only one price. What is the minimum price at which both countries will engage in trade?
References
U.S. Census Bureau. 2015. “U.S. International Trade in Goods and Services: December 2014.” Accessed April 13, 2015. http://www.bea.gov/newsreleases/international/trade/2015/pdf/trad1214.pdf.
U.S. Census Bureau. U.S. Bureau of Economic Analysis. 2015. “U.S. International Trade in Goods and Services February 2015.” Accessed April 10, 2015. https://www.census.gov/foreign-trade/Press-Release/current_press_release/ft900.pdf.
Vernengo, Matias. “What Do Undergraduates Really Need to Know About Trade and Finance?” in Political Economy and Contemporary Capitalism: Radical Perspectives on Economic Theory and Policy, ed. Ron Baiman, Heather Boushey, and Dawn Saunders. M. E. Sharpe Inc, 2000. Armonk. 177-183.
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The Benefits of Reducing Barriers to International Trade
Overview
By the end of this section, you will be able to:
- Explain tarrifs as barriers to trade
- Identify at least two benefits of reducing barriers to international trade
Tariffs are taxes that governments place on imported goods for a variety of reasons. Some of these reasons include protecting sensitive industries, for humanitarian reasons, and protecting against dumping. Traditionally, tariffs were used simply as a political tool to protect certain vested economic, social, and cultural interests. The World Trade Organization (WTO) is committed to lowering barriers to trade. The world’s nations meet through the WTO to negotiate how they can reduce barriers to trade, such as tariffs. WTO negotiations happen in “rounds,” where all countries negotiate one agreement to encourage trade, take a year or two off, and then start negotiating a new agreement. The current round of negotiations is called the Doha Round because it was officially launched in Doha, the capital city of Qatar, in November 2001. In 2009, economists from the World Bank summarized recent research and found that the Doha round of negotiations would increase the size of the world economy by $160 billion to $385 billion per year, depending on the precise deal that ended up being negotiated.
In the context of a global economy that currently produces more than $30 trillion of goods and services each year, this amount is not huge: it is an increase of 1% or less. But before dismissing the gains from trade too quickly, it is worth remembering two points.
- First, a gain of a few hundred billion dollars is enough money to deserve attention! Moreover, remember that this increase is not a one-time event; it would persist each year into the future.
- Second, the estimate of gains may be on the low side because some of the gains from trade are not measured especially well in economic statistics. For example, it is difficult to measure the potential advantages to consumers of having a variety of products available and a greater degree of competition among producers. Perhaps the most important unmeasured factor is that trade between countries, especially when firms are splitting up the value chain of production, often involves a transfer of knowledge that can involve skills in production, technology, management, finance, and law.
Low-income countries benefit more from trade than high-income countries do. In some ways, the giant U.S. economy has less need for international trade, because it can already take advantage of internal trade within its economy. However, many smaller national economies around the world, in regions like Latin America, Africa, the Middle East, and Asia, have much more limited possibilities for trade inside their countries or their immediate regions. Without international trade, they may have little ability to benefit from comparative advantage, slicing up the value chain, or economies of scale. Moreover, smaller economies often have fewer competitive firms making goods within their economy, and thus firms have less pressure from other firms to provide the goods and prices that consumers want.
The economic gains from expanding international trade are measured in hundreds of billions of dollars, and the gains from international trade as a whole probably reach well into the trillions of dollars. The potential for gains from trade may be especially high among the smaller and lower-income countries of the world.
Visit this website for a list of some benefits of trade.
From Interpersonal to International Trade
Most people find it easy to believe that they, personally, would not be better off if they tried to grow and process all of their own food, to make all of their own clothes, to build their own cars and houses from scratch, and so on. Instead, we all benefit from living in economies where people and firms can specialize and trade with each other.
The benefits of trade do not stop at national boundaries, either. Earlier we explained that the division of labor could increase output for three reasons: (1) workers with different characteristics can specialize in the types of production where they have a comparative advantage; (2) firms and workers who specialize in a certain product become more productive with learning and practice; and (3) economies of scale. These three reasons apply from the individual and community level right up to the international level. If it makes sense to you that interpersonal, intercommunity, and interstate trade offer economic gains, it should make sense that international trade offers gains, too.
International trade currently involves about $20 trillion worth of goods and services moving around the globe. Any economic force of that size, even if it confers overall benefits, is certain to cause disruption and controversy. This chapter has only made the case that trade brings economic benefits. Other chapters discuss, in detail, the public policy arguments over whether to restrict international trade.
It’s Apple’s (Global) iPhone
Apple Corporation uses a global platform to produce the iPhone. Now that you understand the concept of comparative advantage, you can see why the engineering and design of the iPhone is done in the United States. The United States has built up a comparative advantage over the years in designing and marketing products, and sacrifices fewer resources to design high-tech devices relative to other countries. China has a comparative advantage in assembling the phone due to its large skilled labor force. Korea has a comparative advantage in producing components. Korea focuses its production by increasing its scale, learning better ways to produce screens and computer chips, and uses innovation to lower average costs of production. Apple, in turn, benefits because it can purchase these quality products at lower prices. Put the global assembly line together and you have the device with which we are all so familiar.
Key Concepts and Summary
Tariffs are placed on imported goods as a way of protecting sensitive industries, for humanitarian reasons, and for protection against dumping. Traditionally, tariffs were used as a political tool to protect certain vested economic, social, and cultural interests. The WTO has been, and continues to be, a way for nations to meet and negotiate in order to reduce barriers to trade. The gains of international trade are very large, especially for smaller countries, but are beneficial to all.
Self-Check Question
If the removal of trade barriers is so beneficial to international economic growth, why would a nation continue to restrict trade on some imported or exported products?
Hint:
A nation might restrict trade on imported products to protect an industry that is important for national security. For example, nation X and nation Y may be geopolitical rivals, each with ambitions of increased political and economic strength. Even if nation Y has comparative advantage in the production of missile defense systems, it is unlikely that nation Y would seek to export those goods to nation X. It is also the case that, for some nations, the production of a particular good is a key component of national identity. In Japan, the production of rice is culturally very important. It may be difficult for Japan to import rice from a nation like Vietnam, even if Vietnam has a comparative advantage in rice production.
Review Question
Are the gains from international trade more likely to be relatively more important to large or small countries?
Critical Thinking Questions
In World Trade Organization meetings, what do you think low-income countries lobby for?
Why might a low-income country put up barriers to trade, such as tariffs on imports?
Can a nation’s comparative advantage change over time? What factors would make it change?
Problems
If trade increases world GDP by 1% per year, what is the global impact of this increase over 10 years? How does this increase compare to the annual GDP of a country like Sri Lanka? Discuss. Hint: To answer this question, here are steps you may want to consider. Go to the World Development Indicators (online) published by the World Bank. Find the current level of World GDP in constant international dollars. Also, find the GDP of Sri Lanka in constant international dollars. Once you have these two numbers, compute the amount the additional increase in global incomes due to trade and compare that number to Sri Lanka’s GDP.
References
World Trade Organization. “The Doha Round.” Accessed October 2013. http://www.wto.org/english/tratop_e/dda_e/dda_e.htm.
The World Bank. “Data: World Development Indicators.” Accessed October 2013. http://data.worldbank.org/data-catalog/world-development-indicators.
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The Respiratory System
Introduction
Figure 22.1 Mountain Climbers The thin air at high elevations can strain the human respiratory system. (credit: “bortescristian”/flickr.com)
CHAPTER OBJECTIVES
After studying this chapter, you will be able to:
- List the structures of the respiratory system
- List the major functions of the respiratory system
- Outline the forces that allow for air movement into and out of the lungs
- Outline the process of gas exchange
- Summarize the process of oxygen and carbon dioxide transport within the respiratory system
- Create a flow chart illustrating how respiration is controlled
- Discuss how the respiratory system responds to exercise
- Describe the development of the respiratory system in the embryo
Hold your breath. Really! See how long you can hold your breath as you continue reading…How long can you do it? Chances are you are feeling uncomfortable already. A typical human cannot survive without breathing for more than 3 minutes, and even if you wanted to hold your breath longer, your autonomic nervous system would take control. This is because every cell in the body needs to run the oxidative stages of cellular respiration, the process by which energy is produced in the form of adenosine triphosphate (ATP). For oxidative phosphorylation to occur, oxygen is used as a reactant and carbon dioxide is released as a waste product. You may be surprised to learn that although oxygen is a critical need for cells, it is actually the accumulation of carbon dioxide that primarily drives your need to breathe. Carbon dioxide is exhaled and oxygen is inhaled through the respiratory system, which includes muscles to move air into and out of the lungs, passageways through which air moves, and microscopic gas exchange surfaces covered by capillaries. The circulatory system transports gases from the lungs to tissues throughout the body and vice versa. A variety of diseases can affect the respiratory system, such as asthma, emphysema, chronic obstruction pulmonary disorder (COPD), and lung cancer. All of these conditions affect the gas exchange process and result in labored breathing and other difficulties.
Organs and Structures of the Respiratory System
- List the structures that make up the respiratory system
- Describe how the respiratory system processes oxygen and CO2
- Compare and contrast the functions of upper respiratory tract with the lower respiratory tract
The major organs of the respiratory system function primarily to provide oxygen to body tissues for cellular respiration, remove the waste product carbon dioxide, and help to maintain acid-base balance. Portions of the respiratory system are also used for non-vital functions, such as sensing odors, speech production, and for straining, such as during childbirth or coughing (Figure 22.2).
Figure 22.2 Major Respiratory Structures The major respiratory structures span the nasal cavity to the diaphragm.
Functionally, the respiratory system can be divided into a conducting zone and a respiratory zone. The conducting zone of the respiratory system includes the organs and structures not directly involved in gas exchange. The gas exchange occurs in the respiratory zone.
Conducting Zone
The major functions of the conducting zone are to provide a route for incoming and outgoing air, remove debris and pathogens from the incoming air, and warm and humidify the incoming air. Several structures within the conducting zone perform other functions as well. The epithelium of the nasal passages, for example, is essential to sensing odors, and the bronchial epithelium that lines the lungs can metabolize some airborne carcinogens.
The Nose and its Adjacent Structures
The major entrance and exit for the respiratory system is through the nose. When discussing the nose, it is helpful to divide it into two major sections: the external nose, and the nasal cavity or internal nose.
The external nose consists of the surface and skeletal structures that result in the outward appearance of the nose and contribute to its numerous functions (Figure 22.3). The root is the region of the nose located between the eyebrows. The bridge is the part of the nose that connects the root to the rest of the nose. The dorsum nasi is the length of the nose. The apex is the tip of the nose. On either side of the apex, the nostrils are formed by the alae (singular = ala). An ala is a cartilaginous structure that forms the lateral side of each naris (plural = nares), or nostril opening. The philtrum is the concave surface that connects the apex of the nose to the upper lip.
Figure 22.3 Nose This illustration shows features of the external nose (top) and skeletal features of the nose (bottom).
Underneath the thin skin of the nose are its skeletal features (see Figure 22.3, lower illustration). While the root and bridge of the nose consist of bone, the protruding portion of the nose is composed of cartilage. As a result, when looking at a skull, the nose is missing. The nasal bone is one of a pair of bones that lies under the root and bridge of the nose. The nasal bone articulates superiorly with the frontal bone and laterally with the maxillary bones. Septal cartilage is flexible hyaline cartilage connected to the nasal bone, forming the dorsum nasi. The alar cartilage consists of the apex of the nose; it surrounds the naris.
The nares open into the nasal cavity, which is separated into left and right sections by the nasal septum (Figure 22.4). The nasal septum is formed anteriorly by a portion of the septal cartilage (the flexible portion you can touch with your fingers) and posteriorly by the perpendicular plate of the ethmoid bone (a cranial bone located just posterior to the nasal bones) and the thin vomer bones (whose name refers to its plough shape). Each lateral wall of the nasal cavity has three bony projections, called the superior, middle, and inferior nasal conchae. The inferior conchae are separate bones, whereas the superior and middle conchae are portions of the ethmoid bone. Conchae serve to increase the surface area of the nasal cavity and to disrupt the flow of air as it enters the nose, causing air to bounce along the epithelium, where it is cleaned and warmed. The conchae and meatuses also conserve water and prevent dehydration of the nasal epithelium by trapping water during exhalation. The floor of the nasal cavity is composed of the palate. The hard palate at the anterior region of the nasal cavity is composed of bone. The soft palate at the posterior portion of the nasal cavity consists of muscle tissue. Air exits the nasal cavities via the internal nares and moves into the pharynx.
Figure 22.4 Upper Airway
Several bones that help form the walls of the nasal cavity have air-containing spaces called the paranasal sinuses, which serve to warm and humidify incoming air. Sinuses are lined with a mucosa. Each paranasal sinus is named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. The sinuses produce mucus and lighten the weight of the skull.
The nares and anterior portion of the nasal cavities are lined with mucous membranes, containing sebaceous glands and hair follicles that serve to prevent the passage of large debris, such as dirt, through the nasal cavity. An olfactory epithelium used to detect odors is found deeper in the nasal cavity.
The conchae, meatuses, and paranasal sinuses are lined by respiratory epithelium composed of pseudostratified ciliated columnar epithelium (Figure 22.5). The epithelium contains goblet cells, one of the specialized, columnar epithelial cells that produce mucus to trap debris. The cilia of the respiratory epithelium help remove the mucus and debris from the nasal cavity with a constant beating motion, sweeping materials towards the throat to be swallowed. Interestingly, cold air slows the movement of the cilia, resulting in accumulation of mucus that may in turn lead to a runny nose during cold weather. This moist epithelium functions to warm and humidify incoming air. Capillaries located just beneath the nasal epithelium warm the air by convection. Serous and mucus-producing cells also secrete the lysozyme enzyme and proteins called defensins, which have antibacterial properties. Immune cells that patrol the connective tissue deep to the respiratory epithelium provide additional protection.
Figure 22.5 Pseudostratified Ciliated Columnar Epithelium Respiratory epithelium is pseudostratified ciliated columnar epithelium. Seromucous glands provide lubricating mucus. LM × 680. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)
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Pharynx
The pharynx is a tube formed by skeletal muscle and lined by mucous membrane that is continuous with that of the nasal cavities (see Figure 22.4). The pharynx is divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx (Figure 22.6).
Figure 22.6 Divisions of the Pharynx The pharynx is divided into three regions: the nasopharynx, the oropharynx, and the laryngopharynx.
The nasopharynx is flanked by the conchae of the nasal cavity, and it serves only as an airway. At the top of the nasopharynx are the pharyngeal tonsils. A pharyngeal tonsil, also called an adenoid, is an aggregate of lymphoid reticular tissue similar to a lymph node that lies at the superior portion of the nasopharynx. The function of the pharyngeal tonsil is not well understood, but it contains a rich supply of lymphocytes and is covered with ciliated epithelium that traps and destroys invading pathogens that enter during inhalation. The pharyngeal tonsils are large in children, but interestingly, tend to regress with age and may even disappear. The uvula is a small bulbous, teardrop-shaped structure located at the apex of the soft palate. Both the uvula and soft palate move like a pendulum during swallowing, swinging upward to close off the nasopharynx to prevent ingested materials from entering the nasal cavity. In addition, auditory (Eustachian) tubes that connect to each middle ear cavity open into the nasopharynx. This connection is why colds often lead to ear infections.
The oropharynx is a passageway for both air and food. The oropharynx is bordered superiorly by the nasopharynx and anteriorly by the oral cavity. The fauces is the opening at the connection between the oral cavity and the oropharynx. As the nasopharynx becomes the oropharynx, the epithelium changes from pseudostratified ciliated columnar epithelium to stratified squamous epithelium. The oropharynx contains two distinct sets of tonsils, the palatine and lingual tonsils. A palatine tonsil is one of a pair of structures located laterally in the oropharynx in the area of the fauces. The lingual tonsil is located at the base of the tongue. Similar to the pharyngeal tonsil, the palatine and lingual tonsils are composed of lymphoid tissue, and trap and destroy pathogens entering the body through the oral or nasal cavities.
The laryngopharynx is inferior to the oropharynx and posterior to the larynx. It continues the route for ingested material and air until its inferior end, where the digestive and respiratory systems diverge. The stratified squamous epithelium of the oropharynx is continuous with the laryngopharynx. Anteriorly, the laryngopharynx opens into the larynx, whereas posteriorly, it enters the esophagus.
Larynx
The larynx is a cartilaginous structure inferior to the laryngopharynx that connects the pharynx to the trachea and helps regulate the volume of air that enters and leaves the lungs (Figure 22.7). The structure of the larynx is formed by several pieces of cartilage. Three large cartilage pieces—the thyroid cartilage (anterior), epiglottis (superior), and cricoid cartilage (inferior)—form the major structure of the larynx. The thyroid cartilage is the largest piece of cartilage that makes up the larynx. The thyroid cartilage consists of the laryngeal prominence, or “Adam’s apple,” which tends to be more prominent in males. The thick cricoid cartilage forms a ring, with a wide posterior region and a thinner anterior region. Three smaller, paired cartilages—the arytenoids, corniculates, and cuneiforms—attach to the epiglottis and the vocal cords and muscle that help move the vocal cords to produce speech.
Figure 22.7 Larynx The larynx extends from the laryngopharynx and the hyoid bone to the trachea.
The epiglottis, attached to the thyroid cartilage, is a very flexible piece of elastic cartilage that covers the opening of the trachea (see Figure 22.4). When in the “closed” position, the unattached end of the epiglottis rests on the glottis. The glottis is composed of the vestibular folds, the true vocal cords, and the space between these folds (Figure 22.8). A vestibular fold, or false vocal cord, is one of a pair of folded sections of mucous membrane. A true vocal cord is one of the white, membranous folds attached by muscle to the thyroid and arytenoid cartilages of the larynx on their outer edges. The inner edges of the true vocal cords are free, allowing oscillation to produce sound. The size of the membranous folds of the true vocal cords differs between individuals, producing voices with different pitch ranges. Folds in males tend to be larger than those in females, which create a deeper voice. The act of swallowing causes the pharynx and larynx to lift upward, allowing the pharynx to expand and the epiglottis of the larynx to swing downward, closing the opening to the trachea. These movements produce a larger area for food to pass through, while preventing food and beverages from entering the trachea.
Figure 22.8 Vocal Cords The true vocal cords and vestibular folds of the larynx are viewed inferiorly from the laryngopharynx.
Continuous with the laryngopharynx, the superior portion of the larynx is lined with stratified squamous epithelium, transitioning into pseudostratified ciliated columnar epithelium that contains goblet cells. Similar to the nasal cavity and nasopharynx, this specialized epithelium produces mucus to trap debris and pathogens as they enter the trachea. The cilia beat the mucus upward towards the laryngopharynx, where it can be swallowed down the esophagus.
Trachea
The trachea (windpipe) extends from the larynx toward the lungs (Figure 22.9a). The trachea is formed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage that are connected by dense connective tissue. The trachealis muscle and elastic connective tissue together form the fibroelastic membrane, a flexible membrane that closes the posterior surface of the trachea, connecting the C-shaped cartilages. The fibroelastic membrane allows the trachea to stretch and expand slightly during inhalation and exhalation, whereas the rings of cartilage provide structural support and prevent the trachea from collapsing. In addition, the trachealis muscle can be contracted to force air through the trachea during exhalation. The trachea is lined with pseudostratified ciliated columnar epithelium, which is continuous with the larynx. The esophagus borders the trachea posteriorly.
Figure 22.9 Trachea (a) The tracheal tube is formed by stacked, C-shaped pieces of hyaline cartilage. (b) The layer visible in this cross-section of tracheal wall tissue between the hyaline cartilage and the lumen of the trachea is the mucosa, which is composed of pseudostratified ciliated columnar epithelium that contains goblet cells. LM × 1220. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)
Bronchial Tree
The trachea branches into the right and left primary bronchi at the carina. These bronchi are also lined by pseudostratified ciliated columnar epithelium containing mucus-producing goblet cells (Figure 22.9b). The carina is a raised structure that contains specialized nervous tissue that induces violent coughing if a foreign body, such as food, is present. Rings of cartilage, similar to those of the trachea, support the structure of the bronchi and prevent their collapse. The primary bronchi enter the lungs at the hilum, a concave region where blood vessels, lymphatic vessels, and nerves also enter the lungs. The bronchi continue to branch into bronchial a tree. A bronchial tree (or respiratory tree) is the collective term used for these multiple-branched bronchi. The main function of the bronchi, like other conducting zone structures, is to provide a passageway for air to move into and out of each lung. In addition, the mucous membrane traps debris and pathogens.
A bronchiole branches from the tertiary bronchi. Bronchioles, which are about 1 mm in diameter, further branch until they become the tiny terminal bronchioles, which lead to the structures of gas exchange. There are more than 1000 terminal bronchioles in each lung. The muscular walls of the bronchioles do not contain cartilage like those of the bronchi. This muscular wall can change the size of the tubing to increase or decrease airflow through the tube.
Respiratory Zone
In contrast to the conducting zone, the respiratory zone includes structures that are directly involved in gas exchange. The respiratory zone begins where the terminal bronchioles join a respiratory bronchiole, the smallest type of bronchiole (Figure 22.10), which then leads to an alveolar duct, opening into a cluster of alveoli.
Figure 22.10 Respiratory Zone Bronchioles lead to alveolar sacs in the respiratory zone, where gas exchange occurs.
Alveoli
An alveolar duct is a tube composed of smooth muscle and connective tissue, which opens into a cluster of alveoli. An alveolus is one of the many small, grape-like sacs that are attached to the alveolar ducts.
An alveolar sac is a cluster of many individual alveoli that are responsible for gas exchange. An alveolus is approximately 200 μm in diameter with elastic walls that allow the alveolus to stretch during air intake, which greatly increases the surface area available for gas exchange. Alveoli are connected to their neighbors by alveolar pores, which help maintain equal air pressure throughout the alveoli and lung (Figure 22.11).
Figure 22.11 Structures of the Respiratory Zone (a) The alveolus is responsible for gas exchange. (b) A micrograph shows the alveolar structures within lung tissue. LM × 178. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)
The alveolar wall consists of three major cell types: type I alveolar cells, type II alveolar cells, and alveolar macrophages. A type I alveolar cell is a squamous epithelial cell of the alveoli, which constitute up to 97 percent of the alveolar surface area. These cells are about 25 nm thick and are highly permeable to gases. A type II alveolar cell is interspersed among the type I cells and secretes pulmonary surfactant, a substance composed of phospholipids and proteins that reduces the surface tension of the alveoli. Roaming around the alveolar wall is the alveolar macrophage, a phagocytic cell of the immune system that removes debris and pathogens that have reached the alveoli.
The simple squamous epithelium formed by type I alveolar cells is attached to a thin, elastic basement membrane. This epithelium is extremely thin and borders the endothelial membrane of capillaries. Taken together, the alveoli and capillary membranes form a respiratory membrane that is approximately 0.5 μm (micrometers) thick. The respiratory membrane allows gases to cross by simple diffusion, allowing oxygen to be picked up by the blood for transport and CO2 to be released into the air of the alveoli.
DISEASES OF THE...
Respiratory System: Asthma
Asthma is common condition that affects the lungs in both adults and children. Approximately 8.2 percent of adults (18.7 million) and 9.4 percent of children (7 million) in the United States suffer from asthma. In addition, asthma is the most frequent cause of hospitalization in children.
Asthma is a chronic disease characterized by inflammation and edema of the airway, and bronchospasms (that is, constriction of the bronchioles), which can inhibit air from entering the lungs. In addition, excessive mucus secretion can occur, which further contributes to airway occlusion (Figure 22.12). Cells of the immune system, such as eosinophils and mononuclear cells, may also be involved in infiltrating the walls of the bronchi and bronchioles.
Bronchospasms occur periodically and lead to an “asthma attack.” An attack may be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or by exercise and stress.
Figure 22.12 Normal and Bronchial Asthma Tissues (a) Normal lung tissue does not have the characteristics of lung tissue during (b) an asthma attack, which include thickened mucosa, increased mucus-producing goblet cells, and eosinophil infiltrates.
Symptoms of an asthma attack involve coughing, shortness of breath, wheezing, and tightness of the chest. Symptoms of a severe asthma attack that requires immediate medical attention would include difficulty breathing that results in blue (cyanotic) lips or face, confusion, drowsiness, a rapid pulse, sweating, and severe anxiety. The severity of the condition, frequency of attacks, and identified triggers influence the type of medication that an individual may require. Longer-term treatments are used for those with more severe asthma. Short-term, fast-acting drugs that are used to treat an asthma attack are typically administered via an inhaler. For young children or individuals who have difficulty using an inhaler, asthma medications can be administered via a nebulizer.
In many cases, the underlying cause of the condition is unknown. However, recent research has demonstrated that certain viruses, such as human rhinovirus C (HRVC), and the bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae that are contracted in infancy or early childhood, may contribute to the development of many cases of asthma.
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The Lungs
- Describe the overall function of the lung
- Summarize the blood flow pattern associated with the lungs
- Outline the anatomy of the blood supply to the lungs
- Describe the pleura of the lungs and their function
A major organ of the respiratory system, each lung houses structures of both the conducting and respiratory zones. The main function of the lungs is to perform the exchange of oxygen and carbon dioxide with air from the atmosphere. To this end, the lungs exchange respiratory gases across a very large epithelial surface area—about 70 square meters—that is highly permeable to gases.
Gross Anatomy of the Lungs
The lungs are pyramid-shaped, paired organs that are connected to the trachea by the right and left bronchi; on the inferior surface, the lungs are bordered by the diaphragm. The diaphragm is the flat, dome-shaped muscle located at the base of the lungs and thoracic cavity. The lungs are enclosed by the pleurae, which are attached to the mediastinum. The right lung is shorter and wider than the left lung, and the left lung occupies a smaller volume than the right. The cardiac notch is an indentation on the surface of the left lung, and it allows space for the heart (Figure 22.13). The apex of the lung is the superior region, whereas the base is the opposite region near the diaphragm. The costal surface of the lung borders the ribs. The mediastinal surface faces the midline.
Figure 22.13 Gross Anatomy of the Lungs
Each lung is composed of smaller units called lobes. Fissures separate these lobes from each other. The right lung consists of three lobes: the superior, middle, and inferior lobes. The left lung consists of two lobes: the superior and inferior lobes. A bronchopulmonary segment is a division of a lobe, and each lobe houses multiple bronchopulmonary segments. Each segment receives air from its own tertiary bronchus and is supplied with blood by its own artery. Some diseases of the lungs typically affect one or more bronchopulmonary segments, and in some cases, the diseased segments can be surgically removed with little influence on neighboring segments. A pulmonary lobule is a subdivision formed as the bronchi branch into bronchioles. Each lobule receives its own large bronchiole that has multiple branches. An interlobular septum is a wall, composed of connective tissue, which separates lobules from one another.
Blood Supply and Nervous Innervation of the Lungs
The blood supply of the lungs plays an important role in gas exchange and serves as a transport system for gases throughout the body. In addition, innervation by the both the parasympathetic and sympathetic nervous systems provides an important level of control through dilation and constriction of the airway.
Blood Supply
The major function of the lungs is to perform gas exchange, which requires blood from the pulmonary circulation. This blood supply contains deoxygenated blood and travels to the lungs where erythrocytes, also known as red blood cells, pick up oxygen to be transported to tissues throughout the body. The pulmonary artery is an artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli. The pulmonary artery branches multiple times as it follows the bronchi, and each branch becomes progressively smaller in diameter. One arteriole and an accompanying venule supply and drain one pulmonary lobule. As they near the alveoli, the pulmonary arteries become the pulmonary capillary network. The pulmonary capillary network consists of tiny vessels with very thin walls that lack smooth muscle fibers. The capillaries branch and follow the bronchioles and structure of the alveoli. It is at this point that the capillary wall meets the alveolar wall, creating the respiratory membrane. Once the blood is oxygenated, it drains from the alveoli by way of multiple pulmonary veins, which exit the lungs through the hilum.
Nervous Innervation
Dilation and constriction of the airway are achieved through nervous control by the parasympathetic and sympathetic nervous systems. The parasympathetic system causes bronchoconstriction, whereas the sympathetic nervous system stimulates bronchodilation. Reflexes such as coughing, and the ability of the lungs to regulate oxygen and carbon dioxide levels, also result from this autonomic nervous system control. Sensory nerve fibers arise from the vagus nerve, and from the second to fifth thoracic ganglia. The pulmonary plexus is a region on the lung root formed by the entrance of the nerves at the hilum. The nerves then follow the bronchi in the lungs and branch to innervate muscle fibers, glands, and blood vessels.
Pleura of the Lungs
Each lung is enclosed within a cavity that is surrounded by the pleura. The pleura (plural = pleurae) is a serous membrane that surrounds the lung. The right and left pleurae, which enclose the right and left lungs, respectively, are separated by the mediastinum. The pleurae consist of two layers. The visceral pleura is the layer that is superficial to the lungs, and extends into and lines the lung fissures (Figure 22.14). In contrast, the parietal pleura is the outer layer that connects to the thoracic wall, the mediastinum, and the diaphragm. The visceral and parietal pleurae connect to each other at the hilum. The pleural cavity is the space between the visceral and parietal layers.
Figure 22.14 Parietal and Visceral Pleurae of the Lungs
The pleurae perform two major functions: They produce pleural fluid and create cavities that separate the major organs. Pleural fluid is secreted by mesothelial cells from both pleural layers and acts to lubricate their surfaces. This lubrication reduces friction between the two layers to prevent trauma during breathing, and creates surface tension that helps maintain the position of the lungs against the thoracic wall. This adhesive characteristic of the pleural fluid causes the lungs to enlarge when the thoracic wall expands during ventilation, allowing the lungs to fill with air. The pleurae also create a division between major organs that prevents interference due to the movement of the organs, while preventing the spread of infection.
EVERYDAY CONNECTION
The Effects of Second-Hand Tobacco Smoke
The burning of a tobacco cigarette creates multiple chemical compounds that are released through mainstream smoke, which is inhaled by the smoker, and through sidestream smoke, which is the smoke that is given off by the burning cigarette. Second-hand smoke, which is a combination of sidestream smoke and the mainstream smoke that is exhaled by the smoker, has been demonstrated by numerous scientific studies to cause disease. At least 40 chemicals in sidestream smoke have been identified that negatively impact human health, leading to the development of cancer or other conditions, such as immune system dysfunction, liver toxicity, cardiac arrhythmias, pulmonary edema, and neurological dysfunction. Furthermore, second-hand smoke has been found to harbor at least 250 compounds that are known to be toxic, carcinogenic, or both. Some major classes of carcinogens in second-hand smoke are polyaromatic hydrocarbons (PAHs), N-nitrosamines, aromatic amines, formaldehyde, and acetaldehyde.
Tobacco and second-hand smoke are considered to be carcinogenic. Exposure to second-hand smoke can cause lung cancer in individuals who are not tobacco users themselves. It is estimated that the risk of developing lung cancer is increased by up to 30 percent in nonsmokers who live with an individual who smokes in the house, as compared to nonsmokers who are not regularly exposed to second-hand smoke. Children are especially affected by second-hand smoke. Children who live with an individual who smokes inside the home have a larger number of lower respiratory infections, which are associated with hospitalizations, and higher risk of sudden infant death syndrome (SIDS). Second-hand smoke in the home has also been linked to a greater number of ear infections in children, as well as worsening symptoms of asthma.
The Process of Breathing
- Describe the mechanisms that drive breathing
- Discuss how pressure, volume, and resistance are related
- List the steps involved in pulmonary ventilation
- Discuss the physical factors related to breathing
- Discuss the meaning of respiratory volume and capacities
- Define respiratory rate
- Outline the mechanisms behind the control of breathing
- Describe the respiratory centers of the medulla oblongata
- Describe the respiratory centers of the pons
- Discuss factors that can influence the respiratory rate
Pulmonary ventilation is the act of breathing, which can be described as the movement of air into and out of the lungs. The major mechanisms that drive pulmonary ventilation are atmospheric pressure (Patm); the air pressure within the alveoli, called intra-alveolar pressure (Palv); and the pressure within the pleural cavity, called intrapleural pressure (Pip).
Mechanisms of Breathing
The intra-alveolar and intrapleural pressures are dependent on certain physical features of the lung. However, the ability to breathe—to have air enter the lungs during inspiration and air leave the lungs during expiration—is dependent on the air pressure of the atmosphere and the air pressure within the lungs.
Pressure Relationships
Inspiration (or inhalation) and expiration (or exhalation) are dependent on the differences in pressure between the atmosphere and the lungs. In a gas, pressure is a force created by the movement of gas molecules that are confined. For example, a certain number of gas molecules in a two-liter container has more room than the same number of gas molecules in a one-liter container (Figure 22.15). In this case, the force exerted by the movement of the gas molecules against the walls of the two-liter container is lower than the force exerted by the gas molecules in the one-liter container. Therefore, the pressure is lower in the two-liter container and higher in the one-liter container. At a constant temperature, changing the volume occupied by the gas changes the pressure, as does changing the number of gas molecules. Boyle’s law describes the relationship between volume and pressure in a gas at a constant temperature. Boyle discovered that the pressure of a gas is inversely proportional to its volume: If volume increases, pressure decreases. Likewise, if volume decreases, pressure increases. Pressure and volume are inversely related (P = k/V). Therefore, the pressure in the one-liter container (one-half the volume of the two-liter container) would be twice the pressure in the two-liter container. Boyle’s law is expressed by the following formula:
𝑃1𝑉1=𝑃2𝑉2P1V1=P2V2
In this formula, P1 represents the initial pressure and V1 represents the initial volume, whereas the final pressure and volume are represented by P2 and V2, respectively. If the two- and one-liter containers were connected by a tube and the volume of one of the containers were changed, then the gases would move from higher pressure (lower volume) to lower pressure (higher volume).
Figure 22.15 Boyle's Law In a gas, pressure increases as volume decreases.
Pulmonary ventilation is dependent on three types of pressure: atmospheric, intra-alveolar, and intrapleural. Atmospheric pressureis the amount of force that is exerted by gases in the air surrounding any given surface, such as the body. Atmospheric pressure can be expressed in terms of the unit atmosphere, abbreviated atm, or in millimeters of mercury (mm Hg). One atm is equal to 760 mm Hg, which is the atmospheric pressure at sea level. Typically, for respiration, other pressure values are discussed in relation to atmospheric pressure. Therefore, negative pressure is pressure lower than the atmospheric pressure, whereas positive pressure is pressure that it is greater than the atmospheric pressure. A pressure that is equal to the atmospheric pressure is expressed as zero.
Intra-alveolar pressure (intrapulmonary pressure) is the pressure of the air within the alveoli, which changes during the different phases of breathing (Figure 22.16). Because the alveoli are connected to the atmosphere via the tubing of the airways (similar to the two- and one-liter containers in the example above), the intrapulmonary pressure of the alveoli always equalizes with the atmospheric pressure.
Figure 22.16 Intrapulmonary and Intrapleural Pressure Relationships Intra-alveolar pressure changes during the different phases of the cycle. It equalizes at 760 mm Hg but does not remain at 760 mm Hg.
Intrapleural pressure is the pressure of the air within the pleural cavity, between the visceral and parietal pleurae. Similar to intra-alveolar pressure, intrapleural pressure also changes during the different phases of breathing. However, due to certain characteristics of the lungs, the intrapleural pressure is always lower than, or negative to, the intra-alveolar pressure (and therefore also to atmospheric pressure). Although it fluctuates during inspiration and expiration, intrapleural pressure remains approximately –4 mm Hg throughout the breathing cycle.
Competing forces within the thorax cause the formation of the negative intrapleural pressure. One of these forces relates to the elasticity of the lungs themselves—elastic tissue pulls the lungs inward, away from the thoracic wall. Surface tension of alveolar fluid, which is mostly water, also creates an inward pull of the lung tissue. This inward tension from the lungs is countered by opposing forces from the pleural fluid and thoracic wall. Surface tension within the pleural cavity pulls the lungs outward. Too much or too little pleural fluid would hinder the creation of the negative intrapleural pressure; therefore, the level must be closely monitored by the mesothelial cells and drained by the lymphatic system. Since the parietal pleura is attached to the thoracic wall, the natural elasticity of the chest wall opposes the inward pull of the lungs. Ultimately, the outward pull is slightly greater than the inward pull, creating the –4 mm Hg intrapleural pressure relative to the intra-alveolar pressure. Transpulmonary pressure is the difference between the intrapleural and intra-alveolar pressures, and it determines the size of the lungs. A higher transpulmonary pressure corresponds to a larger lung.
Physical Factors Affecting Ventilation
In addition to the differences in pressures, breathing is also dependent upon the contraction and relaxation of muscle fibers of both the diaphragm and thorax. The lungs themselves are passive during breathing, meaning they are not involved in creating the movement that helps inspiration and expiration. This is because of the adhesive nature of the pleural fluid, which allows the lungs to be pulled outward when the thoracic wall moves during inspiration. The recoil of the thoracic wall during expiration causes compression of the lungs. Contraction and relaxation of the diaphragm and intercostals muscles (found between the ribs) cause most of the pressure changes that result in inspiration and expiration. These muscle movements and subsequent pressure changes cause air to either rush in or be forced out of the lungs.
Other characteristics of the lungs influence the effort that must be expended to ventilate. Resistance is a force that slows motion, in this case, the flow of gases. The size of the airway is the primary factor affecting resistance. A small tubular diameter forces air through a smaller space, causing more collisions of air molecules with the walls of the airways. The following formula helps to describe the relationship between airway resistance and pressure changes:
𝐹=∆𝑃/𝑅F=∆P/RAs noted earlier, there is surface tension within the alveoli caused by water present in the lining of the alveoli. This surface tension tends to inhibit expansion of the alveoli. However, pulmonary surfactant secreted by type II alveolar cells mixes with that water and helps reduce this surface tension. Without pulmonary surfactant, the alveoli would collapse during expiration.
Thoracic wall compliance is the ability of the thoracic wall to stretch while under pressure. This can also affect the effort expended in the process of breathing. In order for inspiration to occur, the thoracic cavity must expand. The expansion of the thoracic cavity directly influences the capacity of the lungs to expand. If the tissues of the thoracic wall are not very compliant, it will be difficult to expand the thorax to increase the size of the lungs.
Pulmonary Ventilation
The difference in pressures drives pulmonary ventilation because air flows down a pressure gradient, that is, air flows from an area of higher pressure to an area of lower pressure. Air flows into the lungs largely due to a difference in pressure; atmospheric pressure is greater than intra-alveolar pressure, and intra-alveolar pressure is greater than intrapleural pressure. Air flows out of the lungs during expiration based on the same principle; pressure within the lungs becomes greater than the atmospheric pressure.
Pulmonary ventilation comprises two major steps: inspiration and expiration. Inspiration is the process that causes air to enter the lungs, and expiration is the process that causes air to leave the lungs (Figure 22.17). A respiratory cycle is one sequence of inspiration and expiration. In general, two muscle groups are used during normal inspiration: the diaphragm and the external intercostal muscles. Additional muscles can be used if a bigger breath is required. When the diaphragm contracts, it moves inferiorly toward the abdominal cavity, creating a larger thoracic cavity and more space for the lungs. Contraction of the external intercostal muscles moves the ribs upward and outward, causing the rib cage to expand, which increases the volume of the thoracic cavity. Due to the adhesive force of the pleural fluid, the expansion of the thoracic cavity forces the lungs to stretch and expand as well. This increase in volume leads to a decrease in intra-alveolar pressure, creating a pressure lower than atmospheric pressure. As a result, a pressure gradient is created that drives air into the lungs.
Figure 22.17 Inspiration and Expiration Inspiration and expiration occur due to the expansion and contraction of the thoracic cavity, respectively.
The process of normal expiration is passive, meaning that energy is not required to push air out of the lungs. Instead, the elasticity of the lung tissue causes the lung to recoil, as the diaphragm and intercostal muscles relax following inspiration. In turn, the thoracic cavity and lungs decrease in volume, causing an increase in intrapulmonary pressure. The intrapulmonary pressure rises above atmospheric pressure, creating a pressure gradient that causes air to leave the lungs.
There are different types, or modes, of breathing that require a slightly different process to allow inspiration and expiration. Quiet breathing, also known as eupnea, is a mode of breathing that occurs at rest and does not require the cognitive thought of the individual. During quiet breathing, the diaphragm and external intercostals must contract.
A deep breath, called diaphragmatic breathing, requires the diaphragm to contract. As the diaphragm relaxes, air passively leaves the lungs. A shallow breath, called costal breathing, requires contraction of the intercostal muscles. As the intercostal muscles relax, air passively leaves the lungs.
In contrast, forced breathing, also known as hyperpnea, is a mode of breathing that can occur during exercise or actions that require the active manipulation of breathing, such as singing. During forced breathing, inspiration and expiration both occur due to muscle contractions. In addition to the contraction of the diaphragm and intercostal muscles, other accessory muscles must also contract. During forced inspiration, muscles of the neck, including the scalenes, contract and lift the thoracic wall, increasing lung volume. During forced expiration, accessory muscles of the abdomen, including the obliques, contract, forcing abdominal organs upward against the diaphragm. This helps to push the diaphragm further into the thorax, pushing more air out. In addition, accessory muscles (primarily the internal intercostals) help to compress the rib cage, which also reduces the volume of the thoracic cavity.
Respiratory Volumes and Capacities
Respiratory volume is the term used for various volumes of air moved by or associated with the lungs at a given point in the respiratory cycle. There are four major types of respiratory volumes: tidal, residual, inspiratory reserve, and expiratory reserve (Figure 22.18). Tidal volume (TV) is the amount of air that normally enters the lungs during quiet breathing, which is about 500 milliliters. Expiratory reserve volume (ERV) is the amount of air you can forcefully exhale past a normal tidal expiration, up to 1200 milliliters for men. Inspiratory reserve volume (IRV) is produced by a deep inhalation, past a tidal inspiration. This is the extra volume that can be brought into the lungs during a forced inspiration. Residual volume (RV) is the air left in the lungs if you exhale as much air as possible. The residual volume makes breathing easier by preventing the alveoli from collapsing. Respiratory volume is dependent on a variety of factors, and measuring the different types of respiratory volumes can provide important clues about a person’s respiratory health (Figure 22.19).
Figure 22.18 Respiratory Volumes and Capacities These two graphs show (a) respiratory volumes and (b) the combination of volumes that results in respiratory capacity.
Figure 22.19 Pulmonary Function Testing
Respiratory capacity is the combination of two or more selected volumes, which further describes the amount of air in the lungs during a given time. For example, total lung capacity (TLC) is the sum of all of the lung volumes (TV, ERV, IRV, and RV), which represents the total amount of air a person can hold in the lungs after a forceful inhalation. TLC is about 6000 mL air for men, and about 4200 mL for women. Vital capacity (VC) is the amount of air a person can move into or out of his or her lungs, and is the sum of all of the volumes except residual volume (TV, ERV, and IRV), which is between 4000 and 5000 milliliters. Inspiratory capacity (IC) is the maximum amount of air that can be inhaled past a normal tidal expiration, is the sum of the tidal volume and inspiratory reserve volume. On the other hand, the functional residual capacity (FRC) is the amount of air that remains in the lung after a normal tidal expiration; it is the sum of expiratory reserve volume and residual volume (see Figure 22.18).
INTERACTIVE LINK
Watch this video to learn more about lung volumes and spirometers. Explain how spirometry test results can be used to diagnose respiratory diseases or determine the effectiveness of disease treatment.
In addition to the air that creates respiratory volumes, the respiratory system also contains anatomical dead space, which is air that is present in the airway that never reaches the alveoli and therefore never participates in gas exchange. Alveolar dead spaceinvolves air found within alveoli that are unable to function, such as those affected by disease or abnormal blood flow. Total dead space is the anatomical dead space and alveolar dead space together, and represents all of the air in the respiratory system that is not being used in the gas exchange process.
Respiratory Rate and Control of Ventilation
Breathing usually occurs without thought, although at times you can consciously control it, such as when you swim under water, sing a song, or blow bubbles. The respiratory rate is the total number of breaths, or respiratory cycles, that occur each minute. Respiratory rate can be an important indicator of disease, as the rate may increase or decrease during an illness or in a disease condition. The respiratory rate is controlled by the respiratory center located within the medulla oblongata in the brain, which responds primarily to changes in carbon dioxide, oxygen, and pH levels in the blood.
The normal respiratory rate of a child decreases from birth to adolescence. A child under 1 year of age has a normal respiratory rate between 30 and 60 breaths per minute, but by the time a child is about 10 years old, the normal rate is closer to 18 to 30. By adolescence, the normal respiratory rate is similar to that of adults, 12 to 18 breaths per minute.
Ventilation Control Centers
The control of ventilation is a complex interplay of multiple regions in the brain that signal the muscles used in pulmonary ventilation to contract (Table 22.1). The result is typically a rhythmic, consistent ventilation rate that provides the body with sufficient amounts of oxygen, while adequately removing carbon dioxide.
Summary of Ventilation Regulation
| System component | Function |
|---|---|
| Medullary respiratory renter | Sets the basic rhythm of breathing |
| Ventral respiratory group (VRG) | Generates the breathing rhythm and integrates data coming into the medulla |
| Dorsal respiratory group (DRG) | Integrates input from the stretch receptors and the chemoreceptors in the periphery |
| Pontine respiratory group (PRG) | Influences and modifies the medulla oblongata’s functions |
| Aortic body | Monitors blood PCO2, PO2, and pH |
| Carotid body | Monitors blood PCO2, PO2, and pH |
| Hypothalamus | Monitors emotional state and body temperature |
| Cortical areas of the brain | Control voluntary breathing |
| Proprioceptors | Send impulses regarding joint and muscle movements |
| Pulmonary irritant reflexes | Protect the respiratory zones of the system from foreign material |
| Inflation reflex | Protects the lungs from over-inflating |
Table 22.1
Neurons that innervate the muscles of the respiratory system are responsible for controlling and regulating pulmonary ventilation. The major brain centers involved in pulmonary ventilation are the medulla oblongata and the pontine respiratory group (Figure 22.20).
Figure 22.20 Respiratory Centers of the Brain
The medulla oblongata contains the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). The DRG is involved in maintaining a constant breathing rhythm by stimulating the diaphragm and intercostal muscles to contract, resulting in inspiration. When activity in the DRG ceases, it no longer stimulates the diaphragm and intercostals to contract, allowing them to relax, resulting in expiration. The VRG is involved in forced breathing, as the neurons in the VRG stimulate the accessory muscles involved in forced breathing to contract, resulting in forced inspiration. The VRG also stimulates the accessory muscles involved in forced expiration to contract.
The second respiratory center of the brain is located within the pons, called the pontine respiratory group, and consists of the apneustic and pneumotaxic centers. The apneustic center is a double cluster of neuronal cell bodies that stimulate neurons in the DRG, controlling the depth of inspiration, particularly for deep breathing. The pneumotaxic center is a network of neurons that inhibits the activity of neurons in the DRG, allowing relaxation after inspiration, and thus controlling the overall rate.
Factors That Affect the Rate and Depth of Respiration
The respiratory rate and the depth of inspiration are regulated by the medulla oblongata and pons; however, these regions of the brain do so in response to systemic stimuli. It is a dose-response, negative-feedback relationship in which the greater the stimulus, the greater the response. Thus, increasing stimuli results in forced breathing. Multiple systemic factors are involved in stimulating the brain to produce pulmonary ventilation.
The major factor that stimulates the medulla oblongata and pons to produce respiration is surprisingly not oxygen concentration, but rather the concentration of carbon dioxide in the blood. As you recall, carbon dioxide is a waste product of cellular respiration and can be toxic. Concentrations of chemicals are sensed by chemoreceptors. A central chemoreceptor is one of the specialized receptors that are located in the brain and brainstem, whereas a peripheral chemoreceptor is one of the specialized receptors located in the carotid arteries and aortic arch. Concentration changes in certain substances, such as carbon dioxide or hydrogen ions, stimulate these receptors, which in turn signal the respiration centers of the brain. In the case of carbon dioxide, as the concentration of CO2 in the blood increases, it readily diffuses across the blood-brain barrier, where it collects in the extracellular fluid. As will be explained in more detail later, increased carbon dioxide levels lead to increased levels of hydrogen ions, decreasing pH. The increase in hydrogen ions in the brain triggers the central chemoreceptors to stimulate the respiratory centers to initiate contraction of the diaphragm and intercostal muscles. As a result, the rate and depth of respiration increase, allowing more carbon dioxide to be expelled, which brings more air into and out of the lungs promoting a reduction in the blood levels of carbon dioxide, and therefore hydrogen ions, in the blood. In contrast, low levels of carbon dioxide in the blood cause low levels of hydrogen ions in the brain, leading to a decrease in the rate and depth of pulmonary ventilation, producing shallow, slow breathing.
Another factor involved in influencing the respiratory activity of the brain is systemic arterial concentrations of hydrogen ions. Increasing carbon dioxide levels can lead to increased H+ levels, as mentioned above, as well as other metabolic activities, such as lactic acid accumulation after strenuous exercise. Peripheral chemoreceptors of the aortic arch and carotid arteries sense arterial levels of hydrogen ions. When peripheral chemoreceptors sense decreasing, or more acidic, pH levels, they stimulate an increase in ventilation to remove carbon dioxide from the blood at a quicker rate. Removal of carbon dioxide from the blood helps to reduce hydrogen ions, thus increasing systemic pH.
Blood levels of oxygen are also important in influencing respiratory rate. The peripheral chemoreceptors are responsible for sensing large changes in blood oxygen levels. If blood oxygen levels become quite low—about 60 mm Hg or less—then peripheral chemoreceptors stimulate an increase in respiratory activity. The chemoreceptors are only able to sense dissolved oxygen molecules, not the oxygen that is bound to hemoglobin. As you recall, the majority of oxygen is bound by hemoglobin; when dissolved levels of oxygen drop, hemoglobin releases oxygen. Therefore, a large drop in oxygen levels is required to stimulate the chemoreceptors of the aortic arch and carotid arteries.
The hypothalamus and other brain regions associated with the limbic system also play roles in influencing the regulation of breathing by interacting with the respiratory centers. The hypothalamus and other regions associated with the limbic system are involved in regulating respiration in response to emotions, pain, and temperature. For example, an increase in body temperature causes an increase in respiratory rate. Feeling excited or the fight-or-flight response will also result in an increase in respiratory rate.
DISORDERS OF THE...
Respiratory System: Sleep Apnea
Sleep apnea is a chronic disorder that can occur in children or adults, and is characterized by the cessation of breathing during sleep. These episodes may last for several seconds or several minutes, and may differ in the frequency with which they are experienced. Sleep apnea leads to poor sleep, which is reflected in the symptoms of fatigue, evening napping, irritability, memory problems, and morning headaches. In addition, many individuals with sleep apnea experience a dry throat in the morning after waking from sleep, which may be due to excessive snoring.
There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea. Obstructive sleep apnea is caused by an obstruction of the airway during sleep, which can occur at different points in the airway, depending on the underlying cause of the obstruction. For example, the tongue and throat muscles of some individuals with obstructive sleep apnea may relax excessively, causing the muscles to push into the airway. Another example is obesity, which is a known risk factor for sleep apnea, as excess adipose tissue in the neck region can push the soft tissues towards the lumen of the airway, causing the trachea to narrow.
In central sleep apnea, the respiratory centers of the brain do not respond properly to rising carbon dioxide levels and therefore do not stimulate the contraction of the diaphragm and intercostal muscles regularly. As a result, inspiration does not occur and breathing stops for a short period. In some cases, the cause of central sleep apnea is unknown. However, some medical conditions, such as stroke and congestive heart failure, may cause damage to the pons or medulla oblongata. In addition, some pharmacologic agents, such as morphine, can affect the respiratory centers, causing a decrease in the respiratory rate. The symptoms of central sleep apnea are similar to those of obstructive sleep apnea.
A diagnosis of sleep apnea is usually done during a sleep study, where the patient is monitored in a sleep laboratory for several nights. The patient’s blood oxygen levels, heart rate, respiratory rate, and blood pressure are monitored, as are brain activity and the volume of air that is inhaled and exhaled. Treatment of sleep apnea commonly includes the use of a device called a continuous positive airway pressure (CPAP) machine during sleep. The CPAP machine has a mask that covers the nose, or the nose and mouth, and forces air into the airway at regular intervals. This pressurized air can help to gently force the airway to remain open, allowing more normal ventilation to occur. Other treatments include lifestyle changes to decrease weight, eliminate alcohol and other sleep apnea–promoting drugs, and changes in sleep position. In addition to these treatments, patients with central sleep apnea may need supplemental oxygen during sleep.
Gas Exchange
- Compare the composition of atmospheric air and alveolar air
- Describe the mechanisms that drive gas exchange
- Discuss the importance of sufficient ventilation and perfusion, and how the body adapts when they are insufficient
- Discuss the process of external respiration
- Describe the process of internal respiration
The purpose of the respiratory system is to perform gas exchange. Pulmonary ventilation provides air to the alveoli for this gas exchange process. At the respiratory membrane, where the alveolar and capillary walls meet, gases move across the membranes, with oxygen entering the bloodstream and carbon dioxide exiting. It is through this mechanism that blood is oxygenated and carbon dioxide, the waste product of cellular respiration, is removed from the body.
Gas Exchange
In order to understand the mechanisms of gas exchange in the lung, it is important to understand the underlying principles of gases and their behavior. In addition to Boyle’s law, several other gas laws help to describe the behavior of gases.
Gas Laws and Air Composition
Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure. In natural systems, gases are normally present as a mixture of different types of molecules. For example, the atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, and this gaseous mixture exerts a certain pressure referred to as atmospheric pressure (Table 22.2). Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure 22.21). Total pressure is the sum of all the partial pressures of a gaseous mixture. Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture.
Partial Pressures of Atmospheric Gases
| Gas | Percent of total composition | Partial pressure (mm Hg) |
|---|---|---|
| Nitrogen (N2) | 78.6 | 597.4 |
| Oxygen (O2) | 20.9 | 158.8 |
| Water (H2O) | 0.4 | 3.0 |
| Carbon dioxide (CO2) | 0.04 | 0.3 |
| Others | 0.06 | 0.5 |
| Total composition/total atmospheric pressure | 100% | 760.0 |
Table 22.2
Figure 22.21 Partial and Total Pressures of a Gas Partial pressure is the force exerted by a gas. The sum of the partial pressures of all the gases in a mixture equals the total pressure.
Partial pressure is extremely important in predicting the movement of gases. Recall that gases tend to equalize their pressure in two regions that are connected. A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower. In addition, the greater the partial pressure difference between the two areas, the more rapid is the movement of gases.
Solubility of Gases in Liquids
Henry’s law describes the behavior of gases when they come into contact with a liquid, such as blood. Henry’s law states that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas. The greater the partial pressure of the gas, the greater the number of gas molecules that will dissolve in the liquid. The concentration of the gas in a liquid is also dependent on the solubility of the gas in the liquid. For example, although nitrogen is present in the atmosphere, very little nitrogen dissolves into the blood, because the solubility of nitrogen in blood is very low. The exception to this occurs in scuba divers; the composition of the compressed air that divers breathe causes nitrogen to have a higher partial pressure than normal, causing it to dissolve in the blood in greater amounts than normal. Too much nitrogen in the bloodstream results in a serious condition that can be fatal if not corrected. Gas molecules establish an equilibrium between those molecules dissolved in liquid and those in air.
The composition of air in the atmosphere and in the alveoli differs. In both cases, the relative concentration of gases is nitrogen > oxygen > water vapor > carbon dioxide. The amount of water vapor present in alveolar air is greater than that in atmospheric air (Table 22.3). Recall that the respiratory system works to humidify incoming air, thereby causing the air present in the alveoli to have a greater amount of water vapor than atmospheric air. In addition, alveolar air contains a greater amount of carbon dioxide and less oxygen than atmospheric air. This is no surprise, as gas exchange removes oxygen from and adds carbon dioxide to alveolar air. Both deep and forced breathing cause the alveolar air composition to be changed more rapidly than during quiet breathing. As a result, the partial pressures of oxygen and carbon dioxide change, affecting the diffusion process that moves these materials across the membrane. This will cause oxygen to enter and carbon dioxide to leave the blood more quickly.
Composition and Partial Pressures of Alveolar Air
| Gas | Percent of total composition | Partial pressure (mm Hg) |
|---|---|---|
| Nitrogen (N2) | 74.9 | 569 |
| Oxygen (O2) | 13.7 | 104 |
| Water (H2O) | 6.2 | 40 |
| Carbon dioxide (CO2) | 5.2 | 47 |
| Total composition/total alveolar pressure | 100% | 760.0 |
Table 22.3
Ventilation and Perfusion
Two important aspects of gas exchange in the lung are ventilation and perfusion. Ventilation is the movement of air into and out of the lungs, and perfusion is the flow of blood in the pulmonary capillaries. For gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible. However, factors such as regional gravity effects on blood, blocked alveolar ducts, or disease can cause ventilation and perfusion to be imbalanced.
The partial pressure of oxygen in alveolar air is about 104 mm Hg, whereas the partial pressure of oxygenated blood in pulmonary veins is about 100 mm Hg. When ventilation is sufficient, oxygen enters the alveoli at a high rate, and the partial pressure of oxygen in the alveoli remains high. In contrast, when ventilation is insufficient, the partial pressure of oxygen in the alveoli drops. Without the large difference in partial pressure between the alveoli and the blood, oxygen does not diffuse efficiently across the respiratory membrane. The body has mechanisms that counteract this problem. In cases when ventilation is not sufficient for an alveolus, the body redirects blood flow to alveoli that are receiving sufficient ventilation. This is achieved by constricting the pulmonary arterioles that serves the dysfunctional alveolus, which redirects blood to other alveoli that have sufficient ventilation. At the same time, the pulmonary arterioles that serve alveoli receiving sufficient ventilation vasodilate, which brings in greater blood flow. Factors such as carbon dioxide, oxygen, and pH levels can all serve as stimuli for adjusting blood flow in the capillary networks associated with the alveoli.
Ventilation is regulated by the diameter of the airways, whereas perfusion is regulated by the diameter of the blood vessels. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli. A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate. As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow.
Gas Exchange
Gas exchange occurs at two sites in the body: in the lungs, where oxygen is picked up and carbon dioxide is released at the respiratory membrane, and at the tissues, where oxygen is released and carbon dioxide is picked up. External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. Internal respiration is the exchange of gases with the internal environment, and occurs in the tissues. The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes. Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs.
External Respiration
The pulmonary artery carries deoxygenated blood into the lungs from the heart, where it branches and eventually becomes the capillary network composed of pulmonary capillaries. These pulmonary capillaries create the respiratory membrane with the alveoli (Figure 22.22). As the blood is pumped through this capillary network, gas exchange occurs. Although a small amount of the oxygen is able to dissolve directly into plasma from the alveoli, most of the oxygen is picked up by erythrocytes (red blood cells) and binds to a protein called hemoglobin, a process described later in this chapter. Oxygenated hemoglobin is red, causing the overall appearance of bright red oxygenated blood, which returns to the heart through the pulmonary veins. Carbon dioxide is released in the opposite direction of oxygen, from the blood to the alveoli. Some of the carbon dioxide is returned on hemoglobin, but can also be dissolved in plasma or is present as a converted form, also explained in greater detail later in this chapter.
External respiration occurs as a function of partial pressure differences in oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries.
Figure 22.22 External Respiration In external respiration, oxygen diffuses across the respiratory membrane from the alveolus to the capillary, whereas carbon dioxide diffuses out of the capillary into the alveolus.
Although the solubility of oxygen in blood is not high, there is a drastic difference in the partial pressure of oxygen in the alveoli versus in the blood of the pulmonary capillaries. This difference is about 64 mm Hg: The partial pressure of oxygen in the alveoli is about 104 mm Hg, whereas its partial pressure in the blood of the capillary is about 40 mm Hg. This large difference in partial pressure creates a very strong pressure gradient that causes oxygen to rapidly cross the respiratory membrane from the alveoli into the blood.
The partial pressure of carbon dioxide is also different between the alveolar air and the blood of the capillary. However, the partial pressure difference is less than that of oxygen, about 5 mm Hg. The partial pressure of carbon dioxide in the blood of the capillary is about 45 mm Hg, whereas its partial pressure in the alveoli is about 40 mm Hg. However, the solubility of carbon dioxide is much greater than that of oxygen—by a factor of about 20—in both blood and alveolar fluids. As a result, the relative concentrations of oxygen and carbon dioxide that diffuse across the respiratory membrane are similar.
Internal Respiration
Internal respiration is gas exchange that occurs at the level of body tissues (Figure 22.23). Similar to external respiration, internal respiration also occurs as simple diffusion due to a partial pressure gradient. However, the partial pressure gradients are opposite of those present at the respiratory membrane. The partial pressure of oxygen in tissues is low, about 40 mm Hg, because oxygen is continuously used for cellular respiration. In contrast, the partial pressure of oxygen in the blood is about 100 mm Hg. This creates a pressure gradient that causes oxygen to dissociate from hemoglobin, diffuse out of the blood, cross the interstitial space, and enter the tissue. Hemoglobin that has little oxygen bound to it loses much of its brightness, so that blood returning to the heart is more burgundy in color.
Considering that cellular respiration continuously produces carbon dioxide, the partial pressure of carbon dioxide is lower in the blood than it is in the tissue, causing carbon dioxide to diffuse out of the tissue, cross the interstitial fluid, and enter the blood. It is then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form. By the time blood returns to the heart, the partial pressure of oxygen has returned to about 40 mm Hg, and the partial pressure of carbon dioxide has returned to about 45 mm Hg. The blood is then pumped back to the lungs to be oxygenated once again during external respiration.
Figure 22.23 Internal Respiration Oxygen diffuses out of the capillary and into cells, whereas carbon dioxide diffuses out of cells and into the capillary.
EVERYDAY CONNECTION
Hyperbaric Chamber Treatment
A type of device used in some areas of medicine that exploits the behavior of gases is hyperbaric chamber treatment. A hyperbaric chamber is a unit that can be sealed and expose a patient to either 100 percent oxygen with increased pressure or a mixture of gases that includes a higher concentration of oxygen than normal atmospheric air, also at a higher partial pressure than the atmosphere. There are two major types of chambers: monoplace and multiplace. Monoplace chambers are typically for one patient, and the staff tending to the patient observes the patient from outside of the chamber (Figure 22.24). Some facilities have special monoplace hyperbaric chambers that allow multiple patients to be treated at once, usually in a sitting or reclining position, to help ease feelings of isolation or claustrophobia. Multiplace chambers are large enough for multiple patients to be treated at one time, and the staff attending these patients is present inside the chamber. In a multiplace chamber, patients are often treated with air via a mask or hood, and the chamber is pressurized.
Figure 22.24 Hyperbaric Chamber (credit: “komunews”/flickr.com)
Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure. In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning. Exposure to and poisoning by carbon monoxide is difficult to reverse, because hemoglobin’s affinity for carbon monoxide is much stronger than its affinity for oxygen, causing carbon monoxide to replace oxygen in the blood. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream. At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen. An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair. Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures.
Transport of Gases
- Describe the principles of oxygen transport
- Describe the structure of hemoglobin
- Compare and contrast fetal and adult hemoglobin
- Describe the principles of carbon dioxide transport
The other major activity in the lungs is the process of respiration, the process of gas exchange. The function of respiration is to provide oxygen for use by body cells during cellular respiration and to eliminate carbon dioxide, a waste product of cellular respiration, from the body. In order for the exchange of oxygen and carbon dioxide to occur, both gases must be transported between the external and internal respiration sites. Although carbon dioxide is more soluble than oxygen in blood, both gases require a specialized transport system for the majority of the gas molecules to be moved between the lungs and other tissues.
Oxygen Transport in the Blood
Even though oxygen is transported via the blood, you may recall that oxygen is not very soluble in liquids. A small amount of oxygen does dissolve in the blood and is transported in the bloodstream, but it is only about 1.5% of the total amount. The majority of oxygen molecules are carried from the lungs to the body’s tissues by a specialized transport system, which relies on the erythrocyte—the red blood cell. Erythrocytes contain a metalloprotein, hemoglobin, which serves to bind oxygen molecules to the erythrocyte (Figure 22.25). Heme is the portion of hemoglobin that contains iron, and it is heme that binds oxygen. One hemoglobin molecule contains iron-containing Heme molecules, and because of this, each hemoglobin molecule is capable of carrying up to four molecules of oxygen. As oxygen diffuses across the respiratory membrane from the alveolus to the capillary, it also diffuses into the red blood cell and is bound by hemoglobin. The following reversible chemical reaction describes the production of the final product, oxyhemoglobin (Hb–O2), which is formed when oxygen binds to hemoglobin. Oxyhemoglobin is a bright red-colored molecule that contributes to the bright red color of oxygenated blood.
Hb + O2↔Hb − O2Hb + O2↔Hb − O2
In this formula, Hb represents reduced hemoglobin, that is, hemoglobin that does not have oxygen bound to it. There are multiple factors involved in how readily heme binds to and dissociates from oxygen, which will be discussed in the subsequent sections.
Figure 22.25 Erythrocyte and Hemoglobin Hemoglobin consists of four subunits, each of which contains one molecule of iron.
Function of Hemoglobin
Hemoglobin is composed of subunits, a protein structure that is referred to as a quaternary structure. Each of the four subunits that make up hemoglobin is arranged in a ring-like fashion, with an iron atom covalently bound to the heme in the center of each subunit. Binding of the first oxygen molecule causes a conformational change in hemoglobin that allows the second molecule of oxygen to bind more readily. As each molecule of oxygen is bound, it further facilitates the binding of the next molecule, until all four heme sites are occupied by oxygen. The opposite occurs as well: After the first oxygen molecule dissociates and is “dropped off” at the tissues, the next oxygen molecule dissociates more readily. When all four heme sites are occupied, the hemoglobin is said to be saturated. When one to three heme sites are occupied, the hemoglobin is said to be partially saturated. Therefore, when considering the blood as a whole, the percent of the available heme units that are bound to oxygen at a given time is called hemoglobin saturation. Hemoglobin saturation of 100 percent means that every heme unit in all of the erythrocytes of the body is bound to oxygen. In a healthy individual with normal hemoglobin levels, hemoglobin saturation generally ranges from 95 percent to 99 percent.
Oxygen Dissociation from Hemoglobin
Partial pressure is an important aspect of the binding of oxygen to and disassociation from heme. An oxygen–hemoglobin dissociation curve is a graph that describes the relationship of partial pressure to the binding of oxygen to heme and its subsequent dissociation from heme (Figure 22.26). Remember that gases travel from an area of higher partial pressure to an area of lower partial pressure. In addition, the affinity of an oxygen molecule for heme increases as more oxygen molecules are bound. Therefore, in the oxygen–hemoglobin saturation curve, as the partial pressure of oxygen increases, a proportionately greater number of oxygen molecules are bound by heme. Not surprisingly, the oxygen–hemoglobin saturation/dissociation curve also shows that the lower the partial pressure of oxygen, the fewer oxygen molecules are bound to heme. As a result, the partial pressure of oxygen plays a major role in determining the degree of binding of oxygen to heme at the site of the respiratory membrane, as well as the degree of dissociation of oxygen from heme at the site of body tissues.
Figure 22.26 Oxygen-Hemoglobin Dissociation and Effects of pH and Temperature These three graphs show (a) the relationship between the partial pressure of oxygen and hemoglobin saturation, (b) the effect of pH on the oxygen–hemoglobin dissociation curve, and (c) the effect of temperature on the oxygen–hemoglobin dissociation curve.
The mechanisms behind the oxygen–hemoglobin saturation/dissociation curve also serve as automatic control mechanisms that regulate how much oxygen is delivered to different tissues throughout the body. This is important because some tissues have a higher metabolic rate than others. Highly active tissues, such as muscle, rapidly use oxygen to produce ATP, lowering the partial pressure of oxygen in the tissue to about 20 mm Hg. The partial pressure of oxygen inside capillaries is about 100 mm Hg, so the difference between the two becomes quite high, about 80 mm Hg. As a result, a greater number of oxygen molecules dissociate from hemoglobin and enter the tissues. The reverse is true of tissues, such as adipose (body fat), which have lower metabolic rates. Because less oxygen is used by these cells, the partial pressure of oxygen within such tissues remains relatively high, resulting in fewer oxygen molecules dissociating from hemoglobin and entering the tissue interstitial fluid. Although venous blood is said to be deoxygenated, some oxygen is still bound to hemoglobin in its red blood cells. This provides an oxygen reserve that can be used when tissues suddenly demand more oxygen.
Factors other than partial pressure also affect the oxygen–hemoglobin saturation/dissociation curve. For example, a higher temperature promotes hemoglobin and oxygen to dissociate faster, whereas a lower temperature inhibits dissociation (see Figure 22.26, middle). However, the human body tightly regulates temperature, so this factor may not affect gas exchange throughout the body. The exception to this is in highly active tissues, which may release a larger amount of energy than is given off as heat. As a result, oxygen readily dissociates from hemoglobin, which is a mechanism that helps to provide active tissues with more oxygen.
Certain hormones, such as androgens, epinephrine, thyroid hormones, and growth hormone, can affect the oxygen–hemoglobin saturation/disassociation curve by stimulating the production of a compound called 2,3-bisphosphoglycerate (BPG) by erythrocytes. BPG is a byproduct of glycolysis. Because erythrocytes do not contain mitochondria, glycolysis is the sole method by which these cells produce ATP. BPG promotes the disassociation of oxygen from hemoglobin. Therefore, the greater the concentration of BPG, the more readily oxygen dissociates from hemoglobin, despite its partial pressure.
The pH of the blood is another factor that influences the oxygen–hemoglobin saturation/dissociation curve (see Figure 22.26). The Bohr effect is a phenomenon that arises from the relationship between pH and oxygen’s affinity for hemoglobin: A lower, more acidic pH promotes oxygen dissociation from hemoglobin. In contrast, a higher, or more basic, pH inhibits oxygen dissociation from hemoglobin. The greater the amount of carbon dioxide in the blood, the more molecules that must be converted, which in turn generates hydrogen ions and thus lowers blood pH. Furthermore, blood pH may become more acidic when certain byproducts of cell metabolism, such as lactic acid, carbonic acid, and carbon dioxide, are released into the bloodstream.
Hemoglobin of the Fetus
The fetus has its own circulation with its own erythrocytes; however, it is dependent on the mother for oxygen. Blood is supplied to the fetus by way of the umbilical cord, which is connected to the placenta and separated from maternal blood by the chorion. The mechanism of gas exchange at the chorion is similar to gas exchange at the respiratory membrane. However, the partial pressure of oxygen is lower in the maternal blood in the placenta, at about 35 to 50 mm Hg, than it is in maternal arterial blood. The difference in partial pressures between maternal and fetal blood is not large, as the partial pressure of oxygen in fetal blood at the placenta is about 20 mm Hg. Therefore, there is not as much diffusion of oxygen into the fetal blood supply. The fetus’ hemoglobin overcomes this problem by having a greater affinity for oxygen than maternal hemoglobin (Figure 22.27). Both fetal and adult hemoglobin have four subunits, but two of the subunits of fetal hemoglobin have a different structure that causes fetal hemoglobin to have a greater affinity for oxygen than does adult hemoglobin.
Figure 22.27 Oxygen-Hemoglobin Dissociation Curves in Fetus and AdultFetal hemoglobin has a greater affinity for oxygen than does adult hemoglobin.
Carbon Dioxide Transport in the Blood
Carbon dioxide is transported by three major mechanisms. The first mechanism of carbon dioxide transport is by blood plasma, as some carbon dioxide molecules dissolve in the blood. The second mechanism is transport in the form of bicarbonate (HCO3–), which also dissolves in plasma. The third mechanism of carbon dioxide transport is similar to the transport of oxygen by erythrocytes (Figure 22.28).
Figure 22.28 Carbon Dioxide Transport Carbon dioxide is transported by three different methods: (a) in erythrocytes; (b) after forming carbonic acid (H2CO3 ), which is dissolved in plasma; (c) and in plasma.
Dissolved Carbon Dioxide
Although carbon dioxide is not considered to be highly soluble in blood, a small fraction—about 7 to 10 percent—of the carbon dioxide that diffuses into the blood from the tissues dissolves in plasma. The dissolved carbon dioxide then travels in the bloodstream and when the blood reaches the pulmonary capillaries, the dissolved carbon dioxide diffuses across the respiratory membrane into the alveoli, where it is then exhaled during pulmonary ventilation.
Bicarbonate Buffer
A large fraction—about 70 percent—of the carbon dioxide molecules that diffuse into the blood is transported to the lungs as bicarbonate. Most bicarbonate is produced in erythrocytes after carbon dioxide diffuses into the capillaries, and subsequently into red blood cells. Carbonic anhydrase (CA) causes carbon dioxide and water to form carbonic acid (H2CO3), which dissociates into two ions: bicarbonate (HCO3–) and hydrogen (H+). The following formula depicts this reaction:
CO2 + H2O CA↔ H2CO3↔H+ + HCO3−CO2 + H2O CA↔ H2CO3↔H+ + HCO3−
Bicarbonate tends to build up in the erythrocytes, so that there is a greater concentration of bicarbonate in the erythrocytes than in the surrounding blood plasma. As a result, some of the bicarbonate will leave the erythrocytes and move down its concentration gradient into the plasma in exchange for chloride (Cl–) ions. This phenomenon is referred to as the chloride shift and occurs because by exchanging one negative ion for another negative ion, neither the electrical charge of the erythrocytes nor that of the blood is altered.
At the pulmonary capillaries, the chemical reaction that produced bicarbonate (shown above) is reversed, and carbon dioxide and water are the products. Much of the bicarbonate in the plasma re-enters the erythrocytes in exchange for chloride ions. Hydrogen ions and bicarbonate ions join to form carbonic acid, which is converted into carbon dioxide and water by carbonic anhydrase. Carbon dioxide diffuses out of the erythrocytes and into the plasma, where it can further diffuse across the respiratory membrane into the alveoli to be exhaled during pulmonary ventilation.
Carbaminohemoglobin
About 20 percent of carbon dioxide is bound by hemoglobin and is transported to the lungs. Carbon dioxide does not bind to iron as oxygen does; instead, carbon dioxide binds amino acid moieties on the globin portions of hemoglobin to form carbaminohemoglobin, which forms when hemoglobin and carbon dioxide bind. When hemoglobin is not transporting oxygen, it tends to have a bluish-purple tone to it, creating the darker maroon color typical of deoxygenated blood. The following formula depicts this reversible reaction:
CO2 + Hb↔HbCO2CO2 + Hb↔HbCO2
Similar to the transport of oxygen by heme, the binding and dissociation of carbon dioxide to and from hemoglobin is dependent on the partial pressure of carbon dioxide. Because carbon dioxide is released from the lungs, blood that leaves the lungs and reaches body tissues has a lower partial pressure of carbon dioxide than is found in the tissues. As a result, carbon dioxide leaves the tissues because of its higher partial pressure, enters the blood, and then moves into red blood cells, binding to hemoglobin. In contrast, in the pulmonary capillaries, the partial pressure of carbon dioxide is high compared to within the alveoli. As a result, carbon dioxide dissociates readily from hemoglobin and diffuses across the respiratory membrane into the air.
In addition to the partial pressure of carbon dioxide, the oxygen saturation of hemoglobin and the partial pressure of oxygen in the blood also influence the affinity of hemoglobin for carbon dioxide. The Haldane effect is a phenomenon that arises from the relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide. Hemoglobin that is saturated with oxygen does not readily bind carbon dioxide. However, when oxygen is not bound to heme and the partial pressure of oxygen is low, hemoglobin readily binds to carbon dioxide.
INTERACTIVE LINK
Watch this video to see the transport of oxygen from the lungs to the tissues. Why is oxygenated blood bright red, whereas deoxygenated blood tends to be more of a purple color?
Modifications in Respiratory Functions
- Define the terms hyperpnea and hyperventilation
- Describe the effect of exercise on the respiratory system
- Describe the effect of high altitude on the respiratory system
- Discuss the process of acclimatization
At rest, the respiratory system performs its functions at a constant, rhythmic pace, as regulated by the respiratory centers of the brain. At this pace, ventilation provides sufficient oxygen to all the tissues of the body. However, there are times that the respiratory system must alter the pace of its functions in order to accommodate the oxygen demands of the body.
Hyperpnea
Hyperpnea is an increased depth and rate of ventilation to meet an increase in oxygen demand as might be seen in exercise or disease, particularly diseases that target the respiratory or digestive tracts. This does not significantly alter blood oxygen or carbon dioxide levels, but merely increases the depth and rate of ventilation to meet the demand of the cells. In contrast, hyperventilationis an increased ventilation rate that is independent of the cellular oxygen needs and leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH.
Interestingly, exercise does not cause hyperpnea as one might think. Muscles that perform work during exercise do increase their demand for oxygen, stimulating an increase in ventilation. However, hyperpnea during exercise appears to occur before a drop in oxygen levels within the muscles can occur. Therefore, hyperpnea must be driven by other mechanisms, either instead of or in addition to a drop in oxygen levels. The exact mechanisms behind exercise hyperpnea are not well understood, and some hypotheses are somewhat controversial. However, in addition to low oxygen, high carbon dioxide, and low pH levels, there appears to be a complex interplay of factors related to the nervous system and the respiratory centers of the brain.
First, a conscious decision to partake in exercise, or another form of physical exertion, results in a psychological stimulus that may trigger the respiratory centers of the brain to increase ventilation. In addition, the respiratory centers of the brain may be stimulated through the activation of motor neurons that innervate muscle groups that are involved in the physical activity. Finally, physical exertion stimulates proprioceptors, which are receptors located within the muscles, joints, and tendons, which sense movement and stretching; proprioceptors thus create a stimulus that may also trigger the respiratory centers of the brain. These neural factors are consistent with the sudden increase in ventilation that is observed immediately as exercise begins. Because the respiratory centers are stimulated by psychological, motor neuron, and proprioceptor inputs throughout exercise, the fact that there is also a sudden decrease in ventilation immediately after the exercise ends when these neural stimuli cease, further supports the idea that they are involved in triggering the changes of ventilation.
High Altitude Effects
An increase in altitude results in a decrease in atmospheric pressure. Although the proportion of oxygen relative to gases in the atmosphere remains at 21 percent, its partial pressure decreases (Table 22.4). As a result, it is more difficult for a body to achieve the same level of oxygen saturation at high altitude than at low altitude, due to lower atmospheric pressure. In fact, hemoglobin saturation is lower at high altitudes compared to hemoglobin saturation at sea level. For example, hemoglobin saturation is about 67 percent at 19,000 feet above sea level, whereas it reaches about 98 percent at sea level.
Partial Pressure of Oxygen at Different Altitudes
| Example location | Altitude (feet above sea level) | Atmospheric pressure (mm Hg) | Partial pressure of oxygen (mm Hg) |
|---|---|---|---|
| New York City, New York | 0 | 760 | 159 |
| Boulder, Colorado | 5000 | 632 | 133 |
| Aspen, Colorado | 8000 | 565 | 118 |
| Pike’s Peak, Colorado | 14,000 | 447 | 94 |
| Denali (Mt. McKinley), Alaska | 20,000 | 350 | 73 |
| Mt. Everest, Tibet | 29,000 | 260 | 54 |
Table 22.4
As you recall, partial pressure is extremely important in determining how much gas can cross the respiratory membrane and enter the blood of the pulmonary capillaries. A lower partial pressure of oxygen means that there is a smaller difference in partial pressures between the alveoli and the blood, so less oxygen crosses the respiratory membrane. As a result, fewer oxygen molecules are bound by hemoglobin. Despite this, the tissues of the body still receive a sufficient amount of oxygen during rest at high altitudes. This is due to two major mechanisms. First, the number of oxygen molecules that enter the tissue from the blood is nearly equal between sea level and high altitudes. At sea level, hemoglobin saturation is higher, but only a quarter of the oxygen molecules are actually released into the tissue. At high altitudes, a greater proportion of molecules of oxygen are released into the tissues. Secondly, at high altitudes, a greater amount of BPG is produced by erythrocytes, which enhances the dissociation of oxygen from hemoglobin. Physical exertion, such as skiing or hiking, can lead to altitude sickness due to the low amount of oxygen reserves in the blood at high altitudes. At sea level, there is a large amount of oxygen reserve in venous blood (even though venous blood is thought of as “deoxygenated”) from which the muscles can draw during physical exertion. Because the oxygen saturation is much lower at higher altitudes, this venous reserve is small, resulting in pathological symptoms of low blood oxygen levels. You may have heard that it is important to drink more water when traveling at higher altitudes than you are accustomed to. This is because your body will increase micturition (urination) at high altitudes to counteract the effects of lower oxygen levels. By removing fluids, blood plasma levels drop but not the total number of erythrocytes. In this way, the overall concentration of erythrocytes in the blood increases, which helps tissues obtain the oxygen they need.
Acute mountain sickness (AMS), or altitude sickness, is a condition that results from acute exposure to high altitudes due to a low partial pressure of oxygen at high altitudes. AMS typically can occur at 2400 meters (8000 feet) above sea level. AMS is a result of low blood oxygen levels, as the body has acute difficulty adjusting to the low partial pressure of oxygen. In serious cases, AMS can cause pulmonary or cerebral edema. Symptoms of AMS include nausea, vomiting, fatigue, lightheadedness, drowsiness, feeling disoriented, increased pulse, and nosebleeds. The only treatment for AMS is descending to a lower altitude; however, pharmacologic treatments and supplemental oxygen can improve symptoms. AMS can be prevented by slowly ascending to the desired altitude, allowing the body to acclimate, as well as maintaining proper hydration.
Acclimatization
Especially in situations where the ascent occurs too quickly, traveling to areas of high altitude can cause AMS. Acclimatization is the process of adjustment that the respiratory system makes due to chronic exposure to a high altitude. Over a period of time, the body adjusts to accommodate the lower partial pressure of oxygen. The low partial pressure of oxygen at high altitudes results in a lower oxygen saturation level of hemoglobin in the blood. In turn, the tissue levels of oxygen are also lower. As a result, the kidneys are stimulated to produce the hormone erythropoietin (EPO), which stimulates the production of erythrocytes, resulting in a greater number of circulating erythrocytes in an individual at a high altitude over a long period. With more red blood cells, there is more hemoglobin to help transport the available oxygen. Even though there is low saturation of each hemoglobin molecule, there will be more hemoglobin present, and therefore more oxygen in the blood. Over time, this allows the person to partake in physical exertion
Embryonic Development of the Respiratory System
- Create a timeline of the phases of respiratory development in the fetus
- Propose reasons for fetal breathing movements
- Explain how the lungs become inflated after birth
Development of the respiratory system begins early in the fetus. It is a complex process that includes many structures, most of which arise from the endoderm. Towards the end of development, the fetus can be observed making breathing movements. Until birth, however, the mother provides all of the oxygen to the fetus as well as removes all of the fetal carbon dioxide via the placenta.
Time Line
The development of the respiratory system begins at about week 4 of gestation. By week 28, enough alveoli have matured that a baby born prematurely at this time can usually breathe on its own. The respiratory system, however, is not fully developed until early childhood, when a full complement of mature alveoli is present.
Weeks 4–7
Respiratory development in the embryo begins around week 4. Ectodermal tissue from the anterior head region invaginates posteriorly to form olfactory pits, which fuse with endodermal tissue of the developing pharynx. An olfactory pit is one of a pair of structures that will enlarge to become the nasal cavity. At about this same time, the lung bud forms. The lung bud is a dome-shaped structure composed of tissue that bulges from the foregut. The foregut is endoderm just inferior to the pharyngeal pouches. The laryngotracheal bud is a structure that forms from the longitudinal extension of the lung bud as development progresses. The portion of this structure nearest the pharynx becomes the trachea, whereas the distal end becomes more bulbous, forming bronchial buds. A bronchial bud is one of a pair of structures that will eventually become the bronchi and all other lower respiratory structures (Figure 22.29).
Figure 22.29 Development of the Lower Respiratory System
Weeks 7–16
Bronchial buds continue to branch as development progresses until all of the segmental bronchi have been formed. Beginning around week 13, the lumens of the bronchi begin to expand in diameter. By week 16, respiratory bronchioles form. The fetus now has all major lung structures involved in the airway.
Weeks 16–24
Once the respiratory bronchioles form, further development includes extensive vascularization, or the development of the blood vessels, as well as the formation of alveolar ducts and alveolar precursors. At about week 19, the respiratory bronchioles have formed. In addition, cells lining the respiratory structures begin to differentiate to form type I and type II pneumocytes. Once type II cells have differentiated, they begin to secrete small amounts of pulmonary surfactant. Around week 20, fetal breathing movements may begin.
Weeks 24–Term
Major growth and maturation of the respiratory system occurs from week 24 until term. More alveolar precursors develop, and larger amounts of pulmonary surfactant are produced. Surfactant levels are not generally adequate to create effective lung compliance until about the eighth month of pregnancy. The respiratory system continues to expand, and the surfaces that will form the respiratory membrane develop further. At this point, pulmonary capillaries have formed and continue to expand, creating a large surface area for gas exchange. The major milestone of respiratory development occurs at around week 28, when sufficient alveolar precursors have matured so that a baby born prematurely at this time can usually breathe on its own. However, alveoli continue to develop and mature into childhood. A full complement of functional alveoli does not appear until around 8 years of age.
Fetal “Breathing”
Although the function of fetal breathing movements is not entirely clear, they can be observed starting at 20–21 weeks of development. Fetal breathing movements involve muscle contractions that cause the inhalation of amniotic fluid and exhalation of the same fluid, with pulmonary surfactant and mucus. Fetal breathing movements are not continuous and may include periods of frequent movements and periods of no movements. Maternal factors can influence the frequency of breathing movements. For example, high blood glucose levels, called hyperglycemia, can boost the number of breathing movements. Conversely, low blood glucose levels, called hypoglycemia, can reduce the number of fetal breathing movements. Tobacco use is also known to lower fetal breathing rates. Fetal breathing may help tone the muscles in preparation for breathing movements once the fetus is born. It may also help the alveoli to form and mature. Fetal breathing movements are considered a sign of robust health.
Birth
Prior to birth, the lungs are filled with amniotic fluid, mucus, and surfactant. As the fetus is squeezed through the birth canal, the fetal thoracic cavity is compressed, expelling much of this fluid. Some fluid remains, however, but is rapidly absorbed by the body shortly after birth. The first inhalation occurs within 10 seconds after birth and not only serves as the first inspiration, but also acts to inflate the lungs. Pulmonary surfactant is critical for inflation to occur, as it reduces the surface tension of the alveoli. Preterm birth around 26 weeks frequently results in severe respiratory distress, although with current medical advancements, some babies may survive. Prior to 26 weeks, sufficient pulmonary surfactant is not produced, and the surfaces for gas exchange have not formed adequately; therefore, survival is low.
DISORDERS OF THE...
Respiratory System: Respiratory Distress Syndrome
Respiratory distress syndrome (RDS) primarily occurs in infants born prematurely. Up to 50 percent of infants born between 26 and 28 weeks and fewer than 30 percent of infants born between 30 and 31 weeks develop RDS. RDS results from insufficient production of pulmonary surfactant, thereby preventing the lungs from properly inflating at birth. A small amount of pulmonary surfactant is produced beginning at around 20 weeks; however, this is not sufficient for inflation of the lungs. As a result, dyspnea occurs and gas exchange cannot be performed properly. Blood oxygen levels are low, whereas blood carbon dioxide levels and pH are high.
The primary cause of RDS is premature birth, which may be due to a variety of known or unknown causes. Other risk factors include gestational diabetes, cesarean delivery, second-born twins, and family history of RDS. The presence of RDS can lead to other serious disorders, such as septicemia (infection of the blood) or pulmonary hemorrhage. Therefore, it is important that RDS is immediately recognized and treated to prevent death and reduce the risk of developing other disorders.
Medical advances have resulted in an improved ability to treat RDS and support the infant until proper lung development can occur. At the time of delivery, treatment may include resuscitation and intubation if the infant does not breathe on his or her own. These infants would need to be placed on a ventilator to mechanically assist with the breathing process. If spontaneous breathing occurs, application of nasal continuous positive airway pressure (CPAP) may be required. In addition, pulmonary surfactant is typically administered. Death due to RDS has been reduced by 50 percent due to the introduction of pulmonary surfactant therapy. Other therapies may include corticosteroids, supplemental oxygen, and assisted ventilation. Supportive therapies, such as temperature regulation, nutritional support, and antibiotics, may be administered to the premature infant as well.
Key Terms
- acclimatization
- process of adjustment that the respiratory system makes due to chronic exposure to high altitudes
- acute mountain sickness (AMS)
- condition that occurs a result of acute exposure to high altitude due to a low partial pressure of oxygen
- ala
- (plural = alae) small, flaring structure of a nostril that forms the lateral side of the nares
- alar cartilage
- cartilage that supports the apex of the nose and helps shape the nares; it is connected to the septal cartilage and connective tissue of the alae
- alveolar dead space
- air space within alveoli that are unable to participate in gas exchange
- alveolar duct
- small tube that leads from the terminal bronchiole to the respiratory bronchiole and is the point of attachment for alveoli
- alveolar macrophage
- immune system cell of the alveolus that removes debris and pathogens
- alveolar pore
- opening that allows airflow between neighboring alveoli
- alveolar sac
- cluster of alveoli
- alveolus
- small, grape-like sac that performs gas exchange in the lungs
- anatomical dead space
- air space present in the airway that never reaches the alveoli and therefore never participates in gas exchange
- apex
- tip of the external nose
- apneustic center
- network of neurons within the pons that stimulate the neurons in the dorsal respiratory group; controls the depth of inspiration
- atmospheric pressure
- amount of force that is exerted by gases in the air surrounding any given surface
- Bohr effect
- relationship between blood pH and oxygen dissociation from hemoglobin
- Boyle’s law
- relationship between volume and pressure as described by the formula: P1V1 = P2V2
- bridge
- portion of the external nose that lies in the area of the nasal bones
- bronchial bud
- structure in the developing embryo that forms when the laryngotracheal bud extends and branches to form two bulbous structures
- bronchial tree
- collective name for the multiple branches of the bronchi and bronchioles of the respiratory system
- bronchiole
- branch of bronchi that are 1 mm or less in diameter and terminate at alveolar sacs
- bronchoconstriction
- decrease in the size of the bronchiole due to contraction of the muscular wall
- bronchodilation
- increase in the size of the bronchiole due to contraction of the muscular wall
- bronchus
- tube connected to the trachea that branches into many subsidiaries and provides a passageway for air to enter and leave the lungs
- carbaminohemoglobin
- bound form of hemoglobin and carbon dioxide
- carbonic anhydrase (CA)
- enzyme that catalyzes the reaction that causes carbon dioxide and water to form carbonic acid
- cardiac notch
- indentation on the surface of the left lung that allows space for the heart
- central chemoreceptor
- one of the specialized receptors that are located in the brain that sense changes in hydrogen ion, oxygen, or carbon dioxide concentrations in the brain
- chloride shift
- facilitated diffusion that exchanges bicarbonate (HCO3–) with chloride (Cl–) ions
- conducting zone
- region of the respiratory system that includes the organs and structures that provide passageways for air and are not directly involved in gas exchange
- cricoid cartilage
- portion of the larynx composed of a ring of cartilage with a wide posterior region and a thinner anterior region; attached to the esophagus
- Dalton’s law
- statement of the principle that a specific gas type in a mixture exerts its own pressure, as if that specific gas type was not part of a mixture of gases
- dorsal respiratory group (DRG)
- region of the medulla oblongata that stimulates the contraction of the diaphragm and intercostal muscles to induce inspiration
- dorsum nasi
- intermediate portion of the external nose that connects the bridge to the apex and is supported by the nasal bone
- epiglottis
- leaf-shaped piece of elastic cartilage that is a portion of the larynx that swings to close the trachea during swallowing
- expiration
- (also, exhalation) process that causes the air to leave the lungs
- expiratory reserve volume (ERV)
- amount of air that can be forcefully exhaled after a normal tidal exhalation
- external nose
- region of the nose that is easily visible to others
- external respiration
- gas exchange that occurs in the alveoli
- fauces
- portion of the posterior oral cavity that connects the oral cavity to the oropharynx
- fibroelastic membrane
- specialized membrane that connects the ends of the C-shape cartilage in the trachea; contains smooth muscle fibers
- forced breathing
- (also, hyperpnea) mode of breathing that occurs during exercise or by active thought that requires muscle contraction for both inspiration and expiration
- foregut
- endoderm of the embryo towards the head region
- functional residual capacity (FRC)
- sum of ERV and RV, which is the amount of air that remains in the lungs after a tidal expiration
- glottis
- opening between the vocal folds through which air passes when producing speech
- Haldane effect
- relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide
- Henry’s law
- statement of the principle that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas
- hilum
- concave structure on the mediastinal surface of the lungs where blood vessels, lymphatic vessels, nerves, and a bronchus enter the lung
- hyperpnea
- increased rate and depth of ventilation due to an increase in oxygen demand that does not significantly alter blood oxygen or carbon dioxide levels
- hyperventilation
- increased ventilation rate that leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH
- inspiration
- (also, inhalation) process that causes air to enter the lungs
- inspiratory capacity (IC)
- sum of the TV and IRV, which is the amount of air that can maximally be inhaled past a tidal expiration
- inspiratory reserve volume (IRV)
- amount of air that enters the lungs due to deep inhalation past the tidal volume
- internal respiration
- gas exchange that occurs at the level of body tissues
- intra-alveolar pressure
- (intrapulmonary pressure) pressure of the air within the alveoli
- intrapleural pressure
- pressure of the air within the pleural cavity
- laryngeal prominence
- region where the two lamina of the thyroid cartilage join, forming a protrusion known as “Adam’s apple”
- laryngopharynx
- portion of the pharynx bordered by the oropharynx superiorly and esophagus and trachea inferiorly; serves as a route for both air and food
- laryngotracheal
- bud forms from the lung bud, has a tracheal end and bulbous bronchial buds at the distal end
- larynx
- cartilaginous structure that produces the voice, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs
- lingual tonsil
- lymphoid tissue located at the base of the tongue
- lung
- organ of the respiratory system that performs gas exchange
- lung bud
- median dome that forms from the endoderm of the foregut
- meatus
- one of three recesses (superior, middle, and inferior) in the nasal cavity attached to the conchae that increase the surface area of the nasal cavity
- naris
- (plural = nares) opening of the nostrils
- nasal bone
- bone of the skull that lies under the root and bridge of the nose and is connected to the frontal and maxillary bones
- nasal septum
- wall composed of bone and cartilage that separates the left and right nasal cavities
- nasopharynx
- portion of the pharynx flanked by the conchae and oropharynx that serves as an airway
- olfactory pit
- invaginated ectodermal tissue in the anterior portion of the head region of an embryo that will form the nasal cavity
- oropharynx
- portion of the pharynx flanked by the nasopharynx, oral cavity, and laryngopharynx that is a passageway for both air and food
- oxygen–hemoglobin dissociation curve
- graph that describes the relationship of partial pressure to the binding and disassociation of oxygen to and from heme
- oxyhemoglobin
- (Hb–O2) bound form of hemoglobin and oxygen
- palatine tonsil
- one of the paired structures composed of lymphoid tissue located anterior to the uvula at the roof of isthmus of the fauces
- paranasal sinus
- one of the cavities within the skull that is connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consists of frontal, maxillary, sphenoidal, and ethmoidal sinuses
- parietal pleura
- outermost layer of the pleura that connects to the thoracic wall, mediastinum, and diaphragm
- partial pressure
- force exerted by each gas in a mixture of gases
- peripheral chemoreceptor
- one of the specialized receptors located in the aortic arch and carotid arteries that sense changes in pH, carbon dioxide, or oxygen blood levels
- pharyngeal tonsil
- structure composed of lymphoid tissue located in the nasopharynx
- pharynx
- region of the conducting zone that forms a tube of skeletal muscle lined with respiratory epithelium; located between the nasal conchae and the esophagus and trachea
- philtrum
- concave surface of the face that connects the apex of the nose to the top lip
- pleural cavity
- space between the visceral and parietal pleurae
- pleural fluid
- substance that acts as a lubricant for the visceral and parietal layers of the pleura during the movement of breathing
- pneumotaxic center
- network of neurons within the pons that inhibit the activity of the neurons in the dorsal respiratory group; controls rate of breathing
- pulmonary artery
- artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli
- pulmonary plexus
- network of autonomic nervous system fibers found near the hilum of the lung
- pulmonary surfactant
- substance composed of phospholipids and proteins that reduces the surface tension of the alveoli; made by type II alveolar cells
- pulmonary ventilation
- exchange of gases between the lungs and the atmosphere; breathing
- quiet breathing
- (also, eupnea) mode of breathing that occurs at rest and does not require the cognitive thought of the individual
- residual volume (RV)
- amount of air that remains in the lungs after maximum exhalation
- respiratory bronchiole
- specific type of bronchiole that leads to alveolar sacs
- respiratory cycle
- one sequence of inspiration and expiration
- respiratory epithelium
- ciliated lining of much of the conducting zone that is specialized to remove debris and pathogens, and produce mucus
- respiratory membrane
- alveolar and capillary wall together, which form an air-blood barrier that facilitates the simple diffusion of gases
- respiratory rate
- total number of breaths taken each minute
- respiratory volume
- varying amounts of air within the lung at a given time
- respiratory zone
- includes structures of the respiratory system that are directly involved in gas exchange
- root
- region of the external nose between the eyebrows
- thoracic wall compliance
- ability of the thoracic wall to stretch while under pressure
- thyroid cartilage
- largest piece of cartilage that makes up the larynx and consists of two lamina
- tidal volume (TV)
- amount of air that normally enters the lungs during quiet breathing
- total dead space
- sum of the anatomical dead space and alveolar dead space
- total lung capacity (TLC)
- total amount of air that can be held in the lungs; sum of TV, ERV, IRV, and RV
- total pressure
- sum of all the partial pressures of a gaseous mixture
- trachea
- tube composed of cartilaginous rings and supporting tissue that connects the lung bronchi and the larynx; provides a route for air to enter and exit the lung
- trachealis muscle
- smooth muscle located in the fibroelastic membrane of the trachea
- transpulmonary pressure
- pressure difference between the intrapleural and intra-alveolar pressures
- true vocal cord
- one of the pair of folded, white membranes that have a free inner edge that oscillates as air passes through to produce sound
- type I alveolar cell
- squamous epithelial cells that are the major cell type in the alveolar wall; highly permeable to gases
- type II alveolar cell
- cuboidal epithelial cells that are the minor cell type in the alveolar wall; secrete pulmonary surfactant
- ventilation
- movement of air into and out of the lungs; consists of inspiration and expiration
- ventral respiratory group (VRG)
- region of the medulla oblongata that stimulates the contraction of the accessory muscles involved in respiration to induce forced inspiration and expiration
- vestibular fold
- part of the folded region of the glottis composed of mucous membrane; supports the epiglottis during swallowing
- visceral pleura
- innermost layer of the pleura that is superficial to the lungs and extends into the lung fissures
- vital capacity (VC)
- sum of TV, ERV, and IRV, which is all the volumes that participate in gas exchange
Chapter Review
22.1 Organs and Structures of the Respiratory System
The respiratory system is responsible for obtaining oxygen and getting rid of carbon dioxide, and aiding in speech production and in sensing odors. From a functional perspective, the respiratory system can be divided into two major areas: the conducting zone and the respiratory zone. The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles. The nasal passages contain the conchae and meatuses that expand the surface area of the cavity, which helps to warm and humidify incoming air, while removing debris and pathogens. The pharynx is composed of three major sections: the nasopharynx, which is continuous with the nasal cavity; the oropharynx, which borders the nasopharynx and the oral cavity; and the laryngopharynx, which borders the oropharynx, trachea, and esophagus. The respiratory zone includes the structures of the lung that are directly involved in gas exchange: the terminal bronchioles and alveoli.
The lining of the conducting zone is composed mostly of pseudostratified ciliated columnar epithelium with goblet cells. The mucus traps pathogens and debris, whereas beating cilia move the mucus superiorly toward the throat, where it is swallowed. As the bronchioles become smaller and smaller, and nearer the alveoli, the epithelium thins and is simple squamous epithelium in the alveoli. The endothelium of the surrounding capillaries, together with the alveolar epithelium, forms the respiratory membrane. This is a blood-air barrier through which gas exchange occurs by simple diffusion.
22.2 The Lungs
The lungs are the major organs of the respiratory system and are responsible for performing gas exchange. The lungs are paired and separated into lobes; The left lung consists of two lobes, whereas the right lung consists of three lobes. Blood circulation is very important, as blood is required to transport oxygen from the lungs to other tissues throughout the body. The function of the pulmonary circulation is to aid in gas exchange. The pulmonary artery provides deoxygenated blood to the capillaries that form respiratory membranes with the alveoli, and the pulmonary veins return newly oxygenated blood to the heart for further transport throughout the body. The lungs are innervated by the parasympathetic and sympathetic nervous systems, which coordinate the bronchodilation and bronchoconstriction of the airways. The lungs are enclosed by the pleura, a membrane that is composed of visceral and parietal pleural layers. The space between these two layers is called the pleural cavity. The mesothelial cells of the pleural membrane create pleural fluid, which serves as both a lubricant (to reduce friction during breathing) and as an adhesive to adhere the lungs to the thoracic wall (to facilitate movement of the lungs during ventilation).
22.3 The Process of Breathing
Pulmonary ventilation is the process of breathing, which is driven by pressure differences between the lungs and the atmosphere. Atmospheric pressure is the force exerted by gases present in the atmosphere. The force exerted by gases within the alveoli is called intra-alveolar (intrapulmonary) pressure, whereas the force exerted by gases in the pleural cavity is called intrapleural pressure. Typically, intrapleural pressure is lower, or negative to, intra-alveolar pressure. The difference in pressure between intrapleural and intra-alveolar pressures is called transpulmonary pressure. In addition, intra-alveolar pressure will equalize with the atmospheric pressure. Pressure is determined by the volume of the space occupied by a gas and is influenced by resistance. Air flows when a pressure gradient is created, from a space of higher pressure to a space of lower pressure. Boyle’s law describes the relationship between volume and pressure. A gas is at lower pressure in a larger volume because the gas molecules have more space to in which to move. The same quantity of gas in a smaller volume results in gas molecules crowding together, producing increased pressure.
Resistance is created by inelastic surfaces, as well as the diameter of the airways. Resistance reduces the flow of gases. The surface tension of the alveoli also influences pressure, as it opposes the expansion of the alveoli. However, pulmonary surfactant helps to reduce the surface tension so that the alveoli do not collapse during expiration. The ability of the lungs to stretch, called lung compliance, also plays a role in gas flow. The more the lungs can stretch, the greater the potential volume of the lungs. The greater the volume of the lungs, the lower the air pressure within the lungs.
Pulmonary ventilation consists of the process of inspiration (or inhalation), where air enters the lungs, and expiration (or exhalation), where air leaves the lungs. During inspiration, the diaphragm and external intercostal muscles contract, causing the rib cage to expand and move outward, and expanding the thoracic cavity and lung volume. This creates a lower pressure within the lung than that of the atmosphere, causing air to be drawn into the lungs. During expiration, the diaphragm and intercostals relax, causing the thorax and lungs to recoil. The air pressure within the lungs increases to above the pressure of the atmosphere, causing air to be forced out of the lungs. However, during forced exhalation, the internal intercostals and abdominal muscles may be involved in forcing air out of the lungs.
Respiratory volume describes the amount of air in a given space within the lungs, or which can be moved by the lung, and is dependent on a variety of factors. Tidal volume refers to the amount of air that enters the lungs during quiet breathing, whereas inspiratory reserve volume is the amount of air that enters the lungs when a person inhales past the tidal volume. Expiratory reserve volume is the extra amount of air that can leave with forceful expiration, following tidal expiration. Residual volume is the amount of air that is left in the lungs after expelling the expiratory reserve volume. Respiratory capacity is the combination of two or more volumes. Anatomical dead space refers to the air within the respiratory structures that never participates in gas exchange, because it does not reach functional alveoli. Respiratory rate is the number of breaths taken per minute, which may change during certain diseases or conditions.
Both respiratory rate and depth are controlled by the respiratory centers of the brain, which are stimulated by factors such as chemical and pH changes in the blood. These changes are sensed by central chemoreceptors, which are located in the brain, and peripheral chemoreceptors, which are located in the aortic arch and carotid arteries. A rise in carbon dioxide or a decline in oxygen levels in the blood stimulates an increase in respiratory rate and depth.
22.4 Gas Exchange
The behavior of gases can be explained by the principles of Dalton’s law and Henry’s law, both of which describe aspects of gas exchange. Dalton’s law states that each specific gas in a mixture of gases exerts force (its partial pressure) independently of the other gases in the mixture. Henry’s law states that the amount of a specific gas that dissolves in a liquid is a function of its partial pressure. The greater the partial pressure of a gas, the more of that gas will dissolve in a liquid, as the gas moves toward equilibrium. Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure. The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli. The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar.
Ventilation is the process that moves air into and out of the alveoli, and perfusion affects the flow of blood in the capillaries. Both are important in gas exchange, as ventilation must be sufficient to create a high partial pressure of oxygen in the alveoli. If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation. External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences.
22.5 Transport of Gases
Oxygen is primarily transported through the blood by erythrocytes. These cells contain a metalloprotein called hemoglobin, which is composed of four subunits with a ring-like structure. Each subunit contains one atom of iron bound to a molecule of heme. Heme binds oxygen so that each hemoglobin molecule can bind up to four oxygen molecules. When all of the heme units in the blood are bound to oxygen, hemoglobin is considered to be saturated. Hemoglobin is partially saturated when only some heme units are bound to oxygen. An oxygen–hemoglobin saturation/dissociation curve is a common way to depict the relationship of how easily oxygen binds to or dissociates from hemoglobin as a function of the partial pressure of oxygen. As the partial pressure of oxygen increases, the more readily hemoglobin binds to oxygen. At the same time, once one molecule of oxygen is bound by hemoglobin, additional oxygen molecules more readily bind to hemoglobin. Other factors such as temperature, pH, the partial pressure of carbon dioxide, and the concentration of 2,3-bisphosphoglycerate can enhance or inhibit the binding of hemoglobin and oxygen as well. Fetal hemoglobin has a different structure than adult hemoglobin, which results in fetal hemoglobin having a greater affinity for oxygen than adult hemoglobin.
Carbon dioxide is transported in blood by three different mechanisms: as dissolved carbon dioxide, as bicarbonate, or as carbaminohemoglobin. A small portion of carbon dioxide remains. The largest amount of transported carbon dioxide is as bicarbonate, formed in erythrocytes. For this conversion, carbon dioxide is combined with water with the aid of an enzyme called carbonic anhydrase. This combination forms carbonic acid, which spontaneously dissociates into bicarbonate and hydrogen ions. As bicarbonate builds up in erythrocytes, it is moved across the membrane into the plasma in exchange for chloride ions by a mechanism called the chloride shift. At the pulmonary capillaries, bicarbonate re-enters erythrocytes in exchange for chloride ions, and the reaction with carbonic anhydrase is reversed, recreating carbon dioxide and water. Carbon dioxide then diffuses out of the erythrocyte and across the respiratory membrane into the air. An intermediate amount of carbon dioxide binds directly to hemoglobin to form carbaminohemoglobin. The partial pressures of carbon dioxide and oxygen, as well as the oxygen saturation of hemoglobin, influence how readily hemoglobin binds carbon dioxide. The less saturated hemoglobin is and the lower the partial pressure of oxygen in the blood is, the more readily hemoglobin binds to carbon dioxide. This is an example of the Haldane effect.
22.6 Modifications in Respiratory Functions
Normally, the respiratory centers of the brain maintain a consistent, rhythmic breathing cycle. However, in certain cases, the respiratory system must adjust to situational changes in order to supply the body with sufficient oxygen. For example, exercise results in increased ventilation, and chronic exposure to a high altitude results in a greater number of circulating erythrocytes. Hyperpnea, an increase in the rate and depth of ventilation, appears to be a function of three neural mechanisms that include a psychological stimulus, motor neuron activation of skeletal muscles, and the activation of proprioceptors in the muscles, joints, and tendons. As a result, hyperpnea related to exercise is initiated when exercise begins, as opposed to when tissue oxygen demand actually increases.
In contrast, acute exposure to a high altitude, particularly during times of physical exertion, does result in low blood and tissue levels of oxygen. This change is caused by a low partial pressure of oxygen in the air, because the atmospheric pressure at high altitudes is lower than the atmospheric pressure at sea level. This can lead to a condition called acute mountain sickness (AMS) with symptoms that include headaches, disorientation, fatigue, nausea, and lightheadedness. Over a long period of time, a person’s body will adjust to the high altitude, a process called acclimatization. During acclimatization, the low tissue levels of oxygen will cause the kidneys to produce greater amounts of the hormone erythropoietin, which stimulates the production of erythrocytes. Increased levels of circulating erythrocytes provide an increased amount of hemoglobin that helps supply an individual with more oxygen, preventing the symptoms of AMS.
22.7 Embryonic Development of the Respiratory System
The development of the respiratory system in the fetus begins at about 4 weeks and continues into childhood. Ectodermal tissue in the anterior portion of the head region invaginates posteriorly, forming olfactory pits, which ultimately fuse with endodermal tissue of the early pharynx. At about this same time, an protrusion of endodermal tissue extends anteriorly from the foregut, producing a lung bud, which continues to elongate until it forms the laryngotracheal bud. The proximal portion of this structure will mature into the trachea, whereas the bulbous end will branch to form two bronchial buds. These buds then branch repeatedly, so that at about week 16, all major airway structures are present. Development progresses after week 16 as respiratory bronchioles and alveolar ducts form, and extensive vascularization occurs. Alveolar type I cells also begin to take shape. Type II pulmonary cells develop and begin to produce small amounts of surfactant. As the fetus grows, the respiratory system continues to expand as more alveoli develop and more surfactant is produced. Beginning at about week 36 and lasting into childhood, alveolar precursors mature to become fully functional alveoli. At birth, compression of the thoracic cavity forces much of the fluid in the lungs to be expelled. The first inhalation inflates the lungs. Fetal breathing movements begin around week 20 or 21, and occur when contractions of the respiratory muscles cause the fetus to inhale and exhale amniotic fluid. These movements continue until birth and may help to tone the muscles in preparation for breathing after birth and are a sign of good health.
Interactive Link Questions
Visit this site to learn more about what happens during an asthma attack. What are the three changes that occur inside the airways during an asthma attack?
2.Watch this video to learn more about lung volumes and spirometers. Explain how spirometry test results can be used to diagnose respiratory diseases or determine the effectiveness of disease treatment.
3.Watch this video to see the transport of oxygen from the lungs to the tissues. Why is oxygenated blood bright red, whereas deoxygenated blood tends to be more of a purple color?
Review Questions
Which of the following anatomical structures is not part of the conducting zone?
- pharynx
- nasal cavity
- alveoli
- bronchi
What is the function of the conchae in the nasal cavity?
- increase surface area
- exchange gases
- maintain surface tension
- maintain air pressure
The fauces connects which of the following structures to the oropharynx?
- nasopharynx
- laryngopharynx
- nasal cavity
- oral cavity
Which of the following are structural features of the trachea?
- C-shaped cartilage
- smooth muscle fibers
- cilia
- all of the above
Which of the following structures is not part of the bronchial tree?
- alveoli
- bronchi
- terminal bronchioles
- respiratory bronchioles
What is the role of alveolar macrophages?
- to secrete pulmonary surfactant
- to secrete antimicrobial proteins
- to remove pathogens and debris
- to facilitate gas exchange
Which of the following structures separates the lung into lobes?
- mediastinum
- fissure
- root
- pleura
A section of the lung that receives its own tertiary bronchus is called the ________.
- bronchopulmonary segment
- pulmonary lobule
- interpulmonary segment
- respiratory segment
The ________ circulation picks up oxygen for cellular use and drops off carbon dioxide for removal from the body.
- pulmonary
- interlobular
- respiratory
- bronchial
The pleura that surrounds the lungs consists of two layers, the ________.
- visceral and parietal pleurae.
- mediastinum and parietal pleurae.
- visceral and mediastinum pleurae.
- none of the above
Which of the following processes does atmospheric pressure play a role in?
- pulmonary ventilation
- production of pulmonary surfactant
- resistance
- surface tension
A decrease in volume leads to a(n) ________ pressure.
- decrease in
- equalization of
- increase in
- zero
The pressure difference between the intra-alveolar and intrapleural pressures is called ________.
- atmospheric pressure
- pulmonary pressure
- negative pressure
- transpulmonary pressure
Gas flow decreases as ________ increases.
- resistance
- pressure
- airway diameter
- friction
Contraction of the external intercostal muscles causes which of the following to occur?
- The diaphragm moves downward.
- The rib cage is compressed.
- The thoracic cavity volume decreases.
- The ribs and sternum move upward.
Which of the following prevents the alveoli from collapsing?
- residual volume
- tidal volume
- expiratory reserve volume
- inspiratory reserve volume
Gas moves from an area of ________ partial pressure to an area of ________ partial pressure.
- low; high
- low; low
- high; high
- high; low
When ventilation is not sufficient, which of the following occurs?
- The capillary constricts.
- The capillary dilates.
- The partial pressure of oxygen in the affected alveolus increases.
- The bronchioles dilate.
Gas exchange that occurs at the level of the tissues is called ________.
- external respiration
- interpulmonary respiration
- internal respiration
- pulmonary ventilation
The partial pressure of carbon dioxide is 45 mm Hg in the blood and 40 mm Hg in the alveoli. What happens to the carbon dioxide?
- It diffuses into the blood.
- It diffuses into the alveoli.
- The gradient is too small for carbon dioxide to diffuse.
- It decomposes into carbon and oxygen.
Oxyhemoglobin forms by a chemical reaction between which of the following?
- hemoglobin and carbon dioxide
- carbonic anhydrase and carbon dioxide
- hemoglobin and oxygen
- carbonic anhydrase and oxygen
Which of the following factors play a role in the oxygen–hemoglobin saturation/dissociation curve?
- temperature
- pH
- BPG
- all of the above
Which of the following occurs during the chloride shift?
- Chloride is removed from the erythrocyte.
- Chloride is exchanged for bicarbonate.
- Bicarbonate is removed from the erythrocyte.
- Bicarbonate is removed from the blood.
A low partial pressure of oxygen promotes hemoglobin binding to carbon dioxide. This is an example of the ________.
- Haldane effect
- Bohr effect
- Dalton’s law
- Henry’s law
Increased ventilation that results in an increase in blood pH is called ________.
- hyperventilation
- hyperpnea
- acclimatization
- apnea
Exercise can trigger symptoms of AMS due to which of the following?
- low partial pressure of oxygen
- low atmospheric pressure
- abnormal neural signals
- small venous reserve of oxygen
Which of the following stimulates the production of erythrocytes?
- AMS
- high blood levels of carbon dioxide
- low atmospheric pressure
- erythropoietin
The olfactory pits form from which of the following?
- mesoderm
- cartilage
- ectoderm
- endoderm
A full complement of mature alveoli are present by ________.
- early childhood, around 8 years of age
- birth
- 37 weeks
- 16 weeks
If a baby is born prematurely before type II cells produce sufficient pulmonary surfactant, which of the following might you expect?
- difficulty expressing fluid
- difficulty inflating the lungs
- difficulty with pulmonary capillary flow
- no difficulty as type I cells can provide enough surfactant for normal breathing
When do fetal breathing movements begin?
- around week 20
- around week 37
- around week 16
- after birth
What happens to the fluid that remains in the lungs after birth?
- It reduces the surface tension of the alveoli.
- It is expelled shortly after birth.
- It is absorbed shortly after birth.
- It lubricates the pleurae.
Critical Thinking Questions
Describe the three regions of the pharynx and their functions.
37.If a person sustains an injury to the epiglottis, what would be the physiological result?
38.Compare and contrast the conducting and respiratory zones.
39.Compare and contrast the right and left lungs.
40.Why are the pleurae not damaged during normal breathing?
41.Describe what is meant by the term “lung compliance.”
42.Outline the steps involved in quiet breathing.
43.What is respiratory rate and how is it controlled?
44.Compare and contrast Dalton’s law and Henry’s law.
45.A smoker develops damage to several alveoli that then can no longer function. How does this affect gas exchange?
46.Compare and contrast adult hemoglobin and fetal hemoglobin.
47.Describe the relationship between the partial pressure of oxygen and the binding of oxygen to hemoglobin.
48.Describe three ways in which carbon dioxide can be transported.
49.Describe the neural factors involved in increasing ventilation during exercise.
50.What is the major mechanism that results in acclimatization?
51.During what timeframe does a fetus have enough mature structures to breathe on its own if born prematurely? Describe the other structures that develop during this phase.
52.Describe fetal breathing movements and their purpose.
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2025-03-18T00:37:11.473485
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https://oercommons.org/courseware/lesson/58771/overview
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The Digestive System
Introduction
Figure 23.1 Eating Apples Eating may be one of the simple pleasures in life, but digesting even one apple requires the coordinated work of many organs. (credit: “Aimanness Photography”/Flickr)
CHAPTER OBJECTIVES
After studying this chapter, you will be able to:
- List and describe the functional anatomy of the organs and accessory organs of the digestive system
- Discuss the processes and control of ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation
- Discuss the roles of the liver, pancreas, and gallbladder in digestion
- Compare and contrast the digestion of the three macronutrients
The digestive system is continually at work, yet people seldom appreciate the complex tasks it performs in a choreographed biologic symphony. Consider what happens when you eat an apple. Of course, you enjoy the apple’s taste as you chew it, but in the hours that follow, unless something goes amiss and you get a stomachache, you don’t notice that your digestive system is working. You may be taking a walk or studying or sleeping, having forgotten all about the apple, but your stomach and intestines are busy digesting it and absorbing its vitamins and other nutrients. By the time any waste material is excreted, the body has appropriated all it can use from the apple. In short, whether you pay attention or not, the organs of the digestive system perform their specific functions, allowing you to use the food you eat to keep you going. This chapter examines the structure and functions of these organs, and explores the mechanics and chemistry of the digestive processes.
Overview of the Digestive System
By the end of this section, you will be able to:
- Identify the organs of the alimentary canal from proximal to distal, and briefly state their function
- Identify the accessory digestive organs and briefly state their function
Describe the four fundamental tissue layers of the alimentary canal
Contrast the contributions of the enteric and autonomic nervous systems to digestive system functioning
- Explain how the peritoneum anchors the digestive organs
The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process (Figure 23.2).
Figure 23.2 Components of the Digestive System All digestive organs play integral roles in the life-sustaining process of digestion.
As is the case with all body systems, the digestive system does not work in isolation; it functions cooperatively with the other systems of the body. Consider for example, the interrelationship between the digestive and cardiovascular systems. Arteries supply the digestive organs with oxygen and processed nutrients, and veins drain the digestive tract. These intestinal veins, constituting the hepatic portal system, are unique; they do not return blood directly to the heart. Rather, this blood is diverted to the liver where its nutrients are off-loaded for processing before blood completes its circuit back to the heart. At the same time, the digestive system provides nutrients to the heart muscle and vascular tissue to support their functioning. The interrelationship of the digestive and endocrine systems is also critical. Hormones secreted by several endocrine glands, as well as endocrine cells of the pancreas, the stomach, and the small intestine, contribute to the control of digestion and nutrient metabolism. In turn, the digestive system provides the nutrients to fuel endocrine function. Table 23.1 gives a quick glimpse at how these other systems contribute to the functioning of the digestive system.
Contribution of Other Body Systems to the Digestive System
| Body system | Benefits received by the digestive system |
|---|---|
| Cardiovascular | Blood supplies digestive organs with oxygen and processed nutrients |
| Endocrine | Endocrine hormones help regulate secretion in digestive glands and accessory organs |
| Integumentary | Skin helps protect digestive organs and synthesizes vitamin D for calcium absorption |
| Lymphatic | Mucosa-associated lymphoid tissue and other lymphatic tissue defend against entry of pathogens; lacteals absorb lipids; and lymphatic vessels transport lipids to bloodstream |
| Muscular | Skeletal muscles support and protect abdominal organs |
| Nervous | Sensory and motor neurons help regulate secretions and muscle contractions in the digestive tract |
| Respiratory | Respiratory organs provide oxygen and remove carbon dioxide |
| Skeletal | Bones help protect and support digestive organs |
| Urinary | Kidneys convert vitamin D into its active form, allowing calcium absorption in the small intestine |
Table 23.1
Digestive System Organs
The easiest way to understand the digestive system is to divide its organs into two main categories. The first group is the organs that make up the alimentary canal. Accessory digestive organs comprise the second group and are critical for orchestrating the breakdown of food and the assimilation of its nutrients into the body. Accessory digestive organs, despite their name, are critical to the function of the digestive system.
Alimentary Canal Organs
Also called the gastrointestinal (GI) tract or gut, the alimentary canal (aliment- = “to nourish”) is a one-way tube about 7.62 meters (25 feet) in length during life and closer to 10.67 meters (35 feet) in length when measured after death, once smooth muscle tone is lost. The main function of the organs of the alimentary canal is to nourish the body. This tube begins at the mouth and terminates at the anus. Between those two points, the canal is modified as the pharynx, esophagus, stomach, and small and large intestines to fit the functional needs of the body. Both the mouth and anus are open to the external environment; thus, food and wastes within the alimentary canal are technically considered to be outside the body. Only through the process of absorption do the nutrients in food enter into and nourish the body’s “inner space.”
Accessory Structures
Each accessory digestive organ aids in the breakdown of food (Figure 23.3). Within the mouth, the teeth and tongue begin mechanical digestion, whereas the salivary glands begin chemical digestion. Once food products enter the small intestine, the gallbladder, liver, and pancreas release secretions—such as bile and enzymes—essential for digestion to continue. Together, these are called accessory organs because they sprout from the lining cells of the developing gut (mucosa) and augment its function; indeed, you could not live without their vital contributions, and many significant diseases result from their malfunction. Even after development is complete, they maintain a connection to the gut by way of ducts.
Histology of the Alimentary Canal
Throughout its length, the alimentary tract is composed of the same four tissue layers; the details of their structural arrangements vary to fit their specific functions. Starting from the lumen and moving outwards, these layers are the mucosa, submucosa, muscularis, and serosa, which is continuous with the mesentery (see Figure 23.3).
Figure 23.3 Layers of the Alimentary Canal The wall of the alimentary canal has four basic tissue layers: the mucosa, submucosa, muscularis, and serosa.
The mucosa is referred to as a mucous membrane, because mucus production is a characteristic feature of gut epithelium. The membrane consists of epithelium, which is in direct contact with ingested food, and the lamina propria, a layer of connective tissue analogous to the dermis. In addition, the mucosa has a thin, smooth muscle layer, called the muscularis mucosa (not to be confused with the muscularis layer, described below).
Epithelium—In the mouth, pharynx, esophagus, and anal canal, the epithelium is primarily a non-keratinized, stratified squamous epithelium. In the stomach and intestines, it is a simple columnar epithelium. Notice that the epithelium is in direct contact with the lumen, the space inside the alimentary canal. Interspersed among its epithelial cells are goblet cells, which secrete mucus and fluid into the lumen, and enteroendocrine cells, which secrete hormones into the interstitial spaces between cells. Epithelial cells have a very brief lifespan, averaging from only a couple of days (in the mouth) to about a week (in the gut). This process of rapid renewal helps preserve the health of the alimentary canal, despite the wear and tear resulting from continued contact with foodstuffs.
Lamina propria—In addition to loose connective tissue, the lamina propria contains numerous blood and lymphatic vessels that transport nutrients absorbed through the alimentary canal to other parts of the body. The lamina propria also serves an immune function by housing clusters of lymphocytes, making up the mucosa-associated lymphoid tissue (MALT). These lymphocyte clusters are particularly substantial in the distal ileum where they are known as Peyer’s patches. When you consider that the alimentary canal is exposed to foodborne bacteria and other foreign matter, it is not hard to appreciate why the immune system has evolved a means of defending against the pathogens encountered within it.
Muscularis mucosa—This thin layer of smooth muscle is in a constant state of tension, pulling the mucosa of the stomach and small intestine into undulating folds. These folds dramatically increase the surface area available for digestion and absorption.
As its name implies, the submucosa lies immediately beneath the mucosa. A broad layer of dense connective tissue, it connects the overlying mucosa to the underlying muscularis. It includes blood and lymphatic vessels (which transport absorbed nutrients), and a scattering of submucosal glands that release digestive secretions. Additionally, it serves as a conduit for a dense branching network of nerves, the submucosal plexus, which functions as described below.
The third layer of the alimentary canal is the muscularis (also called the muscularis externa). The muscularis in the small intestine is made up of a double layer of smooth muscle: an inner circular layer and an outer longitudinal layer. The contractions of these layers promote mechanical digestion, expose more of the food to digestive chemicals, and move the food along the canal. In the most proximal and distal regions of the alimentary canal, including the mouth, pharynx, anterior part of the esophagus, and external anal sphincter, the muscularis is made up of skeletal muscle, which gives you voluntary control over swallowing and defecation. The basic two-layer structure found in the small intestine is modified in the organs proximal and distal to it. The stomach is equipped for its churning function by the addition of a third layer, the oblique muscle. While the colon has two layers like the small intestine, its longitudinal layer is segregated into three narrow parallel bands, the tenia coli, which make it look like a series of pouches rather than a simple tube.
The serosa is the portion of the alimentary canal superficial to the muscularis. Present only in the region of the alimentary canal within the abdominal cavity, it consists of a layer of visceral peritoneum overlying a layer of loose connective tissue. Instead of serosa, the mouth, pharynx, and esophagus have a dense sheath of collagen fibers called the adventitia. These tissues serve to hold the alimentary canal in place near the ventral surface of the vertebral column.
Nerve Supply
As soon as food enters the mouth, it is detected by receptors that send impulses along the sensory neurons of cranial nerves. Without these nerves, not only would your food be without taste, but you would also be unable to feel either the food or the structures of your mouth, and you would be unable to avoid biting yourself as you chew, an action enabled by the motor branches of cranial nerves.
Intrinsic innervation of much of the alimentary canal is provided by the enteric nervous system, which runs from the esophagus to the anus, and contains approximately 100 million motor, sensory, and interneurons (unique to this system compared to all other parts of the peripheral nervous system). These enteric neurons are grouped into two plexuses. The myenteric plexus(plexus of Auerbach) lies in the muscularis layer of the alimentary canal and is responsible for motility, especially the rhythm and force of the contractions of the muscularis. The submucosal plexus (plexus of Meissner) lies in the submucosal layer and is responsible for regulating digestive secretions and reacting to the presence of food (see Figure 23.3).
Extrinsic innervations of the alimentary canal are provided by the autonomic nervous system, which includes both sympathetic and parasympathetic nerves. In general, sympathetic activation (the fight-or-flight response) restricts the activity of enteric neurons, thereby decreasing GI secretion and motility. In contrast, parasympathetic activation (the rest-and-digest response) increases GI secretion and motility by stimulating neurons of the enteric nervous system.
Blood Supply
The blood vessels serving the digestive system have two functions. They transport the protein and carbohydrate nutrients absorbed by mucosal cells after food is digested in the lumen. Lipids are absorbed via lacteals, tiny structures of the lymphatic system. The blood vessels’ second function is to supply the organs of the alimentary canal with the nutrients and oxygen needed to drive their cellular processes.
Specifically, the more anterior parts of the alimentary canal are supplied with blood by arteries branching off the aortic arch and thoracic aorta. Below this point, the alimentary canal is supplied with blood by arteries branching from the abdominal aorta. The celiac trunk services the liver, stomach, and duodenum, whereas the superior and inferior mesenteric arteries supply blood to the remaining small and large intestines.
The veins that collect nutrient-rich blood from the small intestine (where most absorption occurs) empty into the hepatic portal system. This venous network takes the blood into the liver where the nutrients are either processed or stored for later use. Only then does the blood drained from the alimentary canal viscera circulate back to the heart. To appreciate just how demanding the digestive process is on the cardiovascular system, consider that while you are “resting and digesting,” about one-fourth of the blood pumped with each heartbeat enters arteries serving the intestines.
The Peritoneum
The digestive organs within the abdominal cavity are held in place by the peritoneum, a broad serous membranous sac made up of squamous epithelial tissue surrounded by connective tissue. It is composed of two different regions: the parietal peritoneum, which lines the abdominal wall, and the visceral peritoneum, which envelopes the abdominal organs (Figure 23.4). The peritoneal cavity is the space bounded by the visceral and parietal peritoneal surfaces. A few milliliters of watery fluid act as a lubricant to minimize friction between the serosal surfaces of the peritoneum.
Figure 23.4 The Peritoneum A cross-section of the abdomen shows the relationship between abdominal organs and the peritoneum (darker lines).
DISORDERS OF THE...
Digestive System: Peritonitis
Inflammation of the peritoneum is called peritonitis. Chemical peritonitis can develop any time the wall of the alimentary canal is breached, allowing the contents of the lumen entry into the peritoneal cavity. For example, when an ulcer perforates the stomach wall, gastric juices spill into the peritoneal cavity. Hemorrhagic peritonitis occurs after a ruptured tubal pregnancy or traumatic injury to the liver or spleen fills the peritoneal cavity with blood. Even more severe peritonitis is associated with bacterial infections seen with appendicitis, colonic diverticulitis, and pelvic inflammatory disease (infection of uterine tubes, usually by sexually transmitted bacteria). Peritonitis is life threatening and often results in emergency surgery to correct the underlying problem and intensive antibiotic therapy. When your great grandparents and even your parents were young, the mortality from peritonitis was high. Aggressive surgery, improvements in anesthesia safety, the advance of critical care expertise, and antibiotics have greatly improved the mortality rate from this condition. Even so, the mortality rate still ranges from 30 to 40 percent.
The visceral peritoneum includes multiple large folds that envelope various abdominal organs, holding them to the dorsal surface of the body wall. Within these folds are blood vessels, lymphatic vessels, and nerves that innervate the organs with which they are in contact, supplying their adjacent organs. The five major peritoneal folds are described in Table 23.2. Note that during fetal development, certain digestive structures, including the first portion of the small intestine (called the duodenum), the pancreas, and portions of the large intestine (the ascending and descending colon, and the rectum) remain completely or partially posterior to the peritoneum. Thus, the location of these organs is described as retroperitoneal.
The Five Major Peritoneal Folds
| Fold | Description |
|---|---|
| Greater omentum | Apron-like structure that lies superficial to the small intestine and transverse colon; a site of fat deposition in people who are overweight |
| Falciform ligament | Anchors the liver to the anterior abdominal wall and inferior border of the diaphragm |
| Lesser omentum | Suspends the stomach from the inferior border of the liver; provides a pathway for structures connecting to the liver |
| Mesentery | Vertical band of tissue anterior to the lumbar vertebrae and anchoring all of the small intestine except the initial portion (the duodenum) |
| Mesocolon | Attaches two portions of the large intestine (the transverse and sigmoid colon) to the posterior abdominal wall |
Table 23.2
INTERACTIVE LINK
By clicking on this link you can watch a short video of what happens to the food you eat, as it passes from your mouth to your intestine. Along the way, note how the food changes consistency and form. How does this change in consistency facilitate your gaining nutrients from food?
Digestive System Processes and Regulation
- Discuss six fundamental activities of the digestive system, giving an example of each
- Compare and contrast the neural and hormonal controls involved in digestion
The digestive system uses mechanical and chemical activities to break food down into absorbable substances during its journey through the digestive system. Table 23.3 provides an overview of the basic functions of the digestive organs.
INTERACTIVE LINK
Visit this site for an overview of digestion of food in different regions of the digestive tract. Note the route of non-fat nutrients from the small intestine to their release as nutrients to the body.
Functions of the Digestive Organs
| Organ | Major functions | Other functions |
|---|---|---|
| Mouth |
|
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| Pharynx |
|
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| Esophagus |
|
|
| Stomach |
|
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| Small intestine |
|
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| Accessory organs |
|
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| Large intestine |
|
|
Table 23.3
Digestive Processes
The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation.
The first of these processes, ingestion, refers to the entry of food into the alimentary canal through the mouth. There, the food is chewed and mixed with saliva, which contains enzymes that begin breaking down the carbohydrates in the food plus some lipid digestion via lingual lipase. Chewing increases the surface area of the food and allows an appropriately sized bolus to be produced.
Food leaves the mouth when the tongue and pharyngeal muscles propel it into the esophagus. This act of swallowing, the last voluntary act until defecation, is an example of propulsion, which refers to the movement of food through the digestive tract. It includes both the voluntary process of swallowing and the involuntary process of peristalsis. Peristalsis consists of sequential, alternating waves of contraction and relaxation of alimentary wall smooth muscles, which act to propel food along (Figure 23.5). These waves also play a role in mixing food with digestive juices. Peristalsis is so powerful that foods and liquids you swallow enter your stomach even if you are standing on your head.
Figure 23.5 Peristalsis Peristalsis moves food through the digestive tract with alternating waves of muscle contraction and relaxation.
Digestion includes both mechanical and chemical processes. Mechanical digestion is a purely physical process that does not change the chemical nature of the food. Instead, it makes the food smaller to increase both surface area and mobility. It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with saliva. Although there may be a tendency to think that mechanical digestion is limited to the first steps of the digestive process, it occurs after the food leaves the mouth, as well. The mechanical churning of food in the stomach serves to further break it apart and expose more of its surface area to digestive juices, creating an acidic “soup” called chyme. Segmentation, which occurs mainly in the small intestine, consists of localized contractions of circular muscle of the muscularis layer of the alimentary canal. These contractions isolate small sections of the intestine, moving their contents back and forth while continuously subdividing, breaking up, and mixing the contents. By moving food back and forth in the intestinal lumen, segmentation mixes food with digestive juices and facilitates absorption.
In chemical digestion, starting in the mouth, digestive secretions break down complex food molecules into their chemical building blocks (for example, proteins into separate amino acids). These secretions vary in composition, but typically contain water, various enzymes, acids, and salts. The process is completed in the small intestine.
Food that has been broken down is of no value to the body unless it enters the bloodstream and its nutrients are put to work. This occurs through the process of absorption, which takes place primarily within the small intestine. There, most nutrients are absorbed from the lumen of the alimentary canal into the bloodstream through the epithelial cells that make up the mucosa. Lipids are absorbed into lacteals and are transported via the lymphatic vessels to the bloodstream (the subclavian veins near the heart). The details of these processes will be discussed later.
In defecation, the final step in digestion, undigested materials are removed from the body as feces.
AGING AND THE...
Digestive System: From Appetite Suppression to Constipation
Age-related changes in the digestive system begin in the mouth and can affect virtually every aspect of the digestive system. Taste buds become less sensitive, so food isn’t as appetizing as it once was. A slice of pizza is a challenge, not a treat, when you have lost teeth, your gums are diseased, and your salivary glands aren’t producing enough saliva. Swallowing can be difficult, and ingested food moves slowly through the alimentary canal because of reduced strength and tone of muscular tissue. Neurosensory feedback is also dampened, slowing the transmission of messages that stimulate the release of enzymes and hormones.
Pathologies that affect the digestive organs—such as hiatal hernia, gastritis, and peptic ulcer disease—can occur at greater frequencies as you age. Problems in the small intestine may include duodenal ulcers, maldigestion, and malabsorption. Problems in the large intestine include hemorrhoids, diverticular disease, and constipation. Conditions that affect the function of accessory organs—and their abilities to deliver pancreatic enzymes and bile to the small intestine—include jaundice, acute pancreatitis, cirrhosis, and gallstones.
In some cases, a single organ is in charge of a digestive process. For example, ingestion occurs only in the mouth and defecation only in the anus. However, most digestive processes involve the interaction of several organs and occur gradually as food moves through the alimentary canal (Figure 23.6).
Figure 23.6 Digestive Processes The digestive processes are ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
Some chemical digestion occurs in the mouth. Some absorption can occur in the mouth and stomach, for example, alcohol and aspirin.
Regulatory Mechanisms
Neural and endocrine regulatory mechanisms work to maintain the optimal conditions in the lumen needed for digestion and absorption. These regulatory mechanisms, which stimulate digestive activity through mechanical and chemical activity, are controlled both extrinsically and intrinsically.
Neural Controls
The walls of the alimentary canal contain a variety of sensors that help regulate digestive functions. These include mechanoreceptors, chemoreceptors, and osmoreceptors, which are capable of detecting mechanical, chemical, and osmotic stimuli, respectively. For example, these receptors can sense when the presence of food has caused the stomach to expand, whether food particles have been sufficiently broken down, how much liquid is present, and the type of nutrients in the food (lipids, carbohydrates, and/or proteins). Stimulation of these receptors provokes an appropriate reflex that furthers the process of digestion. This may entail sending a message that activates the glands that secrete digestive juices into the lumen, or it may mean the stimulation of muscles within the alimentary canal, thereby activating peristalsis and segmentation that move food along the intestinal tract.
The walls of the entire alimentary canal are embedded with nerve plexuses that interact with the central nervous system and other nerve plexuses—either within the same digestive organ or in different ones. These interactions prompt several types of reflexes. Extrinsic nerve plexuses orchestrate long reflexes, which involve the central and autonomic nervous systems and work in response to stimuli from outside the digestive system. Short reflexes, on the other hand, are orchestrated by intrinsic nerve plexuses within the alimentary canal wall. These two plexuses and their connections were introduced earlier as the enteric nervous system. Short reflexes regulate activities in one area of the digestive tract and may coordinate local peristaltic movements and stimulate digestive secretions. For example, the sight, smell, and taste of food initiate long reflexes that begin with a sensory neuron delivering a signal to the medulla oblongata. The response to the signal is to stimulate cells in the stomach to begin secreting digestive juices in preparation for incoming food. In contrast, food that distends the stomach initiates short reflexes that cause cells in the stomach wall to increase their secretion of digestive juices.
Hormonal Controls
A variety of hormones are involved in the digestive process. The main digestive hormone of the stomach is gastrin, which is secreted in response to the presence of food. Gastrin stimulates the secretion of gastric acid by the parietal cells of the stomach mucosa. Other GI hormones are produced and act upon the gut and its accessory organs. Hormones produced by the duodenum include secretin, which stimulates a watery secretion of bicarbonate by the pancreas; cholecystokinin (CCK), which stimulates the secretion of pancreatic enzymes and bile from the liver and release of bile from the gallbladder; and gastric inhibitory peptide, which inhibits gastric secretion and slows gastric emptying and motility. These GI hormones are secreted by specialized epithelial cells, called endocrinocytes, located in the mucosal epithelium of the stomach and small intestine. These hormones then enter the bloodstream, through which they can reach their target organs.
The Mouth, Pharynx, and Esophagus
- Describe the structures of the mouth, including its three accessory digestive organs
- Group the 32 adult teeth according to name, location, and function
- Describe the process of swallowing, including the roles of the tongue, upper esophageal sphincter, and epiglottis
- Trace the pathway food follows from ingestion into the mouth through release into the stomach
In this section, you will examine the anatomy and functions of the three main organs of the upper alimentary canal—the mouth, pharynx, and esophagus—as well as three associated accessory organs—the tongue, salivary glands, and teeth.
The Mouth
The cheeks, tongue, and palate frame the mouth, which is also called the oral cavity (or buccal cavity). The structures of the mouth are illustrated in Figure 23.7.
At the entrance to the mouth are the lips, or labia (singular = labium). Their outer covering is skin, which transitions to a mucous membrane in the mouth proper. Lips are very vascular with a thin layer of keratin; hence, the reason they are "red." They have a huge representation on the cerebral cortex, which probably explains the human fascination with kissing! The lips cover the orbicularis oris muscle, which regulates what comes in and goes out of the mouth. The labial frenulum is a midline fold of mucous membrane that attaches the inner surface of each lip to the gum. The cheeks make up the oral cavity’s sidewalls. While their outer covering is skin, their inner covering is mucous membrane. This membrane is made up of non-keratinized, stratified squamous epithelium. Between the skin and mucous membranes are connective tissue and buccinator muscles. The next time you eat some food, notice how the buccinator muscles in your cheeks and the orbicularis oris muscle in your lips contract, helping you keep the food from falling out of your mouth. Additionally, notice how these muscles work when you are speaking.
The pocket-like part of the mouth that is framed on the inside by the gums and teeth, and on the outside by the cheeks and lips is called the oral vestibule. Moving farther into the mouth, the opening between the oral cavity and throat (oropharynx) is called the fauces (like the kitchen "faucet"). The main open area of the mouth, or oral cavity proper, runs from the gums and teeth to the fauces.
When you are chewing, you do not find it difficult to breathe simultaneously. The next time you have food in your mouth, notice how the arched shape of the roof of your mouth allows you to handle both digestion and respiration at the same time. This arch is called the palate. The anterior region of the palate serves as a wall (or septum) between the oral and nasal cavities as well as a rigid shelf against which the tongue can push food. It is created by the maxillary and palatine bones of the skull and, given its bony structure, is known as the hard palate. If you run your tongue along the roof of your mouth, you’ll notice that the hard palate ends in the posterior oral cavity, and the tissue becomes fleshier. This part of the palate, known as the soft palate, is composed mainly of skeletal muscle. You can therefore manipulate, subconsciously, the soft palate—for instance, to yawn, swallow, or sing (see Figure 23.7).
Figure 23.7 Mouth The mouth includes the lips, tongue, palate, gums, and teeth.
A fleshy bead of tissue called the uvula drops down from the center of the posterior edge of the soft palate. Although some have suggested that the uvula is a vestigial organ, it serves an important purpose. When you swallow, the soft palate and uvula move upward, helping to keep foods and liquid from entering the nasal cavity. Unfortunately, it can also contribute to the sound produced by snoring. Two muscular folds extend downward from the soft palate, on either side of the uvula. Toward the front, the palatoglossal arch lies next to the base of the tongue; behind it, the palatopharyngeal arch forms the superior and lateral margins of the fauces. Between these two arches are the palatine tonsils, clusters of lymphoid tissue that protect the pharynx. The lingual tonsils are located at the base of the tongue.
The Tongue
Perhaps you have heard it said that the tongue is the strongest muscle in the body. Those who stake this claim cite its strength proportionate to its size. Although it is difficult to quantify the relative strength of different muscles, it remains indisputable that the tongue is a workhorse, facilitating ingestion, mechanical digestion, chemical digestion (lingual lipase), sensation (of taste, texture, and temperature of food), swallowing, and vocalization.
The tongue is attached to the mandible, the styloid processes of the temporal bones, and the hyoid bone. The hyoid is unique in that it only distantly/indirectly articulates with other bones. The tongue is positioned over the floor of the oral cavity. A medial septum extends the entire length of the tongue, dividing it into symmetrical halves.
Beneath its mucous membrane covering, each half of the tongue is composed of the same number and type of intrinsic and extrinsic skeletal muscles. The intrinsic muscles (those within the tongue) are the longitudinalis inferior, longitudinalis superior, transversus linguae, and verticalis linguae muscles. These allow you to change the size and shape of your tongue, as well as to stick it out, if you wish. Having such a flexible tongue facilitates both swallowing and speech.
As you learned in your study of the muscular system, the extrinsic muscles of the tongue are the mylohyoid, hyoglossus, styloglossus, and genioglossus muscles. These muscles originate outside the tongue and insert into connective tissues within the tongue. The mylohyoid is responsible for raising the tongue, the hyoglossus pulls it down and back, the styloglossus pulls it up and back, and the genioglossus pulls it forward. Working in concert, these muscles perform three important digestive functions in the mouth: (1) position food for optimal chewing, (2) gather food into a bolus (rounded mass), and (3) position food so it can be swallowed.
The top and sides of the tongue are studded with papillae, extensions of lamina propria of the mucosa, which are covered in stratified squamous epithelium (Figure 23.8). Fungiform papillae, which are mushroom shaped, cover a large area of the tongue; they tend to be larger toward the rear of the tongue and smaller on the tip and sides. In contrast, filiform papillae are long and thin. Fungiform papillae contain taste buds, and filiform papillae have touch receptors that help the tongue move food around in the mouth. The filiform papillae create an abrasive surface that performs mechanically, much like a cat’s rough tongue that is used for grooming. Lingual glands in the lamina propria of the tongue secrete mucus and a watery serous fluid that contains the enzyme lingual lipase, which plays a minor role in breaking down triglycerides but does not begin working until it is activated in the stomach. A fold of mucous membrane on the underside of the tongue, the lingual frenulum, tethers the tongue to the floor of the mouth. People with the congenital anomaly ankyloglossia, also known by the non-medical term “tongue tie,” have a lingual frenulum that is too short or otherwise malformed. Severe ankyloglossia can impair speech and must be corrected with surgery.
Figure 23.8 Tongue This superior view of the tongue shows the locations and types of lingual papillae.
The Salivary Glands
Many small salivary glands are housed within the mucous membranes of the mouth and tongue. These minor exocrine glands are constantly secreting saliva, either directly into the oral cavity or indirectly through ducts, even while you sleep. In fact, an average of 1 to 1.5 liters of saliva is secreted each day. Usually just enough saliva is present to moisten the mouth and teeth. Secretion increases when you eat, because saliva is essential to moisten food and initiate the chemical breakdown of carbohydrates. Small amounts of saliva are also secreted by the labial glands in the lips. In addition, the buccal glands in the cheeks, palatal glands in the palate, and lingual glands in the tongue help ensure that all areas of the mouth are supplied with adequate saliva.
The Major Salivary Glands
Outside the oral mucosa are three pairs of major salivary glands, which secrete the majority of saliva into ducts that open into the mouth:
- The submandibular glands, which are in the floor of the mouth, secrete saliva into the mouth through the submandibular ducts.
- The sublingual glands, which lie below the tongue, use the lesser sublingual ducts to secrete saliva into the oral cavity.
- The parotid glands lie between the skin and the masseter muscle, near the ears. They secrete saliva into the mouth through the parotid duct, which is located near the second upper molar tooth (Figure 23.9).
Saliva
Saliva is essentially (98 to 99.5 percent) water. The remaining 4.5 percent is a complex mixture of ions, glycoproteins, enzymes, growth factors, and waste products. Perhaps the most important ingredient in saliva from the perspective of digestion is the enzyme salivary amylase, which initiates the breakdown of carbohydrates. Food does not spend enough time in the mouth to allow all the carbohydrates to break down, but salivary amylase continues acting until it is inactivated by stomach acids. Bicarbonate and phosphate ions function as chemical buffers, maintaining saliva at a pH between 6.35 and 6.85. Salivary mucus helps lubricate food, facilitating movement in the mouth, bolus formation, and swallowing. Saliva contains immunoglobulin A, which prevents microbes from penetrating the epithelium, and lysozyme, which makes saliva antimicrobial. Saliva also contains epidermal growth factor, which might have given rise to the adage “a mother’s kiss can heal a wound.”
Each of the major salivary glands secretes a unique formulation of saliva according to its cellular makeup. For example, the parotid glands secrete a watery solution that contains salivary amylase. The submandibular glands have cells similar to those of the parotid glands, as well as mucus-secreting cells. Therefore, saliva secreted by the submandibular glands also contains amylase but in a liquid thickened with mucus. The sublingual glands contain mostly mucous cells, and they secrete the thickest saliva with the least amount of salivary amylase.
Figure 23.9 Salivary glands The major salivary glands are located outside the oral mucosa and deliver saliva into the mouth through ducts.
HOMEOSTATIC IMBALANCES
The Parotid Glands: Mumps
Infections of the nasal passages and pharynx can attack any salivary gland. The parotid glands are the usual site of infection with the virus that causes mumps (paramyxovirus). Mumps manifests by enlargement and inflammation of the parotid glands, causing a characteristic swelling between the ears and the jaw. Symptoms include fever and throat pain, which can be severe when swallowing acidic substances such as orange juice.
In about one-third of men who are past puberty, mumps also causes testicular inflammation, typically affecting only one testis and rarely resulting in sterility. With the increasing use and effectiveness of mumps vaccines, the incidence of mumps has decreased dramatically. According to the U.S. Centers for Disease Control and Prevention (CDC), the number of mumps cases dropped from more than 150,000 in 1968 to fewer than 1700 in 1993 to only 11 reported cases in 2011.
Regulation of Salivation
The autonomic nervous system regulates salivation (the secretion of saliva). In the absence of food, parasympathetic stimulation keeps saliva flowing at just the right level for comfort as you speak, swallow, sleep, and generally go about life. Over-salivation can occur, for example, if you are stimulated by the smell of food, but that food is not available for you to eat. Drooling is an extreme instance of the overproduction of saliva. During times of stress, such as before speaking in public, sympathetic stimulation takes over, reducing salivation and producing the symptom of dry mouth often associated with anxiety. When you are dehydrated, salivation is reduced, causing the mouth to feel dry and prompting you to take action to quench your thirst.
Salivation can be stimulated by the sight, smell, and taste of food. It can even be stimulated by thinking about food. You might notice whether reading about food and salivation right now has had any effect on your production of saliva.
How does the salivation process work while you are eating? Food contains chemicals that stimulate taste receptors on the tongue, which send impulses to the superior and inferior salivatory nuclei in the brain stem. These two nuclei then send back parasympathetic impulses through fibers in the glossopharyngeal and facial nerves, which stimulate salivation. Even after you swallow food, salivation is increased to cleanse the mouth and to water down and neutralize any irritating chemical remnants, such as that hot sauce in your burrito. Most saliva is swallowed along with food and is reabsorbed, so that fluid is not lost.
The Teeth
The teeth, or dentes (singular = dens), are organs similar to bones that you use to tear, grind, and otherwise mechanically break down food.
Types of Teeth
During the course of your lifetime, you have two sets of teeth (one set of teeth is a dentition). Your 20 deciduous teeth, or baby teeth, first begin to appear at about 6 months of age. Between approximately age 6 and 12, these teeth are replaced by 32 permanent teeth. Moving from the center of the mouth toward the side, these are as follows (Figure 23.10):
- The eight incisors, four top and four bottom, are the sharp front teeth you use for biting into food.
- The four cuspids (or canines) flank the incisors and have a pointed edge (cusp) to tear up food. These fang-like teeth are superb for piercing tough or fleshy foods.
- Posterior to the cuspids are the eight premolars (or bicuspids), which have an overall flatter shape with two rounded cusps useful for mashing foods.
- The most posterior and largest are the 12 molars, which have several pointed cusps used to crush food so it is ready for swallowing. The third members of each set of three molars, top and bottom, are commonly referred to as the wisdom teeth, because their eruption is commonly delayed until early adulthood. It is not uncommon for wisdom teeth to fail to erupt; that is, they remain impacted. In these cases, the teeth are typically removed by orthodontic surgery.
Figure 23.10 Permanent and Deciduous Teeth This figure of two human dentitions shows the arrangement of teeth in the maxilla and mandible, and the relationship between the deciduous and permanent teeth.
Anatomy of a Tooth
The teeth are secured in the alveolar processes (sockets) of the maxilla and the mandible. Gingivae (commonly called the gums) are soft tissues that line the alveolar processes and surround the necks of the teeth. Teeth are also held in their sockets by a connective tissue called the periodontal ligament.
The two main parts of a tooth are the crown, which is the portion projecting above the gum line, and the root, which is embedded within the maxilla and mandible. Both parts contain an inner pulp cavity, containing loose connective tissue through which run nerves and blood vessels. The region of the pulp cavity that runs through the root of the tooth is called the root canal. Surrounding the pulp cavity is dentin, a bone-like tissue. In the root of each tooth, the dentin is covered by an even harder bone-like layer called cementum. In the crown of each tooth, the dentin is covered by an outer layer of enamel, the hardest substance in the body (Figure 23.11).
Although enamel protects the underlying dentin and pulp cavity, it is still nonetheless susceptible to mechanical and chemical erosion, or what is known as tooth decay. The most common form, dental caries (cavities) develops when colonies of bacteria feeding on sugars in the mouth release acids that cause soft tissue inflammation and degradation of the calcium crystals of the enamel. The digestive functions of the mouth are summarized in Table 23.4.
Figure 23.11 The Structure of the Tooth This longitudinal section through a molar in its alveolar socket shows the relationships between enamel, dentin, and pulp.
Digestive Functions of the Mouth
| Structure | Action | Outcome |
|---|---|---|
| Lips and cheeks | Confine food between teeth |
|
| Salivary glands | Secrete saliva |
|
| Tongue’s extrinsic muscles | Move tongue sideways, and in and out |
|
| Tongue’s intrinsic muscles | Change tongue shape |
|
| Taste buds | Sense food in mouth and sense taste |
|
| Lingual glands | Secrete lingual lipase |
|
| Teeth | Shred and crush food |
|
Table 23.4
The Pharynx
The pharynx (throat) is involved in both digestion and respiration. It receives food and air from the mouth, and air from the nasal cavities. When food enters the pharynx, involuntary muscle contractions close off the air passageways.
A short tube of skeletal muscle lined with a mucous membrane, the pharynx runs from the posterior oral and nasal cavities to the opening of the esophagus and larynx. It has three subdivisions. The most superior, the nasopharynx, is involved only in breathing and speech. The other two subdivisions, the oropharynx and the laryngopharynx, are used for both breathing and digestion. The oropharynx begins inferior to the nasopharynx and is continuous below with the laryngopharynx (Figure 23.12). The inferior border of the laryngopharynx connects to the esophagus, whereas the anterior portion connects to the larynx, allowing air to flow into the bronchial tree.
Figure 23.12 Pharynx The pharynx runs from the nostrils to the esophagus and the larynx.
Histologically, the wall of the oropharynx is similar to that of the oral cavity. The mucosa includes a stratified squamous epithelium that is endowed with mucus-producing glands. During swallowing, the elevator skeletal muscles of the pharynx contract, raising and expanding the pharynx to receive the bolus of food. Once received, these muscles relax and the constrictor muscles of the pharynx contract, forcing the bolus into the esophagus and initiating peristalsis.
Usually during swallowing, the soft palate and uvula rise reflexively to close off the entrance to the nasopharynx. At the same time, the larynx is pulled superiorly and the cartilaginous epiglottis, its most superior structure, folds inferiorly, covering the glottis (the opening to the larynx); this process effectively blocks access to the trachea and bronchi. When the food “goes down the wrong way,” it goes into the trachea. When food enters the trachea, the reaction is to cough, which usually forces the food up and out of the trachea, and back into the pharynx.
The Esophagus
The esophagus is a muscular tube that connects the pharynx to the stomach. It is approximately 25.4 cm (10 in) in length, located posterior to the trachea, and remains in a collapsed form when not engaged in swallowing. As you can see in Figure 23.13, the esophagus runs a mainly straight route through the mediastinum of the thorax. To enter the abdomen, the esophagus penetrates the diaphragm through an opening called the esophageal hiatus.
Passage of Food through the Esophagus
The upper esophageal sphincter, which is continuous with the inferior pharyngeal constrictor, controls the movement of food from the pharynx into the esophagus. The upper two-thirds of the esophagus consists of both smooth and skeletal muscle fibers, with the latter fading out in the bottom third of the esophagus. Rhythmic waves of peristalsis, which begin in the upper esophagus, propel the bolus of food toward the stomach. Meanwhile, secretions from the esophageal mucosa lubricate the esophagus and food. Food passes from the esophagus into the stomach at the lower esophageal sphincter (also called the gastroesophageal or cardiac sphincter). Recall that sphincters are muscles that surround tubes and serve as valves, closing the tube when the sphincters contract and opening it when they relax. The lower esophageal sphincter relaxes to let food pass into the stomach, and then contracts to prevent stomach acids from backing up into the esophagus. Surrounding this sphincter is the muscular diaphragm, which helps close off the sphincter when no food is being swallowed. When the lower esophageal sphincter does not completely close, the stomach’s contents can reflux (that is, back up into the esophagus), causing heartburn or gastroesophageal reflux disease (GERD).
Figure 23.13 Esophagus The upper esophageal sphincter controls the movement of food from the pharynx to the esophagus. The lower esophageal sphincter controls the movement of food from the esophagus to the stomach.
Histology of the Esophagus
The mucosa of the esophagus is made up of an epithelial lining that contains non-keratinized, stratified squamous epithelium, with a layer of basal and parabasal cells. This epithelium protects against erosion from food particles. The mucosa’s lamina propria contains mucus-secreting glands. The muscularis layer changes according to location: In the upper third of the esophagus, the muscularis is skeletal muscle. In the middle third, it is both skeletal and smooth muscle. In the lower third, it is smooth muscle. As mentioned previously, the most superficial layer of the esophagus is called the adventitia, not the serosa. In contrast to the stomach and intestines, the loose connective tissue of the adventitia is not covered by a fold of visceral peritoneum. The digestive functions of the esophagus are identified in Table 23.5.
Digestive Functions of the Esophagus
| Action | Outcome |
|---|---|
| Upper esophageal sphincter relaxation | Allows the bolus to move from the laryngopharynx to the esophagus |
| Peristalsis | Propels the bolus through the esophagus |
| Lower esophageal sphincter relaxation | Allows the bolus to move from the esophagus into the stomach and prevents chime from entering the esophagus |
| Mucus secretion | Lubricates the esophagus, allowing easy passage of the bolus |
Table 23.5
Deglutition
Deglutition is another word for swallowing—the movement of food from the mouth to the stomach. The entire process takes about 4 to 8 seconds for solid or semisolid food, and about 1 second for very soft food and liquids. Although this sounds quick and effortless, deglutition is, in fact, a complex process that involves both the skeletal muscle of the tongue and the muscles of the pharynx and esophagus. It is aided by the presence of mucus and saliva. There are three stages in deglutition: the voluntary phase, the pharyngeal phase, and the esophageal phase (Figure 23.14). The autonomic nervous system controls the latter two phases.
Figure 23.14 Deglutition Deglutition includes the voluntary phase and two involuntary phases: the pharyngeal phase and the esophageal phase.
The Voluntary Phase
The voluntary phase of deglutition (also known as the oral or buccal phase) is so called because you can control when you swallow food. In this phase, chewing has been completed and swallowing is set in motion. The tongue moves upward and backward against the palate, pushing the bolus to the back of the oral cavity and into the oropharynx. Other muscles keep the mouth closed and prevent food from falling out. At this point, the two involuntary phases of swallowing begin.
The Pharyngeal Phase
In the pharyngeal phase, stimulation of receptors in the oropharynx sends impulses to the deglutition center (a collection of neurons that controls swallowing) in the medulla oblongata. Impulses are then sent back to the uvula and soft palate, causing them to move upward and close off the nasopharynx. The laryngeal muscles also constrict to prevent aspiration of food into the trachea. At this point, deglutition apnea takes place, which means that breathing ceases for a very brief time. Contractions of the pharyngeal constrictor muscles move the bolus through the oropharynx and laryngopharynx. Relaxation of the upper esophageal sphincter then allows food to enter the esophagus.
The Esophageal Phase
The entry of food into the esophagus marks the beginning of the esophageal phase of deglutition and the initiation of peristalsis. As in the previous phase, the complex neuromuscular actions are controlled by the medulla oblongata. Peristalsis propels the bolus through the esophagus and toward the stomach. The circular muscle layer of the muscularis contracts, pinching the esophageal wall and forcing the bolus forward. At the same time, the longitudinal muscle layer of the muscularis also contracts, shortening this area and pushing out its walls to receive the bolus. In this way, a series of contractions keeps moving food toward the stomach. When the bolus nears the stomach, distention of the esophagus initiates a short reflex relaxation of the lower esophageal sphincter that allows the bolus to pass into the stomach. During the esophageal phase, esophageal glands secrete mucus that lubricates the bolus and minimizes friction.
INTERACTIVE LINK
Watch this animation to see how swallowing is a complex process that involves the nervous system to coordinate the actions of upper respiratory and digestive activities. During which stage of swallowing is there a risk of food entering respiratory pathways and how is this risk blocked?
The Stomach
- Label on a diagram the four main regions of the stomach, its curvatures, and its sphincter
- Identify the four main types of secreting cells in gastric glands, and their important products
- Explain why the stomach does not digest itself
- Describe the mechanical and chemical digestion of food entering the stomach
Although a minimal amount of carbohydrate digestion occurs in the mouth, chemical digestion really gets underway in the stomach. An expansion of the alimentary canal that lies immediately inferior to the esophagus, the stomach links the esophagus to the first part of the small intestine (the duodenum) and is relatively fixed in place at its esophageal and duodenal ends. In between, however, it can be a highly active structure, contracting and continually changing position and size. These contractions provide mechanical assistance to digestion. The empty stomach is only about the size of your fist, but can stretch to hold as much as 4 liters of food and fluid, or more than 75 times its empty volume, and then return to its resting size when empty. Although you might think that the size of a person’s stomach is related to how much food that individual consumes, body weight does not correlate with stomach size. Rather, when you eat greater quantities of food—such as at holiday dinner—you stretch the stomach more than when you eat less.
Popular culture tends to refer to the stomach as the location where all digestion takes place. Of course, this is not true. An important function of the stomach is to serve as a temporary holding chamber. You can ingest a meal far more quickly than it can be digested and absorbed by the small intestine. Thus, the stomach holds food and parses only small amounts into the small intestine at a time. Foods are not processed in the order they are eaten; rather, they are mixed together with digestive juices in the stomach until they are converted into chyme, which is released into the small intestine.
As you will see in the sections that follow, the stomach plays several important roles in chemical digestion, including the continued digestion of carbohydrates and the initial digestion of proteins and triglycerides. Little if any nutrient absorption occurs in the stomach, with the exception of the negligible amount of nutrients in alcohol.
Structure
There are four main regions in the stomach: the cardia, fundus, body, and pylorus (Figure 23.15). The cardia (or cardiac region) is the point where the esophagus connects to the stomach and through which food passes into the stomach. Located inferior to the diaphragm, above and to the left of the cardia, is the dome-shaped fundus. Below the fundus is the body, the main part of the stomach. The funnel-shaped pylorus connects the stomach to the duodenum. The wider end of the funnel, the pyloric antrum, connects to the body of the stomach. The narrower end is called the pyloric canal, which connects to the duodenum. The smooth muscle pyloric sphincter is located at this latter point of connection and controls stomach emptying. In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into a large fold called a ruga.
Figure 23.15 Stomach The stomach has four major regions: the cardia, fundus, body, and pylorus. The addition of an inner oblique smooth muscle layer gives the muscularis the ability to vigorously churn and mix food.
The convex lateral surface of the stomach is called the greater curvature; the concave medial border is the lesser curvature. The stomach is held in place by the lesser omentum, which extends from the liver to the lesser curvature, and the greater omentum, which runs from the greater curvature to the posterior abdominal wall.
Histology
The wall of the stomach is made of the same four layers as most of the rest of the alimentary canal, but with adaptations to the mucosa and muscularis for the unique functions of this organ. In addition to the typical circular and longitudinal smooth muscle layers, the muscularis has an inner oblique smooth muscle layer (Figure 23.16). As a result, in addition to moving food through the canal, the stomach can vigorously churn food, mechanically breaking it down into smaller particles.
Figure 23.16 Histology of the Stomach The stomach wall is adapted for the functions of the stomach. In the epithelium, gastric pits lead to gastric glands that secrete gastric juice. The gastric glands (one gland is shown enlarged on the right) contain different types of cells that secrete a variety of enzymes, including hydrochloride acid, which activates the protein-digesting enzyme pepsin.
The stomach mucosa’s epithelial lining consists only of surface mucus cells, which secrete a protective coat of alkaline mucus. A vast number of gastric pits dot the surface of the epithelium, giving it the appearance of a well-used pincushion, and mark the entry to each gastric gland, which secretes a complex digestive fluid referred to as gastric juice.
Although the walls of the gastric pits are made up primarily of mucus cells, the gastric glands are made up of different types of cells. The glands of the cardia and pylorus are composed primarily of mucus-secreting cells. Cells that make up the pyloric antrum secrete mucus and a number of hormones, including the majority of the stimulatory hormone, gastrin. The much larger glands of the fundus and body of the stomach, the site of most chemical digestion, produce most of the gastric secretions. These glands are made up of a variety of secretory cells. These include parietal cells, chief cells, mucous neck cells, and enteroendocrine cells.
Parietal cells—Located primarily in the middle region of the gastric glands are parietal cells, which are among the most highly differentiated of the body’s epithelial cells. These relatively large cells produce both hydrochloric acid (HCl) and intrinsic factor. HCl is responsible for the high acidity (pH 1.5 to 3.5) of the stomach contents and is needed to activate the protein-digesting enzyme, pepsin. The acidity also kills much of the bacteria you ingest with food and helps to denature proteins, making them more available for enzymatic digestion. Intrinsic factor is a glycoprotein necessary for the absorption of vitamin B12in the small intestine.
Chief cells—Located primarily in the basal regions of gastric glands are chief cells, which secrete pepsinogen, the inactive proenzyme form of pepsin. HCl is necessary for the conversion of pepsinogen to pepsin.
Mucous neck cells—Gastric glands in the upper part of the stomach contain mucous neck cells that secrete thin, acidic mucus that is much different from the mucus secreted by the goblet cells of the surface epithelium. The role of this mucus is not currently known.
Enteroendocrine cells—Finally, enteroendocrine cells found in the gastric glands secrete various hormones into the interstitial fluid of the lamina propria. These include gastrin, which is released mainly by enteroendocrine G cells.
Table 23.6 describes the digestive functions of important hormones secreted by the stomach.
INTERACTIVE LINK
Watch this animation that depicts the structure of the stomach and how this structure functions in the initiation of protein digestion. This view of the stomach shows the characteristic rugae. What is the function of these rugae?
Hormones Secreted by the Stomach
| Hormone | Production site | Production stimulus | Target organ | Action |
|---|---|---|---|---|
| Gastrin | Stomach mucosa, mainly G cells of the pyloric antrum | Presence of peptides and amino acids in stomach | Stomach | Increases secretion by gastric glands; promotes gastric emptying |
| Gastrin | Stomach mucosa, mainly G cells of the pyloric antrum | Presence of peptides and amino acids in stomach | Small intestine | Promotes intestinal muscle contraction |
| Gastrin | Stomach mucosa, mainly G cells of the pyloric antrum | Presence of peptides and amino acids in stomach | Ileocecal valve | Relaxes valve |
| Gastrin | Stomach mucosa, mainly G cells of the pyloric antrum | Presence of peptides and amino acids in stomach | Large intestine | Triggers mass movements |
| Ghrelin | Stomach mucosa, mainly fundus | Fasting state (levels increase just prior to meals) | Hypothalamus | Regulates food intake, primarily by stimulating hunger and satiety |
| Histamine | Stomach mucosa | Presence of food in the stomach | Stomach | Stimulates parietal cells to release HCl |
| Serotonin | Stomach mucosa | Presence of food in the stomach | Stomach | Contracts stomach muscle |
| Somatostatin | Mucosa of stomach, especially pyloric antrum; also duodenum | Presence of food in the stomach; sympathetic axon stimulation | Stomach | Restricts all gastric secretions, gastric motility, and emptying |
| Somatostatin | Mucosa of stomach, especially pyloric antrum; also duodenum | Presence of food in the stomach; sympathetic axon stimulation | Pancreas | Restricts pancreatic secretions |
| Somatostatin | Mucosa of stomach, especially pyloric antrum; also duodenum | Presence of food in the stomach; sympathetic axon stimulation | Small intestine | Reduces intestinal absorption by reducing blood flow |
Table 23.6
Gastric Secretion
The secretion of gastric juice is controlled by both nerves and hormones. Stimuli in the brain, stomach, and small intestine activate or inhibit gastric juice production. This is why the three phases of gastric secretion are called the cephalic, gastric, and intestinal phases (Figure 23.17). However, once gastric secretion begins, all three phases can occur simultaneously.
Figure 23.17 The Three Phases of Gastric Secretion Gastric secretion occurs in three phases: cephalic, gastric, and intestinal. During each phase, the secretion of gastric juice can be stimulated or inhibited.
The cephalic phase (reflex phase) of gastric secretion, which is relatively brief, takes place before food enters the stomach. The smell, taste, sight, or thought of food triggers this phase. For example, when you bring a piece of sushi to your lips, impulses from receptors in your taste buds or the nose are relayed to your brain, which returns signals that increase gastric secretion to prepare your stomach for digestion. This enhanced secretion is a conditioned reflex, meaning it occurs only if you like or want a particular food. Depression and loss of appetite can suppress the cephalic reflex.
The gastric phase of secretion lasts 3 to 4 hours, and is set in motion by local neural and hormonal mechanisms triggered by the entry of food into the stomach. For example, when your sushi reaches the stomach, it creates distention that activates the stretch receptors. This stimulates parasympathetic neurons to release acetylcholine, which then provokes increased secretion of gastric juice. Partially digested proteins, caffeine, and rising pH stimulate the release of gastrin from enteroendocrine G cells, which in turn induces parietal cells to increase their production of HCl, which is needed to create an acidic environment for the conversion of pepsinogen to pepsin, and protein digestion. Additionally, the release of gastrin activates vigorous smooth muscle contractions. However, it should be noted that the stomach does have a natural means of avoiding excessive acid secretion and potential heartburn. Whenever pH levels drop too low, cells in the stomach react by suspending HCl secretion and increasing mucous secretions.
The intestinal phase of gastric secretion has both excitatory and inhibitory elements. The duodenum has a major role in regulating the stomach and its emptying. When partially digested food fills the duodenum, intestinal mucosal cells release a hormone called intestinal (enteric) gastrin, which further excites gastric juice secretion. This stimulatory activity is brief, however, because when the intestine distends with chyme, the enterogastric reflex inhibits secretion. One of the effects of this reflex is to close the pyloric sphincter, which blocks additional chyme from entering the duodenum.
The Mucosal Barrier
The mucosa of the stomach is exposed to the highly corrosive acidity of gastric juice. Gastric enzymes that can digest protein can also digest the stomach itself. The stomach is protected from self-digestion by the mucosal barrier. This barrier has several components. First, the stomach wall is covered by a thick coating of bicarbonate-rich mucus. This mucus forms a physical barrier, and its bicarbonate ions neutralize acid. Second, the epithelial cells of the stomach's mucosa meet at tight junctions, which block gastric juice from penetrating the underlying tissue layers. Finally, stem cells located where gastric glands join the gastric pits quickly replace damaged epithelial mucosal cells, when the epithelial cells are shed. In fact, the surface epithelium of the stomach is completely replaced every 3 to 6 days.
HOMEOSTATIC IMBALANCES
Ulcers: When the Mucosal Barrier Breaks Down
As effective as the mucosal barrier is, it is not a “fail-safe” mechanism. Sometimes, gastric juice eats away at the superficial lining of the stomach mucosa, creating erosions, which mostly heal on their own. Deeper and larger erosions are called ulcers.
Why does the mucosal barrier break down? A number of factors can interfere with its ability to protect the stomach lining. The majority of all ulcers are caused by either excessive intake of non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin, or Helicobacter pylori infection.
Antacids help relieve symptoms of ulcers such as “burning” pain and indigestion. When ulcers are caused by NSAID use, switching to other classes of pain relievers allows healing. When caused by H. pylori infection, antibiotics are effective.
A potential complication of ulcers is perforation: Perforated ulcers create a hole in the stomach wall, resulting in peritonitis (inflammation of the peritoneum). These ulcers must be repaired surgically.
Digestive Functions of the Stomach
The stomach participates in virtually all the digestive activities with the exception of ingestion and defecation. Although almost all absorption takes place in the small intestine, the stomach does absorb some nonpolar substances, such as alcohol and aspirin.
Mechanical Digestion
Within a few moments after food enters your stomach, mixing waves begin to occur at intervals of approximately 20 seconds. A mixing wave is a unique type of peristalsis that mixes and softens the food with gastric juices to create chyme. The initial mixing waves are relatively gentle, but these are followed by more intense waves, starting at the body of the stomach and increasing in force as they reach the pylorus. It is fair to say that long before your sushi exits through the pyloric sphincter, it bears little resemblance to the sushi you ate.
The pylorus, which holds around 30 mL (1 fluid ounce) of chyme, acts as a filter, permitting only liquids and small food particles to pass through the mostly, but not fully, closed pyloric sphincter. In a process called gastric emptying, rhythmic mixing waves force about 3 mL of chyme at a time through the pyloric sphincter and into the duodenum. Release of a greater amount of chyme at one time would overwhelm the capacity of the small intestine to handle it. The rest of the chyme is pushed back into the body of the stomach, where it continues mixing. This process is repeated when the next mixing waves force more chyme into the duodenum.
Gastric emptying is regulated by both the stomach and the duodenum. The presence of chyme in the duodenum activates receptors that inhibit gastric secretion. This prevents additional chyme from being released by the stomach before the duodenum is ready to process it.
Chemical Digestion
The fundus plays an important role, because it stores both undigested food and gases that are released during the process of chemical digestion. Food may sit in the fundus of the stomach for a while before being mixed with the chyme. While the food is in the fundus, the digestive activities of salivary amylase continue until the food begins mixing with the acidic chyme. Ultimately, mixing waves incorporate this food with the chyme, the acidity of which inactivates salivary amylase and activates lingual lipase. Lingual lipase then begins breaking down triglycerides into free fatty acids, and mono- and diglycerides.
The breakdown of protein begins in the stomach through the actions of HCl and the enzyme pepsin. During infancy, gastric glands also produce rennin, an enzyme that helps digest milk protein.
Its numerous digestive functions notwithstanding, there is only one stomach function necessary to life: the production of intrinsic factor. The intestinal absorption of vitamin B12, which is necessary for both the production of mature red blood cells and normal neurological functioning, cannot occur without intrinsic factor. People who undergo total gastrectomy (stomach removal)—for life-threatening stomach cancer, for example—can survive with minimal digestive dysfunction if they receive vitamin B12injections.
The contents of the stomach are completely emptied into the duodenum within 2 to 4 hours after you eat a meal. Different types of food take different amounts of time to process. Foods heavy in carbohydrates empty fastest, followed by high-protein foods. Meals with a high triglyceride content remain in the stomach the longest. Since enzymes in the small intestine digest fats slowly, food can stay in the stomach for 6 hours or longer when the duodenum is processing fatty chyme. However, note that this is still a fraction of the 24 to 72 hours that full digestion typically takes from start to finish.
The Small and Large Intestines
- Compare and contrast the location and gross anatomy of the small and large intestines
- Identify three main adaptations of the small intestine wall that increase its absorptive capacity
- Describe the mechanical and chemical digestion of chyme upon its release into the small intestine
- List three features unique to the wall of the large intestine and identify their contributions to its function
- Identify the beneficial roles of the bacterial flora in digestive system functioning
- Trace the pathway of food waste from its point of entry into the large intestine through its exit from the body as feces
The word intestine is derived from a Latin root meaning “internal,” and indeed, the two organs together nearly fill the interior of the abdominal cavity. In addition, called the small and large bowel, or colloquially the “guts,” they constitute the greatest mass and length of the alimentary canal and, with the exception of ingestion, perform all digestive system functions.
The Small Intestine
Chyme released from the stomach enters the small intestine, which is the primary digestive organ in the body. Not only is this where most digestion occurs, it is also where practically all absorption occurs. The longest part of the alimentary canal, the small intestine is about 3.05 meters (10 feet) long in a living person (but about twice as long in a cadaver due to the loss of muscle tone). Since this makes it about five times longer than the large intestine, you might wonder why it is called “small.” In fact, its name derives from its relatively smaller diameter of only about 2.54 cm (1 in), compared with 7.62 cm (3 in) for the large intestine. As we’ll see shortly, in addition to its length, the folds and projections of the lining of the small intestine work to give it an enormous surface area, which is approximately 200 m2, more than 100 times the surface area of your skin. This large surface area is necessary for complex processes of digestion and absorption that occur within it.
Structure
The coiled tube of the small intestine is subdivided into three regions. From proximal (at the stomach) to distal, these are the duodenum, jejunum, and ileum (Figure 23.18).
The shortest region is the 25.4-cm (10-in) duodenum, which begins at the pyloric sphincter. Just past the pyloric sphincter, it bends posteriorly behind the peritoneum, becoming retroperitoneal, and then makes a C-shaped curve around the head of the pancreas before ascending anteriorly again to return to the peritoneal cavity and join the jejunum. The duodenum can therefore be subdivided into four segments: the superior, descending, horizontal, and ascending duodenum.
Of particular interest is the hepatopancreatic ampulla (ampulla of Vater). Located in the duodenal wall, the ampulla marks the transition from the anterior portion of the alimentary canal to the mid-region, and is where the bile duct (through which bile passes from the liver) and the main pancreatic duct (through which pancreatic juice passes from the pancreas) join. This ampulla opens into the duodenum at a tiny volcano-shaped structure called the major duodenal papilla. The hepatopancreatic sphincter (sphincter of Oddi) regulates the flow of both bile and pancreatic juice from the ampulla into the duodenum.
Figure 23.18 Small Intestine The three regions of the small intestine are the duodenum, jejunum, and ileum.
The jejunum is about 0.9 meters (3 feet) long (in life) and runs from the duodenum to the ileum. Jejunum means “empty” in Latin and supposedly was so named by the ancient Greeks who noticed it was always empty at death. No clear demarcation exists between the jejunum and the final segment of the small intestine, the ileum.
The ileum is the longest part of the small intestine, measuring about 1.8 meters (6 feet) in length. It is thicker, more vascular, and has more developed mucosal folds than the jejunum. The ileum joins the cecum, the first portion of the large intestine, at the ileocecal sphincter (or valve). The jejunum and ileum are tethered to the posterior abdominal wall by the mesentery. The large intestine frames these three parts of the small intestine.
Parasympathetic nerve fibers from the vagus nerve and sympathetic nerve fibers from the thoracic splanchnic nerve provide extrinsic innervation to the small intestine. The superior mesenteric artery is its main arterial supply. Veins run parallel to the arteries and drain into the superior mesenteric vein. Nutrient-rich blood from the small intestine is then carried to the liver via the hepatic portal vein.
Histology
The wall of the small intestine is composed of the same four layers typically present in the alimentary system. However, three features of the mucosa and submucosa are unique. These features, which increase the absorptive surface area of the small intestine more than 600-fold, include circular folds, villi, and microvilli (Figure 23.19). These adaptations are most abundant in the proximal two-thirds of the small intestine, where the majority of absorption occurs.
Figure 23.19 Histology of the Small Intestine (a) The absorptive surface of the small intestine is vastly enlarged by the presence of circular folds, villi, and microvilli. (b) Micrograph of the circular folds. (c) Micrograph of the villi. (d) Electron micrograph of the microvilli. From left to right, LM x 56, LM x 508, EM x 196,000. (credit b-d: Micrograph provided by the Regents of University of Michigan Medical School © 2012)
Circular folds
Also called a plica circulare, a circular fold is a deep ridge in the mucosa and submucosa. Beginning near the proximal part of the duodenum and ending near the middle of the ileum, these folds facilitate absorption. Their shape causes the chyme to spiral, rather than move in a straight line, through the small intestine. Spiraling slows the movement of chyme and provides the time needed for nutrients to be fully absorbed.
Villi
Within the circular folds are small (0.5–1 mm long) hairlike vascularized projections called villi (singular = villus) that give the mucosa a furry texture. There are about 20 to 40 villi per square millimeter, increasing the surface area of the epithelium tremendously. The mucosal epithelium, primarily composed of absorptive cells, covers the villi. In addition to muscle and connective tissue to support its structure, each villus contains a capillary bed composed of one arteriole and one venule, as well as a lymphatic capillary called a lacteal. The breakdown products of carbohydrates and proteins (sugars and amino acids) can enter the bloodstream directly, but lipid breakdown products are absorbed by the lacteals and transported to the bloodstream via the lymphatic system.
Microvilli
As their name suggests, microvilli (singular = microvillus) are much smaller (1 µm) than villi. They are cylindrical apical surface extensions of the plasma membrane of the mucosa’s epithelial cells, and are supported by microfilaments within those cells. Although their small size makes it difficult to see each microvillus, their combined microscopic appearance suggests a mass of bristles, which is termed the brush border. Fixed to the surface of the microvilli membranes are enzymes that finish digesting carbohydrates and proteins. There are an estimated 200 million microvilli per square millimeter of small intestine, greatly expanding the surface area of the plasma membrane and thus greatly enhancing absorption.
Intestinal Glands
In addition to the three specialized absorptive features just discussed, the mucosa between the villi is dotted with deep crevices that each lead into a tubular intestinal gland (crypt of Lieberkühn), which is formed by cells that line the crevices (see Figure 23.19). These produce intestinal juice, a slightly alkaline (pH 7.4 to 7.8) mixture of water and mucus. Each day, about 0.95 to 1.9 liters (1 to 2 quarts) are secreted in response to the distention of the small intestine or the irritating effects of chyme on the intestinal mucosa.
The submucosa of the duodenum is the only site of the complex mucus-secreting duodenal glands (Brunner’s glands), which produce a bicarbonate-rich alkaline mucus that buffers the acidic chyme as it enters from the stomach.
The roles of the cells in the small intestinal mucosa are detailed in Table 23.7.
Cells of the Small Intestinal Mucosa
| Cell type | Location in the mucosa | Function |
|---|---|---|
| Absorptive | Epithelium/intestinal glands | Digestion and absorption of nutrients in chyme |
| Goblet | Epithelium/intestinal glands | Secretion of mucus |
| Paneth | Intestinal glands | Secretion of the bactericidal enzyme lysozyme; phagocytosis |
| G cells | Intestinal glands of duodenum | Secretion of the hormone intestinal gastrin |
| I cells | Intestinal glands of duodenum | Secretion of the hormone cholecystokinin, which stimulates release of pancreatic juices and bile |
| K cells | Intestinal glands | Secretion of the hormone glucose-dependent insulinotropic peptide, which stimulates the release of insulin |
| M cells | Intestinal glands of duodenum and jejunum | Secretion of the hormone motilin, which accelerates gastric emptying, stimulates intestinal peristalsis, and stimulates the production of pepsin |
| S cells | Intestinal glands | Secretion of the hormone secretin |
Table 23.7
Intestinal MALT
The lamina propria of the small intestine mucosa is studded with quite a bit of MALT. In addition to solitary lymphatic nodules, aggregations of intestinal MALT, which are typically referred to as Peyer’s patches, are concentrated in the distal ileum, and serve to keep bacteria from entering the bloodstream. Peyer’s patches are most prominent in young people and become less distinct as you age, which coincides with the general activity of our immune system.
INTERACTIVE LINK
Watch this animation that depicts the structure of the small intestine, and, in particular, the villi. Epithelial cells continue the digestion and absorption of nutrients and transport these nutrients to the lymphatic and circulatory systems. In the small intestine, the products of food digestion are absorbed by different structures in the villi. Which structure absorbs and transports fats?
Mechanical Digestion in the Small Intestine
The movement of intestinal smooth muscles includes both segmentation and a form of peristalsis called migrating motility complexes. The kind of peristaltic mixing waves seen in the stomach are not observed here.
If you could see into the small intestine when it was going through segmentation, it would look as if the contents were being shoved incrementally back and forth, as the rings of smooth muscle repeatedly contract and then relax. Segmentation in the small intestine does not force chyme through the tract. Instead, it combines the chyme with digestive juices and pushes food particles against the mucosa to be absorbed. The duodenum is where the most rapid segmentation occurs, at a rate of about 12 times per minute. In the ileum, segmentations are only about eight times per minute (Figure 23.20).
Figure 23.20 Segmentation Segmentation separates chyme and then pushes it back together, mixing it and providing time for digestion and absorption.
When most of the chyme has been absorbed, the small intestinal wall becomes less distended. At this point, the localized segmentation process is replaced by transport movements. The duodenal mucosa secretes the hormone motilin, which initiates peristalsis in the form of a migrating motility complex. These complexes, which begin in the duodenum, force chyme through a short section of the small intestine and then stop. The next contraction begins a little bit farther down than the first, forces chyme a bit farther through the small intestine, then stops. These complexes move slowly down the small intestine, forcing chyme on the way, taking around 90 to 120 minutes to finally reach the end of the ileum. At this point, the process is repeated, starting in the duodenum.
The ileocecal valve, a sphincter, is usually in a constricted state, but when motility in the ileum increases, this sphincter relaxes, allowing food residue to enter the first portion of the large intestine, the cecum. Relaxation of the ileocecal sphincter is controlled by both nerves and hormones. First, digestive activity in the stomach provokes the gastroileal reflex, which increases the force of ileal segmentation. Second, the stomach releases the hormone gastrin, which enhances ileal motility, thus relaxing the ileocecal sphincter. After chyme passes through, backward pressure helps close the sphincter, preventing backflow into the ileum. Because of this reflex, your lunch is completely emptied from your stomach and small intestine by the time you eat your dinner. It takes about 3 to 5 hours for all chyme to leave the small intestine.
Chemical Digestion in the Small Intestine
The digestion of proteins and carbohydrates, which partially occurs in the stomach, is completed in the small intestine with the aid of intestinal and pancreatic juices. Lipids arrive in the intestine largely undigested, so much of the focus here is on lipid digestion, which is facilitated by bile and the enzyme pancreatic lipase.
Moreover, intestinal juice combines with pancreatic juice to provide a liquid medium that facilitates absorption. The intestine is also where most water is absorbed, via osmosis. The small intestine’s absorptive cells also synthesize digestive enzymes and then place them in the plasma membranes of the microvilli. This distinguishes the small intestine from the stomach; that is, enzymatic digestion occurs not only in the lumen, but also on the luminal surfaces of the mucosal cells.
For optimal chemical digestion, chyme must be delivered from the stomach slowly and in small amounts. This is because chyme from the stomach is typically hypertonic, and if large quantities were forced all at once into the small intestine, the resulting osmotic water loss from the blood into the intestinal lumen would result in potentially life-threatening low blood volume. In addition, continued digestion requires an upward adjustment of the low pH of stomach chyme, along with rigorous mixing of the chyme with bile and pancreatic juices. Both processes take time, so the pumping action of the pylorus must be carefully controlled to prevent the duodenum from being overwhelmed with chyme.
DISORDERS OF THE...
Small Intestine: Lactose Intolerance
Lactose intolerance is a condition characterized by indigestion caused by dairy products. It occurs when the absorptive cells of the small intestine do not produce enough lactase, the enzyme that digests the milk sugar lactose. In most mammals, lactose intolerance increases with age. In contrast, some human populations, most notably Caucasians, are able to maintain the ability to produce lactase as adults.
In people with lactose intolerance, the lactose in chyme is not digested. Bacteria in the large intestine ferment the undigested lactose, a process that produces gas. In addition to gas, symptoms include abdominal cramps, bloating, and diarrhea. Symptom severity ranges from mild discomfort to severe pain; however, symptoms resolve once the lactose is eliminated in feces.
The hydrogen breath test is used to help diagnose lactose intolerance. Lactose-tolerant people have very little hydrogen in their breath. Those with lactose intolerance exhale hydrogen, which is one of the gases produced by the bacterial fermentation of lactose in the colon. After the hydrogen is absorbed from the intestine, it is transported through blood vessels into the lungs. There are a number of lactose-free dairy products available in grocery stores. In addition, dietary supplements are available. Taken with food, they provide lactase to help digest lactose.
The Large Intestine
The large intestine is the terminal part of the alimentary canal. The primary function of this organ is to finish absorption of nutrients and water, synthesize certain vitamins, form feces, and eliminate feces from the body.
Structure
The large intestine runs from the appendix to the anus. It frames the small intestine on three sides. Despite its being about one-half as long as the small intestine, it is called large because it is more than twice the diameter of the small intestine, about 3 inches.
Subdivisions
The large intestine is subdivided into four main regions: the cecum, the colon, the rectum, and the anus. The ileocecal valve, located at the opening between the ileum and the large intestine, controls the flow of chyme from the small intestine to the large intestine.
Cecum
The first part of the large intestine is the cecum, a sac-like structure that is suspended inferior to the ileocecal valve. It is about 6 cm (2.4 in) long, receives the contents of the ileum, and continues the absorption of water and salts. The appendix (or vermiform appendix) is a winding tube that attaches to the cecum. Although the 7.6-cm (3-in) long appendix contains lymphoid tissue, suggesting an immunologic function, this organ is generally considered vestigial. However, at least one recent report postulates a survival advantage conferred by the appendix: In diarrheal illness, the appendix may serve as a bacterial reservoir to repopulate the enteric bacteria for those surviving the initial phases of the illness. Moreover, its twisted anatomy provides a haven for the accumulation and multiplication of enteric bacteria. The mesoappendix, the mesentery of the appendix, tethers it to the mesentery of the ileum.
Colon
The cecum blends seamlessly with the colon. Upon entering the colon, the food residue first travels up the ascending colon on the right side of the abdomen. At the inferior surface of the liver, the colon bends to form the right colic flexure (hepatic flexure) and becomes the transverse colon. The region defined as hindgut begins with the last third of the transverse colon and continues on. Food residue passing through the transverse colon travels across to the left side of the abdomen, where the colon angles sharply immediately inferior to the spleen, at the left colic flexure (splenic flexure). From there, food residue passes through the descending colon, which runs down the left side of the posterior abdominal wall. After entering the pelvis inferiorly, it becomes the s-shaped sigmoid colon, which extends medially to the midline (Figure 23.21). The ascending and descending colon, and the rectum (discussed next) are located in the retroperitoneum. The transverse and sigmoid colon are tethered to the posterior abdominal wall by the mesocolon.
Figure 23.21 Large Intestine The large intestine includes the cecum, colon, and rectum.
HOMEOSTATIC IMBALANCES
Colorectal Cancer
Each year, approximately 140,000 Americans are diagnosed with colorectal cancer, and another 49,000 die from it, making it one of the most deadly malignancies. People with a family history of colorectal cancer are at increased risk. Smoking, excessive alcohol consumption, and a diet high in animal fat and protein also increase the risk. Despite popular opinion to the contrary, studies support the conclusion that dietary fiber and calcium do not reduce the risk of colorectal cancer.
Colorectal cancer may be signaled by constipation or diarrhea, cramping, abdominal pain, and rectal bleeding. Bleeding from the rectum may be either obvious or occult (hidden in feces). Since most colon cancers arise from benign mucosal growths called polyps, cancer prevention is focused on identifying these polyps. The colonoscopy is both diagnostic and therapeutic. Colonoscopy not only allows identification of precancerous polyps, the procedure also enables them to be removed before they become malignant. Screening for fecal occult blood tests and colonoscopy is recommended for those over 50 years of age.
Rectum
Food residue leaving the sigmoid colon enters the rectum in the pelvis, near the third sacral vertebra. The final 20.3 cm (8 in) of the alimentary canal, the rectum extends anterior to the sacrum and coccyx. Even though rectum is Latin for “straight,” this structure follows the curved contour of the sacrum and has three lateral bends that create a trio of internal transverse folds called the rectal valves. These valves help separate the feces from gas to prevent the simultaneous passage of feces and gas.
Anal Canal
Finally, food residue reaches the last part of the large intestine, the anal canal, which is located in the perineum, completely outside of the abdominopelvic cavity. This 3.8–5 cm (1.5–2 in) long structure opens to the exterior of the body at the anus. The anal canal includes two sphincters. The internal anal sphincter is made of smooth muscle, and its contractions are involuntary. The external anal sphincter is made of skeletal muscle, which is under voluntary control. Except when defecating, both usually remain closed.
Histology
There are several notable differences between the walls of the large and small intestines (Figure 23.22). For example, few enzyme-secreting cells are found in the wall of the large intestine, and there are no circular folds or villi. Other than in the anal canal, the mucosa of the colon is simple columnar epithelium made mostly of enterocytes (absorptive cells) and goblet cells. In addition, the wall of the large intestine has far more intestinal glands, which contain a vast population of enterocytes and goblet cells. These goblet cells secrete mucus that eases the movement of feces and protects the intestine from the effects of the acids and gases produced by enteric bacteria. The enterocytes absorb water and salts as well as vitamins produced by your intestinal bacteria.
Figure 23.22 Histology of the large Intestine (a) The histologies of the large intestine and small intestine (not shown) are adapted for the digestive functions of each organ. (b) This micrograph shows the colon’s simple columnar epithelium and goblet cells. LM x 464. (credit b: Micrograph provided by the Regents of University of Michigan Medical School © 2012)
Anatomy
Three features are unique to the large intestine: teniae coli, haustra, and epiploic appendages (Figure 23.23). The teniae coli are three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end. Tonic contractions of the teniae coli bunch up the colon into a succession of pouches called haustra (singular = haustrum), which are responsible for the wrinkled appearance of the colon. Attached to the teniae coli are small, fat-filled sacs of visceral peritoneum called epiploic appendages. The purpose of these is unknown. Although the rectum and anal canal have neither teniae coli nor haustra, they do have well-developed layers of muscularis that create the strong contractions needed for defecation.
Figure 23.23 Teniae Coli, Haustra, and Epiploic Appendages
The stratified squamous epithelial mucosa of the anal canal connects to the skin on the outside of the anus. This mucosa varies considerably from that of the rest of the colon to accommodate the high level of abrasion as feces pass through. The anal canal’s mucous membrane is organized into longitudinal folds, each called an anal column, which house a grid of arteries and veins. Two superficial venous plexuses are found in the anal canal: one within the anal columns and one at the anus.
Depressions between the anal columns, each called an anal sinus, secrete mucus that facilitates defecation. The pectinate line(or dentate line) is a horizontal, jagged band that runs circumferentially just below the level of the anal sinuses, and represents the junction between the hindgut and external skin. The mucosa above this line is fairly insensitive, whereas the area below is very sensitive. The resulting difference in pain threshold is due to the fact that the upper region is innervated by visceral sensory fibers, and the lower region is innervated by somatic sensory fibers.
Bacterial Flora
Most bacteria that enter the alimentary canal are killed by lysozyme, defensins, HCl, or protein-digesting enzymes. However, trillions of bacteria live within the large intestine and are referred to as the bacterial flora. Most of the more than 700 species of these bacteria are nonpathogenic commensal organisms that cause no harm as long as they stay in the gut lumen. In fact, many facilitate chemical digestion and absorption, and some synthesize certain vitamins, mainly biotin, pantothenic acid, and vitamin K. Some are linked to increased immune response. A refined system prevents these bacteria from crossing the mucosal barrier. First, peptidoglycan, a component of bacterial cell walls, activates the release of chemicals by the mucosa’s epithelial cells, which draft immune cells, especially dendritic cells, into the mucosa. Dendritic cells open the tight junctions between epithelial cells and extend probes into the lumen to evaluate the microbial antigens. The dendritic cells with antigens then travel to neighboring lymphoid follicles in the mucosa where T cells inspect for antigens. This process triggers an IgA-mediated response, if warranted, in the lumen that blocks the commensal organisms from infiltrating the mucosa and setting off a far greater, widespread systematic reaction.
Digestive Functions of the Large Intestine
The residue of chyme that enters the large intestine contains few nutrients except water, which is reabsorbed as the residue lingers in the large intestine, typically for 12 to 24 hours. Thus, it may not surprise you that the large intestine can be completely removed without significantly affecting digestive functioning. For example, in severe cases of inflammatory bowel disease, the large intestine can be removed by a procedure known as a colectomy. Often, a new fecal pouch can be crafted from the small intestine and sutured to the anus, but if not, an ileostomy can be created by bringing the distal ileum through the abdominal wall, allowing the watery chyme to be collected in a bag-like adhesive appliance.
Mechanical Digestion
In the large intestine, mechanical digestion begins when chyme moves from the ileum into the cecum, an activity regulated by the ileocecal sphincter. Right after you eat, peristalsis in the ileum forces chyme into the cecum. When the cecum is distended with chyme, contractions of the ileocecal sphincter strengthen. Once chyme enters the cecum, colon movements begin.
Mechanical digestion in the large intestine includes a combination of three types of movements. The presence of food residues in the colon stimulates a slow-moving haustral contraction. This type of movement involves sluggish segmentation, primarily in the transverse and descending colons. When a haustrum is distended with chyme, its muscle contracts, pushing the residue into the next haustrum. These contractions occur about every 30 minutes, and each last about 1 minute. These movements also mix the food residue, which helps the large intestine absorb water. The second type of movement is peristalsis, which, in the large intestine, is slower than in the more proximal portions of the alimentary canal. The third type is a mass movement. These strong waves start midway through the transverse colon and quickly force the contents toward the rectum. Mass movements usually occur three or four times per day, either while you eat or immediately afterward. Distension in the stomach and the breakdown products of digestion in the small intestine provoke the gastrocolic reflex, which increases motility, including mass movements, in the colon. Fiber in the diet both softens the stool and increases the power of colonic contractions, optimizing the activities of the colon.
Chemical Digestion
Although the glands of the large intestine secrete mucus, they do not secrete digestive enzymes. Therefore, chemical digestion in the large intestine occurs exclusively because of bacteria in the lumen of the colon. Through the process of saccharolytic fermentation, bacteria break down some of the remaining carbohydrates. This results in the discharge of hydrogen, carbon dioxide, and methane gases that create flatus (gas) in the colon; flatulence is excessive flatus. Each day, up to 1500 mL of flatus is produced in the colon. More is produced when you eat foods such as beans, which are rich in otherwise indigestible sugars and complex carbohydrates like soluble dietary fiber.
Absorption, Feces Formation, and Defecation
The small intestine absorbs about 90 percent of the water you ingest (either as liquid or within solid food). The large intestine absorbs most of the remaining water, a process that converts the liquid chyme residue into semisolid feces (“stool”). Feces is composed of undigested food residues, unabsorbed digested substances, millions of bacteria, old epithelial cells from the GI mucosa, inorganic salts, and enough water to let it pass smoothly out of the body. Of every 500 mL (17 ounces) of food residue that enters the cecum each day, about 150 mL (5 ounces) become feces.
Feces are eliminated through contractions of the rectal muscles. You help this process by a voluntary procedure called Valsalva’s maneuver, in which you increase intra-abdominal pressure by contracting your diaphragm and abdominal wall muscles, and closing your glottis.
The process of defecation begins when mass movements force feces from the colon into the rectum, stretching the rectal wall and provoking the defecation reflex, which eliminates feces from the rectum. This parasympathetic reflex is mediated by the spinal cord. It contracts the sigmoid colon and rectum, relaxes the internal anal sphincter, and initially contracts the external anal sphincter. The presence of feces in the anal canal sends a signal to the brain, which gives you the choice of voluntarily opening the external anal sphincter (defecating) or keeping it temporarily closed. If you decide to delay defecation, it takes a few seconds for the reflex contractions to stop and the rectal walls to relax. The next mass movement will trigger additional defecation reflexes until you defecate.
If defecation is delayed for an extended time, additional water is absorbed, making the feces firmer and potentially leading to constipation. On the other hand, if the waste matter moves too quickly through the intestines, not enough water is absorbed, and diarrhea can result. This can be caused by the ingestion of foodborne pathogens. In general, diet, health, and stress determine the frequency of bowel movements. The number of bowel movements varies greatly between individuals, ranging from two or three per day to three or four per week.
INTERACTIVE LINK
By watching this animation you will see that for the various food groups—proteins, fats, and carbohydrates—digestion begins in different parts of the digestion system, though all end in the same place. Of the three major food classes (carbohydrates, fats, and proteins), which is digested in the mouth, the stomach, and the small intestine?
Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder
- State the main digestive roles of the liver, pancreas, and gallbladder
- Identify three main features of liver histology that are critical to its function
- Discuss the composition and function of bile
- Identify the major types of enzymes and buffers present in pancreatic juice
Chemical digestion in the small intestine relies on the activities of three accessory digestive organs: the liver, pancreas, and gallbladder (Figure 23.24). The digestive role of the liver is to produce bile and export it to the duodenum. The gallbladder primarily stores, concentrates, and releases bile. The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.
Figure 23.24 Accessory Organs The liver, pancreas, and gallbladder are considered accessory digestive organs, but their roles in the digestive system are vital.
The Liver
The liver is the largest gland in the body, weighing about three pounds in an adult. It is also one of the most important organs. In addition to being an accessory digestive organ, it plays a number of roles in metabolism and regulation. The liver lies inferior to the diaphragm in the right upper quadrant of the abdominal cavity and receives protection from the surrounding ribs.
The liver is divided into two primary lobes: a large right lobe and a much smaller left lobe. In the right lobe, some anatomists also identify an inferior quadrate lobe and a posterior caudate lobe, which are defined by internal features. The liver is connected to the abdominal wall and diaphragm by five peritoneal folds referred to as ligaments. These are the falciform ligament, the coronary ligament, two lateral ligaments, and the ligamentum teres hepatis. The falciform ligament and ligamentum teres hepatis are actually remnants of the umbilical vein, and separate the right and left lobes anteriorly. The lesser omentum tethers the liver to the lesser curvature of the stomach.
The porta hepatis (“gate to the liver”) is where the hepatic artery and hepatic portal vein enter the liver. These two vessels, along with the common hepatic duct, run behind the lateral border of the lesser omentum on the way to their destinations. As shown in Figure 23.25, the hepatic artery delivers oxygenated blood from the heart to the liver. The hepatic portal vein delivers partially deoxygenated blood containing nutrients absorbed from the small intestine and actually supplies more oxygen to the liver than do the much smaller hepatic arteries. In addition to nutrients, drugs and toxins are also absorbed. After processing the bloodborne nutrients and toxins, the liver releases nutrients needed by other cells back into the blood, which drains into the central vein and then through the hepatic vein to the inferior vena cava. With this hepatic portal circulation, all blood from the alimentary canal passes through the liver. This largely explains why the liver is the most common site for the metastasis of cancers that originate in the alimentary canal.
Figure 23.25 Microscopic Anatomy of the Liver The liver receives oxygenated blood from the hepatic artery and nutrient-rich deoxygenated blood from the hepatic portal vein.
Histology
The liver has three main components: hepatocytes, bile canaliculi, and hepatic sinusoids. A hepatocyte is the liver’s main cell type, accounting for around 80 percent of the liver's volume. These cells play a role in a wide variety of secretory, metabolic, and endocrine functions. Plates of hepatocytes called hepatic laminae radiate outward from the portal vein in each hepatic lobule.
Between adjacent hepatocytes, grooves in the cell membranes provide room for each bile canaliculus (plural = canaliculi). These small ducts accumulate the bile produced by hepatocytes. From here, bile flows first into bile ductules and then into bile ducts. The bile ducts unite to form the larger right and left hepatic ducts, which themselves merge and exit the liver as the common hepatic duct. This duct then joins with the cystic duct from the gallbladder, forming the common bile duct through which bile flows into the small intestine.
A hepatic sinusoid is an open, porous blood space formed by fenestrated capillaries from nutrient-rich hepatic portal veins and oxygen-rich hepatic arteries. Hepatocytes are tightly packed around the fenestrated endothelium of these spaces, giving them easy access to the blood. From their central position, hepatocytes process the nutrients, toxins, and waste materials carried by the blood. Materials such as bilirubin are processed and excreted into the bile canaliculi. Other materials including proteins, lipids, and carbohydrates are processed and secreted into the sinusoids or just stored in the cells until called upon. The hepatic sinusoids combine and send blood to a central vein. Blood then flows through a hepatic vein into the inferior vena cava. This means that blood and bile flow in opposite directions. The hepatic sinusoids also contain star-shaped reticuloendothelial cells(Kupffer cells), phagocytes that remove dead red and white blood cells, bacteria, and other foreign material that enter the sinusoids. The portal triad is a distinctive arrangement around the perimeter of hepatic lobules, consisting of three basic structures: a bile duct, a hepatic artery branch, and a hepatic portal vein branch.
Bile
Recall that lipids are hydrophobic, that is, they do not dissolve in water. Thus, before they can be digested in the watery environment of the small intestine, large lipid globules must be broken down into smaller lipid globules, a process called emulsification. Bile is a mixture secreted by the liver to accomplish the emulsification of lipids in the small intestine.
Hepatocytes secrete about one liter of bile each day. A yellow-brown or yellow-green alkaline solution (pH 7.6 to 8.6), bile is a mixture of water, bile salts, bile pigments, phospholipids (such as lecithin), electrolytes, cholesterol, and triglycerides. The components most critical to emulsification are bile salts and phospholipids, which have a nonpolar (hydrophobic) region as well as a polar (hydrophilic) region. The hydrophobic region interacts with the large lipid molecules, whereas the hydrophilic region interacts with the watery chyme in the intestine. This results in the large lipid globules being pulled apart into many tiny lipid fragments of about 1 µm in diameter. This change dramatically increases the surface area available for lipid-digesting enzyme activity. This is the same way dish soap works on fats mixed with water.
Bile salts act as emulsifying agents, so they are also important for the absorption of digested lipids. While most constituents of bile are eliminated in feces, bile salts are reclaimed by the enterohepatic circulation. Once bile salts reach the ileum, they are absorbed and returned to the liver in the hepatic portal blood. The hepatocytes then excrete the bile salts into newly formed bile. Thus, this precious resource is recycled.
Bilirubin, the main bile pigment, is a waste product produced when the spleen removes old or damaged red blood cells from the circulation. These breakdown products, including proteins, iron, and toxic bilirubin, are transported to the liver via the splenic vein of the hepatic portal system. In the liver, proteins and iron are recycled, whereas bilirubin is excreted in the bile. It accounts for the green color of bile. Bilirubin is eventually transformed by intestinal bacteria into stercobilin, a brown pigment that gives your stool its characteristic color! In some disease states, bile does not enter the intestine, resulting in white (‘acholic’) stool with a high fat content, since virtually no fats are broken down or absorbed.
Hepatocytes work non-stop, but bile production increases when fatty chyme enters the duodenum and stimulates the secretion of the gut hormone secretin. Between meals, bile is produced but conserved. The valve-like hepatopancreatic ampulla closes, allowing bile to divert to the gallbladder, where it is concentrated and stored until the next meal.
INTERACTIVE LINK
Watch this video to see the structure of the liver and how this structure supports the functions of the liver, including the processing of nutrients, toxins, and wastes. At rest, about 1500 mL of blood per minute flow through the liver. What percentage of this blood flow comes from the hepatic portal system?
The Pancreas
The soft, oblong, glandular pancreas lies transversely in the retroperitoneum behind the stomach. Its head is nestled into the “c-shaped” curvature of the duodenum with the body extending to the left about 15.2 cm (6 in) and ending as a tapering tail in the hilum of the spleen. It is a curious mix of exocrine (secreting digestive enzymes) and endocrine (releasing hormones into the blood) functions (Figure 23.26).
Figure 23.26 Exocrine and Endocrine Pancreas The pancreas has a head, a body, and a tail. It delivers pancreatic juice to the duodenum through the pancreatic duct.
The exocrine part of the pancreas arises as little grape-like cell clusters, each called an acinus (plural = acini), located at the terminal ends of pancreatic ducts. These acinar cells secrete enzyme-rich pancreatic juice into tiny merging ducts that form two dominant ducts. The larger duct fuses with the common bile duct (carrying bile from the liver and gallbladder) just before entering the duodenum via a common opening (the hepatopancreatic ampulla). The smooth muscle sphincter of the hepatopancreatic ampulla controls the release of pancreatic juice and bile into the small intestine. The second and smaller pancreatic duct, the accessory duct (duct of Santorini), runs from the pancreas directly into the duodenum, approximately 1 inch above the hepatopancreatic ampulla. When present, it is a persistent remnant of pancreatic development.
Scattered through the sea of exocrine acini are small islands of endocrine cells, the islets of Langerhans. These vital cells produce the hormones pancreatic polypeptide, insulin, glucagon, and somatostatin.
Pancreatic Juice
The pancreas produces over a liter of pancreatic juice each day. Unlike bile, it is clear and composed mostly of water along with some salts, sodium bicarbonate, and several digestive enzymes. Sodium bicarbonate is responsible for the slight alkalinity of pancreatic juice (pH 7.1 to 8.2), which serves to buffer the acidic gastric juice in chyme, inactivate pepsin from the stomach, and create an optimal environment for the activity of pH-sensitive digestive enzymes in the small intestine. Pancreatic enzymes are active in the digestion of sugars, proteins, and fats.
The pancreas produces protein-digesting enzymes in their inactive forms. These enzymes are activated in the duodenum. If produced in an active form, they would digest the pancreas (which is exactly what occurs in the disease, pancreatitis). The intestinal brush border enzyme enteropeptidase stimulates the activation of trypsin from trypsinogen of the pancreas, which in turn changes the pancreatic enzymes procarboxypeptidase and chymotrypsinogen into their active forms, carboxypeptidase and chymotrypsin.
The enzymes that digest starch (amylase), fat (lipase), and nucleic acids (nuclease) are secreted in their active forms, since they do not attack the pancreas as do the protein-digesting enzymes.
Pancreatic Secretion
Regulation of pancreatic secretion is the job of hormones and the parasympathetic nervous system. The entry of acidic chyme into the duodenum stimulates the release of secretin, which in turn causes the duct cells to release bicarbonate-rich pancreatic juice. The presence of proteins and fats in the duodenum stimulates the secretion of CCK, which then stimulates the acini to secrete enzyme-rich pancreatic juice and enhances the activity of secretin. Parasympathetic regulation occurs mainly during the cephalic and gastric phases of gastric secretion, when vagal stimulation prompts the secretion of pancreatic juice.
Usually, the pancreas secretes just enough bicarbonate to counterbalance the amount of HCl produced in the stomach. Hydrogen ions enter the blood when bicarbonate is secreted by the pancreas. Thus, the acidic blood draining from the pancreas neutralizes the alkaline blood draining from the stomach, maintaining the pH of the venous blood that flows to the liver.
The Gallbladder
The gallbladder is 8–10 cm (~3–4 in) long and is nested in a shallow area on the posterior aspect of the right lobe of the liver. This muscular sac stores, concentrates, and, when stimulated, propels the bile into the duodenum via the common bile duct. It is divided into three regions. The fundus is the widest portion and tapers medially into the body, which in turn narrows to become the neck. The neck angles slightly superiorly as it approaches the hepatic duct. The cystic duct is 1–2 cm (less than 1 in) long and turns inferiorly as it bridges the neck and hepatic duct.
The simple columnar epithelium of the gallbladder mucosa is organized in rugae, similar to those of the stomach. There is no submucosa in the gallbladder wall. The wall’s middle, muscular coat is made of smooth muscle fibers. When these fibers contract, the gallbladder’s contents are ejected through the cystic duct and into the bile duct (Figure 23.27). Visceral peritoneum reflected from the liver capsule holds the gallbladder against the liver and forms the outer coat of the gallbladder. The gallbladder's mucosa absorbs water and ions from bile, concentrating it by up to 10-fold.
Figure 23.27 Gallbladder The gallbladder stores and concentrates bile, and releases it into the two-way cystic duct when it is needed by the small intestine.
Chemical Digestion and Absorption: A Closer Look
- Identify the locations and primary secretions involved in the chemical digestion of carbohydrates, proteins, lipids, and nucleic acids
- Compare and contrast absorption of the hydrophilic and hydrophobic nutrients
As you have learned, the process of mechanical digestion is relatively simple. It involves the physical breakdown of food but does not alter its chemical makeup. Chemical digestion, on the other hand, is a complex process that reduces food into its chemical building blocks, which are then absorbed to nourish the cells of the body (Figure 23.28). In this section, you will look more closely at the processes of chemical digestion and absorption.
Figure 23.28 Digestion and Absorption Digestion begins in the mouth and continues as food travels through the small intestine. Most absorption occurs in the small intestine.
Chemical Digestion
Large food molecules (for example, proteins, lipids, nucleic acids, and starches) must be broken down into subunits that are small enough to be absorbed by the lining of the alimentary canal. This is accomplished by enzymes through hydrolysis. The many enzymes involved in chemical digestion are summarized in Table 23.8.
The Digestive Enzymes
| Enzyme Category | Enzyme Name | Source | Substrate | Product |
|---|---|---|---|---|
| Salivary Enzymes | Lingual lipase | Lingual glands | Triglycerides | Free fatty acids, and mono- and diglycerides |
| Salivary Enzymes | Salivary amylase | Salivary glands | Polysaccharides | Disaccharides and trisaccharides |
| Gastric enzymes | Gastric lipase | Chief cells | Triglycerides | Fatty acids and monoacylglycerides |
| Gastric enzymes | Pepsin* | Chief cells | Proteins | Peptides |
| Brush border enzymes | α-Dextrinase | Small intestine | α-Dextrins | Glucose |
| Brush border enzymes | Enteropeptidase | Small intestine | Trypsinogen | Trypsin |
| Brush border enzymes | Lactase | Small intestine | Lactose | Glucose and galactose |
| Brush border enzymes | Maltase | Small intestine | Maltose | Glucose |
| Brush border enzymes | Nucleosidases and phosphatases | Small intestine | Nucleotides | Phosphates, nitrogenous bases, and pentoses |
| Brush border enzymes | Peptidases | Small intestine |
|
|
| Brush border enzymes | Sucrase | Small intestine | Sucrose | Glucose and fructose |
| Pancreatic enzymes | Carboxy-peptidase* | Pancreatic acinar cells | Amino acids at the carboxyl end of peptides | Amino acids and peptides |
| Pancreatic enzymes | Chymotrypsin* | Pancreatic acinar cells | Proteins | Peptides |
| Pancreatic enzymes | Elastase* | Pancreatic acinar cells | Proteins | Peptides |
| Pancreatic enzymes | Nucleases | Pancreatic acinar cells |
| Nucleotides |
| Pancreatic enzymes | Pancreatic amylase | Pancreatic acinar cells | Polysaccharides (starches) | α-Dextrins, disaccharides (maltose), trisaccharides (maltotriose) |
| Pancreatic enzymes | Pancreatic lipase | Pancreatic acinar cells | Triglycerides that have been emulsified by bile salts | Fatty acids and monoacylglycerides |
| Pancreatic enzymes | Trypsin* | Pancreatic acinar cells | Proteins | Peptides |
Table 23.8 *These enzymes have been activated by other substances.
Carbohydrate Digestion
The average American diet is about 50 percent carbohydrates, which may be classified according to the number of monomers they contain of simple sugars (monosaccharides and disaccharides) and/or complex sugars (polysaccharides). Glucose, galactose, and fructose are the three monosaccharides that are commonly consumed and are readily absorbed. Your digestive system is also able to break down the disaccharide sucrose (regular table sugar: glucose + fructose), lactose (milk sugar: glucose + galactose), and maltose (grain sugar: glucose + glucose), and the polysaccharides glycogen and starch (chains of monosaccharides). Your bodies do not produce enzymes that can break down most fibrous polysaccharides, such as cellulose. While indigestible polysaccharides do not provide any nutritional value, they do provide dietary fiber, which helps propel food through the alimentary canal.
The chemical digestion of starches begins in the mouth and has been reviewed above.
In the small intestine, pancreatic amylase does the ‘heavy lifting’ for starch and carbohydrate digestion (Figure 23.29). After amylases break down starch into smaller fragments, the brush border enzyme α-dextrinase starts working on α-dextrin, breaking off one glucose unit at a time. Three brush border enzymes hydrolyze sucrose, lactose, and maltose into monosaccharides. Sucrase splits sucrose into one molecule of fructose and one molecule of glucose; maltase breaks down maltose and maltotriose into two and three glucose molecules, respectively; and lactase breaks down lactose into one molecule of glucose and one molecule of galactose. Insufficient lactase can lead to lactose intolerance.
Figure 23.29 Carbohydrate Digestion Flow Chart Carbohydrates are broken down into their monomers in a series of steps.
Protein Digestion
Proteins are polymers composed of amino acids linked by peptide bonds to form long chains. Digestion reduces them to their constituent amino acids. You usually consume about 15 to 20 percent of your total calorie intake as protein.
The digestion of protein starts in the stomach, where HCl and pepsin break proteins into smaller polypeptides, which then travel to the small intestine (Figure 23.30). Chemical digestion in the small intestine is continued by pancreatic enzymes, including chymotrypsin and trypsin, each of which act on specific bonds in amino acid sequences. At the same time, the cells of the brush border secrete enzymes such as aminopeptidase and dipeptidase, which further break down peptide chains. This results in molecules small enough to enter the bloodstream (Figure 23.31).
Figure 23.30 Digestion of Protein The digestion of protein begins in the stomach and is completed in the small intestine.
Figure 23.31 Digestion of Protein Flow Chart Proteins are successively broken down into their amino acid components.
Lipid Digestion
A healthy diet limits lipid intake to 35 percent of total calorie intake. The most common dietary lipids are triglycerides, which are made up of a glycerol molecule bound to three fatty acid chains. Small amounts of dietary cholesterol and phospholipids are also consumed.
The three lipases responsible for lipid digestion are lingual lipase, gastric lipase, and pancreatic lipase. However, because the pancreas is the only consequential source of lipase, virtually all lipid digestion occurs in the small intestine. Pancreatic lipase breaks down each triglyceride into two free fatty acids and a monoglyceride. The fatty acids include both short-chain (less than 10 to 12 carbons) and long-chain fatty acids.
Nucleic Acid Digestion
The nucleic acids DNA and RNA are found in most of the foods you eat. Two types of pancreatic nuclease are responsible for their digestion: deoxyribonuclease, which digests DNA, and ribonuclease, which digests RNA. The nucleotides produced by this digestion are further broken down by two intestinal brush border enzymes (nucleosidase and phosphatase) into pentoses, phosphates, and nitrogenous bases, which can be absorbed through the alimentary canal wall. The large food molecules that must be broken down into subunits are summarized Table 23.9
Absorbable Food Substances
| Source | Substance |
|---|---|
| Carbohydrates | Monosaccharides: glucose, galactose, and fructose |
| Proteins | Single amino acids, dipeptides, and tripeptides |
| Triglycerides | Monoacylglycerides, glycerol, and free fatty acids |
| Nucleic acids | Pentose sugars, phosphates, and nitrogenous bases |
Table 23.9
Absorption
The mechanical and digestive processes have one goal: to convert food into molecules small enough to be absorbed by the epithelial cells of the intestinal villi. The absorptive capacity of the alimentary canal is almost endless. Each day, the alimentary canal processes up to 10 liters of food, liquids, and GI secretions, yet less than one liter enters the large intestine. Almost all ingested food, 80 percent of electrolytes, and 90 percent of water are absorbed in the small intestine. Although the entire small intestine is involved in the absorption of water and lipids, most absorption of carbohydrates and proteins occurs in the jejunum. Notably, bile salts and vitamin B12 are absorbed in the terminal ileum. By the time chyme passes from the ileum into the large intestine, it is essentially indigestible food residue (mainly plant fibers like cellulose), some water, and millions of bacteria (Figure 23.32).
Figure 23.32 Digestive Secretions and Absorption of Water Absorption is a complex process, in which nutrients from digested food are harvested.
Absorption can occur through five mechanisms: (1) active transport, (2) passive diffusion, (3) facilitated diffusion, (4) co-transport (or secondary active transport), and (5) endocytosis. As you will recall from Chapter 3, active transport refers to the movement of a substance across a cell membrane going from an area of lower concentration to an area of higher concentration (up the concentration gradient). In this type of transport, proteins within the cell membrane act as “pumps,” using cellular energy (ATP) to move the substance. Passive diffusion refers to the movement of substances from an area of higher concentration to an area of lower concentration, while facilitated diffusion refers to the movement of substances from an area of higher to an area of lower concentration using a carrier protein in the cell membrane. Co-transport uses the movement of one molecule through the membrane from higher to lower concentration to power the movement of another from lower to higher. Finally, endocytosis is a transportation process in which the cell membrane engulfs material. It requires energy, generally in the form of ATP.
Because the cell’s plasma membrane is made up of hydrophobic phospholipids, water-soluble nutrients must use transport molecules embedded in the membrane to enter cells. Moreover, substances cannot pass between the epithelial cells of the intestinal mucosa because these cells are bound together by tight junctions. Thus, substances can only enter blood capillaries by passing through the apical surfaces of epithelial cells and into the interstitial fluid. Water-soluble nutrients enter the capillary blood in the villi and travel to the liver via the hepatic portal vein.
In contrast to the water-soluble nutrients, lipid-soluble nutrients can diffuse through the plasma membrane. Once inside the cell, they are packaged for transport via the base of the cell and then enter the lacteals of the villi to be transported by lymphatic vessels to the systemic circulation via the thoracic duct. The absorption of most nutrients through the mucosa of the intestinal villi requires active transport fueled by ATP. The routes of absorption for each food category are summarized in Table 23.10.
Absorption in the Alimentary Canal
| Food | Breakdown products | Absorption mechanism | Entry to bloodstream | Destination |
|---|---|---|---|---|
| Carbohydrates | Glucose | Co-transport with sodium ions | Capillary blood in villi | Liver via hepatic portal vein |
| Carbohydrates | Galactose | Co-transport with sodium ions | Capillary blood in villi | Liver via hepatic portal vein |
| Carbohydrates | Fructose | Facilitated diffusion | Capillary blood in villi | Liver via hepatic portal vein |
| Protein | Amino acids | Co-transport with sodium ions | Capillary blood in villi | Liver via hepatic portal vein |
| Lipids | Long-chain fatty acids | Diffusion into intestinal cells, where they are combined with proteins to create chylomicrons | Lacteals of villi | Systemic circulation via lymph entering thoracic duct |
| Lipids | Monoacylglycerides | Diffusion into intestinal cells, where they are combined with proteins to create chylomicrons | Lacteals of villi | Systemic circulation via lymph entering thoracic duct |
| Lipids | Short-chain fatty acids | Simple diffusion | Capillary blood in villi | Liver via hepatic portal vein |
| Lipids | Glycerol | Simple diffusion | Capillary blood in villi | Liver via hepatic portal vein |
| Nucleic Acids | Nucleic acid digestion products | Active transport via membrane carriers | Capillary blood in villi | Liver via hepatic portal vein |
Table 23.10
Carbohydrate Absorption
All carbohydrates are absorbed in the form of monosaccharides. The small intestine is highly efficient at this, absorbing monosaccharides at an estimated rate of 120 grams per hour. All normally digested dietary carbohydrates are absorbed; indigestible fibers are eliminated in the feces. The monosaccharides glucose and galactose are transported into the epithelial cells by common protein carriers via secondary active transport (that is, co-transport with sodium ions). The monosaccharides leave these cells via facilitated diffusion and enter the capillaries through intercellular clefts. The monosaccharide fructose (which is in fruit) is absorbed and transported by facilitated diffusion alone. The monosaccharides combine with the transport proteins immediately after the disaccharides are broken down.
Protein Absorption
Active transport mechanisms, primarily in the duodenum and jejunum, absorb most proteins as their breakdown products, amino acids. Almost all (95 to 98 percent) protein is digested and absorbed in the small intestine. The type of carrier that transports an amino acid varies. Most carriers are linked to the active transport of sodium. Short chains of two amino acids (dipeptides) or three amino acids (tripeptides) are also transported actively. However, after they enter the absorptive epithelial cells, they are broken down into their amino acids before leaving the cell and entering the capillary blood via diffusion.
Lipid Absorption
About 95 percent of lipids are absorbed in the small intestine. Bile salts not only speed up lipid digestion, they are also essential to the absorption of the end products of lipid digestion. Short-chain fatty acids are relatively water soluble and can enter the absorptive cells (enterocytes) directly. The small size of short-chain fatty acids enables them to be absorbed by enterocytes via simple diffusion, and then take the same path as monosaccharides and amino acids into the blood capillary of a villus.
The large and hydrophobic long-chain fatty acids and monoacylglycerides are not so easily suspended in the watery intestinal chyme. However, bile salts and lecithin resolve this issue by enclosing them in a micelle, which is a tiny sphere with polar (hydrophilic) ends facing the watery environment and hydrophobic tails turned to the interior, creating a receptive environment for the long-chain fatty acids. The core also includes cholesterol and fat-soluble vitamins. Without micelles, lipids would sit on the surface of chyme and never come in contact with the absorptive surfaces of the epithelial cells. Micelles can easily squeeze between microvilli and get very near the luminal cell surface. At this point, lipid substances exit the micelle and are absorbed via simple diffusion.
The free fatty acids and monoacylglycerides that enter the epithelial cells are reincorporated into triglycerides. The triglycerides are mixed with phospholipids and cholesterol, and surrounded with a protein coat. This new complex, called a chylomicron, is a water-soluble lipoprotein. After being processed by the Golgi apparatus, chylomicrons are released from the cell (Figure 23.33). Too big to pass through the basement membranes of blood capillaries, chylomicrons instead enter the large pores of lacteals. The lacteals come together to form the lymphatic vessels. The chylomicrons are transported in the lymphatic vessels and empty through the thoracic duct into the subclavian vein of the circulatory system. Once in the bloodstream, the enzyme lipoprotein lipase breaks down the triglycerides of the chylomicrons into free fatty acids and glycerol. These breakdown products then pass through capillary walls to be used for energy by cells or stored in adipose tissue as fat. Liver cells combine the remaining chylomicron remnants with proteins, forming lipoproteins that transport cholesterol in the blood.
Figure 23.33 Lipid Absorption Unlike amino acids and simple sugars, lipids are transformed as they are absorbed through epithelial cells.
Nucleic Acid Absorption
The products of nucleic acid digestion—pentose sugars, nitrogenous bases, and phosphate ions—are transported by carriers across the villus epithelium via active transport. These products then enter the bloodstream.
Mineral Absorption
The electrolytes absorbed by the small intestine are from both GI secretions and ingested foods. Since electrolytes dissociate into ions in water, most are absorbed via active transport throughout the entire small intestine. During absorption, co-transport mechanisms result in the accumulation of sodium ions inside the cells, whereas anti-port mechanisms reduce the potassium ion concentration inside the cells. To restore the sodium-potassium gradient across the cell membrane, a sodium-potassium pump requiring ATP pumps sodium out and potassium in.
In general, all minerals that enter the intestine are absorbed, whether you need them or not. Iron and calcium are exceptions; they are absorbed in the duodenum in amounts that meet the body’s current requirements, as follows:
Iron—The ionic iron needed for the production of hemoglobin is absorbed into mucosal cells via active transport. Once inside mucosal cells, ionic iron binds to the protein ferritin, creating iron-ferritin complexes that store iron until needed. When the body has enough iron, most of the stored iron is lost when worn-out epithelial cells slough off. When the body needs iron because, for example, it is lost during acute or chronic bleeding, there is increased uptake of iron from the intestine and accelerated release of iron into the bloodstream. Since women experience significant iron loss during menstruation, they have around four times as many iron transport proteins in their intestinal epithelial cells as do men.
Calcium—Blood levels of ionic calcium determine the absorption of dietary calcium. When blood levels of ionic calcium drop, parathyroid hormone (PTH) secreted by the parathyroid glands stimulates the release of calcium ions from bone matrices and increases the reabsorption of calcium by the kidneys. PTH also upregulates the activation of vitamin D in the kidney, which then facilitates intestinal calcium ion absorption.
Vitamin Absorption
The small intestine absorbs the vitamins that occur naturally in food and supplements. Fat-soluble vitamins (A, D, E, and K) are absorbed along with dietary lipids in micelles via simple diffusion. This is why you are advised to eat some fatty foods when you take fat-soluble vitamin supplements. Most water-soluble vitamins (including most B vitamins and vitamin C) also are absorbed by simple diffusion. An exception is vitamin B12, which is a very large molecule. Intrinsic factor secreted in the stomach binds to vitamin B12, preventing its digestion and creating a complex that binds to mucosal receptors in the terminal ileum, where it is taken up by endocytosis.
Water Absorption
Each day, about nine liters of fluid enter the small intestine. About 2.3 liters are ingested in foods and beverages, and the rest is from GI secretions. About 90 percent of this water is absorbed in the small intestine. Water absorption is driven by the concentration gradient of the water: The concentration of water is higher in chyme than it is in epithelial cells. Thus, water moves down its concentration gradient from the chyme into cells. As noted earlier, much of the remaining water is then absorbed in the colon.
Key Terms
- absorption
- passage of digested products from the intestinal lumen through mucosal cells and into the bloodstream or lacteals
- accessory digestive organ
- includes teeth, tongue, salivary glands, gallbladder, liver, and pancreas
- accessory duct
- (also, duct of Santorini) duct that runs from the pancreas into the duodenum
- acinus
- cluster of glandular epithelial cells in the pancreas that secretes pancreatic juice in the pancreas
- alimentary canal
- continuous muscular digestive tube that extends from the mouth to the anus
- aminopeptidase
- brush border enzyme that acts on proteins
- anal canal
- final segment of the large intestine
- anal column
- long fold of mucosa in the anal canal
- anal sinus
- recess between anal columns
- appendix
- (vermiform appendix) coiled tube attached to the cecum
- ascending colon
- first region of the colon
- bacterial flora
- bacteria in the large intestine
- bile
- alkaline solution produced by the liver and important for the emulsification of lipids
- bile canaliculus
- small duct between hepatocytes that collects bile
- bilirubin
- main bile pigment, which is responsible for the brown color of feces
- body
- mid-portion of the stomach
- bolus
- mass of chewed food
- brush border
- fuzzy appearance of the small intestinal mucosa created by microvilli
- cardia
- (also, cardiac region) part of the stomach surrounding the cardiac orifice (esophageal hiatus)
- cecum
- pouch forming the beginning of the large intestine
- cementum
- bone-like tissue covering the root of a tooth
- central vein
- vein that receives blood from hepatic sinusoids
- cephalic phase
- (also, reflex phase) initial phase of gastric secretion that occurs before food enters the stomach
- chemical digestion
- enzymatic breakdown of food
- chief cell
- gastric gland cell that secretes pepsinogen
- chylomicron
- large lipid-transport compound made up of triglycerides, phospholipids, cholesterol, and proteins
- chyme
- soupy liquid created when food is mixed with digestive juices
- circular fold
- (also, plica circulare) deep fold in the mucosa and submucosa of the small intestine
- colon
- part of the large intestine between the cecum and the rectum
- common bile duct
- structure formed by the union of the common hepatic duct and the gallbladder’s cystic duct
- common hepatic duct
- duct formed by the merger of the two hepatic ducts
- crown
- portion of tooth visible superior to the gum line
- cuspid
- (also, canine) pointed tooth used for tearing and shredding food
- cystic duct
- duct through which bile drains and enters the gallbladder
- deciduous tooth
- one of 20 “baby teeth”
- defecation
- elimination of undigested substances from the body in the form of feces
- deglutition
- three-stage process of swallowing
- dens
- tooth
- dentin
- bone-like tissue immediately deep to the enamel of the crown or cementum of the root of a tooth
- dentition
- set of teeth
- deoxyribonuclease
- pancreatic enzyme that digests DNA
- descending colon
- part of the colon between the transverse colon and the sigmoid colon
- dipeptidase
- brush border enzyme that acts on proteins
- duodenal gland
- (also, Brunner’s gland) mucous-secreting gland in the duodenal submucosa
- duodenum
- first part of the small intestine, which starts at the pyloric sphincter and ends at the jejunum
- enamel
- covering of the dentin of the crown of a tooth
- enteroendocrine cell
- gastric gland cell that releases hormones
- enterohepatic circulation
- recycling mechanism that conserves bile salts
- enteropeptidase
- intestinal brush-border enzyme that activates trypsinogen to trypsin
- epiploic appendage
- small sac of fat-filled visceral peritoneum attached to teniae coli
- esophagus
- muscular tube that runs from the pharynx to the stomach
- external anal sphincter
- voluntary skeletal muscle sphincter in the anal canal
- fauces
- opening between the oral cavity and the oropharynx
- feces
- semisolid waste product of digestion
- flatus
- gas in the intestine
- fundus
- dome-shaped region of the stomach above and to the left of the cardia
- G cell
- gastrin-secreting enteroendocrine cell
- gallbladder
- accessory digestive organ that stores and concentrates bile
- gastric emptying
- process by which mixing waves gradually cause the release of chyme into the duodenum
- gastric gland
- gland in the stomach mucosal epithelium that produces gastric juice
- gastric phase
- phase of gastric secretion that begins when food enters the stomach
- gastric pit
- narrow channel formed by the epithelial lining of the stomach mucosa
- gastrin
- peptide hormone that stimulates secretion of hydrochloric acid and gut motility
- gastrocolic reflex
- propulsive movement in the colon activated by the presence of food in the stomach
- gastroileal reflex
- long reflex that increases the strength of segmentation in the ileum
- gingiva
- gum
- haustral contraction
- slow segmentation in the large intestine
- haustrum
- small pouch in the colon created by tonic contractions of teniae coli
- hepatic artery
- artery that supplies oxygenated blood to the liver
- hepatic lobule
- hexagonal-shaped structure composed of hepatocytes that radiate outward from a central vein
- hepatic portal vein
- vein that supplies deoxygenated nutrient-rich blood to the liver
- hepatic sinusoid
- blood capillaries between rows of hepatocytes that receive blood from the hepatic portal vein and the branches of the hepatic artery
- hepatic vein
- vein that drains into the inferior vena cava
- hepatocytes
- major functional cells of the liver
- hepatopancreatic ampulla
- (also, ampulla of Vater) bulb-like point in the wall of the duodenum where the bile duct and main pancreatic duct unite
- hepatopancreatic sphincter
- (also, sphincter of Oddi) sphincter regulating the flow of bile and pancreatic juice into the duodenum
- hydrochloric acid (HCl)
- digestive acid secreted by parietal cells in the stomach
- ileocecal sphincter
- sphincter located where the small intestine joins with the large intestine
- ileum
- end of the small intestine between the jejunum and the large intestine
- incisor
- midline, chisel-shaped tooth used for cutting into food
- ingestion
- taking food into the GI tract through the mouth
- internal anal sphincter
- involuntary smooth muscle sphincter in the anal canal
- intestinal gland
- (also, crypt of Lieberkühn) gland in the small intestinal mucosa that secretes intestinal juice
- intestinal juice
- mixture of water and mucus that helps absorb nutrients from chyme
- intestinal phase
- phase of gastric secretion that begins when chyme enters the intestine
- intrinsic factor
- glycoprotein required for vitamin B12 absorption in the small intestine
- jejunum
- middle part of the small intestine between the duodenum and the ileum
- labial frenulum
- midline mucous membrane fold that attaches the inner surface of the lips to the gums
- labium
- lip
- lactase
- brush border enzyme that breaks down lactose into glucose and galactose
- lacteal
- lymphatic capillary in the villi
- large intestine
- terminal portion of the alimentary canal
- laryngopharynx
- part of the pharynx that functions in respiration and digestion
- left colic flexure
- (also, splenic flexure) point where the transverse colon curves below the inferior end of the spleen
- lingual frenulum
- mucous membrane fold that attaches the bottom of the tongue to the floor of the mouth
- lingual lipase
- digestive enzyme from glands in the tongue that acts on triglycerides
- lipoprotein lipase
- enzyme that breaks down triglycerides in chylomicrons into fatty acids and monoglycerides
- liver
- largest gland in the body whose main digestive function is the production of bile
- lower esophageal sphincter
- smooth muscle sphincter that regulates food movement from the esophagus to the stomach
- main pancreatic duct
- (also, duct of Wirsung) duct through which pancreatic juice drains from the pancreas
- major duodenal papilla
- point at which the hepatopancreatic ampulla opens into the duodenum
- maltase
- brush border enzyme that breaks down maltose and maltotriose into two and three molecules of glucose, respectively
- mass movement
- long, slow, peristaltic wave in the large intestine
- mastication
- chewing
- mechanical digestion
- chewing, mixing, and segmentation that prepares food for chemical digestion
- mesoappendix
- mesentery of the appendix
- micelle
- tiny lipid-transport compound composed of bile salts and phospholipids with a fatty acid and monoacylglyceride core
- microvillus
- small projection of the plasma membrane of the absorptive cells of the small intestinal mucosa
- migrating motility complex
- form of peristalsis in the small intestine
- mixing wave
- unique type of peristalsis that occurs in the stomach
- molar
- tooth used for crushing and grinding food
- motilin
- hormone that initiates migrating motility complexes
- motility
- movement of food through the GI tract
- mucosa
- innermost lining of the alimentary canal
- mucosal barrier
- protective barrier that prevents gastric juice from destroying the stomach itself
- mucous neck cell
- gastric gland cell that secretes a uniquely acidic mucus
- muscularis
- muscle (skeletal or smooth) layer of the alimentary canal wall
- myenteric plexus
- (plexus of Auerbach) major nerve supply to alimentary canal wall; controls motility
- nucleosidase
- brush border enzyme that digests nucleotides
- oral cavity
- (also, buccal cavity) mouth
- oral vestibule
- part of the mouth bounded externally by the cheeks and lips, and internally by the gums and teeth
- oropharynx
- part of the pharynx continuous with the oral cavity that functions in respiration and digestion
- palatoglossal arch
- muscular fold that extends from the lateral side of the soft palate to the base of the tongue
- palatopharyngeal arch
- muscular fold that extends from the lateral side of the soft palate to the side of the pharynx
- pancreas
- accessory digestive organ that secretes pancreatic juice
- pancreatic amylase
- enzyme secreted by the pancreas that completes the chemical digestion of carbohydrates in the small intestine
- pancreatic juice
- secretion of the pancreas containing digestive enzymes and bicarbonate
- pancreatic lipase
- enzyme secreted by the pancreas that participates in lipid digestion
- pancreatic nuclease
- enzyme secreted by the pancreas that participates in nucleic acid digestion
- parietal cell
- gastric gland cell that secretes hydrochloric acid and intrinsic factor
- parotid gland
- one of a pair of major salivary glands located inferior and anterior to the ears
- pectinate line
- horizontal line that runs like a ring, perpendicular to the inferior margins of the anal sinuses
- pepsinogen
- inactive form of pepsin
- peristalsis
- muscular contractions and relaxations that propel food through the GI tract
- permanent tooth
- one of 32 adult teeth
- pharynx
- throat
- phosphatase
- brush border enzyme that digests nucleotides
- porta hepatis
- “gateway to the liver” where the hepatic artery and hepatic portal vein enter the liver
- portal triad
- bile duct, hepatic artery branch, and hepatic portal vein branch
- premolar
- (also, bicuspid) transitional tooth used for mastication, crushing, and grinding food
- propulsion
- voluntary process of swallowing and the involuntary process of peristalsis that moves food through the digestive tract
- pulp cavity
- deepest portion of a tooth, containing nerve endings and blood vessels
- pyloric antrum
- wider, more superior part of the pylorus
- pyloric canal
- narrow, more inferior part of the pylorus
- pyloric sphincter
- sphincter that controls stomach emptying
- pylorus
- lower, funnel-shaped part of the stomach that is continuous with the duodenum
- rectal valve
- one of three transverse folds in the rectum where feces is separated from flatus
- rectum
- part of the large intestine between the sigmoid colon and anal canal
- reticuloendothelial cell
- (also, Kupffer cell) phagocyte in hepatic sinusoids that filters out material from venous blood from the alimentary canal
- retroperitoneal
- located posterior to the peritoneum
- ribonuclease
- pancreatic enzyme that digests RNA
- right colic flexure
- (also, hepatic flexure) point, at the inferior surface of the liver, where the ascending colon turns abruptly to the left
- root
- portion of a tooth embedded in the alveolar processes beneath the gum line
- ruga
- fold of alimentary canal mucosa and submucosa in the empty stomach and other organs
- saccharolytic fermentation
- anaerobic decomposition of carbohydrates
- saliva
- aqueous solution of proteins and ions secreted into the mouth by the salivary glands
- salivary amylase
- digestive enzyme in saliva that acts on starch
- salivary gland
- an exocrine gland that secretes a digestive fluid called saliva
- salivation
- secretion of saliva
- segmentation
- alternating contractions and relaxations of non-adjacent segments of the intestine that move food forward and backward, breaking it apart and mixing it with digestive juices
- serosa
- outermost layer of the alimentary canal wall present in regions within the abdominal cavity
- sigmoid colon
- end portion of the colon, which terminates at the rectum
- small intestine
- section of the alimentary canal where most digestion and absorption occurs
- soft palate
- posterior region of the bottom portion of the nasal cavity that consists of skeletal muscle
- stomach
- alimentary canal organ that contributes to chemical and mechanical digestion of food from the esophagus before releasing it, as chyme, to the small intestine
- sublingual gland
- one of a pair of major salivary glands located beneath the tongue
- submandibular gland
- one of a pair of major salivary glands located in the floor of the mouth
- submucosa
- layer of dense connective tissue in the alimentary canal wall that binds the overlying mucosa to the underlying muscularis
- submucosal plexus
- (plexus of Meissner) nerve supply that regulates activity of glands and smooth muscle
- sucrase
- brush border enzyme that breaks down sucrose into glucose and fructose
- tenia coli
- one of three smooth muscle bands that make up the longitudinal muscle layer of the muscularis in all of the large intestine except the terminal end
- tongue
- accessory digestive organ of the mouth, the bulk of which is composed of skeletal muscle
- transverse colon
- part of the colon between the ascending colon and the descending colon
- upper esophageal sphincter
- skeletal muscle sphincter that regulates food movement from the pharynx to the esophagus
- Valsalva’s maneuver
- voluntary contraction of the diaphragm and abdominal wall muscles and closing of the glottis, which increases intra-abdominal pressure and facilitates defecation
- villus
- projection of the mucosa of the small intestine
- voluntary phase
- initial phase of deglutition, in which the bolus moves from the mouth to the oropharynx
- α-dextrin
- breakdown product of starch
- α-dextrinase
- brush border enzyme that acts on α-dextrins
Chapter Review
23.1 Overview of the Digestive System
The digestive system includes the organs of the alimentary canal and accessory structures. The alimentary canal forms a continuous tube that is open to the outside environment at both ends. The organs of the alimentary canal are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The accessory digestive structures include the teeth, tongue, salivary glands, liver, pancreas, and gallbladder. The wall of the alimentary canal is composed of four basic tissue layers: mucosa, submucosa, muscularis, and serosa. The enteric nervous system provides intrinsic innervation, and the autonomic nervous system provides extrinsic innervation.
23.2 Digestive System Processes and Regulation
The digestive system ingests and digests food, absorbs released nutrients, and excretes food components that are indigestible. The six activities involved in this process are ingestion, motility, mechanical digestion, chemical digestion, absorption, and defecation. These processes are regulated by neural and hormonal mechanisms.
23.3 The Mouth, Pharynx, and Esophagus
In the mouth, the tongue and the teeth begin mechanical digestion, and saliva begins chemical digestion. The pharynx, which plays roles in breathing and vocalization as well as digestion, runs from the nasal and oral cavities superiorly to the esophagus inferiorly (for digestion) and to the larynx anteriorly (for respiration). During deglutition (swallowing), the soft palate rises to close off the nasopharynx, the larynx elevates, and the epiglottis folds over the glottis. The esophagus includes an upper esophageal sphincter made of skeletal muscle, which regulates the movement of food from the pharynx to the esophagus. It also has a lower esophageal sphincter, made of smooth muscle, which controls the passage of food from the esophagus to the stomach. Cells in the esophageal wall secrete mucus that eases the passage of the food bolus.
23.4 The Stomach
The stomach participates in all digestive activities except ingestion and defecation. It vigorously churns food. It secretes gastric juices that break down food and absorbs certain drugs, including aspirin and some alcohol. The stomach begins the digestion of protein and continues the digestion of carbohydrates and fats. It stores food as an acidic liquid called chyme, and releases it gradually into the small intestine through the pyloric sphincter.
23.5 The Small and Large Intestines
The three main regions of the small intestine are the duodenum, the jejunum, and the ileum. The small intestine is where digestion is completed and virtually all absorption occurs. These two activities are facilitated by structural adaptations that increase the mucosal surface area by 600-fold, including circular folds, villi, and microvilli. There are around 200 million microvilli per square millimeter of small intestine, which contain brush border enzymes that complete the digestion of carbohydrates and proteins. Combined with pancreatic juice, intestinal juice provides the liquid medium needed to further digest and absorb substances from chyme. The small intestine is also the site of unique mechanical digestive movements. Segmentation moves the chyme back and forth, increasing mixing and opportunities for absorption. Migrating motility complexes propel the residual chyme toward the large intestine.
The main regions of the large intestine are the cecum, the colon, and the rectum. The large intestine absorbs water and forms feces, and is responsible for defecation. Bacterial flora break down additional carbohydrate residue, and synthesize certain vitamins. The mucosa of the large intestinal wall is generously endowed with goblet cells, which secrete mucus that eases the passage of feces. The entry of feces into the rectum activates the defecation reflex.
23.6 Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder
Chemical digestion in the small intestine cannot occur without the help of the liver and pancreas. The liver produces bile and delivers it to the common hepatic duct. Bile contains bile salts and phospholipids, which emulsify large lipid globules into tiny lipid droplets, a necessary step in lipid digestion and absorption. The gallbladder stores and concentrates bile, releasing it when it is needed by the small intestine.
The pancreas produces the enzyme- and bicarbonate-rich pancreatic juice and delivers it to the small intestine through ducts. Pancreatic juice buffers the acidic gastric juice in chyme, inactivates pepsin from the stomach, and enables the optimal functioning of digestive enzymes in the small intestine.
23.7 Chemical Digestion and Absorption: A Closer Look
The small intestine is the site of most chemical digestion and almost all absorption. Chemical digestion breaks large food molecules down into their chemical building blocks, which can then be absorbed through the intestinal wall and into the general circulation. Intestinal brush border enzymes and pancreatic enzymes are responsible for the majority of chemical digestion. The breakdown of fat also requires bile.
Most nutrients are absorbed by transport mechanisms at the apical surface of enterocytes. Exceptions include lipids, fat-soluble vitamins, and most water-soluble vitamins. With the help of bile salts and lecithin, the dietary fats are emulsified to form micelles, which can carry the fat particles to the surface of the enterocytes. There, the micelles release their fats to diffuse across the cell membrane. The fats are then reassembled into triglycerides and mixed with other lipids and proteins into chylomicrons that can pass into lacteals. Other absorbed monomers travel from blood capillaries in the villus to the hepatic portal vein and then to the liver.
Interactive Link Questions
By clicking on this link, you can watch a short video of what happens to the food you eat as it passes from your mouth to your intestine. Along the way, note how the food changes consistency and form. How does this change in consistency facilitate your gaining nutrients from food?
2.Visit this site for an overview of digestion of food in different regions of the digestive tract. Note the route of non-fat nutrients from the small intestine to their release as nutrients to the body.
3.Watch this animation to see how swallowing is a complex process that involves the nervous system to coordinate the actions of upper respiratory and digestive activities. During which stage of swallowing is there a risk of food entering respiratory pathways and how is this risk blocked?
4.Watch this animation that depicts the structure of the stomach and how this structure functions in the initiation of protein digestion. This view of the stomach shows the characteristic rugae. What is the function of these rugae?
5.Watch this animation that depicts the structure of the small intestine, and, in particular, the villi. Epithelial cells continue the digestion and absorption of nutrients and transport these nutrients to the lymphatic and circulatory systems. In the small intestine, the products of food digestion are absorbed by different structures in the villi. Which structure absorbs and transports fats?
6.By watching this animation, you will see that for the various food groups—proteins, fats, and carbohydrates—digestion begins in different parts of the digestion system, though all end in the same place. Of the three major food classes (carbohydrates, fats, and proteins), which is digested in the mouth, the stomach, and the small intestine?
7.Watch this video to see the structure of the liver and how this structure supports the functions of the liver, including the processing of nutrients, toxins, and wastes. At rest, about 1500 mL of blood per minute flow through the liver. What percentage of this blood flow comes from the hepatic portal system?
Review Questions
Which of these organs is not considered an accessory digestive structure?
- mouth
- salivary glands
- pancreas
- liver
Which of the following organs is supported by a layer of adventitia rather than serosa?
- esophagus
- stomach
- small intestine
- large intestine
Which of the following membranes covers the stomach?
- falciform ligament
- mesocolon
- parietal peritoneum
- visceral peritoneum
Which of these processes occurs in the mouth?
- ingestion
- mechanical digestion
- chemical digestion
- all of the above
Which of these processes occurs throughout most of the alimentary canal?
- ingestion
- propulsion
- segmentation
- absorption
Which of the following stimuli activates sensors in the walls of digestive organs?
- breakdown products of digestion
- distension
- pH of chyme
- all of the above
Which of these statements about reflexes in the GI tract is false?
- Short reflexes are provoked by nerves near the GI tract.
- Short reflexes are mediated by the enteric nervous system.
- Food that distends the stomach initiates long reflexes.
- Long reflexes can be provoked by stimuli originating outside the GI tract.
Which of these ingredients in saliva is responsible for activating salivary amylase?
- mucus
- phosphate ions
- chloride ions
- urea
Which of these statements about the pharynx is true?
- It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.
- The oropharynx is continuous superiorly with the nasopharynx.
- The nasopharynx is involved in digestion.
- The laryngopharynx is composed partially of cartilage.
Which structure is located where the esophagus penetrates the diaphragm?
- esophageal hiatus
- cardiac orifice
- upper esophageal sphincter
- lower esophageal sphincter
Which phase of deglutition involves contraction of the longitudinal muscle layer of the muscularis?
- voluntary phase
- buccal phase
- pharyngeal phase
- esophageal phase
Which of these cells secrete hormones?
- parietal cells
- mucous neck cells
- enteroendocrine cells
- chief cells
Where does the majority of chemical digestion in the stomach occur?
- fundus and body
- cardia and fundus
- body and pylorus
- body
During gastric emptying, chyme is released into the duodenum through the ________.
- esophageal hiatus
- pyloric antrum
- pyloric canal
- pyloric sphincter
Parietal cells secrete ________.
- gastrin
- hydrochloric acid
- pepsin
- pepsinogen
In which part of the alimentary canal does most digestion occur?
- stomach
- proximal small intestine
- distal small intestine
- ascending colon
Which of these is most associated with villi?
- haustra
- lacteals
- bacterial flora
- intestinal glands
What is the role of the small intestine’s MALT?
- secreting mucus
- buffering acidic chyme
- activating pepsin
- preventing bacteria from entering the bloodstream
Which part of the large intestine attaches to the appendix?
- cecum
- ascending colon
- transverse colon
- descending colon
Which of these statements about bile is true?
- About 500 mL is secreted daily.
- Its main function is the denaturation of proteins.
- It is synthesized in the gallbladder.
- Bile salts are recycled.
Pancreatic juice ________.
- deactivates bile.
- is secreted by pancreatic islet cells.
- buffers chyme.
- is released into the cystic duct.
Where does the chemical digestion of starch begin?
- mouth
- esophagus
- stomach
- small intestine
Which of these is involved in the chemical digestion of protein?
- pancreatic amylase
- trypsin
- sucrase
- pancreatic nuclease
Where are most fat-digesting enzymes produced?
- small intestine
- gallbladder
- liver
- pancreas
Which of these nutrients is absorbed mainly in the duodenum?
- glucose
- iron
- sodium
- water
Critical Thinking Questions
Explain how the enteric nervous system supports the digestive system. What might occur that could result in the autonomic nervous system having a negative impact on digestion?
34.What layer of the alimentary canal tissue is capable of helping to protect the body against disease, and through what mechanism?
35.Offer a theory to explain why segmentation occurs and peristalsis slows in the small intestine.
36.It has been several hours since you last ate. Walking past a bakery, you catch a whiff of freshly baked bread. What type of reflex is triggered, and what is the result?
37.The composition of saliva varies from gland to gland. Discuss how saliva produced by the parotid gland differs in action from saliva produced by the sublingual gland.
38.During a hockey game, the puck hits a player in the mouth, knocking out all eight of his most anterior teeth. Which teeth did the player lose and how does this loss affect food ingestion?
39.What prevents swallowed food from entering the airways?
40.Explain the mechanism responsible for gastroesophageal reflux.
41.Describe the three processes involved in the esophageal phase of deglutition.
42.Explain how the stomach is protected from self-digestion and why this is necessary.
43.Describe unique anatomical features that enable the stomach to perform digestive functions.
44.Explain how nutrients absorbed in the small intestine pass into the general circulation.
45.Why is it important that chyme from the stomach is delivered to the small intestine slowly and in small amounts?
46.Describe three of the differences between the walls of the large and small intestines.
47.Why does the pancreas secrete some enzymes in their inactive forms, and where are these enzymes activated?
48.Describe the location of hepatocytes in the liver and how this arrangement enhances their function.
49.Explain the role of bile salts and lecithin in the emulsification of lipids (fats).
50.How is vitamin B12 absorbed?
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oercommons
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2025-03-18T00:37:11.657388
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"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
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https://oercommons.org/courseware/lesson/58772/overview
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Metabolism and Nutrition
Introduction
Figure 24.1 Metabolism Metabolism is the sum of all energy-requiring and energy-consuming processes of the body. Many factors contribute to overall metabolism, including lean muscle mass, the amount and quality of food consumed, and the physical demands placed on the human body. (credit: "tableatny"/flickr.com)
CHAPTER OBJECTIVES
After studying this chapter, you will be able to:
- Describe the processes involved in anabolic and catabolic reactions
- List and describe the steps necessary for carbohydrate, lipid, and protein metabolism
- Explain the processes that regulate glucose levels during the absorptive and postabsorptive states
- Explain how metabolism is essential to maintaining body temperature (thermoregulation)
- Summarize the importance of vitamins and minerals in the diet
Eating is essential to life. Many of us look to eating as not only a necessity, but also a pleasure. You may have been told since childhood to start the day with a good breakfast to give you the energy to get through most of the day. You most likely have heard about the importance of a balanced diet, with plenty of fruits and vegetables. But what does this all mean to your body and the physiological processes it carries out each day? You need to absorb a range of nutrients so that your cells have the building blocks for metabolic processes that release the energy for the cells to carry out their daily jobs, to manufacture new proteins, cells, and body parts, and to recycle materials in the cell.
This chapter will take you through some of the chemical reactions essential to life, the sum of which is referred to as metabolism. The focus of these discussions will be anabolic reactions and catabolic reactions. You will examine the various chemical reactions that are important to sustain life, including why you must have oxygen, how mitochondria transfer energy, and the importance of certain “metabolic” hormones and vitamins.
Metabolism varies, depending on age, gender, activity level, fuel consumption, and lean body mass. Your own metabolic rate fluctuates throughout life. By modifying your diet and exercise regimen, you can increase both lean body mass and metabolic rate. Factors affecting metabolism also play important roles in controlling muscle mass. Aging is known to decrease the metabolic rate by as much as 5 percent per year. Additionally, because men tend have more lean muscle mass then women, their basal metabolic rate (metabolic rate at rest) is higher; therefore, men tend to burn more calories than women do. Lastly, an individual’s inherent metabolic rate is a function of the proteins and enzymes derived from their genetic background. Thus, your genes play a big role in your metabolism. Nonetheless, each person’s body engages in the same overall metabolic processes.
Overview of Metabolic Reactions
- Describe the process by which polymers are broken down into monomers
- Describe the process by which monomers are combined into polymers
- Discuss the role of ATP in metabolism
- Explain oxidation-reduction reactions
- Describe the hormones that regulate anabolic and catabolic reactions
Metabolic processes are constantly taking place in the body. Metabolism is the sum of all of the chemical reactions that are involved in catabolism and anabolism. The reactions governing the breakdown of food to obtain energy are called catabolic reactions. Conversely, anabolic reactions use the energy produced by catabolic reactions to synthesize larger molecules from smaller ones, such as when the body forms proteins by stringing together amino acids. Both sets of reactions are critical to maintaining life.
Because catabolic reactions produce energy and anabolic reactions use energy, ideally, energy usage would balance the energy produced. If the net energy change is positive (catabolic reactions release more energy than the anabolic reactions use), then the body stores the excess energy by building fat molecules for long-term storage. On the other hand, if the net energy change is negative (catabolic reactions release less energy than anabolic reactions use), the body uses stored energy to compensate for the deficiency of energy released by catabolism.
Catabolic Reactions
Catabolic reactions break down large organic molecules into smaller molecules, releasing the energy contained in the chemical bonds. These energy releases (conversions) are not 100 percent efficient. The amount of energy released is less than the total amount contained in the molecule. Approximately 40 percent of energy yielded from catabolic reactions is directly transferred to the high-energy molecule adenosine triphosphate (ATP). ATP, the energy currency of cells, can be used immediately to power molecular machines that support cell, tissue, and organ function. This includes building new tissue and repairing damaged tissue. ATP can also be stored to fulfill future energy demands. The remaining 60 percent of the energy released from catabolic reactions is given off as heat, which tissues and body fluids absorb.
Structurally, ATP molecules consist of an adenine, a ribose, and three phosphate groups (Figure 24.2). The chemical bond between the second and third phosphate groups, termed a high-energy bond, represents the greatest source of energy in a cell. It is the first bond that catabolic enzymes break when cells require energy to do work. The products of this reaction are a molecule of adenosine diphosphate (ADP) and a lone phosphate group (Pi). ATP, ADP, and Pi are constantly being cycled through reactions that build ATP and store energy, and reactions that break down ATP and release energy.
Figure 24.2 Structure of ATP Molecule Adenosine triphosphate (ATP) is the energy molecule of the cell. During catabolic reactions, ATP is created and energy is stored until needed during anabolic reactions.
The energy from ATP drives all bodily functions, such as contracting muscles, maintaining the electrical potential of nerve cells, and absorbing food in the gastrointestinal tract. The metabolic reactions that produce ATP come from various sources (Figure 24.3).
Figure 24.3 Sources of ATP During catabolic reactions, proteins are broken down into amino acids, lipids are broken down into fatty acids, and polysaccharides are broken down into monosaccharides. These building blocks are then used for the synthesis of molecules in anabolic reactions.
Of the four major macromolecular groups (carbohydrates, lipids, proteins, and nucleic acids) that are processed by digestion, carbohydrates are considered the most common source of energy to fuel the body. They take the form of either complex carbohydrates, polysaccharides like starch and glycogen, or simple sugars (monosaccharides) like glucose and fructose. Sugar catabolism breaks polysaccharides down into their individual monosaccharides. Among the monosaccharides, glucose is the most common fuel for ATP production in cells, and as such, there are a number of endocrine control mechanisms to regulate glucose concentration in the bloodstream. Excess glucose is either stored as an energy reserve in the liver and skeletal muscles as the complex polymer glycogen, or it is converted into fat (triglyceride) in adipose cells (adipocytes).
Among the lipids (fats), triglycerides are most often used for energy via a metabolic process called β-oxidation. About one-half of excess fat is stored in adipocytes that accumulate in the subcutaneous tissue under the skin, whereas the rest is stored in adipocytes in other tissues and organs.
Proteins, which are polymers, can be broken down into their monomers, individual amino acids. Amino acids can be used as building blocks of new proteins or broken down further for the production of ATP. When one is chronically starving, this use of amino acids for energy production can lead to a wasting away of the body, as more and more proteins are broken down.
Nucleic acids are present in most of the foods you eat. During digestion, nucleic acids including DNA and various RNAs are broken down into their constituent nucleotides. These nucleotides are readily absorbed and transported throughout the body to be used by individual cells during nucleic acid metabolism.
Anabolic Reactions
In contrast to catabolic reactions, anabolic reactions involve the joining of smaller molecules into larger ones. Anabolic reactions combine monosaccharides to form polysaccharides, fatty acids to form triglycerides, amino acids to form proteins, and nucleotides to form nucleic acids. These processes require energy in the form of ATP molecules generated by catabolic reactions. Anabolic reactions, also called biosynthesis reactions, create new molecules that form new cells and tissues, and revitalize organs.
Hormonal Regulation of Metabolism
Catabolic and anabolic hormones in the body help regulate metabolic processes. Catabolic hormones stimulate the breakdown of molecules and the production of energy. These include cortisol, glucagon, adrenaline/epinephrine, and cytokines. All of these hormones are mobilized at specific times to meet the needs of the body. Anabolic hormones are required for the synthesis of molecules and include growth hormone, insulin-like growth factor, insulin, testosterone, and estrogen. Table 24.1summarizes the function of each of the catabolic hormones and Table 24.2 summarizes the functions of the anabolic hormones.
Catabolic Hormones
| Hormone | Function |
|---|---|
| Cortisol | Released from the adrenal gland in response to stress; its main role is to increase blood glucose levels by gluconeogenesis (breaking down fats and proteins) |
| Glucagon | Released from alpha cells in the pancreas either when starving or when the body needs to generate additional energy; it stimulates the breakdown of glycogen in the liver to increase blood glucose levels; its effect is the opposite of insulin; glucagon and insulin are a part of a negative-feedback system that stabilizes blood glucose levels |
| Adrenaline/epinephrine | Released in response to the activation of the sympathetic nervous system; increases heart rate and heart contractility, constricts blood vessels, is a bronchodilator that opens (dilates) the bronchi of the lungs to increase air volume in the lungs, and stimulates gluconeogenesis |
Table 24.1
Anabolic Hormones
| Hormone | Function |
|---|---|
| Growth hormone (GH) | Synthesized and released from the pituitary gland; stimulates the growth of cells, tissues, and bones |
| Insulin-like growth factor (IGF) | Stimulates the growth of muscle and bone while also inhibiting cell death (apoptosis) |
| Insulin | Produced by the beta cells of the pancreas; plays an essential role in carbohydrate and fat metabolism, controls blood glucose levels, and promotes the uptake of glucose into body cells; causes cells in muscle, adipose tissue, and liver to take up glucose from the blood and store it in the liver and muscle as glycogen; its effect is the opposite of glucagon; glucagon and insulin are a part of a negative-feedback system that stabilizes blood glucose levels |
| Testosterone | Produced by the testes in males and the ovaries in females; stimulates an increase in muscle mass and strength as well as the growth and strengthening of bone |
| Estrogen | Produced primarily by the ovaries, it is also produced by the liver and adrenal glands; its anabolic functions include increasing metabolism and fat deposition |
Table 24.2
DISORDERS OF THE...
Metabolic Processes: Cushing Syndrome and Addison’s Disease
As might be expected for a fundamental physiological process like metabolism, errors or malfunctions in metabolic processing lead to a pathophysiology or—if uncorrected—a disease state. Metabolic diseases are most commonly the result of malfunctioning proteins or enzymes that are critical to one or more metabolic pathways. Protein or enzyme malfunction can be the consequence of a genetic alteration or mutation. However, normally functioning proteins and enzymes can also have deleterious effects if their availability is not appropriately matched with metabolic need. For example, excessive production of the hormone cortisol (see Table 24.1) gives rise to Cushing syndrome. Clinically, Cushing syndrome is characterized by rapid weight gain, especially in the trunk and face region, depression, and anxiety. It is worth mentioning that tumors of the pituitary that produce adrenocorticotropic hormone (ACTH), which subsequently stimulates the adrenal cortex to release excessive cortisol, produce similar effects. This indirect mechanism of cortisol overproduction is referred to as Cushing disease.
Patients with Cushing syndrome can exhibit high blood glucose levels and are at an increased risk of becoming obese. They also show slow growth, accumulation of fat between the shoulders, weak muscles, bone pain (because cortisol causes proteins to be broken down to make glucose via gluconeogenesis), and fatigue. Other symptoms include excessive sweating (hyperhidrosis), capillary dilation, and thinning of the skin, which can lead to easy bruising. The treatments for Cushing syndrome are all focused on reducing excessive cortisol levels. Depending on the cause of the excess, treatment may be as simple as discontinuing the use of cortisol ointments. In cases of tumors, surgery is often used to remove the offending tumor. Where surgery is inappropriate, radiation therapy can be used to reduce the size of a tumor or ablate portions of the adrenal cortex. Finally, medications are available that can help to regulate the amounts of cortisol.
Insufficient cortisol production is equally problematic. Adrenal insufficiency, or Addison’s disease, is characterized by the reduced production of cortisol from the adrenal gland. It can result from malfunction of the adrenal glands—they do not produce enough cortisol—or it can be a consequence of decreased ACTH availability from the pituitary. Patients with Addison’s disease may have low blood pressure, paleness, extreme weakness, fatigue, slow or sluggish movements, lightheadedness, and salt cravings due to the loss of sodium and high blood potassium levels (hyperkalemia). Victims also may suffer from loss of appetite, chronic diarrhea, vomiting, mouth lesions, and patchy skin color. Diagnosis typically involves blood tests and imaging tests of the adrenal and pituitary glands. Treatment involves cortisol replacement therapy, which usually must be continued for life.
Oxidation-Reduction Reactions
The chemical reactions underlying metabolism involve the transfer of electrons from one compound to another by processes catalyzed by enzymes. The electrons in these reactions commonly come from hydrogen atoms, which consist of an electron and a proton. A molecule gives up a hydrogen atom, in the form of a hydrogen ion (H+) and an electron, breaking the molecule into smaller parts. The loss of an electron, or oxidation, releases a small amount of energy; both the electron and the energy are then passed to another molecule in the process of reduction, or the gaining of an electron. These two reactions always happen together in an oxidation-reduction reaction (also called a redox reaction)—when an electron is passed between molecules, the donor is oxidized and the recipient is reduced. Oxidation-reduction reactions often happen in a series, so that a molecule that is reduced is subsequently oxidized, passing on not only the electron it just received but also the energy it received. As the series of reactions progresses, energy accumulates that is used to combine Pi and ADP to form ATP, the high-energy molecule that the body uses for fuel.
Oxidation-reduction reactions are catalyzed by enzymes that trigger the removal of hydrogen atoms. Coenzymes work with enzymes and accept hydrogen atoms. The two most common coenzymes of oxidation-reduction reactions are nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD). Their respective reduced coenzymes are NADH and FADH2, which are energy-containing molecules used to transfer energy during the creation of ATP.
Carbohydrate Metabolism
- Explain the processes of glycolysis
- Describe the pathway of a pyruvate molecule through the Krebs cycle
- Explain the transport of electrons through the electron transport chain
- Describe the process of ATP production through oxidative phosphorylation
- Summarize the process of gluconeogenesis
Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen atoms. The family of carbohydrates includes both simple and complex sugars. Glucose and fructose are examples of simple sugars, and starch, glycogen, and cellulose are all examples of complex sugars. The complex sugars are also called polysaccharides and are made of multiple monosaccharide molecules. Polysaccharides serve as energy storage (e.g., starch and glycogen) and as structural components (e.g., chitin in insects and cellulose in plants).
During digestion, carbohydrates are broken down into simple, soluble sugars that can be transported across the intestinal wall into the circulatory system to be transported throughout the body. Carbohydrate digestion begins in the mouth with the action of salivary amylase on starches and ends with monosaccharides being absorbed across the epithelium of the small intestine. Once the absorbed monosaccharides are transported to the tissues, the process of cellular respiration begins (Figure 24.4). This section will focus first on glycolysis, a process where the monosaccharide glucose is oxidized, releasing the energy stored in its bonds to produce ATP.
Figure 24.4 Cellular Respiration Cellular respiration oxidizes glucose molecules through glycolysis, the Krebs cycle, and oxidative phosphorylation to produce ATP.
Glycolysis
Glucose is the body’s most readily available source of energy. After digestive processes break polysaccharides down into monosaccharides, including glucose, the monosaccharides are transported across the wall of the small intestine and into the circulatory system, which transports them to the liver. In the liver, hepatocytes either pass the glucose on through the circulatory system or store excess glucose as glycogen. Cells in the body take up the circulating glucose in response to insulin and, through a series of reactions called glycolysis, transfer some of the energy in glucose to ADP to form ATP (Figure 24.5). The last step in glycolysis produces the product pyruvate.
Glycolysis begins with the phosphorylation of glucose by hexokinase to form glucose-6-phosphate. This step uses one ATP, which is the donor of the phosphate group. Under the action of phosphofructokinase, glucose-6-phosphate is converted into fructose-6-phosphate. At this point, a second ATP donates its phosphate group, forming fructose-1,6-bisphosphate. This six-carbon sugar is split to form two phosphorylated three-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, which are both converted into glyceraldehyde-3-phosphate. The glyceraldehyde-3-phosphate is further phosphorylated with groups donated by dihydrogen phosphate present in the cell to form the three-carbon molecule 1,3-bisphosphoglycerate. The energy of this reaction comes from the oxidation of (removal of electrons from) glyceraldehyde-3-phosphate. In a series of reactions leading to pyruvate, the two phosphate groups are then transferred to two ADPs to form two ATPs. Thus, glycolysis uses two ATPs but generates four ATPs, yielding a net gain of two ATPs and two molecules of pyruvate. In the presence of oxygen, pyruvate continues on to the Krebs cycle (also called the citric acid cycle or tricarboxylic acid cycle (TCA), where additional energy is extracted and passed on.
Figure 24.5 Glycolysis Overview During the energy-consuming phase of glycolysis, two ATPs are consumed, transferring two phosphates to the glucose molecule. The glucose molecule then splits into two three-carbon compounds, each containing a phosphate. During the second phase, an additional phosphate is added to each of the three-carbon compounds. The energy for this endergonic reaction is provided by the removal (oxidation) of two electrons from each three-carbon compound. During the energy-releasing phase, the phosphates are removed from both three-carbon compounds and used to produce four ATP molecules.
INTERACTIVE LINK
Watch this video to learn about glycolysis.
Glycolysis can be divided into two phases: energy consuming (also called chemical priming) and energy yielding. The first phase is the energy-consuming phase, so it requires two ATP molecules to start the reaction for each molecule of glucose. However, the end of the reaction produces four ATPs, resulting in a net gain of two ATP energy molecules.
Glycolysis can be expressed as the following equation:
Glucose + 2ATP + 2NAD+ + 4ADP + 2P𝑖 → 2 Pyruvate + 4ATP + 2NADH + 2H+Glucose + 2ATP + 2NAD+ + 4ADP + 2Pi → 2 Pyruvate + 4ATP + 2NADH + 2H+This equation states that glucose, in combination with ATP (the energy source), NAD+ (a coenzyme that serves as an electron acceptor), and inorganic phosphate, breaks down into two pyruvate molecules, generating four ATP molecules—for a net yield of two ATP—and two energy-containing NADH coenzymes. The NADH that is produced in this process will be used later to produce ATP in the mitochondria. Importantly, by the end of this process, one glucose molecule generates two pyruvate molecules, two high-energy ATP molecules, and two electron-carrying NADH molecules.
The following discussions of glycolysis include the enzymes responsible for the reactions. When glucose enters a cell, the enzyme hexokinase (or glucokinase, in the liver) rapidly adds a phosphate to convert it into glucose-6-phosphate. A kinase is a type of enzyme that adds a phosphate molecule to a substrate (in this case, glucose, but it can be true of other molecules also). This conversion step requires one ATP and essentially traps the glucose in the cell, preventing it from passing back through the plasma membrane, thus allowing glycolysis to proceed. It also functions to maintain a concentration gradient with higher glucose levels in the blood than in the tissues. By establishing this concentration gradient, the glucose in the blood will be able to flow from an area of high concentration (the blood) into an area of low concentration (the tissues) to be either used or stored. Hexokinase is found in nearly every tissue in the body. Glucokinase, on the other hand, is expressed in tissues that are active when blood glucose levels are high, such as the liver. Hexokinase has a higher affinity for glucose than glucokinase and therefore is able to convert glucose at a faster rate than glucokinase. This is important when levels of glucose are very low in the body, as it allows glucose to travel preferentially to those tissues that require it more.
In the next step of the first phase of glycolysis, the enzyme glucose-6-phosphate isomerase converts glucose-6-phosphate into fructose-6-phosphate. Like glucose, fructose is also a six carbon-containing sugar. The enzyme phosphofructokinase-1 then adds one more phosphate to convert fructose-6-phosphate into fructose-1-6-bisphosphate, another six-carbon sugar, using another ATP molecule. Aldolase then breaks down this fructose-1-6-bisphosphate into two three-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The triosephosphate isomerase enzyme then converts dihydroxyacetone phosphate into a second glyceraldehyde-3-phosphate molecule. Therefore, by the end of this chemical-priming or energy-consuming phase, one glucose molecule is broken down into two glyceraldehyde-3-phosphate molecules.
The second phase of glycolysis, the energy-yielding phase, creates the energy that is the product of glycolysis. Glyceraldehyde-3-phosphate dehydrogenase converts each three-carbon glyceraldehyde-3-phosphate produced during the energy-consuming phase into 1,3-bisphosphoglycerate. This reaction releases an electron that is then picked up by NAD+ to create an NADH molecule. NADH is a high-energy molecule, like ATP, but unlike ATP, it is not used as energy currency by the cell. Because there are two glyceraldehyde-3-phosphate molecules, two NADH molecules are synthesized during this step. Each 1,3-bisphosphoglycerate is subsequently dephosphorylated (i.e., a phosphate is removed) by phosphoglycerate kinase into 3-phosphoglycerate. Each phosphate released in this reaction can convert one molecule of ADP into one high-energy ATP molecule, resulting in a gain of two ATP molecules.
The enzyme phosphoglycerate mutase then converts the 3-phosphoglycerate molecules into 2-phosphoglycerate. The enolase enzyme then acts upon the 2-phosphoglycerate molecules to convert them into phosphoenolpyruvate molecules. The last step of glycolysis involves the dephosphorylation of the two phosphoenolpyruvate molecules by pyruvate kinase to create two pyruvate molecules and two ATP molecules.
In summary, one glucose molecule breaks down into two pyruvate molecules, and creates two net ATP molecules and two NADH molecules by glycolysis. Therefore, glycolysis generates energy for the cell and creates pyruvate molecules that can be processed further through the aerobic Krebs cycle (also called the citric acid cycle or tricarboxylic acid cycle); converted into lactic acid or alcohol (in yeast) by fermentation; or used later for the synthesis of glucose through gluconeogenesis.
Anaerobic Respiration
When oxygen is limited or absent, pyruvate enters an anaerobic pathway. In these reactions, pyruvate can be converted into lactic acid. In addition to generating an additional ATP, this pathway serves to keep the pyruvate concentration low so glycolysis continues, and it oxidizes NADH into the NAD+ needed by glycolysis. In this reaction, lactic acid replaces oxygen as the final electron acceptor. Anaerobic respiration occurs in most cells of the body when oxygen is limited or mitochondria are absent or nonfunctional. For example, because erythrocytes (red blood cells) lack mitochondria, they must produce their ATP from anaerobic respiration. This is an effective pathway of ATP production for short periods of time, ranging from seconds to a few minutes. The lactic acid produced diffuses into the plasma and is carried to the liver, where it is converted back into pyruvate or glucose via the Cori cycle. Similarly, when a person exercises, muscles use ATP faster than oxygen can be delivered to them. They depend on glycolysis and lactic acid production for rapid ATP production.
Aerobic Respiration
In the presence of oxygen, pyruvate can enter the Krebs cycle where additional energy is extracted as electrons are transferred from the pyruvate to the receptors NAD+, GDP, and FAD, with carbon dioxide being a “waste product” (Figure 24.6). The NADH and FADH2 pass electrons on to the electron transport chain, which uses the transferred energy to produce ATP. As the terminal step in the electron transport chain, oxygen is the terminal electron acceptor and creates water inside the mitochondria.
Figure 24.6 Aerobic versus Anaerobic Respiration The process of anaerobic respiration converts glucose into two lactate molecules in the absence of oxygen or within erythrocytes that lack mitochondria. During aerobic respiration, glucose is oxidized into two pyruvate molecules.
Krebs Cycle/Citric Acid Cycle/Tricarboxylic Acid Cycle
The pyruvate molecules generated during glycolysis are transported across the mitochondrial membrane into the inner mitochondrial matrix, where they are metabolized by enzymes in a pathway called the Krebs cycle (Figure 24.7). The Krebs cycle is also commonly called the citric acid cycle or the tricarboxylic acid (TCA) cycle. During the Krebs cycle, high-energy molecules, including ATP, NADH, and FADH2, are created. NADH and FADH2 then pass electrons through the electron transport chain in the mitochondria to generate more ATP molecules.
Figure 24.7 Krebs Cycle During the Krebs cycle, each pyruvate that is generated by glycolysis is converted into a two-carbon acetyl CoA molecule. The acetyl CoA is systematically processed through the cycle and produces high-energy NADH, FADH2, and ATP molecules.
INTERACTIVE LINK
Watch this animation to observe the Krebs cycle.
The three-carbon pyruvate molecule generated during glycolysis moves from the cytoplasm into the mitochondrial matrix, where it is converted by the enzyme pyruvate dehydrogenase into a two-carbon acetyl coenzyme A (acetyl CoA) molecule. This reaction is an oxidative decarboxylation reaction. It converts the three-carbon pyruvate into a two-carbon acetyl CoA molecule, releasing carbon dioxide and transferring two electrons that combine with NAD+ to form NADH. Acetyl CoA enters the Krebs cycle by combining with a four-carbon molecule, oxaloacetate, to form the six-carbon molecule citrate, or citric acid, at the same time releasing the coenzyme A molecule.
The six-carbon citrate molecule is systematically converted to a five-carbon molecule and then a four-carbon molecule, ending with oxaloacetate, the beginning of the cycle. Along the way, each citrate molecule will produce one ATP, one FADH2, and three NADH. The FADH2 and NADH will enter the oxidative phosphorylation system located in the inner mitochondrial membrane. In addition, the Krebs cycle supplies the starting materials to process and break down proteins and fats.
To start the Krebs cycle, citrate synthase combines acetyl CoA and oxaloacetate to form a six-carbon citrate molecule; CoA is subsequently released and can combine with another pyruvate molecule to begin the cycle again. The aconitase enzyme converts citrate into isocitrate. In two successive steps of oxidative decarboxylation, two molecules of CO2 and two NADH molecules are produced when isocitrate dehydrogenase converts isocitrate into the five-carbon α-ketoglutarate, which is then catalyzed and converted into the four-carbon succinyl CoA by α-ketoglutarate dehydrogenase. The enzyme succinyl CoA dehydrogenase then converts succinyl CoA into succinate and forms the high-energy molecule GTP, which transfers its energy to ADP to produce ATP. Succinate dehydrogenase then converts succinate into fumarate, forming a molecule of FADH2. Fumarase then converts fumarate into malate, which malate dehydrogenase then converts back into oxaloacetate while reducing NAD+ to NADH. Oxaloacetate is then ready to combine with the next acetyl CoA to start the Krebs cycle again (see Figure 24.7). For each turn of the cycle, three NADH, one ATP (through GTP), and one FADH2 are created. Each carbon of pyruvate is converted into CO2, which is released as a byproduct of oxidative (aerobic) respiration.
Oxidative Phosphorylation and the Electron Transport Chain
The electron transport chain (ETC) uses the NADH and FADH2 produced by the Krebs cycle to generate ATP. Electrons from NADH and FADH2 are transferred through protein complexes embedded in the inner mitochondrial membrane by a series of enzymatic reactions. The electron transport chain consists of a series of four enzyme complexes (Complex I – Complex IV) and two coenzymes (ubiquinone and Cytochrome c), which act as electron carriers and proton pumps used to transfer H+ ions into the space between the inner and outer mitochondrial membranes (Figure 24.8). The ETC couples the transfer of electrons between a donor (like NADH) and an electron acceptor (like O2) with the transfer of protons (H+ ions) across the inner mitochondrial membrane, enabling the process of oxidative phosphorylation. In the presence of oxygen, energy is passed, stepwise, through the electron carriers to collect gradually the energy needed to attach a phosphate to ADP and produce ATP. The role of molecular oxygen, O2, is as the terminal electron acceptor for the ETC. This means that once the electrons have passed through the entire ETC, they must be passed to another, separate molecule. These electrons, O2, and H+ ions from the matrix combine to form new water molecules. This is the basis for your need to breathe in oxygen. Without oxygen, electron flow through the ETC ceases.
Figure 24.8 Electron Transport Chain The electron transport chain is a series of electron carriers and ion pumps that are used to pump H+ ions out of the inner mitochondrial matrix.
INTERACTIVE LINK
Watch this video to learn about the electron transport chain.
The electrons released from NADH and FADH2 are passed along the chain by each of the carriers, which are reduced when they receive the electron and oxidized when passing it on to the next carrier. Each of these reactions releases a small amount of energy, which is used to pump H+ ions across the inner membrane. The accumulation of these protons in the space between the membranes creates a proton gradient with respect to the mitochondrial matrix.
Also embedded in the inner mitochondrial membrane is an amazing protein pore complex called ATP synthase. Effectively, it is a turbine that is powered by the flow of H+ ions across the inner membrane down a gradient and into the mitochondrial matrix. As the H+ ions traverse the complex, the shaft of the complex rotates. This rotation enables other portions of ATP synthase to encourage ADP and Pi to create ATP. In accounting for the total number of ATP produced per glucose molecule through aerobic respiration, it is important to remember the following points:
- A net of two ATP are produced through glycolysis (four produced and two consumed during the energy-consuming stage). However, these two ATP are used for transporting the NADH produced during glycolysis from the cytoplasm into the mitochondria. Therefore, the net production of ATP during glycolysis is zero.
- In all phases after glycolysis, the number of ATP, NADH, and FADH2 produced must be multiplied by two to reflect how each glucose molecule produces two pyruvate molecules.
- In the ETC, about three ATP are produced for every oxidized NADH. However, only about two ATP are produced for every oxidized FADH2. The electrons from FADH2 produce less ATP, because they start at a lower point in the ETC (Complex II) compared to the electrons from NADH (Complex I) (see Figure 24.8).
Therefore, for every glucose molecule that enters aerobic respiration, a net total of 36 ATPs are produced (Figure 24.9).
Figure 24.9 Carbohydrate Metabolism Carbohydrate metabolism involves glycolysis, the Krebs cycle, and the electron transport chain.
Gluconeogenesis
Gluconeogenesis is the synthesis of new glucose molecules from pyruvate, lactate, glycerol, or the amino acids alanine or glutamine. This process takes place primarily in the liver during periods of low glucose, that is, under conditions of fasting, starvation, and low carbohydrate diets. So, the question can be raised as to why the body would create something it has just spent a fair amount of effort to break down? Certain key organs, including the brain, can use only glucose as an energy source; therefore, it is essential that the body maintain a minimum blood glucose concentration. When the blood glucose concentration falls below that certain point, new glucose is synthesized by the liver to raise the blood concentration to normal.
Gluconeogenesis is not simply the reverse of glycolysis. There are some important differences (Figure 24.10). Pyruvate is a common starting material for gluconeogenesis. First, the pyruvate is converted into oxaloacetate. Oxaloacetate then serves as a substrate for the enzyme phosphoenolpyruvate carboxykinase (PEPCK), which transforms oxaloacetate into phosphoenolpyruvate (PEP). From this step, gluconeogenesis is nearly the reverse of glycolysis. PEP is converted back into 2-phosphoglycerate, which is converted into 3-phosphoglycerate. Then, 3-phosphoglycerate is converted into 1,3 bisphosphoglycerate and then into glyceraldehyde-3-phosphate. Two molecules of glyceraldehyde-3-phosphate then combine to form fructose-1-6-bisphosphate, which is converted into fructose 6-phosphate and then into glucose-6-phosphate. Finally, a series of reactions generates glucose itself. In gluconeogenesis (as compared to glycolysis), the enzyme hexokinase is replaced by glucose-6-phosphatase, and the enzyme phosphofructokinase-1 is replaced by fructose-1,6-bisphosphatase. This helps the cell to regulate glycolysis and gluconeogenesis independently of each other.
As will be discussed as part of lipolysis, fats can be broken down into glycerol, which can be phosphorylated to form dihydroxyacetone phosphate or DHAP. DHAP can either enter the glycolytic pathway or be used by the liver as a substrate for gluconeogenesis.
Figure 24.10 Gluconeogenesis Gluconeogenesis is the synthesis of glucose from pyruvate, lactate, glycerol, alanine, or glutamate.
AGING AND THE...
Body’s Metabolic Rate
The human body’s metabolic rate decreases nearly 2 percent per decade after age 30. Changes in body composition, including reduced lean muscle mass, are mostly responsible for this decrease. The most dramatic loss of muscle mass, and consequential decline in metabolic rate, occurs between 50 and 70 years of age. Loss of muscle mass is the equivalent of reduced strength, which tends to inhibit seniors from engaging in sufficient physical activity. This results in a positive-feedback system where the reduced physical activity leads to even more muscle loss, further reducing metabolism.
There are several things that can be done to help prevent general declines in metabolism and to fight back against the cyclic nature of these declines. These include eating breakfast, eating small meals frequently, consuming plenty of lean protein, drinking water to remain hydrated, exercising (including strength training), and getting enough sleep. These measures can help keep energy levels from dropping and curb the urge for increased calorie consumption from excessive snacking. While these strategies are not guaranteed to maintain metabolism, they do help prevent muscle loss and may increase energy levels. Some experts also suggest avoiding sugar, which can lead to excess fat storage. Spicy foods and green tea might also be beneficial. Because stress activates cortisol release, and cortisol slows metabolism, avoiding stress, or at least practicing relaxation techniques, can also help.
Lipid Metabolism
- Explain how energy can be derived from fat
- Explain the purpose and process of ketogenesis
- Describe the process of ketone body oxidation
- Explain the purpose and the process of lipogenesis
Fats (or triglycerides) within the body are ingested as food or synthesized by adipocytes or hepatocytes from carbohydrate precursors (Figure 24.11). Lipid metabolism entails the oxidation of fatty acids to either generate energy or synthesize new lipids from smaller constituent molecules. Lipid metabolism is associated with carbohydrate metabolism, as products of glucose (such as acetyl CoA) can be converted into lipids.
Figure 24.11 Triglyceride Broken Down into a Monoglyceride A triglyceride molecule (a) breaks down into a monoglyceride (b).
Lipid metabolism begins in the intestine where ingested triglycerides are broken down into smaller chain fatty acids and subsequently into monoglyceride molecules (see Figure 24.11b) by pancreatic lipases, enzymes that break down fats after they are emulsified by bile salts. When food reaches the small intestine in the form of chyme, a digestive hormone called cholecystokinin (CCK) is released by intestinal cells in the intestinal mucosa. CCK stimulates the release of pancreatic lipase from the pancreas and stimulates the contraction of the gallbladder to release stored bile salts into the intestine. CCK also travels to the brain, where it can act as a hunger suppressant.
Together, the pancreatic lipases and bile salts break down triglycerides into free fatty acids. These fatty acids can be transported across the intestinal membrane. However, once they cross the membrane, they are recombined to again form triglyceride molecules. Within the intestinal cells, these triglycerides are packaged along with cholesterol molecules in phospholipid vesicles called chylomicrons (Figure 24.12). The chylomicrons enable fats and cholesterol to move within the aqueous environment of your lymphatic and circulatory systems. Chylomicrons leave the enterocytes by exocytosis and enter the lymphatic system via lacteals in the villi of the intestine. From the lymphatic system, the chylomicrons are transported to the circulatory system. Once in the circulation, they can either go to the liver or be stored in fat cells (adipocytes) that comprise adipose (fat) tissue found throughout the body.
Figure 24.12 Chylomicrons Chylomicrons contain triglycerides, cholesterol molecules, and other apolipoproteins (protein molecules). They function to carry these water-insoluble molecules from the intestine, through the lymphatic system, and into the bloodstream, which carries the lipids to adipose tissue for storage.
Lipolysis
To obtain energy from fat, triglycerides must first be broken down by hydrolysis into their two principal components, fatty acids and glycerol. This process, called lipolysis, takes place in the cytoplasm. The resulting fatty acids are oxidized by β-oxidation into acetyl CoA, which is used by the Krebs cycle. The glycerol that is released from triglycerides after lipolysis directly enters the glycolysis pathway as DHAP. Because one triglyceride molecule yields three fatty acid molecules with as much as 16 or more carbons in each one, fat molecules yield more energy than carbohydrates and are an important source of energy for the human body. Triglycerides yield more than twice the energy per unit mass when compared to carbohydrates and proteins. Therefore, when glucose levels are low, triglycerides can be converted into acetyl CoA molecules and used to generate ATP through aerobic respiration.
The breakdown of fatty acids, called fatty acid oxidation or beta (β)-oxidation, begins in the cytoplasm, where fatty acids are converted into fatty acyl CoA molecules. This fatty acyl CoA combines with carnitine to create a fatty acyl carnitine molecule, which helps to transport the fatty acid across the mitochondrial membrane. Once inside the mitochondrial matrix, the fatty acyl carnitine molecule is converted back into fatty acyl CoA and then into acetyl CoA (Figure 24.13). The newly formed acetyl CoA enters the Krebs cycle and is used to produce ATP in the same way as acetyl CoA derived from pyruvate.
Figure 24.13 Breakdown of Fatty Acids During fatty acid oxidation, triglycerides can be broken down into acetyl CoA molecules and used for energy when glucose levels are low.
Ketogenesis
If excessive acetyl CoA is created from the oxidation of fatty acids and the Krebs cycle is overloaded and cannot handle it, the acetyl CoA is diverted to create ketone bodies. These ketone bodies can serve as a fuel source if glucose levels are too low in the body. Ketones serve as fuel in times of prolonged starvation or when patients suffer from uncontrolled diabetes and cannot utilize most of the circulating glucose. In both cases, fat stores are liberated to generate energy through the Krebs cycle and will generate ketone bodies when too much acetyl CoA accumulates.
In this ketone synthesis reaction, excess acetyl CoA is converted into hydroxymethylglutaryl CoA (HMG CoA). HMG CoA is a precursor of cholesterol and is an intermediate that is subsequently converted into β-hydroxybutyrate, the primary ketone body in the blood (Figure 24.14).
Figure 24.14 Ketogenesis Excess acetyl CoA is diverted from the Krebs cycle to the ketogenesis pathway. This reaction occurs in the mitochondria of liver cells. The result is the production of β-hydroxybutyrate, the primary ketone body found in the blood.
Ketone Body Oxidation
Organs that have classically been thought to be dependent solely on glucose, such as the brain, can actually use ketones as an alternative energy source. This keeps the brain functioning when glucose is limited. When ketones are produced faster than they can be used, they can be broken down into CO2 and acetone. The acetone is removed by exhalation. One symptom of ketogenesis is that the patient’s breath smells sweet like alcohol. This effect provides one way of telling if a diabetic is properly controlling the disease. The carbon dioxide produced can acidify the blood, leading to diabetic ketoacidosis, a dangerous condition in diabetics.
Ketones oxidize to produce energy for the brain. beta (β)-hydroxybutyrate is oxidized to acetoacetate and NADH is released. An HS-CoA molecule is added to acetoacetate, forming acetoacetyl CoA. The carbon within the acetoacetyl CoA that is not bonded to the CoA then detaches, splitting the molecule in two. This carbon then attaches to another free HS-CoA, resulting in two acetyl CoA molecules. These two acetyl CoA molecules are then processed through the Krebs cycle to generate energy (Figure 24.15).
Figure 24.15 Ketone Oxidation When glucose is limited, ketone bodies can be oxidized to produce acetyl CoA to be used in the Krebs cycle to generate energy.
Lipogenesis
When glucose levels are plentiful, the excess acetyl CoA generated by glycolysis can be converted into fatty acids, triglycerides, cholesterol, steroids, and bile salts. This process, called lipogenesis, creates lipids (fat) from the acetyl CoA and takes place in the cytoplasm of adipocytes (fat cells) and hepatocytes (liver cells). When you eat more glucose or carbohydrates than your body needs, your system uses acetyl CoA to turn the excess into fat. Although there are several metabolic sources of acetyl CoA, it is most commonly derived from glycolysis. Acetyl CoA availability is significant, because it initiates lipogenesis. Lipogenesis begins with acetyl CoA and advances by the subsequent addition of two carbon atoms from another acetyl CoA; this process is repeated until fatty acids are the appropriate length. Because this is a bond-creating anabolic process, ATP is consumed. However, the creation of triglycerides and lipids is an efficient way of storing the energy available in carbohydrates. Triglycerides and lipids, high-energy molecules, are stored in adipose tissue until they are needed.
Although lipogenesis occurs in the cytoplasm, the necessary acetyl CoA is created in the mitochondria and cannot be transported across the mitochondrial membrane. To solve this problem, pyruvate is converted into both oxaloacetate and acetyl CoA. Two different enzymes are required for these conversions. Oxaloacetate forms via the action of pyruvate carboxylase, whereas the action of pyruvate dehydrogenase creates acetyl CoA. Oxaloacetate and acetyl CoA combine to form citrate, which can cross the mitochondrial membrane and enter the cytoplasm. In the cytoplasm, citrate is converted back into oxaloacetate and acetyl CoA. Oxaloacetate is converted into malate and then into pyruvate. Pyruvate crosses back across the mitochondrial membrane to wait for the next cycle of lipogenesis. The acetyl CoA is converted into malonyl CoA that is used to synthesize fatty acids. Figure 24.16 summarizes the pathways of lipid metabolism.
Figure 24.16 Lipid Metabolism Lipids may follow one of several pathways during metabolism. Glycerol and fatty acids follow different pathways.
Protein Metabolism
- Describe how the body digests proteins
- Explain how the urea cycle prevents toxic concentrations of nitrogen
- Differentiate between glucogenic and ketogenic amino acids
- Explain how protein can be used for energy
Much of the body is made of protein, and these proteins take on a myriad of forms. They represent cell signaling receptors, signaling molecules, structural members, enzymes, intracellular trafficking components, extracellular matrix scaffolds, ion pumps, ion channels, oxygen and CO2 transporters (hemoglobin). That is not even the complete list! There is protein in bones (collagen), muscles, and tendons; the hemoglobin that transports oxygen; and enzymes that catalyze all biochemical reactions. Protein is also used for growth and repair. Amid all these necessary functions, proteins also hold the potential to serve as a metabolic fuel source. Proteins are not stored for later use, so excess proteins must be converted into glucose or triglycerides, and used to supply energy or build energy reserves. Although the body can synthesize proteins from amino acids, food is an important source of those amino acids, especially because humans cannot synthesize all of the 20 amino acids used to build proteins.
The digestion of proteins begins in the stomach. When protein-rich foods enter the stomach, they are greeted by a mixture of the enzyme pepsin and hydrochloric acid (HCl; 0.5 percent). The latter produces an environmental pH of 1.5–3.5 that denatures proteins within food. Pepsin cuts proteins into smaller polypeptides and their constituent amino acids. When the food-gastric juice mixture (chyme) enters the small intestine, the pancreas releases sodium bicarbonate to neutralize the HCl. This helps to protect the lining of the intestine. The small intestine also releases digestive hormones, including secretin and CCK, which stimulate digestive processes to break down the proteins further. Secretin also stimulates the pancreas to release sodium bicarbonate. The pancreas releases most of the digestive enzymes, including the proteases trypsin, chymotrypsin, and elastase, which aid protein digestion. Together, all of these enzymes break complex proteins into smaller individual amino acids (Figure 24.17), which are then transported across the intestinal mucosa to be used to create new proteins, or to be converted into fats or acetyl CoA and used in the Krebs cycle.
Figure 24.17 Digestive Enzymes and Hormones Enzymes in the stomach and small intestine break down proteins into amino acids. HCl in the stomach aids in proteolysis, and hormones secreted by intestinal cells direct the digestive processes.
In order to avoid breaking down the proteins that make up the pancreas and small intestine, pancreatic enzymes are released as inactive proenzymes that are only activated in the small intestine. In the pancreas, vesicles store trypsin and chymotrypsin as trypsinogen and chymotrypsinogen. Once released into the small intestine, an enzyme found in the wall of the small intestine, called enterokinase, binds to trypsinogen and converts it into its active form, trypsin. Trypsin then binds to chymotrypsinogen to convert it into the active chymotrypsin. Trypsin and chymotrypsin break down large proteins into smaller peptides, a process called proteolysis. These smaller peptides are catabolized into their constituent amino acids, which are transported across the apical surface of the intestinal mucosa in a process that is mediated by sodium-amino acid transporters. These transporters bind sodium and then bind the amino acid to transport it across the membrane. At the basal surface of the mucosal cells, the sodium and amino acid are released. The sodium can be reused in the transporter, whereas the amino acids are transferred into the bloodstream to be transported to the liver and cells throughout the body for protein synthesis.
Freely available amino acids are used to create proteins. If amino acids exist in excess, the body has no capacity or mechanism for their storage; thus, they are converted into glucose or ketones, or they are decomposed. Amino acid decomposition results in hydrocarbons and nitrogenous waste. However, high concentrations of nitrogen are toxic. The urea cycle processes nitrogen and facilitates its excretion from the body.
Urea Cycle
The urea cycle is a set of biochemical reactions that produces urea from ammonium ions in order to prevent a toxic level of ammonium in the body. It occurs primarily in the liver and, to a lesser extent, in the kidney. Prior to the urea cycle, ammonium ions are produced from the breakdown of amino acids. In these reactions, an amine group, or ammonium ion, from the amino acid is exchanged with a keto group on another molecule. This transamination event creates a molecule that is necessary for the Krebs cycle and an ammonium ion that enters into the urea cycle to be eliminated.
In the urea cycle, ammonium is combined with CO2, resulting in urea and water. The urea is eliminated through the kidneys in the urine (Figure 24.18).
Figure 24.18 Urea Cycle Nitrogen is transaminated, creating ammonia and intermediates of the Krebs cycle. Ammonia is processed in the urea cycle to produce urea that is eliminated through the kidneys.
Amino acids can also be used as a source of energy, especially in times of starvation. Because the processing of amino acids results in the creation of metabolic intermediates, including pyruvate, acetyl CoA, acetoacyl CoA, oxaloacetate, and α-ketoglutarate, amino acids can serve as a source of energy production through the Krebs cycle (Figure 24.19). Figure 24.20summarizes the pathways of catabolism and anabolism for carbohydrates, lipids, and proteins.
Figure 24.19 Energy from Amino Acids Amino acids can be broken down into precursors for glycolysis or the Krebs cycle. Amino acids (in bold) can enter the cycle through more than one pathway.
Figure 24.20 Catabolic and Anabolic Pathways Nutrients follow a complex pathway from ingestion through anabolism and catabolism to energy production.
DISORDERS OF THE...
Metabolism: Pyruvate Dehydrogenase Complex Deficiency and Phenylketonuria
Pyruvate dehydrogenase complex deficiency (PDCD) and phenylketonuria (PKU) are genetic disorders. Pyruvate dehydrogenase is the enzyme that converts pyruvate into acetyl CoA, the molecule necessary to begin the Krebs cycle to produce ATP. With low levels of the pyruvate dehydrogenase complex (PDC), the rate of cycling through the Krebs cycle is dramatically reduced. This results in a decrease in the total amount of energy that is produced by the cells of the body. PDC deficiency results in a neurodegenerative disease that ranges in severity, depending on the levels of the PDC enzyme. It may cause developmental defects, muscle spasms, and death. Treatments can include diet modification, vitamin supplementation, and gene therapy; however, damage to the central nervous system usually cannot be reversed.
PKU affects about 1 in every 15,000 births in the United States. People afflicted with PKU lack sufficient activity of the enzyme phenylalanine hydroxylase and are therefore unable to break down phenylalanine into tyrosine adequately. Because of this, levels of phenylalanine rise to toxic levels in the body, which results in damage to the central nervous system and brain. Symptoms include delayed neurological development, hyperactivity, mental retardation, seizures, skin rash, tremors, and uncontrolled movements of the arms and legs. Pregnant women with PKU are at a high risk for exposing the fetus to too much phenylalanine, which can cross the placenta and affect fetal development. Babies exposed to excess phenylalanine in utero may present with heart defects, physical and/or mental retardation, and microcephaly. Every infant in the United States and Canada is tested at birth to determine whether PKU is present. The earlier a modified diet is begun, the less severe the symptoms will be. The person must closely follow a strict diet that is low in phenylalanine to avoid symptoms and damage. Phenylalanine is found in high concentrations in artificial sweeteners, including aspartame. Therefore, these sweeteners must be avoided. Some animal products and certain starches are also high in phenylalanine, and intake of these foods should be carefully monitored.
Metabolic States of the Body
- Describe what defines each of the three metabolic states
- Describe the processes that occur during the absorptive state of metabolism
- Describe the processes that occur during the postabsorptive state of metabolism
- Explain how the body processes glucose when the body is starved of fuel
You eat periodically throughout the day; however, your organs, especially the brain, need a continuous supply of glucose. How does the body meet this constant demand for energy? Your body processes the food you eat both to use immediately and, importantly, to store as energy for later demands. If there were no method in place to store excess energy, you would need to eat constantly in order to meet energy demands. Distinct mechanisms are in place to facilitate energy storage, and to make stored energy available during times of fasting and starvation.
The Absorptive State
The absorptive state, or the fed state, occurs after a meal when your body is digesting the food and absorbing the nutrients (anabolism exceeds catabolism). Digestion begins the moment you put food into your mouth, as the food is broken down into its constituent parts to be absorbed through the intestine. The digestion of carbohydrates begins in the mouth, whereas the digestion of proteins and fats begins in the stomach and small intestine. The constituent parts of these carbohydrates, fats, and proteins are transported across the intestinal wall and enter the bloodstream (sugars and amino acids) or the lymphatic system (fats). From the intestines, these systems transport them to the liver, adipose tissue, or muscle cells that will process and use, or store, the energy.
Depending on the amounts and types of nutrients ingested, the absorptive state can linger for up to 4 hours. The ingestion of food and the rise of glucose concentrations in the bloodstream stimulate pancreatic beta cells to release insulin into the bloodstream, where it initiates the absorption of blood glucose by liver hepatocytes, and by adipose and muscle cells. Once inside these cells, glucose is immediately converted into glucose-6-phosphate. By doing this, a concentration gradient is established where glucose levels are higher in the blood than in the cells. This allows for glucose to continue moving from the blood to the cells where it is needed. Insulin also stimulates the storage of glucose as glycogen in the liver and muscle cells where it can be used for later energy needs of the body. Insulin also promotes the synthesis of protein in muscle. As you will see, muscle protein can be catabolized and used as fuel in times of starvation.
If energy is exerted shortly after eating, the dietary fats and sugars that were just ingested will be processed and used immediately for energy. If not, the excess glucose is stored as glycogen in the liver and muscle cells, or as fat in adipose tissue; excess dietary fat is also stored as triglycerides in adipose tissues.
Figure 24.21 summarizes the metabolic processes occurring in the body during the absorptive state.
Figure 24.21 Absorptive State During the absorptive state, the body digests food and absorbs the nutrients.
The Postabsorptive State
The postabsorptive state, or the fasting state, occurs when the food has been digested, absorbed, and stored. You commonly fast overnight, but skipping meals during the day puts your body in the postabsorptive state as well. During this state, the body must rely initially on stored glycogen. Glucose levels in the blood begin to drop as it is absorbed and used by the cells. In response to the decrease in glucose, insulin levels also drop. Glycogen and triglyceride storage slows. However, due to the demands of the tissues and organs, blood glucose levels must be maintained in the normal range of 80–120 mg/dL. In response to a drop in blood glucose concentration, the hormone glucagon is released from the alpha cells of the pancreas. Glucagon acts upon the liver cells, where it inhibits the synthesis of glycogen and stimulates the breakdown of stored glycogen back into glucose. This glucose is released from the liver to be used by the peripheral tissues and the brain. As a result, blood glucose levels begin to rise. Gluconeogenesis will also begin in the liver to replace the glucose that has been used by the peripheral tissues.
After ingestion of food, fats and proteins are processed as described previously; however, the glucose processing changes a bit. The peripheral tissues preferentially absorb glucose. The liver, which normally absorbs and processes glucose, will not do so after a prolonged fast. The gluconeogenesis that has been ongoing in the liver will continue after fasting to replace the glycogen stores that were depleted in the liver. After these stores have been replenished, excess glucose that is absorbed by the liver will be converted into triglycerides and fatty acids for long-term storage. Figure 24.22 summarizes the metabolic processes occurring in the body during the postabsorptive state.
Figure 24.22 Postabsorptive State During the postabsorptive state, the body must rely on stored glycogen for energy.
Starvation
When the body is deprived of nourishment for an extended period of time, it goes into “survival mode.” The first priority for survival is to provide enough glucose or fuel for the brain. The second priority is the conservation of amino acids for proteins. Therefore, the body uses ketones to satisfy the energy needs of the brain and other glucose-dependent organs, and to maintain proteins in the cells (see Figure 24.2). Because glucose levels are very low during starvation, glycolysis will shut off in cells that can use alternative fuels. For example, muscles will switch from using glucose to fatty acids as fuel. As previously explained, fatty acids can be converted into acetyl CoA and processed through the Krebs cycle to make ATP. Pyruvate, lactate, and alanine from muscle cells are not converted into acetyl CoA and used in the Krebs cycle, but are exported to the liver to be used in the synthesis of glucose. As starvation continues, and more glucose is needed, glycerol from fatty acids can be liberated and used as a source for gluconeogenesis.
After several days of starvation, ketone bodies become the major source of fuel for the heart and other organs. As starvation continues, fatty acids and triglyceride stores are used to create ketones for the body. This prevents the continued breakdown of proteins that serve as carbon sources for gluconeogenesis. Once these stores are fully depleted, proteins from muscles are released and broken down for glucose synthesis. Overall survival is dependent on the amount of fat and protein stored in the body.
Energy and Heat Balance
- Describe how the body regulates temperature
- Explain the significance of the metabolic rate
The body tightly regulates the body temperature through a process called thermoregulation, in which the body can maintain its temperature within certain boundaries, even when the surrounding temperature is very different. The core temperature of the body remains steady at around 36.5–37.5 °C (or 97.7–99.5 °F). In the process of ATP production by cells throughout the body, approximately 60 percent of the energy produced is in the form of heat used to maintain body temperature. Thermoregulation is an example of negative feedback.
The hypothalamus in the brain is the master switch that works as a thermostat to regulate the body’s core temperature (Figure 24.23). If the temperature is too high, the hypothalamus can initiate several processes to lower it. These include increasing the circulation of the blood to the surface of the body to allow for the dissipation of heat through the skin and initiation of sweating to allow evaporation of water on the skin to cool its surface. Conversely, if the temperature falls below the set core temperature, the hypothalamus can initiate shivering to generate heat. The body uses more energy and generates more heat. In addition, thyroid hormone will stimulate more energy use and heat production by cells throughout the body. An environment is said to be thermoneutral when the body does not expend or release energy to maintain its core temperature. For a naked human, this is an ambient air temperature of around 84 °F. If the temperature is higher, for example, when wearing clothes, the body compensates with cooling mechanisms. The body loses heat through the mechanisms of heat exchange.
Figure 24.23 Hypothalamus Controls Thermoregulation The hypothalamus controls thermoregulation.
Mechanisms of Heat Exchange
When the environment is not thermoneutral, the body uses four mechanisms of heat exchange to maintain homeostasis: conduction, convection, radiation, and evaporation. Each of these mechanisms relies on the property of heat to flow from a higher concentration to a lower concentration; therefore, each of the mechanisms of heat exchange varies in rate according to the temperature and conditions of the environment.
Conduction is the transfer of heat by two objects that are in direct contact with one another. It occurs when the skin comes in contact with a cold or warm object. For example, when holding a glass of ice water, the heat from your skin will warm the glass and in turn melt the ice. Alternatively, on a cold day, you might warm up by wrapping your cold hands around a hot mug of coffee. Only about 3 percent of the body’s heat is lost through conduction.
Convection is the transfer of heat to the air surrounding the skin. The warmed air rises away from the body and is replaced by cooler air that is subsequently heated. Convection can also occur in water. When the water temperature is lower than the body’s temperature, the body loses heat by warming the water closest to the skin, which moves away to be replaced by cooler water. The convection currents created by the temperature changes continue to draw heat away from the body more quickly than the body can replace it, resulting in hyperthermia. About 15 percent of the body’s heat is lost through convection.
Radiation is the transfer of heat via infrared waves. This occurs between any two objects when their temperatures differ. A radiator can warm a room via radiant heat. On a sunny day, the radiation from the sun warms the skin. The same principle works from the body to the environment. About 60 percent of the heat lost by the body is lost through radiation.
Evaporation is the transfer of heat by the evaporation of water. Because it takes a great deal of energy for a water molecule to change from a liquid to a gas, evaporating water (in the form of sweat) takes with it a great deal of energy from the skin. However, the rate at which evaporation occurs depends on relative humidity—more sweat evaporates in lower humidity environments. Sweating is the primary means of cooling the body during exercise, whereas at rest, about 20 percent of the heat lost by the body occurs through evaporation.
Metabolic Rate
The metabolic rate is the amount of energy consumed minus the amount of energy expended by the body. The basal metabolic rate (BMR) describes the amount of daily energy expended by humans at rest, in a neutrally temperate environment, while in the postabsorptive state. It measures how much energy the body needs for normal, basic, daily activity. About 70 percent of all daily energy expenditure comes from the basic functions of the organs in the body. Another 20 percent comes from physical activity, and the remaining 10 percent is necessary for body thermoregulation or temperature control. This rate will be higher if a person is more active or has more lean body mass. As you age, the BMR generally decreases as the percentage of less lean muscle mass decreases.
Nutrition and Diet
- Explain how different foods can affect metabolism
- Describe a healthy diet, as recommended by the U.S. Department of Agriculture (USDA)
- List reasons why vitamins and minerals are critical to a healthy diet
The carbohydrates, lipids, and proteins in the foods you eat are used for energy to power molecular, cellular, and organ system activities. Importantly, the energy is stored primarily as fats. The quantity and quality of food that is ingested, digested, and absorbed affects the amount of fat that is stored as excess calories. Diet—both what you eat and how much you eat—has a dramatic impact on your health. Eating too much or too little food can lead to serious medical issues, including cardiovascular disease, cancer, anorexia, and diabetes, among others. Combine an unhealthy diet with unhealthy environmental conditions, such as smoking, and the potential medical complications increase significantly.
Food and Metabolism
The amount of energy that is needed or ingested per day is measured in calories. The nutritional Calorie (C) is the amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C. This is different from the calorie (c) used in the physical sciences, which is the amount of heat it takes to raise 1 g of water by 1 °C. When we refer to "calorie," we are referring to the nutritional Calorie.
On average, a person needs 1500 to 2000 calories per day to sustain (or carry out) daily activities. The total number of calories needed by one person is dependent on their body mass, age, height, gender, activity level, and the amount of exercise per day. If exercise is regular part of one’s day, more calories are required. As a rule, people underestimate the number of calories ingested and overestimate the amount they burn through exercise. This can lead to ingestion of too many calories per day. The accumulation of an extra 3500 calories adds one pound of weight. If an excess of 200 calories per day is ingested, one extra pound of body weight will be gained every 18 days. At that rate, an extra 20 pounds can be gained over the course of a year. Of course, this increase in calories could be offset by increased exercise. Running or jogging one mile burns almost 100 calories.
The type of food ingested also affects the body’s metabolic rate. Processing of carbohydrates requires less energy than processing of proteins. In fact, the breakdown of carbohydrates requires the least amount of energy, whereas the processing of proteins demands the most energy. In general, the amount of calories ingested and the amount of calories burned determines the overall weight. To lose weight, the number of calories burned per day must exceed the number ingested. Calories are in almost everything you ingest, so when considering calorie intake, beverages must also be considered.
To help provide guidelines regarding the types and quantities of food that should be eaten every day, the USDA has updated their food guidelines from MyPyramid to MyPlate. They have put the recommended elements of a healthy meal into the context of a place setting of food. MyPlate categorizes food into the standard six food groups: fruits, vegetables, grains, protein foods, dairy, and oils. The accompanying website gives clear recommendations regarding quantity and type of each food that you should consume each day, as well as identifying which foods belong in each category. The accompanying graphic (Figure 24.24) gives a clear visual with general recommendations for a healthy and balanced meal. The guidelines recommend to “Make half your plate fruits and vegetables.” The other half is grains and protein, with a slightly higher quantity of grains than protein. Dairy products are represented by a drink, but the quantity can be applied to other dairy products as well.
Figure 24.24 MyPlate The U.S. Department of Agriculture developed food guidelines called MyPlate to help demonstrate how to maintain a healthy lifestyle.
ChooseMyPlate.gov provides extensive online resources for planning a healthy diet and lifestyle, including offering weight management tips and recommendations for physical activity. It also includes the SuperTracker, a web-based application to help you analyze your own diet and physical activity.
EVERYDAY CONNECTION
Metabolism and Obesity
Obesity in the United States is epidemic. The rate of obesity has been steadily rising since the 1980s. In the 1990s, most states reported that less than 10 percent of their populations was obese, and the state with the highest rate reported that only 15 percent of their population was considered obese. By 2010, the U.S. Centers for Disease Control and Prevention reported that nearly 36 percent of adults over 20 years old were obese and an additional 33 percent were overweight, leaving only about 30 percent of the population at a healthy weight. These studies find the highest levels of obesity are concentrated in the southern states. They also find the level of childhood obesity is rising.
Obesity is defined by the body mass index (BMI), which is a measure of an individual’s weight-to-height ratio. The normal, or healthy, BMI range is between 18 and 24.9 kg/m2. Overweight is defined as a BMI of 25 to 29.9 kg/m2, and obesity is considered to be a BMI greater than 30 kg/m2. Obesity can arise from a number of factors, including overeating, poor diet, sedentary lifestyle, limited sleep, genetic factors, and even diseases or drugs. Severe obesity (morbid obesity) or long-term obesity can result in serious medical conditions, including coronary heart disease; type 2 diabetes; endometrial, breast, or colon cancer; hypertension (high blood pressure); dyslipidemia (high cholesterol or elevated triglycerides); stroke; liver disease; gall bladder disease; sleep apnea or respiratory diseases; osteoarthritis; and infertility. Research has shown that losing weight can help reduce or reverse the complications associated with these conditions.
Vitamins
Vitamins are organic compounds found in foods and are a necessary part of the biochemical reactions in the body. They are involved in a number of processes, including mineral and bone metabolism, and cell and tissue growth, and they act as cofactors for energy metabolism. The B vitamins play the largest role of any vitamins in metabolism (Table 24.3 and Table 24.4).
You get most of your vitamins through your diet, although some can be formed from the precursors absorbed during digestion. For example, the body synthesizes vitamin A from the β-carotene in orange vegetables like carrots and sweet potatoes. Vitamins are either fat-soluble or water-soluble. Fat-soluble vitamins A, D, E, and K, are absorbed through the intestinal tract with lipids in chylomicrons. Vitamin D is also synthesized in the skin through exposure to sunlight. Because they are carried in lipids, fat-soluble vitamins can accumulate in the lipids stored in the body. If excess vitamins are retained in the lipid stores in the body, hypervitaminosis can result.
Water-soluble vitamins, including the eight B vitamins and vitamin C, are absorbed with water in the gastrointestinal tract. These vitamins move easily through bodily fluids, which are water based, so they are not stored in the body. Excess water-soluble vitamins are excreted in the urine. Therefore, hypervitaminosis of water-soluble vitamins rarely occurs, except with an excess of vitamin supplements.
Fat-soluble Vitamins
| Vitamin and alternative name | Sources | Recommended daily allowance | Function | Problems associated with deficiency |
|---|---|---|---|---|
| A retinal or β-carotene | Yellow and orange fruits and vegetables, dark green leafy vegetables, eggs, milk, liver | 700–900 µg | Eye and bone development, immune function | Night blindness, epithelial changes, immune system deficiency |
| D cholecalciferol | Dairy products, egg yolks; also synthesized in the skin from exposure to sunlight | 5–15 µg | Aids in calcium absorption, promoting bone growth | Rickets, bone pain, muscle weakness, increased risk of death from cardiovascular disease, cognitive impairment, asthma in children, cancer |
| E tocopherols | Seeds, nuts, vegetable oils, avocados, wheat germ | 15 mg | Antioxidant | Anemia |
| K phylloquinone | Dark green leafy vegetables, broccoli, Brussels sprouts, cabbage | 90–120 µg | Blood clotting, bone health | Hemorrhagic disease of newborn in infants; uncommon in adults |
Table 24.3
Water-soluble Vitamins
| Vitamin and alternative name | Sources | Recommended daily allowance | Function | Problems associated with deficiency |
|---|---|---|---|---|
| B1 thiamine | Whole grains, enriched bread and cereals, milk, meat | 1.1–1.2 mg | Carbohydrate metabolism | Beriberi, Wernicke-Korsikoff syndrome |
| B2 riboflavin | Brewer’s yeast, almonds, milk, organ meats, legumes, enriched breads and cereals, broccoli, asparagus | 1.1–1.3 mg | Synthesis of FAD for metabolism, production of red blood cells | Fatigue, slowed growth, digestive problems, light sensitivity, epithelial problems like cracks in the corners of the mouth |
| B3 niacin | Meat, fish, poultry, enriched breads and cereals, peanuts | 14–16 mg | Synthesis of NAD, nerve function, cholesterol production | Cracked, scaly skin; dementia; diarrhea; also known as pellagra |
| B5 pantothenic acid | Meat, poultry, potatoes, oats, enriched breads and cereals, tomatoes | 5 mg | Synthesis of coenzyme A in fatty acid metabolism | Rare: symptoms may include fatigue, insomnia, depression, irritability |
| B6 pyridoxine | Potatoes, bananas, beans, seeds, nuts, meat, poultry, fish, eggs, dark green leafy vegetables, soy, organ meats | 1.3–1.5 mg | Sodium and potassium balance, red blood cell synthesis, protein metabolism | Confusion, irritability, depression, mouth and tongue sores |
| B7 biotin | Liver, fruits, meats | 30 µg | Cell growth, metabolism of fatty acids, production of blood cells | Rare in developed countries; symptoms include dermatitis, hair loss, loss of muscular coordination |
| B9 folic acid | Liver, legumes, dark green leafy vegetables, enriched breads and cereals, citrus fruits | 400 µg | DNA/protein synthesis | Poor growth, gingivitis, appetite loss, shortness of breath, gastrointestinal problems, mental deficits |
| B12 cyanocobalamin | Fish, meat, poultry, dairy products, eggs | 2.4 µg | Fatty acid oxidation, nerve cell function, red blood cell production | Pernicious anemia, leading to nerve cell damage |
| C ascorbic acid | Citrus fruits, red berries, peppers, tomatoes, broccoli, dark green leafy vegetables | 75–90 mg | Necessary to produce collagen for formation of connective tissue and teeth, and for wound healing | Dry hair, gingivitis, bleeding gums, dry and scaly skin, slow wound healing, easy bruising, compromised immunity; can lead to scurvy |
Table 24.4
Minerals
Minerals in food are inorganic compounds that work with other nutrients to ensure the body functions properly. Minerals cannot be made in the body; they come from the diet. The amount of minerals in the body is small—only 4 percent of the total body mass—and most of that consists of the minerals that the body requires in moderate quantities: potassium, sodium, calcium, phosphorus, magnesium, and chloride.
The most common minerals in the body are calcium and phosphorous, both of which are stored in the skeleton and necessary for the hardening of bones. Most minerals are ionized, and their ionic forms are used in physiological processes throughout the body. Sodium and chloride ions are electrolytes in the blood and extracellular tissues, and iron ions are critical to the formation of hemoglobin. There are additional trace minerals that are still important to the body’s functions, but their required quantities are much lower.
Like vitamins, minerals can be consumed in toxic quantities (although it is rare). A healthy diet includes most of the minerals your body requires, so supplements and processed foods can add potentially toxic levels of minerals. Table 24.5 and Table 24.6provide a summary of minerals and their function in the body.
Major Minerals
| Mineral | Sources | Recommended daily allowance | Function | Problems associated with deficiency |
|---|---|---|---|---|
| Potassium | Meats, some fish, fruits, vegetables, legumes, dairy products | 4700 mg | Nerve and muscle function; acts as an electrolyte | Hypokalemia: weakness, fatigue, muscle cramping, gastrointestinal problems, cardiac problems |
| Sodium | Table salt, milk, beets, celery, processed foods | 2300 mg | Blood pressure, blood volume, muscle and nerve function | Rare |
| Calcium | Dairy products, dark green leafy vegetables, blackstrap molasses, nuts, brewer’s yeast, some fish | 1000 mg | Bone structure and health; nerve and muscle functions, especially cardiac function | Slow growth, weak and brittle bones |
| Phosphorous | Meat, milk | 700 mg | Bone formation, metabolism, ATP production | Rare |
| Magnesium | Whole grains, nuts, leafy green vegetables | 310–420 mg | Enzyme activation, production of energy, regulation of other nutrients | Agitation, anxiety, sleep problems, nausea and vomiting, abnormal heart rhythms, low blood pressure, muscular problems |
| Chloride | Most foods, salt, vegetables, especially seaweed, tomatoes, lettuce, celery, olives | 2300 mg | Balance of body fluids, digestion | Loss of appetite, muscle cramps |
Table 24.5
Trace Minerals
| Mineral | Sources | Recommended daily allowance | Function | Problems associated with deficiency |
|---|---|---|---|---|
| Iron | Meat, poultry, fish, shellfish, legumes, nuts, seeds, whole grains, dark leafy green vegetables | 8–18 mg | Transport of oxygen in blood, production of ATP | Anemia, weakness, fatigue |
| Zinc | Meat, fish, poultry, cheese, shellfish | 8–11 mg | Immunity, reproduction, growth, blood clotting, insulin and thyroid function | Loss of appetite, poor growth, weight loss, skin problems, hair loss, vision problems, lack of taste or smell |
| Copper | Seafood, organ meats, nuts, legumes, chocolate, enriched breads and cereals, some fruits and vegetables | 900 µg | Red blood cell production, nerve and immune system function, collagen formation, acts as an antioxidant | Anemia, low body temperature, bone fractures, low white blood cell concentration, irregular heartbeat, thyroid problems |
| Iodine | Fish, shellfish, garlic, lima beans, sesame seeds, soybeans, dark leafy green vegetables | 150 µg | Thyroid function | Hypothyroidism: fatigue, weight gain, dry skin, temperature sensitivity |
| Sulfur | Eggs, meat, poultry, fish, legumes | None | Component of amino acids | Protein deficiency |
| Fluoride | Fluoridated water | 3–4 mg | Maintenance of bone and tooth structure | Increased cavities, weak bones and teeth |
| Manganese | Nuts, seeds, whole grains, legumes | 1.8–2.3 mg | Formation of connective tissue and bones, blood clotting, sex hormone development, metabolism, brain and nerve function | Infertility, bone malformation, weakness, seizures |
| Cobalt | Fish, nuts, leafy green vegetables, whole grains | None | Component of B12 | None |
| Selenium | Brewer’s yeast, wheat germ, liver, butter, fish, shellfish, whole grains | 55 µg | Antioxidant, thyroid function, immune system function | Muscle pain |
| Chromium | Whole grains, lean meats, cheese, black pepper, thyme, brewer’s yeast | 25–35 µg | Insulin function | High blood sugar, triglyceride, and cholesterol levels |
| Molybdenum | Legumes, whole grains, nuts | 45 µg | Cofactor for enzymes | Rare |
Table 24.6
Key Terms
- absorptive state
- also called the fed state; the metabolic state occurring during the first few hours after ingesting food in which the body is digesting food and absorbing the nutrients
- acetyl coenzyme A (acetyl CoA)
- starting molecule of the Krebs cycle
- anabolic hormones
- hormones that stimulate the synthesis of new, larger molecules
- anabolic reactions
- reactions that build smaller molecules into larger molecules
- ATP synthase
- protein pore complex that creates ATP
- basal metabolic rate (BMR)
- amount of energy expended by the body at rest
- beta (β)-hydroxybutyrate
- primary ketone body produced in the body
- beta (β)-oxidation
- fatty acid oxidation
- bile salts
- salts that are released from the liver in response to lipid ingestion and surround the insoluble triglycerides to aid in their conversion to monoglycerides and free fatty acids
- biosynthesis reactions
- reactions that create new molecules, also called anabolic reactions
- body mass index (BMI)
- relative amount of body weight compared to the overall height; a BMI ranging from 18–24.9 is considered normal weight, 25–29.9 is considered overweight, and greater than 30 is considered obese
- calorie
- amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C
- catabolic hormones
- hormones that stimulate the breakdown of larger molecules
- catabolic reactions
- reactions that break down larger molecules into their constituent parts
- cellular respiration
- production of ATP from glucose oxidation via glycolysis, the Krebs cycle, and oxidative phosphorylation
- cholecystokinin (CCK)
- hormone that stimulates the release of pancreatic lipase and the contraction of the gallbladder to release bile salts
- chylomicrons
- vesicles containing cholesterol and triglycerides that transport lipids out of the intestinal cells and into the lymphatic and circulatory systems
- chymotrypsin
- pancreatic enzyme that digests protein
- chymotrypsinogen
- proenzyme that is activated by trypsin into chymotrypsin
- citric acid cycle
- also called the Krebs cycle or the tricarboxylic acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
- conduction
- transfer of heat through physical contact
- convection
- transfer of heat between the skin and air or water
- elastase
- pancreatic enzyme that digests protein
- electron transport chain (ETC)
- ATP production pathway in which electrons are passed through a series of oxidation-reduction reactions that forms water and produces a proton gradient
- energy-consuming phase
- first phase of glycolysis, in which two molecules of ATP are necessary to start the reaction
- energy-yielding phase
- second phase of glycolysis, during which energy is produced
- enterokinase
- enzyme located in the wall of the small intestine that activates trypsin
- evaporation
- transfer of heat that occurs when water changes from a liquid to a gas
- FADH2
- high-energy molecule needed for glycolysis
- fatty acid oxidation
- breakdown of fatty acids into smaller chain fatty acids and acetyl CoA
- flavin adenine dinucleotide (FAD)
- coenzyme used to produce FADH2
- glucokinase
- cellular enzyme, found in the liver, which converts glucose into glucose-6-phosphate upon uptake into the cell
- gluconeogenesis
- process of glucose synthesis from pyruvate or other molecules
- glucose-6-phosphate
- phosphorylated glucose produced in the first step of glycolysis
- glycogen
- form that glucose assumes when it is stored
- glycolysis
- series of metabolic reactions that breaks down glucose into pyruvate and produces ATP
- hexokinase
- cellular enzyme, found in most tissues, that converts glucose into glucose-6-phosphate upon uptake into the cell
- hydroxymethylglutaryl CoA (HMG CoA)
- molecule created in the first step of the creation of ketone bodies from acetyl CoA
- inactive proenzymes
- forms in which proteases are stored and released to prevent the inappropriate digestion of the native proteins of the stomach, pancreas, and small intestine
- insulin
- hormone secreted by the pancreas that stimulates the uptake of glucose into the cells
- ketone bodies
- alternative source of energy when glucose is limited, created when too much acetyl CoA is created during fatty acid oxidation
- Krebs cycle
- also called the citric acid cycle or the tricarboxylic acid cycle, converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
- lipogenesis
- synthesis of lipids that occurs in the liver or adipose tissues
- lipolysis
- breakdown of triglycerides into glycerol and fatty acids
- metabolic rate
- amount of energy consumed minus the amount of energy expended by the body
- metabolism
- sum of all catabolic and anabolic reactions that take place in the body
- minerals
- inorganic compounds required by the body to ensure proper function of the body
- monoglyceride molecules
- lipid consisting of a single fatty acid chain attached to a glycerol backbone
- monosaccharide
- smallest, monomeric sugar molecule
- NADH
- high-energy molecule needed for glycolysis
- nicotinamide adenine dinucleotide (NAD)
- coenzyme used to produce NADH
- oxidation
- loss of an electron
- oxidation-reduction reaction
- (also, redox reaction) pair of reactions in which an electron is passed from one molecule to another, oxidizing one and reducing the other
- oxidative phosphorylation
- process that converts high-energy NADH and FADH2 into ATP
- pancreatic lipases
- enzymes released from the pancreas that digest lipids in the diet
- pepsin
- enzyme that begins to break down proteins in the stomach
- polysaccharides
- complex carbohydrates made up of many monosaccharides
- postabsorptive state
- also called the fasting state; the metabolic state occurring after digestion when food is no longer the body’s source of energy and it must rely on stored glycogen
- proteolysis
- process of breaking proteins into smaller peptides
- pyruvate
- three-carbon end product of glycolysis and starting material that is converted into acetyl CoA that enters the Krebs cycle
- radiation
- transfer of heat via infrared waves
- reduction
- gaining of an electron
- salivary amylase
- digestive enzyme that is found in the saliva and begins the digestion of carbohydrates in the mouth
- secretin
- hormone released in the small intestine to aid in digestion
- sodium bicarbonate
- anion released into the small intestine to neutralize the pH of the food from the stomach
- terminal electron acceptor
- oxygen, the recipient of the free hydrogen at the end of the electron transport chain
- thermoneutral
- external temperature at which the body does not expend any energy for thermoregulation, about 84 °F
- thermoregulation
- process of regulating the temperature of the body
- transamination
- transfer of an amine group from one molecule to another as a way to turn nitrogen waste into ammonia so that it can enter the urea cycle
- tricarboxylic acid cycle (TCA)
- also called the Krebs cycle or the citric acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules
- triglycerides
- lipids, or fats, consisting of three fatty acid chains attached to a glycerol backbone
- trypsin
- pancreatic enzyme that activates chymotrypsin and digests protein
- trypsinogen
- proenzyme form of trypsin
- urea cycle
- process that converts potentially toxic nitrogen waste into urea that can be eliminated through the kidneys
- vitamins
- organic compounds required by the body to perform biochemical reactions like metabolism and bone, cell, and tissue growth
Chapter Review
24.1 Overview of Metabolic Reactions
Metabolism is the sum of all catabolic (break down) and anabolic (synthesis) reactions in the body. The metabolic rate measures the amount of energy used to maintain life. An organism must ingest a sufficient amount of food to maintain its metabolic rate if the organism is to stay alive for very long.
Catabolic reactions break down larger molecules, such as carbohydrates, lipids, and proteins from ingested food, into their constituent smaller parts. They also include the breakdown of ATP, which releases the energy needed for metabolic processes in all cells throughout the body.
Anabolic reactions, or biosynthetic reactions, synthesize larger molecules from smaller constituent parts, using ATP as the energy source for these reactions. Anabolic reactions build bone, muscle mass, and new proteins, fats, and nucleic acids. Oxidation-reduction reactions transfer electrons across molecules by oxidizing one molecule and reducing another, and collecting the released energy to convert Pi and ADP into ATP. Errors in metabolism alter the processing of carbohydrates, lipids, proteins, and nucleic acids, and can result in a number of disease states.
24.2 Carbohydrate Metabolism
Metabolic enzymes catalyze catabolic reactions that break down carbohydrates contained in food. The energy released is used to power the cells and systems that make up your body. Excess or unutilized energy is stored as fat or glycogen for later use. Carbohydrate metabolism begins in the mouth, where the enzyme salivary amylase begins to break down complex sugars into monosaccharides. These can then be transported across the intestinal membrane into the bloodstream and then to body tissues. In the cells, glucose, a six-carbon sugar, is processed through a sequence of reactions into smaller sugars, and the energy stored inside the molecule is released. The first step of carbohydrate catabolism is glycolysis, which produces pyruvate, NADH, and ATP. Under anaerobic conditions, the pyruvate can be converted into lactate to keep glycolysis working. Under aerobic conditions, pyruvate enters the Krebs cycle, also called the citric acid cycle or tricarboxylic acid cycle. In addition to ATP, the Krebs cycle produces high-energy FADH2 and NADH molecules, which provide electrons to the oxidative phosphorylation process that generates more high-energy ATP molecules. For each molecule of glucose that is processed in glycolysis, a net of 36 ATPs can be created by aerobic respiration.
Under anaerobic conditions, ATP production is limited to those generated by glycolysis. While a total of four ATPs are produced by glycolysis, two are needed to begin glycolysis, so there is a net yield of two ATP molecules.
In conditions of low glucose, such as fasting, starvation, or low carbohydrate diets, glucose can be synthesized from lactate, pyruvate, glycerol, alanine, or glutamate. This process, called gluconeogenesis, is almost the reverse of glycolysis and serves to create glucose molecules for glucose-dependent organs, such as the brain, when glucose levels fall below normal.
24.3 Lipid Metabolism
Lipids are available to the body from three sources. They can be ingested in the diet, stored in the adipose tissue of the body, or synthesized in the liver. Fats ingested in the diet are digested in the small intestine. The triglycerides are broken down into monoglycerides and free fatty acids, then imported across the intestinal mucosa. Once across, the triglycerides are resynthesized and transported to the liver or adipose tissue. Fatty acids are oxidized through fatty acid or β-oxidation into two-carbon acetyl CoA molecules, which can then enter the Krebs cycle to generate ATP. If excess acetyl CoA is created and overloads the capacity of the Krebs cycle, the acetyl CoA can be used to synthesize ketone bodies. When glucose is limited, ketone bodies can be oxidized and used for fuel. Excess acetyl CoA generated from excess glucose or carbohydrate ingestion can be used for fatty acid synthesis or lipogenesis. Acetyl CoA is used to create lipids, triglycerides, steroid hormones, cholesterol, and bile salts. Lipolysis is the breakdown of triglycerides into glycerol and fatty acids, making them easier for the body to process.
24.4 Protein Metabolism
Digestion of proteins begins in the stomach, where HCl and pepsin begin the process of breaking down proteins into their constituent amino acids. As the chyme enters the small intestine, it mixes with bicarbonate and digestive enzymes. The bicarbonate neutralizes the acidic HCl, and the digestive enzymes break down the proteins into smaller peptides and amino acids. Digestive hormones secretin and CCK are released from the small intestine to aid in digestive processes, and digestive proenzymes are released from the pancreas (trypsinogen and chymotrypsinogen). Enterokinase, an enzyme located in the wall of the small intestine, activates trypsin, which in turn activates chymotrypsin. These enzymes liberate the individual amino acids that are then transported via sodium-amino acid transporters across the intestinal wall into the cell. The amino acids are then transported into the bloodstream for dispersal to the liver and cells throughout the body to be used to create new proteins. When in excess, the amino acids are processed and stored as glucose or ketones. The nitrogen waste that is liberated in this process is converted to urea in the urea acid cycle and eliminated in the urine. In times of starvation, amino acids can be used as an energy source and processed through the Krebs cycle.
24.5 Metabolic States of the Body
There are three main metabolic states of the body: absorptive (fed), postabsorptive (fasting), and starvation. During any given day, your metabolism switches between absorptive and postabsorptive states. Starvation states happen very rarely in generally well-nourished individuals. When the body is fed, glucose, fats, and proteins are absorbed across the intestinal membrane and enter the bloodstream and lymphatic system to be used immediately for fuel. Any excess is stored for later fasting stages. As blood glucose levels rise, the pancreas releases insulin to stimulate the uptake of glucose by hepatocytes in the liver, muscle cells/fibers, and adipocytes (fat cells), and to promote its conversion to glycogen. As the postabsorptive state begins, glucose levels drop, and there is a corresponding drop in insulin levels. Falling glucose levels trigger the pancreas to release glucagon to turn off glycogen synthesis in the liver and stimulate its breakdown into glucose. The glucose is released into the bloodstream to serve as a fuel source for cells throughout the body. If glycogen stores are depleted during fasting, alternative sources, including fatty acids and proteins, can be metabolized and used as fuel. When the body once again enters the absorptive state after fasting, fats and proteins are digested and used to replenish fat and protein stores, whereas glucose is processed and used first to replenish the glycogen stores in the peripheral tissues, then in the liver. If the fast is not broken and starvation begins to set in, during the initial days, glucose produced from gluconeogenesis is still used by the brain and organs. After a few days, however, ketone bodies are created from fats and serve as the preferential fuel source for the heart and other organs, so that the brain can still use glucose. Once these stores are depleted, proteins will be catabolized first from the organs with fast turnover, such as the intestinal lining. Muscle will be spared to prevent the wasting of muscle tissue; however, these proteins will be used if alternative stores are not available.
24.6 Energy and Heat Balance
Some of the energy from the food that is ingested is used to maintain the core temperature of the body. Most of the energy derived from the food is released as heat. The core temperature is kept around 36.5–37.5 °C (97.7–99.5 °F). This is tightly regulated by the hypothalamus in the brain, which senses changes in the core temperature and operates like a thermostat to increase sweating or shivering, or inducing other mechanisms to return the temperature to its normal range. The body can also gain or lose heat through mechanisms of heat exchange. Conduction transfers heat from one object to another through physical contact. Convection transfers heat to air or water. Radiation transfers heat via infrared radiation. Evaporation transfers heat as water changes state from a liquid to a gas.
24.7 Nutrition and Diet
Nutrition and diet affect your metabolism. More energy is required to break down fats and proteins than carbohydrates; however, all excess calories that are ingested will be stored as fat in the body. On average, a person requires 1500 to 2000 calories for normal daily activity, although routine exercise will increase that amount. If you ingest more than that, the remainder is stored for later use. Conversely, if you ingest less than that, the energy stores in your body will be depleted. Both the quantity and quality of the food you eat affect your metabolism and can affect your overall health. Eating too much or too little can result in serious medical conditions, including cardiovascular disease, cancer, and diabetes.
Vitamins and minerals are essential parts of the diet. They are needed for the proper function of metabolic pathways in the body. Vitamins are not stored in the body, so they must be obtained from the diet or synthesized from precursors available in the diet. Minerals are also obtained from the diet, but they are also stored, primarily in skeletal tissues.
Review Questions
A monosaccharide is formed from a polysaccharide in what kind of reaction?
- oxidation–reduction reaction
- anabolic reaction
- catabolic reaction
- biosynthetic reaction
If anabolic reactions exceed catabolic reactions, the result will be ________.
- weight loss
- weight gain
- metabolic rate change
- development of disease
When NAD becomes NADH, the coenzyme has been ________.
- reduced
- oxidized
- metabolized
- hydrolyzed
Anabolic reactions use energy by ________.
- turning ADP into ATP
- removing a phosphate group from ATP
- producing heat
- breaking down molecules into smaller parts
Glycolysis results in the production of two ________ molecules from a single molecule of glucose. In the absence of ________, the end product of glycolysis is ________.
- acetyl CoA, pyruvate, lactate
- ATP, carbon, pyruvate
- pyruvate, oxygen, lactate
- pyruvate, carbon, acetyl CoA
The Krebs cycle converts ________ through a cycle of reactions. In the process, ATP, ________, and ________ are produced.
- acetyl CoA; FAD, NAD
- acetyl CoA; FADH2; NADH
- pyruvate; NAD; FADH2
- pyruvate; oxygen; oxaloacetate
Which pathway produces the most ATP molecules?
- lactic acid fermentation
- the Krebs cycle
- the electron transport chain
- glycolysis
Aerobic cellular respiration results in the production of these two products.
- NADH and FADH2
- ATP and pyruvate
- ATP and glucose
- ATP and H2O
When NAD+ becomes NADH, the coenzyme has been ________.
- reduced
- oxidized
- metabolized
- hydrolyzed
Lipids in the diet can be ________.
- broken down into energy for the body
- stored as triglycerides for later use
- converted into acetyl CoA
- all of the above
The gallbladder provides ________ that aid(s) in transport of lipids across the intestinal membrane.
- lipases
- cholesterol
- proteins
- bile salts
Triglycerides are transported by chylomicrons because ________.
- they cannot move easily in the blood stream because they are fat based, while the blood is water based
- they are too small to move by themselves
- the chylomicrons contain enzymes they need for anabolism
- they cannot fit across the intestinal membrane
Which molecule produces the most ATP?
- carbohydrates
- FADH2
- triglycerides
- NADH
Which molecules can enter the Krebs cycle?
- chylomicrons
- acetyl CoA
- monoglycerides
- ketone bodies
Acetyl CoA can be converted to all of the following except ________.
- ketone bodies
- fatty acids
- polysaccharides
- triglycerides
Digestion of proteins begins in the ________ where ________ and ________ mix with food to break down protein into ________.
- stomach; amylase; HCl; amino acids
- mouth; pepsin; HCl; fatty acids
- stomach; lipase; HCl; amino acids
- stomach; pepsin; HCl; amino acids
Amino acids are needed to ________.
- build new proteins
- serve as fat stores
- supply energy for the cell
- create red blood cells
If an amino acid is not used to create new proteins, it can be ________.
- converted to acetyl CoA
- converted to glucose or ketones
- converted to nitrogen
- stored to be used later
During the absorptive state, glucose levels are ________, insulin levels are ________, and glucagon levels ________.
- high; low; stay the same
- low; low; stay the same
- high; high; are high
- high; high; are low
Starvation sets in after 3 to 4 days without food. Which hormones change in response to low glucose levels?
- glucagon and insulin
- ketones and glucagon
- insulin, glucose, and glucagon
- insulin and ketones
The postabsorptive state relies on stores of ________ in the ________.
- insulin; pancreas
- glucagon; pancreas
- glycogen; liver
- glucose; liver
The body’s temperature is controlled by the ________. This temperature is always kept between ________.
- pituitary; 36.5–37.5 °C
- hypothalamus; 97.7–99.5 °F
- hypothalamus; 36.5–37.5 °F
- pituitary; 97.7–99.5 °F
Fever increases the body temperature and can induce chills to help cool the temperature back down. What other mechanisms are in place to regulate the body temperature?
- shivering
- sweating
- erection of the hairs on the arms and legs
- all of the above
The heat you feel on your chair when you stand up was transferred from your skin via ________.
- conduction
- convection
- radiation
- evaporation
A crowded room warms up through the mechanism of ________.
- conduction
- convection
- radiation
- evaporation
A deficiency in vitamin A can result in ________.
- improper bone development
- scurvy
- improper eye development or sight
- all of the above
Rickets results in improper bone development in children that arises from the malabsorption of calcium and a deficiency in ________.
- vitamin D
- vitamin C
- vitamin B12
- niacin
Consuming which type of food will help the most with weight loss?
- fats
- vegetables
- lean meats
- fruits
Which of the following is stored in the body?
- thiamine
- phosphorous
- folic acid
- vitamin C
Critical Thinking Questions
Describe how metabolism can be altered.
31.Describe how Addison’s disease can be treated.
32.Explain how glucose is metabolized to yield ATP.
33.Insulin is released when food is ingested and stimulates the uptake of glucose into the cell. Discuss the mechanism cells employ to create a concentration gradient to ensure continual uptake of glucose from the bloodstream.
34.Discuss how carbohydrates can be stored as fat.
35.If a diabetic’s breath smells like alcohol, what could this mean?
36.Amino acids are not stored in the body. Describe how excess amino acids are processed in the cell.
37.Release of trypsin and chymotrypsin in their active form can result in the digestion of the pancreas or small intestine itself. What mechanism does the body employ to prevent its self-destruction?
38.In type II diabetes, insulin is produced but is nonfunctional. These patients are described as “starving in a sea of plenty,” because their blood glucose levels are high, but none of the glucose is transported into the cells. Describe how this leads to malnutrition.
39.Ketone bodies are used as an alternative source of fuel during starvation. Describe how ketones are synthesized.
40.How does vasoconstriction help increase the core temperature of the body?
41.How can the ingestion of food increase the body temperature?
42.Weight loss and weight gain are complex processes. What are some of the main factors that influence weight gain in people?
43.Some low-fat or non-fat foods contain a large amount of sugar to replace the fat content of the food. Discuss how this leads to increased fat in the body (and weight gain) even though the item is non-fat.
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oercommons
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2025-03-18T00:37:11.781098
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"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/58772/overview",
"title": "Anatomy and Physiology, Energy, Maintenance, and Environmental Exchange",
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https://oercommons.org/courseware/lesson/58773/overview
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The Urinary System
Introduction
Figure 25.1 Sewage Treatment Plant (credit: “eutrophication&hypoxia”/flickr.com)
CHAPTER OBJECTIVES
After studying this chapter, you will be able to:
- Describe the composition of urine
- Label structures of the urinary system
- Characterize the roles of each of the parts of the urinary system
- Illustrate the macroscopic and microscopic structures of the kidney
- Trace the flow of blood through the kidney
- Outline how blood is filtered in the kidney nephron
- Provide symptoms of kidney failure
- List some of the solutes filtered, secreted, and reabsorbed in different parts of the nephron
- Describe the role of a portal system in the kidney
- Explain how urine osmolarity is hormonally regulated
- Describe the regulation of major ions by the kidney
- Summarize the role of the kidneys in maintaining acid–base balance
The urinary system has roles you may be well aware of: cleansing the blood and ridding the body of wastes probably come to mind. However, there are additional, equally important functions played by the system. Take for example, regulation of pH, a function shared with the lungs and the buffers in the blood. Additionally, the regulation of blood pressure is a role shared with the heart and blood vessels. What about regulating the concentration of solutes in the blood? Did you know that the kidney is important in determining the concentration of red blood cells? Eighty-five percent of the erythropoietin (EPO) produced to stimulate red blood cell production is produced in the kidneys. The kidneys also perform the final synthesis step of vitamin D production, converting calcidiol to calcitriol, the active form of vitamin D.
If the kidneys fail, these functions are compromised or lost altogether, with devastating effects on homeostasis. The affected individual might experience weakness, lethargy, shortness of breath, anemia, widespread edema (swelling), metabolic acidosis, rising potassium levels, heart arrhythmias, and more. Each of these functions is vital to your well-being and survival. The urinary system, controlled by the nervous system, also stores urine until a convenient time for disposal and then provides the anatomical structures to transport this waste liquid to the outside of the body. Failure of nervous control or the anatomical structures leading to a loss of control of urination results in a condition called incontinence.
This chapter will help you to understand the anatomy of the urinary system and how it enables the physiologic functions critical to homeostasis. It is best to think of the kidney as a regulator of plasma makeup rather than simply a urine producer. As you read each section, ask yourself this question: “What happens if this does not work?” This question will help you to understand how the urinary system maintains homeostasis and affects all the other systems of the body and the quality of one’s life.
INTERACTIVE LINK
Watch this video from the Howard Hughes Medical Institute for an introduction to the urinary system.
Physical Characteristics of Urine
- Compare and contrast blood plasma, glomerular filtrate, and urine characteristics
- Describe the characteristics of a normal urine sample, including normal range of pH, osmolarity, and volume
The urinary system’s ability to filter the blood resides in about 2 to 3 million tufts of specialized capillaries—the glomeruli—distributed more or less equally between the two kidneys. Because the glomeruli filter the blood based mostly on particle size, large elements like blood cells, platelets, antibodies, and albumen are excluded. The glomerulus is the first part of the nephron, which then continues as a highly specialized tubular structure responsible for creating the final urine composition. All other solutes, such as ions, amino acids, vitamins, and wastes, are filtered to create a filtrate composition very similar to plasma. The glomeruli create about 200 liters (189 quarts) of this filtrate every day, yet you excrete less than two liters of waste you call urine.
Characteristics of the urine change, depending on influences such as water intake, exercise, environmental temperature, nutrient intake, and other factors (Table 25.1). Some of the characteristics such as color and odor are rough descriptors of your state of hydration. For example, if you exercise or work outside, and sweat a great deal, your urine will turn darker and produce a slight odor, even if you drink plenty of water. Athletes are often advised to consume water until their urine is clear. This is good advice; however, it takes time for the kidneys to process body fluids and store it in the bladder. Another way of looking at this is that the quality of the urine produced is an average over the time it takes to make that urine. Producing clear urine may take only a few minutes if you are drinking a lot of water or several hours if you are working outside and not drinking much.
Normal Urine Characteristics
| Characteristic | Normal values |
|---|---|
| Color | Pale yellow to deep amber |
| Odor | Odorless |
| Volume | 750–2000 mL/24 hour |
| pH | 4.5–8.0 |
| Specific gravity | 1.003–1.032 |
| Osmolarity | 40–1350 mOsmol/kg |
| Urobilinogen | 0.2–1.0 mg/100 mL |
| White blood cells | 0–2 HPF (per high-power field of microscope) |
| Leukocyte esterase | None |
| Protein | None or trace |
| Bilirubin | <0.3 mg/100 mL |
| Ketones | None |
| Nitrites | None |
| Blood | None |
| Glucose | None |
Table 25.1
Urinalysis (urine analysis) often provides clues to renal disease. Normally, only traces of protein are found in urine, and when higher amounts are found, damage to the glomeruli is the likely basis. Unusually large quantities of urine may point to diseases like diabetes mellitus or hypothalamic tumors that cause diabetes insipidus. The color of urine is determined mostly by the breakdown products of red blood cell destruction (Figure 25.2). The “heme” of hemoglobin is converted by the liver into water-soluble forms that can be excreted into the bile and indirectly into the urine. This yellow pigment is urochrome. Urine color may also be affected by certain foods like beets, berries, and fava beans. A kidney stone or a cancer of the urinary system may produce sufficient bleeding to manifest as pink or even bright red urine. Diseases of the liver or obstructions of bile drainage from the liver impart a dark “tea” or “cola” hue to the urine. Dehydration produces darker, concentrated urine that may also possess the slight odor of ammonia. Most of the ammonia produced from protein breakdown is converted into urea by the liver, so ammonia is rarely detected in fresh urine. The strong ammonia odor you may detect in bathrooms or alleys is due to the breakdown of urea into ammonia by bacteria in the environment. About one in five people detect a distinctive odor in their urine after consuming asparagus; other foods such as onions, garlic, and fish can impart their own aromas! These food-caused odors are harmless.
Figure 25.2 Urine Color
Urine volume varies considerably. The normal range is one to two liters per day (Table 25.2). The kidneys must produce a minimum urine volume of about 500 mL/day to rid the body of wastes. Output below this level may be caused by severe dehydration or renal disease and is termed oliguria. The virtual absence of urine production is termed anuria. Excessive urine production is polyuria, which may be due to diabetes mellitus or diabetes insipidus. In diabetes mellitus, blood glucose levels exceed the number of available sodium-glucose transporters in the kidney, and glucose appears in the urine. The osmotic nature of glucose attracts water, leading to its loss in the urine. In the case of diabetes insipidus, insufficient pituitary antidiuretic hormone (ADH) release or insufficient numbers of ADH receptors in the collecting ducts means that too few water channels are inserted into the cell membranes that line the collecting ducts of the kidney. Insufficient numbers of water channels (aquaporins) reduce water absorption, resulting in high volumes of very dilute urine.
Urine Volumes
| Volume condition | Volume | Causes |
|---|---|---|
| Normal | 1–2 L/day | |
| Polyuria | >2.5 L/day | Diabetes mellitus; diabetes insipidus; excess caffeine or alcohol; kidney disease; certain drugs, such as diuretics; sickle cell anemia; excessive water intake |
| Oliguria | 300–500 mL/day | Dehydration; blood loss; diarrhea; cardiogenic shock; kidney disease; enlarged prostate |
| Anuria | <50 mL/day | Kidney failure; obstruction, such as kidney stone or tumor; enlarged prostate |
Table 25.2
The pH (hydrogen ion concentration) of the urine can vary more than 1000-fold, from a normal low of 4.5 to a maximum of 8.0. Diet can influence pH; meats lower the pH, whereas citrus fruits, vegetables, and dairy products raise the pH. Chronically high or low pH can lead to disorders, such as the development of kidney stones or osteomalacia.
Specific gravity is a measure of the quantity of solutes per unit volume of a solution and is traditionally easier to measure than osmolarity. Urine will always have a specific gravity greater than pure water (water = 1.0) due to the presence of solutes. Laboratories can now measure urine osmolarity directly, which is a more accurate indicator of urinary solutes than specific gravity. Remember that osmolarity is the number of osmoles or milliosmoles per liter of fluid (mOsmol/L). Urine osmolarity ranges from a low of 50–100 mOsmol/L to as high as 1200 mOsmol/L H2O.
Cells are not normally found in the urine. The presence of leukocytes may indicate a urinary tract infection. Leukocyte esteraseis released by leukocytes; if detected in the urine, it can be taken as indirect evidence of a urinary tract infection (UTI).
Protein does not normally leave the glomerular capillaries, so only trace amounts of protein should be found in the urine, approximately 10 mg/100 mL in a random sample. If excessive protein is detected in the urine, it usually means that the glomerulus is damaged and is allowing protein to “leak” into the filtrate.
Ketones are byproducts of fat metabolism. Finding ketones in the urine suggests that the body is using fat as an energy source in preference to glucose. In diabetes mellitus when there is not enough insulin (type I diabetes mellitus) or because of insulin resistance (type II diabetes mellitus), there is plenty of glucose, but without the action of insulin, the cells cannot take it up, so it remains in the bloodstream. Instead, the cells are forced to use fat as their energy source, and fat consumed at such a level produces excessive ketones as byproducts. These excess ketones will appear in the urine. Ketones may also appear if there is a severe deficiency of proteins or carbohydrates in the diet.
Nitrates (NO3–) occur normally in the urine. Gram-negative bacteria metabolize nitrate into nitrite (NO2–), and its presence in the urine is indirect evidence of infection.
There should be no blood found in the urine. It may sometimes appear in urine samples as a result of menstrual contamination, but this is not an abnormal condition. Now that you understand what the normal characteristics of urine are, the next section will introduce you to how you store and dispose of this waste product and how you make it.
Gross Anatomy of Urine Transport
- Identify the ureters, urinary bladder, and urethra, as well as their location, structure, histology, and function
- Compare and contrast male and female urethras
- Describe the micturition reflex
- Describe voluntary and involuntary neural control of micturition
Rather than start with urine formation, this section will start with urine excretion. Urine is a fluid of variable composition that requires specialized structures to remove it from the body safely and efficiently. Blood is filtered, and the filtrate is transformed into urine at a relatively constant rate throughout the day. This processed liquid is stored until a convenient time for excretion. All structures involved in the transport and storage of the urine are large enough to be visible to the naked eye. This transport and storage system not only stores the waste, but it protects the tissues from damage due to the wide range of pH and osmolarity of the urine, prevents infection by foreign organisms, and for the male, provides reproductive functions.
Urethra
The urethra transports urine from the bladder to the outside of the body for disposal. The urethra is the only urologic organ that shows any significant anatomic difference between males and females; all other urine transport structures are identical (Figure 25.3).
Figure 25.3 Female and Male Urethras The urethra transports urine from the bladder to the outside of the body. This image shows (a) a female urethra and (b) a male urethra.
The urethra in both males and females begins inferior and central to the two ureteral openings forming the three points of a triangular-shaped area at the base of the bladder called the trigone (Greek tri- = “triangle” and the root of the word “trigonometry”). The urethra tracks posterior and inferior to the pubic symphysis (see Figure 25.3a). In both males and females, the proximal urethra is lined by transitional epithelium, whereas the terminal portion is a nonkeratinized, stratified squamous epithelium. In the male, pseudostratified columnar epithelium lines the urethra between these two cell types. Voiding is regulated by an involuntary autonomic nervous system-controlled internal urinary sphincter, consisting of smooth muscle and voluntary skeletal muscle that forms the external urinary sphincter below it.
Female Urethra
The external urethral orifice is embedded in the anterior vaginal wall inferior to the clitoris, superior to the vaginal opening (introitus), and medial to the labia minora. Its short length, about 4 cm, is less of a barrier to fecal bacteria than the longer male urethra and the best explanation for the greater incidence of UTI in women. Voluntary control of the external urethral sphincter is a function of the pudendal nerve. It arises in the sacral region of the spinal cord, traveling via the S2–S4 nerves of the sacral plexus.
Male Urethra
The male urethra passes through the prostate gland immediately inferior to the bladder before passing below the pubic symphysis (see Figure 25.3b). The length of the male urethra varies between men but averages 20 cm in length. It is divided into four regions: the preprostatic urethra, the prostatic urethra, the membranous urethra, and the spongy or penile urethra. The preprostatic urethra is very short and incorporated into the bladder wall. The prostatic urethra passes through the prostate gland. During sexual intercourse, it receives sperm via the ejaculatory ducts and secretions from the seminal vesicles. Paired Cowper’s glands (bulbourethral glands) produce and secrete mucus into the urethra to buffer urethral pH during sexual stimulation. The mucus neutralizes the usually acidic environment and lubricates the urethra, decreasing the resistance to ejaculation. The membranous urethra passes through the deep muscles of the perineum, where it is invested by the overlying urethral sphincters. The spongy urethra exits at the tip (external urethral orifice) of the penis after passing through the corpus spongiosum. Mucous glands are found along much of the length of the urethra and protect the urethra from extremes of urine pH. Innervation is the same in both males and females.
Bladder
The urinary bladder collects urine from both ureters (Figure 25.4). The bladder lies anterior to the uterus in females, posterior to the pubic bone and anterior to the rectum. During late pregnancy, its capacity is reduced due to compression by the enlarging uterus, resulting in increased frequency of urination. In males, the anatomy is similar, minus the uterus, and with the addition of the prostate inferior to the bladder. The bladder is partially retroperitoneal (outside the peritoneal cavity) with its peritoneal-covered “dome” projecting into the abdomen when the bladder is distended with urine.
Figure 25.4 Bladder (a) Anterior cross section of the bladder. (b) The detrusor muscle of the bladder (source: monkey tissue) LM × 448. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)
INTERACTIVE LINK
View the University of Michigan WebScope to explore the tissue sample in greater detail.
The bladder is a highly distensible organ comprised of irregular crisscrossing bands of smooth muscle collectively called the detrusor muscle. The interior surface is made of transitional cellular epithelium that is structurally suited for the large volume fluctuations of the bladder. When empty, it resembles columnar epithelia, but when stretched, it “transitions” (hence the name) to a squamous appearance (see Figure 25.4). Volumes in adults can range from nearly zero to 500–600 mL.
The detrusor muscle contracts with significant force in the young. The bladder’s strength diminishes with age, but voluntary contractions of abdominal skeletal muscles can increase intra-abdominal pressure to promote more forceful bladder emptying. Such voluntary contraction is also used in forceful defecation and childbirth.
Micturition Reflex
Micturition is a less-often used, but proper term for urination or voiding. It results from an interplay of involuntary and voluntary actions by the internal and external urethral sphincters. When bladder volume reaches about 150 mL, an urge to void is sensed but is easily overridden. Voluntary control of urination relies on consciously preventing relaxation of the external urethral sphincter to maintain urinary continence. As the bladder fills, subsequent urges become harder to ignore. Ultimately, voluntary constraint fails with resulting incontinence, which will occur as bladder volume approaches 300 to 400 mL.
Normal micturition is a result of stretch receptors in the bladder wall that transmit nerve impulses to the sacral region of the spinal cord to generate a spinal reflex. The resulting parasympathetic neural outflow causes contraction of the detrusor muscle and relaxation of the involuntary internal urethral sphincter. At the same time, the spinal cord inhibits somatic motor neurons, resulting in the relaxation of the skeletal muscle of the external urethral sphincter. The micturition reflex is active in infants but with maturity, children learn to override the reflex by asserting external sphincter control, thereby delaying voiding (potty training). This reflex may be preserved even in the face of spinal cord injury that results in paraplegia or quadriplegia. However, relaxation of the external sphincter may not be possible in all cases, and therefore, periodic catheterization may be necessary for bladder emptying.
Nerves involved in the control of urination include the hypogastric, pelvic, and pudendal (Figure 25.5). Voluntary micturition requires an intact spinal cord and functional pudendal nerve arising from the sacral micturition center. Since the external urinary sphincter is voluntary skeletal muscle, actions by cholinergic neurons maintain contraction (and thereby continence) during filling of the bladder. At the same time, sympathetic nervous activity via the hypogastric nerves suppresses contraction of the detrusor muscle. With further bladder stretch, afferent signals traveling over sacral pelvic nerves activate parasympathetic neurons. This activates efferent neurons to release acetylcholine at the neuromuscular junctions, producing detrusor contraction and bladder emptying.
Figure 25.5 Nerves Innervating the Urinary System
Ureters
The kidneys and ureters are completely retroperitoneal, and the bladder has a peritoneal covering only over the dome. As urine is formed, it drains into the calyces of the kidney, which merge to form the funnel-shaped renal pelvis in the hilum of each kidney. The renal pelvis narrows to become the ureter of each kidney. As urine passes through the ureter, it does not passively drain into the bladder but rather is propelled by waves of peristalsis. As the ureters enter the pelvis, they sweep laterally, hugging the pelvic walls. As they approach the bladder, they turn medially and pierce the bladder wall obliquely. This is important because it creates an one-way valve (a physiological sphincter rather than an anatomical sphincter) that allows urine into the bladder but prevents reflux of urine from the bladder back into the ureter. Children born lacking this oblique course of the ureter through the bladder wall are susceptible to “vesicoureteral reflux,” which dramatically increases their risk of serious UTI. Pregnancy also increases the likelihood of reflux and UTI.
The ureters are approximately 30 cm long. The inner mucosa is lined with transitional epithelium (Figure 25.6) and scattered goblet cells that secrete protective mucus. The muscular layer of the ureter consists of longitudinal and circular smooth muscles that create the peristaltic contractions to move the urine into the bladder without the aid of gravity. Finally, a loose adventitial layer composed of collagen and fat anchors the ureters between the parietal peritoneum and the posterior abdominal wall.
Figure 25.6 Ureter Peristaltic contractions help to move urine through the lumen with contributions from fluid pressure and gravity. LM × 128. (Micrograph provided by the Regents of the University of Michigan Medical School © 2012)
Gross Anatomy of the Kidney
- Describe the external structure of the kidney, including its location, support structures, and covering
- Identify the major internal divisions and structures of the kidney
- Identify the major blood vessels associated with the kidney and trace the path of blood through the kidney
- Compare and contrast the cortical and juxtamedullary nephrons
- Name structures found in the cortex and medulla
- Describe the physiological characteristics of the cortex and medulla
The kidneys lie on either side of the spine in the retroperitoneal space between the parietal peritoneum and the posterior abdominal wall, well protected by muscle, fat, and ribs. They are roughly the size of your fist, and the male kidney is typically a bit larger than the female kidney. The kidneys are well vascularized, receiving about 25 percent of the cardiac output at rest.
INTERACTIVE LINK
There have never been sufficient kidney donations to provide a kidney to each person needing one. Watch this videoto learn about the TED (Technology, Entertainment, Design) Conference held in March 2011. In this video, Dr. Anthony Atala discusses a cutting-edge technique in which a new kidney is “printed.” The successful utilization of this technology is still several years in the future, but imagine a time when you can print a replacement organ or tissue on demand.
External Anatomy
The left kidney is located at about the T12 to L3 vertebrae, whereas the right is lower due to slight displacement by the liver. Upper portions of the kidneys are somewhat protected by the eleventh and twelfth ribs (Figure 25.7). Each kidney weighs about 125–175 g in males and 115–155 g in females. They are about 11–14 cm in length, 6 cm wide, and 4 cm thick, and are directly covered by a fibrous capsule composed of dense, irregular connective tissue that helps to hold their shape and protect them. This capsule is covered by a shock-absorbing layer of adipose tissue called the renal fat pad, which in turn is encompassed by a tough renal fascia. The fascia and, to a lesser extent, the overlying peritoneum serve to firmly anchor the kidneys to the posterior abdominal wall in a retroperitoneal position.
Figure 25.7 Kidneys The kidneys are slightly protected by the ribs and are surrounded by fat for protection (not shown).
On the superior aspect of each kidney is the adrenal gland. The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption.
Internal Anatomy
A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the medulla(Figure 25.8). The renal columns are connective tissue extensions that radiate downward from the cortex through the medulla to separate the most characteristic features of the medulla, the renal pyramids and renal papillae. The papillae are bundles of collecting ducts that transport urine made by nephrons to the calyces of the kidney for excretion. The renal columns also serve to divide the kidney into 6–8 lobes and provide a supportive framework for vessels that enter and exit the cortex. The pyramids and renal columns taken together constitute the kidney lobes.
Figure 25.8 Left Kidney
Renal Hilum
The renal hilum is the entry and exit site for structures servicing the kidneys: vessels, nerves, lymphatics, and ureters. The medial-facing hila are tucked into the sweeping convex outline of the cortex. Emerging from the hilum is the renal pelvis, which is formed from the major and minor calyxes in the kidney. The smooth muscle in the renal pelvis funnels urine via peristalsis into the ureter. The renal arteries form directly from the descending aorta, whereas the renal veins return cleansed blood directly to the inferior vena cava. The artery, vein, and renal pelvis are arranged in an anterior-to-posterior order.
Nephrons and Vessels
The renal artery first divides into segmental arteries, followed by further branching to form interlobar arteries that pass through the renal columns to reach the cortex (Figure 25.9). The interlobar arteries, in turn, branch into arcuate arteries, cortical radiate arteries, and then into afferent arterioles. The afferent arterioles service about 1.3 million nephrons in each kidney.
Figure 25.9 Blood Flow in the Kidney
Nephrons are the “functional units” of the kidney; they cleanse the blood and balance the constituents of the circulation. The afferent arterioles form a tuft of high-pressure capillaries about 200 µm in diameter, the glomerulus. The rest of the nephron consists of a continuous sophisticated tubule whose proximal end surrounds the glomerulus in an intimate embrace—this is Bowman’s capsule. The glomerulus and Bowman’s capsule together form the renal corpuscle. As mentioned earlier, these glomerular capillaries filter the blood based on particle size. After passing through the renal corpuscle, the capillaries form a second arteriole, the efferent arteriole (Figure 25.10). These will next form a capillary network around the more distal portions of the nephron tubule, the peritubular capillaries and vasa recta, before returning to the venous system. As the glomerular filtrate progresses through the nephron, these capillary networks recover most of the solutes and water, and return them to the circulation. Since a capillary bed (the glomerulus) drains into a vessel that in turn forms a second capillary bed, the definition of a portal system is met. This is the only portal system in which an arteriole is found between the first and second capillary beds. (Portal systems also link the hypothalamus to the anterior pituitary, and the blood vessels of the digestive viscera to the liver.)
Figure 25.10 Blood Flow in the Nephron The two capillary beds are clearly shown in this figure. The efferent arteriole is the connecting vessel between the glomerulus and the peritubular capillaries and vasa recta.
INTERACTIVE LINK
Visit this link to view an interactive tutorial of the flow of blood through the kidney.
Cortex
In a dissected kidney, it is easy to identify the cortex; it appears lighter in color compared to the rest of the kidney. All of the renal corpuscles as well as both the proximal convoluted tubules (PCTs) and distal convoluted tubules are found here. Some nephrons have a short loop of Henle that does not dip beyond the cortex. These nephrons are called cortical nephrons. About 15 percent of nephrons have long loops of Henle that extend deep into the medulla and are called juxtamedullary nephrons.
Microscopic Anatomy of the Kidney
- Distinguish the histological differences between the renal cortex and medulla
- Describe the structure of the filtration membrane
- Identify the major structures and subdivisions of the renal corpuscles, renal tubules, and renal capillaries
- Discuss the function of the peritubular capillaries and vasa recta
- Identify the location of the juxtaglomerular apparatus and describe the cells that line it
- Describe the histology of the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting ducts
The renal structures that conduct the essential work of the kidney cannot be seen by the naked eye. Only a light or electron microscope can reveal these structures. Even then, serial sections and computer reconstruction are necessary to give us a comprehensive view of the functional anatomy of the nephron and its associated blood vessels.
Nephrons: The Functional Unit
Nephrons take a simple filtrate of the blood and modify it into urine. Many changes take place in the different parts of the nephron before urine is created for disposal. The term forming urine will be used hereafter to describe the filtrate as it is modified into true urine. The principle task of the nephron population is to balance the plasma to homeostatic set points and excrete potential toxins in the urine. They do this by accomplishing three principle functions—filtration, reabsorption, and secretion. They also have additional secondary functions that exert control in three areas: blood pressure (via production of renin), red blood cell production (via the hormone EPO), and calcium absorption (via conversion of calcidiol into calcitriol, the active form of vitamin D).
Renal Corpuscle
As discussed earlier, the renal corpuscle consists of a tuft of capillaries called the glomerulus that is largely surrounded by Bowman’s (glomerular) capsule. The glomerulus is a high-pressure capillary bed between afferent and efferent arterioles. Bowman’s capsule surrounds the glomerulus to form a lumen, and captures and directs this filtrate to the PCT. The outermost part of Bowman’s capsule, the parietal layer, is a simple squamous epithelium. It transitions onto the glomerular capillaries in an intimate embrace to form the visceral layer of the capsule. Here, the cells are not squamous, but uniquely shaped cells (podocytes) extending finger-like arms (pedicels) to cover the glomerular capillaries (Figure 25.11). These projections interdigitate to form filtration slits, leaving small gaps between the digits to form a sieve. As blood passes through the glomerulus, 10 to 20 percent of the plasma filters between these sieve-like fingers to be captured by Bowman’s capsule and funneled to the PCT. Where the fenestrae (windows) in the glomerular capillaries match the spaces between the podocyte “fingers,” the only thing separating the capillary lumen and the lumen of Bowman’s capsule is their shared basement membrane (Figure 25.12). These three features comprise what is known as the filtration membrane. This membrane permits very rapid movement of filtrate from capillary to capsule though pores that are only 70 nm in diameter.
Figure 25.11 Podocytes Podocytes interdigitate with structures called pedicels and filter substances in a way similar to fenestrations. In (a), the large cell body can be seen at the top right corner, with branches extending from the cell body. The smallest finger-like extensions are the pedicels. Pedicels on one podocyte always interdigitate with the pedicels of another podocyte. (b) This capillary has three podocytes wrapped around it.
Figure 25.12 Fenestrated Capillary Fenestrations allow many substances to diffuse from the blood based primarily on size.
The fenestrations prevent filtration of blood cells or large proteins, but allow most other constituents through. These substances cross readily if they are less than 4 nm in size and most pass freely up to 8 nm in size. An additional factor affecting the ability of substances to cross this barrier is their electric charge. The proteins associated with these pores are negatively charged, so they tend to repel negatively charged substances and allow positively charged substances to pass more readily. The basement membrane prevents filtration of medium-to-large proteins such as globulins. There are also mesangial cells in the filtration membrane that can contract to help regulate the rate of filtration of the glomerulus. Overall, filtration is regulated by fenestrations in capillary endothelial cells, podocytes with filtration slits, membrane charge, and the basement membrane between capillary cells. The result is the creation of a filtrate that does not contain cells or large proteins, and has a slight predominance of positively charged substances.
Lying just outside Bowman’s capsule and the glomerulus is the juxtaglomerular apparatus (JGA) (Figure 25.13). At the juncture where the afferent and efferent arterioles enter and leave Bowman’s capsule, the initial part of the distal convoluted tubule (DCT) comes into direct contact with the arterioles. The wall of the DCT at that point forms a part of the JGA known as the macula densa. This cluster of cuboidal epithelial cells monitors the fluid composition of fluid flowing through the DCT. In response to the concentration of Na+ in the fluid flowing past them, these cells release paracrine signals. They also have a single, nonmotile cilium that responds to the rate of fluid movement in the tubule. The paracrine signals released in response to changes in flow rate and Na+ concentration are adenosine triphosphate (ATP) and adenosine.
Figure 25.13 Juxtaglomerular Apparatus and Glomerulus (a) The JGA allows specialized cells to monitor the composition of the fluid in the DCT and adjust the glomerular filtration rate. (b) This micrograph shows the glomerulus and surrounding structures. LM × 1540. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)
A second cell type in this apparatus is the juxtaglomerular cell. This is a modified, smooth muscle cell lining the afferent arteriole that can contract or relax in response to ATP or adenosine released by the macula densa. Such contraction and relaxation regulate blood flow to the glomerulus. If the osmolarity of the filtrate is too high (hyperosmotic), the juxtaglomerular cells will contract, decreasing the glomerular filtration rate (GFR) so less plasma is filtered, leading to less urine formation and greater retention of fluid. This will ultimately decrease blood osmolarity toward the physiologic norm. If the osmolarity of the filtrate is too low, the juxtaglomerular cells will relax, increasing the GFR and enhancing the loss of water to the urine, causing blood osmolarity to rise. In other words, when osmolarity goes up, filtration and urine formation decrease and water is retained. When osmolarity goes down, filtration and urine formation increase and water is lost by way of the urine. The net result of these opposing actions is to keep the rate of filtration relatively constant. A second function of the macula densa cells is to regulate renin release from the juxtaglomerular cells of the afferent arteriole (Figure 25.14). Active renin is a protein comprised of 304 amino acids that cleaves several amino acids from angiotensinogen to produce angiotensin I. Angiotensin I is not biologically active until converted to angiotensin II by angiotensin-converting enzyme (ACE) from the lungs. Angiotensin II is a systemic vasoconstrictor that helps to regulate blood pressure by increasing it. Angiotensin II also stimulates the release of the steroid hormone aldosterone from the adrenal cortex. Aldosterone stimulates Na+ reabsorption by the kidney, which also results in water retention and increased blood pressure.
Figure 25.14 Conversion of Angiotensin I to Angiotensin II The enzyme renin converts the pro-enzyme angiotensin I; the lung-derived enzyme ACE converts angiotensin I into active angiotensin II.
Proximal Convoluted Tubule (PCT)
Filtered fluid collected by Bowman’s capsule enters into the PCT. It is called convoluted due to its tortuous path. Simple cuboidal cells form this tubule with prominent microvilli on the luminal surface, forming a brush border. These microvilli create a large surface area to maximize the absorption and secretion of solutes (Na+, Cl–, glucose, etc.), the most essential function of this portion of the nephron. These cells actively transport ions across their membranes, so they possess a high concentration of mitochondria in order to produce sufficient ATP.
Loop of Henle
The descending and ascending portions of the loop of Henle (sometimes referred to as the nephron loop) are, of course, just continuations of the same tubule. They run adjacent and parallel to each other after having made a hairpin turn at the deepest point of their descent. The descending loop of Henle consists of an initial short, thick portion and long, thin portion, whereas the ascending loop consists of an initial short, thin portion followed by a long, thick portion. The descending thick portion consists of simple cuboidal epithelium similar to that of the PCT. The descending and ascending thin portions consists of simple squamous epithelium. As you will see later, these are important differences, since different portions of the loop have different permeabilities for solutes and water. The ascending thick portion consists of simple cuboidal epithelium similar to the DCT.
Distal Convoluted Tubule (DCT)
The DCT, like the PCT, is very tortuous and formed by simple cuboidal epithelium, but it is shorter than the PCT. These cells are not as active as those in the PCT; thus, there are fewer microvilli on the apical surface. However, these cells must also pump ions against their concentration gradient, so you will find of large numbers of mitochondria, although fewer than in the PCT.
Collecting Ducts
The collecting ducts are continuous with the nephron but not technically part of it. In fact, each duct collects filtrate from several nephrons for final modification. Collecting ducts merge as they descend deeper in the medulla to form about 30 terminal ducts, which empty at a papilla. They are lined with simple squamous epithelium with receptors for ADH. When stimulated by ADH, these cells will insert aquaporin channel proteins into their membranes, which as their name suggests, allow water to pass from the duct lumen through the cells and into the interstitial spaces to be recovered by the vasa recta. This process allows for the recovery of large amounts of water from the filtrate back into the blood. In the absence of ADH, these channels are not inserted, resulting in the excretion of water in the form of dilute urine. Most, if not all, cells of the body contain aquaporin molecules, whose channels are so small that only water can pass. At least 10 types of aquaporins are known in humans, and six of those are found in the kidney. The function of all aquaporins is to allow the movement of water across the lipid-rich, hydrophobic cell membrane (Figure 25.15).
Figure 25.15 Aquaporin Water Channel Positive charges inside the channel prevent the leakage of electrolytes across the cell membrane, while allowing water to move due to osmosis.
Physiology of Urine Formation
- Describe the hydrostatic and colloid osmotic forces that favor and oppose filtration
- Describe glomerular filtration rate (GFR), state the average value of GFR, and explain how clearance rate can be used to measure GFR
- Predict specific factors that will increase or decrease GFR
- State the percent of the filtrate that is normally reabsorbed and explain why the process of reabsorption is so important
- Calculate daily urine production
- List common symptoms of kidney failure
Having reviewed the anatomy and microanatomy of the urinary system, now is the time to focus on the physiology. You will discover that different parts of the nephron utilize specific processes to produce urine: filtration, reabsorption, and secretion. You will learn how each of these processes works and where they occur along the nephron and collecting ducts. The physiologic goal is to modify the composition of the plasma and, in doing so, produce the waste product urine.
Failure of the renal anatomy and/or physiology can lead suddenly or gradually to renal failure. In this event, a number of symptoms, signs, or laboratory findings point to the diagnosis (Table 25.3).
Symptoms of Kidney Failure
| Weakness |
| Lethargy |
| Shortness of breath |
| Widespread edema |
| Anemia |
| Metabolic acidosis |
| Metabolic alkalosis |
| Heart arrhythmias |
| Uremia (high urea level in the blood) |
| Loss of appetite |
| Fatigue |
| Excessive urination |
| Oliguria (too little urine output) |
Table 25.3
Glomerular Filtration Rate (GFR)
The volume of filtrate formed by both kidneys per minute is termed the glomerular filtration rate (GFR). The heart pumps about 5 L blood per min under resting conditions. Approximately 20 percent or one liter enters the kidneys to be filtered. On average, this liter results in the production of about 125 mL/min filtrate produced in men (range of 90 to 140 mL/min) and 105 mL/min filtrate produced in women (range of 80 to 125 mL/min). This amount equates to a volume of about 180 L/day in men and 150 L/day in women. Ninety-nine percent of this filtrate is returned to the circulation by reabsorption so that only about 1–2 liters of urine are produced per day (Table 25.4).
Calculating Urine Formation per Day
| Flow per minute (mL) | Calculation | |
|---|---|---|
| Renal blood flow | 1050 | Cardiac output is about 5000 mL/minute, of which 21 percent flows through the kidney. 5000*0.21 = 1050 mL blood/min |
| Renal plasma flow | 578 | Renal plasma flow equals the blood flow per minute times the hematocrit. If a person has a hematocrit of 45, then the renal plasma flow is 55 percent. 1050*0.55 = 578 mL plasma/min |
| Glomerular filtration rate | 110 | The GFR is the amount of plasma entering Bowman’s capsule per minute. It is the renal plasma flow times the fraction that enters the renal capsule (19 percent). 578*0.19 = 110 mL filtrate/min |
| Urine | 1296 ml/day | The filtrate not recovered by the kidney is the urine that will be eliminated. It is the GFR times the fraction of the filtrate that is not reabsorbed (0.8 percent). 110*.008 = 0.9 mL urine /min Multiply urine/min times 60 minutes times 24 hours to get daily urine production. 0.9*60*24 = 1296 mL/day urine |
Table 25.4
GFR is influenced by the hydrostatic pressure and colloid osmotic pressure on either side of the capillary membrane of the glomerulus. Recall that filtration occurs as pressure forces fluid and solutes through a semipermeable barrier with the solute movement constrained by particle size. Hydrostatic pressure is the pressure produced by a fluid against a surface. If you have a fluid on both sides of a barrier, both fluids exert a pressure in opposing directions. Net fluid movement will be in the direction of the lower pressure. Osmosis is the movement of solvent (water) across a membrane that is impermeable to a solute in the solution. This creates a pressure, osmotic pressure, which will exist until the solute concentration is the same on both sides of a semipermeable membrane. As long as the concentration differs, water will move. Glomerular filtration occurs when glomerular hydrostatic pressure exceeds the luminal hydrostatic pressure of Bowman’s capsule. There is also an opposing force, the osmotic pressure, which is typically higher in the glomerular capillary.
To understand why this is so, look more closely at the microenvironment on either side of the filtration membrane. You will find osmotic pressure exerted by the solutes inside the lumen of the capillary as well as inside of Bowman’s capsule. Since the filtration membrane limits the size of particles crossing the membrane, the osmotic pressure inside the glomerular capillary is higher than the osmotic pressure in Bowman’s capsule. Recall that cells and the medium-to-large proteins cannot pass between the podocyte processes or through the fenestrations of the capillary endothelial cells. This means that red and white blood cells, platelets, albumins, and other proteins too large to pass through the filter remain in the capillary, creating an average colloid osmotic pressure of 30 mm Hg within the capillary. The absence of proteins in Bowman’s space (the lumen within Bowman’s capsule) results in an osmotic pressure near zero. Thus, the only pressure moving fluid across the capillary wall into the lumen of Bowman’s space is hydrostatic pressure. Hydrostatic (fluid) pressure is sufficient to push water through the membrane despite the osmotic pressure working against it. The sum of all of the influences, both osmotic and hydrostatic, results in a net filtration pressure (NFP) of about 10 mm Hg (Figure 25.16).
Figure 25.16 Net Filtration Pressure The NFP is the sum of osmotic and hydrostatic pressures.
A proper concentration of solutes in the blood is important in maintaining osmotic pressure both in the glomerulus and systemically. There are disorders in which too much protein passes through the filtration slits into the kidney filtrate. This excess protein in the filtrate leads to a deficiency of circulating plasma proteins. In turn, the presence of protein in the urine increases its osmolarity; this holds more water in the filtrate and results in an increase in urine volume. Because there is less circulating protein, principally albumin, the osmotic pressure of the blood falls. Less osmotic pressure pulling water into the capillaries tips the balance towards hydrostatic pressure, which tends to push it out of the capillaries. The net effect is that water is lost from the circulation to interstitial tissues and cells. This “plumps up” the tissues and cells, a condition termed systemic edema.
Net Filtration Pressure (NFP)
NFP determines filtration rates through the kidney. It is determined as follows:
NFP = Glomerular blood hydrostatic pressure (GBHP) – [capsular hydrostatic pressure (CHP) + blood colloid osmotic pressure (BCOP)] = 10 mm Hg
That is:
NFP = GBHP – [CHP + BCOP] = 10 mm Hg
Or:
NFP = 55 – [15 + 30] = 10 mm Hg
As you can see, there is a low net pressure across the filtration membrane. Intuitively, you should realize that minor changes in osmolarity of the blood or changes in capillary blood pressure result in major changes in the amount of filtrate formed at any given point in time. The kidney is able to cope with a wide range of blood pressures. In large part, this is due to the autoregulatory nature of smooth muscle. When you stretch it, it contracts. Thus, when blood pressure goes up, smooth muscle in the afferent capillaries contracts to limit any increase in blood flow and filtration rate. When blood pressure drops, the same capillaries relax to maintain blood flow and filtration rate. The net result is a relatively steady flow of blood into the glomerulus and a relatively steady filtration rate in spite of significant systemic blood pressure changes. Mean arterial blood pressure is calculated by adding 1/3 of the difference between the systolic and diastolic pressures to the diastolic pressure. Therefore, if the blood pressure is 110/80, the difference between systolic and diastolic pressure is 30. One third of this is 10, and when you add this to the diastolic pressure of 80, you arrive at a calculated mean arterial pressure of 90 mm Hg. Therefore, if you use mean arterial pressure for the GBHP in the formula for calculating NFP, you can determine that as long as mean arterial pressure is above approximately 60 mm Hg, the pressure will be adequate to maintain glomerular filtration. Blood pressures below this level will impair renal function and cause systemic disorders that are severe enough to threaten survival. This condition is called shock.
Determination of the GFR is one of the tools used to assess the kidney’s excretory function. This is more than just an academic exercise. Since many drugs are excreted in the urine, a decline in renal function can lead to toxic accumulations. Additionally, administration of appropriate drug dosages for those drugs primarily excreted by the kidney requires an accurate assessment of GFR. GFR can be estimated closely by intravenous administration of inulin. Inulin is a plant polysaccharide that is neither reabsorbed nor secreted by the kidney. Its appearance in the urine is directly proportional to the rate at which it is filtered by the renal corpuscle. However, since measuring inulin clearance is cumbersome in the clinical setting, most often, the GFR is estimated by measuring naturally occurring creatinine, a protein-derived molecule produced by muscle metabolism that is not reabsorbed and only slightly secreted by the nephron.
Tubular Reabsorption
- List specific transport mechanisms occurring in different parts of the nephron, including active transport, osmosis, facilitated diffusion, and passive electrochemical gradients
- List the different membrane proteins of the nephron, including channels, transporters, and ATPase pumps
- Compare and contrast passive and active tubular reabsorption
- Explain why the differential permeability or impermeability of specific sections of the nephron tubules is necessary for urine formation
- Describe how and where water, organic compounds, and ions are reabsorbed in the nephron
- Explain the role of the loop of Henle, the vasa recta, and the countercurrent multiplication mechanisms in the concentration of urine
- List the locations in the nephron where tubular secretion occurs
With up to 180 liters per day passing through the nephrons of the kidney, it is quite obvious that most of that fluid and its contents must be reabsorbed. That recovery occurs in the PCT, loop of Henle, DCT, and the collecting ducts (Table 25.5 and Figure 25.17). Various portions of the nephron differ in their capacity to reabsorb water and specific solutes. While much of the reabsorption and secretion occur passively based on concentration gradients, the amount of water that is reabsorbed or lost is tightly regulated. This control is exerted directly by ADH and aldosterone, and indirectly by renin. Most water is recovered in the PCT, loop of Henle, and DCT. About 10 percent (about 18 L) reaches the collecting ducts. The collecting ducts, under the influence of ADH, can recover almost all of the water passing through them, in cases of dehydration, or almost none of the water, in cases of over-hydration.
Figure 25.17 Locations of Secretion and Reabsorption in the Nephron
Substances Secreted or Reabsorbed in the Nephron and Their Locations
| Substance | PCT | Loop of Henle | DCT | Collecting ducts |
|---|---|---|---|---|
| Glucose | Almost 100 percent reabsorbed; secondary active transport with Na+ | |||
| Oligopeptides, proteins, amino acids | Almost 100 percent reabsorbed; symport with Na+ | |||
| Vitamins | Reabsorbed | |||
| Lactate | Reabsorbed | |||
| Creatinine | Secreted | |||
| Urea | 50 percent reabsorbed by diffusion; also secreted | Secretion, diffusion in descending limb | Reabsorption in medullary collecting ducts; diffusion | |
| Sodium | 65 percent actively reabsorbed | 25 percent reabsorbed in thick ascending limb; active transport | 5 percent reabsorbed; active | 5 percent reabsorbed, stimulated by aldosterone; active |
| Chloride | Reabsorbed, symport with Na+, diffusion | Reabsorbed in thin and thick ascending limb; diffusion in ascending limb | Reabsorbed; diffusion | Reabsorbed; symport |
| Water | 67 percent reabsorbed osmotically with solutes | 15 percent reabsorbed in descending limb; osmosis | 8 percent reabsorbed if ADH; osmosis | Variable amounts reabsorbed, controlled by ADH, osmosis |
| Bicarbonate | 80–90 percent symport reabsorption with Na+ | Reabsorbed, symport with Na+ and antiport with Cl–; in ascending limb | Reabsorbed antiport with Cl– | |
| H+ | Secreted; diffusion | Secreted; active | Secreted; active | |
| NH4+ | Secreted; diffusion | Secreted; diffusion | Secreted; diffusion | |
| HCO3– | Reabsorbed; diffusion | Reabsorbed; diffusion in ascending limb | Reabsorbed; diffusion | Reabsorbed; antiport with Na+ |
| Some drugs | Secreted | Secreted; active | Secreted; active | |
| Potassium | 65 percent reabsorbed; diffusion | 20 percent reabsorbed in thick ascending limb; symport | Secreted; active | Secretion controlled by aldosterone; active |
| Calcium | Reabsorbed; diffusion | Reabsorbed in thick ascending limb; diffusion | Reabsorbed if parathyroid hormone present; active | |
| Magnesium | Reabsorbed; diffusion | Reabsorbed in thick ascending limb; diffusion | Reabsorbed | |
| Phosphate | 85 percent reabsorbed, inhibited by parathyroid hormone, diffusion | Reabsorbed; diffusion |
Table 25.5
Mechanisms of Recovery
Mechanisms by which substances move across membranes for reabsorption or secretion include active transport, diffusion, facilitated diffusion, secondary active transport, and osmosis. These were discussed in an earlier chapter, and you may wish to review them.
Active transport utilizes energy, usually the energy found in a phosphate bond of ATP, to move a substance across a membrane from a low to a high concentration. It is very specific and must have an appropriately shaped receptor for the substance to be transported. An example would be the active transport of Na+ out of a cell and K+ into a cell by the Na+/K+ pump. Both ions are moved in opposite directions from a lower to a higher concentration.
Simple diffusion moves a substance from a higher to a lower concentration down its concentration gradient. It requires no energy and only needs to be soluble.
Facilitated diffusion is similar to diffusion in that it moves a substance down its concentration gradient. The difference is that it requires specific membrane receptors or channel proteins for movement. The movement of glucose and, in certain situations, Na+ ions, is an example of facilitated diffusion. In some cases of mediated transport, two different substances share the same channel protein port; these mechanisms are described by the terms symport and antiport.
Symport mechanisms move two or more substances in the same direction at the same time, whereas antiport mechanisms move two or more substances in opposite directions across the cell membrane. Both mechanisms may utilize concentration gradients maintained by ATP pumps. As described previously, when active transport powers the transport of another substance in this way, it is called “secondary active transport.” Glucose reabsorption in the kidneys is by secondary active transport. Na+/K+ ATPases on the basal membrane of a tubular cell constantly pump Na+ out of the cell, maintaining a strong electrochemical gradient for Na+ to move into the cell from the tubular lumen. On the luminal (apical) surface, a Na+/glucose symport protein assists both Na+ and glucose movement into the cell. The cotransporter moves glucose into the cell against its concentration gradient as Na+ moves down the electrochemical gradient created by the basal membranes Na+/K+ ATPases. The glucose molecule then diffuses across the basal membrane by facilitated diffusion into the interstitial space and from there into peritubular capillaries.
Most of the Ca++, Na+, glucose, and amino acids must be reabsorbed by the nephron to maintain homeostatic plasma concentrations. Other substances, such as urea, K+, ammonia (NH3), creatinine, and some drugs are secreted into the filtrate as waste products. Acid–base balance is maintained through actions of the lungs and kidneys: The lungs rid the body of H+, whereas the kidneys secrete or reabsorb H+ and HCO3– (Table 25.6). In the case of urea, about 50 percent is passively reabsorbed by the PCT. More is recovered by in the collecting ducts as needed. ADH induces the insertion of urea transporters and aquaporin channel proteins.
Substances Filtered and Reabsorbed by the Kidney per 24 Hours
| Substance | Amount filtered (grams) | Amount reabsorbed (grams) | Amount in urine (grams) |
|---|---|---|---|
| Water | 180 L | 179 L | 1 L |
| Proteins | 10–20 | 10–20 | 0 |
| Chlorine | 630 | 625 | 5 |
| Sodium | 540 | 537 | 3 |
| Bicarbonate | 300 | 299.7 | 0.3 |
| Glucose | 180 | 180 | 0 |
| Urea | 53 | 28 | 25 |
| Potassium | 28 | 24 | 4 |
| Uric acid | 8.5 | 7.7 | 0.8 |
| Creatinine | 1.4 | 0 | 1.4 |
Table 25.6
Reabsorption and Secretion in the PCT
The renal corpuscle filters the blood to create a filtrate that differs from blood mainly in the absence of cells and large proteins. From this point to the ends of the collecting ducts, the filtrate or forming urine is undergoing modification through secretion and reabsorption before true urine is produced. The first point at which the forming urine is modified is in the PCT. Here, some substances are reabsorbed, whereas others are secreted. Note the use of the term “reabsorbed.” All of these substances were “absorbed” in the digestive tract—99 percent of the water and most of the solutes filtered by the nephron must be reabsorbed. Water and substances that are reabsorbed are returned to the circulation by the peritubular and vasa recta capillaries. It is important to understand the difference between the glomerulus and the peritubular and vasa recta capillaries. The glomerulus has a relatively high pressure inside its capillaries and can sustain this by dilating the afferent arteriole while constricting the efferent arteriole. This assures adequate filtration pressure even as the systemic blood pressure varies. Movement of water into the peritubular capillaries and vasa recta will be influenced primarily by osmolarity and concentration gradients. Sodium is actively pumped out of the PCT into the interstitial spaces between cells and diffuses down its concentration gradient into the peritubular capillary. As it does so, water will follow passively to maintain an isotonic fluid environment inside the capillary. This is called obligatory water reabsorption, because water is “obliged” to follow the Na+ (Figure 25.18).
Figure 25.18 Substances Reabsorbed and Secreted by the PCT
More substances move across the membranes of the PCT than any other portion of the nephron. Many of these substances (amino acids and glucose) use symport mechanisms for transport along with Na+. Antiport, active transport, diffusion, and facilitated diffusion are additional mechanisms by which substances are moved from one side of a membrane to the other. Recall that cells have two surfaces: apical and basal. The apical surface is the one facing the lumen or open space of a cavity or tube, in this case, the inside of the PCT. The basal surface of the cell faces the connective tissue base to which the cell attaches (basement membrane) or the cell membrane closer to the basement membrane if there is a stratified layer of cells. In the PCT, there is a single layer of simple cuboidal endothelial cells against the basement membrane. The numbers and particular types of pumps and channels vary between the apical and basilar surfaces. A few of the substances that are transported with Na+(symport mechanism) on the apical membrane include Cl–, Ca++, amino acids, glucose, and PO3−4PO43−+ using ATP on the basal membrane. Most of the substances transported by a symport mechanism on the apical membrane are transported by facilitated diffusion on the basal membrane. At least three ions, K+, Ca++, and Mg++, diffuse laterally between adjacent cell membranes (transcellular).
About 67 percent of the water, Na+, and K+ entering the nephron is reabsorbed in the PCT and returned to the circulation. Almost 100 percent of glucose, amino acids, and other organic substances such as vitamins are normally recovered here. Some glucose may appear in the urine if circulating glucose levels are high enough that all the glucose transporters in the PCT are saturated, so that their capacity to move glucose is exceeded (transport maximum, or Tm). In men, the maximum amount of glucose that can be recovered is about 375 mg/min, whereas in women, it is about 300 mg/min. This recovery rate translates to an arterial concentration of about 200 mg/dL. Though an exceptionally high sugar intake might cause sugar to appear briefly in the urine, the appearance of glycosuria usually points to type I or II diabetes mellitus. The transport of glucose from the lumen of the PCT to the interstitial space is similar to the way it is absorbed by the small intestine. Both glucose and Na+ bind simultaneously to the same symport proteins on the apical surface of the cell to be transported in the same direction, toward the interstitial space. Sodium moves down its electrochemical and concentration gradient into the cell and takes glucose with it. Na+ is then actively pumped out of the cell at the basal surface of the cell into the interstitial space. Glucose leaves the cell to enter the interstitial space by facilitated diffusion. The energy to move glucose comes from the Na+/K+ ATPase that pumps Na+out of the cell on the basal surface. Fifty percent of Cl– and variable quantities of Ca++, Mg++, and HPO2−4HPO42− are also recovered in the PCT.
Recovery of bicarbonate (HCO3–) is vital to the maintenance of acid–base balance, since it is a very powerful and fast-acting buffer. An important enzyme is used to catalyze this mechanism: carbonic anhydrase (CA). This same enzyme and reaction is used in red blood cells in the transportation of CO2, in the stomach to produce hydrochloric acid, and in the pancreas to produce HCO3– to buffer acidic chyme from the stomach. In the kidney, most of the CA is located within the cell, but a small amount is bound to the brush border of the membrane on the apical surface of the cell. In the lumen of the PCT, HCO3–combines with hydrogen ions to form carbonic acid (H2CO3). This is enzymatically catalyzed into CO2 and water, which diffuse across the apical membrane into the cell. Water can move osmotically across the lipid bilayer membrane due to the presence of aquaporin water channels. Inside the cell, the reverse reaction occurs to produce bicarbonate ions (HCO3–). These bicarbonate ions are cotransported with Na+ across the basal membrane to the interstitial space around the PCT (Figure 25.19). At the same time this is occurring, a Na+/H+ antiporter excretes H+ into the lumen, while it recovers Na+. Note how the hydrogen ion is recycled so that bicarbonate can be recovered. Also, note that a Na+ gradient is created by the Na+/K+ pump.
HCO3−+ H+↔H2CO3↔CO2 + H2OHCO3−+ H+↔H2CO3↔CO2 + H2O
The significant recovery of solutes from the PCT lumen to the interstitial space creates an osmotic gradient that promotes water recovery. As noted before, water moves through channels created by the aquaporin proteins. These proteins are found in all cells in varying amounts and help regulate water movement across membranes and through cells by creating a passageway across the hydrophobic lipid bilayer membrane. Changing the number of aquaporin proteins in membranes of the collecting ducts also helps to regulate the osmolarity of the blood. The movement of many positively charged ions also creates an electrochemical gradient. This charge promotes the movement of negative ions toward the interstitial spaces and the movement of positive ions toward the lumen.
Figure 25.19 Reabsorption of Bicarbonate from the PCT
Reabsorption and Secretion in the Loop of Henle
The loop of Henle consists of two sections: thick and thin descending and thin and thick ascending sections. The loops of cortical nephrons do not extend into the renal medulla very far, if at all. Juxtamedullary nephrons have loops that extend variable distances, some very deep into the medulla. The descending and ascending portions of the loop are highly specialized to enable recovery of much of the Na+ and water that were filtered by the glomerulus. As the forming urine moves through the loop, the osmolarity will change from isosmotic with blood (about 278–300 mOsmol/kg) to both a very hypertonic solution of about 1200 mOsmol/kg and a very hypotonic solution of about 100 mOsmol/kg. These changes are accomplished by osmosis in the descending limb and active transport in the ascending limb. Solutes and water recovered from these loops are returned to the circulation by way of the vasa recta.
Descending Loop
The majority of the descending loop is comprised of simple squamous epithelial cells; to simplify the function of the loop, this discussion focuses on these cells. These membranes have permanent aquaporin channel proteins that allow unrestricted movement of water from the descending loop into the surrounding interstitium as osmolarity increases from about 300 mOsmol/kg to about 1200 mOsmol/kg. This increase results in reabsorption of up to 15 percent of the water entering the nephron. Modest amounts of urea, Na+, and other ions are also recovered here.
Most of the solutes that were filtered in the glomerulus have now been recovered along with a majority of water, about 82 percent. As the forming urine enters the ascending loop, major adjustments will be made to the concentration of solutes to create what you perceive as urine.
Ascending Loop
The ascending loop is made of very short thin and longer thick portions. Once again, to simplify the function, this section only considers the thick portion. The thick portion is lined with simple cuboidal epithelium without a brush border. It is completely impermeable to water due to the absence of aquaporin proteins, but ions, mainly Na+ and CL–, are actively reabsorbed by a cotransport system. This has two significant effects: Removal of NaCl while retaining water leads to a hypoosomotic filtrate by the time it reaches the DCT; pumping NaCl into the interstitial space contributes to the hyperosmotic environment in the kidney medulla.
The Na+/K+ ATPase pumps in the basal membrane create an electrochemical gradient, allowing reabsorption of Cl– by Na+/Cl–symporters in the apical membrane. At the same time that Na+ is actively pumped from the basal side of the cell into the interstitial fluid, Cl– follows the Na+ from the lumen into the interstitial fluid by a paracellular route between cells through leaky tight junctions. These are found between cells of the ascending loop, where they allow certain solutes to move according to their concentration gradient. Most of the K+ that enters the cell via symporters returns to the lumen (down its concentration gradient) through leaky channels in the apical membrane. Note the environment now created in the interstitial space: With the “back door exiting” K+, there is one Na+ and two Cl– ions left in the interstitium surrounding the ascending loop. Therefore, in comparison to the lumen of the loop, the interstitial space is now a negatively charged environment. This negative charge attracts cations (Na+, K+, Ca++, and Mg++) from the lumen via a paracellular route to the interstitial space and vasa recta.
Countercurrent Multiplier System
The structure of the loop of Henle and associated vasa recta create a countercurrent multiplier system (Figure 25.20). The countercurrent term comes from the fact that the descending and ascending loops are next to each other and their fluid flows in opposite directions (countercurrent). The multiplier term is due to the action of solute pumps that increase (multiply) the concentrations of urea and Na+ deep in the medulla.
Figure 25.20 Countercurrent Multiplier System
As discussed above, the ascending loop actively reabsorbs NaCl out of the forming urine into the interstitial spaces. In addition, collecting ducts have urea pumps that actively pump urea into the interstitial spaces. This results in the recovery of NaCl to the circulation via the vasa recta and creates a high osmolar environment in the depths of the medulla.
Ammonia (NH3) is a toxic byproduct of protein metabolism. It is formed as amino acids are deaminated by liver hepatocytes. That means that the amine group, NH2, is removed from amino acids as they are broken down. Most of the resulting ammonia is converted into urea by liver hepatocytes. Urea is not only less toxic but is utilized to aid in the recovery of water by the loop of Henle and collecting ducts. At the same time that water is freely diffusing out of the descending loop through aquaporin channels into the interstitial spaces of the medulla, urea freely diffuses into the lumen of the descending loop as it descends deeper into the medulla, much of it to be reabsorbed from the forming urine when it reaches the collecting duct. Thus, the movement of Na+ and urea into the interstitial spaces by these mechanisms creates the hyperosmotic environment of the medulla. The net result of this countercurrent multiplier system is to recover both water and Na+ in the circulation.
The amino acid glutamine can be deaminated by the kidney. As NH2 from the amino acid is converted into NH3 and pumped into the lumen of the PCT, Na+ and HCO3– are excreted into the interstitial fluid of the renal pyramid via a symport mechanism. When this process occurs in the cells of the PCT, the added benefit is a net loss of a hydrogen ion (complexed to ammonia to form the weak acid NH4+) in the urine and a gain of a bicarbonate ion (HCO3–) in the blood. Ammonia and bicarbonate are exchanged in a one-to-one ratio. This exchange is yet another means by which the body can buffer and excrete acid. The presence of aquaporin channels in the descending loop allows prodigious quantities of water to leave the loop and enter the hyperosmolar interstitium of the pyramid, where it is returned to the circulation by the vasa recta. As the loop turns to become the ascending loop, there is an absence of aquaporin channels, so water cannot leave the loop. However, in the basal membrane of cells of the thick ascending loop, ATPase pumps actively remove Na+ from the cell. A Na+/K+/2Cl– symporter in the apical membrane passively allows these ions to enter the cell cytoplasm from the lumen of the loop down a concentration gradient created by the pump. This mechanism works to dilute the fluid of the ascending loop ultimately to approximately 50–100 mOsmol/L.
At the transition from the DCT to the collecting duct, about 20 percent of the original water is still present and about 10 percent of the sodium. If no other mechanism for water reabsorption existed, about 20–25 liters of urine would be produced. Now consider what is happening in the adjacent capillaries, the vasa recta. They are recovering both solutes and water at a rate that preserves the countercurrent multiplier system. In general, blood flows slowly in capillaries to allow time for exchange of nutrients and wastes. In the vasa recta particularly, this rate of flow is important for two additional reasons. The flow must be slow to allow blood cells to lose and regain water without either crenating or bursting. Second, a rapid flow would remove too much Na+ and urea, destroying the osmolar gradient that is necessary for the recovery of solutes and water. Thus, by flowing slowly to preserve the countercurrent mechanism, as the vasa recta descend, Na+ and urea are freely able to enter the capillary, while water freely leaves; as they ascend, Na+ and urea are secreted into the surrounding medulla, while water reenters and is removed.
INTERACTIVE LINK
Watch this video to learn about the countercurrent multiplier system.
Reabsorption and Secretion in the Distal Convoluted Tubule
Approximately 80 percent of filtered water has been recovered by the time the dilute forming urine enters the DCT. The DCT will recover another 10–15 percent before the forming urine enters the collecting ducts. Aldosterone increases the amount of Na+/K+ATPase in the basal membrane of the DCT and collecting duct. The movement of Na+ out of the lumen of the collecting duct creates a negative charge that promotes the movement of Cl– out of the lumen into the interstitial space by a paracellular route across tight junctions. Peritubular capillaries receive the solutes and water, returning them to the circulation.
Cells of the DCT also recover Ca++ from the filtrate. Receptors for parathyroid hormone (PTH) are found in DCT cells and when bound to PTH, induce the insertion of calcium channels on their luminal surface. The channels enhance Ca++ recovery from the forming urine. In addition, as Na+ is pumped out of the cell, the resulting electrochemical gradient attracts Ca++ into the cell. Finally, calcitriol (1,25 dihydroxyvitamin D, the active form of vitamin D) is very important for calcium recovery. It induces the production of calcium-binding proteins that transport Ca++ into the cell. These binding proteins are also important for the movement of calcium inside the cell and aid in exocytosis of calcium across the basolateral membrane. Any Ca++ not reabsorbed at this point is lost in the urine.
Collecting Ducts and Recovery of Water
Solutes move across the membranes of the collecting ducts, which contain two distinct cell types, principal cells and intercalated cells. A principal cell possesses channels for the recovery or loss of sodium and potassium. An intercalated cellsecretes or absorbs acid or bicarbonate. As in other portions of the nephron, there is an array of micromachines (pumps and channels) on display in the membranes of these cells.
Regulation of urine volume and osmolarity are major functions of the collecting ducts. By varying the amount of water that is recovered, the collecting ducts play a major role in maintaining the body’s normal osmolarity. If the blood becomes hyperosmotic, the collecting ducts recover more water to dilute the blood; if the blood becomes hyposmotic, the collecting ducts recover less of the water, leading to concentration of the blood. Another way of saying this is: If plasma osmolarity rises, more water is recovered and urine volume decreases; if plasma osmolarity decreases, less water is recovered and urine volume increases. This function is regulated by the posterior pituitary hormone ADH (vasopressin). With mild dehydration, plasma osmolarity rises slightly. This increase is detected by osmoreceptors in the hypothalamus, which stimulates the release of ADH from the posterior pituitary. If plasma osmolarity decreases slightly, the opposite occurs.
When stimulated by ADH, aquaporin channels are inserted into the apical membrane of principal cells, which line the collecting ducts. As the ducts descend through the medulla, the osmolarity surrounding them increases (due to the countercurrent mechanisms described above). If aquaporin water channels are present, water will be osmotically pulled from the collecting duct into the surrounding interstitial space and into the peritubular capillaries. Therefore, the final urine will be more concentrated. If less ADH is secreted, fewer aquaporin channels are inserted and less water is recovered, resulting in dilute urine. By altering the number of aquaporin channels, the volume of water recovered or lost is altered. This, in turn, regulates the blood osmolarity, blood pressure, and osmolarity of the urine.
As Na+ is pumped from the forming urine, water is passively recaptured for the circulation; this preservation of vascular volume is critically important for the maintenance of a normal blood pressure. Aldosterone is secreted by the adrenal cortex in response to angiotensin II stimulation. As an extremely potent vasoconstrictor, angiotensin II functions immediately to increase blood pressure. By also stimulating aldosterone production, it provides a longer-lasting mechanism to support blood pressure by maintaining vascular volume (water recovery).
In addition to receptors for ADH, principal cells have receptors for the steroid hormone aldosterone. While ADH is primarily involved in the regulation of water recovery, aldosterone regulates Na+ recovery. Aldosterone stimulates principal cells to manufacture luminal Na+ and K+ channels as well as Na+/K+ ATPase pumps on the basal membrane of the cells. When aldosterone output increases, more Na+ is recovered from the forming urine and water follows the Na+ passively. As the pump recovers Na+ for the body, it is also pumping K+ into the forming urine, since the pump moves K+ in the opposite direction. When aldosterone decreases, more Na+ remains in the forming urine and more K+ is recovered in the circulation. Symport channels move Na+ and Cl– together. Still other channels in the principal cells secrete K+ into the collecting duct in direct proportion to the recovery of Na+.
Intercalated cells play significant roles in regulating blood pH. Intercalated cells reabsorb K+ and HCO3– while secreting H+. This function lowers the acidity of the plasma while increasing the acidity of the urine.
Regulation of Renal Blood Flow
- Describe the myogenic and tubuloglomerular feedback mechanisms and explain how they affect urine volume and composition
- Describe the function of the juxtaglomerular apparatus
It is vital that the flow of blood through the kidney be at a suitable rate to allow for filtration. This rate determines how much solute is retained or discarded, how much water is retained or discarded, and ultimately, the osmolarity of blood and the blood pressure of the body.
Sympathetic Nerves
The kidneys are innervated by the sympathetic neurons of the autonomic nervous system via the celiac plexus and splanchnic nerves. Reduction of sympathetic stimulation results in vasodilation and increased blood flow through the kidneys during resting conditions. When the frequency of action potentials increases, the arteriolar smooth muscle constricts (vasoconstriction), resulting in diminished glomerular flow, so less filtration occurs. Under conditions of stress, sympathetic nervous activity increases, resulting in the direct vasoconstriction of afferent arterioles (norepinephrine effect) as well as stimulation of the adrenal medulla. The adrenal medulla, in turn, produces a generalized vasoconstriction through the release of epinephrine. This includes vasoconstriction of the afferent arterioles, further reducing the volume of blood flowing through the kidneys. This process redirects blood to other organs with more immediate needs. If blood pressure falls, the sympathetic nerves will also stimulate the release of renin. Additional renin increases production of the powerful vasoconstrictor angiotensin II. Angiotensin II, as discussed above, will also stimulate aldosterone production to augment blood volume through retention of more Na+ and water. Only a 10 mm Hg pressure differential across the glomerulus is required for normal GFR, so very small changes in afferent arterial pressure significantly increase or decrease GFR.
Autoregulation
The kidneys are very effective at regulating the rate of blood flow over a wide range of blood pressures. Your blood pressure will decrease when you are relaxed or sleeping. It will increase when exercising. Yet, despite these changes, the filtration rate through the kidney will change very little. This is due to two internal autoregulatory mechanisms that operate without outside influence: the myogenic mechanism and the tubuloglomerular feedback mechanism.
Arteriole Myogenic Mechanism
The myogenic mechanism regulating blood flow within the kidney depends upon a characteristic shared by most smooth muscle cells of the body. When you stretch a smooth muscle cell, it contracts; when you stop, it relaxes, restoring its resting length. This mechanism works in the afferent arteriole that supplies the glomerulus. When blood pressure increases, smooth muscle cells in the wall of the arteriole are stretched and respond by contracting to resist the pressure, resulting in little change in flow. When blood pressure drops, the same smooth muscle cells relax to lower resistance, allowing a continued even flow of blood.
Tubuloglomerular Feedback
The tubuloglomerular feedback mechanism involves the JGA and a paracrine signaling mechanism utilizing ATP, adenosine, and nitric oxide (NO). This mechanism stimulates either contraction or relaxation of afferent arteriolar smooth muscle cells (Table 25.7). Recall that the DCT is in intimate contact with the afferent and efferent arterioles of the glomerulus. Specialized macula densa cells in this segment of the tubule respond to changes in the fluid flow rate and Na+ concentration. As GFR increases, there is less time for NaCl to be reabsorbed in the PCT, resulting in higher osmolarity in the filtrate. The increased fluid movement more strongly deflects single nonmotile cilia on macula densa cells. This increased osmolarity of the forming urine, and the greater flow rate within the DCT, activates macula densa cells to respond by releasing ATP and adenosine (a metabolite of ATP). ATP and adenosine act locally as paracrine factors to stimulate the myogenic juxtaglomerular cells of the afferent arteriole to constrict, slowing blood flow and reducing GFR. Conversely, when GFR decreases, less Na+ is in the forming urine, and most will be reabsorbed before reaching the macula densa, which will result in decreased ATP and adenosine, allowing the afferent arteriole to dilate and increase GFR. NO has the opposite effect, relaxing the afferent arteriole at the same time ATP and adenosine are stimulating it to contract. Thus, NO fine-tunes the effects of adenosine and ATP on GFR.
Paracrine Mechanisms Controlling Glomerular Filtration Rate
| Change in GFR | NaCl Absorption | Role of ATP and adenosine/Role of NO | Effect on GFR |
|---|---|---|---|
| Increased GFR | Tubular NaCl increases | ATP and adenosine increase, causing vasoconstriction | Vasoconstriction slows GFR |
| Decreased GFR | Tubular NaCl decreases | ATP and adenosine decrease, causing vasodilation | Vasodilation increases GFR |
| Increased GFR | Tubular NaCl increases | NO increases, causing vasodilation | Vasodilation increases GFR |
| Decreased GFR | Tubular NaCl decreases | NO decreases, causing vasoconstricton | Vasoconstriction decreases GFR |
Table 25.7
Endocrine Regulation of Kidney Function
- Describe how each of the following functions in the extrinsic control of GFR: renin–angiotensin mechanism, natriuretic peptides, and sympathetic adrenergic activity
- Describe how each of the following works to regulate reabsorption and secretion, so as to affect urine volume and composition: renin–angiotensin system, aldosterone, antidiuretic hormone, and natriuretic peptides
- Name and define the roles of other hormones that regulate kidney control
Several hormones have specific, important roles in regulating kidney function. They act to stimulate or inhibit blood flow. Some of these are endocrine, acting from a distance, whereas others are paracrine, acting locally.
Renin–Angiotensin–Aldosterone
Renin is an enzyme that is produced by the granular cells of the afferent arteriole at the JGA. It enzymatically converts angiotensinogen (made by the liver, freely circulating) into angiotensin I. Its release is stimulated by prostaglandins and NO from the JGA in response to decreased extracellular fluid volume.
ACE is not a hormone but it is functionally important in regulating systemic blood pressure and kidney function. It is produced in the lungs but binds to the surfaces of endothelial cells in the afferent arterioles and glomerulus. It enzymatically converts inactive angiotensin I into active angiotensin II. ACE is important in raising blood pressure. People with high blood pressure are sometimes prescribed ACE inhibitors to lower their blood pressure.
Angiotensin II is a potent vasoconstrictor that plays an immediate role in the regulation of blood pressure. It acts systemically to cause vasoconstriction as well as constriction of both the afferent and efferent arterioles of the glomerulus. In instances of blood loss or dehydration, it reduces both GFR and renal blood flow, thereby limiting fluid loss and preserving blood volume. Its release is usually stimulated by decreases in blood pressure, and so the preservation of adequate blood pressure is its primary role.
Aldosterone, often called the “salt-retaining hormone,” is released from the adrenal cortex in response to angiotensin II or directly in response to increased plasma K+. It promotes Na+ reabsorption by the nephron, promoting the retention of water. It is also important in regulating K+, promoting its excretion. (This dual effect on two minerals and its origin in the adrenal cortex explains its designation as a mineralocorticoid.) As a result, renin has an immediate effect on blood pressure due to angiotensin II–stimulated vasoconstriction and a prolonged effect through Na+ recovery due to aldosterone. At the same time that aldosterone causes increased recovery of Na+, it also causes greater loss of K+. Progesterone is a steroid that is structurally similar to aldosterone. It binds to the aldosterone receptor and weakly stimulates Na+ reabsorption and increased water recovery. This process is unimportant in men due to low levels of circulating progesterone. It may cause increased retention of water during some periods of the menstrual cycle in women when progesterone levels increase.
Antidiuretic Hormone (ADH)
Diuretics are drugs that can increase water loss by interfering with the recapture of solutes and water from the forming urine. They are often prescribed to lower blood pressure. Coffee, tea, and alcoholic beverages are familiar diuretics. ADH, a 9-amino acid peptide released by the posterior pituitary, works to do the exact opposite. It promotes the recovery of water, decreases urine volume, and maintains plasma osmolarity and blood pressure. It does so by stimulating the movement of aquaporin proteins into the apical cell membrane of principal cells of the collecting ducts to form water channels, allowing the transcellular movement of water from the lumen of the collecting duct into the interstitial space in the medulla of the kidney by osmosis. From there, it enters the vasa recta capillaries to return to the circulation. Water is attracted by the high osmotic environment of the deep kidney medulla.
Endothelin
Endothelins, 21-amino acid peptides, are extremely powerful vasoconstrictors. They are produced by endothelial cells of the renal blood vessels, mesangial cells, and cells of the DCT. Hormones stimulating endothelin release include angiotensin II, bradykinin, and epinephrine. They do not typically influence blood pressure in healthy people. On the other hand, in people with diabetic kidney disease, endothelin is chronically elevated, resulting in sodium retention. They also diminish GFR by damaging the podocytes and by potently vasoconstricting both the afferent and efferent arterioles.
Natriuretic Hormones
Natriuretic hormones are peptides that stimulate the kidneys to excrete sodium—an effect opposite that of aldosterone. Natriuretic hormones act by inhibiting aldosterone release and therefore inhibiting Na+ recovery in the collecting ducts. If Na+remains in the forming urine, its osmotic force will cause a concurrent loss of water. Natriuretic hormones also inhibit ADH release, which of course will result in less water recovery. Therefore, natriuretic peptides inhibit both Na+ and water recovery. One example from this family of hormones is atrial natriuretic hormone (ANH), a 28-amino acid peptide produced by heart atria in response to over-stretching of the atrial wall. The over-stretching occurs in persons with elevated blood pressure or heart failure. It increases GFR through concurrent vasodilation of the afferent arteriole and vasoconstriction of the efferent arteriole. These events lead to an increased loss of water and sodium in the forming urine. It also decreases sodium reabsorption in the DCT. There is also B-type natriuretic peptide (BNP) of 32 amino acids produced in the ventricles of the heart. It has a 10-fold lower affinity for its receptor, so its effects are less than those of ANH. Its role may be to provide “fine tuning” for the regulation of blood pressure. BNP’s longer biologic half-life makes it a good diagnostic marker of congestive heart failure (Figure 25.21).
Parathyroid Hormone
Parathyroid hormone (PTH) is an 84-amino acid peptide produced by the parathyroid glands in response to decreased circulating Ca++ levels. Among its targets is the PCT, where it stimulates the hydroxylation of calcidiol to calcitriol (1,25-hydroxycholecalciferol, the active form of vitamin D). It also blocks reabsorption of phosphate (PO3–), causing its loss in the urine. The retention of phosphate would result in the formation of calcium phosphate in the plasma, reducing circulating Ca++levels. By ridding the blood of phosphate, higher circulating Ca++ levels are permitted.
Figure 25.21 Major Hormones That Influence GFR and RFB
Regulation of Fluid Volume and Composition
- Explain the mechanism of action of diuretics
- Explain why the differential permeability or impermeability of specific sections of the nephron tubules is necessary for urine formation
The major hormones influencing total body water are ADH, aldosterone, and ANH. Circumstances that lead to fluid depletion in the body include blood loss and dehydration. Homeostasis requires that volume and osmolarity be preserved. Blood volume is important in maintaining sufficient blood pressure, and there are nonrenal mechanisms involved in its preservation, including vasoconstriction, which can act within seconds of a drop in pressure. Thirst mechanisms are also activated to promote the consumption of water lost through respiration, evaporation, or urination. Hormonal mechanisms are activated to recover volume while maintaining a normal osmotic environment. These mechanisms act principally on the kidney.
Volume-sensing Mechanisms
The body cannot directly measure blood volume, but blood pressure can be measured. Blood pressure often reflects blood volume and is measured by baroreceptors in the aorta and carotid sinuses. When blood pressure increases, baroreceptors send more frequent action potentials to the central nervous system, leading to widespread vasodilation. Included in this vasodilation are the afferent arterioles supplying the glomerulus, resulting in increased GFR, and water loss by the kidneys. If pressure decreases, fewer action potentials travel to the central nervous system, resulting in more sympathetic stimulation-producing vasoconstriction, which will result in decreased filtration and GFR, and water loss.
Decreased blood pressure is also sensed by the granular cells in the afferent arteriole of the JGA. In response, the enzyme renin is released. You saw earlier in the chapter that renin activity leads to an almost immediate rise in blood pressure as activated angiotensin II produces vasoconstriction. The rise in pressure is sustained by the aldosterone effects initiated by angiotensin II; this includes an increase in Na+ retention and water volume. As an aside, late in the menstrual cycle, progesterone has a modest influence on water retention. Due to its structural similarity to aldosterone, progesterone binds to the aldosterone receptor in the collecting duct of the kidney, causing the same, albeit weaker, effect on Na+ and water retention.
Cardiomyocytes of the atria also respond to greater stretch (as blood pressure rises) by secreting ANH. ANH opposes the action of aldosterone by inhibiting the recovery of Na+ by the DCT and collecting ducts. More Na+ is lost, and as water follows, total blood volume and pressure decline. In low-pressure states, ANH does not seem to have much effect.
ADH is also called vasopressin. Early researchers found that in cases of unusually high secretion of ADH, the hormone caused vasoconstriction (vasopressor activity, hence the name). Only later were its antidiuretic properties identified. Synthetic ADH is still used occasionally to stem life-threatening esophagus bleeding in alcoholics.
When blood volume drops 5–10 percent, causing a decrease in blood pressure, there is a rapid and significant increase in ADH release from the posterior pituitary. Immediate vasoconstriction to increase blood pressure is the result. ADH also causes activation of aquaporin channels in the collecting ducts to affect the recovery of water to help restore vascular volume.
Diuretics and Fluid Volume
A diuretic is a compound that increases urine volume. Three familiar drinks contain diuretic compounds: coffee, tea, and alcohol. The caffeine in coffee and tea works by promoting vasodilation in the nephron, which increases GFR. Alcohol increases GFR by inhibiting ADH release from the posterior pituitary, resulting in less water recovery by the collecting duct. In cases of high blood pressure, diuretics may be prescribed to reduce blood volume and, thereby, reduce blood pressure. The most frequently prescribed anti-hypertensive diuretic is hydrochlorothiazide. It inhibits the Na+/ Cl– symporter in the DCT and collecting duct. The result is a loss of Na+ with water following passively by osmosis.
Osmotic diuretics promote water loss by osmosis. An example is the indigestible sugar mannitol, which is most often administered to reduce brain swelling after head injury. However, it is not the only sugar that can produce a diuretic effect. In cases of poorly controlled diabetes mellitus, glucose levels exceed the capacity of the tubular glucose symporters, resulting in glucose in the urine. The unrecovered glucose becomes a powerful osmotic diuretic. Classically, in the days before glucose could be detected in the blood and urine, clinicians identified diabetes mellitus by the three Ps: polyuria (diuresis), polydipsia (increased thirst), and polyphagia (increased hunger).
Regulation of Extracellular Na+
Sodium has a very strong osmotic effect and attracts water. It plays a larger role in the osmolarity of the plasma than any other circulating component of the blood. If there is too much Na+ present, either due to poor control or excess dietary consumption, a series of metabolic problems ensue. There is an increase in total volume of water, which leads to hypertension (high blood pressure). Over a long period, this increases the risk of serious complications such as heart attacks, strokes, and aneurysms. It can also contribute to system-wide edema (swelling).
Mechanisms for regulating Na+ concentration include the renin–angiotensin–aldosterone system and ADH (see Figure 25.14). Aldosterone stimulates the uptake of Na+ on the apical cell membrane of cells in the DCT and collecting ducts, whereas ADH helps to regulate Na+ concentration indirectly by regulating the reabsorption of water.
Regulation of Extracellular K+
Potassium is present in a 30-fold greater concentration inside the cell than outside the cell. A generalization can be made that K+ and Na+ concentrations will move in opposite directions. When more Na+ is reabsorbed, more K+ is secreted; when less Na+is reabsorbed (leading to excretion by the kidney), more K+ is retained. When aldosterone causes a recovery of Na+ in the nephron, a negative electrical gradient is created that promotes the secretion of K+ and Cl– into the lumen.
Regulation of Cl–
Chloride is important in acid–base balance in the extracellular space and has other functions, such as in the stomach, where it combines with hydrogen ions in the stomach lumen to form hydrochloric acid, aiding digestion. Its close association with Na+ in the extracellular environment makes it the dominant anion of this compartment, and its regulation closely mirrors that of Na+.
Regulation of Ca++ and Phosphate
The parathyroid glands monitor and respond to circulating levels of Ca++ in the blood. When levels drop too low, PTH is released to stimulate the DCT to reabsorb Ca++ from the forming urine. When levels are adequate or high, less PTH is released and more Ca++ remains in the forming urine to be lost. Phosphate levels move in the opposite direction. When Ca++ levels are low, PTH inhibits reabsorption of HPO2−4HPO42− so that its blood level drops, allowing Ca++ levels to rise. PTH also stimulates the renal conversion of calcidiol into calcitriol, the active form of vitamin D. Calcitriol then stimulates the intestines to absorb more Ca++from the diet.
Regulation of H+, Bicarbonate, and pH
The acid–base homeostasis of the body is a function of chemical buffers and physiologic buffering provided by the lungs and kidneys. Buffers, especially proteins, HCO2−3HCO32−+ as needed to resist a change in pH. They can act within fractions of a second. The lungs can rid the body of excess acid very rapidly (seconds to minutes) through the conversion of HCO3– into CO2, which is then exhaled. It is rapid but has limited capacity in the face of a significant acid challenge. The kidneys can rid the body of both acid and base. The renal capacity is large but slow (minutes to hours). The cells of the PCT actively secrete H+ into the forming urine as Na+ is reabsorbed. The body rids itself of excess H+and raises blood pH. In the collecting ducts, the apical surfaces of intercalated cells have proton pumps that actively secrete H+into the luminal, forming urine to remove it from the body.
As hydrogen ions are pumped into the forming urine, it is buffered by bicarbonate (HCO3–), H2PO4– (dihydrogen phosphate ion), or ammonia (forming NH4+, ammonium ion). Urine pH typically varies in a normal range from 4.5 to 8.0.
Regulation of Nitrogen Wastes
Nitrogen wastes are produced by the breakdown of proteins during normal metabolism. Proteins are broken down into amino acids, which in turn are deaminated by having their nitrogen groups removed. Deamination converts the amino (NH2) groups into ammonia (NH3), ammonium ion (NH4+), urea, or uric acid (Figure 25.22). Ammonia is extremely toxic, so most of it is very rapidly converted into urea in the liver. Human urinary wastes typically contain primarily urea with small amounts of ammonium and very little uric acid.
Figure 25.22 Nitrogen Wastes
Elimination of Drugs and Hormones
Water-soluble drugs may be excreted in the urine and are influenced by one or all of the following processes: glomerular filtration, tubular secretion, or tubular reabsorption. Drugs that are structurally small can be filtered by the glomerulus with the filtrate. Large drug molecules such as heparin or those that are bound to plasma proteins cannot be filtered and are not readily eliminated. Some drugs can be eliminated by carrier proteins that enable secretion of the drug into the tubule lumen. There are specific carriers that eliminate basic (such as dopamine or histamine) or acidic drugs (such as penicillin or indomethacin). As is the case with other substances, drugs may be both filtered and reabsorbed passively along a concentration gradient.
The Urinary System and Homeostasis
- Describe the role of the kidneys in vitamin D activation
- Describe the role of the kidneys in regulating erythropoiesis
- Provide specific examples to demonstrate how the urinary system responds to maintain homeostasis in the body
- Explain how the urinary system relates to other body systems in maintaining homeostasis
- Predict factors or situations affecting the urinary system that could disrupt homeostasis
- Predict the types of problems that would occur in the body if the urinary system could not maintain homeostasis
All systems of the body are interrelated. A change in one system may affect all other systems in the body, with mild to devastating effects. A failure of urinary continence can be embarrassing and inconvenient, but is not life threatening. The loss of other urinary functions may prove fatal. A failure to synthesize vitamin D is one such example.
Vitamin D Synthesis
In order for vitamin D to become active, it must undergo a hydroxylation reaction in the kidney, that is, an –OH group must be added to calcidiol to make calcitriol (1,25-dihydroxycholecalciferol). Activated vitamin D is important for absorption of Ca++ in the digestive tract, its reabsorption in the kidney, and the maintenance of normal serum concentrations of Ca++ and phosphate. Calcium is vitally important in bone health, muscle contraction, hormone secretion, and neurotransmitter release. Inadequate Ca++ leads to disorders like osteoporosis and osteomalacia in adults and rickets in children. Deficits may also result in problems with cell proliferation, neuromuscular function, blood clotting, and the inflammatory response. Recent research has confirmed that vitamin D receptors are present in most, if not all, cells of the body, reflecting the systemic importance of vitamin D. Many scientists have suggested it be referred to as a hormone rather than a vitamin.
Erythropoiesis
EPO is a 193-amino acid protein that stimulates the formation of red blood cells in the bone marrow. The kidney produces 85 percent of circulating EPO; the liver, the remainder. If you move to a higher altitude, the partial pressure of oxygen is lower, meaning there is less pressure to push oxygen across the alveolar membrane and into the red blood cell. One way the body compensates is to manufacture more red blood cells by increasing EPO production. If you start an aerobic exercise program, your tissues will need more oxygen to cope, and the kidney will respond with more EPO. If erythrocytes are lost due to severe or prolonged bleeding, or under produced due to disease or severe malnutrition, the kidneys come to the rescue by producing more EPO. Renal failure (loss of EPO production) is associated with anemia, which makes it difficult for the body to cope with increased oxygen demands or to supply oxygen adequately even under normal conditions. Anemia diminishes performance and can be life threatening.
Blood Pressure Regulation
Due to osmosis, water follows where Na+ leads. Much of the water the kidneys recover from the forming urine follows the reabsorption of Na+. ADH stimulation of aquaporin channels allows for regulation of water recovery in the collecting ducts. Normally, all of the glucose is recovered, but loss of glucose control (diabetes mellitus) may result in an osmotic dieresis severe enough to produce severe dehydration and death. A loss of renal function means a loss of effective vascular volume control, leading to hypotension (low blood pressure) or hypertension (high blood pressure), which can lead to stroke, heart attack, and aneurysm formation.
The kidneys cooperate with the lungs, liver, and adrenal cortex through the renin–angiotensin–aldosterone system (see Figure 25.14). The liver synthesizes and secretes the inactive precursor angiotensinogen. When the blood pressure is low, the kidney synthesizes and releases renin. Renin converts angiotensinogen into angiotensin I, and ACE produced in the lung converts angiotensin I into biologically active angiotensin II (Figure 25.23). The immediate and short-term effect of angiotensin II is to raise blood pressure by causing widespread vasoconstriction. angiotensin II also stimulates the adrenal cortex to release the steroid hormone aldosterone, which results in renal reabsorption of Na+ and its associated osmotic recovery of water. The reabsorption of Na+ helps to raise and maintain blood pressure over a longer term.
Figure 25.23 The Enzyme Renin Converts the Pro-enzyme Angiotensin
Regulation of Osmolarity
Blood pressure and osmolarity are regulated in a similar fashion. Severe hypo-osmolarity can cause problems like lysis (rupture) of blood cells or widespread edema, which is due to a solute imbalance. Inadequate solute concentration (such as protein) in the plasma results in water moving toward an area of greater solute concentration, in this case, the interstitial space and cell cytoplasm. If the kidney glomeruli are damaged by an autoimmune illness, large quantities of protein may be lost in the urine. The resultant drop in serum osmolarity leads to widespread edema that, if severe, may lead to damaging or fatal brain swelling. Severe hypertonic conditions may arise with severe dehydration from lack of water intake, severe vomiting, or uncontrolled diarrhea. When the kidney is unable to recover sufficient water from the forming urine, the consequences may be severe (lethargy, confusion, muscle cramps, and finally, death) .
Recovery of Electrolytes
Sodium, calcium, and potassium must be closely regulated. The role of Na+ and Ca++ homeostasis has been discussed at length. Failure of K+ regulation can have serious consequences on nerve conduction, skeletal muscle function, and most significantly, on cardiac muscle contraction and rhythm.
pH Regulation
Recall that enzymes lose their three-dimensional conformation and, therefore, their function if the pH is too acidic or basic. This loss of conformation may be a consequence of the breaking of hydrogen bonds. Move the pH away from the optimum for a specific enzyme and you may severely hamper its function throughout the body, including hormone binding, central nervous system signaling, or myocardial contraction. Proper kidney function is essential for pH homeostasis.
EVERYDAY CONNECTION
Stem Cells and Repair of Kidney Damage
Stem cells are unspecialized cells that can reproduce themselves via cell division, sometimes after years of inactivity. Under certain conditions, they may differentiate into tissue-specific or organ-specific cells with special functions. In some cases, stem cells may continually divide to produce a mature cell and to replace themselves. Stem cell therapy has an enormous potential to improve the quality of life or save the lives of people suffering from debilitating or life-threatening diseases. There have been several studies in animals, but since stem cell therapy is still in its infancy, there have been limited experiments in humans.
Acute kidney injury can be caused by a number of factors, including transplants and other surgeries. It affects 7–10 percent of all hospitalized patients, resulting in the deaths of 35–40 percent of inpatients. In limited studies using mesenchymal stem cells, there have been fewer instances of kidney damage after surgery, the length of hospital stays has been reduced, and there have been fewer readmissions after release.
How do these stem cells work to protect or repair the kidney? Scientists are unsure at this point, but some evidence has shown that these stem cells release several growth factors in endocrine and paracrine ways. As further studies are conducted to assess the safety and effectiveness of stem cell therapy, we will move closer to a day when kidney injury is rare, and curative treatments are routine.
Key Terms
- anatomical sphincter
- smooth or skeletal muscle surrounding the lumen of a vessel or hollow organ that can restrict flow when contracted
- angiotensin I
- protein produced by the enzymatic action of renin on angiotensinogen; inactive precursor of angiotensin II
- angiotensin II
- protein produced by the enzymatic action of ACE on inactive angiotensin I; actively causes vasoconstriction and stimulates aldosterone release by the adrenal cortex
- angiotensin-converting enzyme (ACE)
- enzyme produced by the lungs that catalyzes the reaction of inactive angiotensin I into active angiotensin II
- angiotensinogen
- inactive protein in the circulation produced by the liver; precursor of angiotensin I; must be modified by the enzymes renin and ACE to be activated
- anuria
- absence of urine produced; production of 50 mL or less per day
- aquaporin
- protein-forming water channels through the lipid bilayer of the cell; allows water to cross; activation in the collecting ducts is under the control of ADH
- Bowman’s capsule
- cup-shaped sack lined by a simple squamous epithelium (parietal surface) and specialized cells called podocytes (visceral surface) that participate in the filtration process; receives the filtrate which then passes on to the PCTs
- brush border
- formed by microvilli on the surface of certain cuboidal cells; in the kidney it is found in the PCT; increases surface area for absorption in the kidney
- calyces
- cup-like structures receiving urine from the collecting ducts where it passes on to the renal pelvis and ureter
- cortical nephrons
- nephrons with loops of Henle that do not extend into the renal medulla
- countercurrent multiplier system
- involves the descending and ascending loops of Henle directing forming urine in opposing directions to create a concentration gradient when combined with variable permeability and sodium pumping
- detrusor muscle
- smooth muscle in the bladder wall; fibers run in all directions to reduce the size of the organ when emptying it of urine
- distal convoluted tubules
- portions of the nephron distal to the loop of Henle that receive hyposmotic filtrate from the loop of Henle and empty into collecting ducts
- diuretic
- compound that increases urine output, leading to decreased water conservation
- efferent arteriole
- arteriole carrying blood from the glomerulus to the capillary beds around the convoluted tubules and loop of Henle; portion of the portal system
- endothelins
- group of vasoconstrictive, 21-amino acid peptides; produced by endothelial cells of the renal blood vessels, mesangial cells, and cells of the DCT
- external urinary sphincter
- skeletal muscle; must be relaxed consciously to void urine
- fenestrations
- small windows through a cell, allowing rapid filtration based on size; formed in such a way as to allow substances to cross through a cell without mixing with cell contents
- filtration slits
- formed by pedicels of podocytes; substances filter between the pedicels based on size
- forming urine
- filtrate undergoing modifications through secretion and reabsorption before true urine is produced
- glomerular filtration rate (GFR)
- rate of renal filtration
- glomerulus
- tuft of capillaries surrounded by Bowman’s capsule; filters the blood based on size
- glycosuria
- presence of glucose in the urine; caused by high blood glucose levels that exceed the ability of the kidneys to reabsorb the glucose; usually the result of untreated or poorly controlled diabetes mellitus
- incontinence
- loss of ability to control micturition
- intercalated cell
- specialized cell of the collecting ducts that secrete or absorb acid or bicarbonate; important in acid–base balance
- internal urinary sphincter
- smooth muscle at the juncture of the bladder and urethra; relaxes as the bladder fills to allow urine into the urethra
- inulin
- plant polysaccharide injected to determine GFR; is neither secreted nor absorbed by the kidney, so its appearance in the urine is directly proportional to its filtration rate
- juxtaglomerular apparatus (JGA)
- located at the juncture of the DCT and the afferent and efferent arterioles of the glomerulus; plays a role in the regulation of renal blood flow and GFR
- juxtaglomerular cell
- modified smooth muscle cells of the afferent arteriole; secretes renin in response to a drop in blood pressure
- juxtamedullary nephrons
- nephrons adjacent to the border of the cortex and medulla with loops of Henle that extend into the renal medulla
- leaky tight junctions
- tight junctions in which the sealing strands of proteins between the membranes of adjacent cells are fewer in number and incomplete; allows limited intercellular movement of solvent and solutes
- leukocyte esterase
- enzyme produced by leukocytes that can be detected in the urine and that serves as an indirect indicator of urinary tract infection
- loop of Henle
- descending and ascending portions between the proximal and distal convoluted tubules; those of cortical nephrons do not extend into the medulla, whereas those of juxtamedullary nephrons do extend into the medulla
- macula densa
- cells found in the part of the DCT forming the JGA; sense Na+ concentration in the forming urine
- medulla
- inner region of kidney containing the renal pyramids
- mesangial
- contractile cells found in the glomerulus; can contract or relax to regulate filtration rate
- micturition
- also called urination or voiding
- myogenic mechanism
- mechanism by which smooth muscle responds to stretch by contracting; an increase in blood pressure causes vasoconstriction and a decrease in blood pressure causes vasodilation so that blood flow downstream remains steady
- nephrons
- functional units of the kidney that carry out all filtration and modification to produce urine; consist of renal corpuscles, proximal and distal convoluted tubules, and descending and ascending loops of Henle; drain into collecting ducts
- net filtration pressure (NFP)
- pressure of fluid across the glomerulus; calculated by taking the hydrostatic pressure of the capillary and subtracting the colloid osmotic pressure of the blood and the hydrostatic pressure of Bowman’s capsule
- oliguria
- below normal urine production of 400–500 mL/day
- osteomalacia
- softening of bones due to a lack of mineralization with calcium and phosphate; most often due to lack of vitamin D; in children, osteomalacia is termed rickets; not to be confused with osteoporosis
- pedicels
- finger-like projections of podocytes surrounding glomerular capillaries; interdigitate to form a filtration membrane
- peritubular capillaries
- second capillary bed of the renal portal system; surround the proximal and distal convoluted tubules; associated with the vasa recta
- physiological sphincter
- sphincter consisting of circular smooth muscle indistinguishable from adjacent muscle but possessing differential innervations, permitting its function as a sphincter; structurally weak
- podocytes
- cells forming finger-like processes; form the visceral layer of Bowman’s capsule; pedicels of the podocytes interdigitate to form a filtration membrane
- polyuria
- urine production in excess of 2.5 L/day; may be caused by diabetes insipidus, diabetes mellitus, or excessive use of diuretics
- principal cell
- found in collecting ducts and possess channels for the recovery or loss of sodium and potassium; under the control of aldosterone; also have aquaporin channels under ADH control to regulate recovery of water
- proximal convoluted tubules (PCTs)
- tortuous tubules receiving filtrate from Bowman’s capsule; most active part of the nephron in reabsorption and secretion
- renal columns
- extensions of the renal cortex into the renal medulla; separates the renal pyramids; contains blood vessels and connective tissues
- renal corpuscle
- consists of the glomerulus and Bowman’s capsule
- renal cortex
- outer part of kidney containing all of the nephrons; some nephrons have loops of Henle extending into the medulla
- renal fat pad
- adipose tissue between the renal fascia and the renal capsule that provides protective cushioning to the kidney
- renal hilum
- recessed medial area of the kidney through which the renal artery, renal vein, ureters, lymphatics, and nerves pass
- renal papillae
- medullary area of the renal pyramids where collecting ducts empty urine into the minor calyces
- renal pyramids
- six to eight cone-shaped tissues in the medulla of the kidney containing collecting ducts and the loops of Henle of juxtamedullary nephrons
- renin
- enzyme produced by juxtaglomerular cells in response to decreased blood pressure or sympathetic nervous activity; catalyzes the conversion of angiotensinogen into angiotensin I
- retroperitoneal
- outside the peritoneal cavity; in the case of the kidney and ureters, between the parietal peritoneum and the abdominal wall
- sacral micturition center
- group of neurons in the sacral region of the spinal cord that controls urination; acts reflexively unless its action is modified by higher brain centers to allow voluntary urination
- specific gravity
- weight of a liquid compared to pure water, which has a specific gravity of 1.0; any solute added to water will increase its specific gravity
- systemic edema
- increased fluid retention in the interstitial spaces and cells of the body; can be seen as swelling over large areas of the body, particularly the lower extremities
- trigone
- area at the base of the bladder marked by the two ureters in the posterior–lateral aspect and the urethral orifice in the anterior aspect oriented like points on a triangle
- tubuloglomerular feedback
- feedback mechanism involving the JGA; macula densa cells monitor Na+ concentration in the terminal portion of the ascending loop of Henle and act to cause vasoconstriction or vasodilation of afferent and efferent arterioles to alter GFR
- urethra
- transports urine from the bladder to the outside environment
- urinalysis
- analysis of urine to diagnose disease
- urochrome
- heme-derived pigment that imparts the typical yellow color of urine
- vasa recta
- branches of the efferent arterioles that parallel the course of the loops of Henle and are continuous with the peritubular capillaries; with the glomerulus, form a portal system
Chapter Review
25.1 Physical Characteristics of Urine
The kidney glomerulus filters blood mainly based on particle size to produce a filtrate lacking cells or large proteins. Most of the ions and molecules in the filtrate are needed by the body and must be reabsorbed farther down the nephron tubules, resulting in the formation of urine. Urine characteristics change depending on water intake, exercise, environmental temperature, and nutrient intake. Urinalysis analyzes characteristics of the urine and is used to diagnose diseases. A minimum of 400 to 500 mL urine must be produced daily to rid the body of wastes. Excessive quantities of urine may indicate diabetes insipidus or diabetes mellitus. The pH range of urine is 4.5 to 8.0, and is affected by diet. Osmolarity ranges from 50 to 1200 milliosmoles, and is a reflection of the amount of water being recovered or lost by renal nephrons.
25.2 Gross Anatomy of Urine Transport
The urethra is the only urinary structure that differs significantly between males and females. This is due to the dual role of the male urethra in transporting both urine and semen. The urethra arises from the trigone area at the base of the bladder. Urination is controlled by an involuntary internal sphincter of smooth muscle and a voluntary external sphincter of skeletal muscle. The shorter female urethra contributes to the higher incidence of bladder infections in females. The male urethra receives secretions from the prostate gland, Cowper’s gland, and seminal vesicles as well as sperm. The bladder is largely retroperitoneal and can hold up to 500–600 mL urine. Micturition is the process of voiding the urine and involves both involuntary and voluntary actions. Voluntary control of micturition requires a mature and intact sacral micturition center. It also requires an intact spinal cord. Loss of control of micturition is called incontinence and results in voiding when the bladder contains about 250 mL urine. The ureters are retroperitoneal and lead from the renal pelvis of the kidney to the trigone area at the base of the bladder. A thick muscular wall consisting of longitudinal and circular smooth muscle helps move urine toward the bladder by way of peristaltic contractions.
25.3 Gross Anatomy of the Kidney
As noted previously, the structure of the kidney is divided into two principle regions—the peripheral rim of cortex and the central medulla. The two kidneys receive about 25 percent of cardiac output. They are protected in the retroperitoneal space by the renal fat pad and overlying ribs and muscle. Ureters, blood vessels, lymph vessels, and nerves enter and leave at the renal hilum. The renal arteries arise directly from the aorta, and the renal veins drain directly into the inferior vena cava. Kidney function is derived from the actions of about 1.3 million nephrons per kidney; these are the “functional units.” A capillary bed, the glomerulus, filters blood and the filtrate is captured by Bowman’s capsule. A portal system is formed when the blood flows through a second capillary bed surrounding the proximal and distal convoluted tubules and the loop of Henle. Most water and solutes are recovered by this second capillary bed. This filtrate is processed and finally gathered by collecting ducts that drain into the minor calyces, which merge to form major calyces; the filtrate then proceeds to the renal pelvis and finally the ureters.
25.4 Microscopic Anatomy of the Kidney
The functional unit of the kidney, the nephron, consists of the renal corpuscle, PCT, loop of Henle, and DCT. Cortical nephrons have short loops of Henle, whereas juxtamedullary nephrons have long loops of Henle extending into the medulla. About 15 percent of nephrons are juxtamedullary. The glomerulus is a capillary bed that filters blood principally based on particle size. The filtrate is captured by Bowman’s capsule and directed to the PCT. A filtration membrane is formed by the fused basement membranes of the podocytes and the capillary endothelial cells that they embrace. Contractile mesangial cells further perform a role in regulating the rate at which the blood is filtered. Specialized cells in the JGA produce paracrine signals to regulate blood flow and filtration rates of the glomerulus. Other JGA cells produce the enzyme renin, which plays a central role in blood pressure regulation. The filtrate enters the PCT where absorption and secretion of several substances occur. The descending and ascending limbs of the loop of Henle consist of thick and thin segments. Absorption and secretion continue in the DCT but to a lesser extent than in the PCT. Each collecting duct collects forming urine from several nephrons and responds to the posterior pituitary hormone ADH by inserting aquaporin water channels into the cell membrane to fine tune water recovery.
25.5 Physiology of Urine Formation
The entire volume of the blood is filtered through the kidneys about 300 times per day, and 99 percent of the water filtered is recovered. The GFR is influenced by hydrostatic pressure and colloid osmotic pressure. Under normal circumstances, hydrostatic pressure is significantly greater and filtration occurs. The hydrostatic pressure of the glomerulus depends on systemic blood pressure, autoregulatory mechanisms, sympathetic nervous activity, and paracrine hormones. The kidney can function normally under a wide range of blood pressures due to the autoregulatory nature of smooth muscle.
25.6 Tubular Reabsorption
The kidney regulates water recovery and blood pressure by producing the enzyme renin. It is renin that starts a series of reactions, leading to the production of the vasoconstrictor angiotensin II and the salt-retaining steroid aldosterone. Water recovery is also powerfully and directly influenced by the hormone ADH. Even so, it only influences the last 10 percent of water available for recovery after filtration at the glomerulus, because 90 percent of water is recovered before reaching the collecting ducts. Depending on the body’s fluid status at any given time, the collecting ducts can recover none or almost all of the water reaching them.
Mechanisms of solute recovery include active transport, simple diffusion, and facilitated diffusion. Most filtered substances are reabsorbed. Urea, NH3, creatinine, and some drugs are filtered or secreted as wastes. H+ and HCO3– are secreted or reabsorbed as needed to maintain acid–base balance. Movement of water from the glomerulus is primarily due to pressure, whereas that of peritubular capillaries and vasa recta is due to osmolarity and concentration gradients. The PCT is the most metabolically active part of the nephron and uses a wide array of protein micromachines to maintain homeostasis—symporters, antiporters, and ATPase active transporters—in conjunction with diffusion, both simple and facilitated. Almost 100 percent of glucose, amino acids, and vitamins are recovered in the PCT. Bicarbonate (HCO3–) is recovered using the same enzyme, carbonic anhydrase (CA), found in erythrocytes. The recovery of solutes creates an osmotic gradient to promote the recovery of water. The descending loop of the juxtaglomerular nephrons reaches an osmolarity of up to 1200 mOsmol/kg, promoting the recovery of water. The ascending loop is impervious to water but actively recovers Na+, reducing filtrate osmolarity to 50–100 mOsmol/kg. The descending and ascending loop and vasa recta form a countercurrent multiplier system to increase Na+concentration in the kidney medulla. The collecting ducts actively pump urea into the medulla, further contributing to the high osmotic environment. The vasa recta recover the solute and water in the medulla, returning them to the circulation. Nearly 90 percent of water is recovered before the forming urine reaches the DCT, which will recover another 10 percent. Calcium recovery in the DCT is influenced by PTH and active vitamin D. In the collecting ducts, ADH stimulates aquaporin channel insertion to increase water recovery and thereby regulate osmolarity of the blood. Aldosterone stimulates Na+ recovery by the collecting duct.
25.7 Regulation of Renal Blood Flow
The kidneys are innervated by sympathetic nerves of the autonomic nervous system. Sympathetic nervous activity decreases blood flow to the kidney, making more blood available to other areas of the body during times of stress. The arteriolar myogenic mechanism maintains a steady blood flow by causing arteriolar smooth muscle to contract when blood pressure increases and causing it to relax when blood pressure decreases. Tubuloglomerular feedback involves paracrine signaling at the JGA to cause vasoconstriction or vasodilation to maintain a steady rate of blood flow.
25.8 Endocrine Regulation of Kidney Function
Endocrine hormones act from a distance and paracrine hormones act locally. The renal enzyme renin converts angiotensinogen into angiotensin I. The lung enzyme, ACE, converts angiotensin I into active angiotensin II. Angiotensin II is an active vasoconstrictor that increases blood pressure. Angiotensin II also stimulates aldosterone release from the adrenal cortex, causing the collecting duct to retain Na+, which promotes water retention and a longer-term rise in blood pressure. ADH promotes water recovery by the collecting ducts by stimulating the insertion of aquaporin water channels into cell membranes. Endothelins are elevated in cases of diabetic kidney disease, increasing Na+ retention and decreasing GFR. Natriuretic hormones, released primarily from the atria of the heart in response to stretching of the atrial walls, stimulate Na+ excretion and thereby decrease blood pressure. PTH stimulates the final step in the formation of active vitamin D3 and reduces phosphate reabsorption, resulting in higher circulating Ca++ levels.
25.9 Regulation of Fluid Volume and Composition
The major hormones regulating body fluids are ADH, aldosterone and ANH. Progesterone is similar in structure to aldosterone and can bind to and weakly stimulate aldosterone receptors, providing a similar but diminished response. Blood pressure is a reflection of blood volume and is monitored by baroreceptors in the aortic arch and carotid sinuses. When blood pressure increases, more action potentials are sent to the central nervous system, resulting in greater vasodilation, greater GFR, and more water lost in the urine. ANH is released by the cardiomyocytes when blood pressure increases, causing Na+ and water loss. ADH at high levels causes vasoconstriction in addition to its action on the collecting ducts to recover more water. Diuretics increase urine volume. Mechanisms for controlling Na+ concentration in the blood include the renin–angiotensin–aldosterone system and ADH. When Na+ is retained, K+ is excreted; when Na+ is lost, K+ is retained. When circulating Ca++ decreases, PTH stimulates the reabsorption of Ca++ and inhibits reabsorption of HPO2−4HPO42−2, and excretion of acid or base by the kidneys. The breakdown of amino acids produces ammonia. Most ammonia is converted into less-toxic urea in the liver and excreted in the urine. Regulation of drugs is by glomerular filtration, tubular secretion, and tubular reabsorption.
25.10 The Urinary System and Homeostasis
The effects of failure of parts of the urinary system may range from inconvenient (incontinence) to fatal (loss of filtration and many others). The kidneys catalyze the final reaction in the synthesis of active vitamin D that in turn helps regulate Ca++. The kidney hormone EPO stimulates erythrocyte development and promotes adequate O2 transport. The kidneys help regulate blood pressure through Na+ and water retention and loss. The kidneys work with the adrenal cortex, lungs, and liver in the renin–angiotensin–aldosterone system to regulate blood pressure. They regulate osmolarity of the blood by regulating both solutes and water. Three electrolytes are more closely regulated than others: Na+, Ca++, and K+. The kidneys share pH regulation with the lungs and plasma buffers, so that proteins can preserve their three-dimensional conformation and thus their function.
Review Questions
Diabetes insipidus or diabetes mellitus would most likely be indicated by ________.
- anuria
- polyuria
- oliguria
- none of the above
The color of urine is determined mainly by ________.
- diet
- filtration rate
- byproducts of red blood cell breakdown
- filtration efficiency
Production of less than 50 mL/day of urine is called ________.
- normal
- polyuria
- oliguria
- anuria
Peristaltic contractions occur in the ________.
- urethra
- bladder
- ureters
- urethra, bladder, and ureters
Somatic motor neurons must be ________ to relax the external urethral sphincter to allow urination.
- stimulated
- inhibited
Which part of the urinary system is not completely retroperitoneal?
- kidneys
- ureters
- bladder
- nephrons
The renal pyramids are separated from each other by extensions of the renal cortex called ________.
- renal medulla
- minor calyces
- medullary cortices
- renal columns
The primary structure found within the medulla is the ________.
- loop of Henle
- minor calyces
- portal system
- ureter
The right kidney is slightly lower because ________.
- it is displaced by the liver
- it is displace by the heart
- it is slightly smaller
- it needs protection of the lower ribs
Blood filtrate is captured in the lumen of the ________.
- glomerulus
- Bowman’s capsule
- calyces
- renal papillae
What are the names of the capillaries following the efferent arteriole?
- arcuate and medullary
- interlobar and interlobular
- peritubular and vasa recta
- peritubular and medullary
The functional unit of the kidney is called ________.
- the renal hilus
- the renal corpuscle
- the nephron
- Bowman’s capsule
________ pressure must be greater on the capillary side of the filtration membrane to achieve filtration.
- Osmotic
- Hydrostatic
Production of urine to modify plasma makeup is the result of ________.
- filtration
- absorption
- secretion
- filtration, absorption, and secretion
Systemic blood pressure must stay above 60 so that the proper amount of filtration occurs.
- true
- false
Aquaporin channels are only found in the collecting duct.
- true
- false
Most absorption and secretion occurs in this part of the nephron.
- proximal convoluted tubule
- descending loop of Henle
- ascending loop of Henle
- distal convoluted tubule
- collecting ducts
The fine tuning of water recovery or disposal occurs in ________.
- the proximal convoluted tubule
- the collecting ducts
- the ascending loop of Henle
- the distal convoluted tubule
Vasodilation of blood vessels to the kidneys is due to ________.
- more frequent action potentials
- less frequent action potentials
When blood pressure increases, blood vessels supplying the kidney will ________ to mount a steady rate of filtration.
- contract
- relax
Which of these three paracrine chemicals cause vasodilation?
- ATP
- adenosine
- nitric oxide
What hormone directly opposes the actions of natriuretic hormones?
- renin
- nitric oxide
- dopamine
- aldosterone
Which of these is a vasoconstrictor?
- nitric oxide
- natriuretic hormone
- bradykinin
- angiotensin II
What signal causes the heart to secrete atrial natriuretic hormone?
- increased blood pressure
- decreased blood pressure
- increased Na+ levels
- decreased Na+ levels
Which of these beverages does not have a diuretic effect?
- tea
- coffee
- alcohol
- milk
Progesterone can bind to receptors for which hormone that, when released, activates water retention?
- aldosterone
- ADH
- PTH
- ANH
Renin is released in response to ________.
- increased blood pressure
- decreased blood pressure
- ACE
- diuretics
Which step in vitamin D production does the kidney perform?
- converts cholecalciferol into calcidiol
- converts calcidiol into calcitriol
- stores vitamin D
- none of these
Which hormone does the kidney produce that stimulates red blood cell production?
- thrombopoeitin
- vitamin D
- EPO
- renin
If there were no aquaporin channels in the collecting duct, ________.
- you would develop systemic edema
- you would retain excess Na+
- you would lose vitamins and electrolytes
- you would suffer severe dehydration
Critical Thinking Questions
What is suggested by the presence of white blood cells found in the urine?
32.Both diabetes mellitus and diabetes insipidus produce large urine volumes, but how would other characteristics of the urine differ between the two diseases?
33.Why are females more likely to contract bladder infections than males?
34.Describe how forceful urination is accomplished.
35.What anatomical structures provide protection to the kidney?
36.How does the renal portal system differ from the hypothalamo–hypophyseal and digestive portal systems?
37.Name the structures found in the renal hilum.
38.Which structures make up the renal corpuscle?
39.What are the major structures comprising the filtration membrane?
40.Give the formula for net filtration pressure.
41.Name at least five symptoms of kidney failure.
42.Which vessels and what part of the nephron are involved in countercurrent multiplication?
43.Give the approximate osmolarity of fluid in the proximal convoluted tubule, deepest part of the loop of Henle, distal convoluted tubule, and the collecting ducts.
44.Explain what happens to Na+ concentration in the nephron when GFR increases.
45.If you want the kidney to excrete more Na+ in the urine, what do you want the blood flow to do?
46.What organs produce which hormones or enzymes in the renin–angiotensin system?
47.PTH affects absorption and reabsorption of what?
48.Why is ADH also called vasopressin?
49.How can glucose be a diuretic?
50.How does lack of protein in the blood cause edema?
51.Which three electrolytes are most closely regulated by the kidney?
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https://oercommons.org/courseware/lesson/58774/overview
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Fluid, Electrolyte, and Acid-Base Balance
Introduction
Figure 26.1 Venus Williams Perspiring on the Tennis Court The body has critically important mechanisms for balancing the intake and output of bodily fluids. An athlete must continuously replace the water and electrolytes lost in sweat. (credit: “Edwin Martinez1”/Wikimedia Commons)
CHAPTER OBJECTIVES
After studying this chapter, you will be able to:
- Identify the body’s main fluid compartments
- Define plasma osmolality and identify two ways in which plasma osmolality is maintained
- Identify the six ions most important to the function of the body
- Define buffer and discuss the role of buffers in the body
- Explain why bicarbonate must be conserved rather than reabsorbed in the kidney
- Identify the normal range of blood pH and name the conditions where one has a blood pH that is either too high or too low
Homeostasis, or the maintenance of constant conditions in the body, is a fundamental property of all living things. In the human body, the substances that participate in chemical reactions must remain within narrows ranges of concentration. Too much or too little of a single substance can disrupt your bodily functions. Because metabolism relies on reactions that are all interconnected, any disruption might affect multiple organs or even organ systems. Water is the most ubiquitous substance in the chemical reactions of life. The interactions of various aqueous solutions—solutions in which water is the solvent—are continuously monitored and adjusted by a large suite of interconnected feedback systems in your body. Understanding the ways in which the body maintains these critical balances is key to understanding good health.
Body Fluids and Fluid Compartments
- Explain the importance of water in the body
- Contrast the composition of the intracellular fluid with that of the extracellular fluid
- Explain the importance of protein channels in the movement of solutes
- Identify the causes and symptoms of edema
The chemical reactions of life take place in aqueous solutions. The dissolved substances in a solution are called solutes. In the human body, solutes vary in different parts of the body, but may include proteins—including those that transport lipids, carbohydrates, and, very importantly, electrolytes. Often in medicine, a mineral dissociated from a salt that carries an electrical charge (an ion) is called and electrolyte. For instance, sodium ions (Na+) and chloride ions (Cl-) are often referred to as electrolytes.
In the body, water moves through semi-permeable membranes of cells and from one compartment of the body to another by a process called osmosis. Osmosis is basically the diffusion of water from regions of higher concentration to regions of lower concentration, along an osmotic gradient across a semi-permeable membrane. As a result, water will move into and out of cells and tissues, depending on the relative concentrations of the water and solutes found there. An appropriate balance of solutes inside and outside of cells must be maintained to ensure normal function.
Body Water Content
Human beings are mostly water, ranging from about 75 percent of body mass in infants to about 50–60 percent in adult men and women, to as low as 45 percent in old age. The percent of body water changes with development, because the proportions of the body given over to each organ and to muscles, fat, bone, and other tissues change from infancy to adulthood (Figure 26.2). Your brain and kidneys have the highest proportions of water, which composes 80–85 percent of their masses. In contrast, teeth have the lowest proportion of water, at 8–10 percent.
Figure 26.2 Water Content of the Body’s Organs and Tissues Water content varies in different body organs and tissues, from as little as 8 percent in the teeth to as much as 85 percent in the brain.
Fluid Compartments
Body fluids can be discussed in terms of their specific fluid compartment, a location that is largely separate from another compartment by some form of a physical barrier. The intracellular fluid (ICF) compartment is the system that includes all fluid enclosed in cells by their plasma membranes. Extracellular fluid (ECF) surrounds all cells in the body. Extracellular fluid has two primary constituents: the fluid component of the blood (called plasma) and the interstitial fluid (IF) that surrounds all cells not in the blood (Figure 26.3).
Figure 26.3 Fluid Compartments in the Human Body The intracellular fluid (ICF) is the fluid within cells. The interstitial fluid (IF) is part of the extracellular fluid (ECF) between the cells. Blood plasma is the second part of the ECF. Materials travel between cells and the plasma in capillaries through the IF.
Intracellular Fluid
The ICF lies within cells and is the principal component of the cytosol/cytoplasm. The ICF makes up about 60 percent of the total water in the human body, and in an average-size adult male, the ICF accounts for about 25 liters (seven gallons) of fluid (Figure 26.4). This fluid volume tends to be very stable, because the amount of water in living cells is closely regulated. If the amount of water inside a cell falls to a value that is too low, the cytosol becomes too concentrated with solutes to carry on normal cellular activities; if too much water enters a cell, the cell may burst and be destroyed.
Figure 26.4 A Pie Graph Showing the Proportion of Total Body Fluid in Each of the Body’s Fluid Compartments Most of the water in the body is intracellular fluid. The second largest volume is the interstitial fluid, which surrounds cells that are not blood cells.
Extracellular Fluid
The ECF accounts for the other one-third of the body’s water content. Approximately 20 percent of the ECF is found in plasma. Plasma travels through the body in blood vessels and transports a range of materials, including blood cells, proteins (including clotting factors and antibodies), electrolytes, nutrients, gases, and wastes. Gases, nutrients, and waste materials travel between capillaries and cells through the IF. Cells are separated from the IF by a selectively permeable cell membrane that helps regulate the passage of materials between the IF and the interior of the cell.
The body has other water-based ECF. These include the cerebrospinal fluid that bathes the brain and spinal cord, lymph, the synovial fluid in joints, the pleural fluid in the pleural cavities, the pericardial fluid in the cardiac sac, the peritoneal fluid in the peritoneal cavity, and the aqueous humor of the eye. Because these fluids are outside of cells, these fluids are also considered components of the ECF compartment.
Composition of Body Fluids
The compositions of the two components of the ECF—plasma and IF—are more similar to each other than either is to the ICF (Figure 26.5). Blood plasma has high concentrations of sodium, chloride, bicarbonate, and protein. The IF has high concentrations of sodium, chloride, and bicarbonate, but a relatively lower concentration of protein. In contrast, the ICF has elevated amounts of potassium, phosphate, magnesium, and protein. Overall, the ICF contains high concentrations of potassium and phosphate (HPO2−4HPO42−
Figure 26.5 The Concentrations of Different Elements in Key Bodily Fluids The graph shows the composition of the ICF, IF, and plasma. The compositions of plasma and IF are similar to one another but are quite different from the composition of the ICF.
INTERACTIVE LINK
Watch this video to learn more about body fluids, fluid compartments, and electrolytes. When blood volume decreases due to sweating, from what source is water taken in by the blood?
Most body fluids are neutral in charge. Thus, cations, or positively charged ions, and anions, or negatively charged ions, are balanced in fluids. As seen in the previous graph, sodium (Na+) ions and chloride (Cl-) ions are concentrated in the ECF of the body, whereas potassium (K+) ions are concentrated inside cells. Although sodium and potassium can “leak” through “pores” into and out of cells, respectively, the high levels of potassium and low levels of sodium in the ICF are maintained by sodium-potassium pumps in the cell membranes. These pumps use the energy supplied by ATP to pump sodium out of the cell and potassium into the cell (Figure 26.6).
Figure 26.6 The Sodium-Potassium Pump The sodium-potassium pump is powered by ATP to transfer sodium out of the cytoplasm and into the ECF. The pump also transfers potassium out of the ECF and into the cytoplasm. (credit: modification of work by Mariana Ruiz Villarreal)
Fluid Movement between Compartments
Hydrostatic pressure, the force exerted by a fluid against a wall, causes movement of fluid between compartments. The hydrostatic pressure of blood is the pressure exerted by blood against the walls of the blood vessels by the pumping action of the heart. In capillaries, hydrostatic pressure (also known as capillary blood pressure) is higher than the opposing “colloid osmotic pressure” in blood—a “constant” pressure primarily produced by circulating albumin—at the arteriolar end of the capillary (Figure 26.7). This pressure forces plasma and nutrients out of the capillaries and into surrounding tissues. Fluid and the cellular wastes in the tissues enter the capillaries at the venule end, where the hydrostatic pressure is less than the osmotic pressure in the vessel. Filtration pressure squeezes fluid from the plasma in the blood to the IF surrounding the tissue cells. The surplus fluid in the interstitial space that is not returned directly back to the capillaries is drained from tissues by the lymphatic system, and then re-enters the vascular system at the subclavian veins.
Figure 26.7 Capillary Exchange Net filtration occurs near the arterial end of the capillary since capillary hydrostatic pressure (CHP) is greater than blood colloidal osmotic pressure (BCOP). There is no net movement of fluid near the midpoint of the capillary since CHP = BCOP. Net reabsorption occurs near the venous end of the capillary since BCOP is greater than CHP.
INTERACTIVE LINK
Watch this video to see an explanation of the dynamics of fluid in the body’s compartments. What happens in the tissue when capillary blood pressure is less than osmotic pressure?
Hydrostatic pressure is especially important in governing the movement of water in the nephrons of the kidneys to ensure proper filtering of the blood to form urine. As hydrostatic pressure in the kidneys increases, the amount of water leaving the capillaries also increases, and more urine filtrate is formed. If hydrostatic pressure in the kidneys drops too low, as can happen in dehydration, the functions of the kidneys will be impaired, and less nitrogenous wastes will be removed from the bloodstream. Extreme dehydration can result in kidney failure.
Fluid also moves between compartments along an osmotic gradient. Recall that an osmotic gradient is produced by the difference in concentration of all solutes on either side of a semi-permeable membrane. The magnitude of the osmotic gradient is proportional to the difference in the concentration of solutes on one side of the cell membrane to that on the other side. Water will move by osmosis from the side where its concentration is high (and the concentration of solute is low) to the side of the membrane where its concentration is low (and the concentration of solute is high). In the body, water moves by osmosis from plasma to the IF (and the reverse) and from the IF to the ICF (and the reverse). In the body, water moves constantly into and out of fluid compartments as conditions change in different parts of the body.
For example, if you are sweating, you will lose water through your skin. Sweating depletes your tissues of water and increases the solute concentration in those tissues. As this happens, water diffuses from your blood into sweat glands and surrounding skin tissues that have become dehydrated because of the osmotic gradient. Additionally, as water leaves the blood, it is replaced by the water in other tissues throughout your body that are not dehydrated. If this continues, dehydration spreads throughout the body. When a dehydrated person drinks water and rehydrates, the water is redistributed by the same gradient, but in the opposite direction, replenishing water in all of the tissues.
Solute Movement between Compartments
The movement of some solutes between compartments is active, which consumes energy and is an active transport process, whereas the movement of other solutes is passive, which does not require energy. Active transport allows cells to move a specific substance against its concentration gradient through a membrane protein, requiring energy in the form of ATP. For example, the sodium-potassium pump employs active transport to pump sodium out of cells and potassium into cells, with both substances moving against their concentration gradients.
Passive transport of a molecule or ion depends on its ability to pass through the membrane, as well as the existence of a concentration gradient that allows the molecules to diffuse from an area of higher concentration to an area of lower concentration. Some molecules, like gases, lipids, and water itself (which also utilizes water channels in the membrane called aquaporins), slip fairly easily through the cell membrane; others, including polar molecules like glucose, amino acids, and ions do not. Some of these molecules enter and leave cells using facilitated transport, whereby the molecules move down a concentration gradient through specific protein channels in the membrane. This process does not require energy. For example, glucose is transferred into cells by glucose transporters that use facilitated transport (Figure 26.8).
Figure 26.8 Facilitated Diffusion Glucose molecules use facilitated diffusion to move down a concentration gradient through the carrier protein channels in the membrane. (credit: modification of work by Mariana Ruiz Villarreal)
DISORDERS OF THE...
Fluid Balance: Edema
Edema is the accumulation of excess water in the tissues. It is most common in the soft tissues of the extremities. The physiological causes of edema include water leakage from blood capillaries. Edema is almost always caused by an underlying medical condition, by the use of certain therapeutic drugs, by pregnancy, by localized injury, or by an allergic reaction. In the limbs, the symptoms of edema include swelling of the subcutaneous tissues, an increase in the normal size of the limb, and stretched, tight skin. One quick way to check for subcutaneous edema localized in a limb is to press a finger into the suspected area. Edema is likely if the depression persists for several seconds after the finger is removed (which is called “pitting”).
Pulmonary edema is excess fluid in the air sacs of the lungs, a common symptom of heart and/or kidney failure. People with pulmonary edema likely will experience difficulty breathing, and they may experience chest pain. Pulmonary edema can be life threatening, because it compromises gas exchange in the lungs, and anyone having symptoms should immediately seek medical care.
In pulmonary edema resulting from heart failure, excessive leakage of water occurs because fluids get “backed up” in the pulmonary capillaries of the lungs, when the left ventricle of the heart is unable to pump sufficient blood into the systemic circulation. Because the left side of the heart is unable to pump out its normal volume of blood, the blood in the pulmonary circulation gets “backed up,” starting with the left atrium, then into the pulmonary veins, and then into pulmonary capillaries. The resulting increased hydrostatic pressure within pulmonary capillaries, as blood is still coming in from the pulmonary arteries, causes fluid to be pushed out of them and into lung tissues.
Other causes of edema include damage to blood vessels and/or lymphatic vessels, or a decrease in osmotic pressure in chronic and severe liver disease, where the liver is unable to manufacture plasma proteins (Figure 26.9). A decrease in the normal levels of plasma proteins results in a decrease of colloid osmotic pressure (which counterbalances the hydrostatic pressure) in the capillaries. This process causes loss of water from the blood to the surrounding tissues, resulting in edema.
Figure 26.9 Edema An allergic reaction can cause capillaries in the hand to leak excess fluid that accumulates in the tissues. (credit: Jane Whitney)
Mild, transient edema of the feet and legs may be caused by sitting or standing in the same position for long periods of time, as in the work of a toll collector or a supermarket cashier. This is because deep veins in the lower limbs rely on skeletal muscle contractions to push on the veins and thus “pump” blood back to the heart. Otherwise, the venous blood pools in the lower limbs and can leak into surrounding tissues.
Medications that can result in edema include vasodilators, calcium channel blockers used to treat hypertension, non-steroidal anti-inflammatory drugs, estrogen therapies, and some diabetes medications. Underlying medical conditions that can contribute to edema include congestive heart failure, kidney damage and kidney disease, disorders that affect the veins of the legs, and cirrhosis and other liver disorders.
Therapy for edema usually focuses on elimination of the cause. Activities that can reduce the effects of the condition include appropriate exercises to keep the blood and lymph flowing through the affected areas. Other therapies include elevation of the affected part to assist drainage, massage and compression of the areas to move the fluid out of the tissues, and decreased salt intake to decrease sodium and water retention.
Water Balance
- Explain how water levels in the body influence the thirst cycle
- Identify the main route by which water leaves the body
- Describe the role of ADH and its effect on body water levels
- Define dehydration and identify common causes of dehydration
On a typical day, the average adult will take in about 2500 mL (almost 3 quarts) of aqueous fluids. Although most of the intake comes through the digestive tract, about 230 mL (8 ounces) per day is generated metabolically, in the last steps of aerobic respiration. Additionally, each day about the same volume (2500 mL) of water leaves the body by different routes; most of this lost water is removed as urine. The kidneys also can adjust blood volume though mechanisms that draw water out of the filtrate and urine. The kidneys can regulate water levels in the body; they conserve water if you are dehydrated, and they can make urine more dilute to expel excess water if necessary. Water is lost through the skin through evaporation from the skin surface without overt sweating and from air expelled from the lungs. This type of water loss is called insensible water loss because a person is usually unaware of it.
Regulation of Water Intake
Osmolality is the ratio of solutes in a solution to a volume of solvent in a solution. Plasma osmolality is thus the ratio of solutes to water in blood plasma. A person’s plasma osmolality value reflects his or her state of hydration. A healthy body maintains plasma osmolality within a narrow range, by employing several mechanisms that regulate both water intake and output.
Drinking water is considered voluntary. So how is water intake regulated by the body? Consider someone who is experiencing dehydration, a net loss of water that results in insufficient water in blood and other tissues. The water that leaves the body, as exhaled air, sweat, or urine, is ultimately extracted from blood plasma. As the blood becomes more concentrated, the thirst response—a sequence of physiological processes—is triggered (Figure 26.10). Osmoreceptors are sensory receptors in the thirst center in the hypothalamus that monitor the concentration of solutes (osmolality) of the blood. If blood osmolality increases above its ideal value, the hypothalamus transmits signals that result in a conscious awareness of thirst. The person should (and normally does) respond by drinking water. The hypothalamus of a dehydrated person also releases antidiuretic hormone (ADH) through the posterior pituitary gland. ADH signals the kidneys to recover water from urine, effectively diluting the blood plasma. To conserve water, the hypothalamus of a dehydrated person also sends signals via the sympathetic nervous system to the salivary glands in the mouth. The signals result in a decrease in watery, serous output (and an increase in stickier, thicker mucus output). These changes in secretions result in a “dry mouth” and the sensation of thirst.
Figure 26.10 A Flowchart Showing the Thirst Response The thirst response begins when osmoreceptors detect a decrease in water levels in the blood.
Decreased blood volume resulting from water loss has two additional effects. First, baroreceptors, blood-pressure receptors in the arch of the aorta and the carotid arteries in the neck, detect a decrease in blood pressure that results from decreased blood volume. The heart is ultimately signaled to increase its rate and/or strength of contractions to compensate for the lowered blood pressure.
Second, the kidneys have a renin-angiotensin hormonal system that increases the production of the active form of the hormone angiotensin II, which helps stimulate thirst, but also stimulates the release of the hormone aldosterone from the adrenal glands. Aldosterone increases the reabsorption of sodium in the distal tubules of the nephrons in the kidneys, and water follows this reabsorbed sodium back into the blood.
If adequate fluids are not consumed, dehydration results and a person’s body contains too little water to function correctly. A person who repeatedly vomits or who has diarrhea may become dehydrated, and infants, because their body mass is so low, can become dangerously dehydrated very quickly. Endurance athletes such as distance runners often become dehydrated during long races. Dehydration can be a medical emergency, and a dehydrated person may lose consciousness, become comatose, or die, if his or her body is not rehydrated quickly.
Regulation of Water Output
Water loss from the body occurs predominantly through the renal system. A person produces an average of 1.5 liters (1.6 quarts) of urine per day. Although the volume of urine varies in response to hydration levels, there is a minimum volume of urine production required for proper bodily functions. The kidney excretes 100 to 1200 milliosmoles of solutes per day to rid the body of a variety of excess salts and other water-soluble chemical wastes, most notably creatinine, urea, and uric acid. Failure to produce the minimum volume of urine means that metabolic wastes cannot be effectively removed from the body, a situation that can impair organ function. The minimum level of urine production necessary to maintain normal function is about 0.47 liters (0.5 quarts) per day.
The kidneys also must make adjustments in the event of ingestion of too much fluid. Diuresis, which is the production of urine in excess of normal levels, begins about 30 minutes after drinking a large quantity of fluid. Diuresis reaches a peak after about 1 hour, and normal urine production is reestablished after about 3 hours.
Role of ADH
Antidiuretic hormone (ADH), also known as vasopressin, controls the amount of water reabsorbed from the collecting ducts and tubules in the kidney. This hormone is produced in the hypothalamus and is delivered to the posterior pituitary for storage and release (Figure 26.11). When the osmoreceptors in the hypothalamus detect an increase in the concentration of blood plasma, the hypothalamus signals the release of ADH from the posterior pituitary into the blood.
Figure 26.11 Antidiuretic Hormone (ADH) ADH is produced in the hypothalamus and released by the posterior pituitary gland. It causes the kidneys to retain water, constricts arterioles in the peripheral circulation, and affects some social behaviors in mammals.
ADH has two major effects. It constricts the arterioles in the peripheral circulation, which reduces the flow of blood to the extremities and thereby increases the blood supply to the core of the body. ADH also causes the epithelial cells that line the renal collecting tubules to move water channel proteins, called aquaporins, from the interior of the cells to the apical surface, where these proteins are inserted into the cell membrane (Figure 26.12). The result is an increase in the water permeability of these cells and, thus, a large increase in water passage from the urine through the walls of the collecting tubules, leading to more reabsorption of water into the bloodstream. When the blood plasma becomes less concentrated and the level of ADH decreases, aquaporins are removed from collecting tubule cell membranes, and the passage of water out of urine and into the blood decreases.
Figure 26.12 Aquaporins The binding of ADH to receptors on the cells of the collecting tubule results in aquaporins being inserted into the plasma membrane, shown in the lower cell. This dramatically increases the flow of water out of the tubule and into the bloodstream.
A diuretic is a compound that increases urine output and therefore decreases water conservation by the body. Diuretics are used to treat hypertension, congestive heart failure, and fluid retention associated with menstruation. Alcohol acts as a diuretic by inhibiting the release of ADH. Additionally, caffeine, when consumed in high concentrations, acts as a diuretic.
Electrolyte Balance
- List the role of the six most important electrolytes in the body
- Name the disorders associated with abnormally high and low levels of the six electrolytes
- Identify the predominant extracellular anion
- Describe the role of aldosterone on the level of water in the body
The body contains a large variety of ions, or electrolytes, which perform a variety of functions. Some ions assist in the transmission of electrical impulses along cell membranes in neurons and muscles. Other ions help to stabilize protein structures in enzymes. Still others aid in releasing hormones from endocrine glands. All of the ions in plasma contribute to the osmotic balance that controls the movement of water between cells and their environment.
Electrolytes in living systems include sodium, potassium, chloride, bicarbonate, calcium, phosphate, magnesium, copper, zinc, iron, manganese, molybdenum, copper, and chromium. In terms of body functioning, six electrolytes are most important: sodium, potassium, chloride, bicarbonate, calcium, and phosphate.
Roles of Electrolytes
These six ions aid in nerve excitability, endocrine secretion, membrane permeability, buffering body fluids, and controlling the movement of fluids between compartments. These ions enter the body through the digestive tract. More than 90 percent of the calcium and phosphate that enters the body is incorporated into bones and teeth, with bone serving as a mineral reserve for these ions. In the event that calcium and phosphate are needed for other functions, bone tissue can be broken down to supply the blood and other tissues with these minerals. Phosphate is a normal constituent of nucleic acids; hence, blood levels of phosphate will increase whenever nucleic acids are broken down.
Excretion of ions occurs mainly through the kidneys, with lesser amounts lost in sweat and in feces. Excessive sweating may cause a significant loss, especially of sodium and chloride. Severe vomiting or diarrhea will cause a loss of chloride and bicarbonate ions. Adjustments in respiratory and renal functions allow the body to regulate the levels of these ions in the ECF.
Table 26.1 lists the reference values for blood plasma, cerebrospinal fluid (CSF), and urine for the six ions addressed in this section. In a clinical setting, sodium, potassium, and chloride are typically analyzed in a routine urine sample. In contrast, calcium and phosphate analysis requires a collection of urine across a 24-hour period, because the output of these ions can vary considerably over the course of a day. Urine values reflect the rates of excretion of these ions. Bicarbonate is the one ion that is not normally excreted in urine; instead, it is conserved by the kidneys for use in the body’s buffering systems.
Electrolyte and Ion Reference Values
| Name | Chemical symbol | Plasma | CSF | Urine |
|---|---|---|---|---|
| Sodium | Na+ | 136.00–146.00 (mM) | 138.00–150.00 (mM) | 40.00–220.00 (mM) |
| Potassium | K+ | 3.50–5.00 (mM) | 0.35–3.5 (mM) | 25.00–125.00 (mM) |
| Chloride | Cl- | 98.00–107.00 (mM) | 118.00–132.00 (mM) | 110.00–250.00 (mM) |
| Bicarbonate | HCO3- | 22.00–29.00 (mM) | ------ | ------ |
| Calcium | Ca++ | 2.15–2.55 (mmol/day) | ------ | Up to 7.49 (mmol/day) |
| Phosphate | HPO2−4HPO42− | 0.81–1.45 (mmol/day) | ------ | 12.90–42.00 (mmol/day) |
Table 26.1
Sodium
Sodium is the major cation of the extracellular fluid. It is responsible for one-half of the osmotic pressure gradient that exists between the interior of cells and their surrounding environment. People eating a typical Western diet, which is very high in NaCl, routinely take in 130 to 160 mmol/day of sodium, but humans require only 1 to 2 mmol/day. This excess sodium appears to be a major factor in hypertension (high blood pressure) in some people. Excretion of sodium is accomplished primarily by the kidneys. Sodium is freely filtered through the glomerular capillaries of the kidneys, and although much of the filtered sodium is reabsorbed in the proximal convoluted tubule, some remains in the filtrate and urine, and is normally excreted.
Hyponatremia is a lower-than-normal concentration of sodium, usually associated with excess water accumulation in the body, which dilutes the sodium. An absolute loss of sodium may be due to a decreased intake of the ion coupled with its continual excretion in the urine. An abnormal loss of sodium from the body can result from several conditions, including excessive sweating, vomiting, or diarrhea; the use of diuretics; excessive production of urine, which can occur in diabetes; and acidosis, either metabolic acidosis or diabetic ketoacidosis.
A relative decrease in blood sodium can occur because of an imbalance of sodium in one of the body’s other fluid compartments, like IF, or from a dilution of sodium due to water retention related to edema or congestive heart failure. At the cellular level, hyponatremia results in increased entry of water into cells by osmosis, because the concentration of solutes within the cell exceeds the concentration of solutes in the now-diluted ECF. The excess water causes swelling of the cells; the swelling of red blood cells—decreasing their oxygen-carrying efficiency and making them potentially too large to fit through capillaries—along with the swelling of neurons in the brain can result in brain damage or even death.
Hypernatremia is an abnormal increase of blood sodium. It can result from water loss from the blood, resulting in the hemoconcentration of all blood constituents. Hormonal imbalances involving ADH and aldosterone may also result in higher-than-normal sodium values.
Potassium
Potassium is the major intracellular cation. It helps establish the resting membrane potential in neurons and muscle fibers after membrane depolarization and action potentials. In contrast to sodium, potassium has very little effect on osmotic pressure. The low levels of potassium in blood and CSF are due to the sodium-potassium pumps in cell membranes, which maintain the normal potassium concentration gradients between the ICF and ECF. The recommendation for daily intake/consumption of potassium is 4700 mg. Potassium is excreted, both actively and passively, through the renal tubules, especially the distal convoluted tubule and collecting ducts. Potassium participates in the exchange with sodium in the renal tubules under the influence of aldosterone, which also relies on basolateral sodium-potassium pumps.
Hypokalemia is an abnormally low potassium blood level. Similar to the situation with hyponatremia, hypokalemia can occur because of either an absolute reduction of potassium in the body or a relative reduction of potassium in the blood due to the redistribution of potassium. An absolute loss of potassium can arise from decreased intake, frequently related to starvation. It can also come about from vomiting, diarrhea, or alkalosis.
Some insulin-dependent diabetic patients experience a relative reduction of potassium in the blood from the redistribution of potassium. When insulin is administered and glucose is taken up by cells, potassium passes through the cell membrane along with glucose, decreasing the amount of potassium in the blood and IF, which can cause hyperpolarization of the cell membranes of neurons, reducing their responses to stimuli.
Hyperkalemia, an elevated potassium blood level, also can impair the function of skeletal muscles, the nervous system, and the heart. Hyperkalemia can result from increased dietary intake of potassium. In such a situation, potassium from the blood ends up in the ECF in abnormally high concentrations. This can result in a partial depolarization (excitation) of the plasma membrane of skeletal muscle fibers, neurons, and cardiac cells of the heart, and can also lead to an inability of cells to repolarize. For the heart, this means that it won’t relax after a contraction, and will effectively “seize” and stop pumping blood, which is fatal within minutes. Because of such effects on the nervous system, a person with hyperkalemia may also exhibit mental confusion, numbness, and weakened respiratory muscles.
Chloride
Chloride is the predominant extracellular anion. Chloride is a major contributor to the osmotic pressure gradient between the ICF and ECF, and plays an important role in maintaining proper hydration. Chloride functions to balance cations in the ECF, maintaining the electrical neutrality of this fluid. The paths of secretion and reabsorption of chloride ions in the renal system follow the paths of sodium ions.
Hypochloremia, or lower-than-normal blood chloride levels, can occur because of defective renal tubular absorption. Vomiting, diarrhea, and metabolic acidosis can also lead to hypochloremia. Hyperchloremia, or higher-than-normal blood chloride levels, can occur due to dehydration, excessive intake of dietary salt (NaCl) or swallowing of sea water, aspirin intoxication, congestive heart failure, and the hereditary, chronic lung disease, cystic fibrosis. In people who have cystic fibrosis, chloride levels in sweat are two to five times those of normal levels, and analysis of sweat is often used in the diagnosis of the disease.
INTERACTIVE LINK
Read this article for an explanation of the effect of seawater on humans. What effect does drinking seawater have on the body?
Bicarbonate
Bicarbonate is the second most abundant anion in the blood. Its principal function is to maintain your body’s acid-base balance by being part of buffer systems. This role will be discussed in a different section.
Bicarbonate ions result from a chemical reaction that starts with carbon dioxide (CO2) and water, two molecules that are produced at the end of aerobic metabolism. Only a small amount of CO2 can be dissolved in body fluids. Thus, over 90 percent of the CO2 is converted into bicarbonate ions, HCO3–, through the following reactions:
CO2 + H2O↔H2CO3↔HCO3- + H+CO2 + H2O↔H2CO3↔HCO3- + H+
The bidirectional arrows indicate that the reactions can go in either direction, depending on the concentrations of the reactants and products. Carbon dioxide is produced in large amounts in tissues that have a high metabolic rate. Carbon dioxide is converted into bicarbonate in the cytoplasm of red blood cells through the action of an enzyme called carbonic anhydrase. Bicarbonate is transported in the blood. Once in the lungs, the reactions reverse direction, and CO2 is regenerated from bicarbonate to be exhaled as metabolic waste.
Calcium
About two pounds of calcium in your body are bound up in bone, which provides hardness to the bone and serves as a mineral reserve for calcium and its salts for the rest of the tissues. Teeth also have a high concentration of calcium within them. A little more than one-half of blood calcium is bound to proteins, leaving the rest in its ionized form. Calcium ions, Ca2+, are necessary for muscle contraction, enzyme activity, and blood coagulation. In addition, calcium helps to stabilize cell membranes and is essential for the release of neurotransmitters from neurons and of hormones from endocrine glands.
Calcium is absorbed through the intestines under the influence of activated vitamin D. A deficiency of vitamin D leads to a decrease in absorbed calcium and, eventually, a depletion of calcium stores from the skeletal system, potentially leading to rickets in children and osteomalacia in adults, contributing to osteoporosis.
Hypocalcemia, or abnormally low calcium blood levels, is seen in hypoparathyroidism, which may follow the removal of the thyroid gland, because the four nodules of the parathyroid gland are embedded in it. Hypercalcemia, or abnormally high calcium blood levels, is seen in primary hyperparathyroidism. Some malignancies may also result in hypercalcemia.
Phosphate
Phosphate is present in the body in three ionic forms: H2PO4−H2PO4−, HPO2−4HPO42−, and PO3−4PO43−. The most common form is HPO2−4HPO42−. Bone and teeth bind up 85 percent of the body’s phosphate as part of calcium-phosphate salts. Phosphate is found in phospholipids, such as those that make up the cell membrane, and in ATP, nucleotides, and buffers.
Hypophosphatemia, or abnormally low phosphate blood levels, occurs with heavy use of antacids, during alcohol withdrawal, and during malnourishment. In the face of phosphate depletion, the kidneys usually conserve phosphate, but during starvation, this conservation is impaired greatly. Hyperphosphatemia, or abnormally increased levels of phosphates in the blood, occurs if there is decreased renal function or in cases of acute lymphocytic leukemia. Additionally, because phosphate is a major constituent of the ICF, any significant destruction of cells can result in dumping of phosphate into the ECF.
Regulation of Sodium and Potassium
Sodium is reabsorbed from the renal filtrate, and potassium is excreted into the filtrate in the renal collecting tubule. The control of this exchange is governed principally by two hormones—aldosterone and angiotensin II.
Aldosterone
Recall that aldosterone increases the excretion of potassium and the reabsorption of sodium in the distal tubule. Aldosterone is released if blood levels of potassium increase, if blood levels of sodium severely decrease, or if blood pressure decreases. Its net effect is to conserve and increase water levels in the plasma by reducing the excretion of sodium, and thus water, from the kidneys. In a negative feedback loop, increased osmolality of the ECF (which follows aldosterone-stimulated sodium absorption) inhibits the release of the hormone (Figure 26.13).
Figure 26.13 The Aldosterone Feedback Loop Aldosterone, which is released by the adrenal gland, facilitates reabsorption of Na+ and thus the reabsorption of water.
Angiotensin II
Angiotensin II causes vasoconstriction and an increase in systemic blood pressure. This action increases the glomerular filtration rate, resulting in more material filtered out of the glomerular capillaries and into Bowman’s capsule. Angiotensin II also signals an increase in the release of aldosterone from the adrenal cortex.
In the distal convoluted tubules and collecting ducts of the kidneys, aldosterone stimulates the synthesis and activation of the sodium-potassium pump (Figure 26.14). Sodium passes from the filtrate, into and through the cells of the tubules and ducts, into the ECF and then into capillaries. Water follows the sodium due to osmosis. Thus, aldosterone causes an increase in blood sodium levels and blood volume. Aldosterone’s effect on potassium is the reverse of that of sodium; under its influence, excess potassium is pumped into the renal filtrate for excretion from the body.
Figure 26.14 The Renin-Angiotensin System Angiotensin II stimulates the release of aldosterone from the adrenal cortex.
Regulation of Calcium and Phosphate
Calcium and phosphate are both regulated through the actions of three hormones: parathyroid hormone (PTH), dihydroxyvitamin D (calcitriol), and calcitonin. All three are released or synthesized in response to the blood levels of calcium.
PTH is released from the parathyroid gland in response to a decrease in the concentration of blood calcium. The hormone activates osteoclasts to break down bone matrix and release inorganic calcium-phosphate salts. PTH also increases the gastrointestinal absorption of dietary calcium by converting vitamin D into dihydroxyvitamin D (calcitriol), an active form of vitamin D that intestinal epithelial cells require to absorb calcium.
PTH raises blood calcium levels by inhibiting the loss of calcium through the kidneys. PTH also increases the loss of phosphate through the kidneys.
Calcitonin is released from the thyroid gland in response to elevated blood levels of calcium. The hormone increases the activity of osteoblasts, which remove calcium from the blood and incorporate calcium into the bony matrix.
Acid-Base Balance
- Identify the most powerful buffer system in the body
- Explain the way in which the respiratory system affects blood pH
Proper physiological functioning depends on a very tight balance between the concentrations of acids and bases in the blood. Acid-balance balance is measured using the pH scale, as shown in Figure 26.15. A variety of buffering systems permits blood and other bodily fluids to maintain a narrow pH range, even in the face of perturbations. A buffer is a chemical system that prevents a radical change in fluid pH by dampening the change in hydrogen ion concentrations in the case of excess acid or base. Most commonly, the substance that absorbs the ions is either a weak acid, which takes up hydroxyl ions, or a weak base, which takes up hydrogen ions.
Figure 26.15 The pH Scale This chart shows where many common substances fall on the pH scale.
Buffer Systems in the Body
The buffer systems in the human body are extremely efficient, and different systems work at different rates. It takes only seconds for the chemical buffers in the blood to make adjustments to pH. The respiratory tract can adjust the blood pH upward in minutes by exhaling CO2 from the body. The renal system can also adjust blood pH through the excretion of hydrogen ions (H+) and the conservation of bicarbonate, but this process takes hours to days to have an effect.
The buffer systems functioning in blood plasma include plasma proteins, phosphate, and bicarbonate and carbonic acid buffers. The kidneys help control acid-base balance by excreting hydrogen ions and generating bicarbonate that helps maintain blood plasma pH within a normal range. Protein buffer systems work predominantly inside cells.
Protein Buffers in Blood Plasma and Cells
Nearly all proteins can function as buffers. Proteins are made up of amino acids, which contain positively charged amino groups and negatively charged carboxyl groups. The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers. Buffering by proteins accounts for two-thirds of the buffering power of the blood and most of the buffering within cells.
Hemoglobin as a Buffer
Hemoglobin is the principal protein inside of red blood cells and accounts for one-third of the mass of the cell. During the conversion of CO2 into bicarbonate, hydrogen ions liberated in the reaction are buffered by hemoglobin, which is reduced by the dissociation of oxygen. This buffering helps maintain normal pH. The process is reversed in the pulmonary capillaries to re-form CO2, which then can diffuse into the air sacs to be exhaled into the atmosphere. This process is discussed in detail in the chapter on the respiratory system.
Phosphate Buffer
Phosphates are found in the blood in two forms: sodium dihydrogen phosphate (Na2H2PO4−Na2H2PO4−Na2HPO2-4Na2HPO42- Na2HPO2-4Na2HPO42- comes into contact with a strong acid, such as HCl, the base picks up a second hydrogen ion to form the weak acid Na2H2PO4−Na2H2PO4− and sodium chloride, NaCl. When Na2HPO24−Na2HPO42− (the weak acid) comes into contact with a strong base, such as sodium hydroxide (NaOH), the weak acid reverts back to the weak base and produces water. Acids and bases are still present, but they hold onto the ions.
HCl + Na2HPO4→NaH2PO4 + NaClHCl + Na2HPO4→NaH2PO4 + NaCl
(strong acid) + (weak base) → (weak acid) + (salt)(strong acid) + (weak base) → (weak acid) + (salt)
NaOH + NaH2PO4→Na2HPO4 + H2ONaOH + NaH2PO4→Na2HPO4 + H2O
(strong base) + (weak acid) → (weak base) + (water)(strong base) + (weak acid) → (weak base) + (water)
Bicarbonate-Carbonic Acid Buffer
The bicarbonate-carbonic acid buffer works in a fashion similar to phosphate buffers. The bicarbonate is regulated in the blood by sodium, as are the phosphate ions. When sodium bicarbonate (NaHCO3), comes into contact with a strong acid, such as HCl, carbonic acid (H2CO3), which is a weak acid, and NaCl are formed. When carbonic acid comes into contact with a strong base, such as NaOH, bicarbonate and water are formed.
NaHCO3 + HCl → H2CO3+NaClNaHCO3 + HCl → H2CO3+NaCl
(sodium bicarbonate) + (strong acid) → (weak acid) + (salt)(sodium bicarbonate) + (strong acid) → (weak acid) + (salt)
H2CO3 + NaOH→HCO3- + H2OH2CO3 + NaOH→HCO3- + H2O
(weak acid) + (strong base)→(bicarbonate) + (water)(weak acid) + (strong base)→(bicarbonate) + (water)
As with the phosphate buffer, a weak acid or weak base captures the free ions, and a significant change in pH is prevented. Bicarbonate ions and carbonic acid are present in the blood in a 20:1 ratio if the blood pH is within the normal range. With 20 times more bicarbonate than carbonic acid, this capture system is most efficient at buffering changes that would make the blood more acidic. This is useful because most of the body’s metabolic wastes, such as lactic acid and ketones, are acids. Carbonic acid levels in the blood are controlled by the expiration of CO2 through the lungs. In red blood cells, carbonic anhydrase forces the dissociation of the acid, rendering the blood less acidic. Because of this acid dissociation, CO2 is exhaled (see equations above). The level of bicarbonate in the blood is controlled through the renal system, where bicarbonate ions in the renal filtrate are conserved and passed back into the blood. However, the bicarbonate buffer is the primary buffering system of the IF surrounding the cells in tissues throughout the body.
Respiratory Regulation of Acid-Base Balance
The respiratory system contributes to the balance of acids and bases in the body by regulating the blood levels of carbonic acid (Figure 26.16). CO2 in the blood readily reacts with water to form carbonic acid, and the levels of CO2 and carbonic acid in the blood are in equilibrium. When the CO2 level in the blood rises (as it does when you hold your breath), the excess CO2 reacts with water to form additional carbonic acid, lowering blood pH. Increasing the rate and/or depth of respiration (which you might feel the “urge” to do after holding your breath) allows you to exhale more CO2. The loss of CO2 from the body reduces blood levels of carbonic acid and thereby adjusts the pH upward, toward normal levels. As you might have surmised, this process also works in the opposite direction. Excessive deep and rapid breathing (as in hyperventilation) rids the blood of CO2 and reduces the level of carbonic acid, making the blood too alkaline. This brief alkalosis can be remedied by rebreathing air that has been exhaled into a paper bag. Rebreathing exhaled air will rapidly bring blood pH down toward normal.
Figure 26.16 Respiratory Regulation of Blood pH The respiratory system can reduce blood pH by removing CO2 from the blood.
The chemical reactions that regulate the levels of CO2 and carbonic acid occur in the lungs when blood travels through the lung’s pulmonary capillaries. Minor adjustments in breathing are usually sufficient to adjust the pH of the blood by changing how much CO2 is exhaled. In fact, doubling the respiratory rate for less than 1 minute, removing “extra” CO2, would increase the blood pH by 0.2. This situation is common if you are exercising strenuously over a period of time. To keep up the necessary energy production, you would produce excess CO2 (and lactic acid if exercising beyond your aerobic threshold). In order to balance the increased acid production, the respiration rate goes up to remove the CO2. This helps to keep you from developing acidosis.
The body regulates the respiratory rate by the use of chemoreceptors, which primarily use CO2 as a signal. Peripheral blood sensors are found in the walls of the aorta and carotid arteries. These sensors signal the brain to provide immediate adjustments to the respiratory rate if CO2 levels rise or fall. Yet other sensors are found in the brain itself. Changes in the pH of CSF affect the respiratory center in the medulla oblongata, which can directly modulate breathing rate to bring the pH back into the normal range.
Hypercapnia, or abnormally elevated blood levels of CO2, occurs in any situation that impairs respiratory functions, including pneumonia and congestive heart failure. Reduced breathing (hypoventilation) due to drugs such as morphine, barbiturates, or ethanol (or even just holding one’s breath) can also result in hypercapnia. Hypocapnia, or abnormally low blood levels of CO2, occurs with any cause of hyperventilation that drives off the CO2, such as salicylate toxicity, elevated room temperatures, fever, or hysteria.
Renal Regulation of Acid-Base Balance
The renal regulation of the body’s acid-base balance addresses the metabolic component of the buffering system. Whereas the respiratory system (together with breathing centers in the brain) controls the blood levels of carbonic acid by controlling the exhalation of CO2, the renal system controls the blood levels of bicarbonate. A decrease of blood bicarbonate can result from the inhibition of carbonic anhydrase by certain diuretics or from excessive bicarbonate loss due to diarrhea. Blood bicarbonate levels are also typically lower in people who have Addison’s disease (chronic adrenal insufficiency), in which aldosterone levels are reduced, and in people who have renal damage, such as chronic nephritis. Finally, low bicarbonate blood levels can result from elevated levels of ketones (common in unmanaged diabetes mellitus), which bind bicarbonate in the filtrate and prevent its conservation.
Bicarbonate ions, HCO3-, found in the filtrate, are essential to the bicarbonate buffer system, yet the cells of the tubule are not permeable to bicarbonate ions. The steps involved in supplying bicarbonate ions to the system are seen in Figure 26.17 and are summarized below:
- Step 1: Sodium ions are reabsorbed from the filtrate in exchange for H+ by an antiport mechanism in the apical membranes of cells lining the renal tubule.
- Step 2: The cells produce bicarbonate ions that can be shunted to peritubular capillaries.
- Step 3: When CO2 is available, the reaction is driven to the formation of carbonic acid, which dissociates to form a bicarbonate ion and a hydrogen ion.
- Step 4: The bicarbonate ion passes into the peritubular capillaries and returns to the blood. The hydrogen ion is secreted into the filtrate, where it can become part of new water molecules and be reabsorbed as such, or removed in the urine.
Figure 26.17 Conservation of Bicarbonate in the Kidney Tubular cells are not permeable to bicarbonate; thus, bicarbonate is conserved rather than reabsorbed. Steps 1 and 2 of bicarbonate conservation are indicated.
It is also possible that salts in the filtrate, such as sulfates, phosphates, or ammonia, will capture hydrogen ions. If this occurs, the hydrogen ions will not be available to combine with bicarbonate ions and produce CO2. In such cases, bicarbonate ions are not conserved from the filtrate to the blood, which will also contribute to a pH imbalance and acidosis.
The hydrogen ions also compete with potassium to exchange with sodium in the renal tubules. If more potassium is present than normal, potassium, rather than the hydrogen ions, will be exchanged, and increased potassium enters the filtrate. When this occurs, fewer hydrogen ions in the filtrate participate in the conversion of bicarbonate into CO2 and less bicarbonate is conserved. If there is less potassium, more hydrogen ions enter the filtrate to be exchanged with sodium and more bicarbonate is conserved.
Chloride ions are important in neutralizing positive ion charges in the body. If chloride is lost, the body uses bicarbonate ions in place of the lost chloride ions. Thus, lost chloride results in an increased reabsorption of bicarbonate by the renal system.
DISORDERS OF THE...
Acid-Base Balance: Ketoacidosis
Diabetic acidosis, or ketoacidosis, occurs most frequently in people with poorly controlled diabetes mellitus. When certain tissues in the body cannot get adequate amounts of glucose, they depend on the breakdown of fatty acids for energy. When acetyl groups break off the fatty acid chains, the acetyl groups then non-enzymatically combine to form ketone bodies, acetoacetic acid, beta-hydroxybutyric acid, and acetone, all of which increase the acidity of the blood. In this condition, the brain isn’t supplied with enough of its fuel—glucose—to produce all of the ATP it requires to function.
Ketoacidosis can be severe and, if not detected and treated properly, can lead to diabetic coma, which can be fatal. A common early symptom of ketoacidosis is deep, rapid breathing as the body attempts to drive off CO2 and compensate for the acidosis. Another common symptom is fruity-smelling breath, due to the exhalation of acetone. Other symptoms include dry skin and mouth, a flushed face, nausea, vomiting, and stomach pain. Treatment for diabetic coma is ingestion or injection of sugar; its prevention is the proper daily administration of insulin.
A person who is diabetic and uses insulin can initiate ketoacidosis if a dose of insulin is missed. Among people with type 2 diabetes, those of Hispanic and African-American descent are more likely to go into ketoacidosis than those of other ethnic backgrounds, although the reason for this is unknown.
Disorders of Acid-Base Balance
- Identify the three blood variables considered when making a diagnosis of acidosis or alkalosis
- Identify the source of compensation for blood pH problems of a respiratory origin
- Identify the source of compensation for blood pH problems of a metabolic/renal origin
Normal arterial blood pH is restricted to a very narrow range of 7.35 to 7.45. A person who has a blood pH below 7.35 is considered to be in acidosis (actually, “physiological acidosis,” because blood is not truly acidic until its pH drops below 7), and a continuous blood pH below 7.0 can be fatal. Acidosis has several symptoms, including headache and confusion, and the individual can become lethargic and easily fatigued (Figure 26.18). A person who has a blood pH above 7.45 is considered to be in alkalosis, and a pH above 7.8 is fatal. Some symptoms of alkalosis include cognitive impairment (which can progress to unconsciousness), tingling or numbness in the extremities, muscle twitching and spasm, and nausea and vomiting. Both acidosis and alkalosis can be caused by either metabolic or respiratory disorders.
As discussed earlier in this chapter, the concentration of carbonic acid in the blood is dependent on the level of CO2 in the body and the amount of CO2 gas exhaled through the lungs. Thus, the respiratory contribution to acid-base balance is usually discussed in terms of CO2 (rather than of carbonic acid). Remember that a molecule of carbonic acid is lost for every molecule of CO2 exhaled, and a molecule of carbonic acid is formed for every molecule of CO2 retained.
Figure 26.18 Symptoms of Acidosis and Alkalosis Symptoms of acidosis affect several organ systems. Both acidosis and alkalosis can be diagnosed using a blood test.
Metabolic Acidosis: Primary Bicarbonate Deficiency
Metabolic acidosis occurs when the blood is too acidic (pH below 7.35) due to too little bicarbonate, a condition called primary bicarbonate deficiency. At the normal pH of 7.40, the ratio of bicarbonate to carbonic acid buffer is 20:1. If a person’s blood pH drops below 7.35, then he or she is in metabolic acidosis. The most common cause of metabolic acidosis is the presence of organic acids or excessive ketones in the blood. Table 26.2 lists some other causes of metabolic acidosis.
Common Causes of Metabolic Acidosis and Blood Metabolites
| Cause | Metabolite |
|---|---|
| Diarrhea | Bicarbonate |
| Uremia | Phosphoric, sulfuric, and lactic acids |
| Diabetic ketoacidosis | Increased ketones |
| Strenuous exercise | Lactic acid |
| Methanol | Formic acid* |
| Paraldehyde | β-Hydroxybutyric acid* |
| Isopropanol | Propionic acid* |
| Ethylene glycol | Glycolic acid, and some oxalic and formic acids* |
| Salicylate/aspirin | Sulfasalicylic acid (SSA)* |
Table 26.2 *Acid metabolites from ingested chemical.
The first three of the eight causes of metabolic acidosis listed are medical (or unusual physiological) conditions. Strenuous exercise can cause temporary metabolic acidosis due to the production of lactic acid. The last five causes result from the ingestion of specific substances. The active form of aspirin is its metabolite, sulfasalicylic acid. An overdose of aspirin causes acidosis due to the acidity of this metabolite. Metabolic acidosis can also result from uremia, which is the retention of urea and uric acid. Metabolic acidosis can also arise from diabetic ketoacidosis, wherein an excess of ketones is present in the blood. Other causes of metabolic acidosis are a decrease in the excretion of hydrogen ions, which inhibits the conservation of bicarbonate ions, and excessive loss of bicarbonate ions through the gastrointestinal tract due to diarrhea.
Metabolic Alkalosis: Primary Bicarbonate Excess
Metabolic alkalosis is the opposite of metabolic acidosis. It occurs when the blood is too alkaline (pH above 7.45) due to too much bicarbonate (called primary bicarbonate excess).
A transient excess of bicarbonate in the blood can follow ingestion of excessive amounts of bicarbonate, citrate, or antacids for conditions such as stomach acid reflux—known as heartburn. Cushing’s disease, which is the chronic hypersecretion of adrenocorticotrophic hormone (ACTH) by the anterior pituitary gland, can cause chronic metabolic alkalosis. The oversecretion of ACTH results in elevated aldosterone levels and an increased loss of potassium by urinary excretion. Other causes of metabolic alkalosis include the loss of hydrochloric acid from the stomach through vomiting, potassium depletion due to the use of diuretics for hypertension, and the excessive use of laxatives.
Respiratory Acidosis: Primary Carbonic Acid/CO2 Excess
Respiratory acidosis occurs when the blood is overly acidic due to an excess of carbonic acid, resulting from too much CO2 in the blood. Respiratory acidosis can result from anything that interferes with respiration, such as pneumonia, emphysema, or congestive heart failure.
Respiratory Alkalosis: Primary Carbonic Acid/CO2 Deficiency
Respiratory alkalosis occurs when the blood is overly alkaline due to a deficiency in carbonic acid and CO2 levels in the blood. This condition usually occurs when too much CO2 is exhaled from the lungs, as occurs in hyperventilation, which is breathing that is deeper or more frequent than normal. An elevated respiratory rate leading to hyperventilation can be due to extreme emotional upset or fear, fever, infections, hypoxia, or abnormally high levels of catecholamines, such as epinephrine and norepinephrine. Surprisingly, aspirin overdose—salicylate toxicity—can result in respiratory alkalosis as the body tries to compensate for initial acidosis.
INTERACTIVE LINK
Watch this video to see a demonstration of the effect altitude has on blood pH. What effect does high altitude have on blood pH, and why?
Compensation Mechanisms
Various compensatory mechanisms exist to maintain blood pH within a narrow range, including buffers, respiration, and renal mechanisms. Although compensatory mechanisms usually work very well, when one of these mechanisms is not working properly (like kidney failure or respiratory disease), they have their limits. If the pH and bicarbonate to carbonic acid ratio are changed too drastically, the body may not be able to compensate. Moreover, extreme changes in pH can denature proteins. Extensive damage to proteins in this way can result in disruption of normal metabolic processes, serious tissue damage, and ultimately death.
Respiratory Compensation
Respiratory compensation for metabolic acidosis increases the respiratory rate to drive off CO2 and readjust the bicarbonate to carbonic acid ratio to the 20:1 level. This adjustment can occur within minutes. Respiratory compensation for metabolic alkalosis is not as adept as its compensation for acidosis. The normal response of the respiratory system to elevated pH is to increase the amount of CO2 in the blood by decreasing the respiratory rate to conserve CO2. There is a limit to the decrease in respiration, however, that the body can tolerate. Hence, the respiratory route is less efficient at compensating for metabolic alkalosis than for acidosis.
Metabolic Compensation
Metabolic and renal compensation for respiratory diseases that can create acidosis revolves around the conservation of bicarbonate ions. In cases of respiratory acidosis, the kidney increases the conservation of bicarbonate and secretion of H+through the exchange mechanism discussed earlier. These processes increase the concentration of bicarbonate in the blood, reestablishing the proper relative concentrations of bicarbonate and carbonic acid. In cases of respiratory alkalosis, the kidneys decrease the production of bicarbonate and reabsorb H+ from the tubular fluid. These processes can be limited by the exchange of potassium by the renal cells, which use a K+-H+ exchange mechanism (antiporter).
Diagnosing Acidosis and Alkalosis
Lab tests for pH, CO2 partial pressure (pCO2), and HCO3– can identify acidosis and alkalosis, indicating whether the imbalance is respiratory or metabolic, and the extent to which compensatory mechanisms are working. The blood pH value, as shown in Table 26.3, indicates whether the blood is in acidosis, the normal range, or alkalosis. The pCO2 and total HCO3– values aid in determining whether the condition is metabolic or respiratory, and whether the patient has been able to compensate for the problem. Table 26.3 lists the conditions and laboratory results that can be used to classify these conditions. Metabolic acid-base imbalances typically result from kidney disease, and the respiratory system usually responds to compensate.
Types of Acidosis and Alkalosis
| pH | pCO2 | Total HCO3– | |
|---|---|---|---|
| Metabolic acidosis | ↓ | N, then ↓ | ↓ |
| Respiratory acidosis | ↓ | ↑ | N, then ↑ |
| Metabolic alkalosis | ↑ | N, then↑ | ↑ |
| Respiratory alkalosis | ↑ | ↓ | N, then ↓ |
Table 26.3 Reference values (arterial): pH: 7.35–7.45; pCO2: male: 35–48 mm Hg, female: 32–45 mm Hg; total venous bicarbonate: 22–29 mM. N denotes normal; ↑ denotes a rising or increased value; and ↓ denotes a falling or decreased value.
Metabolic acidosis is problematic, as lower-than-normal amounts of bicarbonate are present in the blood. The pCO2 would be normal at first, but if compensation has occurred, it would decrease as the body reestablishes the proper ratio of bicarbonate and carbonic acid/CO2.
Respiratory acidosis is problematic, as excess CO2 is present in the blood. Bicarbonate levels would be normal at first, but if compensation has occurred, they would increase in an attempt to reestablish the proper ratio of bicarbonate and carbonic acid/CO2.
Alkalosis is characterized by a higher-than-normal pH. Metabolic alkalosis is problematic, as elevated pH and excess bicarbonate are present. The pCO2 would again be normal at first, but if compensation has occurred, it would increase as the body attempts to reestablish the proper ratios of bicarbonate and carbonic acid/CO2.
Respiratory alkalosis is problematic, as CO2 deficiency is present in the bloodstream. The bicarbonate concentration would be normal at first. When renal compensation occurs, however, the bicarbonate concentration in blood decreases as the kidneys attempt to reestablish the proper ratios of bicarbonate and carbonic acid/CO2 by eliminating more bicarbonate to bring the pH into the physiological range.
Key Terms
- antidiuretic hormone (ADH)
- also known as vasopressin, a hormone that increases the volume of water reabsorbed from the collecting tubules of the kidney
- dehydration
- state of containing insufficient water in blood and other tissues
- dihydroxyvitamin D
- active form of vitamin D required by the intestinal epithelial cells for the absorption of calcium
- diuresis
- excess production of urine
- extracellular fluid (ECF)
- fluid exterior to cells; includes the interstitial fluid, blood plasma, and fluids found in other reservoirs in the body
- fluid compartment
- fluid inside all cells of the body constitutes a compartment system that is largely segregated from other systems
- hydrostatic pressure
- pressure exerted by a fluid against a wall, caused by its own weight or pumping force
- hypercalcemia
- abnormally increased blood levels of calcium
- hypercapnia
- abnormally elevated blood levels of CO2
- hyperchloremia
- higher-than-normal blood chloride levels
- hyperkalemia
- higher-than-normal blood potassium levels
- hypernatremia
- abnormal increase in blood sodium levels
- hyperphosphatemia
- abnormally increased blood phosphate levels
- hypocalcemia
- abnormally low blood levels of calcium
- hypocapnia
- abnormally low blood levels of CO2
- hypochloremia
- lower-than-normal blood chloride levels
- hypokalemia
- abnormally decreased blood levels of potassium
- hyponatremia
- lower-than-normal levels of sodium in the blood
- hypophosphatemia
- abnormally low blood phosphate levels
- interstitial fluid (IF)
- fluid in the small spaces between cells not contained within blood vessels
- intracellular fluid (ICF)
- fluid in the cytosol of cells
- metabolic acidosis
- condition wherein a deficiency of bicarbonate causes the blood to be overly acidic
- metabolic alkalosis
- condition wherein an excess of bicarbonate causes the blood to be overly alkaline
- plasma osmolality
- ratio of solutes to a volume of solvent in the plasma; plasma osmolality reflects a person’s state of hydration
- respiratory acidosis
- condition wherein an excess of carbonic acid or CO2 causes the blood to be overly acidic
- respiratory alkalosis
- condition wherein a deficiency of carbonic acid/CO2 levels causes the blood to be overly alkaline
Chapter Review
26.1 Body Fluids and Fluid Compartments
Your body is mostly water. Body fluids are aqueous solutions with differing concentrations of materials, called solutes. An appropriate balance of water and solute concentrations must be maintained to ensure cellular functions. If the cytosol becomes too concentrated due to water loss, cell functions deteriorate. If the cytosol becomes too dilute due to water intake by cells, cell membranes can be damaged, and the cell can burst. Hydrostatic pressure is the force exerted by a fluid against a wall and causes movement of fluid between compartments. Fluid can also move between compartments along an osmotic gradient. Active transport processes require ATP to move some solutes against their concentration gradients between compartments. Passive transport of a molecule or ion depends on its ability to pass easily through the membrane, as well as the existence of a high to low concentration gradient.
26.2 Water Balance
Homeostasis requires that water intake and output be balanced. Most water intake comes through the digestive tract via liquids and food, but roughly 10 percent of water available to the body is generated at the end of aerobic respiration during cellular metabolism. Urine produced by the kidneys accounts for the largest amount of water leaving the body. The kidneys can adjust the concentration of the urine to reflect the body’s water needs, conserving water if the body is dehydrated or making urine more dilute to expel excess water when necessary. ADH is a hormone that helps the body to retain water by increasing water reabsorption by the kidneys.
26.3 Electrolyte Balance
Electrolytes serve various purposes, such as helping to conduct electrical impulses along cell membranes in neurons and muscles, stabilizing enzyme structures, and releasing hormones from endocrine glands. The ions in plasma also contribute to the osmotic balance that controls the movement of water between cells and their environment. Imbalances of these ions can result in various problems in the body, and their concentrations are tightly regulated. Aldosterone and angiotensin II control the exchange of sodium and potassium between the renal filtrate and the renal collecting tubule. Calcium and phosphate are regulated by PTH, calcitriol, and calcitonin.
26.4 Acid-Base Balance
A variety of buffering systems exist in the body that helps maintain the pH of the blood and other fluids within a narrow range—between pH 7.35 and 7.45. A buffer is a substance that prevents a radical change in fluid pH by absorbing excess hydrogen or hydroxyl ions. Most commonly, the substance that absorbs the ion is either a weak acid, which takes up a hydroxyl ion (OH-), or a weak base, which takes up a hydrogen ion (H+). Several substances serve as buffers in the body, including cell and plasma proteins, hemoglobin, phosphates, bicarbonate ions, and carbonic acid. The bicarbonate buffer is the primary buffering system of the IF surrounding the cells in tissues throughout the body. The respiratory and renal systems also play major roles in acid-base homeostasis by removing CO2 and hydrogen ions, respectively, from the body.
26.5 Disorders of Acid-Base Balance
Acidosis and alkalosis describe conditions in which a person's blood is, respectively, too acidic (pH below 7.35) and too alkaline (pH above 7.45). Each of these conditions can be caused either by metabolic problems related to bicarbonate levels or by respiratory problems related to carbonic acid and CO2 levels. Several compensatory mechanisms allow the body to maintain a normal pH.
Interactive Link Questions
Watch this video to learn more about body fluids, fluid compartments, and electrolytes. When blood volume decreases due to sweating, from what source is water taken in by the blood?
2.Watch this video to see an explanation of the dynamics of fluid in the body’s compartments. What happens in tissues when capillary blood pressure is less than osmotic pressure?
3.Read this article for an explanation of the effect of seawater on humans. What effect does drinking seawater have on the body?
4.Watch this video to see a demonstration of the effect altitude has on blood pH. What effect does high altitude have on blood pH, and why?
Review Questions
Solute contributes to the movement of water between cells and the surrounding medium by ________.
- osmotic pressure
- hydrostatic pressure
- Brownian movement
- random motion
A cation has a(n) ________ charge.
- neutral
- positive
- alternating
- negative
Interstitial fluid (IF) is ________.
- the fluid in the cytosol of the cells
- the fluid component of blood
- the fluid that bathes all of the body’s cells except for blood cells
- the intracellular fluids found between membranes
The largest amount of water comes into the body via ________.
- metabolism
- foods
- liquids
- humidified air
The largest amount of water leaves the body via ________.
- the GI tract
- the skin as sweat
- expiration
- urine
Insensible water loss is water lost via ________.
- skin evaporation and in air from the lungs
- urine
- excessive sweating
- vomiting or diarrhea
How soon after drinking a large glass of water will a person start increasing their urine output?
- 5 minutes
- 30 minutes
- 1 hour
- 3 hours
Bone serves as a mineral reserve for which two ions?
- sodium and potassium
- calcium and phosphate
- chloride and bicarbonate
- calcium and bicarbonate
Electrolytes are lost mostly through ________.
- renal function
- sweating
- feces
- respiration
The major cation in extracellular fluid is ________.
- sodium
- potassium
- chloride
- bicarbonate
The major cation in intracellular fluid is ________.
- sodium
- potassium
- chloride
- bicarbonate
The major anion in extracellular fluid is ________.
- sodium
- potassium
- chloride
- bicarbonate
Most of the body’s calcium is found in ________.
- teeth
- bone
- plasma
- extracellular fluids
Abnormally increased blood levels of sodium are termed ________.
- hyperkalemia
- hyperchloremia
- hypernatremia
- hypercalcemia
The ion with the lowest blood level is ________.
- sodium
- potassium
- chloride
- bicarbonate
Which two ions are most affected by aldosterone?
- sodium and potassium
- chloride and bicarbonate
- calcium and phosphate
- sodium and phosphate
Which of the following is the most important buffer inside red blood cells?
- plasma proteins
- hemoglobin
- phosphate buffers
- bicarbonate: carbonic acid buffer
Which explanation best describes why plasma proteins can function as buffers?
- Plasma proteins combine with bicarbonate to make a stronger buffer.
- Plasma proteins are immune to damage from acids.
- Proteins have both positive and negative charges on their surface.
- Proteins are alkaline.
The buffer that is adjusted to control acid-base balance is ________.
- plasma protein
- hemoglobin
- phosphate buffer
- bicarbonate: carbonic acid buffer
Carbonic acid levels are controlled through the ________.
- respiratory system
- renal system
- digestive system
- metabolic rate of cells
Bicarbonate ion concentrations in the blood are controlled through the ________.
- respiratory system
- renal system
- digestive system
- metabolic rate of cells
Which reaction is catalyzed by carbonic anhydrase?
- HPO2-4+H+↔H2PO4-HPO42-+H+↔H2PO4-
- CO2 + H2O↔H2CO3CO2 + H2O↔H2CO3
- H2PO4−+OH−↔HPO2−4+H2OH2PO4−+OH−↔HPO42−+H2O
- H2CO3↔HCO3−+ H+H2CO3↔HCO3−+ H+
Which of the following is a cause of metabolic acidosis?
- excessive HCl loss
- increased aldosterone
- diarrhea
- prolonged use of diuretics
Which of the following is a cause of respiratory acidosis?
- emphysema
- low blood K+
- increased aldosterone
- increased blood ketones
At a pH of 7.40, the carbonic acid ratio is ________.
- 35:1
- 4:1
- 20:1
- 3:1
Which of the following is characterized as metabolic alkalosis?
- increased pH, decreased pCO2, decreased HCO3–
- increased pH, increased pCO2, increased HCO3–
- decreased pH, decreased pCO2, decreased HCO3–
- decreased pH, increased pCO2, increased HCO3–
Critical Thinking Questions
Plasma contains more sodium than chloride. How can this be if individual ions of sodium and chloride exactly balance each other out, and plasma is electrically neutral?
32.How is fluid moved from compartment to compartment?
33.Describe the effect of ADH on renal collecting tubules.
34.Why is it important for the amount of water intake to equal the amount of water output?
35.Explain how the CO2 generated by cells and exhaled in the lungs is carried as bicarbonate in the blood.
36.How can one have an imbalance in a substance, but not actually have elevated or deficient levels of that substance in the body?
37.Describe the conservation of bicarbonate ions in the renal system.
38.Describe the control of blood carbonic acid levels through the respiratory system.
39.Case Study: Bob is a 64-year-old male admitted to the emergency room for asthma. His laboratory results are as follows: pH 7.31, pCO2 higher than normal, and total HCO3– also higher than normal. Classify his acid-base balance as acidosis or alkalosis, and as metabolic or respiratory. Is there evidence of compensation? Propose the mechanism by which asthma contributed to the lab results seen.
40.Case Study: Kim is a 38-year-old women admitted to the hospital for bulimia. Her laboratory results are as follows: pH 7.48, pCO2 in the normal range, and total HCO3– higher than normal. Classify her acid-base balance as acidosis or alkalosis, and as metabolic or respiratory. Is there evidence of compensation? Propose the mechanism by which bulimia contributed to the lab results seen.
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https://oercommons.org/courseware/lesson/79219/overview
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Readings
Overview
The goal of this chapter is to help support your academic success by helping you avoid or effectively manage problems and challenges in college involving your health or wellness. The Health in College section defines components of health and presents evidence-based strategies to help lower your risks for illness or injury. The Wellness in College section defines elements of wellness along a mind-body-spirit continuum and emphasizes the roles each can play in your well-being. Look for information in bold font to assist you in acquiring key knowledge.
Introduction
Why Learn About Health and Wellness in College?
Are you surprised to find information on health and wellness in a first-year college seminar course? If you answered yes, I’m not surprised! But your academic success in college depends on many factors, and two that are important but often overlooked are your health and well-being.
Table 1 lists the top 10 problems or challenges a representative sample of college students in the United States reported experiencing over the previous 12 months that negatively impacted their academic performance (American College Health Association, 2020). The percentage of the sampled students reporting each one is also listed.
Table 1.
Top 10 Problems or Challenges Negatively Impacting College Students’ Academic Performance
Problem or Challenge | Percentage |
Procrastination | 47.2% |
Stress | 30.4% |
Cold/Virus or other respiratory illness or Flu | 24.4% |
Anxiety | 21.1% |
Sleep difficulties | 20.3% |
Depression | 17.9% |
Ongoing or chronic medical conditions | 16.3% |
Finances | 14.2% |
Intimate Relationships | 12.2% |
Family | 10.8% |
Note: Adapted from “National College Health Assessment Undergraduate Student Reference Group Executive Summary Fall 2019,” by the American College Health Association, 2020. https://www.acha.org/documents/ncha/NCHA-III_Fall_2019_Undergraduate_Reference_Group_Executive_Summary.pdf
How many do you see that involve health and wellness? My answer is, “All of them!” Stress, anxiety, and depression can manifest as procrastination or sleep difficulties and can affect concentration, critical thinking, and attendance. Chronic stress and sleep deprivation can lower immune function and lead to infections like colds and flu with symptoms that interfere with academic activities. Problems with finances or important relationships can be stressful and damaging to college student success and are hard to manage if students feel anxious, depressed, or fatigued.
Learning Objectives
After completing this chapter, students should be able to:
- Demonstrate awareness of recommendations for attitudes, behaviors, and activities to support their own health.
- Demonstrate awareness of models for wellness and resources to support each dimension of wellness in college success.
- Identify strategies to improve their own health and wellness in college.
References
American College Health Association. (2020). American college health association-national college health assessment III: Undergraduate student reference group executive summary fall 2019. Silver Spring, MD: Author.
Health in College
What Do We Mean by “Health”?
Although health and wellness are overlapping and interconnected concepts, health is defined as the condition of being sound in body, mind, or spirit, especially freedom from physical disease or pain (Merriam-Webster, n.d.-a). In other words, health can be identified as the normal or optimal functioning of all components of a human being—body, mind, and spirit—and the absence of disease, illness, dysfunction, or pain. Health has three components: physical, mental, and spiritual.
- Physical refers to how well your body functions so you can comfortably perform desired daily activities.
- Mental refers to how well your brain functions to feel, think, and take in information.
- Spiritual refers to how well your mind functions to maintain self-awareness and connectedness with things outside yourself as well as a sense of purpose and meaning in your life.
The health of individuals and populations is determined by many factors: (a) behaviors, or what they do; (b) environment, or where and with what or whom they do it; and (c) resources, or whatever affects and directs their environment and behavior. Some resources, like the behavior of working out in the environment of a gym, are within an individual’s control, and some resources, like muscle strength determined by genetics and physiologic development, are not. Successful students maximize the positive impact of behaviors and environmental elements under their control by knowing their options, prioritizing their goals, and applying their resources to make good choices. They are also aware and accepting of things beyond their control and adapt in ways to maximize the positive and minimize any negative impact.
How Can Students Stay Healthy in College?
Table 2 lists the top conditions reported by a representative sample of U.S. college students as diagnosed by a health care professional within the last 12 months.
Table 2. Top 10 Health Conditions Diagnosed in College Students
Illness | Frequency |
Respiratory illnesses | 59.7% |
Urinary tract infection | 10.8% |
Stomach or intestinal virus or bug, food poisoning, or gastritis | 9.7% |
Orthopedic injury | 9.7% |
Concussion | 3.3% |
Mononucleosis (mono) | 2.2% |
Chlamydia or Gonorrhea | 1.8% |
Note: Adapted from “National College Health Assessment Undergraduate Student Reference Group Executive Summary Fall 2019,” by the American College Health Association, 2020. https://www.acha.org/documents/ncha/NCHA-III_Fall_2019_Undergraduate_Reference_Group_Executive_Summary.pdf
Students can stay healthy in college and prevent or avoid these health issues by directing their attitudes, behaviors, and activities toward optimizing goals in five areas: nutrition, activity and exercise, rest and sleep, safety, and health maintenance.
Nutrition
Humans need protein, carbohydrates, fats, vitamins, minerals, and water for adequate functioning of body and mind. Most adults need an average of 1800-2400 kilocalories (kcals) per day to fuel the chemical, electrical, and mechanical processes required to keep us alive, awake, thinking, and moving.
These 10 tips can help you maintain adequate nutrition:
- Vary your meals. Eat a variety of foods to obtain all necessary nutrients for health. Recreational Sports and the Nutrition Graduate Program at Sam Houston State University provide a resource called Nutrition Education, and you can sign up to get help from graduate dietetic interns to learn how to eat better while in college.
- Stock healthy foods. Keep healthy foods and snacks in your room, kitchen, or backpack. Watch for added calories and fats by reading labels. If you are struggling with food insecurity, check out the SHSU Food Pantry, organized by the Food Pantry@SHSU student organization.
- Avoid stress eating. The key is to recognize you feel stressed, not hungry. Take a moment when you are stressed out and consider how you feel physically. Do you have a headache, is your jaw or neck tight, do you feel jitters or “butterflies” in your chest or stomach, do you feel lightheaded or tingly? Address the stress without food.
- Drink enough water. Stay hydrated to improve your concentration and avoid headaches. Many chemical reactions in your body depend on a water molecule, like burning fat or building muscle. The Institute of Medicine (2005) recommends 72 ounces of water per day for women and 96 ounces per day for men.
- Limit sugary beverages. Unlike sugars in fruits that are accompanied by vitamins, minerals, and fiber, sucrose (table sugar) adds nothing to your body except calories. For instance, drinking just one 12 ounce sugary soda per day adds an average of one extra pound every 23 days!
- Eat your produce. Consume fruits and vegetables for filling fluid and fiber as well as vitamins and minerals. Fresh is best, but any fruit or vegetable when prepared without added sugar or fat is a healthier choice. You have adult taste buds now—try those Brussels sprouts, you never know!
- Limit junk food. Stay away from the oils, sugars, calories, and preservatives they contain. Chips, cookies, candies, and donuts are mostly “empty calories” as they do not provide necessary nutrients, which is why we call them junk foods! Spend your calories wisely and make better nutritional choices for your body and brain.
- Watch your portions. The typical American diet contains too much of the wrong foods – red meat and breads, potatoes, and table sugar that make us 12th in the world for obesity (Central Intelligence Agency, 2016). For help with figuring portion sizes and keeping track of calories, try the Start Simple with MyPlate app.
- Indulge only occasionally. Treat yourself once in a while, maybe as a reward for a week of healthy eating. But make it an intentional choice. Be mindful of what and how much you are eating; a package of chocolate chip cookies will undo the healthful eating of a whole week, so plan your splurge thoughtfully.
- Watch for disordered eating. Binge eating disorder is the most common eating disorder in the United States, and anorexia or bulimia with starvation and/or purging by self-induced vomiting or use of medications are potentially life threatening. For help, visit the Student Health Center or the Student Counseling Center.
To learn about how nutrition can impact your academic performance, watch the TEDEd Share video, “How the food you eat affects your brain” by Mia Nacamulli.
"How the food you eat affects your brain" by Mia Nacamulli, TedED,
located at https://youtu.be/xyQY8a-ng6g
Attributions
How the food you eat affects your brain" by Mia Nacamulli, TedED, located at https://youtu.be/xyQY8a-ng6g
References
American College Health Association. (2020). American college health association-national college health assessment III: Undergraduate student reference group executive summary fall 2019. Silver Spring, MD: Author.
Central Intelligence Agency. (2016). The world fact book. https://www.cia.gov/library/publications/the-world-factbook/rankorder/2228rank.html
U.S. Department of Agriculture. (2020). Dietary guidelines for Americans 2020-2025. https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf
Activity and Exercise
Adults need at least 150 minutes of moderate-intensity physical activity each week (U.S. Department of Health & Human Services, 2018). Benefits of aerobic exercise include improved heart health and mental health, with improvements noted in symptoms of anxiety and depression. Exercise can also increase physical stamina and executive function (cognitive processes important for reasoning, planning, and problem solving).
Here are 10 tips for maintaining adequate activity and exercise:
- Walk to class. Burn calories, get fit, and reduce stress while doing the perfect exercise for our bodies.
- Bike to class. Burn calories, get there faster, and save money on gas and parking.
- Hit the gym. Choose free weights, machine weights, or cardiovascular equipment at SHSU’s Recreational Sports Center.
- Take a class. Recreation Sports at SHSU offers group fitness classes, virtual classes on-demand, personal training, fitness workshops, certifications, free weights, weight machines, and cardiovascular exercise equipment. There are even virtual fitness classes, free to SHSU students registered with Recreation Movement.
- Play a sport. Intramural Sports offers flag football, basketball, volleyball, soccer, softball, racquetball, golf, and tennis. Club Sports offers climbing, inline hockey, lacrosse, marksmanship, martial arts-hapkido, paintball, powerlifting, quidditch, rugby, soccer, tennis, trap and skeet, ultimate frisbee, volleyball, and wrestling.
- Stretch out daily. The American College of Sports Medicine (2018) recommends healthy adults do flexibility exercises (stretches, yoga, or tai chi) for all major muscle-tendon groups—neck, shoulders, chest, trunk, lower back, hips, legs, and ankles—at least two times a week, holding each stretch for a total of 60 seconds.
- Vary your routine. Mix it up and work different muscles to avoid boredom. Aquatics and Safety offers an outdoor seasonally heated swimming pool, lap lanes, water volleyball, water basketball, swim instruction, and American Red Cross safety training courses.
- Share the activity. Bring a friend for mutual accountability and more fun. Outdoor Recreation offers adventure trips, clinics and workshops on outdoor activities and skills, a climbing center, and equipment rentals for camping, climbing, or water recreation.
- Find open spaces. Use the spaces on and around the SHSU campus to walk, run, or play. Keep an eye out for signs on campus marking an updated walking route, and learn more about local options at Texas Parks and Wildlife’s Interactive Map of Huntsville State Park Trails.
- Enjoy your activity. Find ways to have fun while staying active. This will make sticking with the activity easier, and increase your odds of incorporating physical exercise and mobility into your regular health routine.
References
U.S. Department of Health and Human Services. (2018). Physical activity guidelines for Americans (2nd ed.). https://health.gov/sites/default/files/2019-09/physical_activity_guidelines_2nd_edition.pdf
American College of Sports Medicine. (2018). ACSM's guidelines for exercise testing and prescription (10th ed). Philadelphia: Wolters Kluwer.
Rest and Sleep
Most adults need 7 to 9 hours of sleep daily. Sleep is a biological requirement for humans, and it allows rebuilding and repair of body and mind from the physical, mental, and emotional stresses of the day. Without it, academic and social functioning, and physical and mental health, are compromised.
Here are 10 tips for maintaining adequate rest and sleep:
- Keep a schedule. Go to sleep and wake up at the same times each day to train your body and mind.
- Sleep 7+ hours. Get 7–9 hours of sleep each night to optimize your academic performance.
- Nap for 20. Nap for no more than 20 minutes to avoid compromising your sleep that night.
- Avoid bed studying. Find another place to study to help avoid bedtime anxiety and insomnia.
- Create bedtime routines. Shower, journal, pray, take a bath—just do it every night.
- Avoid bedtime consumption. Abstain from eating or drinking (especially caffeine) for at least 3 hours before bed.
- Set the mood. Make your room dark and quiet, or use a sleep mask and ear plugs, for more restful sleep.
- Negotiate sleep time. Set healthy boundaries with friends, family, roommates, and significant others.
- Avoid all-nighters. Increase concentration and critical thinking tomorrow by sleeping tonight.
- Appreciate your rest. Protect your physical and mental health with adequate sleep.
Sleep = Brainpower
For more on the importance of sleep in learning, watch the TEDEd Share video by Claudia Aguirre
"What would happen if you didn’t sleep?" by Claudia Aguirre, TedED,
located at https://youtu.be/dqONk48l5vY
Attributions
"What would happen if you didn’t sleep?" by Claudia Aguirre, TedED, located at https://youtu.be/dqONk48l5vY
Safety in College
Events like weather emergencies present risks to safety and are beyond our control, although SHSU KatSafe helps with preparedness. But other risks for injury or trauma increase with our lack of awareness of our surroundings. This can occur from distractions from new environments or experiences. It can also occur from altered perceptions due to lack of sleep or from alcohol or other substances, which affect judgment and increase risk for injury from violence or self-harm. It can even occur from poorly controlled chronic health conditions like asthma or diabetes. Students can expect to improve their health and sense of well-being as well as their knowledge, physical fitness, self-awareness, social interactions, and prospects for financial security and a satisfying occupation while at college, but they must also be prepared to protect themselves as much as possible from risks to their health and safety.
Violence
A risk category not often discussed is violence. Under the federal law known as the Jeanne Clery Act, universities that receive federal student aid must report certain categories of offenses, crimes, and arrests involving their campuses. In the Daily Crime Log, as reported by SHSU for the Huntsville campus to date in calendar year 2020, there have been reports of the following occurring in campus housing and other areas on campus: robbery, burglaries, thefts, simple assaults, vandalism, stalking, dating violence, forcible sex offenses, and arrests for drug abuse and liquor law violations.
In one study of undergraduate students from colleges in the Northeast, non-consensual sexual contact by physical force or inability to consent was reported by 26.4% of women, 23.1% of transgender, genderqueer, and nonbinary individuals, and 6.9% of men (Cantor et al., 2019). This study also showed students are at highest risk for nonconsensual sexual contact in the first few months of their first and second semesters.
References
Cantor, D., Fisher, B., Chibnall, S., Townsend, R., Lee, H., Bruce, C., & Thomas, G. (2019, September 3). Report on the AAU campus climate survey on sexual assault and sexual misconduct. Association of American Universities. https://www.aau.edu/key-issues/campus-climate-and-safety/aau-campus-climate-survey-2019.
Alcohol Use
Another important risk category for college students is alcohol use. Harmful and underage drinking increases students’ risks for academic problems like missing class and getting behind in homework. Other increased risks are for injuries, assault, involvement with the police, unsafe sexual behavior, sexual assault, and physical and mental health problems, including alcohol use disorder, suicide attempts, and death.
The following is from an agency of the National Institutes of Health: “Thousands of college students are transported to the emergency room each year for alcohol overdose, which occurs when there is so much alcohol in the bloodstream that areas of the brain controlling basic life-support functions—such as breathing, heart rate, and temperature control—begin to shut down.
Signs of this dangerous condition can include the following:
- Mental confusion, stupor
- Difficulty remaining conscious or inability to wake up
- Vomiting
- Seizures
- Slow breathing (fewer than eight breaths per minute)
- Irregular breathing (10 seconds or more between breaths)
- Slow heart rate
- Clammy skin
- Dulled responses, such as no gag reflex (which prevents choking)
- Extremely low body temperature, bluish skin color, or paleness
Alcohol overdose can lead to permanent brain damage or death, so a person showing any of these signs requires immediate medical attention. Do not wait for the person to have all the symptoms, and be aware a person who has passed out can die. Call 911 if you suspect alcohol overdose.” (National Institute on Alcohol Abuse and Alcoholism, 2019, College Drinking, paragraph 25, Alcohol Overdose and College Students.)
Here are ten tips for maintaining adequate safety from injury and trauma are:
- Know your contacts. Give someone - a trusted friend or roommate - your emergency contact names and numbers, and let someone know your plans when going out. Keep the following numbers in your phone:
- SHSU University Police (936-294-1000) or 911 for immediate assistance or to report crimes1
- SHSU University Police (936-294-1800) for nonemergency, security escort, or vehicle assist
- Silent Witness to anonymously report crimes or suspicious activity
- SHSU Title IX Office. Students can also call 936-294-3080 to report alleged gender-based discrimination, sexual misconduct, or retaliation by or against an SHSU student, faculty member, or staff employee.
- Huntsville Memorial Hospital Sexual Assault Resources (1-888-801-5565)
Anyone, of any sex, race, and ability, gender, gender identity, and gender expression can experience sexual assault. If you’ve been sexually assaulted - even if you are not sure - you can speak to the SANE (Sexual Assault Nurse Examiner) on-call. A dedicated SANE nurse will return your call within 30 minutes with free, confidential help day or night.
- Be a buddy. Do what you can to protect someone whose senses or judgment are compromised – protest, distract, or get help when you see anyone being assaulted or forced to do anything against their will or if unable to consent. Bearkats should not be bystanders! (Learn more about the bystander effect at Psychology Today.)
- Avoid “bars & cars.” Avoid illicit drug use or drinking to the point of mental or physical impairment. At that point, you have already destroyed brain cells. How many can you spare? There is no “safe” level of alcohol or drug use for driving, and you could be betting your life on whether a designated driver stays sober.
- Be KatSafe. Pay attention to the KatSafe Information for emergency information regarding active shooter or bomb threats, evacuations, medical emergencies, or inclement weather that put SHSU campuses and students at risk.
- Advocate for yourself. Speak up for what you need so you can get it, and speak up for what you want to avoid. Peer pressure does not disappear at high school graduation. It is usually easier to recover from embarrassment or other social consequences than from injury due to trauma or violence. Be proactive with your safety.
- Quit smoking/vaping. Avoid injury to tissues in your mouth, throat, and lungs from inhaled chemicals that increase your risks for bronchitis and pneumonia short term, and facial wrinkles and cancer long term. Watch for new data on risks from chemicals inhaled in concentrated form with vaping - preliminary data are negative. To get help on campus to quit, visit the Student Health Center or the Student Counseling Center.
- Wear protective gear. Avoid ankle sprains, shin splints, foot/knee pain, slips, trips, and falls with supportive shoes for walking on campus or exercising. Avoid injury when biking or playing sports with appropriate helmet, gloves, pads, etc.
- Unload your backpack. Avoid back, shoulder, and neck pain or injuries by lightening the load and going through your pack daily, balancing the load by wearing your backpack properly with straps over both shoulders, and concentrating on good posture while carrying your backpack.
- Identify health providers. To insure continued medical care for chronic medical conditions, transfer health records from your primary care provider to a local physician, the SHSU Student Health Center, or the SHSU Physicians Clinic in Conroe.
- Play your part. There is hope and treatment for anyone in any situation who is thinking about harming or killing themselves. We need everyone alive and well—only you can play your part, and everyone’s part is important.
References
National Institute on Alcohol Abuse and Alcoholism. (2019, November 15). College drinking. https://www.niaaa.nih.gov/publications/brochures-and-fact-sheets/college-drinking
[1] A victim of sexual assault can seek help, medical or otherwise, without contact with law enforcement by confidential report of the incident to a designated CSA (Campus Security Authority): residential advisors, provosts, deans, directors, advisors, coaches, and others who have received required training.
Crisis
The following resources are available if you or a friend are in crisis:
Student Counseling Center Walk-In Clinic (for crisis intervention)
1608 Avenue J., Box 209, Huntsville, TX 77341-2059
Phone: 936.294.1720 | Fax: 936.294.2639
24-Hour Referral Sources
From their website: “Crisis intervention services are designed to assist students who are confronting life-threatening circumstances, current or recent traumatic experiences, serious mental illness, and concerns about the safety of self or others. Crisis situations include but are not limited to the following:
- Students who are suicidal and/or are making overt references to suicide
- Students who are unable to provide basic levels of care for themselves
- Students who are so profoundly depressed that assessment for hospitalization should be considered
- Students who are unable to resolve a crisis and experiencing severe anxiety.”
The American Foundation for Suicide Prevention provides resources for those who may be in crisis, and recommends: “If a person says they are considering suicide:
- Take the person seriously
- Stay with them
- Help them remove lethal means
- Escort them to mental health services or an emergency room.”
- On campus: the Student Health Center, Counseling Center, or University Police Department
- Off campus in Huntsville: Huntsville Memorial Hospital or Huntsville Police Department
- Tri-County MHMR
7045 Hwy 75 South, Huntsville, TX 77340
Phone: (936) 295-0072 - Suicide Hotline: 1-800-273-8255
- Crisis Hotline: 1-800-784-2433
To learn more about suicide prevention, watch the AFSP National’s video College Students and Mental Health.
"It's Real: College Students and Mental Health?" by AFSPNational,
located at https://youtu.be/YN69VIDKBFs
Attributions
"It's Real: College Students and Mental Health?" by AFSPNational, located at https://youtu.be/YN69VIDKBFs
Health Maintenance
Protecting your health includes proper nutrition, activity, sleep, and safety, but there are also some directed activities against specific risks to your health involving infectious diseases, sexual contact, stress management, and mental health conditions.
Read these 10 tips for maintaining adequate protection against infectious diseases such as pink eye, respiratory infections like colds or flu (influenza), mono (mononucleosis), strep throat (streptococcal pharyngitis), bronchitis and pneumonia, gastroenteritis, urinary tract infections, and bacterial dermatitis, and sexually transmitted infections:
- Wash your hands for 20 seconds with soap and water or with alcohol-based hand rub before and after eating, using the bathroom, touching your face, having sex, shaking hands, and after coughing or sneezing.
- Avoid your face. Try not to touch your eyes, nose, or mouth. Follow your doctor’s or the manufacturer’s recommendations for contact lens wear and cleaning. Replace liquid eyeliners or mascaras every 3 months.
- Stay home sick. Per the Student Absence Notification Policy, a nonemergency student absence includes minor illness, regular doctor's visit, dentist appointments, or prearranged trips. An emergency student absence includes unprecedented / emergency situations and/or the absence is for an extended period.
- Avoid ill friends. Provide lots of sympathy, homework help, and soup packets, but stay away from people who are feverish, snotty, sneezy, coughing, pukey, or who have diarrhea or open sores. You will not be able to help them or yourself if you get sick, too.
- Get your shots - influenza vaccine every year and the three-shot vaccine series against HPV (human papilloma virus that causes genital warts and cervical or penile cancer). And stay up to date on recommendations for the COVID-19 vaccine. Contact the Student Health Center for more information.
- See a doctor. Get medical care when you are sick or in pain. For mild symptoms, you can try these over-the-counter remedies:
Mild symptom Medication to try Example of brand name No longer mild; see a doctor if... Fever, aches, pain acetaminophen Tylenol High fever, severe pain Sore throat benzocaine Cepacol Difficulty swallowing Cough or congestion guaifenesin Mucinex Difficulty breathing Upset stomach bismuth Pepto-Bismol Vomiting everything or severe abdominal pain Heartburn or "sour stomach" calcium carbonate Tums Vomiting blood or severe abdominal pain Diarrhea loperamide Imodium Multiple loose stools or stools with blood Skin inflammation hydrocortisone Cortisone creme Infected skin Skin itching diphenhydramine Benadryl cream Spreading rash - Get yourself tested. Any genital discharge, pain, itching, sore, or lump should be evaluated by a health care provider. Because some do not cause symptoms, the only way to know for sure if you have a sexually transmitted infection (STI) is to get tested. Per Texas law testing is confidential, even if younger than 18.
- Always use protection. Using a condom correctly every time you have sex reduces the risk of pregnancy and infection with all STIs. (You can still get certain STIs, like herpes or HPV, from skin to skin contact with your partner.) Learn more from the CDC’s Condom Fact Sheet.
- Discuss important issues. Consent, known infection risks, STI testing results, means of protection from infection and pregnancy, and mutually acceptable sex practices are the minimum topics for safe sex with a new partner. No one reads minds, so be clear about your expectations and protect your health.
- Think about pregnancy. If you decide to be sexually active while in college, take the opportunity with your health provider to discuss contraception (birth control).
Just In Case…
Watch the Planned Parenthood video, "How Does the Morning After Pill/Emergency Contraception Work?" Emergency contraception is available at the Student Health Center and 24-hour pharmacies, including the one in Huntsville.
"How Does the Morning After Pill/Emergency Contraception Work?" by Planned Parenthood,
located at https://youtu.be/zN8fEakox5I
Attributions
"How Does the Morning After Pill/Emergency Contraception Work?" by Planned Parenthood, located at https://youtu.be/zN8fEakox5I
Wellness in College
What Do We Mean by “Wellness”?
Wellness is defined as the quality or state of being in good health, especially as an actively sought goal (Merriam-Webster, n.d.-b). Wellness can be viewed as the intentional presence of physical, mental, and spiritual health. The SHSU Health Campus Initiative ELEVATE promotes the “healthy choice as the easy choice” by using the eight dimensions of wellness model which also includes the three components of health: physical, mental, and spiritual.
The eight components of wellness are:
- Physical wellness is about maintaining a healthy body through good nutrition, regular exercise, and avoidance of harmful habits.
- Intellectual (or Mental) wellness includes an openness to new concepts and participation in creative, stimulating mental activities.
- Spiritual wellness is about developing our sense of purpose and meaning in life and is based on a core set of values and beliefs.
- Emotional wellness is the awareness and acceptance of feelings and emotions.
- Social wellness is the ability to interact with others and to live up to the expectations and demands of our personal roles. Social emotional learning is the awareness and understanding of emotions in oneself and in others; an ability to manage one’s own emotions; tolerance to differences in others’ values, cultures, and perspectives; flexibility in one’s own interpersonal behavior; and an ability to take an active role in cultivating productive relationships with others (Wyatt & Bloemker, 2013).
- Environmental wellness is an awareness of the delicate state of the earth and the effects of your daily habits on the physical environment.
- Financial wellness involves being aware of your financial situation and managing it, so you are prepared for financial changes. (See Unit 3: Financial Literacy.)
- Occupational wellness is the ability to enjoy a chosen career and/or contribute to society through volunteer activities.
A list of resources and websites to support your wellness are provided here:
Resource | Website |
OrgLINK (Student Organizations) | https://shsu.campuslabs.com/engage/ |
Huntsville Walker County Religious Organizations | http://www.chamber.huntsville.tx.us/list/ql/religious-organizations-21 |
Student Counseling Center | https://www.shsu.edu/counseling |
Student Activities | https://www.shsu.edu/studentactivities |
Greek Life | https://www.shsu.edu/greeklife |
Leadership Initiatives | https://www.shsu.edu/leadership |
Student Money Management Center | https://www.shsu.edu/dept/smmc/
|
Career Services | https://www.shsu.edu/dept/career-services/ |
Watch Joanne Davila’s TEDxSBU talk Skills for Healthy Romantic Relationships
"Skills for Healthy Romantic Relationships" by Joanne Davila, TEDx,
located at https://youtu.be/gh5VhaicC6g
References
Merriam-Webster. (n.d.-b). Wellness. In Merriam-Webster.com dictionary. Retrieved December, 2020, from https://www.merriam-webster.com/dictionary/wellness.
Wyatt, J. B., & Bloemker, G. A. (2013). Social and emotional learning in a freshman seminar. Higher Education Studies, 3(1), 106-114
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2025-03-18T00:37:12.128458
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https://oercommons.org/courseware/lesson/79220/overview
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Learning Activities
Overview
Learning Activities for Unit 2.
Activity 2.1
Answers to the learning check are provided below:
- Can you explain why health and wellness would be important to college students?
- Answer: They affect academic performance.
- Can you list three of the most common health issues that negatively affect college students’ academic performance?
- Answer: (any three) Procrastination, Stress, Cold/Virus or other respiratory illness or Flu, Anxiety, Sleep difficulties, Depression, Ongoing or chronic medical conditions, Finances, Intimate Relationships, Family
- What are the three components of health?
- Answer: [Physical, Mental and Spiritual]
- List the eight components of wellness.
- Answer: Physical, Mental or Intellectual, Spiritual, Emotional, Social, Financial, Occupational, Environmental
- Where could you go on campus to address your physical health or wellness?
- Answer: Student Health Center
- Where could you go on campus to address your emotional wellness?
- Answer: Student Counseling Center]
Learning Check
Health can be seen as the normal or optimal functioning of all components of a human being—body, mind, and spirit—and the absence of disease, illness, dysfunction, or pain. Health is important in college because it supports academic performance. Some of the top issues college students report adversely affect their academic performance are respiratory illness like colds, influenza, and other viral illnesses, depression, and chronic medical conditions.
Answer the questions below for a quick assessment of your learning in this unit.
- Can you explain why health and wellness would be important to college students?
- Can you list three of the most common health issues that negatively affect college students’ academic performance?
- What are the three components of health?
- List the eight components of wellness.
- Where could you go on campus to address your physical health or wellness?
- Where could you go on campus to address your emotional wellness?
Activity 2.2
Identify Your Wellness Behaviors and Activities
Directions
- Make a table using the 8 dimensions of wellness: physical, mental/intellectual, spiritual, emotional, social, environmental, financial, and occupational.
- Next to each dimension, list activities or behaviors you currently incorporate into your regular routine.
- Next to that, list activities or behaviors you would like to incorporate into your regular routine.
- If you need some ideas, check out this examples in the table below.
Table 1. Wellness Plan
Dimension | Current activity or behavior | Planned activity or behavior |
Physical | Walk to class | Use cardio equipment at the Rec Center for 25 min, 5 times/week |
Mental | Participate in study groups | Visit the Academic Success Center |
Spiritual | Say a nightly prayer | Find a like-minded group of worship |
Emotional | Quiet time/self-reflection | Daily meditation, pursue a hobby |
Social | Meet new classmates | Join a campus club or organization |
Environmental | Use dining hall recycling bins | Recycle paper in computer lab or Newton Gresham Library |
Financial | Pay bills, monitor bank account | Set up a budget for this semester |
Occupational | Follow degree plan | Visit Career Services |
For more information, visit "Creating a healthier life: A Step-by-Step Guide to Wellness" from Substance Abuse and Mental Health Services Administration: https://store.samhsa.gov/sites/default/files/d7/priv/sma16-4958.pdf
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oercommons
|
2025-03-18T00:37:12.163545
| null |
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"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/79220/overview",
"title": "Foundations for College Success, Health & Wellness",
"author": null
}
|
https://oercommons.org/courseware/lesson/79221/overview
|
Sign in to see your Hubs
Sign in to see your Groups
Create a standalone learning module, lesson, assignment, assessment or activity
Submit OER from the web for review by our librarians
Please log in to save materials. Log in
or
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oercommons
|
2025-03-18T00:37:12.189543
| null |
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/79221/overview",
"title": "Foundations for College Success, Health & Wellness",
"author": null
}
|
https://oercommons.org/courseware/lesson/65956/overview
|
FOOD PYRAMID
Overview
Toddler-Food-Pyramid
Healthy eating is about having a varied, balanced diet and enjoying lots of different foods. The food pyramid will help you choose a healthy and varied diet for your child.
Children can decide how much food they need, so don’t make them eat until their plates are empty.
The Toddler Food Pyramid:
Sparingly; Others
2: Meat, Fish and Alternatives.
3: Milk, Cheese, and Yoghurt.
2-4: Fruit and Vegetables.
4: Cereals, Bread and Potatoes.
Food groups
The following are suggested servings from each of the Food Pyramid shelves. Offer the recommended serving from each Food Pyramid shelf every day.
Toddler-Food-Pyramid
Healthy eating is about having a varied, balanced diet and enjoying lots of different foods. The food pyramid will help you choose a healthy and varied diet for your child.
Children can decide how much food they need, so don’t make them eat until their plates are empty.
The Toddler Food Pyramid:
Sparingly; Others
2: Meat, Fish and Alternatives.
3: Milk, Cheese, and Yoghurt.
2-4: Fruit and Vegetables.
4: Cereals, Bread and Potatoes.
Food groups
The following are suggested servings from each of the Food Pyramid shelves. Offer the recommended serving from each Food Pyramid shelf every day.
Bread, cereals and potatoes — Provide energy to help work and play
Recommended servings per day:
1-3 years: 4 servings
3-5 years: 4-6+ servings
1 Serving = any of the following
- 1 slice of bread or a small bread roll
- 1 small bowl of cereal (eg 30g variety size pack)
- 2 cream crackers
- 1 medium potato
- 3 dessert spoons of boiled rice or pasta
Active children may need more servings from this food group to give them enough energy.
Remember — children’s appetites can vary, offer younger children smaller portion sizes more often.
Fruit & vegetables — Provide vitamins and minerals, essential for good health
Recommended servings per day:
1-3 years: 2-4 servings
3-4 years: 4 or more servings
5 years and over: 5 servings
1 Serving = any of the following
- 1 medium sized fresh fruit for example
- Small glass of unsweetened pure fruit juice — dilute with plenty of water
- Small bowl of tinned fruit in natural juice, small bowl of chopped fruit, fresh fruit salad
- 3 dessert-spoons of stewed fruit
- 2 tablespoons of vegetables or 3 dessert-spoons of salad
- Bowl of home-made vegetable soup
Milk, cheese and yoghurt — Provide calcium for healthy bones and teeth
Recommended servings per day:
1-3 years: 3 servings
3-5 years: 3 servings
1 Serving = any of the following
- 1 glass of full fat milk (1/3 pint of milk)
- 1 carton of yoghurt
- Matchbox sized piece of cheese (1oz)
- 2 cheese slices
- Small bowl of milk pudding
- 2 fromage frais
Low fat milk is not suitable as the main drink for children under 2 years of age. You can gradually introduce it after 2 years of age provided your child is a good eater and has a varied diet. Skimmed milk is not suitable for children under 5 years.
Meat, fish and alternatives — Provide protein for growth and development
Recommended servings per day:
1-3 years: 2 small servings
3-5 years: 2 servings
1 Serving = any of the following
- Small pork or lamb chop
- 2 slices roast or boiled meat
- 2 slices of chicken or turkey
- Medium fillet of fish
- 2 eggs
- 6 tablespoons of baked beans, peas, lentils
Top Shelf of the Food Pyramid
Foods such as sweets, chocolate, biscuits, cakes, fizzy drinks and savoury snacks, like crisps, are on the top shelf of the Food Pyramid.
These foods should not be a part of your child’s daily diet. Filling up on foods from this shelf spoils your child’s appetite for more nutritious food.
Sugary food and drinks are not good for your child’s teeth.
Suitable snacks:
Fresh fruit such as pears, satsumas, bananas, kiwi fruit
Cheese cubes, slices
Crackers or rice cakes and cheese
Bread- toast, rolls, baps, pitta bread
Fruit brack, malt loaf, banana bread
Scones- plain, fruit or wholemeal
Small sandwiches
Yoghurt
Fromage frais
Homemade milkshake using yoghurt and fruit
Unsweetened breakfast cereal with milk (don’t add sugar)
Homemade soup
Vegetable slices, sticks or wedges
Milk
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oercommons
|
2025-03-18T00:37:12.216079
|
05/02/2020
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/65956/overview",
"title": "FOOD PYRAMID",
"author": "AMEENA BEEBI"
}
|
https://oercommons.org/courseware/lesson/123403/overview
|
| Cranfield Test 1 | Cranfield Test 2 | Smart Retrieval experiment | MEDLARS Test | The STAIRS project | TREC Experiment: The Text Retrieval Conference |
Introduction | The Cranfield 1 study, led by C. W. Cleverdon, was the first comprehensive assessment of information retrieval systems conducted in Cranfield, UK. Cleverdon's 1962 report on the first Cranfield Study, which started in 1957. | Cranfield 2 the second phase of the Cranfield studies started in 1963 and ended in 1966.The Cranfield 2 was a controlled experiment designed to look into the elements of index languages and how they affect retrieval system performance. | Gerard Salton evaluated the several searching options provided by the SMART retrieval system under laboratory conditions. The system was introduced in 1964 and is based on the processing of abstracts in natural language forms. | From August 1966 to July 1967, the US National Library of Medicine's Medical Literature Analysis and Retrieval System (MEDLARS) performance was evaluated. The operational database of MEDLARS, a database of biomedical papers, was used for the test, Medical Subject Headings thesaurus (MeSH) entries are being taken out. | Blair and Maron (1985) released a report on a large-scale experiment designed to assess a full-text search and retrieval system’s retrieval efficacy. The Storage and Information Retrieval System (STAIRS) Study is the name given to this. | The TREC studies, which were to be conducted by the National Institute of Science and Technology (NIST) and financed by the US Defence Advanced Research Projects Agency (DARPA) in 1991, allowed information retrieval researchers to expand from small data sets to bigger tests. |
Scope | 18,000 indexed items and 1200 search topics were used in the investigation. The documents were selected evenly from the general public, with half being research reports and the other half being magazine pieces. Field of high-speed aerodynamics, which is a subfield of aeronautics. | The Cranfield 2 test was created for information retrieval research, specifically to assess how well IR systems can employ user queries to extract pertinent information from a vast collection of documents. | Enhances accuracy and relevance by utilising cutting-edge methods such as machine learning, natural language processing (NLP), and semantic comprehension. Smart retrieval interprets the meaning of searches by doing more than just matching keywords. | The MEDLARS test's intentions were to assess the current MEDLARS system and identify areas for improvement. At the time of the test, there were roughly 7,00,00 items in the document collection that was accessible on the MEDLARS service. | The STAIRS evaluation’s primary goal was to determine how well the system could retrieve every document and only those that are pertinent to a particular request and recall and precision metrics were employed to achieve this. | In several TREC studies, a broad variety of information retrieval techniques were examined (i.e. from TREC 1 in 1992 to TREC 12 in 2003). Boolean search, statistical and probabilistic indexing, and term weighting strategies are a few noteworthy examples. |
Methodology | The project made use of pre-made enquiries that were created prior to the start of the real search. In all, 400 queries were created, and the system handled each one in its three stages. As a result, the system processed 1200 search requests in total. | Documents from a predetermined corpus are used. It usually contains 1,400 items (research papers, articles, etc.) for Cranfield 2. The retrieval system is tested using a set of 75 queries. These queries are examples of common search terms that a user might use to find specific information in the corpus of documents. | For this experiment, journals were used. Eight distinct individuals with knowledge of the topic, either as librarians or library science students, were requested to create 48 distinct search queries in the documentation area using clear, grammatically accurate English. After each of the eight individuals submitted their inquiry, a total of 48 queries were examined utilizing the several search options provided by the SMART system against a file containing 1268 data. | From the user community, 21 user groups were chosen. 302 search requests were made by the user group that was chosen. The system operator created each query in terms of MeSH and carried out searches. Following a search, users get the sample output for pertinent evaluation. The articles' photocopies, instead were provided for the relevance assessment, rather than just as references. | Nearly 40,000 documents, or about 350,000 pages of hard copy text used in the defence of a major corporate lawsuit, made up the database that the STAIRS study looked at. | The tree-eval package, which provided roughly 85 distinct numbers for a run, including recall and accuracy measurements at different cut-off points and a single value summary measure for recall and precision, was used to evaluate the ad hoc retrieval tasks in TREC. |
Results | With a recall percentage ranging from 60% to 90% and an overall average of 80%, all four systems were functioning effectively. It was found that retrieving papers in general aeronautics domains had success rates that were 4-5% higher than those in specialized fields like high-speed aerodynamics. | Because the test-performing index languages were made up of uncontrolled single words that appeared in papers, the Cranfield 2 test results were surprising. | It was observed from a ranking of the recall-precision graphs produced by the various processing techniques, that Changes in the relevance judgements had no effect on the relative performance of the different retrieval methods, despite the fact that the groups’ general consistency of relevance agreements was not very high. The ranking of alternative search methods was the same across four sets of relevance evaluations. | However, the memory and precision ratios of all 302 queries were analysed, and the individual ratios were averaged using the MEDLARS test. | Eleven of the 51 requests were used to test sampling strategies and account for potential bias when assessing retrieval and sample testing, while 40 of the requests had their recall and precision values determined. | Despite many experimental designs, the performance level remained the same. As an example, some groups used the topic statements to automatically produce queries, while others did so manually; feedback on relevancy was absent from numerous systems; the computer platform utilised varied from personal computers to supercomputers; Variations in the precision-recall curve were negligible; and Despite the similarity of the precision-recall results, there was a significant disarray in the actual documents recovered. |
Limitation | The artificial nature of this study, which had no impact on real-life situations, was one of its primary complaints. | Various word, phrase, or combination units made up each index language of both. The questions and documents were created in the same manner. As a result, the relative efficacy of the languages with varying levels of specificity would be assessed by matching questions to documents. | It was shown that changes in the relevance judgements had no effect on the SMART evaluation outcome. For the collection of data being studied, the recall-precision outcome was essentially invariant. | A number of suggestions for enhancing MEDLARS performance were derived from the test’s outcomes: The creation of another search request is one of the significant modifications made to the MEDLARS as a result of this test. | As mentioned, “It was impossibly difficult for users to predict the exact words, their combinations, and phrases used in all or most of the relevant documents and only in those documents”. This was one of the reasons why STAIRS did not work. | The primary challenge of TREC focusses on methodological problems. The conventional laboratory paradigm was used for TREC investigations which is extremely challenging to convey to people looking up material online as compared to in a traditional library setting. |
Path breaking approach | More real-world complexity, such as personalized search, multimodal data, and interactive evaluation, will be incorporated into the conventional framework of controlled evaluation based on precision and recall. | According to Cranfield 2, retrieval systems might not function very well and are challenging to greatly improve. It’s highly likely that Cranfield 2 promoted caution in system analysis and carrying out experiments. | In the future of SMART retrieval research, keyword-based, static models will be replaced by intelligent, interactive, personalised, and multimodal systems driven by deep learning, artificial intelligence, and natural language processing. | The MeSH system, which was initially developed for MEDLARS, is still in use today to facilitate effective PubMed and MEDLINE searching and information retrieval. | The potential growth of information retrieval, according to the Stairs Project, lies in scalable, user-centered, and semantic retrieval systems. | As IR develops, TREC will remain a driving force behind innovation, helping researchers and practitioners test and refine systems that will impact information retrieval in future generations. |
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oercommons
|
2025-03-18T00:37:12.269855
|
12/26/2024
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/123403/overview",
"title": "DIFFERENT EVALUATION OF INFORMATION RETRIEVAL EXPERIMENTS",
"author": "SULTANA KHATUN SHEIKH"
}
|
https://oercommons.org/courseware/lesson/86239/overview
|
Mercury Poisoning
Overview
The video describes the overall causes, reducing methods of mercury poisoning.
What is mercury poisoning ?
Mercury poisoning refers to a toxicity from mercury consumption, like fishes, waste from the medical and hospitals and also volcanic eruptions. Mercury is a metal that interrupts in the same way as the other metals in the D block elements.
Methyl mecury in the environment is constantly recycled through a biogeochemical cycle. The metal can be converted into methyl mercury by certain bacteria. This mercury processing bacteria are consumed by the next organisms up the food chain until finally consumed by the humans.
The usual amount of mercury found is at the levels of anywhere between 0.01 ppm to 0.5 ppm. Minamata is a neurological disease that came into existence in May 1956, Japan. It is caused by poisoning due to the ingestion of methyl mercury contaminated fish.
Using mercury inks, paints, dyes and lamps must be strictly prohibited. So much mercury from thermometers, medical equipments, and household appliances are some that must be recycled.
Consuming foods with mercury is the most common cause of this type of poisoning. You can help prevent toxicity by limiting your exposure to this potentially dangerous metal.
Thankyou.
Apps Used - Adobe Spark & Animaker
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oercommons
|
2025-03-18T00:37:12.287564
|
09/29/2021
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/86239/overview",
"title": "Mercury Poisoning",
"author": "Sanika More"
}
|
https://oercommons.org/courseware/lesson/107075/overview
|
Case study Low Salt Diet
Case study Low Salt Diet
Case study Low Salt Diet
Case study Low Salt Diet
Case study Low Salt Diet
Case Study Renal Diet
Texture Modification Case Study
Healing from Within
Overview
In this course, the students will be applying the principles of diet therapy in planning and preparation of therapeutic diets for various diseases and conditions.
Overview
Medical nutrition therapy (MNT) is an evidence-based, individualized nutrition process meant to help treat certain medical conditions. This platform serves as an interactive educational materials for dietitians and public on various therapeutic diets and various case management based on MNT. This OER platform will provide you unlimited access to various types of therapeutic diets and the case management
Course Description
In this course, the students will be applying the principles of diet therapy in planning and preparation of therapeutic diets for various diseases and conditions.
Learning Objectives
At the end of the course, students should be able to:
1. Explain the pathophysiology, medical and nutrition therapy of selected diseases and medical conditions.
2. Design proper nutrition care plans using the principles of nutrition care process, including assessment, planning, intervention, and evaluation from the given case studies based on standard nutrition guidelines
3. Perform skills in preparing appropriate therapeutic diets and calculate the nutrients content of the therapeutic menu prepared based on standard guidelines
Who are We?
We are Dietetics lecturers with years of teaching experience in Nutrition and Dietetics.
Module 1
Module 2
Module 3
Module 4
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oercommons
|
2025-03-18T00:37:12.316083
|
07/25/2023
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/107075/overview",
"title": "Healing from Within",
"author": "SYAHRUL BARIAH ABDUL HAMID"
}
|
https://oercommons.org/courseware/lesson/116971/overview
|
FAD Syllabus: UNCP HST1010
Overview
Syllabus shared by a UNC System faculty member.
Sample Syllabus
HST 1010: American Civilizations to 1877
Spring 2024 UNC Pembroke
Instructor Information & Contacts
Hi! I'm Dr. [FACULTY MEMBER NAME], Professor and Chair in the Department of History at UNCP. I have been teaching here since 2008 and History 1010 is my most frequently-taught course. You can find me in my office, [OFFICE LOCATION], which is inside the History Department suite on the second floor of the Dial Building, just down the hall from our classroom.
The best times to find me in my office are Mondays and Tuesdays from 2-5 pm, and Wednesdays and Fridays from 9:30-11 am. These are the hours I have set aside to chat with whomever drops by or calls my office. If you'd like to hold a zoom or webex meeting during my office hours, I can email you a link. If none of those times work for you, let me know and we will set up an appointment.
My office phone number is [TELEPHONE NUMBER]; voicemails left on that number also come to my email, so I get messages quickly even if I'm not on campus. You can use [FACULTY MEMBER EMAIL ADDRESS], but the best way to email me is actually through the Canvas Inbox. That way, you can find me as your HST 1010 instructor and not have to worry about how to spell my name.
I typically respond to emails and voicemails within 24 hours, though on a weekend the response might be that we need to follow up on a weekday if it involves other people on campus. I generally do not respond to emails or voicemails between 9 pm and 7 am, and I will also do my best not to bother you with messages or announcements on weekends and evenings.
Course Overview
This class meets in person on Mondays, Wednesdays, and Fridays, from 11:15 am-12:05 pm in Dial
221. We will meet in person on all days, barring a few professional obligations that require the professor to be elsewhere. This syllabus and the course plan are subject to change as needed to accommodate inclement weather or other emergencies, or to better meet the instructional needs of the students.
This 3-credit course fulfills the university's general education requirement for History under Section
II.A. It can also serve as a general education elective (Section IV) if you have already taken a general education history course. Finally, this course helps meet the introductory history requirement for the major, minor, and academic concentration in History.
This course provides students with a survey of the major political, economic, social, and cultural developments in the United States to 1877. Students who successfully complete this course will be able to:
- Differentiate between primary, secondary, and tertiary sources, read and analyze primary sources from 1600-1877, and use primary sources in written assignments.
- Describe and compare the economic, social, and religious trends in each of the four regions of British North America during the colonial era.
- Describe the key events that led to the creation of the United States of America as an independent nation.
- Analyze the political, social, and economic consequences of the Market Revolution.
- Describe the process of emancipation and Reconstruction.
Requirements and Materials
I expect you to attend and participate in all class meetings and submit all assignments, doing your own best work. As this is a fully in-person class, there are no provisions for remote attendance. There is room built into the schedule for an occasional missed class meeting; you should make plans to get notes from any missed sessions from a classmate. If you need to miss two or more class meetings in a row due to illness or emergency, please get in touch ASAP so we can arrange notetaking and possibly make-up assignments.
You will need reliable access to Canvas, as well as a method for taking notes both inside and outside of class, and a binder or folder to keep track of handouts and returned assignments. This class does not have an assigned physical textbook, but instead will use a combination of free online resources, primarily an online textbook and document collection called The American Yawp. All texts will be posted to Canvas. You will sometimes need to print materials and bring them to class with you.
Assignments and Grading
Participation (100 points total): For each class meeting, you will have the opportunity to earn up to 3 points for participation in rapid-response quizzes and various types of discussions. With perfect attendance and perfect scores, you could actually earn up to 120 points for participation, so consider that your reserve for up to 6 necessary absences or a chance to earn some built-in extra credit.
Exams (100 points total, 25 points each): Exams will be completed in the classroom on paper and contain a combination of multiple-choice and short essay questions. The Unit 1 Exam takes place on Friday, February 2; the Unit 2 Exam is scheduled for Friday, March 1; and the Unit 3 Exam takes place on Friday, April 5. The Unit 4 Exam is scheduled during our final exam slot on Friday, May 3, at 8 am, and it is not a cumulative final exam. You must complete all four exams in order to earn a passing grade in the course, regardless of overall score.
Grading Scale
A 188-200 points | B- 159-163.9 points | D+ 132-135.9 points |
A- 180-187.9 points | C+ 152-158.9 points | D 124-131.9 points |
B+ 174-179.9 points | C 142-151.9 points | D- 116-123.9 points |
B 164-173.9 points | C- 136-141.9 points | F 0-115.9 points |
University Policies
Americans with Disabilities Act (ADA) Statement
Federal laws require UNCP to accommodate students with documented learning, physical, chronic health, psychological, visual or hearing disabilities. In post-secondary school settings, academic accommodations are not automatic; to receive accommodations, students must make a formal request and must supply documentation from a qualified professional to support that
request. Students who believe they qualify must contact the Accessibility Resource Center (ARC) in the Joseph B. Oxendine Administrative Building (formerly West Hall), Suite 110 or call 910-521- 6695 to begin the accommodation process. All discussions remain confidential. Accommodations cannot be provided retroactively. More information for students about the services provided by ARC and the accommodation process may be found at the following
link: https://www.uncp.edu/departments/accessibility-resource-center
Absences for University-Sanctioned Events
If a student is representing the University in an official capacity (e.g.: academic conference, student government, course field trips, ROTC events, athletics, band) at an official University- sanctioned event, that absence shall be excused. Students are responsible for all coursework missed and must make up the work within three university business days after the student returns to campus. Any student who anticipates missing more than 15% of the course should not enroll in the course without prior approval from the instructor.
It is the responsibility of the student to communicate with the professor or instructor about classes missed for any reason, including University sanctioned events. Students must provide official documentation of proposed University-sanctioned events that will result in excused absences during the first week of each semester. Prior written documentation must be provided for each excused absence.
Religious Holiday Policy Statement
Students are allowed two excused absences each semester from class or other scheduled academic activity to observe a religious holy day of their faith. Students must submit written notification of the absences to their instructors within two weeks of the beginning of the semester. Students should not be penalized for these absences, and shall be permitted a reasonable amount of time to make up tests or other work missed due to an excused absence for a religious observance. A student who is to be excused from class for a religious observance is not required to provide a second-party certification of the reason for the absence. Furthermore, a student who believes that he or she has been unreasonably denied an education benefit due to religious beliefs or practices may seek redress through the student grievance procedure.
Academic Honor Code
Academic honor and integrity are essential to the existence of a university community and students are important members of that community. All UNCP students expected to abide by the policies and procedures of the Academic Honor Code, available here: https://www.uncp.edu/pr/pol- 020505-academic-honor-code-policy
What you should know about Intellectual Property: Instructors may require students to post their own work or, with the student's permission, may post a student's work on the online course site. Students must be informed of this (in the syllabus or in some other written format) at the beginning of the course. They must also be told if their work will be retained in the course site beyond the duration of the term and whether others will have access to it. No evaluative commentary or grade information from the instructor may be included with student work if the work includes information identifying its creator. Students' copyrights in their work shall be governed by the UNC Pembroke Copyright Policy.
Alternative Format Statement
All university publications, including syllabi, are available in alternative formats upon request. Please contact the Accessibility Resource Center in Joseph B. Oxendine Administrative Building, Suite 110 or at 910-521-6695.
Schedule (subject to change—see Canvas for daily assignments)
Unit I: Colonial America (January 8-February 2)
Textbook Readings:
- Chapter 1 Part II: The First Americans
- Chapter 2: Colliding Cultures
- Chapter 3: British North America
- Chapter 4: Colonial Society Primary Source Readings & Discussions:
- Early Encounters in Native New York (January 10)
- Three Accounts of King Philip’s War (January 24)
- Salem Witch Trials testimony & data maps (January 26)
- Reactions to the George Whitfield Revivals (January 31) Exam 1: Friday, February 2
Unit 2: Founding the New Nation (February 5-March 1)
Textbook Readings:
- Chapter 5: The American Revolution
- Chapter 6: A New Nation
- Chapter 7: The Early Republic Primary Source Readings & Discussions:
- The Declaration of Independence and excerpts from Common Sense (February 7)
- Annotated Excerpt from The Federalist #51 (February 14)
- Relevant excerpts from US Constitution and letters by Hamilton & Jefferson on National Bank debate (February 16)
- Bill of Rights and Washington Letter to Touro Synagogue (February 19)
- Tecumseh’s Address to the Osage (February 26) Exam 2: Friday, March 1
Unit 3: The Market Revolution (March 11-April 5)
Textbook Readings:
- Chapter 8 Part II: Early Republic Economic Development
- Chapter 8 Part VI: The Rise of Industrial Labor in Antebellum America
- Chapter 9: Democracy in America
- Chapter 10: Religion and Reform
- Chapter 11 Part III: Cotton and Slavery
- Chapter 12: Manifest Destiny Primary Source Readings & Discussions
- Mill Girls letters & diaries (March 13)
- Indian Removal Case Studies (March 20)
- Robert Purvis, “Appeal of 40,000 Citizens to the People of Pennsylvania” and John C. Calhoun, “Slavery a Positive Good” (March 25)
- Seneca Falls Declaration (March 27)
- 19th century maps and images depicting “the West” and “Manifest Destiny” (April 3) Exam 3: Friday, April 5
Unit 4: The Civil War Era (April 8-May 3)
Textbook Readings:
- Chapter 13: The Sectional Crisis
- Chapter 14: The Civil War
- Chapter 15: Reconstruction Primary Source Readings & Discussions:
- Alexander Stephens Cornerstone Speech & Abraham Lincoln Inaugural Address (April 12)
- Emancipation documents, including excerpts from Preliminary and Final Emancipation Proclamations (April 17)
- Battlefield Photographs (April 19)
- Jourdan Anderson Letter and Mississippi Black Codes (April 22)
- Fourteenth and Fifteenth Amendments (April 24) Exam 4: Friday, May 3 (final exam slot)
|
oercommons
|
2025-03-18T00:37:12.430676
|
06/18/2024
|
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"url": "https://oercommons.org/courseware/lesson/116971/overview",
"title": "FAD Syllabus: UNCP HST1010",
"author": "UNC System"
}
|
https://oercommons.org/courseware/lesson/103743/overview
|
IHE Accessibility in OER Implementation Guide
Overview
Our teams Landscape Analysis to uncover key structures and supports that can guide our work to support Accessibility in OER.
May 11 - Section One: Landscape Analysis for Accessibility in OER in Local Context (Work on during May 11th implementation)
In this section, you and your team will engage in a Landscape Analysis to uncover key structures and supports that can guide your work to support Accessibility in OER. We exnourage to explore some of the questions from each category. You may or may not answer all of these questions, but this is an offering. We ask that you complete Parts One, Two and Six.
Part One: Initial Thoughts
Explore the possibilities of OER classroom materials, both what exists and the how to create, and creating a guidelines document for faculty.
Part Two: Introductory probing questions:
We currently don't measure it. We have a new faculty member taking over accessibility services this year, but not much else in place.
OER is currently done on an individual basis, with approximately 3 faculty exploring the possibilities. There is not centralized resource or data to assist (besides one helpful librarian!)
Part Three: Clarifying questions for accessibility:
Accessibility Services Coordinator
We have a voluntary UDL Academy on campus and we will be requiring use of UDL in a general education program currently under design.
Our librarian, Bree!
All of them! Outside of the Accessibility Services Coordinator we have not had much attention to this area until the pandemic.
Part Four: Clarifying questions for OER:
There isn't organizational support or any specific office or role devoted to this. We have a Center for Excellence in Learning and Teaching and UDL academy, but both are voluntary and without sufficient funding. These are also not focused specifically on curricula.
What is our organizational structure that supports OER? The librarian is available for specific questions, but no specific structure dedicated to OER.
Who generates most of the curricular resources in our organization? It's left to each faculty member on their own, with support available from the librarian.
Where do most educators get support with curricular resources? We really don't have anyone in that dedicated role.
What content areas might have the largest gaps in access to curricular resources/OER? All
Part Five: Clarifying questions for Faculty learning and engagement:
What Professional Learning (PL) structures have the best participation rates for our educators? CELT and our UDL Academy are both voluntary participation, although they are encouraged by the Provost. CELT this year had a participation rate of around 30%. The UDL Academy is open to 15 people maximum per year, but funding for future years is uncertain.
What PL structures have the best "production" rates for our educators? Same as previous. We are seeing the same people participate across opportunities, but also have a large group who don't participate in anything.
What incentive do we have to offer people for participating in learning and engagement? Limited, and grant based.
Who are the educators that would be most creative with accessibility and OER? The cohort attending, with a few additional.
Who are the educators that would benefit the most from accessibility and OER? Everyone
Part Six: Final Probing questions:
What is our current goal for Accessibility in OER and why is that our goal? Raising awareness and creating a guidelines document to support all faculty.
Who have we not yet included while thinking about this work? Students and staff.
What barriers remain when considering this work? Time and money.
What would genuine change look like for our organization for this work? Centralized organizational structure for support, more funding both for developement and incentives.
Section Two: Team Focus (Finish before May 25th to share during Implementation Session Two)
Identifying and Describing a Problem of Practice
The following questions should help your team ensure that you are focusing your collaboration.
What is your Team’s specific goal for this series? You may consider using AEM Quality Indicators for Creating Accessible Materials to help add to or narrow your work. Since we lack a centralized hub/caretaker for accessability information, we are going to focus on #1 from the AEM Quality Indicators and develop a proposal for a coordinated system for the university.
What other partners might support this work? IT, our accessibility services coordinator, the team, chair of general education, and academic dean.
What is your desired timeframe for this work? To have a plan completed over the summer that we can present heading into next year. (Deadline August 15th)
How will you include diverse voices and experiences in this work? Present at the All-Faculty back-to-school meeting.
Please create a Focus Question that explains your goal and provides specific topics that you would like feedback on. This is what you will share in your breakout groups for feedback. How do we collate existing work/resources and plan for additional needs in an easily located space?
(Save for during May 25th's session.) What feedback did you receive from another team during the May 25th Implementation Session? Be sure to have a section for getting started that won't overwhelm people with too many details.
Section Three: Team Work Time and Next Steps (Complete by the end of Implementation Session Three)
Sharing and Next Steps
What was your redefined goal for this series? Creating awareness of accessibility issues and establishing a central webpage containing information and resources.
What does your team want to celebrate? We had our first meeting with additional people! Our group of employees interesting in and working on accessibility on campus is growing.
What did your team accomplish? If you have links to resources, please include them here. We met with our Accessibility Services Coordinator and a member of marketing this week to start discussions about raising awareness of accessibility resources on campus. This meeting also highlighted some areas for potential growth in what we offer both students and employees that we can start working to address. Individually, we also learned a lot about new tools and ideas.
What are your team’s next steps? (1) Create a website. (2) Support our new Accessibility Services Coordinator in reaching out to students and faculty regarding available services. (3) Continue collaborating.
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3.3 Plant Biotechnology
3.3 Plant Germplasm
3_Influence-of-Genetic-Engineering-on-Agriculture-and-Germplasm-Conservation
Exercise 3a Herbaceous Cuttings
Exercise 3b Flower Reproductive Parts Dissection
Influence of Genetic Engineering on Agriculture and Germplasm Conservation
Overview
Plant tissue cultures being grown at a USDA facility. USDA, Lance Cheung, Public domain, via Wikimedia Commons
Did you have an idea for improving this content? We’d love your input.
Introduction
Learning Objectives
- Compare conventional breeding and genetic engineering.
- List the advantages and disadvantages of plant breeding.
- Explain the steps in molecular cloning.
- List examples of genetically engireered, transgenic crops.
- Define germplasm.
- Explain the significance of germplasm conservation.
- Describe USDA-ARS National Plant Germplasm System.
Key Terms
biotechnology - use of biological agents for technological advancement
clone - exact replica of an organism, a cell, DNA molecule
contig - larger sequence of DNA assembled from overlapping shorter sequences
conventional breeding - crossing or mating the organisms with preferred traits and selecting the progeny that produces those traits or a combination of traits.
cytogenetic mapping - a technique that uses a microscope to create a map from stained chromosomes
ex-situ conservation - conserving an organism outside of its natural habitat, such as a zoo
foreign DNA - DNA that belongs to a different species or DNA that is artificially synthesized
gene targeting - method for altering the sequence of a specific gene by introducing the modified version on a vector
genetic engineering - alteration of the genetic makeup of an organism
genetic recombination - DNA exchange between homologous chromosome pairs
genetically modified organism (GMO) - an organism whose genome has been artificially changed
germplasm - a collection of all genetic material stored as seeds, tissues, and live samples.
in-situ conservation - conserving an organism in its natural habitat
recombinant DNA - combining DNA fragments from two different sources or organisms
recombinant protein - a gene's protein product derived by molecular cloning
transgenic - organism that receives DNA from a different species
Introduction
Plants are the source of food for humans as well as livestock. Farmers have historically developed ways to select plant varieties with desirable traits, long before modern-day biotechnology practices were established. conventional breeding relies on crossing or mating the organisms with preferred traits and selecting the progeny that produces those traits or a combination of traits. conventional breeding has generated many present-day crops from wild relatives over thousands of years. However, modern scientific techniques have led to faster and more efficient practices. Staples like corn, potatoes, and tomatoes were the first crop plants that scientists genetically engineered. Biotechnology creates organisms by using a targeted approach to modify specific traits, changing an organism's genomic composition or DNA. Since the discovery of the structure of DNA in 1953, the biotechnology field has proliferated through both academic research and private companies. The primary applications of this technology are in medicine (vaccine and antibiotic production) and agriculture (crop genetic modification to increase yields). Biotechnology has many industrial applications, such as increasing fermentation, treating oil spills, and producing biofuels. Similarly, the collection and maintenance of germplasm, is critical for advancements in technology. Germplasm is a collection of all genetic material stored as seeds, tissues, and live samples. The conservation and documentation of all the samples and related documentation provide vital information useful in biotechnology.
DNA and Recombinant DNA
To understand the basic techniques used to work with nucleic acids, it is important to remember a few basic facts:
- Nucleic acids are macromolecules made of nucleotides—a sugar, a phosphate, and a nitrogenous base—linked by phosphodiester bonds. The phosphate groups on these molecules each have a net negative charge.
- An entire set of DNA molecules in the nucleus is called the genome. DNA has two complementary strands linked by hydrogen bonds between the paired bases. Exposure to high temperatures (DNA denaturation) can separate the two strands and cooling can reanneal them.
- The DNA polymerase enzyme can replicate the DNA.
- Unlike DNA, located in the eukaryotic cells' nucleus, RNA molecules leave the nucleus.
- The most common type of RNA that researchers analyze is messenger RNA (mRNA) because it represents the protein-coding genes that are actively expressed. However, RNA molecules present some other challenges to analysis, as they are often less stable than DNA.
Access for free at https://openstax.org/books/biology-2e/pages/17-1-biotechnology
Molecular Cloning
In general, the word “cloning” means the creation of a perfect replica; however, in biology, the re-creation of a whole organism is referred to as “reproductive cloning.” Long before attempts were made to clone an entire organism, researchers learned how to reproduce desired regions or fragments of the genome, a process that is referred to as molecular cloning. The technique offered methods to create new medicines and overcome difficulties with existing ones. Scientists have repurposed and engineered plasmids as vectors for molecular cloning and the large-scale production of important reagents, such as insulin and human growth hormone. Cloning small genome fragments allows researchers to manipulate and study-specific genes (and their protein products) or noncoding regions in isolation. A plasmid, or vector, is a small circular DNA molecule that replicates independently of the chromosomal DNA.
In cloning, scientists can use the plasmid molecules to provide a "folder" in which to insert the desired DNA fragment. Plasmids are usually introduced into a bacterial host for proliferation. In the bacterial context, scientists call the DNA fragment from the genome of the studied organism, foreign DNA —or a transgene; to differentiate it from the bacterium's DNA—or the host DNA.
Plasmids occur naturally in bacterial populations (such as Escherichia coli) and have genes that can contribute favorable traits to the organism, such as antibiotic resistance (the ability to be unaffected by antibiotics). An important feature of plasmid vectors is the ease with which scientists can introduce a foreign DNA fragment via the multiple cloning site (MCS). The MCS is a short DNA sequence containing multiple sites that different commonly available restriction endonucleases can cut. Restriction endonucleases recognize specific DNA sequences and cut them in a predictable manner. They are naturally produced by bacteria as a defense mechanism against foreign DNA. Many restriction endonucleases make staggered cuts in the two DNA strands, such that the cut ends have a 2- or 4-base single-stranded overhang. Because these overhangs are capable of annealing with complementary overhangs, we call them “sticky ends.” Adding the enzyme DNA ligase permanently joins the DNA fragments via phosphodiester bonds. In this way, scientists can splice any DNA fragment generated by restriction endonuclease cleavage between the plasmid DNA's two ends that have been cut with the same restriction endonuclease (Figure 3.3.1).
Plasmids with foreign DNA inserted into them are called recombinant DNA molecules (Figure 3.3.1) because they are created artificially and do not occur in nature. They are also called chimeric molecules because the origin of different molecule parts of molecules can be traced back to different species of biological organisms or even to chemical synthesis. We call proteins that are expressed from recombinant DNA molecules recombinant protein.
Not all recombinant plasmids can express genes. The recombinant DNA may need to move into a different vector (or host) that is better designed for gene expression. Scientists may also engineer plasmids to express proteins only when certain environmental factors stimulate them, so they can control the recombinant proteins' expression.
Genetic Engineering
Scientists have genetically modified bacteria, plants, and animals since the early 1970s for academic, medical, agricultural, and industrial purposes. Genetic engineering is the alteration of an organism’s genotype using recombinant DNA technology to modify an organism’s DNA for the purpose of achieving desirable traits. The addition of foreign DNA in the form of recombinant DNA vectors generated by molecular cloning is the most common method of genetic engineering. The organism that receives the recombinant DNA is a genetically modified organism (GMO). In the US, GMOs such as Roundup-ready soybeans and borer-resistant corn are part of many common processed foods. If the foreign DNA comes from a different species, the host organism is transgenic, Bt corn and Bt cotton are two such examples of transgenic plants.
Gene Targeting
Although classical methods of studying gene function began with a given phenotype and determined the genetic basis of that phenotype, modern techniques allow researchers to start at the DNA sequence level and ask: "What does this gene or DNA element do?" This technique is called reverse genetics, and it has resulted in reversing the classic genetic methodology. This method would be like damaging a body part to determine its function. For instance, an insect that loses a wing cannot fly. The classical genetic method would compare insects that cannot fly with insects that can fly and observe that the non-flying insects have lost wings; this would result in understanding that the function of the wing is flight. Similarly, mutating or deleting genes provides researchers with clues about gene function. We collectively call these methods they use to disable gene function – gene targeting. Gene targeting is the use of recombinant DNA vectors to alter a particular gene's expression, either by introducing mutations in a gene or by eliminating a certain gene's expression by deleting a part or all the gene sequences from the organism's genome.
Access for free at https://openstax.org/books/biology-2e/pages/17-1-biotechnology
Plant Biotechnology
Plant biotechnology includes techniques used to adapt plants for specific needs or a possibility. Situations that combine multiple needs and opportunities are common. For example, a single crop may be required to provide sustainable food and healthful nutrition, protection of the environment, and opportunities for jobs and income. Finding or developing suitable plants is typically a highly complex challenge. Plant biotechnologies utilize tools and resources from genetics, genomics, marker-assisted selection (MAS), and transgenic (genetically engineered) crops to assist in developing new varieties and/or new traits in plants. This allows researchers to detect and map genes, discover their functions, select specific genes in genetic resources and breeding, and transfer genes for specific traits into plants where they are needed, for example, research and development of disease-resistant crops.
Most public research on transgenic crops focuses on one or two general objectives:
- a better understanding of all aspects of the transgenic/genetic engineering process, for enhancing efficiency, precision, and proper expression of the added genes or nucleic acid molecules
- and a wider range of useful and valuable traits, including complex traits.
National Institute of Food and Agriculture (NIFA) a U.S federal government body, funds research, training, and extension for developing and using biotechnologies for food and agriculture. Areas of work include, but are not limited to:
- genetic structures and mechanisms,
- methods for transgenic biotechnology (also known as genetic engineering),
- identification of traits and genes that can contribute to national and global goals for agriculture,
- plant genome sequences—molecular markers and bioinformatics,
- gene editing/genome editing,
- and synthetic biology.
Transgenic and genetically modified Plants
Manipulating the DNA of plants—creating GMOs—has helped to create desirable traits, such as disease resistance, herbicide and pesticide resistance, better nutritional value, and better shelf-life (Figure 3.3.2). As mentioned in the previous section, GMOs are plants that receive recombinant DNA) and transgenic plants receive DNA from other species. Because they are not natural, government agencies closely monitor transgenic plants and other GMOs to ensure that they are fit for human consumption and do not endanger other plant and animal life. To prevent foreign genes from spreading to other species in the environment, extensive testing is required to ensure ecological stability. Let us discuss some common methods used in developing tansgenic and genetically modified plants.
Explore the Nature Education article on GMOs by using this link.
Explore US Food & Drug Administration page on GMOs
Transformation of Plants Using Agrobacterium tumefaciens
Gene transfer occurs naturally between species in microbial populations. Many viruses that cause human diseases, such as cancer, act by incorporating their DNA into the human genome. In plants, tumors caused by the bacterium Agrobacterium tumefaciens occur by DNA transfer from the bacterium to the plant. Although the tumors do not kill the plants, they stunt the plants and they become more susceptible to harsh environmental conditions. A. tumefaciens affects many plants, such as walnuts, grapes, nut trees, and beets.
The artificial introduction of DNA into plant cells is more challenging because of the thick cell wall compared to animal cells. Researchers use the natural transfer of DNA from Agrobacterium to introduce DNA fragments of their choice into plant hosts. In nature, the disease-causing A. tumefaciens have a set of plasmids—Ti plasmids (tumor-inducing plasmids) —that contain genes to produce tumors in plants. DNA from the Ti plasmid integrates into the infected plant cell’s genome. Researchers manipulate the Ti plasmids to remove the tumor-causing genes and insert the desired DNA fragment for transfer into the plant genome. This newly engineered plasmid also carries antibiotic resistance genes to aid selection and researchers can propagate them in E. coli cells as well. Agrobacterium has been used as a vector to transform many GMOs such as canola, sugar beet, cotton, and soybean.
The Organic Insecticide Bacillus thuringiensis
Bt maize and Bt cotton are two examples of genetically modified crops with B. thuringiensis toxin. Bacillus thuringiensis (Bt) is a bacterium (Figure 3.3.3) that produces protein crystals (figure 3.3.4) during sporulation that is toxic to many insect species that affect plants. Insects need to ingest Bt toxin to activate the toxin. Insects that have eaten Bt toxin stop feeding on the plants within a few hours. After the toxin activates in the insects' intestines, they die within a couple of days (Figure 3.3.6). Modern biotechnology has allowed plants to encode their own crystal Bt toxin that acts against insects. Scientists have cloned the crystal toxin genes from Bt and introduced them into plants. Bt toxin is safe for the environment and non-toxic to humans and other mammals, and organic farmers have approved it as a natural insecticide. This reduces the use of synthetic spray pesticides.
Let us look at the basics of one of the techniques used in creating genetically modified plants with Bt toxin.
Step 1. Scientists identify the trait that is desired (for example, insect resistance).
Step 2. Find an organism that already has that trait - Bacillus thuringiensis (Bt) produces toxins against insects.
Step 3. Gene governing the production of toxins is excised using enzymes called restriction enzymes.
Step 4. Excised gene is utilized to create a DNA construct that includes the gene of interest or reporter gene as well as promoter and terminator sequences for proper transformation.
Step 5. DNA constructs are coated on gold particles and delivered to the undifferentiated plant cells or directly into a plant using a gene gun (Figure 3.3.5).
Step 6. The cells that absorb the DNA construct are stable and are selected and grown under with nutritive medium and treated with plant hormones to cause differentiation to form new plants.
Step 7. Newly formed young plants are grown and monitored in greenhouses and tested in fields. After a comprehensive evaluation, introduced for commercial purposes.
Study the use and impact of Bt Corn in this Nature article.
Here are some examples of successfully developed transgenic or genetically modified plants.
Flavr Savr Tomato
The first genetically modified crop on the market was the Flavr Savr Tomato, created in 1994. Scientists used antisense RNA technology to slow the softening and rotting process caused by fungal infections, which led to the increased shelf life of this tomato. Additional genetic modification improved the tomato's flavor. However, the Flavr Savr tomato did not successfully stay in the market because of problems maintaining and shipping the crop.
Golden Rice
Golden rice (Figure 3.3.8) was created to combat widespread vitamin A deficiency in children that live in developing nations, especially Africa, South Asia, and Southeast Asia (Figure 3.3.7). Golden rice is genetically modified to produce beta-carotene in the endosperm. Beta carotene is converted to vitamin A by the human body. Vitamin A is critical for normal vision, growth, and immune reaction. Night blindness is an early sign of vitamin A deficiency. Prolonged deficiency can cause complete blindness, as well as premature death. According to WHO, as many as 250,000 to 500,000 children are affected by this deficiency and about half of these children die within 12 months of losing their sight. The first country to adopt Golden Rice for production and consumption was the Philippines. However, due to misinformation and misunderstandings about genetically modified organisms, fewer countries have adopted the commercial use of golden rice.
Visit the USDA National Institute of Food & Agriculture to know more about plant biotechnology.
Kew's Millenium seed bank.
Access for free at https://openstax.org/books/biology-2e/pages/17-1-biotechnology
Plant Germplasm
Since the domestication of plants—over many thousands of years, humans have collected the seeds and other plant material for the purpose of propagation over growing seasons or years. germplasm is a collection of any plant material or data that can be utilized to conserve and investigate the genetic composition of a species. Germplasm includes seeds, vegetative parts of a plant, plant tissue culture collection samples, DNA samples, cultivars, landraces, crop wild relatives (CWR), and accessions with the relevant documentation and data on these collections (Veerala et al, 2021) (Figure 3.3.9). Genetic diversity of plants is critical, and acquisition, maintenance, research & analysis, documentation, conservation, and distribution are vital to the conservation of plant diversity.
Food security, dietary expectations, availability of feed for animals, medicine, fibers, and oils, as well as demands for fuel, continue to grow alongside the expanding human population. According to Byrne et al., 2018, a 25 to 70% increase in global agricultural production is required to meet food demand by 2050. With increased agricultural demands comes the increased risk of environmental deterioration due to soil erosion, greenhouse gas emissions, and nutrient runoff to waterways; additionally, global climate changes are presenting new challenges, such as increasing temperatures, water scarcity, and new emerging pests. Genetic engineering can aid in the needed response to these growing concerns, along with plant breeding, improved horticulture practices, integrated pest management, sustainable farming practices, and research in the various fields that inform better plant science.
Effective conservation and efficient use and access to the diversity of germplasm dictate the production of cultivars/accessions that are more suited to the various environmental conditions such as drought, flooding, soil salinity, nutrient-deficient soils as well as pathogen/pest infestation, and increased nutritional quality, and increased crop yield.
National Plant Germplasm System (NPGS)
USDA-ARS National Plant Germplasm System (NPGS) is the primary body involved in the preservation of germplasm resources in the United States. NPGS is made up of many laboratories and research stations (table 1). Multiple USDA offices and USDA Animal and Plant Health Inspection Service participate in acquiring, quarantining, and distributing of NPGS collections with collaboration. The complete and comprehensive database of NPGS collections is administered via the National Germplasm resource Laboratory, Beltsville, Maryland. NPGS is part of an international collaboration called the GRIN-Global project. (National Research Council 1991. The U.S. National Plant Germplasm System).
Visit the website of the USDA plant germplasm collection.
Collection/Facility | Location | Number of collections |
National seed storage laboratory | Fort Collins, Colorado | 230,000 accessions |
4 Regional stations | Pullman, Washington. Ames, Iowa Geneva, New York Griffin, GA
| 135,000 accessions of 4000 species |
10 National clonal germplasm repositories |
| 27,000 accessions of 3000 species |
National small grain collection | Aberdeen, Idaho | 110,000 accessions |
Interregional Research Project-1 | Sturgeon Bay, Wisconsin | 3500 potato accessions |
Multiple collections in universities/USDA laboratories |
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Unit 3 Lab Exercises
Exercise 3a: Herbaceous Cuttings
Students learn the techniques and procedures for propagating plants through herbaceous cuttings, including steps for selecting, preparing, and planting cuttings to ensure successful growth and development.
Exercise 3b: Flower Reproductive Parts Dissection
Students dissect a flower to identify and study its reproductive parts, including the stamen, pistil, and ovary. This exercise aims to help students understand the structure and function of these components in plant reproduction.
Attributions
Biology 2e By Mary Ann Clark, Matthew Douglas, Jung Choi. OpenStax is licensed under Creative Commons Attribution License v4.0
Priyanka, V.; Kumar, R.; Dhaliwal, I.; Kaushik, P. Germplasm Conservation: Instrumental in Agricultural Biodiversity—A Review. Sustainability 2021, 13, 6743. https://doi.org/10.3390/su13126743
Sustaining the Future of plant breeding: The critical role of the USDA-ARS National Plant Germplasm System by Patrick F Byrne, Gayle M Volk, Candice Gardner, Michael A Gore, Philipp W. Simon and Stephen Smith. Crop Science, 58:451-468 (2018). doi: 10.2135/crp[sco2017.05.0303
Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA. This is an open-access article distributed under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Published January 12, 2018
https://acsess.onlinelibrary.wiley.com/doi/10.2135/cropsci2017.05.0303
National Research Council 1991. The U.S. National Plant Germplasm System. Washington, DC: The National Academies Press. Https://doi.org/10.17226/1583
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1.3 Components of Prokaryotic Cell
1.4 Components of Eukaryotic Cell
1.5 Components of a Plant Cell
1_The-Cell
The Cell
Overview
Red and cyan fluorescent proteins marking plant cell nuclei. Fernan Federici
CC-BY-NC-SA-2.0
Botany by Melissa Ha, Maria Morrow & Kammy Algiers
https://bio.libretexts.org/Bookshelves/Botany/Botany_(Ha_Morrow_and_Algiers)
A Photographic Atlas for Botany by Maria Morrow https://bio.libretexts.org/Bookshelves/Botany/A_Photographic_Atlas_for_Botany_(Morrow)
Introduction to Botany By Alexey Shipunov
https://bio.libretexts.org/Bookshelves/Botany/Introduction_to_Botany_(Shipunov)
Plant Anatomy and Physiology by Sean Bellairs
https://bio.libretexts.org/Bookshelves/Botany/Book%3A_Plant_Anatomy_and_Physiology_(Bellairs)
Did you have an idea for improving this content? We’d love your input.
Introduction
Learning Objectives
- Define cell.
- Summarize the main components of a light microscope.
- List the features of a prokaryotic cell.
- Define cell theory.
- Explain how the surface area to volume ratio regulates cell size.
- List and describe the cellular components of a eukaryotic cell.
- Identify characteristic features of a plant cell.
- Explain the structure and function of the cell wall, chloroplast, central vacuole, and plasmodesmata in the plant cell.
Key Terms
cell theory/unified cell theory - a biological concept that states that all organisms are made up of cells; the cell is the basic unit of life, and new cells arise from existing cells
cell wall - rigid cell covering comprised of various molecules that protect the cell, provides structural support, and give shape to the cell
cellulose - the main component of cell wall, made up of glucose polymer
central vacuole - large plant cell organelle that regulates the cell’s storage compartment, holds water, and plays a significant role in cell growth as the site of macromolecule degradation
chlorophyll - the green pigment that captures the light energy that drives the light reactions of photosynthesis
chloroplast - plant cell organelle that carries out photosynthesis
endoplasmic reticulum (ER) - series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids
eukaryotic cell - a cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs
light microscope - an instrument that magnifies an object using a beam of visible light that passes and bends through a lens system to visualize a specimen
lignin - phenolic polymer, a component of plant cell wall
nucleus - cell organelle that houses the cell’s DNA and directs ribosome and protein synthesis
pectin - polysaccharide commonly found in the primary cell wall of plants
peptidoglycan - polysaccharide commonly found in the bacterial cell wall
plasma membrane - phospholipid bilayer with embedded (integral) or attached (peripheral) proteins, and separates the cell's internal content from its surrounding environment
plasmodesma - (plural = plasmodesmata) channel that passes between adjacent cell walls of plant cells, connects their cytoplasm, and allows transporting of materials from cell to cell
primary cell wall - outermost cell wall in a plant cell, primary made up of cellulose and pectin; usually flexible and permeable
prokaryote - a unicellular organism that lacks a nucleus or any other membrane-bound organelle
secondary cell wall - cell wall between the primary cell wall and plasma membrane in a plant cell; usually rigid and impermeable
Introduction
Close your eyes and picture a brick wall. What is the wall's basic building block? It is a single brick. Like a brick wall, cells are the building blocks that make up our body.
Our body has many kinds of cells, each specialized for a specific purpose. Just as we use a variety of materials to build a home, the human body is constructed from many cell types. Given their enormous variety, cells from all organisms—even ones as diverse as bacteria, onions, and humans—share certain fundamental characteristics.
Microscopy, Cell Theory & Cell Size
A cell is the smallest unit of all living things. We call “living things” – organism(s). Whether it is a single-cell organism (like bacteria) or a multi-cellular organism (like a human). Thus, cells are the basic building blocks of all organisms.
Several cells of one kind that interconnect with each other and perform a shared function make a tissue. These tissues combine to form an organ (your stomach, heart, or brain), and several organs comprise an organ system (such as the digestive system, circulatory system, or nervous system). Several systems that function together form an organism (like a human being). Here, we will examine the structure and function of cells.
All cells can be broadly categorized as prokaryotic and eukaryotic. For example, we classify both animal and plant cells as eukaryotic cells, whereas we classify bacterial cells as prokaryotic. Before discussing the criteria for determining whether a cell is prokaryotic or eukaryotic, we will first examine how biologists study cells.
Microscopy
Cells vary in size. To give you a sense of cell size, a typical human red blood cell is about eight-millionths of a meter or eight micrometers (abbreviated as eight µm) in diameter. A pinhead is about two-thousandths of a meter (two mm) in diameter. That means about 250 red blood cells could fit on a pinhead. With few exceptions, we cannot see individual cells with the naked eye, so scientists use microscopes (micro- ="small; -scope = "to look at") to study them. A microscope is an instrument that magnifies an object. We photograph most cells with a microscope, so we can call these images micrographs.
The optics of a microscope’s lenses change the image orientation that the user sees. A specimen that is right-side up and facing right on the microscope slide will appear upside-down and facing left when one views through a microscope, and vice versa. Similarly, if one moves the slide left while looking through the microscope, it will appear to move right, and if one moves it down, it will seem to move up. This occurs because microscopes use two sets of lenses to magnify the image. Because of how light travels through the lenses, this two-lens system produces an inverted image (binocular, or dissecting microscopes, work in a similar manner, but include an additional magnification system that makes the final image appear to be upright).
Light Microscope
Most student microscopes are light microscopes (figure 1.1a). In this type of microscope, visible light passes and bends through the lens system to enable the user to see the specimen. Light microscopes are advantageous for viewing living organisms, but since individual cells are generally transparent, their components are not distinguishable unless they are colored with special stains. Staining, however, usually kills the cells.
Two parameters that are important in microscopy are magnification and resolving power. Magnification is the process of enlarging an object in appearance. Resolving power is the microscope's ability to distinguish two adjacent structures as separate: the higher the resolution, the better the image's clarity and detail. Light microscopes that students commonly use in the laboratory magnify up to approximately 400 times. Light microscopes can magnify up to 1,000 times when oil immersion lenses are used. To gain a better understanding of cellular structure and function, scientists typically use electron microscopes.
Electron Microscope
In contrast to light microscopes, electron microscopes (figure 1.1.1b) use a beam of electrons instead of a beam of light. Not only does this allow for higher magnification and, thus, more detail, but it also provides higher resolving power. There are two main types of electron microscopes, transmission electron microscope (TEM) and scanning electron microscope (SEM). In a scanning electron microscope, a beam of electrons moves back and forth across a cell’s surface, creating details of cell surface characteristics. In a transmission electron microscope, the electron beam penetrates the cell and provides details of a cell’s internal structures. As you might imagine, electron microscopes are significantly bulkier and more expensive than light microscopes.
To learn more about light microscopes, visit this site.
Cell theory
The microscopes we use today are far more complex than those that Dutch shopkeeper Antony van Leeuwenhoek, used in the 1600s. Skilled in crafting lenses, van Leeuwenhoek observed the movements of single-celled organisms, which he collectively termed “animalcules.” In the 1665 publication Micrographia, experimental scientist Robert Hooke coined the term “cell” for the box-like structures he observed when viewing cork tissue through a lens. In the 1670s, van Leeuwenhoek discovered bacteria and protozoa. Later advances in lenses, microscope construction, and staining techniques enabled other scientists to see some components inside cells. By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory, which states that one or more cells comprise all living things, the cell is the basic unit of life, and new cells arise from existing cells. Rudolf Virchow later made important contributions to this theory.
Cells fall into one of two broad categories: prokaryotic and eukaryotic. We classify only the predominantly single-celled organisms Bacteria and Archaea as prokaryotes (pro- = “before”; -Kary- = “nucleus”). Animal cells, plants, fungi, and protists (protozoa) are all eukaryotes (EU- = “true”).
Cell Size
At 0.1 to 5.0 µm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10 to 100 µm. The prokaryotes' small size allows ions and organic molecules that enter them to quickly diffuse to other parts of the cell. Similarly, any waste produced within a prokaryotic cell can quickly diffuse. This is not the case in eukaryotic cells, which have developed different structural adaptations to enhance intracellular transport. Small size, in general, is necessary for all cells, whether prokaryotic or eukaryotic. Let’s examine why that is so.
First, we’ll consider the area and volume of a typical cell. Not all cells are spherical in shape, but most tend to approximate a sphere. You may remember from your high school geometry course that the formula for the surface area of a sphere is 4πr2, while the formula for its volume is 4πr3/3. Thus, as the radius of a cell increases, its surface area increases as the square of its radius, but its volume increases as the cube of its radius (much more rapidly). Therefore, as a cell increases in size, it's surface area-to-volume ratio decreases. This same principle would apply if the cell had a cube shape (figure 1.1.2). If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. In other words, as a cell grows, it becomes less efficient. One way to become more efficient is to divide. Other ways are to increase surface area by creating inward or outward projections of the cell membrane, becoming flat or thin and elongated, or by developing organelles that perform specific tasks. These adaptations lead to the development of more sophisticated cells, which we call eukaryotic cells.
For another perspective on cell size, try the HowBig interactive at this site.
Access for free at https://openstax.org/books/biology-2e/pages/4-1-studying-cells
Components of Prokaryotic Cell
All cells share four common components: 1) a plasma membrane, an outer covering that separates the cell’s interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like cytosol within the cell in which there are other cellular components; 3) DNA, the cell's genetic material; and 4) ribosome, which synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.
A prokaryote is a simple, mostly single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is in the cell's central part: the nucleoid (figure 1.1.3)
Most prokaryotes have a Peptidoglycan cell wall, and many have a polysaccharide capsule (figure 1.1.3). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion. Pili exchange genetic material during conjugation, the process by which one bacterium transfers genetic material to another through direct contact. Bacteria use Fimbriae to attach to a host cell.
Access for free at https://openstax.org/books/biology-2e/pages/4-2-prokaryotic-cells
Components of Eukaryotic Cell
Have you ever heard the phrase “form follows function?” It’s a philosophy that many industries follow. In architecture, this means that buildings should be constructed to support the activities that will be carried out inside them. For example, a skyscraper should include several elevator banks. A hospital should place its emergency room where it is easily accessible.
Our natural world also utilizes the principle of form following function, especially in cell biology, and this will become clear as we explore eukaryotic (figure 1.1.4). Unlike prokaryote cells, eukaryotic cells have 1) a membrane-bound nucleus; 2) numerous membrane-bound organelles, such as the endoplasmic reticulum, Golgi apparatus, chloroplast, mitochondria, and others; and 3) several, rod-shaped chromosomes. Because a membrane surrounds the eukaryotic cell’s nucleus, it has a “true nucleus.” The word “organelle” means “little organ,” and, as we already mentioned, organelles have specialized cellular functions, just as your body's organs have specialized functions.
At this point, it should be clear to you that eukaryotic cells have a more complex structure than prokaryotic cells. Organelles allow different functions to be compartmentalized in different areas of the cell. Before turning to organelles, let’s first examine two important components of the cell: the plasma membrane and the cytoplasm.
The Plasma Membrane
Like prokaryotes, eukaryotic cells have a plasma membrane (figure 1.1.5), a phospholipid bilayer with embedded proteins that separate the internal contents of the cell from its surrounding environment. A phospholipid is a lipid molecule with two fatty acid chains and a phosphate-containing group. The plasma membrane controls the passage of organic molecules, ions, water, and oxygen into and out of the cell. Wastes (such as carbon dioxide and ammonia) also leave the cell by passing through the plasma membrane.
The Cytoplasm
The cytoplasm is the cell's entire region between the plasma membrane and the nuclear envelope (a structure we will discuss shortly). It is comprised of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals (figure 1.1.4). Even though the cytoplasm consists of 70 to 80 percent water, it has a semi-solid consistency, which comes from the proteins within it. However, proteins are not the only organic molecules in the cytoplasm. Glucose and other simple sugars, polysaccharides, amino acids, nucleic acids, fatty acids, and derivatives of glycerol are also there. Ions of sodium, potassium, calcium and many other elements also dissolve in the cytoplasm. Many metabolic reactions, including protein synthesis, take place in the cytoplasm.
The Nucleus
Typically, the nucleus is the most prominent organelle in a cell (figure 1.1.4). The nucleus (plural = nuclei) houses the cell’s DNA and directs the synthesis of ribosomes and proteins. Let’s look at it in more detail (figure 1.1.6).
The Nuclear Envelope
The nuclear envelope is a double-membrane structure that constitutes the nucleus' outermost portion (figure 1.1.6). Both the nuclear envelope's inner and outer membranes are phospholipid bilayers. The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm. The nucleoplasm is the semi-solid fluid inside the nucleus, where we find the chromatin and the nucleolus.
Chromatin and Chromosomes
To understand chromatin, it is helpful to first explore chromosomes, structures within the nucleus that are made up of DNA, the hereditary material. You may remember that in prokaryotes, DNA is organized into a single circular chromosome. In eukaryotes, chromosomes are linear structures. Every eukaryotic species has a specific number of chromosomes in the nucleus of each cell. For example, in humans, the chromosome number is 46, while in fruit flies, it is 8. Chromosomes are only visible and distinguishable from one another when the cell is getting ready to divide. When the cell is in the growth and maintenance phases of its life cycle, proteins attach to chromosomes. During this stage, they resemble an unwound, jumbled bunch of threads. We call these unwound protein-chromosome complexes chromatin (figure1.1.6 & 1.1.7). Chromatin describes the material that makes up the chromosomes both when condensed and decondensed.
The Nucleolus
We already know that the nucleus directs the synthesis of ribosomes, but how does it do this? Some chromosomes have sections of DNA that encode ribosomal RNA. A darkly staining area within the nucleus called the nucleolus (plural = nucleoli) aggregates the ribosomal RNA with associated proteins to assemble the ribosomal subunits that are then transported out through the pores in the nuclear envelope to the cytoplasm (figure 1.1.6).
Ribosomes
Ribosomes are the cellular structures responsible for protein synthesis. When we view them through an electron microscope, ribosomes appear either as clusters (polyribosomes) or as single, tiny dots that float freely in the cytoplasm. They may be attached to the cytoplasmic surfaces of the plasma membrane, on the endoplasmic reticulum, and the nuclear envelope (figure 1.1.4). Electron microscopy shows us that ribosomes, which are large protein and RNA complexes, consist of two subunits: large and small (figure 1.1.8). Ribosomes receive their “orders” for protein synthesis from the nucleus where the DNA transcribes into messenger RNA (mRNA). The mRNA travels to the ribosomes, which translate the code, provided by the sequence of the nitrogenous bases in the mRNA, into a specific order of amino acids in a protein. Amino acids are the building blocks of proteins.
Because protein synthesis is an essential function of all cells (including enzymes, hormones, antibodies, pigments, structural components, and surface receptors), there are ribosomes in practically every cell. Ribosomes are particularly abundant in cells that synthesize large amounts of protein. For example, the pancreas is responsible for creating several digestive enzymes and the cells that produce these enzymes contain many ribosomes. Thus, we see another example of the structure following function.
Mitochondria
Scientists often call mitochondria (singular = mitochondrion) “powerhouses” or “energy factories” of both plant and animal cells because they are responsible for making adenosine triphosphate (ATP) — the cell’s main energy-carrying molecule. Cellular respiration is the process of making ATP using the chemical energy in glucose and other nutrients. In mitochondria, this process uses oxygen and produces carbon dioxide as a waste product. Mitochondria are oval-shaped, double-membrane organelles (figure 1.1.9) that have their own ribosomes and DNA. Each membrane is a phospholipid bilayer embedded with proteins. The inner layer has inward projections or folds called cristae. The inner lumen of mitochondria is filled with viscous fluid called matrix, made up of enzymes, certain vitamins & minerals in different forms, ions, small and large proteins, DNA, and ribosomes.
Peroxisomes
Peroxisomes are small, round organelles enclosed by single membranes. They carry out oxidation reactions that break down fatty acids and amino acids. They also detoxify many poisons that may enter the body. (Many of these oxidation reactions release hydrogen peroxide H2O2, which would be damaging to cells; however, when these reactions are confined to peroxisomes, enzymes safely break down the H2O2 into oxygen and water.) For example, peroxisomes in liver cells detoxify alcohol. Glyoxysomes, which are specialized peroxisomes in plants, are responsible for converting stored fats into sugars. Plant cells contain many different types of peroxisomes that play a role in metabolism, pathogen defense, and stress response, to mention a few.
Vesicles and Vacuoles
Vesicles and vacuoles are membrane-bound sacs that function in storage and transport. Other than the fact that vacuoles are somewhat larger than vesicles, there is a very subtle distinction between them. Vesicle membranes can fuse with either the plasma membrane or other membrane systems within the cell. The vacuole's membrane does not fuse with the membranes of other cellular components. Additionally, some agents such as enzymes within plant vacuoles break down macromolecules.
Endomembrane System
Scientists have long noticed that bacteria, mitochondria, and chloroplast are similar in size. We also know that bacteria have DNA and ribosomes, just like mitochondria and chloroplasts. Scientists believe that host cells and bacteria formed an endosymbiotic relationship when the host cells ingested both aerobic and autotrophic bacteria (cyanobacteria) but did not destroy them. Through many millions of years of evolution, these ingested bacteria became more specialized in their functions, with the aerobic bacteria becoming mitochondria and the autotrophic bacteria becoming chloroplasts. The endomembrane system (endo = “within”) is a group of membranes and organelles (figure 1.1.4) in eukaryotic cells that works together to modify, package, and transport lipids and proteins. It includes the nuclear envelope, lysosomes, and vesicles, which we have already mentioned, as well as the endoplasmic reticulum and Golgi apparatus, which we will cover shortly. Although not technically within the cell, the plasma membrane is included in the endomembrane system because, as you will see, it interacts with the other endomembranous organelles. The endomembrane system does not include either mitochondria or chloroplast membranes.
The Endoplasmic Reticulum
The endoplasmic reticulum (ER) (figure 1.1.4) is a series of interconnected membranous sacs and tubules. The ER's membrane, which is a phospholipid bilayer embedded with proteins, is continuous with the nuclear envelope. The inner hollow space of ER is called lumen or cisternal space. ER is responsible for modifying proteins, and their transportation as well as for synthesizing lipids. However, these two functions take place in two different areas of the ER: the rough ER and the smooth ER, respectively.
Rough Endoplasmic Reticulum
Scientists have named the rough endoplasmic reticulum (RER) as such because the ribosomes attached to its cytoplasmic surface give it a studded appearance when viewing it through an electron microscope (figure 1.1.10). Ribosomes transfer their newly synthesized proteins into the RER's lumen where they undergo structural modifications, such as folding or acquiring side chains. These modified proteins incorporate into cellular membranes—the ER or the ER's or other organelles' membranes. The proteins can also secrete from the cell (such as protein hormones, and enzymes). The RER also makes phospholipids for cellular membranes. If the phospholipids or modified proteins are not destined to stay in the RER, they will reach their destinations via transport vesicles that bud from the RER’s membrane (figure 1.1.11).
Since the RER is engaged in modifying proteins (such as enzymes, for example) that secrete from the cell, you would be correct in assuming that the RER is abundant in cells that secrete proteins.
Smooth Endoplasmic Reticulum
The smooth endoplasmic reticulum (SER) is continuous with the RER but has few or no ribosomes on its cytoplasmic surface (figure 1.1.11). SER functions include the synthesis of carbohydrates, lipids, and steroid hormones; detoxification of medications and poisons; and storing calcium ions. In muscle cells, a specialized SER, the sarcoplasmic reticulum, is responsible for storing calcium ions that are needed to trigger the muscle cells' coordinated contractions.
The Golgi Apparatus
We have already mentioned that vesicles can bud from the ER and transport their contents elsewhere, but where do the vesicles go? Before reaching their final destination, the lipids or proteins within the transport vesicles still need sorting, packaging, and tagging so that they end up in the right place. Sorting, tagging, packaging, and distributing lipids and proteins takes place in the Golgi apparatus (also called the Golgi body), a series of flattened membranous sacs (figure 1.1.12).
The side of the Golgi apparatus that is closer to the ER is called the cis face. The opposite side is the trans face. The transport vesicles that formed from the ER travel to the cis face, fuse with it, and empty their contents into the lumen of the Golgi apparatus. As the proteins and lipids travel through the Golgi, they undergo further modifications that allow them to be sorted. The most frequent modification is adding short-chain sugar molecules. These newly modified proteins and lipids are then tagged with phosphate groups or other small molecules to travel to their target destinations. Finally, the modified and tagged proteins are packaged into secretory vesicles that bud from the Golgi's trans face. While some of these vesicles deposit their contents into other cell parts where they will be used, other secretory vesicles fuse with the plasma membrane and release their contents outside the cell.
In another example of form following function, cells that engage in a great deal of secretory activity (such as salivary gland cells that secrete digestive enzymes or immune system cells that secrete antibodies) have an abundance of Golgi. In a plant cell, the Golgi apparatus has the additional role of synthesizing polysaccharides, some of which are incorporated into the cell wall and some of which other cell parts use.
Lysosomes
The lysosomes are the cell’s “garbage disposal.” Enzymes within the lysosomes aid in breaking down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles. Most plant cells do not have lysosomes, though many of these lysosomal enzymes are present in the vacuole of the plant cell. Lysosomes are also part of the endomembrane system.
You can watch an excellent animation of the endomembrane system here. At the end of the animation, there is a short self-assessment.
Cytoskeleton
If you were to remove all the organelles from a cell, would the plasma membrane and the cytoplasm be the only components left? No. Within the cytoplasm, there would still be ions and organic molecules, plus a network of protein fibers that help maintain the cell's shape, secure some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable cells within the all eukaryotic organisms to move. Collectively, scientists call this network of protein fibers the cytoskeleton. There are three types of fibers within the cytoskeleton: microfilaments, intermediate filaments, and microtubules (figure 1.1.13). Here, we will examine each.
Microfilaments
Also called actin filaments (figure 1.1.14), microfilaments are the narrowest. They function in cellular movement, have a diameter of about 7 nm, and are made up of intertwined strands of two globular proteins. Microfilaments also provide some rigidity and help cells to change their shape. Microfilaments function in muscle contraction, cytoplasmic streaming, maintaining the cell shape, internal transport and cytokinesis.
Intermediate Filaments
Intermediate filaments are filaments with a diameter of about 8 to 10 nm (figure 1.1.15). You are probably most familiar with keratin, the fibrous protein that strengthens your hair, nails, and the skin's epidermis. Intermediate filaments have no role in cell movement. Their function is purely structural. They bear tension, thus maintaining the cell's shape, and anchor the nucleus and other organelles in place. The intermediate filaments are the most diverse group of cytoskeletal elements. The research is ongoing to understand the function of intermediate filaments in plants.
Microtubules
As their name implies, microtubules are small hollow tubes. With a diameter of about 25 nm, microtubules are the widest component of cytoskeletons. Two globular proteins, α-tubulin and β-tubulin are polymerized as dimers, which then associate with other such dimers laterally to form tubular structures called protofilaments. One of the common arrangements is of 13 protofilaments joined to each other, side by side, to form a microtubule (figure 1.1.16). They help the cell resist compression, provide a track along which vesicles move through the cell, and pull replicated chromosomes to opposite ends of a dividing cell. Like microfilaments, microtubules can disassemble and reform quickly. Microtubules participate in cell division in plant cells.
You have now completed a broad survey of prokaryotic and eukaryotic cell components. For a summary of cellular components in prokaryotic and eukaryotic cells, see table 1.1
Cell Component | Function | Present in Prokaryotes? | Present in Animal Cells? | Present in Plant Cells? |
Plasma membrane | Separates cell from the external environment; controls passage of organic molecules, ions, water, oxygen, and wastes into and out of a cell | Yes | Yes | Yes |
Cytoplasm | Provides turgor pressure to plant cells as the fluid inside the central vacuole; site of many metabolic reactions; medium in which organelles are found | Yes | Yes | Yes |
Nucleolus | The darkened area within the nucleus where ribosomal subunits are synthesized. | No | Yes | Yes |
Nucleus | A cell organelle that houses DNA and directs the synthesis of ribosomes and proteins | No | Yes | Yes |
Ribosomes | Protein synthesis | Yes | Yes | Yes |
Mitochondria | ATP production/cellular respiration | No | Yes | Yes |
Peroxisomes | Oxidize and thus break down fatty acids and amino acids, and detoxify poisons | No | Yes | Yes |
Vesicles and vacuoles | Storage and transport; digestive function in plant cells | No | Yes | Yes |
Centrosome | Unspecified role in cell division in animal cells; microtubule source in animal cells | No | Yes | No |
Lysosomes | Digestion of macromolecules; recycling of worn-out organelles | No | Yes | Some |
Cell wall | Protection, structural support, and maintenance of cell shape | Yes, primarily peptidoglycan | No | Yes, primarily cellulose |
Chloroplasts | Photosynthesis | No | No | Yes |
Endoplasmic reticulum | Modifies proteins and synthesizes lipids | No | Yes | Yes |
Golgi apparatus | Modifies, sorts, tags, packages, and distributes lipids and proteins | No | Yes | Yes |
Cytoskeleton | Maintains cell’s shape, secures organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move independently | Yes | Yes | Yes |
Flagella | Cellular locomotion | Some | Some | No, except for some plant sperm cells |
Cilia | Cellular locomotion, movement of particles along plasma membrane's extracellular surface, and filtration | Some | Some | No |
Extracellular Structure
If you work on a group project, you need to communicate with others (at least your group members and the teacher). As you might expect, if cells are to work together, they must communicate with each other. Let’s look at how cells communicate with each other. Animal cells release materials into the extracellular space. The primary component of these materials is collagen. Collagen fibers are interwoven with proteoglycans, which are carbohydrate-containing protein molecules. Collectively, we call these materials the extracellular matrix. Plant cells do not secrete collagen but produce a rigid cell wall.
Access for free at https://openstax.org/books/biology-2e/pages/4-3-eukaryotic-cells
Components of a Plant Cell
At this point, you know that all eukaryotic cell has a plasma membrane, cytoplasm, a nucleus, ribosomes, mitochondria, peroxisomes, and in some vacuoles, microtubule organizing centers (MTOCs). Animal cells and plant cells have lysosomes, though lysosomes in plants operate differently and are not very common. There are some striking differences between animal and plant cells. In animal cells centrioles are associated with the MTOC, a complex we call the centrosome. Plant cells lack centrioles. Plant cells have a cell wall, chloroplasts, and other specialized plastids, and a large central vacuole, whereas animal cells do not.
The Cell Wall
If you examine figure 1.1.4 b, the plant cell diagram, you will see a structure external to the plasma membrane. This is the cell wall, a rigid covering that protects the cell, provides structural support, and gives shape to the cell. Fungal and some protistan cells also have cell walls. While the prokaryotic cell walls' chief component is peptidoglycan, the major organic molecule in the plant’s (and some protists') cell wall is cellulose — a polysaccharide comprised of glucose units (figure 1.1.17). Have you ever noticed that when you bite into a raw vegetable, like celery, it crunches? That’s because you are tearing the rigid cell walls of a celery stalk with your teeth.
Central Vacuole
Previously, we mentioned vacuoles as essential components of plant cells. If you look at figure 1.1.4b, you will see that each plant cell has a large central vacuole that occupies most of the space inside the cell. The central vacuole plays a key role in regulating the cell’s concentration of water in changing environmental conditions. Have you ever noticed that if you forget to water a plant for a few days, it wilts? That’s because as the water concentration in the soil becomes lower than the water concentration in the plant, water moves out of the central vacuoles and cytoplasm. As the central vacuole shrinks, it leaves the cell wall unsupported. This loss of support to the plant's cell walls results in a wilted appearance. The central vacuole also supports the cell's expansion. When the central vacuole holds more water, the cell becomes larger without having to invest considerable energy in synthesizing new cytoplasm.
Chloroplasts
Like the mitochondria, chloroplasts have their own DNA and ribosomes, but chloroplasts have an entirely different function. Chloroplasts are plant cell organelles that carry out photosynthesis. Photosynthesis is the series of reactions that use carbon dioxide, water, and light energy to make glucose and oxygen. This is a major difference between plants and animals. Plants (autotrophs) can make their own food, like sugars that is used in cellular respiration to provide ATP energy generated in the plant mitochondria. Animals (heterotrophs) must ingest their food.
Like mitochondria, chloroplasts have outer and inner membranes, but within the space enclosed by a chloroplast’s inner membrane is a set of interconnected and stacked fluid-filled membrane sacs we call thylakoids (figure 1.1.18). Each thylakoid stack is a granum (plural = grana). We call the fluid enclosed by the inner membrane that surrounds the grana the stroma. The chloroplasts contain a green pigment, chlorophyll, which captures the light energy that drives the reactions of photosynthesis. Like plant cells, photosynthetic protists also have chloroplasts. Some bacteria perform photosynthesis, but their chlorophyll is different from that of plants and is not present inside an organelle.
Intercellular Junctions
Cells can also communicate with each other via direct contact or intercellular junctions. There are differences in the ways that plant and animal and fungal cells communicate. Plasmodesmata are junctions between plant cells, whereas, animal cell contacts include tight junctions, gap junctions, and desmosomes. Only plasmodesmata are discussed here.
Plasmodesmata
In general, long stretches of the plasma membranes of neighboring plant cells cannot touch one another because the cell wall that surrounds each cell separates them (figure 1.1.4b). How then, can a plant transfer water and other soil nutrients from its roots, through its stems, and to its leaves? Such transport uses the vascular tissues (xylem and phloem) primarily. There also exist structural modifications, which we call plasmodesmata (singular = plasmodesma). Numerous channels pass between adjacent cell walls of plant cells connecting their cytoplasm, and enabling the transport of materials from cell to cell, and thus throughout the plant (figure 1.1.19).
Access for free at https://openstax.org/books/biology-2e/pages/4-3-eukaryotic-cells
Attributions
Biology 2e by Clark Mary Ann, Douglas Matthew, Choi Jung. OpenStax is licensed under Creative Commons Attribution License V 4.0
Introduction to Organismal Biology at https://sites.gatech.edu/organismalbio/ is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Botany by Melissa Ha, Maria Morrow, and Kammy Algiers is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Melissa Ha, Maria Morrow, & Kammy Algiers.
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oercommons
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2025-03-18T00:37:12.692179
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Life Science
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"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/84551/overview",
"title": "Statewide Dual Credit Introduction to Plant Science, Plant Form, The Cell",
"author": "Forestry and Agriculture"
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https://oercommons.org/courseware/lesson/87592/overview
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3.3 Vascular Tissue
3.4 Ground Tissue & Cell Types
3_Plant-Tissues-and-Cell-Types
Plant Tissues and Cell Types
Overview
Introduction
Learning Objectives
- List three types of tissues in plants.
- Describe the identifying features of dermal tissue.
- List the most common modifications of dermal tissue.
- List two types of vascular tissues.
- Explain the structure of xylem tracheids and vessels.
- Explain the structure of phloem sieve tube members and companion cells.
- Differentiate between xylem and phloem.
- List the three types of plant cells.
- List the identifying features of parenchyma, collenchyma and sclerenchyma and their modifications.
Key Terms
adventitious root - an above ground root that arises from a plant part other than the radicle of the plant embryo
apical bud - bud formed at the tip of the shoot
apical meristem - meristematic tissue located at the tips of stems and roots; enables a plant to extend in length
axillary bud - bud located in the axil of a leaf, area of the stem where the petiole connects to the stem
bark - the tough, waterproof, outer epidermal layer of cork cells
bulb - modified underground stem that consists of a large bud surrounded by numerous leaf scales
Casparian strip - waxy coating that forces water to cross endodermal plasma membranes before entering the vascular cylinder, instead of moving between endodermal cells
collenchyma cell - elongated plant cell with unevenly thickened walls; provides structural support to the stem and leaves
companion cell - phloem cell that is connected to sieve-tube cells; has large amounts of ribosomes and mitochondria
compound leaf - a leaf in which the leaf blade is subdivided to form leaflets, all attached to the midrib
corm - rounded, fleshy underground stem that contains stored food
cortex - ground tissue found between the vascular tissue and the epidermis in a stem or root
cuticle - waxy covering on the outside of the leaf and stem that prevents the loss of water
dermal tissue - a protective plant tissue covering the outermost part of the plant; controls the gas exchange
endodermis - a layer of cells in the root that forms a selective barrier between the ground tissue and the vascular tissue, allowing water and minerals to enter the root while excluding toxins and pathogens
epidermis - a single layer of cells found in plant dermal tissue; covers and protects underlying tissue
fibrous root system - type of root system in which the roots arise from the base of the stem in a cluster, forming a dense network of roots; found in monocots
ground tissue - plant tissue involved in photosynthesis; provides support, and stores water and sugars
guard cells - paired cells on either side of a stoma that control the stomatal opening and thereby regulate the movement of gases and water vapor
intercalary meristem - meristematic tissue located at nodes and the bases of leaf blades; found only in monocots
internode - region between nodes on the stem
lamina - leaf blade
lateral meristem - also called secondary meristem, meristematic tissue that enables a plant to increase in thickness or girth caused by the vascular cambium and cork cambium
lenticel - opening on the surface of mature woody stems that facilitates gas exchange
meristem - plant region of continuous growth
meristematic tissue - tissue containing cells that constantly divide; contributes to plant growth
node - point along the stem at which leaves, flowers, or aerial roots originate
palmately compound leaf - leaf type with leaflets that emerge from a point, resembling the palm of a hand
parenchyma cell - most common type of plant cell; found in the stem, root, leaf, and in fruit pulp; site of photosynthesis and starch storage
pericycle - outer boundary of the stele from which lateral roots can arise
periderm - outermost covering of woody stems; consists of the cork cambium, cork cells, and the phelloderm
permanent tissue - plant tissue composed of cells that are no longer actively dividing
petiole - stalk of the leaf
phyllotaxy - arrangement of leaves on a stem
pinnately compound leaf - leaf type with a divided leaf blade consisting of leaflets arranged on both sides of the midrib
pith - ground tissue found towards the interior of the vascular tissue in a stem or root
primary growth - growth resulting in an increase in length of the stem and the root; caused by cell division in the shoot or root apical meristem
rhizome - modified underground stem that grows horizontally to the soil surface and has nodes and internodes
root cap - protective cells covering the tip of the growing root
root hair - hair-like structure that is an extension of epidermal cells; increases the root surface area and aids in absorption of water and minerals
root system - belowground portion of the plant that supports the plant and absorbs water and minerals
runner - stolon that runs above the ground and produces new clone plants at nodes
sclerenchyma cell - plant cell that has thick secondary walls and provides structural support, usually dead at maturity
sessile - leaf without a petiole that is attached directly to the plant stem
shoot system - aboveground portion of the plant; consists of nonreproductive plant parts, such as leaves and stems, and reproductive parts, such as flowers and fruits
sieve-tube cell - (sieve-tube members in angiosperms) phloem cell arranged end to end to form a sieve tube that transports organic substances, such as sugars and amino acids
simple leaf - leaf type in which the lamina is completely undivided or merely lobed
sink - growing parts of a plant, such as roots and young leaves, which require photosynthate
source - organ that produces photosynthate for a plant
stele - inner portion of the root containing the vascular tissue; surrounded by the endodermis
stipule - small green structure found on either side of the leaf stalk or petiole
stolon - modified stem that runs parallel to the ground and can give rise to new plants at the nodes
tap root system - type of root system with a main root that grows vertically with few lateral roots; found in dicots
tendril - modified stem consisting of slender, twining strands used for support or climbing
thorn - modified stem branch appearing as a sharp outgrowth that protects the plant
tracheid - xylem cell with thick secondary walls that helps transport water
translocation - mass transport of photosynthates from source to sink in vascular plants
transpiration - loss of water vapor to the atmosphere through stomata
trichome - hair-like structure on the epidermal surface
tuber - modified underground stem adapted for starch storage; has many adventitious buds
vascular bundle - strands of plant tissue made up of xylem and phloem
vascular stele - strands of root tissue made up of xylem and phloem
vascular tissue - tissue made up of xylem and phloem that transports food and water throughout the plant
venation - pattern of veins in a leaf; may be parallel (as in monocots), reticulate (as in dicots), or dichotomous (as in ginkgo biloba)
vessel element - xylem cell that is shorter than a tracheid and has thinner walls
whorled - pattern of leaf arrangement in which three or more leaves are connected at a node
Introduction
Plants are multicellular eukaryotes with tissue systems made of various cell types that carry out specific functions. Plant tissue systems fall into one of two general types: meristematic tissue or permanent (or non-meristematic) tissue. Cells of the meristematic tissue are found in meristems, which are plant regions of continuous cell division and growth. Meristematic tissue cells are either undifferentiated or incompletely differentiated, and they continue to divide and contribute to the growth of the plant. In contrast, permanent tissue consists of plant cells that are no longer actively dividing.
There are two types of meristematic tissues, based on their location in the plant. Apical meristem or primary meristem contain meristematic tissue located at the tips of stems and roots, which enable a plant to extend in length. Lateral meristem or secondary meristem facilitate growth in thickness or girth in a maturing woody plant. Intercalary meristem is found in some monocots such as grasses. Meristems produce cells that quickly differentiate, or specialize, and become permanent tissue. Such cells take on specific roles and lose their ability to divide further. They differentiate into three main types: dermal, vascular, and ground tissue.
Permanent tissues are either simple (composed of similar cell types) or complex (composed of different cell types). Dermal tissue, for example, is a simple tissue that covers the outer surface of the plant and controls gas exchange. Dermal tissue covers and protects the plant, while vascular tissue transports water, minerals, and sugars to different parts of the plant. Vascular tissue is an example of a complex tissue and is made of two specialized conducting tissues: xylem and phloem.
Xylem tissue transports water and nutrients from the roots to different parts of the plant and includes three different cell types: vessel elements and tracheids (both of which conduct water), and xylem parenchyma. Phloem tissue, which transports organic compounds from the site of photosynthesis to other parts of the plant, consists of four different cell types: sieve elements (which conduct photosynthates), companion cells, phloem parenchyma, and phloem fibers. Gymnosperms lack sieve elements and companion cells. Cells carrying out similar function in gymnosperms are called sieve cells. Unlike xylem conducting cells, phloem conducting cells are alive at maturity. The xylem and phloem always lie adjacent to each other (Figure 1.3.1). In stems, the xylem and the phloem form a structure called a vascular bundle; in roots, this is termed the vascular stele or vascular cylinder.
Ground tissue serves as a site for photosynthesis, provides a supporting matrix for the vascular tissue, and helps to store water and sugars.
Any part of a plant has three tissue systems: dermal, vascular, and ground tissue. Each is distinguished by characteristic cell types that perform specific tasks necessary for the plant’s growth and survival.
Access for free at https://openstax.org/books/biology-2e/pages/30-1-the-plant-body
Dermal Tissue
Dermal Tissue
The dermal tissue of the stem consists primarily of epidermis, a single layer of cells covering and protecting the underlying tissue. Woody plants have a tough, waterproof outer layer of cork cells commonly known as bark, which further protects the plant from damage. Epidermal cells are the most numerous and least differentiated of the cells in the epidermis. The epidermis of a leaf also contains openings known as stomata, through which the exchange of gases takes place (Figure 1.3.2). Two cells, known as guard cells, surround each leaf stoma, controlling its opening and closing and thus regulating the uptake of carbon dioxide and the release of oxygen and water vapor. Trichomes are hair-like structures on the epidermal surface. They help to reduce transpiration (the loss of water by aboveground plant parts), increase solar reflectance, and store compounds that defend the leaves against predation by herbivores.
Access for free at https://openstax.org/books/biology-2e/pages/30-2-stems
Vascular Tissue
Vascular Tissue
The xylem and phloem that make up the vascular tissue of the stem are arranged in distinct strands called vascular bundles, which run up and down the length of the stem. When the stem is viewed in cross section, the vascular bundles of dicot stems are arranged in a ring. In plants with stems that live for more than one year, the individual bundles grow together and produce the characteristic growth rings. In monocot stems, the vascular bundles are randomly scattered throughout the ground tissue (Figure 1.3.3).
Xylem tissue has three types of cells: xylem parenchyma, tracheids, and vessel elements. The latter two types conduct water and are dead at maturity. Tracheids are xylem cells with thick secondary cell walls that are lignified. Water moves from one tracheid to another through regions on the side walls known as pits, where secondary walls are absent. Vessel elements are xylem cells with thinner walls; they are shorter than tracheids. Each vessel element is connected to the next by means of a perforation plate at the end walls of the element. Water moves through the perforation plates to travel up the plant.
Phloem tissue is composed of sieve-tube cells, companion cells, phloem parenchyma, and phloem fibers. A series of sieve-elements (also called sieve-tube members) are arranged end to end to make up a long sieve tube, which transports organic substances such as sugars and amino acids. The sugars flow from one sieve-tube cell to the next through perforated sieve plates, which are found at the end junctions between two cells. Although still alive at maturity, the nucleus and other cell components of the sieve-tube cells have disintegrated. Companion cells are found alongside the sieve-tube cells, providing them with metabolic support. The companion cells contain more ribosomes and mitochondria than the sieve-tube cells, which lack some cellular organelles.
Access for free at https://openstax.org/books/biology-2e/pages/30-2-stems
Ground Tissue & Cell Types
Ground Tissue
Plant tissues that are not dermal or vascular are considered ground tissue. Cell of ground tisses perform many differnent types of functions, such as photosynthesis, storage, based on their location. In a stem ground tissue mostly contains parenchyma cells, but may also contain collenchyma and sclerenchyma cells that help support the stem. The ground tissue towards the interior of the vascular tissue in a stem or root is known as pith, while the layer of tissue between the vascular tissue and the epidermis is known as the cortex.
Let us look at three types of plant cells, parenchyma, collenchyma, and sclerenchyma cells.
Parenchyma cells are the most common plant cells (Figure 1.3.4). They are found in the stem, the root, the inside of the leaf, and the pulp of the fruit. These cells are somewhat spherical and have thin primary wall. This help in exchange of raw material and waste products between outside and the inside of the cell. Parenchyma cells are responsible for metabolic functions, such as photosynthesis, and they help repair and heal wounds. Some parenchyma cells also store starch. Parenchyma cells rarely show formation of secondary wall.
Collenchyma cells are elongated cells with unevenly thickened walls (Figure 1.3.5). They provide structural support, mainly to the stem and leaves. These cells are alive at maturity and are usually found below the epidermis. The “strings” of a celery stalk are an example of collenchyma cells.
Sclerenchyma cells also provide support to the plant, but unlike collenchyma cells, many of them are dead at maturity. There are two types of sclerenchyma cells: fibers and sclereids. Both types have secondary cell walls that are thickened with deposits of lignin—an organic compound that is a key component of wood. Fibers are long, slender cells; sclereids are smaller-sized. Sclereids give pears their gritty texture. Humans use sclerenchyma fibers to make linen and rope (Figure 1.3.6).
Access for free at https://openstax.org/books/biology-2e/pages/30-2-stems
Dig Deeper
Watch Botany Without Borders, a video produced by the Botanical Society of America about the importance of plants.
Attributions
Title: Browallia americana L.: entire flowering plant with separate parts of fruit and seeds. Coloured etching by M. Bouchard, 1774.
Work Type: Scientific illustrations
Date: 1774
Description: Browallia demissa pedunculis unifloris. H.Cliff.318.t.17. - Hort.Ups.179. - Linn.Sp.Plant.773
Repository: Wellcome Collection
Collection: Open Artstor: Wellcome Collection
ID Number: V0042766ER
Source: Image and original data from Wellcome Collection
License: Creative Commons: Attribution
Use of this image is in accordance with the applicable Terms & Conditions
Biology 2e by Clark Mary Ann, Douglas Matthew, Choi Jung. OpenStax is licensed under Creative Commons Attribution License V 4.0
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https://oercommons.org/courseware/lesson/91183/overview
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Ensuring Ethical Marketing and Sales
Overview
Provided by: Lumen Learning. License: CC BY: Attribution
Outcome: Ensuring Ethical Marketing and Sales
What you’ll learn to do: describe measures companies take to encourage ethical behavior
Ethical issues arise at both an organizational level and an individual level. A single individual can engage in unethical behavior, but most ethical breaches that have significant impact on a business occur when many individuals come together to act unethically. This section will review the steps that businesses take at each level to define ethical behavior and create a culture that encourages employees to do the right thing.
The way to gain a good reputation is to endeavor to be what you desire to appear.—Socrates
The specific things you’ll learn in this section include:
- Explain the importance of ethics policies and a culture of accountability for all employees
- Identify the unique ethical considerations and roles for company executives
- Describe how companies manage ethical behavior of marketing employees
Learning Activities
The learning activities for this section include the following:
- Reading: A Culture of Accountability
- Reading: Executive Role in Ethics
- Reading: Ethics for Marketing Employees
- Simulation: Ethics
Licenses and Attributions
CC licensed content, Original
- Outcome: Ensuring Ethical Marketing and Sales. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: A Culture of Accountability
At the beginning of this module we discussed the 2015 revelation that Volkswagen installed emissions-altering software in eleven million diesel vehicles worldwide, which caused the cars to pass emissions tests they should have failed. Consider, for a moment, how many employees would have to be involved in order to achieve this level of fraud? This was not the handiwork of a single employee but the result of a pattern of unethical behavior in the company. When the Ethics & Compliance Initiative (ECI) released the results of its 2013 National Business Ethics Survey, it noted that these types of broad, organizational breaches are fairly common.
The survey shows that a significant amount of misconduct involves continuous, ongoing behavior rather than one-time incidents: Employees say that more than a quarter (26 percent) of observed misconduct represents an ongoing pattern of behavior. Another 41 percent said the behavior has been repeated at least a second time. Only one-third (33 percent) of rule breaking represents a one-time incident.1
In the case of Volkswagen, an early internal investigation pointed to a “culture of tolerance” for ethical compromises. Employees were pushed to do what was needed to meet corporate objectives at any cost.
The organizational culture is comprised of the values and beliefs that an organization shares, which create its social environment. The culture of a large organization can be difficult to understand since it is influenced by many different factors. Still, many research studies point to leadership and policies as being instrumental in building an ethical organizational culture.
Policies That Encourage Ethical Behavior
Many companies have a specific policy that defines appropriate behavior. The policy is often called the Standards for Business Conduct. As the name suggests, the policy is intended to set the standards for acceptable behavior; it’s not meant to be an exhaustive list of every type of ethical behavior.
Many of these policies do the following:
- Define the threshold for behavior: While it should go without saying that employees are expected to be law abiding, companies choose to be quite explicit about stating that they require their employees to follow the law.
- Create expectations for behavior: The policies identify common issues that employees may encounter—such as accepting gifts from suppliers—and explain how they should be handled.
- Set policy: establish company protocols for handling confidential information, including customer data, etc.
- Give guidance on making judgment calls: Companies often define how they would like employees to make decisions when guidelines do not adequately cover them.
- Describe reporting and enforcement procedures: There is generally a process for reporting and addressing issues, as well as information about how the company will protect those reporting concerns.
Let’s examine some examples from company policies to see how some of these components are addressed.
The Legal Threshold
The ethics policy generally begins by reminding employees that they are required to act in accordance with the law. For companies that engage in business across the globe this can be complex. Starwood Hotels and Resorts addresses this issue in their Code of Business Conduct and Ethics:
You must, at all times, obey the laws of the jurisdictions where we conduct business. Starwood conducts business all around the world. Our associates are citizens of many countries. As a result, our operations are subject to the laws of many jurisdictions. It is often challenging for us to understand how those various laws apply to our businesses. However, whether you are a Starwood associate or member of the Board of Directors, you are expected to conduct yourself in accordance with applicable law.
Starwood is a company organized under the laws of the United States and is generally subject to U.S. federal law. From time to time, the laws of the United States conflict with laws of a city, town, country or other jurisdiction where we conduct business. If there is a conflict between the applicable laws, seek guidance from the Office of the General Counsel (Legal).2
Starwood has established a clear expectation to follow the law, acknowledged the complexity of their business environment, and provided direction when employees need help.
Creating Expectations for Behavior
In the course of a normal business day, many service employees receive tips. Where is the line between an appropriate tip and a gift? Starbucks has defined this for employees in its Standards of Business Conduct:
A gift or favor should not be accepted or given if it might create a sense of obligation, compromise your professional judgment or create the appearance of doing so. In deciding whether a gift is appropriate, you should consider its value and whether public disclosure of the gift would embarrass you or Starbucks.
A gift of money should never be given or accepted. (Some retail partners, however, may accept customary tips for service well done.) As a general rule, partners should limit gifts to or from any one vendor or business associate to US $75 per year. A gift of nominal value may be given or accepted if it is a common business courtesy, such as coffee samples, a coffee cup, pens or a similar token. However, during traditional gift-giving seasons in areas where it is customary to exchange gifts of money, such as China, Japan, Malaysia, Singapore and Thailand, partners should not solicit but may exchange cash with nongovernmental business associates in nominal amounts up to the equivalent of US $20.3
It is very common for company’s to set a threshold for giving and receiving gifts. These specific guidelines help employees navigate what would otherwise be a judgment call and make it easier to identify an ethical breach and initiate corrective action.
Setting Policy
United Parcel Service (UPS) groups the sections of its Code of Business Conduct into stakeholder groups: our company, our people, our customers, our shareholders, and our communities. This enables the company to address a range of workforce expectations, such as workplace safety:
UPS is committed to a safe work environment that is free of threats, intimidation, and physical harm. Everyone has a right to work in a safe environment and everyone shares the responsibility for ensuring the safety of others. We have zero tolerance for workplace violence, and we will investigate and take appropriate action up to and including dismissal regarding any threats to a safe workplace.
UPS prohibits violent behavior in the workplace including, but not limited to, physical assaults, fighting, threatening comments, intimidation, threats through electronic communications including social media, and the intentional or reckless destruction of property of the company, employee, UPS representative, or customer. Comments or behavior that reasonably could be interpreted as intent to do harm to people or property will be considered a threat. We also prohibit the unauthorized possession and/or use of weapons by any employee or UPS representative while at work, on company property, or while on company business.4
The UPS policy is very specific about its expectations of employees in ensuring a safe work environment.
Judgment Calls
No policy will address every issue, nor should it try. Most policies try to guide employees in the way they should make judgment calls. In its Standards of Business Conduct, American Airlines addresses this issue specifically:
Remember, your best resource about what’s right or wrong is your own conscience. So if you find yourself in a difficult situation, think before you act. And ask yourself the following questions:
- Is it legal? If it’s not legal, don’t do it.
- Is it ethical? If it feels wrong, it probably is wrong.
- How would it look in the newspaper? If you wouldn’t feel comfortable if your friends and family knew about your actions, you probably shouldn’t do it.5
These policies are an important tool in building a culture of accountability and ethical behavior in a company, but the policies must be upheld by all the employees, and senior leaders play a significant role in reinforcing their importance.
- http://www.ethics.org/
- https://secure.ethicspoint.com/domain/media/en/gui/711/code_en.pdf
- https://globalassets.starbucks.com/assets/eecd184d6d2141d58966319744393d1f.pdf
- https://www.ups.com/media/en/code_bus_conduct.pdf
- https://www.aa.com/i18n/amrcorp/corporateInformation/facts/ethics.jsp
Licenses and Attributions
CC licensed content, Original
- A Culture of Accountability. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: Executive Role in Ethics
Consider the following observation by the ECI on the results of the National Business Ethics survey:
Managers–those expected to act as role models or enforce discipline–are responsible for a large share of workplace misconduct (60 percent) and senior managers are more likely than lower-level managers to break rules. Surveyed employees said that members of management are responsible for six of every ten instances of misconduct and they pointed the finger at senior managers in 24 percent of observed rule breaking. Middle managers were identified as the culprit 19 percent of the time and first-line supervisors were identified as bad actors 17 percent of the time.1
If you’re thinking about ways of boosting or ensuring ethical behavior in an organization, this is an interesting and alarming finding. In a supplemental report on Ethical Leadership, ECI reports that employees at all sizes of companies draw conclusions about their leaders’ character primarily on the basis of the following:
- The overall character of their leaders as experienced through personal interactions;
- How senior managers handle crises; and
- The policies and procedures adopted by senior leaders to manage the company.
Employees want to know, for example, whether leaders treat lower level employees with dignity and respect, share credit when good things happen, and uphold standards even when it reduces revenues and profits. They watch to see whether leaders are steady in crisis, hold themselves accountable or, alternatively, shift blame to others. Workers also look at day-to-day management decisions to gauge whether ethical behavior is recognized and rewarded, or whether praise and promotions go to workers who bend the rules.2
These findings suggest the important role that executives play in building ethical organizations—ethics and integrity tend to start (or fail) at the top and trickle down.
Executives Set Company Objectives
When executives establish specific, measurable objectives for the company, those objectives determine where people will focus their time and effort. When the objectives cannot be met and there are dire personal consequences for failure, such conditions can lead to the compromise of ethics and standards. In the National Business Ethics Survey, 70 percent of employees identified pressure to meet unrealistic business objectives as most likely to cause them to compromise their ethical standards, and 75 percent identified either their senior or middle management as the primary source of pressure they feel to compromise the standards of their organizations.
Former Volkswagen CEO, Martin Winterkorn
In the Volkswagen case, internal investigations have questioned how both the company culture and the behavior of former CEO Martin Winterkorn contributed to a systemic ethical breach. Like many chief executives, Martin Winterkorn was a demanding boss who didn’t like failure, but critics say the pressure on managers at Volkswagen was unusual, which may go some way toward explaining the carmaker’s crisis. When he became CEO in 2007, Winterkorn set an objective to make VW the world’s biggest carmaker, which would require tremendous growth in the highly competitive U.S. car market. In the years since, VW has nearly doubled its global annual sales to 10 million cars and its revenue to $225 billion. In early 2015, VW finally approached its goal, selling marginally more vehicles than the world’s number-one automaker, Toyota of Japan. One former sales executive said that the pressure soared under the target.”If you didn’t like it, you moved of your own accord or you were performance-managed out of the business,” he said.3
In describing a Winterkorn’s leadership style, a former VW executive confidentially told Reuters New Agency, “There was always a distance, a fear and a respect . . . If he would come and visit or you had to go to him, your pulse would go up. If you presented bad news, those were the moments that it could become quite unpleasant and loud and quite demeaning.”
A week after U.S. regulators revealed the company’s cheating, Bernd Osterloh, the employee representative on VW’s supervisory board, sent a letter to VW staff suggesting the change that was needed: “We need in the future a climate in which problems aren’t hidden but can be openly communicated to superiors,” said Osterloh. “We need a culture in which it’s possible and permissible to argue with your superior about the best way to go.”4
In Fortune magazine, Dr. Paul Argenti suggested, “Rather than playing the blame game, executives should ask if pressures to grow at all costs might have created dishonest employees.”5
It seems likely that aggressive corporate objectives (and more specifically marketing objectives related to market share) played a contributing role in the Volkswagen ethics scandal. Moreover, when executives set aggressive goals, it becomes more important to cultivate communication channels to openly address issues. This was obviously not the case at Volkswagen.
Executives Create Company Policy
In the previous reading we reviewed a number of company policies that address ethical conduct. Executives play an important role in creating those policies—and by visibly following and upholding them. As the survey data cited above suggest, employees look to executives to decide whether standards-of-business-conduct policies should be observed and respected. When executives bend the rules or turn a blind eye to bad behavior, the policies lose value and executives lose the respect of employees. This opens the door to a range of unanticipated issues, as employees look to ethical norms outside stated policy and beyond the executives’ control.
Executives Hire and Promote Company Managers
Internal promotions send very strong signals about what is important to a company. When the company hires an employee from a different company, she is likely not well known by most employees. If the company promotes an employee who is already working at the company, others know him and understand what he has done to deserve the promotion. If the company promotes individuals to management positions when they have displayed questionable ethics in the workplace, it creates two issues. First, it creates a level of managers who are more likely to encourage their employees to achieve business results at any cost, even when ethics are compromised. Second, it sends a message to all employees that business results are more important than ethics.
- http://www.ethics.org/
- http://www.ethics.org/
- http://www.reuters.com/article/us-volkswagen-emissions-culture-idUSKCN0S40MT20151010
- http://www.reuters.com/article/us-volkswagen-emissions-culture-idUSKCN0S40MT20151010
- http://fortune.com/2015/10/13/biggest-culprit-in-volkswagen-emissions-scandal/
Licenses and Attributions
CC licensed content, Original
- Executive Role in Ethics. Provided by: Lumen Learning. License: CC BY: Attribution
CC licensed content, Shared previously
- Martin Winterkorn. Authored by: Volkswagon AG. Provided by: Wikimedia. Located at: https://commons.wikimedia.org/wiki/File:Martin_Winterkorn_2013-09-09_001.jpg. License: CC BY: Attribution
Reading: Ethics for Marketing Employees
If you are hired to work in marketing at a typical company, there will likely be clear ethical standards defined in a company policy and some level of compliance among employees at all levels in the company. You will witness ethical breaches and need to decide whether to report them or not. You will see examples of outstanding ethics and have the opportunity to participate in debates about ethical disagreements and issues. No company is perfect, but most are trying to be ethical.
How can you, as a marketer, make a difference? Marketers have a specific set of responsibilities when it comes to preventing and addressing ethical issues. These are described below.
Demonstrate Respect for Your Target Customer
Marketing is not a game of manipulation. Good marketing provides compelling solutions and informs customers to help them make good selections and realize value. Recognize the customer’s need for an offering that is easy to use and includes clear instructions and appropriate warnings. Remain available to customers to hear complaints. Be humble enough to recognize that not everyone wants to hear your messages. If you demonstrate respect for the consumer, you will find new opportunities to provide value. If you treat consumers like a commodity to be manipulated, a host of ethical issues will clutter your path.
Prepare the Sales Team to Sell Effectively and Ethically
If personal sales are a part of the business plan, then marketers have an important responsibility to prepare the sales team for success. Often marketers are asked to create the message, and sales reps are asked to deliver it. When the sales rep is prepared with a strong value proposition, effective communication materials and presentations, and thorough market research, the sales rep can do her best work. When the marketing mix is not hitting the mark, the sales rep’s is much more difficult, and there is a greater risk of ethical issues. It is the marketer’s responsibility to prepare sales reps to be successful without compromising their integrity.
Demonstrate High Personal Standards in Business Relationships
Marketers often entertain and give gifts. It is not unusual for the marketing team to create the gift list for all customers. Marketers cultivate business relationships and distributor relationships, too. If marketing demonstrates a high standard for professionalism and ethics in these relationships, it sends a strong message and increases the expectation that others will, as well.
Provide Fair Value to the Target Customer
Many ethical issues result from some level of deception involving misstatement of value to the customer. Be accurate in communications to customers about the value that a product provides. Be clear in pricing and contracts. Pricing strategies that confuse customers and cost more than the customer initially believed are never a good long-term strategy.
Play Nicely in the Competitive Environment
Companies in a competitive market shift positions and introduce innovations to give them new competitive advantage. This is the very nature of a competitive marketplace. Treat competitors with respect and learn from their approaches. Do thorough competitive research to understand them better. Do not seek to gain confidential information about competitors or their products.
Be Truthful
Seek to create a relationship of trust with your target customer through honest, helpful communication. This is such a simple but important recommendation for all marketers. If customers trust the product, the company, and the brand, business results improve, and the company has greater flexibility to introduce new products or make market adjustments.
Licenses and Attributions
CC licensed content, Original
- Ethics for Marketing Employees. Provided by: Lumen Learning. License: CC BY: Attribution
CC licensed content, Shared previously
- Integrity. Authored by: atalou. Located at: https://www.flickr.com/photos/natalieguinsler/5565750498/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
Simulation: Ethics
Try It
Play the simulation below multiple times to see how different choices influence the outcome. All simulations allow unlimited attempts so you can gain experience applying the concepts.
Licenses and Attributions
CC licensed content, Shared previously
- Simulation: Ethics. Authored by: Clark Aldrich for Lumen Learning. License: CC BY: Attribution
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"url": "https://oercommons.org/courseware/lesson/91183/overview",
"title": "Statewide Dual Credit Principles of Marketing, Ethics and Social Responsibility, Ensuring Ethical Marketing and Sales",
"author": "Anna McCollum"
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https://oercommons.org/courseware/lesson/91181/overview
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Regulatory Laws
Overview
Provided by: Lumen Learning. License: CC BY: Attribution
Outcome: Regulatory Laws
What you’ll learn to do: explain the laws that regulate marketing
While there are situations in which we expect individuals to act according to higher moral laws, at a basic level we always expect business professionals to follow the law. Most of the laws that impact marketers fall into a category called consumer protection. Consumer protection laws are created to ensure the rights of consumers and to create a fair marketplace for consumers.
The History of Consumer Protection
Historically, consumer protection laws in the United States have been specific formal legal responses to address public outrage over the disclosure of industry abuses and crises. For example, in 1905 a man named Upton Sinclair exposed the terrible worker conditions in the American meat-packing industry. His work sparked public outrage and, in turn, led to the creation of the Food & Drug Administration and the first comprehensive inspection and regulation of food safety in the United States.1
Similarly, in the 1960s consumer advocate Ralph Nadar took on automobile safety, highlighting the immense profits made by auto companies relative to their investment in customer safety. In 1966 Congress unanimously passed the National Traffic and Motor Vehicle Safety Act, and the National Highway Traffic Safety Administration gained consumer protection powers. The number of vehicular deaths in the U.S. reached a high of 50,000 in 1960 and have continued to fall despite a larger number of drivers on the road.
Government Consumer Protection and Enforcement Agencies
A number of governments agencies are charged with protecting consumers. The U.S. Federal Trade Commission (FTC) was created in 1914 and is charged with protecting America’s consumers and promoting competition. The commission includes individual divisions that oversee a range of activities that are of importance to marketers, including the following:
- Privacy and identity protection
- Advertising practices
- Marketing practices
- Financial practices
The FTC’s Bureau of Consumer Protection stops unfair, deceptive, and fraudulent business practices by collecting complaints and conducting investigations, suing companies and people who break the law, developing rules to maintain a fair marketplace, and educating consumers and businesses about their rights and responsibilities.
In addition to government-based agencies, consumer associations and other nonprofit entities also play an important role in protecting the consumer.
As a marketer, it is important to understand the current laws and consider where there are risks to consumers that might lead to new legislation.
The specific things you’ll learn in this section include:
- Explain product liability and its impact on marketing
- Explain privacy law and its impact on marketing
- Explain fraud in the marketing process and its impact
Learning Activities
The learning activities for this section include the following:
- Reading: Product Liability
- Reading: Privacy Laws
- Reading: Fraud in Marketing
- Spencer Weber Waller, Jillian G. Brady, and R.J. Acosta, "Consumer Protection in the United States: An Overview," http://www.luc.edu/media/lucedu/law/centers/antitrust/pdfs/publications/workingpapers/USConsumerProtectionFormatted.pdf.
Licenses and Attributions
CC licensed content, Original
- Outcome: Regulatory Laws. Provided by: Lumen Learning. License: CC BY: Attribution
- Image: Motor Vehicle Crash Deaths 1975u20132017. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: Product Liability
Introduction
Product liability is the legal liability a manufacturer or trader incurs for producing or selling a faulty product.
There is not a single federal law or code that covers all product liability. Fourteen states have adopted the Uniform Commercial Code, which governs business transactions between states. Specifically, Article 2 of the code includes the requirements for contract formation and breach, which are important in many product liability cases. In general, product liability laws come about as a result of civil court cases being prosecuted at the state level.
The courts are increasingly holding sellers responsible for the safety of their products. The U.S. courts generally maintain that the producer of a product is liable for any product defect that causes injury in the course of normal use. Liability can even result if a court or a jury decides that a product’s design, construction, or operating instructions and safety warnings make the product unreasonably dangerous to use.
Types of Product Defects
There are three types of product defects that incur product liability: design defects, manufacturing defects, and defects in marketing.
Design Defects
Design defects exist before the product is manufactured. There is something in the design of the product that is inherently unsafe, regardless of how well it is manufactured. Since “product” is one of the primary elements of the marketing mix, the marketer bears responsibility for ensuring that the design results in a product that is safe and that the product will fulfill the promises of the other aspects of the marketing mix such as promotional commitments.
Hoverboard
Let’s look at a current example of a product design going awry. One of the hottest holiday gift items in 2015 is the hoverboard self-balancing scooter. The premium models often cost more than $1,000, but several companies have created less expensive versions by using lower-cost board components. One expensive component that has been downgraded in the cheaper models is the rechargeable lithium-ion battery. Many less expensive boards use a lower-quality (and lower-priced) mass-produced battery cell. These cheaper batteries are more likely to have quality issues that might cause them to break and burst into flame when they are repeatedly bumped, which is a regular occurrence during the normal use of the scooter. After more than ten reported fires, the U.S. Consumer Product Safety Commission opened a case to investigate the hoverboard fires.
Manufacturing Defects
Manufacturing defects occur while a product is being constructed, produced, or assembled. Specifically, when a product departs from its intended design, even though all possible care was exercised in the preparation and marketing of the product1, it is a manufacturing defect. The manufacturer may be very careful with the design, the material selection, the development of the manufacturing process, and the quality-assurance guidelines. Nevertheless, if a poorly manufactured product leaves the manufacturers facility and causes injury when used for any of its intended purposes, then there is a defect in manufacturing.
It might seem that manufacturing defects occur only in product sales and not in the service industry, but there’s a very well-known case in this category: the McDonald’s coffee case.
On February 27, 1992, a seventy-nine-year-old woman named Stella Liebeck went to McDonald’s with her grandson, Chris. They got the coffee, and Chris pulled into a parking space so that Stella could add cream and sugar. Since the car had a curved dash and lacked cup holders, Stella put the cup between her knees and removed the lid. When she did, the cup fell backward, burning her groin, thighs, genitalia, and buttocks. Liebeck was taken to the hospital, where it was discovered that she had third-degree burns on 6 percent of her body and other burns on 16 percent of her body. She required multiple skin grafts and was in the hospital for eight days. Liebeck spent two years recovering from the injury, lost 20 percent of her bodyweight after the accident, and was left permanently scarred by the ordeal.
Liebeck wrote a letter to McDonald’s asking them to pay her medical bills, which totaled around $10,500 in 1992 (approximately $16,110 today). The company offered her $800. Liebeck and McDonald’s exchanged several more letters, but the company refused to increase their $800 offer, so Liebeck hired a law firm.
Liebeck’s lawyers conducted a study of coffee temperatures. They discovered that coffee brewed at home is usually served at 135–145°F and coffee served at most fast-food restaurants is in the 160–175°F range. McDonald’s, however, served its coffee at 190°F, which can cause third-degree burns on human skin after two to seven seconds of contact. No safety study of any kind was undertaken by either McDonald’s or the consultant who recommended the hotter temperature.
Moreover, Liebeck’s lawyers also discovered more than seven hundred other burn claims—many of them for third-degree burns—from McDonald’s customers between February 1983 and March 1992. In court, McDonald’s quality-control manager, Christopher Appleton, testified that McDonald’s served around 20 million cups of coffee a year and that seven hundred incidents during nine years was statistically insignificant. While this was factually accurate, the jury did not like to hear that McDonald’s considered seven hundred burned customer to be insignificant.
The jury found in Liebeck’s favor. They awarded her $200,000 in compensatory damages, but that amount was later reduced to $160,000 because they felt that the spill was 20 percent Liebeck’s fault. The jury made headlines when it came to the punitive damages, however, which they settled at $2.7 million. The jurors defended the amount, saying that it was to punish the company for its callous attitude toward Ms. Liebeck and the 700+ other McDonald’s customers who had suffered burns. Although it sounds like a lot, $2.7 million represented only two days’ worth of McDonald’s coffee sales, and the jurors felt that was fair.
The judge agreed, accusing McDonald’s of “willful, wanton, and reckless behavior” for ignoring all the customer complaints.
McDonald’s process for making coffee constituted a manufacturing defect, which resulted in many customer injuries and generated significant product liability for the company.
Marketing Defects
Marketing defects result from flaws in the way a product is marketed. Examples include improper labeling, poor or incomplete instructions, or inadequate safety warnings. Often marketing defects are referred to as a “failure to warn.” It is important for the marketer to think not only about the warnings that the user might need when using the product as intended but also about other, potentially dangerous uses for which the product was not intended.
For example, fabric used in children’s sleepwear must meet certain flammability requirements to prevent the risk of injury from fires. Certain comfortable children’s clothing that does not meet the flammability requirement can be confused with sleepwear. For this reason, such clothing will often contain a warning label that reads, “Not intended for sleepwear.”
Over time, product liability has shifted more to the side of the injured product user. Consumer advocates like Ralph Nader argue that, for too long, product liability favored producers at the expense of the product user. They assert that it’s the threat of lawsuits and huge settlements and restitutions that force companies to make safe products. While a discussion of all aspects of product liability is beyond the scope of this course, it is clear that liability has and will continue to have a tremendous impact on consumers and manufacturers alike. These two groups are not the only ones affected, either. Retailers, franchises, wholesalers, sellers of mass-produced homes, and building-site developers and engineers are all subject to liability legislation.
- Restatement of Torts, Third, Apportionment of Liability (2000)
Licenses and Attributions
CC licensed content, Shared previously
- Manufacturing Defects. Authored by: Jim Cofer. Located at: http://jimcofer.com/personal/2012/01/19/righting-the-wrongs-the-mcdonalds-coffee-case/. Project: Righting the Wrongs: The McDonald's Coffee Case. License: CC BY-NC-SA: Attribution-NonCommercial-ShareAlike
- Chapter 5: External Considerations in Marketing, from Introducing Marketing. Authored by: John Burnett. Project: Global Text. License: CC BY: Attribution
- Hoverboard. Provided by: Soar Boards. Located at: https://en.wikipedia.org/wiki/Self-balancing_two-wheeled_board#/media/File:Red_self-balancing_two-wheeled_board_with_a_person_standing_on_it.png. License: CC BY: Attribution
- Lawsuits Welcome. Authored by: Chris Tengi. Located at: https://www.flickr.com/photos/cjtengi/2022308688/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
Reading: Privacy Laws
What does privacy mean in today’s world? Privacy is the ability of an individual or group to seclude themselves, or information about themselves, and thereby express themselves selectively. Most of us expect some level of privacy, but the boundaries around privacy can differ depending on the individual and the situation.
The right-to-privacy issue has gotten more complicated as our culture has come to rely so heavily on digital communication—for everything from social networking to education to conducting business. Marketers have been quick to capitalize on the potential of digital technology to yield creative, aggressive techniques for reaching their target buyers. Sometimes these aggressive tactics cause a public backlash that results in new laws. For example, intrusive telephone marketing activities led to the passage of the the Do-Not-Call Implementation Act of 2003, which permits individuals to register their phone number to prevent marketing calls from organizations with which they don’t have an existing relationship. The act was intended to protect consumers from a violation of privacy (incessant sales phone calls particularly during the evening hours), and it closed down many businesses that had used telephone solicitation as their primary sales channel.
What follows is an overview of important privacy laws that have a particular impact on marketers. These are areas in which marketers need to be thinking ahead of the law. While there are plenty of perfectly legal marketing tactics that utilize personal information, if they are a nuisance to prospective customers, they are probably not good marketing and may be affected by future legislation when the public decides it has had enough.
Email Spam
Have you received email messages without giving permission to the sender? The Controlling the Assault of Non-Solicited Pornography and Marketing (CAN-SPAM) Act, passed in 2003, establishes federal standards for commercial email. Consumers must be given the opportunity to opt out of receiving future solicitations, as in this opt-out notice provided by the clothing company Abercrombie & Fitch:
This is a product offering from Abercrombie & Fitch. You have received this email since you submitted your email address to our list of subscribers. To unsubscribe, please click here and submit your email address. Please see our Website Terms of Use, and to know how we use your personal data, please see our Privacy Policy.
Despite its name, the CAN-SPAM Act doesn’t apply just to bulk email. It covers all commercial messages, which the law defines as “any electronic mail message the primary purpose of which is the commercial advertisement or promotion of a commercial product or service,” including email that promotes content on commercial Web sites. The law makes no exception for business-to-business email. That means that all email—even, for example, a message to former customers announcing a new product line—must comply with the law. Each separate email in violation of the CAN-SPAM Act is subject to penalties of up to $16,000, so non-compliance can be very costly. The good news is that following the law isn’t complicated.
Managing Customer Data
Sometimes companies and organization possess personal data about their customers that is collected during the course of doing business. The most obvious examples are medical organizations that keep confidential patient records, financial institutions that capture your financial data, and educational institutions that record student test scores and grades. Other companies might know your contact information, your purchase patterns, and your Internet-shopping or search history. These organization all have important legal responsibilities to protect your data.
The Federal Trade Commission (FTC) gives access to an important source of information about the necessity of securing sensitive data: the lessons contained in the more than fifty law enforcement actions taken by the FTC so far. These are settlements—no findings have been made by a court—and the details of the orders apply just to the companies involved, but learning about alleged lapses that have led to law enforcement actions can help your company improve its practices. Most of these alleged practices involve basic, fundamental security missteps or oversights. Without getting into the details of those cases, below are ten practical tips that we can learn from them. Distilling the facts of those cases down to their essence, here are ten lessons to learn that touch on vulnerabilities that could affect your company, along with practical guidance on how to reduce the risks they pose.
- Start with security: only collect customer data when necessary; be transparent; and treat the data with extreme care.
- Control and restrict access to sensitive data.
- Require strong, secure passwords and authentication; protect access to sensitive data
- Store sensitive personal information securely and protect it during transmission: use best-in-class security technology.
- Segment your network and monitor who’s trying to get in and out
- Secure remote access to your network: put sensible access limits in place.
- Apply sound security practices when developing new products; train engineers in security and test for common vulnerabilities.
- Make sure your service providers implement reasonable security measures: write security into contracts and verify compliance.
- Establish procedures to keep your security current and address vulnerabilities that may arise; heed credible security warnings.
- Secure paper, physical media, and devices—not all data are stored digitally.
These may seem like overly technical considerations that aren’t important to someone working in a marketing organization, but in the same way that it is important for a marketer to protect its company from product liability suits, it is important to protect customers from security breaches related to the company’s products, services, and marketing activities.
Protecting Privacy Online
The Internet provides unprecedented opportunities for the collection and sharing of information from and about consumers. But studies show that consumers have very strong concerns about the security and confidentiality of their personal information in the online marketplace. Many consumers also report reluctance to engage in online commerce, partly because they fear that their personal information can be misused. These consumer concerns present an opportunity for marketers to build consumer trust by implementing sound practices for protecting consumers’ information privacy.
The FTC recommends four Fair Information Practice Principles. These are guidelines that represent widely accepted concepts concerning fair information practice in an electronic marketplace.
Notice
Consumers should be given notice of an entity’s information practices before any personal information is collected from them, including, at a minimum, identification of the entity collecting the data, the uses to which the data will be put, and any potential recipients of the data.
Choice
Choice and consent in an online information-gathering sense means giving consumers options to control how their data is used. Specifically, choice relates to secondary uses of information beyond the immediate needs of the information collector to complete the consumer’s transaction. The two typical types of choice models are “opt-in” or “opt-out.” The opt-in method requires that consumers give permission for their information to be used for other purposes. Without the consumer taking these affirmative steps in an opt-in system, the information gatherer assumes that it cannot use the information for any other purpose. The opt-out method requires consumers to affirmatively decline permission for other uses. Without the consumer taking these affirmative steps in an opt-out system, the information gatherer assumes that it can use the consumer’s information for other purposes.
Access
Access, as defined in the Fair Information Practice Principles, includes not only a consumer’s ability to view the data collected but also to verify and contest its accuracy. This access must be inexpensive and timely in order to be useful to the consumer.
Security
Information collectors should ensure that the data they collect is accurate and secure. They can improve the integrity of data by cross-referencing it with only reputable databases and by providing access for the consumer to verify it. Information collectors can keep their data secure by protecting against both internal and external security threats. They can limit access within their company to only necessary employees to protect against internal threats, and they can use encryption and other computer-based security systems to stop outside threats.
In June 1998, the FTC issued a report to Congress noting that while more than 85 percent of all Web sites collected personal information from consumers, only 14 percent of the sites in the FTC’s random sample of commercial Web sites provided any notice to consumers of the personal information they collect or how they use it. In May 2000, the FTC issued a follow-up report that showed significant improvement in the percent of Web sites that post at least some privacy disclosures; still, only 20 percent of the random sample sites were found to have implemented all four fair information practices: notice, choice, access, and security. Even when the survey looked at the percentage of sites implementing the two critical practices of notice and choice, only 41 percent of the random sample provided such privacy disclosures.
In the evolving field of privacy law there is an opportunity for marketers build trust with target customers by setting standards that are higher than the legal requirements and by respecting customers’ desire for privacy.
Licenses and Attributions
CC licensed content, Original
- Revision and adaptation. Provided by: Lumen Learning. License: CC BY-SA: Attribution-ShareAlike
CC licensed content, Shared previously
- Fair Information Practice Principles. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/FTC_Fair_Information_Practice. License: CC BY-NC-SA: Attribution-NonCommercial-ShareAlike
- Privacy. Authored by: g4ll4is. Located at: https://www.flickr.com/photos/g4ll4is/8521624548/. License: CC BY-SA: Attribution-ShareAlike
- Tech Privacy. Authored by: Bernard Goldbach. Located at: https://www.flickr.com/photos/topgold/5534004979/. License: CC BY: Attribution
Public domain content
- Email Spam. Provided by: Federal Trade Commission. Located at: https://www.ftc.gov/system/files/documents/plain-language/bus61-can-spam-act-compliance-guide-business.pdf. Project: The CAN-SPAM Act: A Compliance Guide for Business. License: Public Domain: No Known Copyright
- Managing Customer Data. Provided by: Federal Trade Commission. Located at: https://www.ftc.gov/system/files/documents/plain-language/pdf0205-startwithsecurity.pdf. Project: Start with Security: A Guide for Business. License: Public Domain: No Known Copyright
- Protecting Privacy Online. Provided by: Federal Trade Commission. Located at: https://www.ftc.gov/system/files/documents/plain-language/bus28-advertising-and-marketing-internet-rules-road.pdf. Project: Advertising and Marketing on the Internet. License: Public Domain: No Known Copyright
Reading: Fraud in Marketing
Fraud is the deliberate deception of someone else with the intent of causing damage. The damage need not be physical damage—in fact, it is often financial.1
The Federal Trade Commission has determined that a representation, omission, or practice is deceptive if it is likely to:
- mislead consumers and
- affect consumers’ behavior or decisions about the product or service.
When it comes to marketing fraud, the two key words are deliberate deception. In a legal setting, a judge asked to rule on a marketing fraud case would need to evaluate the extent of the deception and the impact of the deception on the consumer. For our purposes, though, it is more useful to begin outside the courtroom with the basic starting point of marketing: the goal of marketing is not to deceive the customer; it is, in fact, to build trust.
When we consider the elements of the marketing mix—product, price, promotion, and distribution—there are opportunities for deception in each area.
Product: Is the product designed and manufactured as the customer would expect, given the other elements of the marketing mix? Is the customer warned about the product’s limitations or uses that are not recommended?
Price: Is the total price of the product fairly presented to the customer? Is the price charged for the product the same as the price posted or advertised? Has something been marketed as “free” and, if so, does it meet FTC guidelines for the definition of free? Does the company disclose information about finance charges?
Promotion: Can claims made to consumers be substantiated? Are disclaimers clear and conspicuous? For products marketed to children, is extra care taken to accurately represent the product?
Place (Distribution): Does the distribution channel deliver the product at the price and quality promised? Do other companies in the distribution channel (wholesalers, retailers) perform as promised and deliver on expectations set for product, price, and promotions?
Marketing Fraud in Education
Sadly, it is easy enough to find a case of pervasive marketing fraud that any student can understand: Corinthian Colleges.
As you review the following press release from the Consumer Financial Protection Bureau, consider the following questions:
- Where was the Corinthian Colleges chain deliberately deceptive in presenting its offering to students?
- Where was Corinthian deliberately deceptive in the way it represented pricing?
- Where was the company’s promotion of its offering deceptive?
CFPB Sues For-Profit Corinthian Colleges for Predatory Lending Scheme2
Bureau Seeks More than $500 Million In Relief For Borrowers of Corinthian’s Private Student Loans
WASHINGTON, D.C. — Today, the Consumer Financial Protection Bureau (CFPB) sued for-profit college chain Corinthian Colleges, Inc. for its illegal predatory lending scheme. The Bureau alleges that Corinthian lured tens of thousands of students to take out private loans to cover expensive tuition costs by advertising bogus job prospects and career services. Corinthian then used illegal debt collection tactics to strong-arm students into paying back those loans while still in school. To protect current and past students of the Corinthian schools, the Bureau is seeking to halt these practices and is requesting the court to grant relief to the students who collectively have taken out more than $500 million in private student loans.
“For too many students, Corinthian has turned the American dream of higher education into an ongoing nightmare of debt and despair,” said CFPB Director Richard Corday. “We believe Corinthian lured consumers into predatory loans by lying about their future job prospects, and then used illegal debt collection tactics to strong-arm students at school. We want to put an end to these predatory practices and get relief for the students who are bearing the weight of more than half a billion dollars in Corinthian’s private student loans.”
Corinthian Colleges, Inc. is one of the largest for-profit, post-secondary education companies in the United States. The publicly traded company has more than 100 school campuses across the country. The company operates schools under the names Everest, Heald, and WyoTech. As of last March, the company had approximately 74,000 students.
In June, the U.S. Department of Education delayed Corinthian’s access to federal student aid dollars because of reports of malfeasance. Since then, Corinthian has been scaling down its operations as part of an agreement with the Department of Education. However, Corinthian continues to enroll new students.
Today’s CFPB lawsuit alleges a pervasive culture across the Everest, Heald, and WyoTech schools that allowed employees to routinely deceive and illegally harass private student loan borrowers. Under the Dodd-Frank Wall Street Reform and Consumer Protection Act, the CFPB has the authority to take action against institutions engaging in unfair, deceptive, or abusive practices. Based on its investigation, the CFPB alleges that the schools made deceptive representations about career opportunities that induced prospective students to take out private student loans, and then used illegal tactics to collect on those loans. Today’s lawsuit covers the period from July 21, 2011 to the present.
Lured into Loans by Lies
Most students who attend Everest, Heald, and WyoTech schools come from economically disadvantaged backgrounds and many are the first in their families to seek an education beyond a high school diploma. According to internal Corinthian documents, most students lived in households with very low income. Today’s lawsuit alleges that the schools owned by Corinthian Colleges, Inc. advertised their education as a gateway to good jobs and better careers. It alleges that throughout the Corinthian schools, consumers were lured into loans by lies, including:
Sham job placement rates: The CFPB alleges that Corinthian’s school representatives led students to think that when they graduated they were likely to land good jobs and sufficient salaries to repay their private student loans. But the CFPB believes that Corinthian inflated the job placement rates at its schools. Based on its investigation, the CFPB alleges that this included creating fictitious employers and reporting students as being placed at those fake employers.
One-day long “career”: According to the CFPB’s investigation, Corinthian schools told students they would have promising career options with an Everest, Heald, or WyoTech degree. But Corinthian counted a “career” as a job that merely lasted one day, with the promise of a second day.
Pay for placement: The CFPB also alleges that the Corinthian schools further inflated advertised job placement rates by paying employers to temporarily hire graduates. The schools did not inform students about these payments or that these jobs were temporary.
Craigslist career counseling: According to the CFPB’s investigation, the Corinthian schools promised students extensive and lasting career services that were not delivered. Students often had trouble contacting anyone in the career services office or getting any meaningful support. The limited career services included distributing generally available job postings from websites like Craigslist.
Predatory Loans
Tuition and fees for some Corinthian programs were more than five times the cost of similar programs at public colleges. In 2013, the Corinthian tuition and fees for an associate’s degree was $33,000 to $43,000. The tuition and fees for a bachelor’s degree at Corinthian cost $60,000 to $75,000.
The CFPB believes the Corinthian colleges deliberately inflated tuition prices to be higher than federal loan limits so that most students were forced to rely on additional sources of funding. The Corinthian schools then relied on deceptive statements regarding its education program to induce students into taking out its high-cost private student loans, known as “Genesis loans.” Today’s lawsuit alleges that under the Genesis loan program:
Interest rates were more than twice as expensive: Corinthian sold its students predatory loans that typically had substantially higher interest rates than federal loans. In July 2011, the Genesis loan interest rate was about 15 percent with an origination fee of 6 percent. Meanwhile, the interest rate for federal student loans during that time was about 3 percent to 7 percent, with low or no origination fees.
Loans were likely to fail: Corinthian expected that most of its students would ultimately default on their Genesis loans. In fact, more than 60 percent of Corinthian school students defaulted on their loans within three years. The Everest, Heald, and WyoTech schools did not tell students about these high default rates. Defaulting on private student loans can have grave consequences for consumers, including affecting a borrower’s job prospects and making it difficult to get any kind of loan for years.
Strong-Armed by Illegal Debt Collection Tactics
Under the Genesis loan program, nearly all student borrowers were required to make monthly loan payments while attending school. This is unusual; federal loans and almost all other sources of private student loans do not require repayment until after graduation. This put pressure on Everest, Heald, and WyoTech students to come up with funding while attending school. Today’s lawsuit alleges that Corinthian took advantage of this position of power to engage in aggressive debt collection tactics. The CFPB alleges that Corinthian’s campus staff members received bonuses based in part on their success in collecting payments from students. The debt collection tactics included:
Pulling students out of class: The CFPB’s investigation revealed that Corinthian’s efforts to collect payments included shaming students by pulling them out of class. Financial aid officers would inform instructors and other staff that students were past due on their Genesis loans. Corinthian schools also required students to meet with campus presidents to discuss the seriousness of the overdue loans. At one Corinthian campus, students and employees referred to one financial aid staff member as the “Grim Reaper” because the staff member so frequently pulled students out of class to collect debts.
Putting education in jeopardy: According to the CFPB’s investigation, the Corinthian colleges jeopardized students’ academic experience by denying them education until they paid up. They blocked students’ access to school computer terminals and other academic resources. The Corinthian schools also prevented students from attending and registering for class, and from receiving their books for their next classes.
Withholding diplomas: According to the CFPB investigation, Corinthian schools informed students that they could not participate in the graduation ceremony or would have their certificate withheld if they were not current on their Genesis loan in-school payments. In many cases, financial aid staff threatened that if students did not become current on their loans, they could not graduate or start their externships. Some former students stated that Corinthian schools continue to withhold their certificates because they are unable to make payments on their Genesis loans.
Halting Illegal Conduct and Obtaining Relief for Private Student Loan Borrowers
Today’s lawsuit seeks, among other things, compensation for the tens of thousands of students who took out Genesis loans. The CFPB estimates that from July 2011 through March 2014, students took out approximately 130,000 private student loans to pay tuition and fees at Everest, Heald, or WyoTech colleges. Some of these loans have been paid back in part or in full; the total outstanding balance of these loans is in excess of $569 million.
The CFPB is seeking redress for all the private student loans made since July 21, 2011, including those that have been paid off. In its lawsuit, the CFPB is also seeking to keep Corinthian from continuing the illegal conduct described above, and to prevent new students from being harmed.
Today the CFPB is also publishing a special notice for current and former Corinthian students to help them navigate their options in this time of uncertainty, including information on loan discharge options.
The Close of the Corinthian College Story
In May 2015, Corinthian Colleges declared bankruptcy.3
In October 2015, the CFPB won its case against Corinthian Colleges in federal court.
As a fellow student you will be pleased to hear that the federal government is providing loan relief for students who were victims of financial fraud.4
From a marketer’s point of view, the story demonstrates a number of different types of fraud, which had devastating consequences for both shareholders and stakeholders. Deliberate deception was part of the company’s strategy, and it played a dominant role in all aspects of marketing.
- https://www.law.cornell.edu/wex/fraud
- http://www.consumerfinance.gov/newsroom/cfpb-sues-for-profit-corinthian-colleges-for-predatory-lending-scheme/
- http://www.bloomberg.com/news/articles/2015-05-07/for-profit-college-implosion-intensifies-as-campuses-shut-down?cmpid=the_street
- https://studentaid.ed.gov/sa/about/announcements/corinthian
Licenses and Attributions
CC licensed content, Original
- Fraud in Marketing. Provided by: Lumen Learning. License: CC BY: Attribution
Public domain content
- Press Release: CFPB Sues For-Profit Corinthian Colleges for Predatory Lending Scheme. Provided by: Consumer Financial Protection Bureau. Located at: http://www.consumerfinance.gov/newsroom/cfpb-sues-for-profit-corinthian-colleges-for-predatory-lending-scheme/. License: Public Domain: No Known Copyright
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oercommons
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2025-03-18T00:37:12.880627
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03/22/2022
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"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91181/overview",
"title": "Statewide Dual Credit Principles of Marketing, Ethics and Social Responsibility, Regulatory Laws",
"author": "Anna McCollum"
}
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https://oercommons.org/courseware/lesson/91196/overview
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Learning Hacks
Overview
Provided by: Lumen Learning. License: CC BY: Attribution
Learning Hacks: Should I Ask For Help?
The Hack
If you aren’t sure if you are understanding, reach out to a peer or a teacher for help.
If you are embarrassed or worried what people might think of you because you reached out for help, try reaching out using technology, like email or chat message, as many students perceive this as less threatening.
The Story
Recognizing when you need help is hard. It requires a skill called metacognition. Metacognition means being aware of your own learning. It means you know when you are learning something and when you aren’t quite getting it. When you aren’t understanding something there are many ways to try to figure it out, but one of the most effective ways to learn is to reach out to someone who already knows the material to help you learn what you aren’t understanding.
The Research
Kitsantas and Chow studied (1) in which scenarios students are most likely to ask for help, (2) which kinds of students are more likely to ask for help, and (3) whether reaching out for help improved student success. They found that (1) students are more likely to reach out for help in an online environment because students perceive it as lower risk than if they had to reach out for help in person, (2) students with high self-efficacy, or belief in their abilities, were more likely to seek help, and (3) students that reach out more frequently did better in their courses than students who did not ask for help.
The Source
Kitsantas, A., & Chow, A. (2007). College students’ perceived threat and preference for seeking help in traditional, distributed, and distance learning environments. Computers & Education, 48(3), 383-395.
Licenses and Attributions
CC licensed content, Original
- Learning Hacks: Should I Ask For Help?. Authored by: Lumen Learning. License: CC BY: Attribution
CC licensed content, Shared previously
- Image with help me spelled out in cereal bowl. Authored by: frankieleon. Located at: https://commons.wikimedia.org/wiki/File:HELP_ME_(4278905797).jpg. License: CC BY: Attribution
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oercommons
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2025-03-18T00:37:12.899365
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03/22/2022
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{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91196/overview",
"title": "Statewide Dual Credit Principles of Marketing, Consumer Behavior, Learning Hacks",
"author": "Anna McCollum"
}
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https://oercommons.org/courseware/lesson/91169/overview
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Segmentation Decisions
Overview
The Principles of Marketing textbook contains fifteen modules—roughly one module per week for a 16-week semester.
Outcome: Segmentation Decisions
What you’ll learn to do: explain the process of selecting an appropriate segmentation approach and deciding which customer segments to target for marketing activities
Now that you’ve learned about common segmentation approaches, how do you know when to apply them? When is geographic segmentation a better fit than demographic segmentation? When should you consider using both at the same time?
It comes down to your marketing goals: What are you trying to achieve?
The following section explains the process of aligning your goals with your segmentation approach and target market.
Learning Activities
The learning activities for this section include the following:
- Reading: Choosing a Segmentation Approach and Target Segments
- Case Study: eHarmony
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Outcome: Segmentation Decisions. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: Choosing a Segmentation Approach and Target Segments
Conducting a Market Segmentation
As you have seen, there are many different ways a company can segment its market, and the optimal method varies from one product to another. Good market segmentation starts by identifying the total market for the product: all the individuals who might conceivably need a product and have the means to purchase it. The total market for accounting software, say, is different from the total market for Lego building sets or the total market for chewing gum.
The next step is to identify marketing goals you want to achieve with the segmentation strategy. Do you want to generate awareness and sales in a local community that has never heard of your company? Do you want to get occasional customers to buy your product regularly? Do you want loyal supporters to dig deeper into their pockets and spend more of their money on your goods or services? Your segmentation approach should offer the best fit for your specific marketing goals.
Your marketing goals point you toward the segmentation criteria that will be most useful to achieve your marketing objectives. For example, if your goal is to build loyalty or increase frequency of purchase, behavioral segmentation is important to consider. If your goal is to broaden your customer base within a given region, geographic segmentation may be useful.
As you identify segmentation criteria that will help you understand the total market and meet your marketing goals, you’ll develop the basis for your segmentation approach. Next, you conduct research to collect segmentation data. Analyzing the market data can tell you whether your segmentation approach makes sense and where you may need to adjust the criteria to yield useful, valid market-segment data.
After conducting research and analysis of segmentation data, you should be able to diagram and profile different segments within your total market. A typical segmentation diagram could look like this:
Evaluating Your Segmentation Approach
An ideal market segment meets all of the following conditions:
- It’s possible to measure. If you can’t measure it, you can’t collect data to know who the segment is or how to reach them.
- It’s profitable. Segments must have the resources to purchase the product and be large enough to earn a profit for the company; otherwise they aren’t worth pursuing.
- It’s stable. Segments need to stick around long enough for you to execute your marketing plan.
- It’s reachable. It must be possible for marketers to reach potential customers via the organization’s promotion and distribution channel(s).
- It’s internally homogeneous. Potential customers in the same segment must prefer the same product qualities and exhibit similar characteristics that are pertinent to the segmentation approach.
- It’s externally heterogeneous. Potential customers from different segments have different product quality preferences and characteristics that affect their purchasing decisions.
- It’s responsive. Segments should respond consistently to a given market stimulus or marketing mix. If they do not, then marketing efforts directed at them will not be well spent.
- It’s cost-effective. Worthwhile market segments can be reached by marketing activities in a cost-effective manner. If too expensive to reach, then serving this segment will negatively impact profits.
- It helps determine the marketing mix. Ideally, when you have identified a market segment, you’ll have insight into ways of shaping the combination of product, promotion, price, and place to fit that segment’s needs.
If your segmentation approach fails to meet any of these conditions, you should go back to the drawing board to refine it. If any one of these factors is not in place, your market segmentation may actually undermine the effectiveness of your marketing and business. But with all these factors in place, market segmentation will point you toward the most promising customer groups in your target market.
For example, if you’re trying to launch a print services company in a large city, targeting “all business owners” isn’t cost effective, and the individuals within this group are actually quite different. That means that no single marketing mix will be effective with everyone in this segment. Instead, you would be better served by researching types of businesses (by industry, size, etc.), geographic locations, and other relevant factors to help you identify and target logical segments with shared characteristics.
Keep in mind that market segmentation is an ongoing activity that needs periodic evaluation to ensure that the approach still makes sense. Since markets are dynamic and people and products change over time, the basis for segmentation must also evolve.
Selecting Target Segments
Rolex focuses on a single market segment—those who want a luxury watch—and is thus a prime example of the concentration strategy of market segmentation.
Once an actionable segmentation approach is in place, marketing organizations typically follow one of two major segmentation strategies: a concentration strategy or a multisegment strategy.
In the concentration strategy, a company chooses to focus its marketing efforts on only one market segment. Only one marketing mix is developed: the combination of product offerings, promotional communications, distribution, and pricing targeted to that single market segment. The primary advantage of this strategy is that it enables the organization to analyze the needs and wants of only one segment and then focus all its efforts on that segment. The primary disadvantage of concentration is that if demand in the segment declines, the organization’s sales and financial position will also decline.
In the multisegment strategy, a company focuses its marketing efforts on two or more distinct market segments. The organization develops a distinct marketing mix for each segment. Then they develop marketing programs tailored to each of these segments. This strategy is advantageous because it may increase total sales with more marketing programs targeting more customers. The disadvantage is the higher costs, which stem from the need for multiple marketing programs that may include segment-specific product differentiation, promotions and communication, distribution/delivery channels, and pricing.
How do you choose?
Selecting the target segments boils down the following questions, which connect to the “ideal segment” conditions listed above:
- Whose needs can you best satisfy?
- Who will be the most profitable customers?
- Can you reach and serve each target segment effectively?
- Are the segments large and profitable enough to support your business?
- Do you have the resources available to effectively reach and serve each target segment?
As you answer these questions with regard to the different market segments you have defined, you will confirm which segments are most likely to be good targets for your product(s). These segments become your target market—the object of your targeting strategy, marketing mix, and marketing activities.
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Conducting a Market Segmentation. Authored by: Lumen Learning. License: CC BY: Attribution
- Revision and adaptation. Provided by: Lumen Learning. License: CC BY: Attribution
CC LICENSED CONTENT, SHARED PREVIOUSLY
- Criteria for Segmentation. From Marketing 2014. Provided by: Boundless. Located at: https://courses.lumenlearning.com/boundless-marketing/. License: CC BY-SA: Attribution-ShareAlike
- Introducing Marketing, Chapter 2: Understanding and Approaching the Market. Authored by: John Burnett. Provided by: Global Text. Located at: http://solr.bccampus.ca:8001/bcc/file/ddbe3343-9796-4801-a0cb-7af7b02e3191/1/Core%20Concepts%20of%20Marketing.pdf. License: CC BY: Attribution
- Goth Triplets. Authored by: Fluffy Steve. Located at: https://www.flickr.com/photos/fluffy_steve/3625314011/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
- Rolex Datejust. Authored by: Bruno Soares. Provided by: Flickr. Located at: https://flic.kr/p/8YBwNP. License: CC BY: Attribution
Case Study: eHarmony Targets Women
Segmentation Success: A Dating Web Site for Women
When it was launched in 2000, eHarmony quickly made its mark as a new brand and new category in the online dating landscape: a dating site for the serious relationship seeker, particularly women. By focusing on women as its target segment, eHarmony made wise, profitable choices about its product and user experience to address this group’s unique needs.
eHarmony entered an online market dominated by two well-established brands, Match.com and Yahoo, and it seemed to violate all the standard practices and conventional wisdom of the industry at the time. Unlike other dating sites, eHarmony decided not to allow users to search and browse their Web site for potential mates. Instead, it requires participants to complete an exhaustive questionnaire before they can receive any information about prospective suitors.
This process creates a much better user experience for eHarmony’s target demographic in a couple ways. First, women don’t feel like they are being judged solely on their looks. They perceive that they are being matched according to a complex array of compatibility criteria—not just superficial markers like age or income. Second, the entire eHarmony process is very time-consuming. It takes at least forty minutes to fill out the initial questionnaire, and users must court their potential mates through a series of essay questions and then write reviews of any contenders. By making the process so time-consuming, eHarmony has the natural effect of weeding out non-serious users and helping women to feel less vulnerable. This makes the product much better for the serious female relationship seeker who doesn’t want to waste time on or take a chance with casual dating.
In the following eHarmony ad, notice how the company differentiates itself from competitors:
The result of creating a product suited to women seeking marriage or long-term relationships has had two huge financial benefits for eHarmony. First, they can charge much more and enjoy much better margins than competitors. Because the customer perceives more value in being matched with a “soul mate” than in just being helped to “find a date,” eHarmony is able to charge more than other dating sites ($50 per month versus $20 per month). Second, eHarmony is able to generate revenue from women users much more effectively than other dating sites (many of which make most of their money on men): almost 60% of eHarmony’s paying users are women.
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Revision and Adaptation. Provided by: Lumen Learning. License: CC BY-SA: Attribution-ShareAlike
CC LICENSED CONTENT, SHARED PREVIOUSLY
- Measuring a Successful Segmentation, from Marketing 2014. Provided by: Boundless. Located at: https://courses.lumenlearning.com/boundless-marketing/. License: CC BY-SA: Attribution-ShareAlike
- American Bullfrog on a Lily Pad. Authored by: Katja Schulz. Located at: https://www.flickr.com/photos/treegrow/7915817762/. License: CC BY: Attribution
ALL RIGHTS RESERVED CONTENT
- eHarmony Commercial. Provided by: eHarmony. Located at: https://www.youtube.com/watch?v=k_7YgxeoKFI. License: All Rights Reserved. License Terms: Standard YouTube license
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oercommons
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2025-03-18T00:37:12.932750
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03/22/2022
|
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"url": "https://oercommons.org/courseware/lesson/91169/overview",
"title": "Statewide Dual Credit Principles of Marketing, Segmentation and Targeting, Segmentation Decisions",
"author": "Anna McCollum"
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https://oercommons.org/courseware/lesson/91211/overview
|
Elements of Brand
Overview
Provided by: Lumen Learning. License: CC BY: Attribution
Outcome: Elements of Brand
What you’ll learn to do: describe the elements of brand and how brands add value to an organization’s products and services
If you walk through a parking lot at school, work, or the local mall, chances are good that you could identify all the car brands just by looking at hood emblems. When you spot someone with a “swoosh” on her T-shirt, you probably already know she’s wearing Nike-brand apparel without even asking. How is it possible to know so much just by looking at an image or a shape? The answer is branding!
These familiar symbols are the tangible marks of branding in our everyday lives. But brands are much more than just logos and names. Brands also encompass everything else that contributes to your perception of that brand and what it represents.
The specific things you’ll learn in this section include:
- Define brand
- Explain elements that contribute to a brand and the brand-building process
- Explain how brands contribute value to organizations and consumers
- Describe different types of brands
Learning Activities
The learning activities for this section include the following:
- Reading: Elements of Brand
- Video: REI Builds Brand by Closing on Black Friday
- Reading: Types of Brands
Licenses and Attributions
CC licensed content, Original
- Revision and adaptation. Provided by: Lumen Learning. License: CC BY: Attribution
CC licensed content, Shared previously
- Outcome: Branding. Authored by: Linda Williams and Lumen Learning. Located at: https://courses.candelalearning.com/masterybusiness2xngcxmasterfall2015/chapter/branding/. License: CC BY: Attribution
Reading: Elements of Brand
What Is a Brand?
Brands are interesting, powerful concoctions of the marketplace that create tremendous value for organizations and for individuals. Because brands serve several functions, we can define the term “brand” in the following ways:
- A brand is an identifier: a name, sign, symbol, design, term, or some combination of these things that identifies an offering and helps simplify choice for the consumer.
- A brand is a promise: the promise of what a company or offering will provide to the people who interact with it.
- A brand is an asset: a reputation in the marketplace that can drive price premiums and customer preference for goods from a particular provider.
- A brand is a set of perceptions: the sum total of everything individuals believe, think, see, know, feel, hear, and experience about a product, service, or organization.
- A brand is “mind share”: the unique position a company or offering holds in the customer’s mind, based on their past experiences and what they expect in the future.
A brand consists of all the features that distinguish the goods and services of one seller from another: name, term, design, style, symbols, customer touch points, etc. Together, all elements of the brand work as a psychological trigger or stimulus that causes an association to all other thoughts one has had about this brand.
Brands are a combination of tangible and intangible elements, such as the following:
- Visual design elements (i.e., logo, color, typography, images, tagline, packaging, etc.)
- Distinctive product features (i.e. quality, design sensibility, personality, etc.)
- Intangible aspects of customers’ experience with a product or company (i.e. reputation, customer experience, etc.)
Branding–the act of creating or building a brand–may take place at multiple levels: company brands, individual product brands, or branded product lines. Any entity that works to build consumer loyalty can also be considered a brand, such as celebrities (Lady Gaga, e.g.), events (Susan G. Komen Race for the Cure, e.g.), and places (Las Vegas, e.g.).
History of Branding
The word “brand” is derived from the Old Norse brand meaning “to burn,” which refers to the practice of producers burning their mark (or brand) onto their products. Italians are considered among the first to use brands in the form of watermarks on paper in the 1200s. However, in mass-marketing, this concept originated in the nineteenth century with the introduction of packaged goods.
During the Industrial Revolution, the production of many household items, such as soap, was moved from local communities to centralized factories to be mass-produced and sold to the wider markets. When shipping their items, factories branded their logo or insignia on the barrels they used. Eventually these “brands” became trademarks—recognized symbols of a company or product that have been established by use. These new brand marks enabled packaged-goods manufacturers to communicate that their products were distinctive and should be trusted as much as (or more than) local competitors. Campbell Soup, Coca-Cola, Juicy Fruit gum, Aunt Jemima, and Quaker Oats were among the first products to be “branded.”
Brands Create Market Perceptions
A successful brand is much more than just a name or logo. As suggested in one of the definitions above, brand is the sum of perceptions about a company or product in the minds of consumers. Effective brand building can create and sustain a strong, positive, and lasting impression that is difficult to displace. Brands provide external cues to taste, design, performance, quality, value, or other desired attributes if they are developed and managed properly. Brands convey positive or negative messages about a company, product, or service. Brand perceptions are a direct result of past advertising, promotion, product reputation, and customer experience.
A brand can convey multiple levels of meaning, including the following:
- Attributes: specific product features. The Mercedes-Benz brand, for example, suggests expensive, well-built, well-engineered, durable vehicles.
- Benefits: attributes translate into functional and emotional benefits. Mercedes automobiles suggest prestige, luxury, wealth, reliability, self-esteem.
- Values: company values and operational principles. The Mercedes brand evokes company values around excellence, high performance, power.
- Culture: cultural elements of the company and brand. Mercedes represents German precision, discipline, efficiency, quality.
- Personality: strong brands often project a distinctive personality. The Mercedes brand personality combines luxury and efficiency, precision and prestige.
- User: brands may suggest the types of consumers who buy and use the product. Mercedes drivers might be perceived and classified differently than, for example, the drivers of Cadillacs, Corvettes, or BMWs.
Brands Create an Experience
Effective branding encompasses everything that shapes the perception of a company or product in the minds of customers. Names, logos, brand marks, trade characters, and trademarks are commonly associated with brand, but these are just part of the picture. Branding also addresses virtually every aspect of a customer’s experience with a company or product: visual design, quality, distinctiveness, purchasing experience, customer service, and so forth. Branding requires a deep knowledge of customers and how they experience the company or product. Brand-building requires long-term investment in communicating about and delivering the unique value embodied in a company’s “brand,” but this effort can bring long-term rewards.
In consumer and business-to-business markets, branding can influence whether consumers will buy the product and how much they are willing to pay. Branding can also help in new product introduction by creating meaning, market perceptions, and differentiation where nothing existed previously. When companies introduce a new product using an existing brand name (a brand extension or a branded product line), they can build on consumers’ positive perceptions of the established brand to create greater receptivity for the new offering.
Brands Create Value
Brands create value for consumers and organizations in a variety of ways.
Benefits of Branding for the Consumer
Brands help simplify consumer choices. Brands help create trust, so that a person knows what to expect from a branded company, product, or service. Effective branding enables the consumer to easily identify a desirable company or product because the features and benefits have been communicated effectively. Positive, well-established brand associations increase the likelihood that consumers will select, purchase, and consume the product. Dunkin’ Donuts, for example, has an established logo and imagery familiar to many U.S. consumers. The vivid colors and image of a DD cup are easily recognized and distinguished from competitors, and many associate this brand with tasty donuts, good coffee, and great prices.
Benefits of Branding for Product and Service Providers
For companies and other organizations that produce goods, branding helps create loyalty. It decreases the risk of losing market share to the competition by establishing a competitive advantage customers can count on. Strong brands often command premium pricing from consumers who are willing to pay more for a product they know, trust, and perceive as offering good value. Branding can be a great vehicle for effectively reaching target audiences and positioning a company relative to the competition. Working in conjunction with positioning, brand is the ultimate touchstone to guide choices around messaging, visual design, packaging, marketing, communications, and product strategy.
For example, Starbucks’ loyal fan base values and pays premium prices for its coffee. Starbucks’ choices about beverage products, neighborhood shops, the buying experience, and corporate social responsibility all help build the Starbucks brand and communicate its value to a global customer base.
Benefits of Branding for the Retailer
Retailers such as Target, Safeway, and Wal-Mart create brands of their own to create a loyal base of customers. Branding enables these retailers to differentiate themselves from one another and build customer loyalty around the unique experiences they provide. Retailer brand building may focus around the in-store or online shopping environment, product selection, prices, convenience, personal service, customer promotions, product display, etc.
Retailers also benefit from carrying the branded products customers want. Brand-marketing support from retailers or manufacturers can help attract more customers (ideally ones who normally don’t frequent an establishment). For example, a customer who truly values organic brands might decide to visit a Babies R Us to shop for organic household cleaners that are safe to use around babies. This customer might have learned that a company called BabyGanics, which brands itself as making “safe, effective, natural household solutions,” was only available at this particular retailer.
Licenses and Attributions
CC licensed content, Original
- Revision and adaptation. Provided by: Lumen Learning. License: CC BY-SA: Attribution-ShareAlike
CC licensed content, Shared previously
- Reading: Branding. Authored by: Linda Williams and Lumen Learning. Located at: https://courses.candelalearning.com/masterybusiness2xngcxmasterfall2015/chapter/reading-branding-labeling-and-packaging/. License: CC BY-SA: Attribution-ShareAlike
- Mercedes Benz. Authored by: MikesPhotos. Provided by: Pixabay. Located at: https://pixabay.com/photos/car-mercedes-transport-auto-motor-1506922/. License: CC0: No Rights Reserved
- Who We Are: The Coca-Cola Company. Provided by: The Coca-Cola Company. Located at: https://www.youtube.com/watch?v=5b18LXBpVDo. License: All Rights Reserved
- Coca Cola Crown Corks. Authored by: Couleur. Provided by: Pixabay. Located at: https://pixabay.com/photos/coca-cola-crown-corks-red-1218688/. License: CC0: No Rights Reserved
- Dunkin Donuts. Authored by: Kirakirameister. Provided by: Wikimedia Commons. Located at: https://commons.wikimedia.org/wiki/File:Dunkin%27_Donuts_Myeongdong.JPG. License: CC BY-SA: Attribution-ShareAlike
- Starbucks Coffee Sign. Authored by: JerryUnderscore. Provided by: Pixabay. Located at: https://pixabay.com/photos/starbucks-coffee-sign-city-urban-1972319/. License: CC0: No Rights Reserved
Video: REI Builds Brand by Closing on Black Friday
Organizations build their brands through all the ways they communicate and interact with consumers. Sometimes a company takes specific actions to demonstrate what a brand stands for, attract attention, and hopefully deepen customer loyalty because of what their brand represents.
That’s exactly what outdoor retailer REI did when it announced in October 2015 that their doors would be locked on one of the biggest shopping days of the year. Its CEO, Jerry Stritzke, told employees in an email, “While the rest of the world is fighting it out in the aisles, we hope to see you in the great outdoors.” In the following video, Stritzke joins CBS This Morning to explain the company’s decision and how it reflects on the REI brand.
As you watch this video, think about how this announcement might change your perceptions of the avid outdoors enthusiasts REI targets? Even if you don’t fit this target segment, how would this announcement affect your perceptions of the REI brand?
You can view the transcript for “REI Closing on Black Friday” here (opens in new window).
Licenses and Attributions
CC licensed content, Original
- REI Builds Brand by Closing on Black Friday. Provided by: Lumen Learning. License: CC BY: Attribution
CC licensed content, Shared previously
- REI Closing on Black Friday. Provided by: BBC. Located at: https://youtu.be/eEiDcAkEs6I. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
Reading: Types of Brands
There Are Many Types of Brands
Many kinds of things can become brands. Different types of brands include individual products, product ranges, services, organizations, individual persons, groups, events, geographic places, private label brands, media, and e-brands.
Individual Brands
The most common type of brand is a tangible, individual product, such as a car or drink. This can be very specific, such as the Kleenex brand of tissues, or it can encompass a wide range of products. Product brands can also be associated with a range of offerings, such as the Mercedes S-class cars or all varieties of Colgate toothpaste.
Service Brands
A service brand develops as companies move from manufacturing products to delivering complete solutions and intangible services. Service brands are characterized by the need to maintain a consistently high level of service delivery. This category includes the following:
- Classic service brands (such as airlines, hotels, car rentals, and banks)
- Pure service providers (such as member associations)
- Professional service brands (such as advisers of all kinds—accountancy, management consultancy)
- Agents (such as travel agents and estate agents)
- Retail brands (such as supermarkets, fashion stores, and restaurants)
Organization Brands
Organization brands are companies and other entities that deliver products and services. Mercedes and the U.S. Senate each possess strong organization brands, and each has associated qualities that make up their brand. Organizations can also be linked closely with the brand of an individual. For example, the U.S. Democratic party is closely linked with Bill and Hillary Clinton and Barack Obama.
Personal Brands
A person can be considered a brand. It can be comprised of one individual, as in the cases of Oprah Winfrey or Mick Jagger. Or it may be composed of a few individuals, where the branding is associated with different personalities. With the advent of the Internet and social media, the phenomenon of personal branding offers tools and techniques for virtually anyone to create a brand around themselves.
Group Brands
Group branding happens when there is a small group of branded entities that have overlapping, interconnected brand equity. For example, the OWN group brand of the Oprah Winfrey Network and the brand of its known members (Oprah and her team) are strongly connected. Similarly, the Rolling Stones represents a group brand that is strongly associated with the personal brands of its members (most enduringly, Mick Jagger, Keith Richards, Ronnie Wood, and Charlie Watts).
Event Brands
Events can become brands when they strive to deliver a consistent experience that attracts consumer loyalty. Examples include conferences like the TED series; music festivals like Coachella or SXSW; sporting events like the Olympics or NASCAR; and touring Broadway musicals like Wicked. The strength of these brands depends on the experience of people attending the event. Savvy brand managers from product, service, and other types of brands realize the power of event brands and seek to have their brands associated with the event brands through sponsorships. Event sponsorship is now a thriving big business.
Geographic Place Brands
Many places or areas of the world seek to brand themselves to build awareness of the essential qualities they offer. Branded places can range from countries and states to cities, streets, and even buildings. Those who govern or represent these geographies work hard to develop the brand. Geographic branding is used frequently to attract commerce and economic investment, tourism, new residents, and so on.
Private-Label Brands
Private-label brands, also called own brands, or store brands, exist among retailers that possess a particularly strong identity (such as Save-A-Lot). Private labels may denote superior, “select” quality, or lower cost for a quality product.
Media Brands
Media brands include newspapers, magazines, and television channels such as CNN.
E-Brands
E-brands exist only in the virtual world. Many e-brands, such as Amazon.com, have a central focus on providing an online front end for delivering physical products or services. Others provide information and intangible services to benefit consumers. Typically a common denominator among e-brands is the focus on delivering a valued service or experience in the virtual environment.
Licenses and Attributions
CC licensed content, Original
- Revision and adaptation. Provided by: Lumen Learning. License: CC BY-SA: Attribution-ShareAlike
CC licensed content, Shared previously
- Licensing, Chapter 6: Marketing in global markets in Introducing Marketing. Authored by: John Burnett. Provided by: Global Text. Located at: http://solr.bccampus.ca:8001/bcc/file/ddbe3343-9796-4801-a0cb-7af7b02e3191/1/Core%20Concepts%20of%20Marketing.pdf. License: CC BY: Attribution
- Branding, from Introduction to Business. Authored by: Linda Williams and Lumen Learning. Located at: https://courses.candelalearning.com/masterybusiness2xngcxmasterfall2015/chapter/reading-branding-labeling-and-packaging/. License: CC BY-SA: Attribution-ShareAlike
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oercommons
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2025-03-18T00:37:12.973895
|
03/22/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91211/overview",
"title": "Statewide Dual Credit Principles of Marketing, Branding, Elements of Brand",
"author": "Anna McCollum"
}
|
https://oercommons.org/courseware/lesson/93467/overview
|
Integrated Marketing Communication (IMC) Definition
Overview
Provided by: Lumen Learning. License: CC BY: Attribution
Outcome: Integrated Marketing Communication (IMC) Definition
What you’ll learn to do: explain integrated marketing communication (IMC) and its connection to the organization’s marketing strategy
Promotion is a powerful part of the marketing mix because it determines what and how you communicate with target audiences. In today’s world, promotion often has a fancy name: integrated marketing communication (IMC). Why the fancy name?
The number and variety of marketing communication tools have proliferated with the expansion of media, Internet, social, and mobile technologies. Marketers face the multipronged challenge of deciding which messages to communicate, which communication tools to use, and how to make the strongest impact with target segments.
Integrated marketing communication encourages marketers to think about communication in a coordinated way. They ask: How can we orchestrate all the different means of reaching a target segment in order to maximize our impact?
The specific things you’ll learn in this section include:
- Define integrated marketing communication (IMC)
- Explain how IMC strengthens the impact of marketing communication tools
- List the primary marketing communication methods marketers use as part of their IMC strategy
- Explain how marketers use IMC in their campaigns in order to execute marketing strategy
Learning Activities
- Reading: Integrated Marketing Communication (IMC) Definition
- Reading: Marketing Campaigns and IMC
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Outcome: Integrated Marketing Communication (IMC) Definition. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: Integrated Marketing Communication (IMC) Definition
IMC: Making an Impact with Marketing Communication
Having a great product available to your customers at a great price does absolutely nothing for you if your customers don’t know about it. That’s where promotion enters the picture: it does the job of connecting with your target audiences and communicating what you can offer them.
In today’s marketing environment, promotion involves integrated marketing communication (IMC). In a nutshell, IMC involves bringing together a variety of different communication tools to deliver a common message and make a desired impact on customers’ perceptions and behavior. As an experienced consumer in the English-speaking world, you have almost certainly been the target of IMC activities. (Practically every time you “like” a TV show, article, or a meme on Facebook, you are participating in an IMC effort!)
The videos you viewed in this module’s “Why It Matters” section provide ingenious and successful examples of integrated marketing communication, to give you a feel for what IMC is about. Not every IMC effort is that elaborate or creative, but from those examples, you can begin to see what’s possible when you bring together the right combination of ideas and communication tools focused on a common message and target segments.
What Is Marketing Communication?
Defining marketing communication is tricky because, in a real sense, everything an organization does has communication potential. The price placed on a product communicates something very specific about the product. A company that chooses to distribute its products strictly through discount stores sends a distinct message to the market. Marketing communication refers to activities deliberately focused on promoting an offering among target audiences. The following definition helps to clarify this term:
Marketing communication includes all the messages, media, and activities used by an organization to communicate with the market and help persuade target audiences to accept its messages and take action accordingly.
Integrated marketing communication is the the process of coordinating all this activity across different communication methods. Note that a central theme of this definition is persuasion: persuading people to believe something, to desire something, and/or to do something. Effective marketing communication is goal directed, and it is aligned with an organization’s marketing strategy. It aims to deliver a particular message to a specific audience with a targeted purpose of altering perceptions and/or behavior. Integrated marketing communication (IMC) makes this marketing activity more efficient and effective because it relies on multiple communication methods and customer touch points to deliver a consistent message in more ways and in more compelling ways.
The Promotion Mix: Marketing Communication Methods
The promotion mix refers to how marketers combine a range of marketing communication methods to execute their marketing activities. Different methods of marketing communication have distinct advantages and complexities, and it requires skill and experience to deploy them effectively. Not surprisingly, marketing communication methods evolve over time as new communication tools and capabilities become available to marketers and the people they target.
Seven common methods of marketing communication are described below:
- Advertising: Any paid form of presenting ideas, goods, or services by an identified sponsor. Historically, advertising messages have been tailored to a group and employ mass media such as radio, television, newspaper, and magazines. Advertising may also target individuals according to their profile characteristics or behavior; examples are the weekly ads mailed by supermarkets to local residents or online banner ads targeted to individuals based on the sites they visit or their Internet search terms.
- Public relations (PR): The purpose of public relations is to create goodwill between an organization (or the things it promotes) and the “public” or target segments it is trying to reach. This happens through unpaid or earned promotional opportunities: articles, press and media coverage, winning awards, giving presentations at conferences and events, and otherwise getting favorable attention through vehicles not paid for by the sponsor. Although organizations earn rather than pay for the PR attention they receive, they may spend significant resources on the activities, events, and people who generate this attention.
- Personal selling: Personal selling uses people to develop relationships with target audiences for the purpose of selling products and services. Personal selling puts an emphasis on face-to-face interaction, understanding the customer’s needs, and demonstrating how the product or service provides value.
- Sales promotion: Sales promotions are marketing activities that aim to temporarily boost sales of a product or service by adding to the basic value offered, such as “buy one get one free” offers to consumers or “buy twelve cases and get a 10 percent discount” to wholesalers, retailers, or distributors.
- Direct marketing: This method aims to sell products or services directly to consumers rather than going through retailer. Catalogs, telemarketing, mailed brochures, or promotional materials and television home shopping channels are all common traditional direct marketing tools. Email and mobile marketing are two next-generation direct marketing channels.
- Digital marketing: Digital marketing covers a lot of ground, from Web sites to search-engine, content, and social media marketing. Digital marketing tools and techniques evolve rapidly with technological advances, but this umbrella term covers all of the ways in which digital technologies are used to market and sell organizations, products, services, ideas, and experiences.
- Guerrilla marketing: This newer category of marketing communication involves unconventional, innovative, and usually low-cost marketing tactics to engage consumers in the marketing activity, generate attention and achieve maximum exposure for an organization, its products, and/or services. Generally guerrilla marketing is experiential: it creates a novel situation or memorable experience consumers connect to a product or brand.
Most marketing initiatives today incorporate multiple methods: hence the need for IMC. Each of these marketing communication methods will be discussed in further detail later in this module.
The Objectives of Marketing Communication
The basic objectives of all marketing communication methods are (1) to communicate, (2) to compete, and (3) to convince. In order to be effective, organizations should ensure that whatever information they communicate is clear, accurate, truthful, and useful to the stakeholders involved. In fact, being truthful and accurate in marketing communications is more than a matter of integrity; it’s also a matter of legality, since fraudulent marketing communications can end in lawsuits and even the criminal justice system.
Marketing communication is key to competing effectively, particularly in markets where competitors sell essentially the same product at the same price in the same outlets. Only through marketing communications may an organization find ways to appeal to certain segments, differentiate its product, and create enduring brand loyalty. Remaining more appealing or convincing than competitors’ messages is an ongoing challenge.
Ideally, marketing communication is convincing: it should present ideas, products, or services in such a compelling way that target segments are led to take a desired action. The ability to persuade and convince is essential to winning new business, but it may also be necessary to reconvince and retain many consumers and customers. Just because a customer buys a particular brand once or a dozen times, or even for a dozen years, there is no guarantee that the person will stick with the original product. That is why marketers want to make sure he or she is constantly reminded of the product’s unique benefits.
Shifting from Mass Marketing to IMC
Prior to the emergence of integrated marketing communications in the 1990s, mass communications (also called mass marketing)—the practice of relaying information to large segments of the population through television, radio, and other media—dominated marketing. Marketing was a one-way feed. Advertisers broadcasted their offerings and value propositions with little regard for the diverse needs, tastes, and values of consumers.
Often, this “one size fits all” approach was costly and uninformative due to the lack of tools for measuring results (in terms of sales). But as methods for collecting and analyzing consumer data improved—for example, with store scanners and electronic data about consumer purchases—marketers were increasingly able to correlate promotional activities with consumer purchasing patterns. Companies also began to downsize their operations and expand marketing tasks within their organizations.
As these changes were under way, at the same time consumers were gaining access to more and different types of specialized “niche” media along with new ways of consuming media. Cable television, DVRs, and a plethora of digital media have contributed to significant fragmentation of the mass market. While expensive mass-media advertising is still an option, it has less and less of an impact every year. Instead, most organizations find that it’s more cost-effective to reach target segments using other marketing communication strategies. As consumers turn to niche media, marketers’ promotion strategies (and marketing communication) have focused more on individualized patterns of consumption and on segmentation based on consumer tastes and preferences.
Technology has also driven the shift toward integrated marketing communication. Increasingly, organizations use highly targeted, data-based marketing rather than general-focus mass communication and advertising. This approach generates more information that marketers can use for segmentation and targeting based on many different criteria. Virtually unlimited Internet access has increased the online availability of information, goods, services, and ideas. It has brought a proliferation of new and more interactive tools, including mobile technology, that can be used for marketing communication purposes. Broader transparency and access to market information have shifted power away from retailers and manufacturers and toward consumers and their ability to control or manipulate the market in their favor.
With these developments, marketing teams and advertising/creative agencies are expected to understand and provide all marketing communication functions—not just advertising—for their clients. Most organizations now allocate budgets toward a variety of marketing communication methods, not just mass media. Taking full advantage of marketing opportunities that exist in a more diverse and fragmented media landscape, marketing is now viewed as a two-way, interactive conversation between marketers and consumers. Marketing activities seek not only to expose consumers to a message, but to engage them actively in the marketing process. The days of one-way, broadcast-style marketing are over.
A proliferation of marketing communication tools and opportunities means marketers must 1) identify which tools are the best fit for the audience and marketing objectives and 2) deliver a unified message and coordinated approach across these tools. To help execute a marketing strategy, multiple marketing communication methods and tools should deliver a well-coordinated message to engage the right people at the right time, in the right place, and doing the right things. This is what we mean by “integrated” marketing communications.
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Revision and adaptation. Authored by: Lumen Learning. License: CC BY-SA: Attribution-ShareAlike
- Screenshot McDonald's Lamppost. Provided by: Lumen Learning. License: CC BY: Attribution
CC LICENSED CONTENT, SHARED PREVIOUSLY
- Shifting from Fragmented to Integrated Communications. Provided by: Boundless. Located at: https://courses.lumenlearning.com/boundless-marketing/. License: CC BY-SA: Attribution-ShareAlike
- Chapter 8: Communicating to Mass Markets, from Introducing Marketing. . Authored by: John Burnett. Provided by: Global Text. Located at: http://solr.bccampus.ca:8001/bcc/file/ddbe3343-9796-4801-a0cb-7af7b02e3191/1/Core%20Concepts%20of%20Marketing.pdf.. License: CC BY: Attribution
- People On Internet Argue About Dress Colour. Authored by: studio tdes. Located at: https://www.flickr.com/photos/thedailyenglishshow/16725299326/. License: CC BY: Attribution
Reading: Marketing Campaigns and IMC
The Marketing Campaign
Determining which marketing communication methods and tools to use and how best to combine them is a challenge for any marketer planning a promotional strategy. To aid the planning process, marketing managers often use a campaign approach. A campaign is a planned, coordinated series of marketing communication efforts built around a single theme or idea and designed to reach a particular goal. For years, the term “campaign” has been used in connection with advertising, and this term applies equally well to the entire IMC program.
Organizations may conduct many types of IMC campaigns, and several may be run concurrently. Geographically, a firm may have a local, regional, or national campaign, depending upon the available funds, objectives, and market scope. One campaign may be aimed at consumers and another at wholesalers and retailers. Different marketing campaigns might target different segments simultaneously, delivering messages and using communication tools tailored to each segment. Marketers use a marketing plan (sometimes called an IMC plan) to track and execute a set of campaigns over a given period of time.
A campaign revolves around a theme, a central idea, focal point, or purpose. This theme permeates all IMC efforts and works to unify the campaign. The theme may refer to the campaign’s goals—for example, KCRW “Capital Campaign” launched by the popular Los Angeles-based public radio station KCRW to raise $48 million to build a new state-of-the-art media facility for its operations. The theme may also refer to the shift in customer attitudes or behavior that a campaign focuses on—such as new-member campaigns launched by numerous member organizations, from professional associations to school parent-teacher organizations. A theme might take the form of a slogan, such as Coca-Cola’s “Taste the Feeling” campaign or DeBeers’ “A diamond is forever.”
Clear Channel is a marketing company that specializes in outdoor advertising. For their latest advertising campaign in Switzerland, they created a slogan-based theme, “Where Brands Meet People,” and asked their clients to participate in dramatizing it. Dozens of Swiss companies gave their logo to be used as individual “tiles” in three colorful mosaic portraits.1 These mosaics appeared on the web and on the streets of Switzerland. Click here to see a high-resolution image of one mosaic and check out all the brands that make up the mosaics.
Marketing campaigns may also adopt themes that refer to a stage in the product life cycle, such as McDonald’s 2015 “All-Day Breakfast” rollout campaign. Some organizations use the same theme for several campaigns; others develop a different theme for each new campaign.
In a successfully operated campaign, all activities will be well coordinated to build on one another and increase the overall impact. For example, a single campaign might include:
- Advertising: A series of related, well-timed, carefully placed television ads coupled with print advertising in selected magazines and newspapers
- Direct marketing: Direct-to-consumer mail pieces sent to target segments in selected geographic areas, reinforcing the messages from the ads
- Personal selling: Preparation for customer sales representatives about the campaign to equip them to explain and demonstrate the product benefits stressed in advertising
- Sales promotions: In-store display materials reflecting the same messages and design as the ads, emphasizing point-of-sale impact
- Digital marketing: Promotional information on the organization’s Web site that reflects the same messages, design, and offers reflected in the ads; ads themselves may be posted on the Website, YouTube, Facebook, and shared in other social media
- Public relations: A press release announcing something newsworthy in connection to the campaign focus, objectives, and target segment(s)
For each IMC campaign, new display materials must be prepared, all reflecting common objectives, messages, design, and other elements to maximize the campaign’s impact.
People responsible for the physical delivery of the products or services must ensure that the distribution points are well stocked and equipped to deliver in all outlets prior to the start of the campaign. People managing public and media relations should be constantly kept aware of marketing planning, allowing them to identify and coordinate opportunities for earned media attention. Because public relations deals with media, conference/event organizers, and other stakeholders outside the organization, it is extremely important to give enough lead time for the public relations effort to take advantage of optimal timing in support of the overall campaign.
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Revision and adaptation. Provided by: Lumen Learning. License: CC BY: Attribution
CC LICENSED CONTENT, SHARED PREVIOUSLY
- Chapter 8: Communicating to Mass Markets, from Introducing Marketing. Authored by: John Burnett. Provided by: Global Text. Located at: http://solr.bccampus.ca:8001/bcc/file/ddbe3343-9796-4801-a0cb-7af7b02e3191/1/Core%20Concepts%20of%20Marketing.pdf. Project: Global Text. License: CC BY: Attribution
- 1984-01. Authored by: ITU Pictures. Located at: https://www.flickr.com/photos/itupictures/16474896040/. License: CC BY: Attribution
ALL RIGHTS RESERVED CONTENT
- Clear Channel: Where brands meet people. Authored by: Charis Tsevis. Located at: https://youtu.be/u1b5EtGqUOI. License: All Rights Reserved. License Terms: Standard YouTube license
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oercommons
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2025-03-18T00:37:13.011884
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06/06/2022
|
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"url": "https://oercommons.org/courseware/lesson/93467/overview",
"title": "Statewide Dual Credit Principles of Marketing, Promotion: Integrated Marketing Communication (IMC), Integrated Marketing Communication (IMC) Definition",
"author": "Anna McCollum"
}
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https://oercommons.org/courseware/lesson/91212/overview
|
Brand Equity
Overview
Provided by: Lumen Learning. License: CC BY: Attribution
Outcome: Brand Equity
What you’ll learn to do: define brand equity and its role in measuring brand strength
When most people see the Nike swoosh, what makes them think, “Just Do It!”? When kids see Mickey Mouse ears, what makes them think, “Disneyland”? When fans see the international soccer logo, FIFA, what makes them think of corrupt officials and financial misdeeds? When many Americans see the BP logo, what makes them think of environmental disaster in the Gulf of Mexico?
All of these scenarios are examples of brand equity, which are the associations people have about a particular brand. Brand equity translates into a value premium (or deficit) associated with a given brand in the minds of customers. Think of it as the “super bonus” a teen boy feels for a pair of Adidas or Nike sneakers compared with Skechers or no-name shoes. Or think of it as the negativity an airline has to overcome the day after one of its planes goes down in a crash.
Brand equity waxes and wanes with the fortunes of a company, product, and market. As you’ll discover, many things contribute to brand equity, and there are many ways to measure it.
The specific things you’ll learn in this section include:
- Explain the concept of brand equity
- Discuss why and how marketers measure brand equity
Learning Activities
The learning activities for this section include the following:
- Reading: Brand Equity
Licenses and Attributions
CC licensed content, Original
- Outcome: Brand Equity. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: Brand Equity
Brand Equity
In marketing, brand equity refers to the value of a well-known brand that conjures positive (or negative) mental and emotional associations. What does this actually mean? Let’s do a experiment with brand equity in action.
Brand equity is what exists in your mind (or doesn’t yet exist) to help you recognize these branded images and phrases. Brand equity is also the set of positive, negative, or neutral thoughts, beliefs, and emotions you associate with each of the brands. Brand equity can manifest itself in consumer recognition of logos or other visual elements, brand language associations, consumers’ perceptions of quality, and consumers’ perceptions of value or other brand attributes.
For any given product, service, or company, brand equity is considered a key asset because it gives meaning to the brand in the minds of its consumers. Brand equity can help a strong brand remain relevant and competitive in the marketplace, and it can help brands and companies weather storms that threaten their value and existence. Volkswagen, for example, is hoping that the strong brand equity it built during the decades before the 2015 emissions scandal will help restore customer confidence in its company and product brand.
When consumers trust a brand and find it relevant to themselves and their lives, they may select the offerings associated with that brand over those of competitors even at a premium price. For example, Häagen-Dazs and Ben & Jerry’s both command higher prices per pint at the grocery store than many national brands and most store brands of ice cream. Starbucks can sell its coffee at a higher price than solid market competitors because consumers associate the brand with quality, value, and the experience of connecting with other people in a comfortable space. This is why brand equity often correlates directly with a brand’s profitability.
Measuring Brand Equity
Brand equity is strategically important but also difficult to measure (or “quantify”). As a result, many experts have developed tools or metrics to analyze brand equity, although there is no universally accepted way to measure it. For example, while it can be measured quantitatively using numerical values such as profit margins and market share, this approach fails to capture qualitative elements such as prestige and mental and emotional associations.
What to Measure
According to David Aaker, a marketing professor and brand consultant, the following are ten attributes of a brand that can be used to assess its strength, or equity:1
- Price premium: the amount a customer is willing to pay for one brand in comparison to other comparable brands
- Customer satisfaction/loyalty: whether a customer would buy the brand at the next opportunity, or remain loyal to that brand
- Perceived quality: perceptions about whether a brand is of high, average, or inferior quality
- Leadership/popularity: being in market leadership position as a leading brand, a leader in innovation, and/or growing in popularity
- Value: perceptions of whether a brand has good value for the money and whether there are reasons to choose it over competitors
- Brand personality: distinctive, interesting, emotional, and self-expressive benefits associated with a brand
- Organizational associations: the people, values, and programs associated with the brand
- Brand awareness: the degree to which customers are familiar with and have knowledge about a brand
- Market share: share of sales among the competitive set
- Market price and distribution coverage: measures of average selling price relative to competitors and how many people have access to the brand
Marketers can use various research methods to measure each of these attributes. Some organizations invest in complex marketing research projects to measure and track brand equity over time using one or more of these metrics.
Brand Asset Valuator
Young & Rubicam (Y&R), a marketing communications agency, has developed the “brand asset valuator,” a tool used to diagnose the power and value of a brand. The agency uses this tool to survey and measure consumers’ perspectives along the following four dimensions.2
- Differentiation: the defining characteristics of the brand and its distinctiveness relative to competitors
- Relevance: the appropriateness and connection of the brand to a given consumer
- Esteem: consumers’ respect for and attraction to the brand
- Knowledge: consumers’ awareness of the brand and understanding of what it represents
This approach is useful for gaining a detailed understanding of how target audiences perceive a brand, how well they understand it, and how relevant it is in their lives. Y&R uses this methodology to help organizations diagnose whether their brands are rising or fading relative to competitors and help them develop strategies and tactics to strengthen existing brands or freshen up/rebuild those that are waning.
There are several different categories of brands, sorted by their differentiation, relevance, esteem, and knowledge. Note that we’ll also discuss their brand strength (which is their differentiation and relevance) and their brand stature (which is their esteem and knowledge).
- New/Fading Brands have low brand stature and low brand strength. They can be sorted into two categories:
- New has medium differentiation, less relevance, less esteem, and low knowledge.
- Unfocused has low-medium differentiation, low relevance, low esteem, and high-medium knowledge.
- Aspiring Brands have low brand stature and high brand strength. They have high differentiation, medium relevance, slightly less esteem, and slightly less knowledge.
- Power Brands have high brand stature and high brand strength. They can be sorted into two categories:
- Leadership has high differentiation, high relevance, high esteem, and high knowledge.
- Decline has low differentiation and high relevance, high esteem, and high knowledge.
- Eroding Brands have low brand stature and high brand strength. They have low differentiation, slightly higher relevance, slightly higher esteem, and medium knowledge.
Other Methods for Measuring Brand Equity
Brand equity can also be measured using other methods, such as the following:
- As a financial asset: Brand equity can be studied as a financial asset by making a calculation of a brand’s worth as an intangible asset. For example, a company can estimate brand value on the basis of projected profits discounted to a present value. In turn, the present value can be used to calculate the risk profile, market leadership, stability, and global reach. Forbes, Interbrand and other organizations conduct this type of valuation and publish annual lists of the most valuable global brands.
- As a price differential: The price of an equivalent well-known brand can be compared to that of competing, no-name, or private-label products. The value of this price differential can be calculated to estimate the brand’s price premium in terms of past, present, or future revenue.
- As consumer favorability and preference: Several brand-equity methodologies try to map the mind of the consumer to uncover associations with a given brand. For example, projective techniques can be used to identify tangible and intangible attributes, attitudes, and various perceptions about the brand. Under this approach, the brands with the highest levels of awareness and most favorable and unique associations are considered high-equity brands.
- As consumer perceptions: Another brand-equity measurement technique assesses which attributes are most important in influencing customer buying choices, and then measures how well various competitors perform against the most important attributes. This approach helps marketers better understand the customer decision-making process, how brands influence it, and which competitors “own” key attributes that drive customer decisions.
Building Brand Loyalty
One of the most important reasons for building brand equity is to win brand-loyal customers. In marketing, brand loyalty refers to a consumer’s commitment to repurchase or otherwise continue using a particular brand by repeatedly buying a product or service.
The American Marketing Association defines brand loyalty in the following ways:
- The situation in which a consumer generally buys the same manufacturer-originated product or service repeatedly over time rather than buying from multiple suppliers within the category (sales promotion definition)
- The degree to which a consumer consistently purchases the same brand within a product class (consumer behavior definition)
Aside from a consumer’s ability to repurchase a brand, true brand loyalty exists when the customer is committed to the brand and has a high relative attitude toward the brand, which is then demonstrated through repurchase behavior. For example, if Joe has brand loyalty to Company A, he will purchase Company A’s products even if Company B’s products are cheaper and/or of a higher quality. As an organization increases its number of brand-loyal customers, it develops a stronger and more predictable position in the market. As noted above, brand equity and brand loyalty enable an organization to enjoy price premiums over competitors.
Like brand equity, brand loyalty is multidimensional. It is determined by several distinct psychological processes, such as the customers’ perception of value, brand trust, satisfaction, repeat-purchase behavior, and commitment. Commitment and repeated-purchase behavior are considered necessary conditions for brand loyalty, followed by perceived value, satisfaction, and brand trust.
Philip Kotler identifies the following four customer types that exhibit similar patterns of behavior:
- Hard-core Loyals, who buy the brand all the time
- Split Loyals, who are loyal to two or three brands
- Shifting Loyals, who move from one brand to another
- Switchers, who have no loyalty (are possibly “deal-prone,” constantly looking for bargains, or are “vanity prone,” looking for something different)
Understanding the dynamics of these audiences can be very important for marketers, so they know what’s happening among their target segments and where to focus their attention and marketing investment. A large-scale 2013 study across 14 million store visits by 1 million customers found that loyal customers (those visiting the stores 10+times) accounted for about 20 percent of all customers but 80 percent of revenue and 72 percent of all store visits. Obviously, knowing and growing your loyal customer base makes a huge difference.3
Benefits of Brand Loyalty
The benefits of brand loyalty are longer tenure, or staying a customer for longer, and lower sensitivity to price. Recent research found evidence that longer-term customers were indeed less sensitive to price increases.
According to Andrew Ehrenberg, consumers buy “portfolios of brands.” They regularly switch between brands, often because they simply want a change. Thus, “brand penetration” or “brand share” reflects only a statistical chance that the majority of customers will buy that brand next time as part of a portfolio of brands. It does not guarantee that they will remain loyal.
By creating promotions and loyalty programs that encourage the consumer to take some sort of action, companies are building brand loyalty by offering more than just an advertisement. Offering incentives like big prizes creates an environment in which customers see the advertiser as more than just the advertiser. Individuals are far more likely to come back to a company that uses interesting promotions or loyalty programs than a company with a static message of “buy our brand because we’re the best.”
Popular Loyalty Programs
Below are some of the most popular customer loyalty programs used today by many companies. These programs allow organizations to engage their customers beyond traditional advertising and create incentives for consumers to become brand-loyal, repeat customers.
- Sweepstakes and Advergames
- Points-based loyalty programs, awarding prizes for incremental purchase behavior (e.g., frequent-flyer programs
- Branded digital games that engage consumers with prize incentives
- Contests
- Skill tests and user-generated promotions such as video and photo contests
- Social media applications and management
- Social media promotions and offers
- Customer rewards programs (e.g., pay lower prices using a frequent-buyer card)
- Coupons (hard copy and/or digital)
- Promotional auctions—bid for prizes with points earned from incremental purchase behavior
- Email clubs
- Subscription databases—national and/or segmented by market
- SMS Promotions
- iPhone apps
- Branded Web apps
As you’ll see in the following video, customers are well aware that companies are using loyalty programs to court them and win their repeat business—but it doesn’t seem to matter. Customers have come to expect something in exchange for their loyalty.
You can view the transcript for “Give and Take Rewards” (opens in new window).
- https://web.archive.org/web/20150319023659/http://www.iuc-edu.eu/group/sem1_L3/2013%20DNPBM/Lecture%2014%20Measuring%20Brand%20Equity.pdf
- http://young-rubicam.de/tools-wissen/tools/brandasset-valuator/?lang=en
- http://www.marketingprofs.com/chirp/2013/11338/surprising-facts-about-customer-loyalty-marketing-infographic#ixzz2wj6EeIlJ
Licenses and Attributions
CC licensed content, Original
- Revision and adaptation. Provided by: Lumen Learning. License: CC BY-SA: Attribution-ShareAlike
CC licensed content, Shared previously
- Branding, from Introduction to Business. Authored by: Linda Williams and Lumen Learning. Located at: https://courses.candelalearning.com/masterybusiness2xngcxmasterfall2015/chapter/reading-branding-labeling-and-packaging/. License: CC BY-SA: Attribution-ShareAlike
- Give and Take Rewards. Provided by: BBC. Located at: https://youtu.be/yB5Dep1a4Eo. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
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oercommons
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2025-03-18T00:37:13.047758
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03/22/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91212/overview",
"title": "Statewide Dual Credit Principles of Marketing, Branding, Brand Equity",
"author": "Anna McCollum"
}
|
https://oercommons.org/courseware/lesson/91206/overview
|
Repositioning
Overview
Provided by: Lumen Learning. License: CC BY: Attribution
Outcome: Repositioning
What you’ll learn to do: explain repositioning and the associated risks and complexities of repositioning a product or service
Positioning is a powerful tool, but when you position a product, service, or brand, the world doesn’t stand still. Market conditions change. Your customers and competitors change. You change.
Positioning should be designed to last. But for most offerings, you’ll eventually need to revisit your positioning strategy and consider whether to make adjustments. This process has a very logical name: repositioning. In some ways, repositioning is more challenging than initial positioning because you’re building on prior established work, trying to strengthen what’s working and fix what isn’t—it’s a bit like remodeling an old house instead of building one from scratch. In this next reading, you’ll learn more about repositioning, the associated risks and complexities, and the rationale for doing it in the first place.
Learning Activities
The learning activities for this section include the following:
- Reading: Repositioning
Licenses and Attributions
CC licensed content, Original
- Outcome: Repositioning. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: Repositioning
When It’s Time to Change Direction
After they are initially introduced to the market, products, services, and brands are constantly being repositioned as a result of changes in competitive and market situations. Repositioning involves changing the market’s perceptions of an offering so that it can compete more effectively in its present market or in other target segments.
Generally it is good to consider repositioning when you see the need or opportunity to improve demand for the offering. Perhaps sales have slowed down, your target segment is getting smaller, or you’ve developed a new innovation you’d like to introduce to the product. Specific factors that can trigger the decision to reposition a product, service, or brand include the following:
- Competition: New competitors entering or leaving the market; competitors joining forces; a competitor’s innovation that threatens to make your offering obsolete; competitive pricing strategies
- Market environment: Economic slow-down or recovery; changes in consumer confidence, the political climate, or social forces like the movement around social responsibility and sustainability
- Consumer trends: Changing tastes and preferences; evolving attitudes and behaviors such as how consumers use technology to learn about, acquire, or interact with your offering; new segments emerging as targets for your offering
- Internal environment: Changes in organizational leadership and strategy; acquisition or development of new technology; introduction of innovation that offers new competitive advantages and differentiators
The tax preparation service H&R Block provides a useful example. As technology-savvy millennials (people born between 1980 and 2000) began entering the workforce and caring about taxes, H&R Block saw that this sizable young segment overwhelmingly preferred TurboTax and other technology-based, do-it-yourself tools, rather than hiring tax professionals like H&R Block. Even after introducing its own online tax preparation tools, H&R was not able to capture this market segment. With its competitive advantage undermined by technology and its established customer base getting older, H&R Block knew that if it wanted to survive, it had to figure out how to appeal to younger taxpayers.
In 2012 and 2014, the company invested in repositioning campaigns to alter the company’s image and appeal to millennials. The campaigns combined satirical humor, social media, and social responsibility (in the form of charitable donations) to get millennials’ attention and create buzz around the H&R Block brand.1 The following H&R Block video ad from the 2012 “Stache Act” campaign makes the case for a fictional Million Mustache March on Washington to alter the tax code to include a $250 deduction for facial hair grooming materials:
You can view the transcript for “Stache Act Campaign Ad – The Oval Office” here (opens in new window).
The Repositioning Process
The repositioning process is very similar to the original positioning process, but it has a different starting point. The original positioning process focuses on creating a new position or market niche for an offering that wasn’t there previously. The repositioning process, on the other hand, evaluates the established position of a product, service, or brand and focuses on how to alter the positioning–and, with positioning, market perceptions–in order to improve competitiveness.
To change market perceptions, repositioning may involve changes in the tangible product or in its selling price, but this is not always required. Often the new positioning and differentiation are accomplished through changes in the promotional message and approach. It is very common to see companies launch marketing campaigns focused on repositioning a product or service, but few, if any changes, made to the product or service itself. These repositioning efforts often focus on trying to get a current target segment to take another look at a product or service and see it with a new perspective. Repositioning often aims to shift market perceptions in ways that make an offering more appealing to a broader swath of the market.
An important ongoing part of repositioning is to monitor the position of a product, service, or brand over time. This is necessary in order to evaluate what is working or not working about the current position and generate feedback to inform future positioning strategies. A product position, like the score in a ball game, may change readily; keeping track and making necessary adjustments is very important.
Repositioning Risks and Pitfalls
While repositioning is quite common, it carries risks and complexities that marketers must consider. Repositioning happens after initial market perceptions have already been established. Effective repositioning isn’t just creating something new. Instead, it is trying to preserve what is good from the existing market positions and build or shift thinking toward something new. Repositioning offers the opportunity to make something new and better than what you had previously, but it also has the potential to undermine or weaken market perceptions.
Repositioning must always consider carefully what has come before, as well as what’s ahead. In the repositioning process there’s inevitably baggage: residual issues left over from earlier positioning work, which is what led you to the point of needing to reposition. Your product, service, or brand has a history, and people have memories: some people remember what the offering used to stand for, and they will try to figure out how the new positioning fits with their perceptions. Customers, employees, and other stakeholders will have opinions–sometimes very vocal ones–about whether the new positioning is better or worse, effective or ineffective. All of this represents a potential minefield for marketers. Despite these challenges, repositioning can also be very rewarding if you are successful at reshaping perceptions and creating a more powerful, meaningful product, service, or brand.
As you consider repositioning opportunities, try to avoid the following common pitfalls:
- Insufficient research: Marketing research should inform your choices about how to shift positioning in order to improve market perceptions of your product, service, or brand. You should also conduct research to help you understand how your target segment will react to the repositioning, so you’re not caught off guard by adverse reactions.
- A bridge too far: It can be tempting to get wild and crazy with repositioning, especially if you’re trying to freshen things up. While this strategy can work, sometimes marketers go so far in the new direction that customers no longer believe the claims. Their perceptions of the offering can’t accommodate the new message or image, and the offering loses credibility.
- Underestimating “back to basics”: Sometimes repositioning is undertaken because the target segment isn’t sure what a product, service, or brand stands for. Instead of trying to infuse more new ideas and new meaning, marketers are sometimes better served by stripping positioning down to its bare essentials of competitive advantage, benefit, and message. Reinforcing the simple “basics” can be very powerful: this is what customers usually care about most.
- Overpromising: When faced with strong competitive threats, it can be easy for repositioning to overpromise benefits that a product, service, or brand is really ready to deliver. This can be disastrous because it creates customer expectations that the organization cannot live up to. Rarely does this end well.
- Confusing positioning: Repositioning can introduce confusion between the old positioning and the new, especially if they seem to contradict each other. Repositioning needs to offer a clear message for customers; otherwise they are not sure what to believe.
The risks and pitfalls of repositioning are evident in the example of United Airlines and its “Rising” campaign. For decades, United positioned itself as a passenger-center carrier providing great service embodied in the iconic tagline “Fly the Friendly Skies.” Seeking a change in the late 1990s, United introduced a new positioning approach it called “Rising.” Their strategy was to highlight common frustrations with air travel and make bold promises about how United Airlines provided a different, better level of service. However, the airline was unable to operationalize the changes needed to live up to these promises. The company abandoned the campaign after just two years because the positioning–and the airline–had lost credibility with the customer.2
Repositioning Success
Despite the risks, repositioning can be wildly successful when it is handled effectively. A good case in point is the American Red Cross. In 2009, the U.S. had sunk into the Great Recession, and the American Red Cross (ARC) was also feeling the pain. With its budget relying heavily on charitable donations, and with Americans giving less due to the recession, the nonprofit organization faced a budget deficit going into the fourth quarter.
For many nonprofit organizations, the last quarter of the year is prime fundraising season, since people open their wallets for holiday giving. Up until 2009, this was not the case for the Red Cross. Americans gave generously to the organization during disasters, but the ARC wasn’t people’s top choice for holiday giving. Seeing an opportunity in this apparent disconnect, the ARC engaged a creative agency to help repositioning the organization in the minds of potential donors.
Research confirmed that the competitive advantage of the American Red Cross, in consumers’ minds, was providing help in times of disaster. The organization’s then-current positioning of “Change a Life, Starting with Your Own“ shared a powerful emotional message, but it did not reinforce the competitive advantage or create a sense of urgency around giving to the ARC. The repositioning effort developed a new positioning direction expressed in the tag line “Give the gift that saves the day.”
This message reinforced the powerful role that the Red Cross plays in times of disaster and invited Americans to be part of that important work. With words like “give the gift,” it also implanted the idea of the ARC as a great recipient for holiday giving. The following video was created as part of the 2009 integrated marketing campaign that introduced this new positioning.
You can view the transcript for “American Red Cross – Holiday 2009 Campaign” here (opens in new window).
The repositioning was a resounding success. Income increased more than 5 percent compared to prior years. People who saw ads associated with the repositioning campaign were twice as likely to donate as people who didn’t see them. The fourth quarter of 2009 was one of the strongest since 2000. Brand awareness increased by 6 percentage points. The benefits didn’t stop in 2009, either. Building on their success, the ARC expanded the repositioning campaign in 2010. By the end of the year, income had increased 26 percent over 2009, and the average gift size increased 43 percent.3
These impressive results reveal the power of repositioning when it is handled well.
- http://www.theguardian.com/money/us-money-blog/2014/mar/05/hipsters-taxes-brooklyn-ads-hrblock
- http://www.wsj.com/articles/SB94719666565398524
- https://web.archive.org/web/20170310051421/https://russreid.com/2013/02/american-red-cross-integrated-marketing-campaign/
Licenses and Attributions
CC licensed content, Original
- Revision and Adaptation. Authored by: Lumen Learning. License: CC BY: Attribution
- Repositioning Risks and Pitfalls, Repositioning Success. Authored by: Lumen Learning. License: CC BY: Attribution
CC licensed content, Shared previously
- Introducing Marketing, Chapter 7. Introducing and managing the product. Authored by: John Burnett. Provided by: Global Text. Located at: http://solr.bccampus.ca:8001/bcc/file/ddbe3343-9796-4801-a0cb-7af7b02e3191/1/Core%20Concepts%20of%20Marketing.pdf. License: CC BY: Attribution
- Compass Study. Authored by: Calsidyrose. Located at: https://www.flickr.com/photos/calsidyrose/4925267732/. License: CC BY: Attribution
- Suitcases Stacked to the Ceiling. Authored by: Laura Gilmore. Located at: https://www.flickr.com/photos/genbug/3529776320/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives
All rights reserved content
- Stache Act Campaign Ad - The Oval Office. Authored by: 'Stache Act. Located at: https://youtu.be/oZWeYVrdhSc. License: All Rights Reserved. License Terms: Standard YouTube license
- American Red Cross - Holiday 2009 Campaign. Authored by: BlankTV. Located at: https://youtu.be/1QmOw7Snu_M. License: All Rights Reserved. License Terms: Standard YouTube license
|
oercommons
|
2025-03-18T00:37:13.080861
|
03/22/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91206/overview",
"title": "Statewide Dual Credit Principles of Marketing, Positioning, Repositioning",
"author": "Anna McCollum"
}
|
https://oercommons.org/courseware/lesson/91148/overview
|
Marketing Defined
Overview
Marketing Defined
Outcome: Marketing Defined
What you’ll learn to do: define marketing
Marketing is more than just banner ads, television commercials, and people standing on roadsides dressed up like the Statue of Liberty during tax time. It’s a complex set of activities and strategies that influences where we live, what we wear, how we conduct business, and how we spend our time and money. Marketing activities are conducted in an environment that changes quickly both in terms of customer demand and the methods by which consumers obtain information and make purchases. However, before you learn about these complex variables, you will need a good working definition of marketing. The following video has one (actually two).
Let’s move ahead so that you can gain a richer definition and understanding of marketing.
The specific things you’ll learn in this section include:
- Explain how the marketplace addresses customer wants and needs by creating opportunities for the exchange of products, services, and experiences
- Describe the role marketing plays in facilitating the exchange of value
Learning Activities
The learning activities for this section include the following:
- Reading: Marketing Defined
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- Authored by: Linda Williams and Lumen Learning. Provided by: Lumen Learning. License: CC BY: Attribution
ALL RIGHTS RESERVED CONTENT
- What Is Marketing? Two Answers to This One Question. Authored by: firepolemarketing. Located at: https://youtu.be/QePU68FhwiY. License: All Rights Reserved. License Terms: Standard YouTube license
Reading: Marketing Defined
What Is Marketing?
Marketing is a set of activities related to creating, communicating, delivering, and exchanging offerings that have value for others. In business, the function of marketing is to bring value to customers, whom the business seeks to identify, satisfy, and retain. This course will emphasize the role of marketing in business, but many of the concepts will apply to non-profit organizations, advocacy campaigns, and other activities aimed at influencing perceptions and behavior.
The Art of the Exchange
In marketing, the act of obtaining a desired object from someone by offering something of value in return is called the exchange process. The exchange involves:
- the customer (or buyer): a person or organization with a want or need who is willing to give money or some other personal resource to address this need
- the product: a physical good, a service, experience or idea designed to fill the customer’s want or need
- the provider (or seller): the company or organization offering a need-satisfying thing, which may be a product, service, experience or idea
- the transaction: the terms around which both parties agree to trade value-for-value (most often, money for product)
Individuals on both sides try to maximize rewards and minimize costs in their transactions, in order to gain the most profitable outcomes. Ideally, everyone achieves a satisfactory level of reward.
Marketing creates the goods and services that the company offers at a price to its customers. The entire bundle consists of a tangible good, an intangible service, and the price is the company’s offering. When you compare one car to another, for example, you can evaluate each of these dimensions—the tangible, the intangible, and the price—separately. However, you can’t buy one manufacturer’s car, another manufacturer’s service, and a third manufacturer’s price when you actually make a choice. Together, the three make up a single firm’s offer.
Marketing is also responsible for the entire environment in which this exchange of value takes place. Marketing identifies customers, their needs, and how much value they place on getting those needs addressed. Marketing informs the designer of the product to ensure it meets customer needs and provides value proportional to what it costs. Marketing is responsible for communicating with customers about products, explaining who is offering them and why they are desirable. Marketing is also responsible for listening to customers and communicating back to the provider about how well they are satisfying customer needs and opportunities for improvement. Marketing shapes the location and terms of the transaction, as well as the experience customers have after the product is delivered.
Marketing Creates Value for Customers
According to the influential economist and Harvard Business School professor Theodore Levitt, the purpose of all business is to “find and keep customers.” Marketing is instrumental to helping businesses achieve this purpose. It’s a way of thinking about business, rather than just a collection of techniques. It’s much more than just advertising and selling stuff and collecting money. Marketing generates value by creating the connections between people and products, customers and companies.
How does this happen? Boiled down to its essence, the role of marketing is to identify, satisfy, and retain customers.
Before you can create anything of value, first you must identify a want or need that you can address, as well as the prospective customers who possess this want or need.
Next, you work to satisfy these customers by delivering a product or service that addresses these needs at the time customers want it. Key to customer satisfaction is making sure everyone feels they benefit from the exchange. Your customer is happy with the value they get for what they pay. You are happy with the payment you receive in exchange for what you provide.
Effective marketing doesn’t stop there. It also needs to retain customers by creating new opportunities to win customer loyalty and business.
As you will learn in this course, marketing encompasses a variety of activities focused on accomplishing these objectives. How companies approach and conduct day-to-day marketing activities varies widely. For many large, highly visible companies, such as Disney-ABC, Proctor & Gamble, Sony, and Toyota, marketing represents a major expenditure. Such companies rely on effective marketing for business success, and this dependence is reflected in their organizational strategies, budget, and operations. Conversely, for other organizations, particularly those in highly regulated or less competitive industries such as utilities, social services, medical care, or businesses providing one-of-a-kind products, marketing may be much less visible. It could even be as simple as a Web site or an informational brochure.
There is no one model that guarantees marketing success. Effective marketing may be very expensive, or it may cost next to nothing. What marketing must do in all cases is to help the organization identify, satisfy, and retain customers. Regardless of size or complexity, a marketing program is worth the costs only if it facilitates the organization’s ability to reach its goals.
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, ORIGINAL
- What Is Marketing?, Marketing Creates Value for Customers. Authored by: Lumen Learning. License: CC BY: Attribution
- Revision and Adaptation. Authored by: Lumen Learning. License: CC BY: Attribution
- Image: Role of Marketing. Provided by: Lumen Learning. License: CC BY: Attribution
CC LICENSED CONTENT, SHARED PREVIOUSLY
- Chapter 1: Introducing Marketing, from Introducing Marketing. Authored by: John Burnett. Provided by: Global Text. Located at: http://solr.bccampus.ca:8001/bcc/file/ddbe3343-9796-4801-a0cb-7af7b02e3191/1/Core%20Concepts%20of%20Marketing.pdf. License: CC BY: Attribution
- 20140929 Hong Kong Umbrella Revolution. Authored by: Pasu Au Yeung. Located at: https://www.flickr.com/photos/studiokanu/15433515476/. License: CC BY: Attribution
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oercommons
|
2025-03-18T00:37:13.108526
|
03/22/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91148/overview",
"title": "Statewide Dual Credit Principles of Marketing, What is Marketing?, Marketing Defined",
"author": "Anna McCollum"
}
|
https://oercommons.org/courseware/lesson/91163/overview
|
Role of Marketing Plan
Overview
Role of Marketing Plan
Outcome: Role of Marketing Plan
What you’ll learn to do: explain the role of a marketing plan as a guiding document for marketing activities
How do organizations use the marketing mix to achieve results? This requires a clear understanding of the results that the organization hopes to achieve and a plan that brings the activities together.
The following reading gives an overview of the marketing planning process. In a later module we’ll cover the inputs and outputs of this process in much more detail. For now, think about how planning can focus marketing efforts to deliver value to the target customer.
Learning Activities
The learning activities for this section include the following:
- Reading: The Role of the Marketing Plan
- Simulation: Ice Cream Magnate
Licenses and Attributions
CC licensed content, Original
- Outcome: Role of Marketing Plan. Provided by: Lumen Learning. License: CC BY: Attribution
Reading: The Role of the Marketing Plan
The Marketing Plan
Effective marketing requires a plan—specifically, a marketing plan. Although customers should be at the center of any marketing plan, marketing activities do not operate in a vacuum. Instead, marketing is one function within a larger organization, and it operates within a competitive market environment. To ensure the effectiveness of marketing activities, the marketing plan must take all of these factors into account. Furthermore, once a plan is in place, it serves to guide all the marketing activities that an organization undertakes.
The marketing plan can take a variety of formats. It’s often a formal document that is broadly reviewed to create alignment and support across the organization. It can also be a presentation that explains each of the objectives and strategies. Sometimes the elements of the marketing plan are presented on a company’s internal Web site (or intranet), allowing all employees to access the information and see updates.
The format is less important than the impact. The marketing plan identifies the marketing objectives and explains how marketing activities will help the organization achieve its broader goals and objectives. The marketing plan describes how the company will use the marketing mix—product, promotion, place, and price—to achieve its marketing objectives effectively within the competitive market environment. The marketing plan also focuses the company’s resources on reaching target customers and driving them to act.
Marketing Plan Alignment with Company Goals
The executive leadership of a company is charged with creating the framework that aligns and focuses the work of employees: the company’s mission, objectives, and strategy. The company’s mission describes its purpose and explains why it exists. The executive leadership defines corporate goals and the high-level strategies that marketing activities should support.
Informed by corporate goals and strategies, marketers develop marketing objectives to support the broader company goals. They may cover a variety of areas: company growth, sales, market share, profitability, customer perceptions, market penetration, and so forth. The marketing objectives represent a set of measurable goals, tied to marketing activity, that align with and move the company towards its corporate mission and goals.
For example, Bristol-Myers Squibb is a pharmaceutical company with a mission to discover, develop, and deliver innovative medicines that help patients combat and recover from serious diseases. The company’s business strategy focuses on the manufacturing and distribution of medication, but it’s also engaged in medical research and the discovery of new treatments. Both the mission and strategy inform the marketing plan. The company’s marketing objectives and strategy should reinforce customer perceptions about the company’s biotech innovation and commitment to promising pharmaceutical breakthroughs.
Marketing Plan Input: Situation Analysis
Beyond the company’s purpose and focus, the marketing plan must take into account a range of internal and external factors that can be very complex. A situation analysis examines both the internal and external factors that might impact the marketing plan.
Internally, the company has both strengths and weaknesses that will influence the plan, such as its products, workforce, market perceptions, and other characteristics that give it advantages or disadvantages in the market. Outside the organization there are a range of opportunities and threats such as competitors, economic forces, government regulations, and other political factors.
The situation analysis helps refine corporate goals and produce a relevant set of marketing objectives. At the corporate level, typical objectives include profitability, cost savings, growth, market share improvement, risk containment, reputation, and so on. These corporate objectives can be translated into specific, measurable marketing objectives. For example, the marketing objective “Introduce three new products” might lead marketers to support corporate goals on profitability, increased market share, and movement into new markets. A corporate goal of “Increase profit margins” might dictate marketing objectives around product innovation, quality of materials, and the price charged.
Translating Marketing Objectives into Strategies and Tactics
Once the organization has conducted a situation analysis and identified its marketing objectives, the next step is to figure out what strategies will be most effective and the tactics that will be used to carry them out. You will learn more about the differences between strategy and tactics later on; for now, think of the strategy as the “big idea,” or approach, and tactics as “the details”—the specific actions that will be taken to make the big idea a reality and help the organization reach its goals. For example, if you’re a chess player, your strategy might be to “keep your opponent on the defensive,” and one of your tactics might be to “take the opponent’s queen as early in the game as possible.” Your goal, or objective, is to win the game.
Obviously, a marketing plan needs to include actual plans, and that’s where strategy and tactics come in. Though it’s crucial for a marketing plan to be aligned with an organization’s mission and mindful of its target customers, its competitors, and so on, it’s just as important to have a plan of action that spells out exactly how the organization’s resources will be used to reach its goals. Strategies and tactics are the key components of that action plan.
Marketing Plan Implementation and Evaluation
Once the plan is in place, the organization begins to implement the strategies. Successful marketing strategies require effective implementation. For example, if the organization has a promotional strategy to launch a social media campaign, then significant work is required to hone the message, manage social media tools, and encourage customers to engage. The strategy cannot achieve results if it is not executed well.
How will you know if it has been executed well? Marketing organizations need to identify what constitutes a successful marketing campaign and then measure the results to determine whether it had the desired impact. Did it reach the desired customers? Was it cost-effective? Did it generate the sales expected? Were the metrics for the specific elements of the campaign successful? Marketing metrics might include the number of customers viewing an advertisement, the number of social media “shares” or “likes,” the number of visits to a Web site, the proportion of new customers vs. existing customers, customer spending levels, etc. The right set of marketing metrics depends on what you are trying to accomplish with the marketing campaign.
Marketers should capture and analyze the appropriate metrics to understand the the success of marketing activities—to improve planning and future results.
Licenses and Attributions
CC licensed content, Original
- Provided by: Lumen Learning. License: CC BY: Attribution
CC licensed content, Shared previously
- Study of Human Immune Response to HIV. Provided by: NIAID. Located at: https://www.flickr.com/photos/niaid/5613410129/. License: CC BY: Attribution
- Boundless Marketing: definition of marketing plan. Provided by: Boundless. Located at: https://courses.lumenlearning.com/boundless-marketing/. License: CC BY-SA: Attribution-ShareAlike
Simulation: Ice Cream Magnate
Try It
Now that you’ve learned about the marketing mix and how it works, it’s time to give it a try yourself.
The simulation below gives you a chance to take a “great business idea”—in this case, ice cream—and play around with the four Ps of marketing.
Try the simulation a few times to see how different choices lead to different outcomes. In a simulation it’s good try out choices you think are right, as well as those you suspect are wrong, since you can learn from both. All simulations allow unlimited attempts so you can gain experience exploring and applying the concepts.
Licenses and Attributions
CC licensed content, Original
- Ice Cream Magnate. Authored by: Clark Aldrich. Revisions by Lumen Learning. License: CC BY: Attribution
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oercommons
|
2025-03-18T00:37:13.136966
|
03/22/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/91163/overview",
"title": "Statewide Dual Credit Principles of Marketing, Marketing Function, Role of Marketing Plan",
"author": "Anna McCollum"
}
|
https://oercommons.org/courseware/lesson/75331/overview
|
Panel_C_Plot
Editing Data Visualizations Using Inkscape
Overview
This workshop with Mario Trejo will cover how to use Inkscape tools to edit titles, legends, axes and highlight areas of a plot. This workshop is designed for individuals who frequently develop data visualizations using statistical software, but do not necessarily have the coding background to make extensive edits. The workshop will focus on editing output graphics from R and SAS statistical software.
This workshop with Mario Trejo will cover how to use Inkscape tools to edit titles, legends, axes and highlight areas of a plot. This workshop is designed for individuals who frequently develop data visualizations using statistical software, but do not necessarily have the coding background to make extensive edits. The workshop will focus on editing output graphics from R and SAS statistical software.
To begin you can download and install the most recent version of Inkscape here and download the workshop files below. You'll find the workshop recording here or copy and paste the link below.
https://inkscape.org/release/inkscape-1.0.1/
https://arizona.zoom.us/rec/play/qcrX3UMnLGAoKy6tC_swQpC_Ds9nZlqpHrm1_CLcsEkADcUEE64iMT6RVR8QQeJvwD6WStUsWaXvpIYp.fKqD5KgAxU-b02DV?startTime=1605816165000
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oercommons
|
2025-03-18T00:37:13.155421
|
Activity/Lab
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/75331/overview",
"title": "Editing Data Visualizations Using Inkscape",
"author": "Statistics and Probability"
}
|
https://oercommons.org/courseware/lesson/95199/overview
|
Math 400: Calculus 1
Overview
The Open for Antiracism (OFAR) Program – co-led by CCCOER and College of the Canyons – emerged as a response to the growing awareness of structural racism in our educational systems and the realization that adoption of open educational resources (OER) and open pedagogy could be transformative at institutions seeking to improve. The program is designed to give participants a workshop experience where they can better understand anti-racist teaching and how the use of OER and open pedagogy can empower them to involve students in the co-creation of an anti-racist classroom. The capstone project involves developing an action plan for incorporating OER and open pedagogy into a course being taught in the spring semester. OFAR participants are invited to remix this template to design and share their projects and plans for moving this work forward.
Course Description
- Overview:
- This is a rigorous, open, and equitable Calculus I class. It follows the OpenStax Calculus I book and uses the MyOpenMath course created by Larry Green and the ZTC grant as homework and extra resources. As well as lecture notes and worksheets created in Microsoft Word.
The structure of the course is that it follows a flipped class model, where students are required to watch lecture video created off of the lecture notes. Then students work on sectional exercises embedded in Canvas from MyOpenMath and work by themselves on the hard worksheet before the last day of the class during the week. On that day of class students will have the opportunity to work in groups on the worksheet problems.
They will be motivated to work on the problems in their groups because they will then teach the professor their random problem received as well as their group mates have points associated with their group mates work. The way they do this is through a program called GoReact that is embedded in Canvas. The main thing about this program is that students can easily share a recorded video of them teaching the math to the professor and the professor in turn can give video feedback telling the student how much they rock or letting them know what went wrong. These Teach Me Video are the foundation of the course and are the only thing the professor grades for the week unless there is a test. They are fun for both the instructor and students and increase the teacher student relationship as well as the student to student relationship. It is also easy to bump the Teach Me Videos up to make students who didn't fully understand the problem by making them redo the video to get some points back.
- Subject:
- Mathematics, Calculus
- Level:
- Community College / Lower Division
- Material Type:
- Activity/Lab, Assessment, Full Course, Homework/Assignment, Lecture, Lecture Notes, Lesson, Lesson Plan, Module, Textbook
- Syllabus and Course Information:
- The syllabus is all of module 0 in Canvas Commons, the reason I did this is so I have a living syllabus that I can change and add to within Canvas.
- Here is a link to my Canvas Commons Class: https://lor.instructure.com/resources/dfb7b57a4a7e4f3181a6fa75a9d279e3?shared
- Author:
- Andreas Bazos, MyOpenMath, OpenStax, ZTC Grant
Action Plan
- This is a full OER Calculus 1 course, that uses Lecture Notes with Video Solutions, Links to the OpenStax book, MyOpenMath assignments, and worksheets, where the students will be required to Teach the instructor a problem through a video recording software called GoReact. The Teach Me Videos that my students made for me are the biggest anti-racist part of this course as I am getting to know each and every one of my students and their mathematical abilities as much as I can.
Here is a link to my reflection on the changes I made to the course to be antiracist: - https://lrccd.zoom.us/rec/share/N_6iYEChEpnT3Ix5dBtlRFYnKitWmFnH-3uk_XrhsLO3RH4VYHG1cbozNGm0T4y5.uL7gemNk4eeeGGYq
The Teach Me Videos work very well, and you can even get your students to redo them to some of the missed points back. The Create Your Own Teach Me Videos did not work as well as I wanted but that was because I didn't control this enough.
Anti-Racist Assignment / Module
The anti-racist assignment that I created is at the end of Module 13 and asks students to find mathematicians from underrepresented groups.
Here is a link to my Canvas Commons Class: https://lor.instructure.com/resources/dfb7b57a4a7e4f3181a6fa75a9d279e3?shared
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oercommons
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2025-03-18T00:37:13.172797
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Homework/Assignment
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/95199/overview",
"title": "Math 400: Calculus 1",
"author": "Assessment"
}
|
https://oercommons.org/courseware/lesson/114105/overview
|
Lesson Plan
Overview
This is my Environmental Literacy lesson plan.
Environmental Literacy Lesson Plan
| Environmental Literacy Lesson Plan (1 hour and 30 minutes) Teacher: Thitaree Chanthawat (Phitsanulok Vocational College, Thailand) | |
| Title of Lesson Plan: Earth Heroes: Taking Action for Our Planet[a][b] | |
| Audience (Age, English Level): 16 students, ages 15-18 (Vocational Certificate Level) B1 | |
| Two Sentence Overview of the Lesson Plan: | |
Resources Needed:
| |
| Learning Objectives: 1. Identify and understand the causes, effects, and solutions of climate change through the exploration of resources such as the ScienceTREK website. (https://sciencetrek.org/topics/climate)2. Apply critical thinking and creativity to develop innovative solutions to address climate change challenges.3. Engage in collaborative discussion and online collaboration platforms to share ideas, provide feedback, and foster a sense of collective responsibility for environmental stewardship[e][f]. | |
| Warm-Up: (10 minutes) | |
| Time | Activities/Instructions (60 minutes)
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Closing/Debrief (20 minutes)
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[a]What a lovely title! Great focus on ACTION from the start! Bravo!
[b]Thank you
[c]I find it so important to bring focus to joy and optimism in this work of climate action. Thank you for the emphasis on the positive impact students can have!
[d]😃
[e]I am very drawn to this work stewardship. I think by incorporating it into your objectives, you are creating opportunity to further explore this term and its meaning in future activities/conversations. Really great!
[f]😃
[g]I absolutely love this!
[h]💕
[i]Exploring spaces! Moving bodies! Perfection!
[j]Nice purposeful incorporation of technology.
[k]Agreed
[l]Bringing in creativity!
[m]Thank you
[n]We love Padlet!
[o]💕
[p]Flexibility, choice, and reflection! Beautiful!
This lesson brings in so many important elements of an exemplar lesson plan! I absolutely love it and cannot wait to see how it unfolds in the classroom setting. I do hope you keep us posted! Amazing!
[q]😃
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oercommons
|
2025-03-18T00:37:13.204270
|
03/11/2024
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/114105/overview",
"title": "Lesson Plan",
"author": "THITAREE CHANTHAWAT"
}
|
https://oercommons.org/courseware/lesson/65727/overview
|
Navigation support document.reading_amusement park
Overview
Navigation support documents are worksheets that list a set of websites with a task created around them aligned to a teaching objective.
These worksheets can guide learners from one website/ webpage to the next asking them to perform certain learning activities using each link in order to achieve the objective.
Reading
Navigation support document
Skill developed: Reading using websites
Pre- Reading
You have seen varieties of rides in an amusement park. Think about your favourite ride. Did you enjoy riding it?
Go to the following site and look at the various rides in an amusement park
https://id.pinterest.com/pin/167407311121630937/
Open any one picture and try to describe the ride you see – how one enters the ride, the path it takes, what one feels, etc.
While - Reading
Here is a passage about the Incredible Machine in an amusement park. Read the passage and answer questions 1-7.
http://www.englishforeveryone.org/PDFs/7_The_Incredible_Machine_Free_Sample.pdf
Post – Reading
Search the internet for the world’s most dangerous rides or unusual entertainment parks. Save their pictures and share on Padlet. Also write a few sentences about its inventor or the location.
|
oercommons
|
2025-03-18T00:37:13.223495
|
04/29/2020
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/65727/overview",
"title": "Navigation support document.reading_amusement park",
"author": "Kshema Jose"
}
|
https://oercommons.org/courseware/lesson/65998/overview
|
Corporate Readiness
Overview
Corporate Readiness
Corporate Readiness
Corporate Readiness:
Aptitude Skills
Communication Skills
Domain Knowlege
Interpersonal Skills
Personality / Right Attitude
|
oercommons
|
2025-03-18T00:37:13.284268
|
05/02/2020
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/65998/overview",
"title": "Corporate Readiness",
"author": "Sowmya T Srinivasan"
}
|
https://oercommons.org/courseware/lesson/106019/overview
|
Risk Factors and Prevalence of a Language Delay
Overview
This systematic review answers the question of, "Are there risk factors or prevention strategies for language delay?".
Are there risk factors or prevention strategies for language delay?
|
oercommons
|
2025-03-18T00:37:13.301200
|
06/29/2023
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/106019/overview",
"title": "Risk Factors and Prevalence of a Language Delay",
"author": "maddie deller"
}
|
https://oercommons.org/courseware/lesson/99410/overview
|
Bertrand Russell
Overview
This is about Bertrand Russell.
Bertrand Russell on Appearance & Reality
To work on this question, Russell made a distinction between appearance and reality. Putting things simply, he argued that appearance is what we gather from our senses.
Unfortunately, or fortunately if you're into philosophical puzzles, appearance is not always reality. Case in point, that day in the mall, it APPEARED I had run into an acquaintance. In REALITY, I had come across a stranger.
To try to explain this, Russell used the idea of a table. While sitting at a table, he'd say a wooden one, the table appears brown. However, if you stand up and look at it in a different light, it might look lighter than what you consider brown. If you turn off the lights and look at it in the moonlight, it might appear black! Based on all these different appearances, how can you really know the table is brown?
Moving away from the sense of sight, he turned to texture. When you rub your hand across the table, it feels smooth. However, what if you looked at it under a microscope? Although it feels smooth, it would appear to be rough under the microscope. So, how can you realistically be certain whether the table is smooth or rough?
My Thoughts On Bertrand Russel on Appearance & Reality
When considering Russels point of view on appearance and reality I take in my own experiances and thought. Though I understand Russels persepective I believe that apperance this someones reality but reality is based on someones experiances and world view. For example, poeople base attrativness on appearance but that is relative to that person. So in turn in one persons reality someone can be attractive based on appearance but someone might not think that. Over all I believe appearance and reality are both relative and unqiue to each person. We cant generalize it by shared experanices and thoughts.
|
oercommons
|
2025-03-18T00:37:13.318881
|
12/13/2022
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/99410/overview",
"title": "Bertrand Russell",
"author": "Haley Griffith"
}
|
https://oercommons.org/courseware/lesson/90927/overview
|
The Myth of the Missing the Missing Half
Overview
the myth of the missing half in ancient greek
The Myth of the Missing Half
It is believed that when humans were initially created at the beginning of time, they had a different form than they have today. They were both male and female, with four arms, four legs, and a single head composed of two faces.
Plato had Aristophanes, a great Greek theater and comedy writer, narrate the story of the Soulmates in "The Symposium."
Plato describes it like way:
“According to Greek mythology, humans were originally created with four arms, four legs, and a head with two faces. Fearing their power, Zeus split them into two separate parts, condemning them to spend their lives in search of their other halves.”
Let us first define their origin before learning what the Gods feared in them. In nature, there were three genders: Man, Woman, and the "Androgynous," which means "man-woman" in Greek. There were two sets of genitalia for each gender, with the Androgynous possessing both male and female sex. The gender of humans was determined by their origin; Men were Sun children, while Women were Earth child. Androgynous, on the other hand, were Moonchild, born when the Sun and the Earth combined.
And there was a time when humans were bold and powerful beings who dared to threaten the Gods. They threatened to destroy them and reign in their place, therefore establishing themselves as the new Gods. So the Gods had to respond, and they pondered how to deal with the threat posed by humanity, as well as what needed to be done to restore harmony and balance.
They considered fully wrecking humanity, fighting them in a battle and killing them with lightning, as they had done with the Titans. However, if humans were no longer there, there would be no more human sacrifices to Gods, an idea that the Gods hated.
As a result, Zeus created a new plan. They'd divide the humans in half and punish them for their selfishness and vanity. Apart from the suffering they would experience, they would also double the human population, resulting in a doubling of the sacrifices that humans would have to pay to them. As a result, humans all across the world were divided in half.
These new creatures were completely miserable, immersed in their anguish. They were so depressed that they wouldn't eat or drink for days, unaware of the fact that they would die.
Apollo, the God of music, truth and prophecy, healing, and light, couldn't take seeing them like this, so he patched them up, reconstructed their physical shapes, and only left the navel as a memory of their former selves. As a result, humans evolved from double-faced, double-sex creatures with aspects of humanity to single-faced, single-sex creatures with two arms and legs. And they yearned for their soul and bodily counterparts for the rest of their lives.
Their body natures would yearn to be complete with the physical natures of the other sex, and their souls would ache for the other half of their soul, their soulmate, to be whole. And, according to myth, when these two parts find each other, they will have a wordless comprehension of one another, will feel connected and exist in sync with one another, and will experience no greater pleasure.
We may never know if the Soulmate myth is actually a myth or has some reality. Those who have discovered their soulmate, or twin-flame, companion in life, however, consistently describe the experience in the same way: "He was the stranger I recognized. She suddenly felt like home to me. We seemed to have known each other for years. It seemed as though we were meant to be together." So, may we all bravely go on this journey to find the One for us, the One who is us.
And may we never give up our Tue Love pursuit. And the Journey will be tough, with love that is not purely presenting itself as True Love, with us losing trust and possibly settling for anything less as we persuade ourselves that True Love is a myth. May our hearts be strong and we will keep faith in a world full of noise and confusion. Because if we don't, we'll be the ones who pay the price: a life not enjoyed, pleasure not discovered, and home never felt. Because home is not a place. It's a feeling.
|
oercommons
|
2025-03-18T00:37:13.332671
|
Reading Literature
|
{
"license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/",
"url": "https://oercommons.org/courseware/lesson/90927/overview",
"title": "The Myth of the Missing the Missing Half",
"author": "Languages"
}
|
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