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https://oercommons.org/courseware/lesson/15229/overview	Campaigns and Voting Learning Objectives By the end of this section, you will be able to: - Compare campaign methods for elections - Identify strategies campaign managers use to reach voters - Analyze the factors that typically affect a voter’s decision Campaign managers know that to win an election, they must do two things: reach voters with their candidate’s information and get voters to show up at the polls. To accomplish these goals, candidates and their campaigns will often try to target those most likely to vote. Unfortunately, these voters change from election to election and sometimes from year to year. Primary and caucus voters are different from voters who vote only during presidential general elections. Some years see an increase in younger voters turning out to vote. Elections are unpredictable, and campaigns must adapt to be effective. FUNDRAISING Even with a carefully planned and orchestrated presidential run, early fundraising is vital for candidates. Money helps them win, and the ability to raise money identifies those who are viable. In fact, the more money a candidate raises, the more he or she will continue to raise. EMILY’s List, a political action group, was founded on this principle; its name is an acronym for “Early Money Is Like Yeast” (it makes the dough rise). This group helps progressive women candidates gain early campaign contributions, which in turn helps them get further donations (Figure). Early in the 2016 election season, several candidates had fundraised well ahead of their opponents. Hillary Clinton, Jeb Bush, and Ted Cruz were the top fundraisers by July 2015. Clinton reported $47 million, Cruz with $14 million, and Bush with $11 million in contributions. In comparison, Bobby Jindal and George Pataki (who both dropped out relatively early) each reported less than $1 million in contributions during the same period. Bush later reported over $100 million in contributions, while the other Republican candidates continued to report lower contributions. Media stories about Bush’s fundraising discussed his powerful financial networking, while coverage of the other candidates focused on their lack of money. Donald Trump, the eventual Republican nominee and president, showed a comparatively low fundraising amount in the primary phase as he enjoyed much free press coverage because of his notoriety. He also flirted with the idea of being an entirely self-funded candidate. COMPARING PRIMARY AND GENERAL CAMPAIGNS Although candidates have the same goal for primary and general elections, which is to win, these elections are very different from each other and require a very different set of strategies. Primary elections are more difficult for the voter. There are more candidates vying to become their party’s nominee, and party identification is not a useful cue because each party has many candidates rather than just one. In the 2016 presidential election, Republican voters in the early primaries were presented with a number of options, including Mike Huckabee, Donald Trump, Jeb Bush, Ted Cruz, Marco Rubio, John Kasich, Chris Christie, Carly Fiorina, Ben Carson, and more. (Huckabee, Christie, and Fiorina dropped out relatively early.) Democrats had to decide between Hillary Clinton, Bernie Sanders, and Martin O’Malley (who soon dropped out). Voters must find more information about each candidate to decide which is closest to their preferred issue positions. Due to time limitations, voters may not research all the candidates. Nor will all the candidates get enough media or debate time to reach the voters. These issues make campaigning in a primary election difficult, so campaign managers tailor their strategy. First, name recognition is extremely important. Voters are unlikely to cast a vote for an unknown. Some candidates, like Hillary Clinton and Jeb Bush, have held or are related to someone who held national office, but most candidates will be governors, senators, or local politicians who are less well-known nationally. Barack Obama was a junior senator from Illinois and Bill Clinton was a governor from Arkansas prior to running for president. Voters across the country had little information about them, and both candidates needed media time to become known. While well-known candidates have longer records that can be attacked by the opposition, they also have an easier time raising campaign funds because their odds of winning are better. Newer candidates face the challenge of proving themselves during the short primary season and are more likely to lose. In 2016, both eventual party nominees had massive name recognition. Hillary Clinton enjoyed notoriety from having been First Lady, a U.S. senator from New York, and secretary of state. Donald Trump had name recognition from being an iconic real estate tycoon with Trump buildings all over the world plus a reality TV star via shows like The Apprentice. With Arnold Schwarzenegger having successfully campaigned for California governor, perhaps it should not have surprised the country when Trump was elected president. Second, visibility is crucial when a candidate is one in a long parade of faces. Given that voters will want to find quick, useful information about each, candidates will try to get the media’s attention and pick up momentum. Media attention is especially important for newer candidates. Most voters assume a candidate’s website and other campaign material will be skewed, showing only the most positive information. The media, on the other hand, are generally considered more reliable and unbiased than a candidate’s campaign materials, so voters turn to news networks and journalists to pick up information about the candidates’ histories and issue positions. Candidates are aware of voters’ preference for quick information and news and try to get interviews or news coverage for themselves. Candidates also benefit from news coverage that is longer and cheaper than campaign ads. For all these reasons, campaign ads in primary elections rarely mention political parties and instead focus on issue positions or name recognition. Many of the best primary ads help the voters identify issue positions they have in common with the candidate. In 2008, for example, Hillary Clinton ran a holiday ad in which she was seen wrapping presents. Each present had a card with an issue position listed, such as “bring back the troops” or “universal pre-kindergarten.” In a similar, more humorous vein, Mike Huckabee gained name recognition and issue placement with his 2008 primary ad. The “HuckChuck” spot had Chuck Norris repeat Huckabee’s name several times while listing the candidate’s issue positions. Norris’s line, “Mike Huckabee wants to put the IRS out of business,” was one of many statements that repeatedly used Huckabee’s name, increasing voters’ recognition of it (Figure). While neither of these candidates won the nomination, the ads were viewed by millions and were successful as primary ads. By the general election, each party has only one candidate, and campaign ads must accomplish a different goal with different voters. Because most party-affiliated voters will cast a ballot for their party’s candidate, the campaigns must try to reach the independent and undecided, as well as try to convince their party members to get out and vote. Some ads will focus on issue and policy positions, comparing the two main party candidates. Other ads will remind party loyalists why it is important to vote. President Lyndon B. Johnson used the infamous “Daisy Girl” ad, which cut from a little girl counting daisy petals to an atomic bomb being dropped, to explain why voters needed to turn out and vote for him. If the voters stayed home, Johnson implied, his opponent, Republican Barry Goldwater, might start an atomic war. The ad aired once as a paid ad on NBC before it was pulled, but the footage appeared on other news stations as newscasters discussed the controversy over it.Drew Babb, “LBJ’s 1964 Attack Ad ‘Daisy’ Leaves a Legacy for Modern Campaigns,” Washington Post, 5 September 2014; “1964 Johnson vs. Goldwater,” http://www.livingroomcandidate.org/commercials/1964 (November 9, 2015). More recently, Mitt Romney used the economy to remind moderates and independents in 2012 that household incomes had dropped and the national debt increased. The ad’s goal was to reach voters who had not already decided on a candidate and would use the economy as a primary deciding factor. Part of the reason Johnson’s campaign ad worked is that more voters turn out for a general election than for other elections. These additional voters are often less ideological and more independent, making them harder to target but possible to win over. They are also less likely to complete a lot of research on the candidates, so campaigns often try to create emotion-based negative ads. While negative ads may decrease voter turnout by making voters more cynical about politics and the election, voters watch and remember them.Stephen Ansolabehere, Shanto Iyengar, Adam Simon, and Nicholas Valentino. 1994. “Does Attack Advertising Demobilize the Electorate?” The American Political Science Review 88, No. 4: 829–838. Another source of negative ads is from groups outside the campaigns. Sometimes, shadow campaigns, run by political action committees and other organizations without the coordination or guidance of candidates, also use negative ads to reach voters. Even before the Citizens United decision allowed corporations and interest groups to run ads supporting candidates, shadow campaigns existed. In 2004, the Swift Boat Veterans for Truth organization ran ads attacking John Kerry’s military service record, and MoveOn attacked George W. Bush’s decision to commit to the wars in Afghanistan and Iraq. In 2014, super PACs poured more than $300 million into supporting candidates.“Super PACs,” https://www.opensecrets.org/pacs/superpacs.php?cycle=2014 (November 11, 2015). Want to know how much money federal candidates and PACs are raising? Visit the Campaign Finance Disclosure Portal at the Federal Election Commission website. General campaigns also try to get voters to the polls in closely contested states. In 2004, realizing that it would be difficult to convince Ohio Democrats to vote Republican, George W. Bush’s campaign focused on getting the state’s Republican voters to the polls. The volunteers walked through precincts and knocked on Republican doors to raise interest in Bush and the election. Volunteers also called Republican and former Republican households to remind them when and where to vote.…So Goes the Nation. 2006. Directed by Adam Del Deo and James D. Stern. Beverly Hills: Endgame Entertainment. The strategy worked, and it reminded future campaigns that an organized effort to get out the vote is still a viable way to win an election. TECHNOLOGY Campaigns have always been expensive. Also, they have sometimes been negative and nasty. The 1828 “Coffin Handbill” that John Quincy Adams ran, for instance, listed the names and circumstances of the executions his opponent Andrew Jackson had ordered (Figure). This was in addition to gossip and verbal attacks against Jackson’s wife, who had accidentally committed bigamy when she married him without a proper divorce. Campaigns and candidates have not become more amicable in the years since then. Once television became a fixture in homes, campaign advertising moved to the airwaves. Television allowed candidates to connect with the voters through video, allowing them to appeal directly to and connect emotionally with voters. While Adlai Stevenson and Dwight D. Eisenhower were the first to use television in their 1952 and 1956 campaigns, the ads were more like jingles with images. Stevenson’s “Let’s Not Forget the Farmer” ad had a catchy tune, but its animated images were not serious and contributed little to the message. The “Eisenhower Answers America” spots allowed Eisenhower to answer policy questions, but his answers were glib rather than helpful. John Kennedy’s campaign was the first to use images to show voters that the candidate was the choice for everyone. His ad, “Kennedy,” combined the jingle “Kennedy for me” and photographs of a diverse population dealing with life in the United States. The Museum of the Moving Image has collected presidential campaign ads from 1952 through today, including the “Kennedy for Me” spot mentioned above. Take a look and see how candidates have created ads to get the voters’ attention and votes over time. Over time, however, ads became more negative and manipulative. In reaction, the Bipartisan Campaign Reform Act of 2002, or McCain–Feingold, included a requirement that candidates stand by their ad and include a recorded statement within the ad stating that they approved the message. Although ads, especially those run by super PACs, continue to be negative, candidates can no longer dodge responsibility for them. Candidates are also frequently using interviews on late night television to get messages out. Soft news, or infotainment, is a new type of news that combines entertainment and information. Shows like The Daily Show and Last Week Tonight make the news humorous or satirical while helping viewers become more educated about the events around the nation and the world.“Public Knowledge of Current Affairs Little Changed by News and Information Revolutions,” Pew Research Center, April 15, 2007. In 2008, Huckabee, Obama, and McCain visited popular programs like The Daily Show, The Colbert Report, and Late Night with Conan O’Brien to target informed voters in the under-45 age bracket. The candidates were able to show their funny sides and appear like average Americans, while talking a bit about their policy preferences. By fall of 2015, The Late Show with Stephen Colbert had already interviewed most of the potential presidential candidates, including Hillary Clinton, Bernie Sanders, Jeb Bush, Ted Cruz, and Donald Trump. The Internet has given candidates a new platform and a new way to target voters. In the 2000 election, campaigns moved online and created websites to distribute information. They also began using search engine results to target voters with ads. In 2004, Democratic candidate Howard Dean used the Internet to reach out to potential donors. Rather than host expensive dinners to raise funds, his campaign posted footage on his website of the candidate eating a turkey sandwich. The gimmick brought over $200,000 in campaign donations and reiterated Dean’s commitment to be a down-to-earth candidate. Candidates also use social media, such as Facebook, Twitter, and YouTube, to interact with supporters and get the attention of younger voters. VOTER DECISION MAKING When citizens do vote, how do they make their decisions? The election environment is complex and most voters don’t have time to research everything about the candidates and issues. Yet they will need to make a fully rational assessment of the choices for an elected office. To meet this goal, they tend to take shortcuts. One popular shortcut is simply to vote using party affiliation. Many political scientists consider party-line voting to be rational behavior because citizens register for parties based upon either position preference or socialization. Similarly, candidates align with parties based upon their issue positions. A Democrat who votes for a Democrat is very likely selecting the candidate closest to his or her personal ideology. While party identification is a voting cue, it also makes for a logical decision. Citizens also use party identification to make decisions via straight-ticket voting—choosing every Republican or Democratic Party member on the ballot. In some states, such as Texas or Michigan, selecting one box at the top of the ballot gives a single party all the votes on the ballot (Figure). Straight-ticket voting does cause problems in states that include non-partisan positions on the ballot. In Michigan, for example, the top of the ballot (presidential, gubernatorial, senatorial and representative seats) will be partisan, and a straight-ticket vote will give a vote to all the candidates in the selected party. But the middle or bottom of the ballot includes seats for local offices or judicial seats, which are non-partisan. These offices would receive no vote, because the straight-ticket votes go only to partisan seats. In 2010, actors from the former political drama The West Wing came together to create an advertisement for Mary McCormack’s sister Bridget, who was running for a non-partisan seat on the Michigan Supreme Court. The ad reminded straight-ticket voters to cast a ballot for the court seats as well; otherwise, they would miss an important election. McCormack won the seat. Straight-ticket voting does have the advantage of reducing ballot fatigue. Ballot fatigue occurs when someone votes only for the top or important ballot positions, such as president or governor, and stops voting rather than continue to the bottom of a long ballot. In 2012, for example, 70 percent of registered voters in Colorado cast a ballot for the presidential seat, yet only 54 percent voted yes or no on retaining Nathan B. Coats for the state supreme court.“Presidential Electors,” http://www.sos.state.co.us/pubs/elections/Results/Abstract/2012/general/president.html (July 15, 2015); “Judicial Retention–Supreme Court,” http://www.sos.state.co.us/pubs/elections/Results/Abstract/2012/general/retention/supremeCourt.html (July 15, 2015). Voters make decisions based upon candidates’ physical characteristics, such as attractiveness or facial features.Lasse Laustsen. 2014. “Decomposing the Relationship Between Candidates’ Facial Appearance and Electoral Success,” Political Behavior 36, No. 4: 777–791. They may also vote based on gender or race, because they assume the elected official will make policy decisions based on a demographic shared with the voters. Candidates are very aware of voters’ focus on these non-political traits. In 2008, a sizable portion of the electorate wanted to vote for either Hillary Clinton or Barack Obama because they offered new demographics—either the first woman or the first black president. Demographics hurt John McCain that year, because many people believed that at 71 he was too old to be president.Alan Silverleib. 15 June 2008. “Analysis: Age an Issue in the 2008 Campaign?” http://www.cnn.com/2008/POLITICS/06/15/mccain.age/index.html?iref=newssearch. Hillary Clinton faced this situation again in 2016 as she became the first female nominee from a major party. In essence, attractiveness can make a candidate appear more competent, which in turn can help him or her ultimately win.Laustsen. “Decomposing the Relationship,” 777–791. Aside from party identification and demographics, voters will also look at issues or the economy when making a decision. For some single-issue voters, a candidate’s stance on abortion rights will be a major factor, while other voters may look at the candidates’ beliefs on the Second Amendment and gun control. Single-issue voting may not require much more effort by the voter than simply using party identification; however, many voters are likely to seek out a candidate’s position on a multitude of issues before making a decision. They will use the information they find in several ways. Retrospective voting occurs when the voter looks at the candidate’s past actions and the past economic climate and makes a decision only using these factors. This behavior may occur during economic downturns or after political scandals, when voters hold politicians accountable and do not wish to give the representative a second chance. Pocketbook voting occurs when the voter looks at his or her personal finances and circumstances to decide how to vote. Someone having a harder time finding employment or seeing investments suffer during a particular candidate or party’s control of government will vote for a different candidate or party than the incumbent. Prospective voting occurs when the voter applies information about a candidate’s past behavior to decide how the candidate will act in the future. For example, will the candidate’s voting record or actions help the economy and better prepare him or her to be president during an economic downturn? The challenge of this voting method is that the voters must use a lot of information, which might be conflicting or unrelated, to make an educated guess about how the candidate will perform in the future. Voters do appear to rely on prospective and retrospective voting more often than on pocketbook voting. In some cases, a voter may cast a ballot strategically. In these cases, a person may vote for a second- or third-choice candidate, either because his or her preferred candidate cannot win or in the hope of preventing another candidate from winning. This type of voting is likely to happen when there are multiple candidates for one position or multiple parties running for one seat.R. Michael Alvarez and Jonathan Nagler. 2000. “A New Approach for Modelling Strategic Voting in Multiparty Elections,” British Journal of Political Science 30, No. 1: 57–75. In Florida and Oregon, for example, Green Party voters (who tend to be liberal) may choose to vote for a Democrat if the Democrat might otherwise lose to a Republican. Similarly, in Georgia, while a Libertarian may be the preferred candidate, the voter would rather have the Republican candidate win over the Democrat and will vote accordingly.Nathan Thomburgh, “Could Third-Party Candidates Be Spoilers?” Time, 3 November 2008. One other way voters make decisions is through incumbency. In essence, this is retrospective voting, but it requires little of the voter. In congressional and local elections, incumbents win reelection up to 90 percent of the time, a result called the incumbency advantage. What contributes to this advantage and often persuades competent challengers not to run? First, incumbents have name recognition and voting records. The media is more likely to interview them because they have advertised their name over several elections and have voted on legislation affecting the state or district. Incumbents also have won election before, which increases the odds that political action committees and interest groups will give them money; most interest groups will not give money to a candidate destined to lose. Incumbents also have franking privileges, which allows them a limited amount of free mail to communicate with the voters in their district. While these mailings may not be sent in the days leading up to an election—sixty days for a senator and ninety days for a House member—congressional representatives are able to build a free relationship with voters through them.Matthew E. Glassman, “Congressional Franking Privilege: Background and Current Legislation,” Congressional Research Service, CRS Report RS22771, December 11, 2007, http://fas.org/sgp/crs/misc/RS22771.pdf. Moreover, incumbents have exiting campaign organizations, while challengers must build new organizations from the ground up. Lastly, incumbents have more money in their war chests than most challengers. Another incumbent advantage is gerrymandering, the drawing of district lines to guarantee a desired electoral outcome. Every ten years, following the U.S. Census, the number of House of Representatives members allotted to each state is determined based on a state’s population. If a state gains or loses seats in the House, the state must redraw districts to ensure each district has an equal number of citizens. States may also choose to redraw these districts at other times and for other reasons.League of United Latin American Citizens v. Perry, 548 U.S. 399 (2006). If the district is drawn to ensure that it includes a majority of Democratic or Republican Party members within its boundaries, for instance, then candidates from those parties will have an advantage. Gerrymandering helps local legislative candidates and members of the House of Representatives, who win reelection over 90 percent of the time. Senators and presidents do not benefit from gerrymandering because they are not running in a district. Presidents and senators win states, so they benefit only from war chests and name recognition. This is one reason why senators running in 2014, for example, won reelection only 82 percent of the time.“Reelection Rates of the Years,” https://www.opensecrets.org/bigpicture/reelect.php (November 2, 2015). Since 1960, the American National Election Studies has been asking a random sample of voters a battery of questions about how they voted. The data are available at the Inter-university Consortium for Political and Social Research at the University of Michigan. Summary Campaigns must try to convince undecided voters to vote for a candidate and get the party voters to the polls. Early money allows candidates to start a strong campaign and attract other donations. The election year starts with primary campaigns, in which multiple candidates compete for each party’s nomination, and the focus is on name recognition and issue positions. General election campaigns focus on getting party members to the polls. Shadow campaigns and super PACs may run negative ads to influence voters. Modern campaigns use television to create emotions and the Internet to interact with supporters and fundraise. Most voters will cast a ballot for the candidate from their party. Others will consider the issues a candidate supports. Some voters care about what candidates have done in the past, or what they may do in the future, while others are concerned only about their personal finances. Lastly, some citizens will be concerned with the candidate’s physical characteristics. Incumbents have many advantages, including war chests, franking privileges, and gerrymandering. Susan is currently working two part-time jobs and is frustrated about the poor economy. On Election Day, she votes for every challenger on the ballot, because she feels the president and Congress are not doing enough to help her. What type of vote did she cast? - retrospective - prospective - pocketbook - straight ticket Which factor is most likely to lead to the incumbency advantage for a candidate? - candidate’s socioeconomic status - gerrymandering of the candidate’s district - media’s support of the candidate - candidate’s political party Hint: B In what ways is voting your party identification an informed choice? In what ways is it lazy? Do physical characteristics matter when voters assess candidates? If so, how? Hint: Voters tend to vote for candidates who look attractive and competent. They may consider race, gender, height, weight, and other physical attributes.	oercommons	2025-03-18T00:36:04.421638	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15229/overview", "title": "American Government, Individual Agency and Action", "author": null }
https://oercommons.org/courseware/lesson/15230/overview	Direct Democracy Learning Objectives By the end of this section, you will be able to: - Identify the different forms of and reasons for direct democracy - Summarize the steps needed to place initiatives on a ballot - Explain why some policies are made by elected representatives and others by voters The majority of elections in the United States are held to facilitate indirect democracy. Elections allow the people to pick representatives to serve in government and make decisions on the citizens’ behalf. Representatives pass laws, implement taxes, and carry out decisions. Although direct democracy had been used in some of the colonies, the framers of the Constitution granted voters no legislative or executive powers, because they feared the masses would make poor decisions and be susceptible to whims. During the Progressive Era, however, governments began granting citizens more direct political power. States that formed and joined the United States after the Civil War often assigned their citizens some methods of directly implementing laws or removing corrupt politicians. Citizens now use these powers at the ballot to change laws and direct public policy in their states. DIRECT DEMOCRACY DEFINED Direct democracy occurs when policy questions go directly to the voters for a decision. These decisions include funding, budgets, candidate removal, candidate approval, policy changes, and constitutional amendments. Not all states allow direct democracy, nor does the United States government. Direct democracy takes many forms. It may occur locally or statewide. Local direct democracy allows citizens to propose and pass laws that affect local towns or counties. Towns in Massachusetts, for example, may choose to use town meetings, which is a meeting comprised of the town’s eligible voters, to make decisions on budgets, salaries, and local laws.“Citizen’s Guide to Town Meetings,” http://www.sec.state.ma.us/cis/cispdf/Guide_to_Town_Meetings.pdf (November 7, 2015). To learn more about what type of direct democracy is practiced in your state, visit the University of Southern California’s Initiative & Referendum Institute. This site also allows you to look up initiatives and measures that have appeared on state ballots. Statewide direct democracy allows citizens to propose and pass laws that affect state constitutions, state budgets, and more. Most states in the western half of the country allow citizens all forms of direct democracy, while most states on the eastern and southern regions allow few or none of these forms (Figure). States that joined the United States after the Civil War are more likely to have direct democracy, possibly due to the influence of Progressives during the late 1800s and early 1900s. Progressives believed citizens should be more active in government and democracy, a hallmark of direct democracy. There are three forms of direct democracy used in the United States. A referendum asks citizens to confirm or repeal a decision made by the government. A legislative referendum occurs when a legislature passes a law or a series of constitutional amendments and presents them to the voters to ratify with a yes or no vote. A judicial appointment to a state supreme court may require voters to confirm whether the judge should remain on the bench. Popular referendums occur when citizens petition to place a referendum on a ballot to repeal legislation enacted by their state government. This form of direct democracy gives citizens a limited amount of power, but it does not allow them to overhaul policy or circumvent the government. The most common form of direct democracy is the initiative, or proposition. An initiative is normally a law or constitutional amendment proposed and passed by the citizens of a state. Initiatives completely bypass the legislatures and governor, but they are subject to review by the state courts if they are not consistent with the state or national constitution. The process to pass an initiative is not easy and varies from state to state. Most states require that a petitioner or the organizers supporting an initiative file paperwork with the state and include the proposed text of the initiative. This allows the state or local office to determine whether the measure is legal, as well as estimate the cost of implementing it. This approval may come at the beginning of the process or after organizers have collected signatures. The initiative may be reviewed by the state attorney general, as in Oregon’s procedures, or by another state official or office. In Utah, the lieutenant governor reviews measures to ensure they are constitutional. Next, organizers gather registered voters’ signatures on a petition. The number of signatures required is often a percentage of the number of votes from a past election. In California, for example, the required numbers are 5 percent (law) and 8 percent (amendment) of the votes in the last gubernatorial election. This means through 2018, it will take 365,880 signatures to place a law on the ballot and 585,407 to place a constitutional amendment on the ballot.“How to Qualify an Initiative,” http://www.sos.ca.gov/elections/ballot-measures/how-qualify-initiative/ (November 13, 2015). Once the petition has enough signatures from registered voters, it is approved by a state agency or the secretary of state for placement on the ballot. Signatures are verified by the state or a county elections office to ensure the signatures are valid. If the petition is approved, the initiative is then placed on the next ballot, and the organization campaigns to voters. While the process is relatively clear, each step can take a lot of time and effort. First, most states place a time limit on the signature collection period. Organizations may have only 150 days to collect signatures, as in California, or as long as two years, as in Arizona. For larger states, the time limit may pose a dilemma if the organization is trying to collect more than 500,000 signatures from registered voters. Second, the state may limit who may circulate the petition and collect signatures. Some states, like Colorado, restrict what a signature collector may earn, while Oregon bans payments to signature-collecting groups. And the minimum number of signatures required affects the number of ballot measures. Arizona had more than sixty ballot measures on the 2000 general election ballot, because the state requires so few signatures to get an initiative on the ballot. Oklahomans see far fewer ballot measures because the number of required signatures is higher. Another consideration is that, as we’ve seen, voters in primaries are more ideological and more likely to research the issues. Measures that are complex or require a lot of research, such as a lend-lease bond or changes in the state’s eminent-domain language, may do better on a primary ballot. Measures that deal with social policy, such as laws preventing animal cruelty, may do better on a general election ballot, when more of the general population comes out to vote. Proponents for the amendments or laws will take this into consideration as they plan. Finally, the recall is one of the more unusual forms of direct democracy; it allows voters to decide whether to remove a government official from office. All states have ways to remove officials, but removal by voters is less common. The recall of California Governor Gray Davis in 2003 and his replacement by Arnold Schwarzenegger is perhaps one of the more famous such recalls. The recent attempt by voters in Wisconsin to recall Governor Scott Walker show how contentious and expensive a recall can be. Walker spent over $60 million in the election to retain his seat.David A. Fahrenthold and Rachel Weiner, “Gov. Walker Survives Recall in Wisconsin,” Washington Post, 5 June 2012. POLICYMAKING THROUGH DIRECT DEMOCRACY Politicians are often unwilling to wade into highly political waters if they fear it will harm their chances for reelection. When a legislature refuses to act or change current policy, initiatives allow citizens to take part in the policy process and end the impasse. In Colorado, Amendment 64 allowed the recreational use of marijuana by adults, despite concerns that state law would then conflict with national law. Colorado and Washington’s legalization of recreational marijuana use started a trend, leading to more states adopting similar laws. Too Much Democracy? How much direct democracy is too much? When citizens want one policy direction and government prefers another, who should prevail? Consider recent laws and decisions about marijuana. California was the first state to allow the use of medical marijuana, after the passage of Proposition 215 in 1996. Just a few years later, however, in Gonzales v. Raich (2005), the Supreme Court ruled that the U.S. government had the authority to criminalize the use of marijuana. In 2009, Attorney General Eric Holder said the federal government would not seek to prosecute patients using marijuana medically, citing limited resources and other priorities. Perhaps emboldened by the national government’s stance, Colorado voters approved recreational marijuana use in 2012. Since then, other states have followed. Twenty-three states and the District of Columbia now have laws in place that legalize the use of marijuana to varying degrees. In a number of these cases, the decision was made by voters through initiatives and direct democracy (Figure). So where is the problem? First, while citizens of these states believe smoking or consuming marijuana should be legal, the U.S. government does not. The Controlled Substances Act (CSA), passed by Congress in 1970, declares marijuana a dangerous drug and makes its sale a prosecutable act. And despite Holder’s statement, a 2013 memo by James Cole, the deputy attorney general, reminded states that marijuana use is still illegal.James M. Cole, “Memorandum for All United States Attorneys,” U.S. Department of Justice, August 29, 2013, http://www.justice.gov/iso/opa/resources/3052013829132756857467.pdf. But the federal government cannot enforce the CSA on its own; it relies on the states’ help. And while Congress has decided not to prosecute patients using marijuana for medical reasons, it has not waived the Justice Department’s right to prosecute recreational use.“State Medical Marijuana Laws,” http://www.ncsl.org/research/health/state-medical-marijuana-laws.aspx#2 (July 20, 2015). Direct democracy has placed the states and its citizens in an interesting position. States have a legal obligation to enforce state laws and the state constitution, yet they also must follow the laws of the United States. Citizens who use marijuana legally in their state are not using it legally in their country. This leads many to question whether direct democracy gives citizens too much power. Is it a good idea to give citizens the power to pass laws? Or should this power be subjected to checks and balances, as legislative bills are? Why or why not? Direct democracy has drawbacks, however. One is that it requires more of voters. Instead of voting based on party, the voter is expected to read and become informed to make smart decisions. Initiatives can fundamentally change a constitution or raise taxes. Recalls remove politicians from office. These are not small decisions. Most citizens, however, do not have the time to perform a lot of research before voting. Given the high number of measures on some ballots, this may explain why many citizens simply skip ballot measures they do not understand. Direct democracy ballot items regularly earn fewer votes than the choice of a governor or president. When citizens rely on television ads, initiative titles, or advice from others in determining how to vote, they can become confused and make the wrong decisions. In 2008, Californians voted on Proposition 8, titled “Eliminates Rights of Same-Sex Couples to Marry.” A yes vote meant a voter wanted to define marriage as only between a woman and man. Even though the information was clear and the law was one of the shortest in memory, many voters were confused. Some thought of the amendment as the same-sex marriage amendment. In short, some people voted for the initiative because they thought they were voting for same-sex marriage. Others voted against it because they were against same-sex marriage.Jessica Garrison, “Prop. 8 Leaves Some Voters Puzzled,” Los Angeles Times, 31 October 2008. Direct democracy also opens the door to special interests funding personal projects. Any group can create an organization to spearhead an initiative or referendum. And because the cost of collecting signatures can be high in many states, signature collection may be backed by interest groups or wealthy individuals wishing to use the initiative to pass pet projects. The 2003 recall of California governor Gray Davis faced difficulties during the signature collection phase, but $2 million in donations by Representative Darrell Issa (R-CA) helped the organization attain nearly one million signatures.Mark Barabak, “10 memorable moments from the recall of Gov. Gray Davis, 10 years later,” Los Angeles Times, http://www.latimes.com/nation/la-me-recall-pictures-20131001-photogallery.html (August 1, 2015). Many commentators argued that this example showed direct democracy is not always a process by the people, but rather a process used by the wealthy and business. Summary Direct democracy allows the voters in a state to write laws, amend constitutions, remove politicians from office, and approve decisions made by government. Initiatives are laws or constitutional amendments on the ballot. Referendums ask voters to approve a decision by the government. The process for ballot measures requires the collection of signatures from voters, approval of the measure by state government, and a ballot election. Recalls allow citizens to remove politicians from office. While direct democracy does give citizens a say in the policies and laws of their state, it can also be used by businesses and the wealthy to pass policy goals. Initiatives can also lead to bad policy if voters do not research the measure or misunderstand the law. Which of the following is not a step in the initiative process? - approval of initiative petition by state or local government - collection of signatures - state-wide vote during a ballot election - signature or veto by state governor A referendum is not purely direct democracy because the ________. - voters propose something but the governor approves it - voters propose and approve something but the legislature also approves it - government proposes something and the voters approve it - government proposes something and the legislature approves it Hint: C What problems would a voter face when trying to pass an initiative or recall? Why do some argue that direct democracy is simply a way for the wealthy and businesses to get their own policies passed? Hint: People of means can easily form interest groups to propose initiatives/recalls and that have the resources to pay for signature collection. What factors determine whether people turn out to vote in U.S. elections? What can be done to increase voter turnout in the United States? In what ways do primary elections contribute to the rise of partisanship in U.S. politics? How does social media affect elections and campaigns? Is this a positive trend? Why or why not? Should states continue to allow ballot initiatives and other forms of direct democracy? Why or why not? Abrajano, Marisa A., and R. Michael Alvarez. 2012. New Faces, New Voices: The Hispanic Electorate in America. Princeton, NJ: Princeton University Press. Adkins, Randall, ed. 2008. The Evolution of Political Parties, Campaigns, and Elections: Landmark Documents 1787–2007. Washington, DC: CQ Press. Boller, Paul. 2004. Presidential Campaigns: From George Washington to George W. Bush. Oxford: Oxford University Press. The Center for American Women and Politics (cawp.rutgers.edu). The Center for Responsive Politics (opensecrets.org). Craig, Stephen C., and David B. Hill, eds. 2011. The Electoral Challenge: Theory Meets Practice, 2nd ed. Washington, DC: CQ Press. Fiorina, Morris. 1981. Retrospective Voting in American National Elections. New Haven: Yale University Press. Frank, Thomas. 2004. What’s the Matter with Kansas? How Conservatives Won the Heart of America. New York: Henry Holt. Initiative and Reform Institute (http://www.iandrinstitute.org). Interactive Electoral College map (270towin.com). Jacobson, Gary C. 2012. The Politics of Congressional Elections, 8th ed. New York: Pearson. Lewis-Beck, Michael S., William G. Jacoby, Helmut Norpoth, and Herbert F. Weisberg. 2008. American Vote Revisited. Ann Arbor: University of Michigan Press. Lupia, Arthur, and Matthew McCubbins. 1998. Democratic Dilemma: Can Citizens Learn What They Need to Know? Cambridge: Cambridge University Press. Parker, David C. W. 2014. Battle for the Big Sky: Representation and the Politics of Place in the Race for the U.S. Senate. Washington, DC: CQ Press. PolitiFact (www.politifact.com). Polsby, Nelson, Aaron Wildavsky, Steven Schier, and David Hopkins. 2011. Presidential Elections: Strategies and Structures of American Politics. New York: Rowman and Littlefield. Project Vote Smart (votesmart.org).	oercommons	2025-03-18T00:36:04.453742	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15230/overview", "title": "American Government, Individual Agency and Action", "author": null }
https://oercommons.org/courseware/lesson/11834/overview	Introduction to Health and Medicine According to the World Health Organization and ABC Health News, on March 19, 2014 a "mystery" hemorrhagic fever outbreak occurred in Liberia and Sierra Leone. This outbreak was later confirmed to be Ebola, a disease first discovered in what is now the Democratic Republic of Congo. The 2014 outbreak started a chain reaction in West Africa, sickening more than 8,000 people and leaving more than 4,000 dead by October. At the time of this writing, Ebola is national news in the United States, and certainly global news as well. Infection of U.S. medical staff (both in West Africa and at home) has led to much fear and distrust, and discussion of restrictions on flights from West Africa was one proposed way to stop the spread of the disease. Ebola first entered the United States via U.S. missionary medical staff who were infected in West Africa and then transported home for treatment. The case of Thomas Eric Duncan, who unwittingly imported Ebola into the United States as he flew from Liberia to Texas in September 2014 to visit family, increased the level of fear. How do we best respond to this horrific virus? Restrict visitors from West Africa, enhance training and protective gear for all U.S. medical workers and law enforcement? Many concerns surround this disease and few agree upon the appropriate response. You can follow the progression of the outbreak at http://abc7news.com/news/timeline-of-the-ebola-virus-in-america-/348789/. The Ebola case brings many issues to the forefront. Are we in the cross-hairs of a large-scale Ebola epidemic in the United States? Or are the few cases of infection (primarily of health professionals) as far as the disease will spread in the United States? In the short term, how do we best prevent, identify, and treat current and potential cases? The sociology of health encompasses social epidemiology, disease, mental health, disability, and medicalization. The way that we perceive health and illness is in constant evolution. As we learn to control existing diseases, new diseases develop. As our society evolves to be more global, the way that diseases spread evolves with it. What does “health” mean to you? Do you believe that there are too many people taking medications in U.S. society? Are you skeptical about people claiming they are “addicted” to gambling or “addicted” to sex? Can you think of anything that was historically considered a disease but is now considered within a range of normality? Or anything that has recently become known as a disease that before was considered evidence of laziness or other character flaws? Do you believe all children should receive vaccinations? These are questions examined in the sociology of health. Sociologists may also understand these issues more fully by considering them through one of the main theoretical perspectives of the discipline. The functionalist perspective is a macroanalytical perspective that looks at the big picture and focuses on the way that all aspects of society are integral to the continued health and viability of the whole. For those working within the functionalist perspective, the focus is on how healthy individuals have the most to contribute to the stability of society. Functionalists might study the most efficient way to restore “sick” individuals to a healthy state. The conflict perspective is another macroanalytical perspective that focuses on the creation and reproduction of inequality. Someone applying the conflict perspective might focus on inequalities within the health system itself, by looking at disparities in race, ethnicity, gender, and age. Someone applying the interactionist perspective to health might focus on how people understand their health, and how their health affects their relationships with the people in their lives. References ABC News Health News. "Ebola in America, Timeline of a Deadly Virus." Retrieved Oct. 23rd, 2014 (http://abcnews.go.com/Health/ebola-america-timeline/story?id=26159719). Centers for Disease Control. 2011b.“Pertussis.” The Centers for Disease Control and Prevention. Retrieved December 15, 2011 (http://www.cdc.gov/pertussis/outbreaks.html). Conrad, Peter, and Kristin Barker. 2010. “The Social Construction of Illness: Key Insights and Policy Implications.” Journal of Health and Social Behavior 51:67–79. CNN. 2011. “Retracted Autism Study an 'Elaborate Fraud,' British Journal Finds.” CNN, January 5. Retrieved December 16, 2011 (http://www.cnn.com/2011/HEALTH/01/05/autism.vaccines/index.html). Devlin, Kate. 2008. “Measles worry MMR as vaccination rates stall.” The Telegraph, September 24. Retrieved January 19, 2012 (http://www.telegraph.co.uk/news/uknews/3074023/Measles-worries-as-MMR-vaccination-rates-stall.html). Sugerman, David E., Albert E. Barskey, Maryann G. Delea, Ismael R. Ortega-Sanchez, Daoling Bi, Kimberly J. Ralston, Paul A. Rota, Karen Waters-Montijo, and Charles W. LeBaron. 2010. “Measles Outbreak in a Highly Vaccinated Population, San Diego, 2008: Role of the Intentionally Undervaccinated.” Pediatrics 125(4):747–755. Retrieved December 16, 2011 (http://www.pediatricsdigest.mobi/content/125/4/747.full). World Health Organization. 2014. "Global Alert and Response." Retrieved Oct. 23rd 2014 (http://www.who.int/csr/disease/ebola/en/). Zacharyczuk, Colleen. 2011. “Myriad causes contributed to California pertussis outbreak.” Thorofar, NJ: Pediatric Supersite. Retrieved December 16, 2011 (http://www.pediatricsupersite.com/view.aspx?rid=90516).	oercommons	2025-03-18T00:36:04.471600	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11834/overview", "title": "Introduction to Sociology 2e, Health and Medicine", "author": null }
https://oercommons.org/courseware/lesson/11835/overview	The Social Construction of Health Overview - Define the term medical sociology - Understand the difference between the cultural meaning of illness, the social construction of illness, and the social construction of medical knowledge If sociology is the systematic study of human behavior in society, medical sociology is the systematic study of how humans manage issues of health and illness, disease and disorders, and healthcare for both the sick and the healthy. Medical sociologists study the physical, mental, and social components of health and illness. Major topics for medical sociologists include the doctor/patient relationship, the structure and socioeconomics of healthcare, and how culture impacts attitudes toward disease and wellness. The social construction of health is a major research topic within medical sociology. At first glance, the concept of a social construction of health does not seem to make sense. After all, if disease is a measurable, physiological problem, then there can be no question of socially constructing disease, right? Well, it’s not that simple. The idea of the social construction of health emphasizes the socio-cultural aspects of the discipline’s approach to physical, objectively definable phenomena. Sociologists Conrad and Barker (2010) offer a comprehensive framework for understanding the major findings of the last fifty years of development in this concept. Their summary categorizes the findings in the field under three subheadings: the cultural meaning of illness, the social construction of the illness experience, and the social construction of medical knowledge. The Cultural Meaning of Illness Many medical sociologists contend that illnesses have both a biological and an experiential component, and that these components exist independently of each other. Our culture, not our biology, dictates which illnesses are stigmatized and which are not, which are considered disabilities and which are not, and which are deemed contestable (meaning some medical professionals may find the existence of this ailment questionable) as opposed to definitive (illnesses that are unquestionably recognized in the medical profession) (Conrad and Barker 2010). For instance, sociologist Erving Goffman (1963) described how social stigmas hinder individuals from fully integrating into society. In essence, Goffman (1963) suggests we might view illness as a stigma that can push others to view the ill in an undesirable manner. The stigmatization of illness often has the greatest effect on the patient and the kind of care he or she receives. Many contend that our society and even our healthcare institutions discriminate against certain diseases—like mental disorders, AIDS, venereal diseases, and skin disorders (Sartorius 2007). Facilities for these diseases may be sub-par; they may be segregated from other healthcare areas or relegated to a poorer environment. The stigma may keep people from seeking help for their illness, making it worse than it needs to be. Contested illnesses are those that are questioned or questionable by some medical professionals. Disorders like fibromyalgia or chronic fatigue syndrome may be either true illnesses or only in the patients’ heads, depending on the opinion of the medical professional. This dynamic can affect how a patient seeks treatment and what kind of treatment he or she receives. The Social Construction of the Illness Experience The idea of the social construction of the illness experience is based on the concept of reality as a social construction. In other words, there is no objective reality; there are only our own perceptions of it. The social construction of the illness experience deals with such issues as the way some patients control the manner in which they reveal their diseases and the lifestyle adaptations patients develop to cope with their illnesses. In terms of constructing the illness experience, culture and individual personality both play a significant role. For some people, a long-term illness can have the effect of making their world smaller, more defined by the illness than anything else. For others, illness can be a chance for discovery, for re-imaging a new self (Conrad and Barker 2007). Culture plays a huge role in how an individual experiences illness. Widespread diseases like AIDS or breast cancer have specific cultural markers that have changed over the years and that govern how individuals—and society—view them. Today, many institutions of wellness acknowledge the degree to which individual perceptions shape the nature of health and illness. Regarding physical activity, for instance, the Centers for Disease Control (CDC) recommends that individuals use a standard level of exertion to assess their physical activity. This Rating of Perceived Exertion (RPE) gives a more complete view of an individual’s actual exertion level, since heartrate or pulse measurements may be affected by medication or other issues (Centers for Disease Control 2011a). Similarly, many medical professionals use a comparable scale for perceived pain to help determine pain management strategies. The Social Construction of Medical Knowledge Conrad and Barker show how medical knowledge is socially constructed; that is, it can both reflect and reproduce inequalities in gender, class, race, and ethnicity. Conrad and Barker (2011) use the example of the social construction of women’s health and how medical knowledge has changed significantly in the course of a few generations. For instance, in the early nineteenth century, pregnant women were discouraged from driving or dancing for fear of harming the unborn child, much as they are discouraged, with more valid reason, from smoking or drinking alcohol today. Has Breast Cancer Awareness Gone Too Far? Every October, the world turns pink. Football and baseball players wear pink accessories. Skyscrapers and large public buildings are lit with pink lights at night. Shoppers can choose from a huge array of pink products. In 2014, people wanting to support the fight against breast cancer could purchase any of the following pink products: KitchenAid mixers, Master Lock padlocks and bike chains, Wilson tennis rackets, Fiat cars, and Smith & Wesson handguns. You read that correctly. The goal of all these pink products is to raise awareness and money for breast cancer. However, the relentless creep of pink has many people wondering if the pink marketing juggernaut has gone too far. Pink has been associated with breast cancer since 1991, when the Susan G. Komen Foundation handed out pink ribbons at its 1991 Race for the Cure event. Since then, the pink ribbon has appeared on countless products, and then by extension, the color pink has come to represent support for a cure of the disease. No one can argue about the Susan G. Komen Foundation’s mission—to find a cure for breast cancer—or the fact that the group has raised millions of dollars for research and care. However, some people question if, or how much, all these products really help in the fight against breast cancer (Begos 2011). The advocacy group Breast Cancer Action (BCA) position themselves as watchdogs of other agencies fighting breast cancer. They accept no funding from entities, like those in the pharmaceutical industry, with potential profit connections to this health industry. They’ve developed a trademarked “Think Before You Pink” campaign to provoke consumer questioning of the end contributions made to breast cancer by companies hawking pink wares. They do not advise against “pink” purchases; they just want consumers to be informed about how much money is involved, where it comes from, and where it will go. For instance, what percentage of each purchase goes to breast cancer causes? BCA does not judge how much is enough, but it informs customers and then encourages them to consider whether they feel the amount is enough (Think Before You Pink 2012). BCA also suggests that consumers make sure that the product they are buying does not actually contribute to breast cancer, a phenomenon they call “pinkwashing.” This issue made national headlines in 2010, when the Susan G. Komen Foundation partnered with Kentucky Fried Chicken (KFC) on a promotion called “Buckets for the Cure.” For every bucket of grilled or regular fried chicken, KFC would donate fifty cents to the Komen Foundation, with the goal of reaching 8 million dollars: the largest single donation received by the foundation. However, some critics saw the partnership as an unholy alliance. Higher body fat and eating fatty foods has been linked to increased cancer risks, and detractors, including BCA, called the Komen Foundation out on this apparent contradiction of goals. Komen’s response was that the program did a great deal to raise awareness in low-income communities, where Komen previously had little outreach (Hutchison 2010). What do you think? Are fundraising and awareness important enough to trump issues of health? What other examples of “pinkwashing” can you think of? Summary Medical sociology is the systematic study of how humans manage issues of health and illness, disease and disorders, and healthcare for both the sick and the healthy. The social construction of health explains how society shapes and is shaped by medical ideas. Section Quiz Who determines which illnesses are stigmatized? - Therapists - The patients themselves - Society - All of the above Hint: C Chronic fatigue syndrome is an example of _______________. - a stigmatized disease - a contested illness - a disability - demedicalization Hint: B The Rating of Perceived Exertion (RPE) is an example of ________________ - the social construction of health - medicalization - disability accommodations - a contested illness Hint: A Short Answer Pick a common illness and describe which parts of it are medically constructed, and which parts are socially constructed. What diseases are the most stigmatized? Which are the least? Is this different in different cultures or social classes? Further Research Spend some time on the two web sites below. How do they present differing views of the vaccination controversy? Freedom of Choice is Not Free: Vaccination News: http://openstaxcollege.org/l/vaccination_news and Shot by Shot: Stories of Vaccine-Preventable Illnesses:http://openstaxcollege.org/l/shot_by_shot References Begos, Kevin. 2011. “Pinkwashing For Breast Cancer Awareness Questioned.” Retrieved December 16, 2011 (http://www.huffingtonpost.com/2011/10/11/breast-cancer-pink-pinkwashing_n_1005906.html). Centers for Disease Control. 2011a. “Perceived Exertion (Borg Rating of Perceived Exertion Scale).” Centers for Disease Control and Prevention. Retrieved December 12, 2011 (http://www.cdc.gov/physicalactivity/everyone/measuring/exertion.html). Conrad, Peter, and Kristin Barker. 2010. “The Social Construction of Illness: Key Insights and Policy Implications.” Journal of Health and Social Behavior 51:67–79. Goffman, Erving. 1963. Stigma: Notes on the Management of Spoiled Identity. London: Penguin. Hutchison, Courtney. 2010. “Fried Chicken for the Cure?” ABC News Medical Unit. Retrieved December 16, 2011 (http://abcnews.go.com/Health/Wellness/kfc-fights-breast-cancer-fried-chicken/story?id=10458830#.Tutz63ryT4s). Sartorius, Norman. 2007. “Stigmatized Illness and Health Care.” The Croatian Medical Journal 48(3):396–397. Retrieved December 12, 2011 (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2080544/). Think Before You Pink. 2012. “Before You Buy Pink.” Retrieved December 16, 2011 (http://thinkbeforeyoupink.org/?page_id=13). “Vaccines and Immunizations.” 2011. The Centers for Disease Control and Prevention. Retrieved December 16, 2011 (http://www.cdc.gov/vaccines/default.htm). World Health Organization. .n.d. “Definition of Health.” Retrieved December 12, 2011 (http://www.who.int/about/definition/en/print.html). World Health Organization: “Health Promotion Glossary Update.” Retrieved December 12, 2011 (http://www.who.int/healthpromotion/about/HPR%20Glossary_New%20Terms.pdf).	oercommons	2025-03-18T00:36:04.499800	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11835/overview", "title": "Introduction to Sociology 2e, Health and Medicine", "author": null }
https://oercommons.org/courseware/lesson/11836/overview	Global Health Overview - Define social epidemiology - Apply theories of social epidemiology to an understanding of global health issues - Understand the differences between high-income and low-income nations Social epidemiology is the study of the causes and distribution of diseases. Social epidemiology can reveal how social problems are connected to the health of different populations. These epidemiological studies show that the health problems of high-income nations differ greatly from those of low-income nations. Some diseases, like cancer, are universal. But others, like obesity, heart disease, respiratory disease, and diabetes are much more common in high-income countries and are a direct result of a sedentary lifestyle combined with poor diet. High-income nations also have a higher incidence of depression (Bromet et al. 2011). In contrast, low-income nations suffer significantly from malaria and tuberculosis. How does health differ around the world? Some theorists differentiate among three types of countries: core nations, semi-peripheral nations, and peripheral nations. Core nations are those that we think of as highly developed or industrialized, semi-peripheral nations are those that are often called developing or newly industrialized, and peripheral nations are those that are relatively undeveloped. While the most pervasive issue in the U.S. healthcare system is affordable access to healthcare, other core countries have different issues, and semi-peripheral and peripheral nations are faced with a host of additional concerns. Reviewing the status of global health offers insight into the various ways that politics and wealth shape access to healthcare, and it shows which populations are most affected by health disparities. Health in High-Income Nations Obesity, which is on the rise in high-income nations, has been linked to many diseases, including cardiovascular problems, musculoskeletal problems, diabetes, and respiratory issues. According to the Organization for Economic Cooperation and Development (2011), obesity rates are rising in all countries, with the greatest gains being made in the highest-income countries. The United States has the highest obesity rate. Wallace Huffman and his fellow researchers (2006) contend that several factors are contributing to the rise in obesity in developed countries: - Improvements in technology and reduced family size have led to a reduction of work to be done in household production. - Unhealthy market goods, including processed foods, sweetened drinks, and sweet and salty snacks are replacing home-produced goods. - Leisure activities are growing more sedentary, for example, computer games, web surfing, and television viewing. - More workers are shifting from active work (agriculture and manufacturing) to service industries. - Increased access to passive transportation has led to more driving and less walking. Obesity and weight issues have significant societal costs, including lower life expectancies and higher shared healthcare costs. High-income countries also have higher rates of depression than less affluent nations. A recent study (Bromet et al. 2011) shows that the average lifetime prevalence of major depressive episodes in the ten highest-income countries in the study was 14.6 percent; this compared to 11.1 percent in the eight low- and middle-income countries. The researchers speculate that the higher rate of depression may be linked to the greater income inequality that exists in the highest-income nations. Health in Low-Income Nations In peripheral nations with low per capita income, it is not the cost of healthcare that is the most pressing concern. Rather, low-income countries must manage such problems as infectious disease, high infant mortality rates, scarce medical personnel, and inadequate water and sewer systems. Such issues, which high-income countries rarely even think about, are central to the lives of most people in low-income nations. Due to such health concerns, low-income nations have higher rates of infant mortality and lower average life spans. One of the biggest contributors to medical issues in low-income countries is the lack of access to clean water and basic sanitation resources. According to a 2014 UNICEF report, almost half of the developing world’s population lacks improved sanitation facilities. The World Health Organization (WHO) tracks health-related data for 193 countries. In their 2011 World Health Statistics report, they document the following statistics: - Globally, the rate of mortality for children under five was 60 per 1,000 live births. In low-income countries, however, that rate is almost double at 117 per 1,000 live births. In high-income countries, that rate is significantly lower than seven per 1,000 live births. - The most frequent causes of death for children under five were pneumonia and diarrheal diseases, accounting for 18 percent and 15 percent, respectively. These deaths could be easily avoidable with cleaner water and more coverage of available medical care. - The availability of doctors and nurses in low-income countries is one-tenth that of nations with a high income. Challenges in access to medical education and access to patients exacerbate this issue for would-be medical professionals in low-income countries (World Health Organization 2011). Summary Social epidemiology is the study of the causes and distribution of diseases. From a global perspective, the health issues of high-income nations tend toward diseases like cancer as well as those that are linked to obesity, like heart disease, diabetes, and musculoskeletal disorders. Low-income nations are more likely to contend with infectious disease, high infant mortality rates, scarce medical personnel, and inadequate water and sanitation systems. Section Quiz What is social epidemiology? - The study of why some diseases are stigmatized and others are not - The study of why diseases spread - The study of the mental health of a society - The study of the causes and distribution of diseases Hint: D Core nations are also known as __________________ - high-income nations - newly industrialized nations - low-income nations - developing nations Hint: A Many deaths in high-income nations are linked to __________________ - lung cancer - obesity - mental illness - lack of clean water Hint: B According to the World Health Organization, what was the most frequent cause of death for children under five in low-income countries? - Starvation - Thirst - Pneumonia and diarrheal diseases - All of the above Hint: C Short Answer If social epidemiologists studied the United States in the colonial period, what differences would they find between now and then? What do you think are some of the contributing factors to obesity-related diseases in the United States? Further Research Study this map on global life expectancies: http://openstaxcollege.org/l/global_life_expectancies. What trends do you notice? References Bromet et al. 2011. “Cross-National Epidemiology of DSM-IV Major Depressive Episode.” BMC Medicine 9:90. Retrieved December 12, 2011 (http://www.biomedcentral.com/1741-7015/9/90). Huffman, Wallace E., Sonya Kostova Huffman, AbebayehuTegene, and KyrreRickertsen. 2006. “The Economics of Obesity-Related Mortality among High Income Countries” International Association of Agricultural Economists. Retrieved December 12, 2011 (http://purl.umn.edu/25567). Organization for Economic Cooperation and Development. 2011. Health at a Glance 2011: OECD Indicators. OECD Publishing. Retrieved December 12, 2011 (http://dx.doi.org/10.1787/health_glance-2011-en). UNICEF. 2011. “Water, Sanitation and Hygiene.” Retrieved December 12, 2011 (http://www.unicef.org/wash). World Health Organization. 2011. “World Health Statistics 2011.” Retrieved December 12, 2011 (http://www.who.int/gho/publications/world_health_statistics/EN_WHS2011_Part1.pdf).	oercommons	2025-03-18T00:36:04.526473	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11836/overview", "title": "Introduction to Sociology 2e, Health and Medicine", "author": null }
https://oercommons.org/courseware/lesson/11837/overview	Health in the United States Overview - Understand how social epidemiology can be applied to health in the United States - Explain disparities of health based on gender, socioeconomic status, race, and ethnicity - Give an overview of mental health and disability issues in the United States - Explain the terms stigma and medicalization Health in the United States is a complex and often contradictory issue. One the one hand, as one of the wealthiest nations, the United States fares well in health comparisons with the rest of the world. However, the United States also lags behind almost every industrialized country in terms of providing care to all its citizens. The following sections look at different aspects of health in the United States. Health by Race and Ethnicity When looking at the social epidemiology of the United States, it is hard to miss the disparities among races. The discrepancy between black and white Americans shows the gap clearly; in 2008, the average life expectancy for white males was approximately five years longer than for black males: 75.9 compared to 70.9. An even stronger disparity was found in 2007: the infant mortality, which is the number of deaths in a given time or place, rate for blacks was nearly twice that of whites at 13.2 compared to 5.6 per 1,000 live births (U.S. Census Bureau 2011). According to a report from the Henry J. Kaiser Foundation (2007), African Americans also have higher incidence of several other diseases and causes of mortality, from cancer to heart disease to diabetes. In a similar vein, it is important to note that ethnic minorities, including Mexican Americans and Native Americans, also have higher rates of these diseases and causes of mortality than whites. Lisa Berkman (2009) notes that this gap started to narrow during the Civil Rights movement in the 1960s, but it began widening again in the early 1980s. What accounts for these perpetual disparities in health among different ethnic groups? Much of the answer lies in the level of healthcare that these groups receive. The National Healthcare Disparities Report (2010) shows that even after adjusting for insurance differences, racial and ethnic minority groups receive poorer quality of care and less access to care than dominant groups. The Report identified these racial inequalities in care: - Black Americans, American Indians, and Alaskan Natives received inferior care than Caucasian Americans for about 40 percent of measures. - Asian ethnicities received inferior care for about 20 percent of measures. - Among whites, Hispanic whites received 60 percent inferior care of measures compared to non-Hispanic whites (Agency for Health Research and Quality 2010). When considering access to care, the figures were comparable. Health by Socioeconomic Status Discussions of health by race and ethnicity often overlap with discussions of health by socioeconomic status, since the two concepts are intertwined in the United States. As the Agency for Health Research and Quality (2010) notes, “racial and ethnic minorities are more likely than non-Hispanic whites to be poor or near poor,” so many of the data pertaining to subordinate groups is also likely to be pertinent to low socioeconomic groups. Marilyn Winkleby and her research associates (1992) state that “one of the strongest and most consistent predictors of a person's morbidity and mortality experience is that person's socioeconomic status (SES). This finding persists across all diseases with few exceptions, continues throughout the entire lifespan, and extends across numerous risk factors for disease.” Morbidity is the incidence of disease. It is important to remember that economics are only part of the SES picture; research suggests that education also plays an important role. Phelan and Link (2003) note that many behavior-influenced diseases like lung cancer (from smoking), coronary artery disease (from poor eating and exercise habits), and AIDS initially were widespread across SES groups. However, once information linking habits to disease was disseminated, these diseases decreased in high SES groups and increased in low SES groups. This illustrates the important role of education initiatives regarding a given disease, as well as possible inequalities in how those initiatives effectively reach different SES groups. Health by Gender Women are affected adversely both by unequal access to and institutionalized sexism in the healthcare industry. According a recent report from the Kaiser Family Foundation, women experienced a decline in their ability to see needed specialists between 2001 and 2008. In 2008, one quarter of females questioned the quality of her healthcare (Ranji and Salganico 2011). In this report, we also see the explanatory value of intersection theory. Feminist sociologist Patricia Hill Collins developed this theory, which suggests we cannot separate the effects of race, class, gender, sexual orientation, and other attributes. Further examination of the lack of confidence in the healthcare system by women, as identified in the Kaiser study, found, for example, women categorized as low income were more likely (32 percent compared to 23 percent) to express concerns about healthcare quality, illustrating the multiple layers of disadvantage caused by race and sex. We can see an example of institutionalized sexism in the way that women are more likely than men to be diagnosed with certain kinds of mental disorders. Psychologist Dana Becker notes that 75 percent of all diagnoses of Borderline Personality Disorder (BPD) are for women according to the Diagnostic Statistical Manual of Mental Disorders. This diagnosis is characterized by instability of identity, of mood, and of behavior, and Becker argues that it has been used as a catch-all diagnosis for too many women. She further decries the pejorative connotation of the diagnosis, saying that it predisposes many people, both within and outside of the profession of psychotherapy, against women who have been so diagnosed (Becker). Many critics also point to the medicalization of women’s issues as an example of institutionalized sexism. Medicalization refers to the process by which previously normal aspects of life are redefined as deviant and needing medical attention to remedy. Historically and contemporaneously, many aspects of women’s lives have been medicalized, including menstruation, pre-menstrual syndrome, pregnancy, childbirth, and menopause. The medicalization of pregnancy and childbirth has been particularly contentious in recent decades, with many women opting against the medical process and choosing a more natural childbirth. Fox and Worts (1999) find that all women experience pain and anxiety during the birth process, but that social support relieves both as effectively as medical support. In other words, medical interventions are no more effective than social ones at helping with the difficulties of pain and childbirth. Fox and Worts further found that women with supportive partners ended up with less medical intervention and fewer cases of postpartum depression. Of course, access to quality birth care outside the standard medical models may not be readily available to women of all social classes. Medicalization of Sleeplessness How is your “sleep hygiene?” Sleep hygiene refers to the lifestyle and sleep habits that contribute to sleeplessness. Bad habits that can lead to sleeplessness include inconsistent bedtimes, lack of exercise, late-night employment, napping during the day, and sleep environments that include noise, lights, or screen time (National Institutes of Health 2011a). According to the National Institute of Health, examining sleep hygiene is the first step in trying to solve a problem with sleeplessness. For many people in the United States, however, making changes in sleep hygiene does not seem to be enough. According to a 2006 report from the Institute of Medicine, sleeplessness is an underrecognized public health problem affecting up to 70 million people. It is interesting to note that in the months (or years) after this report was released, advertising by the pharmaceutical companies behind Ambien, Lunesta, and Sepracor (three sleep aids) averaged $188 million weekly promoting these drugs (Gellene 2009). According to a study in the American Journal of Public Health (2011), prescriptions for sleep medications increased dramatically from 1993 to 2007. While complaints of sleeplessness during doctor’s office visits more than doubled during this time, insomnia diagnoses increased more than sevenfold, from about 840,000 to 6.1 million. The authors of the study conclude that sleeplessness has been medicalized as insomnia, and that “insomnia may be a public health concern, but potential overtreatment with marginally effective, expensive medications with nontrivial side effects raises definite population health concerns” (Moloney, Konrad, and Zimmer 2011). Indeed, a study published in 2004 in theArchives of Internal Medicine shows that cognitive behavioral therapy, not medication, was the most effective sleep intervention (Jacobs, Pace-Schott, Stickgold, and Otto 2004). A century ago, people who couldn’t sleep were told to count sheep. Now they pop a pill, and all those pills add up to a very lucrative market for the pharmaceutical industry. Is this industry behind the medicalization of sleeplessness, or is it just responding to a need? Mental Health and Disability The treatment received by those defined as mentally ill or disabled varies greatly from country to country. In the post-millennial United States, those of us who have never experienced such a disadvantage take for granted the rights our society guarantees for each citizen. We do not think about the relatively recent nature of the protections, unless, of course, we know someone constantly inconvenienced by the lack of accommodations or misfortune of suddenly experiencing a temporary disability. Mental Health People with mental disorders (a condition that makes it more difficult to cope with everyday life) and people with mental illness (a severe, lasting mental disorder that requires long-term treatment) experience a wide range of effects. According to the National Institute of Mental Health (NIMH), the most common mental disorders in the United States are anxiety disorders. Almost 18 percent of U.S. adults are likely to be affected in a single year, and 28 percent are likely to be affected over the course of a lifetime (National Institute of Mental Health 2005). It is important to distinguish between occasional feelings of anxiety and a true anxiety disorder. Anxiety is a normal reaction to stress that we all feel at some point, but anxiety disorders are feelings of worry and fearfulness that last for months at a time. Anxiety disorders include obsessive compulsive disorder (OCD), panic disorders, posttraumatic stress disorder (PTSD), and both social and specific phobias. The second most common mental disorders in the United States are mood disorders; roughly 10 percent of U.S. adults are likely to be affected yearly, while 21 percent are likely to be affected over the course of a lifetime (National Institute of Mental Health 2005). Major mood disorders are depression, bipolar disorder, and dysthymic disorder. Like anxiety, depression might seem like something that everyone experiences at some point, and it is true that most people feel sad or “blue” at times in their lives. A true depressive episode, however, is more than just feeling sad for a short period. It is a long-term, debilitating illness that usually needs treatment to cure. And bipolar disorder is characterized by dramatic shifts in energy and mood, often affecting the individual’s ability to carry out day-to-day tasks. Bipolar disorder used to be called manic depression because of the way people would swing between manic and depressive episodes. Depending on what definition is used, there is some overlap between mood disorders and personality disorders, which affect 9 percent of people in the United States yearly. The American Psychological Association publishes theDiagnostic and Statistical Manual on Mental Disorders (DSM), and their definition of personality disorders is changing in the fifth edition, which is being revised in 2011 and 2012. After a multilevel review of proposed revisions, the American Psychiatric Association Board of Trustees ultimately decided to retain the DSM-IV categorical approach with the same ten personality disorders (paranoid personality disorder, schizoid personality disorder, schizotypal personality disorder, antisocial personality disorder, borderline personality disorder, histrionic personality, narcissistic personality disorder, avoidant personality disorder, dependent personality disorder and obsessive-compulsive personality disorder. In theDSM-IV, personality disorders represent “an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the culture of the individual who exhibits it” (National Institute of Mental Health). In other words, personality disorders cause people to behave in ways that are seen as abnormal to society but seem normal to them. TheDSM-V proposes broadening this definition by offering five broad personality trait domains to describe personality disorders, some related to the level or type of their disconnect with society. As their application evolves, we will see how their definitions help scholars across disciplines understand the intersection of health issues and how they are defined by social institutions and cultural norms. Another fairly commonly diagnosed mental disorder is Attention-Deficit/Hyperactivity Disorder (ADHD), which statistics suggest affects 9 percent of children and 8 percent of adults on a lifetime basis (National Institute of Mental Health 2005). ADHD is one of the most common childhood disorders, and it is marked by difficulty paying attention, difficulty controlling behavior, and hyperactivity. According to the American Psychological Association (APA), ADHD responds positively to stimulant drugs like Ritalin, which helps people stay focused. However, there is some social debate over whether such drugs are being overprescribed (American Psychological Association). In fact, some critics question whether this disorder is really as widespread as it seems, or if it is a case of over diagnosis. According to the Centers for Disease Control and Prevention, only 5 percent of children have ADHD. However approximately 11 percent of children ages four through seventeen have been diagnosed with ADHD as of 2011. Autism Spectrum Disorders (ASD) have gained a lot of attention in recent years. The term ASD encompasses a group of developmental brain disorders that are characterized by “deficits in social interaction, verbal and nonverbal communication, and engagement in repetitive behaviors or interests” (National Institute of Mental Health). As with the personality disorders described above, the Diagnostic and Statistical Manual on Mental Disorders’ description of these is in the process of being revised. The National Institute of Mental Health (NIMH) distinguishes between serious mental illness and other disorders. The key feature of serious mental illness is that it results in “serious functional impairment, which substantially interferes with or limits one or more major life activities” (National Institute of Mental Health). Thus, the characterization of “serious” refers to the effect of the illness (functional impairment), not the illness itself. Disability Disability refers to a reduction in one’s ability to perform everyday tasks. The World Health Organization makes a distinction between the various terms used to describe handicaps that’s important to the sociological perspective. They use the termimpairment to describe the physical limitations, while reserving the term disability to refer to the social limitation. Before the passage of the Americans with Disabilities Act (ADA) in 1990, people in the United States with disabilities were often excluded from opportunities and social institutions many of us take for granted. This occurred not only through employment and other kinds of discrimination but also through casual acceptance by most people in the United States of a world designed for the convenience of the able-bodied. Imagine being in a wheelchair and trying to use a sidewalk without the benefit of wheelchair-accessible curbs. Imagine as a blind person trying to access information without the widespread availability of Braille. Imagine having limited motor control and being faced with a difficult-to-grasp round door handle. Issues like these are what the ADA tries to address. Ramps on sidewalks, Braille instructions, and more accessible door levers are all accommodations to help people with disabilities. People with disabilities can be stigmatized by their illnesses. Stigmatization means their identity is spoiled; they are labeled as different, discriminated against, and sometimes even shunned. They are labeled (as an interactionist might point out) and ascribed a master status (as a functionalist might note), becoming “the blind girl” or “the boy in the wheelchair” instead of someone afforded a full identity by society. This can be especially true for people who are disabled due to mental illness or disorders. As discussed in the section on mental health, many mental health disorders can be debilitating and can affect a person’s ability to cope with everyday life. This can affect social status, housing, and especially employment. According to the Bureau of Labor Statistics (2011), people with a disability had a higher rate of unemployment than people without a disability in 2010: 14.8 percent to 9.4 percent. This unemployment rate refers only to people actively looking for a job. In fact, eight out of ten people with a disability are considered “out of the labor force;” that is, they do not have jobs and are not looking for them. The combination of this population and the high unemployment rate leads to an employment-population ratio of 18.6 percent among those with disabilities. The employment-population ratio for people without disabilities was much higher, at 63.5 percent (U.S. Bureau of Labor Statistics 2011). Obesity: The Last Acceptable Prejudice What is your reaction to the picture above? Compassion? Fear? Disgust? Many people will look at this picture and make negative assumptions about the man based on his weight. According to a study from the Yale Rudd Center for Food Policy and Obesity, large people are the object of “widespread negative stereotypes that overweight and obese persons are lazy, unmotivated, lacking in self-discipline, less competent, noncompliant, and sloppy” (Puhl and Heuer 2009). Historically, both in the United States and elsewhere, it was considered acceptable to discriminate against people based on prejudiced opinions. Even after slavery was abolished in 1865, the next 100 years of U.S. history saw institutionalized racism and prejudice against black people. In an example of stereotype interchangeability,the same insults that are flung today at the overweight and obese population (lazy, for instance), have been flung at various racial and ethnic groups in earlier history. Of course, no one gives voice to these kinds of views in public now, except when talking about obese people. Why is it considered acceptable to feel prejudice toward—even to hate—obese people? Puhl and Heuer suggest that these feelings stem from the perception that obesity is preventable through self-control, better diet, and more exercise. Highlighting this contention is the fact that studies have shown that people’s perceptions of obesity are more positive when they think the obesity was caused by non-controllable factors like biology (a thyroid condition, for instance) or genetics. Even with some understanding of non-controllable factors that might affect obesity, obese people are still subject to stigmatization. Puhl and Heuer’s study is one of many that document discrimination at work, in the media, and even in the medical profession. Obese people are less likely to get into college than thinner people, and they are less likely to succeed at work. Stigmatization of obese people comes in many forms, from the seemingly benign to the potentially illegal. In movies and television show, overweight people are often portrayed negatively, or as stock characters who are the butt of jokes. One study found that in children’s movies “obesity was equated with negative traits (evil, unattractive, unfriendly, cruel) in 64 percent of the most popular children's videos. In 72 percent of the videos, characters with thin bodies had desirable traits, such as kindness or happiness” (Hines and Thompson 2007). In movies and television for adults, the negative portrayal is often meant to be funny. “Fat suits”—inflatable suits that make people look obese—are commonly used in a way that perpetuates negative stereotypes. Think about the way you have seen obese people portrayed in movies and on television; now think of any other subordinate group being openly denigrated in such a way. It is difficult to find a parallel example. Summary Although people in the United States are generally in good health compared to less developed countries, the United States is still facing challenging issues such as a prevalence of obesity and diabetes. Moreover, people in the United States of historically disadvantaged racial groups, ethnicities, socioeconomic status, and gender experience lower levels of healthcare. Mental health and disability are health issues that are significantly impacted by social norms. Section Quiz Which of the following statements is not true? - The life expectancy of black males in the United States is approximately five years shorter than for white males. - The infant mortality rate for blacks in the United States is almost double than it is for white. - Blacks have lower cancer rates than whites. - Hispanics have worse access to care than non-Hispanic whites. Hint: C The process by which aspects of life that were considered bad or deviant are redefined as sickness and needing medical attention to remedy is called: - deviance - medicalization - demedicalization - intersection theory Hint: B What are the most commonly diagnosed mental disorders in the United States? - ADHD - Mood disorders - Autism spectrum disorders - Anxiety disorders Hint: D Sidewalk ramps and Braille signs are examples of _______________. - disabilities - accommodations required by the Americans with Disabilities Act - forms of accessibility for people with disabilities - both b and c Hint: D The high unemployment rate among the disabled may be a result of ____________. - medicalization - obesity - stigmatization - all of the above Hint: C Short Answer What factors contribute to the disparities in health among racial, ethnic, and gender groups in the United States? Do you know anyone with a mental disorder? How does it affect his or her life? Further Research Is ADHD a valid diagnosis and disease? Some think it is not. This article discusses this history of the issue: http://openstaxcollege.org/l/ADHD_controversy References Agency for Health Research and Quality. 2010. “Disparities in Healthcare Quality Among Racial and Ethnic Minority Groups.” Agency for Health Research and Quality. Retrieved December 13, 2011 (http://www.ahrq.gov/qual/nhqrdr10/nhqrdrminority10.htm) American Psychological Association. 2011a. “A 09 Autism Spectrum Disorder.” American Psychiatric Association DSM-5 Development. Retrieved December 14, 2011. American Psychological Association. 2011b. “Personality Traits.” American Psychiatric Association DSM-5 Development. Retrieved December 14, 2011. American Psychological Association. n.d. “Understanding the Ritalin Debate.” American Psychological Association. Retrieved December 14, 2011 (http://www.apa.org/topics/adhd/ritalin-debate.aspx) Becker, Dana. n.d. “Borderline Personality Disorder: The Disparagement of Women through Diagnosis.” Retrieved December 13, 2011 (http://www.awpsych.org/index.php?option=com_content&view=article&id=109&catid=74&Itemid=126). Berkman, Lisa F. 2009. “Social Epidemiology: Social Determinants of Health in the United States: Are We Losing Ground?” Annual Review of Public Health 30:27–40. Blumenthal, David, and Sarah R. Collins. 2014 "Health Care Coverage under the Affordable Care Act—a Progress Report."New England Journal of Medicine 371 (3): 275–81. Retrieved December 16, 2014(https://owl.english.purdue.edu/owl/resource/717/04/). Fox, B., and D. Worts. 1999. “Revisiting the Critique of Medicalized Childbirth: A Contribution to the Sociology of Birth.” Gender and Society 13(3):326–346. Gellene, Denise. 2009. “Sleeping Pill Use Grows as Economy Keeps People up at Night.” Retrieved December 16, 2011 (http://articles.latimes.com/2009/mar/30/health/he-sleep30). Hines, Susan M., and Kevin J. Thompson. 2007. “Fat Stigmatization in Television Shows and Movies: A Content Analysis.” Obesity 15:712–718. Retrieved December 15, 2011 (http://onlinelibrary.wiley.com/doi/10.1038/oby.2007.635/full). Institute of Medicine. 2006. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Washington DC: National Academies Press. Jacobs, Gregg D., Edward F. Pace-Schott, Robert Stickgold, and Michael W. Otto. 2004. “Cognitive Behavior Therapy and Pharmacotherapy for Insomnia: A Randomized Controlled Trial and Direct Comparison.” Archives of Internal Medicine 164(17):1888–1896. Retrieved December 16, 2011 (http://archinte.jamanetwork.com/article.aspx?articleid=217394 ). James, Cara et al. 2007. “Key Facts: Race, Ethnicity & Medical Care.” The Henry J. Kaiser Family Foundation. Retrieved December 13, 2011 (http://www.kff.org/minorityhealth/upload/6069-02.pdf). Moloney, Mairead Eastin, Thomas R. Konrad, and Catherine R. Zimmer. 2011. “The Medicalization of Sleeplessness: A Public Health Concern.” American Journal of Public Health101:1429–1433. National Institute of Mental Health. 2005. “National Institute of Mental Health Statistics.” Retrieved December 14, 2011 (http://www.nimh.nih.gov/statistics/index.shtml). National Institutes of Health. 2011a. “Insomnia.” The National Institute of Health. Retrieved December 16, 2011 (http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001808/). National Institutes of Health. 2011b. “What is Autism Spectrum Disorder (ASD)?” National Institute of Mental Health. Retrieved December 14, 2011 (http://www.nimh.nih.gov/health/publications/a-parents-guide-to-autism-spectrum-disorder/what-is-autism-spectrum-disorder-asd.shtml). Phelan, Jo C., and Bruce G. Link. 2001. “Conceptualizing Stigma” Annual Review of Sociology 27:363–85. Retrieved December 13, 2011 (http://www.heart-intl.net/HEART/Legal/Comp/ConceptualizingStigma.pdf). Phelan, Jo C., and Bruce G. Link. 2003. “When Income Affects Outcome: Socioeconomic Status and Health.” Research in Profile:6. Retrieved December 13, 2011 (http://www.investigatorawards.org/downloads/research_in_profiles_iss06_feb2003.pdf). Puhl, Rebecca M., and Chelsea A. Heuer. 2009. “The Stigma of Obesity: A Review and Update.” Nature Publishing Group. Retrieved December 15, 2011 (http://www.yaleruddcenter.org/resources/upload/docs/what/bias/WeightBiasStudy.pdf). Ranji, Usha, and Alina Salganico. 2011. “Women's Health Care Chartbook: Key Findings from the Kaiser Women's Health Survey.” The Henry J. Kaiser Family Foundation. Retrieved December 13, 2011 (http://www.kff.org/womenshealth/upload/8164.pdf=). Scheff, Thomas. 1963. Being Mentally Ill: A Sociological Theory. Chicago, IL: Aldine. Szasz, Thomas. 1961. The Myth of Mental Illness: Foundations of a Theory of Personal Conduct. New York, NY: Harper Collins. U.S. Census Bureau. 2011. “Statistical Abstract of the United States: 2012.” 131st ed. Washington, DC. Retrieved December 13, 2011 (http://www.census.gov/compendia/statab). U.S. Bureau of Labor Statistics. 2011. “Persons with a Disability: Labor Force Characteristics News Release.” Bureau of Labor Statistics. Retrieved December 14, 2011 (http://www.bls.gov/news.release/disabl.htm). Winkleby, Marilyn A., D. E. Jatulis, E. Frank, and S. P. Fortmann. 1992. “Socioeconomic Status and Health: How Education, Income, and Occupation Contribute to Risk Factors for Cardiovascular Disease.” American Journal of Public Health 82:6.	oercommons	2025-03-18T00:36:04.566302	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11837/overview", "title": "Introduction to Sociology 2e, Health and Medicine", "author": null }
https://oercommons.org/courseware/lesson/11838/overview	Comparative Health and Medicine Overview - Explain the different types of health care available in the United States - Compare the health care system of the United States with that of other countries There are broad, structural differences among the healthcare systems of different countries. In core nations, those differences might arise in the administration of healthcare, while the care itself is similar. In peripheral and semi-peripheral countries, a lack of basic healthcare administration can be the defining feature of the system. Most countries rely on some combination of modern and traditional medicine. In core countries with large investments in technology, research, and equipment, the focus is usually on modern medicine, with traditional (also called alternative or complementary) medicine playing a secondary role. In the United States, for instance, the American Medical Association (AMA) resolved to support the incorporation of complementary and alternative medicine in medical education. In developing countries, even quickly modernizing ones like China, traditional medicine (often understood as “complementary” by the western world) may still play a larger role. U.S. Healthcare U.S. healthcare coverage can broadly be divided into two main categories: public healthcare (government-funded) andprivate healthcare (privately funded). The two main publicly funded healthcare programs are Medicare, which provides health services to people over sixty-five years old as well as people who meet other standards for disability, and Medicaid, which provides services to people with very low incomes who meet other eligibility requirements. Other government-funded programs include service agencies focused on Native Americans (the Indian Health Service), Veterans (the Veterans Health Administration), and children (the Children’s Health Insurance Program). A controversial issue in 2011 was a proposed constitutional amendment requiring a balanced federal budget, which would almost certainly require billions of dollars in cuts to these programs. As discussed below, the United States already has a significant problem with lack of healthcare coverage for many individuals; if these budget cuts pass, the already heavily burdened programs are sure to suffer, and so are the people they serve (Kogan 2011). The U.S. Census (2011) divides private insurance into employment-based insurance and direct-purchase insurance. Employment-based insurance is health plan coverage that is provided in whole or in part by an employer or union; it can cover just the employee, or the employee and his or her family. Direct purchase insurance is coverage that an individual buys directly from a private company. With all these insurance options, insurance coverage must be almost universal, right? Unfortunately, the U.S. Census Current Population Survey of 2013 shows that 18 percent of people in the United States have no health insurance at all. Equally alarming, a study by the Commonwealth Fund shows that in 2010, 81 million adults were either uninsured or underinsured; that is, people who pay at least 10 percent of their income on healthcare costs not covered by insurance or, for low-income adults, those whose medical expenses or deductibles are at least 5 percent of their income (Schoen, Doty, Robertson, and Collins 2011). The Commonwealth study further reports that while underinsurance has historically been an issue that low-income families faced, today it is affecting middle-income families more and more. Why are so many people uninsured or underinsured? Skyrocketing healthcare costs are part of the issue. Many people cannot afford private health insurance, but their income level is not low enough to meet eligibility standards for government supported insurance. Further, even for those who are eligible for Medicaid, the program is less than perfect. Many physicians refuse to accept Medicaid patients, citing low payments and extensive paperwork (Washington University Center for Health Policy, n.d.). Healthcare in the United States is a complex issue, and it will only get more so with the continued enactment of the Patient Protection and Affordable Care Act (PPACA) of 2010. This Act, sometimes called “ObamaCare” for its most noted advocate, President Barack Obama, represents large-scale federal reform of the United States’ healthcare system. The PPACA aims to address some of the biggest flaws of the current healthcare system. It expands eligibility to programs like Medicaid and CHIP, helps guarantee insurance coverage for people with pre-existing conditions, and establishes regulations to make sure that the premium funds collected by insurers and care providers go directly to medical care. It also includes an individual mandate, which requires everyone to have insurance coverage by 2014 or pay a penalty. A series of provisions, including significant subsidies, are intended to address the discrepancies in income that are currently contributing to high rates of uninsurance and underinsurance. In 2012 the U.S. Supreme Court upheld the constitutionality of the PPACA's individual mandate. According to Blumenthal (2014), 20 million people in the United States have gained health insurance under PPACA. This lowers the number of uninsured people to 13 percent. The PPACA remains contentious. The Supreme Court ruled in the case of National Federation of Independent Businesses v. Sebelius in 2012, that states cannot be forced to participate in the PPACA's Medicaid expansion. This ruling has opened the door to challenges to the PPACA in Congress and the Federal courts, some state governments, conservative groups and independent businesses. A concern to public health officials is fear among some parents that certain vaccines such as the measels, mumps, and rubella (MMR) vaccine are linked to higher risk of autism. According to Uchiyama et al (2007), there is no link between the MMR and autism. However fear of this perceived link pushes some parents to refuse the MMR vaccine for their children. An additional issue in U.S. healthcare has been the push to legalize marijuana in some states. As of this writing, twenty-three states and the District of Columbia allow the use of medical cannabis (Borgelt 2013). Marijuana reform appears to partly be the repackaging of marijuana from a drug to a "medicine." Medical evidence has demonstrated positive responses in treatment of a variety of illnesses, from some cancers to glaucoma and epilepsy. Concerns regarding cost and long term effects of the PPACA continue to be discussed at various societal levels. Healthcare Elsewhere Clearly, healthcare in the United States has some areas for improvement. But how does it compare to healthcare in other countries? Many people in the United States are fond of saying that this country has the best healthcare in the world, and while it is true that the United States has a higher quality of care available than many peripheral or semi-peripheral nations, it is not necessarily the “best in the world.” In a report on how U.S. healthcare compares to that of other countries, researchers found that the United States does “relatively well in some areas—such as cancer care—and less well in others—such as mortality from conditions amenable to prevention and treatment” (Docteur and Berenson 2009). One critique of the Patient Protection and Affordable Care Act is that it will create a system of socialized medicine, a term that for many people in the United States has negative connotations lingering from the Cold War era and earlier. Under a socialized medicine system, the government owns and runs the system. It employs the doctors, nurses, and other staff, and it owns and runs the hospitals (Klein 2009). The best example of socialized medicine is in Great Britain, where the National Health System (NHS) gives free healthcare to all its residents. And despite some U.S. citizens’ knee-jerk reaction to any healthcare changes that hint of socialism, the United States has one socialized system with the Veterans Health Administration. It is important to distinguish between socialized medicine, in which the government owns the healthcare system, and universal healthcare, which is simply a system that guarantees healthcare coverage for everyone. Germany, Singapore, and Canada all have universal healthcare. People often look to Canada’s universal healthcare system, Medicare, as a model for the system. In Canada, healthcare is publicly funded and is administered by the separate provincial and territorial governments. However, the care itself comes from private providers. This is the main difference between universal healthcare and socialized medicine. The Canada Health Act of 1970 required that all health insurance plans must be “available to all eligible Canadian residents, comprehensive in coverage, accessible, portable among provinces, and publicly administered” (International Health Systems Canada 2010). Heated discussions about socialization of medicine and managed-care options seem frivolous when compared with the issues of healthcare systems in developing or underdeveloped countries. In many countries, per capita income is so low, and governments are so fractured, that healthcare as we know it is virtually non-existent. Care that people in developed countries take for granted—like hospitals, healthcare workers, immunizations, antibiotics and other medications, and even sanitary water for drinking and washing—are unavailable to much of the population. Organizations like Doctors Without Borders, UNICEF, and the World Health Organization have played an important role in helping these countries get their most basic health needs met. WHO, which is the health arm of the United Nations, set eight Millennium Development Goals (MDGs) in 2000 with the aim of reaching these goals by 2015. Some of the goals deal more broadly with the socioeconomic factors that influence health, but MDGs 4, 5, and 6 all relate specifically to large-scale health concerns, the likes of which most people in the United States will never contemplate. MDG 4 is to reduce child mortality, MDG 5 aims to improve maternal health, and MDG 6 strives to combat HIV/AIDS, malaria, and other diseases. The goals may not seem particularly dramatic, but the numbers behind them show how serious they are. For MDG 4, the WHO reports that 2009 infant mortality rates in “children under 5 years old in the WHO African Region (127 per 1000 live births) and in low-income countries (117 per 1000 live births) [had dropped], but they were still higher than the 1990 global level of 89 per 1000 live births” (World Health Organization 2011). The fact that these deaths could have been avoided through appropriate medicine and clean drinking water shows the importance of healthcare. Much progress has been made on MDG 5, with maternal deaths decreasing by 34 percent. However, almost all maternal deaths occurred in developing countries, with the African region still experiencing high numbers (World Health Organization 2011). On MDG 6, the WHO is seeing some decreases in per capita incidence rates of malaria, tuberculosis, HIV/AIDS, and other diseases. However, the decreases are often offset by population increases (World Health Organization 2011). Again, the lowest-income countries, especially in the African region, experience the worst problems with disease. An important component of disease prevention and control is epidemiology, or the study of the incidence, distribution, and possible control of diseases. Fear of Ebola contamination, primarily in Western Africa but also to a smaller degree in the United States, became national news in the summer and fall of 2014. Summary There are broad, structural differences among the healthcare systems of different countries. In core nations, those differences include publicly funded healthcare, privately funded healthcare, and combinations of both. In peripheral and semi-peripheral countries, a lack of basic healthcare administration can be the defining feature of the system. Section Quiz Which public healthcare system offers insurance primarily to people over sixty-five years old? - Medicaid - Medicare - Veterans Health Administration - All of the above Hint: B Which program is an example of socialized medicine? - Canada’s system - The United States’ Veterans Health Administration - The United States’ new system under the Patient Protection and Affordable Care Act - Medicaid Hint: B What does the individual mandate provision of the 2010 U.S. healthcare reform do? - Requires everyone to buy insurance from the government - Requires everyone to sign up for Medicaid - Requires everyone to have insurance or pay a penalty - None of the above Hint: C Great Britain’s healthcare system is an example of ______________ - socialized medicine - private healthcare - single-payer private healthcare - universal private healthcare Hint: A What group created the Millennium Development Goals? - UNICEF - The Kaiser Family Foundation - Doctors Without Borders - The World Health Organization Hint: D Short Answer Quiz What do you think are the best and worst parts of the PPACA? Why? Compare and contrast the healthcare system of the United States with the WHO’s Millennium Development Goals. Further Research Project Mosquito Net says that mosquito nets sprayed with insecticide can reduce childhood malaria deaths by half. Read more at http://openstaxcollege.org/l/project_mosquito_net References Anders, George. 1996. Health Against Wealth: HMOs and the Breakdown of Medical Trust. Boston: Houghton Mifflin. Centers for Disease Control and Prevention. 2014 "Attention Deficit/Hyperactivity Disorder (ADHD) Data and Statistics." Retrieved October 13, 2014 (http://www.cdc.gov/ncbddd/adhd/data.html) Docteur, Elizabeth, and Robert A. Berenson. 2009. “How Does the Quality of U.S. Health Care Compare Internationally?” Timely Analysis of Immediate Health Policy Issues 9:1–14. Kaiser Family Foundation. 2011. “Health Coverage of Children: The Role of Medicaid and CHIP.” Retrieved December 13, 2011 ( http://www.kff.org/uninsured/upload/7698-05.pdf ). Kaiser Family Foundation. 2010. “International Health Systems: Canada.” Retrieved December 14, 2011 ( http://www.kaiseredu.org/Issue-Modules/International-Health-Systems/Canada.aspx ). Klein, Ezra. 2009. “Health Reform for Beginners: The Difference between Socialized Medicine, Single-Payer Health Care, and What We'll Be Getting.” The Washington Post, December 14. Retrieved December 15, 2011 (http://www.bloomberg.com/news/2011-12-15/don-t-let-death-panels-kill-a-better-way-to-die-commentary-by-ezra-klein.html). Kogan, Richard. 2011. “Program Cuts Under a Balanced Budget Amendment: How Severe Might They Be?” Center on Budget and Policy Priorities. Retrieved December 15, 2011 (http://www.cbpp.org/cms/?fa=view&id=3619). Pear, Robert. 2011. “In Cuts to Health Programs, Experts See Difficult Task in Protecting Patients.” The New York Times, September 20. Retrieved December 13, 2011 (http://www.nytimes.com/2011/09/21/us/politics/wielding-the-ax-on-medicaid-and-medicare-without-wounding-the-patient.html ). Schoen, C., M.M. Doty, R.H. Robertson, and S.R. Collins. 2011. "Affordable Care Act Reforms Could Reduce the Number of Underinsured U.S. Adults by 70 Percent." Health Affairs 30(9):1762–71. Retrieved December 13, 2011 (http://www.commonwealthfund.org/Publications/In-the-Literature/2011/Sep/Reduce-Uninsured.aspx ). Uchiyma, T., M. Kurosawa, Y. Inaba. 2007. "MMR-Vaccine and Regression in Autism Spectrum Disorders: Negative Results Presented from Japan." Journal of Autism and Deviant Disorders 37(2):210–7. U.S. Census. 2011. “Coverage by Type of Health Insurance: 2009 and 2010.” U.S. Census Bureau, Current Population Survey, 2010 and 2011 Annual Social and Economic Supplements. Retrieved December 13, 2011 ( http://www.census.gov/hhes/www/hlthins/data/incpovhlth/2010/table10.pdf ). U.S. Census. 2011. “CPS Health Insurance Definitions.” Retrieved December 13, 2011 ( http://www.census.gov/hhes/www/hlthins/methodology/definitions/cps.html ). Washington University Center for Health Policy. n.d. “Health Care Access for Medicaid Patients—Physicians and Dentists Interview Study.” Retrieved December 15, 2011 ( http://healthpolicy.wustl.edu/Content/HealthCareAccess.html?OpenDocument ). World Health Organization. 2011. “World Health Statistics 2011.” Retrieved December 12, 2011 ( http://www.who.int/gho/publications/world_health_statistics/EN_WHS2011_Part1.pdf ). World Health Organization. 2014. "Ebola Virus Disease Fact Sheet, Updated September 2014." Retrieved October 19, 2014 (http://www.who.int/mediacentre/factsheets/fs103/en/).	oercommons	2025-03-18T00:36:04.599762	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11838/overview", "title": "Introduction to Sociology 2e, Health and Medicine", "author": null }
https://oercommons.org/courseware/lesson/11839/overview	Theoretical Perspectives on Health and Medicine Overview - Apply functionalist, conflict theorist, and interactionist perspectives to health issues Each of the three major theoretical perspectives approaches the topics of health, illness, and medicine differently. You may prefer just one of the theories that follow, or you may find that combining theories and perspectives provides a fuller picture of how we experience health and wellness. Functionalism According to the functionalist perspective, health is vital to the stability of the society, and therefore sickness is a sanctioned form of deviance. Talcott Parsons (1951) was the first to discuss this in terms of the sick role: patterns of expectations that define appropriate behavior for the sick and for those who take care of them. According to Parsons, the sick person has a specific role with both rights and responsibilities. To start with, she has not chosen to be sick and should not be treated as responsible for her condition. The sick person also has the right of being exempt from normal social roles; she is not required to fulfill the obligation of a well person and can avoid her normal responsibilities without censure. However, this exemption is temporary and relative to the severity of the illness. The exemption also requires legitimation by a physician; that is, a physician must certify that the illness is genuine. The responsibility of the sick person is twofold: to try to get well and to seek technically competent help from a physician. If the sick person stays ill longer than is appropriate (malingers), she may be stigmatized. Parsons argues that since the sick are unable to fulfill their normal societal roles, their sickness weakens the society. Therefore, it is sometimes necessary for various forms of social control to bring the behavior of a sick person back in line with normal expectations. In this model of health, doctors serve as gatekeepers, deciding who is healthy and who is sick—a relationship in which the doctor has all the power. But is it appropriate to allow doctors so much power over deciding who is sick? And what about people who are sick, but are unwilling to leave their positions for any number of reasons (personal/social obligations, financial need, or lack of insurance, for instance). Conflict Perspective Theorists using the conflict perspective suggest that issues with the healthcare system, as with most other social problems, are rooted in capitalist society. According to conflict theorists, capitalism and the pursuit of profit lead to the commodification of health: the changing of something not generally thought of as a commodity into something that can be bought and sold in a marketplace. In this view, people with money and power—the dominant group—are the ones who make decisions about how the healthcare system will be run. They therefore ensure that they will have healthcare coverage, while simultaneously ensuring that subordinate groups stay subordinate through lack of access. This creates significant healthcare—and health—disparities between the dominant and subordinate groups. Alongside the health disparities created by class inequalities, there are a number of health disparities created by racism, sexism, ageism, and heterosexism. When health is a commodity, the poor are more likely to experience illness caused by poor diet, to live and work in unhealthy environments, and are less likely to challenge the system. In the United States, a disproportionate number of racial minorities also have less economic power, so they bear a great deal of the burden of poor health. It is not only the poor who suffer from the conflict between dominant and subordinate groups. For many years now, homosexual couples have been denied spousal benefits, either in the form of health insurance or in terms of medical responsibility. Further adding to the issue, doctors hold a disproportionate amount of power in the doctor/patient relationship, which provides them with extensive social and economic benefits. While conflict theorists are accurate in pointing out certain inequalities in the healthcare system, they do not give enough credit to medical advances that would not have been made without an economic structure to support and reward researchers: a structure dependent on profitability. Additionally, in their criticism of the power differential between doctor and patient, they are perhaps dismissive of the hard-won medical expertise possessed by doctors and not patients, which renders a truly egalitarian relationship more elusive. Symbolic Interactionism According to theorists working in this perspective, health and illness are both socially constructed. As we discussed in the beginning of the chapter, interactionists focus on the specific meanings and causes people attribute to illness. The term medicalization of deviance refers to the process that changes “bad” behavior into “sick” behavior. A related process isdemedicalization, in which “sick” behavior is normalized again. Medicalization and demedicalization affect who responds to the patient, how people respond to the patient, and how people view the personal responsibility of the patient (Conrad and Schneider 1992). An example of medicalization is illustrated by the history of how our society views alcohol and alcoholism. During the nineteenth century, people who drank too much were considered bad, lazy people. They were called drunks, and it was not uncommon for them to be arrested or run out of a town. Drunks were not treated in a sympathetic way because, at that time, it was thought that it was their own fault that they could not stop drinking. During the latter half of the twentieth century, however, people who drank too much were increasingly defined as alcoholics: people with a disease or a genetic predisposition to addiction who were not responsible for their drinking. With alcoholism defined as a disease and not a personal choice, alcoholics came to be viewed with more compassion and understanding. Thus, “badness” was transformed into “sickness.” There are numerous examples of demedicalization in history as well. During the Civil War era, slaves who frequently ran away from their owners were diagnosed with a mental disorder called drapetomania. This has since been reinterpreted as a completely appropriate response to being enslaved. A more recent example is homosexuality, which was labeled a mental disorder or a sexual orientation disturbance by the American Psychological Association until 1973. While interactionism does acknowledge the subjective nature of diagnosis, it is important to remember who most benefits when a behavior becomes defined as illness. Pharmaceutical companies make billions treating illnesses such as fatigue, insomnia, and hyperactivity that may not actually be illnesses in need of treatment, but opportunities for companies to make more money. Summary While the functionalist perspective looks at how health and illness fit into a fully functioning society, the conflict perspective is concerned with how health and illness fit into the oppositional forces in society. The interactionist perspective is concerned with how social interactions construct ideas of health and illness. Section Quiz Which of the following is not part of the rights and responsibilities of a sick person under the functionalist perspective? - The sick person is not responsible for his condition. - The sick person must try to get better. - The sick person can take as long as she wants to get better. - The sick person is exempt from the normal duties of society. Hint: C The class, race, and gender inequalities in our healthcare system support the _____________ perspective. - conflict - interactionist - functionalist - all of the above Hint: A The removal of homosexuality from the DSM is an example of ____________. - medicalization - deviance - interactionist theory - demedicalization Hint: D Short Answer Which theoretical perspective do you think best explains the sociology of health? Why? What examples of medicalization and demedicalization can you think of? Further Research Should alcoholism and other addictions be medicalized? Read and watch a dissenting view: http://openstaxcollege.org/l/addiction_medicalization References Conrad, Peter, and Joseph W. Schneider. 1992. Deviance and Medicalization: From Badness to Sickness. Philadelphia, PA: Temple University Press Parsons, Talcott. 1951. The Social System. Glencoe, IL: Free Press. Scheff, Thomas. 1963. “The Role of the Mentally Ill and the Dynamics of Mental Disorder.” Sociometry 26:436–453.	oercommons	2025-03-18T00:36:04.626129	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11839/overview", "title": "Introduction to Sociology 2e, Health and Medicine", "author": null }
https://oercommons.org/courseware/lesson/11794/overview	Introduction to Global Inequality The April 24, 2013 collapse of the Rana Plaza in Dhaka, Bangladesh that killed over 1,100 people, was the deadliest garment factory accident in history, and it was preventable (International Labour Organization, Department of Communication 2014). In addition to garment factories employing about 5,000 people, the building contained a bank, apartments, childcare facilities, and a variety of shops. Many of these closed the day before the collapse when cracks were discovered in the building walls. When some of the garment workers refused to enter the building, they were threatened with the loss of a month’s pay. Most were young women, aged twenty or younger. They typically worked over thirteen hours a day, with two days off each month. For this work, they took home between twelve and twenty-two cents an hour, or $10.56 to $12.48 a week. Without that pay, most would have been unable to feed their children. In contrast, the U.S. federal minimum wage is $7.25 an hour, and workers receive wages at time-and-a-half rates for work in excess of forty hours a week. Did you buy clothes from Walmart in 2012? What about at The Children’s Place? Did you ever think about where those clothes came from? Of the outsourced garments made in the garment factories, thirty-two were intended for U.S, Canadian, and European stores. In the aftermath of the collapse, it was revealed that Walmart jeans were made in the Ether Tex garment factory on the fifth floor of the Rana Plaza building, while 120,000 pounds of clothing for The Children’s Place were produced in the New Wave Style Factory, also located in the building. Afterward, Walmart and The Children’s Place pledged $1 million and $450,000 (respectively) to the Rana Plaza Trust Fund, but fifteen other companies with clothing made in the building have contributed nothing, including U.S. companies Cato and J.C. Penney (Institute for Global Labour and Human Rights 2014). While you read this chapter, think about the global system that allows U.S. companies to outsource their manufacturing to peripheral nations, where many women and children work in conditions that some characterize as slave labor. Do people in the United States have a responsibility to foreign workers? Should U.S. corporations be held accountable for what happens to garment factory workers who make their clothing? What can you do as a consumer to help such workers? References Butler, Sarah. 2013. “Bangladeshi Factory Deaths Spark Action among High-Street Clothing Chains.” The Guardian. Retrieved November 7, 2014 (http://www.theguardian.com/world/2013/jun/23/rana-plaza-factory-disaster-bangladesh-primark). Institute for Global Labour and Human Rights. 2014. "Rana Plaza: A Look Back and Forward." Global Labour Rights. Retrieved November 7, 2014 (http://www.globallabourrights.org/campaigns/factory-collapse-in-bangladesh). International Labour Organization, Department of Communication. 2014. "Post Rana Plaza: A Vision for the Future." Working Conditions: International Labour Organization. Retreived November 7, 2014 (http://www.ilo.org/global/about-the-ilo/who-we-are/ilo-director-general/statements-and-speeches/WCMS_240382/lang--en/index.htm). Korzeniewicz, Robert, and Timothy Patrick Moran. 2009. Unveiling Inequality: A World Historical Perspective. New York, NY: Russell Sage Foundation.	oercommons	2025-03-18T00:36:04.641517	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11794/overview", "title": "Introduction to Sociology 2e, Global Inequality", "author": null }
https://oercommons.org/courseware/lesson/11795/overview	Global Stratification and Classification Overview - Describe global stratification - Understand how different classification systems have developed - Use terminology from Wallerstein’s world systems approach - Explain the World Bank’s classification of economies Just as the United States' wealth is increasingly concentrated among its richest citizens while the middle class slowly disappears, global inequality is concentrating resources in certain nations and is significantly affecting the opportunities of individuals in poorer and less powerful countries. In fact, a recent Oxfam (2014) report that suggested the richest eighty-five people in the world are worth more than the poorest 3.5 billion combined. TheGINI coefficient measures income inequality between countries using a 100-point scale on which 1 represents complete equality and 100 represents the highest possible inequality. In 2007, the global GINI coefficient that measured the wealth gap between the core nations in the northern part of the world and the mostly peripheral nations in the southern part of the world was 75.5 percent (Korseniewicz and Moran 2009). But before we delve into the complexities of global inequality, let’s consider how the three major sociological perspectives might contribute to our understanding of it. The functionalist perspective is a macroanalytical view that focuses on the way that all aspects of society are integral to the continued health and viability of the whole. A functionalist might focus on why we have global inequality and what social purposes it serves. This view might assert, for example, that we have global inequality because some nations are better than others at adapting to new technologies and profiting from a globalized economy, and that when core nation companies locate in peripheral nations, they expand the local economy and benefit the workers. Conflict theory focuses on the creation and reproduction of inequality. A conflict theorist would likely address the systematic inequality created when core nations exploit the resources of peripheral nations. For example, how many U.S. companies take advantage of overseas workers who lack the constitutional protection and guaranteed minimum wages that exist in the United States? Doing so allows them to maximize profits, but at what cost? The symbolic interaction perspective studies the day-to-day impact of global inequality, the meanings individuals attach to global stratification, and the subjective nature of poverty. Someone applying this view to global inequality would probably focus on understanding the difference between what someone living in a core nation defines as poverty (relative poverty, defined as being unable to live the lifestyle of the average person in your country) and what someone living in a peripheral nation defines as poverty (absolute poverty, defined as being barely able, or unable, to afford basic necessities, such as food). Global Stratification While stratification in the United States refers to the unequal distribution of resources among individuals, global stratification refers to this unequal distribution among nations. There are two dimensions to this stratification: gaps between nations and gaps within nations. When it comes to global inequality, both economic inequality and social inequality may concentrate the burden of poverty among certain segments of the earth’s population (Myrdal 1970). As the chart below illustrates, people’s life expectancy depends heavily on where they happen to be born. \| Country \| Infant Mortality Rate \| Life Expectancy \| \|---\|---\|---\| \| Norway \| 2.48 deaths per 1000 live births \| 81 years \| \| The United States \| 6.17 deaths per 1000 live births \| 79 years \| \| North Korea \| 24.50 deaths per 1000 live births \| 70 years \| \| Afghanistan \| 117.3 deaths per 1000 live births \| 50 years \| Most of us are accustomed to thinking of global stratification as economic inequality. For example, we can compare the United States’ average worker’s wage to America’s average wage. Social inequality, however, is just as harmful as economic discrepancies. Prejudice and discrimination—whether against a certain race, ethnicity, religion, or the like—can create and aggravate conditions of economic equality, both within and between nations. Think about the inequity that existed for decades within the nation of South Africa. Apartheid, one of the most extreme cases of institutionalized and legal racism, created a social inequality that earned it the world’s condemnation. Gender inequity is another global concern. Consider the controversy surrounding female genital mutilation. Nations that practice this female circumcision procedure defend it as a longstanding cultural tradition in certain tribes and argue that the West shouldn’t interfere. Western nations, however, decry the practice and are working to stop it. Inequalities based on sexual orientation and gender identity exist around the globe. According to Amnesty International, a number of crimes are committed against individuals who do not conform to traditional gender roles or sexual orientations (however those are culturally defined). From culturally sanctioned rape to state-sanctioned executions, the abuses are serious. These legalized and culturally accepted forms of prejudice and discrimination exist everywhere—from the United States to Somalia to Tibet—restricting the freedom of individuals and often putting their lives at risk (Amnesty International 2012). Global Classification A major concern when discussing global inequality is how to avoid an ethnocentric bias implying that less-developed nations want to be like those who’ve attained post-industrial global power. Terms such as developing (nonindustrialized) and developed (industrialized) imply that unindustrialized countries are somehow inferior, and must improve to participate successfully in the global economy, a label indicating that all aspects of the economy cross national borders. We must take care how we delineate different countries. Over time, terminology has shifted to make way for a more inclusive view of the world. Cold War Terminology Cold War terminology was developed during the Cold War era (1945–1980). Familiar and still used by many, it classifies countries into first world, second world, and third world nations based on their respective economic development and standards of living. When this nomenclature was developed, capitalistic democracies such as the United States and Japan were considered part of the first world. The poorest, most undeveloped countries were referred to as thethird world and included most of sub-Saharan Africa, Latin America, and Asia. Thesecond world was the in-between category: nations not as limited in development as the third world, but not as well off as the first world, having moderate economies and standard of living, such as China or Cuba. Later, sociologist Manual Castells (1998) added the termfourth world to refer to stigmatized minority groups that were denied a political voice all over the globe (indigenous minority populations, prisoners, and the homeless, for example). Also during the Cold War, global inequality was described in terms of economic development. Along with developing and developed nations, the terms less-developed nation and underdeveloped nation were used. This was the era when the idea of noblesse oblige (first-world responsibility) took root, suggesting that the so-termed developed nations should provide foreign aid to the less-developed and underdeveloped nations in order to raise their standard of living. Immanuel Wallerstein: World Systems Approach Immanuel Wallerstein’s (1979) world systems approach uses an economic basis to understand global inequality. Wallerstein conceived of the global economy as a complex system that supports an economic hierarchy that placed some nations in positions of power with numerous resources and other nations in a state of economic subordination. Those that were in a state of subordination faced significant obstacles to mobilization. Core nations are dominant capitalist countries, highly industrialized, technological, and urbanized. For example, Wallerstein contends that the United States is an economic powerhouse that can support or deny support to important economic legislation with far-reaching implications, thus exerting control over every aspect of the global economy and exploiting both semi-peripheral and peripheral nations. We can look at free trade agreements such as the North American Free Trade Agreement (NAFTA) as an example of how a core nation is able to leverage its power to gain the most advantageous position in the matter of global trade. Peripheral nations have very little industrialization; what they do have often represents the outdated castoffs of core nations or the factories and means of production owned by core nations. They typically have unstable governments, inadequate social programs, and are economically dependent on core nations for jobs and aid. There are abundant examples of countries in this category, such as Vietnam and Cuba. We can be sure the workers in a Cuban cigar factory, for example, which are owned or leased by global core nation companies, are not enjoying the same privileges and rights as U.S. workers. Semi-peripheral nations are in-between nations, not powerful enough to dictate policy but nevertheless acting as a major source for raw material and an expanding middle-class marketplace for core nations, while also exploiting peripheral nations. Mexico is an example, providing abundant cheap agricultural labor to the U.S., and supplying goods to the United States market at a rate dictated by the U.S. without the constitutional protections offered to United States workers. World Bank Economic Classification by Income While the World Bank is often criticized, both for its policies and its method of calculating data, it is still a common source for global economic data. Along with tracking the economy, the World Bank tracks demographics and environmental health to provide a complete picture of whether a nation is high income, middle income, or low income. High-Income Nations The World Bank defines high-income nations as having a gross national income of at least $12,746 per capita. The OECD (Organization for Economic and Cooperative Development) countries make up a group of thirty-four nations whose governments work together to promote economic growth and sustainability. According to the World Bank (2014b), in 2013, the average gross national income (GNI) per capita, or the mean income of the people in a nation, found by dividing total GNI by the total population, of a high-income nation belonging to the OECD was $43,903 per capita and the total population was over one billion (1.045 billion); on average, 81 percent of the population in these nations was urban. Some of these countries include the United States, Germany, Canada, and the United Kingdom (World Bank 2014b). High-income countries face two major issues: capital flight and deindustrialization. Capital flight refers to the movement (flight) of capital from one nation to another, as when General Motors automotive company closed U.S. factories in Michigan and opened factories in Mexico.Deindustrialization, a related issue, occurs as a consequence of capital flight, as no new companies open to replace jobs lost to foreign nations. As expected, global companies move their industrial processes to the places where they can get the most production with the least cost, including the building of infrastructure, training of workers, shipping of goods, and, of course, paying employee wages. This means that as emerging economies create their own industrial zones, global companies see the opportunity for existing infrastructure and much lower costs. Those opportunities lead to businesses closing the factories that provide jobs to the middle class within core nations and moving their industrial production to peripheral and semi-peripheral nations. Capital Flight, Outsourcing, and Jobs in the United States Capital flight describes jobs and infrastructure moving from one nation to another. Look at the U.S. automobile industry. In the early twentieth century, the cars driven in the United States were made here, employing thousands of workers in Detroit and in the companies that produced everything that made building cars possible. However, once the fuel crisis of the 1970s hit and people in the United States increasingly looked to imported cars with better gas mileage, U.S. auto manufacturing began to decline. During the 2007–2009 recession, the U.S. government bailed out the three main auto companies, underscoring their vulnerability. At the same time, Japanese-owned Toyota and Honda and South Korean Kia maintained stable sales levels. Capital flight also occurs when services (as opposed to manufacturing) are relocated. Chances are if you have called the tech support line for your cell phone or Internet provider, you’ve spoken to someone halfway across the globe. This professional might tell you her name is Susan or Joan, but her accent makes it clear that her real name might be Parvati or Indira. It might be the middle of the night in that country, yet these service providers pick up the line saying, “Good morning,” as though they are in the next town over. They know everything about your phone or your modem, often using a remote server to log in to your home computer to accomplish what is needed. These are the workers of the twenty-first century. They are not on factory floors or in traditional sweatshops; they are educated, speak at least two languages, and usually have significant technology skills. They are skilled workers, but they are paid a fraction of what similar workers are paid in the United States. For U.S. and multinational companies, the equation makes sense. India and other semi-peripheral countries have emerging infrastructures and education systems to fill their needs, without core nation costs. As services are relocated, so are jobs. In the United States, unemployment is high. Many college-educated people are unable to find work, and those with only a high school diploma are in even worse shape. We have, as a country, outsourced ourselves out of jobs, and not just menial jobs, but white-collar work as well. But before we complain too bitterly, we must look at the culture of consumerism that we embrace. A flat screen television that might have cost $1,000 a few years ago is now $350. That cost savings has to come from somewhere. When consumers seek the lowest possible price, shop at big box stores for the biggest discount they can get, and generally ignore other factors in exchange for low cost, they are building the market for outsourcing. And as the demand is built, the market will ensure it is met, even at the expense of the people who wanted it in the first place. Middle-Income Nations The World Bank defines middle-income economies areas those with a GNI per capita of more than $1,045 but less than $12,746. According to the World Bank (2014), in 2013, the average GNI per capita of an upper middle income nation was $7,594 per capita with a total population of 2.049 billion, of which 62 percent was urban. Thailand, China, and Namibia are examples of middle-income nations (World Bank 2014a). Perhaps the most pressing issue for middle-income nations is the problem of debt accumulation. As the name suggests, debt accumulation is the buildup of external debt, wherein countries borrow money from other nations to fund their expansion or growth goals. As the uncertainties of the global economy make repaying these debts, or even paying the interest on them, more challenging, nations can find themselves in trouble. Once global markets have reduced the value of a country’s goods, it can be very difficult to ever manage the debt burden. Such issues have plagued middle-income countries in Latin America and the Caribbean, as well as East Asian and Pacific nations (Dogruel and Dogruel 2007). By way of example, even in the European Union, which is composed of more core nations than semi-peripheral nations, the semi-peripheral nations of Italy and Greece face increasing debt burdens. The economic downturns in both Greece and Italy still threaten the economy of the entire European Union. Low-Income Nations The World Bank defines low-income countries as nations whose per capita GNI was $1,045 per capita or less in 2013. According to the World Bank (2014a), in 2013, the average per capita GNI of a low-income nation was $528 per capita and the total population was 796,261,360, with 28 percent located in urban areas. For example, Myanmar, Ethiopia, and Somalia are considered low-income countries. Low-income economies are primarily found in Asia and Africa (World Bank 2014a), where most of the world’s population lives. There are two major challenges that these countries face: women are disproportionately affected by poverty (in a trend toward a global feminization of poverty) and much of the population lives in absolute poverty. Summary Stratification refers to the gaps in resources both between nations and within nations. While economic equality is of great concern, so is social equality, like the discrimination stemming from race, ethnicity, gender, religion, and/or sexual orientation. While global inequality is nothing new, several factors make it more relevant than ever, like the global marketplace and the pace of information sharing. Researchers try to understand global inequality by classifying it according to factors such as how industrialized a nation is, whether a country serves as a means of production or as an owner, and what income a nation produces. Section Quiz A sociologist who focuses on the way that multinational corporations headquartered in core nations exploit the local workers in their peripheral nation factories is using a _________ perspective to understand the global economy. - functional - conflict theory - feminist - symbolic interactionist Hint: B A ____________ perspective theorist might find it particularly noteworthy that wealthy corporations improve the quality of life in peripheral nations by providing workers with jobs, pumping money into the local economy, and improving transportation infrastructure. - functional - conflict - feminist - symbolic interactionist Hint: A A sociologist working from a symbolic interaction perspective would: - study how inequality is created and reproduced - study how corporations can improve the lives of their low-income workers - try to understand how companies provide an advantage to high-income nations compared to low-income nations - want to interview women working in factories to understand how they manage the expectations of their supervisors, make ends meet, and support their households on a day-to-day basis Hint: D France might be classified as which kind of nation? - Global - Core - Semi-peripheral - Peripheral Hint: B In the past, the United States manufactured clothes. Many clothing corporations have shut down their U.S. factories and relocated to China. This is an example of: - conflict theory - OECD - global inequality - capital flight Hint: D Short Answer Consider the matter of rock-bottom prices at Walmart. What would a functionalist think of Walmart's model of squeezing vendors to get the absolute lowest prices so it can pass them along to core nation consumers? Why do you think some scholars find Cold War terminology (“first world” and so on) objectionable? Give an example of the feminization of poverty in core nations. How is it the same or different in peripheral nations? Pretend you are a sociologist studying global inequality by looking at child labor manufacturing Barbie dolls in China. What do you focus on? How will you find this information? What theoretical perspective might you use? Further Research To learn more about the United Nations Millennium Development Goals, look here: http://openstaxcollege.org/l/UN_development_goals To learn more about the existence and impact of global poverty, peruse the data here: http://openstaxcollege.org/l/poverty_data References Amnesty International. 2012. “Sexual Orientation and Gender Identity.” Retrieved January 3, 2012 (http://www.amnesty.org/en/sexual-orientation-and-gender-identity). Castells, Manuel. 1998. End of Millennium. Malden, MA: Blackwell. Central Intelligence Agency. 2012. “The World Factbook.” Retrieved January 5, 2012 (https://www.cia.gov/library/publications/the-world-factbook/wfbExt/region_noa.html). Central Intelligence Agency. 2014. “Country Comparison: Infant Mortality Rate.” Retrieved November 7, 2014 (https://www.cia.gov/library/publications/the-worldfactbook/rankorder/2091rank.html?countryname=Canada&countrycode=ca®ionCode=noa&rank=182#ca). Dogruel, Fatma, and A. Suut Dogruel. 2007. “Foreign Debt Dynamics in Middle Income Countries.” Paper presented January 4, 2007 at Middle East Economic Association Meeting, Allied Social Science Associations, Chicago, IL. Moghadam, Valentine M. 2005. “The Feminization of Poverty and Women’s Human Rights.” Gender Equality and Development Section UNESCO, July. Paris, France. Myrdal, Gunnar. 1970. The Challenge of World Poverty: A World Anti-Poverty Program in Outline. New York: Pantheon. Oxfam. 2014. “Working for the Few: Political Capture and Economic Inequality.” Oxfam.org. Retrieved November 7, 2014 (http://www.oxfam.org/sites/www.oxfam.org/files/bp-working-for-few-political-capture-economic-inequality-200114-summ-en.pdf). United Nations. 2013. "Millennium Development Goals." Retrieved November 7, 2014 (http://www.un.org/millenniumgoals/bkgd.shtml). Wallerstein, Immanuel. 1979. The Capitalist World Economy. Cambridge, England: Cambridge World Press. World Bank. 2014a. “Gender Overview.” Retrieved November 7, 2014 (http://www.worldbank.org/en/topic/gender/overview#1). World Bank. 2014b. “High Income: OECD: Data.” Retrieved November 7, 2014 (http://data.worldbank.org/income-level/OEC). World Bank. 2014c. “Low Income: Data.” Retrieved November 7, 2014 (http://data.worldbank.org/income-level/LIC). World Bank. 2014d. “Upper Middle Income: Data.” Retrieved November 7, 2014 (http://data.worldbank.org/income-level/UMC).	oercommons	2025-03-18T00:36:04.677750	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11795/overview", "title": "Introduction to Sociology 2e, Global Inequality", "author": null }
https://oercommons.org/courseware/lesson/11796/overview	Global Wealth and Poverty Overview - Understand the differences between relative, absolute, and subjective poverty - Describe the economic situation of some of the world’s most impoverished areas - Explain the cyclical impact of the consequences of poverty What does it mean to be poor? Does it mean being a single mother with two kids in New York City, waiting for the next paycheck in order to buy groceries? Does it mean living with almost no furniture in your apartment because your income doesn’t allow for extras like beds or chairs? Or does it mean having to live with the distended bellies of the chronically malnourished throughout the peripheral nations of Sub-Saharan Africa and South Asia? Poverty has a thousand faces and a thousand gradations; there is no single definition that pulls together every part of the spectrum. You might feel you are poor if you can’t afford cable television or buy your own car. Every time you see a fellow student with a new laptop and smartphone you might feel that you, with your ten-year-old desktop computer, are barely keeping up. However, someone else might look at the clothes you wear and the calories you consume and consider you rich. Types of Poverty Social scientists define global poverty in different ways and take into account the complexities and the issues of relativism described above. Relative poverty is a state of living where people can afford necessities but are unable to meet their society’s average standard of living. People often disparage “keeping up with the Joneses”—the idea that you must keep up with the neighbors’ standard of living to not feel deprived. But it is true that you might feel ”poor” if you are living without a car to drive to and from work, without any money for a safety net should a family member fall ill, and without any “extras” beyond just making ends meet. Contrary to relative poverty, people who live in absolute poverty lack even the basic necessities, which typically include adequate food, clean water, safe housing, and access to healthcare. Absolute poverty is defined by the World Bank (2014a) as when someone lives on less than $1.25 a day. According to the most recent estimates, in 2011, about 17 percent of people in the developing world lived at or below $1.25 a day, a decrease of 26 percent compared to ten years ago, and an overall decrease of 35 percent compared to twenty years ago. A shocking number of people––88 million––live in absolute poverty, and close to 3 billion people live on less than $2.50 a day (Shah 2011). If you were forced to live on $2.50 a day, how would you do it? What would you deem worthy of spending money on, and what could you do without? How would you manage the necessities—and how would you make up the gap between what you need to live and what you can afford? Subjective poverty describes poverty that is composed of many dimensions; it is subjectively present when your actual income does not meet your expectations and perceptions. With the concept of subjective poverty, the poor themselves have a greater say in recognizing when it is present. In short, subjective poverty has more to do with how a person or a family defines themselves. This means that a family subsisting on a few dollars a day in Nepal might think of themselves as doing well, within their perception of normal. However, a westerner traveling to Nepal might visit the same family and see extreme need. The Underground Economy Around the World What do the driver of an unlicensed hack cab in New York, a piecework seamstress working from her home in Mumbai, and a street tortilla vendor in Mexico City have in common? They are all members of the underground economy, a loosely defined unregulated market unhindered by taxes, government permits, or human protections. Official statistics before the worldwide recession posit that the underground economy accounted for over 50 percent of nonagricultural work in Latin America; the figure went as high as 80 percent in parts of Asia and Africa (Chen 2001). A recent article in theWall Street Journal discusses the challenges, parameters, and surprising benefits of this informal marketplace. The wages earned in most underground economy jobs, especially in peripheral nations, are a pittance––a few rupees for a handmade bracelet at a market, or maybe 250 rupees ($5 U.S.) for a day’s worth of fruit and vegetable sales (Barta 2009). But these tiny sums mark the difference between survival and extinction for the world’s poor. The underground economy has never been viewed very positively by global economists. After all, its members don’t pay taxes, don’t take out loans to grow their businesses, and rarely earn enough to put money back into the economy in the form of consumer spending. But according to the International Labor Organization (an agency of the United Nations), some 52 million people worldwide will lose their jobs due to the ongoing worldwide recession. And while those in core nations know that high unemployment rates and limited government safety nets can be frightening, their situation is nothing compared to the loss of a job for those barely eking out an existence. Once that job disappears, the chance of staying afloat is very slim. Within the context of this recession, some see the underground economy as a key player in keeping people alive. Indeed, an economist at the World Bank credits jobs created by the informal economy as a primary reason why peripheral nations are not in worse shape during this recession. Women in particular benefit from the informal sector. The majority of economically active women in peripheral nations are engaged in the informal sector, which is somewhat buffered from the economic downturn. The flip side, of course, is that it is equally buffered from the possibility of economic growth. Even in the United States, the informal economy exists, although not on the same scale as in peripheral and semi-peripheral nations. It might include under-the-table nannies, gardeners, and housecleaners, as well as unlicensed street vendors and taxi drivers. There are also those who run informal businesses, like daycares or salons, from their houses. Analysts estimate that this type of labor may make up 10 percent of the overall U.S. economy, a number that will likely grow as companies reduce head counts, leaving more workers to seek other options. In the end, the article suggests that, whether selling medicinal wines in Thailand or woven bracelets in India, the workers of the underground economy at least have what most people want most of all: a chance to stay afloat (Barta 2009). Who Are the Impoverished? Who are the impoverished? Who is living in absolute poverty? The truth that most of us would guess that the richest countries are often those with the least people. Compare the United States, which possesses a relatively small slice of the population pie and owns by far the largest slice of the wealth pie, with India. These disparities have the expected consequence. The poorest people in the world are women and those in peripheral and semi-peripheral nations. For women, the rate of poverty is particularly worsened by the pressure on their time. In general, time is one of the few luxuries the very poor have, but study after study has shown that women in poverty, who are responsible for all family comforts as well as any earnings they can make, have less of it. The result is that while men and women may have the same rate of economic poverty, women are suffering more in terms of overall wellbeing (Buvinic 1997). It is harder for females to get credit to expand businesses, to take the time to learn a new skill, or to spend extra hours improving their craft so as to be able to earn at a higher rate. Global Feminization of Poverty In some ways, the phrase "global feminization of poverty" says it all: around the world, women are bearing a disproportionate percentage of the burden of poverty. This means more women live in poor conditions, receive inadequate healthcare, bear the brunt of malnutrition and inadequate drinking water, and so on. Throughout the 1990s, data indicated that while overall poverty rates were rising, especially in peripheral nations, the rates of impoverishment increased for women nearly 20 percent more than for men (Mogadham 2005). Why is this happening? While myriad variables affect women's poverty, research specializing in this issue identifies three causes (Mogadham 2005): - The expansion in the number of female-headed households - The persistence and consequences of intra-household inequalities and biases against women - The implementation of neoliberal economic policies around the world While women are living longer and healthier lives today compared to ten years ago, around the world many women are denied basic rights, particularly in the workplace. In peripheral nations, they accumulate fewer assets, farm less land, make less money, and face restricted civil rights and liberties. Women can stimulate the economic growth of peripheral nations, but they are often undereducated and lack access to credit needed to start small businesses. In 2013, the United Nations assessed its progress toward achieving its Millennium Development Goals. Goal 3 was to promote gender equality and empower women, and there were encouraging advances in this area. While women’s employment outside the agricultural sector remains under 20 percent in Western Asia, Northern Africa, and Southern Asia, worldwide it increased from 35–40 percent over the twenty-year period ending in 2010 (United Nations 2013). Africa The majority of the poorest countries in the world are in Africa. That is not to say there is not diversity within the countries of that continent; countries like South Africa and Egypt have much lower rates of poverty than Angola and Ethiopia, for instance. Overall, African income levels have been dropping relative to the rest of the world, meaning that Africa as a whole is getting relatively poorer. Making the problem worse, 2014 saw an outbreak of the Ebola virus in western Africa, leading to a public health crisis and an economic downturn due to loss of workers and tourist dollars. Why is Africa in such dire straits? Much of the continent’s poverty can be traced to the availability of land, especially arable land (land that can be farmed). Centuries of struggle over land ownership have meant that much useable land has been ruined or left unfarmed, while many countries with inadequate rainfall have never set up an infrastructure to irrigate. Many of Africa’s natural resources were long ago taken by colonial forces, leaving little agricultural and mineral wealth on the continent. Further, African poverty is worsened by civil wars and inadequate governance that are the result of a continent re-imagined with artificial colonial borders and leaders. Consider the example of Rwanda. There, two ethnic groups cohabitated with their own system of hierarchy and management until Belgians took control of the country in 1915 and rigidly confined members of the population into two unequal ethnic groups. While, historically, members of the Tutsi group held positions of power, the involvement of Belgians led to the Hutu’s seizing power during a 1960s revolt. This ultimately led to a repressive government and genocide against Tutsis that left hundreds of thousands of Rwandans dead or living in diaspora (U.S. Department of State 2011c). The painful rebirth of a self-ruled Africa has meant many countries bear ongoing scars as they try to see their way towards the future (World Poverty 2012a). Asia While the majority of the world’s poorest countries are in Africa, the majority of the world’s poorest people are in Asia. As in Africa, Asia finds itself with disparity in the distribution of poverty, with Japan and South Korea holding much more wealth than India and Cambodia. In fact, most poverty is concentrated in South Asia. One of the most pressing causes of poverty in Asia is simply the pressure that the size of the population puts on its resources. In fact, many believe that China’s success in recent times has much to do with its draconian population control rules. According to the U.S. State department, China’s market-oriented reforms have contributed to its significant reduction of poverty and the speed at which it has experienced an increase in income levels (U.S. Department of State 2011b). However, every part of Asia is feeling the current global recession, from the poorest countries whose aid packages will be hit, to the more industrialized ones whose own industries are slowing down. These factors make the poverty on the ground unlikely to improve any time soon (World Poverty 2012b). MENA The Middle East and North Africa region (MENA) includes oil-rich countries in the Gulf, such as Iran, Iraq, and Kuwait, but also countries that are relatively resource-poor in relationship to their populations, such as Morocco and Yemen. These countries are predominately Islamic. For the last quarter-century, economic growth was slower in MENA than in other developing economies, and almost a quarter of the 300 million people who make up the population live on less than $2.00 a day (World Bank 2013). The International Labour Organization tracks the way income inequality influences social unrest. The two regions with the highest risk of social unrest are Sub-Saharan Africa and the Middle East-North Africa region (International Labour Organization 2012). Increasing unemployment and high socioeconomic inequality in MENA were major factors in the Arab Spring, which—beginning in 2010—toppled dictatorships throughout the Middle East in favor of democratically elected government; unemployment and income inequalities are still being blamed on immigrants, foreign nationals, and ethnic/religious minorities. Sweatshops and Student Protests: Who’s Making Your Team Spirit? Most of us don’t pay too much attention to where our favorite products are made. And certainly when you’re shopping for a college sweatshirt or ball cap to wear to a school football game, you probably don’t turn over the label, check who produced the item, and then research whether or not the company has fair labor practices. But for the members of USAS––United Students Against Sweatshops––that’s exactly what they do. The organization, which was founded in 1997, has waged countless battles against both apparel makers and other multinational corporations that do not meet what USAS considers fair working conditions and wages (USAS 2009). Sometimes their demonstrations take on a sensationalist tone, as in 2006 when twenty Penn State students protested while naked or nearly naked, in order to draw attention to the issue of sweatshop labor. The school is actually already a member of an independent monitoring organization called Worker Rights Consortium (WRC) that monitors working conditions and works to assist colleges and universities with maintaining compliance with their labor code. But the students were protesting in order to have the same code of conduct applied to the factories that provide materials for the goods, not just where the final product is assembled (Chronicle of Higher Education 2006). The USAS organization has chapters on over 250 campuses in the United States and Canada and has waged countless campaigns against companies like Nike and Forever 21 apparel, Taco Bell restaurants, and Sodexo food service. In 2000, members of USAS helped to create the WRC. Schools that affiliate with WRC pay annual fees that help offset the organization’s costs. Over 180 schools are affiliated with the organization. Yet, USAS still sees signs of inequality everywhere. And its members feel that, as current and future workers, they are responsible for ensuring that workers of the world are treated fairly. For them, at least, the global inequality we see everywhere should not be ignored for a team spirit sweatshirt. Consequences of Poverty Not surprisingly, the consequences of poverty are often also causes. The poor often experience inadequate healthcare, limited education, and the inaccessibility of birth control. But those born into these conditions are incredibly challenged in their efforts to break out since these consequences of poverty are also causes of poverty, perpetuating a cycle of disadvantage. According to sociologists Neckerman and Torche (2007) in their analysis of global inequality studies, the consequences of poverty are many. Neckerman and Torche have divided them into three areas. The first, termed “the sedimentation of global inequality,” relates to the fact that once poverty becomes entrenched in an area, it is typically very difficult to reverse. As mentioned above, poverty exists in a cycle where the consequences and causes are intertwined. The second consequence of poverty is its effect on physical and mental health. Poor people face physical health challenges, including malnutrition and high infant mortality rates. Mental health is also detrimentally affected by the emotional stresses of poverty, with relative deprivation carrying the most robust effect. Again, as with the ongoing inequality, the effects of poverty on mental and physical health become more entrenched as time goes on. Neckerman and Torche’s third consequence of poverty is the prevalence of crime. Cross-nationally, crime rates are higher, particularly for violent crime, in countries with higher levels of income inequality (Fajnzylber, Lederman, and Loayza 2002). Slavery While most of us are accustomed to thinking of slavery in terms of the antebellum South, modern day slavery goes hand-in-hand with global inequality. In short, slavery refers to any situation in which people are sold, treated as property, or forced to work for little or no pay. Just as in the pre-Civil War United States, these humans are at the mercy of their employers. Chattel slavery, the form of slavery once practiced in the American South, occurs when one person owns another as property. Child slavery, which may include child prostitution, is a form of chattel slavery. Indebt bondage, or bonded labor, the poor pledge themselves as servants in exchange for the cost of basic necessities like transportation, room, and board. In this scenario, people are paid less than they are charged for room and board. When travel is required, they can arrive in debt for their travel expenses and be unable to work their way free, since their wages do not allow them to ever get ahead. The global watchdog group Anti-Slavery International recognizes other forms of slavery: human trafficking (in which people are moved away from their communities and forced to work against their will), child domestic work and child labor, and certain forms of servile marriage, in which women are little more than chattel slaves (Anti-Slavery International 2012). Summary When looking at the world’s poor, we first have to define the difference between relative poverty, absolute poverty, and subjective poverty. While those in relative poverty might not have enough to live at their country’s standard of living, those in absolute poverty do not have, or barely have, basic necessities such as food. Subjective poverty has more to do with one’s perception of one’s situation. North America and Europe are home to fewer of the world’s poor than Africa, which has most poor countries, or Asia, which has the most people living in poverty. Poverty has numerous negative consequences, from increased crime rates to a detrimental impact on physical and mental health. Section Quiz Slavery in the pre-Civil War U.S. South most closely resembled - chattel slavery - debt bondage - relative poverty - peonage Hint: A Maya is a twelve-year-old girl living in Thailand. She is homeless, and often does not know where she will sleep or when she will eat. We might say that Maya lives in _________ poverty. - subjective - absolute - relative - global Hint: B Mike, a college student, rents a studio apartment. He cannot afford a television and lives on cheap groceries like dried beans and ramen noodles. Since he does not have a regular job, he does not own a car. Mike is living in: - global poverty - absolute poverty - subjective poverty - relative poverty Hint: D Faith has a full-time job and two children. She has enough money for the basics and can pay her rent each month, but she feels that, with her education and experience, her income should be enough for her family to live much better than they do. Faith is experiencing: - global poverty - subjective poverty - absolute poverty - relative poverty Hint: B In a U.S. town, a mining company owns all the stores and most of the houses. It sells goods to the workers at inflated prices, offers house rentals for twice what a mortgage would be, and makes sure to always pay the workers less than needed to cover food and rent. Once the workers are in debt, they have no choice but to continue working for the company, since their skills will not transfer to a new position. This situation most closely resembles: - child slavery - chattel slavery - debt slavery - servile marriage Hint: C Short Answer Consider the concept of subjective poverty. Does it make sense that poverty is in the eye of the beholder? When you see a homeless person, is your reaction different if he or she is seemingly content versus begging? Why? Think of people among your family, your friends, or your classmates who are relatively unequal in terms of wealth. What is their relationship like? What factors come into play? Go to your campus bookstore or visit its web site. Find out who manufactures apparel and novelty items with your school’s insignias. In what countries are these produced? Conduct some research to determine how well your school adheres to the principles advocated by USAS. Further Research Students often think that the United States is immune to the atrocity of human trafficking. Check out the following link to learn more about trafficking in the United States: http://openstaxcollege.org/l/human_trafficking_in_US For more information about the ongoing practices of slavery in the modern world click here: http://openstaxcollege.org/l/anti-slavery References Anti-Slavery International. 2012. “What Is Modern Slavery?” Retrieved January 1, 2012 (http://www.antislavery.org/english/slavery_today/what_is_modern_slavery.aspx). Barta, Patrick. 2009. “The Rise of the Underground.” Wall Street Journal, March 14. Retrieved January 1, 2012 (ttp://online.wsj.com/article/SB123698646833925567.html). Buvinić, M. 1997. “Women in Poverty: A New Global Underclass.” Foreign Policy, Fall (108):1–7. Chen, Martha. 2001. “Women in the Informal Sector: A Global Picture, the Global Movement.” The SAIS Review 21:71–82 Chronicle of Higher Education. 2006. “Nearly Nude Penn State Students Protest Sweatshop Labor.” March 26. Retrieved January 4, 2012 (http://chronicle.com/article/Nearly-Nude-Penn-Staters/36772). Fajnzylber, Pablo, Daniel Lederman, and Norman Loayza. 2002. “Inequality and Violent Crime.” Journal of Law and Economics 45:1–40. International Labour Organization. 2012. “High Unemployment and Growing Inequality Fuel Social Unrest around the World.” Retrieved November 7, 2014 (http://www.ilo.org/global/about-the-ilo/newsroom/comment-analysis/WCMS_179430/lang--en/index.htm). Neckerman, Kathryn, and Florencia Torche. 2007. “Inequality: Causes and Consequences.” Annual Review of Sociology 33:335–357. Shah, Anup. 2011. “Poverty around the World.” Global Issues. Retrieved January 17, 2012 (http://www.globalissues.org/print/article/4). U.S. Department of State. 2011a. “Background Note: Argentina.” Retrieved January 3, 2012 (http://www.state.gov/r/pa/ei/bgn/26516.htm). U.S. Department of State. 2011b. “Background Note: China.” Retrieved January 3, 2012 (http://www.state.gov/r/pa/ei/bgn/18902.htm#econ). U.S. Department of State. 2011c. “Background Note: Rwanda.” Retrieved January 3, 2012 (http://www.state.gov/r/pa/ei/bgn/2861.htm#econ). USAS. 2009. “Mission, Vision and Organizing Philosophy.” August. Retrieved January 2, 2012 (http://usas.org). World Bank. 2013. “Middle East and North Africa." Retrieved November 7, 2014 (http://web.worldbank.org/WBSITE/EXTERNAL/COUNTRIES/MENAEXT/0,,menuPK:247619~pagePK:146748~piPK:146812~theSitePK:256299,00.html). World Bank. 2014e. “Poverty Overview.” Retrieved November 7, 2014 (http://www.worldbank.org/en/topic/poverty/overview). World Poverty. 2012a. “Poverty in Africa, Famine and Disease.” Retrieved January 2, 2012 (http://world-poverty.org/povertyinafrica.aspx). World Poverty. 2012b “Poverty in Asia, Caste and Progress.” Retrieved January 2, 2012 (http://world-poverty.org/povertyinasia.aspx). World Poverty. 2012c. “Poverty in Latin America, Foreign Aid Debt Burdens.” Retrieved January 2, 2012 (http://world-poverty.org/povertyinlatinamerica.aspx).	oercommons	2025-03-18T00:36:04.716652	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11796/overview", "title": "Introduction to Sociology 2e, Global Inequality", "author": null }
https://oercommons.org/courseware/lesson/11797/overview	Theoretical Perspectives on Global Stratification Overview - Describe the modernization and dependency theory perspectives on global stratification As with any social issue, global or otherwise, scholars have developed a variety of theories to study global stratification. The two most widely applied perspectives are modernization theory and dependency theory. Modernization Theory According to modernization theory, low-income countries are affected by their lack of industrialization and can improve their global economic standing through (Armer and Katsillis 2010): - an adjustment of cultural values and attitudes to work - industrialization and other forms of economic growth Critics point out the inherent ethnocentric bias of this theory. It supposes all countries have the same resources and are capable of following the same path. In addition, it assumes that the goal of all countries is to be as “developed” as possible. There is no room within this theory for the possibility that industrialization and technology are not the best goals. There is, of course, some basis for this assumption. Data show that core nations tend to have lower maternal and child mortality rates, longer life spans, and less absolute poverty. It is also true that in the poorest countries, millions of people die from the lack of clean drinking water and sanitation facilities, which are benefits most of us take for granted. At the same time, the issue is more complex than the numbers might suggest. Cultural equality, history, community, and local traditions are all at risk as modernization pushes into peripheral countries. The challenge, then, is to allow the benefits of modernization while maintaining a cultural sensitivity to what already exists. Dependency Theory Dependency theory was created in part as a response to the Western-centric mindset of modernization theory. It states that global inequality is primarily caused by core nations (or high-income nations) exploiting semi-peripheral and peripheral nations (or middle-income and low-income nations), which creates a cycle of dependence (Hendricks 2010). As long as peripheral nations are dependent on core nations for economic stimulus and access to a larger piece of the global economy, they will never achieve stable and consistent economic growth. Further, the theory states that since core nations, as well as the World Bank, choose which countries to make loans to, and for what they will loan funds, they are creating highly segmented labor markets that are built to benefit the dominant market countries. At first glance, it seems this theory ignores the formerly low-income nations that are now considered middle-income nations and are on their way to becoming high-income nations and major players in the global economy, such as China. But some dependency theorists would state that it is in the best interests of core nations to ensure the long-term usefulness of their peripheral and semi-peripheral partners. Following that theory, sociologists have found that entities are more likely to outsource a significant portion of a company’s work if they are the dominant player in the equation; in other words, companies want to see their partner countries healthy enough to provide work, but not so healthy as to establish a threat (Caniels and Roeleveld 2009). Factory Girls We’ve examined functionalist and conflict theorist perspectives on global inequality, as well as modernization and dependency theories. How might a symbolic interactionist approach this topic? The book Factory Girls: From Village to City in Changing China, by Leslie T. Chang, provides this opportunity. Chang follows two young women (Min and Chunming) employed at a handbag plant. They help manufacture coveted purses and bags for the global market. As part of the growing population of young people who are leaving behind the homesteads and farms of rural China, these female factory workers are ready to enter the urban fray and pursue an ambitious income. Although Chang’s study is based in a town many have never heard of (Dongguan), this city produces one-third of all shoes on the planet (Nike and Reebok are major manufacturers here) and 30 percent of the world’s computer disk drives, in addition to an abundance of apparel (Chang 2008). But Chang’s focus is centered less on this global phenomenon on a large scale, than on how it affects these two women. As a symbolic interactionist would do, Chang examines the daily lives and interactions of Min and Chunming—their workplace friendships, family relationships, gadgets and goods—in this evolving global space where young women can leave tradition behind and fashion their own futures. Their story is one that all people, not just scholars, can learn from as we contemplate sociological issues like global economies, cultural traditions and innovations, and opportunities for women in the workforce. Summary Modernization theory and dependency theory are two of the most common lenses sociologists use when looking at the issues of global inequality. Modernization theory posits that countries go through evolutionary stages and that industrialization and improved technology are the keys to forward movement. Dependency theory, on the other hand, sees modernization theory as Eurocentric and patronizing. With this theory, global inequality is the result of core nations creating a cycle of dependence by exploiting resources and labor in peripheral and semi-peripheral countries. Section Quiz One flaw in dependency theory is the unwillingness to recognize _______. - that previously low-income nations such as China have successfully developed their economies and can no longer be classified as dependent on core nations - that previously high-income nations such as China have been economically overpowered by low-income nations entering the global marketplace - that countries such as China are growing more dependent on core nations - that countries such as China do not necessarily want to be more like core nations Hint: A One flaw in modernization theory is the unwillingness to recognize _________. - that semi-peripheral nations are incapable of industrializing - that peripheral nations prevent semi-peripheral nations from entering the global market - its inherent ethnocentric bias - the importance of semi-peripheral nations industrializing Hint: C If a sociologist says that nations evolve toward more advanced technology and more complex industry as their citizens learn cultural values that celebrate hard work and success, she is using _______ theory to study the global economy. - modernization theory - dependency theory - modern dependency theory - evolutionary dependency theory Hint: A If a sociologist points out that core nations dominate the global economy, in part by creating global interest rates and international tariffs that will inevitably favor high-income nations over low-income nations, he is a: - functionalist - dependency theorist - modernization theorist - symbolic interactionist Hint: B Dependency theorists explain global inequality and global stratification by focusing on the way that: - core nations and peripheral nations exploit semi-peripheral nations - semi-peripheral nations exploit core nations - peripheral nations exploit core nations - core nations exploit peripheral nations Hint: D Short Answer There is much criticism that modernization theory is Eurocentric. Do you think dependency theory is also biased? Why, or why not? Compare and contrast modernization theory and dependency theory. Which do you think is more useful for explaining global inequality? Explain, using examples. Further Research For more information about economic modernization, check out the Hudson Institute at http://openstaxcollege.org/l/Hudson_Institute Learn more about economic dependency at the University of Texas Inequality Project: http://openstaxcollege.org/l/Texas_inequality_project References Armer, J. Michael, and John Katsillis. 2010. “Modernization Theory.” Encyclopedia of Sociology, edited by E. F. Borgatta. Retrieved January 5, 2012 (http://edu.learnsoc.org/Chapters/3%20theories%20of%20sociology/11%20modernization%20theory.htm). Caniels, Marjolein, C.J. Roeleveld, and Adriaan Roeleveld. 2009. “Power and Dependence Perspectives on Outsourcing Decisions.” European Management Journal 27:402–417. Retrieved January 4, 2012 (http://ou-nl.academia.edu/MarjoleinCaniels/Papers/645947/Power_and_dependence_perspectives_on_outsourcing_decisions). Chang, Leslie T. 2008. Factory Girls: From Village to City in Changing China. New York: Random House. Hendricks, John. 2010. “Dependency Theory.” Encyclopedia of Sociology, edited by E.F. Borgatta. Retrieved January 5, 2012 (http://edu.learnsoc.org/Chapters/3%20theories%20of%20sociology/5%20dependency%20theory.htm).	oercommons	2025-03-18T00:36:04.745365	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11797/overview", "title": "Introduction to Sociology 2e, Global Inequality", "author": null }
https://oercommons.org/courseware/lesson/11830/overview	Introduction to Work and the Economy What if the U.S. economy thrived solely on basic bartering instead of its bustling agricultural and technological goods? Would you still see a busy building like the one shown in ? In sociology, economy refers to the social institution through which a society’s resources are exchanged and managed. The earliest economies were based on trade, which is often a simple exchange in which people traded one item for another. While today’s economic activities are more complex than those early trades, the underlying goals remain the same: exchanging goods and services allows individuals to meet their needs and wants. In 1893, Émile Durkheim described what he called “mechanical” and “organic” solidarity that correlates to a society’s economy.Mechanical solidarity exists in simpler societies where social cohesion comes from sharing similar work, education, and religion.Organic solidarity arises out of the mutual interdependence created by the specialization of work. The complex U.S. economy, and the economies of other industrialized nations, meet the definition of organic solidarity. Most individuals perform a specialized task to earn money they use to trade for goods and services provided by others who perform different specialized tasks. In a simplified example, an elementary school teacher relies on farmers for food, doctors for healthcare, carpenters to build shelter, and so on. The farmers, doctors, and carpenters all rely on the teacher to educate their children. They are all dependent on each other and their work. Economy is one of human society’s earliest social structures. Our earliest forms of writing (such as Sumerian clay tablets) were developed to record transactions, payments, and debts between merchants. As societies grow and change, so do their economies. The economy of a small farming community is very different from the economy of a large nation with advanced technology. In this chapter, we will examine different types of economic systems and how they have functioned in various societies. Detroit, once the roaring headquarters of the country’s large and profitable automotive industry, had already been in a population decline for several decades as auto manufacturing jobs were being outsourced to other countries and foreign car brands began to take increasing portions of U.S. market share. According to State of Michigan population data (State of Michigan, n.d.), Detroit was home to approximately 1.85 million residents in 1950, which dwindled to slightly more than 700,000 in 2010 following the economic crash. The drastic reduction took its toll on the city. It is estimated that a third of the buildings in Detroit have been abandoned. The current average home price hovers around $7,000, while homes nationwide sell on average for around $200,000. The city has filed for bankruptcy, and its unemployment rate hovers around 30 percent. The Wage Gap in the United States The Equal Pay Act, passed by the U.S. Congress in 1963, was designed to reduce the wage gap between men and women. The act in essence required employers to pay equal wages to men and women who were performing substantially similar jobs. However, more than fifty years later, women continue to make less money than their male counterparts. According to a report released by the White House (National Equal Pay Taskforce 2013), “On average, full-time working women make just 77 cents for every dollar a man makes. This significant gap is more than a statistic—iit has real-life consequences. When women, who make up nearly half the workforce, bring home less money each day, it means they have less for the everyday needs of their families, and over a lifetime of work, far less savings for retirement.” While the Pew Research Center contends that women make 84 cents for every dollar men make, countless studies that have controlled for work experience, education, and other factors unanimously demonstrate that disparity between wages paid to men and to women still exists (Pew Research Center 2014). As shocking as it is, the gap actually widens when we add race and ethnicity to the picture. For example, African American women make on average 64 cents for every dollar a Caucasian male makes. Latina women make 56 cents, or 44 percent less, for every dollar a Caucasian male makes. African American and Latino men also make notably less than Caucasian men. Asian Americans tend to be the only minority that earns as much as or more than Caucasian men. Recent Economic Cconditions In 2015, the United States continued its recovery from the “Great Recession,” arguably the worst economic downturn since the stock market collapse in 1929 and the Great Depression that ensued. The recent recession was brought on, at least in part, by the lending practices of the early twenty-first. During this time, banks provided adjustable-rate mortgages (ARM) to customers with poor credit histories at an attractively low introductory rate. After the introductory rate expired, the interest rate on these ARM loans rose, often dramatically, creating a sizable increase in the borrower’s monthly mortgage payments. As their rates adjusted upward, many of these “subprime” mortgage customers were unable to make their monthly payments and stopped doing so, known as defaulting. The massive rate of loan defaults put a strain on the financial institutions that had made the loans, and this stress rippled throughout the entire economy and around the globe. The United States fell into a period of high and prolonged unemployment, extreme reductions in wealth (except at the very top), stagnant wages, and loss of value in personal property (houses and land). The S&P 500 Index, which measures the overall share value of selected leading companies whose shares are traded on the stock market, fell from a high of 1565 in October 2007 to 676 by March 2009. Today, however, unemployment rates are down in many areas of the United States, the Gross Domestic Product increased 4.6 percent in the second quarter of 2014 (US Department of Commerce–Bureau of Economic Analysis), property owners have noted a slight increase in the valuation of housing, and the stock market appears to be reinvigorated. While these and several other factors indicate the United States is on the road to recovery, many people are still struggling. For most segments of the population, median income has not increased, and in fact it has receded in many cases. The size, income, and wealth of the middle class have been declining since the 1970s— effects that were perhaps hastened by the recession. Today, wealth is distributed inequitably at the top. Corporate profits have increased more than 141 percent, and CEO pay has risen by more than 298 percent. G. William Domhoff (University of California at Santa Cruz) reports that “In 2010, the top 1% of households (the upper class) owned 35.4% of all privately held wealth, and the next 19% (the managerial, professional, and small business stratum) had 53.5%, which means that just 20% of the people owned a remarkable 89%, leaving only 11% of the wealth for the bottom 80% (wage and salary workers).” Economic Impact of the Recession on Different Segments of Population: Most U.S. citizens have struggled financially as a result of the nearly decade-long recession. As noted above, many workers lost their jobs as unemployment rates soared, housing prices—which represent the wealth of the average person—declined sharply, and the cost of living increased significantly. Meanwhile income for the average U.S. worker remains stagnant. One indicator of general economic conditions is the rate at which individuals are accessing the country’s safety net or social welfare programs. Between 2000 and 2013, the number of people relying on the Supplemental Nutrition Assistance Program (SNAP, formerly known as the “food stamp” program), climbed from 17,194,000 to more than 47,636,000. The sharpest increase paralleled the subprime mortgage crisis of 2009, with the rolls rising from 28,000,000 to more than 40,000,000 individuals receiving food assistance in a span of two years (United States Department of Agriculture 2014). The economic downturn had a rippling effect throughout the economy. For instance, it delivered a significant blow to the once-vibrant U.S. automotive industry. While consumers found loans harder to get due to the subprime mortgage lending crisis and increasing fuel costs, they also grew weary of large, gas-guzzling sport utility vehicles (SUVs) that were once the bread-and-butter product of U.S. automakers. As customers became more aware of the environmental impact of such cars and the cost of fuel, the large SUV ceased to be the status symbol it had been during the 1990s and 2000s. It became instead a symbol of excess and waste. All these factors created the perfect storm that nearly decimated the U.S. auto industry. To prevent mass job loss, the government provided emergency loans funded by taxpayer dollars, as well as other forms of financial support, to corporations like General Motors and Chrysler. While the companies survived, the landscape of the U.S. auto industry was changed as result of the economic decline. To realign their businesses in the face of decreased sales and lower manufacturing outputs, many large automotive companies severed their ties with hundreds of dealerships, which affected the dealers’ local economies around the country. References National Equal Pay Task Force. 2013. "Fifty Years After the Equal Pay Act: Assessing the Past, Taking Stock of the Future." Retrieved December 15, 2014. (http://www.whitehouse.gov/sites/default/files/equalpay/equal_pay_task_force_progress_report_june_2013_new.pdf). State of Michigan, The. n.d. "Detrioit's Financial Crisis: What You Need to Know." Retrieved December 15, 2014. (http://www.michigan.gov/documents/detroitcantwait/DetroitFactSheet_412909_7.pdf). U.S. Department of Agriculture. 2014. "Supplemental Nutrition Assistance Program Participation and Costs." Retrieved December 15, 2014. (http://www.fns.usda.gov/sites/default/files/pd/SNAPsummary.pdf).	oercommons	2025-03-18T00:36:04.764790	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11830/overview", "title": "Introduction to Sociology 2e, Work and the Economy", "author": null }
https://oercommons.org/courseware/lesson/11831/overview	Economic Systems Overview - Understand types of economic systems and their historical development - Describe capitalism and socialism both in theory and in practice - Discussion how functionalists, conflict theorists, and symbolic interactionists view the economy and work The dominant economic systems of the modern era are capitalism and socialism, and there have been many variations of each system across the globe. Countries have switched systems as their rulers and economic fortunes have changed. For example, Russia has been transitioning to a market-based economy since the fall of communism in that region of the world. Vietnam, where the economy was devastated by the Vietnam War, restructured to a state-run economy in response, and more recently has been moving toward a socialist-style market economy. In the past, other economic systems reflected the societies that formed them. Many of these earlier systems lasted centuries. These changes in economies raise many questions for sociologists. What are these older economic systems? How did they develop? Why did they fade away? What are the similarities and differences between older economic systems and modern ones? Economics of Agricultural, Industrial, and Postindustrial Societies Our earliest ancestors lived as hunter-gatherers. Small groups of extended families roamed from place to place looking for subsistence. They would settle in an area for a brief time when there were abundant resources. They hunted animals for their meat and gathered wild fruits, vegetables, and cereals. They ate what they caught or gathered their goods as soon as possible, because they had no way of preserving or transporting it. Once the resources of an area ran low, the group had to move on, and everything they owned had to travel with them. Food reserves only consisted of what they could carry. Many sociologists contend that hunter-gatherers did not have a true economy, because groups did not typically trade with other groups due to the scarcity of goods. The Agricultural Revolution The first true economies arrived when people started raising crops and domesticating animals. Although there is still a great deal of disagreement among archeologists as to the exact timeline, research indicates that agriculture began independently and at different times in several places around the world. The earliest agriculture was in the Fertile Crescent in the Middle East around 11,000–10,000 years ago. Next were the valleys of the Indus, Yangtze, and Yellow rivers in India and China, between 10,000 and 9,000 years ago. The people living in the highlands of New Guinea developed agriculture between 9,000 and 6,000 years ago, while people were farming in Sub-Saharan Africa between 5,000 and 4,000 years ago. Agriculture developed later in the western hemisphere, arising in what would become the eastern United States, central Mexico, and northern South America between 5,000 and 3,000 years ago (Diamond 2003). Agriculture began with the simplest of technologies—for example, a pointed stick to break up the soil—but really took off when people harnessed animals to pull an even more efficient tool for the same task: a plow. With this new technology, one family could grow enough crops not only to feed themselves but also to feed others. Knowing there would be abundant food each year as long as crops were tended led people to abandon the nomadic life of hunter-gatherers and settle down to farm. The improved efficiency in food production meant that not everyone had to toil all day in the fields. As agriculture grew, new jobs emerged, along with new technologies. Excess crops needed to be stored, processed, protected, and transported. Farming equipment and irrigation systems needed to be built and maintained. Wild animals needed to be domesticated and herds shepherded. Economies begin to develop because people now had goods and services to trade. At the same time, farmers eventually came to labor for the ruling class. As more people specialized in nonfarming jobs, villages grew into towns and then into cities. Urban areas created the need for administrators and public servants. Disputes over ownership, payments, debts, compensation for damages, and the like led to the need for laws and courts—and the judges, clerks, lawyers, and police who administered and enforced those laws. At first, most goods and services were traded as gifts or through bartering between small social groups (Mauss 1922). Exchanging one form of goods or services for another was known as bartering. This system only works when one person happens to have something the other person needs at the same time. To solve this problem, people developed the idea of a means of exchange that could be used at any time: that is, money.Money refers to an object that a society agrees to assign a value to so it can be exchanged for payment. In early economies, money was often objects like cowry shells, rice, barley, or even rum. Precious metals quickly became the preferred means of exchange in many cultures because of their durability and portability. The first coins were minted in Lydia in what is now Turkey around 650–600 B.C.E. (Goldsborough 2010). Early legal codes established the value of money and the rates of exchange for various commodities. They also established the rules for inheritance, fines as penalties for crimes, and how property was to be divided and taxed (Horne 1915). A symbolic interactionist would note that bartering and money are systems of symbolic exchange. Monetary objects took on a symbolic meaning, one that carries into our modern-day use of cash, checks, and debit cards. The Woman Who Lives without Money Imagine having no money. If you wanted some french fries, needed a new pair of shoes, or were due to get an oil change for your car, how would you get those goods and services? This isn’t just a theoretical question. Think about it. What do those on the outskirts of society do in these situations? Think of someone escaping domestic abuse who gave up everything and has no resources. Or an immigrant who wants to build a new life but who had to leave another life behind to find that opportunity. Or a homeless person who simply wants a meal to eat. This last example, homelessness, is what caused Heidemarie Schwermer to give up money. She was a divorced high school teacher in Germany, and her life took a turn when she relocated her children to a rural town with a significant homeless population. She began to question what serves as currency in a society and decided to try something new. Schwermer founded a business called Gib und Nimm—in English, “give and take.” It operated on a moneyless basis and strived to facilitate people swapping goods and services for other goods and services—no cash allowed (Schwermer 2007). What began as a short experiment has become a new way of life. Schwermer says the change has helped her focus on people’s inner value instead of their outward wealth. She wrote two books that tell her story (she’s donated all proceeds to charity) and, most importantly, a richness in her life she was unable to attain with money. How might our three sociological perspectives view her actions? What would most interest them about her unconventional ways? Would a functionalist consider her aberration of norms a social dysfunction that upsets the normal balance? How would a conflict theorist place her in the social hierarchy? What might a symbolic interactionist make of her choice not to use money—such an important symbol in the modern world? What do you make ofGib und Nimm? As city-states grew into countries and countries grew into empires, their economies grew as well. When large empires broke up, their economies broke up too. The governments of newly formed nations sought to protect and increase their markets. They financed voyages of discovery to find new markets and resources all over the world, which ushered in a rapid progression of economic development. Colonies were established to secure these markets, and wars were financed to take over territory. These ventures were funded in part by raising capital from investors who were paid back from the goods obtained. Governments and private citizens also set up large trading companies that financed their enterprises around the world by selling stocks and bonds. Governments tried to protect their share of the markets by developing a system called mercantilism. Mercantilism is an economic policy based on accumulating silver and gold by controlling colonial and foreign markets through taxes and other charges. The resulting restrictive practices and exacting demands included monopolies, bans on certain goods, high tariffs, and exclusivity requirements. Mercantilistic governments also promoted manufacturing and, with the ability to fund technological improvements, they helped create the equipment that led to the Industrial Revolution. The Industrial Revolution Until the end of the eighteenth century, most manufacturing was done by manual labor. This changed as inventors devised machines to manufacture goods. A small number of innovations led to a large number of changes in the British economy. In the textile industries, the spinning of cotton, worsted yarn, and flax could be done more quickly and less expensively using new machines with names like the Spinning Jenny and the Spinning Mule (Bond 2003). Another important innovation was made in the production of iron: Coke from coal could now be used in all stages of smelting rather than charcoal from wood, which dramatically lowered the cost of iron production while increasing availability (Bond 2003). James Watt ushered in what many scholars recognize as the greatest change, revolutionizing transportation and thereby the entire production of goods with his improved steam engine. As people moved to cities to fill factory jobs, factory production also changed. Workers did their jobs in assembly lines and were trained to complete only one or two steps in the manufacturing process. These advances meant that more finished goods could be manufactured with more efficiency and speed than ever before. The Industrial Revolution also changed agricultural practices. Until that time, many people practiced subsistence farming in which they produced only enough to feed themselves and pay their taxes. New technology introduced gasoline-powered farm tools such as tractors, seed drills, threshers, and combine harvesters. Farmers were encouraged to plant large fields of a single crop to maximize profits. With improved transportation and the invention of refrigeration, produce could be shipped safely all over the world. The Industrial Revolution modernized the world. With growing resources came growing societies and economies. Between 1800 and 2000, the world’s population grew sixfold, while per capita income saw a tenfold jump (Maddison 2003). While many people's lives were improving, the Industrial Revolution also birthed many societal problems. There were inequalities in the system. Owners amassed vast fortunes while laborers, including young children, toiled for long hours in unsafe conditions. Workers’ rights, wage protection, and safe work environments are issues that arose during this period and remain concerns today. Postindustrial Societies and the Information Age Postindustrial societies, also known as information societies, have evolved in modernized nations. One of the most valuable goods of the modern era is information. Those who have the means to produce, store, and disseminate information are leaders in this type of society. One way scholars understand the development of different types of societies (like agricultural, industrial, and postindustrial) is by examining their economies in terms of four sectors: primary, secondary, tertiary, and quaternary. Each has a different focus. The primary sector extracts and produces raw materials (like metals and crops). The secondary sector turns those raw materials into finished goods. The tertiary sector provides services: child care, healthcare, and money management. Finally, the quaternary sector produces ideas; these include the research that leads to new technologies, the management of information, and a society’s highest levels of education and the arts (Kenessey 1987). In underdeveloped countries, the majority of the people work in the primary sector. As economies develop, more and more people are employed in the secondary sector. In well-developed economies, such as those in the United States, Japan, and Western Europe, the majority of the workforce is employed in service industries. In the United States, for example, almost 80 percent of the workforce is employed in the tertiary sector (U.S. Bureau of Labor Statistics 2011). The rapid increase in computer use in all aspects of daily life is a main reason for the transition to an information economy. Fewer people are needed to work in factories because computerized robots now handle many of the tasks. Other manufacturing jobs have been outsourced to less-developed countries as a result of the developing global economy. The growth of the Internet has created industries that exist almost entirely online. Within industries, technology continues to change how goods are produced. For instance, the music and film industries used to produce physical products like CDs and DVDs for distribution. Now those goods are increasingly produced digitally and streamed or downloaded at a much lower physical manufacturing cost. Information and the means to use it creatively have become commodities in a postindustrial economy. Capitalism Scholars don’t always agree on a single definition of capitalism. For our purposes, we will define capitalism as an economic system in which there is private ownership (as opposed to state ownership) and where there is an impetus to produce profit, and thereby wealth. This is the type of economy in place in the United States today. Under capitalism, people invest capital (money or property invested in a business venture) in a business to produce a product or service that can be sold in a market to consumers. The investors in the company are generally entitled to a share of any profit made on sales after the costs of production and distribution are taken out. These investors often reinvest their profits to improve and expand the business or acquire new ones. To illustrate how this works, consider this example. Sarah, Antonio, and Chris each invest $250,000 into a start-up company that offers an innovative baby product. When the company nets $1 million in profits its first year, a portion of that profit goes back to Sarah, Antonio, and Chris as a return on their investment. Sarah reinvests with the same company to fund the development of a second product line, Antonio uses his return to help another start-up in the technology sector, and Chris buys a small yacht for vacations. To provide their product or service, owners hire workers to whom they pay wages. The cost of raw materials, the retail price they charge consumers, and the amount they pay in wages are determined through the law of supply and demand and by competition. When demand exceeds supply, prices tend to rise. When supply exceeds demand, prices tend to fall. When multiple businesses market similar products and services to the same buyers, there is competition. Competition can be good for consumers because it can lead to lower prices and higher quality as businesses try to get consumers to buy from them rather than from their competitors. Wages tend to be set in a similar way. People who have talents, skills, education, or training that is in short supply and is needed by businesses tend to earn more than people without comparable skills. Competition in the workforce helps determine how much people will be paid. In times when many people are unemployed and jobs are scarce, people are often willing to accept less than they would when their services are in high demand. In this scenario, businesses are able to maintain or increase profits by not increasing workers' wages. Capitalism in Practice As capitalists began to dominate the economies of many countries during the Industrial Revolution, the rapid growth of businesses and their tremendous profitability gave some owners the capital they needed to create enormous corporations that could monopolize an entire industry. Many companies controlled all aspects of the production cycle for their industry, from the raw materials, to the production, to the stores in which they were sold. These companies were able to use their wealth to buy out or stifle any competition. In the United States, the predatory tactics used by these large monopolies caused the government to take action. Starting in the late 1800s, the government passed a series of laws that broke up monopolies and regulated how key industries—such as transportation, steel production, and oil and gas exploration and refining—could conduct business. The United States is considered a capitalist country. However, the U.S. government has a great deal of influence on private companies through the laws it passes and the regulations enforced by government agencies. Through taxes, regulations on wages, guidelines to protect worker safety and the environment, plus financial rules for banks and investment firms, the government exerts a certain amount of control over how all companies do business. State and federal governments also own, operate, or control large parts of certain industries, such as the post office, schools, hospitals, highways and railroads, and many water, sewer, and power utilities. Debate over the extent to which the government should be involved in the economy remains an issue of contention today. Some criticize such involvements as socialism (a type of state-run economy), while others believe intervention is necessary to protect the rights of workers and the well-being of the general population. Socialism Socialism is an economic system in which there is government ownership (often referred to as “state run”) of goods and their production, with an impetus to share work and wealth equally among the members of a society. Under socialism, everything that people produce, including services, is considered a social product. Everyone who contributes to the production of a good or to providing a service is entitled to a share in any benefits that come from its sale or use. To make sure all members of society get their fair share, governments must be able to control property, production, and distribution. The focus in socialism is on benefitting society, whereas capitalism seeks to benefit the individual. Socialists claim that a capitalistic economy leads to inequality, with unfair distribution of wealth and individuals who use their power at the expense of society. Socialism strives, ideally, to control the economy to avoid the problems inherent in capitalism. Within socialism, there are diverging views on the extent to which the economy should be controlled. One extreme believes all but the most personal items are public property. Other socialists believe only essential services such as healthcare, education, and utilities (electrical power, telecommunications, and sewage) need direct control. Under this form of socialism, farms, small shops, and businesses can be privately owned but are subject to government regulation. The other area on which socialists disagree is on what level society should exert its control. In communist countries like the former Soviet Union, China, Vietnam, and North Korea, the national government exerts control over the economy centrally. They had the power to tell all businesses what to produce, how much to produce, and what to charge for it. Other socialists believe control should be decentralized so it can be exerted by those most affected by the industries being controlled. An example of this would be a town collectively owning and managing the businesses on which its residents depend. Because of challenges in their economies, several of these communist countries have moved from central planning to letting market forces help determine many production and pricing decisions. Market socialism describes a subtype of socialism that adopts certain traits of capitalism, like allowing limited private ownership or consulting market demands. This could involve situations like profits generated by a company going directly to the employees of the company or being used as public funds (Gregory and Stuart 2003). Many Eastern European and some South American countries have mixed economies. Key industries are nationalized and directly controlled by the government; however, most businesses are privately owned and regulated by the government. Organized socialism never became powerful in the United States. The success of labor unions and the government in securing workers’ rights, joined with the high standard of living enjoyed by most of the workforce, made socialism less appealing than the controlled capitalism practiced here. Socialism in Practice As with capitalism, the basic ideas behind socialism go far back in history. Plato, in ancient Greece, suggested a republic in which people shared their material goods. Early Christian communities believed in common ownership, as did the systems of monasteries set up by various religious orders. Many of the leaders of the French Revolution called for the abolition of all private property, not just the estates of the aristocracy they had overthrown. Thomas More's Utopia, published in 1516, imagined a society with little private property and mandatory labor on a communal farm. Autopia has since come to mean an imagined place or situation in which everything is perfect. Most experimental utopian communities had the abolition of private property as a founding principle. Modern socialism really began as a reaction to the excesses of uncontrolled industrial capitalism in the 1800s and 1900s. The enormous wealth and lavish lifestyles enjoyed by owners contrasted sharply with the miserable conditions of the workers. Some of the first great sociological thinkers studied the rise of socialism. Max Weber admired some aspects of socialism, especially its rationalism and how it could help social reform, but he worried that letting the government have complete control could result in an "iron cage of future bondage" from which there is no escape (Greisman and Ritzer 1981). Pierre-Joseph Proudon (1809−1865) was another early socialist who thought socialism could be used to create utopian communities. In his 1840 book, What Is Property?, he famously stated that “property is theft” (Proudon 1840). By this he meant that if an owner did not work to produce or earn the property, then the owner was stealing it from those who did. Proudon believed economies could work using a principle calledmutualism, under which individuals and cooperative groups would exchange products with one another on the basis of mutually satisfactory contracts (Proudon 1840). By far the most important influential thinker on socialism is Karl Marx. Through his own writings and those with his collaborator, industrialist Friedrich Engels, Marx used a scientific analytical process to show that throughout history, the resolution of class struggles caused changes in economies. He saw the relationships evolving from slave and owner, to serf and lord, to journeyman and master, to worker and owner. Neither Marx nor Engels thought socialism could be used to set up small utopian communities. Rather, they believed a socialist society would be created after workers rebelled against capitalistic owners and seized the means of production. They felt industrial capitalism was a necessary step that raised the level of production in society to a point it could progress to a socialist and then communist state (Marx and Engels 1848). These ideas form the basis of the sociological perspective of social conflict theory. Obama and Socialism: A Few Definitions In the 2008 presidential election, the Republican Party latched onto what is often considered a dirty word to describe then-Senator Barack Obama’s politics: socialist. It may have been because the president was campaigning by telling workers it’s good for everybody when wealth gets spread around. But whatever the reason, the label became a weapon of choice for Republicans during and after the campaign. In 2012, Republican presidential contender Rick Perry continued this battle cry. A New York Times article quotes him as telling a group of Republicans in Texas that President Obama is “hell bent on taking America towards a socialist country” (Wheaton 2011). Meanwhile, during the first few years of his presidency, Obama worked to create universal healthcare coverage and pushed forth a partial takeover of the nation’s failing automotive industry. So does this make him a socialist? What does that really mean, anyway? There is more than one definition of socialism, but it generally refers to an economic or political theory that advocates for shared or governmental ownership and administration of production and distribution of goods. Often held up in counterpoint to capitalism, which encourages private ownership and production, socialism is not typically an all-or-nothing plan. For example, both the United Kingdom and France, as well as other European countries, have socialized medicine, meaning that medical services are run nationally to reach as many people as possible. These nations are, of course, still essentially capitalist countries with free-market economies. So is Obama a socialist because he wants universal healthcare? Or is the word a lightning rod for conservatives who associate it with a lack of personal freedom? By almost any measure, the answer is more the latter. Convergence Theory We have seen how the economies of some capitalist countries such as the United States have features that are very similar to socialism. Some industries, particularly utilities, are either owned by the government or controlled through regulations. Public programs such as welfare, Medicare, and Social Security exist to provide public funds for private needs. We have also seen how several large communist (or formerly communist) countries such as Russia, China, and Vietnam have moved from state-controlled socialism with central planning to market socialism, which allows market forces to dictate prices and wages and for some business to be privately owned. In many formerly communist countries, these changes have led to economic growth compared to the stagnation they experienced under communism (Fidrmuc 2002). In studying the economies of developing countries to see if they go through the same stages as previously developed nations did, sociologists have observed a pattern they call convergence. This describes the theory that societies move toward similarity over time as their economies develop. Convergence theory explains that as a country's economy grows, its societal organization changes to become more like that of an industrialized society. Rather than staying in one job for a lifetime, people begin to move from job to job as conditions improve and opportunities arise. This means the workforce needs continual training and retraining. Workers move from rural areas to cities as they become centers of economic activity, and the government takes a larger role in providing expanded public services (Kerr et al. 1960). Supporters of the theory point to Germany, France, and Japan—countries that rapidly rebuilt their economies after World War II. They point out how, in the 1960s and 1970s, East Asian countries like Singapore, South Korea, and Taiwan converged with countries with developed economies. They are now considered developed countries themselves. To experience this rapid growth, the economies of developing countries must to be able to attract inexpensive capital to invest in new businesses and to improve traditionally low productivity. They need access to new, international markets for buying the goods. If these characteristics are not in place, then their economies cannot catch up. This is why the economies of some countries are diverging rather than converging (Abramovitz 1986). Another key characteristic of economic growth regards the implementation of technology. A developing country can bypass some steps of implementing technology that other nations faced earlier. Television and telephone systems are a good example. While developed countries spent significant time and money establishing elaborate system infrastructures based on metal wires or fiber-optic cables, developing countries today can go directly to cell phone and satellite transmission with much less investment. Another factor affects convergence concerning social structure. Early in their development, countries such as Brazil and Cuba had economies based on cash crops (coffee or sugarcane, for instance) grown on large plantations by unskilled workers. The elite ran the plantations and the government, with little interest in training and educating the populace for other endeavors. This restricted economic growth until the power of the wealthy plantation owners was challenged (Sokoloff and Engerman 2000). Improved economies generally lead to wider social improvement. Society benefits from improved educational systems and allowed people more time to devote to learning and leisure. Theoretical Perspectives on the Economy Now that we’ve developed an understanding of the history and basic components of economies, let’s turn to theory. How might social scientists study these topics? What questions do they ask? What theories do they develop to add to the body of sociological knowledge? Functionalist Perspective Someone taking a functional perspective will most likely view work and the economy as a well-oiled machine that is designed for maximum efficiency. The Davis-Moore thesis, for example, suggests that some social stratification is a social necessity. The need for certain highly skilled positions combined with the relative difficulty of the occupation and the length of time it takes to qualify will result in a higher reward for that job and will provide a financial motivation to engage in more education and a more difficult profession (Davis and Moore 1945). This theory can be used to explain the prestige and salaries that go with careers only available to those with doctorates or medical degrees. The functionalist perspective would assume that the continued health of the economy is vital to the health of the nation, as it ensures the distribution of goods and services. For example, we need food to travel from farms (high-functioning and efficient agricultural systems) via roads (safe and effective trucking and rail routes) to urban centers (high-density areas where workers can gather). However, sometimes a dysfunction––a function with the potential to disrupt social institutions or organization (Merton 1968)––in the economy occurs, usually because some institutions fail to adapt quickly enough to changing social conditions. This lesson has been driven home recently with the bursting of the housing bubble. Due to risky lending practices and an underregulated financial market, we are recovering from the after-effects of the Great Recession, which Merton would likely describe as a major dysfunction. Some of this is cyclical. Markets produce goods as they are supposed to, but eventually the market is saturated and the supply of goods exceeds the demands. Typically the market goes through phases of surplus, or excess, inflation, where the money in your pocket today buys less than it did yesterday, and recession, which occurs when there are two or more consecutive quarters of economic decline. The functionalist would say to let market forces fluctuate in a cycle through these stages. In reality, to control the risk of an economicdepression (a sustained recession across several economic sectors), the U.S. government will often adjust interest rates to encourage more lending—and consequently more spending. In short, letting the natural cycle fluctuate is not a gamble most governments are willing to take. Conflict Perspective For a conflict perspective theorist, the economy is not a source of stability for society. Instead, the economy reflects and reproduces economic inequality, particularly in a capitalist marketplace. The conflict perspective is classically Marxist, with the bourgeoisie (ruling class) accumulating wealth and power by exploiting and perhaps oppressing the proletariat (workers), and regulating those who cannot work (the aged, the infirm) into the great mass of unemployed (Marx and Engels 1848). From the symbolic (though probably made up) statement of Marie Antoinette, who purportedly said, “Let them eat cake” when told that the peasants were starving, to the Occupy Wall Street movement that began during the Great Recession, the sense of inequity is almost unchanged. Conflict theorists believe wealth is concentrated in the hands of those who do not deserve it. As of 2010, 20 percent of Americans owned 90 percent of U.S. wealth (Domhoff 2014). While the inequality might not be as extreme as in pre-revolutionary France, it is enough to make many believe that the United States is not the meritocracy it seems to be. Symbolic Interactionist Perspective Those working in the symbolic interaction perspective take a microanalytical view of society. They focus on the way reality is socially constructed through day-to-day interaction and how society is composed of people communicating based on a shared understanding of symbols. One important symbolic interactionist concept related to work and the economy is career inheritance. This concept means simply that children tend to enter the same or similar occupation as their parents, which is a correlation that has been demonstrated in research studies (Antony 1998). For example, the children of police officers learn the norms and values that will help them succeed in law enforcement, and since they have a model career path to follow, they may find law enforcement even more attractive. Related to career inheritance is career socialization—learning the norms and values of a particular job. Finally, a symbolic interactionist might study what contributes to job satisfaction. Melvin Kohn and his fellow researchers (1990) determined that workers were most likely to be happy when they believed they controlled some part of their work, when they felt they were part of the decision-making processes associated with their work, when they have freedom from surveillance, and when they felt integral to the outcome of their work. Sunyal, Sunyal, and Yasin (2011) found that a greater sense of vulnerability to stress, the more stress experienced by a worker, and a greater amount of perceived risk consistently predicted a lower worker job satisfaction. Summary Economy refers to the social institution through which a society’s resources (goods and services) are managed. The Agricultural Revolution led to development of the first economies that were based on trading goods. Mechanization of the manufacturing process led to the Industrial Revolution and gave rise to two major competing economic systems. Under capitalism, private owners invest their capital and that of others to produce goods and services they can sell in an open market. Prices and wages are set by supply and demand and competition. Under socialism, the means of production is commonly owned, and the economy is controlled centrally by government. Several countries’ economies exhibit a mix of both systems. Convergence theory seeks to explain the correlation between a country’s level of development and changes in its economic structure. Section Quiz Which of these is an example of a commodity? - A restaurant meal - Corn - A college lecture - A book, blog entry, or magazine article Hint: B When did the first economies begin to develop? - When all the hunter-gatherers died - When money was invented - When people began to grow crops and domesticate animals - When the first cities were built Hint: C What is the most important commodity in a postindustrial society? - Electricity - Money - Information - Computers Hint: C In which sector of an economy would someone working as a software developer be? - Primary - Secondary - Tertiary - Quaternary Hint: D Which is an economic policy based on national policies of accumulating silver and gold by controlling markets with colonies and other countries through taxes and customs charges? - Capitalism - Communism - Mercantilism - Mutualism Hint: C Who was the leading theorist on the development of socialism? - Karl Marx - Heidimarie Schwermer - Émile Durkheim - Adam Smith Hint: A The type of socialism now carried on by Russia is a form of ______ socialism. - centrally planned - market - utopian - zero-sum Hint: B Among the reasons socialism never developed into a political movement in the United States was that trade unions _________. - secured workers’ rights - guaranteed health care - broke up monopolies - diversified the workforce Hint: A Which country serves as an example of convergence? - Singapore - North Korea - England - Canada Hint: A Short Answer Explain the difference between state socialism with central planning and market socialism. In what ways can capitalistic and socialistic economies converge? Describe the impact a rapidly growing economy can have on families. How do you think the United States economy will change as we move closer to a technology-driven service economy? Further Research Green jobs have the potential to improve not only your prospects of getting a good job, but the environment as well. To learn more about the green revolution in jobs go to http://openstaxcollege.org/l/greenjobs One alternative to traditional capitalism is to have the workers own the company for which they work. To learn more about company-owned businesses check out: http://openstaxcollege.org/l/company-owned References Abramovitz, Moses. 1986. “Catching Up, Forging Ahead and Falling Behind.” Journal of Economic History 46(2):385–406. Retrieved February 6, 2012 (http://www.jstor.org/pss/2122171). Antony, James. 1998. “Exploring the Factors that Influence Men and Women to Form Medical Career Aspirations.” Journal of College Student Development 39:417–426. Bond, Eric, Sheena Gingerich, Oliver Archer-Antonsen, Liam Purcell, and Elizabeth Macklem. 2003. The Industrial Revolution—Innovations. Retrieved February 6, 2012 (http://industrialrevolution.sea.ca/innovations.html). Davis, Kingsley, and Wilbert Moore. 1945. “Some Principles of Stratification.” American Sociological Review 10:242–249. Diamond, J., and P. Bellwood. 2003. “Farmers and Their Languages: The First Expansions.” Science April 25, pp. 597-603. Domhoff, G. William. 2011. “Wealth Income and Power.” Who Rules America. Retrieved January 25, 2012 (http://www2.ucsc.edu/whorulesamerica/power/wealth.html). European Union. 2014."On the Road to EU Membership." Retrieved December 15, 2014. (http://europa.eu/about-eu/countries/on-the-road-to-eu-membership/index_en.htm). European Union. 2014. "EU Member Countries". Retrieved December 15, 2014. (http://europa.eu/about-eu/countries/member-countries/). Fidrmuc, Jan. 2002. “Economic Reform, Democracy and Growth During Post-Communist Transition.” European Journal of Political Economy 19(30):583–604. Retrieved February 6, 2012 (http://siteresources.worldbank.org/INTDECINEQ/Resources/fidrmuc.pdf). Goldsborough, Reid. 2010. "World's First Coin." Retrieved February 6, 2012 (http://rg.ancients.info/lion/article.html). Gregory, Paul R., and Robert C. Stuart. 2003. Comparing Economic Systems in the Twenty-First Century. Boston, MA: South-Western College Publishing. Greisman, Harvey C., and George Ritzer. 1981 “Max Weber ,Critical Theory, and the Administered World.” Qualitative Sociology 4(1):34–55. Retrieved February 6, 2012 (http://www.springerlink.com/content/k14085t403m33701/). Horne, Charles F. 1915. The Code of Hammurabi : Introduction.Yale University. Retrieved (http://avalon.law.yale.edu/subject_menus/hammenu.asp). Kenessey, Zoltan. 1987. “The Primary, Secondary, Tertiary and Quaternary Sectors of the Economy.” The Review of Income and Wealth 33(4):359–386. Kerr, Clark, John T. Dunlap, Frederick H. Harbison, and Charles A. Myers. 1960. Industrialism and Industrial Man. Cambridge, MA: Harvard University Press. Kohn, Melvin, Atsushi Naoi, Carrie Schoenbach, Carmi Schooler, and Kazimierz Slomczynski. 1990. “Position in the Class Structure and Psychological Functioning in the United States, Japan, and Poland.” American Journal of Sociology 95:964–1008. Maddison, Angus. 2003. The World Economy: Historical Statistics. Paris: Development Centre, OECD. Retrieved February 6, 2012 (http://www.theworldeconomy.org/). Marx, Karl, and Friedrich Engels. 1998 [1848]. The Communist Manifesto. New York: Penguin. Marx, Karl, and Friedrich Engels. 1988 [1844]. Economic and Philosophic Manuscripts of 1844 and the Communist Manifesto, translated by M. Milligan. New York: Prometheus Books. Mauss, Marcel. 1990 [1922]. The Gift: The Form and Reason for Exchange in Archaic Societies, London: Routledge. Merton, Robert. 1968. Social Theory and Social Structure. New York: Free Press. Proudhon, Pierre-Joseph. 2010 [1840]. Property Is Theft! A Pierre-Joseph Proudhon Anthology. Iain McKay Ed. Retrieved February 15, 2012 (http://anarchism.pageabode.com/pjproudhon/property-is-theft). Schwermer, Heidemarie. 2007. “Gib und Nimm.” Retrieved January 22, 2012 (http://www.heidemarieschwermer.com/). Schwermer, Heidemarie. 2011. Living Without Money. Retrieved January 22, 2012 (http://www.livingwithoutmoney.org). Sokoloff, Kenneth L., and Stanley L. Engerman. 2000. “History Lessons: Institutions, Factor Endowments, and Paths of Development in the New World.” Journal of Economic Perspectives 14(3)3:217–232. Sunyal, Ayda, Onur Sunyal, and Fatma Yasin. 2011. “A Comparison of Workers Employed in Hazardous Jobs in Terms of Job Satisfaction, Perceived Job Risk and Stress: Turkish Jean Sandblasting Workers, Dock Workers, Factory Workers and Miners.” Social Indicators Research 102:265–273. U.S. Bureau of Labor Statistics. 2011. “Employment by Major Industry Sector.” Retrieved February 6, 2012 (http://www.bls.gov/emp/ep_table_201.htm).	oercommons	2025-03-18T00:36:04.817184	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11831/overview", "title": "Introduction to Sociology 2e, Work and the Economy", "author": null }
https://oercommons.org/courseware/lesson/11832/overview	Globalization and the Economy Overview - Define globalization and describe its manifestation in modern society - Discuss the pros and cons of globalization from an economic standpoint What Is Globalization? Globalization refers to the process of integrating governments, cultures, and financial markets through international trade into a single world market. Often, the process begins with a single motive, such as market expansion (on the part of a corporation) or increased access to healthcare (on the part of a nonprofit organization). But usually there is a snowball effect, and globalization becomes a mixed bag of economic, philanthropic, entrepreneurial, and cultural efforts. Sometimes the efforts have obvious benefits, even for those who worry about cultural colonialism, such as campaigns to bring clean-water technology to rural areas that do not have access to safe drinking water. Other globalization efforts, however, are more complex. Let us look, for example, at the North American Free Trade Agreement (NAFTA). The agreement is among the countries of North America, including Canada, the United States, and Mexico and allows much freer trade opportunities without the kind of tariffs (taxes) and import laws that restrict international trade. Often, trade opportunities are misrepresented by politicians and economists, who sometimes offer them up as a panacea to economic woes. For example, trade can lead to both increases and decreases in job opportunities. This is because while easier, more lax export laws mean there is the potential for job growth in the United States, imports can mean the exact opposite. As the United States import more goods from outside the country, jobs typically decrease, as more and more products are made overseas. Many prominent economists believed that when NAFTA was created in 1994 it would lead to major gains in jobs. But by 2010, the evidence showed an opposite impact; the data showed 682,900 U.S. jobs lost across all states (Parks 2011). While NAFTA did increase the flow of goods and capital across the northern and southern U.S. borders, it also increased unemployment in Mexico, which spurred greater amounts of illegal immigration motivated by a search for work. There are several forces driving globalization, including the global economy and multinational corporations that control assets, sales, production, and employment (United Nations 1973). Characteristics of multinational corporations include the following: A large share of their capital is collected from a variety of different nations, their business is conducted without regard to national borders, they concentrate wealth in the hands of core nations and already wealthy individuals, and they play a key role in the global economy. We see the emergence of global assembly lines, where products are assembled over the course of several international transactions. For instance, Apple designs its next-generation Mac prototype in the United States, components are made in various peripheral nations, they are then shipped to another peripheral nation such as Malaysia for assembly, and tech support is outsourced to India. Globalization has also led to the development of global commodity chains, where internationally integrated economic links connect workers and corporations for the purpose of manufacture and marketing (Plahe 2005). For example, inmaquiladoras, mostly found in northern Mexico, workers may sew imported precut pieces of fabric into garments. Globalization also brings an international division of labor, in which comparatively wealthy workers from core nations compete with the low-wage labor pool of peripheral and semi-peripheral nations. This can lead to a sense of xenophobia, which is an illogical fear and even hatred of foreigners and foreign goods. Corporations trying to maximize their profits in the United States are conscious of this risk and attempt to “Americanize” their products, selling shirts printed with U.S. flags that were nevertheless made in Mexico. Aspects of Globalization Globalized trade is nothing new. Societies in ancient Greece and Rome traded with other societies in Africa, the Middle East, India, and China. Trade expanded further during the Islamic Golden Age and after the rise of the Mongol Empire. The establishment of colonial empires after the voyages of discovery by European countries meant that trade was going on all over the world. In the nineteenth century, the Industrial Revolution led to even more trade of ever-increasing amounts of goods. However, the advance of technology, especially communications, after World War II and the Cold War triggered the explosive acceleration in the process occurring today. One way to look at the similarities and differences that exist among the economies of different nations is to compare their standards of living. The statistic most commonly used to do this is the domestic process per capita. This is the gross domestic product, or GDP, of a country divided by its population. The table below compares the top 11 countries with the bottom 11 out of the 228 countries listed in the CIA World Factbook. \| Rank \| Country \| GDP - per capita (PPP) \| \|---\|---\|---\| \| 1 \| Qatar \| $102,100 \| \| 2 \| Liechtenstein \| $89,400 \| \| 3 \| Macau \| $88,700 \| \| 4 \| Bermuda \| $86,000 \| \| 5 \| Monaco \| $85,500 \| \| 6 \| Luxembourg \| $77,900 \| \| 7 \| Singapore \| $62,400 \| \| 8 \| Jersey \| $57,000 \| \| 9 \| Norway \| $55,400 \| \| 10 \| Falkland Islands (Islas Malvinas) \| $55,400 \| \| 11 \| Switzerland \| $54,800 \| \| 218 \| Guinea \| $1,100 \| \| 219 \| Tokelau \| $1,000 \| \| 220 \| Madagascar \| $1,000 \| \| 221 \| Malawi \| $900 \| \| 222 \| Niger \| $800 \| \| 223 \| Liberia \| $700 \| \| 224 \| Central African Republic \| $700 \| \| 225 \| Burundi \| $600 \| \| 226 \| Somalia \| $600 \| \| 227 \| Zimbabwe \| $600 \| \| 228 \| Congo, Democratic Republic of the \| $400 \| There are benefits and drawbacks to globalization. Some of the benefits include the exponentially accelerated progress of development, the creation of international awareness and empowerment, and the potential for increased wealth (Abedian 2002). However, experience has shown that countries can also be weakened by globalization. Some critics of globalization worry about the growing influence of enormous international financial and industrial corporations that benefit the most from free trade and unrestricted markets. They fear these corporations can use their vast wealth and resources to control governments to act in their interest rather than that of the local population (Bakan 2004). Indeed, when looking at the countries at the bottom of the list above, we are looking at places where the primary benefactors of mineral exploitation are major corporations and a few key political figures. Other critics oppose globalization for what they see as negative impacts on the environment and local economies. Rapid industrialization, often a key component of globalization, can lead to widespread economic damage due to the lack of regulatory environment (Speth 2003). Further, as there are often no social institutions in place to protect workers in countries where jobs are scarce, some critics state that globalization leads to weak labor movements (Boswell and Stevis 1997). Finally, critics are concerned that wealthy countries can force economically weaker nations to open their markets while protecting their own local products from competition (Wallerstein 1974). This can be particularly true of agricultural products, which are often one of the main exports of poor and developing countries (Koroma 2007). In a 2007 article for the United Nations, Koroma discusses the difficulties faced by “least developed countries” (LDCs) that seek to participate in globalization efforts. These countries typically lack the infrastructure to be flexible and nimble in their production and trade, and therefore are vulnerable to everything from unfavorable weather conditions to international price volatility. In short, rather than offering them more opportunities, the increased competition and fast pace of a globalized market can make it more challenging than ever for LDCs to move forward (Koroma 2007). The increasing use of outsourcing of manufacturing and service-industry jobs to developing countries has caused increased unemployment in some developed countries. Countries that do not develop new jobs to replace those that move, and train their labor force to do them, will find support for globalization weakening. Summary Globalization refers to the process of integrating governments, cultures, and financial markets through international trade into a single world market. There are benefits and drawbacks to globalization. Often the countries that fare the worst are those that depend on natural resource extraction for their wealth. Many critics fear globalization gives too much power to multinational corporations and that political decisions are influenced by these major financial players. Section Quiz Ben lost his job when General Motors closed U.S. factories and opened factories in Mexico. Now, Ben is very anti-immigration and campaigns for large-scale deportation of Mexican nationals, even though, logically, their presence does not harm him and their absence will not restore his job. Ben might be experiencing _____________. - xenophobia - global commodity chains - xenophilia - global assembly line Hint: A Which of the following is not an aspect of globalization? - Integrating governments through international trade - Integrating cultures through international trade - Integrating finance through international trade - Integrating child care through international trade Hint: D One reason critics oppose globalization is that it: - has positive impacts on world trade - has negative impacts on the environment - concentrates wealth in the poorest countries - has negative impacts on political stability Hint: B All of the following are characteristics of global cities, except: - headquarter multinational corporations - exercise significant international political influence - host headquarters of international NGOs - host influential philosophers Hint: D Which of the following is not a characteristic of multinational corporations? - A large share of their capital is collected from a variety of nationalities. - Their business is conducted without regard to national borders. - They concentrate wealth in the hands of core nations. - They are headquartered primarily in the United States. Hint: D Short Answer What impact has globalization had on the music you listen to, the books you read, or the movies or television you watch? What effect can immigration have on the economy of a developing country? Is globalization a danger to local cultures? Why, or why not? Further Research The World Social Forum (WSF) was created in response to the creation of the World Economic Forum (WEF). The WSF is a coalition of organizations dedicated to the idea of a worldwide civil society and presents itself as an alternative to WEF, which it says is too focused on capitalism. To learn more about the WSF, check out http://openstaxcollege.org/l/WSF References Abedian, Araj. 2002. “Economic Globalization: Some Pros and Cons.” Papers from the Sixth Conference of the International Environment Forum, World Summit on Sustainable Development. Johannesburg, South Africa. Retrieved January 24, 2012 (http://iefworld.org/dabed02.htm). Bakan, Joel. 2004. The Corporation: The Pathological Pursuit of Profit and Power.New York: Free Press. Bhagwati, Jagdish. 2004. In Defense of Globalization. New York: Oxford University Press. Boswell, Terry and Dimitris Stevis. 1997. “Globalization and International Labor Organization.” Work and Occupations 24:288–308. Central Intelligence Agency (CIA). 2014. "The World Factbook: Country Comparison: GDP Per Capita (PPP)." Retrieved December 15, 2014. (https://www.cia.gov/library/publications/the-world-factbook/rankorder/2004rank.html). Koroma, Suffyan. 2007. “Globalization, Agriculture, and the Least Developed Countries.” United Nations Ministerial Conference on the Least Developed Countries. Istanbul, Turkey. Plahe, Jagjit. 2005. “The Global Commodity Chain Approach (GCC) Approach and the Organizational Transformation of Agriculture.” Monash University. Retrieved February 6, 2012 (http://www.buseco.monash.edu.au/mgt/research/working-papers/2005/wp63-05.pdf). Parks, James. 2011. “Report: NAFTA Has Cost 683,000 Jobs and Counting,” AFL-CIO Blog, May 3. Retrieved February 6, 2012 (http://blog.aflcio.org/2011/05/03/report-nafta-has-cost-683000-jobs-and-counting). Sassen, Saskia. 2001. The Global City: New York, London, Tokyo. Princeton, NJ: Princeton University Press. Speth, James G., ed. 2003. Worlds Apart: Globalization and the Environment. Washington, DC: Island Press. The United Nations: Department of Economic and Social Affairs. 1973. “Multinational Corporations in World Development.” New York: United Nations Publication. Wallerstein, Immanuel. 1974. The Modern World System. New York: Academic Press.	oercommons	2025-03-18T00:36:04.853192	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11832/overview", "title": "Introduction to Sociology 2e, Work and the Economy", "author": null }
https://oercommons.org/courseware/lesson/11833/overview	Work in the United States Overview - Describe the current U.S. workforce and the trend of polarization - Explain how women and immigrants have changed the modern U.S. workforce - Understand the basic elements of poverty in the United States today The American Dream has always been based on opportunity. There is a great deal of mythologizing about the energetic upstart who can climb to success based on hard work alone. Common wisdom states that if you study hard, develop good work habits, and graduate high school or, even better, college, then you'll have the opportunity to land a good job. That has long been seen as the key to a successful life. And although the reality has always been more complex than suggested by the myth, the worldwide recession that began in 2008 took its toll on the American Dream. During the recession, more than 8 million U.S. workers lost their jobs, and unemployment rates surpassed 10 percent on a national level. Today, while the recovery is still incomplete, many sectors of the economy are hiring, and unemployment rates have receded. Real Money, Virtual Worlds If you are not one of the tens of millions gamers who enjoy World of Warcraft or other online virtual world games, you might not even know what MMORPG stands for. But if you made a living playing massively multiplayer online role-playing games (MMORPGs), as a growing number of enterprising gamers do, then massive multiplayer online role-playing games might matter a bit more. According to an article in Forbes magazine, the online world of gaming has been yielding very real profits for entrepreneurs who are able to buy, sell, and manage online real estate, currency, and more for cash (Holland and Ewalt 2006). If it seems strange that people would pay real money for imaginary goods, consider that for serious gamers the online world is of equal importance to the real one. These entrepreneurs can sell items because the gaming sites have introduced scarcity into the virtual worlds. The game makers have realized that MMORPGs lack tension without a level of scarcity for needed resources or highly desired items. In other words, if anyone can have a palace or a vault full of wealth, then what’s the fun? So how does it work? One of the easiest ways to make such a living is called gold farming, which involves hours of repetitive and boring play, hunting, and shooting animals like dragons that carry a lot of wealth. This virtual wealth can be sold on eBay for real money: a timesaver for players who don’t want to waste their playing time on boring pursuits. Players in parts of Asia engage in gold farming and play eight hours a day or more to sell their gold to players in Western Europe or North America. From virtual prostitutes to power levelers (people who play the game logged in as you so your characters get the wealth and power), to architects, merchants, and even beggars, online players can offer to sell any service or product that others want to buy. Whether buying a magic carpet in World of Warcraft or a stainless-steel kitchen appliance in Second Life, gamers have the same desire to acquire as the rest of us—never mind that their items are virtual. Once a gamer creates the code for an item, she can sell it again and again for real money. And finally, you can sell yourself. According to Forbes, a University of Virginia computer science student sold his World of Warcraft character on eBay for $1,200, due to the high levels of powers and skills it had gained (Holland and Ewalt 2006). So should you quit your day job to make a killing in online games? Probably not. Those who work hard might eke out a decent living, but for most people, grabbing up land that doesn’t really exist or selling your body in animated action scenes is probably not the best opportunity. Still, for some, it offers the ultimate in work-from-home flexibility, even if that home is a mountain cave in a virtual world. Polarization in the Workforce The mix of jobs available in the United States began changing many years before the recession struck, and, as mentioned above, the American Dream has not always been easy to achieve. Geography, race, gender, and other factors have always played a role in the reality of success. More recently, the increased outsourcing—or contracting a job or set of jobs to an outside source—of manufacturing jobs to developing nations has greatly diminished the number of high-paying, often unionized, blue-collar positions available. A similar problem has arisen in the white-collar sector, with many low-level clerical and support positions also being outsourced, as evidenced by the international technical-support call centers in Mumbai, India, and Newfoundland, Canada. The number of supervisory and managerial positions has been reduced as companies streamline their command structures and industries continue to consolidate through mergers. Even highly educated skilled workers such as computer programmers have seen their jobs vanish overseas. The automation of the workplace, which replaces workers with technology, is another cause of the changes in the job market. Computers can be programmed to do many routine tasks faster and less expensively than people who used to do such tasks. Jobs like bookkeeping, clerical work, and repetitive tasks on production assembly lines all lend themselves to automation. Envision your local supermarket’s self-scan checkout aisles. The automated cashiers affixed to the units take the place of paid employees. Now one cashier can oversee transactions at six or more self-scan aisles, which was a job that used to require one cashier per aisle. Despite the ongoing economic recovery, the job market is actually growing in some areas, but in a very polarized fashion. Polarization means that a gap has developed in the job market, with most employment opportunities at the lowest and highest levels and few jobs for those with midlevel skills and education. At one end, there has been strong demand for low-skilled, low-paying jobs in industries like food service and retail. On the other end, some research shows that in certain fields there has been a steadily increasing demand for highly skilled and educated professionals, technologists, and managers. These high-skilled positions also tend to be highly paid (Autor 2010). The fact that some positions are highly paid while others are not is an example of the class system, an economic hierarchy in which movement (both upward and downward) between various rungs of the socioeconomic ladder is possible. Theoretically, at least, the class system as it is organized in the United States is an example of a meritocracy, an economic system that rewards merit––typically in the form of skill and hard work––with upward mobility. A theorist working in the functionalist perspective might point out that this system is designed to reward hard work, which encourages people to strive for excellence in pursuit of reward. A theorist working in the conflict perspective might counter with the thought that hard work does not guarantee success even in a meritocracy, because social capital––the accumulation of a network of social relationships and knowledge that will provide a platform from which to achieve financial success––in the form of connections or higher education are often required to access the high-paying jobs. Increasingly, we are realizing intelligence and hard work aren’t enough. If you lack knowledge of how to leverage the right names, connections, and players, you are unlikely to experience upward mobility. With so many jobs being outsourced or eliminated by automation, what kind of jobs are there a demand for in the United States? While fishing and forestry jobs are in decline, in several markets jobs are increasing. These include community and social service, personal care and service, finance, computer and information services, and healthcare. The chart below, from the U.S. Bureau of Labor Statistics, illustrates areas of projected growth. The professional and related jobs, which include any number of positions, typically require significant education and training and tend to be lucrative career choices. Service jobs, according to the Bureau of Labor Statistics, can include everything from jobs with the fire department to jobs scooping ice cream (Bureau of Labor Statistics 2010). There is a wide variety of training needed, and therefore an equally large wage potential discrepancy. One of the largest areas of growth by industry, rather than by occupational group (as seen above), is in the health field. This growth is across occupations, from associate-level nurse’s aides to management-level assisted-living staff. As baby boomers age, they are living longer than any generation before, and the growth of this population segment requires an increase in capacity throughout our country’s elder care system, from home healthcare nursing to geriatric nutrition. Notably, jobs in farming are in decline. This is an area where those with less education traditionally could be assured of finding steady, if low-wage, work. With these jobs disappearing, more and more workers will find themselves untrained for the types of employment that are available. Another projected trend in employment relates to the level of education and training required to gain and keep a job. As the chart below shows us, growth rates are higher for those with more education. Those with a professional degree or a master’s degree may expect job growth of 20 and 22 percent respectively, and jobs that require a bachelor’s degree are projected to grow 17 percent. At the other end of the spectrum, jobs that require a high school diploma or equivalent are projected to grow at only 12 percent, while jobs that require less than a high school diploma will grow 14 percent. Quite simply, without a degree, it will be more difficult to find a job. It is worth noting that these projections are based on overall growth across all occupation categories, so obviously there will be variations within different occupational areas. However, once again, those who are the least educated will be the ones least able to fulfill the American Dream. In the past, rising education levels in the United States had been able to keep pace with the rise in the number of education-dependent jobs. However, since the late 1970s, men have been enrolling in college at a lower rate than women, and graduating at a rate of almost 10 percent less. The lack of male candidates reaching the education levels needed for skilled positions has opened opportunities for women, minorities, and immigrants (Wang 2011). Women in the Workforce Women have been entering the workforce in ever-increasing numbers for several decades. They have also been finishing college and going on to earn higher degrees at higher rate than men do. This has resulted in many women being better positioned to obtain high-paying, high-skill jobs (Autor 2010). While women are getting more and better jobs and their wages are rising more quickly than men's wages are, U.S. Census statistics show that they are still earning only 77 percent of what men are for the same positions (U.S. Census Bureau 2010). Immigration and the Workforce Simply put, people will move from where there are few or no jobs to places where there are jobs, unless something prevents them from doing so. The process of moving to a country is called immigration. Due to its reputation as the land of opportunity, the United States has long been the destination of all skill levels of workers. While the rate decreased somewhat during the economic slowdown of 2008, immigrants, both legal and illegal, continue to be a major part of the U.S. workforce. In 2005, before the recession arrived, immigrants made up a historic high of 14.7 percent of the workforce (Lowell et al. 2006). During the 1970s through 2000s, the United States experienced both an increase in college-educated immigrants and in immigrants who lacked a high school diploma. With this range across the spectrum, immigrants are well positioned for both the higher-paid jobs and the low-wage low-skill jobs that are predicted to grow in the next decade (Lowell et al. 2006). In the early 2000s, it certainly seemed that the United States was continuing to live up to its reputation of opportunity. But what about during the recession of 2008, when so many jobs were lost and unemployment hovered close to 10 percent? How did immigrant workers fare then? The answer is that as of June 2009, when the National Bureau of Economic Research (NEBR) declared the recession officially over, “foreign-born workers gained 656,000 jobs while native-born workers lost 1.2 million jobs” (Kochhar 2010). As these numbers suggest, the unemployment rate that year decreased for immigrant workers and increased for native workers. The reasons for this trend are not entirely clear. Some Pew research suggests immigrants tend to have greater flexibility to move from job to job and that the immigrant population may have been early victims of the recession, and thus were quicker to rebound (Kochhar 2010). Regardless of the reasons, the 2009 job gains are far from enough to keep them inured from the country’s economic woes. Immigrant earnings are in decline, even as the number of jobs increases, and some theorize that increase in employment may come from a willingness to accept significantly lower wages and benefits. While the political debate is often fueled by conversations about low-wage-earning immigrants, there are actually as many highly skilled––and high-earning––immigrant workers as well. Many immigrants are sponsored by their employers who claim they possess talents, education, and training that are in short supply in the U.S. These sponsored immigrants account for 15 percent of all legal immigrants (Batalova and Terrazas 2010). Interestingly, the U.S. population generally supports these high-level workers, believing they will help lead to economic growth and not be a drain on government services (Hainmueller and Hiscox 2010). On the other hand, illegal immigrants tend to be trapped in extremely low-paying jobs in agriculture, service, and construction with few ways to improve their situation without risking exposure and deportation. Poverty in the United States When people lose their jobs during a recession or in a changing job market, it takes longer to find a new one, if they can find one at all. If they do, it is often at a much lower wage or not full time. This can force people into poverty. In the United States, we tend to have what is called relative poverty, defined as being unable to live the lifestyle of the average person in your country. This must be contrasted with the absolute poverty that is frequently found in underdeveloped countries and defined as the inability, or near-inability, to afford basic necessities such as food (Byrns 2011). We cannot even rely on unemployment statistics to provide a clear picture of total unemployment in the United States. First, unemployment statistics do not take into account underemployment, a state in which a person accepts a lower paying, lower status job than their education and experience qualifies them to perform. Second, unemployment statistics only count those: - who are actively looking for work - who have not earned income from a job in the past four weeks - who are ready, willing, and able to work The unemployment statistics provided by the U.S. government are rarely accurate, because many of the unemployed become discouraged and stop looking for work. Not only that, but these statistics undercount the youngest and oldest workers, the chronically unemployed (e.g., homeless), and seasonal and migrant workers. A certain amount of unemployment is a direct result of the relative inflexibility of the labor market, considered structural unemployment, which describes when there is a societal level of disjuncture between people seeking jobs and the available jobs. This mismatch can be geographic (they are hiring in California, but most unemployed live in Alabama), technological (skilled workers are replaced by machines, as in the auto industry), or can result from any sudden change in the types of jobs people are seeking versus the types of companies that are hiring. Because of the high standard of living in the United States, many people are working at full-time jobs but are still poor by the standards of relative poverty. They are the working poor. The United States has a higher percentage of working poor than many other developed countries (Brady, Fullerton and Cross 2010). In terms of employment, the Bureau of Labor Statistics defines the working poor as those who have spent at least 27 weeks working or looking for work, and yet remain below the poverty line. Many of the facts about the working poor are as expected: Those who work only part time are more likely to be classified as working poor than those with full-time employment; higher levels of education lead to less likelihood of being among the working poor; and those with children under 18 are four times more likely than those without children to fall into this category. In 2009, the working poor included 10.4 million Americans, up almost 17 percent from 2008 (U.S. Bureau of Labor Statistics 2011). Most developed countries such as the United States protect their citizens from absolute poverty by providing different levels of social services such as unemployment insurance, welfare, food assistance, and so on. They may also provide job training and retraining so that people can reenter the job market. In the past, the elderly were particularly vulnerable to falling into poverty after they stopped working; however, pensions, retirement plans, and Social Security were designed to help prevent this. A major concern in the United States is the rising number of young people growing up in poverty. Growing up poor can cut off access to the education and services people need to move out of poverty and into stable employment. As we saw, more education was often a key to stability, and those raised in poverty are the ones least able to find well-paying work, perpetuating a cycle. There is great debate about how much support local, state, and federal governments should give to help the unemployed and underemployed. The decisions made on these issues will have a profound effect on working in the United States. Summary The job market in the United States is meant to be a meritocracy that creates social stratifications based on individual achievement. Economic forces, such as outsourcing and automation, are polarizing the workforce, with most job opportunities being either low-level, low-paying manual jobs or high-level, high-paying jobs based on abstract skills. Women's role in the workforce has increased, although women have not yet achieved full equality. Immigrants play an important role in the U.S. labor market. The changing economy has forced more people into poverty even if they are working. Welfare, Social Security, and other social programs exist to protect people from the worst effects of poverty. Section Quiz Which is evidence that the United States workforce is largely a meritocracy? - Job opportunities are increasing for highly skilled jobs. - Job opportunities are decreasing for midlevel jobs. - Highly skilled jobs pay better than low-skill jobs. - Women tend to make less than men do for the same job. Hint: C If someone does not earn enough money to pay for the essentials of life he or she is said to be _____ poor. - absolutely - essentially - really - working Hint: A About what percentage of the workforce in the United States are legal immigrants? - Less than 1% - 1% - 16% - 66% Hint: C Short Answer As polarization occurs in the U.S. job market, this will affect other social institutions. For example, if midlevel education won’t lead to employment, we could see polarization in educational levels as well. Use the sociological imagination to consider what social institutions may be impacted, and how. Do you believe we have a true meritocracy in the United States? Why, or why not? Further Research The role of women in the workplace is constantly changing. To learn more, check out http://openstaxcollege.org/l/women_workplace The Employment Projections Program of the U.S. Bureau of Labor Statistics looks at a ten-year projection for jobs and employment. To see some trends for the next decade, check out http://openstaxcollege.org/l/BLS References Autor, David. 2010. “The Polarization of Job Opportunities in the U.S. Labor Market Implications for Employment and Earnings.” MIT Department of Economics and National Bureau of Economic Research, April. Retrieved February 15, 2012 (http://econ-www.mit.edu/files/5554). Batalova, Jeanne, and Aaron Terrazas. 2010. “Frequently Requested Statistics on Immigrants and Immigration in the United States.” Migration Policy Institute. Retrieved February 6, 2012 (http://www.migrationinformation.org/USfocus/display.cfm?id=818). Brady, David, Andrew Fullerton, and Jennifer Moren Cross. 2010. “More Than Just Nickels and Dimes: A Cross-National Analysis of Working Poverty in Affluent Democracies.” Social Problems 57:559–585. Retrieved February 15, 2012 (http://www.soc.duke.edu/~brady/web/Bradyetal2010.pdf). DeNavas-Walt, Carmen, and Bernadette D. Proctor. 2013. "Income and Poverty in the United States: 2013." U.S. Census Bureau. Retrieved December 15, 2014. (https://www2.census.gov/library/publications/2014/demographics/p60-249.pdf). Hainmueller, Jens, and Michael J. Hiscox. 2010. “Attitudes Toward Highly Skilled and Low-Skilled Immigration: Evidence from a Survey Experiment.” American Political Science Review 104:61–84. Holland, Laurence H.M. and David M. Ewalt. 2006. “Making Real Money in Virtual Worlds,” Forbes, August 7. Retrieved January 30, 2012 (http://www.forbes.com/2006/08/07/virtual-world-jobs_cx_de_0807virtualjobs.html). Kochhar, Rokesh. 2010. “After the Great Recession: Foreign Born Gain Jobs; Native Born Lose Jobs.” Pew Hispanic Center, October 29. Retrieved January 29, 2012 (http://pewresearch.org/pubs/1784/great-recession-foreign-born-gain-jobs-native-born-lose-jobs). Lowell, Lindsay B., Julia Gelatt, and Jeanne Batalova. 2006. “Immigrants and Labor Force Trends: the Future, Past, and Present.” Migration Policy Institute Insight No. 17. Retrieved February 6, 2012 (http://www.migrationpolicy.org/ITFIAF/TF17_Lowell.pdf). U.S. Bureau of Labor Statistics. 2010. Occupational Outlook Handbook, 2006–2007 ed. Retrieved from February 15, 2012 (www.bls.gov/oco). U.S. Bureau of Labor Statistics. 2010. “Overview of the 2008-2018 Projections.” Occupational Outlook Handbook, 2010–2011 ed. Retrieved February 15, 2012 (http://www.bls.gov/oco/oco2003.htm#industry). U.S. Bureau of Labor Statistics. 2011. “A Profile of the Working Poor, 2009.” Retrieved January 25, 2012 (www.bls.gov/cps/cpswp2009.pdf). U.S Bureau of Labor Statistics. 2012. "Employment Projections–2010–20." U.S. Department of Labor. Retrieved December 15, 2014. (http://www.bls.gov/news.release/archives/ecopro_02012012.pdf). U.S. Bureau of Labor Statistics. 2013. "Occupational Employment Projections to 2022." Deoartment of Labor. Retrieved December 15, 2014. (http://www.bls.gov/opub/mlr/2013/article/pdf/occupational-employment-projections-to-2022.pdf). U.S. Bureau of Labor Statistics. 2013. "Table 7: Employment by Summary Education and Training Assignment, 2012 and Projected 2022." United States Department of Labor. Retrieved December 15, 2014. (http://www.bls.gov/news.release/ecopro.t07.htm). U.S. Census Bureau. 2010. “Income, Poverty, and Health Insurance Coverage in the United States.” Retrieved February 15, 2012 (http://www.census.gov/prod/2011pubs/p60-239.pdf). Wang, Wendy and Kim Parker. 2011. “Women See Value and Benefit of College; Men Lag Behind on Both Fronts.” Pew Social and Demographic Trends, August 17. Retrieved January 30, 2012 (http://www.pewsocialtrends.org/2011/08/17/women-see-value-and-benefits-of-college-men-lag-on-both-fronts-survey-finds/5/#iv-by-the-numbers-gender-race-and-education). Wheaton, Sarah. 2011. “Perry Repeats Socialist Charge Against Obama Policies.” New York Times, September 15. Retrieved January 30, 2012 (http://thecaucus.blogs.nytimes.com/2011/09/15/perry-repeats-socialist-charge-against-obama-policies).	oercommons	2025-03-18T00:36:04.887831	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11833/overview", "title": "Introduction to Sociology 2e, Work and the Economy", "author": null }
https://oercommons.org/courseware/lesson/15191/overview	\| Length \| nanometer \| nm \| 1 nm = 10−9 m \| - 1 mm = 0.039 inch - 1 cm = 0.394 inch - 1 m = 39.37 inches - 1 m = 3.28 feet - 1 m = 1.093 yards - 1 km = 0.621 miles \| \| micrometer \| µm \| 1 µm = 10−6 m \| \| millimeter \| mm \| 1 mm = 0.001 m \| \| centimeter \| cm \| 1 cm = 0.01 m \| \| meter \| m \| - 1 m = 100 cm - 1 m = 1000 mm \| \| kilometer \| km \| 1 km = 1000 m \| \| Mass \| microgram \| µg \| 1 µg = 10−6 g \| - 1 g = 0.035 ounce - 1 kg = 2.205 pounds \| \| milligram \| mg \| 1 mg = 10−3 g \| \| gram \| g \| 1 g = 1000 mg \| \| kilogram \| kg \| 1 kg = 1000 g \| \| Volume \| microliter \| µl \| 1 µl = 10−6 l \| - 1 ml = 0.034 fluid ounce - 1 l = 1.057 quarts - 1 kl = 264.172 gallons \| \| milliliter \| ml \| 1 ml = 10−3 l \| \| liter \| l \| 1 l = 1000 ml \| \| kiloliter \| kl \| 1 kl = 1000 l \| \| Area \| square centimeter \| cm2 \| 1 cm2 = 100 mm2 \| - 1 cm2 = 0.155 square inch - 1 m2 = 10.764 square feet - 1 m2 = 1.196 square yards - 1 ha = 2.471 acres \| \| square meter \| m2 \| 1 m2 = 10,000 cm2 \| \| hectare \| ha \| 1 ha = 10,000 m2 \| \| Temperature \| Celsius \| °C \| — \| 1 °C = 5/9 × (°F − 32) \|	oercommons	2025-03-18T00:36:04.909346	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15191/overview", "title": "Biology, Measurements and the Metric System", "author": null }
https://oercommons.org/courseware/lesson/15189/overview		oercommons	2025-03-18T00:36:04.926762	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15189/overview", "title": "Biology, The Periodic Table of Elements", "author": null }
https://oercommons.org/courseware/lesson/66273/overview	Demographic Composition of the Texas State Legislature Overview Demographic Composition of the Texas State Legislature Learning Objective At the end of this section, you will be able to: - Discuss the demographic composition of the Texas House of Representatives and the Texas Senate Introduction This section describes the demgraphic composition of the Texas House of Representatives and the Texas Senate General Description: Pale, Male, and Stale It’s often been said the Texas State Legislature is “pale, male, and stale.” This may not be quite as accurate as in the past, but the Texas State Legislature is predominantly white, male, and middle-aged, making it far less diverse than Texas as a whole. Descriptive data on the composition of the Texas State Legislature is available at the Legislative Reference Library. Partisan Makeup The Republican Party controls both the Texas State House of Representatives and the Texas State Senate: The Texas State House of Representatives currently has 83 Republicans and 67 Democrats. The Texas State Senate currently has 18 Republicans and 13 Democrats. Gender Makeup The Texas State Legislature is predominantly male. Although their overall count is growing, women remain incredibly outnumbered in the 87th Texas Legislature— just 48 of 181 seats in the House and Senate are currently held by women. Approximately 25% of the Texas State House of Representatives is female (112 males, 38 females) Approximately 32% of the Texas State Senate is female (21 males, 10 females) Taken together, only 27% of the total membership of the Texas State Legislature is female (48 of 181 total members). Notably, with the addition of Democrats Julie Johnson, Jessica González, and Erin Zwiener to the 86th Legislature in 2019, the number of legislators who identify as members of the LGBT community increased from two to five. Age Distribution Description \| House Members \| Senate Members \| Total \| Under 30 \| 0 \| 0 \| 0 \| 30 - 39 \| 16 \| 0 \| 16 \| 40 - 49 \| 43 \| 1 \| 44 \| 50 - 59 \| 44 \| 15 \| 59 \| 60 - 69 \| 29 \| 7 \| 36 \| 70 and over \| 17 \| 8 \| 2 \| Licenses and Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Kris S. Seago. License: CC BY: Attribution Revision and Adaptation: Composition of Texas Legislature. Authored by: John Osterman. License: CC BY: Attribution	oercommons	2025-03-18T00:36:04.957933	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66273/overview", "title": "Texas Government 2.0, The Texas Legislature, Demographic Composition of the Texas State Legislature", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/124433/overview	Vital Signs Theory Micro-credential - 2024- Common Cartridge(Blackboard) V1.2 Vital Signs Theory Micro-credential Course Files Vital Signs Theory Micro-credential Overview This resource contains the full course content for the Vital Signs Theory Micro-credential for healthcare and nursing students. This foundational level micro-credential takes 2-3 hours to complete and includes content formats such as powerpoint lectures, videos, articles, links, and images, assessments, as well as some interactive content. All content was created in collaboration with healthcare employers and SMEs in the healthcare field. Within this resource you will find: all course files, IMSCC file for embedding into Blackboard LMS, and resources and guidance documents for implementation. Vital Signs Theory Micro-credential Course content and Resources Course Description This micro-credential provides an in-depth understanding of vital signs, essential for healthcare professionals in monitoring and assessing patient health. Learners will build on their clinical skills by studying the theory around the four primary vital signs: temperature, pulse rate, respiratory rate, and blood pressure. Learners will understand the physiological mechanisms underlying each vital sign, enhancing comprehension of their importance in clinical practice. Normal ranges for vital signs across different age groups and conditions will be discussed, as well as the ability to identify when readings deviate from these norms. Potential causes of abnormal vital signs and determining appropriate next steps in patient care, including when to escalate concerns will be presented. The importance of maintaining patient safety during assessments and documentation of results will be emphasized. Skills: Blood Pressure \| Temperature \| Respirations \| Pulse \| Vital Signs \| Vital Signs Documentation \| Clinical Skills \| Patient Care \| Patient Safety About: The micro-credential is intended to be taken online independently. It should take between 2-3 hours to complete. It is a foundational level micro-credential, and has been developed with healthcare industry professionals from large healthcare employers in the state of CT. Course Files (ZIP Folder): This folder contains all course files, including PowerPoint presentations, images, and external documents. It also includes a course roadmap, which outlines the intended sequence for building the course from scratch. The embedded links document provides all resource links used within the micro-credential. SCORM File: This Common Cartridge file is designed to directly embed the entire course and its content into a compatible Learning Management System (LMS). It was used in Blackboard Ultra and is formatted to SCORM 1.2. Resources and Guidance Documents (ZIP Folder): This folder contains instructional resources and guidance for instructors on how to effectively use the provided materials. This content was created as part of the CT SHIP grant, lead by CT State Community College - Norwalk. https://ctstate.edu/workforce-development/microcredentials The total cost of CT Statewide Healthcare Industry Pathway project (CT SHIP) was $6.9M. $3.4M (49%) was funded through a U.S. Department of Labor – Employment and Training Administration grant and another $3.5M (51%) was committed through non-federal state and local resources. The Workforce product was funded by the 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 U.S Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on any linked sites and include, but not limited to, the accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership.	oercommons	2025-03-18T00:36:04.981325	02/06/2025	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/124433/overview", "title": "Vital Signs Theory Micro-credential", "author": "Renee Dunbar" }
https://oercommons.org/courseware/lesson/96129/overview	Calculus of Parametric Curves: Calculus 3 project by Briana Yang Overview This Project has been completed as part of a standard 10 weeks Calculus 3 asynhronous online course with optional WebEx office hours during Summer 2022 semester at MassBay Community College, Wellesley Hills, MA. Summary Author: Briana Yang Instructor: Igor V Baryakhtar Subject: Calculus 3 Course number: MA 202-700 Course type: Asynhronous online Semester: Summer 2022, 10 weeks College: MassBay Comminity College, MA Tags: Calculus, Project Based Learning, Active Learning Language: English Media Format: pdf License: CC-BY 4.0 All project content created by Briana Yang Content added to OER Commons by Igor V Baryakhtar	oercommons	2025-03-18T00:36:05.000145	Homework/Assignment	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/96129/overview", "title": "Calculus of Parametric Curves: Calculus 3 project by Briana Yang", "author": "Activity/Lab" }
https://oercommons.org/courseware/lesson/99500/overview	Gender inequalities #2 Gender Inequalities Overview Gender Inequalities and the our experinces as a research team. Ant 100 FY12 Arthur and Sahaja. Gender Inequalities and Its Negative Effect on the World. After our long journey of research, we put into the topic of empowerment of women and gender inequalties. Our team included me (Arthur Movsesyan) and my partner Sahaja. We worked on ways we could limit gender inequalaties and ways we can educate others so it stops. We saw some patterns of bias and agenda such as logical fallacies because a lot of the men we came up to during our research believed that all genders were treated equally. Some people don't know how it feels to be treated like crap because they aren't getting treated like this. Furthermore, this is why my team focused on educating others because we think a lack of education is the cause of this issue. Anthropology plays a big connection with our topic as it shows how unstable our country is with these inequalities. As all our research supported that the equality of all genders would play a big impact in our society by bettering women's resources and making both genders better connected. This goes to show how colonialism, sustainability, and anthropology are all related because all of them show how the world would be a better place by educating each other on whats wrong and humans taking control of their minds to find ways to make this world a better place. Its important to show growth within the economy and us as people overall. This relationship relates to our project as this is our resolution to limiting gender inequalities and finally ending it one day. We wanted to target everyone we can so, people can understand the hardships of women and together we can make a difference. Although this project was rough since, it was an online group project. Our team managed to do a successful job but, next time we need to work on our communication and set up more meetings with our professor to be on track within our work. We should have also met up more in person as we all split up in our own separate ways.	oercommons	2025-03-18T00:36:05.017072	12/17/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/99500/overview", "title": "Gender Inequalities", "author": "Arthur Movsesyan" }
https://oercommons.org/courseware/lesson/66278/overview	Introduction: Texas' Governor and Executive Branch Overview Introduction: Texas' Governor and Executive Branch Learning Objective By the end of this chapter, you will be able to: - Explain the structure and function of the executive branch of the Texas government Introduction In its 2019 session, the Texas Legislature failed to pass a “Sunset” bill that would have continued the existence of the Texas State Board of Plumbing Examiners. The bill had stalled amid controversy over whether or not to phase out this small agency and combine its functions into the larger Texas Department of Licensing and Regulation. Without passage of S.B. 621, Texas faced an interesting problem. With no law requiring plumbers to be licensed and no agency to license them, anybody with a pipe wrench could now go into the plumbing business, performing jobs from replacing a kitchen faucet to complex medical gas piping in a hospital with no license and no training. Shortly after the session, legislators realized what they had done. Some legislators, plumbers, city plumbing inspectors and others began calling for a special legislative session to fix the problem. Instead, Texas Governor Greg Abbott simply issued an executive order extending the existence of the state board through the next regular legislative session. How? "A qualified workforce of licensed plumbers throughout the state, including from areas not directly affected by Hurricane Harvey, will be essential as those funds are being invested in crucial infrastructure, medical facilities, living facilities, and other construction projects,” he said in his order. By extending the board through the next legislative session or until “disaster needs subside,” the governor was able to tap into sweeping powers given to his office to deal with natural disasters. How can a governor in a “weak governor” state sidestep the legislature and resurrect an agency despite legislation to the contrary? In this chapter, we’ll look at the executive branch of state government in Texas. Licensing and Attribution CC LICENSED CONTENT, ORIGINAL The Executive Department and the Office of the Governor of Texas: Introduction. Authored by: Andrew Teas. License: CC BY: Attribution	oercommons	2025-03-18T00:36:05.034331	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66278/overview", "title": "Texas Government 2.0, The Executive Department and the Office of the Governor of Texas, Introduction: Texas' Governor and Executive Branch", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/66284/overview	Glossary Overview Glossary Glossary: Texas' Governor and Executive Branch appointment: the power of the chief executive, whether the president of the United States or the governor of the state, to appoint persons to office. attorney general: an elected state official that serves as the state's chief civil lawyer bureaucracy: the complex structure of offices, tasks, rules, and principles of organization that is employed by all large-scale institutions to coordinate the work of their personnel. comptroller: an elected state official who directs the collection of taxes and other revenues, and estimates revenues for the budgeting process. executive budget: the state budget prepared and submitted by the governor of the legislature, which indicates the governor's spending priorities. land commissioner: an elected state official that acts as the manager of the most publicly-owned lands. lieutenant governor: the second-highest elected official in the state and president of the state senate line-item veto power: enables the governor to veto individual components (or lines) of an appropriations bill. plural executive: a group of officers or major officials that functions in making current decisions or in giving routine orders typically the responsibility of an individual executive officer or official. In Texas, the power of the Governor is limited and distributed amongst other government officials. secretary of state: the state official, appointed by the governor, whose primary responsibility is administering elections veto: the governor's power to turn down legislation; can be overridden by a two-thirds vote of both the House and Senate Licenses and Attributions CC LICENSED CONTENT, ORIGINAL The Executive Department and the Office of the Governor of Texas: Glossary Authored by: Andrew Teas. License: CC BY: Attribution	oercommons	2025-03-18T00:36:05.095129	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66284/overview", "title": "Texas Government 2.0, The Executive Department and the Office of the Governor of Texas, Glossary", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/87991/overview	Rise of Totalitarian Regimes Overview Totalitarianism One of the most disturbing developments of the Interwar Period, between the two world wars, was the rise of totalitarian regimes across the world. Totalitarianism emerged because of widespread dissatisfaction over the outcome and aftermath of the First World War, in conjunction with the exploitation of the impulse toward political democratization occurring across the world totalitarian leaders. These leaders seized control of countries around the world, playing to popular dissatisfaction, toward the end of pursuing their agendas of national and personal aggrandizement. The rise of such regimes, particularly in Italy, Japan, and Germany, led to disastrous consequences for humanity, first and foremost being the Second World War and the Holocaust. Learning Outcomes - Explain the global challenge to liberalism by totalitarianism through the movements of communism, fascism, and National Socialism. - Evaluate the factors that led to the global depression in the 1930s. - Compare and contrast the reactions of nations worldwide to this global depression. Key Terms / Key Concepts totalitarianism: an approach to government defined by a central authority exercising complete control over a society Benito Mussolini: fascist leader of World War II Italy and early fascist leader of post-WWI Europe Adolf Hitler: Nazi leader of World War II Germany, responsible for the Holocaust Totalitarianism After World War I totalitarianism emerged as an approach to government in nations across Eurasia. It was a reaction to the dissatisfaction felt by many citizens in nations where it took hold, including most notably Germany, Italy, and Japan. Totalitarianism is distinct from the absolutist governments of early modern Europe and is defined by the executive branch of a national government, usually the monarchy, enjoying complete control over the government, but not the society. Totalitarianism is also marked by a number of different characteristics, including authoritarianism, national and/or ethnic chauvinism, personality cults, and an industrialized approach to governance. The political developments and organizational and technological advances growing out of the Industrial Revolution made totalitarianism possible. Ironically, the most significant political development that contributed to the rise of totalitarian was the grant of nominal universal male suffrage. Totalitarian leaders such as Benito Mussolini and Adolf Hitler exploited this development, arguing that each had the mandate of his people. Before these developments and advances, during the early modern era, absolutist rulers such as Louis XIV of France could not conceive of totalitarian control over their countries. During the Interwar period totalitarianism took a number of different forms, including fascism and statism, in a range of attitudes toward the governed, from benign to malignant. Fascism Fascism is a form of radical authoritarian nationalism that came to prominence in early 20th-century Europe, characterized by one-party totalitarian regimes, which were run by charismatic dictators, as well as involved glorification of violence, and racist ideology. The first fascist movements emerged in Italy during World War I, then spread to other European countries. Opposed to liberalism, communism, and anarchism, fascism is usually placed on the far-right within the traditional left–right spectrum. Learning Outcomes - Explain the global challenge to liberalism by totalitarianism through the movements of communism, fascism, and National Socialism. - Evaluate the factors that led to the global depression in the 1930s. - Compare and contrast the reactions of nations worldwide to this global depression. Key Terms / Key Concepts fascism: a form of radical authoritarian nationalism that came to prominence in early 20th-century Europe, which holds that liberal democracy is obsolete and that the complete mobilization of society under a totalitarian one-party state is necessary to prepare a nation for armed conflict and to respond effectively to economic difficulties. liberalism - ideology based on the concept of equality of opportunity which emerged in early modern Europe, developed by participants in the Enlightenment, This ideology has become one of the principle ideologies in political and economic discourse, along with a basis for a number of national political parties. communism: a political, social, and economic movement and philosophy in which there are ideally no economic or social classes or private property and resources are owned equally by the people. Karl Marx developed this ideology, with Friedrich Engels, during the mid-nineteenth century in response to the Industrial Revolution. totalitarianism: an approach to government defined by a central authority exercising complete control over a society autarky: the economic and political concept of self-sufficiency Benito Mussolini: fascist leader of World War II Italy and early fascist leader of post-WWI Europe Factors and Developments underlying the Emergence of Totalitarian Regimes A number of factors and developments in the aftermath of World War I fueled the emergence of totalitarian regimes during the twenties and thirties. First, those countries which did succumb to totalitarianism, on both sides, were disappointed in the ending this conflict from them. Second, many, if not most supporters, sought simple and easy solutions to complex problems. Third, totalitarian rulers possessed charisma, even if it appealed to negative emotions. Fascist Ideologies Fascists saw World War I as a revolution that brought massive changes to the nature of war, society, the state, and technology. The advent of total war and the total mass mobilization of belligerent societies had broken down the distinction between civilians and combatants. A “military citizenship” arose in which all citizens were involved with the military in some manner during the war. The war resulted in the rise of a powerful state capable of mobilizing millions of people to serve on the front lines and providing economic production and logistics to support them, as well as having unprecedented authority to intervene in the lives of citizens. In the early twentieth century fascists believed that liberal democracy was obsolete, and they regarded the complete mobilization of society under a totalitarian one-party state as necessary to prepare a nation for armed conflict and respond effectively to economic difficulties. Such a state had to be led by a strong leader—such as a dictator and a martial government composed of the members of the governing fascist party—to forge national unity and maintain a stable and orderly society. Fascism rejected assertions that violence was automatically negative in nature; on the other hand, it viewed political violence, war, and imperialism as means that could achieve national rejuvenation. Fascists advocated a mixed economy with the principal goal of achieving autarky (self-sufficiency) through protectionist and interventionist economic policies. Reaching its apex during the twenties and thirties, fascism was repudiated by the end of the Second World War because of its association with the Axis Powers. Since the end of World War II in 1945, few parties have openly described themselves as fascist, and the term is instead now usually used pejoratively by political opponents. The terms neo-fascist or post-fascist are sometimes applied more formally to describe parties of the far right with ideologies similar to or rooted in 20th century fascist movements. Early History of Fascism The historian Zeev Sternhell has traced the ideological roots of fascism back to the 1880s, and in particular to the fin-de-siècle (French for “end of the century”) theme of that time. This ideology was based on a revolt against materialism, rationalism, positivism, bourgeois society, and democracy. The fin-de-siècle generation supported emotionalism, irrationalism, subjectivism, and vitalism. The fin-de-siècle mindset saw civilization as being in a crisis that required a massive and total solution. Its intellectual school considered the individual only one part of the larger collectivity, which should not be viewed as an atomized numerical sum of individuals. They condemned the rationalistic individualism of liberal society and the dissolution of social links in bourgeois society. The term fascist comes from the Italian word fascismo, derived from fascio meaning a bundle of rods, ultimately from the Latin word fasces. This was the name given to political organizations in Italy known as fasci—groups similar to guilds or syndicates. At first, it was applied mainly to organizations on the political left. The Fascists came to associate the term with the ancient Roman fasces or fascio littorio—a bundle of rods tied around an axe, an ancient Roman symbol of the authority of the civic magistrate carried by his lictors, which could be used for corporal and capital punishment at his command. The symbolism of the fasces suggested strength through unity: a single rod is easily broken, while the bundle is difficult to break. After the end of the World War I, fascism rose out of relative obscurity into international prominence, with fascist regimes forming most notably in Italy, Germany, and Japan, the three of which would be allied in World War II. Fascist Benito Mussolini seized power in Italy in 1922, and Adolf Hitler had successfully consolidated his power in Germany by 1933. Rise of Fascism in Italy After the First World War Italy became the first major European power to embrace fascism, with Benito Mussolini leading the way. Italy was one of a number of nations around the world which came under the control of various forms of totalitarian governments. Italy foreshadowed the emergence of fascism in other countries, and Mussolini became a model for other totalitarian leaders in Europe, including General Francisco Franco in Spain and Adolf Hitler in Germany. Learning Outcomes - Explain the global challenge to liberalism by totalitarianism through the movements of communism, fascism, and National Socialism. - Evaluate the factors that led to the global depression in the 1930s. - Compare and contrast the reactions of nations worldwide to this global depression. Key Terms / Key Concepts Benito Mussolini: fascist leader of World War II Italy and early fascist leader of post-WWI Europe Francisco Franco: a Spanish general who ruled over Spain as a dictator for 36 years from 1939 until his death (He took control of Spain from the government of the Second Spanish Republic after winning the Civil War, and was in power 1978, when the Spanish Constitution of 1978 went into effect.) Adolf Hitler: Nazi leader of World War II Germany, responsible for the Holocaust fascism: a form of radical authoritarian nationalism that came to prominence in early 20th-century Europe, which holds that liberal democracy is obsolete and that the complete mobilization of society under a totalitarian one-party state is necessary to prepare a nation for armed conflict and to respond effectively to economic difficulties. At the outbreak of World War I in August 1914, the Italian political left split over the war. While the Italian Socialist Party (PSI) opposed the war, a number of Italian revolutionary syndicalists supported war against Germany and Austria-Hungary on the grounds that their reactionary regimes had to be defeated to ensure the success of socialism. Angelo Oliviero Olivetti formed a pro-interventionist fascio called the Fasci of International Action in October 1914. Benito Mussolini, upon expulsion from his position as chief editor of the PSI’s newspaper Avanti! for his anti-German stance, joined the interventionist cause in a separate fascio. The fascists and the Italian political right held common ground: both held Marxism in contempt, discounted class consciousness, and believed in the rule of elites. Italian fascists began to accommodate themselves to Italian conservatives by making major alterations to its political agenda—abandoning its previous populism, republicanism, and anticlericalism, while adopting policies in support of free enterprise, and accepting the Roman Catholic Church and the monarchy as institutions in Italy. Fascists identified their primary opponents as the majority of socialists on the left who had opposed intervention in World War I. The first meeting of the Fasci of Revolutionary Action was held on January 24, 1915 and was led by Benito Mussolini. This group first used the term “fascism.” During the first meeting of this group in January 1915, Mussolini declared that it was necessary for Europe to resolve its national problems—including national borders of Italy and elsewhere—“for the ideals of justice and liberty for which oppressed peoples must acquire the right to belong to those national communities from which they descended.” Attempts to hold mass meetings were ineffective, and the organization was regularly harassed by government authorities and socialists. In the next few years, the relatively small group took various political actions. To appeal to Italian conservatives, fascism adopted policies such as promoting family values, including policies designed to reduce the number of women in the workforce by limiting the woman’s role to that of a mother. The fascists banned literature on birth control and increased penalties for abortion in 1926, declaring both crimes against the state. Though fascism adopted a number of positions designed to appeal to reactionaries, the Fascists sought to maintain fascism’s revolutionary character, with Angelo Oliviero Olivetti saying “Fascism would like to be conservative, but it will [be] by being revolutionary.” The Fascists supported revolutionary action and committed to secure law and order to appeal to both conservatives and syndicalists. Mussolini and Fascist Italy Prior to fascism’s accommodation of the political right, Fascism had been a small, urban, northern Italian movement that had about a thousand members. After aligning itself with Italian conservatives, the fascist party rose to prominence using violence and intimidation. In 1919, Benito Mussolini founded the Fasci Italiani di Combattimento in Milan, which became the Partito Nazionale Fascista (National Fascist Party) two years later. In 1920, militant strike activity by industrial workers reached its peak in Italy. Mussolini and the Fascists took advantage of the situation by allying with industrial businesses and attacking workers and peasants in the name of preserving order and internal peace in Italy. The Fascist movement’s membership soared to approximately 250,000 by 1921, with the New National Fascist Party (PNF) Mussolini organized in 1921. Italian fascism, under Mussolini’s control, was rooted in Italian nationalism and the desire to restore and expand Italian territories. Italian fascists deemed such territorial expansion necessary for a nation to assert its superiority and strength, as well as to avoid succumbing to decay. They claimed that modern Italy is the heir to ancient Rome and its legacy, and historically they supported the creation of an Italian Empire to provide spazio vitale (“living space”) for colonization by Italian settlers and to establish control over the Mediterranean Sea. Domestically Italian Fascism promoted a corporatist economic system, whereby employer and employee syndicates were linked together in associations to collectively represent the nation’s economic producers and work alongside the state to set national economic policy. This economic system intended to resolve class conflict through collaboration between the classes. Fascists Under Mussolini Seize Power Mussolini’s Fascist movement took control of the Italian government in 1922, ruling Italy until 1943. Fascist paramilitaries first struck at political opponents in a wave of strikes against socialist offices, along with the homes of socialist leaders. Included in their targets were the headquarters of socialist and Catholic labor unions in Cremona. The Fascists then escalated their strategy by violently occupying a number of northern Italian cities. Along with occupation, the Fascists imposed Italianization upon German-speaking people in Trent and Bolzano. After seizing these cities, the Fascists made plans to take Rome. The Fascists met little serious resistance from authorities in these strikes and occupations, which emboldened them in their next step to take control of Rome. On October 24, 1922, the Fascist party held its annual congress in Naples, where Mussolini ordered Blackshirts to take control of public buildings and trains, as well as converge on three points around Rome. The Fascists managed to seize control of several post offices and trains in northern Italy while the Italian government, led by a left-wing coalition, was internally divided and unable to respond to the Fascist advances. King Victor Emmanuel III of Italy thought the risk of bloodshed in Rome to disperse the Fascists was too high. Victor Emmanuel III decided to appoint Mussolini as Prime Minister of Italy. Mussolini arrived in Rome on October 30 to accept the appointment. Fascist propaganda aggrandized this event, known as “March on Rome,” as a “seizure” of power because of Fascists’ heroic exploits. Mussolini in Power Upon becoming Prime Minister of Italy, Mussolini had to form a coalition government, because the Fascists did not have control over the Italian parliament. Consequently, little drastic change in government policy occurred initially. Repressive police actions were limited at the beginning of Mussolini’s tenure as well. In addition, Mussolini’s coalition government pursued economically liberal policies under the direction of liberal finance minister Alberto De Stefani, a member of the Center Party, including balancing the budget through deep cuts to the civil service. The Fascists’ first attempt to entrench Fascism in Italy began with the Acerbo Law, which guaranteed a plurality of the seats in parliament to any party or coalition list in an election that received 25% or more of the vote. Through considerable Fascist violence and intimidation, the list won a majority of the vote, allowing many seats to go to the Fascists. In the aftermath of the election, a crisis and political scandal erupted after Socialist Party deputy Giacomo Matteoti was kidnapped and murdered by a Fascist. The liberals and the leftist minority in parliament walked out in protest in what became known as the Aventine Secession. During the latter half of the twenties Mussolini progressively solidified his totalitarian control over the government and the country. On January 3, 1925, Mussolini addressed the Fascist-dominated Italian parliament and declared that he was personally responsible for what happened, but insisted that he had done nothing wrong. He proclaimed himself dictator of Italy, assuming full responsibility over the government and announcing the dismissal of parliament. From 1925 to 1929, Mussolini’s fascists further solidified their control over the government and the country by denying opposition deputies access to Parliament and expanding censorship. In a December 1925 decree it was announced that Mussolini was responsible solely to the King. Between 1925 and 1927, Mussolini progressively dismantled virtually all constitutional and conventional restraints on his power, thereby solidifying his control over the government and the country. A law passed on Christmas Eve 1925 changed Mussolini’s formal title from “president of the Council of Ministers” to “head of the government” (though he was still called “Prime Minister” by most non-Italian outlets). Thereafter, he began styling himself as Il Duce (the leader). He was no longer responsible to Parliament and could be removed only by the king. While the Italian constitution stated that ministers were responsible only to the sovereign, in practice it had become all but impossible to govern against the express will of Parliament. The Christmas Eve law ended this practice and made Mussolini the only person competent to determine the body’s agenda. This law transformed Mussolini’s government into a de facto legal dictatorship. Local autonomy was abolished, and podestàs appointed by the Italian Senate replaced elected mayors and councils. Mussolini also extended his control over education, the press, and unions in Italy. All teachers in schools and universities had to swear an oath to defend the fascist regime. Newspaper editors were all personally chosen by Mussolini and no one without a certificate of approval from the fascist party could practice journalism. These certificates were issued in secret; Mussolini thus skillfully created the illusion of a “free press.” The trade unions were also deprived of independence and integrated into what was called the “corporative” system. The aim, although never completely achieved, was inspired by medieval guilds and was meant to place all Italians in various professional organizations or corporations under clandestine governmental control. Totalitarianism in Japan During the 1920s and the 1930s, a growing number of Japanese embraced political totalitarianism, ultranationalism, and militarism, in a mixture resembling fascism, culminating in militaristic leaders of the Army and Navy taking control of the Japanese government. As part of this process the Japanese government embarked upon an ambitious and aggressive effort to expand the Japanese empire westward across east Asia and eastward across the Pacific Ocean. Ultimately, this led to Japan’s defeat in the Second World War, the dismantling of the Japanese empire, and the end of Japan’s authoritarian government. Learning Outcomes - Explain the global challenge to liberalism by totalitarianism through the movements of communism, fascism, and National Socialism. - Evaluate the factors that led to the global depression in the 1930s. - Compare and contrast the reactions of nations worldwide to this global depression. Key Terms / Key Concepts totalitarianism: an approach to government defined by a central authority exercising complete control over a society militarism: the belief or the desire of a government or people for a country to maintain a strong military capability and be prepared to use it aggressively to defend or promote national interests; the glorification of the military; the ideals of a professional military class; the “predominance of the armed forces in the administration or policy of the state" statism: the belief that the state should control either economic or social policy or both, sometimes taking the form of totalitarianism, but not necessarily. It is effectively the opposite of anarchism Showa era: period in Japanese history corresponding to the reign of Emperor Showa (Hirohito) from 1926 to 1989 Treaty of Versailles: the most important of the peace treaties that ended World War I, which was signed on June 28, 1919, exactly five years after the assassination of Archduke Franz Ferdinand fascism: a form of radical authoritarian nationalism that came to prominence in early 20th-century Europe, which holds that liberal democracy is obsolete and that the complete mobilization of society under a totalitarian one-party state is necessary to prepare a nation for armed conflict and to respond effectively to economic difficulties. League of Nations: an intergovernmental organization founded on January 10, 1920, as a result of the Paris Peace Conference that ended the First World War; the first international organization whose principal mission was to maintain world peace. Its primary goals as stated in its Covenant included preventing wars through collective security and disarmament and settling international disputes through negotiation and arbitration. Statism in Japan Statism in Japan was a totalitarian political ideology which developed from the Meiji Restoration of 1868 into the 1930s. It is sometimes also referred to as Japanese fascism or Shōwa nationalism, after Japanese Emperor Showa (or Hirohito), who reigned as the emperor of Japan from 1926 to 1989. The period of Hirohito’s reign is also known as the Showa era. This statist movement dominated Japanese politics during the first part of the Shōwa period. It is characterized by a mixture of ideas including chauvinistic Japanese nationalism, militarism, and “state capitalism.”. Contemporary Japanese political philosophers and thinkers developed and advanced these ideas as part of their vision for Japan as an authoritarian and homogenous society with an empire that would stretch across the eastern half of Asia and the Pacific Ocean, making Japan one of the world’s leading powers. Development of Statist Ideology One of the catalysts for the development of statist ideology in Japan after World War I was the discriminatory treatment of Japan by Western Allied Powers. The 1919 Treaty of Versailles that ended World War I did not recognize the Empire of Japan’s territorial claims to the same extent that it did British and French imperial territorial claims. Subsequent international naval treaties between Western powers and the Empire of Japan, signed in Washington, D.C. in 1921 and in London in 1930, imposed prejudicial limitations on Japanese naval shipbuilding that put the Imperial Japanese Navy at a disadvantage vis-a-vis the British, the French, and the U.S. Navies. These measures were correctly considered by many in Japan as refusal by the Western powers to consider Japan an equal partner, as well as a part of a pattern of prejudicial treatment that Japan had had to endure at the hands of the Western power in its efforts to secure recognition as a world power since the 1868 Meiji Restoration. These treaties provoked a surge of nationalism among many Japanese, who saw the discriminatory provisions as a threat to Japanese interests. Consequently, ultranationalist leaders pushed for an end to Japanese participation in such conciliatory diplomacy that put the Japanese empire at a disadvantage. During the 1920s a growing number of Japanese came to reject economic, strategic, military, and diplomatic cooperation with the U.S. and European powers as prejudicial to Japanese interests. By 1931 many in Japan had come to accept military dictatorship and aggressive territorial expansion as the best ways to protect Japan. In the 1920s and 1930s, the supporters of Japanese statism used the slogan Showa Restoration, which implied that a new resolution was needed to replace the existing political order dominated by corrupt politicians and capitalists, with one which (in their eyes), would fulfill the original goals of the Meiji Restoration of direct Imperial rule via military proxies. Early Shōwa statism is sometimes given the retrospective label “fascism,” but this was not a self-appellation and it is not entirely clear that the comparison is accurate. When authoritarian tools of the state such as the Kempeitai were put into use in the early Shōwa period, they were employed to protect the rule of law under the Meiji Constitution from perceived enemies on both the left and the right. This included the Ministry of Home Affairs arresting left-wing political dissidents beginning in 1930. From 1930 through 1933 the Ministry made over 30,000 such arrests. Nationalist Politics during the Shōwa Period Left-wing groups had been subject to violent suppression by the end of the Taishō period, and radical right-wing groups, inspired by fascism and Japanese nationalism, rapidly grew in popularity. The extreme right became influential throughout the Japanese government and society, notably within the Kwantung Army, a Japanese army stationed in China along the Japanese-owned South Manchuria Railroad. During the Manchurian Incident of 1931, radical army officers bombed a small portion of the South Manchuria Railroad and, falsely attributing the attack to the Chinese, invaded Manchuria. The Kwantung Army conquered Manchuria and set up the puppet government of Manchukuo there without permission from the Japanese government. International criticism of Japan following the invasion led to Japan withdrawing from the League of Nations. The withdrawal from the League of Nations meant that Japan was politically isolated. Japan had no strong allies and its actions had been internationally condemned, while internally popular nationalism was booming. Local leaders such as mayors, teachers, and Shinto priests were recruited by the various movements to indoctrinate the populace with ultra-nationalist ideals. They had little time for the pragmatic ideas of the business elite and party politicians. Their loyalty lay to the emperor and the military. In March 1932 the “League of Blood” assassination plot and the chaos surrounding the trial of its conspirators further eroded the rule of democratic law in Shōwa Japan. In May of the same year, a group of right-wing Army and Navy officers succeeded in assassinating Prime Minister Inukai Tsuyoshi. The plot fell short of staging a complete coup d’état, but effectively ended rule by political parties in Japan. Japan’s expansionist vision grew increasingly bold. Many of Japan’s political elite aspired to have Japan acquire new territory for resource extraction and settlement of surplus population. These ambitions led to the outbreak of the Second Sino-Japanese War in 1937. After their victory in the Chinese capital, the Japanese military committed the infamous Nanking Massacre. The Japanese military failed to defeat the Chinese government led by Chiang Kai-shek and the war descended into a bloody stalemate that lasted until 1945. Japan’s stated war aim was to establish the Greater East Asia Co-Prosperity Sphere, a vast pan-Asian union under Japanese domination. Hirohito’s role in Japan’s foreign wars remains a subject of controversy, with various historians portraying him as either a powerless figurehead or an enabler and supporter of Japanese militarism. The United States opposed Japan’s invasion of China and responded with increasingly stringent economic sanctions intended to deprive Japan of the resources to continue its war in China. Japan reacted by forging an alliance with Germany and Italy in 1940, known as the Tripartite Pact, which worsened its relations with the U.S. In July 1941, the United States, Great Britain, and the Netherlands froze all Japanese assets when Japan completed its invasion of French Indochina by occupying the southern half of the country, further increasing tension in the Pacific. Decline of Democracy in Europe between the World Wars The development of fascism in Italy, Germany, and Spain occurred in the larger context of the decline of democracy in Europe. The conditions of economic hardship caused by the Great Depression brought about significant social unrest around the world, leading to a major surge of fascism and in many cases, the collapse of democratic governments in Europe. Learning Outcomes - Explain the global challenge to liberalism by totalitarianism through the movements of communism, fascism, and National Socialism. - Evaluate the factors that led to the global depression in the 1930s. - Compare and contrast the reactions of nations worldwide to this global depression. Key Terms / Key Concepts fascism: a form of radical authoritarian nationalism that came to prominence in early 20th-century Europe, which holds that liberal democracy is obsolete and that the complete mobilization of society under a totalitarian one-party state is necessary to prepare a nation for armed conflict and to respond effectively to economic difficulties. Beer Hall Putsch: a failed coup attempt by the Nazi Party leader Adolf Hitler to seize power in Munich, Bavaria, during November 8 – 9, 1923 (About two thousand men marched to the center of Munich where they confronted the police, resulting in the death of 16 Nazis and four policemen.) Adolf Hitler: Nazi leader of World War II Germany, responsible for the Holocaust Initial Surge of Fascism The March on Rome, through which Mussolini became Prime Minister of Italy, brought Fascism international attention. One early admirer of the Italian Fascists was Adolf Hitler, who, less than a month after the March, had begun to model himself and the Nazi Party upon Mussolini and the Fascists. The Nazis, led by Hitler and the German war hero Erich Ludendorff, attempted a “March on Berlin” modeled upon the March on Rome, which resulted in the failed Beer Hall Putsch in Munich in November 1923. The Nazis briefly captured Bavarian Minister President Gustav Ritter von Kahr and announced the creation of a new German government to be led by a triumvirate of von Kahr, Hitler, and Ludendorff. The Beer Hall Putsch was crushed by Bavarian police, and Hitler and other leading Nazis were arrested and detained until 1925. Another early admirer of Italian Fascism was Gyula Gömbös—leader of the Hungarian National Defence Association (known by its acronym MOVE) and a self-defined “national socialist.” In 1919 Gömbös spoke of the need for major changes in property and in 1923 stated the need for a “March on Budapest.” Though it was opposed to the Italian government due to Yugoslav border disputes with Italy, Yugoslavia briefly had a significant fascist movement: the Organization of Yugoslav Nationalists (ORJUNA). ORJUNA supported Yugoslavism and the creation of a corporatist economy, as well as opposed democracy and took part in violent attacks on communists. ORJUNA was dissolved in 1929 when the King of Yugoslavia banned political parties and created a royal dictatorship, though ORJUNA supported the King’s decision. Amid a political crisis in Spain involving increased strike activity and rising support for anarchism, Spanish army commander Miguel Primo de Rivera engaged in a successful coup against the Spanish government in 1923 and installed himself as a dictator as head of a conservative military junta that dismantled the established party system of government. Upon achieving power, Primo de Rivera sought to resolve the economic crisis by presenting himself as a compromise arbitrator figure between workers and bosses, and his regime created a corporatist economic system based on the Italian Fascist model. A variety of para-fascist governments that borrowed elements from fascism were formed during the Great Depression, including those of Greece, Lithuania, Poland, and Yugoslavia. In Lithuania in 1926, Antanas Smetona rose to power and founded a fascist regime under his Lithuanian Nationalist Union. The Great Depression and the Spread of Fascism The events of the Great Depression resulted in an international surge of fascism and the creation of several fascist regimes and regimes that adopted fascist policies. According to historian Philip Morgan, “the onset of the Great Depression…was the greatest stimulus yet to the diffusion and expansion of fascism outside Italy.” Fascist propaganda blamed the problems of the long depression of the 1930s on minorities and scapegoats: “Judeo-Masonic-bolshevik” conspiracies, left-wing internationalism, and the presence of immigrants.” In Germany, it contributed to the rise of the National Socialist German Workers’ Party, which resulted in the demise of the Weimar Republic and the establishment of the fascist regime under the leadership of Adolf Hitler: Nazi Germany. With the rise of Hitler and the Nazis to power in 1933, liberal democracy was dissolved in Germany, and the Nazis mobilized the country for war, with expansionist territorial aims against several countries. In the 1930s the Nazis implemented racial laws that deliberately discriminated against, disenfranchised, and persecuted Jews and other racial and minority groups. The Great Depression contributed to the growth of fascist movements elsewhere in Europe. Hungarian fascist Gyula Gömbös rose to power as Prime Minister of Hungary in 1932 and attempted to entrench his Party of National Unity throughout the country; he created an eight-hour workday and a 48-hour work week in industry, sought to entrench a corporatist economy, and pursued irredentist claims on Hungary’s neighbors. The fascist Iron Guard movement in Romania soared in political support after 1933, gaining representation in the Romanian government. An Iron Guard member assassinated Romanian prime minister Ion Duca. During the February 6, 1934 crisis, France faced the greatest domestic political turmoil since the Dreyfus Affair when the fascist Francist Movement and multiple far-right movements rioted en masse in Paris against the French government, resulting in major political violence. Totalitarianism beyond Europe Fascism also expanded its influence outside Europe, especially in East Asia, the Middle East, and South America. In China, Wang Jingwei’s Kai-tsu p’ai (Reorganization) faction of the Kuomintang (Nationalist Party of China) supported Nazism in the late 1930s. In Japan, a Nazi movement called the Tōhōkai was formed by Seigō Nakano. The Al-Muthanna Club of Iraq was a pan-Arab movement that supported Nazism and exercised its influence in the Iraqi government through cabinet minister Saib Shawkat, who formed a paramilitary youth movement. Learning Outcomes - Explain the global challenge to liberalism by totalitarianism through the movements of communism, fascism, and National Socialism. - Evaluate the factors that led to the global depression in the 1930s. - Compare and contrast the reactions of nations worldwide to this global depression. Key Terms / Key Concepts fascism: a form of radical authoritarian nationalism that came to prominence in early 20th-century Europe, which holds that liberal democracy is obsolete and that the complete mobilization of society under a totalitarian one-party state is necessary to prepare a nation for armed conflict and to respond effectively to economic difficulties. National Socialism: fascist and totalitarian ideology associated with Adolf Hitler, also known as Nazism, characterized by antisemitism, anticommunism, and scientific racism Several, mostly short-lived fascist governments and prominent fascist movements were formed in South America during this period. Argentine President General José Félix Uriburu proposed that Argentina be reorganized along corporatist and fascist lines. Peruvian president Luis Miguel Sánchez Cerro founded the Revolutionary Union in 1931 as the state party for his dictatorship; it was later taken over by Raúl Ferrero Rebagliati who sought to mobilize mass support for the group’s nationalism in a manner akin to fascism. Ferrero even started a paramilitary Blackshirts arm as a copy of the Italian group, although the Union lost heavily in the 1936 elections and faded into obscurity. In Paraguay in 1940, Paraguayan President General Higinio Morínigo began his rule as a dictator with the support of pro-fascist military officers, appealed to the masses, exiled opposition leaders, and only abandoned his pro-fascist policies after the end of World War II. The Brazilian Integralists, led by Plínio Salgado, claimed as many as 200,000 members, although following coup attempts it faced a crackdown from the Estado Novo of Getúlio Vargas in 1937. In the 1930s, the National Socialist Movement of Chile gained seats in Chile’s parliament and attempted a coup d’état that resulted in the Seguro Obrero massacre of 1938. Fascism in its Epoch Fascism in its Epoch is a 1963 book by historian and philosopher Ernst Nolte, widely regarded as his magnum opus and a seminal work on the history of fascism. The book, translated into English in 1965 as The Three Faces of Fascism, argues that fascism arose as a form of resistance to and a reaction against modernity. Nolte subjected German Nazism, Italian Fascism, and the French Action Française movements to a comparative analysis. Nolte’s conclusion was that fascism was the great anti-movement: it was anti-liberal, anti-communist, anti-capitalist, and anti-bourgeois. In Nolte’s view, fascism was the rejection of everything the modern world had to offer and was an essentially negative phenomenon. Nolte argued that fascism functioned at three levels: in the world of politics as a form of opposition to Marxism, at the sociological level in opposition to bourgeois values, and in the “metapolitical” world as “resistance to transcendence” (“transcendence” in German can be translated as the “spirit of modernity”). In regard to the Holocaust, Nolte contended that because Adolf Hitler identified Jews with modernity, the basic thrust of Nazi policies towards Jews had always aimed at genocide: “Auschwitz was contained in the principles of Nazi racist theory like the seed in the fruit.” Nolte believed that for Hitler, Jews represented “the historical process itself.” Attributions Images courtesy of Wikimedia Commons Title Image - Nürnberg, Reichsparteitag, SA- und SS-Appell, September 1934. Attribution: Bundesarchiv, Bild 102-04062A / Georg Pahl / CC-BY-SA 3.0, CC BY-SA 3.0 DE <https://creativecommons.org/licenses/by-sa/3.0/de/deed.en>, via Wikimedia Commons. Provided by: Wikipedia Location: https://commons.wikimedia.org/wiki/File:Bundesarchiv_Bild_102-04062A,_N%C3%BCrnberg,_Reichsparteitag,_SA-_und_SS-Appell.jpg License: CC BY-SA: Attribution-ShareAlike Boundless World History "The Rise of Fascism" Adapted from https://courses.lumenlearning.com/boundless-worldhistory/chapter/the-rise-of-fascism/ CC LICENSED CONTENT, SHARED PREVIOUSLY Curation and Revision. Provided by: Boundless.com. License: CC BY-SA: Attribution-ShareAlike CC LICENSED CONTENT, SPECIFIC ATTRIBUTION Italian Fascism. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Italian_Fascism. License: CC BY-SA: Attribution-ShareAlike Fascism. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism. License: CC BY-SA: Attribution-ShareAlike March_on_Rome.jpg. 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Located at: https://en.wikipedia.org/wiki/Showa_period. License: CC BY-SA: Attribution-ShareAlike History of Japan. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/History_of_Japan. License: CC BY-SA: Attribution-ShareAlike March_on_Rome.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism#/media/File:March_on_Rome.jpg. License: CC BY-SA: Attribution-ShareAlike Hitlermusso2_edit.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism#/media/File:Hitlermusso2_edit.jpg. License: CC BY-SA: Attribution-ShareAlike 400px-Emperor_Shu014dwa_Army_1938-1-8.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Showa_period#/media/File:Emperor_Showa_Army_1938-1-8.jpg. License: CC BY-SA: Attribution-ShareAlike Francoist Spain. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Francoist_Spain. License: CC BY-SA: Attribution-ShareAlike Francisco Franco. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Francisco_Franco. License: CC BY-SA: Attribution-ShareAlike Falangism. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Falangism. License: CC BY-SA: Attribution-ShareAlike March_on_Rome.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism#/media/File:March_on_Rome.jpg. License: CC BY-SA: Attribution-ShareAlike Hitlermusso2_edit.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism#/media/File:Hitlermusso2_edit.jpg. License: CC BY-SA: Attribution-ShareAlike 400px-Emperor_Shu014dwa_Army_1938-1-8.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Showa_period#/media/File:Emperor_Showa_Army_1938-1-8.jpg. License: CC BY-SA: Attribution-ShareAlike Francisco_Franco_en_1964.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Francisco_Franco#/media/File:Francisco_Franco_en_1964.jpg. License: CC BY-SA: Attribution-ShareAlike Fascism. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism. License: CC BY-SA: Attribution-ShareAlike Fascism and ideology. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism_and_ideology. License: CC BY-SA: Attribution-ShareAlike Fascism In Its Epoch. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism_In_Its_Epoch. License: CC BY-SA: Attribution-ShareAlike March_on_Rome.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism#/media/File:March_on_Rome.jpg. License: CC BY-SA: Attribution-ShareAlike Hitlermusso2_edit.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism#/media/File:Hitlermusso2_edit.jpg. License: CC BY-SA: Attribution-ShareAlike 400px-Emperor_Shu014dwa_Army_1938-1-8.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Showa_period#/media/File:Emperor_Showa_Army_1938-1-8.jpg. License: CC BY-SA: Attribution-ShareAlike Francisco_Franco_en_1964.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Francisco_Franco#/media/File:Francisco_Franco_en_1964.jpg. License: CC BY-SA: Attribution-ShareAlike Bundesarchiv_Bild_119-1486,_Hitler-Putsch,_Mu00fcnchen,_Marienplatz.jpg. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Fascism#/media/File:Bundesarchiv_Bild_119-1486,_Hitler-Putsch,_Munchen,_Marienplatz.jpg. License: CC BY-SA: Attribution-ShareAlike	oercommons	2025-03-18T00:36:05.148260	Neil Greenwood	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/87991/overview", "title": "Statewide Dual Credit World History, The Catastrophe of the Modern Era: 1919-Present CE, Chapter 13: Post WWI, Rise of Totalitarian Regimes", "author": "Anna McCollum" }
https://oercommons.org/courseware/lesson/87984/overview	The Russian Revolution, the Russian Civil War, and the Formation of the Soviet Union Overview The Russian Revolution: October 1917 On October 25, 1917, Bolshevik leader Vladimir Lenin led his leftist revolutionaries in a successful revolt against the ineffective Provisional Government, an event known as the October Revolution. The Revolution resulted not only in the dissolution of Russia’s Provisional Government but also the execution of Tsar Nicholas II and members of the royal family. The monarchy was then replaced with a communist government that ruled with an intolerant, and often violent, fist for over seventy years. This event remains the seminal turning point in Russian history and for much of Eastern Europe in the twentieth century. Learning Objectives - Explain the key events and people of the Russian Revolution of October 1917 - Examine the long-term consequences and legacies of the Russian Revolution Key Terms / Key Concepts Vladimir Lenin: lead revolutionary and head of the Bolshevik party during the October Russian Revolution in 1917 Leon Trotsky: head of the Petrograd Soviet; an intellectual socialist and eventual righthand man to Lenin soviets: small, locally-elected councils of men with ties to socialist ideas supporting workers, soldiers, and peasantry Bolsheviks: political party of Vladimir Lenin that was considered extreme, and later became the basis of the Russian communist party July Days: four to five days in mid-July 1917 when soldiers, sailors, and workers held armed protests against the Provisional Government “Peace, Land, Bread!”: Lenin’s famous slogan that won the heart and support of the Russian peasantry during his “April Theses” speech in April 1917 October Revolution: successful Russian Revolution that overthrew the democratic Provisional Government and established the Bolsheviks as a military dictatorship Execution of the royal family: plan hatched by Lenin and the Bolsheviks to eliminate any chance of a restoration of the imperial family in Russia Ipatiev House: site where the tsar and his family were executed by the Bolsheviks Background: Vladimir Lenin Vladimir Ilyich Ulyanov, forever remembered by his pseudonym, Lenin, was born some four-hundred miles southeast of Moscow in 1870 in the city of Simbirsk (now Ulyanovsk), Russia. Lenin grew up in a middle-class home and excelled in school. Before reaching adulthood, though, his comfortable lifestyle endured two personal catastrophes that, perhaps, shaped his future career. His father died unexpectedly from a brain bleed when Lenin was a teenager. Not long after, Lenin’s older brother, Alexander, was arrested and later executed for conspiring to assassinate the Tsar. Historians often cite these events as decisive turning points in young Lenin’s life. Ones that inspired the increasing revolutionary attitude that materialized during his time at Kazan University. Exceedingly intelligent, Lenin eventually attended law school. His passion, however, resided in the words of communism’s founder, Karl Marx. Lenin’s revolutionary activity began in earnest around the turn of the century. He moved to Saint Petersburg, married a Marxist schoolteacher, and began writing anti-monarchist, Marxist pieces. Notably, he wrote for the Marxist paper, Iskra (Spark in English). During his time writing for Iskra he adopted the pseudonym, “N. Lenin.” His activities ultimately resulted in several temporary exiles, notably to Zurich, Switzerland. But by the time of his exile, Lenin had recruited a strong group of supporters in Russia. One that would continue throughout his exile, and grow stronger during World War I. The February Revolution In many ways, February Revolution of 1917 was the opening act in the larger Russian Revolution that would occur in October 1917. For over two years, Russian urban populations had suffered from reduced to meager food and fuel rations because of Russian participation in World War I. In February 1917, women in Saint Petersburg led a protest for increased rations and government reform. The protests quickly gained momentum as people from all walks of life joined the revolt. Saint Petersburg’s streets filled with demonstrators. With the tsar at the front, Tsarina Alexandra was left to handle the growing crisis. Instead of confronting or comforting the crowd, Alexandra remained inside her palace with her children. Enormous strikes of hundreds of thousands of workers erupted across the city. From afar, Nicholas attempted to send his guards and policemen to quell the rebellion. Instead, most of his forces sided with the peasants. On March 15, 1917, Nicholas II abdicated. By doing so, the power in Russia fell from the hands of an imperial dynasty to a shaky Provisional Government. Importantly, while the Provisional Government under Alexander Kerensky initially acted as the governing body responsible for foreign affairs, a smaller group was gaining momentum in Russia: the soviets. These groups were small, usually local councils comprised of elected officials. These officials were characterized as anti-monarchal socialists who represented the goals of the people. Notably, Saint Petersburg was home to the Petrograd Soviet. At its head was a man who later became a close ally of Lenin—Leon Trotsky. As the Revolution gained momentum, so too did the power and popularity of the Soviets, as well as the most radical of the socialist movements, which was led by the Bolsheviks and headed by Vladimir Lenin. Vladimir Lenin’s return to Russia from his exile in Zurich, Switzerland is one of legend. News of the February Revolution had reached him, and he deemed it the right moment for a socialist state to take hold in Russia. But the question remained: how could he return to Russia from Switzerland? After several failed efforts, Lenin found an unlikely solution in the form of the German government. Eager to see Russia knocked out of the war and correctly believing that Lenin could help churn up the revolution in Russia, the Germans proposed a deal. They offered him safe passage from Zurich through Germany in a sealed train car that carried other Russian revolutionaries. The train passed into Sweden and Finland. Then Lenin slipped back into Russia in disguise. The German gamble would soon pay off as Lenin and his associates stirred up far more discontent and rebellion than the thousands of mutinying Russian soldiers at the front. On April 16, 1917, Lenin delivered a speech from Finland Station in Saint Petersburg titled the “April Theses.” In this speech, he highlighted the goals for his political party, the Bolsheviks. Among his demands was the claim that all power be handed over to the Soviets. He emerged as a champion of the workers, farmers, sailors, and soldiers by declaring, “Peace, Land, and Bread!" Neither he, nor his party, supported Russian war efforts. Instead, they supported peace, a redistribution of land among the working class, and improved diets for Russia’s suffering population. Unsurprisingly, as support for Lenin’s party grew, the popularity of the Provisional Government quickly diminished. The July Days The summer of 1917 proved far more challenging for Russia than anyone expected. With the tsar’s abdication, three-hundred years of imperial rule had ended overnight. The shaky Provisional Government made attempts to implement democratic rule, but they also chose to remain a committed ally in World War I. This decision likely caused their ultimate downfall. Russians across the country were exhausted and tired of the costs of World War I. Historians have since estimated that nearly two million Russian soldiers were killed in the war, while nearly five million were wounded. Combined these figures suggest that over half of Russia’s army was a casualty in World War I—a far higher figure than any other army in the war. Moreover, the war had exhausted Russia’s natural resources. In July, mobs of sailors, soldiers, and workers banded together to protest the Provisional Government’s decision to remain in the war. These armed demonstrations were known later as the July Days. The goal of demonstrators was to overthrow the Provisional Government—which the working class feared would still put too much government power in the hands of a few, educated elites. But due to disorganization among political factions, the coup failed. Lenin, the head of the Bolshevik Party, was temporarily forced to flee over the border into Finland. The October Revolution By the fall of 1917, Russian food and fuel scarcity ravaged St. Petersburg. Exhaustion and anger permeated every walk of society. For Lenin and the Bolsheviks, it was a perfect recipe for a revolution. Lenin slipped across the border from Finland and met with the man who would become his righthand—Leon Trotsky. As head of the Petrograd Soviet, Trotsky knew more about the city and its people than Lenin did. Together, they organized the foundation of the Russian Revolution. On October 25, 1917, the Bolsheviks organized forces and led an attack on the Provisional Government. Alexander Kerensky tried to organize forces to counter the attack but failed to find enough soldiers. Confronted by superior numbers, Kerensky was forced to flee for his life. The Provisional Government collapsed. Bolshevik forces stormed the tsar’s former residence, the Winter Palace, and seized innumerable priceless treasures, while simultaneously destroying all symbols associated with the imperial rule of the Romanovs. In a climactic moment, Lenin delivered a speech to a crowd that “all rule had passed to the Soviets.” Almost overnight, Russia had transformed from a fledgling democracy to a communist, military dictatorship unseen before (or since) in history. This dictatorship would later be revealed to the world as the Soviet Union. On October 26, the Bolsheviks presented The Decree on Land. It allowed peasants to seize private land from the nobility and redistribute it among themselves. The Bolsheviks viewed themselves as representing an alliance of workers and peasants and memorialized that understanding with the hammer and sickle on the red flag of the Soviet Union. Other decrees resulted in the following: - All private property was seized by the state. - All Russian banks were nationalized. - Private bank accounts were confiscated. - The Church’s properties (including bank accounts) were seized. - All foreign debts were repudiated. - Control of the factories was given to the Soviets. - Wages were fixed at higher rates than during the war, and a shorter, eight-hour working day was introduced. The success of the October Revolution transformed the Russian state into a soviet republic. A coalition of anti-Bolshevik groups attempted to unseat the new government in the Russian Civil War from 1918 to 1922, but they would prove horribly unsuccessful. The Last Days of the Romanovs In March 1917, the last Romanov tsar, Nicholas II, abdicated not only on behalf of himself, but also on behalf of his ailing, hemophiliac son, Alexei. His younger brother, Michael, also quickly refused the throne and was later murdered by Bolshevik supporters in the woods outside of Perm, near the Ural Mountains. Nicholas remained under house arrest with his wife, children, and a handful of servants at their home—Tsarskoe Selo—for six months. In August 1917, Alexander Kerensky decided to move the family to a more secure location, far removed from the capital city. With effort, the Romanovs were transported to a former governor’s palace in Tobolsk, Siberia. For nearly nine months, the family enjoyed relative peace. The tsar and his children enjoyed short walks, reading, music, and even such menial chores as sawing wood. However, conditions for the royal family took a turn for the worse in late 1917 after the Bolsheviks seized power in Saint Petersburg. Throughout all of this, the royal family remained steadfast in their Orthodox faith. Believing that their prayers would be answered and help would soon arrive. Their hopes were destined to be ill-founded. In April 1918, a seasoned Bolshevik guard prepared the family for a final relocation. This time, they would be moved right into the heart of Bolshevik territory. Though they did not know it, plans were made for the execution of the royal family. In April 1918, the family arrived at what would be their final location, the Ipatiev House in Yekaterinburg, Russia. Secretly nicknamed the “House of Special Purpose,” the grandiose home was designated as the future execution site of the royal family. Indeed, the final days of the Romanov family were, as one historian described, a “living Hell.” Bolshevik guards painted over the family’s windows, restricting their view to the outside world. Walks were limited to half-an-hour in a courtyard, once a day. Dinners were served to the royal family after they’d been spat into. And lewd drawings and innuendos were presented to the Romanov daughters. Moreover, the family remained under the constant guard of their Bolshevik captors who restricted their every action. In the early hours of July 17, 1918, Yakov Yurovsky, the chief Bolshevik guard, awoke the family and ordered them to get dressed. To quell their fears, he said the family was being transferred to a new location for their safety. The family was then led into the house cellar. Alexei, unable to walk due to a previous, severe hemophilia bleed, was carried by his father. The seven Romanovs then sat or stood with their servants and waited for instructions. Nearly an hour passed before the Bolshevik guards returned. This time, armed. Yakov Yurovsky said, “Your friends have tried to save you. They have failed you. We now must shoot you.” Reports indicate that the tsar, naïve to the end of his life, had only time to exclaim, “What? What?” before numerous shots were fired upon him. Nicholas and Alexandra died instantly. However, many of the untrained Bolshevik guards, little more than thugs, were uncomfortable executing the tsar’s children. An almost mystical charm initially seemed to protect the daughters. Reports of the events indicate that bullets ricocheted off their dresses, and the executioners resorted to using bayonets and the butt-ends of their rifles to attempt to murder Olga, Tatiana, Marie, and Anastasia. When that failed, Yurovsky and his lieutenant shot the daughters in the back of the head. Later, the executioners discovered the young women had sewn jewels into their dresses in such numbers that they had acted as bullet-proof vests. Yurovsky saw too, that amazingly Alexei had survived the execution. He walked to the “heir of all the Russias,” who still lay in his father’s arms, and savagely kicked the boy before shooting him twice in the back of the head. Similarly, each of the servants were brutally beaten and shot to death. The execution of the royal family had lasted far longer than planned. And the subsequent destruction and burial of the bodies in the Ural Mountains proved disorganized. Almost immediately, rumors circulated that one of the children, likely Anastasia, had survived the massacre and escaped. The rumors escalated in 1988 when the remains of the tsar, his wife, and three of their daughters were excavated and positively identified through DNA analysis. In 2007, though, the rumors were definitively quashed when the remains of Alexei, and his sister (likely Marie) were discovered and positively identified through DNA analysis. In recognition for their devout faith, the Russian Orthodox Church has proclaimed the seven Romanovs, “passion bearers” or members of the faith who remain devout in the hour of their death. This was based on accounts of the family trying to make the sign of the cross as they met their brutal deaths. Impact The Russian Revolution is a pivotal event in modern history. It not only extinguished imperial rule in Russia but also experiments in democracy. The Bolshevik party would reorganize themselves and become the backbone of Soviet communism during the 1920s. Today, the legacies of the Russian Revolution remained mixed. While the rights of workers and the lower classes were touted as the future backbone of Russia, enacting those measures proved difficult. The country erupted into a violent civil war at the end of World War I, as well as engaged in equally brutal wars across parts of Eastern Europe, notably Poland and Ukraine. Moreover, the largest communist and military dictatorship in history would emerge in the shape of the Soviet Union. The Russian Civil War and the Formation of the Soviet Union The Russian Civil War, which erupted 1918 shortly after the October Revolution, was fought mainly between the “Reds,” led by the Bolsheviks, and the “Whites,” a politically diverse coalition of anti-Bolsheviks. An excessively brutal and bloody conflict, it ended in a Bolshevik victory in 1921. By the end of 1922, a pair of treaties had been signed between Russia and territories from present-day Ukraine, Belarus, and Georgia. Thus, the Soviet Union was born. Learning Objectives - Understand the course of the Russian Civil War and its legacies. - Examine the reasons for the formation of the Soviet Union. - Evaluate the pros and cons of the building of the Soviet Union. Key Terms / Key Concepts Red Army: fighting force that supported Lenin, the Russian Revolution, and Bolshevism during the Russian Civil War White Army: fighting force that did not support the Russian Revolution, Lenin, or Bolshevism during the Russian Civil War Russian Civil War: excessively bloody civil war in Russia (1918 – 1921) between the Bolshevik Red Army and the anti-Bolshevik forces, known as the White Army The Red Terror: brutal campaign of elimination and suppression carried out by the Bolsheviks against political enemies during the Russian Civil War The White Terror: brutal campaign of elimination of Bolshevik forces during the Russian Civil War by the White Army, which included mass-murders Soviet Union (USSR): formed in 1922, the union of the communist Russian state with territory from present-day Ukraine, Belarus, and Georgia, that expanded through the subsequent decades Communism: a political, social, and economic movement and philosophy in which there are ideally no economic or social classes or private property and resources are owned equally by the people Cheka: secret police of the Soviet Union that was infamous for its use of violence in the suppression of dissenters and political enemies during the Russian Civil War and after New Economic Plan (NEP): Soviet economic program in which the Russian state would control all significant industry and financial agencies, while individuals could own small plots of land and engage in low-level trade for personal benefit Kulaks: Russian peasant farmers who were considered “wealthy” by the Bolsheviks and targeted as enemies of the communist state war communism: Bolshevik economic practice in the Civil War that allowed the state to seize grain and crop yields to feed the Red Army The Russian Civil War The Russian Civil War (1917 – 1922) was a multi-party war in the former Russian Empire fought immediately after the Russian Revolution of 1917 during which many groups vied to determine Russia’s future. The two largest combatant groups were the Red Army, fighting for the Bolshevik form of socialism, and the loosely allied forces known as the White Army, which included groups with diverse interests. Some favored monarchism, while others favored capitalism or alternative forms of socialism. The White Army had support from Great Britain, France, the U.S., and Japan, while the Red Army possessed internal support, which ultimately proved much more effective. Background In 1917, Russia was a massive, multi-ethnic country that struggled to prosper under tsarist rule; additionally, it suffered enormously in World War I. It is perhaps, no wonder that the country would quickly dissolve into civil war following the chaos of the October Revolution, as agendas and vying viewpoints clashed. Lenin won support of the workers and small-time farmers by declaring, “Peace, Land, Bread!” And in 1918, Russia signed the Treaty of Brest-Litovsk which ceded significant Russian territory over to Germany, including the Baltic states. Many Russians who had supported the Revolution of 1917 turned against the Bolsheviks following the ratification of the Treaty of Brest-Litovsk. This division sparked the Russian Civil War. For Lenin and his associates, “civil war” was an inevitable step in constructing a communist state, just as class-conflict was a critical step of Marxist theory. For Lenin and the Bolsheviks, it was a step that would inflict mass suffering and casualties, but one that was essential in securing their state. In Bolshevik theory, civil war would root-out the “enemies of the people,” such as monarchists, foreigners, and capitalists. When the war ended, only true people of the communist state would remain. Only then could the state operate in harmony. At the heart of their conflict was the war on the kulaks—Russian farmers who were considered “wealthy” because the had larger farms than their neighbors. Many of Lenin’s inner circle believed the kulaks should be eradicated. To the Bolsheviks, these were people who triumphed over their neighbors for personal profit and supported capitalism. In reality, the kulaks typically were not much better off than many of their neighbors. While most Russian farmers worked on a farm for survival and subsistence, the kulaks might own their own farm of ten or twelve acres and have a few more cows or pigs than the average peasant. But that did not stop the Bolsheviks from waging war on them. War on the Battlefield War erupted in Russia between the “Reds” and “Whites” almost immediately following the October Revolution and escalated after the ratification of the Treaty of Brest-Litovsk. Each side had specific advantages. For the White Army, their strongest advantage was the (limited) support from abroad. Western nations such as England and the United States were democratic and anxious that the Bolshevik’s communist revolution could spread across Europe if it proved successful in Russia. Possibly, it could even spread to the United States were socialism had a small but strong following, thus upending democratic and capitalist values. American, English, and Japanese troops fought on the side of the White Army along Russia’s periphery borders, most notably in far eastern Russia near Vladivostok. But while well-intentioned, the Allies were exhausted from fighting the Germans in World War I. As a result, their military efforts were minimal and had the ultimate effect of leaving the White Army to fight on its own. The Red Army, by contrast, had limited outside support. However, under the careful Organization of Leon Trotsky, the Red Army was exceedingly disciplined and organized. Moreover, it largely was supported by the Russian peasantry. Volunteers and conscripted soldiers swelled the size of the Red Army to over five million at the end of the war. For over three years, the two sides clashed across the Russian landscape, notably in present-day Ukraine and Belarus, the Baltic states, Georgia, and far-eastern Russia. Mass casualties resulted among soldiers and civilians alike as the rules of warfare dissolved and terror raged on both sides. The Red Terror Civil war engulfed Russia immediately following the October Revolution. The two dominant sides of the war were the Red and White Armies. But Lenin had to worry about more than winning a war against a rival army on the battlefield. He also worried about political dissenters among the civilians. Internal, political enemies constituted a significant threat for him. To combat this threat, Lenin created secret police—the Cheka. In August 1918, Lenin narrowly escaped an assassination attempt. This close call gave him the pretext he needed to increase the power of the Cheka. In fact, the agency operated with almost unlimited power. Lenin advocated openly for the agency to use terror and violence to destroy enemies of Bolshevism indiscriminately. His telegram to fellow Bolshevik leaders instructed, “Hang no fewer than one-hundred well-known kulaks, rich-bags, blood-suckers (and make sure the hanging takes place in full view of the people).” By the end of 1918 alone, the Cheka officially reported the execution of nearly 13,000 people. Historians suspect the number to be significantly higher, possibly in the hundreds of thousands. Headed by Lenin’s close associate, Felix Dzerzhinsky, the Cheka acted with brutal force. Not restricted to simply identifying anti-Bolsheviks, the organization waged war against all “enemies of the people.” This included enemies on and off the battlefield. They carried out mass executions, arrests, and imprisonments. Anyone who could potentially be classified as anti-Bolshevik (or anti-communism) was targeted, including intellectuals, church clergy, the middle class, and monarchists. The agency increased its activity and persecution of the opposition as the Russian Civil War continued. The White Terror While the “Red Terror” is remembered because of the Bolshevik victory in the Civil War, there was also a “White Terror” on the battlefield. The “White Terror” were wartime atrocities perpetrated by soldiers in the White Army against the Red Army, civilians, socialists, and revolutionaries; particularly in Eastern Russia. Estimates vary widely on the casualties inflicted on Red Army soldiers and civilians during the White Terror. Some figures suggest twenty-thousand perished, while other numbers suggest the casualties were in the hundreds of thousands. Most of these deaths resulted from mass executions and indiscriminate killings. Notably, the White Army targeted Jews as part of the White Terror. Seen as the natural allies of the Bolsheviks because of communist ideology, the White Army carried out mass executions and killings of Jews in the regions of present-day Ukraine and Georgia. The Effects of "War Communism" In 1917, Lenin and the Bolsheviks introduced a method for sustaining their war effort known as “war communism.” This allowed the Bolsheviks to seize grain and farm yields to feed the Red Army. But it had the unintended, negative effect of forcing urban workers to the countryside to help farm and feed the growing army. As a result, production of industrial goods decreased dramatically. And while the Red Army remained fed, Russian and Ukrainian civilians and farmers starved. In 1921, a massive famine broke out and killed an estimated five million people, mostly civilians. It would not be the last famine wrought by Soviet economic planning. Resistance emerged among the working class, but with his powerful Cheka at his beckoning call, Lenin brutally suppressed all dissent. By the end of the Civil War, between 7 and 12 million people had perished due to the fighting and famine. And the casualties were mostly civilians. Conclusion of the Civil War The Red Army defeated the White Armed Forces of South Russia in Ukraine in 1919. The remains of the White forces were beaten at the island of Crimea in the Black Sea and evacuated in late 1920. Lesser battles of the war continued for two more years. Minor skirmishes with the remnants of the White forces in the Far East continued into 1923. Formation of the Soviet Union The government of the Soviet Union was formed in 1922 with the unification of the Russian, Transcaucasian, Ukrainian, and Byelorussian republics. It was based on the one-party rule of the Communist Party (Bolsheviks), who increasingly developed a totalitarian regime, especially during the reign of Joseph Stalin (1924 – 1953). Creation of the USSR and Early Years On December 29, 1922, a conference of delegations from Russia, Transcaucasia, Ukraine, and Byelorussia (Belarus) approved the Treaty on the Creation of the USSR and the Declaration of the Creation of the USSR, forming the Union of Soviet Socialist Republics (USSR). On February 1, 1924, the USSR was recognized by the British Empire. The same year, a Soviet Constitution was approved, legitimizing the union. An intensive restructuring of the economy, industry, and politics of the country began in the early days of Soviet power in 1917. A large part of this was done according to the Bolshevik Initial Decrees—government documents signed by Vladimir Lenin. One of the most prominent breakthroughs was a plan that envisioned a major restructuring of the Soviet economy based on total electrification of the country. The plan was developed in 1920 and covered a 10- to 15-year period. It included the construction of a network of 30 regional power stations, including ten large hydroelectric power plants and numerous electric-powered large industrial enterprises. The plan became the prototype for subsequent Five-Year Plans and was fulfilled by 1931. In 1921, the Bolsheviks had abandoned their war communism economic plan. In its place emerged the New Economic Policy (NEP). The peasants were freed from wholesale levies of grain and allowed to sell their surplus produce in the open market. Commerce was stimulated by permitting private retail trading. However, the state continued to be responsible for all major business ventures, including banking, transportation, heavy industry, and public utilities. Although the left opposition among the Communists criticized the rich peasants, or kulaks, who benefited from the NEP, the program proved highly beneficial, reviving the economy. The NEP would later come under increasing opposition from within the party following Lenin’s death in early 1924. Significance From 1917 – 1922, Russia was in complete turmoil. The tsarist regime was forever destroyed, exercises in democracy eliminated, and strongman Vladimir Lenin became the face of the Bolshevik effort to establish a communist nation. The Russian Civil War erupted and produced excessive and extreme violence wherever the Red and White Armies waged war; and civilians bore the brunt of the violence on both sides of the conflict. The war marked an ominous start for a new government that claimed to be representing the interests of the peasants. For Lenin and his inner circle though, excessive violence was a necessary step to secure a true, communist nation. While Lenin is responsible for many of the agencies and policies that perpetrated such violence, the Soviet Union would experience a far more ruthless military dictator under Lenin’s successor—Joseph Stalin. Attributions All images from Wikimedia Commons Cole, Joshua and Carol Symes. Western Civilizations: Their History and Their Culture. 3rd Ed. W.W. Norton & Company, New York: 2020. 862-4; 879-881. Service, Robert. A History of Modern Russia: From Nicholas II to Vladimir Putin. Harvard University Press, Cambridge: 2003. 101-122. Boundless World History, “The Russian Revolution” https://courses.lumenlearning.com/boundless-worldhistory/chapter/the-russian-revolution/ https://creativecommons.org/licenses/by-sa/4.0/	oercommons	2025-03-18T00:36:05.214123	Neil Greenwood	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/87984/overview", "title": "Statewide Dual Credit World History, The Catastrophe of the Modern Era: 1919-Present CE, Chapter 13: Post WWI, The Russian Revolution, the Russian Civil War, and the Formation of the Soviet Union", "author": "Anna McCollum" }
https://oercommons.org/courseware/lesson/109847/overview	OpenStax Anatomy and Physiology textbook, 2nd edition Overview I have been teaching Human Anatomy and Physiology at Central Arziona College (CAC) for 25 years. About 3 years ago, the Dean of Academics expressed concern over the cost of the text and lab book for our 2 semester A&P classes. I volunteered to lead an appointed committee to look into OER for anantomy and physiology. The Openstax textbook quickly became the choice of the committee members. After teaching a pilot class with the Openstax textbook, all CAC 2 semester A&P classes switched over to it. We have been using it for all our A& P classes, both on campus and online, for about 1.5 years. Student feedback has been very positive. I have been teaching Human Anatomy and Physiology at Central Arziona College (CAC) for 25 years. About 3 years ago, the Dean of Academics expressed concern over the cost of the text and lab book for our 2 semester A&P classes. I volunteered to lead an appointed committee to look into OER for anantomy and physiology. The Openstax textbook quickly became the choice of the committee members. After teaching a pilot class with the Openstax textbook, all CAC 2 semester A&P classes switched over to it. We have been using it for all our A& P classes, both on campus and online, for about 1.5 years. Student feedback has been very positive.	oercommons	2025-03-18T00:36:05.228824	Textbook	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/109847/overview", "title": "OpenStax Anatomy and Physiology textbook, 2nd edition", "author": "Homework/Assignment" }
https://oercommons.org/courseware/lesson/56352/overview	The Chemical Level of Organization Introduction Figure 2.1 Human DNA Human DNA is described as a double helix that resembles a molecular spiral staircase. In humans the DNA is organized into 46 chromosomes. CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Describe the fundamental composition of matter - Identify the three subatomic particles - Identify the four most abundant elements in the body - Explain the relationship between an atom’s number of electrons and its relative stability - Distinguish between ionic bonds, covalent bonds, and hydrogen bonds - Explain how energy is invested, stored, and released via chemical reactions, particularly those reactions that are critical to life - Explain the importance of the inorganic compounds that contribute to life, such as water, salts, acids, and bases - Compare and contrast the four important classes of organic (carbon-based) compounds—proteins, carbohydrates, lipids and nucleic acids—according to their composition and functional importance to human life The smallest, most fundamental material components of the human body are basic chemical elements. In fact, chemicals called nucleotide bases are the foundation of the genetic code with the instructions on how to build and maintain the human body from conception through old age. There are about three billion of these base pairs in human DNA. Human chemistry includes organic molecules (carbon-based) and biochemicals (those produced by the body). Human chemistry also includes elements. In fact, life cannot exist without many of the elements that are part of the earth. All of the elements that contribute to chemical reactions, to the transformation of energy, and to electrical activity and muscle contraction—elements that include phosphorus, carbon, sodium, and calcium, to name a few—originated in stars. These elements, in turn, can form both the inorganic and organic chemical compounds important to life, including, for example, water, glucose, and proteins. This chapter begins by examining elements and how the structures of atoms, the basic units of matter, determine the characteristics of elements by the number of protons, neutrons, and electrons in the atoms. The chapter then builds the framework of life from there. Elements and Atoms: The Building Blocks of Matter - Discuss the relationships between matter, mass, elements, compounds, atoms, and subatomic particles - Distinguish between atomic number and mass number - Identify the key distinction between isotopes of the same element - Explain how electrons occupy electron shells and their contribution to an atom’s relative stability The substance of the universe—from a grain of sand to a star—is called matter. Scientists define matter as anything that occupies space and has mass. An object’s mass and its weight are related concepts, but not quite the same. An object’s mass is the amount of matter contained in the object, and the object’s mass is the same whether that object is on Earth or in the zero-gravity environment of outer space. An object’s weight, on the other hand, is its mass as affected by the pull of gravity. Where gravity strongly pulls on an object’s mass its weight is greater than it is where gravity is less strong. An object of a certain mass weighs less on the moon, for example, than it does on Earth because the gravity of the moon is less than that of Earth. In other words, weight is variable, and is influenced by gravity. A piece of cheese that weighs a pound on Earth weighs only a few ounces on the moon. Elements and Compounds All matter in the natural world is composed of one or more of the 92 fundamental substances called elements. An element is a pure substance that is distinguished from all other matter by the fact that it cannot be created or broken down by ordinary chemical means. While your body can assemble many of the chemical compounds needed for life from their constituent elements, it cannot make elements. They must come from the environment. A familiar example of an element that you must take in is calcium (Ca++). Calcium is essential to the human body; it is absorbed and used for a number of processes, including strengthening bones. When you consume dairy products your digestive system breaks down the food into components small enough to cross into the bloodstream. Among these is calcium, which, because it is an element, cannot be broken down further. The elemental calcium in cheese, therefore, is the same as the calcium that forms your bones. Some other elements you might be familiar with are oxygen, sodium, and iron. The elements in the human body are shown in Figure 2.2, beginning with the most abundant: oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). Each element’s name can be replaced by a one- or two-letter symbol; you will become familiar with some of these during this course. All the elements in your body are derived from the foods you eat and the air you breathe. Figure 2.2 Elements of the Human Body The main elements that compose the human body are shown from most abundant to least abundant. In nature, elements rarely occur alone. Instead, they combine to form compounds. A compound is a substance composed of two or more elements joined by chemical bonds. For example, the compound glucose is an important body fuel. It is always composed of the same three elements: carbon, hydrogen, and oxygen. Moreover, the elements that make up any given compound always occur in the same relative amounts. In glucose, there are always six carbon and six oxygen units for every twelve hydrogen units. But what, exactly, are these “units” of elements? Atoms and Subatomic Particles An atom is the smallest quantity of an element that retains the unique properties of that element. In other words, an atom of hydrogen is a unit of hydrogen—the smallest amount of hydrogen that can exist. As you might guess, atoms are almost unfathomably small. The period at the end of this sentence is millions of atoms wide. Atomic Structure and Energy Atoms are made up of even smaller subatomic particles, three types of which are important: the proton, neutron, and electron. The number of positively-charged protons and non-charged (“neutral”) neutrons, gives mass to the atom, and the number of each in the nucleus of the atom determine the element. The number of negatively-charged electrons that “spin” around the nucleus at close to the speed of light equals the number of protons. An electron has about 1/2000th the mass of a proton or neutron. Figure 2.3 shows two models that can help you imagine the structure of an atom—in this case, helium (He). In the planetary model, helium’s two electrons are shown circling the nucleus in a fixed orbit depicted as a ring. Although this model is helpful in visualizing atomic structure, in reality, electrons do not travel in fixed orbits, but whiz around the nucleus erratically in a so-called electron cloud. Figure 2.3 Two Models of Atomic Structure (a) In the planetary model, the electrons of helium are shown in fixed orbits, depicted as rings, at a precise distance from the nucleus, somewhat like planets orbiting the sun. (b) In the electron cloud model, the electrons of carbon are shown in the variety of locations they would have at different distances from the nucleus over time. An atom’s protons and electrons carry electrical charges. Protons, with their positive charge, are designated p+. Electrons, which have a negative charge, are designated e–. An atom’s neutrons have no charge: they are electrically neutral. Just as a magnet sticks to a steel refrigerator because their opposite charges attract, the positively charged protons attract the negatively charged electrons. This mutual attraction gives the atom some structural stability. The attraction by the positively charged nucleus helps keep electrons from straying far. The number of protons and electrons within a neutral atom are equal, thus, the atom’s overall charge is balanced. Atomic Number and Mass Number An atom of carbon is unique to carbon, but a proton of carbon is not. One proton is the same as another, whether it is found in an atom of carbon, sodium (Na), or iron (Fe). The same is true for neutrons and electrons. So, what gives an element its distinctive properties—what makes carbon so different from sodium or iron? The answer is the unique quantity of protons each contains. Carbon by definition is an element whose atoms contain six protons. No other element has exactly six protons in its atoms. Moreover, all atoms of carbon, whether found in your liver or in a lump of coal, contain six protons. Thus, the atomic number, which is the number of protons in the nucleus of the atom, identifies the element. Because an atom usually has the same number of electrons as protons, the atomic number identifies the usual number of electrons as well. In their most common form, many elements also contain the same number of neutrons as protons. The most common form of carbon, for example, has six neutrons as well as six protons, for a total of 12 subatomic particles in its nucleus. An element’s mass number is the sum of the number of protons and neutrons in its nucleus. So the most common form of carbon’s mass number is 12. (Electrons have so little mass that they do not appreciably contribute to the mass of an atom.) Carbon is a relatively light element. Uranium (U), in contrast, has a mass number of 238 and is referred to as a heavy metal. Its atomic number is 92 (it has 92 protons) but it contains 146 neutrons; it has the most mass of all the naturally occurring elements. The periodic table of the elements, shown in Figure 2.4, is a chart identifying the 92 elements found in nature, as well as several larger, unstable elements discovered experimentally. The elements are arranged in order of their atomic number, with hydrogen and helium at the top of the table, and the more massive elements below. The periodic table is a useful device because for each element, it identifies the chemical symbol, the atomic number, and the mass number, while organizing elements according to their propensity to react with other elements. The number of protons and electrons in an element are equal. The number of protons and neutrons may be equal for some elements, but are not equal for all. Figure 2.4 The Periodic Table of the Elements (credit: R.A. Dragoset, A. Musgrove, C.W. Clark, W.C. Martin) INTERACTIVE LINK Visit this website to view the periodic table. In the periodic table of the elements, elements in a single column have the same number of electrons that can participate in a chemical reaction. These electrons are known as “valence electrons.” For example, the elements in the first column all have a single valence electron, an electron that can be “donated” in a chemical reaction with another atom. What is the meaning of a mass number shown in parentheses? Isotopes Although each element has a unique number of protons, it can exist as different isotopes. An isotope is one of the different forms of an element, distinguished from one another by different numbers of neutrons. The standard isotope of carbon is 12C, commonly called carbon twelve. 12C has six protons and six neutrons, for a mass number of twelve. All of the isotopes of carbon have the same number of protons; therefore, 13C has seven neutrons, and 14C has eight neutrons. The different isotopes of an element can also be indicated with the mass number hyphenated (for example, C-12 instead of 12C). Hydrogen has three common isotopes, shown in Figure 2.5. Figure 2.5 Isotopes of Hydrogen Protium, designated 1H, has one proton and no neutrons. It is by far the most abundant isotope of hydrogen in nature. Deuterium, designated 2H, has one proton and one neutron. Tritium, designated 3H, has two neutrons. An isotope that contains more than the usual number of neutrons is referred to as a heavy isotope. An example is 14C. Heavy isotopes tend to be unstable, and unstable isotopes are radioactive. A radioactive isotope is an isotope whose nucleus readily decays, giving off subatomic particles and electromagnetic energy. Different radioactive isotopes (also called radioisotopes) differ in their half-life, the time it takes for half of any size sample of an isotope to decay. For example, the half-life of tritium—a radioisotope of hydrogen—is about 12 years, indicating it takes 12 years for half of the tritium nuclei in a sample to decay. Excessive exposure to radioactive isotopes can damage human cells and even cause cancer and birth defects, but when exposure is controlled, some radioactive isotopes can be useful in medicine. For more information, see the Career Connections. CAREER CONNECTION Interventional Radiologist The controlled use of radioisotopes has advanced medical diagnosis and treatment of disease. Interventional radiologists are physicians who treat disease by using minimally invasive techniques involving radiation. Many conditions that could once only be treated with a lengthy and traumatic operation can now be treated non-surgically, reducing the cost, pain, length of hospital stay, and recovery time for patients. For example, in the past, the only options for a patient with one or more tumors in the liver were surgery and chemotherapy (the administration of drugs to treat cancer). Some liver tumors, however, are difficult to access surgically, and others could require the surgeon to remove too much of the liver. Moreover, chemotherapy is highly toxic to the liver, and certain tumors do not respond well to it anyway. In some such cases, an interventional radiologist can treat the tumors by disrupting their blood supply, which they need if they are to continue to grow. In this procedure, called radioembolization, the radiologist accesses the liver with a fine needle, threaded through one of the patient’s blood vessels. The radiologist then inserts tiny radioactive “seeds” into the blood vessels that supply the tumors. In the days and weeks following the procedure, the radiation emitted from the seeds destroys the vessels and directly kills the tumor cells in the vicinity of the treatment. Radioisotopes emit subatomic particles that can be detected and tracked by imaging technologies. One of the most advanced uses of radioisotopes in medicine is the positron emission tomography (PET) scanner, which detects the activity in the body of a very small injection of radioactive glucose, the simple sugar that cells use for energy. The PET camera reveals to the medical team which of the patient’s tissues are taking up the most glucose. Thus, the most metabolically active tissues show up as bright “hot spots” on the images (Figure 2.6). PET can reveal some cancerous masses because cancer cells consume glucose at a high rate to fuel their rapid reproduction. Figure 2.6 PET Scan PET highlights areas in the body where there is relatively high glucose use, which is characteristic of cancerous tissue. This PET scan shows sites of the spread of a large primary tumor to other sites. The Behavior of Electrons In the human body, atoms do not exist as independent entities. Rather, they are constantly reacting with other atoms to form and to break down more complex substances. To fully understand anatomy and physiology you must grasp how atoms participate in such reactions. The key is understanding the behavior of electrons. Although electrons do not follow rigid orbits a set distance away from the atom’s nucleus, they do tend to stay within certain regions of space called electron shells. An electron shell is a layer of electrons that encircle the nucleus at a distinct energy level. The atoms of the elements found in the human body have from one to five electron shells, and all electron shells hold eight electrons except the first shell, which can only hold two. This configuration of electron shells is the same for all atoms. The precise number of shells depends on the number of electrons in the atom. Hydrogen and helium have just one and two electrons, respectively. If you take a look at the periodic table of the elements, you will notice that hydrogen and helium are placed alone on either sides of the top row; they are the only elements that have just one electron shell (Figure 2.7). A second shell is necessary to hold the electrons in all elements larger than hydrogen and helium. Lithium (Li), whose atomic number is 3, has three electrons. Two of these fill the first electron shell, and the third spills over into a second shell. The second electron shell can accommodate as many as eight electrons. Carbon, with its six electrons, entirely fills its first shell, and half-fills its second. With ten electrons, neon (Ne) entirely fills its two electron shells. Again, a look at the periodic table reveals that all of the elements in the second row, from lithium to neon, have just two electron shells. Atoms with more than ten electrons require more than two shells. These elements occupy the third and subsequent rows of the periodic table. Figure 2.7 Electron Shells Electrons orbit the atomic nucleus at distinct levels of energy called electron shells. (a) With one electron, hydrogen only half-fills its electron shell. Helium also has a single shell, but its two electrons completely fill it. (b) The electrons of carbon completely fill its first electron shell, but only half-fills its second. (c) Neon, an element that does not occur in the body, has 10 electrons, filling both of its electron shells. The factor that most strongly governs the tendency of an atom to participate in chemical reactions is the number of electrons in its valence shell. A valence shell is an atom’s outermost electron shell. If the valence shell is full, the atom is stable; meaning its electrons are unlikely to be pulled away from the nucleus by the electrical charge of other atoms. If the valence shell is not full, the atom is reactive; meaning it will tend to react with other atoms in ways that make the valence shell full. Consider hydrogen, with its one electron only half-filling its valence shell. This single electron is likely to be drawn into relationships with the atoms of other elements, so that hydrogen’s single valence shell can be stabilized. All atoms (except hydrogen and helium with their single electron shells) are most stable when there are exactly eight electrons in their valence shell. This principle is referred to as the octet rule, and it states that an atom will give up, gain, or share electrons with another atom so that it ends up with eight electrons in its own valence shell. For example, oxygen, with six electrons in its valence shell, is likely to react with other atoms in a way that results in the addition of two electrons to oxygen’s valence shell, bringing the number to eight. When two hydrogen atoms each share their single electron with oxygen, covalent bonds are formed, resulting in a molecule of water, H2O. In nature, atoms of one element tend to join with atoms of other elements in characteristic ways. For example, carbon commonly fills its valence shell by linking up with four atoms of hydrogen. In so doing, the two elements form the simplest of organic molecules, methane, which also is one of the most abundant and stable carbon-containing compounds on Earth. As stated above, another example is water; oxygen needs two electrons to fill its valence shell. It commonly interacts with two atoms of hydrogen, forming H2O. Incidentally, the name “hydrogen” reflects its contribution to water (hydro- = “water”; -gen = “maker”). Thus, hydrogen is the “water maker.” Chemical Bonds - Explain the relationship between molecules and compounds - Distinguish between ions, cations, and anions - Identify the key difference between ionic and covalent bonds - Distinguish between nonpolar and polar covalent bonds - Explain how water molecules link via hydrogen bonds Atoms separated by a great distance cannot link; rather, they must come close enough for the electrons in their valence shells to interact. But do atoms ever actually touch one another? Most physicists would say no, because the negatively charged electrons in their valence shells repel one another. No force within the human body—or anywhere in the natural world—is strong enough to overcome this electrical repulsion. So when you read about atoms linking together or colliding, bear in mind that the atoms are not merging in a physical sense. Instead, atoms link by forming a chemical bond. A bond is a weak or strong electrical attraction that holds atoms in the same vicinity. The new grouping is typically more stable—less likely to react again—than its component atoms were when they were separate. A more or less stable grouping of two or more atoms held together by chemical bonds is called a molecule. The bonded atoms may be of the same element, as in the case of H2, which is called molecular hydrogen or hydrogen gas. When a molecule is made up of two or more atoms of different elements, it is called a chemical compound. Thus, a unit of water, or H2O, is a compound, as is a single molecule of the gas methane, or CH4. Three types of chemical bonds are important in human physiology, because they hold together substances that are used by the body for critical aspects of homeostasis, signaling, and energy production, to name just a few important processes. These are ionic bonds, covalent bonds, and hydrogen bonds. Ions and Ionic Bonds Recall that an atom typically has the same number of positively charged protons and negatively charged electrons. As long as this situation remains, the atom is electrically neutral. But when an atom participates in a chemical reaction that results in the donation or acceptance of one or more electrons, the atom will then become positively or negatively charged. This happens frequently for most atoms in order to have a full valence shell, as described previously. This can happen either by gaining electrons to fill a shell that is more than half-full, or by giving away electrons to empty a shell that is less than half-full, thereby leaving the next smaller electron shell as the new, full, valence shell. An atom that has an electrical charge—whether positive or negative—is an ion. INTERACTIVE LINK Visit this website to learn about electrical energy and the attraction/repulsion of charges. What happens to the charged electroscope when a conductor is moved between its plastic sheets, and why? Potassium (K), for instance, is an important element in all body cells. Its atomic number is 19. It has just one electron in its valence shell. This characteristic makes potassium highly likely to participate in chemical reactions in which it donates one electron. (It is easier for potassium to donate one electron than to gain seven electrons.) The loss will cause the positive charge of potassium’s protons to be more influential than the negative charge of potassium’s electrons. In other words, the resulting potassium ion will be slightly positive. A potassium ion is written K+, indicating that it has lost a single electron. A positively charged ion is known as a cation. Now consider fluorine (F), a component of bones and teeth. Its atomic number is nine, and it has seven electrons in its valence shell. Thus, it is highly likely to bond with other atoms in such a way that fluorine accepts one electron (it is easier for fluorine to gain one electron than to donate seven electrons). When it does, its electrons will outnumber its protons by one, and it will have an overall negative charge. The ionized form of fluorine is called fluoride, and is written as F–. A negatively charged ion is known as an anion. Atoms that have more than one electron to donate or accept will end up with stronger positive or negative charges. A cation that has donated two electrons has a net charge of +2. Using magnesium (Mg) as an example, this can be written Mg++ or Mg2+. An anion that has accepted two electrons has a net charge of –2. The ionic form of selenium (Se), for example, is typically written Se2–. The opposite charges of cations and anions exert a moderately strong mutual attraction that keeps the atoms in close proximity forming an ionic bond. An ionic bond is an ongoing, close association between ions of opposite charge. The table salt you sprinkle on your food owes its existence to ionic bonding. As shown in Figure 2.8, sodium commonly donates an electron to chlorine, becoming the cation Na+. When chlorine accepts the electron, it becomes the chloride anion, Cl–. With their opposing charges, these two ions strongly attract each other. Figure 2.8 Ionic Bonding (a) Sodium readily donates the solitary electron in its valence shell to chlorine, which needs only one electron to have a full valence shell. (b) The opposite electrical charges of the resulting sodium cation and chloride anion result in the formation of a bond of attraction called an ionic bond. (c) The attraction of many sodium and chloride ions results in the formation of large groupings called crystals. Water is an essential component of life because it is able to break the ionic bonds in salts to free the ions. In fact, in biological fluids, most individual atoms exist as ions. These dissolved ions produce electrical charges within the body. The behavior of these ions produces the tracings of heart and brain function observed as waves on an electrocardiogram (EKG or ECG) or an electroencephalogram (EEG). The electrical activity that derives from the interactions of the charged ions is why they are also called electrolytes. Covalent Bonds Unlike ionic bonds formed by the attraction between a cation’s positive charge and an anion’s negative charge, molecules formed by a covalent bond share electrons in a mutually stabilizing relationship. Like next-door neighbors whose kids hang out first at one home and then at the other, the atoms do not lose or gain electrons permanently. Instead, the electrons move back and forth between the elements. Because of the close sharing of pairs of electrons (one electron from each of two atoms), covalent bonds are stronger than ionic bonds. Nonpolar Covalent Bonds Figure 2.9 shows several common types of covalent bonds. Notice that the two covalently bonded atoms typically share just one or two electron pairs, though larger sharings are possible. The important concept to take from this is that in covalent bonds, electrons in the outermost valence shell are shared to fill the valence shells of both atoms, ultimately stabilizing both of the atoms involved. In a single covalent bond, a single electron is shared between two atoms, while in a double covalent bond, two pairs of electrons are shared between two atoms. There even are triple covalent bonds, where three atoms are shared. Figure 2.9 Covalent Bonding You can see that the covalent bonds shown in Figure 2.9 are balanced. The sharing of the negative electrons is relatively equal, as is the electrical pull of the positive protons in the nucleus of the atoms involved. This is why covalently bonded molecules that are electrically balanced in this way are described as nonpolar; that is, no region of the molecule is either more positive or more negative than any other. Polar Covalent Bonds Groups of legislators with completely opposite views on a particular issue are often described as “polarized” by news writers. In chemistry, a polar molecule is a molecule that contains regions that have opposite electrical charges. Polar molecules occur when atoms share electrons unequally, in polar covalent bonds. The most familiar example of a polar molecule is water (Figure 2.10). The molecule has three parts: one atom of oxygen, the nucleus of which contains eight protons, and two hydrogen atoms, whose nuclei each contain only one proton. Because every proton exerts an identical positive charge, a nucleus that contains eight protons exerts a charge eight times greater than a nucleus that contains one proton. This means that the negatively charged electrons present in the water molecule are more strongly attracted to the oxygen nucleus than to the hydrogen nuclei. Each hydrogen atom’s single negative electron therefore migrates toward the oxygen atom, making the oxygen end of their bond slightly more negative than the hydrogen end of their bond. Figure 2.10 Polar Covalent Bonds in a Water Molecule What is true for the bonds is true for the water molecule as a whole; that is, the oxygen region has a slightly negative charge and the regions of the hydrogen atoms have a slightly positive charge. These charges are often referred to as “partial charges” because the strength of the charge is less than one full electron, as would occur in an ionic bond. As shown in Figure 2.10, regions of weak polarity are indicated with the Greek letter delta (δ) and a plus (+) or minus (–) sign. Even though a single water molecule is unimaginably tiny, it has mass, and the opposing electrical charges on the molecule pull that mass in such a way that it creates a shape somewhat like a triangular tent (see Figure 2.10b). This dipole, with the positive charges at one end formed by the hydrogen atoms at the “bottom” of the tent and the negative charge at the opposite end (the oxygen atom at the “top” of the tent) makes the charged regions highly likely to interact with charged regions of other polar molecules. For human physiology, the resulting bond is one of the most important formed by water—the hydrogen bond. Hydrogen Bonds A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another molecule. In other words, hydrogen bonds always include hydrogen that is already part of a polar molecule. The most common example of hydrogen bonding in the natural world occurs between molecules of water. It happens before your eyes whenever two raindrops merge into a larger bead, or a creek spills into a river. Hydrogen bonding occurs because the weakly negative oxygen atom in one water molecule is attracted to the weakly positive hydrogen atoms of two other water molecules (Figure 2.11). Figure 2.11 Hydrogen Bonds between Water Molecules Notice that the bonds occur between the weakly positive charge on the hydrogen atoms and the weakly negative charge on the oxygen atoms. Hydrogen bonds are relatively weak, and therefore are indicated with a dotted (rather than a solid) line. Water molecules also strongly attract other types of charged molecules as well as ions. This explains why “table salt,” for example, actually is a molecule called a “salt” in chemistry, which consists of equal numbers of positively-charged sodium (Na+) and negatively-charged chloride (Cl–), dissolves so readily in water, in this case forming dipole-ion bonds between the water and the electrically-charged ions (electrolytes). Water molecules also repel molecules with nonpolar covalent bonds, like fats, lipids, and oils. You can demonstrate this with a simple kitchen experiment: pour a teaspoon of vegetable oil, a compound formed by nonpolar covalent bonds, into a glass of water. Instead of instantly dissolving in the water, the oil forms a distinct bead because the polar water molecules repel the nonpolar oil. Chemical Reactions - Distinguish between kinetic and potential energy, and between exergonic and endergonic chemical reactions - Identify four forms of energy important in human functioning - Describe the three basic types of chemical reactions - Identify several factors influencing the rate of chemical reactions One characteristic of a living organism is metabolism, which is the sum total of all of the chemical reactions that go on to maintain that organism’s health and life. The bonding processes you have learned thus far are anabolic chemical reactions; that is, they form larger molecules from smaller molecules or atoms. But recall that metabolism can proceed in another direction: in catabolic chemical reactions, bonds between components of larger molecules break, releasing smaller molecules or atoms. Both types of reaction involve exchanges not only of matter, but of energy. The Role of Energy in Chemical Reactions Chemical reactions require a sufficient amount of energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ones formed. In general, kinetic energy is the form of energy powering any type of matter in motion. Imagine you are building a brick wall. The energy it takes to lift and place one brick atop another is kinetic energy—the energy matter possesses because of its motion. Once the wall is in place, it stores potential energy. Potential energy is the energy of position, or the energy matter possesses because of the positioning or structure of its components. If the brick wall collapses, the stored potential energy is released as kinetic energy as the bricks fall. In the human body, potential energy is stored in the bonds between atoms and molecules. Chemical energy is the form of potential energy in which energy is stored in chemical bonds. When those bonds are formed, chemical energy is invested, and when they break, chemical energy is released. Notice that chemical energy, like all energy, is neither created nor destroyed; rather, it is converted from one form to another. When you eat an energy bar before heading out the door for a hike, the honey, nuts, and other foods the bar contains are broken down and rearranged by your body into molecules that your muscle cells convert to kinetic energy. Chemical reactions that release more energy than they absorb are characterized as exergonic. The catabolism of the foods in your energy bar is an example. Some of the chemical energy stored in the bar is absorbed into molecules your body uses for fuel, but some of it is released—for example, as heat. In contrast, chemical reactions that absorb more energy than they release are endergonic. These reactions require energy input, and the resulting molecule stores not only the chemical energy in the original components, but also the energy that fueled the reaction. Because energy is neither created nor destroyed, where does the energy needed for endergonic reactions come from? In many cases, it comes from exergonic reactions. Forms of Energy Important in Human Functioning You have already learned that chemical energy is absorbed, stored, and released by chemical bonds. In addition to chemical energy, mechanical, radiant, and electrical energy are important in human functioning. - Mechanical energy, which is stored in physical systems such as machines, engines, or the human body, directly powers the movement of matter. When you lift a brick into place on a wall, your muscles provide the mechanical energy that moves the brick. - Radiant energy is energy emitted and transmitted as waves rather than matter. These waves vary in length from long radio waves and microwaves to short gamma waves emitted from decaying atomic nuclei. The full spectrum of radiant energy is referred to as the electromagnetic spectrum. The body uses the ultraviolet energy of sunlight to convert a compound in skin cells to vitamin D, which is essential to human functioning. The human eye evolved to see the wavelengths that comprise the colors of the rainbow, from red to violet, so that range in the spectrum is called “visible light.” - Electrical energy, supplied by electrolytes in cells and body fluids, contributes to the voltage changes that help transmit impulses in nerve and muscle cells. Characteristics of Chemical Reactions All chemical reactions begin with a reactant, the general term for the one or more substances that enter into the reaction. Sodium and chloride ions, for example, are the reactants in the production of table salt. The one or more substances produced by a chemical reaction are called the product. In chemical reactions, the components of the reactants—the elements involved and the number of atoms of each—are all present in the product(s). Similarly, there is nothing present in the products that are not present in the reactants. This is because chemical reactions are governed by the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Just as you can express mathematical calculations in equations such as 2 + 7 = 9, you can use chemical equations to show how reactants become products. As in math, chemical equations proceed from left to right, but instead of an equal sign, they employ an arrow or arrows indicating the direction in which the chemical reaction proceeds. For example, the chemical reaction in which one atom of nitrogen and three atoms of hydrogen produce ammonia would be written as N + 3H→NH3N + 3H→NH3 NH3→N + 3H.NH3→N + 3H. Notice that, in the first example, a nitrogen (N) atom and three hydrogen (H) atoms bond to form a compound. This anabolic reaction requires energy, which is then stored within the compound’s bonds. Such reactions are referred to as synthesis reactions. A synthesis reaction is a chemical reaction that results in the synthesis (joining) of components that were formerly separate (Figure 2.12a). Again, nitrogen and hydrogen are reactants in a synthesis reaction that yields ammonia as the product. The general equation for a synthesis reaction is A + B→AB.A + B→AB. Figure 2.12 The Three Fundamental Chemical Reactions The atoms and molecules involved in the three fundamental chemical reactions can be imagined as words. In the second example, ammonia is catabolized into its smaller components, and the potential energy that had been stored in its bonds is released. Such reactions are referred to as decomposition reactions. A decomposition reaction is a chemical reaction that breaks down or “de-composes” something larger into its constituent parts (see Figure 2.12b). The general equation for a decomposition reaction is: AB→A+BAB→A+B An exchange reaction is a chemical reaction in which both synthesis and decomposition occur, chemical bonds are both formed and broken, and chemical energy is absorbed, stored, and released (see Figure 2.12c). The simplest form of an exchange reaction might be: A+BC→AB+CA+BC→AB+CAB+CD→AC+BDAB+CD→AC+BD AB+CD→AD+BCAB+CD→AD+BC In theory, any chemical reaction can proceed in either direction under the right conditions. Reactants may synthesize into a product that is later decomposed. Reversibility is also a quality of exchange reactions. For instance, A+BC→AB+CA+BC→AB+C AB+C→A+BCAB+C→A+BC A+BC⇄AB+CA+BC⇄AB+C Factors Influencing the Rate of Chemical Reactions If you pour vinegar into baking soda, the reaction is instantaneous; the concoction will bubble and fizz. But many chemical reactions take time. A variety of factors influence the rate of chemical reactions. This section, however, will consider only the most important in human functioning. Properties of the Reactants If chemical reactions are to occur quickly, the atoms in the reactants have to have easy access to one another. Thus, the greater the surface area of the reactants, the more readily they will interact. When you pop a cube of cheese into your mouth, you chew it before you swallow it. Among other things, chewing increases the surface area of the food so that digestive chemicals can more easily get at it. As a general rule, gases tend to react faster than liquids or solids, again because it takes energy to separate particles of a substance, and gases by definition already have space between their particles. Similarly, the larger the molecule, the greater the number of total bonds, so reactions involving smaller molecules, with fewer total bonds, would be expected to proceed faster. In addition, recall that some elements are more reactive than others. Reactions that involve highly reactive elements like hydrogen proceed more quickly than reactions that involve less reactive elements. Reactions involving stable elements like helium are not likely to happen at all. Temperature Nearly all chemical reactions occur at a faster rate at higher temperatures. Recall that kinetic energy is the energy of matter in motion. The kinetic energy of subatomic particles increases in response to increases in thermal energy. The higher the temperature, the faster the particles move, and the more likely they are to come in contact and react. Concentration and Pressure If just a few people are dancing at a club, they are unlikely to step on each other’s toes. But as more and more people get up to dance—especially if the music is fast—collisions are likely to occur. It is the same with chemical reactions: the more particles present within a given space, the more likely those particles are to bump into one another. This means that chemists can speed up chemical reactions not only by increasing the concentration of particles—the number of particles in the space—but also by decreasing the volume of the space, which would correspondingly increase the pressure. If there were 100 dancers in that club, and the manager abruptly moved the party to a room half the size, the concentration of the dancers would double in the new space, and the likelihood of collisions would increase accordingly. Enzymes and Other Catalysts For two chemicals in nature to react with each other they first have to come into contact, and this occurs through random collisions. Because heat helps increase the kinetic energy of atoms, ions, and molecules, it promotes their collision. But in the body, extremely high heat—such as a very high fever—can damage body cells and be life-threatening. On the other hand, normal body temperature is not high enough to promote the chemical reactions that sustain life. That is where catalysts come in. In chemistry, a catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any change. You can think of a catalyst as a chemical change agent. They help increase the rate and force at which atoms, ions, and molecules collide, thereby increasing the probability that their valence shell electrons will interact. The most important catalysts in the human body are enzymes. An enzyme is a catalyst composed of protein or ribonucleic acid (RNA), both of which will be discussed later in this chapter. Like all catalysts, enzymes work by lowering the level of energy that needs to be invested in a chemical reaction. A chemical reaction’s activation energy is the “threshold” level of energy needed to break the bonds in the reactants. Once those bonds are broken, new arrangements can form. Without an enzyme to act as a catalyst, a much larger investment of energy is needed to ignite a chemical reaction (Figure 2.13). Figure 2.13 Enzymes Enzymes decrease the activation energy required for a given chemical reaction to occur. (a) Without an enzyme, the energy input needed for a reaction to begin is high. (b) With the help of an enzyme, less energy is needed for a reaction to begin. Enzymes are critical to the body’s healthy functioning. They assist, for example, with the breakdown of food and its conversion to energy. In fact, most of the chemical reactions in the body are facilitated by enzymes. Inorganic Compounds Essential to Human Functioning - Compare and contrast inorganic and organic compounds - Identify the properties of water that make it essential to life - Explain the role of salts in body functioning - Distinguish between acids and bases, and explain their role in pH - Discuss the role of buffers in helping the body maintain pH homeostasis The concepts you have learned so far in this chapter govern all forms of matter, and would work as a foundation for geology as well as biology. This section of the chapter narrows the focus to the chemistry of human life; that is, the compounds important for the body’s structure and function. In general, these compounds are either inorganic or organic. - An inorganic compound is a substance that does not contain both carbon and hydrogen. A great many inorganic compounds do contain hydrogen atoms, such as water (H2O) and the hydrochloric acid (HCl) produced by your stomach. In contrast, only a handful of inorganic compounds contain carbon atoms. Carbon dioxide (CO2) is one of the few examples. - An organic compound, then, is a substance that contains both carbon and hydrogen. Organic compounds are synthesized via covalent bonds within living organisms, including the human body. Recall that carbon and hydrogen are the second and third most abundant elements in your body. You will soon discover how these two elements combine in the foods you eat, in the compounds that make up your body structure, and in the chemicals that fuel your functioning. The following section examines the three groups of inorganic compounds essential to life: water, salts, acids, and bases. Organic compounds are covered later in the chapter. Water As much as 70 percent of an adult’s body weight is water. This water is contained both within the cells and between the cells that make up tissues and organs. Its several roles make water indispensable to human functioning. Water as a Lubricant and Cushion Water is a major component of many of the body’s lubricating fluids. Just as oil lubricates the hinge on a door, water in synovial fluid lubricates the actions of body joints, and water in pleural fluid helps the lungs expand and recoil with breathing. Watery fluids help keep food flowing through the digestive tract, and ensure that the movement of adjacent abdominal organs is friction free. Water also protects cells and organs from physical trauma, cushioning the brain within the skull, for example, and protecting the delicate nerve tissue of the eyes. Water cushions a developing fetus in the mother’s womb as well. Water as a Heat Sink A heat sink is a substance or object that absorbs and dissipates heat but does not experience a corresponding increase in temperature. In the body, water absorbs the heat generated by chemical reactions without greatly increasing in temperature. Moreover, when the environmental temperature soars, the water stored in the body helps keep the body cool. This cooling effect happens as warm blood from the body’s core flows to the blood vessels just under the skin and is transferred to the environment. At the same time, sweat glands release warm water in sweat. As the water evaporates into the air, it carries away heat, and then the cooler blood from the periphery circulates back to the body core. Water as a Component of Liquid Mixtures A mixture is a combination of two or more substances, each of which maintains its own chemical identity. In other words, the constituent substances are not chemically bonded into a new, larger chemical compound. The concept is easy to imagine if you think of powdery substances such as flour and sugar; when you stir them together in a bowl, they obviously do not bond to form a new compound. The room air you breathe is a gaseous mixture, containing three discrete elements—nitrogen, oxygen, and argon—and one compound, carbon dioxide. There are three types of liquid mixtures, all of which contain water as a key component. These are solutions, colloids, and suspensions. For cells in the body to survive, they must be kept moist in a water-based liquid called a solution. In chemistry, a liquid solution consists of a solvent that dissolves a substance called a solute. An important characteristic of solutions is that they are homogeneous; that is, the solute molecules are distributed evenly throughout the solution. If you were to stir a teaspoon of sugar into a glass of water, the sugar would dissolve into sugar molecules separated by water molecules. The ratio of sugar to water in the left side of the glass would be the same as the ratio of sugar to water in the right side of the glass. If you were to add more sugar, the ratio of sugar to water would change, but the distribution—provided you had stirred well—would still be even. Water is considered the “universal solvent” and it is believed that life cannot exist without water because of this. Water is certainly the most abundant solvent in the body; essentially all of the body’s chemical reactions occur among compounds dissolved in water. Because water molecules are polar, with regions of positive and negative electrical charge, water readily dissolves ionic compounds and polar covalent compounds. Such compounds are referred to as hydrophilic, or “water-loving.” As mentioned above, sugar dissolves well in water. This is because sugar molecules contain regions of hydrogen-oxygen polar bonds, making it hydrophilic. Nonpolar molecules, which do not readily dissolve in water, are called hydrophobic, or “water-fearing.” Concentrations of Solutes Various mixtures of solutes and water are described in chemistry. The concentration of a given solute is the number of particles of that solute in a given space (oxygen makes up about 21 percent of atmospheric air). In the bloodstream of humans, glucose concentration is usually measured in milligram (mg) per deciliter (dL), and in a healthy adult averages about 100 mg/dL. Another method of measuring the concentration of a solute is by its molarilty—which is moles (M) of the molecules per liter (L). The mole of an element is its atomic weight, while a mole of a compound is the sum of the atomic weights of its components, called the molecular weight. An often-used example is calculating a mole of glucose, with the chemical formula C6H12O6. Using the periodic table, the atomic weight of carbon (C) is 12.011 grams (g), and there are six carbons in glucose, for a total atomic weight of 72.066 g. Doing the same calculations for hydrogen (H) and oxygen (O), the molecular weight equals 180.156g (the “gram molecular weight” of glucose). When water is added to make one liter of solution, you have one mole (1M) of glucose. This is particularly useful in chemistry because of the relationship of moles to “Avogadro’s number.” A mole of any solution has the same number of particles in it: 6.02 × 1023. Many substances in the bloodstream and other tissue of the body are measured in thousandths of a mole, or millimoles (mM). A colloid is a mixture that is somewhat like a heavy solution. The solute particles consist of tiny clumps of molecules large enough to make the liquid mixture opaque (because the particles are large enough to scatter light). Familiar examples of colloids are milk and cream. In the thyroid glands, the thyroid hormone is stored as a thick protein mixture also called a colloid. A suspension is a liquid mixture in which a heavier substance is suspended temporarily in a liquid, but over time, settles out. This separation of particles from a suspension is called sedimentation. An example of sedimentation occurs in the blood test that establishes sedimentation rate, or sed rate. The test measures how quickly red blood cells in a test tube settle out of the watery portion of blood (known as plasma) over a set period of time. Rapid sedimentation of blood cells does not normally happen in the healthy body, but aspects of certain diseases can cause blood cells to clump together, and these heavy clumps of blood cells settle to the bottom of the test tube more quickly than do normal blood cells. The Role of Water in Chemical Reactions Two types of chemical reactions involve the creation or the consumption of water: dehydration synthesis and hydrolysis. - In dehydration synthesis, one reactant gives up an atom of hydrogen and another reactant gives up a hydroxyl group (OH) in the synthesis of a new product. In the formation of their covalent bond, a molecule of water is released as a byproduct (Figure 2.14). This is also sometimes referred to as a condensation reaction. - In hydrolysis, a molecule of water disrupts a compound, breaking its bonds. The water is itself split into H and OH. One portion of the severed compound then bonds with the hydrogen atom, and the other portion bonds with the hydroxyl group. These reactions are reversible, and play an important role in the chemistry of organic compounds (which will be discussed shortly). Figure 2.14 Dehydration Synthesis and Hydrolysis Monomers, the basic units for building larger molecules, form polymers (two or more chemically-bonded monomers). (a) In dehydration synthesis, two monomers are covalently bonded in a reaction in which one gives up a hydroxyl group and the other a hydrogen atom. A molecule of water is released as a byproduct during dehydration reactions. (b) In hydrolysis, the covalent bond between two monomers is split by the addition of a hydrogen atom to one and a hydroxyl group to the other, which requires the contribution of one molecule of water. Salts Recall that salts are formed when ions form ionic bonds. In these reactions, one atom gives up one or more electrons, and thus becomes positively charged, whereas the other accepts one or more electrons and becomes negatively charged. You can now define a salt as a substance that, when dissolved in water, dissociates into ions other than H+ or OH–. This fact is important in distinguishing salts from acids and bases, discussed next. A typical salt, NaCl, dissociates completely in water (Figure 2.15). The positive and negative regions on the water molecule (the hydrogen and oxygen ends respectively) attract the negative chloride and positive sodium ions, pulling them away from each other. Again, whereas nonpolar and polar covalently bonded compounds break apart into molecules in solution, salts dissociate into ions. These ions are electrolytes; they are capable of conducting an electrical current in solution. This property is critical to the function of ions in transmitting nerve impulses and prompting muscle contraction. Figure 2.15 Dissociation of Sodium Chloride in Water Notice that the crystals of sodium chloride dissociate not into molecules of NaCl, but into Na+ cations and Cl–anions, each completely surrounded by water molecules. Many other salts are important in the body. For example, bile salts produced by the liver help break apart dietary fats, and calcium phosphate salts form the mineral portion of teeth and bones. Acids and Bases Acids and bases, like salts, dissociate in water into electrolytes. Acids and bases can very much change the properties of the solutions in which they are dissolved. Acids An acid is a substance that releases hydrogen ions (H+) in solution (Figure 2.16a). Because an atom of hydrogen has just one proton and one electron, a positively charged hydrogen ion is simply a proton. This solitary proton is highly likely to participate in chemical reactions. Strong acids are compounds that release all of their H+ in solution; that is, they ionize completely. Hydrochloric acid (HCl), which is released from cells in the lining of the stomach, is a strong acid because it releases all of its H+ in the stomach’s watery environment. This strong acid aids in digestion and kills ingested microbes. Weak acids do not ionize completely; that is, some of their hydrogen ions remain bonded within a compound in solution. An example of a weak acid is vinegar, or acetic acid; it is called acetate after it gives up a proton. Figure 2.16 Acids and Bases (a) In aqueous solution, an acid dissociates into hydrogen ions (H+) and anions. Nearly every molecule of a strong acid dissociates, producing a high concentration of H+. (b) In aqueous solution, a base dissociates into hydroxyl ions (OH–) and cations. Nearly every molecule of a strong base dissociates, producing a high concentration of OH–. Bases A base is a substance that releases hydroxyl ions (OH–) in solution, or one that accepts H+ already present in solution (see Figure 2.16b). The hydroxyl ions (also known as hydroxide ions) or other basic substances combine with H+ present to form a water molecule, thereby removing H+ and reducing the solution’s acidity. Strong bases release most or all of their hydroxyl ions; weak bases release only some hydroxyl ions or absorb only a few H+. Food mixed with hydrochloric acid from the stomach would burn the small intestine, the next portion of the digestive tract after the stomach, if it were not for the release of bicarbonate (HCO3–), a weak base that attracts H+. Bicarbonate accepts some of the H+ protons, thereby reducing the acidity of the solution. The Concept of pH The relative acidity or alkalinity of a solution can be indicated by its pH. A solution’s pH is the negative, base-10 logarithm of the hydrogen ion (H+) concentration of the solution. As an example, a pH 4 solution has an H+ concentration that is ten times greater than that of a pH 5 solution. That is, a solution with a pH of 4 is ten times more acidic than a solution with a pH of 5. The concept of pH will begin to make more sense when you study the pH scale, like that shown in Figure 2.17. The scale consists of a series of increments ranging from 0 to 14. A solution with a pH of 7 is considered neutral—neither acidic nor basic. Pure water has a pH of 7. The lower the number below 7, the more acidic the solution, or the greater the concentration of H+. The concentration of hydrogen ions at each pH value is 10 times different than the next pH. For instance, a pH value of 4 corresponds to a proton concentration of 10–4 M, or 0.0001M, while a pH value of 5 corresponds to a proton concentration of 10–5 M, or 0.00001M. The higher the number above 7, the more basic (alkaline) the solution, or the lower the concentration of H+. Human urine, for example, is ten times more acidic than pure water, and HCl is 10,000,000 times more acidic than water. Figure 2.17 The pH Scale Buffers The pH of human blood normally ranges from 7.35 to 7.45, although it is typically identified as pH 7.4. At this slightly basic pH, blood can reduce the acidity resulting from the carbon dioxide (CO2) constantly being released into the bloodstream by the trillions of cells in the body. Homeostatic mechanisms (along with exhaling CO2 while breathing) normally keep the pH of blood within this narrow range. This is critical, because fluctuations—either too acidic or too alkaline—can lead to life-threatening disorders. All cells of the body depend on homeostatic regulation of acid–base balance at a pH of approximately 7.4. The body therefore has several mechanisms for this regulation, involving breathing, the excretion of chemicals in urine, and the internal release of chemicals collectively called buffers into body fluids. A buffer is a solution of a weak acid and its conjugate base. A buffer can neutralize small amounts of acids or bases in body fluids. For example, if there is even a slight decrease below 7.35 in the pH of a bodily fluid, the buffer in the fluid—in this case, acting as a weak base—will bind the excess hydrogen ions. In contrast, if pH rises above 7.45, the buffer will act as a weak acid and contribute hydrogen ions. HOMEOSTATIC IMBALANCES Acids and Bases Excessive acidity of the blood and other body fluids is known as acidosis. Common causes of acidosis are situations and disorders that reduce the effectiveness of breathing, especially the person’s ability to exhale fully, which causes a buildup of CO2 (and H+) in the bloodstream. Acidosis can also be caused by metabolic problems that reduce the level or function of buffers that act as bases, or that promote the production of acids. For instance, with severe diarrhea, too much bicarbonate can be lost from the body, allowing acids to build up in body fluids. In people with poorly managed diabetes (ineffective regulation of blood sugar), acids called ketones are produced as a form of body fuel. These can build up in the blood, causing a serious condition called diabetic ketoacidosis. Kidney failure, liver failure, heart failure, cancer, and other disorders also can prompt metabolic acidosis. In contrast, alkalosis is a condition in which the blood and other body fluids are too alkaline (basic). As with acidosis, respiratory disorders are a major cause; however, in respiratory alkalosis, carbon dioxide levels fall too low. Lung disease, aspirin overdose, shock, and ordinary anxiety can cause respiratory alkalosis, which reduces the normal concentration of H+. Metabolic alkalosis often results from prolonged, severe vomiting, which causes a loss of hydrogen and chloride ions (as components of HCl). Medications also can prompt alkalosis. These include diuretics that cause the body to lose potassium ions, as well as antacids when taken in excessive amounts, for instance by someone with persistent heartburn or an ulcer. Organic Compounds Essential to Human Functioning - Identify four types of organic molecules essential to human functioning - Explain the chemistry behind carbon’s affinity for covalently bonding in organic compounds - Provide examples of three types of carbohydrates, and identify the primary functions of carbohydrates in the body - Discuss four types of lipids important in human functioning - Describe the structure of proteins, and discuss their importance to human functioning - Identify the building blocks of nucleic acids, and the roles of DNA, RNA, and ATP in human functioning Organic compounds typically consist of groups of carbon atoms covalently bonded to hydrogen, usually oxygen, and often other elements as well. Created by living things, they are found throughout the world, in soils and seas, commercial products, and every cell of the human body. The four types most important to human structure and function are carbohydrates, lipids, proteins, and nucleotides. Before exploring these compounds, you need to first understand the chemistry of carbon. The Chemistry of Carbon What makes organic compounds ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four electrons in their valence shell, and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence shells by donating or accepting four electrons. Instead, they readily share electrons via covalent bonds. Commonly, carbon atoms share with other carbon atoms, often forming a long carbon chain referred to as a carbon skeleton. When they do share, however, they do not share all their electrons exclusively with each other. Rather, carbon atoms tend to share electrons with a variety of other elements, one of which is always hydrogen. Carbon and hydrogen groupings are called hydrocarbons. If you study the figures of organic compounds in the remainder of this chapter, you will see several with chains of hydrocarbons in one region of the compound. Many combinations are possible to fill carbon’s four “vacancies.” Carbon may share electrons with oxygen or nitrogen or other atoms in a particular region of an organic compound. Moreover, the atoms to which carbon atoms bond may also be part of a functional group. A functional group is a group of atoms linked by strong covalent bonds and tending to function in chemical reactions as a single unit. You can think of functional groups as tightly knit “cliques” whose members are unlikely to be parted. Five functional groups are important in human physiology; these are the hydroxyl, carboxyl, amino, methyl and phosphate groups (Table 2.1). Carbon’s affinity for covalent bonding means that many distinct and relatively stable organic molecules nevertheless readily form larger, more complex molecules. Any large molecule is referred to as macromolecule (macro- = “large”), and the organic compounds in this section all fit this description. However, some macromolecules are made up of several “copies” of single units called monomer (mono- = “one”; -mer = “part”). Like beads in a long necklace, these monomers link by covalent bonds to form long polymers (poly- = “many”). There are many examples of monomers and polymers among the organic compounds. Monomers form polymers by engaging in dehydration synthesis (see Figure 2.14). As was noted earlier, this reaction results in the release of a molecule of water. Each monomer contributes: One gives up a hydrogen atom and the other gives up a hydroxyl group. Polymers are split into monomers by hydrolysis (-lysis = “rupture”). The bonds between their monomers are broken, via the donation of a molecule of water, which contributes a hydrogen atom to one monomer and a hydroxyl group to the other. Carbohydrates The term carbohydrate means “hydrated carbon.” Recall that the root hydro- indicates water. A carbohydrate is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are found in the same two-to-one relative proportions they have in water. In fact, the chemical formula for a “generic” molecule of carbohydrate is (CH2O)n. Carbohydrates are referred to as saccharides, a word meaning “sugars.” Three forms are important in the body. Monosaccharides are the monomers of carbohydrates. Disaccharides (di- = “two”) are made up of two monomers. Polysaccharides are the polymers, and can consist of hundreds to thousands of monomers. Monosaccharides A monosaccharide is a monomer of carbohydrates. Five monosaccharides are important in the body. Three of these are the hexose sugars, so called because they each contain six atoms of carbon. These are glucose, fructose, and galactose, shown in Figure 2.18a. The remaining monosaccharides are the two pentose sugars, each of which contains five atoms of carbon. They are ribose and deoxyribose, shown in Figure 2.18b. Figure 2.18 Five Important Monosaccharides Disaccharides A disaccharide is a pair of monosaccharides. Disaccharides are formed via dehydration synthesis, and the bond linking them is referred to as a glycosidic bond (glyco- = “sugar”). Three disaccharides (shown in Figure 2.19) are important to humans. These are sucrose, commonly referred to as table sugar; lactose, or milk sugar; and maltose, or malt sugar. As you can tell from their common names, you consume these in your diet; however, your body cannot use them directly. Instead, in the digestive tract, they are split into their component monosaccharides via hydrolysis. Figure 2.19 Three Important Disaccharides All three important disaccharides form by dehydration synthesis. INTERACTIVE LINK Watch this video to observe the formation of a disaccharide. What happens when water encounters a glycosidic bond? Polysaccharides Polysaccharides can contain a few to a thousand or more monosaccharides. Three are important to the body (Figure 2.20): - Starches are polymers of glucose. They occur in long chains called amylose or branched chains called amylopectin, both of which are stored in plant-based foods and are relatively easy to digest. - Glycogen is also a polymer of glucose, but it is stored in the tissues of animals, especially in the muscles and liver. It is not considered a dietary carbohydrate because very little glycogen remains in animal tissues after slaughter; however, the human body stores excess glucose as glycogen, again, in the muscles and liver. - Cellulose, a polysaccharide that is the primary component of the cell wall of green plants, is the component of plant food referred to as “fiber”. In humans, cellulose/fiber is not digestible; however, dietary fiber has many health benefits. It helps you feel full so you eat less, it promotes a healthy digestive tract, and a diet high in fiber is thought to reduce the risk of heart disease and possibly some forms of cancer. Figure 2.20 Three Important Polysaccharides Three important polysaccharides are starches, glycogen, and fiber. Functions of Carbohydrates The body obtains carbohydrates from plant-based foods. Grains, fruits, and legumes and other vegetables provide most of the carbohydrate in the human diet, although lactose is found in dairy products. Although most body cells can break down other organic compounds for fuel, all body cells can use glucose. Moreover, nerve cells (neurons) in the brain, spinal cord, and through the peripheral nervous system, as well as red blood cells, can use only glucose for fuel. In the breakdown of glucose for energy, molecules of adenosine triphosphate, better known as ATP, are produced. Adenosine triphosphate (ATP) is composed of a ribose sugar, an adenine base, and three phosphate groups. ATP releases free energy when its phosphate bonds are broken, and thus supplies ready energy to the cell. More ATP is produced in the presence of oxygen (O2) than in pathways that do not use oxygen. The overall reaction for the conversion of the energy in glucose to energy stored in ATP can be written: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATPC6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATPIn addition to being a critical fuel source, carbohydrates are present in very small amounts in cells’ structure. For instance, some carbohydrate molecules bind with proteins to produce glycoproteins, and others combine with lipids to produce glycolipids, both of which are found in the membrane that encloses the contents of body cells. Lipids A lipid is one of a highly diverse group of compounds made up mostly of hydrocarbons. The few oxygen atoms they contain are often at the periphery of the molecule. Their nonpolar hydrocarbons make all lipids hydrophobic. In water, lipids do not form a true solution, but they may form an emulsion, which is the term for a mixture of solutions that do not mix well. Triglycerides A triglyceride is one of the most common dietary lipid groups, and the type found most abundantly in body tissues. This compound, which is commonly referred to as a fat, is formed from the synthesis of two types of molecules (Figure 2.21): - A glycerol backbone at the core of triglycerides, consists of three carbon atoms. - Three fatty acids, long chains of hydrocarbons with a carboxyl group and a methyl group at opposite ends, extend from each of the carbons of the glycerol. Figure 2.21 Triglycerides Triglycerides are composed of glycerol attached to three fatty acids via dehydration synthesis. Notice that glycerol gives up a hydrogen atom, and the carboxyl groups on the fatty acids each give up a hydroxyl group. Triglycerides form via dehydration synthesis. Glycerol gives up hydrogen atoms from its hydroxyl groups at each bond, and the carboxyl group on each fatty acid chain gives up a hydroxyl group. A total of three water molecules are thereby released. Fatty acid chains that have no double carbon bonds anywhere along their length and therefore contain the maximum number of hydrogen atoms are called saturated fatty acids. These straight, rigid chains pack tightly together and are solid or semi-solid at room temperature (Figure 2.22a). Butter and lard are examples, as is the fat found on a steak or in your own body. In contrast, fatty acids with one double carbon bond are kinked at that bond (Figure 2.22b). These monounsaturated fatty acids are therefore unable to pack together tightly, and are liquid at room temperature. Polyunsaturated fatty acids contain two or more double carbon bonds, and are also liquid at room temperature. Plant oils such as olive oil typically contain both mono- and polyunsaturated fatty acids. Figure 2.22 Fatty Acid Shapes The level of saturation of a fatty acid affects its shape. (a) Saturated fatty acid chains are straight. (b) Unsaturated fatty acid chains are kinked. Whereas a diet high in saturated fatty acids increases the risk of heart disease, a diet high in unsaturated fatty acids is thought to reduce the risk. This is especially true for the omega-3 unsaturated fatty acids found in cold-water fish such as salmon. These fatty acids have their first double carbon bond at the third hydrocarbon from the methyl group (referred to as the omega end of the molecule). Finally, trans fatty acids found in some processed foods, including some stick and tub margarines, are thought to be even more harmful to the heart and blood vessels than saturated fatty acids. Trans fats are created from unsaturated fatty acids (such as corn oil) when chemically treated to produce partially hydrogenated fats. As a group, triglycerides are a major fuel source for the body. When you are resting or asleep, a majority of the energy used to keep you alive is derived from triglycerides stored in your fat (adipose) tissues. Triglycerides also fuel long, slow physical activity such as gardening or hiking, and contribute a modest percentage of energy for vigorous physical activity. Dietary fat also assists the absorption and transport of the nonpolar fat-soluble vitamins A, D, E, and K. Additionally, stored body fat protects and cushions the body’s bones and internal organs, and acts as insulation to retain body heat. Fatty acids are also components of glycolipids, which are sugar-fat compounds found in the cell membrane. Lipoproteins are compounds in which the hydrophobic triglycerides are packaged in protein envelopes for transport in body fluids. Phospholipids As its name suggests, a phospholipid is a bond between the glycerol component of a lipid and a phosphorous molecule. In fact, phospholipids are similar in structure to triglycerides. However, instead of having three fatty acids, a phospholipid is generated from a diglyceride, a glycerol with just two fatty acid chains (Figure 2.23). The third binding site on the glycerol is taken up by the phosphate group, which in turn is attached to a polar “head” region of the molecule. Recall that triglycerides are nonpolar and hydrophobic. This still holds for the fatty acid portion of a phospholipid compound. However, the head of a phospholipid contains charges on the phosphate groups, as well as on the nitrogen atom. These charges make the phospholipid head hydrophilic. Therefore, phospholipids are said to have hydrophobic tails, containing the neutral fatty acids, and hydrophilic heads, containing the charged phosphate groups and nitrogen atom. Figure 2.23 Other Important Lipids (a) Phospholipids are composed of two fatty acids, glycerol, and a phosphate group. (b) Sterols are ring-shaped lipids. Shown here is cholesterol. (c) Prostaglandins are derived from unsaturated fatty acids. Prostaglandin E2 (PGE2) includes hydroxyl and carboxyl groups. Steroids A steroid compound (referred to as a sterol) has as its foundation a set of four hydrocarbon rings bonded to a variety of other atoms and molecules (see Figure 2.23b). Although both plants and animals synthesize sterols, the type that makes the most important contribution to human structure and function is cholesterol, which is synthesized by the liver in humans and animals and is also present in most animal-based foods. Like other lipids, cholesterol’s hydrocarbons make it hydrophobic; however, it has a polar hydroxyl head that is hydrophilic. Cholesterol is an important component of bile acids, compounds that help emulsify dietary fats. In fact, the word root chole- refers to bile. Cholesterol is also a building block of many hormones, signaling molecules that the body releases to regulate processes at distant sites. Finally, like phospholipids, cholesterol molecules are found in the cell membrane, where their hydrophobic and hydrophilic regions help regulate the flow of substances into and out of the cell. Prostaglandins Like a hormone, a prostaglandin is one of a group of signaling molecules, but prostaglandins are derived from unsaturated fatty acids (see Figure 2.23c). One reason that the omega-3 fatty acids found in fish are beneficial is that they stimulate the production of certain prostaglandins that help regulate aspects of blood pressure and inflammation, and thereby reduce the risk for heart disease. Prostaglandins also sensitize nerves to pain. One class of pain-relieving medications called nonsteroidal anti-inflammatory drugs (NSAIDs) works by reducing the effects of prostaglandins. Proteins You might associate proteins with muscle tissue, but in fact, proteins are critical components of all tissues and organs. A protein is an organic molecule composed of amino acids linked by peptide bonds. Proteins include the keratin in the epidermis of skin that protects underlying tissues, the collagen found in the dermis of skin, in bones, and in the meninges that cover the brain and spinal cord. Proteins are also components of many of the body’s functional chemicals, including digestive enzymes in the digestive tract, antibodies, the neurotransmitters that neurons use to communicate with other cells, and the peptide-based hormones that regulate certain body functions (for instance, growth hormone). While carbohydrates and lipids are composed of hydrocarbons and oxygen, all proteins also contain nitrogen (N), and many contain sulfur (S), in addition to carbon, hydrogen, and oxygen. Microstructure of Proteins Proteins are polymers made up of nitrogen-containing monomers called amino acids. An amino acid is a molecule composed of an amino group and a carboxyl group, together with a variable side chain. Just 20 different amino acids contribute to nearly all of the thousands of different proteins important in human structure and function. Body proteins contain a unique combination of a few dozen to a few hundred of these 20 amino acid monomers. All 20 of these amino acids share a similar structure (Figure 2.24). All consist of a central carbon atom to which the following are bonded: - a hydrogen atom - an alkaline (basic) amino group NH2 (see Table 2.1) - an acidic carboxyl group COOH (see Table 2.1) - a variable group Figure 2.24 Structure of an Amino Acid Notice that all amino acids contain both an acid (the carboxyl group) and a base (the amino group) (amine = “nitrogen-containing”). For this reason, they make excellent buffers, helping the body regulate acid–base balance. What distinguishes the 20 amino acids from one another is their variable group, which is referred to as a side chain or an R-group. This group can vary in size and can be polar or nonpolar, giving each amino acid its unique characteristics. For example, the side chains of two amino acids—cysteine and methionine—contain sulfur. Sulfur does not readily participate in hydrogen bonds, whereas all other amino acids do. This variation influences the way that proteins containing cysteine and methionine are assembled. Amino acids join via dehydration synthesis to form protein polymers (Figure 2.25). The unique bond holding amino acids together is called a peptide bond. A peptide bond is a covalent bond between two amino acids that forms by dehydration synthesis. A peptide, in fact, is a very short chain of amino acids. Strands containing fewer than about 100 amino acids are generally referred to as polypeptides rather than proteins. Figure 2.25 Peptide Bond Different amino acids join together to form peptides, polypeptides, or proteins via dehydration synthesis. The bonds between the amino acids are peptide bonds. The body is able to synthesize most of the amino acids from components of other molecules; however, nine cannot be synthesized and have to be consumed in the diet. These are known as the essential amino acids. Free amino acids available for protein construction are said to reside in the amino acid pool within cells. Structures within cells use these amino acids when assembling proteins. If a particular essential amino acid is not available in sufficient quantities in the amino acid pool, however, synthesis of proteins containing it can slow or even cease. Shape of Proteins Just as a fork cannot be used to eat soup and a spoon cannot be used to spear meat, a protein’s shape is essential to its function. A protein’s shape is determined, most fundamentally, by the sequence of amino acids of which it is made (Figure 2.26a). The sequence is called the primary structure of the protein. Figure 2.26 The Shape of Proteins (a) The primary structure is the sequence of amino acids that make up the polypeptide chain. (b) The secondary structure, which can take the form of an alpha-helix or a beta-pleated sheet, is maintained by hydrogen bonds between amino acids in different regions of the original polypeptide strand. (c) The tertiary structure occurs as a result of further folding and bonding of the secondary structure. (d) The quaternary structure occurs as a result of interactions between two or more tertiary subunits. The example shown here is hemoglobin, a protein in red blood cells which transports oxygen to body tissues. Although some polypeptides exist as linear chains, most are twisted or folded into more complex secondary structures that form when bonding occurs between amino acids with different properties at different regions of the polypeptide. The most common secondary structure is a spiral called an alpha-helix. If you were to take a length of string and simply twist it into a spiral, it would not hold the shape. Similarly, a strand of amino acids could not maintain a stable spiral shape without the help of hydrogen bonds, which create bridges between different regions of the same strand (see Figure 2.26b). Less commonly, a polypeptide chain can form a beta-pleated sheet, in which hydrogen bonds form bridges between different regions of a single polypeptide that has folded back upon itself, or between two or more adjacent polypeptide chains. The secondary structure of proteins further folds into a compact three-dimensional shape, referred to as the protein’s tertiary structure (see Figure 2.26c). In this configuration, amino acids that had been very distant in the primary chain can be brought quite close via hydrogen bonds or, in proteins containing cysteine, via disulfide bonds. A disulfide bond is a covalent bond between sulfur atoms in a polypeptide. Often, two or more separate polypeptides bond to form an even larger protein with a quaternary structure (see Figure 2.26d). The polypeptide subunits forming a quaternary structure can be identical or different. For instance, hemoglobin, the protein found in red blood cells is composed of four tertiary polypeptides, two of which are called alpha chains and two of which are called beta chains. When they are exposed to extreme heat, acids, bases, and certain other substances, proteins will denature. Denaturation is a change in the structure of a molecule through physical or chemical means. Denatured proteins lose their functional shape and are no longer able to carry out their jobs. An everyday example of protein denaturation is the curdling of milk when acidic lemon juice is added. The contribution of the shape of a protein to its function can hardly be exaggerated. For example, the long, slender shape of protein strands that make up muscle tissue is essential to their ability to contract (shorten) and relax (lengthen). As another example, bones contain long threads of a protein called collagen that acts as scaffolding upon which bone minerals are deposited. These elongated proteins, called fibrous proteins, are strong and durable and typically hydrophobic. In contrast, globular proteins are globes or spheres that tend to be highly reactive and are hydrophilic. The hemoglobin proteins packed into red blood cells are an example (see Figure 2.26d); however, globular proteins are abundant throughout the body, playing critical roles in most body functions. Enzymes, introduced earlier as protein catalysts, are examples of this. The next section takes a closer look at the action of enzymes. Proteins Function as Enzymes If you were trying to type a paper, and every time you hit a key on your laptop there was a delay of six or seven minutes before you got a response, you would probably get a new laptop. In a similar way, without enzymes to catalyze chemical reactions, the human body would be nonfunctional. It functions only because enzymes function. Enzymatic reactions—chemical reactions catalyzed by enzymes—begin when substrates bind to the enzyme. A substrate is a reactant in an enzymatic reaction. This occurs on regions of the enzyme known as active sites (Figure 2.27). Any given enzyme catalyzes just one type of chemical reaction. This characteristic, called specificity, is due to the fact that a substrate with a particular shape and electrical charge can bind only to an active site corresponding to that substrate. Due to this jigsaw puzzle-like match between an enzyme and its substrates, enzymes are known for their specificity. In fact, as an enzyme binds to its substrate(s), the enzyme structure changes slightly to find the best fit between the transition state (a structural intermediate between the substrate and product) and the active site, just as a rubber glove molds to a hand inserted into it. This active-site modification in the presence of substrate, along with the simultaneous formation of the transition state, is called induced fit. Overall, there is a specifically matched enzyme for each substrate and, thus, for each chemical reaction; however, there is some flexibility as well. Some enzymes have the ability to act on several different structurally related substrates. Figure 2.27 Steps in an Enzymatic Reaction According to the induced-fit model, the active site of the enzyme undergoes conformational changes upon binding with the substrate.(a) Substrates approach active sites on enzyme. (b) Substrates bind to active sites, producing an enzyme–substrate complex. (c) Changes internal to the enzyme–substrate complex facilitate interaction of the substrates. (d) Products are released and the enzyme returns to its original form, ready to facilitate another enzymatic reaction. Binding of a substrate produces an enzyme–substrate complex. It is likely that enzymes speed up chemical reactions in part because the enzyme–substrate complex undergoes a set of temporary and reversible changes that cause the substrates to be oriented toward each other in an optimal position to facilitate their interaction. This promotes increased reaction speed. The enzyme then releases the product(s), and resumes its original shape. The enzyme is then free to engage in the process again, and will do so as long as substrate remains. Other Functions of Proteins Advertisements for protein bars, powders, and shakes all say that protein is important in building, repairing, and maintaining muscle tissue, but the truth is that proteins contribute to all body tissues, from the skin to the brain cells. Also, certain proteins act as hormones, chemical messengers that help regulate body functions, For example, growth hormone is important for skeletal growth, among other roles. As was noted earlier, the basic and acidic components enable proteins to function as buffers in maintaining acid–base balance, but they also help regulate fluid–electrolyte balance. Proteins attract fluid, and a healthy concentration of proteins in the blood, the cells, and the spaces between cells helps ensure a balance of fluids in these various “compartments.” Moreover, proteins in the cell membrane help to transport electrolytes in and out of the cell, keeping these ions in a healthy balance. Like lipids, proteins can bind with carbohydrates. They can thereby produce glycoproteins or proteoglycans, both of which have many functions in the body. The body can use proteins for energy when carbohydrate and fat intake is inadequate, and stores of glycogen and adipose tissue become depleted. However, since there is no storage site for protein except functional tissues, using protein for energy causes tissue breakdown, and results in body wasting. Nucleotides The fourth type of organic compound important to human structure and function are the nucleotides (Figure 2.28). A nucleotide is one of a class of organic compounds composed of three subunits: - one or more phosphate groups - a pentose sugar: either deoxyribose or ribose - a nitrogen-containing base: adenine, cytosine, guanine, thymine, or uracil Nucleotides can be assembled into nucleic acids (DNA or RNA) or the energy compound adenosine triphosphate. Figure 2.28 Nucleotides (a) The building blocks of all nucleotides are one or more phosphate groups, a pentose sugar, and a nitrogen-containing base. (b) The nitrogen-containing bases of nucleotides. (c) The two pentose sugars of DNA and RNA. Nucleic Acids The nucleic acids differ in their type of pentose sugar. Deoxyribonucleic acid (DNA) is nucleotide that stores genetic information. DNA contains deoxyribose (so-called because it has one less atom of oxygen than ribose) plus one phosphate group and one nitrogen-containing base. The “choices” of base for DNA are adenine, cytosine, guanine, and thymine. Ribonucleic acid (RNA) is a ribose-containing nucleotide that helps manifest the genetic code as protein. RNA contains ribose, one phosphate group, and one nitrogen-containing base, but the “choices” of base for RNA are adenine, cytosine, guanine, and uracil. The nitrogen-containing bases adenine and guanine are classified as purines. A purine is a nitrogen-containing molecule with a double ring structure, which accommodates several nitrogen atoms. The bases cytosine, thymine (found in DNA only) and uracil (found in RNA only) are pyramidines. A pyramidine is a nitrogen-containing base with a single ring structure Bonds formed by dehydration synthesis between the pentose sugar of one nucleic acid monomer and the phosphate group of another form a “backbone,” from which the components’ nitrogen-containing bases protrude. In DNA, two such backbones attach at their protruding bases via hydrogen bonds. These twist to form a shape known as a double helix (Figure 2.29). The sequence of nitrogen-containing bases within a strand of DNA form the genes that act as a molecular code instructing cells in the assembly of amino acids into proteins. Humans have almost 22,000 genes in their DNA, locked up in the 46 chromosomes inside the nucleus of each cell (except red blood cells which lose their nuclei during development). These genes carry the genetic code to build one’s body, and are unique for each individual except identical twins. Figure 2.29 DNA In the DNA double helix, two strands attach via hydrogen bonds between the bases of the component nucleotides. In contrast, RNA consists of a single strand of sugar-phosphate backbone studded with bases. Messenger RNA (mRNA) is created during protein synthesis to carry the genetic instructions from the DNA to the cell’s protein manufacturing plants in the cytoplasm, the ribosomes. Adenosine Triphosphate The nucleotide adenosine triphosphate (ATP), is composed of a ribose sugar, an adenine base, and three phosphate groups (Figure 2.30). ATP is classified as a high energy compound because the two covalent bonds linking its three phosphates store a significant amount of potential energy. In the body, the energy released from these high energy bonds helps fuel the body’s activities, from muscle contraction to the transport of substances in and out of cells to anabolic chemical reactions. Figure 2.30 Structure of Adenosine Triphosphate (ATP) When a phosphate group is cleaved from ATP, the products are adenosine diphosphate (ADP) and inorganic phosphate (Pi). This hydrolysis reaction can be written: ATP + H2O → ADP + Pi + energyATP + H2O → ADP + Pi + energy Removal of a second phosphate leaves adenosine monophosphate (AMP) and two phosphate groups. Again, these reactions also liberate the energy that had been stored in the phosphate-phosphate bonds. They are reversible, too, as when ADP undergoes phosphorylation. Phosphorylation is the addition of a phosphate group to an organic compound, in this case, resulting in ATP. In such cases, the same level of energy that had been released during hydrolysis must be reinvested to power dehydration synthesis. Cells can also transfer a phosphate group from ATP to another organic compound. For example, when glucose first enters a cell, a phosphate group is transferred from ATP, forming glucose phosphate (C6H12O6—P) and ADP. Once glucose is phosphorylated in this way, it can be stored as glycogen or metabolized for immediate energy. Key Terms - acid - compound that releases hydrogen ions (H+) in solution - activation energy - amount of energy greater than the energy contained in the reactants, which must be overcome for a reaction to proceed - adenosine triphosphate (ATP) - nucleotide containing ribose and an adenine base that is essential in energy transfer - amino acid - building block of proteins; characterized by an amino and carboxyl functional groups and a variable side-chain - anion - atom with a negative charge - atom - smallest unit of an element that retains the unique properties of that element - atomic number - number of protons in the nucleus of an atom - base - compound that accepts hydrogen ions (H+) in solution - bond - electrical force linking atoms - buffer - solution containing a weak acid or a weak base that opposes wide fluctuations in the pH of body fluids - carbohydrate - class of organic compounds built from sugars, molecules containing carbon, hydrogen, and oxygen in a 1-2-1 ratio - catalyst - substance that increases the rate of a chemical reaction without itself being changed in the process - cation - atom with a positive charge - chemical energy - form of energy that is absorbed as chemical bonds form, stored as they are maintained, and released as they are broken - colloid - liquid mixture in which the solute particles consist of clumps of molecules large enough to scatter light - compound - substance composed of two or more different elements joined by chemical bonds - concentration - number of particles within a given space - covalent bond - chemical bond in which two atoms share electrons, thereby completing their valence shells - decomposition reaction - type of catabolic reaction in which one or more bonds within a larger molecule are broken, resulting in the release of smaller molecules or atoms - denaturation - change in the structure of a molecule through physical or chemical means - deoxyribonucleic acid (DNA) - deoxyribose-containing nucleotide that stores genetic information - disaccharide - pair of carbohydrate monomers bonded by dehydration synthesis via a glycosidic bond - disulfide bond - covalent bond formed within a polypeptide between sulfide groups of sulfur-containing amino acids, for example, cysteine - electron - subatomic particle having a negative charge and nearly no mass; found orbiting the atom’s nucleus - electron shell - area of space a given distance from an atom’s nucleus in which electrons are grouped - element - substance that cannot be created or broken down by ordinary chemical means - enzyme - protein or RNA that catalyzes chemical reactions - exchange reaction - type of chemical reaction in which bonds are both formed and broken, resulting in the transfer of components - functional group - group of atoms linked by strong covalent bonds that tends to behave as a distinct unit in chemical reactions with other atoms - hydrogen bond - dipole-dipole bond in which a hydrogen atom covalently bonded to an electronegative atom is weakly attracted to a second electronegative atom - inorganic compound - substance that does not contain both carbon and hydrogen - ion - atom with an overall positive or negative charge - ionic bond - attraction between an anion and a cation - isotope - one of the variations of an element in which the number of neutrons differ from each other - kinetic energy - energy that matter possesses because of its motion - lipid - class of nonpolar organic compounds built from hydrocarbons and distinguished by the fact that they are not soluble in water - macromolecule - large molecule formed by covalent bonding - mass number - sum of the number of protons and neutrons in the nucleus of an atom - matter - physical substance; that which occupies space and has mass - molecule - two or more atoms covalently bonded together - monosaccharide - monomer of carbohydrate; also known as a simple sugar - neutron - heavy subatomic particle having no electrical charge and found in the atom’s nucleus - nucleotide - class of organic compounds composed of one or more phosphate groups, a pentose sugar, and a base - organic compound - substance that contains both carbon and hydrogen - peptide bond - covalent bond formed by dehydration synthesis between two amino acids - periodic table of the elements - arrangement of the elements in a table according to their atomic number; elements having similar properties because of their electron arrangements compose columns in the table, while elements having the same number of valence shells compose rows in the table - pH - negative logarithm of the hydrogen ion (H+) concentration of a solution - phospholipid - a lipid compound in which a phosphate group is combined with a diglyceride - phosphorylation - addition of one or more phosphate groups to an organic compound - polar molecule - molecule with regions that have opposite charges resulting from uneven numbers of electrons in the nuclei of the atoms participating in the covalent bond - polysaccharide - compound consisting of more than two carbohydrate monomers bonded by dehydration synthesis via glycosidic bonds - potential energy - stored energy matter possesses because of the positioning or structure of its components - product - one or more substances produced by a chemical reaction - prostaglandin - lipid compound derived from fatty acid chains and important in regulating several body processes - protein - class of organic compounds that are composed of many amino acids linked together by peptide bonds - proton - heavy subatomic particle having a positive charge and found in the atom’s nucleus - purine - nitrogen-containing base with a double ring structure; adenine and guanine - pyrimidine - nitrogen-containing base with a single ring structure; cytosine, thiamine, and uracil - radioactive isotope - unstable, heavy isotope that gives off subatomic particles, or electromagnetic energy, as it decays; also called radioisotopes - reactant - one or more substances that enter into the reaction - ribonucleic acid (RNA) - ribose-containing nucleotide that helps manifest the genetic code as protein - solution - homogeneous liquid mixture in which a solute is dissolved into molecules within a solvent - steroid - (also, sterol) lipid compound composed of four hydrocarbon rings bonded to a variety of other atoms and molecules - substrate - reactant in an enzymatic reaction - suspension - liquid mixture in which particles distributed in the liquid settle out over time - synthesis reaction - type of anabolic reaction in which two or more atoms or molecules bond, resulting in the formation of a larger molecule - triglyceride - lipid compound composed of a glycerol molecule bonded with three fatty acid chains - valence shell - outermost electron shell of an atom Chapter Review 2.1 Elements and Atoms: The Building Blocks of Matter The human body is composed of elements, the most abundant of which are oxygen (O), carbon (C), hydrogen (H) and nitrogen (N). You obtain these elements from the foods you eat and the air you breathe. The smallest unit of an element that retains all of the properties of that element is an atom. But, atoms themselves contain many subatomic particles, the three most important of which are protons, neutrons, and electrons. These particles do not vary in quality from one element to another; rather, what gives an element its distinctive identification is the quantity of its protons, called its atomic number. Protons and neutrons contribute nearly all of an atom’s mass; the number of protons and neutrons is an element’s mass number. Heavier and lighter versions of the same element can occur in nature because these versions have different numbers of neutrons. Different versions of an element are called isotopes. The tendency of an atom to be stable or to react readily with other atoms is largely due to the behavior of the electrons within the atom’s outermost electron shell, called its valence shell. Helium, as well as larger atoms with eight electrons in their valence shell, is unlikely to participate in chemical reactions because they are stable. All other atoms tend to accept, donate, or share electrons in a process that brings the electrons in their valence shell to eight (or in the case of hydrogen, to two). 2.2 Chemical Bonds Each moment of life, atoms of oxygen, carbon, hydrogen, and the other elements of the human body are making and breaking chemical bonds. Ions are charged atoms that form when an atom donates or accepts one or more negatively charged electrons. Cations (ions with a positive charge) are attracted to anions (ions with a negative charge). This attraction is called an ionic bond. In covalent bonds, the participating atoms do not lose or gain electrons, but rather share them. Molecules with nonpolar covalent bonds are electrically balanced, and have a linear three-dimensional shape. Molecules with polar covalent bonds have “poles”—regions of weakly positive and negative charge—and have a triangular three-dimensional shape. An atom of oxygen and two atoms of hydrogen form water molecules by means of polar covalent bonds. Hydrogen bonds link hydrogen atoms already participating in polar covalent bonds to anions or electronegative regions of other polar molecules. Hydrogen bonds link water molecules, resulting in the properties of water that are important to living things. 2.3 Chemical Reactions Chemical reactions, in which chemical bonds are broken and formed, require an initial investment of energy. Kinetic energy, the energy of matter in motion, fuels the collisions of atoms, ions, and molecules that are necessary if their old bonds are to break and new ones to form. All molecules store potential energy, which is released when their bonds are broken. Four forms of energy essential to human functioning are: chemical energy, which is stored and released as chemical bonds are formed and broken; mechanical energy, which directly powers physical activity; radiant energy, emitted as waves such as in sunlight; and electrical energy, the power of moving electrons. Chemical reactions begin with reactants and end with products. Synthesis reactions bond reactants together, a process that requires energy, whereas decomposition reactions break the bonds within a reactant and thereby release energy. In exchange reactions, bonds are both broken and formed, and energy is exchanged. The rate at which chemical reactions occur is influenced by several properties of the reactants: temperature, concentration and pressure, and the presence or absence of a catalyst. An enzyme is a catalytic protein that speeds up chemical reactions in the human body. 2.4 Inorganic Compounds Essential to Human Functioning Inorganic compounds essential to human functioning include water, salts, acids, and bases. These compounds are inorganic; that is, they do not contain both hydrogen and carbon. Water is a lubricant and cushion, a heat sink, a component of liquid mixtures, a byproduct of dehydration synthesis reactions, and a reactant in hydrolysis reactions. Salts are compounds that, when dissolved in water, dissociate into ions other than H+ or OH–. In contrast, acids release H+ in solution, making it more acidic. Bases accept H+, thereby making the solution more alkaline (caustic). The pH of any solution is its relative concentration of H+. A solution with pH 7 is neutral. Solutions with pH below 7 are acids, and solutions with pH above 7 are bases. A change in a single digit on the pH scale (e.g., from 7 to 8) represents a ten-fold increase or decrease in the concentration of H+. In a healthy adult, the pH of blood ranges from 7.35 to 7.45. Homeostatic control mechanisms important for keeping blood in a healthy pH range include chemicals called buffers, weak acids and weak bases released when the pH of blood or other body fluids fluctuates in either direction outside of this normal range. 2.5 Organic Compounds Essential to Human Functioning Organic compounds essential to human functioning include carbohydrates, lipids, proteins, and nucleotides. These compounds are said to be organic because they contain both carbon and hydrogen. Carbon atoms in organic compounds readily share electrons with hydrogen and other atoms, usually oxygen, and sometimes nitrogen. Carbon atoms also may bond with one or more functional groups such as carboxyls, hydroxyls, aminos, or phosphates. Monomers are single units of organic compounds. They bond by dehydration synthesis to form polymers, which can in turn be broken by hydrolysis. Carbohydrate compounds provide essential body fuel. Their structural forms include monosaccharides such as glucose, disaccharides such as lactose, and polysaccharides, including starches (polymers of glucose), glycogen (the storage form of glucose), and fiber. All body cells can use glucose for fuel. It is converted via an oxidation-reduction reaction to ATP. Lipids are hydrophobic compounds that provide body fuel and are important components of many biological compounds. Triglycerides are the most abundant lipid in the body, and are composed of a glycerol backbone attached to three fatty acid chains. Phospholipids are compounds composed of a diglyceride with a phosphate group attached at the molecule’s head. The result is a molecule with polar and nonpolar regions. Steroids are lipids formed of four hydrocarbon rings. The most important is cholesterol. Prostaglandins are signaling molecules derived from unsaturated fatty acids. Proteins are critical components of all body tissues. They are made up of monomers called amino acids, which contain nitrogen, joined by peptide bonds. Protein shape is critical to its function. Most body proteins are globular. An example is enzymes, which catalyze chemical reactions. Nucleotides are compounds with three building blocks: one or more phosphate groups, a pentose sugar, and a nitrogen-containing base. DNA and RNA are nucleic acids that function in protein synthesis. ATP is the body’s fundamental molecule of energy transfer. Removal or addition of phosphates releases or invests energy. Interactive Link Questions Visit this website to view the periodic table. In the periodic table of the elements, elements in a single column have the same number of electrons that can participate in a chemical reaction. These electrons are known as “valence electrons.” For example, the elements in the first column all have a single valence electron—an electron that can be “donated” in a chemical reaction with another atom. What is the meaning of a mass number shown in parentheses? 2.Visit this website to learn about electrical energy and the attraction/repulsion of charges. What happens to the charged electroscope when a conductor is moved between its plastic sheets, and why? 3.Watch this video to observe the formation of a disaccharide. What happens when water encounters a glycosidic bond? Review Questions Together, just four elements make up more than 95 percent of the body’s mass. These include ________. - calcium, magnesium, iron, and carbon - oxygen, calcium, iron, and nitrogen - sodium, chlorine, carbon, and hydrogen - oxygen, carbon, hydrogen, and nitrogen The smallest unit of an element that still retains the distinctive behavior of that element is an ________. - electron - atom - elemental particle - isotope The characteristic that gives an element its distinctive properties is its number of ________. - protons - neutrons - electrons - atoms On the periodic table of the elements, mercury (Hg) has an atomic number of 80 and a mass number of 200.59. It has seven stable isotopes. The most abundant of these probably have ________. - about 80 neutrons each - fewer than 80 neutrons each - more than 80 neutrons each - more electrons than neutrons Nitrogen has an atomic number of seven. How many electron shells does it likely have? - one - two - three - four Which of the following is a molecule, but not a compound? - H2O - 2H - H2 - H+ A molecule of ammonia contains one atom of nitrogen and three atoms of hydrogen. These are linked with ________. - ionic bonds - nonpolar covalent bonds - polar covalent bonds - hydrogen bonds When an atom donates an electron to another atom, it becomes - an ion - an anion - nonpolar - all of the above A substance formed of crystals of equal numbers of cations and anions held together by ionic bonds is called a(n) ________. - noble gas - salt - electrolyte - dipole Which of the following statements about chemical bonds is true? - Covalent bonds are stronger than ionic bonds. - Hydrogen bonds occur between two atoms of hydrogen. - Bonding readily occurs between nonpolar and polar molecules. - A molecule of water is unlikely to bond with an ion. The energy stored in a foot of snow on a steep roof is ________. - potential energy - kinetic energy - radiant energy - activation energy The bonding of calcium, phosphorus, and other elements produces mineral crystals that are found in bone. This is an example of a(n) ________ reaction. - catabolic - synthesis - decomposition - exchange AB→A+BAB→A+B is a general notation for a(n) ________ reaction. - anabolic - endergonic - decomposition - exchange ________ reactions release energy. - Catabolic - Exergonic - Decomposition - Catabolic, exergonic, and decomposition Which of the following combinations of atoms is most likely to result in a chemical reaction? - hydrogen and hydrogen - hydrogen and helium - helium and helium - neon and helium Chewing a bite of bread mixes it with saliva and facilitates its chemical breakdown. This is most likely due to the fact that ________. - the inside of the mouth maintains a very high temperature - chewing stores potential energy - chewing facilitates synthesis reactions - saliva contains enzymes CH4 is methane. This compound is ________. - inorganic - organic - reactive - a crystal Which of the following is most likely to be found evenly distributed in water in a homogeneous solution? - sodium ions and chloride ions - NaCl molecules - salt crystals - red blood cells Jenny mixes up a batch of pancake batter, then stirs in some chocolate chips. As she is waiting for the first few pancakes to cook, she notices the chocolate chips sinking to the bottom of the clear glass mixing bowl. The chocolate-chip batter is an example of a ________. - solvent - solute - solution - suspension A substance dissociates into K+ and Cl– in solution. The substance is a(n) ________. - acid - base - salt - buffer Ty is three years old and as a result of a “stomach bug” has been vomiting for about 24 hours. His blood pH is 7.48. What does this mean? - Ty’s blood is slightly acidic. - Ty’s blood is slightly alkaline. - Ty’s blood is highly acidic. - Ty’s blood is within the normal range C6H12O6 is the chemical formula for a ________. - polymer of carbohydrate - pentose monosaccharide - hexose monosaccharide - all of the above What organic compound do brain cells primarily rely on for fuel? - glucose - glycogen - galactose - glycerol Which of the following is a functional group that is part of a building block of proteins? - phosphate - adenine - amino - ribose A pentose sugar is a part of the monomer used to build which type of macromolecule? - polysaccharides - nucleic acids - phosphorylated glucose - glycogen A phospholipid ________. - has both polar and nonpolar regions - is made up of a triglyceride bonded to a phosphate group - is a building block of ATP - can donate both cations and anions in solution In DNA, nucleotide bonding forms a compound with a characteristic shape known as a(n) ________. - beta chain - pleated sheet - alpha helix - double helix Uracil ________. - contains nitrogen - is a pyrimidine - is found in RNA - all of the above The ability of an enzyme’s active sites to bind only substrates of compatible shape and charge is known as ________. - selectivity - specificity - subjectivity - specialty Critical Thinking Questions The most abundant elements in the foods and beverages you consume are oxygen, carbon, hydrogen, and nitrogen. Why might having these elements in consumables be useful? 34.Oxygen, whose atomic number is eight, has three stable isotopes: 16O, 17O, and 18O. Explain what this means in terms of the number of protons and neutrons. 35.Magnesium is an important element in the human body, especially in bones. Magnesium’s atomic number is 12. Is it stable or reactive? Why? If it were to react with another atom, would it be more likely to accept or to donate one or more electrons? 36.Explain why CH4 is one of the most common molecules found in nature. Are the bonds between the atoms ionic or covalent? 37.In a hurry one day, you merely rinse your lunch dishes with water. As you are drying your salad bowl, you notice that it still has an oily film. Why was the water alone not effective in cleaning the bowl? 38.Could two atoms of oxygen engage in ionic bonding? Why or why not? 39.AB+CD→AD+BEAB+CD→AD+BE Is this a legitimate example of an exchange reaction? Why or why not? 40.When you do a load of laundry, why do you not just drop a bar of soap into the washing machine? In other words, why is laundry detergent sold as a liquid or powder? 41.The pH of lemon juice is 2, and the pH of orange juice is 4. Which of these is more acidic, and by how much? What does this mean? 42.During a party, Eli loses a bet and is forced to drink a bottle of lemon juice. Not long thereafter, he begins complaining of having difficulty breathing, and his friends take him to the local emergency room. There, he is given an intravenous solution of bicarbonate. Why? 43.If the disaccharide maltose is formed from two glucose monosaccharides, which are hexose sugars, how many atoms of carbon, hydrogen, and oxygen does maltose contain and why? 44.Once dietary fats are digested and absorbed, why can they not be released directly into the bloodstream?	oercommons	2025-03-18T00:36:05.334720	07/23/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/56352/overview", "title": "Anatomy and Physiology, Levels of Organization, The Chemical Level of Organization", "author": null }
https://oercommons.org/courseware/lesson/92491/overview	chapter 10 chapter 12 chapter 13 chapter 14 Chapter 14-Special Senses Chapter 16 Endocrine sys Chapter 18 blood Chapter 19 Heart chapter 2 Chapter 20 Blood Vessels Chapter 21-A Immune system Chapter 21-B Lymphatic system Chapter 22 Respiratory system Chapter 23 Digestive system Chapter 24 Urinary system Chapter 25 Fluids Chapter 26 Reproductive System chapter 3 chapter 4 chapter 5 chapter 6 chapter 9 Anatomy and Physiology I &II PowerPoints Overview PowerPoints for most of the A&P I & II courses. A&P I slides Those are PowerPoint files for the AP1 course. The axial, appendicular skeleton and muscular system chapters are not included in the slides as I only teach them in the lab. The nervous system chapters are mixed and do not follow the order of the book. In each chapter, there are several "group discussion questions." I assign those questions as pre-class assignments. Students must hand-write the answers and submit them through the LMS before we start the chapter for 4% of their total grade. This way, I guarantee they come and have an idea of what we are covering or are at least familiar with the terms. It must be hand-written to engage students in the activity; therefore, I grade them based on submission. In the lecture, I usually ask the students to check their answers within each group. Some slides have an "easy concept" tag. That indicates that the content of that particular slide is easy, and students can understand it by themselves. That helps me to skip the uncomplicated contents and gives me time to focus on the most challenging concepts. Please feel free to reach out if you have a question, correction, or a comment about the materials. Those are PowerPoint files for the AP1 course. The axial, appendicular skeleton and muscular system chapters are not included in the slides as I only teach them in the lab. The nervous system chapters are mixed and do not follow the order of the book. A&P II slides Those are PowerPoint files for the AP2 course. The blood vessels and the development and inheritance chapters are not included as I don't teach them. The lymphatic and immune system chapter is separated into two separate Powerpoints. . In each chapter, there are several "group discussion questions." I assign those questions as pre-class assignments. Students must hand-write the answers and submit them through the LMS before we start the chapter for 4% of their total grade. This way, I guarantee they come and have an idea of what we are covering or are at least familiar with the terms. It must be hand-written to engage students in the activity; therefore, I grade them based on submission. In the lecture, I usually ask the students to check their answers within each group. Some slides have an "easy concept" tag. That indicates that the content of that particular slide is easy, and students can understand it by themselves. That helps me to skip the uncomplicated contents and gives me time to focus on the most challenging concepts. Please feel free to reach out if you have a question, correction, or a comment about the materials. Those are PowerPoint files for the AP2 course. The blood vessels and the development and inheritance chapters are not included as I don't teach them. The lymphatic and immune system chapter is separated into two separate Powerpoints.	oercommons	2025-03-18T00:36:05.377077	05/05/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/92491/overview", "title": "Anatomy and Physiology I &II PowerPoints", "author": "Ahmed Katsha" }
https://oercommons.org/courseware/lesson/56366/overview	Axial Skeleton Introduction Figure 7.1 Lateral View of the Human Skull CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Describe the functions of the skeletal system and define its two major subdivisions - Identify the bones and bony structures of the skull, the cranial suture lines, the cranial fossae, and the openings in the skull - Discuss the vertebral column and regional variations in its bony components and curvatures - Describe the components of the thoracic cage - Discuss the embryonic development of the axial skeleton The skeletal system forms the rigid internal framework of the body. It consists of the bones, cartilages, and ligaments. Bones support the weight of the body, allow for body movements, and protect internal organs. Cartilage provides flexible strength and support for body structures such as the thoracic cage, the external ear, and the trachea and larynx. At joints of the body, cartilage can also unite adjacent bones or provide cushioning between them. Ligaments are the strong connective tissue bands that hold the bones at a moveable joint together and serve to prevent excessive movements of the joint that would result in injury. Providing movement of the skeleton are the muscles of the body, which are firmly attached to the skeleton via connective tissue structures called tendons. As muscles contract, they pull on the bones to produce movements of the body. Thus, without a skeleton, you would not be able to stand, run, or even feed yourself! Each bone of the body serves a particular function, and therefore bones vary in size, shape, and strength based on these functions. For example, the bones of the lower back and lower limb are thick and strong to support your body weight. Similarly, the size of a bony landmark that serves as a muscle attachment site on an individual bone is related to the strength of this muscle. Muscles can apply very strong pulling forces to the bones of the skeleton. To resist these forces, bones have enlarged bony landmarks at sites where powerful muscles attach. This means that not only the size of a bone, but also its shape, is related to its function. For this reason, the identification of bony landmarks is important during your study of the skeletal system. Bones are also dynamic organs that can modify their strength and thickness in response to changes in muscle strength or body weight. Thus, muscle attachment sites on bones will thicken if you begin a workout program that increases muscle strength. Similarly, the walls of weight-bearing bones will thicken if you gain body weight or begin pounding the pavement as part of a new running regimen. In contrast, a reduction in muscle strength or body weight will cause bones to become thinner. This may happen during a prolonged hospital stay, following limb immobilization in a cast, or going into the weightlessness of outer space. Even a change in diet, such as eating only soft food due to the loss of teeth, will result in a noticeable decrease in the size and thickness of the jaw bones. Divisions of the Skeletal System - Discuss the functions of the skeletal system - Distinguish between the axial skeleton and appendicular skeleton - Define the axial skeleton and its components - Define the appendicular skeleton and its components The skeletal system includes all of the bones, cartilages, and ligaments of the body that support and give shape to the body and body structures. The skeleton consists of the bones of the body. For adults, there are 206 bones in the skeleton. Younger individuals have higher numbers of bones because some bones fuse together during childhood and adolescence to form an adult bone. The primary functions of the skeleton are to provide a rigid, internal structure that can support the weight of the body against the force of gravity, and to provide a structure upon which muscles can act to produce movements of the body. The lower portion of the skeleton is specialized for stability during walking or running. In contrast, the upper skeleton has greater mobility and ranges of motion, features that allow you to lift and carry objects or turn your head and trunk. In addition to providing for support and movements of the body, the skeleton has protective and storage functions. It protects the internal organs, including the brain, spinal cord, heart, lungs, and pelvic organs. The bones of the skeleton serve as the primary storage site for important minerals such as calcium and phosphate. The bone marrow found within bones stores fat and houses the blood-cell producing tissue of the body. The skeleton is subdivided into two major divisions—the axial and appendicular. The Axial Skeleton The skeleton is subdivided into two major divisions—the axial and appendicular. The axial skeleton forms the vertical, central axis of the body and includes all bones of the head, neck, chest, and back (Figure 7.2). It serves to protect the brain, spinal cord, heart, and lungs. It also serves as the attachment site for muscles that move the head, neck, and back, and for muscles that act across the shoulder and hip joints to move their corresponding limbs. The axial skeleton of the adult consists of 80 bones, including the skull, the vertebral column, and the thoracic cage. The skull is formed by 22 bones. Also associated with the head are an additional seven bones, including the hyoid bone and the ear ossicles (three small bones found in each middle ear). The vertebral column consists of 24 bones, each called a vertebra, plus the sacrum and coccyx. The thoracic cage includes the 12 pairs of ribs, and the sternum, the flattened bone of the anterior chest. Figure 7.2 Axial and Appendicular Skeleton The axial skeleton supports the head, neck, back, and chest and thus forms the vertical axis of the body. It consists of the skull, vertebral column (including the sacrum and coccyx), and the thoracic cage, formed by the ribs and sternum. The appendicular skeleton is made up of all bones of the upper and lower limbs. The Appendicular Skeleton The appendicular skeleton includes all bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton. There are 126 bones in the appendicular skeleton of an adult. The bones of the appendicular skeleton are covered in a separate chapter. The Skull - List and identify the bones of the brain case and face - Locate the major suture lines of the skull and name the bones associated with each - Locate and define the boundaries of the anterior, middle, and posterior cranial fossae, the temporal fossa, and infratemporal fossa - Define the paranasal sinuses and identify the location of each - Name the bones that make up the walls of the orbit and identify the openings associated with the orbit - Identify the bones and structures that form the nasal septum and nasal conchae, and locate the hyoid bone - Identify the bony openings of the skull The cranium (skull) is the skeletal structure of the head that supports the face and protects the brain. It is subdivided into the facial bones and the brain case, or cranial vault (Figure 7.3). The facial bones underlie the facial structures, form the nasal cavity, enclose the eyeballs, and support the teeth of the upper and lower jaws. The rounded brain case surrounds and protects the brain and houses the middle and inner ear structures. In the adult, the skull consists of 22 individual bones, 21 of which are immobile and united into a single unit. The 22nd bone is the mandible (lower jaw), which is the only moveable bone of the skull. Figure 7.3 Parts of the Skull The skull consists of the rounded brain case that houses the brain and the facial bones that form the upper and lower jaws, nose, orbits, and other facial structures. INTERACTIVE LINK Watch this video to view a rotating and exploded skull, with color-coded bones. Which bone (yellow) is centrally located and joins with most of the other bones of the skull? Anterior View of Skull The anterior skull consists of the facial bones and provides the bony support for the eyes and structures of the face. This view of the skull is dominated by the openings of the orbits and the nasal cavity. Also seen are the upper and lower jaws, with their respective teeth (Figure 7.4). The orbit is the bony socket that houses the eyeball and muscles that move the eyeball or open the upper eyelid. The upper margin of the anterior orbit is the supraorbital margin. Located near the midpoint of the supraorbital margin is a small opening called the supraorbital foramen. This provides for passage of a sensory nerve to the skin of the forehead. Below the orbit is the infraorbital foramen, which is the point of emergence for a sensory nerve that supplies the anterior face below the orbit. Figure 7.4 Anterior View of Skull An anterior view of the skull shows the bones that form the forehead, orbits (eye sockets), nasal cavity, nasal septum, and upper and lower jaws. Inside the nasal area of the skull, the nasal cavity is divided into halves by the nasal septum. The upper portion of the nasal septum is formed by the perpendicular plate of the ethmoid bone and the lower portion is the vomer bone. Each side of the nasal cavity is triangular in shape, with a broad inferior space that narrows superiorly. When looking into the nasal cavity from the front of the skull, two bony plates are seen projecting from each lateral wall. The larger of these is the inferior nasal concha, an independent bone of the skull. Located just above the inferior concha is the middle nasal concha, which is part of the ethmoid bone. A third bony plate, also part of the ethmoid bone, is the superior nasal concha. It is much smaller and out of sight, above the middle concha. The superior nasal concha is located just lateral to the perpendicular plate, in the upper nasal cavity. Lateral View of Skull A view of the lateral skull is dominated by the large, rounded brain case above and the upper and lower jaws with their teeth below (Figure 7.5). Separating these areas is the bridge of bone called the zygomatic arch. The zygomatic arch is the bony arch on the side of skull that spans from the area of the cheek to just above the ear canal. It is formed by the junction of two bony processes: a short anterior component, the temporal process of the zygomatic bone (the cheekbone) and a longer posterior portion, the zygomatic process of the temporal bone, extending forward from the temporal bone. Thus the temporal process (anteriorly) and the zygomatic process (posteriorly) join together, like the two ends of a drawbridge, to form the zygomatic arch. One of the major muscles that pulls the mandible upward during biting and chewing arises from the zygomatic arch. On the lateral side of the brain case, above the level of the zygomatic arch, is a shallow space called the temporal fossa. Below the level of the zygomatic arch and deep to the vertical portion of the mandible is another space called the infratemporal fossa. Both the temporal fossa and infratemporal fossa contain muscles that act on the mandible during chewing. Figure 7.5 Lateral View of Skull The lateral skull shows the large rounded brain case, zygomatic arch, and the upper and lower jaws. The zygomatic arch is formed jointly by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. The shallow space above the zygomatic arch is the temporal fossa. The space inferior to the zygomatic arch and deep to the posterior mandible is the infratemporal fossa. Bones of the Brain Case The brain case contains and protects the brain. The interior space that is almost completely occupied by the brain is called the cranial cavity. This cavity is bounded superiorly by the rounded top of the skull, which is called the calvaria (skullcap), and the lateral and posterior sides of the skull. The bones that form the top and sides of the brain case are usually referred to as the “flat” bones of the skull. The floor of the brain case is referred to as the base of the skull. This is a complex area that varies in depth and has numerous openings for the passage of cranial nerves, blood vessels, and the spinal cord. Inside the skull, the base is subdivided into three large spaces, called the anterior cranial fossa, middle cranial fossa, and posterior cranial fossa (fossa = “trench or ditch”) (Figure 7.6). From anterior to posterior, the fossae increase in depth. The shape and depth of each fossa corresponds to the shape and size of the brain region that each houses. The boundaries and openings of the cranial fossae (singular = fossa) will be described in a later section. Figure 7.6 Cranial Fossae The bones of the brain case surround and protect the brain, which occupies the cranial cavity. The base of the brain case, which forms the floor of cranial cavity, is subdivided into the shallow anterior cranial fossa, the middle cranial fossa, and the deep posterior cranial fossa. The brain case consists of eight bones. These include the paired parietal and temporal bones, plus the unpaired frontal, occipital, sphenoid, and ethmoid bones. Parietal Bone The parietal bone forms most of the upper lateral side of the skull (see Figure 7.5). These are paired bones, with the right and left parietal bones joining together at the top of the skull. Each parietal bone is also bounded anteriorly by the frontal bone, inferiorly by the temporal bone, and posteriorly by the occipital bone. Temporal Bone The temporal bone forms the lower lateral side of the skull (see Figure 7.5). Common wisdom has it that the temporal bone (temporal = “time”) is so named because this area of the head (the temple) is where hair typically first turns gray, indicating the passage of time. The temporal bone is subdivided into several regions (Figure 7.7). The flattened, upper portion is the squamous portion of the temporal bone. Below this area and projecting anteriorly is the zygomatic process of the temporal bone, which forms the posterior portion of the zygomatic arch. Posteriorly is the mastoid portion of the temporal bone. Projecting inferiorly from this region is a large prominence, the mastoid process, which serves as a muscle attachment site. The mastoid process can easily be felt on the side of the head just behind your earlobe. On the interior of the skull, the petrous portion of each temporal bone forms the prominent, diagonally oriented petrous ridge in the floor of the cranial cavity. Located inside each petrous ridge are small cavities that house the structures of the middle and inner ears. Figure 7.7 Temporal Bone A lateral view of the isolated temporal bone shows the squamous, mastoid, and zygomatic portions of the temporal bone. Important landmarks of the temporal bone, as shown in Figure 7.8, include the following: - External acoustic meatus (ear canal)—This is the large opening on the lateral side of the skull that is associated with the ear. - Internal acoustic meatus—This opening is located inside the cranial cavity, on the medial side of the petrous ridge. It connects to the middle and inner ear cavities of the temporal bone. - Mandibular fossa—This is the deep, oval-shaped depression located on the external base of the skull, just in front of the external acoustic meatus. The mandible (lower jaw) joins with the skull at this site as part of the temporomandibular joint, which allows for movements of the mandible during opening and closing of the mouth. - Articular tubercle—The smooth ridge located immediately anterior to the mandibular fossa. Both the articular tubercle and mandibular fossa contribute to the temporomandibular joint, the joint that provides for movements between the temporal bone of the skull and the mandible. - Styloid process—Posterior to the mandibular fossa on the external base of the skull is an elongated, downward bony projection called the styloid process, so named because of its resemblance to a stylus (a pen or writing tool). This structure serves as an attachment site for several small muscles and for a ligament that supports the hyoid bone of the neck. (See also Figure 7.7.) - Stylomastoid foramen—This small opening is located between the styloid process and mastoid process. This is the point of exit for the cranial nerve that supplies the facial muscles. - Carotid canal—The carotid canal is a zig-zag shaped tunnel that provides passage through the base of the skull for one of the major arteries that supplies the brain. Its entrance is located on the outside base of the skull, anteromedial to the styloid process. The canal then runs anteromedially within the bony base of the skull, and then turns upward to its exit in the floor of the middle cranial cavity, above the foramen lacerum. Figure 7.8 External and Internal Views of Base of Skull (a) The hard palate is formed anteriorly by the palatine processes of the maxilla bones and posteriorly by the horizontal plate of the palatine bones. (b) The complex floor of the cranial cavity is formed by the frontal, ethmoid, sphenoid, temporal, and occipital bones. The lesser wing of the sphenoid bone separates the anterior and middle cranial fossae. The petrous ridge (petrous portion of temporal bone) separates the middle and posterior cranial fossae. Frontal Bone The frontal bone is the single bone that forms the forehead. At its anterior midline, between the eyebrows, there is a slight depression called the glabella (see Figure 7.5). The frontal bone also forms the supraorbital margin of the orbit. Near the middle of this margin, is the supraorbital foramen, the opening that provides passage for a sensory nerve to the forehead. The frontal bone is thickened just above each supraorbital margin, forming rounded brow ridges. These are located just behind your eyebrows and vary in size among individuals, although they are generally larger in males. Inside the cranial cavity, the frontal bone extends posteriorly. This flattened region forms both the roof of the orbit below and the floor of the anterior cranial cavity above (see Figure 7.8b). Occipital Bone The occipital bone is the single bone that forms the posterior skull and posterior base of the cranial cavity (Figure 7.9; see also Figure 7.8). On its outside surface, at the posterior midline, is a small protrusion called the external occipital protuberance, which serves as an attachment site for a ligament of the posterior neck. Lateral to either side of this bump is a superior nuchal line (nuchal = “nape” or “posterior neck”). The nuchal lines represent the most superior point at which muscles of the neck attach to the skull, with only the scalp covering the skull above these lines. On the base of the skull, the occipital bone contains the large opening of the foramen magnum, which allows for passage of the spinal cord as it exits the skull. On either side of the foramen magnum is an oval-shaped occipital condyle. These condyles form joints with the first cervical vertebra and thus support the skull on top of the vertebral column. Figure 7.9 Posterior View of Skull This view of the posterior skull shows attachment sites for muscles and joints that support the skull. Sphenoid Bone The sphenoid bone is a single, complex bone of the central skull (Figure 7.10). It serves as a “keystone” bone, because it joins with almost every other bone of the skull. The sphenoid forms much of the base of the central skull (see Figure 7.8) and also extends laterally to contribute to the sides of the skull (see Figure 7.5). Inside the cranial cavity, the right and left lesser wings of the sphenoid bone, which resemble the wings of a flying bird, form the lip of a prominent ridge that marks the boundary between the anterior and middle cranial fossae. The sella turcica (“Turkish saddle”) is located at the midline of the middle cranial fossa. This bony region of the sphenoid bone is named for its resemblance to the horse saddles used by the Ottoman Turks, with a high back and a tall front. The rounded depression in the floor of the sella turcica is the hypophyseal (pituitary) fossa, which houses the pea-sized pituitary (hypophyseal) gland. The greater wings of the sphenoid bone extend laterally to either side away from the sella turcica, where they form the anterior floor of the middle cranial fossa. The greater wing is best seen on the outside of the lateral skull, where it forms a rectangular area immediately anterior to the squamous portion of the temporal bone. On the inferior aspect of the skull, each half of the sphenoid bone forms two thin, vertically oriented bony plates. These are the medial pterygoid plate and lateral pterygoid plate (pterygoid = “wing-shaped”). The right and left medial pterygoid plates form the posterior, lateral walls of the nasal cavity. The somewhat larger lateral pterygoid plates serve as attachment sites for chewing muscles that fill the infratemporal space and act on the mandible. Figure 7.10 Sphenoid Bone Shown in isolation in (a) superior and (b) posterior views, the sphenoid bone is a single midline bone that forms the anterior walls and floor of the middle cranial fossa. It has a pair of lesser wings and a pair of greater wings. The sella turcica surrounds the hypophyseal fossa. Projecting downward are the medial and lateral pterygoid plates. The sphenoid has multiple openings for the passage of nerves and blood vessels, including the optic canal, superior orbital fissure, foramen rotundum, foramen ovale, and foramen spinosum. Ethmoid Bone The ethmoid bone is a single, midline bone that forms the roof and lateral walls of the upper nasal cavity, the upper portion of the nasal septum, and contributes to the medial wall of the orbit (Figure 7.11 and Figure 7.12). On the interior of the skull, the ethmoid also forms a portion of the floor of the anterior cranial cavity (see Figure 7.8b). Within the nasal cavity, the perpendicular plate of the ethmoid bone forms the upper portion of the nasal septum. The ethmoid bone also forms the lateral walls of the upper nasal cavity. Extending from each lateral wall are the superior nasal concha and middle nasal concha, which are thin, curved projections that extend into the nasal cavity (Figure 7.13). In the cranial cavity, the ethmoid bone forms a small area at the midline in the floor of the anterior cranial fossa. This region also forms the narrow roof of the underlying nasal cavity. This portion of the ethmoid bone consists of two parts, the crista galli and cribriform plates. The crista galli (“rooster’s comb or crest”) is a small upward bony projection located at the midline. It functions as an anterior attachment point for one of the covering layers of the brain. To either side of the crista galli is the cribriform plate (cribrum = “sieve”), a small, flattened area with numerous small openings termed olfactory foramina. Small nerve branches from the olfactory areas of the nasal cavity pass through these openings to enter the brain. The lateral portions of the ethmoid bone are located between the orbit and upper nasal cavity, and thus form the lateral nasal cavity wall and a portion of the medial orbit wall. Located inside this portion of the ethmoid bone are several small, air-filled spaces that are part of the paranasal sinus system of the skull. Figure 7.11 Sagittal Section of Skull This midline view of the sagittally sectioned skull shows the nasal septum. Figure 7.12 Ethmoid Bone The unpaired ethmoid bone is located at the midline within the central skull. It has an upward projection, the crista galli, and a downward projection, the perpendicular plate, which forms the upper nasal septum. The cribriform plates form both the roof of the nasal cavity and a portion of the anterior cranial fossa floor. The lateral sides of the ethmoid bone form the lateral walls of the upper nasal cavity, part of the medial orbit wall, and give rise to the superior and middle nasal conchae. The ethmoid bone also contains the ethmoid air cells. Figure 7.13 Lateral Wall of Nasal Cavity The three nasal conchae are curved bones that project from the lateral walls of the nasal cavity. The superior nasal concha and middle nasal concha are parts of the ethmoid bone. The inferior nasal concha is an independent bone of the skull. Sutures of the Skull A suture is an immobile joint between adjacent bones of the skull. The narrow gap between the bones is filled with dense, fibrous connective tissue that unites the bones. The long sutures located between the bones of the brain case are not straight, but instead follow irregular, tightly twisting paths. These twisting lines serve to tightly interlock the adjacent bones, thus adding strength to the skull for brain protection. The two suture lines seen on the top of the skull are the coronal and sagittal sutures. The coronal suture runs from side to side across the skull, within the coronal plane of section (see Figure 7.5). It joins the frontal bone to the right and left parietal bones. The sagittal suture extends posteriorly from the coronal suture, running along the midline at the top of the skull in the sagittal plane of section (see Figure 7.9). It unites the right and left parietal bones. On the posterior skull, the sagittal suture terminates by joining the lambdoid suture. The lambdoid suture extends downward and laterally to either side away from its junction with the sagittal suture. The lambdoid suture joins the occipital bone to the right and left parietal and temporal bones. This suture is named for its upside-down "V" shape, which resembles the capital letter version of the Greek letter lambda (Λ). The squamous suture is located on the lateral skull. It unites the squamous portion of the temporal bone with the parietal bone (see Figure 7.5). At the intersection of four bones is the pterion, a small, capital-H-shaped suture line region that unites the frontal bone, parietal bone, squamous portion of the temporal bone, and greater wing of the sphenoid bone. It is the weakest part of the skull. The pterion is located approximately two finger widths above the zygomatic arch and a thumb’s width posterior to the upward portion of the zygomatic bone. DISORDERS OF THE... Skeletal System Head and traumatic brain injuries are major causes of immediate death and disability, with bleeding and infections as possible additional complications. According to the Centers for Disease Control and Prevention (2010), approximately 30 percent of all injury-related deaths in the United States are caused by head injuries. The majority of head injuries involve falls. They are most common among young children (ages 0–4 years), adolescents (15–19 years), and the elderly (over 65 years). Additional causes vary, but prominent among these are automobile and motorcycle accidents. Strong blows to the brain-case portion of the skull can produce fractures. These may result in bleeding inside the skull with subsequent injury to the brain. The most common is a linear skull fracture, in which fracture lines radiate from the point of impact. Other fracture types include a comminuted fracture, in which the bone is broken into several pieces at the point of impact, or a depressed fracture, in which the fractured bone is pushed inward. In a contrecoup (counterblow) fracture, the bone at the point of impact is not broken, but instead a fracture occurs on the opposite side of the skull. Fractures of the occipital bone at the base of the skull can occur in this manner, producing a basilar fracture that can damage the artery that passes through the carotid canal. A blow to the lateral side of the head may fracture the bones of the pterion. The pterion is an important clinical landmark because located immediately deep to it on the inside of the skull is a major branch of an artery that supplies the skull and covering layers of the brain. A strong blow to this region can fracture the bones around the pterion. If the underlying artery is damaged, bleeding can cause the formation of a hematoma (collection of blood) between the brain and interior of the skull. As blood accumulates, it will put pressure on the brain. Symptoms associated with a hematoma may not be apparent immediately following the injury, but if untreated, blood accumulation will exert increasing pressure on the brain and can result in death within a few hours. INTERACTIVE LINK View this animation to see how a blow to the head may produce a contrecoup (counterblow) fracture of the basilar portion of the occipital bone on the base of the skull. Why may a basilar fracture be life threatening? Facial Bones of the Skull The facial bones of the skull form the upper and lower jaws, the nose, nasal cavity and nasal septum, and the orbit. The facial bones include 14 bones, with six paired bones and two unpaired bones. The paired bones are the maxilla, palatine, zygomatic, nasal, lacrimal, and inferior nasal conchae bones. The unpaired bones are the vomer and mandible bones. Although classified with the brain-case bones, the ethmoid bone also contributes to the nasal septum and the walls of the nasal cavity and orbit. Maxillary Bone The maxillary bone, often referred to simply as the maxilla (plural = maxillae), is one of a pair that together form the upper jaw, much of the hard palate, the medial floor of the orbit, and the lateral base of the nose (see Figure 7.4). The curved, inferior margin of the maxillary bone that forms the upper jaw and contains the upper teeth is the alveolar process of the maxilla(Figure 7.14). Each tooth is anchored into a deep socket called an alveolus. On the anterior maxilla, just below the orbit, is the infraorbital foramen. This is the point of exit for a sensory nerve that supplies the nose, upper lip, and anterior cheek. On the inferior skull, the palatine process from each maxillary bone can be seen joining together at the midline to form the anterior three-quarters of the hard palate (see Figure 7.8a). The hard palate is the bony plate that forms the roof of the mouth and floor of the nasal cavity, separating the oral and nasal cavities. Figure 7.14 Maxillary Bone The maxillary bone forms the upper jaw and supports the upper teeth. Each maxilla also forms the lateral floor of each orbit and the majority of the hard palate. Palatine Bone The palatine bone is one of a pair of irregularly shaped bones that contribute small areas to the lateral walls of the nasal cavity and the medial wall of each orbit. The largest region of each of the palatine bone is the horizontal plate. The plates from the right and left palatine bones join together at the midline to form the posterior quarter of the hard palate (see Figure 7.8a). Thus, the palatine bones are best seen in an inferior view of the skull and hard palate. HOMEOSTATIC IMBALANCES Cleft Lip and Cleft Palate During embryonic development, the right and left maxilla bones come together at the midline to form the upper jaw. At the same time, the muscle and skin overlying these bones join together to form the upper lip. Inside the mouth, the palatine processes of the maxilla bones, along with the horizontal plates of the right and left palatine bones, join together to form the hard palate. If an error occurs in these developmental processes, a birth defect of cleft lip or cleft palate may result. Cleft lip is a common development defect that affects approximately 1:1000 births, most of which are male. This defect involves a partial or complete failure of the right and left portions of the upper lip to fuse together, leaving a cleft (gap). A more severe developmental defect is cleft palate, which affects the hard palate. The hard palate is the bony structure that separates the nasal cavity from the oral cavity. It is formed during embryonic development by the midline fusion of the horizontal plates from the right and left palatine bones and the palatine processes of the maxilla bones. Cleft palate affects approximately 1:2500 births and is more common in females. It results from a failure of the two halves of the hard palate to completely come together and fuse at the midline, thus leaving a gap between them. This gap allows for communication between the nasal and oral cavities. In severe cases, the bony gap continues into the anterior upper jaw where the alveolar processes of the maxilla bones also do not properly join together above the front teeth. If this occurs, a cleft lip will also be seen. Because of the communication between the oral and nasal cavities, a cleft palate makes it very difficult for an infant to generate the suckling needed for nursing, thus leaving the infant at risk for malnutrition. Surgical repair is required to correct cleft palate defects. Zygomatic Bone The zygomatic bone is also known as the cheekbone. Each of the paired zygomatic bones forms much of the lateral wall of the orbit and the lateral-inferior margins of the anterior orbital opening (see Figure 7.4). The short temporal process of the zygomatic bone projects posteriorly, where it forms the anterior portion of the zygomatic arch (see Figure 7.5). Nasal Bone The nasal bone is one of two small bones that articulate (join) with each other to form the bony base (bridge) of the nose. They also support the cartilages that form the lateral walls of the nose (see Figure 7.11). These are the bones that are damaged when the nose is broken. Lacrimal Bone Each lacrimal bone is a small, rectangular bone that forms the anterior, medial wall of the orbit (see Figure 7.4 and Figure 7.5). The anterior portion of the lacrimal bone forms a shallow depression called the lacrimal fossa, and extending inferiorly from this is the nasolacrimal canal. The lacrimal fluid (tears of the eye), which serves to maintain the moist surface of the eye, drains at the medial corner of the eye into the nasolacrimal canal. This duct then extends downward to open into the nasal cavity, behind the inferior nasal concha. In the nasal cavity, the lacrimal fluid normally drains posteriorly, but with an increased flow of tears due to crying or eye irritation, some fluid will also drain anteriorly, thus causing a runny nose. Inferior Nasal Conchae The right and left inferior nasal conchae form a curved bony plate that projects into the nasal cavity space from the lower lateral wall (see Figure 7.13). The inferior concha is the largest of the nasal conchae and can easily be seen when looking into the anterior opening of the nasal cavity. Vomer Bone The unpaired vomer bone, often referred to simply as the vomer, is triangular-shaped and forms the posterior-inferior part of the nasal septum (see Figure 7.11). The vomer is best seen when looking from behind into the posterior openings of the nasal cavity (see Figure 7.8a). In this view, the vomer is seen to form the entire height of the nasal septum. A much smaller portion of the vomer can also be seen when looking into the anterior opening of the nasal cavity. Mandible The mandible forms the lower jaw and is the only moveable bone of the skull. At the time of birth, the mandible consists of paired right and left bones, but these fuse together during the first year to form the single U-shaped mandible of the adult skull. Each side of the mandible consists of a horizontal body and posteriorly, a vertically oriented ramus of the mandible (ramus = “branch”). The outside margin of the mandible, where the body and ramus come together is called the angle of the mandible(Figure 7.15). The ramus on each side of the mandible has two upward-going bony projections. The more anterior projection is the flattened coronoid process of the mandible, which provides attachment for one of the biting muscles. The posterior projection is the condylar process of the mandible, which is topped by the oval-shaped condyle. The condyle of the mandible articulates (joins) with the mandibular fossa and articular tubercle of the temporal bone. Together these articulations form the temporomandibular joint, which allows for opening and closing of the mouth (see Figure 7.5). The broad U-shaped curve located between the coronoid and condylar processes is the mandibular notch. Important landmarks for the mandible include the following: - Alveolar process of the mandible—This is the upper border of the mandibular body and serves to anchor the lower teeth. - Mental protuberance—The forward projection from the inferior margin of the anterior mandible that forms the chin (mental = “chin”). - Mental foramen—The opening located on each side of the anterior-lateral mandible, which is the exit site for a sensory nerve that supplies the chin. - Mylohyoid line—This bony ridge extends along the inner aspect of the mandibular body (see Figure 7.11). The muscle that forms the floor of the oral cavity attaches to the mylohyoid lines on both sides of the mandible. - Mandibular foramen—This opening is located on the medial side of the ramus of the mandible. The opening leads into a tunnel that runs down the length of the mandibular body. The sensory nerve and blood vessels that supply the lower teeth enter the mandibular foramen and then follow this tunnel. Thus, to numb the lower teeth prior to dental work, the dentist must inject anesthesia into the lateral wall of the oral cavity at a point prior to where this sensory nerve enters the mandibular foramen. - Lingula—This small flap of bone is named for its shape (lingula = “little tongue”). It is located immediately next to the mandibular foramen, on the medial side of the ramus. A ligament that anchors the mandible during opening and closing of the mouth extends down from the base of the skull and attaches to the lingula. Figure 7.15 Isolated Mandible The mandible is the only moveable bone of the skull. The Orbit The orbit is the bony socket that houses the eyeball and contains the muscles that move the eyeball or open the upper eyelid. Each orbit is cone-shaped, with a narrow posterior region that widens toward the large anterior opening. To help protect the eye, the bony margins of the anterior opening are thickened and somewhat constricted. The medial walls of the two orbits are parallel to each other but each lateral wall diverges away from the midline at a 45° angle. This divergence provides greater lateral peripheral vision. The walls of each orbit include contributions from seven skull bones (Figure 7.16). The frontal bone forms the roof and the zygomatic bone forms the lateral wall and lateral floor. The medial floor is primarily formed by the maxilla, with a small contribution from the palatine bone. The ethmoid bone and lacrimal bone make up much of the medial wall and the sphenoid bone forms the posterior orbit. At the posterior apex of the orbit is the opening of the optic canal, which allows for passage of the optic nerve from the retina to the brain. Lateral to this is the elongated and irregularly shaped superior orbital fissure, which provides passage for the artery that supplies the eyeball, sensory nerves, and the nerves that supply the muscles involved in eye movements. Figure 7.16 Bones of the Orbit Seven skull bones contribute to the walls of the orbit. Opening into the posterior orbit from the cranial cavity are the optic canal and superior orbital fissure. The Nasal Septum and Nasal Conchae The nasal septum consists of both bone and cartilage components (Figure 7.17; see also Figure 7.11). The upper portion of the septum is formed by the perpendicular plate of the ethmoid bone. The lower and posterior parts of the septum are formed by the triangular-shaped vomer bone. In an anterior view of the skull, the perpendicular plate of the ethmoid bone is easily seen inside the nasal opening as the upper nasal septum, but only a small portion of the vomer is seen as the inferior septum. A better view of the vomer bone is seen when looking into the posterior nasal cavity with an inferior view of the skull, where the vomer forms the full height of the nasal septum. The anterior nasal septum is formed by the septal cartilage, a flexible plate that fills in the gap between the perpendicular plate of the ethmoid and vomer bones. This cartilage also extends outward into the nose where it separates the right and left nostrils. The septal cartilage is not found in the dry skull. Attached to the lateral wall on each side of the nasal cavity are the superior, middle, and inferior nasal conchae (singular = concha), which are named for their positions (see Figure 7.13). These are bony plates that curve downward as they project into the space of the nasal cavity. They serve to swirl the incoming air, which helps to warm and moisturize it before the air moves into the delicate air sacs of the lungs. This also allows mucus, secreted by the tissue lining the nasal cavity, to trap incoming dust, pollen, bacteria, and viruses. The largest of the conchae is the inferior nasal concha, which is an independent bone of the skull. The middle concha and the superior conchae, which is the smallest, are both formed by the ethmoid bone. When looking into the anterior nasal opening of the skull, only the inferior and middle conchae can be seen. The small superior nasal concha is well hidden above and behind the middle concha. Figure 7.17 Nasal Septum The nasal septum is formed by the perpendicular plate of the ethmoid bone and the vomer bone. The septal cartilage fills the gap between these bones and extends into the nose. Cranial Fossae Inside the skull, the floor of the cranial cavity is subdivided into three cranial fossae (spaces), which increase in depth from anterior to posterior (see Figure 7.6, Figure 7.8b, and Figure 7.11). Since the brain occupies these areas, the shape of each conforms to the shape of the brain regions that it contains. Each cranial fossa has anterior and posterior boundaries and is divided at the midline into right and left areas by a significant bony structure or opening. Anterior Cranial Fossa The anterior cranial fossa is the most anterior and the shallowest of the three cranial fossae. It overlies the orbits and contains the frontal lobes of the brain. Anteriorly, the anterior fossa is bounded by the frontal bone, which also forms the majority of the floor for this space. The lesser wings of the sphenoid bone form the prominent ledge that marks the boundary between the anterior and middle cranial fossae. Located in the floor of the anterior cranial fossa at the midline is a portion of the ethmoid bone, consisting of the upward projecting crista galli and to either side of this, the cribriform plates. Middle Cranial Fossa The middle cranial fossa is deeper and situated posterior to the anterior fossa. It extends from the lesser wings of the sphenoid bone anteriorly, to the petrous ridges (petrous portion of the temporal bones) posteriorly. The large, diagonally positioned petrous ridges give the middle cranial fossa a butterfly shape, making it narrow at the midline and broad laterally. The temporal lobes of the brain occupy this fossa. The middle cranial fossa is divided at the midline by the upward bony prominence of the sella turcica, a part of the sphenoid bone. The middle cranial fossa has several openings for the passage of blood vessels and cranial nerves (see Figure 7.8). Openings in the middle cranial fossa are as follows: - Optic canal—This opening is located at the anterior lateral corner of the sella turcica. It provides for passage of the optic nerve into the orbit. - Superior orbital fissure—This large, irregular opening into the posterior orbit is located on the anterior wall of the middle cranial fossa, lateral to the optic canal and under the projecting margin of the lesser wing of the sphenoid bone. Nerves to the eyeball and associated muscles, and sensory nerves to the forehead pass through this opening. - Foramen rotundum—This rounded opening (rotundum = “round”) is located in the floor of the middle cranial fossa, just inferior to the superior orbital fissure. It is the exit point for a major sensory nerve that supplies the cheek, nose, and upper teeth. - Foramen ovale of the middle cranial fossa—This large, oval-shaped opening in the floor of the middle cranial fossa provides passage for a major sensory nerve to the lateral head, cheek, chin, and lower teeth. - Foramen spinosum—This small opening, located posterior-lateral to the foramen ovale, is the entry point for an important artery that supplies the covering layers surrounding the brain. The branching pattern of this artery forms readily visible grooves on the internal surface of the skull and these grooves can be traced back to their origin at the foramen spinosum. - Carotid canal—This is the zig-zag passageway through which a major artery to the brain enters the skull. The entrance to the carotid canal is located on the inferior aspect of the skull, anteromedial to the styloid process (see Figure 7.8a). From here, the canal runs anteromedially within the bony base of the skull. Just above the foramen lacerum, the carotid canal opens into the middle cranial cavity, near the posterior-lateral base of the sella turcica. - Foramen lacerum—This irregular opening is located in the base of the skull, immediately inferior to the exit of the carotid canal. This opening is an artifact of the dry skull, because in life it is completely filled with cartilage. All the openings of the skull that provide for passage of nerves or blood vessels have smooth margins; the word lacerum (“ragged” or “torn”) tells us that this opening has ragged edges and thus nothing passes through it. Posterior Cranial Fossa The posterior cranial fossa is the most posterior and deepest portion of the cranial cavity. It contains the cerebellum of the brain. The posterior fossa is bounded anteriorly by the petrous ridges, while the occipital bone forms the floor and posterior wall. It is divided at the midline by the large foramen magnum (“great aperture”), the opening that provides for passage of the spinal cord. Located on the medial wall of the petrous ridge in the posterior cranial fossa is the internal acoustic meatus (see Figure 7.11). This opening provides for passage of the nerve from the hearing and equilibrium organs of the inner ear, and the nerve that supplies the muscles of the face. Located at the anterior-lateral margin of the foramen magnum is the hypoglossal canal. These emerge on the inferior aspect of the skull at the base of the occipital condyle and provide passage for an important nerve to the tongue. Immediately inferior to the internal acoustic meatus is the large, irregularly shaped jugular foramen (see Figure 7.8a). Several cranial nerves from the brain exit the skull via this opening. It is also the exit point through the base of the skull for all the venous return blood leaving the brain. The venous structures that carry blood inside the skull form large, curved grooves on the inner walls of the posterior cranial fossa, which terminate at each jugular foramen. Paranasal Sinuses The paranasal sinuses are hollow, air-filled spaces located within certain bones of the skull (Figure 7.18). All of the sinuses communicate with the nasal cavity (paranasal = “next to nasal cavity”) and are lined with nasal mucosa. They serve to reduce bone mass and thus lighten the skull, and they also add resonance to the voice. This second feature is most obvious when you have a cold or sinus congestion. These produce swelling of the mucosa and excess mucus production, which can obstruct the narrow passageways between the sinuses and the nasal cavity, causing your voice to sound different to yourself and others. This blockage can also allow the sinuses to fill with fluid, with the resulting pressure producing pain and discomfort. The paranasal sinuses are named for the skull bone that each occupies. The frontal sinus is located just above the eyebrows, within the frontal bone (see Figure 7.17). This irregular space may be divided at the midline into bilateral spaces, or these may be fused into a single sinus space. The frontal sinus is the most anterior of the paranasal sinuses. The largest sinus is the maxillary sinus. These are paired and located within the right and left maxillary bones, where they occupy the area just below the orbits. The maxillary sinuses are most commonly involved during sinus infections. Because their connection to the nasal cavity is located high on their medial wall, they are difficult to drain. The sphenoid sinus is a single, midline sinus. It is located within the body of the sphenoid bone, just anterior and inferior to the sella turcica, thus making it the most posterior of the paranasal sinuses. The lateral aspects of the ethmoid bone contain multiple small spaces separated by very thin bony walls. Each of these spaces is called an ethmoid air cell. These are located on both sides of the ethmoid bone, between the upper nasal cavity and medial orbit, just behind the superior nasal conchae. Figure 7.18 Paranasal Sinuses The paranasal sinuses are hollow, air-filled spaces named for the skull bone that each occupies. The most anterior is the frontal sinus, located in the frontal bone above the eyebrows. The largest are the maxillary sinuses, located in the right and left maxillary bones below the orbits. The most posterior is the sphenoid sinus, located in the body of the sphenoid bone, under the sella turcica. The ethmoid air cells are multiple small spaces located in the right and left sides of the ethmoid bone, between the medial wall of the orbit and lateral wall of the upper nasal cavity. Hyoid Bone The hyoid bone is an independent bone that does not contact any other bone and thus is not part of the skull (Figure 7.19). It is a small U-shaped bone located in the upper neck near the level of the inferior mandible, with the tips of the “U” pointing posteriorly. The hyoid serves as the base for the tongue above, and is attached to the larynx below and the pharynx posteriorly. The hyoid is held in position by a series of small muscles that attach to it either from above or below. These muscles act to move the hyoid up/down or forward/back. Movements of the hyoid are coordinated with movements of the tongue, larynx, and pharynx during swallowing and speaking. Figure 7.19 Hyoid Bone The hyoid bone is located in the upper neck and does not join with any other bone. It provides attachments for muscles that act on the tongue, larynx, and pharynx. The Vertebral Column - Describe each region of the vertebral column and the number of bones in each region - Discuss the curves of the vertebral column and how these change after birth - Describe a typical vertebra and determine the distinguishing characteristics for vertebrae in each vertebral region and features of the sacrum and the coccyx - Define the structure of an intervertebral disc - Determine the location of the ligaments that provide support for the vertebral column The vertebral column is also known as the spinal column or spine (Figure 7.20). It consists of a sequence of vertebrae (singular = vertebra), each of which is separated and united by an intervertebral disc. Together, the vertebrae and intervertebral discs form the vertebral column. It is a flexible column that supports the head, neck, and body and allows for their movements. It also protects the spinal cord, which passes down the back through openings in the vertebrae. Figure 7.20 Vertebral Column The adult vertebral column consists of 24 vertebrae, plus the sacrum and coccyx. The vertebrae are divided into three regions: cervical C1–C7 vertebrae, thoracic T1–T12 vertebrae, and lumbar L1–L5 vertebrae. The vertebral column is curved, with two primary curvatures (thoracic and sacrococcygeal curves) and two secondary curvatures (cervical and lumbar curves). Regions of the Vertebral Column The vertebral column originally develops as a series of 33 vertebrae, but this number is eventually reduced to 24 vertebrae, plus the sacrum and coccyx. The vertebral column is subdivided into five regions, with the vertebrae in each area named for that region and numbered in descending order. In the neck, there are seven cervical vertebrae, each designated with the letter “C” followed by its number. Superiorly, the C1 vertebra articulates (forms a joint) with the occipital condyles of the skull. Inferiorly, C1 articulates with the C2 vertebra, and so on. Below these are the 12 thoracic vertebrae, designated T1–T12. The lower back contains the L1–L5 lumbar vertebrae. The single sacrum, which is also part of the pelvis, is formed by the fusion of five sacral vertebrae. Similarly, the coccyx, or tailbone, results from the fusion of four small coccygeal vertebrae. However, the sacral and coccygeal fusions do not start until age 20 and are not completed until middle age. An interesting anatomical fact is that almost all mammals have seven cervical vertebrae, regardless of body size. This means that there are large variations in the size of cervical vertebrae, ranging from the very small cervical vertebrae of a shrew to the greatly elongated vertebrae in the neck of a giraffe. In a full-grown giraffe, each cervical vertebra is 11 inches tall. Curvatures of the Vertebral Column The adult vertebral column does not form a straight line, but instead has four curvatures along its length (see Figure 7.20). These curves increase the vertebral column’s strength, flexibility, and ability to absorb shock. When the load on the spine is increased, by carrying a heavy backpack for example, the curvatures increase in depth (become more curved) to accommodate the extra weight. They then spring back when the weight is removed. The four adult curvatures are classified as either primary or secondary curvatures. Primary curves are retained from the original fetal curvature, while secondary curvatures develop after birth. During fetal development, the body is flexed anteriorly into the fetal position, giving the entire vertebral column a single curvature that is concave anteriorly. In the adult, this fetal curvature is retained in two regions of the vertebral column as the thoracic curve, which involves the thoracic vertebrae, and the sacrococcygeal curve, formed by the sacrum and coccyx. Each of these is thus called a primary curve because they are retained from the original fetal curvature of the vertebral column. A secondary curve develops gradually after birth as the child learns to sit upright, stand, and walk. Secondary curves are concave posteriorly, opposite in direction to the original fetal curvature. The cervical curve of the neck region develops as the infant begins to hold their head upright when sitting. Later, as the child begins to stand and then to walk, the lumbar curve of the lower back develops. In adults, the lumbar curve is generally deeper in females. Disorders associated with the curvature of the spine include kyphosis (an excessive posterior curvature of the thoracic region), lordosis (an excessive anterior curvature of the lumbar region), and scoliosis (an abnormal, lateral curvature, accompanied by twisting of the vertebral column). DISORDERS OF THE... Vertebral Column Developmental anomalies, pathological changes, or obesity can enhance the normal vertebral column curves, resulting in the development of abnormal or excessive curvatures (Figure 7.21). Kyphosis, also referred to as humpback or hunchback, is an excessive posterior curvature of the thoracic region. This can develop when osteoporosis causes weakening and erosion of the anterior portions of the upper thoracic vertebrae, resulting in their gradual collapse (Figure 7.22). Lordosis, or swayback, is an excessive anterior curvature of the lumbar region and is most commonly associated with obesity or late pregnancy. The accumulation of body weight in the abdominal region results an anterior shift in the line of gravity that carries the weight of the body. This causes in an anterior tilt of the pelvis and a pronounced enhancement of the lumbar curve. Scoliosis is an abnormal, lateral curvature, accompanied by twisting of the vertebral column. Compensatory curves may also develop in other areas of the vertebral column to help maintain the head positioned over the feet. Scoliosis is the most common vertebral abnormality among girls. The cause is usually unknown, but it may result from weakness of the back muscles, defects such as differential growth rates in the right and left sides of the vertebral column, or differences in the length of the lower limbs. When present, scoliosis tends to get worse during adolescent growth spurts. Although most individuals do not require treatment, a back brace may be recommended for growing children. In extreme cases, surgery may be required. Excessive vertebral curves can be identified while an individual stands in the anatomical position. Observe the vertebral profile from the side and then from behind to check for kyphosis or lordosis. Then have the person bend forward. If scoliosis is present, an individual will have difficulty in bending directly forward, and the right and left sides of the back will not be level with each other in the bent position. Figure 7.21 Abnormal Curvatures of the Vertebral Column (a) Scoliosis is an abnormal lateral bending of the vertebral column. (b) An excessive curvature of the upper thoracic vertebral column is called kyphosis. (c) Lordosis is an excessive curvature in the lumbar region of the vertebral column. Figure 7.22 Osteoporosis Osteoporosis is an age-related disorder that causes the gradual loss of bone density and strength. When the thoracic vertebrae are affected, there can be a gradual collapse of the vertebrae. This results in kyphosis, an excessive curvature of the thoracic region. INTERACTIVE LINK Osteoporosis is a common age-related bone disease in which bone density and strength is decreased. Watch this video to get a better understanding of how thoracic vertebrae may become weakened and may fracture due to this disease. How may vertebral osteoporosis contribute to kyphosis? General Structure of a Vertebra Within the different regions of the vertebral column, vertebrae vary in size and shape, but they all follow a similar structural pattern. A typical vertebra will consist of a body, a vertebral arch, and seven processes (Figure 7.23). The body is the anterior portion of each vertebra and is the part that supports the body weight. Because of this, the vertebral bodies progressively increase in size and thickness going down the vertebral column. The bodies of adjacent vertebrae are separated and strongly united by an intervertebral disc. The vertebral arch forms the posterior portion of each vertebra. It consists of four parts, the right and left pedicles and the right and left laminae. Each pedicle forms one of the lateral sides of the vertebral arch. The pedicles are anchored to the posterior side of the vertebral body. Each lamina forms part of the posterior roof of the vertebral arch. The large opening between the vertebral arch and body is the vertebral foramen, which contains the spinal cord. In the intact vertebral column, the vertebral foramina of all of the vertebrae align to form the vertebral (spinal) canal, which serves as the bony protection and passageway for the spinal cord down the back. When the vertebrae are aligned together in the vertebral column, notches in the margins of the pedicles of adjacent vertebrae together form an intervertebral foramen, the opening through which a spinal nerve exits from the vertebral column (Figure 7.24). Seven processes arise from the vertebral arch. Each paired transverse process projects laterally and arises from the junction point between the pedicle and lamina. The single spinous process (vertebral spine) projects posteriorly at the midline of the back. The vertebral spines can easily be felt as a series of bumps just under the skin down the middle of the back. The transverse and spinous processes serve as important muscle attachment sites. A superior articular process extends or faces upward, and an inferior articular process faces or projects downward on each side of a vertebrae. The paired superior articular processes of one vertebra join with the corresponding paired inferior articular processes from the next higher vertebra. These junctions form slightly moveable joints between the adjacent vertebrae. The shape and orientation of the articular processes vary in different regions of the vertebral column and play a major role in determining the type and range of motion available in each region. Figure 7.23 Parts of a Typical Vertebra A typical vertebra consists of a body and a vertebral arch. The arch is formed by the paired pedicles and paired laminae. Arising from the vertebral arch are the transverse, spinous, superior articular, and inferior articular processes. The vertebral foramen provides for passage of the spinal cord. Each spinal nerve exits through an intervertebral foramen, located between adjacent vertebrae. Intervertebral discs unite the bodies of adjacent vertebrae. Figure 7.24 Intervertebral Disc The bodies of adjacent vertebrae are separated and united by an intervertebral disc, which provides padding and allows for movements between adjacent vertebrae. The disc consists of a fibrous outer layer called the anulus fibrosus and a gel-like center called the nucleus pulposus. The intervertebral foramen is the opening formed between adjacent vertebrae for the exit of a spinal nerve. Regional Modifications of Vertebrae In addition to the general characteristics of a typical vertebra described above, vertebrae also display characteristic size and structural features that vary between the different vertebral column regions. Thus, cervical vertebrae are smaller than lumbar vertebrae due to differences in the proportion of body weight that each supports. Thoracic vertebrae have sites for rib attachment, and the vertebrae that give rise to the sacrum and coccyx have fused together into single bones. Cervical Vertebrae Typical cervical vertebrae, such as C4 or C5, have several characteristic features that differentiate them from thoracic or lumbar vertebrae (Figure 7.25). Cervical vertebrae have a small body, reflecting the fact that they carry the least amount of body weight. Cervical vertebrae usually have a bifid (Y-shaped) spinous process. The spinous processes of the C3–C6 vertebrae are short, but the spine of C7 is much longer. You can find these vertebrae by running your finger down the midline of the posterior neck until you encounter the prominent C7 spine located at the base of the neck. The transverse processes of the cervical vertebrae are sharply curved (U-shaped) to allow for passage of the cervical spinal nerves. Each transverse process also has an opening called the transverse foramen. An important artery that supplies the brain ascends up the neck by passing through these openings. The superior and inferior articular processes of the cervical vertebrae are flattened and largely face upward or downward, respectively. The first and second cervical vertebrae are further modified, giving each a distinctive appearance. The first cervical (C1) vertebra is also called the atlas, because this is the vertebra that supports the skull on top of the vertebral column (in Greek mythology, Atlas was the god who supported the heavens on his shoulders). The C1 vertebra does not have a body or spinous process. Instead, it is ring-shaped, consisting of an anterior arch and a posterior arch. The transverse processes of the atlas are longer and extend more laterally than do the transverse processes of any other cervical vertebrae. The superior articular processes face upward and are deeply curved for articulation with the occipital condyles on the base of the skull. The inferior articular processes are flat and face downward to join with the superior articular processes of the C2 vertebra. The second cervical (C2) vertebra is called the axis, because it serves as the axis for rotation when turning the head toward the right or left. The axis resembles typical cervical vertebrae in most respects, but is easily distinguished by the dens (odontoid process), a bony projection that extends upward from the vertebral body. The dens joins with the inner aspect of the anterior arch of the atlas, where it is held in place by transverse ligament. Figure 7.25 Cervical Vertebrae A typical cervical vertebra has a small body, a bifid spinous process, transverse processes that have a transverse foramen and are curved for spinal nerve passage. The atlas (C1 vertebra) does not have a body or spinous process. It consists of an anterior and a posterior arch and elongated transverse processes. The axis (C2 vertebra) has the upward projecting dens, which articulates with the anterior arch of the atlas. Thoracic Vertebrae The bodies of the thoracic vertebrae are larger than those of cervical vertebrae (Figure 7.26). The characteristic feature for a typical midthoracic vertebra is the spinous process, which is long and has a pronounced downward angle that causes it to overlap the next inferior vertebra. The superior articular processes of thoracic vertebrae face anteriorly and the inferior processes face posteriorly. These orientations are important determinants for the type and range of movements available to the thoracic region of the vertebral column. Thoracic vertebrae have several additional articulation sites, each of which is called a facet, where a rib is attached. Most thoracic vertebrae have two facets located on the lateral sides of the body, each of which is called a costal facet (costal = “rib”). These are for articulation with the head (end) of a rib. An additional facet is located on the transverse process for articulation with the tubercle of a rib. Figure 7.26 Thoracic Vertebrae A typical thoracic vertebra is distinguished by the spinous process, which is long and projects downward to overlap the next inferior vertebra. It also has articulation sites (facets) on the vertebral body and a transverse process for rib attachment. Figure 7.27 Rib Articulation in Thoracic Vertebrae Thoracic vertebrae have superior and inferior articular facets on the vertebral body for articulation with the head of a rib, and a transverse process facet for articulation with the rib tubercle. Lumbar Vertebrae Lumbar vertebrae carry the greatest amount of body weight and are thus characterized by the large size and thickness of the vertebral body (Figure 7.28). They have short transverse processes and a short, blunt spinous process that projects posteriorly. The articular processes are large, with the superior process facing backward and the inferior facing forward. Figure 7.28 Lumbar Vertebrae Lumbar vertebrae are characterized by having a large, thick body and a short, rounded spinous process. Sacrum and Coccyx The sacrum is a triangular-shaped bone that is thick and wide across its superior base where it is weight bearing and then tapers down to an inferior, non-weight bearing apex (Figure 7.29). It is formed by the fusion of five sacral vertebrae, a process that does not begin until after the age of 20. On the anterior surface of the older adult sacrum, the lines of vertebral fusion can be seen as four transverse ridges. On the posterior surface, running down the midline, is the median sacral crest, a bumpy ridge that is the remnant of the fused spinous processes (median = “midline”; while medial = “toward, but not necessarily at, the midline”). Similarly, the fused transverse processes of the sacral vertebrae form the lateral sacral crest. The sacral promontory is the anterior lip of the superior base of the sacrum. Lateral to this is the roughened auricular surface, which joins with the ilium portion of the hipbone to form the immobile sacroiliac joints of the pelvis. Passing inferiorly through the sacrum is a bony tunnel called the sacral canal, which terminates at the sacral hiatus near the inferior tip of the sacrum. The anterior and posterior surfaces of the sacrum have a series of paired openings called sacral foramina (singular = foramen) that connect to the sacral canal. Each of these openings is called a posterior (dorsal) sacral foramen or anterior (ventral) sacral foramen. These openings allow for the anterior and posterior branches of the sacral spinal nerves to exit the sacrum. The superior articular process of the sacrum, one of which is found on either side of the superior opening of the sacral canal, articulates with the inferior articular processes from the L5 vertebra. The coccyx, or tailbone, is derived from the fusion of four very small coccygeal vertebrae (see Figure 7.29). It articulates with the inferior tip of the sacrum. It is not weight bearing in the standing position, but may receive some body weight when sitting. Figure 7.29 Sacrum and Coccyx The sacrum is formed from the fusion of five sacral vertebrae, whose lines of fusion are indicated by the transverse ridges. The fused spinous processes form the median sacral crest, while the lateral sacral crest arises from the fused transverse processes. The coccyx is formed by the fusion of four small coccygeal vertebrae. Intervertebral Discs and Ligaments of the Vertebral Column The bodies of adjacent vertebrae are strongly anchored to each other by an intervertebral disc. This structure provides padding between the bones during weight bearing, and because it can change shape, also allows for movement between the vertebrae. Although the total amount of movement available between any two adjacent vertebrae is small, when these movements are summed together along the entire length of the vertebral column, large body movements can be produced. Ligaments that extend along the length of the vertebral column also contribute to its overall support and stability. Intervertebral Disc An intervertebral disc is a fibrocartilaginous pad that fills the gap between adjacent vertebral bodies (see Figure 7.24). Each disc is anchored to the bodies of its adjacent vertebrae, thus strongly uniting these. The discs also provide padding between vertebrae during weight bearing. Because of this, intervertebral discs are thin in the cervical region and thickest in the lumbar region, which carries the most body weight. In total, the intervertebral discs account for approximately 25 percent of your body height between the top of the pelvis and the base of the skull. Intervertebral discs are also flexible and can change shape to allow for movements of the vertebral column. Each intervertebral disc consists of two parts. The anulus fibrosus is the tough, fibrous outer layer of the disc. It forms a circle (anulus = “ring” or “circle”) and is firmly anchored to the outer margins of the adjacent vertebral bodies. Inside is the nucleus pulposus, consisting of a softer, more gel-like material. It has a high water content that serves to resist compression and thus is important for weight bearing. With increasing age, the water content of the nucleus pulposus gradually declines. This causes the disc to become thinner, decreasing total body height somewhat, and reduces the flexibility and range of motion of the disc, making bending more difficult. The gel-like nature of the nucleus pulposus also allows the intervertebral disc to change shape as one vertebra rocks side to side or forward and back in relation to its neighbors during movements of the vertebral column. Thus, bending forward causes compression of the anterior portion of the disc but expansion of the posterior disc. If the posterior anulus fibrosus is weakened due to injury or increasing age, the pressure exerted on the disc when bending forward and lifting a heavy object can cause the nucleus pulposus to protrude posteriorly through the anulus fibrosus, resulting in a herniated disc (“ruptured” or “slipped” disc) (Figure 7.30). The posterior bulging of the nucleus pulposus can cause compression of a spinal nerve at the point where it exits through the intervertebral foramen, with resulting pain and/or muscle weakness in those body regions supplied by that nerve. The most common sites for disc herniation are the L4/L5 or L5/S1 intervertebral discs, which can cause sciatica, a widespread pain that radiates from the lower back down the thigh and into the leg. Similar injuries of the C5/C6 or C6/C7 intervertebral discs, following forcible hyperflexion of the neck from a collision accident or football injury, can produce pain in the neck, shoulder, and upper limb. Figure 7.30 Herniated Intervertebral Disc Weakening of the anulus fibrosus can result in herniation (protrusion) of the nucleus pulposus and compression of a spinal nerve, resulting in pain and/or muscle weakness in the body regions supplied by that nerve. INTERACTIVE LINK Watch this animation to see what it means to “slip” a disk. Watch this second animation to see one possible treatment for a herniated disc, removing and replacing the damaged disc with an artificial one that allows for movement between the adjacent certebrae. How could lifting a heavy object produce pain in a lower limb? Ligaments of the Vertebral Column Adjacent vertebrae are united by ligaments that run the length of the vertebral column along both its posterior and anterior aspects (Figure 7.31). These serve to resist excess forward or backward bending movements of the vertebral column, respectively. The anterior longitudinal ligament runs down the anterior side of the entire vertebral column, uniting the vertebral bodies. It serves to resist excess backward bending of the vertebral column. Protection against this movement is particularly important in the neck, where extreme posterior bending of the head and neck can stretch or tear this ligament, resulting in a painful whiplash injury. Prior to the mandatory installation of seat headrests, whiplash injuries were common for passengers involved in a rear-end automobile collision. The supraspinous ligament is located on the posterior side of the vertebral column, where it interconnects the spinous processes of the thoracic and lumbar vertebrae. This strong ligament supports the vertebral column during forward bending motions. In the posterior neck, where the cervical spinous processes are short, the supraspinous ligament expands to become the nuchal ligament (nuchae = “nape” or “back of the neck”). The nuchal ligament is attached to the cervical spinous processes and extends upward and posteriorly to attach to the midline base of the skull, out to the external occipital protuberance. It supports the skull and prevents it from falling forward. This ligament is much larger and stronger in four-legged animals such as cows, where the large skull hangs off the front end of the vertebral column. You can easily feel this ligament by first extending your head backward and pressing down on the posterior midline of your neck. Then tilt your head forward and you will fill the nuchal ligament popping out as it tightens to limit anterior bending of the head and neck. Additional ligaments are located inside the vertebral canal, next to the spinal cord, along the length of the vertebral column. The posterior longitudinal ligament is found anterior to the spinal cord, where it is attached to the posterior sides of the vertebral bodies. Posterior to the spinal cord is the ligamentum flavum (“yellow ligament”). This consists of a series of short, paired ligaments, each of which interconnects the lamina regions of adjacent vertebrae. The ligamentum flavum has large numbers of elastic fibers, which have a yellowish color, allowing it to stretch and then pull back. Both of these ligaments provide important support for the vertebral column when bending forward. Figure 7.31 Ligaments of Vertebral Column The anterior longitudinal ligament runs the length of the vertebral column, uniting the anterior sides of the vertebral bodies. The supraspinous ligament connects the spinous processes of the thoracic and lumbar vertebrae. In the posterior neck, the supraspinous ligament enlarges to form the nuchal ligament, which attaches to the cervical spinous processes and to the base of the skull. INTERACTIVE LINK Use this tool to identify the bones, intervertebral discs, and ligaments of the vertebral column. The thickest portions of the anterior longitudinal ligament and the supraspinous ligament are found in which regions of the vertebral column? CAREER CONNECTION Chiropractor Chiropractors are health professionals who use nonsurgical techniques to help patients with musculoskeletal system problems that involve the bones, muscles, ligaments, tendons, or nervous system. They treat problems such as neck pain, back pain, joint pain, or headaches. Chiropractors focus on the patient’s overall health and can also provide counseling related to lifestyle issues, such as diet, exercise, or sleep problems. If needed, they will refer the patient to other medical specialists. Chiropractors use a drug-free, hands-on approach for patient diagnosis and treatment. They will perform a physical exam, assess the patient’s posture and spine, and may perform additional diagnostic tests, including taking X-ray images. They primarily use manual techniques, such as spinal manipulation, to adjust the patient’s spine or other joints. They can recommend therapeutic or rehabilitative exercises, and some also include acupuncture, massage therapy, or ultrasound as part of the treatment program. In addition to those in general practice, some chiropractors specialize in sport injuries, neurology, orthopaedics, pediatrics, nutrition, internal disorders, or diagnostic imaging. To become a chiropractor, students must have 3–4 years of undergraduate education, attend an accredited, four-year Doctor of Chiropractic (D.C.) degree program, and pass a licensure examination to be licensed for practice in their state. With the aging of the baby-boom generation, employment for chiropractors is expected to increase. The Thoracic Cage - Discuss the components that make up the thoracic cage - Identify the parts of the sternum and define the sternal angle - Discuss the parts of a rib and rib classifications The thoracic cage (rib cage) forms the thorax (chest) portion of the body. It consists of the 12 pairs of ribs with their costal cartilages and the sternum (Figure 7.32). The ribs are anchored posteriorly to the 12 thoracic vertebrae (T1–T12). The thoracic cage protects the heart and lungs. Figure 7.32 Thoracic Cage The thoracic cage is formed by the (a) sternum and (b) 12 pairs of ribs with their costal cartilages. The ribs are anchored posteriorly to the 12 thoracic vertebrae. The sternum consists of the manubrium, body, and xiphoid process. The ribs are classified as true ribs (1–7) and false ribs (8–12). The last two pairs of false ribs are also known as floating ribs (11–12). Sternum The sternum is the elongated bony structure that anchors the anterior thoracic cage. It consists of three parts: the manubrium, body, and xiphoid process. The manubrium is the wider, superior portion of the sternum. The top of the manubrium has a shallow, U-shaped border called the jugular (suprasternal) notch. This can be easily felt at the anterior base of the neck, between the medial ends of the clavicles. The clavicular notch is the shallow depression located on either side at the superior-lateral margins of the manubrium. This is the site of the sternoclavicular joint, between the sternum and clavicle. The first ribs also attach to the manubrium. The elongated, central portion of the sternum is the body. The manubrium and body join together at the sternal angle, so called because the junction between these two components is not flat, but forms a slight bend. The second rib attaches to the sternum at the sternal angle. Since the first rib is hidden behind the clavicle, the second rib is the highest rib that can be identified by palpation. Thus, the sternal angle and second rib are important landmarks for the identification and counting of the lower ribs. Ribs 3–7 attach to the sternal body. The inferior tip of the sternum is the xiphoid process. This small structure is cartilaginous early in life, but gradually becomes ossified starting during middle age. Ribs Each rib is a curved, flattened bone that contributes to the wall of the thorax. The ribs articulate posteriorly with the T1–T12 thoracic vertebrae, and most attach anteriorly via their costal cartilages to the sternum. There are 12 pairs of ribs. The ribs are numbered 1–12 in accordance with the thoracic vertebrae. Parts of a Typical Rib The posterior end of a typical rib is called the head of the rib (see Figure 7.27). This region articulates primarily with the costal facet located on the body of the same numbered thoracic vertebra and to a lesser degree, with the costal facet located on the body of the next higher vertebra. Lateral to the head is the narrowed neck of the rib. A small bump on the posterior rib surface is the tubercle of the rib, which articulates with the facet located on the transverse process of the same numbered vertebra. The remainder of the rib is the body of the rib (shaft). Just lateral to the tubercle is the angle of the rib, the point at which the rib has its greatest degree of curvature. The angles of the ribs form the most posterior extent of the thoracic cage. In the anatomical position, the angles align with the medial border of the scapula. A shallow costal groove for the passage of blood vessels and a nerve is found along the inferior margin of each rib. Rib Classifications The bony ribs do not extend anteriorly completely around to the sternum. Instead, each rib ends in a costal cartilage. These cartilages are made of hyaline cartilage and can extend for several inches. Most ribs are then attached, either directly or indirectly, to the sternum via their costal cartilage (see Figure 7.32). The ribs are classified into three groups based on their relationship to the sternum. Ribs 1–7 are classified as true ribs (vertebrosternal ribs). The costal cartilage from each of these ribs attaches directly to the sternum. Ribs 8–12 are called false ribs (vertebrochondral ribs). The costal cartilages from these ribs do not attach directly to the sternum. For ribs 8–10, the costal cartilages are attached to the cartilage of the next higher rib. Thus, the cartilage of rib 10 attaches to the cartilage of rib 9, rib 9 then attaches to rib 8, and rib 8 is attached to rib 7. The last two false ribs (11–12) are also called floating ribs (vertebral ribs). These are short ribs that do not attach to the sternum at all. Instead, their small costal cartilages terminate within the musculature of the lateral abdominal wall. Embryonic Development of the Axial Skeleton - Discuss the two types of embryonic bone development within the skull - Describe the development of the vertebral column and thoracic cage The axial skeleton begins to form during early embryonic development. However, growth, remodeling, and ossification (bone formation) continue for several decades after birth before the adult skeleton is fully formed. Knowledge of the developmental processes that give rise to the skeleton is important for understanding the abnormalities that may arise in skeletal structures. Development of the Skull During the third week of embryonic development, a rod-like structure called the notochord develops dorsally along the length of the embryo. The tissue overlying the notochord enlarges and forms the neural tube, which will give rise to the brain and spinal cord. By the fourth week, mesoderm tissue located on either side of the notochord thickens and separates into a repeating series of block-like tissue structures, each of which is called a somite. As the somites enlarge, each one will split into several parts. The most medial of these parts is called a sclerotome. The sclerotomes consist of an embryonic tissue called mesenchyme, which will give rise to the fibrous connective tissues, cartilages, and bones of the body. The bones of the skull arise from mesenchyme during embryonic development in two different ways. The first mechanism produces the bones that form the top and sides of the brain case. This involves the local accumulation of mesenchymal cells at the site of the future bone. These cells then differentiate directly into bone producing cells, which form the skull bones through the process of intramembranous ossification. As the brain case bones grow in the fetal skull, they remain separated from each other by large areas of dense connective tissue, each of which is called a fontanelle (Figure 7.33). The fontanelles are the soft spots on an infant’s head. They are important during birth because these areas allow the skull to change shape as it squeezes through the birth canal. After birth, the fontanelles allow for continued growth and expansion of the skull as the brain enlarges. The largest fontanelle is located on the anterior head, at the junction of the frontal and parietal bones. The fontanelles decrease in size and disappear by age 2. However, the skull bones remained separated from each other at the sutures, which contain dense fibrous connective tissue that unites the adjacent bones. The connective tissue of the sutures allows for continued growth of the skull bones as the brain enlarges during childhood growth. The second mechanism for bone development in the skull produces the facial bones and floor of the brain case. This also begins with the localized accumulation of mesenchymal cells. However, these cells differentiate into cartilage cells, which produce a hyaline cartilage model of the future bone. As this cartilage model grows, it is gradually converted into bone through the process of endochondral ossification. This is a slow process and the cartilage is not completely converted to bone until the skull achieves its full adult size. At birth, the brain case and orbits of the skull are disproportionally large compared to the bones of the jaws and lower face. This reflects the relative underdevelopment of the maxilla and mandible, which lack teeth, and the small sizes of the paranasal sinuses and nasal cavity. During early childhood, the mastoid process enlarges, the two halves of the mandible and frontal bone fuse together to form single bones, and the paranasal sinuses enlarge. The jaws also expand as the teeth begin to appear. These changes all contribute to the rapid growth and enlargement of the face during childhood. Figure 7.33 Newborn Skull The bones of the newborn skull are not fully ossified and are separated by large areas called fontanelles, which are filled with fibrous connective tissue. The fontanelles allow for continued growth of the skull after birth. At the time of birth, the facial bones are small and underdeveloped, and the mastoid process has not yet formed. Development of the Vertebral Column and Thoracic cage Development of the vertebrae begins with the accumulation of mesenchyme cells from each sclerotome around the notochord. These cells differentiate into a hyaline cartilage model for each vertebra, which then grow and eventually ossify into bone through the process of endochondral ossification. As the developing vertebrae grow, the notochord largely disappears. However, small areas of notochord tissue persist between the adjacent vertebrae and this contributes to the formation of each intervertebral disc. The ribs and sternum also develop from mesenchyme. The ribs initially develop as part of the cartilage model for each vertebra, but in the thorax region, the rib portion separates from the vertebra by the eighth week. The cartilage model of the rib then ossifies, except for the anterior portion, which remains as the costal cartilage. The sternum initially forms as paired hyaline cartilage models on either side of the anterior midline, beginning during the fifth week of development. The cartilage models of the ribs become attached to the lateral sides of the developing sternum. Eventually, the two halves of the cartilaginous sternum fuse together along the midline and then ossify into bone. The manubrium and body of the sternum are converted into bone first, with the xiphoid process remaining as cartilage until late in life. INTERACTIVE LINK View this video to review the two processes that give rise to the bones of the skull and body. What are the two mechanisms by which the bones of the body are formed and which bones are formed by each mechanism? HOMEOSTATIC IMBALANCES Craniosynostosis The premature closure (fusion) of a suture line is a condition called craniosynostosis. This error in the normal developmental process results in abnormal growth of the skull and deformity of the head. It is produced either by defects in the ossification process of the skull bones or failure of the brain to properly enlarge. Genetic factors are involved, but the underlying cause is unknown. It is a relatively common condition, occurring in approximately 1:2000 births, with males being more commonly affected. Primary craniosynostosis involves the early fusion of one cranial suture, whereas complex craniosynostosis results from the premature fusion of several sutures. The early fusion of a suture in primary craniosynostosis prevents any additional enlargement of the cranial bones and skull along this line. Continued growth of the brain and skull is therefore diverted to other areas of the head, causing an abnormal enlargement of these regions. For example, the early disappearance of the anterior fontanelle and premature closure of the sagittal suture prevents growth across the top of the head. This is compensated by upward growth by the bones of the lateral skull, resulting in a long, narrow, wedge-shaped head. This condition, known as scaphocephaly, accounts for approximately 50 percent of craniosynostosis abnormalities. Although the skull is misshapen, the brain still has adequate room to grow and thus there is no accompanying abnormal neurological development. In cases of complex craniosynostosis, several sutures close prematurely. The amount and degree of skull deformity is determined by the location and extent of the sutures involved. This results in more severe constraints on skull growth, which can alter or impede proper brain growth and development. Cases of craniosynostosis are usually treated with surgery. A team of physicians will open the skull along the fused suture, which will then allow the skull bones to resume their growth in this area. In some cases, parts of the skull will be removed and replaced with an artificial plate. The earlier after birth that surgery is performed, the better the outcome. After treatment, most children continue to grow and develop normally and do not exhibit any neurological problems. Key Terms - alveolar process of the mandible - upper border of mandibular body that contains the lower teeth - alveolar process of the maxilla - curved, inferior margin of the maxilla that supports and anchors the upper teeth - angle of the mandible - rounded corner located at outside margin of the body and ramus junction - angle of the rib - portion of rib with greatest curvature; together, the rib angles form the most posterior extent of the thoracic cage - anterior (ventral) sacral foramen - one of the series of paired openings located on the anterior (ventral) side of the sacrum - anterior arch - anterior portion of the ring-like C1 (atlas) vertebra - anterior cranial fossa - shallowest and most anterior cranial fossa of the cranial base that extends from the frontal bone to the lesser wing of the sphenoid bone - anterior longitudinal ligament - ligament that runs the length of the vertebral column, uniting the anterior aspects of the vertebral bodies - anulus fibrosus - tough, fibrous outer portion of an intervertebral disc, which is strongly anchored to the bodies of the adjacent vertebrae - appendicular skeleton - all bones of the upper and lower limbs, plus the girdle bones that attach each limb to the axial skeleton - articular tubercle - smooth ridge located on the inferior skull, immediately anterior to the mandibular fossa - atlas - first cervical (C1) vertebra - axial skeleton - central, vertical axis of the body, including the skull, vertebral column, and thoracic cage - axis - second cervical (C2) vertebra - body of the rib - shaft portion of a rib - brain case - portion of the skull that contains and protects the brain, consisting of the eight bones that form the cranial base and rounded upper skull - calvaria - (also, skullcap) rounded top of the skull - carotid canal - zig-zag tunnel providing passage through the base of the skull for the internal carotid artery to the brain; begins anteromedial to the styloid process and terminates in the middle cranial cavity, near the posterior-lateral base of the sella turcica - cervical curve - posteriorly concave curvature of the cervical vertebral column region; a secondary curve of the vertebral column - cervical vertebrae - seven vertebrae numbered as C1–C7 that are located in the neck region of the vertebral column - clavicular notch - paired notches located on the superior-lateral sides of the sternal manubrium, for articulation with the clavicle - coccyx - small bone located at inferior end of the adult vertebral column that is formed by the fusion of four coccygeal vertebrae; also referred to as the “tailbone” - condylar process of the mandible - thickened upward projection from posterior margin of mandibular ramus - condyle - oval-shaped process located at the top of the condylar process of the mandible - coronal suture - joint that unites the frontal bone to the right and left parietal bones across the top of the skull - coronoid process of the mandible - flattened upward projection from the anterior margin of the mandibular ramus - costal cartilage - hyaline cartilage structure attached to the anterior end of each rib that provides for either direct or indirect attachment of most ribs to the sternum - costal facet - site on the lateral sides of a thoracic vertebra for articulation with the head of a rib - costal groove - shallow groove along the inferior margin of a rib that provides passage for blood vessels and a nerve - cranial cavity - interior space of the skull that houses the brain - cranium - skull - cribriform plate - small, flattened areas with numerous small openings, located to either side of the midline in the floor of the anterior cranial fossa; formed by the ethmoid bone - crista galli - small upward projection located at the midline in the floor of the anterior cranial fossa; formed by the ethmoid bone - dens - bony projection (odontoid process) that extends upward from the body of the C2 (axis) vertebra - ear ossicles - three small bones located in the middle ear cavity that serve to transmit sound vibrations to the inner ear - ethmoid air cell - one of several small, air-filled spaces located within the lateral sides of the ethmoid bone, between the orbit and upper nasal cavity - ethmoid bone - unpaired bone that forms the roof and upper, lateral walls of the nasal cavity, portions of the floor of the anterior cranial fossa and medial wall of orbit, and the upper portion of the nasal septum - external acoustic meatus - ear canal opening located on the lateral side of the skull - external occipital protuberance - small bump located at the midline on the posterior skull - facet - small, flattened area on a bone for an articulation (joint) with another bone, or for muscle attachment - facial bones - fourteen bones that support the facial structures and form the upper and lower jaws and the hard palate - false ribs - vertebrochondral ribs 8–12 whose costal cartilage either attaches indirectly to the sternum via the costal cartilage of the next higher rib or does not attach to the sternum at all - floating ribs - vertebral ribs 11–12 that do not attach to the sternum or to the costal cartilage of another rib - fontanelle - expanded area of fibrous connective tissue that separates the brain case bones of the skull prior to birth and during the first year after birth - foramen lacerum - irregular opening in the base of the skull, located inferior to the exit of carotid canal - foramen magnum - large opening in the occipital bone of the skull through which the spinal cord emerges and the vertebral arteries enter the cranium - foramen ovale of the middle cranial fossa - oval-shaped opening in the floor of the middle cranial fossa - foramen rotundum - round opening in the floor of the middle cranial fossa, located between the superior orbital fissure and foramen ovale - foramen spinosum - small opening in the floor of the middle cranial fossa, located lateral to the foramen ovale - frontal bone - unpaired bone that forms forehead, roof of orbit, and floor of anterior cranial fossa - frontal sinus - air-filled space within the frontal bone; most anterior of the paranasal sinuses - glabella - slight depression of frontal bone, located at the midline between the eyebrows - greater wings of sphenoid bone - lateral projections of the sphenoid bone that form the anterior wall of the middle cranial fossa and an area of the lateral skull - hard palate - bony structure that forms the roof of the mouth and floor of the nasal cavity, formed by the palatine process of the maxillary bones and the horizontal plate of the palatine bones - head of the rib - posterior end of a rib that articulates with the bodies of thoracic vertebrae - horizontal plate - medial extension from the palatine bone that forms the posterior quarter of the hard palate - hyoid bone - small, U-shaped bone located in upper neck that does not contact any other bone - hypoglossal canal - paired openings that pass anteriorly from the anterior-lateral margins of the foramen magnum deep to the occipital condyles - hypophyseal (pituitary) fossa - shallow depression on top of the sella turcica that houses the pituitary (hypophyseal) gland - inferior articular process - bony process that extends downward from the vertebral arch of a vertebra that articulates with the superior articular process of the next lower vertebra - inferior nasal concha - one of the paired bones that project from the lateral walls of the nasal cavity to form the largest and most inferior of the nasal conchae - infraorbital foramen - opening located on anterior skull, below the orbit - infratemporal fossa - space on lateral side of skull, below the level of the zygomatic arch and deep (medial) to the ramus of the mandible - internal acoustic meatus - opening into petrous ridge, located on the lateral wall of the posterior cranial fossa - intervertebral disc - structure located between the bodies of adjacent vertebrae that strongly joins the vertebrae; provides padding, weight bearing ability, and enables vertebral column movements - intervertebral foramen - opening located between adjacent vertebrae for exit of a spinal nerve - jugular (suprasternal) notch - shallow notch located on superior surface of sternal manubrium - jugular foramen - irregularly shaped opening located in the lateral floor of the posterior cranial cavity - kyphosis - (also, humpback or hunchback) excessive posterior curvature of the thoracic vertebral column region - lacrimal bone - paired bones that contribute to the anterior-medial wall of each orbit - lacrimal fossa - shallow depression in the anterior-medial wall of the orbit, formed by the lacrimal bone that gives rise to the nasolacrimal canal - lambdoid suture - inverted V-shaped joint that unites the occipital bone to the right and left parietal bones on the posterior skull - lamina - portion of the vertebral arch on each vertebra that extends between the transverse and spinous process - lateral pterygoid plate - paired, flattened bony projections of the sphenoid bone located on the inferior skull, lateral to the medial pterygoid plate - lateral sacral crest - paired irregular ridges running down the lateral sides of the posterior sacrum that was formed by the fusion of the transverse processes from the five sacral vertebrae - lesser wings of the sphenoid bone - lateral extensions of the sphenoid bone that form the bony lip separating the anterior and middle cranial fossae - ligamentum flavum - series of short ligaments that unite the lamina of adjacent vertebrae - lingula - small flap of bone located on the inner (medial) surface of mandibular ramus, next to the mandibular foramen - lordosis - (also, swayback) excessive anterior curvature of the lumbar vertebral column region - lumbar curve - posteriorly concave curvature of the lumbar vertebral column region; a secondary curve of the vertebral column - lumbar vertebrae - five vertebrae numbered as L1–L5 that are located in lumbar region (lower back) of the vertebral column - mandible - unpaired bone that forms the lower jaw bone; the only moveable bone of the skull - mandibular foramen - opening located on the inner (medial) surface of the mandibular ramus - mandibular fossa - oval depression located on the inferior surface of the skull - mandibular notch - large U-shaped notch located between the condylar process and coronoid process of the mandible - manubrium - expanded, superior portion of the sternum - mastoid process - large bony prominence on the inferior, lateral skull, just behind the earlobe - maxillary bone - (also, maxilla) paired bones that form the upper jaw and anterior portion of the hard palate - maxillary sinus - air-filled space located with each maxillary bone; largest of the paranasal sinuses - medial pterygoid plate - paired, flattened bony projections of the sphenoid bone located on the inferior skull medial to the lateral pterygoid plate; form the posterior portion of the nasal cavity lateral wall - median sacral crest - irregular ridge running down the midline of the posterior sacrum that was formed from the fusion of the spinous processes of the five sacral vertebrae - mental foramen - opening located on the anterior-lateral side of the mandibular body - mental protuberance - inferior margin of anterior mandible that forms the chin - middle cranial fossa - centrally located cranial fossa that extends from the lesser wings of the sphenoid bone to the petrous ridge - middle nasal concha - nasal concha formed by the ethmoid bone that is located between the superior and inferior conchae - mylohyoid line - bony ridge located along the inner (medial) surface of the mandibular body - nasal bone - paired bones that form the base of the nose - nasal cavity - opening through skull for passage of air - nasal conchae - curved bony plates that project from the lateral walls of the nasal cavity; include the superior and middle nasal conchae, which are parts of the ethmoid bone, and the independent inferior nasal conchae bone - nasal septum - flat, midline structure that divides the nasal cavity into halves, formed by the perpendicular plate of the ethmoid bone, vomer bone, and septal cartilage - nasolacrimal canal - passage for drainage of tears that extends downward from the medial-anterior orbit to the nasal cavity, terminating behind the inferior nasal conchae - neck of the rib - narrowed region of a rib, next to the rib head - notochord - rod-like structure along dorsal side of the early embryo; largely disappears during later development but does contribute to formation of the intervertebral discs - nuchal ligament - expanded portion of the supraspinous ligament within the posterior neck; interconnects the spinous processes of the cervical vertebrae and attaches to the base of the skull - nucleus pulposus - gel-like central region of an intervertebral disc; provides for padding, weight-bearing, and movement between adjacent vertebrae - occipital bone - unpaired bone that forms the posterior portions of the brain case and base of the skull - occipital condyle - paired, oval-shaped bony knobs located on the inferior skull, to either side of the foramen magnum - optic canal - opening spanning between middle cranial fossa and posterior orbit - orbit - bony socket that contains the eyeball and associated muscles - palatine bone - paired bones that form the posterior quarter of the hard palate and a small area in floor of the orbit - palatine process - medial projection from the maxilla bone that forms the anterior three quarters of the hard palate - paranasal sinuses - cavities within the skull that are connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consist of frontal, maxillary, sphenoidal, and ethmoidal sinuses - parietal bone - paired bones that form the upper, lateral sides of the skull - pedicle - portion of the vertebral arch that extends from the vertebral body to the transverse process - perpendicular plate of the ethmoid bone - downward, midline extension of the ethmoid bone that forms the superior portion of the nasal septum - petrous ridge - petrous portion of the temporal bone that forms a large, triangular ridge in the floor of the cranial cavity, separating the middle and posterior cranial fossae; houses the middle and inner ear structures - posterior (dorsal) sacral foramen - one of the series of paired openings located on the posterior (dorsal) side of the sacrum - posterior arch - posterior portion of the ring-like C1 (atlas) vertebra - posterior cranial fossa - deepest and most posterior cranial fossa; extends from the petrous ridge to the occipital bone - posterior longitudinal ligament - ligament that runs the length of the vertebral column, uniting the posterior sides of the vertebral bodies - primary curve - anteriorly concave curvatures of the thoracic and sacrococcygeal regions that are retained from the original fetal curvature of the vertebral column - pterion - H-shaped suture junction region that unites the frontal, parietal, temporal, and sphenoid bones on the lateral side of the skull - ramus of the mandible - vertical portion of the mandible - ribs - thin, curved bones of the chest wall - sacral canal - bony tunnel that runs through the sacrum - sacral foramina - series of paired openings for nerve exit located on both the anterior (ventral) and posterior (dorsal) aspects of the sacrum - sacral hiatus - inferior opening and termination of the sacral canal - sacral promontory - anterior lip of the base (superior end) of the sacrum - sacrococcygeal curve - anteriorly concave curvature formed by the sacrum and coccyx; a primary curve of the vertebral column - sacrum - single bone located near the inferior end of the adult vertebral column that is formed by the fusion of five sacral vertebrae; forms the posterior portion of the pelvis - sagittal suture - joint that unites the right and left parietal bones at the midline along the top of the skull - sclerotome - medial portion of a somite consisting of mesenchyme tissue that will give rise to bone, cartilage, and fibrous connective tissues - scoliosis - abnormal lateral curvature of the vertebral column - secondary curve - posteriorly concave curvatures of the cervical and lumbar regions of the vertebral column that develop after the time of birth - sella turcica - elevated area of sphenoid bone located at midline of the middle cranial fossa - septal cartilage - flat cartilage structure that forms the anterior portion of the nasal septum - skeleton - bones of the body - skull - bony structure that forms the head, face, and jaws, and protects the brain; consists of 22 bones - somite - one of the paired, repeating blocks of tissue located on either side of the notochord in the early embryo - sphenoid bone - unpaired bone that forms the central base of skull - sphenoid sinus - air-filled space located within the sphenoid bone; most posterior of the paranasal sinuses - spinous process - unpaired bony process that extends posteriorly from the vertebral arch of a vertebra - squamous suture - joint that unites the parietal bone to the squamous portion of the temporal bone on the lateral side of the skull - sternal angle - junction line between manubrium and body of the sternum and the site for attachment of the second rib to the sternum - sternum - flattened bone located at the center of the anterior chest - styloid process - downward projecting, elongated bony process located on the inferior aspect of the skull - stylomastoid foramen - opening located on inferior skull, between the styloid process and mastoid process - superior articular process - bony process that extends upward from the vertebral arch of a vertebra that articulates with the inferior articular process of the next higher vertebra - superior articular process of the sacrum - paired processes that extend upward from the sacrum to articulate (join) with the inferior articular processes from the L5 vertebra - superior nasal concha - smallest and most superiorly located of the nasal conchae; formed by the ethmoid bone - superior nuchal line - paired bony lines on the posterior skull that extend laterally from the external occipital protuberance - superior orbital fissure - irregularly shaped opening between the middle cranial fossa and the posterior orbit - supraorbital foramen - opening located on anterior skull, at the superior margin of the orbit - supraorbital margin - superior margin of the orbit - supraspinous ligament - ligament that interconnects the spinous processes of the thoracic and lumbar vertebrae - suture - junction line at which adjacent bones of the skull are united by fibrous connective tissue - temporal bone - paired bones that form the lateral, inferior portions of the skull, with squamous, mastoid, and petrous portions - temporal fossa - shallow space on the lateral side of the skull, above the level of the zygomatic arch - temporal process of the zygomatic bone - short extension from the zygomatic bone that forms the anterior portion of the zygomatic arch - thoracic cage - consists of 12 pairs of ribs and sternum - thoracic curve - anteriorly concave curvature of the thoracic vertebral column region; a primary curve of the vertebral column - thoracic vertebrae - twelve vertebrae numbered as T1–T12 that are located in the thoracic region (upper back) of the vertebral column - transverse foramen - opening found only in the transverse processes of cervical vertebrae - transverse process - paired bony processes that extends laterally from the vertebral arch of a vertebra - true ribs - vertebrosternal ribs 1–7 that attach via their costal cartilage directly to the sternum - tubercle of the rib - small bump on the posterior side of a rib for articulation with the transverse process of a thoracic vertebra - vertebra - individual bone in the neck and back regions of the vertebral column - vertebral (spinal) canal - bony passageway within the vertebral column for the spinal cord that is formed by the series of individual vertebral foramina - vertebral arch - bony arch formed by the posterior portion of each vertebra that surrounds and protects the spinal cord - vertebral column - entire sequence of bones that extend from the skull to the tailbone - vertebral foramen - opening associated with each vertebra defined by the vertebral arch that provides passage for the spinal cord - vomer bone - unpaired bone that forms the inferior and posterior portions of the nasal septum - xiphoid process - small process that forms the inferior tip of the sternum - zygomatic arch - elongated, free-standing arch on the lateral skull, formed anteriorly by the temporal process of the zygomatic bone and posteriorly by the zygomatic process of the temporal bone - zygomatic bone - cheekbone; paired bones that contribute to the lateral orbit and anterior zygomatic arch - zygomatic process of the temporal bone - extension from the temporal bone that forms the posterior portion of the zygomatic arch Chapter Review 7.1 Divisions of the Skeletal System The skeletal system includes all of the bones, cartilages, and ligaments of the body. It serves to support the body, protect the brain and other internal organs, and provides a rigid structure upon which muscles can pull to generate body movements. It also stores fat and the tissue responsible for the production of blood cells. The skeleton is subdivided into two parts. The axial skeleton forms a vertical axis that includes the head, neck, back, and chest. It has 80 bones and consists of the skull, vertebral column, and thoracic cage. The adult vertebral column consists of 24 vertebrae plus the sacrum and coccyx. The thoracic cage is formed by 12 pairs of ribs and the sternum. The appendicular skeleton consists of 126 bones in the adult and includes all of the bones of the upper and lower limbs plus the bones that anchor each limb to the axial skeleton. 7.2 The Skull The skull consists of the brain case and the facial bones. The brain case surrounds and protects the brain, which occupies the cranial cavity inside the skull. It consists of the rounded calvaria and a complex base. The brain case is formed by eight bones, the paired parietal and temporal bones plus the unpaired frontal, occipital, sphenoid, and ethmoid bones. The narrow gap between the bones is filled with dense, fibrous connective tissue that unites the bones. The sagittal suture joins the right and left parietal bones. The coronal suture joins the parietal bones to the frontal bone, the lamboid suture joins them to the occipital bone, and the squamous suture joins them to the temporal bone. The facial bones support the facial structures and form the upper and lower jaws. These consist of 14 bones, with the paired maxillary, palatine, zygomatic, nasal, lacrimal, and inferior conchae bones and the unpaired vomer and mandible bones. The ethmoid bone also contributes to the formation of facial structures. The maxilla forms the upper jaw and the mandible forms the lower jaw. The maxilla also forms the larger anterior portion of the hard palate, which is completed by the smaller palatine bones that form the posterior portion of the hard palate. The floor of the cranial cavity increases in depth from front to back and is divided into three cranial fossae. The anterior cranial fossa is located between the frontal bone and lesser wing of the sphenoid bone. A small area of the ethmoid bone, consisting of the crista galli and cribriform plates, is located at the midline of this fossa. The middle cranial fossa extends from the lesser wing of the sphenoid bone to the petrous ridge (petrous portion of temporal bone). The right and left sides are separated at the midline by the sella turcica, which surrounds the shallow hypophyseal fossa. Openings through the skull in the floor of the middle fossa include the optic canal and superior orbital fissure, which open into the posterior orbit, the foramen rotundum, foramen ovale, and foramen spinosum, and the exit of the carotid canal with its underlying foramen lacerum. The deep posterior cranial fossa extends from the petrous ridge to the occipital bone. Openings here include the large foramen magnum, plus the internal acoustic meatus, jugular foramina, and hypoglossal canals. Additional openings located on the external base of the skull include the stylomastoid foramen and the entrance to the carotid canal. The anterior skull has the orbits that house the eyeballs and associated muscles. The walls of the orbit are formed by contributions from seven bones: the frontal, zygomatic, maxillary, palatine, ethmoid, lacrimal, and sphenoid. Located at the superior margin of the orbit is the supraorbital foramen, and below the orbit is the infraorbital foramen. The mandible has two openings, the mandibular foramen on its inner surface and the mental foramen on its external surface near the chin. The nasal conchae are bony projections from the lateral walls of the nasal cavity. The large inferior nasal concha is an independent bone, while the middle and superior conchae are parts of the ethmoid bone. The nasal septum is formed by the perpendicular plate of the ethmoid bone, the vomer bone, and the septal cartilage. The paranasal sinuses are air-filled spaces located within the frontal, maxillary, sphenoid, and ethmoid bones. On the lateral skull, the zygomatic arch consists of two parts, the temporal process of the zygomatic bone anteriorly and the zygomatic process of the temporal bone posteriorly. The temporal fossa is the shallow space located on the lateral skull above the level of the zygomatic arch. The infratemporal fossa is located below the zygomatic arch and deep to the ramus of the mandible. The hyoid bone is located in the upper neck and does not join with any other bone. It is held in position by muscles and serves to support the tongue above, the larynx below, and the pharynx posteriorly. 7.3 The Vertebral Column The vertebral column forms the neck and back. The vertebral column originally develops as 33 vertebrae, but is eventually reduced to 24 vertebrae, plus the sacrum and coccyx. The vertebrae are divided into the cervical region (C1–C7 vertebrae), the thoracic region (T1–T12 vertebrae), and the lumbar region (L1–L5 vertebrae). The sacrum arises from the fusion of five sacral vertebrae and the coccyx from the fusion of four small coccygeal vertebrae. The vertebral column has four curvatures, the cervical, thoracic, lumbar, and sacrococcygeal curves. The thoracic and sacrococcygeal curves are primary curves retained from the original fetal curvature. The cervical and lumbar curves develop after birth and thus are secondary curves. The cervical curve develops as the infant begins to hold up the head, and the lumbar curve appears with standing and walking. A typical vertebra consists of an enlarged anterior portion called the body, which provides weight-bearing support. Attached posteriorly to the body is a vertebral arch, which surrounds and defines the vertebral foramen for passage of the spinal cord. The vertebral arch consists of the pedicles, which attach to the vertebral body, and the laminae, which come together to form the roof of the arch. Arising from the vertebral arch are the laterally projecting transverse processes and the posteriorly oriented spinous process. The superior articular processes project upward, where they articulate with the downward projecting inferior articular processes of the next higher vertebrae. A typical cervical vertebra has a small body, a bifid (Y-shaped) spinous process, and U-shaped transverse processes with a transverse foramen. In addition to these characteristics, the axis (C2 vertebra) also has the dens projecting upward from the vertebral body. The atlas (C1 vertebra) differs from the other cervical vertebrae in that it does not have a body, but instead consists of bony ring formed by the anterior and posterior arches. The atlas articulates with the dens from the axis. A typical thoracic vertebra is distinguished by its long, downward projecting spinous process. Thoracic vertebrae also have articulation facets on the body and transverse processes for attachment of the ribs. Lumbar vertebrae support the greatest amount of body weight and thus have a large, thick body. They also have a short, blunt spinous process. The sacrum is triangular in shape. The median sacral crest is formed by the fused vertebral spinous processes and the lateral sacral crest is derived from the fused transverse processes. Anterior (ventral) and posterior (dorsal) sacral foramina allow branches of the sacral spinal nerves to exit the sacrum. The auricular surfaces are articulation sites on the lateral sacrum that anchor the sacrum to the hipbones to form the pelvis. The coccyx is small and derived from the fusion of four small vertebrae. The intervertebral discs fill in the gaps between the bodies of adjacent vertebrae. They provide strong attachments and padding between the vertebrae. The outer, fibrous layer of a disc is called the anulus fibrosus. The gel-like interior is called the nucleus pulposus. The disc can change shape to allow for movement between vertebrae. If the anulus fibrosus is weakened or damaged, the nucleus pulposus can protrude outward, resulting in a herniated disc. The anterior longitudinal ligament runs along the full length of the anterior vertebral column, uniting the vertebral bodies. The supraspinous ligament is located posteriorly and interconnects the spinous processes of the thoracic and lumbar vertebrae. In the neck, this ligament expands to become the nuchal ligament. The nuchal ligament is attached to the cervical spinous processes and superiorly to the base of the skull, out to the external occipital protuberance. The posterior longitudinal ligament runs within the vertebral canal and unites the posterior sides of the vertebral bodies. The ligamentum flavum unites the lamina of adjacent vertebrae. 7.4 The Thoracic Cage The thoracic cage protects the heart and lungs. It is composed of 12 pairs of ribs with their costal cartilages and the sternum. The ribs are anchored posteriorly to the 12 thoracic vertebrae. The sternum consists of the manubrium, body, and xiphoid process. The manubrium and body are joined at the sternal angle, which is also the site for attachment of the second ribs. Ribs are flattened, curved bones and are numbered 1–12. Posteriorly, the head of the rib articulates with the costal facets located on the bodies of thoracic vertebrae and the rib tubercle articulates with the facet located on the vertebral transverse process. The angle of the ribs forms the most posterior portion of the thoracic cage. The costal groove in the inferior margin of each rib carries blood vessels and a nerve. Anteriorly, each rib ends in a costal cartilage. True ribs (1–7) attach directly to the sternum via their costal cartilage. The false ribs (8–12) either attach to the sternum indirectly or not at all. Ribs 8–10 have their costal cartilages attached to the cartilage of the next higher rib. The floating ribs (11–12) are short and do not attach to the sternum or to another rib. 7.5 Embryonic Development of the Axial Skeleton Formation of the axial skeleton begins during early embryonic development with the appearance of the rod-like notochord along the dorsal length of the early embryo. Repeating, paired blocks of tissue called somites then appear along either side of notochord. As the somites grow, they split into parts, one of which is called a sclerotome. This consists of mesenchyme, the embryonic tissue that will become the bones, cartilages, and connective tissues of the body. Mesenchyme in the head region will produce the bones of the skull via two different mechanisms. The bones of the brain case arise via intramembranous ossification in which embryonic mesenchyme tissue converts directly into bone. At the time of birth, these bones are separated by fontanelles, wide areas of fibrous connective tissue. As the bones grow, the fontanelles are reduced to sutures, which allow for continued growth of the skull throughout childhood. In contrast, the cranial base and facial bones are produced by the process of endochondral ossification, in which mesenchyme tissue initially produces a hyaline cartilage model of the future bone. The cartilage model allows for growth of the bone and is gradually converted into bone over a period of many years. The vertebrae, ribs, and sternum also develop via endochondral ossification. Mesenchyme accumulates around the notochord and produces hyaline cartilage models of the vertebrae. The notochord largely disappears, but remnants of the notochord contribute to formation of the intervertebral discs. In the thorax region, a portion of the vertebral cartilage model splits off to form the ribs. These then become attached anteriorly to the developing cartilage model of the sternum. Growth of the cartilage models for the vertebrae, ribs, and sternum allow for enlargement of the thoracic cage during childhood and adolescence. The cartilage models gradually undergo ossification and are converted into bone. Interactive Link Questions Watch this video to view a rotating and exploded skull with color-coded bones. Which bone (yellow) is centrally located and joins with most of the other bones of the skull? 2.View this animation to see how a blow to the head may produce a contrecoup (counterblow) fracture of the basilar portion of the occipital bone on the base of the skull. Why may a basilar fracture be life threatening? 3.Osteoporosis is a common age-related bone disease in which bone density and strength is decreased. Watch this videoto get a better understanding of how thoracic vertebrae may become weakened and may fractured due to this disease. How may vertebral osteoporosis contribute to kyphosis? 4.Watch this animation to see what it means to “slip” a disk. Watch this second animation to see one possible treatment for a herniated disc, removing and replacing the damaged disc with an artificial one that allows for movement between the adjacent certebrae. How could lifting a heavy object produce pain in a lower limb? 5.Use this tool to identify the bones, intervertebral discs, and ligaments of the vertebral column. The thickest portions of the anterior longitudinal ligament and the supraspinous ligament are found in which regions of the vertebral column? 6.View this video to review the two processes that give rise to the bones of the skull and body. What are the two mechanisms by which the bones of the body are formed and which bones are formed by each mechanism? Review Questions Which of the following is part of the axial skeleton? - shoulder bones - thigh bone - foot bones - vertebral column Which of the following is a function of the axial skeleton? - allows for movement of the wrist and hand - protects nerves and blood vessels at the elbow - supports trunk of body - allows for movements of the ankle and foot The axial skeleton ________. - consists of 126 bones - forms the vertical axis of the body - includes all bones of the body trunk and limbs - includes only the bones of the lower limbs Which of the following is a bone of the brain case? - parietal bone - zygomatic bone - maxillary bone - lacrimal bone The lambdoid suture joins the parietal bone to the ________. - frontal bone - occipital bone - other parietal bone - temporal bone The middle cranial fossa ________. - is bounded anteriorly by the petrous ridge - is bounded posteriorly by the lesser wing of the sphenoid bone - is divided at the midline by a small area of the ethmoid bone - has the foramen rotundum, foramen ovale, and foramen spinosum The paranasal sinuses are ________. - air-filled spaces found within the frontal, maxilla, sphenoid, and ethmoid bones only - air-filled spaces found within all bones of the skull - not connected to the nasal cavity - divided at the midline by the nasal septum Parts of the sphenoid bone include the ________. - sella turcica - squamous portion - glabella - zygomatic process The bony openings of the skull include the ________. - carotid canal, which is located in the anterior cranial fossa - superior orbital fissure, which is located at the superior margin of the anterior orbit - mental foramen, which is located just below the orbit - hypoglossal canal, which is located in the posterior cranial fossa The cervical region of the vertebral column consists of ________. - seven vertebrae - 12 vertebrae - five vertebrae - a single bone derived from the fusion of five vertebrae The primary curvatures of the vertebral column ________. - include the lumbar curve - are remnants of the original fetal curvature - include the cervical curve - develop after the time of birth A typical vertebra has ________. - a vertebral foramen that passes through the body - a superior articular process that projects downward to articulate with the superior portion of the next lower vertebra - lamina that spans between the transverse process and spinous process - a pair of laterally projecting spinous processes A typical lumbar vertebra has ________. - a short, rounded spinous process - a bifid spinous process - articulation sites for ribs - a transverse foramen Which is found only in the cervical region of the vertebral column? - nuchal ligament - ligamentum flavum - supraspinous ligament - anterior longitudinal ligament The sternum ________. - consists of only two parts, the manubrium and xiphoid process - has the sternal angle located between the manubrium and body - receives direct attachments from the costal cartilages of all 12 pairs of ribs - articulates directly with the thoracic vertebrae The sternal angle is the ________. - junction between the body and xiphoid process - site for attachment of the clavicle - site for attachment of the floating ribs - junction between the manubrium and body The tubercle of a rib ________. - is for articulation with the transverse process of a thoracic vertebra - is for articulation with the body of a thoracic vertebra - provides for passage of blood vessels and a nerve - is the area of greatest rib curvature True ribs are ________. - ribs 8–12 - attached via their costal cartilage to the next higher rib - made entirely of bone, and thus do not have a costal cartilage - attached via their costal cartilage directly to the sternum Embryonic development of the axial skeleton involves ________. - intramembranous ossification, which forms the facial bones. - endochondral ossification, which forms the ribs and sternum - the notochord, which produces the cartilage models for the vertebrae - the formation of hyaline cartilage models, which give rise to the flat bones of the skull A fontanelle ________. - is the cartilage model for a vertebra that later is converted into bone - gives rise to the facial bones and vertebrae - is the rod-like structure that runs the length of the early embryo - is the area of fibrous connective tissue found at birth between the brain case bones Critical Thinking Questions Define the two divisions of the skeleton. 28.Discuss the functions of the axial skeleton. 29.Define and list the bones that form the brain case or support the facial structures. 30.Identify the major sutures of the skull, their locations, and the bones united by each. 31.Describe the anterior, middle, and posterior cranial fossae and their boundaries, and give the midline structure that divides each into right and left areas. 32.Describe the parts of the nasal septum in both the dry and living skull. 33.Describe the vertebral column and define each region. 34.Describe a typical vertebra. 35.Describe the sacrum. 36.Describe the structure and function of an intervertebral disc. 37.Define the ligaments of the vertebral column. 38.Define the parts and functions of the thoracic cage. 39.Describe the parts of the sternum. 40.Discuss the parts of a typical rib. 41.Define the classes of ribs. 42.Discuss the processes by which the brain-case bones of the skull are formed and grow during skull enlargement. 43.Discuss the process that gives rise to the base and facial bones of the skull. 44.Discuss the development of the vertebrae, ribs, and sternum.	oercommons	2025-03-18T00:36:05.507314	07/23/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/56366/overview", "title": "Anatomy and Physiology, Support and Movement, Axial Skeleton", "author": null }
https://oercommons.org/courseware/lesson/58775/overview	The Reproductive System Introduction Figure 27.1 Ovulation Following a surge of luteinizing hormone (LH), an oocyte (immature egg cell) will be released into the uterine tube, where it will then be available to be fertilized by a male’s sperm. Ovulation marks the end of the follicular phase of the ovarian cycle and the start of the luteal phase. CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Describe the anatomy of the male and female reproductive systems, including their accessory structures - Explain the role of hypothalamic and pituitary hormones in male and female reproductive function - Trace the path of a sperm cell from its initial production through fertilization of an oocyte - Explain the events in the ovary prior to ovulation - Describe the development and maturation of the sex organs and the emergence of secondary sex characteristics during puberty Small, uncoordinated, and slick with amniotic fluid, a newborn encounters the world outside of her mother’s womb. We do not often consider that a child’s birth is proof of the healthy functioning of both her mother’s and father’s reproductive systems. Moreover, her parents’ endocrine systems had to secrete the appropriate regulating hormones to induce the production and release of unique male and female gametes, reproductive cells containing the parents’ genetic material (one set of 23 chromosomes). Her parent’s reproductive behavior had to facilitate the transfer of male gametes—the sperm—to the female reproductive tract at just the right time to encounter the female gamete, an oocyte (egg). Finally, combination of the gametes (fertilization) had to occur, followed by implantation and development. In this chapter, you will explore the male and female reproductive systems, whose healthy functioning can culminate in the powerful sound of a newborn’s first cry. Anatomy and Physiology of the Male Reproductive System - Describe the structure and function of the organs of the male reproductive system - Describe the structure and function of the sperm cell - Explain the events during spermatogenesis that produce haploid sperm from diploid cells - Identify the importance of testosterone in male reproductive function Unique for its role in human reproduction, a gamete is a specialized sex cell carrying 23 chromosomes—one half the number in body cells. At fertilization, the chromosomes in one male gamete, called a sperm (or spermatozoon), combine with the chromosomes in one female gamete, called an oocyte. The function of the male reproductive system (Figure 27.2) is to produce sperm and transfer them to the female reproductive tract. The paired testes are a crucial component in this process, as they produce both sperm and androgens, the hormones that support male reproductive physiology. In humans, the most important male androgen is testosterone. Several accessory organs and ducts aid the process of sperm maturation and transport the sperm and other seminal components to the penis, which delivers sperm to the female reproductive tract. In this section, we examine each of these different structures, and discuss the process of sperm production and transport. Figure 27.2 Male Reproductive System The structures of the male reproductive system include the testes, the epididymides, the penis, and the ducts and glands that produce and carry semen. Sperm exit the scrotum through the ductus deferens, which is bundled in the spermatic cord. The seminal vesicles and prostate gland add fluids to the sperm to create semen. Scrotum The testes are located in a skin-covered, highly pigmented, muscular sack called the scrotum that extends from the body behind the penis (see Figure 27.2). This location is important in sperm production, which occurs within the testes, and proceeds more efficiently when the testes are kept 2 to 4°C below core body temperature. The dartos muscle makes up the subcutaneous muscle layer of the scrotum (Figure 27.3). It continues internally to make up the scrotal septum, a wall that divides the scrotum into two compartments, each housing one testis. Descending from the internal oblique muscle of the abdominal wall are the two cremaster muscles, which cover each testis like a muscular net. By contracting simultaneously, the dartos and cremaster muscles can elevate the testes in cold weather (or water), moving the testes closer to the body and decreasing the surface area of the scrotum to retain heat. Alternatively, as the environmental temperature increases, the scrotum relaxes, moving the testes farther from the body core and increasing scrotal surface area, which promotes heat loss. Externally, the scrotum has a raised medial thickening on the surface called the raphae. Figure 27.3 The Scrotum and Testes This anterior view shows the structures of the scrotum and testes. Testes The testes (singular = testis) are the male gonads—that is, the male reproductive organs. They produce both sperm and androgens, such as testosterone, and are active throughout the reproductive lifespan of the male. Paired ovals, the testes are each approximately 4 to 5 cm in length and are housed within the scrotum (see Figure 27.3). They are surrounded by two distinct layers of protective connective tissue (Figure 27.4). The outer tunica vaginalis is a serous membrane that has both a parietal and a thin visceral layer. Beneath the tunica vaginalis is the tunica albuginea, a tough, white, dense connective tissue layer covering the testis itself. Not only does the tunica albuginea cover the outside of the testis, it also invaginates to form septa that divide the testis into 300 to 400 structures called lobules. Within the lobules, sperm develop in structures called seminiferous tubules. During the seventh month of the developmental period of a male fetus, each testis moves through the abdominal musculature to descend into the scrotal cavity. This is called the “descent of the testis.” Cryptorchidism is the clinical term used when one or both of the testes fail to descend into the scrotum prior to birth. Figure 27.4 Anatomy of the Testis This sagittal view shows the seminiferous tubules, the site of sperm production. Formed sperm are transferred to the epididymis, where they mature. They leave the epididymis during an ejaculation via the ductus deferens. The tightly coiled seminiferous tubules form the bulk of each testis. They are composed of developing sperm cells surrounding a lumen, the hollow center of the tubule, where formed sperm are released into the duct system of the testis. Specifically, from the lumens of the seminiferous tubules, sperm move into the straight tubules (or tubuli recti), and from there into a fine meshwork of tubules called the rete testes. Sperm leave the rete testes, and the testis itself, through the 15 to 20 efferent ductules that cross the tunica albuginea. Inside the seminiferous tubules are six different cell types. These include supporting cells called sustentacular cells, as well as five types of developing sperm cells called germ cells. Germ cell development progresses from the basement membrane—at the perimeter of the tubule—toward the lumen. Let’s look more closely at these cell types. Sertoli Cells Surrounding all stages of the developing sperm cells are elongate, branching Sertoli cells. Sertoli cells are a type of supporting cell called a sustentacular cell, or sustentocyte, that are typically found in epithelial tissue. Sertoli cells secrete signaling molecules that promote sperm production and can control whether germ cells live or die. They extend physically around the germ cells from the peripheral basement membrane of the seminiferous tubules to the lumen. Tight junctions between these sustentacular cells create the blood–testis barrier, which keeps bloodborne substances from reaching the germ cells and, at the same time, keeps surface antigens on developing germ cells from escaping into the bloodstream and prompting an autoimmune response. Germ Cells The least mature cells, the spermatogonia (singular = spermatogonium), line the basement membrane inside the tubule. Spermatogonia are the stem cells of the testis, which means that they are still able to differentiate into a variety of different cell types throughout adulthood. Spermatogonia divide to produce primary and secondary spermatocytes, then spermatids, which finally produce formed sperm. The process that begins with spermatogonia and concludes with the production of sperm is called spermatogenesis. Spermatogenesis As just noted, spermatogenesis occurs in the seminiferous tubules that form the bulk of each testis (see Figure 27.4). The process begins at puberty, after which time sperm are produced constantly throughout a man’s life. One production cycle, from spermatogonia through formed sperm, takes approximately 64 days. A new cycle starts approximately every 16 days, although this timing is not synchronous across the seminiferous tubules. Sperm counts—the total number of sperm a man produces—slowly decline after age 35, and some studies suggest that smoking can lower sperm counts irrespective of age. The process of spermatogenesis begins with mitosis of the diploid spermatogonia (Figure 27.5). Because these cells are diploid (2n), they each have a complete copy of the father’s genetic material, or 46 chromosomes. However, mature gametes are haploid (1n), containing 23 chromosomes—meaning that daughter cells of spermatogonia must undergo a second cellular division through the process of meiosis. Figure 27.5 Spermatogenesis (a) Mitosis of a spermatogonial stem cell involves a single cell division that results in two identical, diploid daughter cells (spermatogonia to primary spermatocyte). Meiosis has two rounds of cell division: primary spermatocyte to secondary spermatocyte, and then secondary spermatocyte to spermatid. This produces four haploid daughter cells (spermatids). (b) In this electron micrograph of a cross-section of a seminiferous tubule from a rat, the lumen is the light-shaded area in the center of the image. The location of the primary spermatocytes is near the basement membrane, and the early spermatids are approaching the lumen (tissue source: rat). EM × 900. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Two identical diploid cells result from spermatogonia mitosis. One of these cells remains a spermatogonium, and the other becomes a primary spermatocyte, the next stage in the process of spermatogenesis. As in mitosis, DNA is replicated in a primary spermatocyte, before it undergoes a cell division called meiosis I. During meiosis I each of the 23 pairs of chromosomes separates. This results in two cells, called secondary spermatocytes, each with only half the number of chromosomes. Now a second round of cell division (meiosis II) occurs in both of the secondary spermatocytes. During meiosis II each of the 23 replicated chromosomes divides, similar to what happens during mitosis. Thus, meiosis results in separating the chromosome pairs. This second meiotic division results in a total of four cells with only half of the number of chromosomes. Each of these new cells is a spermatid. Although haploid, early spermatids look very similar to cells in the earlier stages of spermatogenesis, with a round shape, central nucleus, and large amount of cytoplasm. A process called spermiogenesis transforms these early spermatids, reducing the cytoplasm, and beginning the formation of the parts of a true sperm. The fifth stage of germ cell formation—spermatozoa, or formed sperm—is the end result of this process, which occurs in the portion of the tubule nearest the lumen. Eventually, the sperm are released into the lumen and are moved along a series of ducts in the testis toward a structure called the epididymis for the next step of sperm maturation. Structure of Formed Sperm Sperm are smaller than most cells in the body; in fact, the volume of a sperm cell is 85,000 times less than that of the female gamete. Approximately 100 to 300 million sperm are produced each day, whereas women typically ovulate only one oocyte per month. As is true for most cells in the body, the structure of sperm cells speaks to their function. Sperm have a distinctive head, mid-piece, and tail region (Figure 27.6). The head of the sperm contains the extremely compact haploid nucleus with very little cytoplasm. These qualities contribute to the overall small size of the sperm (the head is only 5 μm long). A structure called the acrosome covers most of the head of the sperm cell as a “cap” that is filled with lysosomal enzymes important for preparing sperm to participate in fertilization. Tightly packed mitochondria fill the mid-piece of the sperm. ATP produced by these mitochondria will power the flagellum, which extends from the neck and the mid-piece through the tail of the sperm, enabling it to move the entire sperm cell. The central strand of the flagellum, the axial filament, is formed from one centriole inside the maturing sperm cell during the final stages of spermatogenesis. Figure 27.6 Structure of Sperm Sperm cells are divided into a head, containing DNA; a mid-piece, containing mitochondria; and a tail, providing motility. The acrosome is oval and somewhat flattened. Sperm Transport To fertilize an egg, sperm must be moved from the seminiferous tubules in the testes, through the epididymis, and—later during ejaculation—along the length of the penis and out into the female reproductive tract. Role of the Epididymis From the lumen of the seminiferous tubules, the immotile sperm are surrounded by testicular fluid and moved to the epididymis(plural = epididymides), a coiled tube attached to the testis where newly formed sperm continue to mature (see Figure 27.4). Though the epididymis does not take up much room in its tightly coiled state, it would be approximately 6 m (20 feet) long if straightened. It takes an average of 12 days for sperm to move through the coils of the epididymis, with the shortest recorded transit time in humans being one day. Sperm enter the head of the epididymis and are moved along predominantly by the contraction of smooth muscles lining the epididymal tubes. As they are moved along the length of the epididymis, the sperm further mature and acquire the ability to move under their own power. Once inside the female reproductive tract, they will use this ability to move independently toward the unfertilized egg. The more mature sperm are then stored in the tail of the epididymis (the final section) until ejaculation occurs. Duct System During ejaculation, sperm exit the tail of the epididymis and are pushed by smooth muscle contraction to the ductus deferens(also called the vas deferens). The ductus deferens is a thick, muscular tube that is bundled together inside the scrotum with connective tissue, blood vessels, and nerves into a structure called the spermatic cord (see Figure 27.2 and Figure 27.3). Because the ductus deferens is physically accessible within the scrotum, surgical sterilization to interrupt sperm delivery can be performed by cutting and sealing a small section of the ductus (vas) deferens. This procedure is called a vasectomy, and it is an effective form of male birth control. Although it may be possible to reverse a vasectomy, clinicians consider the procedure permanent, and advise men to undergo it only if they are certain they no longer wish to father children. INTERACTIVE LINK Watch this video to learn about a vasectomy. As described in this video, a vasectomy is a procedure in which a small section of the ductus (vas) deferens is removed from the scrotum. This interrupts the path taken by sperm through the ductus deferens. If sperm do not exit through the vas, either because the man has had a vasectomy or has not ejaculated, in what region of the testis do they remain? From each epididymis, each ductus deferens extends superiorly into the abdominal cavity through the inguinal canal in the abdominal wall. From here, the ductus deferens continues posteriorly to the pelvic cavity, ending posterior to the bladder where it dilates in a region called the ampulla (meaning “flask”). Sperm make up only 5 percent of the final volume of semen, the thick, milky fluid that the male ejaculates. The bulk of semen is produced by three critical accessory glands of the male reproductive system: the seminal vesicles, the prostate, and the bulbourethral glands. Seminal Vesicles As sperm pass through the ampulla of the ductus deferens at ejaculation, they mix with fluid from the associated seminal vesicle (see Figure 27.2). The paired seminal vesicles are glands that contribute approximately 60 percent of the semen volume. Seminal vesicle fluid contains large amounts of fructose, which is used by the sperm mitochondria to generate ATP to allow movement through the female reproductive tract. The fluid, now containing both sperm and seminal vesicle secretions, next moves into the associated ejaculatory duct, a short structure formed from the ampulla of the ductus deferens and the duct of the seminal vesicle. The paired ejaculatory ducts transport the seminal fluid into the next structure, the prostate gland. Prostate Gland As shown in Figure 27.2, the centrally located prostate gland sits anterior to the rectum at the base of the bladder surrounding the prostatic urethra (the portion of the urethra that runs within the prostate). About the size of a walnut, the prostate is formed of both muscular and glandular tissues. It excretes an alkaline, milky fluid to the passing seminal fluid—now called semen—that is critical to first coagulate and then decoagulate the semen following ejaculation. The temporary thickening of semen helps retain it within the female reproductive tract, providing time for sperm to utilize the fructose provided by seminal vesicle secretions. When the semen regains its fluid state, sperm can then pass farther into the female reproductive tract. The prostate normally doubles in size during puberty. At approximately age 25, it gradually begins to enlarge again. This enlargement does not usually cause problems; however, abnormal growth of the prostate, or benign prostatic hyperplasia (BPH), can cause constriction of the urethra as it passes through the middle of the prostate gland, leading to a number of lower urinary tract symptoms, such as a frequent and intense urge to urinate, a weak stream, and a sensation that the bladder has not emptied completely. By age 60, approximately 40 percent of men have some degree of BPH. By age 80, the number of affected individuals has jumped to as many as 80 percent. Treatments for BPH attempt to relieve the pressure on the urethra so that urine can flow more normally. Mild to moderate symptoms are treated with medication, whereas severe enlargement of the prostate is treated by surgery in which a portion of the prostate tissue is removed. Another common disorder involving the prostate is prostate cancer. According to the Centers for Disease Control and Prevention (CDC), prostate cancer is the second most common cancer in men. However, some forms of prostate cancer grow very slowly and thus may not ever require treatment. Aggressive forms of prostate cancer, in contrast, involve metastasis to vulnerable organs like the lungs and brain. There is no link between BPH and prostate cancer, but the symptoms are similar. Prostate cancer is detected by a medical history, a blood test, and a rectal exam that allows physicians to palpate the prostate and check for unusual masses. If a mass is detected, the cancer diagnosis is confirmed by biopsy of the cells. Bulbourethral Glands The final addition to semen is made by two bulbourethral glands (or Cowper’s glands) that release a thick, salty fluid that lubricates the end of the urethra and the vagina, and helps to clean urine residues from the penile urethra. The fluid from these accessory glands is released after the male becomes sexually aroused, and shortly before the release of the semen. It is therefore sometimes called pre-ejaculate. It is important to note that, in addition to the lubricating proteins, it is possible for bulbourethral fluid to pick up sperm already present in the urethra, and therefore it may be able to cause pregnancy. INTERACTIVE LINK Watch this video to explore the structures of the male reproductive system and the path of sperm, which starts in the testes and ends as the sperm leave the penis through the urethra. Where are sperm deposited after they leave the ejaculatory duct? The Penis The penis is the male organ of copulation (sexual intercourse). It is flaccid for non-sexual actions, such as urination, and turgid and rod-like with sexual arousal. When erect, the stiffness of the organ allows it to penetrate into the vagina and deposit semen into the female reproductive tract. Figure 27.7 Cross-Sectional Anatomy of the Penis Three columns of erectile tissue make up most of the volume of the penis. The shaft of the penis surrounds the urethra (Figure 27.7). The shaft is composed of three column-like chambers of erectile tissue that span the length of the shaft. Each of the two larger lateral chambers is called a corpus cavernosum (plural = corpora cavernosa). Together, these make up the bulk of the penis. The corpus spongiosum, which can be felt as a raised ridge on the erect penis, is a smaller chamber that surrounds the spongy, or penile, urethra. The end of the penis, called the glans penis, has a high concentration of nerve endings, resulting in very sensitive skin that influences the likelihood of ejaculation (see Figure 27.2). The skin from the shaft extends down over the glans and forms a collar called the prepuce (or foreskin). The foreskin also contains a dense concentration of nerve endings, and both lubricate and protect the sensitive skin of the glans penis. A surgical procedure called circumcision, often performed for religious or social reasons, removes the prepuce, typically within days of birth. Both sexual arousal and REM sleep (during which dreaming occurs) can induce an erection. Penile erections are the result of vasocongestion, or engorgement of the tissues because of more arterial blood flowing into the penis than is leaving in the veins. During sexual arousal, nitric oxide (NO) is released from nerve endings near blood vessels within the corpora cavernosa and spongiosum. Release of NO activates a signaling pathway that results in relaxation of the smooth muscles that surround the penile arteries, causing them to dilate. This dilation increases the amount of blood that can enter the penis and induces the endothelial cells in the penile arterial walls to also secrete NO and perpetuate the vasodilation. The rapid increase in blood volume fills the erectile chambers, and the increased pressure of the filled chambers compresses the thin-walled penile venules, preventing venous drainage of the penis. The result of this increased blood flow to the penis and reduced blood return from the penis is erection. Depending on the flaccid dimensions of a penis, it can increase in size slightly or greatly during erection, with the average length of an erect penis measuring approximately 15 cm. DISORDERS OF THE... Male Reproductive System Erectile dysfunction (ED) is a condition in which a man has difficulty either initiating or maintaining an erection. The combined prevalence of minimal, moderate, and complete ED is approximately 40 percent in men at age 40, and reaches nearly 70 percent by 70 years of age. In addition to aging, ED is associated with diabetes, vascular disease, psychiatric disorders, prostate disorders, the use of some drugs such as certain antidepressants, and problems with the testes resulting in low testosterone concentrations. These physical and emotional conditions can lead to interruptions in the vasodilation pathway and result in an inability to achieve an erection. Recall that the release of NO induces relaxation of the smooth muscles that surround the penile arteries, leading to the vasodilation necessary to achieve an erection. To reverse the process of vasodilation, an enzyme called phosphodiesterase (PDE) degrades a key component of the NO signaling pathway called cGMP. There are several different forms of this enzyme, and PDE type 5 is the type of PDE found in the tissues of the penis. Scientists discovered that inhibiting PDE5 increases blood flow, and allows vasodilation of the penis to occur. PDEs and the vasodilation signaling pathway are found in the vasculature in other parts of the body. In the 1990s, clinical trials of a PDE5 inhibitor called sildenafil were initiated to treat hypertension and angina pectoris (chest pain caused by poor blood flow through the heart). The trial showed that the drug was not effective at treating heart conditions, but many men experienced erection and priapism (erection lasting longer than 4 hours). Because of this, a clinical trial was started to investigate the ability of sildenafil to promote erections in men suffering from ED. In 1998, the FDA approved the drug, marketed as Viagra®. Since approval of the drug, sildenafil and similar PDE inhibitors now generate over a billion dollars a year in sales, and are reported to be effective in treating approximately 70 to 85 percent of cases of ED. Importantly, men with health problems—especially those with cardiac disease taking nitrates—should avoid Viagra or talk to their physician to find out if they are a candidate for the use of this drug, as deaths have been reported for at-risk users. Testosterone Testosterone, an androgen, is a steroid hormone produced by Leydig cells. The alternate term for Leydig cells, interstitial cells, reflects their location between the seminiferous tubules in the testes. In male embryos, testosterone is secreted by Leydig cells by the seventh week of development, with peak concentrations reached in the second trimester. This early release of testosterone results in the anatomical differentiation of the male sexual organs. In childhood, testosterone concentrations are low. They increase during puberty, activating characteristic physical changes and initiating spermatogenesis. Functions of Testosterone The continued presence of testosterone is necessary to keep the male reproductive system working properly, and Leydig cells produce approximately 6 to 7 mg of testosterone per day. Testicular steroidogenesis (the manufacture of androgens, including testosterone) results in testosterone concentrations that are 100 times higher in the testes than in the circulation. Maintaining these normal concentrations of testosterone promotes spermatogenesis, whereas low levels of testosterone can lead to infertility. In addition to intratesticular secretion, testosterone is also released into the systemic circulation and plays an important role in muscle development, bone growth, the development of secondary sex characteristics, and maintaining libido (sex drive) in both males and females. In females, the ovaries secrete small amounts of testosterone, although most is converted to estradiol. A small amount of testosterone is also secreted by the adrenal glands in both sexes. Control of Testosterone The regulation of testosterone concentrations throughout the body is critical for male reproductive function. The intricate interplay between the endocrine system and the reproductive system is shown in Figure 27.8. Figure 27.8 Regulation of Testosterone Production The hypothalamus and pituitary gland regulate the production of testosterone and the cells that assist in spermatogenesis. GnRH activates the anterior pituitary to produce LH and FSH, which in turn stimulate Leydig cells and Sertoli cells, respectively. The system is a negative feedback loop because the end products of the pathway, testosterone and inhibin, interact with the activity of GnRH to inhibit their own production. The regulation of Leydig cell production of testosterone begins outside of the testes. The hypothalamus and the pituitary gland in the brain integrate external and internal signals to control testosterone synthesis and secretion. The regulation begins in the hypothalamus. Pulsatile release of a hormone called gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the endocrine release of hormones from the pituitary gland. Binding of GnRH to its receptors on the anterior pituitary gland stimulates release of the two gonadotropins: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These two hormones are critical for reproductive function in both men and women. In men, FSH binds predominantly to the Sertoli cells within the seminiferous tubules to promote spermatogenesis. FSH also stimulates the Sertoli cells to produce hormones called inhibins, which function to inhibit FSH release from the pituitary, thus reducing testosterone secretion. These polypeptide hormones correlate directly with Sertoli cell function and sperm number; inhibin B can be used as a marker of spermatogenic activity. In men, LH binds to receptors on Leydig cells in the testes and upregulates the production of testosterone. A negative feedback loop predominantly controls the synthesis and secretion of both FSH and LH. Low blood concentrations of testosterone stimulate the hypothalamic release of GnRH. GnRH then stimulates the anterior pituitary to secrete LH into the bloodstream. In the testis, LH binds to LH receptors on Leydig cells and stimulates the release of testosterone. When concentrations of testosterone in the blood reach a critical threshold, testosterone itself will bind to androgen receptors on both the hypothalamus and the anterior pituitary, inhibiting the synthesis and secretion of GnRH and LH, respectively. When the blood concentrations of testosterone once again decline, testosterone no longer interacts with the receptors to the same degree and GnRH and LH are once again secreted, stimulating more testosterone production. This same process occurs with FSH and inhibin to control spermatogenesis. AGING AND THE... Male Reproductive System Declines in Leydig cell activity can occur in men beginning at 40 to 50 years of age. The resulting reduction in circulating testosterone concentrations can lead to symptoms of andropause, also known as male menopause. While the reduction in sex steroids in men is akin to female menopause, there is no clear sign—such as a lack of a menstrual period—to denote the initiation of andropause. Instead, men report feelings of fatigue, reduced muscle mass, depression, anxiety, irritability, loss of libido, and insomnia. A reduction in spermatogenesis resulting in lowered fertility is also reported, and sexual dysfunction can also be associated with andropausal symptoms. Whereas some researchers believe that certain aspects of andropause are difficult to tease apart from aging in general, testosterone replacement is sometimes prescribed to alleviate some symptoms. Recent studies have shown a benefit from androgen replacement therapy on the new onset of depression in elderly men; however, other studies caution against testosterone replacement for long-term treatment of andropause symptoms, showing that high doses can sharply increase the risk of both heart disease and prostate cancer. Anatomy and Physiology of the Female Reproductive System - Describe the structure and function of the organs of the female reproductive system - List the steps of oogenesis - Describe the hormonal changes that occur during the ovarian and menstrual cycles - Trace the path of an oocyte from ovary to fertilization The female reproductive system functions to produce gametes and reproductive hormones, just like the male reproductive system; however, it also has the additional task of supporting the developing fetus and delivering it to the outside world. Unlike its male counterpart, the female reproductive system is located primarily inside the pelvic cavity (Figure 27.9). Recall that the ovaries are the female gonads. The gamete they produce is called an oocyte. We’ll discuss the production of oocytes in detail shortly. First, let’s look at some of the structures of the female reproductive system. Figure 27.9 Female Reproductive System The major organs of the female reproductive system are located inside the pelvic cavity. External Female Genitals The external female reproductive structures are referred to collectively as the vulva (Figure 27.10). The mons pubis is a pad of fat that is located at the anterior, over the pubic bone. After puberty, it becomes covered in pubic hair. The labia majora (labia = “lips”; majora = “larger”) are folds of hair-covered skin that begin just posterior to the mons pubis. The thinner and more pigmented labia minora (labia = “lips”; minora = “smaller”) extend medial to the labia majora. Although they naturally vary in shape and size from woman to woman, the labia minora serve to protect the female urethra and the entrance to the female reproductive tract. The superior, anterior portions of the labia minora come together to encircle the clitoris (or glans clitoris), an organ that originates from the same cells as the glans penis and has abundant nerves that make it important in sexual sensation and orgasm. The hymen is a thin membrane that sometimes partially covers the entrance to the vagina. An intact hymen cannot be used as an indication of “virginity”; even at birth, this is only a partial membrane, as menstrual fluid and other secretions must be able to exit the body, regardless of penile–vaginal intercourse. The vaginal opening is located between the opening of the urethra and the anus. It is flanked by outlets to the Bartholin’s glands (or greater vestibular glands). Figure 27.10 The Vulva The external female genitalia are referred to collectively as the vulva. Vagina The vagina, shown at the bottom of Figure 27.9 and Figure 27.9, is a muscular canal (approximately 10 cm long) that serves as the entrance to the reproductive tract. It also serves as the exit from the uterus during menses and childbirth. The outer walls of the anterior and posterior vagina are formed into longitudinal columns, or ridges, and the superior portion of the vagina—called the fornix—meets the protruding uterine cervix. The walls of the vagina are lined with an outer, fibrous adventitia; a middle layer of smooth muscle; and an inner mucous membrane with transverse folds called rugae. Together, the middle and inner layers allow the expansion of the vagina to accommodate intercourse and childbirth. The thin, perforated hymen can partially surround the opening to the vaginal orifice. The hymen can be ruptured with strenuous physical exercise, penile–vaginal intercourse, and childbirth. The Bartholin’s glands and the lesser vestibular glands (located near the clitoris) secrete mucus, which keeps the vestibular area moist. The vagina is home to a normal population of microorganisms that help to protect against infection by pathogenic bacteria, yeast, or other organisms that can enter the vagina. In a healthy woman, the most predominant type of vaginal bacteria is from the genus Lactobacillus. This family of beneficial bacterial flora secretes lactic acid, and thus protects the vagina by maintaining an acidic pH (below 4.5). Potential pathogens are less likely to survive in these acidic conditions. Lactic acid, in combination with other vaginal secretions, makes the vagina a self-cleansing organ. However, douching—or washing out the vagina with fluid—can disrupt the normal balance of healthy microorganisms, and actually increase a woman’s risk for infections and irritation. Indeed, the American College of Obstetricians and Gynecologists recommend that women do not douche, and that they allow the vagina to maintain its normal healthy population of protective microbial flora. Ovaries The ovaries are the female gonads (see Figure 27.9). Paired ovals, they are each about 2 to 3 cm in length, about the size of an almond. The ovaries are located within the pelvic cavity, and are supported by the mesovarium, an extension of the peritoneum that connects the ovaries to the broad ligament. Extending from the mesovarium itself is the suspensory ligament that contains the ovarian blood and lymph vessels. Finally, the ovary itself is attached to the uterus via the ovarian ligament. The ovary comprises an outer covering of cuboidal epithelium called the ovarian surface epithelium that is superficial to a dense connective tissue covering called the tunica albuginea. Beneath the tunica albuginea is the cortex, or outer portion, of the organ. The cortex is composed of a tissue framework called the ovarian stroma that forms the bulk of the adult ovary. Oocytes develop within the outer layer of this stroma, each surrounded by supporting cells. This grouping of an oocyte and its supporting cells is called a follicle. The growth and development of ovarian follicles will be described shortly. Beneath the cortex lies the inner ovarian medulla, the site of blood vessels, lymph vessels, and the nerves of the ovary. You will learn more about the overall anatomy of the female reproductive system at the end of this section. The Ovarian Cycle The ovarian cycle is a set of predictable changes in a female’s oocytes and ovarian follicles. During a woman’s reproductive years, it is a roughly 28-day cycle that can be correlated with, but is not the same as, the menstrual cycle (discussed shortly). The cycle includes two interrelated processes: oogenesis (the production of female gametes) and folliculogenesis (the growth and development of ovarian follicles). Oogenesis Gametogenesis in females is called oogenesis. The process begins with the ovarian stem cells, or oogonia (Figure 27.11). Oogonia are formed during fetal development, and divide via mitosis, much like spermatogonia in the testis. Unlike spermatogonia, however, oogonia form primary oocytes in the fetal ovary prior to birth. These primary oocytes are then arrested in this stage of meiosis I, only to resume it years later, beginning at puberty and continuing until the woman is near menopause (the cessation of a woman’s reproductive functions). The number of primary oocytes present in the ovaries declines from one to two million in an infant, to approximately 400,000 at puberty, to zero by the end of menopause. The initiation of ovulation—the release of an oocyte from the ovary—marks the transition from puberty into reproductive maturity for women. From then on, throughout a woman’s reproductive years, ovulation occurs approximately once every 28 days. Just prior to ovulation, a surge of luteinizing hormone triggers the resumption of meiosis in a primary oocyte. This initiates the transition from primary to secondary oocyte. However, as you can see in Figure 27.11, this cell division does not result in two identical cells. Instead, the cytoplasm is divided unequally, and one daughter cell is much larger than the other. This larger cell, the secondary oocyte, eventually leaves the ovary during ovulation. The smaller cell, called the first polar body, may or may not complete meiosis and produce second polar bodies; in either case, it eventually disintegrates. Therefore, even though oogenesis produces up to four cells, only one survives. Figure 27.11 Oogenesis The unequal cell division of oogenesis produces one to three polar bodies that later degrade, as well as a single haploid ovum, which is produced only if there is penetration of the secondary oocyte by a sperm cell. How does the diploid secondary oocyte become an ovum—the haploid female gamete? Meiosis of a secondary oocyte is completed only if a sperm succeeds in penetrating its barriers. Meiosis II then resumes, producing one haploid ovum that, at the instant of fertilization by a (haploid) sperm, becomes the first diploid cell of the new offspring (a zygote). Thus, the ovum can be thought of as a brief, transitional, haploid stage between the diploid oocyte and diploid zygote. The larger amount of cytoplasm contained in the female gamete is used to supply the developing zygote with nutrients during the period between fertilization and implantation into the uterus. Interestingly, sperm contribute only DNA at fertilization —not cytoplasm. Therefore, the cytoplasm and all of the cytoplasmic organelles in the developing embryo are of maternal origin. This includes mitochondria, which contain their own DNA. Scientific research in the 1980s determined that mitochondrial DNA was maternally inherited, meaning that you can trace your mitochondrial DNA directly to your mother, her mother, and so on back through your female ancestors. EVERYDAY CONNECTION Mapping Human History with Mitochondrial DNA When we talk about human DNA, we’re usually referring to nuclear DNA; that is, the DNA coiled into chromosomal bundles in the nucleus of our cells. We inherit half of our nuclear DNA from our father, and half from our mother. However, mitochondrial DNA (mtDNA) comes only from the mitochondria in the cytoplasm of the fat ovum we inherit from our mother. She received her mtDNA from her mother, who got it from her mother, and so on. Each of our cells contains approximately 1700 mitochondria, with each mitochondrion packed with mtDNA containing approximately 37 genes. Mutations (changes) in mtDNA occur spontaneously in a somewhat organized pattern at regular intervals in human history. By analyzing these mutational relationships, researchers have been able to determine that we can all trace our ancestry back to one woman who lived in Africa about 200,000 years ago. Scientists have given this woman the biblical name Eve, although she is not, of course, the first Homo sapiens female. More precisely, she is our most recent common ancestor through matrilineal descent. This doesn’t mean that everyone’s mtDNA today looks exactly like that of our ancestral Eve. Because of the spontaneous mutations in mtDNA that have occurred over the centuries, researchers can map different “branches” off of the “main trunk” of our mtDNA family tree. Your mtDNA might have a pattern of mutations that aligns more closely with one branch, and your neighbor’s may align with another branch. Still, all branches eventually lead back to Eve. But what happened to the mtDNA of all of the other Homo sapiens females who were living at the time of Eve? Researchers explain that, over the centuries, their female descendants died childless or with only male children, and thus, their maternal line—and its mtDNA—ended. Folliculogenesis Again, ovarian follicles are oocytes and their supporting cells. They grow and develop in a process called folliculogenesis, which typically leads to ovulation of one follicle approximately every 28 days, along with death to multiple other follicles. The death of ovarian follicles is called atresia, and can occur at any point during follicular development. Recall that, a female infant at birth will have one to two million oocytes within her ovarian follicles, and that this number declines throughout life until menopause, when no follicles remain. As you’ll see next, follicles progress from primordial, to primary, to secondary and tertiary stages prior to ovulation—with the oocyte inside the follicle remaining as a primary oocyte until right before ovulation. Folliculogenesis begins with follicles in a resting state. These small primordial follicles are present in newborn females and are the prevailing follicle type in the adult ovary (Figure 27.12). Primordial follicles have only a single flat layer of support cells, called granulosa cells, that surround the oocyte, and they can stay in this resting state for years—some until right before menopause. After puberty, a few primordial follicles will respond to a recruitment signal each day, and will join a pool of immature growing follicles called primary follicles. Primary follicles start with a single layer of granulosa cells, but the granulosa cells then become active and transition from a flat or squamous shape to a rounded, cuboidal shape as they increase in size and proliferate. As the granulosa cells divide, the follicles—now called secondary follicles (see Figure 27.12)—increase in diameter, adding a new outer layer of connective tissue, blood vessels, and theca cells—cells that work with the granulosa cells to produce estrogens. Within the growing secondary follicle, the primary oocyte now secretes a thin acellular membrane called the zona pellucida that will play a critical role in fertilization. A thick fluid, called follicular fluid, that has formed between the granulosa cells also begins to collect into one large pool, or antrum. Follicles in which the antrum has become large and fully formed are considered tertiary follicles (or antral follicles). Several follicles reach the tertiary stage at the same time, and most of these will undergo atresia. The one that does not die will continue to grow and develop until ovulation, when it will expel its secondary oocyte surrounded by several layers of granulosa cells from the ovary. Keep in mind that most follicles don’t make it to this point. In fact, roughly 99 percent of the follicles in the ovary will undergo atresia, which can occur at any stage of folliculogenesis. Figure 27.12 Folliculogenesis (a) The maturation of a follicle is shown in a clockwise direction proceeding from the primordial follicles. FSH stimulates the growth of a tertiary follicle, and LH stimulates the production of estrogen by granulosa and theca cells. Once the follicle is mature, it ruptures and releases the oocyte. Cells remaining in the follicle then develop into the corpus luteum. (b) In this electron micrograph of a secondary follicle, the oocyte, theca cells (thecae folliculi), and developing antrum are clearly visible. EM × 1100. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Hormonal Control of the Ovarian Cycle The process of development that we have just described, from primordial follicle to early tertiary follicle, takes approximately two months in humans. The final stages of development of a small cohort of tertiary follicles, ending with ovulation of a secondary oocyte, occur over a course of approximately 28 days. These changes are regulated by many of the same hormones that regulate the male reproductive system, including GnRH, LH, and FSH. As in men, the hypothalamus produces GnRH, a hormone that signals the anterior pituitary gland to produce the gonadotropins FSH and LH (Figure 27.13). These gonadotropins leave the pituitary and travel through the bloodstream to the ovaries, where they bind to receptors on the granulosa and theca cells of the follicles. FSH stimulates the follicles to grow (hence its name of follicle-stimulating hormone), and the five or six tertiary follicles expand in diameter. The release of LH also stimulates the granulosa and theca cells of the follicles to produce the sex steroid hormone estradiol, a type of estrogen. This phase of the ovarian cycle, when the tertiary follicles are growing and secreting estrogen, is known as the follicular phase. The more granulosa and theca cells a follicle has (that is, the larger and more developed it is), the more estrogen it will produce in response to LH stimulation. As a result of these large follicles producing large amounts of estrogen, systemic plasma estrogen concentrations increase. Following a classic negative feedback loop, the high concentrations of estrogen will stimulate the hypothalamus and pituitary to reduce the production of GnRH, LH, and FSH. Because the large tertiary follicles require FSH to grow and survive at this point, this decline in FSH caused by negative feedback leads most of them to die (atresia). Typically only one follicle, now called the dominant follicle, will survive this reduction in FSH, and this follicle will be the one that releases an oocyte. Scientists have studied many factors that lead to a particular follicle becoming dominant: size, the number of granulosa cells, and the number of FSH receptors on those granulosa cells all contribute to a follicle becoming the one surviving dominant follicle. Figure 27.13 Hormonal Regulation of Ovulation The hypothalamus and pituitary gland regulate the ovarian cycle and ovulation. GnRH activates the anterior pituitary to produce LH and FSH, which stimulate the production of estrogen and progesterone by the ovaries. When only the one dominant follicle remains in the ovary, it again begins to secrete estrogen. It produces more estrogen than all of the developing follicles did together before the negative feedback occurred. It produces so much estrogen that the normal negative feedback doesn’t occur. Instead, these extremely high concentrations of systemic plasma estrogen trigger a regulatory switch in the anterior pituitary that responds by secreting large amounts of LH and FSH into the bloodstream (see Figure 27.13). The positive feedback loop by which more estrogen triggers release of more LH and FSH only occurs at this point in the cycle. It is this large burst of LH (called the LH surge) that leads to ovulation of the dominant follicle. The LH surge induces many changes in the dominant follicle, including stimulating the resumption of meiosis of the primary oocyte to a secondary oocyte. As noted earlier, the polar body that results from unequal cell division simply degrades. The LH surge also triggers proteases (enzymes that cleave proteins) to break down structural proteins in the ovary wall on the surface of the bulging dominant follicle. This degradation of the wall, combined with pressure from the large, fluid-filled antrum, results in the expulsion of the oocyte surrounded by granulosa cells into the peritoneal cavity. This release is ovulation. In the next section, you will follow the ovulated oocyte as it travels toward the uterus, but there is one more important event that occurs in the ovarian cycle. The surge of LH also stimulates a change in the granulosa and theca cells that remain in the follicle after the oocyte has been ovulated. This change is called luteinization (recall that the full name of LH is luteinizing hormone), and it transforms the collapsed follicle into a new endocrine structure called the corpus luteum, a term meaning “yellowish body” (see Figure 27.12). Instead of estrogen, the luteinized granulosa and theca cells of the corpus luteum begin to produce large amounts of the sex steroid hormone progesterone, a hormone that is critical for the establishment and maintenance of pregnancy. Progesterone triggers negative feedback at the hypothalamus and pituitary, which keeps GnRH, LH, and FSH secretions low, so no new dominant follicles develop at this time. The post-ovulatory phase of progesterone secretion is known as the luteal phase of the ovarian cycle. If pregnancy does not occur within 10 to 12 days, the corpus luteum will stop secreting progesterone and degrade into the corpus albicans, a nonfunctional “whitish body” that will disintegrate in the ovary over a period of several months. During this time of reduced progesterone secretion, FSH and LH are once again stimulated, and the follicular phase begins again with a new cohort of early tertiary follicles beginning to grow and secrete estrogen. The Uterine Tubes The uterine tubes (also called fallopian tubes or oviducts) serve as the conduit of the oocyte from the ovary to the uterus (Figure 27.14). Each of the two uterine tubes is close to, but not directly connected to, the ovary and divided into sections. The isthmus is the narrow medial end of each uterine tube that is connected to the uterus. The wide distal infundibulum flares out with slender, finger-like projections called fimbriae. The middle region of the tube, called the ampulla, is where fertilization often occurs. The uterine tubes also have three layers: an outer serosa, a middle smooth muscle layer, and an inner mucosal layer. In addition to its mucus-secreting cells, the inner mucosa contains ciliated cells that beat in the direction of the uterus, producing a current that will be critical to move the oocyte. Following ovulation, the secondary oocyte surrounded by a few granulosa cells is released into the peritoneal cavity. The nearby uterine tube, either left or right, receives the oocyte. Unlike sperm, oocytes lack flagella, and therefore cannot move on their own. So how do they travel into the uterine tube and toward the uterus? High concentrations of estrogen that occur around the time of ovulation induce contractions of the smooth muscle along the length of the uterine tube. These contractions occur every 4 to 8 seconds, and the result is a coordinated movement that sweeps the surface of the ovary and the pelvic cavity. Current flowing toward the uterus is generated by coordinated beating of the cilia that line the outside and lumen of the length of the uterine tube. These cilia beat more strongly in response to the high estrogen concentrations that occur around the time of ovulation. As a result of these mechanisms, the oocyte–granulosa cell complex is pulled into the interior of the tube. Once inside, the muscular contractions and beating cilia move the oocyte slowly toward the uterus. When fertilization does occur, sperm typically meet the egg while it is still moving through the ampulla. INTERACTIVE LINK Watch this video to observe ovulation and its initiation in response to the release of FSH and LH from the pituitary gland. What specialized structures help guide the oocyte from the ovary into the uterine tube? If the oocyte is successfully fertilized, the resulting zygote will begin to divide into two cells, then four, and so on, as it makes its way through the uterine tube and into the uterus. There, it will implant and continue to grow. If the egg is not fertilized, it will simply degrade—either in the uterine tube or in the uterus, where it may be shed with the next menstrual period. Figure 27.14 Ovaries, Uterine Tubes, and Uterus This anterior view shows the relationship of the ovaries, uterine tubes (oviducts), and uterus. Sperm enter through the vagina, and fertilization of an ovulated oocyte usually occurs in the distal uterine tube. From left to right, LM × 400, LM × 20. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) The open-ended structure of the uterine tubes can have significant health consequences if bacteria or other contagions enter through the vagina and move through the uterus, into the tubes, and then into the pelvic cavity. If this is left unchecked, a bacterial infection (sepsis) could quickly become life-threatening. The spread of an infection in this manner is of special concern when unskilled practitioners perform abortions in non-sterile conditions. Sepsis is also associated with sexually transmitted bacterial infections, especially gonorrhea and chlamydia. These increase a woman’s risk for pelvic inflammatory disease (PID), infection of the uterine tubes or other reproductive organs. Even when resolved, PID can leave scar tissue in the tubes, leading to infertility. INTERACTIVE LINK Watch this series of videos to look at the movement of the oocyte through the ovary. The cilia in the uterine tube promote movement of the oocyte. What would likely occur if the cilia were paralyzed at the time of ovulation? The Uterus and Cervix The uterus is the muscular organ that nourishes and supports the growing embryo (see Figure 27.14). Its average size is approximately 5 cm wide by 7 cm long (approximately 2 in by 3 in) when a female is not pregnant. It has three sections. The portion of the uterus superior to the opening of the uterine tubes is called the fundus. The middle section of the uterus is called the body of uterus (or corpus). The cervix is the narrow inferior portion of the uterus that projects into the vagina. The cervix produces mucus secretions that become thin and stringy under the influence of high systemic plasma estrogen concentrations, and these secretions can facilitate sperm movement through the reproductive tract. Several ligaments maintain the position of the uterus within the abdominopelvic cavity. The broad ligament is a fold of peritoneum that serves as a primary support for the uterus, extending laterally from both sides of the uterus and attaching it to the pelvic wall. The round ligament attaches to the uterus near the uterine tubes, and extends to the labia majora. Finally, the uterosacral ligament stabilizes the uterus posteriorly by its connection from the cervix to the pelvic wall. The wall of the uterus is made up of three layers. The most superficial layer is the serous membrane, or perimetrium, which consists of epithelial tissue that covers the exterior portion of the uterus. The middle layer, or myometrium, is a thick layer of smooth muscle responsible for uterine contractions. Most of the uterus is myometrial tissue, and the muscle fibers run horizontally, vertically, and diagonally, allowing the powerful contractions that occur during labor and the less powerful contractions (or cramps) that help to expel menstrual blood during a woman’s period. Anteriorly directed myometrial contractions also occur near the time of ovulation, and are thought to possibly facilitate the transport of sperm through the female reproductive tract. The innermost layer of the uterus is called the endometrium. The endometrium contains a connective tissue lining, the lamina propria, which is covered by epithelial tissue that lines the lumen. Structurally, the endometrium consists of two layers: the stratum basalis and the stratum functionalis (the basal and functional layers). The stratum basalis layer is part of the lamina propria and is adjacent to the myometrium; this layer does not shed during menses. In contrast, the thicker stratum functionalis layer contains the glandular portion of the lamina propria and the endothelial tissue that lines the uterine lumen. It is the stratum functionalis that grows and thickens in response to increased levels of estrogen and progesterone. In the luteal phase of the menstrual cycle, special branches off of the uterine artery called spiral arteries supply the thickened stratum functionalis. This inner functional layer provides the proper site of implantation for the fertilized egg, and—should fertilization not occur—it is only the stratum functionalis layer of the endometrium that sheds during menstruation. Recall that during the follicular phase of the ovarian cycle, the tertiary follicles are growing and secreting estrogen. At the same time, the stratum functionalis of the endometrium is thickening to prepare for a potential implantation. The post-ovulatory increase in progesterone, which characterizes the luteal phase, is key for maintaining a thick stratum functionalis. As long as a functional corpus luteum is present in the ovary, the endometrial lining is prepared for implantation. Indeed, if an embryo implants, signals are sent to the corpus luteum to continue secreting progesterone to maintain the endometrium, and thus maintain the pregnancy. If an embryo does not implant, no signal is sent to the corpus luteum and it degrades, ceasing progesterone production and ending the luteal phase. Without progesterone, the endometrium thins and, under the influence of prostaglandins, the spiral arteries of the endometrium constrict and rupture, preventing oxygenated blood from reaching the endometrial tissue. As a result, endometrial tissue dies and blood, pieces of the endometrial tissue, and white blood cells are shed through the vagina during menstruation, or the menses. The first menses after puberty, called menarche, can occur either before or after the first ovulation. The Menstrual Cycle Now that we have discussed the maturation of the cohort of tertiary follicles in the ovary, the build-up and then shedding of the endometrial lining in the uterus, and the function of the uterine tubes and vagina, we can put everything together to talk about the three phases of the menstrual cycle—the series of changes in which the uterine lining is shed, rebuilds, and prepares for implantation. The timing of the menstrual cycle starts with the first day of menses, referred to as day one of a woman’s period. Cycle length is determined by counting the days between the onset of bleeding in two subsequent cycles. Because the average length of a woman’s menstrual cycle is 28 days, this is the time period used to identify the timing of events in the cycle. However, the length of the menstrual cycle varies among women, and even in the same woman from one cycle to the next, typically from 21 to 32 days. Just as the hormones produced by the granulosa and theca cells of the ovary “drive” the follicular and luteal phases of the ovarian cycle, they also control the three distinct phases of the menstrual cycle. These are the menses phase, the proliferative phase, and the secretory phase. Menses Phase The menses phase of the menstrual cycle is the phase during which the lining is shed; that is, the days that the woman menstruates. Although it averages approximately five days, the menses phase can last from 2 to 7 days, or longer. As shown in Figure 27.15, the menses phase occurs during the early days of the follicular phase of the ovarian cycle, when progesterone, FSH, and LH levels are low. Recall that progesterone concentrations decline as a result of the degradation of the corpus luteum, marking the end of the luteal phase. This decline in progesterone triggers the shedding of the stratum functionalis of the endometrium. Figure 27.15 Hormone Levels in Ovarian and Menstrual Cycles The correlation of the hormone levels and their effects on the female reproductive system is shown in this timeline of the ovarian and menstrual cycles. The menstrual cycle begins at day one with the start of menses. Ovulation occurs around day 14 of a 28-day cycle, triggered by the LH surge. Proliferative Phase Once menstrual flow ceases, the endometrium begins to proliferate again, marking the beginning of the proliferative phase of the menstrual cycle (see Figure 27.15). It occurs when the granulosa and theca cells of the tertiary follicles begin to produce increased amounts of estrogen. These rising estrogen concentrations stimulate the endometrial lining to rebuild. Recall that the high estrogen concentrations will eventually lead to a decrease in FSH as a result of negative feedback, resulting in atresia of all but one of the developing tertiary follicles. The switch to positive feedback—which occurs with the elevated estrogen production from the dominant follicle—then stimulates the LH surge that will trigger ovulation. In a typical 28-day menstrual cycle, ovulation occurs on day 14. Ovulation marks the end of the proliferative phase as well as the end of the follicular phase. Secretory Phase In addition to prompting the LH surge, high estrogen levels increase the uterine tube contractions that facilitate the pick-up and transfer of the ovulated oocyte. High estrogen levels also slightly decrease the acidity of the vagina, making it more hospitable to sperm. In the ovary, the luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum, marking the beginning of the luteal phase of the ovarian cycle. In the uterus, progesterone from the corpus luteum begins the secretory phase of the menstrual cycle, in which the endometrial lining prepares for implantation (see Figure 27.15). Over the next 10 to 12 days, the endometrial glands secrete a fluid rich in glycogen. If fertilization has occurred, this fluid will nourish the ball of cells now developing from the zygote. At the same time, the spiral arteries develop to provide blood to the thickened stratum functionalis. If no pregnancy occurs within approximately 10 to 12 days, the corpus luteum will degrade into the corpus albicans. Levels of both estrogen and progesterone will fall, and the endometrium will grow thinner. Prostaglandins will be secreted that cause constriction of the spiral arteries, reducing oxygen supply. The endometrial tissue will die, resulting in menses—or the first day of the next cycle. DISORDERS OF THE... Female Reproductive System Research over many years has confirmed that cervical cancer is most often caused by a sexually transmitted infection with human papillomavirus (HPV). There are over 100 related viruses in the HPV family, and the characteristics of each strain determine the outcome of the infection. In all cases, the virus enters body cells and uses its own genetic material to take over the host cell’s metabolic machinery and produce more virus particles. HPV infections are common in both men and women. Indeed, a recent study determined that 42.5 percent of females had HPV at the time of testing. These women ranged in age from 14 to 59 years and differed in race, ethnicity, and number of sexual partners. Of note, the prevalence of HPV infection was 53.8 percent among women aged 20 to 24 years, the age group with the highest infection rate. HPV strains are classified as high or low risk according to their potential to cause cancer. Though most HPV infections do not cause disease, the disruption of normal cellular functions in the low-risk forms of HPV can cause the male or female human host to develop genital warts. Often, the body is able to clear an HPV infection by normal immune responses within 2 years. However, the more serious, high-risk infection by certain types of HPV can result in cancer of the cervix (Figure 27.16). Infection with either of the cancer-causing variants HPV 16 or HPV 18 has been linked to more than 70 percent of all cervical cancer diagnoses. Although even these high-risk HPV strains can be cleared from the body over time, infections persist in some individuals. If this happens, the HPV infection can influence the cells of the cervix to develop precancerous changes. Risk factors for cervical cancer include having unprotected sex; having multiple sexual partners; a first sexual experience at a younger age, when the cells of the cervix are not fully mature; failure to receive the HPV vaccine; a compromised immune system; and smoking. The risk of developing cervical cancer is doubled with cigarette smoking. Figure 27.16 Development of Cervical Cancer In most cases, cells infected with the HPV virus heal on their own. In some cases, however, the virus continues to spread and becomes an invasive cancer. When the high-risk types of HPV enter a cell, two viral proteins are used to neutralize proteins that the host cells use as checkpoints in the cell cycle. The best studied of these proteins is p53. In a normal cell, p53 detects DNA damage in the cell’s genome and either halts the progression of the cell cycle—allowing time for DNA repair to occur—or initiates apoptosis. Both of these processes prevent the accumulation of mutations in a cell’s genome. High-risk HPV can neutralize p53, keeping the cell in a state in which fast growth is possible and impairing apoptosis, allowing mutations to accumulate in the cellular DNA. The prevalence of cervical cancer in the United States is very low because of regular screening exams called pap smears. Pap smears sample cells of the cervix, allowing the detection of abnormal cells. If pre-cancerous cells are detected, there are several highly effective techniques that are currently in use to remove them before they pose a danger. However, women in developing countries often do not have access to regular pap smears. As a result, these women account for as many as 80 percent of the cases of cervical cancer worldwide. In 2006, the first vaccine against the high-risk types of HPV was approved. There are now two HPV vaccines available: Gardasil® and Cervarix®. Whereas these vaccines were initially only targeted for women, because HPV is sexually transmitted, both men and women require vaccination for this approach to achieve its maximum efficacy. A recent study suggests that the HPV vaccine has cut the rates of HPV infection by the four targeted strains at least in half. Unfortunately, the high cost of manufacturing the vaccine is currently limiting access to many women worldwide. The Breasts Whereas the breasts are located far from the other female reproductive organs, they are considered accessory organs of the female reproductive system. The function of the breasts is to supply milk to an infant in a process called lactation. The external features of the breast include a nipple surrounded by a pigmented areola (Figure 27.17), whose coloration may deepen during pregnancy. The areola is typically circular and can vary in size from 25 to 100 mm in diameter. The areolar region is characterized by small, raised areolar glands that secrete lubricating fluid during lactation to protect the nipple from chafing. When a baby nurses, or draws milk from the breast, the entire areolar region is taken into the mouth. Breast milk is produced by the mammary glands, which are modified sweat glands. The milk itself exits the breast through the nipple via 15 to 20 lactiferous ducts that open on the surface of the nipple. These lactiferous ducts each extend to a lactiferous sinus that connects to a glandular lobe within the breast itself that contains groups of milk-secreting cells in clusters called alveoli (see Figure 27.17). The clusters can change in size depending on the amount of milk in the alveolar lumen. Once milk is made in the alveoli, stimulated myoepithelial cells that surround the alveoli contract to push the milk to the lactiferous sinuses. From here, the baby can draw milk through the lactiferous ducts by suckling. The lobes themselves are surrounded by fat tissue, which determines the size of the breast; breast size differs between individuals and does not affect the amount of milk produced. Supporting the breasts are multiple bands of connective tissue called suspensory ligaments that connect the breast tissue to the dermis of the overlying skin. Figure 27.17 Anatomy of the Breast During lactation, milk moves from the alveoli through the lactiferous ducts to the nipple. During the normal hormonal fluctuations in the menstrual cycle, breast tissue responds to changing levels of estrogen and progesterone, which can lead to swelling and breast tenderness in some individuals, especially during the secretory phase. If pregnancy occurs, the increase in hormones leads to further development of the mammary tissue and enlargement of the breasts. Hormonal Birth Control Birth control pills take advantage of the negative feedback system that regulates the ovarian and menstrual cycles to stop ovulation and prevent pregnancy. Typically they work by providing a constant level of both estrogen and progesterone, which negatively feeds back onto the hypothalamus and pituitary, thus preventing the release of FSH and LH. Without FSH, the follicles do not mature, and without the LH surge, ovulation does not occur. Although the estrogen in birth control pills does stimulate some thickening of the endometrial wall, it is reduced compared with a normal cycle and is less likely to support implantation. Some birth control pills contain 21 active pills containing hormones, and 7 inactive pills (placebos). The decline in hormones during the week that the woman takes the placebo pills triggers menses, although it is typically lighter than a normal menstrual flow because of the reduced endometrial thickening. Newer types of birth control pills have been developed that deliver low-dose estrogens and progesterone for the entire cycle (these are meant to be taken 365 days a year), and menses never occurs. While some women prefer to have the proof of a lack of pregnancy that a monthly period provides, menstruation every 28 days is not required for health reasons, and there are no reported adverse effects of not having a menstrual period in an otherwise healthy individual. Because birth control pills function by providing constant estrogen and progesterone levels and disrupting negative feedback, skipping even just one or two pills at certain points of the cycle (or even being several hours late taking the pill) can lead to an increase in FSH and LH and result in ovulation. It is important, therefore, that the woman follow the directions on the birth control pill package to successfully prevent pregnancy. AGING AND THE... Female Reproductive System Female fertility (the ability to conceive) peaks when women are in their twenties, and is slowly reduced until a women reaches 35 years of age. After that time, fertility declines more rapidly, until it ends completely at the end of menopause. Menopause is the cessation of the menstrual cycle that occurs as a result of the loss of ovarian follicles and the hormones that they produce. A woman is considered to have completed menopause if she has not menstruated in a full year. After that point, she is considered postmenopausal. The average age for this change is consistent worldwide at between 50 and 52 years of age, but it can normally occur in a woman’s forties, or later in her fifties. Poor health, including smoking, can lead to earlier loss of fertility and earlier menopause. As a woman reaches the age of menopause, depletion of the number of viable follicles in the ovaries due to atresia affects the hormonal regulation of the menstrual cycle. During the years leading up to menopause, there is a decrease in the levels of the hormone inhibin, which normally participates in a negative feedback loop to the pituitary to control the production of FSH. The menopausal decrease in inhibin leads to an increase in FSH. The presence of FSH stimulates more follicles to grow and secrete estrogen. Because small, secondary follicles also respond to increases in FSH levels, larger numbers of follicles are stimulated to grow; however, most undergo atresia and die. Eventually, this process leads to the depletion of all follicles in the ovaries, and the production of estrogen falls off dramatically. It is primarily the lack of estrogens that leads to the symptoms of menopause. The earliest changes occur during the menopausal transition, often referred to as peri-menopause, when a women’s cycle becomes irregular but does not stop entirely. Although the levels of estrogen are still nearly the same as before the transition, the level of progesterone produced by the corpus luteum is reduced. This decline in progesterone can lead to abnormal growth, or hyperplasia, of the endometrium. This condition is a concern because it increases the risk of developing endometrial cancer. Two harmless conditions that can develop during the transition are uterine fibroids, which are benign masses of cells, and irregular bleeding. As estrogen levels change, other symptoms that occur are hot flashes and night sweats, trouble sleeping, vaginal dryness, mood swings, difficulty focusing, and thinning of hair on the head along with the growth of more hair on the face. Depending on the individual, these symptoms can be entirely absent, moderate, or severe. After menopause, lower amounts of estrogens can lead to other changes. Cardiovascular disease becomes as prevalent in women as in men, possibly because estrogens reduce the amount of cholesterol in the blood vessels. When estrogen is lacking, many women find that they suddenly have problems with high cholesterol and the cardiovascular issues that accompany it. Osteoporosis is another problem because bone density decreases rapidly in the first years after menopause. The reduction in bone density leads to a higher incidence of fractures. Hormone therapy (HT), which employs medication (synthetic estrogens and progestins) to increase estrogen and progestin levels, can alleviate some of the symptoms of menopause. In 2002, the Women’s Health Initiative began a study to observe women for the long-term outcomes of hormone replacement therapy over 8.5 years. However, the study was prematurely terminated after 5.2 years because of evidence of a higher than normal risk of breast cancer in patients taking estrogen-only HT. The potential positive effects on cardiovascular disease were also not realized in the estrogen-only patients. The results of other hormone replacement studies over the last 50 years, including a 2012 study that followed over 1,000 menopausal women for 10 years, have shown cardiovascular benefits from estrogen and no increased risk for cancer. Some researchers believe that the age group tested in the 2002 trial may have been too old to benefit from the therapy, thus skewing the results. In the meantime, intense debate and study of the benefits and risks of replacement therapy is ongoing. Current guidelines approve HT for the reduction of hot flashes or flushes, but this treatment is generally only considered when women first start showing signs of menopausal changes, is used in the lowest dose possible for the shortest time possible (5 years or less), and it is suggested that women on HT have regular pelvic and breast exams. Development of the Male and Female Reproductive Systems - Explain how bipotential tissues are directed to develop into male or female sex organs - Name the rudimentary duct systems in the embryo that are precursors to male or female internal sex organs - Describe the hormonal changes that bring about puberty, and the secondary sex characteristics of men and women The development of the reproductive systems begins soon after fertilization of the egg, with primordial gonads beginning to develop approximately one month after conception. Reproductive development continues in utero, but there is little change in the reproductive system between infancy and puberty. Development of the Sexual Organs in the Embryo and Fetus Females are considered the “fundamental” sex—that is, without much chemical prompting, all fertilized eggs would develop into females. To become a male, an individual must be exposed to the cascade of factors initiated by a single gene on the male Y chromosome. This is called the SRY (Sex-determining Region of the Y chromosome). Because females do not have a Y chromosome, they do not have the SRY gene. Without a functional SRY gene, an individual will be female. In both male and female embryos, the same group of cells has the potential to develop into either the male or female gonads; this tissue is considered bipotential. The SRY gene actively recruits other genes that begin to develop the testes, and suppresses genes that are important in female development. As part of this SRY-prompted cascade, germ cells in the bipotential gonads differentiate into spermatogonia. Without SRY, different genes are expressed, oogonia form, and primordial follicles develop in the primitive ovary. Soon after the formation of the testis, the Leydig cells begin to secrete testosterone. Testosterone can influence tissues that are bipotential to become male reproductive structures. For example, with exposure to testosterone, cells that could become either the glans penis or the glans clitoris form the glans penis. Without testosterone, these same cells differentiate into the clitoris. Not all tissues in the reproductive tract are bipotential. The internal reproductive structures (for example the uterus, uterine tubes, and part of the vagina in females; and the epididymis, ductus deferens, and seminal vesicles in males) form from one of two rudimentary duct systems in the embryo. For proper reproductive function in the adult, one set of these ducts must develop properly, and the other must degrade. In males, secretions from sustentacular cells trigger a degradation of the female duct, called the Müllerian duct. At the same time, testosterone secretion stimulates growth of the male tract, the Wolffian duct. Without such sustentacular cell secretion, the Müllerian duct will develop; without testosterone, the Wolffian duct will degrade. Thus, the developing offspring will be female. For more information and a figure of differentiation of the gonads, seek additional content on fetal development. INTERACTIVE LINK A baby’s gender is determined at conception, and the different genitalia of male and female fetuses develop from the same tissues in the embryo. View this animation to see a comparison of the development of structures of the female and male reproductive systems in a growing fetus. Where are the testes located for most of gestational time? Further Sexual Development Occurs at Puberty Puberty is the stage of development at which individuals become sexually mature. Though the outcomes of puberty for boys and girls are very different, the hormonal control of the process is very similar. In addition, though the timing of these events varies between individuals, the sequence of changes that occur is predictable for male and female adolescents. As shown in Figure 27.18, a concerted release of hormones from the hypothalamus (GnRH), the anterior pituitary (LH and FSH), and the gonads (either testosterone or estrogen) is responsible for the maturation of the reproductive systems and the development of secondary sex characteristics, which are physical changes that serve auxiliary roles in reproduction. The first changes begin around the age of eight or nine when the production of LH becomes detectable. The release of LH occurs primarily at night during sleep and precedes the physical changes of puberty by several years. In pre-pubertal children, the sensitivity of the negative feedback system in the hypothalamus and pituitary is very high. This means that very low concentrations of androgens or estrogens will negatively feed back onto the hypothalamus and pituitary, keeping the production of GnRH, LH, and FSH low. As an individual approaches puberty, two changes in sensitivity occur. The first is a decrease of sensitivity in the hypothalamus and pituitary to negative feedback, meaning that it takes increasingly larger concentrations of sex steroid hormones to stop the production of LH and FSH. The second change in sensitivity is an increase in sensitivity of the gonads to the FSH and LH signals, meaning the gonads of adults are more responsive to gonadotropins than are the gonads of children. As a result of these two changes, the levels of LH and FSH slowly increase and lead to the enlargement and maturation of the gonads, which in turn leads to secretion of higher levels of sex hormones and the initiation of spermatogenesis and folliculogenesis. In addition to age, multiple factors can affect the age of onset of puberty, including genetics, environment, and psychological stress. One of the more important influences may be nutrition; historical data demonstrate the effect of better and more consistent nutrition on the age of menarche in girls in the United States, which decreased from an average age of approximately 17 years of age in 1860 to the current age of approximately 12.75 years in 1960, as it remains today. Some studies indicate a link between puberty onset and the amount of stored fat in an individual. This effect is more pronounced in girls, but has been documented in both sexes. Body fat, corresponding with secretion of the hormone leptin by adipose cells, appears to have a strong role in determining menarche. This may reflect to some extent the high metabolic costs of gestation and lactation. In girls who are lean and highly active, such as gymnasts, there is often a delay in the onset of puberty. Figure 27.18 Hormones of Puberty During puberty, the release of LH and FSH from the anterior pituitary stimulates the gonads to produce sex hormones in both male and female adolescents. Signs of Puberty Different sex steroid hormone concentrations between the sexes also contribute to the development and function of secondary sexual characteristics. Examples of secondary sexual characteristics are listed in Table 27.1. Development of the Secondary Sexual Characteristics \| Male \| Female \| \|---\|---\| \| Increased larynx size and deepening of the voice \| Deposition of fat, predominantly in breasts and hips \| \| Increased muscular development \| Breast development \| \| Growth of facial, axillary, and pubic hair, and increased growth of body hair \| Broadening of the pelvis and growth of axillary and pubic hair \| Table 27.1 As a girl reaches puberty, typically the first change that is visible is the development of the breast tissue. This is followed by the growth of axillary and pubic hair. A growth spurt normally starts at approximately age 9 to 11, and may last two years or more. During this time, a girl’s height can increase 3 inches a year. The next step in puberty is menarche, the start of menstruation. In boys, the growth of the testes is typically the first physical sign of the beginning of puberty, which is followed by growth and pigmentation of the scrotum and growth of the penis. The next step is the growth of hair, including armpit, pubic, chest, and facial hair. Testosterone stimulates the growth of the larynx and thickening and lengthening of the vocal folds, which causes the voice to drop in pitch. The first fertile ejaculations typically appear at approximately 15 years of age, but this age can vary widely across individual boys. Unlike the early growth spurt observed in females, the male growth spurt occurs toward the end of puberty, at approximately age 11 to 13, and a boy’s height can increase as much as 4 inches a year. In some males, pubertal development can continue through the early 20s. Key Terms - alveoli - (of the breast) milk-secreting cells in the mammary gland - ampulla - (of the uterine tube) middle portion of the uterine tube in which fertilization often occurs - antrum - fluid-filled chamber that characterizes a mature tertiary (antral) follicle - areola - highly pigmented, circular area surrounding the raised nipple and containing areolar glands that secrete fluid important for lubrication during suckling - Bartholin’s glands - (also, greater vestibular glands) glands that produce a thick mucus that maintains moisture in the vulva area; also referred to as the greater vestibular glands - blood–testis barrier - tight junctions between Sertoli cells that prevent bloodborne pathogens from gaining access to later stages of spermatogenesis and prevent the potential for an autoimmune reaction to haploid sperm - body of uterus - middle section of the uterus - broad ligament - wide ligament that supports the uterus by attaching laterally to both sides of the uterus and pelvic wall - bulbourethral glands - (also, Cowper’s glands) glands that secrete a lubricating mucus that cleans and lubricates the urethra prior to and during ejaculation - cervix - elongate inferior end of the uterus where it connects to the vagina - clitoris - (also, glans clitoris) nerve-rich area of the vulva that contributes to sexual sensation during intercourse - corpus albicans - nonfunctional structure remaining in the ovarian stroma following structural and functional regression of the corpus luteum - corpus cavernosum - either of two columns of erectile tissue in the penis that fill with blood during an erection - corpus luteum - transformed follicle after ovulation that secretes progesterone - corpus spongiosum - (plural = corpora cavernosa) column of erectile tissue in the penis that fills with blood during an erection and surrounds the penile urethra on the ventral portion of the penis - ductus deferens - (also, vas deferens) duct that transports sperm from the epididymis through the spermatic cord and into the ejaculatory duct; also referred as the vas deferens - ejaculatory duct - duct that connects the ampulla of the ductus deferens with the duct of the seminal vesicle at the prostatic urethra - endometrium - inner lining of the uterus, part of which builds up during the secretory phase of the menstrual cycle and then sheds with menses - epididymis - (plural = epididymides) coiled tubular structure in which sperm start to mature and are stored until ejaculation - fimbriae - fingerlike projections on the distal uterine tubes - follicle - ovarian structure of one oocyte and surrounding granulosa (and later theca) cells - folliculogenesis - development of ovarian follicles from primordial to tertiary under the stimulation of gonadotropins - fundus - (of the uterus) domed portion of the uterus that is superior to the uterine tubes - gamete - haploid reproductive cell that contributes genetic material to form an offspring - glans penis - bulbous end of the penis that contains a large number of nerve endings - gonadotropin-releasing hormone (GnRH) - hormone released by the hypothalamus that regulates the production of follicle-stimulating hormone and luteinizing hormone from the pituitary gland - gonads - reproductive organs (testes in men and ovaries in women) that produce gametes and reproductive hormones - granulosa cells - supportive cells in the ovarian follicle that produce estrogen - hymen - membrane that covers part of the opening of the vagina - infundibulum - (of the uterine tube) wide, distal portion of the uterine tube terminating in fimbriae - inguinal canal - opening in abdominal wall that connects the testes to the abdominal cavity - isthmus - narrow, medial portion of the uterine tube that joins the uterus - labia majora - hair-covered folds of skin located behind the mons pubis - labia minora - thin, pigmented, hairless flaps of skin located medial and deep to the labia majora - lactiferous ducts - ducts that connect the mammary glands to the nipple and allow for the transport of milk - lactiferous sinus - area of milk collection between alveoli and lactiferous duct - Leydig cells - cells between the seminiferous tubules of the testes that produce testosterone; a type of interstitial cell - mammary glands - glands inside the breast that secrete milk - menarche - first menstruation in a pubertal female - menses - shedding of the inner portion of the endometrium out though the vagina; also referred to as menstruation - menses phase - phase of the menstrual cycle in which the endometrial lining is shed - menstrual cycle - approximately 28-day cycle of changes in the uterus consisting of a menses phase, a proliferative phase, and a secretory phase - mons pubis - mound of fatty tissue located at the front of the vulva - Müllerian duct - duct system present in the embryo that will eventually form the internal female reproductive structures - myometrium - smooth muscle layer of uterus that allows for uterine contractions during labor and expulsion of menstrual blood - oocyte - cell that results from the division of the oogonium and undergoes meiosis I at the LH surge and meiosis II at fertilization to become a haploid ovum - oogenesis - process by which oogonia divide by mitosis to primary oocytes, which undergo meiosis to produce the secondary oocyte and, upon fertilization, the ovum - oogonia - ovarian stem cells that undergo mitosis during female fetal development to form primary oocytes - ovarian cycle - approximately 28-day cycle of changes in the ovary consisting of a follicular phase and a luteal phase - ovaries - female gonads that produce oocytes and sex steroid hormones (notably estrogen and progesterone) - ovulation - release of a secondary oocyte and associated granulosa cells from an ovary - ovum - haploid female gamete resulting from completion of meiosis II at fertilization - penis - male organ of copulation - perimetrium - outer epithelial layer of uterine wall - polar body - smaller cell produced during the process of meiosis in oogenesis - prepuce - (also, foreskin) flap of skin that forms a collar around, and thus protects and lubricates, the glans penis; also referred as the foreskin - primary follicles - ovarian follicles with a primary oocyte and one layer of cuboidal granulosa cells - primordial follicles - least developed ovarian follicles that consist of a single oocyte and a single layer of flat (squamous) granulosa cells - proliferative phase - phase of the menstrual cycle in which the endometrium proliferates - prostate gland - doughnut-shaped gland at the base of the bladder surrounding the urethra and contributing fluid to semen during ejaculation - puberty - life stage during which a male or female adolescent becomes anatomically and physiologically capable of reproduction - rugae - (of the vagina) folds of skin in the vagina that allow it to stretch during intercourse and childbirth - scrotum - external pouch of skin and muscle that houses the testes - secondary follicles - ovarian follicles with a primary oocyte and multiple layers of granulosa cells - secondary sex characteristics - physical characteristics that are influenced by sex steroid hormones and have supporting roles in reproductive function - secretory phase - phase of the menstrual cycle in which the endometrium secretes a nutrient-rich fluid in preparation for implantation of an embryo - semen - ejaculatory fluid composed of sperm and secretions from the seminal vesicles, prostate, and bulbourethral glands - seminal vesicle - gland that produces seminal fluid, which contributes to semen - seminiferous tubules - tube structures within the testes where spermatogenesis occurs - Sertoli cells - cells that support germ cells through the process of spermatogenesis; a type of sustentacular cell - sperm - (also, spermatozoon) male gamete - spermatic cord - bundle of nerves and blood vessels that supplies the testes; contains ductus deferens - spermatid - immature sperm cells produced by meiosis II of secondary spermatocytes - spermatocyte - cell that results from the division of spermatogonium and undergoes meiosis I and meiosis II to form spermatids - spermatogenesis - formation of new sperm, occurs in the seminiferous tubules of the testes - spermatogonia - (singular = spermatogonium) diploid precursor cells that become sperm - spermiogenesis - transformation of spermatids to spermatozoa during spermatogenesis - suspensory ligaments - bands of connective tissue that suspend the breast onto the chest wall by attachment to the overlying dermis - tertiary follicles - (also, antral follicles) ovarian follicles with a primary or secondary oocyte, multiple layers of granulosa cells, and a fully formed antrum - testes - (singular = testis) male gonads - theca cells - estrogen-producing cells in a maturing ovarian follicle - uterine tubes - (also, fallopian tubes or oviducts) ducts that facilitate transport of an ovulated oocyte to the uterus - uterus - muscular hollow organ in which a fertilized egg develops into a fetus - vagina - tunnel-like organ that provides access to the uterus for the insertion of semen and from the uterus for the birth of a baby - vulva - external female genitalia - Wolffian duct - duct system present in the embryo that will eventually form the internal male reproductive structures Chapter Review 27.1 Anatomy and Physiology of the Male Reproductive System Gametes are the reproductive cells that combine to form offspring. Organs called gonads produce the gametes, along with the hormones that regulate human reproduction. The male gametes are called sperm. Spermatogenesis, the production of sperm, occurs within the seminiferous tubules that make up most of the testis. The scrotum is the muscular sac that holds the testes outside of the body cavity. Spermatogenesis begins with mitotic division of spermatogonia (stem cells) to produce primary spermatocytes that undergo the two divisions of meiosis to become secondary spermatocytes, then the haploid spermatids. During spermiogenesis, spermatids are transformed into spermatozoa (formed sperm). Upon release from the seminiferous tubules, sperm are moved to the epididymis where they continue to mature. During ejaculation, sperm exit the epididymis through the ductus deferens, a duct in the spermatic cord that leaves the scrotum. The ampulla of the ductus deferens meets the seminal vesicle, a gland that contributes fructose and proteins, at the ejaculatory duct. The fluid continues through the prostatic urethra, where secretions from the prostate are added to form semen. These secretions help the sperm to travel through the urethra and into the female reproductive tract. Secretions from the bulbourethral glands protect sperm and cleanse and lubricate the penile (spongy) urethra. The penis is the male organ of copulation. Columns of erectile tissue called the corpora cavernosa and corpus spongiosum fill with blood when sexual arousal activates vasodilatation in the blood vessels of the penis. Testosterone regulates and maintains the sex organs and sex drive, and induces the physical changes of puberty. Interplay between the testes and the endocrine system precisely control the production of testosterone with a negative feedback loop. 27.2 Anatomy and Physiology of the Female Reproductive System The external female genitalia are collectively called the vulva. The vagina is the pathway into and out of the uterus. The man’s penis is inserted into the vagina to deliver sperm, and the baby exits the uterus through the vagina during childbirth. The ovaries produce oocytes, the female gametes, in a process called oogenesis. As with spermatogenesis, meiosis produces the haploid gamete (in this case, an ovum); however, it is completed only in an oocyte that has been penetrated by a sperm. In the ovary, an oocyte surrounded by supporting cells is called a follicle. In folliculogenesis, primordial follicles develop into primary, secondary, and tertiary follicles. Early tertiary follicles with their fluid-filled antrum will be stimulated by an increase in FSH, a gonadotropin produced by the anterior pituitary, to grow in the 28-day ovarian cycle. Supporting granulosa and theca cells in the growing follicles produce estrogens, until the level of estrogen in the bloodstream is high enough that it triggers negative feedback at the hypothalamus and pituitary. This results in a reduction of FSH and LH, and most tertiary follicles in the ovary undergo atresia (they die). One follicle, usually the one with the most FSH receptors, survives this period and is now called the dominant follicle. The dominant follicle produces more estrogen, triggering positive feedback and the LH surge that will induce ovulation. Following ovulation, the granulosa cells of the empty follicle luteinize and transform into the progesterone-producing corpus luteum. The ovulated oocyte with its surrounding granulosa cells is picked up by the infundibulum of the uterine tube, and beating cilia help to transport it through the tube toward the uterus. Fertilization occurs within the uterine tube, and the final stage of meiosis is completed. The uterus has three regions: the fundus, the body, and the cervix. It has three layers: the outer perimetrium, the muscular myometrium, and the inner endometrium. The endometrium responds to estrogen released by the follicles during the menstrual cycle and grows thicker with an increase in blood vessels in preparation for pregnancy. If the egg is not fertilized, no signal is sent to extend the life of the corpus luteum, and it degrades, stopping progesterone production. This decline in progesterone results in the sloughing of the inner portion of the endometrium in a process called menses, or menstruation. The breasts are accessory sexual organs that are utilized after the birth of a child to produce milk in a process called lactation. Birth control pills provide constant levels of estrogen and progesterone to negatively feed back on the hypothalamus and pituitary, and suppress the release of FSH and LH, which inhibits ovulation and prevents pregnancy. 27.3 Development of the Male and Female Reproductive Systems The reproductive systems of males and females begin to develop soon after conception. A gene on the male’s Y chromosome called SRY is critical in stimulating a cascade of events that simultaneously stimulate testis development and repress the development of female structures. Testosterone produced by Leydig cells in the embryonic testis stimulates the development of male sexual organs. If testosterone is not present, female sexual organs will develop. Whereas the gonads and some other reproductive tissues are considered bipotential, the tissue that forms the internal reproductive structures stems from ducts that will develop into only male (Wolffian) or female (Müllerian) structures. To be able to reproduce as an adult, one of these systems must develop properly and the other must degrade. Further development of the reproductive systems occurs at puberty. The initiation of the changes that occur in puberty is the result of a decrease in sensitivity to negative feedback in the hypothalamus and pituitary gland, and an increase in sensitivity of the gonads to FSH and LH stimulation. These changes lead to increases in either estrogen or testosterone, in female and male adolescents, respectively. The increase in sex steroid hormones leads to maturation of the gonads and other reproductive organs. The initiation of spermatogenesis begins in boys, and girls begin ovulating and menstruating. Increases in sex steroid hormones also lead to the development of secondary sex characteristics such as breast development in girls and facial hair and larynx growth in boys. Interactive Link Questions Watch this video to learn about vasectomy. As described in this video, a vasectomy is a procedure in which a small section of the ductus (vas) deferens is removed from the scrotum. This interrupts the path taken by sperm through the ductus deferens. If sperm do not exit through the vas, either because the man has had a vasectomy or has not ejaculated, in what region of the testis do they remain? 2.Watch this video to explore the structures of the male reproductive system and the path of sperm that starts in the testes and ends as the sperm leave the penis through the urethra. Where are sperm deposited after they leave the ejaculatory duct? 3.Watch this video to observe ovulation and its initiation in response to the release of FSH and LH from the pituitary gland. What specialized structures help guide the oocyte from the ovary into the uterine tube? 4.Watch this series of videos to look at the movement of the oocyte through the ovary. The cilia in the uterine tube promote movement of the oocyte. What would likely occur if the cilia were paralyzed at the time of ovulation? 5.A baby’s gender is determined at conception, and the different genitalia of male and female fetuses develop from the same tissues in the embryo. View this animation that compares the development of structures of the female and male reproductive systems in a growing fetus. Where are the testes located for most of gestational time? Review Questions What are male gametes called? - ova - sperm - testes - testosterone Leydig cells ________. - secrete testosterone - activate the sperm flagellum - support spermatogenesis - secrete seminal fluid Which hypothalamic hormone contributes to the regulation of the male reproductive system? - luteinizing hormone - gonadotropin-releasing hormone - follicle-stimulating hormone - androgens What is the function of the epididymis? - sperm maturation and storage - produces the bulk of seminal fluid - provides nitric oxide needed for erections - spermatogenesis Spermatogenesis takes place in the ________. - prostate gland - glans penis - seminiferous tubules - ejaculatory duct What are the female gonads called? - oocytes - ova - oviducts - ovaries When do the oogonia undergo mitosis? - before birth - at puberty - at the beginning of each menstrual cycle - during fertilization From what structure does the corpus luteum originate? - uterine corpus - dominant follicle - fallopian tube - corpus albicans Where does fertilization of the egg by the sperm typically occur? - vagina - uterus - uterine tube - ovary Why do estrogen levels fall after menopause? - The ovaries degrade. - There are no follicles left to produce estrogen. - The pituitary secretes a menopause-specific hormone. - The cells of the endometrium degenerate. The vulva includes the ________. - lactiferous duct, rugae, and hymen - lactiferous duct, endometrium, and bulbourethral glands - mons pubis, endometrium, and hymen - mons pubis, labia majora, and Bartholin’s glands What controls whether an embryo will develop testes or ovaries? - pituitary gland - hypothalamus - Y chromosome - presence or absence of estrogen Without SRY expression, an embryo will develop ________. - male reproductive structures - female reproductive structures - no reproductive structures - male reproductive structures 50 percent of the time and female reproductive structures 50 percent of the time The timing of puberty can be influenced by which of the following? - genes - stress - amount of body fat - all of the above Critical Thinking Questions Briefly explain why mature gametes carry only one set of chromosomes. 21.What special features are evident in sperm cells but not in somatic cells, and how do these specializations function? 22.What do each of the three male accessory glands contribute to the semen? 23.Describe how penile erection occurs. 24.While anabolic steroids (synthetic testosterone) bulk up muscles, they can also affect testosterone production in the testis. Using what you know about negative feedback, describe what would happen to testosterone production in the testis if a male takes large amounts of synthetic testosterone. 25.Follow the path of ejaculated sperm from the vagina to the oocyte. Include all structures of the female reproductive tract that the sperm must swim through to reach the egg. 26.Identify some differences between meiosis in men and women. 27.Explain the hormonal regulation of the phases of the menstrual cycle. 28.Endometriosis is a disorder in which endometrial cells implant and proliferate outside of the uterus—in the uterine tubes, on the ovaries, or even in the pelvic cavity. Offer a theory as to why endometriosis increases a woman’s risk of infertility. 29.Identify the changes in sensitivity that occur in the hypothalamus, pituitary, and gonads as a boy or girl approaches puberty. Explain how these changes lead to the increases of sex steroid hormone secretions that drive many pubertal changes. 30.Explain how the internal female and male reproductive structures develop from two different duct systems. 31.Explain what would occur during fetal development to an XY individual with a mutation causing a nonfunctional SRYgene.	oercommons	2025-03-18T00:36:05.606690	10/14/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/58775/overview", "title": "Anatomy and Physiology, Human Development and the Continuity of Life, The Reproductive System", "author": null }
https://oercommons.org/courseware/lesson/101308/overview	Death and Dying Overview To think about the fact that death is a part of life, we introduce this concept here. Testing Testing. 1, 2, and 3.	oercommons	2025-03-18T00:36:05.633090	02/24/2023	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/101308/overview", "title": "Death and Dying", "author": "Kristin Juarez" }
https://oercommons.org/courseware/lesson/72075/overview	Chapter 4 Reading Guide Overview This reading guide is intended to be used with the Open Stax Anatomy and Physiology textbook. Open Stax Anatomy and Physiology Chapter 4 Reading Guide Human Anatomy and Physiology Chapter 4: The Tissue Level of Organization 4.1 Types of Tissues The Four Types of Tissues - _____________ – (epithelium), are sheets of cells that cover the exterior surfaces of the body, line internal cavities and passageways, and form glands. - _____________ – binds the cells and organs of the body together - Functions in the protection, support, and integration of all body parts. - _____________ – excitable cells respond to stimulation and contraction to provide movement - Three major types: skeletal (voluntary), smooth, and cardiac. - ____________________ – excitable cells that transmit electrochemical impulses throughout the body. - Embryonic Origin of Tissues - _____________ – A single cell formed by the fusion of sperm and egg. - Undergoes repeated mitotic cell divisions (cleavage) to form an embryo. - These first embryonic cells are _____________, meaning that each one of these cells has the capacity to form a new organism - As cell division and cellular specialization continues three distinct germ layers form in the embryo. - _____________ – outer layer - _____________ – middle layer - _____________– inner layer Tissue Membranes - ____________________– a thin layer of sheet of cells that covers the outside of the body, the organs, and internal passageways that lead to the exterior of the body, and the lining of the movable joint cavities - Two types of tissue membranes - Connective tissue - Epithelial membranes - Figure 4.4 Tissue Membranes - Connective Tissue Membranes - ____________________________ is formed from connective tissue - ____________________– lines the cavity of a freely movable joint - E.g. shoulder, elbow, and knee - Synovial fluid is produced by the synovial membrane which exchanges water and nutrients with blood. Epithelial membranes - ____________________ is formed of epithelium attached to a layer of connective tissue (your skin). - ____________________– a composite of connective and epithelial tissues - Line the body cavities - Hollow passageways (blood vessels) - Digestive, respiratory, excretory, and reproductive tracts - ____________________ – connective tissue that underlies the fragile epithelial layer. - ____________________ – an epithelial membrane derived from mesothelium, line all body cavities that do not open to the exterior. - Secrete serous fluid which reduces internal friction - _____________ membranes cover the lungs - _____________ covers the heart - _____________ – covers the abdominal organs and forms mesenteries - ____________________ – the skin - Stratified squamous epithelium resting on top of connective tissue - 4.2: Epithelial Tissue - Characteristics of Epithelial Tissue - Large sheets of cells covering all body surfaces inside and outside. - Forms most of the glandular tissue of the body. - Derived from all three germ layers - Important structural and functional features - No extracellular material - Epithelial cells form specialized intercellular connections called ____________________. - Cells exhibit polarity between the exposed (_____________) surface and the _____________ surface (attached to underlying tissues). - ____________________ secreted by epithelial cells attaches the basal surface to underlying connective tissue. - _____________ is secreted by underlying connective tissue attaches to the basal lamina to form a ____________________ that holds it all together. - Avascular does not have its own blood supply. - Continuously dividing to replace damaged and dead cells. Cell to Cell Junctions - Three basic types that allow interaction between cells. - ____________________– separates cells into apical and basal compartments. - Two adjacent epithelia cells linked by tight junctions have no extra cellular space between them, thus blocking the movement of substances between cells. - ____________________ – stabilize epithelial tissues, common on the lateral and basal surfaces, and provide strong, flexible connections. - ____________________ – occur in patches and link cells together. - ____________________– link cells to the basal lamina. - _____________– influence the shape and folding of epithelial tissue. - ____________________ – forms an intercellular passageway between adjacent cells. Allow the movement of small molecules and ions between cells. - Classification of Epithelial Tissues - Figure 4.6 Cells of Epithelial Tissue - Simple Epithelium - ______________________________Cells appear as flat scales - Absorption of chemical compounds, diffusion of gases - Line blood vessels (_____________), alveoli of lungs, segments of kidney tubules - Forms ____________________ that forms the surface layer of serous membranes. - Stratified Epithelium - Consists of stacked layers of cells that protect against wear and tear. - ____________________ - Most common type of stratified epithelium in the body. - Apical cells are squamous with the basal layer consisting of columnar or cuboidal cells. - The top layer may be covered with dead, keratinized cells (as in human skin). - The lining of the mouth is an example of unkeratinized stratified squamous epithelium. - Stratified cuboidal and stratified columnar epithelium is found in certain glands or ducts but is mostly uncommon in the human body. - ____________________ is found only in the urinary system, the shape of the cells changes as it is stretched. Glandular Epithelium - Glands are structures that synthesize and secrete chemical substances - Classification of glands - ____________________ – ductless glands that release secretions directly into surrounding tissues and fluids. - Secrete hormones into the interstitial fluid, the blood stream and delivered to targets. - Pituitary gland, thymus, adrenal cortex, pancreas, and gonads - ____________________– secretions leave through a duct opening directly or indirectly into the external environment. - Mucous, sweat, saliva, and breast milk. - Structure of exocrine glands - Unicellular – goblet cells that are found in mucous membranes - Multicellular - Serous glands secrete directly into the body cavity - Simple glands release secretions through s single tubular duct - Compound glands – the duct is divided not one or more branches Methods and Types of Secretion - ____________________ – secretion by vesicles where the contents are released by exocytosis - Goblet cells, sweat glands - ____________________Secretions accumulate at the apical end of the cell, which pinches off and is released. - Apocrine sweat glands in the axillary and genital areas - ____________________ - Involves the rupture and destruction of the gland cell. - New gland cells replace the lost cells. - Sebaceous glands of the skin and scalp. - ____________________ - Produce watery, blood plasma like secretions rich in enzymes. - ____________________ - Releases products rich in mucin. 4.3 Connective Tissue: Shapes and Protects - Characteristics of Connective Tissue - Composed of cells dispersed throughout an extracellular _____________. - A mixture of secretions produced by the connective tissue cells embedded in it. - The major component is an amorphous ____________________with protein fibers. This substance may be liquid or mineralized. - Functions of Connective Tissues - Support and connect other tissues - Protection - Defend the body from microorganisms - Transport of fluids, waste, and hormones - Store surplus energy as fat and contribute to thermal insulation of the body. Embryonic Connective Tissue - All connective tissue derives from the mesoderm layer of the embryo. - _____________ - the first connective tissue found in the embryo, is the stem cell line from which all connective tissues develop from. - _____________ connective tissue (Wharton’s jelly) – only forms in umbilical cord, not present after birth. - Classification of Connective Tissue - _____________ Tissue Proper – consist of a variety of cell types and protein fibers embedded in ground substance - _____________ connective tissue – Fibers are loosely organized leaving large spaces between - _____________ connective tissue – Reinforced by bundles of fibers closely packed together that provide strength, elasticity, and protection - _____________ connective tissue – includes bone and cartilage - Few distinct cell types with tightly packed fibers - _____________ connective tissue – lymph and blood - Specialized cells circulate in a watery fluid containing dissolved salts, nutrients, gases, and dissolved proteins. - Connective Tissue Proper - Cell Types - _____________ are the dominant cell type, form the extracellular matrix. - _____________ – less active and the second most common cell type. - _____________ store lipids - _____________ – multipotent adult stem cell can differentiate into any type of connective tissue cell needed. - _____________ – type of leukocyte, essential component of immune system - _____________– involved in inflammatory responses, release histamine. - Connective Tissue Fibers and Ground Substance - _____________ fibers – made of fibrous protein subunits, form long and straight fibers - Flexible with great tensile strength, resist stretching give tendons and ligaments their resilience and strength. - _____________ fibers contain the protein elastin, may be stretched, and return to its original shape - Found in skin and elastic ligaments of the vertebral column. - _____________ fiber – formed from the same protein subunits as collagen fibers. - Fibers are narrow and arranged in a branched network. - Most abundant in the liver and spleen. - Anchor and provide structural support to the functional cells, blood vessels and nerves of those organs (parenchyma) - Ground substance - Secreted by fibroblasts, made of polysaccharides, specifically hyaluronic acid, and proteins - Loose Connective Tissue - Found between organs, acts as a shock absorber, and binds tissues together. - ____________________– make of fat storage cells (adipocytes) with little extracellular matrix. - _____________contributes to lipid storage and insulation - _____________ – thermogenic as it breaks down heat is released - _____________ tissue underlies most epithelia and represents the connective tissue component of epithelial membranes - _____________ tissue forms a mesh-like supportive framework for soft organs, spleen, and liver. Dense Connective Tissue - Contains more collagen fibers than loose connective tissue, has greater resistance to stretching. - Two major categories of dense connective tissue - R_____________ – Contain elastic fibers along with collagen fibers that are parallel to each other, enhancing tensile strength and resistance to stretching. - Ligaments and tendons, and vocal fold ligaments. - Ir_____________ – Fibers proceed in random directions, tissue may form a mesh, - Dermis of skin, arterial vessel walls Supportive Connective Tissues - Allow the body to maintain its posture and protect internal organs. - Cartilage - Ground substance contains chondroitin sulfates - _____________ – cartilage cells embedded in ground substance - _____________ – (lacuna) space occupied by chondrocytes. - Enveloped by the perichondrium, a layer of dense irregular connective tissue - Avascular - Three main types of cartilage - H_____________ – most abundant found in rib cage, nose, and lines joints, forms the embryonic skeleton. - F____________________ – tough with thick bundles of collagen fibers, form menisci of the knee and vertebral discs. - E_____________ – contain elastic fibers, your earlobe. - Figure 4.16 Types of Cartilage - Bone is the hardest connective tissue. It provides protection and support. - An extracellular matrix of collagen fibers embedded in mineralized ground substance called hydroxyapatite, a form of calcium phosphate. - Osteocytes – bone cells located inside lacunae - Highly vascularized - Types of bone tissue - Ca_____________ – has a spongy appearance, lighter than compact bone - Found in the interior of bones and at the end of long bones. - Co_____________ – is solid and has greater structural strength Fluid Connective Tissue - Specialized cells circulate in a liquid extracellular matrix. - All blood cells are derived from hematopoietic stem cells found in red bone marrow. - E_____________ – red blood cells contain hemoglobin and transport oxygen and carbon dioxide. - L_____________ – white blood cells defend against microorganisms or harmful molecules - Pl_____________ – cell fragments involved in blood clotting. - L_____________ – consists of a liquid matrix and white blood cells - L_____________ capillaries capture excess interstitial fluid and transport it back to the blood vessels - Specialized lymphatic capillaries (l_____________) transport absorbed fat away from the intestine and deliver it to the blood. 4.4 Muscle Tissue and Motion - Characteristics of Muscle Tissue - Responds to stimuli - Allows movement - Made up of contractile cells - Movement may be voluntary or involuntary - Classifications of Muscle Tissue - 3 types according to structure and function - Sk_____________ - C_____________ - Sm_____________ - Comparison of Structure and Properties of Muscle Tissue Types - Sk_____________ muscle: - Attached to bones, contraction make movement possible - Shivering generates heat - Derived from mesoderm, myoblasts give rise to myocytes (muscle fibers). - Fibers are arranged in bundles surrounded by connective tissues - Microscopic appearance shows striations with many nuclei - Striations are composed of the contractile protein's a______ and m________ - Skeletal muscle fibers are many myocytes joined end to end to form a long muscle fiber. - _____________ muscle - Forms the contractile walls of the heart - Cardiomyocytes are single cells with a centrally located nucleus. - Each cell contracts on its own without external stimulation - Cardiomyocytes attach to others with intercalated discs (specialized cell junctions). - Under involuntary control - _____________ muscle - Involuntary movements in the internal organs - Contractile component of the digestive, urinary, and reproductive tracts. - Airways and arteries - Spindle shaped cells, single nucleus, no visible striations 4.5: Nervous Tissue Mediates Perception and Response - Characteristics of Nervous tissue - Excitable, sends and receives electrochemical signals to provide the body with information. - Nervous tissue is composed of - N_____________ - Generate nerve impulses (action potentials) - Display distinct morphology - Three main parts - _____ body includes most of the cytoplasm, organelles, and nucleus - D__________ are numerous branches off the cell body - A_____– a single long process, extending from the cell body, wrapped in an insulating material called _______. - N_________ - Support and nourish neurons - Have very complex roles in the functioning of the brain and nervous system - A_____________ – distinct star shape abundant in CNS, regulate ion concentrations, uptake and breakdown of neurotransmitters, formation of blood – brain barrier. - O____________________ – produce myelin in the CNS. - S_____________ cells – produce myelin in the peripheral nervous system 4.6: Tissue Injury and Aging - Tissue Injury and Repair - Inflammation – the body’s initial response to any injury - Limits the extent of injury, helps eliminate the cause of injury, initiates repair and regeneration of damaged tissue. - N_____________ – accidental cell death is one cause of inflammation - Ap_____________ – programmed cell death, destroys cells not needed by the body does not cause inflammation. - _____________ inflammation is resolved over time by the healing of tissue - _____________ inflammation is when inflammation persists over time and leads to diseased conditions such as: - Arthritis - Tuberculosis - Four cardinal signs of inflammation have been known since antiquity - Redness, swelling, pain and local heat along with loss of function. - Upon tissue injury - Damaged cells release chemical signals - Mast cells release h_____________ a vasodilator - V_____________ – widening of the blood vessels in the injured area which increases blood flow leading to redness and heat - This attracts white blood cells to the damaged area - Local blood vessels endothelium becomes leaky allowing white blood cells and fluid to move into the interstitial space causing e_____ a localized swelling. - Stretched pain receptors cause pain. - Cl_________ occurs (coagulation) reducing blood loss forming a fibrin patch to bind the edges of the wound together resulting in scab formation. - Fibroblasts replace collagen and lost extracellular material. - A_____________ the growth of new blood vessels occurs - New tissue forms (granulation tissue) - P___________ union – describes the healing of a wound when the edges are close together. - S_____________ union – describes a gaping wound in which the edges are pulled together by _____________ contraction, which results in scar formation. - Sutures are recommended for wounds more than ¼ inch deep to promote primary union and avoid scar formation.	oercommons	2025-03-18T00:36:05.688955	09/04/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/72075/overview", "title": "Chapter 4 Reading Guide", "author": "Bryon Spicci" }
https://oercommons.org/courseware/lesson/73505/overview	Figure 1.15 Dorsal and Ventral Body Cavities (stripped) Overview Testable Fig 1.15 from section 1.6 of OpenStax Anatomy and Physiology. Stripped-away the boxes and lines. 1.6 Anatomical Terminology - Dorsal and Ventral Body Cavities Testable image from section 1.6 of OpenStax Anatomy and Physiology. Stripped-away the boxes and lines.	oercommons	2025-03-18T00:36:05.707560	Diagram/Illustration	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/73505/overview", "title": "Figure 1.15 Dorsal and Ventral Body Cavities (stripped)", "author": "Assessment" }
https://oercommons.org/courseware/lesson/105105/overview	OREGON MATH STANDARDS (2021): [1.OA] Overview The intent of clarifying statements is to provide additional guidance for educators to communicate the intent of the standard to support the future development of curricular resources and assessments aligned to the 2021 math standards. Clarifying statements can be in the form of succinct sentences or paragraphs that attend to one of four types of clarifications: (1) Student Experiences; (2) Examples; (3) Boundaries; and (4) Connection to Math Practices. 2021 Oregon Math Guidance: 1.OA.A.1 Cluster: 1.OA.A - Represent and solve problems involving addition and subtraction. STANDARD: 1.OA.A.1 Standards Statement (2021): Use addition and subtraction within 20 to solve and represent problems in authentic contexts involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| 1.OA.D.8, K.OA.A.1, K.OA.A.2 \| 1.OA.A.2, 2.OA.A.1 \| 1.DR.B.2 \| 1.OA.A.1 1.OA.A Crosswalk \| Standards Guidance: Clarifications - Students should be given opportunities to use mental reasoning to solve problems involving number strings within 20. - Students should also solve problem situations with an unknown in all positions. - Students recognize and represent taking from, taking apart, and comparing situations as either subtraction or addition with a missing addend. Boundaries - Students should not be encouraged to use key/clue words because they will not work with subsequent problem types. - The unknown quantity should be represented in all positions. Terminology - Addition and Subtraction Situations by Grade Level are presented in Table 1 pictured here, which include: - adding to, - taking from, - putting together, taking apart, and - comparing, with unknowns in all positions. - Please reference pages 9 and 14 in the Progression document for additional information. Teaching Strategies - Symbols can be used to represent unknown amounts in equations. - Use the relationship between addition and subtraction within 20 (knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (6 + 7 is the same as 6 + 6 + 1 = 12 + 1 = 13). - Students should be provided with learning experiences to develop strategies such as: - Advanced Counting; Counting On, Making Ten, Decomposing a number leading to a ten - Counting All: 5 + 2 = . The student counts five counters. The student adds two more. The student counts 1, 2, 3, 4, 5, 6, 7 to get the answer. - Counting Back: 12 – 3 = . The student counts twelve counters. The student removes a counter and says 11, removes another counter and says 10, and removes a third counter and says 9. The student knows the answer is 9 since they counted back 3. Examples - Represent addition and subtraction word problems using objects, drawings, and equations. Write an addition or subtraction equation with a symbol for the unknown number in different position, such as: - 13 + 5 = n, 13 - 5 = n, 13 + n= 18, 18 - n= 13. - Recognize and represent adding to and putting together situations as addition. - Illustrative Mathematics: - Student Achievement Partners: 2021 Oregon Math Guidance: 1.OA.A.2 Cluster: 1.OA.A - Represent and solve problems involving addition and subtraction. STANDARD: 1.OA.A.2 Standards Statement (2021): Solve problems that call for addition of three whole numbers whose sum is less than or equal to 20 using objects, drawings or equations. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| 1.OA.A.1 \| N/A \| 1.DR.B.2 \| 1.OA.A.2 1.OA.A Crosswalk \| Standards Guidance: Clarifications - Students should understand subtraction as an unknown-addend problem. - Students are not expected to know nor use the term inverse. Terminology - The terms below are used to clarify expectations for the teaching professional. Students are not required to use this terminology when engaging with the learning objective. - Addend – a number that is added to another number in an addition expression or equation. For example, in the expression 5 + 8, 5 and 8 are both addends. - An inverse relationship shows the relationship between addition and subtraction where addition can be used to find the quantity of a set after some in the set are removed. For example, 3+2 = 5 is related to 5 - 3 = 2 because of the inverse relationship. Boundaries - Problems should be within 20. Examples - Solve word problems by using objects, drawings or equations to represent the quantities in the problem. - Solve word problems with an equation where a symbol stands for the unknown. For example, 5 + 4 + 6 = ___. - Understand that objects, drawings, and equations are interchangeable representations of a story problem. - There are 14 birds in the tree. 8 of them flew away. How many birds are left in the tree? - The student thinks of 14 – 8 = as 8 + = 14 - Jenny had 10 pencils and gave some to Eric. Jenny now has 8 pencils. How many pencils did she give to Eric? - The student thinks of 10 - = 8 as + 8 = 10 - Illustrative Mathematics: 2021 Oregon Math Guidance: 1.OA.B.3 Cluster: 1.OA.B - Understand and apply properties of operations and the relationship between addition and subtraction. STANDARD: 1.OA.B.3 Standards Statement (2021): Apply properties of operations as strategies to add and subtract. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| K.OA.A.2 \| 1.OA.C.6 \| 2.NBT.B.9, 3.NBT.A.2 \| 1.OA.B.3 1.OA.B Crosswalk \| Standards Guidance: Clarifications - Students should solve problem situations with an unknown in all positions. - Understand that numbers can be added flexibly. - Students do not necessarily have to justify their representations or solution using properties, but they can begin to learn to recognize these properties in action and discuss their use after solving. (Please reference page 15 in the Progression document) Boundaries - Students should not be encouraged to use key/clue words because they will not work with subsequent problem types. - The unknown quantity should be represented in all positions. - The terminology above is used to clarify expectations for the teaching professional. Students are not required to use this terminology when engaging with the learning objective. Terminology - Properties of operations used as strategies include: - Commutative property of addition: For example, if 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. - Associative property of addition: For example, add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. - Addend – any number that is added to another number in an addition expression or equation. For example, in the expression 7 + 3, 7 and 3 are addends. Examples - Illustrative Mathematics: 2021 Oregon Math Guidance: 1.OA.B.4 Cluster: 1.OA.B - Understand and apply properties of operations and the relationship between addition and subtraction. STANDARD: 1.OA.B.4 Standards Statement (2021): Understand subtraction as an unknown-addend problem. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| K.OA.A.2 \| 1.OA.C.6 \| 2.NBT.B.9, 3.NBT.A.2 \| 1.OA.B.4 1.OA.B Crosswalk \| Standards Guidance: Teaching Strategies - Restate a subtraction problem as a missing addend problem using the relationship between addition and subtraction. - Recognize the inverse relationship between subtraction and addition within 20 and use this inverse relationship to solve real-life problems. Progressions - Put Together/Take Apart problems with Addend Unknown afford students the opportunity to see subtraction as the opposite of addition in a different way than as reversing the action, namely as finding an unknown addend. - The meaning of subtraction as an unknown-addend addition problem is one of the essential understandings students will need in middle school in order to extend arithmetic to negative rational numbers. (Please reference page 13 in the Progression document). Examples - Subtract 10 – 8 by finding the number that makes 10 when added to 8. - Understand that subtraction is equivalent to an unknown-addend problem because both ask for the unknown part in a situation where the total and another part are known. - Illustrative Mathematics: - Student Achievement Partners: 2021 Oregon Math Guidance: 1.OA.C.5 Cluster: 1.OA.C - Add and subtract within 20. STANDARD: 1.OA.C.5 Standards Statement (2021): Relate counting to addition and subtraction. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| K.NCC.B.4 \| 1.OA.C.6 \| N/A \| 1.OA.C.5 1.OA.C Crosswalk \| Standards Guidance: Clarifications - Students should be able to relate counting to addition and subtraction by counting all, counting on, and counting back when making sense of contextual addition and subtraction problems within 20. Teaching Strategies - Students should understand how addition and subtraction relate by solving situations in context. - Students should use strategies to count up, count back, etc., to model this relationship on tools such as ten frames, rekenreks, number lines (predetermined and open), etc. - Relate counting on to addition. For example, recognize counting on two after 15 as solving 15+2. - Relate counting back to subtraction. For example, recognize counting back two from 15 as solving 15-2. - Relate counting between two numbers to finding their difference. For example, recognize counting two number between 15 and 17 as solving 17-15. Progression - Unlike counting down, counting on reinforces that subtraction is an unknown-addend problem. Learning to think of and solve subtractions as unknown addend problems makes subtraction as easy as addition (or even easier), and it emphasizes the relationship between addition and subtraction. (Please reference page 20 in the Progression document). Examples - When students count on 3 from 4, they should write this as 4+3=7. - When students count on for subtraction, 3 from 7, they should connect this to 7−3=4. Students write "7−3= ?” and think “I count on 3+ ?=7.” - Illustrative Mathematics: 2021 Oregon Math Guidance: 1.OA.C.6 Cluster: 1.OA.C - Add and subtract within 20. STANDARD: 1.OA.C.6 Standards Statement (2021): Add and subtract within 20, demonstrating fluency for addition and subtraction within 10 with accurate, efficient, and flexible strategies. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| K.OA.A.2, K.OA.A.3, K.OA.A.4, K.OA.A.5, 1.OA.C.5, 1.OA.B.4, 1.OA.B.3 \| 2.OA.B.2 \| 1.NBT.C.4 \| 1.OA.C.6 1.OA.C Crosswalk \| Standards Guidance: Terminology - Fluently/Fluency – To achieve fluency, students should be able to choose flexibly among methods and strategies to solve mathematical problems accurately and efficiently. - Accuracy includes attending to precision. - Efficiency includes using well-understood strategy with ease. - Flexibility involves using strategies such as making 5 or making 10. Boundaries - Fluency does not lend itself to timed tests or speed. Progression - Students might use the commutative property of addition to change ? + 6 = 15 to 6 + ? = 15, then count on or use methods to compose 4 (to make ten) plus 5 (ones in the 15) to find 9. - Students might reverse the action in the situation represented by ? - 6 = 9 so that is becomes 9 + 6 = ?. Or they might use their knowledge that the total is the first number in a subtraction equation and the last number in an addition equation to rewrite the situation equation as a solution equation: ? - 6 = 9 becomes 9 + 6 = ? or 6 + 9 = ?. (Please reference page 16 in the Progression document). Examples - Use strategies such as counting on; making ten, for example 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14; decomposing a number leading to a ten for example, 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9; - Use the relationship between addition and subtraction, for example, knowing that 8 + 4 = 12, one knows 12 – 8 = 4; - Create equivalent but easier or known sums, for example, adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13. - Illustrative Mathematics: - Student Achievement Partners: 2021 Oregon Math Guidance: 1.OA.D.7 Cluster: 1.OA.D - Work with addition and subtraction equations. STANDARD: 1.OA.D.7 Standards Statement (2021): Use the meaning of the equal sign to determine whether equations involving addition and subtraction are true or false. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| N/A \| 1.OA.D.8, 2.OA.C.3, 2.OA.C.4 \| N/A \| 1.OA.D.7 1.OA.D Crosswalk \| Standards Guidance: Clarifications - Students should explore and explain the relationship of the equal sign to quantities and orally justify if equations involving addition and subtraction are “true” (equal) or “false” (not equal). Teaching Strategies - Use the meaning of the equal sign (“is the same as”) to determine if two expressions involving a whole number and/or addition or subtraction expressions are equivalent. Examples - Determine if the equation is true or false, for example determining that 3-1 = 2+3 is false because the expressions do not have equal values. - Which of the following equations are true and which are false? How do you know? - 6 = 6 (True/Correct Statement) - 7 = 8 – 1 (True/Correct Statement) - 5 + 2 = 2 + 5 (True/Correct Statement) - 4 + 1 = 5 + 2 (False/Incorrect Statement) - Illustrative Mathematics: 2021 Oregon Math Guidance: 1.OA.D.8 Cluster: 1.OA.D - Work with addition and subtraction equations. STANDARD: 1.OA.D.8 Standards Statement (2021): Determine the unknown whole number in an addition or subtraction equation relating three whole numbers. Connections: Preceding Pathway Content (2021) \| Subsequent Pathway Content (2021) \| Cross Domain Connections (2021) \| Common Core (CCSS) (2010) \| 1.OA.D.7 \| 1.OA.A.1 \| N/A \| 1.OA.D.8 1.OA.D Crosswalk \| Standards Guidance: Clarifications - Determine the unknown whole number relating three whole numbers, with the unknown in any position. Teaching Strategies - Symbols can be used to represent unknown amounts in equations. Progressions - Students advancement of methods can be clearly seen in the context of situations with unknown addends. These are the situations that can be represented by an addition equation with one unknown addend, e.g., 9 + = 13. Students can start solving for some unknown addend problems by trial and error or by knowing the relevant decomposition of the total. But a more advanced counting on solution involves seeing the 9 as part of 13, and understanding that counting the 9 things can be “taken as done” if we begin the count from 9. (Please reference page 14 in the Progression document). Examples - Students should be given the opportunity to find missing part given a known part and total, such as: - A missing addend in an addition equation, for example 3+_=5. - A missing subtrahend in a subtraction equation, for example 5-_=2. - A missing difference in a subtraction equation, for example 5-3=_ - Students should be given the opportunity to find missing totals given known parts, such as: - A missing sum in an addition equation, for example 3+2=_. - A missing minuend in a subtraction equation, for example _-2=3. - Determine the unknown number that makes the equation true in each of the equations: 8 + ? = 10, 5 = – 3, 3 + 4 = ∆. These are some possible ways to record equations that indicate an unknown number. - Illustrative Mathematics: - Student Achievement Partners:	oercommons	2025-03-18T00:36:05.835665	06/12/2023	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/105105/overview", "title": "OREGON MATH STANDARDS (2021): [1.OA]", "author": "Mark Freed" }
https://oercommons.org/courseware/lesson/71359/overview	excel Overview este material esta didicado para estudiantes de secundaria contiene : - ARCHIVOS EN PDF - VIDEOS EXCEL 2016 Introducción. Elementos de Excel (I) Excel es un programa del tipo Hoja de Cálculo que permite realizar operaciones con números organizados en una cuadrícula. Es útil para realizar desde simples sumas hasta cálculos de préstamos hipotecarios. Si no has trabajado nunca con Excel en este tema básico puedes ver con más detalle qué es y para qué sirve una hoja de cálculo . Ahora vamos a ver cuáles son los elementos básicos de Excel 2016, la pantalla, las barras, etc, para saber diferenciar entre cada uno de ellos. Aprenderás cómo se llaman, dónde están y para qué sirven. También cómo obtener ayuda, por si en algún momento no sabes cómo seguir trabajando. Cuando conozcas todo esto estarás en disposición de empezar a crear hojas de cálculo en el siguiente tema.	oercommons	2025-03-18T00:36:05.850652	08/18/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/71359/overview", "title": "excel", "author": "nelson franklin pacco garcia" }
https://oercommons.org/courseware/lesson/102366/overview	https://drive.google.com/file/d/1LhtyAtbcQnUonW606tYV31lF2ipQMjGP/view?usp=sharing Powerful Implementation Driver of MTSS2 Assistive Technology in the Schools: Introduction to Assistive Technology Overview The Assistive Technology in the Schools Course aims to to familiarize educators and parents with assistive technology devices and services, and provide a foundational understanding of what it means to consider, assess, and implement assistive technology (AT) with students to remove learning barriers. This course includes four modules: Introduction to Assistive Technology, AT Consideration, AT Assessment, and AT Implementation. This first module, Introduction to Assistive Technology, highlights the difference between accessible technology and assistive technology. This module explores examples of how assistive technology devices and services can help reduce learning barriers for students with disabilities across learning environments. Module Objective: - Participants will be able to understand and describe inclusive technology and the difference between accessible educational material(AEM), accessible technology, and assistive technology(AT). - Participants will be able to identify 3 examples of assistive technology devices/tools that have the potential to remove learning barriers for students. - Participants will be able to identify 2 examples of assistive technology services within the education system. Module Description & Goals Assistive Technology in the Schools Course Overview The purpose of the course, Assistive Technology in the Schools, is to familiarize educators and parents with assistive technology devices and services. The modules will provide an understanding of what it means to consider, assess, and implement assistive technology to remove learning barriers for students. This course includes four modules: Introduction to Assistive Technology, AT Consideration, AT Assessment, and AT Implementation. Module 1 Introduction to Assistive Technology This first module, Introduction to Assistive Technology, highlights the difference between accessible technology and assistive technology. This module explores examples of how assistive technology devices and services can help reduce learning barriers for students with disabilities within the education system. Module Objective: - Participants will be able to understand and describe inclusive technology and the difference between accessible educational material(AEM), accessible technology, and assistive technology(AT). - Participants will be able to identify 3 examples of assistive technology devices/tools that have the potential to remove learning barriers for students. - Participants will be able to identify 2 examples of assistive technology services within the schools. Module Sections Assistive Technology in Action What are Assistive Technology Services Resources to Learn More About Assistive Technology What is Assistive Technology? Defining Assistive Technology Assistive technology (AT) is technology used by individuals with disabilities to perform functions that might otherwise be difficult or impossible. The following video provides examples of assistive technology. How does Assistive Technology Relate to "Inclusive Technologies?" Inclusive technologies, also referred to as accessible technologies or universal technologies, reduce or remove barriers to student learning experiences. The Center on Inclusive Technology & Education Systems (CITES) describes inclusive technologies as having 3 categories: - Accessible Educational Materials (AEM) - Accessible Technology - Assistive Technology (AT) Accessible Educational Materials(AEM) Accessible Educational Materials Print and technology-based educational materials, including printed and electronic textbooks and related core materials that are designed or enhanced in a way that makes them usable across the widest range of learner variability, regardless of format (e.g., print, digital, graphic, audio, video). The National Instructional Materials Access Center (NIMAC) is a federally funded online file repository of accessible source files for textbooks, as well as other kinds of educational materials. Learn more about AEM in this video, AEM In Simple Language. (4.34 min.) Accessible Technology Accessible technologies are "the hardware and software that are designed to provide all learners with access to the content in digital materials. Examples of accessible technologies include an application that allows the user to write or verbalize their responses, a mobile phone with an optional zoom display, and a PDF with high color contrast." This definition is the language used in the Individuals with Disability Education Act (IDEA) and was highlighted in Myths & Facts Surrounding Assistive Technology Devices and Services released by the Office of Special Education Programs (OSEP). Assistive Technology Devices The Individuals with Disabilities Education Act (IDEA) defines assistive technology devices as "any item, piece of equipment, or product system, whether acquired commercially off the shelf, modified, or customized, that is used to increase, maintain, or improve the functional capabilities of a child with a disability. In plain language, assistive technology is a technology that assists a student in removing the barriers that can prevent the student from accessing their education. _________________________________________________________________________ Myths & Facts MYTH: AT always involves an electronic device and is always high-tech. FACT: Many AT devices or tools may be computer-based, but items like visual schedules and calendars, binder clips, squishy balls, or stickers may also be considered AT. \| The IRIS Center, a technical assistance center funded by the U.S. Department of Education’s Office of Special Education Programs (OSEP) created a chart that categorizes AT devices into low-tech, mid-tech, and high-tech devices. In Myths and Facts Surrounding Assistive Devices and Services, the Office of Special Education Programs (OSEP) provides the following chart, giving examples of assistive technology devices. Type \| Definition \| Example \| \| Low-Tech \| Devices that are readily available, inexpensive, and typically do not require batteries or electricity \| \| \| Mid-Tech \| Devices that are usually digital and may require batteries or another power source \| \| \| High-Tech \| Devices that are typically computer-based, likely to have sophisticated features, and can be tailored to the specific needs of an individual student \| \| Assistive technology can make a dramatic difference in a student's ability to access curriculum, express their knowledge, and optimize learning in general education classrooms. As a student's IEP team identifies barriers to their student's learning, assistive technology options can be explored to improve academic, behavioral, and social/emotional outcomes. The visual below depicts an array of assistive technology tools for learning. Assistive Technology in Action The article, 20+ Examples of Assistive Technology to Help Kids Learn provides many examples of assistive technology and how it removes barriers for students across learning environments. This resource from We Are Teachers also shares videos and written examples of students using assistive technology. Student Examples Meet Alex In this video, we hear how Alex blooms with learning using assistive technology. A learning disability was holding him back in school. Alex uses speech-to-text to get his thoughts out for written expression. Alex improved from barely being able to craft a few sentences His teacher describes how assistive technology has allowed Alex to show us what he knows and what he is capable of in school. Meet Jean. In this video, we see how Jean uses an iPad to access the general education curriculum, complete assignments, and participate in state testing. She also uses hearing aids with technology that converts her hearing aids to headphones to improve access to curriculum, books, and music. Her teachers share how assistive technology increases Jean's independence at school. Meet Arial. Arial is a 6-year-old girl who loves to read, laugh and play. She has cerebral palsy and uses her eyes to access a communication device that allows her to talk. Communication devices are often called augmentative alternative communication (AAC). Her AAC gives her a voice of her own, allowing her to interact with her friends and participate in her learning in general education. Meet Aiden Aiden is a boy with lots to say. He has hearing loss, low vision, and autism. Assistive technology has helped Aiden communicate his thoughts and participate in school. The team reports that his behaviors have significantly improved because he can use his augmentative alternative communication device to communicate, reducing his frustration. In this video, his team shares their journey in trialing and determining the AAC and AT that Aiden required. More Examples of Assistive Technology: \| Jeff is a student with low vision who uses a screen reader to read internet articles in science and to access his science book. With this technology, he can access the general education curriculum across content areas and make progress toward grade-level standards. Without this technology, Jeff would not have equitable access to curriculum. \| \| Alex is a student with dyslexia who listens to audiobooks for ELA class. With this technology, he has full equitable access to his general education ELA curriculum. Without this technology, he would not have access to the required reading in ELA, nor would he be equipped to complete assignments and participate in class discussions and assessments. \| \| \| Leah is a student with dysgraphia who uses a combination of word prediction and speech-to-text to write a report for a history class. She uses text-to-speech to listen to what she has written to edit her work before turning it in. With these assistive technologies, Leah is excelling across content areas because she can express her learning in both assignments and assessments. \| In each example above, the student can do the same work as their peers with the help of assistive technology. They require assistive technology to either access the general education curriculum or to express their learning. For these students, assistive technology removes learning and participation barriers and creates a more inclusive equitable learning experience. __________________________________________________________________________ Myth: Assistive technology may prevent students from learning certain skills or that it is cheating. Fact: AT supports increased learning opportunities, vocabulary, productivity, and student motivation. The next video provides more insights into how you can address this myth. \| What are Assistive Technology Services? According to the Individuals with Disabilities in Education Act (IDEA), each time an IEP Team develops, reviews, or revises a child’s IEP, the IEP Team must consider whether the child requires AT devices and AT services. In previous sections, we explored AT devices. In this section, we will define assistive technology services. In this video, Chris Bugaj defines both AT devices and AT services. In later modules, we will dive deeper into what it means to consider AT devices and services within the IEP. Assistive Technology Services: "The term “assistive technology service” means any service that directly assists a child with a disability in the selection, acquisition, or use of an assistive technology device." Assistive technology services include the evaluation, acquisition, adaptation, customization, coordination, training, and assistance for the student and staff to make sure the student can use and benefit from the assistive technology. In future modules, we will address the consideration of AT devices and AT services within the Individual Education Program (IEP) team meeting. An example of an AT service could be training for the student who will be using assistive technology, as well as training for staff or parents who will be supporting the student with implementing AT. ________________________________________________________________________ MYTH: Children can learn to use an AT device on their own; educators have no obligation to provide training to a child or to their family. FACT: It is the responsibility of the LEA (Local Education Agency) to ensure that the child with a disability, parents, and educators know how the AT device works through the provision of AT services. \| Resources to learn more about Assistive Technology Explore Resources to Learn More About Assistive Technology To explore the topic of Assistive Technology Implementation further, select from these articles, websites, and videos to read about the topic and explore some examples. Read & Learn \| Watch & Learn \| What is Assistive Technology? (Assistive Technology Industry Association) AT Internet Modules on Assessment (login to access) What is Augmentative Alternative Communication (AAC)? (American Speech-Language-Hearing Association) \| Assistive Technology! (a 3-minute video giving an overview of Assistive Technology) Understanding Assistive Tech -Simply Said (2-minute video introducing AT in schools) A Teacher's View of Assistive Technology (9 min video with various teachers explaining how they use and implement AT in the classroom with their students.) \| \| Learning more about technology to support reading \| Learn more about technology to support writing \| Washington State Agencies Designed to Support Assistive Technology Within most states, there are state or regional agencies that exist to support school districts with consultation and lending library support for AT assessment. Within Washington State, there are two such agencies. They are as follows: Inclusive Technology within Multi-Tiered Systems of Support (MTSS) A common education initiative, Multi-Tiered Systems of Support (MTSS), aims to provide inclusive education for all students. As discussed in section one, inclusive technology includes Accessible Educational Material (AEM), accessible technology, and assistive technology (AT). Understanding how inclusive technologies integrate into the MTSS is essential to supporting students who require assistive technology (AT). This video explains more about inclusive technologies within MTSS: Inclusive Technologies as Powerful Implementation Drivers within MTSS Accessible Educational Material (AEM), accessible technology, and assistive technology are powerful implementation drivers within a Multi-Tiered System of Support (MTSS) because they help to ensure equitable access to core curriculum across all tiers of intervention. AEM paired with technology enables the removal of learning barriers by assuring accessible instructional content and personalization of tools to access that content. This promotes engagement, as well as academic and behavioral success by fostering an environment where all learners can thrive. Providing AEM and accessible technologies aligns with Universal Design for Learning (UDL) which emphasizes giving students different ways to learn, show what they know, and stay engaged in their learning. Accessible Educational Material (AEM) and accessible technology set the stage for inclusive learning and move us away from only providing accessibility on the basis of “necessity.” \| Reflections on Learning Reflection 1. Consider the definition of accessible technology in section 1. What is one kind of accessible technology you would like to incorporate into your practice? 2. Consider a learning barrier that one of your students is facing. Could assistive technology reduce or eliminate the learning barrier? What is one technology you could try with your student? 3. Use the attached document entitled "AT: Putting Learning into Action" to consider a student you work with and the learning barriers they face. Are there AT devices and services that may eliminate or reduce learning barriers? This form will help you record your thoughts as you think through possible solutions. 3. Reflect on where are you on the continuum. \| Knowledge level 1 \| Understanding \| Application \| \|---\|---\|---\| \| \| \| We invite you to explore the three other modules in the AT in the Schools course. Research & Glossary Research Articles & References Biegun, D., Peterson, Y., McNaught, J., & Sutterfield, C. (2020). Including Student Voice in IEP Meetings Through Use of Assistive Technology. Teaching Exceptional Children, 52(5), 348–350. https://doi.org/10.1177/0040059920920148 DeCoste, D. C., & Bowser, M. G. (2020). The Evolving Landscape of Assistive Technology in K-12 Settings. Assistive Technology Outcomes and Benefits, 14(1), 94–110. Jones, & Hinesmon-Matthews, L. J. (2014). Effective Assistive Technology Consideration and Implications for Diverse Students. Computers in the Schools, 31(3), 220–232. https://doi.org/10.1080/07380569.2014.932682 Marino, M. T., Marino, E. C., & Shaw, S. F. (2006). Making Informed Assistive Technology Decisions for Students with High Incidence Disabilities. Teaching Exceptional Children, 38(6), 18–25. https://doi.org/10.1177/00400599060380060 Peterson-Karlan, & Parette, H. P. (2007). Evidence-Based Practice and the Consideration of Assistive Technology: Effectiveness and Outcomes. Assistive Technology Outcomes and Benefits, 4(1), 130–139. Quinn, B. S., Behrmann, M., Mastropieri, M., Chung, Y., Bausch, M. E., & Ault, M. J. (2009). Who is Using Assistive Technology in Schools? Journal of Special Education Technology, 24(1), 1–13. https://doi.org/10.1177/016264340902400101 Watts, O’Brian, M., & Wojcik, B. W. (2003). Four Models of Assistive Technology Consideration: How Do They Compare to Recommended Educational Assessment Practices? Journal of Special Education Technology, 19(1), 43–56. https://doi.org/10.1177/016264340401900104 Glossary Assistive Technology (AT) - products, equipment, and systems that enhance learning, working, and daily living for persons with disabilities. (https://www.atia.org/home/at-resources/what-is-at/#what-is-assistive-technology) Educational Barriers - Characteristics of curriculum, including instruction, that make it inaccessible to students. An example of this is text that cannot be read by a screen reader or text to speech app. Note: The student or student special needs are Never the barriers.	oercommons	2025-03-18T00:36:05.901386	Full Course	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/102366/overview", "title": "Assistive Technology in the Schools: Introduction to Assistive Technology", "author": "Technology" }
https://oercommons.org/courseware/lesson/122724/overview	Introduction to Global Challenges and Solutions Activity Overview This activity uses legos to introduce students to a course focused on global challenges and solutions. Overview Overview: This activity introduces students to the topic of global challenges and encourages them to think creatively about solutions using LEGO bricks. Discipline This activity could be used in any social sciences course that addresses global challenges. Learning Objectives 1. Students will identify key aspects of a specific global challenge and discuss its significance within their campus or local community context. 2. Students will collaboratively design and build a practical, micro-level solution to a global challenge, fostering innovation and critical thinking. 3. Students will practice effective collaboration, reflect on the creative process, and articulate the impact and feasibility of their proposed solutions. Time Needed This exercise will take approximately 45-minutes to complete. Materials Needed LEGO sets (enough for small groups of 3-4 students) Printed cards with different global challenges with specific application to your campus or local community (e.g., climate change, clean water access, poverty, renewable energy, etc.) Timer Large paper for group reflection (markers etc) Sticky notes for gallery walk Lesson Instructions Introduction (5 minutes): 1. Briefly introduce the concept of global challenge 2. Explain that today’s activity will involve using LEGO bricks to think creatively about solutions to global challenges. Form Groups (2 minutes): 1. Divide the students into small groups of 3-4. 2. Distribute a set of LEGO bricks to each group. Challenge Assignment (3 minutes): 1. Give each group a card with a specific global challenge written on it. 2. Explain that their task is to build a model that represents a solution to their assigned challenge using the LEGO bricks. 3. Let them know if should be a practical, “mirco” level solution that could be implemented on their campus/in their community. Building Phase (10 minutes): 1. Set a timer for 10 minutes. 2. Encourage the groups to discuss and build their solutions. Remind them to think creatively and collaboratively. Presentation (7 minutes): 1. Once the time is up, have each group present their LEGO model to the class. 2. Ask them to explain the challenge they were addressing and how their model represents a solution. Reflection (10 minutes): Have students go back to their small groups and reflect on the experience. Ask them to draw/take notes of the large pieces of white paper and hang them up around the room. Use (some of) the following questions to guide the reflection: What did you learn about the global challenge your group addressed? Why do you think this challenge is important to solve? How did your group come up with the solution represented by your LEGO model? What were some of the ideas that you considered but didn’t use? Why did you choose the final idea? How did your group work together to build the model? What roles did each member take on? What challenges did you face while working as a team, and how did you overcome them? How do you think your solution could make a difference in addressing the global challenge? What are some potential limitations or obstacles to implementing your solution in the real world? Gallery Walk (10 minutes): 1. After the students hang up their reflections (with their LEGO models visible), invite all groups to do a gallery walk to read/reflect on the notes different groups made. 2. Invite students to make comments on the large pieces of white paper by adding sticky notes. - Comments might focus on how peers think the solution could make a positive difference in addressing the global challenge or potential limittions or obstacles to implementing the solution. Discussion (3 minutes): Highlight the importance of creativity and collaboration in solving global challenges.	oercommons	2025-03-18T00:36:05.925014	Melissa Nelson	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/122724/overview", "title": "Introduction to Global Challenges and Solutions Activity", "author": "Anne Stone" }
https://oercommons.org/courseware/lesson/55424/overview	Diversity and Cultural Competency Overview Diversity: the art of thinking independently together. —Malcolm Forbes, entrepreneur, founder of Forbes magazine LEARNING OBJECTIVES By the end of this section, you will be able to: - Define diversity and identify many aspects of diversity - Differentiate between surface diversity and deep diversity, and explain the relationship between the two - Define and apply principles of cultural competency - Explore the positive effects of diversity in an educational setting Diversity and Cultural Competency Diversity and Cultural Competency Introduction Cultural diversity is found everywhere in college, and it should be respected, appreciated, and celebrated. To be successful as a college student, it is critical that you understand and can describe your own diverse background. Being self-aware allows you to identify what makes you who you are while recognizing the differences that exist between you, other students, your professors, and all the members of a campus community. This section will discuss the factors that make up a person’s culture and how one can effectively communicate and work with people who may be different. You will also learn about aspects of a college culture in order to successfully navigate this new world. Diversity: the art of thinking independently together. —Malcolm Forbes, entrepreneur, founder of Forbes magazine What Is Diversity? There are few words in the English language that have more diverse interpretations than diversity. What does diversity mean? Better yet—what does diversity mean to you? And what does it mean to your best friend, your teacher, your parents, your religious leader, or the person standing behind you in a grocery store? For each of us, diversity has unique meaning. Below are a few of the many definitions offered by college students at a 2010 conference on the topic of diversity. Which of these definitions rings out to you as most accurate and thoughtful? Which definitions could use some embellishment or clarification, in your opinion? Diversity is a group of people who are different in the same place. Diversity to me is the ability for differences to coexist together, with some type of mutual understanding or acceptance present. Acceptance of different viewpoints is key. Tolerance of thought, ideas, people with differing viewpoints, backgrounds, and life experiences. Anything that sets one individual apart from another. People with different opinions, backgrounds (degrees and social experience), religious beliefs, political beliefs, sexual orientations, heritage, and life experience. Dissimilar Having a multitude of people from different backgrounds and cultures together in the same environment working for the same goals. Difference in students’ background, especially race and gender. Differences in characteristics of humans. Diversity is a satisfying mix of ideas, cultures, races, genders, economic statuses and other characteristics necessary for promoting growth and learning among a group. Diversity is the immersion and comprehensive integration of various cultures, experiences, and people. Heterogeneity brings about opportunities to share, learn and grow from the journeys of others. Without it, limitations arise and knowledge is gained in the absence of understanding. Diversity is not tolerance for difference but inclusion of those who are not the majority. It should not be measured as a count or a fraction—that is somehow demeaning. Success at maintaining diversity would be when we no longer ask if we are diverse enough, because it has become the norm, not remarkable.[1] Diversity means different things to people, and it can be understood differently in different environments. In the context of your college experience, diversity generally refers to people around you who differ by race, culture, ethnicity, religion, socioeconomic status, sexual orientation, abilities, opinions, political views, and in other ways. When it comes to diversity on the college campus, we also think about how groups interact with one another, given their differences (even if they are just perceived differences.) How do diverse populations experience and explore their relationships? “More and more organizations define diversity really broadly,” says Eric Peterson, who works on diversity issues for the Society for Human Resource Management (SHRM). “Really, it’s any way any group of people can differ significantly from another group of people—appearance, sexual orientation, veteran status, your level in the organization. It has moved far beyond the legally protected categories that we’ve always looked at.”[2] These are just some of the types of diversity you are likely to encounter on college campuses and in our society generally. In the following video, students from Juniata College describe what diversity means to them and explain why it’s an important aspect of their college experience. Surface Diversity and Deep Diversity Surface diversity and deep diversity are categories of personal attributes—or differences in attributes—that people perceive to exist between people or groups of people. Surface-level diversity refers to differences you can generally observe in others, like ethnicity, race, gender, age, culture, language, disability, etc. You can quickly and easily observe these features in a person. And people often do just that, making subtle judgments at the same time, which can lead to bias or discrimination. For example, if a teacher believes that older students perform better than younger students, she may give slightly higher grades to the older students than the younger students. This bias is based on a perception of the attribute of age, which is surface-level diversity. Deep-level diversity, on the other hand, reflects differences that are less visible, like personality, attitude, beliefs, and values. These attributes are generally communicated verbally and non-verbally, so they are not easily noticeable or measurable. You may not detect deep-level diversity in a classmate, for example, until you get to know him or her, at which point you may find that you are either comfortable with these deeper character levels, or perhaps not. But once you gain this deeper level of awareness, you may focus less on surface diversity. For example, at the beginning of a term, a classmate belonging to a minority ethnic group whose native language is not English (surface diversity) may be treated differently by fellow classmates in another ethnic group. But as the term gets underway, classmates begin discovering the person’s values and beliefs (deep-level diversity), which they find they are comfortable with. The surface-level attributes of language and perhaps skin color become more “transparent” (less noticeable) as comfort is gained with deep-level attributes. The following video is a quick summary of the differences between surface-level and deep-level diversity. (link: http://bit.ly/C20SurfaceDeepDiv) As we’ll use the term here, diversity refers to the great variety of human characteristics—ways that we are different even as we are all human and share more similarities than differences. These differences are an essential part of what enriches humanity. Aspects of diversity may be cultural, biological, or personal in nature. Diversity generally involves things that may significantly affect some people’s perceptions of others—not just any way people happen to be different. For example, having different tastes in music, movies, or books is not what we usually refer to as diversity. When discussing diversity, it is often difficult to avoid seeming to generalize about different types of people—and such generalizations can seem similar to dangerous stereotypes. The following descriptions are meant only to suggest that individuals are different from other individuals in many possible ways and that we can all learn things from people whose ideas, beliefs, attitudes, values, backgrounds, experiences, and behaviors are different from our own. This is a primary reason college admissions departments frequently seek diversity in the student body. Following are various aspects of diversity: - Race: Race refers to what we generally think of as biological differences and is often defined by what some think of as skin color. Such perceptions are often at least as much social as they are biological. - Ethnicity: Ethnicity is a cultural distinction that is different from race. Ethnic groups share a common identity and a perceived cultural heritage that often involves shared ways of speaking and behaving, religion, traditions, and other traits. The term “ethnic” also refers to such a group that is a minority within the larger society. Race and ethnicity are sometimes interrelated but not automatically so. - Cultural background: Culture, like ethnicity, refers to shared characteristics, language, beliefs, behaviors, and identity. We are all influenced by our culture to some extent. While ethnic groups are typically smaller groups within a larger society, the larger society itself is often called the “dominant culture.” The term is often used rather loosely to refer to any group with identifiable shared characteristics. - Educational background: Colleges do not use a cookie-cutter approach to admit only students with identical academic skills. A diversity of educational background helps ensure a free flow of ideas and challenges those who might become set in their ways. - Geography: People from different places within the United States or the world often have a range of differences in ideas, attitudes, and behaviors. - Socioeconomic background: People’s identities are influenced by how they grow up, and part of that background involves socioeconomic factors. Socioeconomic diversity can contribute to a wide variety of ideas and attitudes. - Gender roles: Women hold virtually all professional and social roles, including those once dominated by men, and men have taken on many roles, such as raising a child, that were formerly occupied mostly by women. These changing roles have brought diverse new ideas and attitudes to college campuses. - Gender identity: Gender identity is one’s personal experience of one’s own gender. Gender identity can correlate with the sex at birth – male or female, or can differ from it completely: males may identify as female or vice versa, or a person may identify as a third gender or as falling somewhere along the continuum between male and female. - Age: While younger students attending college immediately after high school are generally within the same age range, older students returning to school bring a diversity of age. Because they often have broader life experiences, many older students bring different ideas and attitudes to the campus. - Sexual orientation: Gays and lesbians make up a significant percentage of people in American society and students on college campuses. Exposure to this diversity helps others overcome stereotypes and become more accepting of human differences. - Religion: For many people, religion is not just a Sunday morning practice but a larger spiritual force that infuses their lives. Religion helps shape different ways of thinking and behaving. - Political views: A diversity of political views helps broaden the level of discourse on campuses concerning current events and the roles of government and leadership at all levels. - Physical ability: Some students have athletic talents. Some students have physical disabilities. Physical differences among students bring yet another kind of diversity to colleges—a diversity that both widens opportunities for a college education and also helps all students better understand how people relate to the world in physical as well as intellectual ways. Cultural Competency As a college student, you are likely to find yourself in diverse classrooms, organizations, and – eventually – workplaces. It is important to prepare yourself to be able to adapt to diverse environments. Cultural competency can be defined as the ability to recognize and adapt to cultural differences and similarities. It involves “(a) the cultivation of deep cultural self-awareness and understanding (i.e., how one’s own beliefs, values, perceptions, interpretations, judgments, and behaviors are influenced by one’s cultural community or communities) and (b) increased cultural other-understanding (i.e., comprehension of the different ways people from other cultural groups make sense of and respond to the presence of cultural differences).”1 In other words, cultural competency requires you to be aware of your own cultural practices, values, and experiences, and to be able to read, interpret, and respond to those of others. Such awareness will help you successfully navigate the cultural differences you will encounter in diverse environments. Cultural competency is critical to working and building relationships with people from different cultures; it is so critical, in fact, that it is now one of the most highly desired skills in the modern workforce.2 In the following video, representatives from Rutgers University Behavioral Health Care elaborate on the concept of cultural competency: We don’t automatically understand differences among people and celebrate the value of those differences. Cultural competency is a skill that you can learn and improve upon over time and with practice. What actions can you take to build your cultural competency skills? KEY TAKEAWAYS - Diversity refers to a great variety of human characteristics and ways in which people differ. - Surface-level diversity refers to characteristics you can easily observe, while deep-level diversity refers to attributes that are not visible and must be communicated in order to understand. - Cultural competency is the ability to recognize and adapt to cultural differences and similarities. - Diverse environments expose you to new perspectives and can help deepen your learning. - Bennett, J. M. (2015). "Intercultural Competence Development." The SAGE Encyclopedia of Intercultural Competence. Thousand Oaks, CA: SAGE Publications, Inc. - Bennett, J. M. (2015). "Intercultural Competence Development." The SAGE Encyclopedia of Intercultural Competence. Thousand Oaks, CA: SAGE Publications, Inc. - "10 Reasons Why We Need Diversity on College Campuses." Center for American Progress. 2016. Web. 2 Feb 2016. ACTIVITY: DEVELOPING YOUR CULTURAL COMPETENCY Objective - Define and apply principles of cultural competency Instructions This activity will help you examine ways in which you can develop your awareness of and commitment to diversity on campus. Answer the following questions to the best of your ability: - What are my plans for expanding myself personally and intellectually in college? - What kind of community will help me expand most fully, with diversity as a factor in my expansion? - What are my comfort zones, and how might I expand them to connect with more diverse groups? - Do I want to be challenged by new viewpoints, or will I feel more comfortable connecting with people who are like me? - What are my biggest questions about diversity? - Submit this assignment according to directions from your instructor. Consider the following strategies to help you answer the questions: - Examine extracurricular activities. Can you get involved with clubs or organizations that promote and expand diversity? - Review your college’s curriculum. In what ways does it reflect diversity? Does it have departments and courses on historically unrepresented peoples, e.g., cultural and ethnic studies, and gender and sexuality studies. Look for study-abroad programs, as well. - Read your college’s mission statement. Read the mission statement of other colleges. How do they match up with your values and beliefs? How do they align with the value of diversity? - Inquire with friends, faculty, colleagues, family. Be open about diversity. What does it mean to others? What positive effects has it had on them? Ask people about diversity. - Research can help. You might consult college literature, Web sites, resource centers and organizations on campus, etc. LICENSES AND ATTRIBUTIONS LICENSES AND ATTRIBUTIONS CC LICENSED CONTENT, ORIGINAL - Diversity and Cultural Competency. Authored by: Laura Lucas. Provided by: Austin Community College. License: CC BY: Attribution CC LICENSED CONTENT, SPECIFIC ATTRIBUTION - Chapter cover image. Authored by: maxlkt. Provided by: Pixabay. Located at: https://pixabay.com/en/hand-united-hands-united-together-1917895/. License: CC0: No Rights Reserved - Gender Identity. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Gender_identity. License: CC BY-SA: Attribution-ShareAlike - 9.2 Living with Diversity. Provided by: University of Minnesota Libraries. Located at: http://open.lib.umn.edu/collegesuccess/chapter/9-2-living-with-diversity/. License: CC BY-NC-SA: Attribution-NonCommercial-ShareAlike ALL RIGHTS RESERVED CONTENT - Cultural Competency at Rutgers University Behavioral Health Care. Provided by: UBHC Production Studio. Located at: https://www.youtube.com/watch?v=c-h1ZuRXBpg. License: All Rights Reserved. License Terms: Standard YouTube License LUMEN LEARNING AUTHORED CONTENT - Diversity and Accessibility. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/diversity-and-accessibility/. License: CC BY: Attribution	oercommons	2025-03-18T00:36:06.025856	Daniella Washington	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/55424/overview", "title": "Diversity and Cultural Competency", "author": "Module" }
https://oercommons.org/courseware/lesson/65713/overview	Education Standards Bellingham Temperature Blank Pictograph Blank Rain Bar Graph Brewster Temperature Colville Rain Colville Temperature Grandview Rain Grandview Temperature Kindergarten Analyze and Interpret Data Teacher Directions KinderRainyGraph KinderSnowyGraph KinderSunnyGraph Long Beach Rain Long Beach Temperature Neah Bay Rain Neah Bay Temperature Our Weather Prediction Our Weather Prediction for Ozette Plants on Our Plates Pullman Rain Pullman Temperature Third Grade Analyzing and Interpreting Data Weather Data Locations Native American Stories Science Connections Overview The original Native American story component lesson was developed as part of an Office of Superintendent of Public Instruction (OSPI) and Washington State Leadership and Assistance for Science Education Reform (LASER) project funded through an EPA Region 10 grant. The stories were told by Roger Fernandes of the Lower Elwha Klallam tribe. Mr. Fernandes has been given permission by the tribes to tell these stories. As these lessons and stories were shared prior to the adoption of the Washington State Science Learning Standards in 2013, there was a need to align these stories with the current science standards. This resource provides a current alignment and possible lesson suggestions on how these stories can be incorporated into the classroom. This alignment work has been funded by the NGSS & Climate Science Proviso of the Washington State Legislature as a part of North Central Educational Service District's award. Introduction The original Native American story component lesson was developed as part of an Office of Superintendent of Public Instruction (OSPI) and Washington State Leadership and Assistance for Science Education Reform (LASER) project funded through an EPA Region 10 grant. The stories were told by Roger Fernandes of the Lower Elwha Klallam tribe. Mr. Fernandes has been given permission by the tribes to tell these stories. As these lessons and stories were shared prior to the adoption of the Washington State Science Learning Standards in 2013, there was a need to align these stories with the current science standards. This resource provides a current alignment and possible lesson suggestions on how these stories can be incorporated into the classroom. This alignment work has been funded by the NGSS & Climate Science Proviso of the Washington State Legislature as a part of North Central Educational Service District's award. Attribution NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press \| Public License All the stories in this collection are read by Roger Fernandes of the Lower Elwa Klallam tribe. The stories and video retelling are included in this lesson with permission and do not fall under the open license for this resource. License Except where otherwise noted, this work by Mechelle LaLanne for North Central Educational Service District is licensed under a Creative Commons Attribution 4.0 International License. All logos and trademarks are property of their respective owners. This resource contains links to websites operated by third parties. These links are provided for your convenience only and do not constitute or imply any endorsement or monitoring by North Central Educational Service District. Please confirm the license status of any third-party resources and understand their terms of use before reusing them. Blue-Jay and Bear (Chehalis, Western WA) Blue-Jay and Bear (Chehalis, Western WA) Blue-Jay and Bear is a story from the Chehalis People near Longview, WA. This story is about Blue-Jay and his desire to be able to do the things other animals are able to do and how Bear takes care of him after Blue-Jay becomes injured. Video Transcript Washington State Science Learning Standards The connections made to these standards are based on the description of the structure and function of Fishing Duck's external parts and Bear's padded feet. 1-LS1-1: Use materials to design a solution to a human problem by mimicking how plants and/or animals use their external parts to help them survive, grow, and meet their needs.* [Clarification Statement: Examples of human problems that can be solved by mimicking plant or animal solutions could include designing clothing or equipment to protect bicyclists by mimicking turtle shells, acorn shells, and animal scales; stabilizing structures by mimicking animal tails and roots on plants; keeping out intruders by mimicking thorns on branches and animal quills; and, detecting intruders by mimicking eyes and ears.] 4-LS1-1: Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction. [Clarification Statement: Examples of structures could include thorns, stems, roots, colored petals, heart, stomach, lung, brain, and skin.] [Assessment Boundary: Assessment is limited to macroscopic structures within plant and animal systems.] First Grade Inspired by Nature STEM Storyline \| Educational Service DIstrict 112 \| CC BY Explore the practice of biomimicry by answering the driving question: How can we use our understanding of nature to help our family solve a problem? (Also aligned to 1-LS3) Fourth Grade Animal Mouth Structures \| PBS Learning Media \| free online This is a resource vetted by NSTA that allows students to explore how the mouth structures of different animals help them meet their needs. Beaver and Mouse (Tulalip, Western WA) Beaver and Mouse (Tulalip, Western, WA) This story is about Beaver who really wants to talk with Field Mouse and when he does, Field Mouse tells him that he is too fat. Beaver remembers how useful Cedar Tree is and how Cedar Tree could help him. Video Transcript Washington State Science Learning Standards 2-PS1-2: Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose.* [Clarification Statement: Examples of properties could include, strength, flexibility, hardness, texture, and absorbency.] [Assessment Boundary: Assessment of quantitative measurements is limited to length.] K-2-ETS1-2: Develop a simple sketch, drawing, or physical model to illustrate how the shape of an object helps it function as needed to solve a given problem. 3-5-ETS1-2: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. General Resources Beaver video for K-5 Beavers. (2020). Retrieved April 29, 2020, from PBS LearningMedia website: https://thinktv.pbslearningmedia.org/resource/tdc02.sci.life.colt.beaver/beavers/#.XqnL0ZNKjBI Cedar Clothing Exhibit Clothing \| AMNH. (2020). Retrieved April 29, 2020, from American Museum of Natural History website: https://www.amnh.org/exhibitions/permanent/northwest-coast/kwakwa-ka-wakw/kwakwa-ka-wakw-collection/clothing Kindergarten- Second Grade Have students review the different weave patterns and sketch a clothing design for various weather. Basketry. (2020). Retrieved April 29, 2020, from Burkemuseum.org website: https://www.burkemuseum.org/static/baskets/Teachersguideforbasketry.htm Third-Fifth Grade Students examine different types of fabric and their characteristics. Using magnifying glasses and sandpaper, they test and observe the weave and wear quality of fabric samples. By comparing the qualities of different fabrics they come to understand why so many different types of fabric exist and are able to recognize or suggest different uses for them. Compare Fabric Materials - Activity. (2018, February 10). Retrieved April 29, 2020, from TeachEngineering.org website: https://www.teachengineering.org/activities/view/compare_fabric_materials Changer and Dog Salmon (All tribes, Western WA) Changer and Dog Salmon (All Tribes, Western, WA) This story describes how Changer who was born of an Earth mother who was carried into the Sky World and married a Star. Changer was stolen by the Dog Salmon People and when he was to return to his mother, he made his first transformation. Video Transcript Washington State Science Learning Standards HS-ESS2-7: Construct an argument based on evidence about the simultaneous coevolution of Earth’s systems and life on Earth. [Clarification Statement: Emphasis is on the dynamic causes, effects, and feedbacks between the biosphere and Earth’s other systems, whereby geoscience factors control the evolution of life, which in turn continuously alters Earth’s surface. Examples include how photosynthetic life altered the atmosphere through the production of oxygen, which in turn increased weathering rates and allowed for the evolution of animal life; how microbial life on land increased the formation of soil, which in turn allowed for the evolution of land plants; or how the evolution of corals created reefs that altered patterns of erosion and deposition along coastlines and provided habitats for the evolution of new life forms.] [Assessment Boundary: Assessment does not include a comprehensive understanding of the mechanisms of how the biosphere interacts with all of Earth’s other systems.] Resources Evolutionary history of Pacific salmon in dynamic environments is an article that describes the evoultionary history of the Pacific salmon in a changing landscape. This could be a great resource as a teacher to develop a lesson. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3352440/ Waples, R. S., Pess, G. R., & Beechie, T. (2008). Evolutionary history of Pacific salmon in dynamic environments. Evolutionary applications, 1(2), 189–206. https://doi.org/10.1111/j.1752-4571.2008.00023.x The Coming of Slehal (All tribes, Western, WA) The Coming of Slehal (All tribes, Western, WA) This story is about the order of the world and how it came to be. Video Transcript Washington State Science Learning Standards MS-LS2-4: Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations. [Clarification Statement: Emphasis is on recognizing patterns in data and making warranted inferences about changes in populations, and on evaluating empirical evidence supporting arguments about changes to ecosystems.] HS-LS2-6: Evaluate claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem. [Clarification Statement: Examples of changes in ecosystem conditions could include modest biological or physical changes, such as moderate hunting or a seasonal flood; and extreme changes, such as volcanic eruption or sea level rise.] HS-LS4-6: Create or revise a simulation to test a solution to mitigate adverse impacts of human activity on biodiversity.* [Clarification Statement: Emphasis is on testing solutions for a proposed problem related to threatened or endangered species, or to genetic variation of organisms for multiple species.] Middle School Link to WA History Curriculum, OSPI Tribal Sovereignty Curriculum for the Social Studies Indian-Ed.Org \| WA – Contemporary Washington State. (2020). Retrieved May 5, 2020, from Indian-ed.org website: http://www.indian-ed.org/curriculum/middle-school-curriculum/wa-contemporary-washington-state/ The Invasive Species Council has a unit with several lesson. Lesson 3 aligns well, but you could really use most of their activities. Palador. (2020, February 6). School Curriculum - Invasive Species Council. Retrieved May 5, 2020, from Invasive Species Council website: https://invasivespecies.wa.gov/educational-materials/teacher-curriculum/ High School Link to the Northwest Indian Fisheries Commission Treaty Hunting Rights FAQ Treaty Hunting Rights FAQ. (2008, June 5). Retrieved May 5, 2020, from Northwest Indian Fisheries Commission website: https://nwifc.org/about-us/wildlife/treaty-hunting-rights-faq/ Population Dynamics 5E Instructional Model Plan from New Visions for Public Schools Population Dynamics 5E Instructional Model Plan - New Visions Science Curriculum. (2020). Retrieved May 5, 2020, from New Visions - Science website: https://curriculum.newvisions.org/science/resources/resource/living-environment-unit-7-5E-instructional-model-plan-population-dynamics-5e-instructional-model-plan/ Coyote and Bear (All tribes, Eastern WA) Coyote and Bear (All tribes, Eastern WA) Video Transcript Washington State Science Learning Standards 1-LS3-1: Make observations to construct an evidence-based account that young plants and animals are like, but not exactly like, their parents. [Clarification Statement: Examples of patterns could include features plants or animals share. Examples of observations could include leaves from the same kind of plant are the same shape but can differ in size; and, a particular breed of dog looks like its parents but is not exactly the same.] [Assessment Boundary: Assessment does not include inheritance or animals that undergo metamorphosis or hybrids.] 4-LS1-1: Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction. [Clarification Statement: Examples of structures could include thorns, stems, roots, colored petals, heart, stomach, lung, brain, and skin.] [Assessment Boundary: Assessment is limited to macroscopic structures within plant and animal systems.] First Grade Plants on Our Plates. (n.d.). Retrieved from https://www.wastatelaser.org/wp-content/uploads/Plants_on_Our_Plates.pdf Fourth Grade That's Not a Plant, It's a Weed! Discovering Functions of External Plant Parts; What Makes a Plant a Plant? Mary Ellen Kanthack. (2015, July 10). That’s Not a Plant, It’s a Weed! Discovering Functions of External Plant Parts; What Makes a Plant a Plant? Retrieved May 5, 2020, from BetterLesson website: https://betterlesson.com/lesson/603965/that-s-not-a-plant-it-s-a-weed-discovering-functions-of-external-plant-parts-what-makes-a-plant-a-plant?from=cc_lesson Father Ocean (All tribes, Western WA) Father Ocean (All tribes, Western WA) This story is about Ocean’s children, the Clouds, and how they would travel across the land. Video Transcript Washington State Science Learning Standards K-ESS2-1: Use and share observations of local weather conditions to describe patterns over time. [Clarification Statement: Examples of qualitative observations could include descriptions of the weather (such as sunny, cloudy, rainy, and warm); examples of quantitative observations could include numbers of sunny, windy, and rainy days in a month. Examples of patterns could include that it is usually cooler in the morning than in the afternoon and the number of sunny days versus cloudy days in different months.] [Assessment Boundary: Assessment of quantitative observations limited to whole numbers and relative measures such as warmer/cooler.] 3-ESS2-1: Represent data in tables and graphical displays to describe typical weather conditions expected during a particular season. [Clarification Statement: Examples of data could include average temperature, precipitation, and wind direction.] [Assessment Boundary: Assessment of graphical displays is limited to pictographs and bar graphs. Assessment does not include climate change.] 5-ESS2-1: Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact. [Clarification Statement: Examples could include the influence of the ocean on ecosystems, landform shape, and climate; the influence of the atmosphere on landforms and ecosystems through weather and climate; and the influence of mountain ranges on winds and clouds in the atmosphere. The geosphere, hydrosphere, atmosphere, and biosphere are each a system.] [Assessment Boundary: Assessment is limited to the interactions of two systems at a time.] MS-ESS2-4: Develop a model to describe the cycling of water through Earth's systems driven by energy from the sun and the force of gravity. [Clarification Statement: Emphasis is on the ways water changes its state as it moves through the multiple pathways of the hydrologic cycle. Examples of models can be conceptual or physical.] [Assessment Boundary: A quantitative understanding of the latent heats of vaporization and fusion is not assessed.] MS-ESS2-5: Collect data to provide evidence for how the motions and complex interactions of air masses result in changes in weather conditions. [Clarification Statement: Emphasis is on how air masses flow from regions of high pressure to low pressure, causing weather (defined by temperature, pressure, humidity, precipitation, and wind) at a fixed location to change over time, and how sudden changes in weather can result when different air masses collide. Emphasis is on how weather can be predicted within probabilistic ranges. Examples of data can be provided to students (such as weather maps, diagrams, and visualizations) or obtained through laboratory experiments (such as with condensation).] [Assessment Boundary: Assessment does not include recalling the names of cloud types or weather symbols used on weather maps or the reported diagrams from weather stations.] MS-ESS2-6: Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates. [Clarification Statement: Emphasis is on how patterns vary by latitude, altitude, and geographic land distribution. Emphasis of atmospheric circulation is on the sunlight-driven latitudinal banding, the Coriolis effect, and resulting prevailing winds; emphasis of ocean circulation is on the transfer of heat by the global ocean convection cycle, which is constrained by the Coriolis effect and the outlines of continents. Examples of models can be diagrams, maps and globes, or digital representations.] [Assessment Boundary: Assessment does not include the dynamics of the Coriolis effect.] Kindergarten Feeling Hot, Hot, Hot! \| Kilauea School and Maunawili School for Gather, Reason, Communicate \| CC BY SA Addresses Patterns in Daily Temperature and the Phenomenon focus is: We are hotter and sweatier after lunch recess than morning recess. The investigation is about patterns and graphing with simple data. Includes formative assessment. Analyzing and Interpreting Data - Kindergarten Develop for the Climate Science Proviso Canvas Course hosted by Capital Region ESD in Tumwater. (See attached resources) Third Grade Analyzing and Interpreting Data - Third Grade Develop for the Climate Science Proviso Canvas Course hosted by Capital Region ESD in Tumwater. (See attached resources) Fifth Grade Nelson, K. (2015, July 10). Researching The Rain Shadow Effect. Retrieved May 13, 2020, from BetterLesson website: https://betterlesson.com/lesson/634353/researching-the-rain-shadow-effect?from=cc_lesson Middle School Grade, & Macnevin, L. (n.d.). General Science: Weather and Heat Transfers. Retrieved from https://ambitiousscienceteaching.org/wp-content/uploads/2017/06/Gen-Sci-Weather-and-Heat-Transfer.pdf The Gossiping Clam (Puget Sound, Western WA) The Gossiping Clam (Puget Sound, Western WA) This is a story about the Clams being everywhere and gossiping about you until a little clam gossips about Raven and Raven takes the clams and pushed them under the sand on the beach. Video Transcript Washington State Science Learning Standards 3-LS4-1: Analyze and interpret data from fossils to provide evidence of the organisms and the environments in which they lived long ago. [Clarification Statement: Examples of data could include type, size, and distributions of fossil organisms. Examples of fossils and environments could include marine fossils found on dry land, tropical plant fossils found in Arctic areas, and fossils of extinct organisms.] [Assessment Boundary: Assessment does not include identification of specific fossils or present plants and animals. Assessment is limited to major fossil types and relative ages.] MS-LS4-1: Analyze and interpret data for patterns in the fossil record that document the existence, diversity, extinction, and change of life forms throughout the history of life on Earth under the assumption that natural laws operate today as in the past. [Clarification Statement: Emphasis is on finding patterns of changes in the level of complexity of anatomical structures in organisms and the chronological order of fossil appearance in the rock layers.] [Assessment Boundary: Assessment does not include the names of individual species or geological eras in the fossil record.] Third Grade Mud Fossils. (2014, July 22). Retrieved May 13, 2020, from Earth Science Week website: https://www.earthsciweek.org/classroom-activities/mud-fossils Middle School NSTA. (2019). Deep Thinking Over Geologic Time. Retrieved May 13, 2020, from Nsta.org website: https://ngss.nsta.org/Resource.aspx?ResourceID=999 Handout: http://static.nsta.org/connections/middleschool/201712Handout.pdf Student Guide: http://static.nsta.org/connections/middleschool/201712StudentGuide.pdf Teacher Guide: http://static.nsta.org/connections/middleschool/201712TeacherGuideNew.pdf ay-ay-ásh (Yakama, Eastern WA) ay-ay-ásh (Yakima, Eastern WA) This story is about a little girl who didn't listen very well to her family, adults, or other children and was called ay-ay-ásh (pronounced i-i-esh meaning stupid) by everyone. Cedar tree taught her to weave a basket, but it took several attempts for her to make a basket that would hold water. Video Transcript Washington State Science Learning Standards K-2-ETS1-1: Ask questions, make observations, and gather information about a situation people want to change to define a simple problem that can be solved through the development of a new or improved object or tool. K-2-ETS1-2: Develop a simple sketch, drawing, or physical model to illustrate how the shape of an object helps it function as needed to solve a given problem. K-2-ETS1-3: Analyze data from tests of two objects designed to solve the same problem to compare the strengths and weaknesses of how each performs. 3-5-ETS1-1. Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost. 3-5-ETS1-2. Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. 3-5-ETS1-3. Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved. MS-ETS1-1:Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions. MS-ETS1-2: Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem. MS-ETS1-3: Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success. HS-ETS1-1: Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants. HS-ETS1-2: Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering. HS-ETS1-3: Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts. K-2 Kindergarten – Designing Paper Baskets – PictureSTEM. (2017). Retrieved May 13, 2020, from Picturestem.org website: http://picturestem.org/picturestem-units/kindergarten-baskets/ First Grade – Designing Hamster Habitats – PictureSTEM. (2018). Retrieved May 13, 2020, from Picturestem.org website: http://picturestem.org/picturestem-units/first-grade-hamsters/ Second Grade – Designing Toy Box Organizers – PictureSTEM. (2017). Retrieved May 13, 2020, from Picturestem.org website: http://picturestem.org/picturestem-units/second-grade-toy-box/ 3-5 Entwined with Life: Native American Basketry - Home - Burke Museum. (2020). Retrieved May 13, 2020, from Burkemuseum.org website: https://www.burkemuseum.org/static/baskets/index.html https://www.burkemuseum.org/static/baskets/Teachersguideforbasketry.html Middle School Roots of Wisdom - Education Resources. (2015). Retrieved May 13, 2020, from Omsi.edu website: https://omsi.edu/exhibitions/row/education-resources/ https://omsi.edu/exhibitions/row/docs/Roots-of-Wisdom_Weaving-Activity-Guide.pdf High School Teachings of the Tree People : : Curriculum for Engaged Learning Through Film. (n.d.). Retrieved from https://www.newday.com/sites/default/files/resources/TeachingsCurriculum.pdf - Use the weaving lesson and incorporate specific criteria and constraints. - To rent the film https://www.newday.com/film/teachings-tree-people-work-bruce-miller The Huckleberry Medicine (Puget Sound, Western WA) The Huckleberry Medicine (Puget Sound, Western WA) A man's daughter became ill and nothing seemed to help her condition. The father prayed for help to the spirits and the ancestors and he had a dream about how to help his daughter. Video Transcript Washington State Science Learning Standards MS-LS1-3: Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. [Clarification Statement: Emphasis is on the conceptual understanding that cells form tissues and tissues form organs specialized for particular body functions. Examples could include the interaction of subsystems within a system and the normal functioning of those systems.] [Assessment Boundary: Assessment does not include the mechanism of one body system independent of others. Assessment is limited to the circulatory, excretory, digestive, respiratory, muscular, and nervous systems.] MS-LS1-5: Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms. [Clarification Statement: Examples of local environmental conditions could include availability of food, light, space, and water. Examples of genetic factors could include large breed cattle and species of grass affecting growth of organisms. Examples of evidence could include drought decreasing plant growth, fertilizer increasing plant growth, different varieties of plant seeds growing at different rates in different conditions, and fish growing larger in large ponds than they do in small ponds.] [Assessment Boundary: Assessment does not include genetic mechanisms, gene regulation, or biochemical processes.] MS-PS1-3: Gather and make sense of information to describe that synthetic materials come from natural resources and impact society. [Clarification Statement: Emphasis is on natural resources that undergo a chemical process to form the synthetic material. Examples of new materials could include new medicine, foods, and alternative fuels.] [Assessment Boundary: Assessment is limited to qualitative information.] Resources Straus, K. M., & Chudler, E. H. (2016). Online Teaching Resources about Medicinal Plants and Ethnobotany. CBE—Life Sciences Education, 15(4), fe9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5132387/ Middle School Lessons - Sowing the Seeds of Neuroscience. (2013). Lessons - Sowing the Seeds of Neuroscience. Retrieved May 13, 2020, from Neuroseeds.org website: http://www.neuroseeds.org/Lessons Columbia River Story (All tribes, Eastern WA) Columbia River Story (All tribes, Eastern WA) A man's daughter became ill and nothing seemed to help her condition. The father prayed for help to the spirits and the ancestors and he had a dream about how to help his daughter. Video Transcript Washington State Science Learning Standards 4-ESS2-1: Make observations and/or measurements to provide evidence of the effects of weathering or the rate of erosion by water, ice, wind, or vegetation. [Clarification Statement: Examples of variables to test could include angle of slope in the downhill movement of water, amount of vegetation, speed of wind, relative rate of deposition, cycles of freezing and thawing of water, cycles of heating and cooling, and volume of water flow.] [Assessment Boundary: Assessment is limited to a single form of weathering or erosion.] 4-ESS2-2: Analyze and interpret data from maps to describe patterns of Earth’s features. [Clarification Statement: Maps can include topographic maps of Earth’s land and ocean floor, as well as maps of the locations of mountains, continental boundaries, volcanoes, and earthquakes.] MS-ESS2-2: Construct an explanation based on evidence for how geoscience processes have changed Earth's surface at varying time and spatial scales. [Clarification Statement: Emphasis is on how processes change Earth’s surface at time and spatial scales that can be large (such as slow plate motions or the uplift of large mountain ranges) or small (such as rapid landslides or microscopic geochemical reactions), and how many geoscience processes (such as earthquakes, volcanoes, and meteor impacts) usually behave gradually but are punctuated by catastrophic events. Examples of geoscience processes include surface weathering and deposition by the movements of water, ice, and wind. Emphasis is on geoscience processes that shape local geographic features, where appropriate.] HS-ESS2-1: Develop a model to illustrate how Earth’s internal and surface processes operate at different spatial and temporal scales to form continental and ocean-floor features. [Clarification Statement: Emphasis is on how the appearance of land features (such as mountains, valleys, and plateaus) and sea-floor features (such as trenches, ridges, and seamounts) are a result of both constructive forces (such as volcanism, tectonic uplift, and orogeny) and destructive mechanisms (such as weathering, mass wasting, and coastal erosion).] [Assessment Boundary: Assessment does not include memorization of the details of the formation of specific geographic features of Earth’s surface.] HS-ESS2-2: Analyze geoscience data to make the claim that one change to Earth's surface can create feedbacks that cause changes to other Earth systems. [Clarification Statement: Examples should include climate feedbacks, such as how an increase in greenhouse gases causes a rise in global temperatures that melts glacial ice, which reduces the amount of sunlight reflected from Earth's surface, increasing surface temperatures and further reducing the amount of ice. Examples could also be taken from other system interactions, such as how the loss of ground vegetation causes an increase in water runoff and soil erosion; how dammed rivers increase groundwater recharge, decrease sediment transport, and increase coastal erosion; or how the loss of wetlands causes a decrease in local humidity that further reduces the wetland extent.] HS-ESS2-5: Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes. [Clarification Statement: Emphasis is on mechanical and chemical investigations with water and a variety of solid materials to provide the evidence for connections between the hydrologic cycle and system interactions commonly known as the rock cycle. Examples of mechanical investigations include stream transportation and deposition using a stream table, erosion using variations in soil moisture content, or frost wedging by the expansion of water as it freezes. Examples of chemical investigations include chemical weathering and recrystallization (by testing the solubility of different materials) or melt generation (by examining how water lowers the melting temperature of most solids).] Resources An Introduction to the Ice Age Floods – Ice Age Floods Institute. (2020). Retrieved May 13, 2020, from Iafi.org website: https://iafi.org/about-the-ice-age-floods/introduction/ NOVA \| Mystery of the Megaflood \| Explore the Scablands (non-Flash) \| PBS. (2020). Retrieved May 13, 2020, from Pbs.org website: https://www.pbs.org/wgbh/nova/megaflood/scab-nf.html Glacial Lake Missoula and the Ice Age Floods. (2020). Retrieved May 13, 2020, from Glaciallakemissoula.org website: http://www.glaciallakemissoula.org/story.html Ice Age Floods-Discover Glacial Lake Missoula and Lake Bonneville. (2015, November 3). Retrieved May 13, 2020, from Hugefloods.com website: http://hugefloods.com/ Sculpted by Floods: The Northwest’s Ice Age Legacy \| PBS LearningMedia. (2020). Retrieved May 13, 2020, from PBS LearningMedia website: https://www.pbslearningmedia.org/resource/sculpted-by-floods-the-northwests-ice-age-legacy/sculpted-by-floods-the-northwests-ice-age-legacy/support-materials/ Fourth Grade Glaciers, Water and Wind, Oh My! - Activity. (2019, October 9). Retrieved May 13, 2020, from TeachEngineering.org website: https://www.teachengineering.org/activities/view/cub_earth_lesson5_activity1 Grade 4 - 4-ESS2 Earth’s Systems. (2020). Retrieved May 13, 2020, from Exploringnature.org website: https://www.exploringnature.org/db/view/Grade-4-4-ESS2-Earthrsquos-Systems Middle School Goldberg, A. (2013, November 15). AUTHENTIC LANDSCAPES INDOORS. Retrieved May 13, 2020, from Nsta.org website: http://digital.nsta.org/publication/?i=184198&article_id=1562453&view=articleBrowser&ver=html5 High School See Resources section above. Coyote’s Deal with the Wind (Spokane. Eastern WA) Coyote’s Deal with the Wind (Spokane. Eastern WA) This story shares about how the Wind would blow through the land and how Coyote set a trap to capture the Wind. Video Transcript Washington State Science Learning Standards 2-ESS2-1: Compare multiple solutions designed to slow or prevent wind or water from changing the shape of the land.* [Clarification Statement: Examples of solutions could include different designs of dikes and windbreaks to hold back wind and water, and different designs for using shrubs, grass, and trees to hold back the land.] 3-ESS2-1: Represent data in tables and graphical displays to describe typical weather conditions expected during a particular season. [Clarification Statement: Examples of data could include average temperature, precipitation, and wind direction.] [Assessment Boundary: Assessment of graphical displays is limited to pictographs and bar graphs. Assessment does not include climate change.] 4-ESS2-1: Make observations and/or measurements to provide evidence of the effects of weathering or the rate of erosion by water, ice, wind, or vegetation. [Clarification Statement: Examples of variables to test could include angle of slope in the downhill movement of water, amount of vegetation, speed of wind, relative rate of deposition, cycles of freezing and thawing of water, cycles of heating and cooling, and volume of water flow.] [Assessment Boundary: Assessment is limited to a single form of weathering or erosion.] MS-ESS2-5: Collect data to provide evidence for how the motions and complex interactions of air masses result in changes in weather conditions. [Clarification Statement: Emphasis is on how air masses flow from regions of high pressure to low pressure, causing weather (defined by temperature, pressure, humidity, precipitation, and wind) at a fixed location to change over time, and how sudden changes in weather can result when different air masses collide. Emphasis is on how weather can be predicted within probabilistic ranges. Examples of data can be provided to students (such as weather maps, diagrams, and visualizations) or obtained through laboratory experiments (such as with condensation).] [Assessment Boundary: Assessment does not include recalling the names of cloud types or weather symbols used on weather maps or the reported diagrams from weather stations.] MS-ESS2-6: Develop and use a model to describe how unequal heating and rotation of the Earth cause patterns of atmospheric and oceanic circulation that determine regional climates. [Clarification Statement: Emphasis is on how patterns vary by latitude, altitude, and geographic land distribution. Emphasis of atmospheric circulation is on the sunlight-driven latitudinal banding, the Coriolis effect, and resulting prevailing winds; emphasis of ocean circulation is on the transfer of heat by the global ocean convection cycle, which is constrained by the Coriolis effect and the outlines of continents. Examples of models can be diagrams, maps and globes, or digital representations.] [Assessment Boundary: Assessment does not include the dynamics of the Coriolis effect.] Second Grade Collins, M. (2015, June). Preventing Wind Erosion. Retrieved May 13, 2020, from BetterLesson website: https://betterlesson.com/lesson/637474/preventing-wind-erosion?from=search_results Faber, J. (2015, June 15). How Can Wind Change the Shape of the Land? Retrieved May 13, 2020, from BetterLesson website: https://betterlesson.com/lesson/632923/how-can-wind-change-the-shape-of-the-land Third Grade Espin, M. (2015, March 2). Which Way Does The Wind Blow? A Weather Vane Can Show You! Retrieved May 13, 2020, from BetterLesson website: https://betterlesson.com/lesson/635186/which-way-does-the-wind-blow-a-weather-vane-can-show-you?from=cc_lesson STEM: Weather. (2013). Retrieved May 13, 2020, from Thinkport.org website: http://weather.thinkport.org/home.html Fourth Grade Experiment: Demonstrating Wind Erosion. (n.d.). Retrieved from https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs141p2_035714.pdf Middle School Tornado Alley! (Middle School NGSS Unit) https://www.oercommons.org/authoring/28983-tornado-alley-middle-school-ngss-unit How Fire Came to Earth (All tribes, Eastern WA) How Fire Came to Earth (All tribes, Eastern WA)) This story shares how the animals went to the Sky World to get fire. Video Transcript Washington State Science Learning Standards 5-PS1-3: Make observations and measurements to identify materials based on their properties. [Clarification Statement: Examples of materials to be identified could include baking soda and other powders, metals, minerals, and liquids. Examples of properties could include color, hardness, reflectivity, electrical conductivity, thermal conductivity, response to magnetic forces, and solubility; density is not intended as an identifiable property.] [Assessment Boundary: Assessment does not include density or distinguishing mass and weight.] MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. [Clarification Statement: Examples of reactions could include burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride.] [Assessment boundary: Assessment is limited to analysis of the following properties: density, melting point, boiling point, solubility, flammability, and odor.] Fifth Grade Mystery Powders. (2018). Retrieved May 13, 2020, from Uen.org website: https://www.uen.org/lessonplan/view/2176 Middle School What’s This Stuff? \| PBS LearningMedia. (2020). Retrieved May 13, 2020, from PBS LearningMedia website: https://www.pbslearningmedia.org/resource/nvms.sci.phys.matter.makingstuff/whats-this-stuff/	oercommons	2025-03-18T00:36:06.356913	Environmental Science	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/65713/overview", "title": "Native American Stories Science Connections", "author": "Elementary Education" }
https://oercommons.org/courseware/lesson/98096/overview	Service-Learning Manual Overview Resource for teachers and students in programs that require service-learning. Service-Learning Manual Walters State Community College Service-Learning Manual For Intro to Social Work Dr. Angie Elkins Service-Learning Service-learning is a teaching strategy that uses meaningful community service, combined with guided reflections, to enrich and enhance student learning. Service-learning incorporates two fundamental components: SERVICE, a project that meets an identifiable community need; and LEARNING, classroom activities and reflection which connect the service project to the academic curriculum. What exactly is service-learning? Service-learning is a blending of academic study and community service. Academic credit is given for the actual learning that occurs during the volunteering and not just for the clock hours of service to the community. Students can choose to be placed in one of many available non profit agencies, educational sites, and government offices. They are then given specific assignments, based on both an academic learning plan and the specific need of the community site. Service-learning is, therefore, an effort to promote the fact that much learning takes place when we can connect classroom instruction to real-life situations. Furthermore, emphasis is placed on linking what students are doing at their individual sites with broader community issues and involvement. What is the difference between service-learning, volunteerism, and internships? Service-Learning There are a number of core requirements that students have to meet before they can be given credit for these classes and/or projects. These requirements ensure that students reflect upon what they are doing and evaluate what they are learning. Volunteering Volunteering is a worthwhile activity, but we generally do not learn from our volunteering in the same way, nor do we connect it to classroom instruction and academic course content. Internships Internships place little or no emphasis on the student providing service to the site, whereas service-learning emphasizes the student making a contribution to the community while the student uses the site as a vehicle for learning. How do I demonstrate what I am learning and how am I graded? You demonstrate what you are learning by what you write in your reflective journal, your verbal exchanges with your faculty supervisor, and your final analytical paper. Each participating faculty supervisor will tell you ahead of time what their basic requirements are for a specific grade. Student responsibilities to agencies - To be open and honest at your site from the beginning - To participate in any training that is required by the particular agency - To respect confidentiality - Maintain professionalism: observe dress codes, report on time, avoid gossip, etc... - To understand commitments of time and task and to fulfill them - To seek honest feedback - If in doubt, seek advice - To accept guidance and direction when they are offered - To enter into service with enthusiasm and commitment - To be considerate of the agency, your supervisor, other volunteers and staff, and any clients that the agency serves - To be effective advocates for change as needed - To utilize all your talents and experiences in order to do a good job for the agency Guidelines for reflective journals As a student in Intro to Social Work, you will be required to complete 15 weekly journals related to your service-learning experience through the class discussion boards. Journals do not have a length requirement but your response should fully answer the writing prompt and show connection to your service-learning experience and/or the materials covered in class. You must reply to at least one classmate for each journal and connect your response to the service-learning experience and/or materials covered in class. Keeping a reflective journal Keeping a journal is an excellent way for you to reconstruct, reflect on, and think about your involvement experience. Processing your service through your perceptions and emotions helps you to gain insight into what you are experiencing and how you are feeling about it. A journal also serves as a useful record of your service and learning. To be most effective, a journal should not just be a log of events. It should be a way for you to analyze the activities you are engaged in and the new things you are learning, to note important events, and to relate your objectives and goals to what you are learning and doing. This journal involves weekly writing prompts designed to create conversation about the experiences you have during your service-learning and relate it back to the materials covered in the classroom. Each week you will be required to fully respond to the writing prompt and reply to at least one other student. Both posts should connect the writing prompt to the service-learning and/or the course materials. Guidelines for writing an analytical paper Your final paper for this class is an analytical paper related to your service-learning. This paper is a minimum of 3 pages. The outline below is a starting point. You do not have to answer all the questions as they may not apply to you or your organization. However, please include the three sections. - Part 1: Description (approximately 1 page) - What were your duties and responsibilities? - What was your work situation and environment? - What are the goals of the agency? - What skills did you acquire as a result of your service-learning experience? - How did the service-learning experience evolve and change during the semester? - Part 2: Evaluation (approximately 1 - 2 pages) - What does service mean in your life? - What impact do you feel you had on the community? - What are the community needs? - What did you learn: - From your service-learning experience? - About the agency you worked in, the supervisor/s you worked for, the responsibilities of this office/supervisor? - About the strengths and limitations of this site in carrying out its responsibilities to the community? - About the experience of working in an agency/school/government setting? - About yourself - your own strengths and limitations; about how this experience affected your own personal goals and career objectives? - How could you improve the quality of your service? - If you were in charge of the place where you volunteer, what would you do to improve it? Would you have the volunteers do anything different from what you are doing? Would you treat them differently? - Part 3: Integration (approximately 1 - 2 pages) - How has the service-learning experience changed what you thought you knew about local schools, government offices, community service agencies, or special interest groups? - How has your experience affected your evaluation of our political system/society? - Has this service-learning experience helped you to develop a sense of civic responsibility? (i.e. more insight into social/public policy formation and legislation, and how to advocate to make a difference). Give examples. - What specific problem(s) or issue(s) did you encounter during your service learning experience that either broadened your interest in our political/social system or increased your awareness of connections between community needs and policy formation? - How has your experience affected your educational goals? - How would you change the service-learning experience to make it a more valuable learning experience? - Were there any conflicts between your service responsibilities and learning objectives? - Does race and socio-economic background affect the service you are doing? For example, who “does” service - in terms of ethnicity/race and socio-economic background? Do different groups have different reasons for doing service? - Why is service predominantly done by females, by humanities not science majors? How can these tendencies be changed? - How do those persons in the community, who are being served, perceive you and/or the site you represent? - Does your site conduct needs assessments to establish community needs? - How has this experience helped you to integrate knowledge gained in the classroom? - Relate your experience to the materials covered in the classroom - what connections did you see? Service-learning forms These forms must be completed and turned in BEFORE you begin your service-learning. - Complete your service-learning application here: Application - Print and sign your Release/Hold Harmless agreement form and submit a photograph or scan of the form in the appropriate dropbox. - Print your Referral Confirmation Form, take it to your agency and complete it with your agency supervisor. Submit a photograph or scan of the form in the appropriate dropbox. - Print your Volunteer Placement Agreement, take it to your agency and have your agency supervisor complete it. Submit a photograph or scan of the form in the appropriate dropbox. Use this log to keep track of your hours as you complete your service-learning. This form must be completed by your supervisor AFTER you complete your service-learning. - Print this form Final Student Evaluation, give it to your agency supervisor and ask that they email it back to your professor. My email is listed at the top of the page. Note: This form must come directly from your supervisor to your professor.	oercommons	2025-03-18T00:36:06.384063	Assessment	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/98096/overview", "title": "Service-Learning Manual", "author": "Activity/Lab" }
https://oercommons.org/courseware/lesson/116479/overview	Decoding Emotions in Ourselves and Others Overview Clil Didactic Sequence: Decoding Emotions in Ourselves and Others_ Highschool Learning Objectives: - Students will be able to identify and name basic emotions. - Students will be able to describe the physiological and behavioral changes associated with emotions. - Students will be able to recognize emotions in facial expressions, body language, and tone of voice. - Students will be able to analyze the influence of emotions on thoughts and actions. - Students will be able to develop strategies for managing emotions effectively. Sequence of Activities: Unit 1: The Emotional Landscape (2 sessions) - CLIL Standards: Science (Biology) - English Standards: Reading comprehension, vocabulary development - ICT Standards: Online research, multimedia presentations Activities: - Brainstorming: Begin by asking students to brainstorm a list of emotions they experience. Write these on the board and categorize them (positive, negative, neutral). Discuss the universality of emotions and how they are expressed across cultures. - Emotional Rollercoaster: Divide the class into small groups and assign each group a different emotion (e.g., joy, anger, fear). Students research the physiological changes associated with their assigned emotion (increased heart rate, sweating, etc.) and create a short skit or multimedia presentation demonstrating these changes. - "Feeling Faces" Activity: Present students with high-quality images depicting various facial expressions (https://greatergood.berkeley.edu/quizzes/ei_quiz). Ask them to identify the emotions conveyed and discuss the role of facial expressions in nonverbal communication. Unit 2: Emotional Intelligence (2 sessions) - CLIL Standards: Psychology - English Standards: Critical thinking, persuasive writing - ICT Standards: Online discussions, data analysis tools (optional) Activities: - The EQ Test: Introduce the concept of emotional intelligence (EQ) and its importance in personal and social interactions. Students can take an online EQ quiz (there are many free options available) to gain insights into their own emotional strengths and weaknesses. Facilitate a class discussion on the importance of developing EQ. - Emotional Regulation Strategies: Students research and discuss various strategies for managing emotions effectively (e.g., deep breathing, relaxation techniques, positive self-talk). Encourage them to create a personalized "emotional toolbox" with strategies they find helpful. - Persuasive Writing: Students write a persuasive essay arguing for the importance of emotional intelligence in achieving success in a chosen field (e.g., business, healthcare, arts). Unit 3: Emotions in Literature (2 sessions) - CLIL Standards: Literature - English Standards: Literary analysis, character development - ICT Standards: Online literature resources, multimedia presentations (optional) Activities: - Literary Detectives: Students select a short story or poem (ensure it is age-appropriate) rich in emotional content. As a class, analyze the characters' emotions, how they are expressed in the text (figurative language, word choice), and the impact of emotions on the plot. - Character Portrayals: Divide the class into pairs. Each pair selects a scene from the chosen literary work where emotions play a key role. Students create a short role-play depicting the scene, focusing on accurately portraying the characters' emotions through dialogue, facial expressions, and body language. Assessment: - Participation in class discussions and activities - Presentations and skits created by students - EQ quiz results (optional) - Persuasive essay - Literary analysis assignments Resources: - Greater Good Science Center at UC Berkeley: https://greatergood.berkeley.edu/ - National Institute of Mental Health: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7749626/ - LearningRX: https://psychcentral.com/health/ways-to-manage-your-emotions - Project Happiness: https://projecthappiness.org/ Differentiation: - Provide students with graphic organizers or templates to support vocabulary development and note-taking. - Offer alternative assignments for students who struggle with writing, such as creating visual representations of emotions. - Allow students to choose literary works that resonate with their interests.	oercommons	2025-03-18T00:36:06.401513	05/30/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/116479/overview", "title": "Decoding Emotions in Ourselves and Others", "author": "Gabriela Andrade" }
https://oercommons.org/courseware/lesson/15391/overview	Introduction What comes to mind when you think about therapy for psychological problems? You might picture someone lying on a couch talking about his childhood while the therapist sits and takes notes, à la Sigmund Freud. But can you envision a therapy session in which someone is wearing virtual reality headgear to conquer a fear of snakes? In this chapter, you will see that approaches to therapy include both psychological and biological interventions, all with the goal of alleviating distress. Because psychological problems can originate from various sources—biology, genetics, childhood experiences, conditioning, and sociocultural influences—psychologists have developed many different therapeutic techniques and approaches. The Ocean Therapy program shown in Figure uses multiple approaches to support the mental health of veterans in the group. References Abbass, A., Kisely, S., & Kroenke, K. (2006). Short-term psychodynamic psychotherapy for somatic disorders: Systematic review and meta-analysis of clinical trials. Psychotherapy and Psychosomatics, 78, 265–274. Ahmed, S., Wilson, K. B., Henriksen, R. C., & Jones, J. W. (2011). What does it mean to be a culturally competent counselor? Journal for Social Action in Counseling and Psychology, 3(1), 17–28. Alavi, A., Sharifi, B., Ghanizadeh, A., & Dehbozorgi, G. (2013). Effectiveness of cognitive-behavioral therapy in decreasing suicidal ideation and hopelessness of the adolescents with previous suicidal attempts. Iranian Journal of Pediatrics, 23(4), 467–472. Alegría, M., Chatterji, P., Wells, K., Cao, Z., Chen, C. N., Takeuchi, D., . . . Meng, X. L. (2008). Disparity in depression treatment among racial and ethnic minority populations in the United States. Psychiatric Services, 59(11), 1264–1272. American Psychological Association. (2005). Policy statement on evidence-based practice in psychology. 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Stanford, CA: Stanford University Press.	oercommons	2025-03-18T00:36:06.431183	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15391/overview", "title": "Psychology, Therapy and Treatment", "author": null }
https://oercommons.org/courseware/lesson/15392/overview	Mental Health Treatment: Past and Present Overview By the end of this section, you will be able to: - Explain how people with psychological disorders have been treated throughout the ages - Discuss deinstitutionalization - Discuss the ways in which mental health services are delivered today - Distinguish between voluntary and involuntary treatment Before we explore the various approaches to therapy used today, let’s begin our study of therapy by looking at how many people experience mental illness and how many receive treatment. According to the U.S. Department of Health and Human Services (2013), 19% of U.S. adults experienced mental illness in 2012. For teens (ages 13–18), the rate is similar to that of adults, and for children ages 8–15, current estimates suggest that 13% experience mental illness in a given year (National Institute of Mental Health [NIMH], n.d.-a) With many different treatment options available, approximately how many people receive mental health treatment per year? According to the Substance Abuse and Mental Health Services Administration (SAMHSA), in 2008, 13.4% of adults received treatment for a mental health issue (NIMH, n.d.-b). These percentages, shown in Figure, reflect the number of adults who received care in inpatient and outpatient settings and/or used prescription medication for psychological disorders. Children and adolescents also receive mental health services. The Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey (NHANES) found that approximately half (50.6%) of children with mental disorders had received treatment for their disorder within the past year (NIMH, n.d.-c). However, there were some differences between treatment rates by category of disorder (Figure). For example, children with anxiety disorders were least likely to have received treatment in the past year, while children with ADHD or a conduct disorder were more likely to receive treatment. Can you think of some possible reasons for these differences in receiving treatment? Considering the many forms of treatment for mental health disorders available today, how did these forms of treatment emerge? Let’s take a look at the history of mental health treatment from the past (with some questionable approaches in light of modern understanding of mental illness) to where we are today. TREATMENT IN THE PAST For much of history, the mentally ill have been treated very poorly. It was believed that mental illness was caused by demonic possession, witchcraft, or an angry god (Szasz, 1960). For example, in medieval times, abnormal behaviors were viewed as a sign that a person was possessed by demons. If someone was considered to be possessed, there were several forms of treatment to release spirits from the individual. The most common treatment was exorcism, often conducted by priests or other religious figures: Incantations and prayers were said over the person’s body, and she may have been given some medicinal drinks. Another form of treatment for extreme cases of mental illness was trephining: A small hole was made in the afflicted individual’s skull to release spirits from the body. Most people treated in this manner died. In addition to exorcism and trephining, other practices involved execution or imprisonment of people with psychological disorders. Still others were left to be homeless beggars. Generally speaking, most people who exhibited strange behaviors were greatly misunderstood and treated cruelly. The prevailing theory of psychopathology in earlier history was the idea that mental illness was the result of demonic possession by either an evil spirit or an evil god because early beliefs incorrectly attributed all unexplainable phenomena to deities deemed either good or evil. From the late 1400s to the late 1600s, a common belief perpetuated by some religious organizations was that some people made pacts with the devil and committed horrible acts, such as eating babies (Blumberg, 2007). These people were considered to be witches and were tried and condemned by courts—they were often burned at the stake. Worldwide, it is estimated that tens of thousands of mentally ill people were killed after being accused of being witches or under the influence of witchcraft (Hemphill, 1966) By the 18th century, people who were considered odd and unusual were placed in asylums (Figure). Asylums were the first institutions created for the specific purpose of housing people with psychological disorders, but the focus was ostracizing them from society rather than treating their disorders. Often these people were kept in windowless dungeons, beaten, chained to their beds, and had little to no contact with caregivers. In the late 1700s, a French physician, Philippe Pinel, argued for more humane treatment of the mentally ill. He suggested that they be unchained and talked to, and that’s just what he did for patients at La Salpêtrière in Paris in 1795 (Figure). Patients benefited from this more humane treatment, and many were able to leave the hospital. In the 19th century, Dorothea Dix led reform efforts for mental health care in the United States (Figure). She investigated how those who are mentally ill and poor were cared for, and she discovered an underfunded and unregulated system that perpetuated abuse of this population (Tiffany, 1891). Horrified by her findings, Dix began lobbying various state legislatures and the U.S. Congress for change (Tiffany, 1891). Her efforts led to the creation of the first mental asylums in the United States. Despite reformers’ efforts, however, a typical asylum was filthy, offered very little treatment, and often kept people for decades. At Willard Psychiatric Center in upstate New York, for example, one treatment was to submerge patients in cold baths for long periods of time. Electroshock treatment was also used, and the way the treatment was administered often broke patients’ backs; in 1943, doctors at Willard administered 1,443 shock treatments (Willard Psychiatric Center, 2009). (Electroshock is now called electroconvulsive treatment, and the therapy is still used, but with safeguards and under anesthesia. A brief application of electric stimulus is used to produce a generalized seizure. Controversy continues over its effectiveness versus the side effects.) Many of the wards and rooms were so cold that a glass of water would be frozen by morning (Willard Psychiatric Center, 2009). Willard’s doors were not closed until 1995. Conditions like these remained commonplace until well into the 20th century. Starting in 1954 and gaining popularity in the 1960s, antipsychotic medications were introduced. These proved a tremendous help in controlling the symptoms of certain psychological disorders, such as psychosis. Psychosis was a common diagnosis of individuals in mental hospitals, and it was often evidenced by symptoms like hallucinations and delusions, indicating a loss of contact with reality. Then in 1963, Congress passed and John F. Kennedy signed the Mental Retardation Facilities and Community Mental Health Centers Construction Act, which provided federal support and funding for community mental health centers (National Institutes of Health, 2013). This legislation changed how mental health services were delivered in the United States. It started the process of deinstitutionalization, the closing of large asylums, by providing for people to stay in their communities and be treated locally. In 1955, there were 558,239 severely mentally ill patients institutionalized at public hospitals (Torrey, 1997). By 1994, by percentage of the population, there were 92% fewer hospitalized individuals (Torrey, 1997). MENTAL HEALTH TREATMENT TODAY Today, there are community mental health centers across the nation. They are located in neighborhoods near the homes of clients, and they provide large numbers of people with mental health services of various kinds and for many kinds of problems. Unfortunately, part of what occurred with deinstitutionalization was that those released from institutions were supposed to go to newly created centers, but the system was not set up effectively. Centers were underfunded, staff was not trained to handle severe illnesses such as schizophrenia, there was high staff burnout, and no provision was made for the other services people needed, such as housing, food, and job training. Without these supports, those people released under deinstitutionalization often ended up homeless. Even today, a large portion of the homeless population is considered to be mentally ill (Figure). Statistics show that 26% of homeless adults living in shelters experience mental illness (U.S. Department of Housing and Urban Development [HUD], 2011). Another group of the mentally ill population is involved in the corrections system. According to a 2006 special report by the Bureau of Justice Statistics (BJS), approximately 705,600 mentally ill adults were incarcerated in the state prison system, and another 78,800 were incarcerated in the federal prison system. A further 479,000 were in local jails. According to the study, “people with mental illnesses are overrepresented in probation and parole populations at estimated rates ranging from two to four times the general population” (Prins & Draper, 2009, p. 23). The Treatment Advocacy Center reported that the growing number of mentally ill inmates has placed a burden on the correctional system (Torrey et al., 2014). Today, instead of asylums, there are psychiatric hospitals run by state governments and local community hospitals focused on short-term care. In all types of hospitals, the emphasis is on short-term stays, with the average length of stay being less than two weeks and often only several days. This is partly due to the very high cost of psychiatric hospitalization, which can be about $800 to $1000 per night (Stensland, Watson, & Grazier, 2012). Therefore, insurance coverage often limits the length of time a person can be hospitalized for treatment. Usually individuals are hospitalized only if they are an imminent threat to themselves or others. View this timeline showing the history of mental institutions in the United States. Most people suffering from mental illnesses are not hospitalized. If someone is feeling very depressed, complains of hearing voices, or feels anxious all the time, he or she might seek psychological treatment. A friend, spouse, or parent might refer someone for treatment. The individual might go see his primary care physician first and then be referred to a mental health practitioner. Some people seek treatment because they are involved with the state’s child protective services—that is, their children have been removed from their care due to abuse or neglect. The parents might be referred to psychiatric or substance abuse facilities and the children would likely receive treatment for trauma. If the parents are interested in and capable of becoming better parents, the goal of treatment might be family reunification. For other children whose parents are unable to change—for example, the parent or parents who are heavily addicted to drugs and refuse to enter treatment—the goal of therapy might be to help the children adjust to foster care and/or adoption (Figure). Some people seek therapy because the criminal justice system referred them or required them to go. For some individuals, for example, attending weekly counseling sessions might be a condition of parole. If an individual is mandated to attend therapy, she is seeking services involuntarily. Involuntary treatment refers to therapy that is not the individual’s choice. Other individuals might voluntarily seek treatment. Voluntary treatment means the person chooses to attend therapy to obtain relief from symptoms. Psychological treatment can occur in a variety of places. An individual might go to a community mental health center or a practitioner in private or community practice. A child might see a school counselor, school psychologist, or school social worker. An incarcerated person might receive group therapy in prison. There are many different types of treatment providers, and licensing requirements vary from state to state. Besides psychologists and psychiatrists, there are clinical social workers, marriage and family therapists, and trained religious personnel who also perform counseling and therapy. A range of funding sources pay for mental health treatment: health insurance, government, and private pay. In the past, even when people had health insurance, the coverage would not always pay for mental health services. This changed with the Mental Health Parity and Addiction Equity Act of 2008, which requires group health plans and insurers to make sure there is parity of mental health services (U.S. Department of Labor, n.d.). This means that co-pays, total number of visits, and deductibles for mental health and substance abuse treatment need to be equal to and cannot be more restrictive or harsher than those for physical illnesses and medical/surgical problems. Finding treatment sources is also not always easy: there may be limited options, especially in rural areas and low-income urban areas; waiting lists; poor quality of care available for indigent patients; and financial obstacles such as co-pays, deductibles, and time off from work. Over 85% of the l,669 federally designated mental health professional shortage areas are rural; often primary care physicians and law enforcement are the first-line mental health providers (Ivey, Scheffler, & Zazzali, 1998), although they do not have the specialized training of a mental health professional, who often would be better equipped to provide care. Availability, accessibility, and acceptability (the stigma attached to mental illness) are all problems in rural areas. Approximately two-thirds of those with symptoms receive no care at all (U.S. Department of Health and Human Services, 2005; Wagenfeld, Murray, Mohatt, & DeBruiynb, 1994). At the end of 2013, the U.S. Department of Agriculture announced an investment of $50 million to help improve access and treatment for mental health problems as part of the Obama administration’s effort to strengthen rural communities. Summary It was once believed that people with psychological disorders, or those exhibiting strange behavior, were possessed by demons. These people were forced to take part in exorcisms, were imprisoned, or executed. Later, asylums were built to house the mentally ill, but the patients received little to no treatment, and many of the methods used were cruel. Philippe Pinel and Dorothea Dix argued for more humane treatment of people with psychological disorders. In the mid-1960s, the deinstitutionalization movement gained support and asylums were closed, enabling people with mental illness to return home and receive treatment in their own communities. Some did go to their family homes, but many became homeless due to a lack of resources and support mechanisms. Today, instead of asylums, there are psychiatric hospitals run by state governments and local community hospitals, with the emphasis on short-term stays. However, most people suffering from mental illness are not hospitalized. A person suffering symptoms could speak with a primary care physician, who most likely would refer him to someone who specializes in therapy. The person can receive outpatient mental health services from a variety of sources, including psychologists, psychiatrists, marriage and family therapists, school counselors, clinical social workers, and religious personnel. These therapy sessions would be covered through insurance, government funds, or private (self) pay. Review Questions Who of the following does not support the humane and improved treatment of mentally ill persons? - Philippe Pinel - medieval priests - Dorothea Dix - All of the above Hint: B The process of closing large asylums and providing for people to stay in the community to be treated locally is known as ________. - deinstitutionalization - exorcism - deactivation - decentralization Hint: A Joey was convicted of domestic violence. As part of his sentence, the judge has ordered that he attend therapy for anger management. This is considered ________ treatment. - involuntary - voluntary - forced - mandatory Hint: A Today, most people with psychological problems are not hospitalized. Typically they are only hospitalized if they ________. - have schizophrenia - have insurance - are an imminent threat to themselves or others - require therapy Hint: C Critical Thinking Questions People with psychological disorders have been treated poorly throughout history. Describe some efforts to improve treatment, include explanations for the success or lack thereof. Hint: Beginning in the Middle Ages and up until the mid-20th century, the mentally ill were misunderstood and treated cruelly. In the 1700s, Philippe Pinel advocated for patients to be unchained, and he was able to affect this in a Paris hospital. In the 1800s, Dorothea Dix urged the government to provide better funded and regulated care, which led to the creation of asylums, but treatment generally remained quite poor. Federally mandated deinstitutionalization in the 1960s began the elimination of asylums, but it was often inadequate in providing the infrastructure for replacement treatment. Usually someone is hospitalized only if they are an imminent threat to themselves or others. Describe a situation that might meet these criteria. Hint: Frank is severely depressed. He lost his job one year ago and has not been able to find another one. A few months after losing his job, his home was foreclosed and his wife left him. Lately, he has been thinking that he would be better off dead. He’s begun giving his possessions away and has purchased a handgun. He plans to kill himself on what would have been his 20th wedding anniversary, which is coming up in a few weeks. Personal Application Questions Do you think there is a stigma associated with mentally ill persons today? Why or why not? What are some places in your community that offer mental health services? Would you feel comfortable seeking assistance at one of these facilities? Why or why not?	oercommons	2025-03-18T00:36:06.463980	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15392/overview", "title": "Psychology, Therapy and Treatment", "author": null }
https://oercommons.org/courseware/lesson/15393/overview	Types of Treatment Overview By the end of this section, you will be able to: - Distinguish between psychotherapy and biomedical therapy - Recognize various orientations to psychotherapy - Discuss psychotropic medications and recognize which medications are used to treat specific psychological disorders One of the goals of therapy is to help a person stop repeating and reenacting destructive patterns and to start looking for better solutions to difficult situations. This goal is reflected in the following poem: Autobiography in Five Short Chapters by Portia Nelson (1993) Chapter One I walk down the street. There is a deep hole in the sidewalk. I fall in. I am lost. . . . I am helpless. It isn't my fault. It takes forever to find a way out. Chapter Two I walk down the same street. There is a deep hole in the sidewalk. I pretend I don't see it. I fall in again. I can't believe I am in this same place. But, it isn't my fault. It still takes a long time to get out. Chapter Three I walk down the same street. There is a deep hole in the sidewalk. I see it is there. I still fall in . . . it's a habit . . . but, my eyes are open. I know where I am. It is my fault. I get out immediately. Chapter Four I walk down the same street. There is a deep hole in the sidewalk. I walk around it. Chapter Five I walk down another street. Two types of therapy are psychotherapy and biomedical therapy. Both types of treatment help people with psychological disorders, such as depression, anxiety, and schizophrenia. Psychotherapy is a psychological treatment that employs various methods to help someone overcome personal problems, or to attain personal growth. In modern practice, it has evolved ino what is known as psychodynamic therapy, which will be discussed later. Biomedical therapy involves medication and/or medical procedures to treat psychological disorders. First, we will explore the various psychotherapeutic orientations outlined in Table (many of these orientations were discussed in the Introduction chapter). \| Type \| Description \| Example \| \|---\|---\|---\| \| Psychodynamic psychotherapy \| Talk therapy based on belief that the unconscious and childhood conflicts impact behavior \| Patient talks about his past \| \| Play therapy \| Psychoanalytical therapy wherein interaction with toys is used instead of talk; used in child therapy \| Patient (child) acts out family scenes with dolls \| \| Behavior therapy \| Principles of learning applied to change undesirable behaviors \| Patient learns to overcome fear of elevators through several stages of relaxation techniques \| \| Cognitive therapy \| Awareness of cognitive process helps patients eliminate thought patterns that lead to distress \| Patient learns not to overgeneralize failure based on single failure \| \| Cognitive-behavioral therapy \| Work to change cognitive distortions and self-defeating behaviors \| Patient learns to identify self-defeating behaviors to overcome an eating disorder \| \| Humanistic therapy \| Increase self-awareness and acceptance through focus on conscious thoughts \| Patient learns to articulate thoughts that keep her from achieving her goals \| PSYCHOTHERAPY TECHNIQUES: PSYCHOANALYSIS Psychoanalysis was developed by Sigmund Freud and was the first form of psychotherapy. It was the dominant therapeutic technique in the early 20th century, but it has since waned significantly in popularity. Freud believed most of our psychological problems are the result of repressed impulses and trauma experienced in childhood, and he believed psychoanalysis would help uncover long-buried feelings. In a psychoanalyst’s office, you might see a patient lying on a couch speaking of dreams or childhood memories, and the therapist using various Freudian methods such as free association and dream analysis (Figure). In free association, the patient relaxes and then says whatever comes to mind at the moment. However, Freud felt that the ego would at times try to block, or repress, unacceptable urges or painful conflicts during free association. Consequently, a patient would demonstrate resistance to recalling these thoughts or situations. In dream analysis, a therapist interprets the underlying meaning of dreams. Psychoanalysis is a therapy approach that typically takes years. Over the course of time, the patient reveals a great deal about himself to the therapist. Freud suggested that during this patient-therapist relationship, the patient comes to develop strong feelings for the therapist—maybe positive feelings, maybe negative feelings. Freud called this transference: the patient transfers all the positive or negative emotions associated with the patient’s other relationships to the psychoanalyst. For example, Crystal is seeing a psychoanalyst. During the years of therapy, she comes to see her therapist as a father figure. She transfers her feelings about her father onto her therapist, perhaps in an effort to gain the love and attention she did not receive from her own father. Today, Freud’s psychoanalytical perspective has been expanded upon by the developments of subsequent theories and methodologies: the psychodynamic perspective. This approach to therapy remains centered on the role of people’s internal drives and forces, but treatment is less intensive than Freud’s original model. View a brief video that presents an overview of psychoanalysis theory, research, and practice. PSYCHOTHERAPY: PLAY THERAPY Play therapy is often used with children since they are not likely to sit on a couch and recall their dreams or engage in traditional talk therapy. This technique uses a therapeutic process of play to “help clients prevent or resolve psychosocial difficulties and achieve optimal growth” (O’Connor, 2000, p. 7). The idea is that children play out their hopes, fantasies, and traumas while using dolls, stuffed animals, and sandbox figurines (Figure). Play therapy can also be used to help a therapist make a diagnosis. The therapist observes how the child interacts with toys (e.g., dolls, animals, and home settings) in an effort to understand the roots of the child’s disturbed behavior. Play therapy can be nondirective or directive. In nondirective play therapy, children are encouraged to work through their problems by playing freely while the therapist observes (LeBlanc & Ritchie, 2001). In directive play therapy, the therapist provides more structure and guidance in the play session by suggesting topics, asking questions, and even playing with the child (Harter, 1977). PSYCHOTHERAPY: BEHAVIOR THERAPY In psychoanalysis, therapists help their patients look into their past to uncover repressed feelings. In behavior therapy, a therapist employs principles of learning to help clients change undesirable behaviors—rather than digging deeply into one’s unconscious. Therapists with this orientation believe that dysfunctional behaviors, like phobias and bedwetting, can be changed by teaching clients new, more constructive behaviors. Behavior therapy employs both classical and operant conditioning techniques to change behavior. One type of behavior therapy utilizes classical conditioning techniques. Therapists using these techniques believe that dysfunctional behaviors are conditioned responses. Applying the conditioning principles developed by Ivan Pavlov, these therapists seek to recondition their clients and thus change their behavior. Emmie is eight years old, and frequently wets her bed at night. She’s been invited to several sleepovers, but she won’t go because of her problem. Using a type of conditioning therapy, Emmie begins to sleep on a liquid-sensitive bed pad that is hooked to an alarm. When moisture touches the pad, it sets off the alarm, waking up Emmie. When this process is repeated enough times, Emmie develops an association between urinary relaxation and waking up, and this stops the bedwetting. Emmie has now gone three weeks without wetting her bed and is looking forward to her first sleepover this weekend. One commonly used classical conditioning therapeutic technique is counterconditioning: a client learns a new response to a stimulus that has previously elicited an undesirable behavior. Two counterconditioning techniques are aversive conditioning and exposure therapy. Aversive conditioning uses an unpleasant stimulus to stop an undesirable behavior. Therapists apply this technique to eliminate addictive behaviors, such as smoking, nail biting, and drinking. In aversion therapy, clients will typically engage in a specific behavior (such as nail biting) and at the same time are exposed to something unpleasant, such as a mild electric shock or a bad taste. After repeated associations between the unpleasant stimulus and the behavior, the client can learn to stop the unwanted behavior. Aversion therapy has been used effectively for years in the treatment of alcoholism (Davidson, 1974; Elkins, 1991; Streeton & Whelan, 2001). One common way this occurs is through a chemically based substance known as Antabuse. When a person takes Antabuse and then consumes alcohol, uncomfortable side effects result including nausea, vomiting, increased heart rate, heart palpitations, severe headache, and shortness of breath. Antabuse is repeatedly paired with alcohol until the client associates alcohol with unpleasant feelings, which decreases the client’s desire to consume alcohol. Antabuse creates a conditioned aversion to alcohol because it replaces the original pleasure response with an unpleasant one. In exposure therapy, a therapist seeks to treat clients’ fears or anxiety by presenting them with the object or situation that causes their problem, with the idea that they will eventually get used to it. This can be done via reality, imagination, or virtual reality. Exposure therapy was first reported in 1924 by Mary Cover Jones, who is considered the mother of behavior therapy. Jones worked with a boy named Peter who was afraid of rabbits. Her goal was to replace Peter’s fear of rabbits with a conditioned response of relaxation, which is a response that is incompatible with fear (Figure). How did she do it? Jones began by placing a caged rabbit on the other side of a room with Peter while he ate his afternoon snack. Over the course of several days, Jones moved the rabbit closer and closer to where Peter was seated with his snack. After two months of being exposed to the rabbit while relaxing with his snack, Peter was able to hold the rabbit and pet it while eating (Jones, 1924). Thirty years later, Joseph Wolpe (1958) refined Jones’s techniques, giving us the behavior therapy technique of exposure therapy that is used today. A popular form of exposure therapy is systematic desensitization, wherein a calm and pleasant state is gradually associated with increasing levels of anxiety-inducing stimuli. The idea is that you can’t be nervous and relaxed at the same time. Therefore, if you can learn to relax when you are facing environmental stimuli that make you nervous or fearful, you can eventually eliminate your unwanted fear response (Wolpe, 1958) (Figure). How does exposure therapy work? Jayden is terrified of elevators. Nothing bad has ever happened to him on an elevator, but he’s so afraid of elevators that he will always take the stairs. That wasn’t a problem when Jayden worked on the second floor of an office building, but now he has a new job—on the 29th floor of a skyscraper in downtown Los Angeles. Jayden knows he can’t climb 29 flights of stairs in order to get to work each day, so he decided to see a behavior therapist for help. The therapist asks Jayden to first construct a hierarchy of elevator-related situations that elicit fear and anxiety. They range from situations of mild anxiety such as being nervous around the other people in the elevator, to the fear of getting an arm caught in the door, to panic-provoking situations such as getting trapped or the cable snapping. Next, the therapist uses progressive relaxation. She teaches Jayden how to relax each of his muscle groups so that he achieves a drowsy, relaxed, and comfortable state of mind. Once he’s in this state, she asks Jayden to imagine a mildly anxiety-provoking situation. Jayden is standing in front of the elevator thinking about pressing the call button. If this scenario causes Jayden anxiety, he lifts his finger. The therapist would then tell Jayden to forget the scene and return to his relaxed state. She repeats this scenario over and over until Jayden can imagine himself pressing the call button without anxiety. Over time the therapist and Jayden use progressive relaxation and imagination to proceed through all of the situations on Jayden’s hierarchy until he becomes desensitized to each one. After this, Jayden and the therapist begin to practice what he only previously envisioned in therapy, gradually going from pressing the button to actually riding an elevator. The goal is that Jayden will soon be able to take the elevator all the way up to the 29th floor of his office without feeling any anxiety. Sometimes, it’s too impractical, expensive, or embarrassing to re-create anxiety- producing situations, so a therapist might employ virtual reality exposure therapy by using a simulation to help conquer fears. Virtual reality exposure therapy has been used effectively to treat numerous anxiety disorders such as the fear of public speaking, claustrophobia (fear of enclosed spaces), aviophobia (fear of flying), and post-traumatic stress disorder (PTSD), a trauma and stressor-related disorder (Gerardi, Cukor, Difede, Rizzo, & Rothbaum, 2010). A new virtual reality exposure therapy is being used to treat PTSD in soldiers. Virtual Iraq is a simulation that mimics Middle Eastern cities and desert roads with situations similar to those soldiers experienced while deployed in Iraq. This method of virtual reality exposure therapy has been effective in treating PTSD for combat veterans. Approximately 80% of participants who completed treatment saw clinically significant reduction in their symptoms of PTSD, anxiety, and depression (Rizzo et al., 2010). Watch this Virtual Iraq video showing soldiers being treated via simulation. Some behavior therapies employ operant conditioning. Recall what you learned about operant conditioning: We have a tendency to repeat behaviors that are reinforced. What happens to behaviors that are not reinforced? They become extinguished. These principles can be applied to help people with a wide range of psychological problems. For instance, operant conditioning techniques designed to reinforce positive behaviors and punish unwanted behaviors have been an effective tool to help children with autism (Lovaas, 1987, 2003; Sallows & Graupner, 2005; Wolf & Risley, 1967). This technique is called Applied Behavior Analysis (ABA). In this treatment, child-specific reinforcers (e.g., stickers, praise, candy, bubbles, and extra play time) are used to reward and motivate autistic children when they demonstrate desired behaviors such as sitting on a chair when requested, verbalizing a greeting, or making eye contact. Punishment such as a timeout or a sharp “No!” from the therapist or parent might be used to discourage undesirable behaviors such as pinching, scratching, and pulling hair. One popular operant conditioning intervention is called the token economy. This involves a controlled setting where individuals are reinforced for desirable behaviors with tokens, such as a poker chip, that can be exchanged for items or privileges. Token economies are often used in psychiatric hospitals to increase patient cooperation and activity levels. Patients are rewarded with tokens when they engage in positive behaviors (e.g., making their beds, brushing their teeth, coming to the cafeteria on time, and socializing with other patients). They can later exchange the tokens for extra TV time, private rooms, visits to the canteen, and so on (Dickerson, Tenhula, & Green-Paden, 2005). PSYCHOTHERAPY: COGNITIVE THERAPY Cognitive therapy is a form of psychotherapy that focuses on how a person’s thoughts lead to feelings of distress. The idea behind cognitive therapy is that how you think determines how you feel and act. Cognitive therapists help their clients change dysfunctional thoughts in order to relieve distress. They help a client see how they misinterpret a situation (cognitive distortion). For example, a client may overgeneralize. Because Ray failed one test in his Psychology 101 course, he feels he is stupid and worthless. These thoughts then cause his mood to worsen. Therapists also help clients recognize when they blow things out of proportion. Because Ray failed his Psychology 101 test, he has concluded that he’s going to fail the entire course and probably flunk out of college altogether. These errors in thinking have contributed to Ray’s feelings of distress. His therapist will help him challenge these irrational beliefs, focus on their illogical basis, and correct them with more logical and rational thoughts and beliefs. Cognitive therapy was developed by psychiatrist Aaron Beck in the 1960s. His initial focus was on depression and how a client’s self-defeating attitude served to maintain a depression despite positive factors in her life (Beck, Rush, Shaw, & Emery, 1979) (Figure). Through questioning, a cognitive therapist can help a client recognize dysfunctional ideas, challenge catastrophizing thoughts about themselves and their situations, and find a more positive way to view things (Beck, 2011). View a brief video in which Judith Beck talks about cognitive therapy and conducts a session with a client. PSYCHOTHERAPY: COGNITIVE-BEHAVIORAL THERAPY Cognitive-behavioral therapists focus much more on present issues than on a patient’s childhood or past, as in other forms of psychotherapy. One of the first forms of cognitive-behavioral therapy was rational emotive therapy (RET), which was founded by Albert Ellis and grew out of his dislike of Freudian psychoanalysis (Daniel, n.d.). Behaviorists such as Joseph Wolpe also influenced Ellis’s therapeutic approach (National Association of Cognitive-Behavioral Therapists, 2009). Cognitive-behavioral therapy (CBT) helps clients examine how their thoughts affect their behavior. It aims to change cognitive distortions and self-defeating behaviors. In essence, this approach is designed to change the way people think as well as how they act. It is similar to cognitive therapy in that CBT attempts to make individuals aware of their irrational and negative thoughts and helps people replace them with new, more positive ways of thinking. It is also similar to behavior therapies in that CBT teaches people how to practice and engage in more positive and healthy approaches to daily situations. In total, hundreds of studies have shown the effectiveness of cognitive-behavioral therapy in the treatment of numerous psychological disorders such as depression, PTSD, anxiety disorders, eating disorders, bipolar disorder, and substance abuse (Beck Institute for Cognitive Behavior Therapy, n.d.). For example, CBT has been found to be effective in decreasing levels of hopelessness and suicidal thoughts in previously suicidal teenagers (Alavi, Sharifi, Ghanizadeh, & Dehbozorgi, 2013). Cognitive-behavioral therapy has also been effective in reducing PTSD in specific populations, such as transit workers (Lowinger & Rombom, 2012). Cognitive-behavioral therapy aims to change cognitive distortions and self-defeating behaviors using techniques like the ABC model. With this model, there is an Action (sometimes called an activating event), the Belief about the event, and the Consequences of this belief. Let’s say, Jon and Joe both go to a party. Jon and Joe each have met a young woman at the party: Jon is talking with Megan most of the party, and Joe is talking with Amanda. At the end of the party, Jon asks Megan for her phone number and Joe asks Amanda. Megan tells Jon she would rather not give him her number, and Amanda tells Joe the same thing. Both Jon and Joe are surprised, as they thought things were going well. What can Jon and Joe tell themselves about why the women were not interested? Let’s say Jon tells himself he is a loser, or is ugly, or “has no game.” Jon then gets depressed and decides not to go to another party, which starts a cycle that keeps him depressed. Joe tells himself that he had bad breath, goes out and buys a new toothbrush, goes to another party, and meets someone new. Jon’s belief about what happened results in a consequence of further depression, whereas Joe’s belief does not. Jon is internalizing the attribution or reason for the rebuffs, which triggers his depression. On the other hand, Joe is externalizing the cause, so his thinking does not contribute to feelings of depression. Cognitive-behavioral therapy examines specific maladaptive and automatic thoughts and cognitive distortions. Some examples of cognitive distortions are all-or-nothing thinking, overgeneralization, and jumping to conclusions. In overgeneralization, someone takes a small situation and makes it huge—for example, instead of saying, “This particular woman was not interested in me,” the man says, “I am ugly, a loser, and no one is ever going to be interested in me.” All or nothing thinking, which is a common type of cognitive distortion for people suffering from depression, reflects extremes. In other words, everything is black or white. After being turned down for a date, Jon begins to think, “No woman will ever go out with me. I’m going to be alone forever.” He begins to feel anxious and sad as he contemplates his future. The third kind of distortion involves jumping to conclusions—assuming that people are thinking negatively about you or reacting negatively to you, even though there is no evidence. Consider the example of Savannah and Hillaire, who recently met at a party. They have a lot in common, and Savannah thinks they could become friends. She calls Hillaire to invite her for coffee. Since Hillaire doesn’t answer, Savannah leaves her a message. Several days go by and Savannah never hears back from her potential new friend. Maybe Hillaire never received the message because she lost her phone or she is too busy to return the phone call. But if Savannah believes that Hillaire didn’t like Savannah or didn’t want to be her friend, she is demonstrating the cognitive distortion of jumping to conclusions. How effective is CBT? One client said this about his cognitive-behavioral therapy: I have had many painful episodes of depression in my life, and this has had a negative effect on my career and has put considerable strain on my friends and family. The treatments I have received, such as taking antidepressants and psychodynamic counseling, have helped [me] to cope with the symptoms and to get some insights into the roots of my problems. CBT has been by far the most useful approach I have found in tackling these mood problems. It has raised my awareness of how my thoughts impact on my moods. How the way I think about myself, about others and about the world can lead me into depression. It is a practical approach, which does not dwell so much on childhood experiences, whilst acknowledging that it was then that these patterns were learned. It looks at what is happening now, and gives tools to manage these moods on a daily basis. (Martin, 2007, n.p.) PSYCHOTHERAPY: HUMANISTIC THERAPY Humanistic psychology focuses on helping people achieve their potential. So it makes sense that the goal of humanistic therapy is to help people become more self-aware and accepting of themselves. In contrast to psychoanalysis, humanistic therapists focus on conscious rather than unconscious thoughts. They also emphasize the patient’s present and future, as opposed to exploring the patient’s past. Psychologist Carl Rogers developed a therapeutic orientation known as Rogerian, or client-centered therapy. Note the change from patients to clients. Rogers (1951) felt that the term patient suggested the person seeking help was sick and looking for a cure. Since this is a form of nondirective therapy, a therapeutic approach in which the therapist does not give advice or provide interpretations but helps the person to identify conflicts and understand feelings, Rogers (1951) emphasized the importance of the person taking control of his own life to overcome life’s challenges. In client-centered therapy, the therapist uses the technique of active listening. In active listening, the therapist acknowledges, restates, and clarifies what the client expresses. Therapists also practice what Rogers called unconditional positive regard, which involves not judging clients and simply accepting them for who they are. Rogers (1951) also felt that therapists should demonstrate genuineness, empathy, and acceptance toward their clients because this helps people become more accepting of themselves, which results in personal growth. EVALUATING VARIOUS FORMS OF PSYCHOTHERAPY How can we assess the effectiveness of psychotherapy? Is one technique more effective than another? For anyone considering therapy, these are important questions. According to the American Psychological Association, three factors work together to produce successful treatment. The first is the use of evidence-based treatment that is deemed appropriate for your particular issue. The second important factor is the clinical expertise of the psychologist or therapist. The third factor is your own characteristics, values, preferences, and culture. Many people begin psychotherapy feeling like their problem will never be resolved; however, psychotherapy helps people see that they can do things to make their situation better. Psychotherapy can help reduce a person’s anxiety, depression, and maladaptive behaviors. Through psychotherapy, individuals can learn to engage in healthy behaviors designed to help them better express emotions, improve relationships, think more positively, and perform more effectively at work or school. Many studies have explored the effectiveness of psychotherapy. For example, one large-scale study that examined 16 meta-analyses of CBT reported that it was equally effective or more effective than other therapies in treating PTSD, generalized anxiety disorder, depression, and social phobia (Butlera, Chapmanb, Formanc, & Becka, 2006). Another study found that CBT was as effective at treating depression (43% success rate) as prescription medication (50% success rate) compared to the placebo rate of 25% (DeRubeis et al., 2005). Another meta-analysis found that psychodynamic therapy was also as effective at treating these types of psychological issues as CBT (Shedler, 2010). However, no studies have found one psychotherapeutic approach more effective than another (Abbass, Kisely, & Kroenke, 2006; Chorpita et al., 2011), nor have they shown any relationship between a client’s treatment outcome and the level of the clinician’s training or experience (Wampold, 2007). Regardless of which type of psychotherapy an individual chooses, one critical factor that determines the success of treatment is the person’s relationship with the psychologist or therapist. BIOMEDICAL THERAPIES Individuals can be prescribed biologically based treatments or psychotropic medications that are used to treat mental disorders. While these are often used in combination with psychotherapy, they also are taken by individuals not in therapy. This is known as biomedical therapy. Medications used to treat psychological disorders are called psychotropic medications and are prescribed by medical doctors, including psychiatrists. In Louisiana and New Mexico, psychologists are able to prescribe some types of these medications (American Psychological Association, 2014). Different types and classes of medications are prescribed for different disorders. A depressed person might be given an antidepressant, a bipolar individual might be given a mood stabilizer, and a schizophrenic individual might be given an antipsychotic. These medications treat the symptoms of a psychological disorder. They can help people feel better so that they can function on a daily basis, but they do not cure the disorder. Some people may only need to take a psychotropic medication for a short period of time. Others with severe disorders like bipolar disorder or schizophrenia may need to take psychotropic medication for a long time. Table shows the types of medication and how they are used. \| Type of Medication \| Used to Treat \| Brand Names of Commonly Prescribed Medications \| How They Work \| Side Effects \| \|---\|---\|---\|---\|---\| \| Antipsychotics (developed in the 1950s) \| Schizophrenia and other types of severe thought disorders \| Haldol, Mellaril, Prolixin, Thorazine \| Treat positive psychotic symptoms such as auditory and visual hallucinations, delusions, and paranoia by blocking the neurotransmitter dopamine \| Long-term use can lead to tardive dyskinesia, involuntary movements of the arms, legs, tongue and facial muscles, resulting in Parkinson’s-like tremors \| \| Atypical Antipsychotics (developed in the late 1980s) \| Schizophrenia and other types of severe thought disorders \| Abilify, Risperdal, Clozaril \| Treat the negative symptoms of schizophrenia, such as withdrawal and apathy, by targeting both dopamine and serotonin receptors; newer medications may treat both positive and negative symptoms \| Can increase the risk of obesity and diabetes as well as elevate cholesterol levels; constipation, dry mouth, blurred vision, drowsiness, and dizziness \| \| Anti-depressants \| Depression and increasingly for anxiety \| Paxil, Prozac, Zoloft (selective serotonin reuptake inhibitors, [SSRIs]); Tofranil and Elavil (tricyclics) \| Alter levels of neurotransmitters such as serotonin and norepinephrine \| SSRIs: headache, nausea, weight gain, drowsiness, reduced sex drive Tricyclics: dry mouth, constipation, blurred vision, drowsiness, reduced sex drive, increased risk of suicide \| \| Anti-anxiety agents \| Anxiety and agitation that occur in OCD, PTSD, panic disorder, and social phobia \| Xanax, Valium, Ativan \| Depress central nervous system activity \| Drowsiness, dizziness, headache, fatigue, lightheadedness \| \| Mood Stabilizers \| Bipolar disorder \| Lithium, Depakote, Lamictal, Tegretol \| Treat episodes of mania as well as depression \| Excessive thirst, irregular heartbeat, itching/rash, swelling (face, mouth, and extremities), nausea, loss of appetite \| \| Stimulants \| ADHD \| Adderall, Ritalin \| Improve ability to focus on a task and maintain attention \| Decreased appetite, difficulty sleeping, stomachache, headache \| Another biologically based treatment that continues to be used, although infrequently, is electroconvulsive therapy (ECT) (formerly known by its unscientific name as electroshock therapy). It involves using an electrical current to induce seizures to help alleviate the effects of severe depression. The exact mechanism is unknown, although it does help alleviate symptoms for people with severe depression who have not responded to traditional drug therapy (Pagnin, de Queiroz, Pini, & Cassano, 2004). About 85% of people treated with ECT improve (Reti, n.d.). However, the memory loss associated with repeated administrations has led to it being implemented as a last resort (Donahue, 2000; Prudic, Peyser, & Sackeim, 2000). A more recent alternative is transcranial magnetic stimulation (TMS), a procedure approved by the FDA in 2008 that uses magnetic fields to stimulate nerve cells in the brain to improve depression symptoms; it is used when other treatments have not worked (Mayo Clinic, 2012). Evidence-based Practice A buzzword in therapy today is evidence-based practice. However, it’s not a novel concept but one that has been used in medicine for at least two decades. Evidence-based practice is used to reduce errors in treatment selection by making clinical decisions based on research (Sackett & Rosenberg, 1995). In any case, evidence-based treatment is on the rise in the field of psychology. So what is it, and why does it matter? In an effort to determine which treatment methodologies are evidenced-based, professional organizations such as the American Psychological Association (APA) have recommended that specific psychological treatments be used to treat certain psychological disorders (Chambless & Ollendick, 2001). According to the APA (2005), “Evidence-based practice in psychology (EBPP) is the integration of the best available research with clinical expertise in the context of patient characteristics, culture, and preferences” (p. 1). The foundational idea behind evidence based treatment is that best practices are determined by research evidence that has been compiled by comparing various forms of treatment (Charman & Barkham, 2005). These treatments are then operationalized and placed in treatment manuals—trained therapists follow these manuals. The benefits are that evidence-based treatment can reduce variability between therapists to ensure that a specific approach is delivered with integrity (Charman & Barkham, 2005). Therefore, clients have a higher chance of receiving therapeutic interventions that are effective at treating their specific disorder. While EBPP is based on randomized control trials, critics of EBPP reject it stating that the results of trials cannot be applied to individuals and instead determinations regarding treatment should be based on a therapist’s judgment (Mullen & Streiner, 2004). Summary Psychoanalysis was developed by Sigmund Freud. Freud’s theory is that a person’s psychological problems are the result of repressed impulses or childhood trauma. The goal of the therapist is to help a person uncover buried feelings by using techniques such as free association and dream analysis. Play therapy is a psychodynamic therapy technique often used with children. The idea is that children play out their hopes, fantasies, and traumas, using dolls, stuffed animals, and sandbox figurines. In behavior therapy, a therapist employs principles of learning from classical and operant conditioning to help clients change undesirable behaviors. Counterconditioning is a commonly used therapeutic technique in which a client learns a new response to a stimulus that has previously elicited an undesirable behavior via classical conditioning. Principles of operant conditioning can be applied to help people deal with a wide range of psychological problems. Token economy is an example of a popular operant conditioning technique. Cognitive therapy is a technique that focuses on how thoughts lead to feelings of distress. The idea behind cognitive therapy is that how you think determines how you feel and act. Cognitive therapists help clients change dysfunctional thoughts in order to relieve distress. Cognitive-behavioral therapy explores how our thoughts affect our behavior. Cognitive-behavioral therapy aims to change cognitive distortions and self-defeating behaviors. Humanistic therapy focuses on helping people achieve their potential. One form of humanistic therapy developed by Carl Rogers is known as client-centered or Rogerian therapy. Client-centered therapists use the techniques of active listening, unconditional positive regard, genuineness, and empathy to help clients become more accepting of themselves. Often in combination with psychotherapy, people can be prescribed biologically based treatments such as psychotropic medications and/or other medical procedures such as electro-convulsive therapy. Review Questions The idea behind ________ is that how you think determines how you feel and act. - cognitive therapy - cognitive-behavioral therapy - behavior therapy - client-centered therapy Hint: A Mood stabilizers, such as lithium, are used to treat ________. - anxiety disorders - depression - bipolar disorder - ADHD Hint: C Clay is in a therapy session. The therapist asks him to relax and say whatever comes to his mind at the moment. This therapist is using ________, which is a technique of ________. - active listening; client-centered therapy - systematic desensitization; behavior therapy - transference; psychoanalysis - free association; psychoanalysis Hint: D Critical Thinking Question Imagine that you are a psychiatrist. Your patient, Pat, comes to you with the following symptoms: anxiety and feelings of sadness. Which therapeutic approach would you recommend and why? Hint: I would recommend psychodynamic talk therapy or cognitive therapy to help the person see how her thoughts and behaviors are having negative effects. Personal Application Question If you were to choose a therapist practicing one of the techniques presented in this section, which kind of therapist would you choose and why?	oercommons	2025-03-18T00:36:06.510342	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15393/overview", "title": "Psychology, Therapy and Treatment", "author": null }
https://oercommons.org/courseware/lesson/15394/overview	Treatment Modalities Overview By the end of this section, you will be able to: - Distinguish between the various modalities of treatment - Discuss benefits of group therapy Once a person seeks treatment, whether voluntarily or involuntarily, he has an intake done to assess his clinical needs. An intake is the therapist’s first meeting with the client. The therapist gathers specific information to address the client’s immediate needs, such as the presenting problem, the client’s support system, and insurance status. The therapist informs the client about confidentiality, fees, and what to expect in treatment. Confidentiality means the therapist cannot disclose confidential communications to any third party unless mandated or permitted by law to do so. During the intake, the therapist and client will work together to discuss treatment goals. Then a treatment plan will be formulated, usually with specific measurable objectives. Also, the therapist and client will discuss how treatment success will be measured and the estimated length of treatment. There are several different modalities of treatment (Figure): Individual therapy, family therapy, couples therapy, and group therapy are the most common. INDIVIDUAL THERAPY In individual therapy, also known as individual psychotherapy or individual counseling, the client and clinician meet one-on-one (usually from 45 minutes to 1 hour). These meetings typically occur weekly or every other week, and sessions are conducted in a confidential and caring environment (Figure). The clinician will work with clients to help them explore their feelings, work through life challenges, identify aspects of themselves and their lives that they wish to change, and set goals to help them work towards these changes. A client might see a clinician for only a few sessions, or the client may attend individual therapy sessions for a year or longer. The amount of time spent in therapy depends on the needs of the client as well as her personal goals. GROUP THERAPY In group therapy, a clinician meets together with several clients with similar problems (Figure). When children are placed in group therapy, it is particularly important to match clients for age and problems. One benefit of group therapy is that it can help decrease a client’s shame and isolation about a problem while offering needed support, both from the therapist and other members of the group (American Psychological Association, 2014). A nine-year-old sexual abuse victim, for example, may feel very embarrassed and ashamed. If he is placed in a group with other sexually abused boys, he will realize that he is not alone. A child struggling with poor social skills would likely benefit from a group with a specific curriculum to foster special skills. A woman suffering from post-partum depression could feel less guilty and more supported by being in a group with similar women. Group therapy also has some specific limitations. Members of the group may be afraid to speak in front of other people because sharing secrets and problems with complete strangers can be stressful and overwhelming. There may be personality clashes and arguments among group members. There could also be concerns about confidentiality: Someone from the group might share what another participant said to people outside of the group. Another benefit of group therapy is that members can confront each other about their patterns. For those with some types of problems, such as sexual abusers, group therapy is the recommended treatment. Group treatment for this population is considered to have several benefits: Group treatment is more economical than individual, couples, or family therapy. Sexual abusers often feel more comfortable admitting and discussing their offenses in a treatment group where others are modeling openness. Clients often accept feedback about their behavior more willingly from other group members than from therapists. Finally, clients can practice social skills in group treatment settings. (McGrath, Cumming, Burchard, Zeoli, & Ellerby, 2009) Groups that have a strong educational component are called psycho-educational groups. For example, a group for children whose parents have cancer might discuss in depth what cancer is, types of treatment for cancer, and the side effects of treatments, such as hair loss. Often, group therapy sessions with children take place in school. They are led by a school counselor, a school psychologist, or a school social worker. Groups might focus on test anxiety, social isolation, self-esteem, bullying, or school failure (Shechtman, 2002). Whether the group is held in school or in a clinician’s office, group therapy has been found to be effective with children facing numerous kinds of challenges (Shechtman, 2002). During a group session, the entire group could reflect on an individual’s problem or difficulties, and others might disclose what they have done in that situation. When a clinician is facilitating a group, the focus is always on making sure that everyone benefits and participates in the group and that no one person is the focus of the entire session. Groups can be organized in various ways: some have an overarching theme or purpose, some are time-limited, some have open membership that allows people to come and go, and some are closed. Some groups are structured with planned activities and goals, while others are unstructured: There is no specific plan, and group members themselves decide how the group will spend its time and on what goals it will focus. This can become a complex and emotionally charged process, but it is also an opportunity for personal growth (Page & Berkow, 1994). COUPLES THERAPY Couples therapy involves two people in an intimate relationship who are having difficulties and are trying to resolve them (Figure). The couple may be dating, partnered, engaged, or married. The primary therapeutic orientation used in couples counseling is cognitive-behavioral therapy (Rathus & Sanderson, 1999). Couples meet with a therapist to discuss conflicts and/or aspects of their relationship that they want to change. The therapist helps them see how their individual backgrounds, beliefs, and actions are affecting their relationship. Often, a therapist tries to help the couple resolve these problems, as well as implement strategies that will lead to a healthier and happier relationship, such as how to listen, how to argue, and how to express feelings. However, sometimes, after working with a therapist, a couple will realize that they are too incompatible and will decide to separate. Some couples seek therapy to work out their problems, while others attend therapy to determine whether staying together is the best solution. Counseling couples in a high-conflict and volatile relationship can be difficult. In fact, psychologists Peter Pearson and Ellyn Bader, who founded the Couples Institute in Palo Alto, California, have compared the experience of the clinician in couples’ therapy to be like “piloting a helicopter in a hurricane” (Weil, 2012, para. 7). FAMILY THERAPY Family therapy is a special form of group therapy, consisting of one or more families. Although there are many theoretical orientations in family therapy, one of the most predominant is the systems approach. The family is viewed as an organized system, and each individual within the family is a contributing member who creates and maintains processes within the system that shape behavior (Minuchin, 1985). Each member of the family influences and is influenced by the others. The goal of this approach is to enhance the growth of each family member as well as that of the family as a whole. Often, dysfunctional patterns of communication that develop between family members can lead to conflict. A family with this dynamic might wish to attend therapy together rather than individually. In many cases, one member of the family has problems that detrimentally affect everyone. For example, a mother’s depression, teen daughter’s eating disorder, or father’s alcohol dependence could affect all members of the family. The therapist would work with all members of the family to help them cope with the issue, and to encourage resolution and growth in the case of the individual family member with the problem. With family therapy, the nuclear family (i.e., parents and children) or the nuclear family plus whoever lives in the household (e.g., grandparent) come into treatment. Family therapists work with the whole family unit to heal the family. There are several different types of family therapy. In structural family therapy, the therapist examines and discusses the boundaries and structure of the family: who makes the rules, who sleeps in the bed with whom, how decisions are made, and what are the boundaries within the family. In some families, the parents do not work together to make rules, or one parent may undermine the other, leading the children to act out. The therapist helps them resolve these issues and learn to communicate more effectively. Watch this video to view a structural family session. In strategic family therapy, the goal is to address specific problems within the family that can be dealt with in a relatively short amount of time. Typically, the therapist would guide what happens in the therapy session and design a detailed approach to resolving each member’s problem (Madanes, 1991). Summary There are several modalities of treatment: individual therapy, group therapy, couples therapy, and family therapy are the most common. In an individual therapy session, a client works one-on-one with a trained therapist. In group therapy, usually 5–10 people meet with a trained group therapist to discuss a common issue (e.g., divorce, grief, eating disorders, substance abuse, or anger management). Couples therapy involves two people in an intimate relationship who are having difficulties and are trying to resolve them. The couple may be dating, partnered, engaged, or married. The therapist helps them resolve their problems as well as implement strategies that will lead to a healthier and happier relationship. Family therapy is a special form of group therapy. The therapy group is made up of one or more families. The goal of this approach is to enhance the growth of each individual family member and the family as a whole. Review Questions A treatment modality in which 5–10 people with the same issue or concern meet together with a trained clinician is known as ________. - family therapy - couples therapy - group therapy - self-help group Hint: C What happens during an intake? - The therapist gathers specific information to address the client’s immediate needs such as the presenting problem, the client’s support system, and insurance status. The therapist informs the client about confidentiality, fees, and what to expect in a therapy session. - The therapist guides what happens in the therapy session and designs a detailed approach to resolving each member’s presenting problem. - The therapist meets with a couple to help them see how their individual backgrounds, beliefs, and actions are affecting their relationship. - The therapist examines and discusses with the family the boundaries and structure of the family: For example, who makes the rules, who sleeps in the bed with whom, and how decisions are made. Hint: A Critical Thinking Question Compare and contrast individual and group therapies. Hint: In an individual therapy session, a client works one-on-one with a trained therapist. In group therapy, usually 5–10 people meet with a trained group therapist to discuss a common issue, such as divorce, grief, eating disorder, substance abuse, or anger management. Personal Application Your best friend tells you that she is concerned about her cousin. The cousin—a teenage girl—is constantly coming home after her curfew, and your friend suspects that she has been drinking. What treatment modality would you recommend to your friend and why?	oercommons	2025-03-18T00:36:06.538912	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15394/overview", "title": "Psychology, Therapy and Treatment", "author": null }
https://oercommons.org/courseware/lesson/15395/overview	Substance-Related and Addictive Disorders: A Special Case Overview By the end of this section, you will be able to: - Recognize the goal of substance-related and addictive disorders treatment - Discuss what makes for effective treatment - Describe how comorbid disorders are treated Addiction is often viewed as a chronic disease (Figure). The choice to use a substance is initially voluntary; however, because chronic substance use can permanently alter the neural structure in the prefrontal cortex, an area of the brain associated with decision-making and judgment, a person becomes driven to use drugs and/or alcohol (Muñoz-Cuevas, Athilingam, Piscopo, & Wilbrecht, 2013). This helps explain why relapse rates tend to be high. About 40%–60% of individuals relapse, which means they return to abusing drugs and/or alcohol after a period of improvement (National Institute on Drug Abuse [NIDA], 2008). The goal of substance-related treatment is to help an addicted person stop compulsive drug-seeking behaviors (NIDA, 2012). This means an addicted person will need long-term treatment, similar to a person battling a chronic physical disease such as hypertension or diabetes. Treatment usually includes behavioral therapy and/or medication, depending on the individual (NIDA, 2012). Specialized therapies have also been developed for specific types of substance-related disorders, including alcohol, cocaine, and opioids (McGovern & Carroll, 2003). Substance-related treatment is considered much more cost-effective than incarceration or not treating those with addictions (NIDA, 2012) (Figure). WHAT MAKES TREATMENT EFFECTIVE? Specific factors make substance-related treatment much more effective. One factor is duration of treatment. Generally, the addict needs to be in treatment for at least three months to achieve a positive outcome (Simpson, 1981; Simpson, Joe, & Bracy, 1982; NIDA, 2012). This is due to the psychological, physiological, behavioral, and social aspects of abuse (Simpson, 1981; Simpson et al., 1982; NIDA, 2012). While in treatment, an addict might receive behavior therapy, which can help motivate the addict to participate in the treatment program and teach strategies for dealing with cravings and how to prevent relapse. Also, treatment needs to be holistic and address multiple needs, not just the drug addiction. This means that treatment will address factors such as communication, stress management, relationship issues, parenting, vocational concerns, and legal concerns (McGovern & Carroll, 2003; NIDA, 2012). While individual therapy is used in the treatment of substance-related disorders, group therapy is the most widespread treatment modality (Weiss, Jaffee, de Menil, & Cogley, 2004). The rationale behind using group therapy for addiction treatment is that addicts are much more likely to maintain sobriety in a group format. It has been suggested that this is due to the rewarding and therapeutic benefits of the group, such as support, affiliation, identification, and even confrontation (Center for Substance Abuse Treatment, 2005). For teenagers, the whole family often needs to participate in treatment to address issues such as family dynamics, communication, and relapse prevention. Family involvement in teen drug addiction is vital. Research suggests that greater parental involvement is correlated with a greater reduction in use by teen substance abusers. Also, mothers who participated in treatment displayed better mental health and greater warmth toward their children (Bertrand et al., 2013). However, neither individual nor group therapy has been found to be more effective (Weiss et al., 2004). Regardless of the type of treatment service, the primary focus is on abstinence or at the very least a significant reduction in use (McGovern & Carroll, 2003). Treatment also usually involves medications to detox the addict safely after an overdose, to prevent seizures and agitation that often occur in detox, to prevent reuse of the drug, and to manage withdrawal symptoms. Getting off drugs often involves the use of drugs—some of which can be just as addictive. Detox can be difficult and dangerous. Watch this video to find out more about treating substance-related disorders using the biological, behavioral, and psychodynamic approaches. COMORBID DISORDERS Frequently, a person who is addicted to drugs and/or alcohol has an additional psychological disorder. Saying a person has comorbid disorders means the individual has two or more diagnoses. This can often be a substance-related diagnosis and another psychiatric diagnosis, such as depression, bipolar disorder, or schizophrenia. These individuals fall into the category of mentally ill and chemically addicted (MICA)—their problems are often chronic and expensive to treat, with limited success. Compared with the overall population, substance abusers are twice as likely to have a mood or anxiety disorder. Drug abuse can cause symptoms of mood and anxiety disorders and the reverse is also true—people with debilitating symptoms of a psychiatric disorder may self-medicate and abuse substances. In cases of comorbidity, the best treatment is thought to address both (or multiple) disorders simultaneously (NIDA, 2012). Behavior therapies are used to treat comorbid conditions, and in many cases, psychotropic medications are used along with psychotherapy. For example, evidence suggests that bupropion (trade names: Wellbutrin and Zyban), approved for treating depression and nicotine dependence, might also help reduce craving and use of the drug methamphetamine (NIDA, 2011). However, more research is needed to better understand how these medications work—particularly when combined in patients with comorbidities. Summary Addiction is often viewed as a chronic disease that rewires the brain. This helps explain why relapse rates tend to be high, around 40%–60% (McLellan, Lewis, & O’Brien, & Kleber, 2000). The goal of treatment is to help an addict stop compulsive drug-seeking behaviors. Treatment usually includes behavioral therapy, which can take place individually or in a group setting. Treatment may also include medication. Sometimes a person has comorbid disorders, which usually means that they have a substance-related disorder diagnosis and another psychiatric diagnosis, such as depression, bipolar disorder, or schizophrenia. The best treatment would address both problems simultaneously. Review Questions What is the minimum amount of time addicts should receive treatment if they are to achieve a desired outcome? - 3 months - 6 months - 9 months - 12 months Hint: A When an individual has two or more diagnoses, which often includes a substance-related diagnosis and another psychiatric diagnosis, this is known as ________. - bipolar disorder - comorbid disorder - codependency - bi-morbid disorder Hint: B John was drug-free for almost six months. Then he started hanging out with his addict friends, and he has now started abusing drugs again. This is an example of ________. - release - reversion - re-addiction - relapse Hint: D Critical Thinking Question You are conducting an intake assessment. Your client is a 45-year-old single, employed male with cocaine dependence. He failed a drug screen at work and is mandated to treatment by his employer if he wants to keep his job. Your client admits that he needs help. Why would you recommend group therapy for him? Hint: The rationale behind using group therapy for addiction treatment is that addicts are much more likely to maintain sobriety when treatment is in a group format. It has been suggested that it’s due to the rewarding and therapeutic benefits of the group, such as support, affiliation, identification, and even confrontation. Because this client is single, he may not have family support, so support from the group may be even more important in his ability to recover and maintain his sobriety. Personal Application Question What are some substance-related and addictive disorder treatment facilities in your community, and what types of services do they provide? Would you recommend any of them to a friend or family member with a substance abuse problem? Why or why not?	oercommons	2025-03-18T00:36:06.563772	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15395/overview", "title": "Psychology, Therapy and Treatment", "author": null }
https://oercommons.org/courseware/lesson/15396/overview	The Sociocultural Model and Therapy Utilization Overview By the end of this section, you will be able to: - Explain how the sociocultural model is used in therapy - Discuss barriers to mental health services among ethnic minorities The sociocultural perspective looks at you, your behaviors, and your symptoms in the context of your culture and background. For example, José is an 18-year-old Hispanic male from a traditional family. José comes to treatment because of depression. During the intake session, he reveals that he is gay and is nervous about telling his family. He also discloses that he is concerned because his religious background has taught him that homosexuality is wrong. How does his religious and cultural background affect him? How might his cultural background affect how his family reacts if José were to tell them he is gay? As our society becomes increasingly multiethnic and multiracial, mental health professionals must develop cultural competence (Figure), which means they must understand and address issues of race, culture, and ethnicity. They must also develop strategies to effectively address the needs of various populations for which Eurocentric therapies have limited application (Sue, 2004). For example, a counselor whose treatment focuses on individual decision making may be ineffective at helping a Chinese client with a collectivist approach to problem solving (Sue, 2004). Multicultural counseling and therapy aims to offer both a helping role and process that uses modalities and defines goals consistent with the life experiences and cultural values of clients. It strives to recognize client identities to include individual, group, and universal dimensions, advocate the use of universal and culture-specific strategies and roles in the healing process, and balancs the importance of individualism and collectivism in the assessment, diagnosis, and treatment of client and client systems (Sue, 2001). This therapeutic perspective integrates the impact of cultural and social norms, starting at the beginning of treatment. Therapists who use this perspective work with clients to obtain and integrate information about their cultural patterns into a unique treatment approach based on their particular situation (Stewart, Simmons, & Habibpour, 2012). Sociocultural therapy can include individual, group, family, and couples treatment modalities. Watch this short video to learn more about cultural competence and sociocultural treatments. BARRIERS TO TREATMENT Statistically, ethnic minorities tend to utilize mental health services less frequently than White, middle-class Americans (Alegría et al., 2008; Richman, Kohn-Wood, & Williams, 2007). Why is this so? Perhaps the reason has to do with access and availability of mental health services. Ethnic minorities and individuals of low socioeconomic status (SES) report that barriers to services include lack of insurance, transportation, and time (Thomas & Snowden, 2002). However, researchers have found that even when income levels and insurance variables are taken into account, ethnic minorities are far less likely to seek out and utilize mental health services. And when access to mental health services is comparable across ethnic and racial groups, differences in service utilization remain (Richman et al., 2007). In a study involving thousands of women, it was found that the prevalence rate of anorexia was similar across different races, but that bulimia nervosa was more prevalent among Hispanic and African American women when compared with non-Hispanic whites (Marques et al., 2011). Although they have similar or higher rates of eating disorders, Hispanic and African American women with these disorders tend to seek and engage in treatment far less than Caucasian women. These findings suggest ethnic disparities in access to care, as well as clinical and referral practices that may prevent Hispanic and African American women from receiving care, which could include lack of bilingual treatment, stigma, fear of not being understood, family privacy, and lack of education about eating disorders. Perceptions and attitudes toward mental health services may also contribute to this imbalance. A recent study at King’s College, London, found many complex reasons why people do not seek treatment: self-sufficiency and not seeing the need for help, not seeing therapy as effective, concerns about confidentiality, and the many effects of stigma and shame (Clement et al., 2014). And in another study, African Americans exhibiting depression were less willing to seek treatment due to fear of possible psychiatric hospitalization as well as fear of the treatment itself (Sussman, Robins, & Earls, 1987). Instead of mental health treatment, many African Americans prefer to be self-reliant or use spiritual practices (Snowden, 2001; Belgrave & Allison, 2010). For example, it has been found that the Black church plays a significant role as an alternative to mental health services by providing prevention and treatment-type programs designed to enhance the psychological and physical well-being of its members (Blank, Mahmood, Fox, & Guterbock, 2002). Additionally, people belonging to ethnic groups that already report concerns about prejudice and discrimination are less likely to seek services for a mental illness because they view it as an additional stigma (Gary, 2005; Townes, Cunningham, & Chavez-Korell, 2009; Scott, McCoy, Munson, Snowden, & McMillen, 2011). For example, in one recent study of 462 older Korean Americans (over the age of 60) many participants reported suffering from depressive symptoms. However, 71% indicated they thought depression was a sign of personal weakness, and 14% reported that having a mentally ill family member would bring shame to the family (Jang, Chiriboga, & Okazaki, 2009). Language differences are a further barrier to treatment. In the previous study on Korean Americans’ attitudes toward mental health services, it was found that there were no Korean-speaking mental health professionals where the study was conducted (Orlando and Tampa, Florida) (Jang et al., 2009). Because of the growing number of people from ethnically diverse backgrounds, there is a need for therapists and psychologists to develop knowledge and skills to become culturally competent (Ahmed, Wilson, Henriksen, & Jones, 2011). Those providing therapy must approach the process from the context of the unique culture of each client (Sue & Sue, 2007). Treatment Perceptions By the time a child is a senior in high school, 20% of his classmates—that is 1 in 5—will have experienced a mental health problem (U.S. Department of Health and Human Services, 1999), and 8%—about 1 in 12—will have attempted suicide (Centers for Disease Control and Prevention, 2014). Of those classmates experiencing mental disorders, only 20% will receive professional help (U.S. Public Health Service, 2000). Why? It seems that the public has a negative perception of children and teens with mental health disorders. According to researchers from Indiana University, the University of Virginia, and Columbia University, interviews with over 1,300 U.S. adults show that they believe children with depression are prone to violence and that if a child receives treatment for a psychological disorder, then that child is more likely to be rejected by peers at school. Bernice Pescosolido, author of the study, asserts that this is a misconception. However, stigmatization of psychological disorders is one of the main reasons why young people do not get the help they need when they are having difficulties. Pescosolido and her colleagues caution that this stigma surrounding mental illness, based on misconceptions rather than facts, can be devastating to the emotional and social well-being of our nation’s children. This warning played out as a national tragedy in the 2012 shootings at Sandy Hook Elementary. In her blog, Suzy DeYoung (2013), co-founder of Sandy Hook Promise (the organization parents and concerned others set up in the wake of the school massacre) speaks to treatment perceptions and what happens when children do not receive the mental health treatment they desperately need. I've become accustomed to the reaction when I tell people where I'm from. Eleven months later, it's as consistent as it was back in January. Just yesterday, inquiring as to the availability of a rental house this holiday season, the gentleman taking my information paused to ask, “Newtown, CT? Isn't that where that...that thing happened? A recent encounter in the Massachusetts Berkshires, however, took me by surprise. It was in a small, charming art gallery. The proprietor, a woman who looked to be in her 60s, asked where we were from. My response usually depends on my present mood and readiness for the inevitable dialogue. Sometimes it's simply, Connecticut. This time, I replied, Newtown, CT. The woman's demeanor abruptly shifted from one of amiable graciousness to one of visible agitation. “Oh my god,” she said wide eyed and open mouthed. “Did you know her?” . . . . “Her?” I inquired That woman,” she replied with disdain, “that woman that raised that monster.” “That woman's” name was Nancy Lanza. Her son, Adam, killed her with a rifle blast to the head before heading out to kill 20 children and six educators at Sandy Hook Elementary School in Newtown, CT last December 14th. When Nelba Marquez Greene, whose beautiful 6-year-old daughter, Ana, was killed by Adam Lanza, was recently asked how she felt about “that woman,” this was her reply: “She's a victim herself. And it's time in America that we start looking at mental illness with compassion, and helping people who need it. “This was a family that needed help, an individual that needed help and didn't get it. And what better can come of this, of this time in America, than if we can get help to people who really need it?” (pars. 1–7, 10–15) Fortunately, we are starting to see campaigns related to the destigmatization of mental illness and an increase in public education and awareness. Join the effort by encouraging and supporting those around you to seek help if they need it. To learn more, visit the National Alliance on Mental Illness (NAMI) website (http://www.nami.org/). The nation’s largest nonprofit mental health advocacy and support organization is NAMI. Summary The sociocultural perspective looks at you, your behaviors, and your symptoms in the context of your culture and background. Clinicians using this approach integrate cultural and religious beliefs into the therapeutic process. Research has shown that ethnic minorities are less likely to access mental health services than their White middle-class American counterparts. Barriers to treatment include lack of insurance, transportation, and time; cultural views that mental illness is a stigma; fears about treatment; and language barriers. Review Questions The sociocultural perspective looks at you, your behaviors, and your symptoms in the context of your ________. - education - socioeconomic status - culture and background - age Hint: C Which of the following was not listed as a barrier to mental health treatment? - fears about treatment - language - transportation - being a member of the ethnic majority Hint: D Critical Thinking Question Lashawn is a 24-year-old African American female. For years she has been struggling with bulimia. She knows she has a problem, but she is not willing to seek mental health services. What are some reasons why she may be hesitant to get help? Hint: One reason may be that her culture views having a mental illness as a stigma. Additionally, perhaps she doesn’t have insurance and is worried about the cost of therapy. She could also be afraid that a White counselor would not understand her cultural background, so she would feel uncomfortable sharing things. Also, she may believe she is self-reliant and tell herself that she’s a strong woman who can fix this problem on her own without the help of a therapist. Personal Application Question What is your attitude toward mental health treatment? Would you seek treatment if you were experiencing symptoms or having trouble functioning in your life? Why or why not? In what ways do you think your cultural and/or religious beliefs influence your attitude toward psychological intervention?	oercommons	2025-03-18T00:36:06.589020	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15396/overview", "title": "Psychology, Therapy and Treatment", "author": null }
https://oercommons.org/courseware/lesson/67429/overview	Education Standards Teamwork! Overview This unit is for elementary students grades 3-6. Activities build on cooperation, encouraging communication, team building skills, and participation. The unit includes 4 lessons with a reflection worksheet at the end. These can be used in classroom settings, group counseling, lunch bunch groups or guidance lessons Team Building Activity Teamwork! 3rd-6th grades Lesson/Unit Topic: TEAMWORK! Subject: Elementary Guidance, School Counseling Lessons Target Grade: 3rd-6th grades Author: Loyce Ellingrod Lesson Description: This unit is for elementary students grades 3-6. Activities build on cooperation, encouraging communication, team building skills, and participation. The unit includes 4 lessons with a reflection worksheet at the end. These can be used in classroom settings, group counseling, lunch bunch groups or guidance lessons. Learning goals/outcomes: Students will define team building skills and what teamwork is. Students will participate in a variety of team building activities. Students will demonstrate using encouraging words with their team members. Students will demonstrate personal safety when participating in activities. Students will determine why listening skills are needed for effective teamwork. Wyoming Standards: Career-Vocational Standards: CV5.2.1 Students identify and practice compromise and conflict resolutions skills CV5.2.3 Students identify and participate in group roles and responstiblities while demosntrating respect and awareness of diverstiy. ASCA Behavior Standards: B-SS 6: Use effective collaboration and cooperation skills. Teacher Planning: - Equipment/materials needed: computer, TV or Smartboard; whiteboard, markers, supplies for variety of games (check each day’s activity) colored pencils, 8x11 white paper, worksheet - Time required for lesson: 4-5 days--30 minute sessions Technology Use: __X____Yes ______No Instructional Plan: Introduction: With elbow partners or assigned partners, have students list any “teams” they know. As a group they will share their lists. How do they know these are “teams”? On board, list 5 characteristics of a team (example: more than 1 person, common goal, work together to win a game, help each other etc.) - Real-World Connection: We see teams around us everywhere. We need to know how to be a successful member of a team in sports, school and in future jobs and family life. - Activities: Day 1: Watch video: T.E.A.M work TED Youth talk as a group. When finished dicuss the main points from his talk. Put the letters “T.E.A.M.” down the side of the board. Write the words that he mentioned for each letter. Discuss what each means. Play the Balloon Toss Game: Give directions: - As a whole group (may divide into 2 groups depending on the size of class-12-15 members per circle) make a circle standing around the floor. (Move all desks/chairs away from the circle’s area. Large groups may need to move to another space such as a corner of the gym or playground.) - Have a balloon ready for each circle. Explain that they have to work to keep the balloon in the air (not touch the floor, walls, chairs etc.) When they start they need to gently tap the balloon in the air to another person in their circle. They need to stay planted in their area of the circle (can’t move around). They tap the ball and count each tap. The group’s highest number of taps without stopping is the winner. If there is only one group they work to get over 100 or more taps. No jumping, running or pushing others. The teacher can remove any students who can’t follow the rules. If the balloon touches the floor etc. they start their counting the taps over. The teacher can stop the activity at any time to talk about working together, staying in the area, correct ways to tap etc. - Record the highest number of taps for each group or attempts when done. If there is more than one section of groups doing this activity, they can challenge themselves to beat another group’s total. Have the group return to their original seats. Review TEAM words. Teacher provides each student with a sheet of white paper. Draw these words on a white paper (copy from the board) with colored pencils. Draw a picture of a team. Put names on paper. Hand into the teacher. Day 2: Review TEAM words from the previous lesson. As a group: Brainstorm “encouraging” words we can use when we are working with others. List these on the board. (examples: good job!; keep trying; keep going; nice try etc.) Play the Monkey game (use Barrel of Monkeys sets-1 per set for 4-6 students). Each group of students form a circle sitting on the floor. Remind them to stay in their area and to use encouraging words. Give Directions: - As a group they are to build a chain of monkeys. The only person who can touch the monkeys is the teacher. The group can decide who starts in each group. That person will pick up a monkey and hook it to another monkey, and then pass the chain to the next team member beside them. It continues around the circle until all the monkeys are picked up. (No doubles.) If they fall off, then that member passes it on and the next member picks up one monkey to start over. They can talk during this activitiy-give suggestions, advice and encouraging words. Some students struggle with this because they are shaky or nervous. It’s okay to try and then pass it on if it gets too frustrating. They will usually try again when it is their turn. - Watch each group and record who makes the longest chain or finishes first with all of the monkeys. Have the group return to their original seats. Review encouraging words list. Teacher provides each student with a sheet of white paper. Choose one word from the board to draw on a sheet of paper with colored pencils. Add colors and draw a picture of people using these words. Put the name on the paper. Hand into teacher when done. Day 3: Review encouraging words and TEAM words. Discuss WORK. What does this look like? What is a leader? Follower? Listener? Helper? Write the letters “W.O.R.K.” on the board down the side. Brainstorm and record words from the group for each letter (example: W-we win; O-only together etc.) Decide what words they prefer and use these for the class’s example. Play build a Straw Boat to Float challenge. Divide into groups of 4-5 students or partners, depending on the size of the class, for each boat. Have them sit together facing each other. Give directions: - Give each small group a certain number of drinking straws (dollar store straws work well for this)-usually 12-15 straws per group works best. - Give masking tape strips to each group. This can be limited or not-teacher can decide how much will be used. Also scissors can be allowed if the teacher wants to have them. - Set the time for the activity. Explain they are to build a boat using straws and masking tape. It will be tested to see if it will float in a pan of water. The boat will be tested by putting coins (pennies) one at a time on the boat. The boat that holds the most coins wins. - Let the students design and make their boats together. Walk around and witness their designing, working together, encouraging words and frustrations. - When done, have a pan (old cake pan works) ½ to ¾ full of water and a jar of coins ready. Put the boat into the water for the test. Count the number of coins it holds before it sinks. The team with the most wins! Have the group return to their original seats. Review the WORK words on the board. Teacher provides each student with a sheet of white paper. Draw the words on a white paper with colored pencils. Draw a picture of people working together. Put names on papers. Hand into teacher when done. Day 4: Review TEAMWORK. Discuss how we have shown team building skills in our past lessons. Today’s focus is on communicating (using our listening and speaking skills). We will complete a challenge with talking and sharing ideas the first time and then try it again without talking. Play the Cup Stacking Challenge (this is one variation for this challenge). - Divide into partners. Give each set of partners a set of plastic drinking cups (15 works well). - Partners need to face each with the cups randomly on the table/floor in front of them. - They are going to stack the cups (5 on the bottom in a row, then 4 , 3 and so on to make a pyramid). They need to take turns putting the cups on the stack and then unstacking it. Only one cup at a time. They must wait until their partner puts a cup up before they do theirs. Each group decides who goes first. They can talk and listen to each other this round. The goal is to see how fast they can stack and unstack the cups without dropping them or knocking down the stack. The teacher can set a time limit for this. They keep stacking/unstacking until the teacher calls time. They can count the number of times they stacked & unstacked to give to the teacher. - Second round: they do it again, but this time they can’t talk while they are doing it. Start with the other partner. Again it is timed and see how many times they can stack and unstack the cups. - Following rounds: partners can be moved to new people and process repeated again. time allowed can be changed: be lengthened or shortened as the teacher prefers. Discuss how many times they had; did they get faster with practice: why is talking and listening important when working with others?; How does it help? What is a barrier to good listening? What can we do to overcome the barriers? - Closure and Check for understanding: Have students complete “My Teamwork Reflection” form about their experiences with team building during our lessons. Hand into teacher. Supplemental Information: - Modifications: Different games can be used. These are just ideas that have been used with this age group. - Safety Precautions: Always remind the group/partners of safety rules before, during and after each activity. Students can sit out if they can’t follow the rules. - Comments: These activites have been adapted for older students too. The specific requirements and follow up activities can be changed to meet the age and maturity. - All the artwork from lessons can be put together to be displayed or put onto a bulletin board promoting Teamwork. - Additional resources: 104 Activities that Build: Self-esteem, teamwork, communication, anger management, self-discovery, coping skills by Alanna Jones Activites that Teach by Tom Jackson Still More Activities that Teach by Tom Jackson	oercommons	2025-03-18T00:36:06.622569	05/27/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/67429/overview", "title": "Teamwork!", "author": "Loyce Ellingrod" }
https://oercommons.org/courseware/lesson/68798/overview	Education Standards Activity 2 - Typographic Contrast Activity 3 - Text Hierarchy Calligraphr Template Evaluating Resources for OER Commons Typography - Formative Assessment Using Typography to Communicate Overview This lesson provides an introduction to the importance of typography as an element of design. Goal: The goal of this lesson is to understand that typography is everywhere. The way characters or letters are designed plays a part in the message and in creating a brand for an organization. Every font, letter, and character arrangement plays a part in determining how a message is conveyed. Understanding Basic Elements of Typography 1) Students will read articles and watch PBS video (the linked OER Commons resource). The instructor will informally assess their understanding of the information through group discussion and questioning. 2) Students will complete a short formative assessment covering information in the articles and video. Creation Date: June, 2020 Grade Level: High School - Grades 9-12 Content Area: Media Technology Goal: The goal of this lesson is to understand that typography is everywhere. The way characters or letters are designed plays a part in the message and in creating a brand for an organization. Every font, letter, and character arrangement plays a part in determining how a message is conveyed. Objectives: - To utilize type as a design element. - To differentiate between different styles of typography. - To use fonts to represent specific feelings and emotions. - To explore creative ways to layout typographic elements. Message to students: You will be designing many informational documents and title slides for video for school and community activities. An understanding of typography is imperative to any situation where you want to transmit an idea to another via text. Read these three short articles for an overview of typography: Typography Elements Everyone Needs to Understand Basic Principles for Using Typography Extra - Fonts Used in Famous Logos - Famous fonts: the typefaces behind the biggest logos Watch this PBS video: What is Typography - (this is the linked OER Resource) Activities to Demonstrate Understanding of Typography These three activities will reinforce information learned about typography. While students will be using Google Drawing for these activities, the next step will be to introduce Photoshop Elements and continuing to use the information learned on design activities for the school and community throughout the semester. Students will be using a poster printer that can print on indoor/outdoor canvas to design banners for the school and community organizations. Activity 1 - Comparing Serif, Sans-Serif and Decorative Fonts Click in each box and type your name 3 times. Each name will be put in a different font. Each font should be the type of font listed in the box. When finished, share in Google Classroom. Activity 2 - Contrast of Type Type the quote and fill the space below. Adjust words in the quote by: Size - make some words bigger than others for emphasis. Weight - create emphasis on certain words by making them bold. Color - change the color of the word this should be emphasized. Structure - choose your emphasis word and type it in a completely different typeface. Activity 3 - Typographic Hierarchy Typographic Hierarchy - distinguishes different levels of importance. Organize the information given below using contrasting typographic contrast to emphasize certain words or groups of words as more important or less important than others to capture the attention of incoming freshmen. • Emphasize levels of information through typographic contrast of size, weight, color, structure • Use spatial organization and control hierarchy in both large and small scale • Select appropriate color combinations to support organization and emphasis without reducing legibility/readability Enrichment Activity For Fun - Create Your Own Font From Your Handwriting 1) Go to calligraphr.com 2) Create an account, activate it by confirming in e-mail, log in 3) Start App 3) Create template 4) Choose minimal English, minimal Numbers, minimal Punctuation 5) Click on any characters you don't need and delete 6) Download template and print 7) Fill in each box with your handwriting 8) Take a picture or scan sheet(s) 9) Go back to calligraphr.com, choose My Fonts 9) Upload templates, choose file(s) to upload, upload 11) Preview, Build Font, Name Font 12) Make any adjustments 13) Download, open, install 14) Open new document to find and use font	oercommons	2025-03-18T00:36:06.658612	Assessment	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/68798/overview", "title": "Using Typography to Communicate", "author": "Activity/Lab" }
https://oercommons.org/courseware/lesson/92850/overview	Graphic Design lesson plan Overview graphic design Lesson Plan introduction Based on the Colombian frameworks: - Competencia Tecnológica: Dentro del contexto educativo, la competencia tecnológica se puede definir como la capacidad para seleccionar y utilizar de forma pertinente, responsable y eficiente una variedad de herramientas tecnológicas entendiendo los principios que las rigen, la forma de combinarlas y las licencias que las amparan. - Competencia Comunicativa: La competencia comunicativa se puede definir como la capacidad para expresarse, establecer contacto y relacionarse en espacios virtuales y audiovisuales a través de diversos medios y con el manejo de múltiples lenguajes, de manera sincrónica y asincrónica. - Competencia Pedagógica: La competencia pedagógica se puede definir como la capacidad de utilizar las TIC para fortalecer los procesos de enseñanza y aprendizaje, reconociendo alcances y limitaciones de la incorporación de estas tecnologías en la formación integral de los estudiantes y en su propio desarrollo profesional. - Competencia de Gestión: La competencia de gestión se puede definir como la capacidad para utilizar las TIC en la planeación, organización, administración y evaluación de manera efectiva de los procesos educativos; tanto a nivel de prácticas pedagógicas como de desarrollo institucional. - Competencia Investigativa: La competencia investigativa se define como la capacidad de utilizar las TIC para la transformación del saber y la generación de nuevos conocimientos. Name of student teachers: Laura Daniela Guachetá Salinas María Fernanda Hernández Hernández Nicolás Sanchez Arguelles School/Institution: Rafael Pombo School Class/grade: Students with beginner-intermediate level of English/High School Time & Length of class: 1 hour Achievement: - Review students' knowledge and background about graphic design. - Reinforce the basics of graphic design Lesson objectives: - Define what graphic design is. - Understand the elements and principles of graphic design. - Employ the techniques of color, texture, image and typography to make a good design. Resources and materials: - video beam - pc - Digital platforms (ExeLearning, Genially). - Videos - PPT Skills Focus: - Listening - Reading Language focus: - Vocabulary: Elements of Graphic Design (Color, texture, form, space, line, size, shape) - Functional language: Answering and reading questions. Foreseeable Problems: Problems with the video beam Planned Solutions: Sharing the presentation on students' computers European Framework Digital Competence Facilitating Learners’ Digital Competence Empowering Learners: - Accessibility and inclusion: To consider and respond to learners’ (digital) expectations, abilities, uses and misconceptions, as well as contextual, physical or cognitive constraints to their use of digital technologies. - Differentiation and personalisation: To use digital technologies to address learners’ diverse learning needs, by allowing learners to advance at different levels and speeds, and to follow individual learning pathways and objectives. - Actively engaging learners: To use digital technologies to foster learners’ active and creative engagement with a subject matter. To use digital technologies within pedagogic strategies that foster learners’ transversal skills, deep thinking and creative expression. To open up learning to new, real-world contexts, which involve learners themselves in hands-on activities, scientific investigation or complex problem solving, or in other ways increase learners’ active involvement in complex subject matters. Lesson Plan Development Stage of lesson Pre-Act Time 10 min Procedure (Teacher and Student Activity) To start the lesson, a quiz will be presented in order to evaluate the students' previous knowledge and concepts about graphic design and its basic elements. For this quiz, it will be presented through an app to make it dynamic. After this, there will be a socialization of the results. With the socialization will give way to the following introductory activity to start the class in detail with the subject corresponding to graphic design. Link Activity https://quizizz.com/admin/quiz/6287ed92404f62001e48b3fd/graphic-design Interaction Students (Sts) University Supervisor’s comments Lesson Plan Development Stage of lesson While-Act Time 30 min Procedure (Teacher and Student Activity) To continue, a brainstorming session (1) will be designed in the class to socialize the key ideas or concepts that students have about graphic design and its basic elements. After this, a presentation (2) will be given with the key definitions for graphic design. Based on these key concepts, an interactive video will be presented about: - Color - Texture - Form - Space - Line - Size - Shape Students should take notes to answer the questions and develop the activities presented throughout the video. Link Activity 1. https://www.mindmeister.com/map/2299620842?t=AHSdNhvpQi 3. https://www.oercommons.org/editor/documents/12828 Interaction Teacher (Tch) Students (Sts) University Supervisor’s comments Lesson Plan Development Stage of lesson Post-Act Time 50 min Procedure (Teacher and Student Activity) Finally, an interactive image will be presented in which the students will have to design a simple card. Students will have to choose between typography, background and shape. Link Activity https://view.genial.ly/6287bb6925a6cd001848bf12/interactive-content-graphic-design Interaction Students (Sts) University Supervisor’s comments	oercommons	2025-03-18T00:36:06.683469	05/19/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/92850/overview", "title": "Graphic Design lesson plan", "author": "Daniela Guachetá" }
https://oercommons.org/courseware/lesson/124716/overview	Fact or Fiction: Vitamin Supplements Reading Guided Notes Key - Vitamin T-Chart Guided Notes - Vitamins T-Chart Lesson Plan Outline - Like Dissolves Like Slideshow - Like Dissolves Like Station Rotation - Set Up Station Rotation - Task Cards Station Rotation - Worksheet Station Rotation - Worksheet Key Vitamins Worksheet Like Dissolves Like Lesson Plan Overview Welcome. Our goal is to design high school chemistry lesson plans that integrate fundamental organic chemisty concepts. These lessons aim to bridge the gap between introductory chemistry and organic chemistry, giving students a head start in understanding molecular structures, reactions, and more, in a way that is engaging and accessible. By connecting these core ideas with hands-on experiments, real-world applucations, and interactive learning tools, students will be better equipped to understand the relevance of organic chemistry in everyday life and future scientific studies. For additional organic chemistry lesson plans, view the following: Overview Welcome Our goal is to design high school chemistry lesson plans that integrate fundamental organic chemisty concepts. These lessons aim to bridge the gap between introductory chemistry and organic chemistry, giving students a head start in understanding molecular structures, reactions, and more, in a way that is engaging and accessible. By connecting these core ideas with hands-on experiments, real-world applucations, and interactive learning tools, students will be better equipped to understand the relevance of organic chemistry in everyday life and future scientific studies. For additional organic chemistry lesson plans, view the following: Feedback We value your feedback and would like to know how to make our lesson plans more engaging, accessible, and clear. Please take the following survey for this lesson plan, Like Dissolves Like, by using the following link: Like Dissolves Like Lesson Plan Like Dissolves Like Brief Lesson Description: \| \| Standard (from Utah SEEd Standards): Standard CHEM 2.3 \| \| Specific Learning Outcomes for This Lesson: \| Disclaimer Notice NOTICE The following information, lesson plans, demonstrations, and laboratory experiments (“Materials”) have been prepared with the objective of improving the standards and the quality of high school chemistry education. These Materials have been developed from sources that are considered to be reliable and that represent knowledgeable viewpoints of chemistry education. These Materials may involve the use of hazardous chemicals, operations, and equipment. Not all safety problems associated with the use of these methods, chemicals, and equipment may be addressed in the Materials. It is the responsibility of the user to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before engaging in any experimental procedures described in these Materials. Consult the specific equipment or chemical user manuals for detailed precautions necessary to ensure safe handling and use. Further, it is incumbent upon instructors and those in charge to provide appropriate instruction, supervision, and laboratory conditions, including procedures for safe handling, use, and disposal of chemicals in accordance with local regulations and requirements. No warranty, guarantee, or other form of representation is made by the authors or by Brigham Young University concerning these Materials and their use. The authors and Brigham Young University hereby expressly disclaim any and all responsibility and liability concerning the use of these Materials for any purpose. This disclaimer applies to any liability that is, or may be incurred by, or on behalf of the institutions that make use of these Materials; the faculties, students, or prospective students of those institutions; and any member of the public at large; and includes, but is not limited to, a full disclaimer of any liability that may be incurred with respect to possible inadequate supervision or safety procedures taken by any individual or institution.	oercommons	2025-03-18T00:36:06.713719	Interactive	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/124716/overview", "title": "Like Dissolves Like Lesson Plan", "author": "Homework/Assignment" }
https://oercommons.org/courseware/lesson/123177/overview	Reviewing OER Licensing for License Compatibility Overview This mini-lesson explores how the terms Creative Commons licenses support revising or remixing OER for correct attribution. (Review and deepen knowledge) In Module 1 of this series, we reviewed a definition of open licensing. In this Module, we want to look closely at why the license matters for the processes of revision or remixing. Open licensing refers to when the author chooses terms of use that allow others to use, share or change the work with few restrictions. A non-profit called Creative Commons created a set of open licenses called the Creative Commons licenses that is a standardized way to explain how other users can re-use, redistribute, retain, revise and remix the work. When faculty are planning to revise or remix a resource, they will need to check the terms of the original license. Let's clarify the difference between revising and remixing: - revising an OER will mean making changes to the original OER to edit, adapt or modify a resource with the intent to keep the OER in it's basic orginal format. - remixing OER is when multiple OER are combined in order to create a new resource. For both of these types of iterations, faculty will need to be sure that they are following the terms of the original OER's license. The main limitations are going to be the "No Derivatives" term of use and the "Share Alike" term of use. - No Derivatives means that you cannot make changes and then distribute your changes. The work must only be distributed in its original form. - Share Alike means that you can make changes, but any changes and remixes must have the same license as the original. For example, if an infographic is licensed CC-BY-SA, then it can only be used in other resources that exactly licensed CC-BY-SA. In the chart below, you start on the left column with the OER's original license - for example a textbook licensed CC-BY. Then you use the top row to select the license of the additional material you want to add, for example, an infographic licensed CC-BY-SA that you want to modify. You can combine those two works, but the new combination would need to be licensed CC-BY-SA. Looking at an Example: - If an infographic is licensed CC-BY-NC-SA: - Can you remix the image by adding an audio description? - Yes - this license allows for derivatives - When you remix it, can you license it CC-BY? - No - Any derivatives of the original work need to be modified as CC-BY-NC-SA. - Can you include the infographic in its original form in a textbook licensed CC-BY? - Yes! The infographic must be clearly captioned and given attribution and the textbook must note "licensed CC-BY except where noted." Below are steps for checking the licensing before revising or remixing. - Find the original licensing terms for every existing resource that you wish to change or combine. - Consider finding contact information for each resource in case you need to contact the author. - Use the license compatability chart to check for license alignment. - Create appropriate attributions for each revised or adapted component. - Determine a license for the overall work. - Collaborate with a peer to check the licensing and attributions.	oercommons	2025-03-18T00:36:06.730236	12/18/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123177/overview", "title": "OERizona Advanced OER Skills, Revise and Remix OER, Reviewing OER Licensing for License Compatibility", "author": "Peter Musser" }
https://oercommons.org/courseware/lesson/101075/overview	Introduction to Behavioral Health & Social Services Overview In this course, you will learn about opportunities in behavioral health and human services through career explorations, self-assessments, and charting your personal academic and professional plan. You will also learn about mental health disorders and first responder skills in a mental health crisis. Introduction to Behavioral Health & Social Services In this course, you will learn about opportunities in behavioral health and human services through career explorations, self-assessments, and charting your personal academic and professional plan. You will also learn about mental health disorders and first responder skills in a mental health crisis. Course link: Canvas Commons Use this link to access this course in the Canvas Commons Course download: Common Cartridge Use the attached file to load this course into an LMS other than Canvas.	oercommons	2025-03-18T00:36:06.750183	Full Course	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/101075/overview", "title": "Introduction to Behavioral Health & Social Services", "author": "Social Work" }
https://oercommons.org/courseware/lesson/91770/overview	Life In Brazil: A Free ESL Lesson Plan Overview Brazil, the largest country in South America, also holds a large population of English Language Learners (ELLs). This free ESL lesson plan about life is Brazil is a great opportunity for students to practice using the present simple tense! It is especially useful if you are looking for a fun, light lesson to teach. You can access 150+ more free lessons like this with a free Off2Class account! Off2Class When teaching this lesson, have your student focus on speaking, not learning new grammar and vocabulary. When introducing vocabulary we recommend you encourage the student to talk about each image. Then, you can offer the vocabulary word without asking them to memorize it. The images and vocabulary are presented to encourage the student, rather than force them to learn new lexical items. You can access full teacher notes for this lesson plan by signing up for a free Off2Class account.	oercommons	2025-03-18T00:36:06.767430	04/13/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/91770/overview", "title": "Life In Brazil: A Free ESL Lesson Plan", "author": "Christine Chan" }
https://oercommons.org/courseware/lesson/114960/overview	Rachel Moller - Lecture Note Template Adapting OER to Incorporate UDL (Gavilan College) Overview This template supports faculty and staff as they interrogate their OER and iterate the resource. This template is part of a Canvas course titled Adapting OER to Incorporate UDL. The initial course is offered by ISKME to California Community College faculty and staff and was created with support from the Michelson Foundatin's Spark Grant Program. Background on the Resource and Collaborators Prompts are provided below. Please replace the prompts with your own information. Please note: one template will be created per team unless a team has decided that each person is interrogating a separate OER. In that instance, this section could be copied and pasted into each person's template. Please provide background information on the team members and the resource you have chosen to interrogate and adapt. - Patrick Yuh M.S. - Biology Faculty - Erik Medina M.S. - Math Faculty - Rachel Moller, Ph.D. - Chemistry Faculy - What resource did your team chose to interrogate? - What are your team's goals with interrogating and adapting this resource? - What impact do you envision this will have on students? - What impact do you envision this will have on other faculty and staff at your institution? Rachel Moller - What resource did your team chose to interrogate? - OER Organic Chemistry Textbook on OpenStax - What are your team's goals with interrogating and adapting this resource? - I am planning to make all of my courses zero cost at the begninng of the 2024 acedemic term, so I wanted to investigate the textbook I am planning on using - What impact do you envision this will have on students? - College chemistry will be acheivable and obtainable for all students - What impact do you envision this will have on other faculty and staff at your institution? - This will allow all students to get closer to their overall goals through a high quality education and at no cost. Adaptations to support Open Educational Practices Prompts are provided below. Please replace the prompts with your own information. Please refer to the Characteristics of OER tool. Based on your interrogation of your resource, please share: - What are you planning to adapt to increase the features of the open licensing on this resource? - How long will this take and who will be the main point person working on this? - How will your team keep track of the changes and future impact on students and faculty? Rachel Moller: - What are you planning to adapt to increase the features of the open licensing on this resource? - I will be focusing on backwards design using this resource and figuring out how I can incoporate baward design using this textbook when I switch over the this textbook. This year I just moved over my general chemistry material, and I would like to develop worksheets that are organic relavent to something like I use in my general chemistry courses (please see attached document). I have a lot of accessibility work to do on the note tempaltes - How long will this take and who will be the main point person working on this? - This will take a long time, I am not sure of an exact timeline, but each time I teach organic chemistry, I incorporate and remove activities that help students be more engaged with the material so they can learn the most. I would like to have the foundations (lecture videos and homework) done at the time of their course, however developing material, worksheets, and content is a labor intesive process. - How will your team keep track of the changes and future impact on students and faculty? - Every semester I have students give me feedback on what they liked, what did not serve them, and what they would do differently and have me do differently. I take ideas from what they students need so they can learn the material to the best of their ability. Adaptations to support Accessibility Prompts are provided below. Please replace the prompts with your own information. Please refer to the Characteristics of Accessibility tool. Based on your interrogation of your resource, please share: - What are you planning to adapt to increase the features of Accessibility on this resource? - How long will this take and who will be the main point person working on this? - How will your team keep track of the changes and future impact on students and faculty? Rachel Moller: - What are you planning to adapt to increase the features of Accessibility on this resource? - I have so much work to do on accessibilty. The books I use are alreacy accessible, but the corresponding worksheets I develop for the textbooks have a lot of work that needs to be done with accessabilty. Currently, I use an accessibility checker, but I am highly interested in ANDI and all that it has to offer. I had never heard of ANDI before this workshop. Right now, I make sure that I always use my accessibility checker on Canvas before I publish something. It is really hard to describe chemical structures witth a screen reader. My current videos on YouTube are closed captioned correctly, so that is a step in the accessibilty direction! - How long will this take and who will be the main point person working on this? - We are in charge of our own accessibilty; however we do have a lot of support from our distant education personelle on campus. - How will your team keep track of the changes and future impact on students and faculty? - Using ANDI is a good place to start, and no one in my cohort currently uses it. Adaptations to support UDL Prompts are provided below. Please replace the prompts with your own information. Please refer to the Characteristics of UDL tool. Based on your interrogation of your resource, please share: - What are you planning to adapt to increase the features of UDL on this resource? - DId your team identify any opportunities to co-create with students and what might that look like? - How long will this take and who will be the main point person working on this? - How will your team keep track of the changes and future impact on students and faculty? Rachel Moller - What are you planning to adapt to increase the features of UDL on this resource? - The "solutions" at the end of the textbook are lacking. Having a detailed answer is important for students to understand what could have gone wrong in their work in they do not have a detailed answer. This is one point that my current students really like about the solutions manual for the current textbook we are using. I also need to plan and discover how I can incorporate backward design from the start of switching to a new textbook. I think that this OER textbook will need some extra material to develop this well for this course. - DId your team identify any opportunities to co-create with students and what might that look like? - As mentioned above, I always ask students what worked, what did not, what they would change, how and why, and I really try and incoroprate as much as I can into the next upcoming class. - How long will this take and who will be the main point person working on this? - I will be the main person working on this. I will be asking students to help me determine what they liked, didn't, and be flexibel and fluid in the moment of teaching to accomodate the current student needs. - How will your team keep track of the changes and future impact on students and faculty? - The best resource in my students. I always check in with them multiple times throughout the semester and that will not change. Sharing your iteration Prompts are provided below. Please replace the prompts with your own information. Please attach or link your iterated resource in this section. To help make your experience visible to others who pursue similar work, please share the following: - What aspect of this process stretched your thinking about your resource? - What next steps is your team considering? Rachel Moller - What aspect of this process stretched your thinking about your resource? - I relaized in my responses that truly my best resource are the students. It really is about them and what they need. I found that all of my answers were student centered so having the best resources available to them, at no cost, is going to be hugely beneficial to them. It feels like a really long and overwhelming process, but it is about making small changes that will turn into big changes over time! And really hearing and valuing the student feedback, in the moment, is really hugely beneficial! - What next steps is your team considering?	oercommons	2025-03-18T00:36:06.799231	04/05/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/114960/overview", "title": "Adapting OER to Incorporate UDL (Gavilan College)", "author": "Rachel Moller" }
https://oercommons.org/courseware/lesson/55559/overview	Backward Design Template Class Attention Signals Class Chants Example of a completed plan - by Leta Cirigliano Example of Backward Design Example of Building Background Example of Closure Example of lesson plan with direct instruction Examples of Differentiation Formative Assessments Lesson Planning: Building Background Knowledge Lesson Planning: Closure Lesson Planning: Differentiating Instruction Lesson Planning: Direct Instruction Lesson Planning: Prior Knowledge Lesson Plans: Anticipatory Set Lesson Plans: Assessment Lesson Plans: Class Attention Getters Lesson Plans: Standards and Objectives Lesson Plan Template Lesson Plan that we do collectively Prior Knowledge Example Templates for Exit Slips Using Assessments to Make Instructional Decisions Writing Lesson Plans Overview This module will assist the pre-service teacher in writing lesson plans using the Direct Instruction method. The module is designed for Early Childhood Education, but it can easily be adapted to secondary education majors. Each section of the lesson plan is detailed and, along with his/her classroom, the instructor is encouraged to develop a group lesson plan. As each section of the lesson plan is taught, the class will add that part to the group plan. A blank template is included in the first section. Lesson Plans: Standards and Objectives In this section, you will explore the fundamentals of writing a lesson plan. Attention will be given to backward design, national and state standards, writing clear objectives, and application of writing objectives. In this module, you can develop a practice lesson plan as a class. Decide on a topic for the lesson. Then, after each section is completed, develop that part of the lesson plan as a class. At the end of the module, your class will have a completed lesson plan. After this section, add the standards and objectives to the plan. In this section, you will explore the fundamentals of writing a lesson plan. Attention will be given to backward design, national and state standards, writing clear objectives, and application of writing objectives. Lesson Plans: Assessment Students will learn about formative and summative assessments with an emphasis on formative. There is application in the PPT. When you have completed this section, add formative assessments to your group lesson plan. This section explores assessments, both formative and summative. Formative assessments are typically used in a lesson, while summative assessments are usually used at the end of a unit of learning. Therefore, more attention will be given to the formative assessments. Many examples are provided. Lesson Plans: Class Attention Getters When this section is completed, add ready position to your lesson plan. You can't teach till students are in a ready position, physically and mentally. This section will help you get their attention and get them ready to learn. Lesson Plans: Anticipatory Set When this section is completed, add the Anticipatory Set to the group plan. The Anticipatory Set gets students excited and interested to learn. Lesson Plans: Prior Knowledge and Building Background Knowledge When you have completed this section, add assessing prior knowledge and building background to your group plan. Now that you have the students' attention, you need to be sure they have the proper background knowledge for the new learning. This section will guide you through assessing prior knowledge and building background knowledge. Lesson Plans: Direct Instruction When this section is completed, add the Instruction section to your group plan. This section show the Direct Teaching Method. There is a variation called the Indirect Model, which is inquiry-based learning. This section will help you plan instruction. In the Direct Lesson plan, you will use the I DO, WE DO, YOU DO methods. Lesson Plans: Closure Add closure to your group plan. Each lesson must end with a good closure. This will summarize the lesson and assess whether students gained an understanding of the content. Lesson Plans: Differentiating Instruction Add differentiation throughout the group plan. Consider differentiating the content, process, and product. In order to meet the needs of all learners, you will need to differentiate your plans in many ways. Consider differentiation according to needs of a student with a disability, learning preferences, multiple intelligences, and Bloom's Taxonomy.	oercommons	2025-03-18T00:36:06.843456	06/20/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/55559/overview", "title": "Writing Lesson Plans", "author": "Jeanne Burth" }
https://oercommons.org/courseware/lesson/113652/overview	Education Standards Fun With Words Activity Overview Ready to have a fun and learning-centered activity for your students? You've come to the right place! For this activity, we will be including physical interaction from the students. This will include attempting to form words with their bodies, and other physical movemements of your choosing. This activity comes in two parts. Most useful to students in early elementary grades, Kindergarten -- 2nd grade Word Activity Instruction Ready to have a fun and learning-centered activity for your students? You've come to the right place! For this activity, we will be including physical interaction from the students. This will include attempting to form words with their bodies, and other physical movemements of your choosing. This activity comes in two parts. The first part is an activity where students use their bodies to form words. For example, students will work together to form the word C-A-T. One student forms the letter C, one forms the letter A, and so on. This way, students get to be physical, collaberate with their peers, and learn how to spell! The next activity includes being physical as well. The educator will hold a soft ball in their hands and will either say or have a word presented on Kahoot or other platform, the student then will raise their hand and attempt to spell and pronounce the word correctly. If they get it right, the teacher will toss the lightweight ball to the student. The student will then throw it back to the teacher. Also, These activities can be used for Speech Language Pathologists as well. My Kahoot example provided shows this. For these activities you will need: - Kahoot or other platform that's similar - various sight words or any other words of choosing - a soft ball or other safe throwing object - plenty of space for students to participate! Kahoot example link : https://create.kahoot.it/details/95247f55-52f8-45cc-a362-448731c9fc70 Resources Here are links from two helpful OER activities that helped me make my own activity! "Spell And Play Lesson" - https://oercommons.org/courseware/lesson/103522/student/427100 Spell and Play is an interactive Kindergarten through 2nd grade activity. "Sight Word Spelling" - oeta.pbslearningmedia.org/resource/c1980c3e-74ab-4220-b683-549ad66544aa/sight-word-spelling/?student=true&focus=true Sight Word Spelling has four different activity ideas to help students with their spelling. I chose activity three!	oercommons	2025-03-18T00:36:06.867036	Lexie Kilhoffer	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/113652/overview", "title": "Fun With Words Activity", "author": "Activity/Lab" }
https://oercommons.org/courseware/lesson/122068/overview	OER Evaluation Tools on OER Commons Overview This resource is part of the OERizona Advanced Course and supports OERizona faculty across Arizona in using tools and rubrics to evaluate OER. Using Tools and Rubrics to Evaluate OER When faculty are analyzing OER for potentially integrating it into their courses, their pedagogical and content knowledge automatically begin noting strengths of the resource and areas that may need improvement and customization. Below are several importants points to note about analyzing and evaluating OER: - Each person's background and experiences influence how they evaluate a resource and what they see (and don't see). - Evaluting a resource can be very time-consuming. - OER are often designed to be dynamic resources that invite collaboration and iteration. - Metadata and analytics can be strong tools for helping faculty sort and curate samples that are worthy of deeper analysis. - Artificial Intellignce (AI) is a tool that can both support and hinder the curation of OER. While AI can support the creation of resources and tools, it is difficult to fact-check and give attribution. This impacts the reliability and credibility of any resources created via AI. To support faculty in curating and evaluating OER - and to support faculty who are backwards designing the creation of new OER - there are multiple tools and rubrics built into OER Commons and the OERizona Hub to leverage the collaborative power of Arizona faculty experiences and expertise. - OER Commons has partnered with Achieve to develop an OER Rubric and Evaluation Tool that is built into the platform and collects feedback to support curation and remixing. See below for two videos demonstrating how you can use the features of OER Commons to evaluate OER and add to the OER iterative community. - Video on using the Star and Comment features (___ minute watch) - Video on using the Evaluation Rubric Tool (____minute watch) - OERizona has developed their own evaluation criteria to focus on key indicators of quality for Arizona. These Standards and Criteria to support faculty in evaluating and creating OER are found on the OERizona Hub and will be demonstrated in the next section.	oercommons	2025-03-18T00:36:06.881492	11/21/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/122068/overview", "title": "OERizona Advanced OER Skills, Evaluating OER, OER Evaluation Tools on OER Commons", "author": null }
https://oercommons.org/courseware/lesson/122059/overview	Reviewing OER Licensing Overview This mini-lesson is part of the OERizona Advance Course and explores the basics of the OER Definition, the concept of open licensing and the varying Creative Commons licenses. (Review and deepen knowledge) Open Educational Resources (OER) was a term first officially coined at UNESCO's 2002 Forum on Open Courseware. OER Definition: OER are defined by UNESCO as "Open Educational Resources (OER) are learning, teaching and research materials in any format and medium that reside in the public domain or are under copyright that have been released under an open license, that permit no-cost access, re-use, re-purpose, adaptation and redistribution by others." Open Licensing Definition: - Licensing refers to the terms of use that an author places on an original work they have created. Depending on where in the world the work was created and by whom, different terms of use will indicate how openly others can use, retain, share and change the creation. - Full copyright licensing means that the creator has retained all rights and all requests to use, share or change the work must be sent to the original creator. - Open licensing refers to when the author chooses terms of use that allow others to use, share or change the work with few restrictions. A non-profit called Creative Commons created a set of open licenses called the Creative Commons licenses that is a standardized way to explain how other users can re-use, redistribute, retain, revise and remix the work. Watch the video below to hear a bit more about Creative Commons licensing. Creative Commons Licenses: - The base Creative Commons license is CC BY. - This license enables reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator. The license allows for commercial use. - If the creator is releasing all rights, including attribution, the resource is entered into the Public Domain and best practice includes describing that as CC-0 (pronounced CC-Zero). - Additional restrictions can be added to the CC BY license and sometimes the restrictions are combined. - Share Alike (SA) - if this restriction is added, any changes to the original resource, the modified material must be given the same licensing terms as the original resource. Attribution to the original author must still be given. - Non Commercial (NC) - if this restriction is added, only non-commercial uses of the resource are allowed. Attribution to the original author must still be given. - No Derivatives (ND) - copying and distributing of the material can only occur in the original, unmodified form of the work. No derivatives or adaptations are allowed. - You may see the above combined - such as CC-BY-NC-SA or CC-BY-NC-ND. This "What are Creative Commons licenses?" video from University of Guelph McLaughlin Library walks through the main ideas of Creative Commons licenses with concrete examples. Looking at an Example: - The video above is licensed CC-BY-NC-SA 4.0. - Could you repost it on your website and remove the title and attribution? - No - the CC-BY license requires attribution. - Could you add dubbing to overlay someone speaking the text in a different language? - Yes! The CC-BY license allows modification as long as you give attribution to the original creator, use the same license and don't make any money from your derivative. - Could you play the video at an event where you have charged admission and will make a commercial profit? - No! The CC-BY-NC-SA license does not allow for commercial use.	oercommons	2025-03-18T00:36:06.897877	11/20/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/122059/overview", "title": "OERizona Advanced OER Skills, Evaluating OER, Reviewing OER Licensing", "author": null }
https://oercommons.org/courseware/lesson/123174/overview	Time to Practice - OER Evaluation Overview This resource is part of the OERizona Advanced Course. This section supports faculty in reviewing OER of their choice. In this section, the faculty will review three OER using the OERizona Network Standards. Practicing OER Evaluation In this Module, you have explored OER Commons and the OERizona Hub, which are locations to start your search for high quality OER to use in your courses. To help contribute to the OERizona community, this course will support you in evaluating three different resources. Your evaluations will help curate high quality OER while also increasing the viewpoints of instructors who share the strengths and opportunities for growth within the resources they review. For this section, please follow the below steps: - Make sure that you are logged into OER Commons. - Locate an OER of your choice that already exists on OER Commons. We suggest using the "Advanced Search" feature. - Save the resource to your "My Items" so you can find it again later. We recommend making a folder specifically for this Advanced Course. - Leave a review in the "Comment" section of the resource's landing page. Include the following four things in your comment: - An overview of the resource - One indicator from the OERizona rubric that is a strength in this resource and the specific location in the resource that is a strength. - One indicator from the OERizona rubric that is an area of growth in this resource and the specific location in the resource that is an area of growth. - A note about possible collaboration or iterations that could be made to use this resource in your specific teaching setting. - Repeat. You should review three different items. Be sure the resources are saved in your "My Items" so you can find the URLs to submit at the end of this Module.	oercommons	2025-03-18T00:36:06.911497	12/18/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123174/overview", "title": "OERizona Advanced OER Skills, Evaluating OER, Time to Practice - OER Evaluation", "author": null }
https://oercommons.org/courseware/lesson/67347/overview	How to set up a meeting in Teams Infographic Microsoft Teams 101 Overview In November 2016, Microsoft added a new tool to its already robust Office 365 suite of services – Microsoft Teams. Teams is a chat-based collaboration tool that provides global, remote, and dispersed teams with the ability to work together and share information via a common space. You can utilize cool features like document collaboration, one-on-one chat, team chat, and more. Microsoft Teams is also fully integrated with many other Office 365 services, such as Skype, SharePoint, Exchange, and Yammer. The following core capabilities are included in Teams: Chat – Enjoy public and private conversations with your teams. The deep integration of Skype video into the application brings you popular social features, such as adding emojis and custom memes to your discussions. Hub – Teams offers a shared workspace for the various applications in Microsoft Office including PowerPoint, Word, Excel, Planner, OneNote, SharePoint, Delve, and Power BI. This feature gives you and your teams the option to work natively without having to stress about toggling between applications as you try to get projects completed. Introduction The COVID-19 pandemic has shown corporations that long-term telecommuting is possible, but what if you could make it even easier? Microsoft Teams offers companies the opportunity to stay connected and still achieve their goals. Below is a storyboard of a small shipping company that could have averted their issues by using Microsift Teams. The lesson explores Microsoft Teams and how companies can benefit from Teams based on the software's features and functionality. The lesson also prepares learners for posting files and creating meetings in Microsoft Teams. Percentage of Companies Using Microsoft Teams Glossary Terms to Know Microsoft Teams \| A communication and collaboration platform that combines persistent chat capabilities, video conferencing, file storage, and integration with other Office 365 applications. \| Channels \| Dedicated sections within a team to keep conversations organized by specific topics, projects, and disciplines. \| Teams \| A collection of people, content, and tools surrounding different projects and outcomes within an organization. \| Basic Glossary Review Once reviewed, please proceed to the next section. Goals & Objectives By the end of this course you will be able to: 1. Describe the purpose of Microsoft Teams. 2. Demonstrate adding files to a Teams channel. 3. Create and schedule a meeting in Teams. To complete this lesson, you will need to: 1. Know how to use a digital device (Laptop, phone, etc.). 2. Have a general understanding of Microsoft 365. 3. Recognize and communicate your company's mission statement. 4. Have a Microsoft Teams account for your business. Success Story Schneider Electric: Schneider Electric is a worldwide energy management company that does global work. Schneider Electric used Microsoft Teams to build a successful HR marketing campaign about the importance of Diversity and Inclusion. Purpose and Benefits of Microsoft Teams Purpose: It is a communication and collaboration platform that combines persistent chat capabilities, video conferencing, file storage, and integration with other Office 365 apps. Benefits: 1. Share ideas and expertise in private, chat-based conversations. 2. Create Office Online documents within the browser. 3. Integrate internal or external content & tools with different tabs. 4. Leverage bots to support your daily activities and tasks. Self-Organization and Collaboration: Let’s get started by thinking about how Microsoft Teams allows individual teams to self-organize and collaborate across business scenarios: 1. Teams are a collection of people, content, and tools surrounding different projects and outcomes within an organization. Teams can be private or public. 2. Channels are dedicated sections within a team to keep conversations organized by specific topics, projects, disciplines—whatever works for your team! Files that you share in a channel (on the Files tab) are stored in SharePoint. 3. Meetings. Teams allows you to schedule video or audio meetings for the whole team. To assist you in Teams, Microsoft has provided a great Quick Start Guide. It's recommended to keep this at your desk. Setting up a meeting in Teams 1. Select meeting icon . 2. Then select schedule a meeting. 3. Type in a meeting title and enter a location. 4. Choose a start and end time, and add details if needed. 5. Enter names in the Invite people box to add them to the meeting or add the channel for the project. 6. See everyone's availability in the Attendees list and, if needed, choose a suggested time or select Scheduling assistant to see more available times in a calendar view. 7. Under Select a channel to meet in, select the drop-down arrow to manage your meeting's privacy settings. 8. Select None to keep your meeting private. 9. Select a channel to open the meeting to team members. 10. If your meeting gets posted in a channel, it will appear under the Posts tab. Team members can set agendas, share files, or add comments. 11. At the conclusion of the meeting the individuals can exit the meeting or the meeting organizer can End meeting from within the meeting in Teams to end it and remove all participants from it. Knowledge Check: 1. Select __________ to keep the meeting private. A) Open B) None C) Channel If you chose answer B, you are correct! Sharing files in Teams Creating a meeting and adding files to Teams: This assessment is to give you the opportunity to test your knowledge and skills in setting up a meeting in Teams and adding files to Teams. Your Project Lead or Manager will assess your ability to do the following tasks: Scheduling a meeting by complete the following items: 1. For scheduled meetings, initiate a chat before the meeting begins (to discuss the agenda, for example). - Join a meeting and test different scenarios and workloads: For example, audio only, video, desktop sharing. - Sign in to the Microsoft Teams admin center and change some of the settings for meetings (for example, disable scheduling for private meetings). How does this affect the user experience? - As the meeting organizer, end a meeting for all participants. - Adding files by completing the following items: - Drag and drop one file into your team file folder. - Upload one file into your team file folder. Drag and drop one file into your team file folder. Upload one file into your team file folder. Please download the attached assessment form to be completed and kept in employee training file. Summary Key Takeaways Microsoft Teams is a chat-based collaboration platform complete with document sharing, online meetings, and many more extremely useful features for business communications. Having an excellent team space is key to being able to make creative decisions and communicate with one another. Microsoft Teams has many core components that make it stand out from other collaboration software: - Teams and channels. Teams are made up of channels, which are conversation boards between teammates. - Conversations within channels and teams. All team members can view and add to different conversations in the General channel. - A chat function. - Document storage in SharePoint. - Online video calling and screen sharing. - Online meetings. Teams is incredibly straightforward and user-friendly. There is little to no set up required. How Teams is set up is totally up to the company or business. Assessment Creating a meeting and adding files to Teams: This assessment is to give you the opportunity to test your knowledge and skills in setting up a meeting in Teams and adding files to Teams. Your Project Lead or Manager will assess your ability to do the following tasks: Scheduling a meeting by complete the following items: 1. For scheduled meetings, initiate a chat before the meeting begins (to discuss the agenda, for example). - Join a meeting and test different scenarios and workloads: For example, audio only, video, desktop sharing. - Sign in to the Microsoft Teams admin center and change some of the settings for meetings (for example, disable scheduling for private meetings). How does this affect the user experience? - As the meeting organizer, end a meeting for all participants. - Adding files by completing the following items: - Drag and drop one file into your team file folder. - Upload one file into your team file folder. Drag and drop one file into your team file folder. Upload one file into your team file folder. Please download the attached assessment form to be completed and kept in employee training file.	oercommons	2025-03-18T00:36:07.020661	Diagram/Illustration	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/67347/overview", "title": "Microsoft Teams 101", "author": "Assessment" }
https://oercommons.org/courseware/lesson/15105/overview	Introduction The arctic fox is an example of a complex animal that has adapted to its environment and illustrates the relationships between an animal’s form and function. The structures of animals consist of primary tissues that make up more complex organs and organ systems. Homeostasis allows an animal to maintain a balance between its internal and external environments.	oercommons	2025-03-18T00:36:07.036979	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15105/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15106/overview	Animal Form and Function Overview By the end of this section, you will be able to: - Describe the various types of body plans that occur in animals - Describe limits on animal size and shape - Relate bioenergetics to body size, levels of activity, and the environment Animals vary in form and function. From a sponge to a worm to a goat, an organism has a distinct body plan that limits its size and shape. Animals’ bodies are also designed to interact with their environments, whether in the deep sea, a rainforest canopy, or the desert. Therefore, a large amount of information about the structure of an organism's body (anatomy) and the function of its cells, tissues and organs (physiology) can be learned by studying that organism's environment. Body Plans Animal body plans follow set patterns related to symmetry. They are asymmetrical, radial, or bilateral in form as illustrated in Figure. Asymmetrical animals are animals with no pattern or symmetry; an example of an asymmetrical animal is a sponge. Radial symmetry, as illustrated in Figure, describes when an animal has an up-and-down orientation: any plane cut along its longitudinal axis through the organism produces equal halves, but not a definite right or left side. This plan is found mostly in aquatic animals, especially organisms that attach themselves to a base, like a rock or a boat, and extract their food from the surrounding water as it flows around the organism. Bilateral symmetry is illustrated in the same figure by a goat. The goat also has an upper and lower component to it, but a plane cut from front to back separates the animal into definite right and left sides. Additional terms used when describing positions in the body are anterior (front), posterior (rear), dorsal (toward the back), and ventral (toward the stomach). Bilateral symmetry is found in both land-based and aquatic animals; it enables a high level of mobility. Limits on Animal Size and Shape Animals with bilateral symmetry that live in water tend to have a fusiform shape: this is a tubular shaped body that is tapered at both ends. This shape decreases the drag on the body as it moves through water and allows the animal to swim at high speeds. Table lists the maximum speed of various animals. Certain types of sharks can swim at fifty kilometers an hour and some dolphins at 32 to 40 kilometers per hour. Land animals frequently travel faster, although the tortoise and snail are significantly slower than cheetahs. Another difference in the adaptations of aquatic and land-dwelling organisms is that aquatic organisms are constrained in shape by the forces of drag in the water since water has higher viscosity than air. On the other hand, land-dwelling organisms are constrained mainly by gravity, and drag is relatively unimportant. For example, most adaptations in birds are for gravity not for drag. \| Maximum Speed of Assorted Land Marine Animals \| \|\| \|---\|---\|---\| \| Animal \| Speed (kmh) \| Speed (mph) \| \| Cheetah \| 113 \| 70 \| \| Quarter horse \| 77 \| 48 \| \| Fox \| 68 \| 42 \| \| Shortfin mako shark \| 50 \| 31 \| \| Domestic house cat \| 48 \| 30 \| \| Human \| 45 \| 28 \| \| Dolphin \| 32–40 \| 20–25 \| \| Mouse \| 13 \| 8 \| \| Snail \| 0.05 \| 0.03 \| Most animals have an exoskeleton, including insects, spiders, scorpions, horseshoe crabs, centipedes, and crustaceans. Scientists estimate that, of insects alone, there are over 30 million species on our planet. The exoskeleton is a hard covering or shell that provides benefits to the animal, such as protection against damage from predators and from water loss (for land animals); it also provides for the attachments of muscles. As the tough and resistant outer cover of an arthropod, the exoskeleton may be constructed of a tough polymer such as chitin and is often biomineralized with materials such as calcium carbonate. This is fused to the animal’s epidermis. Ingrowths of the exoskeleton, called apodemes, function as attachment sites for muscles, similar to tendons in more advanced animals (Figure). In order to grow, the animal must first synthesize a new exoskeleton underneath the old one and then shed or molt the original covering. This limits the animal’s ability to grow continually, and may limit the individual’s ability to mature if molting does not occur at the proper time. The thickness of the exoskeleton must be increased significantly to accommodate any increase in weight. It is estimated that a doubling of body size increases body weight by a factor of eight. The increasing thickness of the chitin necessary to support this weight limits most animals with an exoskeleton to a relatively small size. The same principles apply to endoskeletons, but they are more efficient because muscles are attached on the outside, making it easier to compensate for increased mass. An animal with an endoskeleton has its size determined by the amount of skeletal system it needs in order to support the other tissues and the amount of muscle it needs for movement. As the body size increases, both bone and muscle mass increase. The speed achievable by the animal is a balance between its overall size and the bone and muscle that provide support and movement. Limiting Effects of Diffusion on Size and Development The exchange of nutrients and wastes between a cell and its watery environment occurs through the process of diffusion. All living cells are bathed in liquid, whether they are in a single-celled organism or a multicellular one. Diffusion is effective over a specific distance and limits the size that an individual cell can attain. If a cell is a single-celled microorganism, such as an amoeba, it can satisfy all of its nutrient and waste needs through diffusion. If the cell is too large, then diffusion is ineffective and the center of the cell does not receive adequate nutrients nor is it able to effectively dispel its waste. An important concept in understanding how efficient diffusion is as a means of transport is the surface to volume ratio. Recall that any three-dimensional object has a surface area and volume; the ratio of these two quantities is the surface-to-volume ratio. Consider a cell shaped like a perfect sphere: it has a surface area of 4πr2, and a volume of (4/3)πr3. The surface-to-volume ratio of a sphere is 3/r; as the cell gets bigger, its surface to volume ratio decreases, making diffusion less efficient. The larger the size of the sphere, or animal, the less surface area for diffusion it possesses. The solution to producing larger organisms is for them to become multicellular. Specialization occurs in complex organisms, allowing cells to become more efficient at doing fewer tasks. For example, circulatory systems bring nutrients and remove waste, while respiratory systems provide oxygen for the cells and remove carbon dioxide from them. Other organ systems have developed further specialization of cells and tissues and efficiently control body functions. Moreover, surface-to-volume ratio applies to other areas of animal development, such as the relationship between muscle mass and cross-sectional surface area in supporting skeletons, and in the relationship between muscle mass and the generation of dissipation of heat. Link to Learning Visit this interactive site to see an entire animal (a zebrafish embryo) at the cellular and sub-cellular level. Use the zoom and navigation functions for a virtual nanoscopy exploration. Animal Bioenergetics All animals must obtain their energy from food they ingest or absorb. These nutrients are converted to adenosine triphosphate (ATP) for short-term storage and use by all cells. Some animals store energy for slightly longer times as glycogen, and others store energy for much longer times in the form of triglycerides housed in specialized adipose tissues. No energy system is one hundred percent efficient, and an animal’s metabolism produces waste energy in the form of heat. If an animal can conserve that heat and maintain a relatively constant body temperature, it is classified as a warm-blooded animal and called an endotherm. The insulation used to conserve the body heat comes in the forms of fur, fat, or feathers. The absence of insulation in ectothermic animals increases their dependence on the environment for body heat. The amount of energy expended by an animal over a specific time is called its metabolic rate. The rate is measured variously in joules, calories, or kilocalories (1000 calories). Carbohydrates and proteins contain about 4.5 to 5 kcal/g, and fat contains about 9 kcal/g. Metabolic rate is estimated as the basal metabolic rate (BMR) in endothermic animals at rest and as the standard metabolic rate (SMR) in ectotherms. Human males have a BMR of 1600 to 1800 kcal/day, and human females have a BMR of 1300 to 1500 kcal/day. Even with insulation, endothermal animals require extensive amounts of energy to maintain a constant body temperature. An ectotherm such as an alligator has an SMR of 60 kcal/day. Energy Requirements Related to Body Size Smaller endothermic animals have a greater surface area for their mass than larger ones (Figure). Therefore, smaller animals lose heat at a faster rate than larger animals and require more energy to maintain a constant internal temperature. This results in a smaller endothermic animal having a higher BMR, per body weight, than a larger endothermic animal. Energy Requirements Related to Levels of Activity The more active an animal is, the more energy is needed to maintain that activity, and the higher its BMR or SMR. The average daily rate of energy consumption is about two to four times an animal’s BMR or SMR. Humans are more sedentary than most animals and have an average daily rate of only 1.5 times the BMR. The diet of an endothermic animal is determined by its BMR. For example: the type of grasses, leaves, or shrubs that an herbivore eats affects the number of calories that it takes in. The relative caloric content of herbivore foods, in descending order, is tall grasses > legumes > short grasses > forbs (any broad-leaved plant, not a grass) > subshrubs > annuals/biennials. Energy Requirements Related to Environment Animals adapt to extremes of temperature or food availability through torpor. Torpor is a process that leads to a decrease in activity and metabolism and allows animals to survive adverse conditions. Torpor can be used by animals for long periods, such as entering a state of hibernation during the winter months, in which case it enables them to maintain a reduced body temperature. During hibernation, ground squirrels can achieve an abdominal temperature of 0° C (32° F), while a bear’s internal temperature is maintained higher at about 37° C (99° F). If torpor occurs during the summer months with high temperatures and little water, it is called estivation. Some desert animals use this to survive the harshest months of the year. Torpor can occur on a daily basis; this is seen in bats and hummingbirds. While endothermy is limited in smaller animals by surface to volume ratio, some organisms can be smaller and still be endotherms because they employ daily torpor during the part of the day that is coldest. This allows them to conserve energy during the colder parts of the day, when they consume more energy to maintain their body temperature. Animal Body Planes and Cavities A standing vertebrate animal can be divided by several planes. A sagittal plane divides the body into right and left portions. A midsagittal plane divides the body exactly in the middle, making two equal right and left halves. A frontal plane (also called a coronal plane) separates the front from the back. A transverse plane (or, horizontal plane) divides the animal into upper and lower portions. This is sometimes called a cross section, and, if the transverse cut is at an angle, it is called an oblique plane. Figure illustrates these planes on a goat (a four-legged animal) and a human being. Vertebrate animals have a number of defined body cavities, as illustrated in Figure. Two of these are major cavities that contain smaller cavities within them. The dorsal cavity contains the cranial and the vertebral (or spinal) cavities. The ventral cavity contains the thoracic cavity, which in turn contains the pleural cavity around the lungs and the pericardial cavity, which surrounds the heart. The ventral cavity also contains the abdominopelvic cavity, which can be separated into the abdominal and the pelvic cavities. Career Connections Physical AnthropologistPhysical anthropologists study the adaption, variability, and evolution of human beings, plus their living and fossil relatives. They can work in a variety of settings, although most will have an academic appointment at a university, usually in an anthropology department or a biology, genetics, or zoology department. Non-academic positions are available in the automotive and aerospace industries where the focus is on human size, shape, and anatomy. Research by these professionals might range from studies of how the human body reacts to car crashes to exploring how to make seats more comfortable. Other non-academic positions can be obtained in museums of natural history, anthropology, archaeology, or science and technology. These positions involve educating students from grade school through graduate school. Physical anthropologists serve as education coordinators, collection managers, writers for museum publications, and as administrators. Zoos employ these professionals, especially if they have an expertise in primate biology; they work in collection management and captive breeding programs for endangered species. Forensic science utilizes physical anthropology expertise in identifying human and animal remains, assisting in determining the cause of death, and for expert testimony in trials. Section Summary Animal bodies come in a variety of sizes and shapes. Limits on animal size and shape include impacts to their movement. Diffusion affects their size and development. Bioenergetics describes how animals use and obtain energy in relation to their body size, activity level, and environment. Review Questions Which type of animal maintains a constant internal body temperature? - endotherm - ectotherm - coelomate - mesoderm Hint: A The symmetry found in animals that move swiftly is ________. - radial - bilateral - sequential - interrupted Hint: B What term describes the condition of a desert mouse that lowers its metabolic rate and “sleeps” during the hot day? - turgid - hibernation - estivation - normal sleep pattern Hint: C A plane that divides an animal into equal right and left portions is ________. - diagonal - midsagittal - coronal - transverse Hint: B A plane that divides an animal into dorsal and ventral portions is ________. - sagittal - midsagittal - coronal - transverse Hint: D The pleural cavity is a part of which cavity? - dorsal cavity - thoracic cavity - abdominal cavity - pericardial cavity Hint: B Free Response How does diffusion limit the size of an organism? How is this counteracted? Hint: Diffusion is effective over a very short distance. If a cell exceeds this distance in its size, the center of the cell cannot get adequate nutrients nor can it expel enough waste to survive. To compensate for this, cells can loosely adhere to each other in a liquid medium, or develop into multi-celled organisms that use circulatory and respiratory systems to deliver nutrients and remove wastes. What is the relationship between BMR and body size? Why? Hint: Basal Metabolic Rate is an expression of the metabolic processes that occur to maintain an individual’s functioning and body temperature. Smaller bodied animals have a relatively large surface area compared to a much larger animal. The large animal’s large surface area leads to increased heat loss that the animal must compensate for, resulting in a higher BMR. A small animal, having less relative surface area, does not lose as much heat and has a correspondingly lower BMR.	oercommons	2025-03-18T00:36:07.073503	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15106/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15107/overview	Animal Primary Tissues Overview By the end of this section, you will be able to: - Describe epithelial tissues - Discuss the different types of connective tissues in animals - Describe three types of muscle tissues - Describe nervous tissue The tissues of multicellular, complex animals are four primary types: epithelial, connective, muscle, and nervous. Recall that tissues are groups of similar cells group of similar cells carrying out related functions. These tissues combine to form organs—like the skin or kidney—that have specific, specialized functions within the body. Organs are organized into organ systems to perform functions; examples include the circulatory system, which consists of the heart and blood vessels, and the digestive system, consisting of several organs, including the stomach, intestines, liver, and pancreas. Organ systems come together to create an entire organism. Epithelial Tissues Epithelial tissues cover the outside of organs and structures in the body and line the lumens of organs in a single layer or multiple layers of cells. The types of epithelia are classified by the shapes of cells present and the number of layers of cells. Epithelia composed of a single layer of cells is called simple epithelia; epithelial tissue composed of multiple layers is called stratified epithelia. Table summarizes the different types of epithelial tissues. \| Different Types of Epithelial Tissues \| \|\| \|---\|---\|---\| \| Cell shape \| Description \| Location \| \| squamous \| flat, irregular round shape \| simple: lung alveoli, capillaries stratified: skin, mouth, vagina \| \| cuboidal \| cube shaped, central nucleus \| glands, renal tubules \| \| columnar \| tall, narrow, nucleus toward base tall, narrow, nucleus along cell \| simple: digestive tract pseudostratified: respiratory tract \| \| transitional \| round, simple but appear stratified \| urinary bladder \| Squamous Epithelia Squamous epithelial cells are generally round, flat, and have a small, centrally located nucleus. The cell outline is slightly irregular, and cells fit together to form a covering or lining. When the cells are arranged in a single layer (simple epithelia), they facilitate diffusion in tissues, such as the areas of gas exchange in the lungs and the exchange of nutrients and waste at blood capillaries. Figurea illustrates a layer of squamous cells with their membranes joined together to form an epithelium. Image Figureb illustrates squamous epithelial cells arranged in stratified layers, where protection is needed on the body from outside abrasion and damage. This is called a stratified squamous epithelium and occurs in the skin and in tissues lining the mouth and vagina. Cuboidal Epithelia Cuboidal epithelial cells, shown in Figure, are cube-shaped with a single, central nucleus. They are most commonly found in a single layer representing a simple epithelia in glandular tissues throughout the body where they prepare and secrete glandular material. They are also found in the walls of tubules and in the ducts of the kidney and liver. Columnar Epithelia Columnar epithelial cells are taller than they are wide: they resemble a stack of columns in an epithelial layer, and are most commonly found in a single-layer arrangement. The nuclei of columnar epithelial cells in the digestive tract appear to be lined up at the base of the cells, as illustrated in Figure. These cells absorb material from the lumen of the digestive tract and prepare it for entry into the body through the circulatory and lymphatic systems. Columnar epithelial cells lining the respiratory tract appear to be stratified. However, each cell is attached to the base membrane of the tissue and, therefore, they are simple tissues. The nuclei are arranged at different levels in the layer of cells, making it appear as though there is more than one layer, as seen in Figure. This is called pseudostratified, columnar epithelia. This cellular covering has cilia at the apical, or free, surface of the cells. The cilia enhance the movement of mucous and trapped particles out of the respiratory tract, helping to protect the system from invasive microorganisms and harmful material that has been breathed into the body. Goblet cells are interspersed in some tissues (such as the lining of the trachea). The goblet cells contain mucous that traps irritants, which in the case of the trachea keep these irritants from getting into the lungs. Transitional Epithelia Transitional or uroepithelial cells appear only in the urinary system, primarily in the bladder and ureter. These cells are arranged in a stratified layer, but they have the capability of appearing to pile up on top of each other in a relaxed, empty bladder, as illustrated in Figure. As the urinary bladder fills, the epithelial layer unfolds and expands to hold the volume of urine introduced into it. As the bladder fills, it expands and the lining becomes thinner. In other words, the tissue transitions from thick to thin. Art Connection Which of the following statements about types of epithelial cells is false? - Simple columnar epithelial cells line the tissue of the lung. - Simple cuboidal epithelial cells are involved in the filtering of blood in the kidney. - Pseudostratisfied columnar epithilia occur in a single layer, but the arrangement of nuclei makes it appear that more than one layer is present. - Transitional epithelia change in thickness depending on how full the bladder is. Connective Tissues Connective tissues are made up of a matrix consisting of living cells and a non-living substance, called the ground substance. The ground substance is made of an organic substance (usually a protein) and an inorganic substance (usually a mineral or water). The principal cell of connective tissues is the fibroblast. This cell makes the fibers found in nearly all of the connective tissues. Fibroblasts are motile, able to carry out mitosis, and can synthesize whichever connective tissue is needed. Macrophages, lymphocytes, and, occasionally, leukocytes can be found in some of the tissues. Some tissues have specialized cells that are not found in the others. The matrix in connective tissues gives the tissue its density. When a connective tissue has a high concentration of cells or fibers, it has proportionally a less dense matrix. The organic portion or protein fibers found in connective tissues are either collagen, elastic, or reticular fibers. Collagen fibers provide strength to the tissue, preventing it from being torn or separated from the surrounding tissues. Elastic fibers are made of the protein elastin; this fiber can stretch to one and one half of its length and return to its original size and shape. Elastic fibers provide flexibility to the tissues. Reticular fibers are the third type of protein fiber found in connective tissues. This fiber consists of thin strands of collagen that form a network of fibers to support the tissue and other organs to which it is connected. The various types of connective tissues, the types of cells and fibers they are made of, and sample locations of the tissues is summarized in Table. \| Connective Tissues \| \|\|\| \|---\|---\|---\|---\| \| Tissue \| Cells \| Fibers \| Location \| \| loose/areolar \| fibroblasts, macrophages, some lymphocytes, some neutrophils \| few: collagen, elastic, reticular \| around blood vessels; anchors epithelia \| \| dense, fibrous connective tissue \| fibroblasts, macrophages, \| mostly collagen \| irregular: skin regular: tendons, ligaments \| \| cartilage \| chondrocytes, chondroblasts \| hyaline: few collagen fibrocartilage: large amount of collagen \| shark skeleton, fetal bones, human ears, intervertebral discs \| \| bone \| osteoblasts, osteocytes, osteoclasts \| some: collagen, elastic \| vertebrate skeletons \| \| adipose \| adipocytes \| few \| adipose (fat) \| \| blood \| red blood cells, white blood cells \| none \| blood \| Loose/Areolar Connective Tissue Loose connective tissue, also called areolar connective tissue, has a sampling of all of the components of a connective tissue. As illustrated in Figure, loose connective tissue has some fibroblasts; macrophages are present as well. Collagen fibers are relatively wide and stain a light pink, while elastic fibers are thin and stain dark blue to black. The space between the formed elements of the tissue is filled with the matrix. The material in the connective tissue gives it a loose consistency similar to a cotton ball that has been pulled apart. Loose connective tissue is found around every blood vessel and helps to keep the vessel in place. The tissue is also found around and between most body organs. In summary, areolar tissue is tough, yet flexible, and comprises membranes. Fibrous Connective Tissue Fibrous connective tissues contain large amounts of collagen fibers and few cells or matrix material. The fibers can be arranged irregularly or regularly with the strands lined up in parallel. Irregularly arranged fibrous connective tissues are found in areas of the body where stress occurs from all directions, such as the dermis of the skin. Regular fibrous connective tissue, shown in Figure, is found in tendons (which connect muscles to bones) and ligaments (which connect bones to bones). Cartilage Cartilage is a connective tissue with a large amount of the matrix and variable amounts of fibers. The cells, called chondrocytes, make the matrix and fibers of the tissue. Chondrocytes are found in spaces within the tissue called lacunae. A cartilage with few collagen and elastic fibers is hyaline cartilage, illustrated in Figure. The lacunae are randomly scattered throughout the tissue and the matrix takes on a milky or scrubbed appearance with routine histological stains. Sharks have cartilaginous skeletons, as does nearly the entire human skeleton during a specific pre-birth developmental stage. A remnant of this cartilage persists in the outer portion of the human nose. Hyaline cartilage is also found at the ends of long bones, reducing friction and cushioning the articulations of these bones. Elastic cartilage has a large amount of elastic fibers, giving it tremendous flexibility. The ears of most vertebrate animals contain this cartilage as do portions of the larynx, or voice box. Fibrocartilage contains a large amount of collagen fibers, giving the tissue tremendous strength. Fibrocartilage comprises the intervertebral discs in vertebrate animals. Hyaline cartilage found in movable joints such as the knee and shoulder becomes damaged as a result of age or trauma. Damaged hyaline cartilage is replaced by fibrocartilage and results in the joints becoming “stiff.” Bone Bone, or osseous tissue, is a connective tissue that has a large amount of two different types of matrix material. The organic matrix is similar to the matrix material found in other connective tissues, including some amount of collagen and elastic fibers. This gives strength and flexibility to the tissue. The inorganic matrix consists of mineral salts—mostly calcium salts—that give the tissue hardness. Without adequate organic material in the matrix, the tissue breaks; without adequate inorganic material in the matrix, the tissue bends. There are three types of cells in bone: osteoblasts, osteocytes, and osteoclasts. Osteoblasts are active in making bone for growth and remodeling. Osteoblasts deposit bone material into the matrix and, after the matrix surrounds them, they continue to live, but in a reduced metabolic state as osteocytes. Osteocytes are found in lacunae of the bone. Osteoclasts are active in breaking down bone for bone remodeling, and they provide access to calcium stored in tissues. Osteoclasts are usually found on the surface of the tissue. Bone can be divided into two types: compact and spongy. Compact bone is found in the shaft (or diaphysis) of a long bone and the surface of the flat bones, while spongy bone is found in the end (or epiphysis) of a long bone. Compact bone is organized into subunits called osteons, as illustrated in Figure. A blood vessel and a nerve are found in the center of the structure within the Haversian canal, with radiating circles of lacunae around it known as lamellae. The wavy lines seen between the lacunae are microchannels called canaliculi; they connect the lacunae to aid diffusion between the cells. Spongy bone is made of tiny plates called trabeculae these plates serve as struts to give the spongy bone strength. Over time, these plates can break causing the bone to become less resilient. Bone tissue forms the internal skeleton of vertebrate animals, providing structure to the animal and points of attachment for tendons. Adipose Tissue Adipose tissue, or fat tissue, is considered a connective tissue even though it does not have fibroblasts or a real matrix and only has a few fibers. Adipose tissue is made up of cells called adipocytes that collect and store fat in the form of triglycerides, for energy metabolism. Adipose tissues additionally serve as insulation to help maintain body temperatures, allowing animals to be endothermic, and they function as cushioning against damage to body organs. Under a microscope, adipose tissue cells appear empty due to the extraction of fat during the processing of the material for viewing, as seen in Figure. The thin lines in the image are the cell membranes, and the nuclei are the small, black dots at the edges of the cells. Blood Blood is considered a connective tissue because it has a matrix, as shown in Figure. The living cell types are red blood cells (RBC), also called erythrocytes, and white blood cells (WBC), also called leukocytes. The fluid portion of whole blood, its matrix, is commonly called plasma. The cell found in greatest abundance in blood is the erythrocyte. Erythrocytes are counted in millions in a blood sample: the average number of red blood cells in primates is 4.7 to 5.5 million cells per microliter. Erythrocytes are consistently the same size in a species, but vary in size between species. For example, the average diameter of a primate red blood cell is 7.5 µl, a dog is close at 7.0 µl, but a cat’s RBC diameter is 5.9 µl. Sheep erythrocytes are even smaller at 4.6 µl. Mammalian erythrocytes lose their nuclei and mitochondria when they are released from the bone marrow where they are made. Fish, amphibian, and avian red blood cells maintain their nuclei and mitochondria throughout the cell’s life. The principal job of an erythrocyte is to carry and deliver oxygen to the tissues. Leukocytes are the predominant white blood cells found in the peripheral blood. Leukocytes are counted in the thousands in the blood with measurements expressed as ranges: primate counts range from 4,800 to 10,800 cells per µl, dogs from 5,600 to 19,200 cells per µl, cats from 8,000 to 25,000 cells per µl, cattle from 4,000 to 12,000 cells per µl, and pigs from 11,000 to 22,000 cells per µl. Lymphocytes function primarily in the immune response to foreign antigens or material. Different types of lymphocytes make antibodies tailored to the foreign antigens and control the production of those antibodies. Neutrophils are phagocytic cells and they participate in one of the early lines of defense against microbial invaders, aiding in the removal of bacteria that has entered the body. Another leukocyte that is found in the peripheral blood is the monocyte. Monocytes give rise to phagocytic macrophages that clean up dead and damaged cells in the body, whether they are foreign or from the host animal. Two additional leukocytes in the blood are eosinophils and basophils—both help to facilitate the inflammatory response. The slightly granular material among the cells is a cytoplasmic fragment of a cell in the bone marrow. This is called a platelet or thrombocyte. Platelets participate in the stages leading up to coagulation of the blood to stop bleeding through damaged blood vessels. Blood has a number of functions, but primarily it transports material through the body to bring nutrients to cells and remove waste material from them. Muscle Tissues There are three types of muscle in animal bodies: smooth, skeletal, and cardiac. They differ by the presence or absence of striations or bands, the number and location of nuclei, whether they are voluntarily or involuntarily controlled, and their location within the body. Table summarizes these differences. \| Types of Muscles \| \|\|\|\| \|---\|---\|---\|---\|---\| \| Type of Muscle \| Striations \| Nuclei \| Control \| Location \| \| smooth \| no \| single, in center \| involuntary \| visceral organs \| \| skeletal \| yes \| many, at periphery \| voluntary \| skeletal muscles \| \| cardiac \| yes \| single, in center \| involuntary \| heart \| Smooth Muscle Smooth muscle does not have striations in its cells. It has a single, centrally located nucleus, as shown in Figure. Constriction of smooth muscle occurs under involuntary, autonomic nervous control and in response to local conditions in the tissues. Smooth muscle tissue is also called non-striated as it lacks the banded appearance of skeletal and cardiac muscle. The walls of blood vessels, the tubes of the digestive system, and the tubes of the reproductive systems are composed of mostly smooth muscle. Skeletal Muscle Skeletal muscle has striations across its cells caused by the arrangement of the contractile proteins actin and myosin. These muscle cells are relatively long and have multiple nuclei along the edge of the cell. Skeletal muscle is under voluntary, somatic nervous system control and is found in the muscles that move bones. Figure illustrates the histology of skeletal muscle. Cardiac Muscle Cardiac muscle, shown in Figure, is found only in the heart. Like skeletal muscle, it has cross striations in its cells, but cardiac muscle has a single, centrally located nucleus. Cardiac muscle is not under voluntary control but can be influenced by the autonomic nervous system to speed up or slow down. An added feature to cardiac muscle cells is a line than extends along the end of the cell as it abuts the next cardiac cell in the row. This line is called an intercalated disc: it assists in passing electrical impulse efficiently from one cell to the next and maintains the strong connection between neighboring cardiac cells. Nervous Tissues Nervous tissues are made of cells specialized to receive and transmit electrical impulses from specific areas of the body and to send them to specific locations in the body. The main cell of the nervous system is the neuron, illustrated in Figure. The large structure with a central nucleus is the cell body of the neuron. Projections from the cell body are either dendrites specialized in receiving input or a single axon specialized in transmitting impulses. Some glial cells are also shown. Astrocytes regulate the chemical environment of the nerve cell, and oligodendrocytes insulate the axon so the electrical nerve impulse is transferred more efficiently. Other glial cells that are not shown support the nutritional and waste requirements of the neuron. Some of the glial cells are phagocytic and remove debris or damaged cells from the tissue. A nerve consists of neurons and glial cells. Link to Learning Click through the interactive review to learn more about epithelial tissues. Career Connections PathologistA pathologist is a medical doctor or veterinarian who has specialized in the laboratory detection of disease in animals, including humans. These professionals complete medical school education and follow it with an extensive post-graduate residency at a medical center. A pathologist may oversee clinical laboratories for the evaluation of body tissue and blood samples for the detection of disease or infection. They examine tissue specimens through a microscope to identify cancers and other diseases. Some pathologists perform autopsies to determine the cause of death and the progression of disease. Section Summary The basic building blocks of complex animals are four primary tissues. These are combined to form organs, which have a specific, specialized function within the body, such as the skin or kidney. Organs are organized together to perform common functions in the form of systems. The four primary tissues are epithelia, connective tissues, muscle tissues, and nervous tissues. Art Connections Figure Which of the following statements about types of epithelial cells is false? - Simple columnar epithelial cells line the tissue of the lung. - Simple cuboidal epithelial cells are involved in the filtering of blood in the kidney. - Pseudostratisfied columnar epithilia occur in a single layer, but the arrangement of nuclei makes it appear that more than one layer is present. - Transitional epithelia change in thickness depending on how full the bladder is. Hint: Figure A Review Questions Which type of epithelial cell is best adapted to aid diffusion? - squamous - cuboidal - columnar - transitional Hint: C Which type of epithelial cell is found in glands? - squamous - cuboidal - columnar - transitional Hint: B Which type of epithelial cell is found in the urinary bladder? - squamous - cuboidal - columnar - transitional Hint: D Which type of connective tissue has the most fibers? - loose connective tissue - fibrous connective tissue - cartilage - bone Hint: B Which type of connective tissue has a mineralized different matrix? - loose connective tissue - fibrous connective tissue - cartilage - bone Hint: D The cell found in bone that breaks it down is called an ________. - osteoblast - osteocyte - osteoclast - osteon Hint: C The cell found in bone that makes the bone is called an ________. - osteoblast - osteocyte - osteoclast - osteon Hint: A Plasma is the ________. - fibers in blood - matrix of blood - cell that phagocytizes bacteria - cell fragment found in the tissue Hint: B The type of muscle cell under voluntary control is the ________. - smooth muscle - skeletal muscle - cardiac muscle - visceral muscle Hint: B The part of a neuron that contains the nucleus is the - cell body - dendrite - axon - glial Hint: A Free Response How can squamous epithelia both facilitate diffusion and prevent damage from abrasion? Hint: Squamous epithelia can be either simple or stratified. As a single layer of cells, it presents a very thin epithelia that minimally inhibits diffusion. As a stratified epithelia, the surface cells can be sloughed off and the cells in deeper layers protect the underlying tissues from damage. What are the similarities between cartilage and bone? Hint: Both contain cells other than the traditional fibroblast. Both have cells that lodge in spaces within the tissue called lacunae. Both collagen and elastic fibers are found in bone and cartilage. Both tissues participate in vertebrate skeletal development and formation.	oercommons	2025-03-18T00:36:07.123804	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15107/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15108/overview	Homeostasis Overview By the end of this section, you will be able to: - Define homeostasis - Describe the factors affecting homeostasis - Discuss positive and negative feedback mechanisms used in homeostasis - Describe thermoregulation of endothermic and ectothermic animals Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis (“steady state”). These changes might be in the level of glucose or calcium in blood or in external temperatures. Homeostasis means to maintain dynamic equilibrium in the body. It is dynamic because it is constantly adjusting to the changes that the body’s systems encounter. It is equilibrium because body functions are kept within specific ranges. Even an animal that is apparently inactive is maintaining this homeostatic equilibrium. Homeostatic Process The goal of homeostasis is the maintenance of equilibrium around a point or value called a set point. While there are normal fluctuations from the set point, the body’s systems will usually attempt to go back to this point. A change in the internal or external environment is called a stimulus and is detected by a receptor; the response of the system is to adjust the deviation parameter toward the set point. For instance, if the body becomes too warm, adjustments are made to cool the animal. If the blood’s glucose rises after a meal, adjustments are made to lower the blood glucose level by getting the nutrient into tissues that need it or to store it for later use. Control of Homeostasis When a change occurs in an animal’s environment, an adjustment must be made. The receptor senses the change in the environment, then sends a signal to the control center (in most cases, the brain) which in turn generates a response that is signaled to an effector. The effector is a muscle (that contracts or relaxes) or a gland that secretes. Homeostatsis is maintained by negative feedback loops. Positive feedback loops actually push the organism further out of homeostasis, but may be necessary for life to occur. Homeostasis is controlled by the nervous and endocrine system of mammals. Negative Feedback Mechanisms Any homeostatic process that changes the direction of the stimulus is a negative feedback loop. It may either increase or decrease the stimulus, but the stimulus is not allowed to continue as it did before the receptor sensed it. In other words, if a level is too high, the body does something to bring it down, and conversely, if a level is too low, the body does something to make it go up. Hence the term negative feedback. An example is animal maintenance of blood glucose levels. When an animal has eaten, blood glucose levels rise. This is sensed by the nervous system. Specialized cells in the pancreas sense this, and the hormone insulin is released by the endocrine system. Insulin causes blood glucose levels to decrease, as would be expected in a negative feedback system, as illustrated in Figure. However, if an animal has not eaten and blood glucose levels decrease, this is sensed in another group of cells in the pancreas, and the hormone glucagon is released causing glucose levels to increase. This is still a negative feedback loop, but not in the direction expected by the use of the term “negative.” Another example of an increase as a result of the feedback loop is the control of blood calcium. If calcium levels decrease, specialized cells in the parathyroid gland sense this and release parathyroid hormone (PTH), causing an increased absorption of calcium through the intestines and kidneys and, possibly, the breakdown of bone in order to liberate calcium. The effects of PTH are to raise blood levels of the element. Negative feedback loops are the predominant mechanism used in homeostasis. Positive Feedback Loop A positive feedback loop maintains the direction of the stimulus, possibly accelerating it. Few examples of positive feedback loops exist in animal bodies, but one is found in the cascade of chemical reactions that result in blood clotting, or coagulation. As one clotting factor is activated, it activates the next factor in sequence until a fibrin clot is achieved. The direction is maintained, not changed, so this is positive feedback. Another example of positive feedback is uterine contractions during childbirth, as illustrated in Figure. The hormone oxytocin, made by the endocrine system, stimulates the contraction of the uterus. This produces pain sensed by the nervous system. Instead of lowering the oxytocin and causing the pain to subside, more oxytocin is produced until the contractions are powerful enough to produce childbirth. Art Connection State whether each of the following processes is regulated by a positive feedback loop or a negative feedback loop. - A person feels satiated after eating a large meal. - The blood has plenty of red blood cells. As a result, erythropoietin, a hormone that stimulates the production of new red blood cells, is no longer released from the kidney. Set Point It is possible to adjust a system’s set point. When this happens, the feedback loop works to maintain the new setting. An example of this is blood pressure: over time, the normal or set point for blood pressure can increase as a result of continued increases in blood pressure. The body no longer recognizes the elevation as abnormal and no attempt is made to return to the lower set point. The result is the maintenance of an elevated blood pressure that can have harmful effects on the body. Medication can lower blood pressure and lower the set point in the system to a more healthy level. This is called a process of alteration of the set point in a feedback loop. Changes can be made in a group of body organ systems in order to maintain a set point in another system. This is called acclimatization. This occurs, for instance, when an animal migrates to a higher altitude than it is accustomed to. In order to adjust to the lower oxygen levels at the new altitude, the body increases the number of red blood cells circulating in the blood to ensure adequate oxygen delivery to the tissues. Another example of acclimatization is animals that have seasonal changes in their coats: a heavier coat in the winter ensures adequate heat retention, and a light coat in summer assists in keeping body temperature from rising to harmful levels. Link to Learning Feedback mechanisms can be understood in terms of driving a race car along a track: watch a short video lesson on positive and negative feedback loops. Homeostasis: Thermoregulation Body temperature affects body activities. Generally, as body temperature rises, enzyme activity rises as well. For every ten degree centigrade rise in temperature, enzyme activity doubles, up to a point. Body proteins, including enzymes, begin to denature and lose their function with high heat (around 50oC for mammals). Enzyme activity will decrease by half for every ten degree centigrade drop in temperature, to the point of freezing, with a few exceptions. Some fish can withstand freezing solid and return to normal with thawing. Link to Learning Watch this Discovery Channel video on thermoregulation to see illustrations of this process in a variety of animals. Endotherms and Ectotherms Animals can be divided into two groups: some maintain a constant body temperature in the face of differing environmental temperatures, while others have a body temperature that is the same as their environment and thus varies with the environment. Animals that do not control their body temperature are ectotherms. This group has been called cold-blooded, but the term may not apply to an animal in the desert with a very warm body temperature. In contrast to ectotherms, which rely on external temperatures to set their body temperatures, poikilotherms are animals with constantly varying internal temperatures. An animal that maintains a constant body temperature in the face of environmental changes is called a homeotherm. Endotherms are animals that rely on internal sources for body temperature but which can exhibit extremes in temperature. These animals are able to maintain a level of activity at cooler temperature, which an ectotherm cannot due to differing enzyme levels of activity. Heat can be exchanged between an animal and its environment through four mechanisms: radiation, evaporation, convection, and conduction (Figure). Radiation is the emission of electromagnetic “heat” waves. Heat comes from the sun in this manner and radiates from dry skin the same way. Heat can be removed with liquid from a surface during evaporation. This occurs when a mammal sweats. Convection currents of air remove heat from the surface of dry skin as the air passes over it. Heat will be conducted from one surface to another during direct contact with the surfaces, such as an animal resting on a warm rock. Heat Conservation and Dissipation Animals conserve or dissipate heat in a variety of ways. In certain climates, endothermic animals have some form of insulation, such as fur, fat, feathers, or some combination thereof. Animals with thick fur or feathers create an insulating layer of air between their skin and internal organs. Polar bears and seals live and swim in a subfreezing environment and yet maintain a constant, warm, body temperature. The arctic fox, for example, uses its fluffy tail as extra insulation when it curls up to sleep in cold weather. Mammals have a residual effect from shivering and increased muscle activity: arrector pili muscles cause “goose bumps,” causing small hairs to stand up when the individual is cold; this has the intended effect of increasing body temperature. Mammals use layers of fat to achieve the same end. Loss of significant amounts of body fat will compromise an individual’s ability to conserve heat. Endotherms use their circulatory systems to help maintain body temperature. Vasodilation brings more blood and heat to the body surface, facilitating radiation and evaporative heat loss, which helps to cool the body. Vasoconstriction reduces blood flow in peripheral blood vessels, forcing blood toward the core and the vital organs found there, and conserving heat. Some animals have adaptions to their circulatory system that enable them to transfer heat from arteries to veins, warming blood returning to the heart. This is called a countercurrent heat exchange; it prevents the cold venous blood from cooling the heart and other internal organs. This adaption can be shut down in some animals to prevent overheating the internal organs. The countercurrent adaption is found in many animals, including dolphins, sharks, bony fish, bees, and hummingbirds. In contrast, similar adaptations can help cool endotherms when needed, such as dolphin flukes and elephant ears. Some ectothermic animals use changes in their behavior to help regulate body temperature. For example, a desert ectothermic animal may simply seek cooler areas during the hottest part of the day in the desert to keep from getting too warm. The same animals may climb onto rocks to capture heat during a cold desert night. Some animals seek water to aid evaporation in cooling them, as seen with reptiles. Other ectotherms use group activity such as the activity of bees to warm a hive to survive winter. Many animals, especially mammals, use metabolic waste heat as a heat source. When muscles are contracted, most of the energy from the ATP used in muscle actions is wasted energy that translates into heat. Severe cold elicits a shivering reflex that generates heat for the body. Many species also have a type of adipose tissue called brown fat that specializes in generating heat. Neural Control of Thermoregulation The nervous system is important to thermoregulation, as illustrated in Figure. The processes of homeostasis and temperature control are centered in the hypothalamus of the advanced animal brain. Art Connection When bacteria are destroyed by leuckocytes, pyrogens are released into the blood. Pyrogens reset the body’s thermostat to a higher temperature, resulting in fever. How might pyrogens cause the body temperature to rise? The hypothalamus maintains the set point for body temperature through reflexes that cause vasodilation and sweating when the body is too warm, or vasoconstriction and shivering when the body is too cold. It responds to chemicals from the body. When a bacterium is destroyed by phagocytic leukocytes, chemicals called endogenous pyrogens are released into the blood. These pyrogens circulate to the hypothalamus and reset the thermostat. This allows the body’s temperature to increase in what is commonly called a fever. An increase in body temperature causes iron to be conserved, which reduces a nutrient needed by bacteria. An increase in body heat also increases the activity of the animal’s enzymes and protective cells while inhibiting the enzymes and activity of the invading microorganisms. Finally, heat itself may also kill the pathogen. A fever that was once thought to be a complication of an infection is now understood to be a normal defense mechanism. Section Summary Homeostasis is a dynamic equilibrium that is maintained in body tissues and organs. It is dynamic because it is constantly adjusting to the changes that the systems encounter. It is in equilibrium because body functions are kept within a normal range, with some fluctuations around a set point for the processes. Art Connections Figure State whether each of the following processes are regulated by a positive feedback loop or a negative feedback loop. - A person feels satiated after eating a large meal. - The blood has plenty of red blood cells. As a result, erythropoietin, a hormone that stimulates the production of new red blood cells, is no longer released from the kidney. Hint: Figure Both processes are the result of negative feedback loops. Negative feedback loops, which tend to keep a system at equilibrium, are more common than positive feedback loops. Figure When bacteria are destroyed by leuckocytes, pyrogens are released into the blood. Pyrogens reset the body’s thermostat to a higher temperature, resulting in fever. How might pyrogens cause the body temperature to rise? Hint: Figure Pyrogens increase body temperature by causing the blood vessels to constrict, inducing shivering, and stopping sweat glands from secreting fluid. Review Questions When faced with a sudden drop in environmental temperature, an endothermic animal will: - experience a drop in its body temperature - wait to see if it goes lower - increase muscle activity to generate heat - add fur or fat to increase insulation Hint: C Which is an example of negative feedback? - lowering of blood glucose after a meal - blood clotting after an injury - lactation during nursing - uterine contractions during labor Hint: A Which method of heat exchange occurs during direct contact between the source and animal? - radiation - evaporation - convection - conduction Hint: D The body’s thermostat is located in the ________. - homeostatic receptor - hypothalamus - medulla - vasodilation center Hint: B Free Response Why are negative feedback loops used to control body homeostasis? Hint: An adjustment to a change in the internal or external environment requires a change in the direction of the stimulus. A negative feedback loop accomplishes this, while a positive feedback loop would continue the stimulus and result in harm to the animal. Why is a fever a “good thing” during a bacterial infection? Hint: Mammalian enzymes increase activity to the point of denaturation, increasing the chemical activity of the cells involved. Bacterial enzymes have a specific temperature for their most efficient activity and are inhibited at either higher or lower temperatures. Fever results in an increase in the destruction of the invading bacteria by increasing the effectiveness of body defenses and an inhibiting bacterial metabolism. How is a condition such as diabetes a good example of the failure of a set point in humans? Hint: Diabetes is often associated with a lack in production of insulin. Without insulin, blood glucose levels go up after a meal, but never go back down to normal levels.	oercommons	2025-03-18T00:36:07.160992	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15108/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15109/overview	Introduction All living organisms need nutrients to survive. While plants can obtain the molecules required for cellular function through the process of photosynthesis, most animals obtain their nutrients by the consumption of other organisms. At the cellular level, the biological molecules necessary for animal function are amino acids, lipid molecules, nucleotides, and simple sugars. However, the food consumed consists of protein, fat, and complex carbohydrates. Animals must convert these macromolecules into the simple molecules required for maintaining cellular functions, such as assembling new molecules, cells, and tissues. The conversion of the food consumed to the nutrients required is a multi-step process involving digestion and absorption. During digestion, food particles are broken down to smaller components, and later, they are absorbed by the body. One of the challenges in human nutrition is maintaining a balance between food intake, storage, and energy expenditure. Imbalances can have serious health consequences. For example, eating too much food while not expending much energy leads to obesity, which in turn will increase the risk of developing illnesses such as type-2 diabetes and cardiovascular disease. The recent rise in obesity and related diseases makes understanding the role of diet and nutrition in maintaining good health all the more important.	oercommons	2025-03-18T00:36:07.177427	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15109/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15110/overview	Digestive Systems Overview By the end of this section, you will be able to: - Explain the processes of digestion and absorption - Compare and contrast different types of digestive systems - Explain the specialized functions of the organs involved in processing food in the body - Describe the ways in which organs work together to digest food and absorb nutrients Animals obtain their nutrition from the consumption of other organisms. Depending on their diet, animals can be classified into the following categories: plant eaters (herbivores), meat eaters (carnivores), and those that eat both plants and animals (omnivores). The nutrients and macromolecules present in food are not immediately accessible to the cells. There are a number of processes that modify food within the animal body in order to make the nutrients and organic molecules accessible for cellular function. As animals evolved in complexity of form and function, their digestive systems have also evolved to accommodate their various dietary needs. Herbivores, Omnivores, and Carnivores Herbivores are animals whose primary food source is plant-based. Examples of herbivores, as shown in Figure include vertebrates like deer, koalas, and some bird species, as well as invertebrates such as crickets and caterpillars. These animals have evolved digestive systems capable of handling large amounts of plant material. Herbivores can be further classified into frugivores (fruit-eaters), granivores (seed eaters), nectivores (nectar feeders), and folivores (leaf eaters). Carnivores are animals that eat other animals. The word carnivore is derived from Latin and literally means “meat eater.” Wild cats such as lions, shown in Figurea and tigers are examples of vertebrate carnivores, as are snakes and sharks, while invertebrate carnivores include sea stars, spiders, and ladybugs, shown in Figureb. Obligate carnivores are those that rely entirely on animal flesh to obtain their nutrients; examples of obligate carnivores are members of the cat family, such as lions and cheetahs. Facultative carnivores are those that also eat non-animal food in addition to animal food. Note that there is no clear line that differentiates facultative carnivores from omnivores; dogs would be considered facultative carnivores. Omnivores are animals that eat both plant- and animal-derived food. In Latin, omnivore means to eat everything. Humans, bears (shown in Figurea), and chickens are example of vertebrate omnivores; invertebrate omnivores include cockroaches and crayfish (shown in Figureb). Invertebrate Digestive Systems Animals have evolved different types of digestive systems to aid in the digestion of the different foods they consume. The simplest example is that of a gastrovascular cavity and is found in organisms with only one opening for digestion. Platyhelminthes (flatworms), Ctenophora (comb jellies), and Cnidaria (coral, jelly fish, and sea anemones) use this type of digestion. Gastrovascular cavities, as shown in Figurea, are typically a blind tube or cavity with only one opening, the “mouth”, which also serves as an “anus”. Ingested material enters the mouth and passes through a hollow, tubular cavity. Cells within the cavity secrete digestive enzymes that break down the food. The food particles are engulfed by the cells lining the gastrovascular cavity. The alimentary canal, shown in Figureb, is a more advanced system: it consists of one tube with a mouth at one end and an anus at the other. Earthworms are an example of an animal with an alimentary canal. Once the food is ingested through the mouth, it passes through the esophagus and is stored in an organ called the crop; then it passes into the gizzard where it is churned and digested. From the gizzard, the food passes through the intestine, the nutrients are absorbed, and the waste is eliminated as feces, called castings, through the anus. Vertebrate Digestive Systems Vertebrates have evolved more complex digestive systems to adapt to their dietary needs. Some animals have a single stomach, while others have multi-chambered stomachs. Birds have developed a digestive system adapted to eating unmasticated food. Monogastric: Single-chambered Stomach As the word monogastric suggests, this type of digestive system consists of one (“mono”) stomach chamber (“gastric”). Humans and many animals have a monogastric digestive system as illustrated in Figureab. The process of digestion begins with the mouth and the intake of food. The teeth play an important role in masticating (chewing) or physically breaking down food into smaller particles. The enzymes present in saliva also begin to chemically break down food. The esophagus is a long tube that connects the mouth to the stomach. Using peristalsis, or wave-like smooth muscle contractions, the muscles of the esophagus push the food towards the stomach. In order to speed up the actions of enzymes in the stomach, the stomach is an extremely acidic environment, with a pH between 1.5 and 2.5. The gastric juices, which include enzymes in the stomach, act on the food particles and continue the process of digestion. Further breakdown of food takes place in the small intestine where enzymes produced by the liver, the small intestine, and the pancreas continue the process of digestion. The nutrients are absorbed into the blood stream across the epithelial cells lining the walls of the small intestines. The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces; it is stored until it is excreted through the rectum. Avian Birds face special challenges when it comes to obtaining nutrition from food. They do not have teeth and so their digestive system, shown in Figure, must be able to process un-masticated food. Birds have evolved a variety of beak types that reflect the vast variety in their diet, ranging from seeds and insects to fruits and nuts. Because most birds fly, their metabolic rates are high in order to efficiently process food and keep their body weight low. The stomach of birds has two chambers: the proventriculus, where gastric juices are produced to digest the food before it enters the stomach, and the gizzard, where the food is stored, soaked, and mechanically ground. The undigested material forms food pellets that are sometimes regurgitated. Most of the chemical digestion and absorption happens in the intestine and the waste is excreted through the cloaca. Evolution Connection Avian AdaptationsBirds have a highly efficient, simplified digestive system. Recent fossil evidence has shown that the evolutionary divergence of birds from other land animals was characterized by streamlining and simplifying the digestive system. Unlike many other animals, birds do not have teeth to chew their food. In place of lips, they have sharp pointy beaks. The horny beak, lack of jaws, and the smaller tongue of the birds can be traced back to their dinosaur ancestors. The emergence of these changes seems to coincide with the inclusion of seeds in the bird diet. Seed-eating birds have beaks that are shaped for grabbing seeds and the two-compartment stomach allows for delegation of tasks. Since birds need to remain light in order to fly, their metabolic rates are very high, which means they digest their food very quickly and need to eat often. Contrast this with the ruminants, where the digestion of plant matter takes a very long time. Ruminants Ruminants are mainly herbivores like cows, sheep, and goats, whose entire diet consists of eating large amounts of roughage or fiber. They have evolved digestive systems that help them digest vast amounts of cellulose. An interesting feature of the ruminants’ mouth is that they do not have upper incisor teeth. They use their lower teeth, tongue and lips to tear and chew their food. From the mouth, the food travels to the esophagus and on to the stomach. To help digest the large amount of plant material, the stomach of the ruminants is a multi-chambered organ, as illustrated in Figure. The four compartments of the stomach are called the rumen, reticulum, omasum, and abomasum. These chambers contain many microbes that break down cellulose and ferment ingested food. The abomasum is the “true” stomach and is the equivalent of the monogastric stomach chamber where gastric juices are secreted. The four-compartment gastric chamber provides larger space and the microbial support necessary to digest plant material in ruminants. The fermentation process produces large amounts of gas in the stomach chamber, which must be eliminated. As in other animals, the small intestine plays an important role in nutrient absorption, and the large intestine helps in the elimination of waste. Pseudo-ruminants Some animals, such as camels and alpacas, are pseudo-ruminants. They eat a lot of plant material and roughage. Digesting plant material is not easy because plant cell walls contain the polymeric sugar molecule cellulose. The digestive enzymes of these animals cannot break down cellulose, but microorganisms present in the digestive system can. Therefore, the digestive system must be able to handle large amounts of roughage and break down the cellulose. Pseudo-ruminants have a three-chamber stomach in the digestive system. However, their cecum—a pouched organ at the beginning of the large intestine containing many microorganisms that are necessary for the digestion of plant materials—is large and is the site where the roughage is fermented and digested. These animals do not have a rumen but have an omasum, abomasum, and reticulum. Parts of the Digestive System The vertebrate digestive system is designed to facilitate the transformation of food matter into the nutrient components that sustain organisms. Oral Cavity The oral cavity, or mouth, is the point of entry of food into the digestive system, illustrated in Figure. The food consumed is broken into smaller particles by mastication, the chewing action of the teeth. All mammals have teeth and can chew their food. The extensive chemical process of digestion begins in the mouth. As food is being chewed, saliva, produced by the salivary glands, mixes with the food. Saliva is a watery substance produced in the mouths of many animals. There are three major glands that secrete saliva—the parotid, the submandibular, and the sublingual. Saliva contains mucus that moistens food and buffers the pH of the food. Saliva also contains immunoglobulins and lysozymes, which have antibacterial action to reduce tooth decay by inhibiting growth of some bacteria. Saliva also contains an enzyme called salivary amylase that begins the process of converting starches in the food into a disaccharide called maltose. Another enzyme called lipase is produced by the cells in the tongue. Lipases are a class of enzymes that can break down triglycerides. The lingual lipase begins the breakdown of fat components in the food. The chewing and wetting action provided by the teeth and saliva prepare the food into a mass called the bolus for swallowing. The tongue helps in swallowing—moving the bolus from the mouth into the pharynx. The pharynx opens to two passageways: the trachea, which leads to the lungs, and the esophagus, which leads to the stomach. The trachea has an opening called the glottis, which is covered by a cartilaginous flap called the epiglottis. When swallowing, the epiglottis closes the glottis and food passes into the esophagus and not the trachea. This arrangement allows food to be kept out of the trachea. Esophagus The esophagus is a tubular organ that connects the mouth to the stomach. The chewed and softened food passes through the esophagus after being swallowed. The smooth muscles of the esophagus undergo a series of wave like movements called peristalsis that push the food toward the stomach, as illustrated in Figure. The peristalsis wave is unidirectional—it moves food from the mouth to the stomach, and reverse movement is not possible. The peristaltic movement of the esophagus is an involuntary reflex; it takes place in response to the act of swallowing. A ring-like muscle called a sphincter forms valves in the digestive system. The gastro-esophageal sphincter is located at the stomach end of the esophagus. In response to swallowing and the pressure exerted by the bolus of food, this sphincter opens, and the bolus enters the stomach. When there is no swallowing action, this sphincter is shut and prevents the contents of the stomach from traveling up the esophagus. Many animals have a true sphincter; however, in humans, there is no true sphincter, but the esophagus remains closed when there is no swallowing action. Acid reflux or “heartburn” occurs when the acidic digestive juices escape into the esophagus. Stomach A large part of digestion occurs in the stomach, shown in Figure. The stomach is a saclike organ that secretes gastric digestive juices. The pH in the stomach is between 1.5 and 2.5. This highly acidic environment is required for the chemical breakdown of food and the extraction of nutrients. When empty, the stomach is a rather small organ; however, it can expand to up to 20 times its resting size when filled with food. This characteristic is particularly useful for animals that need to eat when food is available. Art Connection Which of the following statements about the digestive system is false? - Chyme is a mixture of food and digestive juices that is produced in the stomach. - Food enters the large intestine before the small intestine. - In the small intestine, chyme mixes with bile, which emulsifies fats. - The stomach is separated from the small intestine by the pyloric sphincter. The stomach is also the major site for protein digestion in animals other than ruminants. Protein digestion is mediated by an enzyme called pepsin in the stomach chamber. Pepsin is secreted by the chief cells in the stomach in an inactive form called pepsinogen. Pepsin breaks peptide bonds and cleaves proteins into smaller polypeptides; it also helps activate more pepsinogen, starting a positive feedback mechanism that generates more pepsin. Another cell type—parietal cells—secrete hydrogen and chloride ions, which combine in the lumen to form hydrochloric acid, the primary acidic component of the stomach juices. Hydrochloric acid helps to convert the inactive pepsinogen to pepsin. The highly acidic environment also kills many microorganisms in the food and, combined with the action of the enzyme pepsin, results in the hydrolysis of protein in the food. Chemical digestion is facilitated by the churning action of the stomach. Contraction and relaxation of smooth muscles mixes the stomach contents about every 20 minutes. The partially digested food and gastric juice mixture is called chyme. Chyme passes from the stomach to the small intestine. Further protein digestion takes place in the small intestine. Gastric emptying occurs within two to six hours after a meal. Only a small amount of chyme is released into the small intestine at a time. The movement of chyme from the stomach into the small intestine is regulated by the pyloric sphincter. When digesting protein and some fats, the stomach lining must be protected from getting digested by pepsin. There are two points to consider when describing how the stomach lining is protected. First, as previously mentioned, the enzyme pepsin is synthesized in the inactive form. This protects the chief cells, because pepsinogen does not have the same enzyme functionality of pepsin. Second, the stomach has a thick mucus lining that protects the underlying tissue from the action of the digestive juices. When this mucus lining is ruptured, ulcers can form in the stomach. Ulcers are open wounds in or on an organ caused by bacteria (Helicobacter pylori) when the mucus lining is ruptured and fails to reform. Small Intestine Chyme moves from the stomach to the small intestine. The small intestine is the organ where the digestion of protein, fats, and carbohydrates is completed. The small intestine is a long tube-like organ with a highly folded surface containing finger-like projections called the villi. The apical surface of each villus has many microscopic projections called microvilli. These structures, illustrated in Figure, are lined with epithelial cells on the luminal side and allow for the nutrients to be absorbed from the digested food and absorbed into the blood stream on the other side. The villi and microvilli, with their many folds, increase the surface area of the intestine and increase absorption efficiency of the nutrients. Absorbed nutrients in the blood are carried into the hepatic portal vein, which leads to the liver. There, the liver regulates the distribution of nutrients to the rest of the body and removes toxic substances, including drugs, alcohol, and some pathogens. Art Connection Which of the following statements about the small intestine is false? - Absorptive cells that line the small intestine have microvilli, small projections that increase surface area and aid in the absorption of food. - The inside of the small intestine has many folds, called villi. - Microvilli are lined with blood vessels as well as lymphatic vessels. - The inside of the small intestine is called the lumen. The human small intestine is over 6m long and is divided into three parts: the duodenum, the jejunum, and the ileum. The “C-shaped,” fixed part of the small intestine is called the duodenum and is shown in Figure. The duodenum is separated from the stomach by the pyloric sphincter which opens to allow chyme to move from the stomach to the duodenum. In the duodenum, chyme is mixed with pancreatic juices in an alkaline solution rich in bicarbonate that neutralizes the acidity of chyme and acts as a buffer. Pancreatic juices also contain several digestive enzymes. Digestive juices from the pancreas, liver, and gallbladder, as well as from gland cells of the intestinal wall itself, enter the duodenum. Bile is produced in the liver and stored and concentrated in the gallbladder. Bile contains bile salts which emulsify lipids while the pancreas produces enzymes that catabolize starches, disaccharides, proteins, and fats. These digestive juices break down the food particles in the chyme into glucose, triglycerides, and amino acids. Some chemical digestion of food takes place in the duodenum. Absorption of fatty acids also takes place in the duodenum. The second part of the small intestine is called the jejunum, shown in Figure. Here, hydrolysis of nutrients is continued while most of the carbohydrates and amino acids are absorbed through the intestinal lining. The bulk of chemical digestion and nutrient absorption occurs in the jejunum. The ileum, also illustrated in Figure is the last part of the small intestine and here the bile salts and vitamins are absorbed into blood stream. The undigested food is sent to the colon from the ileum via peristaltic movements of the muscle. The ileum ends and the large intestine begins at the ileocecal valve. The vermiform, “worm-like,” appendix is located at the ileocecal valve. The appendix of humans secretes no enzymes and has an insignificant role in immunity. Large Intestine The large intestine, illustrated in Figure, reabsorbs the water from the undigested food material and processes the waste material. The human large intestine is much smaller in length compared to the small intestine but larger in diameter. It has three parts: the cecum, the colon, and the rectum. The cecum joins the ileum to the colon and is the receiving pouch for the waste matter. The colon is home to many bacteria or “intestinal flora” that aid in the digestive processes. The colon can be divided into four regions, the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The main functions of the colon are to extract the water and mineral salts from undigested food, and to store waste material. Carnivorous mammals have a shorter large intestine compared to herbivorous mammals due to their diet. Rectum and Anus The rectum is the terminal end of the large intestine, as shown in Figure. The primary role of the rectum is to store the feces until defecation. The feces are propelled using peristaltic movements during elimination. The anus is an opening at the far-end of the digestive tract and is the exit point for the waste material. Two sphincters between the rectum and anus control elimination: the inner sphincter is involuntary and the outer sphincter is voluntary. Accessory Organs The organs discussed above are the organs of the digestive tract through which food passes. Accessory organs are organs that add secretions (enzymes) that catabolize food into nutrients. Accessory organs include salivary glands, the liver, the pancreas, and the gallbladder. The liver, pancreas, and gallbladder are regulated by hormones in response to the food consumed. The liver is the largest internal organ in humans and it plays a very important role in digestion of fats and detoxifying blood. The liver produces bile, a digestive juice that is required for the breakdown of fatty components of the food in the duodenum. The liver also processes the vitamins and fats and synthesizes many plasma proteins. The pancreas is another important gland that secretes digestive juices. The chyme produced from the stomach is highly acidic in nature; the pancreatic juices contain high levels of bicarbonate, an alkali that neutralizes the acidic chyme. Additionally, the pancreatic juices contain a large variety of enzymes that are required for the digestion of protein and carbohydrates. The gallbladder is a small organ that aids the liver by storing bile and concentrating bile salts. When chyme containing fatty acids enters the duodenum, the bile is secreted from the gallbladder into the duodenum. Section Summary Different animals have evolved different types of digestive systems specialized to meet their dietary needs. Humans and many other animals have monogastric digestive systems with a single-chambered stomach. Birds have evolved a digestive system that includes a gizzard where the food is crushed into smaller pieces. This compensates for their inability to masticate. Ruminants that consume large amounts of plant material have a multi-chambered stomach that digests roughage. Pseudo-ruminants have similar digestive processes as ruminants but do not have the four-compartment stomach. Processing food involves ingestion (eating), digestion (mechanical and enzymatic breakdown of large molecules), absorption (cellular uptake of nutrients), and elimination (removal of undigested waste as feces). Many organs work together to digest food and absorb nutrients. The mouth is the point of ingestion and the location where both mechanical and chemical breakdown of food begins. Saliva contains an enzyme called amylase that breaks down carbohydrates. The food bolus travels through the esophagus by peristaltic movements to the stomach. The stomach has an extremely acidic environment. An enzyme called pepsin digests protein in the stomach. Further digestion and absorption take place in the small intestine. The large intestine reabsorbs water from the undigested food and stores waste until elimination. Art Connections Figure Which of the following statements about the digestive system is false? - Chyme is a mixture of food and digestive juices that is produced in the stomach. - Food enters the large intestine before the small intestine. - In the small intestine, chyme mixes with bile, which emulsifies fats. - The stomach is separated from the small intestine by the pyloric sphincter. Hint: Figure B Figure Which of the following statements about the small intestine is false? - Absorptive cells that line the small intestine have microvilli, small projections that increase surface area and aid in the absorption of food. - The inside of the small intestine has many folds, called villi. - Microvilli are lined with blood vessels as well as lymphatic vessels. - The inside of the small intestine is called the lumen. Hint: Figure C Review Questions Which of the following is a pseudo-ruminant? - cow - pig - crow - horse Hint: D Which of the following statements is untrue? - Roughage takes a long time to digest. - Birds eat large quantities at one time so that they can fly long distances. - Cows do not have upper teeth. - In pseudo-ruminants, roughage is digested in the cecum. Hint: B The acidic nature of chyme is neutralized by ________. - potassium hydroxide - sodium hydroxide - bicarbonates - vinegar Hint: C The digestive juices from the liver are delivered to the ________. - stomach - liver - duodenum - colon Hint: C Free Response How does the polygastric digestive system aid in digesting roughage? Hint: Animals with a polygastric digestive system have a multi-chambered stomach. The four compartments of the stomach are called the rumen, reticulum, omasum, and abomasum. These chambers contain many microbes that break down the cellulose and ferment the ingested food. The abomasum is the “true” stomach and is the equivalent of a monogastric stomach chamber where gastric juices are secreted. The four-compartment gastric chamber provides larger space and the microbial support necessary for ruminants to digest plant material. How do birds digest their food in the absence of teeth? Hint: Birds have a stomach chamber called a gizzard. Here, the food is stored, soaked, and ground into finer particles, often using pebbles. Once this process is complete, the digestive juices take over in the proventriculus and continue the digestive process. What is the role of the accessory organs in digestion? Hint: Accessory organs play an important role in producing and delivering digestive juices to the intestine during digestion and absorption. Specifically, the salivary glands, liver, pancreas, and gallbladder play important roles. Malfunction of any of these organs can lead to disease states. Explain how the villi and microvilli aid in absorption. Hint: The villi and microvilli are folds on the surface of the small intestine. These folds increase the surface area of the intestine and provide more area for the absorption of nutrients.	oercommons	2025-03-18T00:36:07.221136	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15110/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15111/overview	Nutrition and Energy Production Overview By the end of this section, you will be able to: - Explain why an animal’s diet should be balanced and meet the needs of the body - Define the primary components of food - Describe the essential nutrients required for cellular function that cannot be synthesized by the animal body - Explain how energy is produced through diet and digestion - Describe how excess carbohydrates and energy are stored in the body Given the diversity of animal life on our planet, it is not surprising that the animal diet would also vary substantially. The animal diet is the source of materials needed for building DNA and other complex molecules needed for growth, maintenance, and reproduction; collectively these processes are called biosynthesis. The diet is also the source of materials for ATP production in the cells. The diet must be balanced to provide the minerals and vitamins that are required for cellular function. Food Requirements What are the fundamental requirements of the animal diet? The animal diet should be well balanced and provide nutrients required for bodily function and the minerals and vitamins required for maintaining structure and regulation necessary for good health and reproductive capability. These requirements for a human are illustrated graphically in Figure Link to Learning The first step in ensuring that you are meeting the food requirements of your body is an awareness of the food groups and the nutrients they provide. To learn more about each food group and the recommended daily amounts, explore this interactive site by the United States Department of Agriculture. Everyday Connection Let’s Move! CampaignObesity is a growing epidemic and the rate of obesity among children is rapidly rising in the United States. To combat childhood obesity and ensure that children get a healthy start in life, first lady Michelle Obama has launched the Let’s Move! campaign. The goal of this campaign is to educate parents and caregivers on providing healthy nutrition and encouraging active lifestyles to future generations. This program aims to involve the entire community, including parents, teachers, and healthcare providers to ensure that children have access to healthy foods—more fruits, vegetables, and whole grains—and consume fewer calories from processed foods. Another goal is to ensure that children get physical activity. With the increase in television viewing and stationary pursuits such as video games, sedentary lifestyles have become the norm. Learn more at www.letsmove.gov. Organic Precursors The organic molecules required for building cellular material and tissues must come from food. Carbohydrates or sugars are the primary source of organic carbons in the animal body. During digestion, digestible carbohydrates are ultimately broken down into glucose and used to provide energy through metabolic pathways. Complex carbohydrates, including polysaccharides, can be broken down into glucose through biochemical modification; however, humans do not produce the enzyme cellulase and lack the ability to derive glucose from the polysaccharide cellulose. In humans, these molecules provide the fiber required for moving waste through the large intestine and a healthy colon. The intestinal flora in the human gut are able to extract some nutrition from these plant fibers. The excess sugars in the body are converted into glycogen and stored in the liver and muscles for later use. Glycogen stores are used to fuel prolonged exertions, such as long-distance running, and to provide energy during food shortage. Excess glycogen can be converted to fats, which are stored in the lower layer of the skin of mammals for insulation and energy storage. Excess digestible carbohydrates are stored by mammals in order to survive famine and aid in mobility. Another important requirement is that of nitrogen. Protein catabolism provides a source of organic nitrogen. Amino acids are the building blocks of proteins and protein breakdown provides amino acids that are used for cellular function. The carbon and nitrogen derived from these become the building block for nucleotides, nucleic acids, proteins, cells, and tissues. Excess nitrogen must be excreted as it is toxic. Fats add flavor to food and promote a sense of satiety or fullness. Fatty foods are also significant sources of energy because one gram of fat contains nine calories. Fats are required in the diet to aid the absorption of fat-soluble vitamins and the production of fat-soluble hormones. Essential Nutrients While the animal body can synthesize many of the molecules required for function from the organic precursors, there are some nutrients that need to be consumed from food. These nutrients are termed essential nutrients, meaning they must be eaten, and the body cannot produce them. The omega-3 alpha-linolenic acid and the omega-6 linoleic acid are essential fatty acids needed to make some membrane phospholipids. Vitamins are another class of essential organic molecules that are required in small quantities for many enzymes to function and, for this reason, are considered to be co-enzymes. Absence or low levels of vitamins can have a dramatic effect on health, as outlined in Table and Table. Both fat-soluble and water-soluble vitamins must be obtained from food. Minerals, listed in Table, are inorganic essential nutrients that must be obtained from food. Among their many functions, minerals help in structure and regulation and are considered co-factors. Certain amino acids also must be procured from food and cannot be synthesized by the body. These amino acids are the “essential” amino acids. The human body can synthesize only 11 of the 20 required amino acids; the rest must be obtained from food. The essential amino acids are listed in Table. \| Water-soluble Essential Vitamins \| \|\|\| \|---\|---\|---\|---\| \| Vitamin \| Function \| Deficiencies Can Lead To \| Sources \| \| Vitamin B1 (Thiamine) \| Needed by the body to process lipids, proteins, and carbohydrates Coenzyme removes CO2 from organic compounds \| Muscle weakness, Beriberi: reduced heart function, CNS problems \| Milk, meat, dried beans, whole grains \| \| Vitamin B2 (Riboflavin) \| Takes an active role in metabolism, aiding in the conversion of food to energy (FAD and FMN) \| Cracks or sores on the outer surface of the lips (cheliosis); inflammation and redness of the tongue; moist, scaly skin inflammation (seborrheic dermatitis) \| Meat, eggs, enriched grains, vegetables \| \| Vitamin B3 (Niacin) \| Used by the body to release energy from carbohydrates and to process alcohol; required for the synthesis of sex hormones; component of coenzyme NAD+ and NADP+ \| Pellagra, which can result in dermatitis, diarrhea, dementia, and death \| Meat, eggs, grains, nuts, potatoes \| \| Vitamin B5 (Pantothenic acid) \| Assists in producing energy from foods (lipids, in particular); component of coenzyme A \| Fatigue, poor coordination, retarded growth, numbness, tingling of hands and feet \| Meat, whole grains, milk, fruits, vegetables \| \| Vitamin B6 (Pyridoxine) \| The principal vitamin for processing amino acids and lipids; also helps convert nutrients into energy \| Irritability, depression, confusion, mouth sores or ulcers, anemia, muscular twitching \| Meat, dairy products, whole grains, orange juice \| \| Vitamin B7 (Biotin) \| Used in energy and amino acid metabolism, fat synthesis, and fat breakdown; helps the body use blood sugar \| Hair loss, dermatitis, depression, numbness and tingling in the extremities; neuromuscular disorders \| Meat, eggs, legumes and other vegetables \| \| Vitamin B9 (Folic acid) \| Assists the normal development of cells, especially during fetal development; helps metabolize nucleic and amino acids \| Deficiency during pregnancy is associated with birth defects, such as neural tube defects and anemia \| Leafy green vegetables, whole wheat, fruits, nuts, legumes \| \| Vitamin B12 (Cobalamin) \| Maintains healthy nervous system and assists with blood cell formation; coenzyme in nucleic acid metabolism \| Anemia, neurological disorders, numbness, loss of balance \| Meat, eggs, animal products \| \| Vitamin C (Ascorbic acid) \| Helps maintain connective tissue: bone, cartilage, and dentin; boosts the immune system \| Scurvy, which results in bleeding, hair and tooth loss; joint pain and swelling; delayed wound healing \| Citrus fruits, broccoli, tomatoes, red sweet bell peppers \| \| Fat-soluble Essential Vitamins \| \|\|\| \|---\|---\|---\|---\| \| Vitamin \| Function \| Deficiencies Can Lead To \| Sources \| \| Vitamin A (Retinol) \| Critical to the development of bones, teeth, and skin; helps maintain eyesight, enhances the immune system, fetal development, gene expression \| Night-blindness, skin disorders, impaired immunity \| Dark green leafy vegetables, yellow-orange vegetables fruits, milk, butter \| \| Vitamin D \| Critical for calcium absorption for bone development and strength; maintains a stable nervous system; maintains a normal and strong heartbeat; helps in blood clotting \| Rickets, osteomalacia, immunity \| Cod liver oil, milk, egg yolk \| \| Vitamin E (Tocopherol) \| Lessens oxidative damage of cells,and prevents lung damage from pollutants; vital to the immune system \| Deficiency is rare; anemia, nervous system degeneration \| Wheat germ oil, unrefined vegetable oils, nuts, seeds, grains \| \| Vitamin K (Phylloquinone) \| Essential to blood clotting \| Bleeding and easy bruising \| Leafy green vegetables, tea \| \| Minerals and Their Function in the Human Body \| \|\|\| \|---\|---\|---\|---\| \| Mineral \| Function \| Deficiencies Can Lead To \| Sources \| \| Calcium \| Needed for muscle and neuron function; heart health; builds bone and supports synthesis and function of blood cells; nerve function \| Osteoporosis, rickets, muscle spasms, impaired growth \| Milk, yogurt, fish, green leafy vegetables, legumes \| \| Chlorine \| Needed for production of hydrochloric acid (HCl) in the stomach and nerve function; osmotic balance \| Muscle cramps, mood disturbances, reduced appetite \| Table salt \| \| Copper (trace amounts) \| Required component of many redox enzymes, including cytochrome c oxidase; cofactor for hemoglobin synthesis \| Copper deficiency is rare \| Liver, oysters, cocoa, chocolate, sesame, nuts \| \| Iodine \| Required for the synthesis of thyroid hormones \| Goiter \| Seafood, iodized salt, dairy products \| \| Iron \| Required for many proteins and enzymes, notably hemoglobin, to prevent anemia \| Anemia, which causes poor concentration, fatigue, and poor immune function \| Red meat, leafy green vegetables, fish (tuna, salmon), eggs, dried fruits, beans, whole grains \| \| Magnesium \| Required co-factor for ATP formation; bone formation; normal membrane functions; muscle function \| Mood disturbances, muscle spasms \| Whole grains, leafy green vegetables \| \| Manganese (trace amounts) \| A cofactor in enzyme functions; trace amounts are required \| Manganese deficiency is rare \| Common in most foods \| \| Molybdenum (trace amounts) \| Acts as a cofactor for three essential enzymes in humans: sulfite oxidase, xanthine oxidase, and aldehyde oxidase \| Molybdenum deficiency is rare \| \| \| Phosphorus \| A component of bones and teeth; helps regulate acid-base balance; nucleotide synthesis \| Weakness, bone abnormalities, calcium loss \| Milk, hard cheese, whole grains, meats \| \| Potassium \| Vital for muscles, heart, and nerve function \| Cardiac rhythm disturbance, muscle weakness \| Legumes, potato skin, tomatoes, bananas \| \| Selenium (trace amounts) \| A cofactor essential to activity of antioxidant enzymes like glutathione peroxidase; trace amounts are required \| Selenium deficiency is rare \| Common in most foods \| \| Sodium \| Systemic electrolyte required for many functions; acid-base balance; water balance; nerve function \| Muscle cramps, fatigue, reduced appetite \| Table salt \| \| Zinc (trace amounts) \| Required for several enzymes such as carboxypeptidase, liver alcohol dehydrogenase, and carbonic anhydrase \| Anemia, poor wound healing, can lead to short stature \| Common in most foods \| \| Greater than 200mg/day required \| \| Essential Amino Acids \| \| \|---\|---\| \| Amino acids that must be consumed \| Amino acids anabolized by the body \| \| isoleucine \| alanine \| \| leucine \| selenocysteine \| \| lysine \| aspartate \| \| methionine \| cysteine \| \| phenylalanine \| glutamate \| \| tryptophan \| glycine \| \| valine \| proline \| \| histidine \| serine \| \| threonine \| tyrosine \| \| arginine* \| asparagine \| \| *The human body can synthesize histidine and arginine, but not in the quantities required, especially for growing children. \| Food Energy and ATP Animals need food to obtain energy and maintain homeostasis. Homeostasis is the ability of a system to maintain a stable internal environment even in the face of external changes to the environment. For example, the normal body temperature of humans is 37°C (98.6°F). Humans maintain this temperature even when the external temperature is hot or cold. It takes energy to maintain this body temperature, and animals obtain this energy from food. The primary source of energy for animals is carbohydrates, mainly glucose. Glucose is called the body’s fuel. The digestible carbohydrates in an animal’s diet are converted to glucose molecules through a series of catabolic chemical reactions. Adenosine triphosphate, or ATP, is the primary energy currency in cells; ATP stores energy in phosphate ester bonds. ATP releases energy when the phosphodiester bonds are broken and ATP is converted to ADP and a phosphate group. ATP is produced by the oxidative reactions in the cytoplasm and mitochondrion of the cell, where carbohydrates, proteins, and fats undergo a series of metabolic reactions collectively called cellular respiration. For example, glycolysis is a series of reactions in which glucose is converted to pyruvic acid and some of its chemical potential energy is transferred to NADH and ATP. ATP is required for all cellular functions. It is used to build the organic molecules that are required for cells and tissues; it provides energy for muscle contraction and for the transmission of electrical signals in the nervous system. When the amount of ATP is available in excess of the body’s requirements, the liver uses the excess ATP and excess glucose to produce molecules called glycogen. Glycogen is a polymeric form of glucose and is stored in the liver and skeletal muscle cells. When blood sugar drops, the liver releases glucose from stores of glycogen. Skeletal muscle converts glycogen to glucose during intense exercise. The process of converting glucose and excess ATP to glycogen and the storage of excess energy is an evolutionarily important step in helping animals deal with mobility, food shortages, and famine. Everyday Connection ObesityObesity is a major health concern in the United States, and there is a growing focus on reducing obesity and the diseases it may lead to, such as type-2 diabetes, cancers of the colon and breast, and cardiovascular disease. How does the food consumed contribute to obesity? Fatty foods are calorie-dense, meaning that they have more calories per unit mass than carbohydrates or proteins. One gram of carbohydrates has four calories, one gram of protein has four calories, and one gram of fat has nine calories. Animals tend to seek lipid-rich food for their higher energy content. The signals of hunger (“time to eat”) and satiety (“time to stop eating”) are controlled in the hypothalamus region of the brain. Foods that are rich in fatty acids tend to promote satiety more than foods that are rich only in carbohydrates. Excess carbohydrate and ATP are used by the liver to synthesize glycogen. The pyruvate produced during glycolysis is used to synthesize fatty acids. When there is more glucose in the body than required, the resulting excess pyruvate is converted into molecules that eventually result in the synthesis of fatty acids within the body. These fatty acids are stored in adipose cells—the fat cells in the mammalian body whose primary role is to store fat for later use. It is important to note that some animals benefit from obesity. Polar bears and seals need body fat for insulation and to keep them from losing body heat during Arctic winters. When food is scarce, stored body fat provides energy for maintaining homeostasis. Fats prevent famine in mammals, allowing them to access energy when food is not available on a daily basis; fats are stored when a large kill is made or lots of food is available. Section Summary Animal diet should be balanced and meet the needs of the body. Carbohydrates, proteins, and fats are the primary components of food. Some essential nutrients are required for cellular function but cannot be produced by the animal body. These include vitamins, minerals, some fatty acids, and some amino acids. Food intake in more than necessary amounts is stored as glycogen in the liver and muscle cells, and in fat cells. Excess adipose storage can lead to obesity and serious health problems. ATP is the energy currency of the cell and is obtained from the metabolic pathways. Excess carbohydrates and energy are stored as glycogen in the body. Review Questions Which of the following statements is not true? - Essential nutrients can be synthesized by the body. - Vitamins are required in small quantities for bodily function. - Some amino acids can be synthesized by the body, while others need to be obtained from diet. - Vitamins come in two categories: fat-soluble and water-soluble. Hint: A Which of the following is a water-soluble vitamin? - vitamin A - vitamin E - vitamin K - vitamin C Hint: D What is the primary fuel for the body? - carbohydrates - lipids - protein - glycogen Hint: A Excess glucose is stored as ________. - fat - glucagon - glycogen - it is not stored in the body Hint: C Free Response What are essential nutrients? Hint: Essential nutrients are those nutrients that must be obtained from the diet because they cannot be produced by the body. Vitamins and minerals are examples of essential nutrients. What is the role of minerals in maintaining good health? Hint: Minerals—such as potassium, sodium, and calcium—are required for the functioning of many cellular processes, including muscle contraction and nerve conduction. While minerals are required in trace amounts, not having minerals in the diet can be potentially harmful. Discuss why obesity is a growing epidemic. Hint: In the United States, obesity, particularly childhood obesity, is a growing concern. Some of the contributors to this situation include sedentary lifestyles and consuming more processed foods and less fruits and vegetables. As a result, even young children who are obese can face health concerns. There are several nations where malnourishment is a common occurrence. What may be some of the health challenges posed by malnutrition? Hint: Malnutrition, often in the form of not getting enough calories or not enough of the essential nutrients, can have severe consequences. Many malnourished children have vision and dental problems, and over the years may develop many serious health problems.	oercommons	2025-03-18T00:36:07.263312	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15111/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15112/overview	Digestive System Processes Overview By the end of this section, you will be able to: - Describe the process of digestion - Detail the steps involved in digestion and absorption - Define elimination - Explain the role of both the small and large intestines in absorption Obtaining nutrition and energy from food is a multi-step process. For true animals, the first step is ingestion, the act of taking in food. This is followed by digestion, absorption, and elimination. In the following sections, each of these steps will be discussed in detail. Ingestion The large molecules found in intact food cannot pass through the cell membranes. Food needs to be broken into smaller particles so that animals can harness the nutrients and organic molecules. The first step in this process is ingestion. Ingestion is the process of taking in food through the mouth. In vertebrates, the teeth, saliva, and tongue play important roles in mastication (preparing the food into bolus). While the food is being mechanically broken down, the enzymes in saliva begin to chemically process the food as well. The combined action of these processes modifies the food from large particles to a soft mass that can be swallowed and can travel the length of the esophagus. Digestion and Absorption Digestion is the mechanical and chemical break down of food into small organic fragments. It is important to break down macromolecules into smaller fragments that are of suitable size for absorption across the digestive epithelium. Large, complex molecules of proteins, polysaccharides, and lipids must be reduced to simpler particles such as simple sugar before they can be absorbed by the digestive epithelial cells. Different organs play specific roles in the digestive process. The animal diet needs carbohydrates, protein, and fat, as well as vitamins and inorganic components for nutritional balance. How each of these components is digested is discussed in the following sections. Carbohydrates The digestion of carbohydrates begins in the mouth. The salivary enzyme amylase begins the breakdown of food starches into maltose, a disaccharide. As the bolus of food travels through the esophagus to the stomach, no significant digestion of carbohydrates takes place. The esophagus produces no digestive enzymes but does produce mucous for lubrication. The acidic environment in the stomach stops the action of the amylase enzyme. The next step of carbohydrate digestion takes place in the duodenum. Recall that the chyme from the stomach enters the duodenum and mixes with the digestive secretion from the pancreas, liver, and gallbladder. Pancreatic juices also contain amylase, which continues the breakdown of starch and glycogen into maltose, a disaccharide. The disaccharides are broken down into monosaccharides by enzymes called maltases, sucrases, and lactases, which are also present in the brush border of the small intestinal wall. Maltase breaks down maltose into glucose. Other disaccharides, such as sucrose and lactose are broken down by sucrase and lactase, respectively. Sucrase breaks down sucrose (or “table sugar”) into glucose and fructose, and lactase breaks down lactose (or “milk sugar”) into glucose and galactose. The monosaccharides (glucose) thus produced are absorbed and then can be used in metabolic pathways to harness energy. The monosaccharides are transported across the intestinal epithelium into the bloodstream to be transported to the different cells in the body. The steps in carbohydrate digestion are summarized in Figure and Table. \| Digestion of Carbohydrates \| \|\|\|\| \|---\|---\|---\|---\|---\| \| Enzyme \| Produced By \| Site of Action \| Substrate Acting On \| End Products \| \| Salivary amylase \| Salivary glands \| Mouth \| Polysaccharides (Starch) \| Disaccharides (maltose), oligosaccharides \| \| Pancreatic amylase \| Pancreas \| Small intestine \| Polysaccharides (starch) \| Disaccharides (maltose), monosaccharides \| \| Oligosaccharidases \| Lining of the intestine; brush border membrane \| Small intestine \| Disaccharides \| Monosaccharides (e.g., glucose, fructose, galactose) \| Protein A large part of protein digestion takes place in the stomach. The enzyme pepsin plays an important role in the digestion of proteins by breaking down the intact protein to peptides, which are short chains of four to nine amino acids. In the duodenum, other enzymes—trypsin, elastase, and chymotrypsin—act on the peptides reducing them to smaller peptides. Trypsin elastase, carboxypeptidase, and chymotrypsin are produced by the pancreas and released into the duodenum where they act on the chyme. Further breakdown of peptides to single amino acids is aided by enzymes called peptidases (those that break down peptides). Specifically, carboxypeptidase, dipeptidase, and aminopeptidase play important roles in reducing the peptides to free amino acids. The amino acids are absorbed into the bloodstream through the small intestines. The steps in protein digestion are summarized in Figure and Table. \| Digestion of Protein \| \|\|\|\| \|---\|---\|---\|---\|---\| \| Enzyme \| Produced By \| Site of Action \| Substrate Acting On \| End Products \| \| Pepsin \| Stomach chief cells \| Stomach \| Proteins \| Peptides \| \| Pancreas \| Small intestine \| Proteins \| Peptides \| \| Carboxypeptidase \| Pancreas \| Small intestine \| Peptides \| Amino acids and peptides \| \| Lining of intestine \| Small intestine \| Peptides \| Amino acids \| Lipids Lipid digestion begins in the stomach with the aid of lingual lipase and gastric lipase. However, the bulk of lipid digestion occurs in the small intestine due to pancreatic lipase. When chyme enters the duodenum, the hormonal responses trigger the release of bile, which is produced in the liver and stored in the gallbladder. Bile aids in the digestion of lipids, primarily triglycerides by emulsification. Emulsification is a process in which large lipid globules are broken down into several small lipid globules. These small globules are more widely distributed in the chyme rather than forming large aggregates. Lipids are hydrophobic substances: in the presence of water, they will aggregate to form globules to minimize exposure to water. Bile contains bile salts, which are amphipathic, meaning they contain hydrophobic and hydrophilic parts. Thus, the bile salts hydrophilic side can interface with water on one side and the hydrophobic side interfaces with lipids on the other. By doing so, bile salts emulsify large lipid globules into small lipid globules. Why is emulsification important for digestion of lipids? Pancreatic juices contain enzymes called lipases (enzymes that break down lipids). If the lipid in the chyme aggregates into large globules, very little surface area of the lipids is available for the lipases to act on, leaving lipid digestion incomplete. By forming an emulsion, bile salts increase the available surface area of the lipids many fold. The pancreatic lipases can then act on the lipids more efficiently and digest them, as detailed in Figure. Lipases break down the lipids into fatty acids and glycerides. These molecules can pass through the plasma membrane of the cell and enter the epithelial cells of the intestinal lining. The bile salts surround long-chain fatty acids and monoglycerides forming tiny spheres called micelles. The micelles move into the brush border of the small intestine absorptive cells where the long-chain fatty acids and monoglycerides diffuse out of the micelles into the absorptive cells leaving the micelles behind in the chyme. The long-chain fatty acids and monoglycerides recombine in the absorptive cells to form triglycerides, which aggregate into globules and become coated with proteins. These large spheres are called chylomicrons. Chylomicrons contain triglycerides, cholesterol, and other lipids and have proteins on their surface. The surface is also composed of the hydrophilic phosphate "heads" of phospholipids. Together, they enable the chylomicron to move in an aqueous environment without exposing the lipids to water. Chylomicrons leave the absorptive cells via exocytosis. Chylomicrons enter the lymphatic vessels, and then enter the blood in the subclavian vein. Vitamins Vitamins can be either water-soluble or lipid-soluble. Fat soluble vitamins are absorbed in the same manner as lipids. It is important to consume some amount of dietary lipid to aid the absorption of lipid-soluble vitamins. Water-soluble vitamins can be directly absorbed into the bloodstream from the intestine. Link to Learning This website has an overview of the digestion of protein, fat, and carbohydrates. Art Connection Which of the following statements about digestive processes is true? - Amylase, maltase, and lactase in the mouth digest carbohydrates. - Trypsin and lipase in the stomach digest protein. - Bile emulsifies lipids in the small intestine. - No food is absorbed until the small intestine. Elimination The final step in digestion is the elimination of undigested food content and waste products. The undigested food material enters the colon, where most of the water is reabsorbed. Recall that the colon is also home to the microflora called “intestinal flora” that aid in the digestion process. The semi-solid waste is moved through the colon by peristaltic movements of the muscle and is stored in the rectum. As the rectum expands in response to storage of fecal matter, it triggers the neural signals required to set up the urge to eliminate. The solid waste is eliminated through the anus using peristaltic movements of the rectum. Common Problems with Elimination Diarrhea and constipation are some of the most common health concerns that affect digestion. Constipation is a condition where the feces are hardened because of excess water removal in the colon. In contrast, if enough water is not removed from the feces, it results in diarrhea. Many bacteria, including the ones that cause cholera, affect the proteins involved in water reabsorption in the colon and result in excessive diarrhea. Emesis Emesis, or vomiting, is elimination of food by forceful expulsion through the mouth. It is often in response to an irritant that affects the digestive tract, including but not limited to viruses, bacteria, emotions, sights, and food poisoning. This forceful expulsion of the food is due to the strong contractions produced by the stomach muscles. The process of emesis is regulated by the medulla. Section Summary Digestion begins with ingestion, where the food is taken in the mouth. Digestion and absorption take place in a series of steps with special enzymes playing important roles in digesting carbohydrates, proteins, and lipids. Elimination describes removal of undigested food contents and waste products from the body. While most absorption occurs in the small intestines, the large intestine is responsible for the final removal of water that remains after the absorptive process of the small intestines. The cells that line the large intestine absorb some vitamins as well as any leftover salts and water. The large intestine (colon) is also where feces is formed. Art Connections Review Questions Where does the majority of protein digestion take place? - stomach - duodenum - mouth - jejunum Hint: A Lipases are enzymes that break down ________. - disaccharides - lipids - proteins - cellulose Hint: B Free Response Explain why some dietary lipid is a necessary part of a balanced diet. Hint: Lipids add flavor to food and promote a sense of satiety or fullness. Fatty foods are sources of high energy; one gram of lipid contains nine calories. Lipids are also required in the diet to aid the absorption of lipid-soluble vitamins and for the production of lipid-soluble hormones.	oercommons	2025-03-18T00:36:07.294960	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15112/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15113/overview	Digestive System Regulation Overview By the end of this section, you will be able to: - Discuss the role of neural regulation in digestive processes - Explain how hormones regulate digestion The brain is the control center for the sensation of hunger and satiety. The functions of the digestive system are regulated through neural and hormonal responses. Neural Responses to Food In reaction to the smell, sight, or thought of food, like that shown in Figure, the first response is that of salivation. The salivary glands secrete more saliva in response to stimulation by the autonomic nervous system triggered by food in preparation for digestion. Simultaneously, the stomach begins to produce hydrochloric acid to digest the food. Recall that the peristaltic movements of the esophagus and other organs of the digestive tract are under the control of the brain. The brain prepares these muscles for movement as well. When the stomach is full, the part of the brain that detects satiety signals fullness. There are three overlapping phases of gastric control—the cephalic phase, the gastric phase, and the intestinal phase—each requires many enzymes and is under neural control as well. Digestive Phases The response to food begins even before food enters the mouth. The first phase of ingestion, called the cephalic phase, is controlled by the neural response to the stimulus provided by food. All aspects—such as sight, sense, and smell—trigger the neural responses resulting in salivation and secretion of gastric juices. The gastric and salivary secretion in the cephalic phase can also take place due to the thought of food. Right now, if you think about a piece of chocolate or a crispy potato chip, the increase in salivation is a cephalic phase response to the thought. The central nervous system prepares the stomach to receive food. The gastric phase begins once the food arrives in the stomach. It builds on the stimulation provided during the cephalic phase. Gastric acids and enzymes process the ingested materials. The gastric phase is stimulated by (1) distension of the stomach, (2) a decrease in the pH of the gastric contents, and (3) the presence of undigested material. This phase consists of local, hormonal, and neural responses. These responses stimulate secretions and powerful contractions. The intestinal phase begins when chyme enters the small intestine triggering digestive secretions. This phase controls the rate of gastric emptying. In addition to gastrin emptying, when chyme enters the small intestine, it triggers other hormonal and neural events that coordinate the activities of the intestinal tract, pancreas, liver, and gallbladder. Hormonal Responses to Food The endocrine system controls the response of the various glands in the body and the release of hormones at the appropriate times. One of the important factors under hormonal control is the stomach acid environment. During the gastric phase, the hormone gastrin is secreted by G cells in the stomach in response to the presence of proteins. Gastrin stimulates the release of stomach acid, or hydrochloric acid (HCl) which aids in the digestion of the proteins. However, when the stomach is emptied, the acidic environment need not be maintained and a hormone called somatostatin stops the release of hydrochloric acid. This is controlled by a negative feedback mechanism. In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase. In order to neutralize the acidic chyme, a hormone called secretin stimulates the pancreas to produce alkaline bicarbonate solution and deliver it to the duodenum. Secretin acts in tandem with another hormone called cholecystokinin (CCK). Not only does CCK stimulate the pancreas to produce the requisite pancreatic juices, it also stimulates the gallbladder to release bile into the duodenum. Link to Learning Visit this website to learn more about the endocrine system. Review the text and watch the animation of how control is implemented in the endocrine system. Another level of hormonal control occurs in response to the composition of food. Foods high in lipids take a long time to digest. A hormone called gastric inhibitory peptide is secreted by the small intestine to slow down the peristaltic movements of the intestine to allow fatty foods more time to be digested and absorbed. Understanding the hormonal control of the digestive system is an important area of ongoing research. Scientists are exploring the role of each hormone in the digestive process and developing ways to target these hormones. Advances could lead to knowledge that may help to battle the obesity epidemic. Section Summary The brain and the endocrine system control digestive processes. The brain controls the responses of hunger and satiety. The endocrine system controls the release of hormones and enzymes required for digestion of food in the digestive tract. Review Questions Which hormone controls the release of bile from the gallbladder - pepsin - amylase - CCK - gastrin Hint: C Which hormone stops acid secretion in the stomach? - gastrin - somatostatin - gastric inhibitory peptide - CCK Hint: B Free Response Describe how hormones regulate digestion. Hint: Hormones control the different digestive enzymes that are secreted in the stomach and the intestine during the process of digestion and absorption. For example, the hormone gastrin stimulates stomach acid secretion in response to food intake. The hormone somatostatin stops the release of stomach acid. Describe one or more scenarios where loss of hormonal regulation of digestion can lead to diseases. Hint: There are many cases where loss of hormonal regulation can lead to illnesses. For example, the bilirubin produced by the breakdown of red blood cells is converted to bile by the liver. When there is malfunction of this process, there is excess bilirubin in the blood and bile levels are low. As a result, the body struggles with dealing with fatty food. This is why a patient suffering from jaundice is asked to eat a diet with almost zero fat.	oercommons	2025-03-18T00:36:07.318326	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15113/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15114/overview	Introduction When you’re reading this book, your nervous system is performing several functions simultaneously. The visual system is processing what is seen on the page; the motor system controls the turn of the pages (or click of the mouse); the prefrontal cortex maintains attention. Even fundamental functions, like breathing and regulation of body temperature, are controlled by the nervous system. A nervous system is an organism’s control center: it processes sensory information from outside (and inside) the body and controls all behaviors—from eating to sleeping to finding a mate.	oercommons	2025-03-18T00:36:07.337045	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15114/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15115/overview	Neurons and Glial Cells Overview By the end of this section, you will be able to: - List and describe the functions of the structural components of a neuron - List and describe the four main types of neurons - Compare the functions of different types of glial cells Nervous systems throughout the animal kingdom vary in structure and complexity, as illustrated by the variety of animals shown in Figure. Some organisms, like sea sponges, lack a true nervous system. Others, like jellyfish, lack a true brain and instead have a system of separate but connected nerve cells (neurons) called a “nerve net.” Echinoderms such as sea stars have nerve cells that are bundled into fibers called nerves. Flatworms of the phylum Platyhelminthes have both a central nervous system (CNS), made up of a small “brain” and two nerve cords, and a peripheral nervous system (PNS) containing a system of nerves that extend throughout the body. The insect nervous system is more complex but also fairly decentralized. It contains a brain, ventral nerve cord, and ganglia (clusters of connected neurons). These ganglia can control movements and behaviors without input from the brain. Octopi may have the most complicated of invertebrate nervous systems—they have neurons that are organized in specialized lobes and eyes that are structurally similar to vertebrate species. Compared to invertebrates, vertebrate nervous systems are more complex, centralized, and specialized. While there is great diversity among different vertebrate nervous systems, they all share a basic structure: a CNS that contains a brain and spinal cord and a PNS made up of peripheral sensory and motor nerves. One interesting difference between the nervous systems of invertebrates and vertebrates is that the nerve cords of many invertebrates are located ventrally whereas the vertebrate spinal cords are located dorsally. There is debate among evolutionary biologists as to whether these different nervous system plans evolved separately or whether the invertebrate body plan arrangement somehow “flipped” during the evolution of vertebrates. Link to Learning Watch this video of biologist Mark Kirschner discussing the “flipping” phenomenon of vertebrate evolution. The nervous system is made up of neurons, specialized cells that can receive and transmit chemical or electrical signals, and glia, cells that provide support functions for the neurons by playing an information processing role that is complementary to neurons. A neuron can be compared to an electrical wire—it transmits a signal from one place to another. Glia can be compared to the workers at the electric company who make sure wires go to the right places, maintain the wires, and take down wires that are broken. Although glia have been compared to workers, recent evidence suggests that also usurp some of the signaling functions of neurons. There is great diversity in the types of neurons and glia that are present in different parts of the nervous system. There are four major types of neurons, and they share several important cellular components. Neurons The nervous system of the common laboratory fly, Drosophila melanogaster, contains around 100,000 neurons, the same number as a lobster. This number compares to 75 million in the mouse and 300 million in the octopus. A human brain contains around 86 billion neurons. Despite these very different numbers, the nervous systems of these animals control many of the same behaviors—from basic reflexes to more complicated behaviors like finding food and courting mates. The ability of neurons to communicate with each other as well as with other types of cells underlies all of these behaviors. Most neurons share the same cellular components. But neurons are also highly specialized—different types of neurons have different sizes and shapes that relate to their functional roles. Parts of a Neuron Like other cells, each neuron has a cell body (or soma) that contains a nucleus, smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria, and other cellular components. Neurons also contain unique structures, illustrated in Figure for receiving and sending the electrical signals that make neuronal communication possible. Dendrites are tree-like structures that extend away from the cell body to receive messages from other neurons at specialized junctions called synapses. Although some neurons do not have any dendrites, some types of neurons have multiple dendrites. Dendrites can have small protrusions called dendritic spines, which further increase surface area for possible synaptic connections. Once a signal is received by the dendrite, it then travels passively to the cell body. The cell body contains a specialized structure, the axon hillock that integrates signals from multiple synapses and serves as a junction between the cell body and an axon. An axon is a tube-like structure that propagates the integrated signal to specialized endings called axon terminals. These terminals in turn synapse on other neurons, muscle, or target organs. Chemicals released at axon terminals allow signals to be communicated to these other cells. Neurons usually have one or two axons, but some neurons, like amacrine cells in the retina, do not contain any axons. Some axons are covered with myelin, which acts as an insulator to minimize dissipation of the electrical signal as it travels down the axon, greatly increasing the speed on conduction. This insulation is important as the axon from a human motor neuron can be as long as a meter—from the base of the spine to the toes. The myelin sheath is not actually part of the neuron. Myelin is produced by glial cells. Along the axon there are periodic gaps in the myelin sheath. These gaps are called nodes of Ranvier and are sites where the signal is “recharged” as it travels along the axon. It is important to note that a single neuron does not act alone—neuronal communication depends on the connections that neurons make with one another (as well as with other cells, like muscle cells). Dendrites from a single neuron may receive synaptic contact from many other neurons. For example, dendrites from a Purkinje cell in the cerebellum are thought to receive contact from as many as 200,000 other neurons. Art Connection Which of the following statements is false? - The soma is the cell body of a nerve cell. - Myelin sheath provides an insulating layer to the dendrites. - Axons carry the signal from the soma to the target. - Dendrites carry the signal to the soma. Types of Neurons There are different types of neurons, and the functional role of a given neuron is intimately dependent on its structure. There is an amazing diversity of neuron shapes and sizes found in different parts of the nervous system (and across species), as illustrated by the neurons shown in Figure. While there are many defined neuron cell subtypes, neurons are broadly divided into four basic types: unipolar, bipolar, multipolar, and pseudounipolar. Figure illustrates these four basic neuron types. Unipolar neurons have only one structure that extends away from the soma. These neurons are not found in vertebrates but are found in insects where they stimulate muscles or glands. A bipolar neuron has one axon and one dendrite extending from the soma. An example of a bipolar neuron is a retinal bipolar cell, which receives signals from photoreceptor cells that are sensitive to light and transmits these signals to ganglion cells that carry the signal to the brain. Multipolar neurons are the most common type of neuron. Each multipolar neuron contains one axon and multiple dendrites. Multipolar neurons can be found in the central nervous system (brain and spinal cord). An example of a multipolar neuron is a Purkinje cell in the cerebellum, which has many branching dendrites but only one axon. Pseudounipolar cells share characteristics with both unipolar and bipolar cells. A pseudounipolar cell has a single process that extends from the soma, like a unipolar cell, but this process later branches into two distinct structures, like a bipolar cell. Most sensory neurons are pseudounipolar and have an axon that branches into two extensions: one connected to dendrites that receive sensory information and another that transmits this information to the spinal cord. Everyday Connection Neurogenesis At one time, scientists believed that people were born with all the neurons they would ever have. Research performed during the last few decades indicates that neurogenesis, the birth of new neurons, continues into adulthood. Neurogenesis was first discovered in songbirds that produce new neurons while learning songs. For mammals, new neurons also play an important role in learning: about 1000 new neurons develop in the hippocampus (a brain structure involved in learning and memory) each day. While most of the new neurons will die, researchers found that an increase in the number of surviving new neurons in the hippocampus correlated with how well rats learned a new task. Interestingly, both exercise and some antidepressant medications also promote neurogenesis in the hippocampus. Stress has the opposite effect. While neurogenesis is quite limited compared to regeneration in other tissues, research in this area may lead to new treatments for disorders such as Alzheimer’s, stroke, and epilepsy. How do scientists identify new neurons? A researcher can inject a compound called bromodeoxyuridine (BrdU) into the brain of an animal. While all cells will be exposed to BrdU, BrdU will only be incorporated into the DNA of newly generated cells that are in S phase. A technique called immunohistochemistry can be used to attach a fluorescent label to the incorporated BrdU, and a researcher can use fluorescent microscopy to visualize the presence of BrdU, and thus new neurons, in brain tissue. Figure is a micrograph which shows fluorescently labeled neurons in the hippocampus of a rat. Link to Learning This site contains more information about neurogenesis, including an interactive laboratory simulation and a video that explains how BrdU labels new cells. Glia While glia are often thought of as the supporting cast of the nervous system, the number of glial cells in the brain actually outnumbers the number of neurons by a factor of ten. Neurons would be unable to function without the vital roles that are fulfilled by these glial cells. Glia guide developing neurons to their destinations, buffer ions and chemicals that would otherwise harm neurons, and provide myelin sheaths around axons. Scientists have recently discovered that they also play a role in responding to nerve activity and modulating communication between nerve cells. When glia do not function properly, the result can be disastrous—most brain tumors are caused by mutations in glia. Types of Glia There are several different types of glia with different functions, two of which are shown in Figure. Astrocytes, shown in Figurea make contact with both capillaries and neurons in the CNS. They provide nutrients and other substances to neurons, regulate the concentrations of ions and chemicals in the extracellular fluid, and provide structural support for synapses. Astrocytes also form the blood-brain barrier—a structure that blocks entrance of toxic substances into the brain. Astrocytes, in particular, have been shown through calcium imaging experiments to become active in response to nerve activity, transmit calcium waves between astrocytes, and modulate the activity of surrounding synapses. Satellite glia provide nutrients and structural support for neurons in the PNS. Microglia scavenge and degrade dead cells and protect the brain from invading microorganisms. Oligodendrocytes, shown in Figureb form myelin sheaths around axons in the CNS. One axon can be myelinated by several oligodendrocytes, and one oligodendrocyte can provide myelin for multiple neurons. This is distinctive from the PNS where a single Schwann cell provides myelin for only one axon as the entire Schwann cell surrounds the axon. Radial glia serve as scaffolds for developing neurons as they migrate to their end destinations. Ependymal cells line fluid-filled ventricles of the brain and the central canal of the spinal cord. They are involved in the production of cerebrospinal fluid, which serves as a cushion for the brain, moves the fluid between the spinal cord and the brain, and is a component for the choroid plexus. Section Summary The nervous system is made up of neurons and glia. Neurons are specialized cells that are capable of sending electrical as well as chemical signals. Most neurons contain dendrites, which receive these signals, and axons that send signals to other neurons or tissues. There are four main types of neurons: unipolar, bipolar, multipolar, and pseudounipolar neurons. Glia are non-neuronal cells in the nervous system that support neuronal development and signaling. There are several types of glia that serve different functions. Art Connections Review Questions Neurons contain ________, which can receive signals from other neurons. - axons - mitochondria - dendrites - Golgi bodies Hint: C A(n) ________ neuron has one axon and one dendrite extending directly from the cell body. - unipolar - bipolar - multipolar - pseudounipolar Hint: B Glia that provide myelin for neurons in the brain are called ________. - Schwann cells - oligodendrocytes - microglia - astrocytes Hint: B Free Response How are neurons similar to other cells? How are they unique? Hint: Neurons contain organelles common to all cells, such as a nucleus and mitochondria. They are unique because they contain dendrites, which can receive signals from other neurons, and axons that can send these signals to other cells. Multiple sclerosis causes demyelination of axons in the brain and spinal cord. Why is this problematic? Hint: Myelin provides insulation for signals traveling along axons. Without myelin, signal transmission can slow down and degrade over time. This would slow down neuronal communication across the nervous system and affect all downstream functions.	oercommons	2025-03-18T00:36:07.367087	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15115/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15116/overview	How Neurons Communicate Overview By the end of this section, you will be able to: - Describe the basis of the resting membrane potential - Explain the stages of an action potential and how action potentials are propagated - Explain the similarities and differences between chemical and electrical synapses - Describe long-term potentiation and long-term depression All functions performed by the nervous system—from a simple motor reflex to more advanced functions like making a memory or a decision—require neurons to communicate with one another. While humans use words and body language to communicate, neurons use electrical and chemical signals. Just like a person in a committee, one neuron usually receives and synthesizes messages from multiple other neurons before “making the decision” to send the message on to other neurons. Nerve Impulse Transmission within a Neuron For the nervous system to function, neurons must be able to send and receive signals. These signals are possible because each neuron has a charged cellular membrane (a voltage difference between the inside and the outside), and the charge of this membrane can change in response to neurotransmitter molecules released from other neurons and environmental stimuli. To understand how neurons communicate, one must first understand the basis of the baseline or ‘resting’ membrane charge. Neuronal Charged Membranes The lipid bilayer membrane that surrounds a neuron is impermeable to charged molecules or ions. To enter or exit the neuron, ions must pass through special proteins called ion channels that span the membrane. Ion channels have different configurations: open, closed, and inactive, as illustrated in Figure. Some ion channels need to be activated in order to open and allow ions to pass into or out of the cell. These ion channels are sensitive to the environment and can change their shape accordingly. Ion channels that change their structure in response to voltage changes are called voltage-gated ion channels. Voltage-gated ion channels regulate the relative concentrations of different ions inside and outside the cell. The difference in total charge between the inside and outside of the cell is called the membrane potential. Link to Learning This video discusses the basis of the resting membrane potential. Resting Membrane Potential A neuron at rest is negatively charged: the inside of a cell is approximately 70 millivolts more negative than the outside (−70 mV, note that this number varies by neuron type and by species). This voltage is called the resting membrane potential; it is caused by differences in the concentrations of ions inside and outside the cell. If the membrane were equally permeable to all ions, each type of ion would flow across the membrane and the system would reach equilibrium. Because ions cannot simply cross the membrane at will, there are different concentrations of several ions inside and outside the cell, as shown in Table. The difference in the number of positively charged potassium ions (K+) inside and outside the cell dominates the resting membrane potential (Figure). When the membrane is at rest, K+ ions accumulate inside the cell due to a net movement with the concentration gradient. The negative resting membrane potential is created and maintained by increasing the concentration of cations outside the cell (in the extracellular fluid) relative to inside the cell (in the cytoplasm). The negative charge within the cell is created by the cell membrane being more permeable to potassium ion movement than sodium ion movement. In neurons, potassium ions are maintained at high concentrations within the cell while sodium ions are maintained at high concentrations outside of the cell. The cell possesses potassium and sodium leakage channels that allow the two cations to diffuse down their concentration gradient. However, the neurons have far more potassium leakage channels than sodium leakage channels. Therefore, potassium diffuses out of the cell at a much faster rate than sodium leaks in. Because more cations are leaving the cell than are entering, this causes the interior of the cell to be negatively charged relative to the outside of the cell. The actions of the sodium potassium pump help to maintain the resting potential, once established. Recall that sodium potassium pumps brings two K+ ions into the cell while removing three Na+ ions per ATP consumed. As more cations are expelled from the cell than taken in, the inside of the cell remains negatively charged relative to the extracellular fluid. It should be noted that chloride ions (Cl–) tend to accumulate outside of the cell because they are repelled by negatively-charged proteins within the cytoplasm. \| Ion Concentration Inside and Outside Neurons \| \|\|\| \|---\|---\|---\|---\| \| Ion \| Extracellular concentration (mM) \| Intracellular concentration (mM) \| Ratio outside/inside \| \| Na+ \| 145 \| 12 \| 12 \| \| K+ \| 4 \| 155 \| 0.026 \| \| Cl− \| 120 \| 4 \| 30 \| \| Organic anions (A−) \| — \| 100 \| Action Potential A neuron can receive input from other neurons and, if this input is strong enough, send the signal to downstream neurons. Transmission of a signal between neurons is generally carried by a chemical called a neurotransmitter. Transmission of a signal within a neuron (from dendrite to axon terminal) is carried by a brief reversal of the resting membrane potential called an action potential. When neurotransmitter molecules bind to receptors located on a neuron’s dendrites, ion channels open. At excitatory synapses, this opening allows positive ions to enter the neuron and results in depolarization of the membrane—a decrease in the difference in voltage between the inside and outside of the neuron. A stimulus from a sensory cell or another neuron depolarizes the target neuron to its threshold potential (-55 mV). Na+ channels in the axon hillock open, allowing positive ions to enter the cell (Figure and Figure). Once the sodium channels open, the neuron completely depolarizes to a membrane potential of about +40 mV. Action potentials are considered an "all-or nothing" event, in that, once the threshold potential is reached, the neuron always completely depolarizes. Once depolarization is complete, the cell must now "reset" its membrane voltage back to the resting potential. To accomplish this, the Na+ channels close and cannot be opened. This begins the neuron's refractory period, in which it cannot produce another action potential because its sodium channels will not open. At the same time, voltage-gated K+ channels open, allowing K+ to leave the cell. As K+ ions leave the cell, the membrane potential once again becomes negative. The diffusion of K+ out of the cell actually hyperpolarizes the cell, in that the membrane potential becomes more negative than the cell's normal resting potential. At this point, the sodium channels will return to their resting state, meaning they are ready to open again if the membrane potential again exceeds the threshold potential. Eventually the extra K+ ions diffuse out of the cell through the potassium leakage channels, bringing the cell from its hyperpolarized state, back to its resting membrane potential. Art Connection Potassium channel blockers, such as amiodarone and procainamide, which are used to treat abnormal electrical activity in the heart, called cardiac dysrhythmia, impede the movement of K+ through voltage-gated K+ channels. Which part of the action potential would you expect potassium channels to affect? Link to Learning This video presents an overview of action potential. Myelin and the Propagation of the Action Potential For an action potential to communicate information to another neuron, it must travel along the axon and reach the axon terminals where it can initiate neurotransmitter release. The speed of conduction of an action potential along an axon is influenced by both the diameter of the axon and the axon’s resistance to current leak. Myelin acts as an insulator that prevents current from leaving the axon; this increases the speed of action potential conduction. In demyelinating diseases like multiple sclerosis, action potential conduction slows because current leaks from previously insulated axon areas. The nodes of Ranvier, illustrated in Figure are gaps in the myelin sheath along the axon. These unmyelinated spaces are about one micrometer long and contain voltage gated Na+ and K+ channels. Flow of ions through these channels, particularly the Na+ channels, regenerates the action potential over and over again along the axon. This ‘jumping’ of the action potential from one node to the next is called saltatory conduction. If nodes of Ranvier were not present along an axon, the action potential would propagate very slowly since Na+ and K+ channels would have to continuously regenerate action potentials at every point along the axon instead of at specific points. Nodes of Ranvier also save energy for the neuron since the channels only need to be present at the nodes and not along the entire axon. Synaptic Transmission The synapse or “gap” is the place where information is transmitted from one neuron to another. Synapses usually form between axon terminals and dendritic spines, but this is not universally true. There are also axon-to-axon, dendrite-to-dendrite, and axon-to-cell body synapses. The neuron transmitting the signal is called the presynaptic neuron, and the neuron receiving the signal is called the postsynaptic neuron. Note that these designations are relative to a particular synapse—most neurons are both presynaptic and postsynaptic. There are two types of synapses: chemical and electrical. Chemical Synapse When an action potential reaches the axon terminal it depolarizes the membrane and opens voltage-gated Na+ channels. Na+ ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated Ca2+ channels to open. Calcium ions entering the cell initiate a signaling cascade that causes small membrane-bound vesicles, called synaptic vesicles, containing neurotransmitter molecules to fuse with the presynaptic membrane. Synaptic vesicles are shown in Figure, which is an image from a scanning electron microscope. Fusion of a vesicle with the presynaptic membrane causes neurotransmitter to be released into the synaptic cleft, the extracellular space between the presynaptic and postsynaptic membranes, as illustrated in Figure. The neurotransmitter diffuses across the synaptic cleft and binds to receptor proteins on the postsynaptic membrane. The binding of a specific neurotransmitter causes particular ion channels, in this case ligand-gated channels, on the postsynaptic membrane to open. Neurotransmitters can either have excitatory or inhibitory effects on the postsynaptic membrane, as detailed in Table. For example, when acetylcholine is released at the synapse between a nerve and muscle (called the neuromuscular junction) by a presynaptic neuron, it causes postsynaptic Na+ channels to open. Na+ enters the postsynaptic cell and causes the postsynaptic membrane to depolarize. This depolarization is called an excitatory postsynaptic potential (EPSP) and makes the postsynaptic neuron more likely to fire an action potential. Release of neurotransmitter at inhibitory synapses causes inhibitory postsynaptic potentials (IPSPs), a hyperpolarization of the presynaptic membrane. For example, when the neurotransmitter GABA (gamma-aminobutyric acid) is released from a presynaptic neuron, it binds to and opens Cl- channels. Cl- ions enter the cell and hyperpolarizes the membrane, making the neuron less likely to fire an action potential. Once neurotransmission has occurred, the neurotransmitter must be removed from the synaptic cleft so the postsynaptic membrane can “reset” and be ready to receive another signal. This can be accomplished in three ways: the neurotransmitter can diffuse away from the synaptic cleft, it can be degraded by enzymes in the synaptic cleft, or it can be recycled (sometimes called reuptake) by the presynaptic neuron. Several drugs act at this step of neurotransmission. For example, some drugs that are given to Alzheimer’s patients work by inhibiting acetylcholinesterase, the enzyme that degrades acetylcholine. This inhibition of the enzyme essentially increases neurotransmission at synapses that release acetylcholine. Once released, the acetylcholine stays in the cleft and can continually bind and unbind to postsynaptic receptors. \| Neurotransmitter Function and Location \| \|\| \|---\|---\|---\| \| Neurotransmitter \| Example \| Location \| \| Acetylcholine \| — \| CNS and/or PNS \| \| Biogenic amine \| Dopamine, serotonin, norepinephrine \| CNS and/or PNS \| \| Amino acid \| Glycine, glutamate, aspartate, gamma aminobutyric acid \| CNS \| \| Neuropeptide \| Substance P, endorphins \| CNS and/or PNS \| Electrical Synapse While electrical synapses are fewer in number than chemical synapses, they are found in all nervous systems and play important and unique roles. The mode of neurotransmission in electrical synapses is quite different from that in chemical synapses. In an electrical synapse, the presynaptic and postsynaptic membranes are very close together and are actually physically connected by channel proteins forming gap junctions. Gap junctions allow current to pass directly from one cell to the next. In addition to the ions that carry this current, other molecules, such as ATP, can diffuse through the large gap junction pores. There are key differences between chemical and electrical synapses. Because chemical synapses depend on the release of neurotransmitter molecules from synaptic vesicles to pass on their signal, there is an approximately one millisecond delay between when the axon potential reaches the presynaptic terminal and when the neurotransmitter leads to opening of postsynaptic ion channels. Additionally, this signaling is unidirectional. Signaling in electrical synapses, in contrast, is virtually instantaneous (which is important for synapses involved in key reflexes), and some electrical synapses are bidirectional. Electrical synapses are also more reliable as they are less likely to be blocked, and they are important for synchronizing the electrical activity of a group of neurons. For example, electrical synapses in the thalamus are thought to regulate slow-wave sleep, and disruption of these synapses can cause seizures. Signal Summation Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron, but often multiple presynaptic inputs must create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential. This process is called summation and occurs at the axon hillock, as illustrated in Figure. Additionally, one neuron often has inputs from many presynaptic neurons—some excitatory and some inhibitory—so IPSPs can cancel out EPSPs and vice versa. It is the net change in postsynaptic membrane voltage that determines whether the postsynaptic cell has reached its threshold of excitation needed to fire an action potential. Together, synaptic summation and the threshold for excitation act as a filter so that random “noise” in the system is not transmitted as important information. Everyday Connection Brain-computer interface Amyotrophic lateral sclerosis (ALS, also called Lou Gehrig’s Disease) is a neurological disease characterized by the degeneration of the motor neurons that control voluntary movements. The disease begins with muscle weakening and lack of coordination and eventually destroys the neurons that control speech, breathing, and swallowing; in the end, the disease can lead to paralysis. At that point, patients require assistance from machines to be able to breathe and to communicate. Several special technologies have been developed to allow “locked-in” patients to communicate with the rest of the world. One technology, for example, allows patients to type out sentences by twitching their cheek. These sentences can then be read aloud by a computer. A relatively new line of research for helping paralyzed patients, including those with ALS, to communicate and retain a degree of self-sufficiency is called brain-computer interface (BCI) technology and is illustrated in Figure. This technology sounds like something out of science fiction: it allows paralyzed patients to control a computer using only their thoughts. There are several forms of BCI. Some forms use EEG recordings from electrodes taped onto the skull. These recordings contain information from large populations of neurons that can be decoded by a computer. Other forms of BCI require the implantation of an array of electrodes smaller than a postage stamp in the arm and hand area of the motor cortex. This form of BCI, while more invasive, is very powerful as each electrode can record actual action potentials from one or more neurons. These signals are then sent to a computer, which has been trained to decode the signal and feed it to a tool—such as a cursor on a computer screen. This means that a patient with ALS can use e-mail, read the Internet, and communicate with others by thinking of moving his or her hand or arm (even though the paralyzed patient cannot make that bodily movement). Recent advances have allowed a paralyzed locked-in patient who suffered a stroke 15 years ago to control a robotic arm and even to feed herself coffee using BCI technology. Despite the amazing advancements in BCI technology, it also has limitations. The technology can require many hours of training and long periods of intense concentration for the patient; it can also require brain surgery to implant the devices. Link to Learning Watch this video in which a paralyzed woman use a brain-controlled robotic arm to bring a drink to her mouth, among other images of brain-computer interface technology in action. Synaptic Plasticity Synapses are not static structures. They can be weakened or strengthened. They can be broken, and new synapses can be made. Synaptic plasticity allows for these changes, which are all needed for a functioning nervous system. In fact, synaptic plasticity is the basis of learning and memory. Two processes in particular, long-term potentiation (LTP) and long-term depression (LTD) are important forms of synaptic plasticity that occur in synapses in the hippocampus, a brain region that is involved in storing memories. Long-term Potentiation (LTP) Long-term potentiation (LTP) is a persistent strengthening of a synaptic connection. LTP is based on the Hebbian principle: cells that fire together wire together. There are various mechanisms, none fully understood, behind the synaptic strengthening seen with LTP. One known mechanism involves a type of postsynaptic glutamate receptor, called NMDA (N-Methyl-D-aspartate) receptors, shown in Figure. These receptors are normally blocked by magnesium ions; however, when the postsynaptic neuron is depolarized by multiple presynaptic inputs in quick succession (either from one neuron or multiple neurons), the magnesium ions are forced out allowing Ca ions to pass into the postsynaptic cell. Next, Ca2+ ions entering the cell initiate a signaling cascade that causes a different type of glutamate receptor, called AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors, to be inserted into the postsynaptic membrane, since activated AMPA receptors allow positive ions to enter the cell. So, the next time glutamate is released from the presynaptic membrane, it will have a larger excitatory effect (EPSP) on the postsynaptic cell because the binding of glutamate to these AMPA receptors will allow more positive ions into the cell. The insertion of additional AMPA receptors strengthens the synapse and means that the postsynaptic neuron is more likely to fire in response to presynaptic neurotransmitter release. Some drugs of abuse co-opt the LTP pathway, and this synaptic strengthening can lead to addiction. Long-term Depression (LTD) Long-term depression (LTD) is essentially the reverse of LTP: it is a long-term weakening of a synaptic connection. One mechanism known to cause LTD also involves AMPA receptors. In this situation, calcium that enters through NMDA receptors initiates a different signaling cascade, which results in the removal of AMPA receptors from the postsynaptic membrane, as illustrated in Figure. The decrease in AMPA receptors in the membrane makes the postsynaptic neuron less responsive to glutamate released from the presynaptic neuron. While it may seem counterintuitive, LTD may be just as important for learning and memory as LTP. The weakening and pruning of unused synapses allows for unimportant connections to be lost and makes the synapses that have undergone LTP that much stronger by comparison. Section Summary Neurons have charged membranes because there are different concentrations of ions inside and outside of the cell. Voltage-gated ion channels control the movement of ions into and out of a neuron. When a neuronal membrane is depolarized to at least the threshold of excitation, an action potential is fired. The action potential is then propagated along a myelinated axon to the axon terminals. In a chemical synapse, the action potential causes release of neurotransmitter molecules into the synaptic cleft. Through binding to postsynaptic receptors, the neurotransmitter can cause excitatory or inhibitory postsynaptic potentials by depolarizing or hyperpolarizing, respectively, the postsynaptic membrane. In electrical synapses, the action potential is directly communicated to the postsynaptic cell through gap junctions—large channel proteins that connect the pre-and postsynaptic membranes. Synapses are not static structures and can be strengthened and weakened. Two mechanisms of synaptic plasticity are long-term potentiation and long-term depression. Art Connections Figure Potassium channel blockers, such as amiodarone and procainamide, which are used to treat abnormal electrical activity in the heart, called cardiac dysrhythmia, impede the movement of K+ through voltage-gated K+ channels. Which part of the action potential would you expect potassium channels to affect? Hint: Figure Potassium channel blockers slow the repolarization phase, but have no effect on depolarization. Review Questions For a neuron to fire an action potential, its membrane must reach ________. - hyperpolarization - the threshold of excitation - the refractory period - inhibitory postsynaptic potential Hint: B After an action potential, the opening of additional voltage-gated ________ channels and the inactivation of sodium channels, cause the membrane to return to its resting membrane potential. - sodium - potassium - calcium - chloride Hint: B What is the term for protein channels that connect two neurons at an electrical synapse? - synaptic vesicles - voltage-gated ion channels - gap junction protein - sodium-potassium exchange pumps Hint: C Free Response How does myelin aid propagation of an action potential along an axon? How do the nodes of Ranvier help this process? Hint: Myelin prevents the leak of current from the axon. Nodes of Ranvier allow the action potential to be regenerated at specific points along the axon. They also save energy for the cell since voltage-gated ion channels and sodium-potassium transporters are not needed along myelinated portions of the axon. What are the main steps in chemical neurotransmission? Hint: An action potential travels along an axon until it depolarizes the membrane at an axon terminal. Depolarization of the membrane causes voltage-gated Ca2+ channels to open and Ca2+ to enter the cell. The intracellular calcium influx causes synaptic vesicles containing neurotransmitter to fuse with the presynaptic membrane. The neurotransmitter diffuses across the synaptic cleft and binds to receptors on the postsynaptic membrane. Depending on the specific neurotransmitter and postsynaptic receptor, this action can cause positive (excitatory postsynaptic potential) or negative (inhibitory postsynaptic potential) ions to enter the cell.	oercommons	2025-03-18T00:36:07.407140	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15116/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15117/overview	The Central Nervous System Overview By the end of this section, you will be able to: - Identify the spinal cord, cerebral lobes, and other brain areas on a diagram of the brain - Describe the basic functions of the spinal cord, cerebral lobes, and other brain areas The central nervous system (CNS) is made up of the brain, a part of which is shown in Figure and spinal cord and is covered with three layers of protective coverings called meninges (from the Greek word for membrane). The outermost layer is the dura mater (Latin for “hard mother”). As the Latin suggests, the primary function for this thick layer is to protect the brain and spinal cord. The dura mater also contains vein-like structures that carry blood from the brain back to the heart. The middle layer is the web-like arachnoid mater. The last layer is the pia mater (Latin for “soft mother”), which directly contacts and covers the brain and spinal cord like plastic wrap. The space between the arachnoid and pia maters is filled with cerebrospinal fluid (CSF). CSF is produced by a tissue called choroid plexus in fluid-filled compartments in the CNS called ventricles. The brain floats in CSF, which acts as a cushion and shock absorber and makes the brain neutrally buoyant. CSF also functions to circulate chemical substances throughout the brain and into the spinal cord. The entire brain contains only about 8.5 tablespoons of CSF, but CSF is constantly produced in the ventricles. This creates a problem when a ventricle is blocked—the CSF builds up and creates swelling and the brain is pushed against the skull. This swelling condition is called hydrocephalus (“water head”) and can cause seizures, cognitive problems, and even death if a shunt is not inserted to remove the fluid and pressure. Brain The brain is the part of the central nervous system that is contained in the cranial cavity of the skull. It includes the cerebral cortex, limbic system, basal ganglia, thalamus, hypothalamus, and cerebellum. There are three different ways that a brain can be sectioned in order to view internal structures: a sagittal section cuts the brain left to right, as shown in Figureb, a coronal section cuts the brain front to back, as shown in Figurea, and a horizontal section cuts the brain top to bottom. Cerebral Cortex The outermost part of the brain is a thick piece of nervous system tissue called the cerebral cortex, which is folded into hills called gyri (singular: gyrus) and valleys called sulci (singular: sulcus). The cortex is made up of two hemispheres—right and left—which are separated by a large sulcus. A thick fiber bundle called the corpus callosum (Latin: “tough body”) connects the two hemispheres and allows information to be passed from one side to the other. Although there are some brain functions that are localized more to one hemisphere than the other, the functions of the two hemispheres are largely redundant. In fact, sometimes (very rarely) an entire hemisphere is removed to treat severe epilepsy. While patients do suffer some deficits following the surgery, they can have surprisingly few problems, especially when the surgery is performed on children who have very immature nervous systems. In other surgeries to treat severe epilepsy, the corpus callosum is cut instead of removing an entire hemisphere. This causes a condition called split-brain, which gives insights into unique functions of the two hemispheres. For example, when an object is presented to patients’ left visual field, they may be unable to verbally name the object (and may claim to not have seen an object at all). This is because the visual input from the left visual field crosses and enters the right hemisphere and cannot then signal to the speech center, which generally is found in the left side of the brain. Remarkably, if a split-brain patient is asked to pick up a specific object out of a group of objects with the left hand, the patient will be able to do so but will still be unable to vocally identify it. Link to Learning See this website to learn more about split-brain patients and to play a game where you can model the split-brain experiments yourself. Each cortical hemisphere contains regions called lobes that are involved in different functions. Scientists use various techniques to determine what brain areas are involved in different functions: they examine patients who have had injuries or diseases that affect specific areas and see how those areas are related to functional deficits. They also conduct animal studies where they stimulate brain areas and see if there are any behavioral changes. They use a technique called transmagnetic stimulation (TMS) to temporarily deactivate specific parts of the cortex using strong magnets placed outside the head; and they use functional magnetic resonance imaging (fMRI) to look at changes in oxygenated blood flow in particular brain regions that correlate with specific behavioral tasks. These techniques, and others, have given great insight into the functions of different brain regions but have also showed that any given brain area can be involved in more than one behavior or process, and any given behavior or process generally involves neurons in multiple brain areas. That being said, each hemisphere of the mammalian cerebral cortex can be broken down into four functionally and spatially defined lobes: frontal, parietal, temporal, and occipital. Figure illustrates these four lobes of the human cerebral cortex. The frontal lobe is located at the front of the brain, over the eyes. This lobe contains the olfactory bulb, which processes smells. The frontal lobe also contains the motor cortex, which is important for planning and implementing movement. Areas within the motor cortex map to different muscle groups, and there is some organization to this map, as shown in Figure. For example, the neurons that control movement of the fingers are next to the neurons that control movement of the hand. Neurons in the frontal lobe also control cognitive functions like maintaining attention, speech, and decision-making. Studies of humans who have damaged their frontal lobes show that parts of this area are involved in personality, socialization, and assessing risk. The parietal lobe is located at the top of the brain. Neurons in the parietal lobe are involved in speech and also reading. Two of the parietal lobe’s main functions are processing somatosensation—touch sensations like pressure, pain, heat, cold—and processing proprioception—the sense of how parts of the body are oriented in space. The parietal lobe contains a somatosensory map of the body similar to the motor cortex. The occipital lobe is located at the back of the brain. It is primarily involved in vision—seeing, recognizing, and identifying the visual world. The temporal lobe is located at the base of the brain by your ears and is primarily involved in processing and interpreting sounds. It also contains the hippocampus (Greek for “seahorse”)—a structure that processes memory formation. The hippocampus is illustrated in Figure. The role of the hippocampus in memory was partially determined by studying one famous epileptic patient, HM, who had both sides of his hippocampus removed in an attempt to cure his epilepsy. His seizures went away, but he could no longer form new memories (although he could remember some facts from before his surgery and could learn new motor tasks). Evolution Connection Cerebral Cortex Compared to other vertebrates, mammals have exceptionally large brains for their body size. An entire alligator’s brain, for example, would fill about one and a half teaspoons. This increase in brain to body size ratio is especially pronounced in apes, whales, and dolphins. While this increase in overall brain size doubtlessly played a role in the evolution of complex behaviors unique to mammals, it does not tell the whole story. Scientists have found a relationship between the relatively high surface area of the cortex and the intelligence and complex social behaviors exhibited by some mammals. This increased surface area is due, in part, to increased folding of the cortical sheet (more sulci and gyri). For example, a rat cortex is very smooth with very few sulci and gyri. Cat and sheep cortices have more sulci and gyri. Chimps, humans, and dolphins have even more. Basal Ganglia Interconnected brain areas called the basal ganglia (or basal nuclei), shown in Figureb, play important roles in movement control and posture. Damage to the basal ganglia, as in Parkinson’s disease, leads to motor impairments like a shuffling gait when walking. The basal ganglia also regulate motivation. For example, when a wasp sting led to bilateral basal ganglia damage in a 25-year-old businessman, he began to spend all his days in bed and showed no interest in anything or anybody. But when he was externally stimulated—as when someone asked to play a card game with him—he was able to function normally. Interestingly, he and other similar patients do not report feeling bored or frustrated by their state. Thalamus The thalamus (Greek for “inner chamber”), illustrated in Figure, acts as a gateway to and from the cortex. It receives sensory and motor inputs from the body and also receives feedback from the cortex. This feedback mechanism can modulate conscious awareness of sensory and motor inputs depending on the attention and arousal state of the animal. The thalamus helps regulate consciousness, arousal, and sleep states. A rare genetic disorder called fatal familial insomnia causes the degeneration of thalamic neurons and glia. This disorder prevents affected patients from being able to sleep, among other symptoms, and is eventually fatal. Hypothalamus Below the thalamus is the hypothalamus, shown in Figure. The hypothalamus controls the endocrine system by sending signals to the pituitary gland, a pea-sized endocrine gland that releases several different hormones that affect other glands as well as other cells. This relationship means that the hypothalamus regulates important behaviors that are controlled by these hormones. The hypothalamus is the body’s thermostat—it makes sure key functions like food and water intake, energy expenditure, and body temperature are kept at appropriate levels. Neurons within the hypothalamus also regulate circadian rhythms, sometimes called sleep cycles. Limbic System The limbic system is a connected set of structures that regulates emotion, as well as behaviors related to fear and motivation. It plays a role in memory formation and includes parts of the thalamus and hypothalamus as well as the hippocampus. One important structure within the limbic system is a temporal lobe structure called the amygdala (Greek for “almond”), illustrated in Figure. The two amygdala are important both for the sensation of fear and for recognizing fearful faces. The cingulate gyrus helps regulate emotions and pain. Cerebellum The cerebellum (Latin for “little brain”), shown in Figure, sits at the base of the brain on top of the brainstem. The cerebellum controls balance and aids in coordinating movement and learning new motor tasks. Brainstem The brainstem, illustrated in Figure, connects the rest of the brain with the spinal cord. It consists of the midbrain, medulla oblongata, and the pons. Motor and sensory neurons extend through the brainstem allowing for the relay of signals between the brain and spinal cord. Ascending neural pathways cross in this section of the brain allowing the left hemisphere of the cerebrum to control the right side of the body and vice versa. The brainstem coordinates motor control signals sent from the brain to the body. The brainstem controls several important functions of the body including alertness, arousal, breathing, blood pressure, digestion, heart rate, swallowing, walking, and sensory and motor information integration. Spinal Cord Connecting to the brainstem and extending down the body through the spinal column is the spinal cord, shown in Figure. The spinal cord is a thick bundle of nerve tissue that carries information about the body to the brain and from the brain to the body. The spinal cord is contained within the bones of the vertebrate column but is able to communicate signals to and from the body through its connections with spinal nerves (part of the peripheral nervous system). A cross-section of the spinal cord looks like a white oval containing a gray butterfly-shape, as illustrated in Figure. Myelinated axons make up the “white matter” and neuron and glial cell bodies make up the “gray matter.” Gray matter is also composed of interneurons, which connect two neurons each located in different parts of the body. Axons and cell bodies in the dorsal (facing the back of the animal) spinal cord convey mostly sensory information from the body to the brain. Axons and cell bodies in the ventral (facing the front of the animal) spinal cord primarily transmit signals controlling movement from the brain to the body. The spinal cord also controls motor reflexes. These reflexes are quick, unconscious movements—like automatically removing a hand from a hot object. Reflexes are so fast because they involve local synaptic connections. For example, the knee reflex that a doctor tests during a routine physical is controlled by a single synapse between a sensory neuron and a motor neuron. While a reflex may only require the involvement of one or two synapses, synapses with interneurons in the spinal column transmit information to the brain to convey what happened (the knee jerked, or the hand was hot). In the United States, there around 10,000 spinal cord injuries each year. Because the spinal cord is the information superhighway connecting the brain with the body, damage to the spinal cord can lead to paralysis. The extent of the paralysis depends on the location of the injury along the spinal cord and whether the spinal cord was completely severed. For example, if the spinal cord is damaged at the level of the neck, it can cause paralysis from the neck down, whereas damage to the spinal column further down may limit paralysis to the legs. Spinal cord injuries are notoriously difficult to treat because spinal nerves do not regenerate, although ongoing research suggests that stem cell transplants may be able to act as a bridge to reconnect severed nerves. Researchers are also looking at ways to prevent the inflammation that worsens nerve damage after injury. One such treatment is to pump the body with cold saline to induce hypothermia. This cooling can prevent swelling and other processes that are thought to worsen spinal cord injuries. Section Summary The vertebrate central nervous system contains the brain and the spinal cord, which are covered and protected by three meninges. The brain contains structurally and functionally defined regions. In mammals, these include the cortex (which can be broken down into four primary functional lobes: frontal, temporal, occipital, and parietal), basal ganglia, thalamus, hypothalamus, limbic system, cerebellum, and brainstem—although structures in some of these designations overlap. While functions may be primarily localized to one structure in the brain, most complex functions, like language and sleep, involve neurons in multiple brain regions. The spinal cord is the information superhighway that connects the brain with the rest of the body through its connections with peripheral nerves. It transmits sensory and motor input and also controls motor reflexes. Review Questions The ________ lobe contains the visual cortex. - frontal - parietal - temporal - occipital Hint: D The ________ connects the two cerebral hemispheres. - limbic system - corpus callosum - cerebellum - pituitary Hint: B Neurons in the ________ control motor reflexes. - thalamus - spinal cord - parietal lobe - hippocampus Hint: B Free Response What methods can be used to determine the function of a particular brain region? Hint: To determine the function of a specific brain area, scientists can look at patients who have damage in that brain area and see what symptoms they exhibit. Researchers can disable the brain structure temporarily using transcranial magnetic stimulation. They can disable or remove the area in an animal model. fMRI can be used to correlate specific functions with increased blood flow to brain regions. What are the main functions of the spinal cord? Hint: The spinal cord transmits sensory information from the body to the brain and motor commands from the brain to the body through its connections with peripheral nerves. It also controls motor reflexes.	oercommons	2025-03-18T00:36:07.439495	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15117/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15118/overview	The Peripheral Nervous System Overview By the end of this section, you will be able to: - Describe the organization and functions of the sympathetic and parasympathetic nervous systems - Describe the organization and function of the sensory-somatic nervous system The peripheral nervous system (PNS) is the connection between the central nervous system and the rest of the body. The CNS is like the power plant of the nervous system. It creates the signals that control the functions of the body. The PNS is like the wires that go to individual houses. Without those “wires,” the signals produced by the CNS could not control the body (and the CNS would not be able to receive sensory information from the body either). The PNS can be broken down into the autonomic nervous system, which controls bodily functions without conscious control, and the sensory-somatic nervous system, which transmits sensory information from the skin, muscles, and sensory organs to the CNS and sends motor commands from the CNS to the muscles. Autonomic Nervous System Art Connection Which of the following statements is false? - The parasympathetic pathway is responsible for resting the body, while the sympathetic pathway is responsible for preparing for an emergency. - Most preganglionic neurons in the sympathetic pathway originate in the spinal cord. - Slowing of the heartbeat is a parasympathetic response. - Parasympathetic neurons are responsible for releasing norepinephrine on the target organ, while sympathetic neurons are responsible for releasing acetylcholine. The autonomic nervous system serves as the relay between the CNS and the internal organs. It controls the lungs, the heart, smooth muscle, and exocrine and endocrine glands. The autonomic nervous system controls these organs largely without conscious control; it can continuously monitor the conditions of these different systems and implement changes as needed. Signaling to the target tissue usually involves two synapses: a preganglionic neuron (originating in the CNS) synapses to a neuron in a ganglion that, in turn, synapses on the target organ, as illustrated in Figure. There are two divisions of the autonomic nervous system that often have opposing effects: the sympathetic nervous system and the parasympathetic nervous system. Sympathetic Nervous System The sympathetic nervous system is responsible for the “fight or flight” response that occurs when an animal encounters a dangerous situation. One way to remember this is to think of the surprise a person feels when encountering a snake (“snake” and “sympathetic” both begin with “s”). Examples of functions controlled by the sympathetic nervous system include an accelerated heart rate and inhibited digestion. These functions help prepare an organism’s body for the physical strain required to escape a potentially dangerous situation or to fend off a predator. Most preganglionic neurons in the sympathetic nervous system originate in the spinal cord, as illustrated in Figure. The axons of these neurons release acetylcholine on postganglionic neurons within sympathetic ganglia (the sympathetic ganglia form a chain that extends alongside the spinal cord). The acetylcholine activates the postganglionic neurons. Postganglionic neurons then release norepinephrine onto target organs. As anyone who has ever felt a rush before a big test, speech, or athletic event can attest, the effects of the sympathetic nervous system are quite pervasive. This is both because one preganglionic neuron synapses on multiple postganglionic neurons, amplifying the effect of the original synapse, and because the adrenal gland also releases norepinephrine (and the closely related hormone epinephrine) into the blood stream. The physiological effects of this norepinephrine release include dilating the trachea and bronchi (making it easier for the animal to breathe), increasing heart rate, and moving blood from the skin to the heart, muscles, and brain (so the animal can think and run). The strength and speed of the sympathetic response helps an organism avoid danger, and scientists have found evidence that it may also increase LTP—allowing the animal to remember the dangerous situation and avoid it in the future. Parasympathetic Nervous System While the sympathetic nervous system is activated in stressful situations, the parasympathetic nervous system allows an animal to “rest and digest.” One way to remember this is to think that during a restful situation like a picnic, the parasympathetic nervous system is in control (“picnic” and “parasympathetic” both start with “p”). Parasympathetic preganglionic neurons have cell bodies located in the brainstem and in the sacral (toward the bottom) spinal cord, as shown in Figure. The axons of the preganglionic neurons release acetylcholine on the postganglionic neurons, which are generally located very near the target organs. Most postganglionic neurons release acetylcholine onto target organs, although some release nitric oxide. The parasympathetic nervous system resets organ function after the sympathetic nervous system is activated (the common adrenaline dump you feel after a ‘fight-or-flight’ event). Effects of acetylcholine release on target organs include slowing of heart rate, lowered blood pressure, and stimulation of digestion. Sensory-Somatic Nervous System The sensory-somatic nervous system is made up of cranial and spinal nerves and contains both sensory and motor neurons. Sensory neurons transmit sensory information from the skin, skeletal muscle, and sensory organs to the CNS. Motor neurons transmit messages about desired movement from the CNS to the muscles to make them contract. Without its sensory-somatic nervous system, an animal would be unable to process any information about its environment (what it sees, feels, hears, and so on) and could not control motor movements. Unlike the autonomic nervous system, which has two synapses between the CNS and the target organ, sensory and motor neurons have only one synapse—one ending of the neuron is at the organ and the other directly contacts a CNS neuron. Acetylcholine is the main neurotransmitter released at these synapses. Humans have 12 cranial nerves, nerves that emerge from or enter the skull (cranium), as opposed to the spinal nerves, which emerge from the vertebral column. Each cranial nerve is accorded a name, which are detailed in Figure. Some cranial nerves transmit only sensory information. For example, the olfactory nerve transmits information about smells from the nose to the brainstem. Other cranial nerves transmit almost solely motor information. For example, the oculomotor nerve controls the opening and closing of the eyelid and some eye movements. Other cranial nerves contain a mix of sensory and motor fibers. For example, the glossopharyngeal nerve has a role in both taste (sensory) and swallowing (motor). Spinal nerves transmit sensory and motor information between the spinal cord and the rest of the body. Each of the 31 spinal nerves (in humans) contains both sensory and motor axons. The sensory neuron cell bodies are grouped in structures called dorsal root ganglia and are shown in Figure. Each sensory neuron has one projection—with a sensory receptor ending in skin, muscle, or sensory organs—and another that synapses with a neuron in the dorsal spinal cord. Motor neurons have cell bodies in the ventral gray matter of the spinal cord that project to muscle through the ventral root. These neurons are usually stimulated by interneurons within the spinal cord but are sometimes directly stimulated by sensory neurons. Section Summary The peripheral nervous system contains both the autonomic and sensory-somatic nervous systems. The autonomic nervous system provides unconscious control over visceral functions and has two divisions: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system is activated in stressful situations to prepare the animal for a “fight or flight” response. The parasympathetic nervous system is active during restful periods. The sensory-somatic nervous system is made of cranial and spinal nerves that transmit sensory information from skin and muscle to the CNS and motor commands from the CNS to the muscles. Art Connections Figure Which of the following statements is false? - The parasympathetic pathway is responsible for relaxing the body, while the sympathetic pathway is responsible for preparing for an emergency. - Most preganglionic neurons in the sympathetic pathway originate in the spinal cord. - Slowing of the heartbeat is a parasympathetic response. - Parasympathetic neurons are responsible for releasing norepinephrine on the target organ, while sympathetic neurons are responsible for releasing acetylcholine. Hint: Figure D Review Questions Activation of the sympathetic nervous system causes: - increased blood flow into the skin - a decreased heart rate - an increased heart rate - increased digestion Hint: C Where are parasympathetic preganglionic cell bodies located? - cerebellum - brainstem - dorsal root ganglia - skin Hint: B ________ is released by motor nerve endings onto muscle. - Acetylcholine - Norepinephrine - Dopamine - Serotonin Hint: A Free Response What are the main differences between the sympathetic and parasympathetic branches of the autonomic nervous system? Hint: The sympathetic nervous system prepares the body for “fight or flight,” whereas the parasympathetic nervous system allows the body to “rest and digest.” Sympathetic neurons release norepinephrine onto target organs; parasympathetic neurons release acetylcholine. Sympathetic neuron cell bodies are located in sympathetic ganglia. Parasympathetic neuron cell bodies are located in the brainstem and sacral spinal cord. Activation of the sympathetic nervous system increases heart rate and blood pressure and decreases digestion and blood flow to the skin. Activation of the parasympathetic nervous system decreases heart rate and blood pressure and increases digestion and blood flow to the skin. What are the main functions of the sensory-somatic nervous system? Hint: The sensory-somatic nervous system transmits sensory information from the skin, muscles, and sensory organs to the CNS. It also sends motor commands from the CNS to the muscles, causing them to contract.	oercommons	2025-03-18T00:36:07.469115	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15118/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15119/overview	Nervous System Disorders Overview By the end of this section, you will be able to: - Describe the symptoms, potential causes, and treatment of several examples of nervous system disorders A nervous system that functions correctly is a fantastically complex, well-oiled machine—synapses fire appropriately, muscles move when needed, memories are formed and stored, and emotions are well regulated. Unfortunately, each year millions of people in the United States deal with some sort of nervous system disorder. While scientists have discovered potential causes of many of these diseases, and viable treatments for some, ongoing research seeks to find ways to better prevent and treat all of these disorders. Neurodegenerative Disorders Neurodegenerative disorders are illnesses characterized by a loss of nervous system functioning that are usually caused by neuronal death. These diseases generally worsen over time as more and more neurons die. The symptoms of a particular neurodegenerative disease are related to where in the nervous system the death of neurons occurs. Spinocerebellar ataxia, for example, leads to neuronal death in the cerebellum. The death of these neurons causes problems in balance and walking. Neurodegenerative disorders include Huntington’s disease, amyotrophic lateral sclerosis, Alzheimer’s disease and other types of dementia disorders, and Parkinson’s disease. Here, Alzheimer’s and Parkinson’s disease will be discussed in more depth. Alzheimer’s Disease Alzheimer’s disease is the most common cause of dementia in the elderly. In 2012, an estimated 5.4 million Americans suffered from Alzheimer’s disease, and payments for their care are estimated at $200 billion. Roughly one in every eight people age 65 or older has the disease. Due to the aging of the baby-boomer generation, there are projected to be as many as 13 million Alzheimer’s patients in the United States in the year 2050. Symptoms of Alzheimer’s disease include disruptive memory loss, confusion about time or place, difficulty planning or executing tasks, poor judgment, and personality changes. Problems smelling certain scents can also be indicative of Alzheimer’s disease and may serve as an early warning sign. Many of these symptoms are also common in people who are aging normally, so it is the severity and longevity of the symptoms that determine whether a person is suffering from Alzheimer’s. Alzheimer’s disease was named for Alois Alzheimer, a German psychiatrist who published a report in 1911 about a woman who showed severe dementia symptoms. Along with his colleagues, he examined the woman’s brain following her death and reported the presence of abnormal clumps, which are now called amyloid plaques, along with tangled brain fibers called neurofibrillary tangles. Amyloid plaques, neurofibrillary tangles, and an overall shrinking of brain volume are commonly seen in the brains of Alzheimer’s patients. Loss of neurons in the hippocampus is especially severe in advanced Alzheimer’s patients. Figure compares a normal brain to the brain of an Alzheimer’s patient. Many research groups are examining the causes of these hallmarks of the disease. One form of the disease is usually caused by mutations in one of three known genes. This rare form of early onset Alzheimer’s disease affects fewer than five percent of patients with the disease and causes dementia beginning between the ages of 30 and 60. The more prevalent, late-onset form of the disease likely also has a genetic component. One particular gene, apolipoprotein E (APOE) has a variant (E4) that increases a carrier’s likelihood of getting the disease. Many other genes have been identified that might be involved in the pathology. Link to Learning Visit this website for video links discussing genetics and Alzheimer’s disease. Unfortunately, there is no cure for Alzheimer’s disease. Current treatments focus on managing the symptoms of the disease. Because decrease in the activity of cholinergic neurons (neurons that use the neurotransmitter acetylcholine) is common in Alzheimer’s disease, several drugs used to treat the disease work by increasing acetylcholine neurotransmission, often by inhibiting the enzyme that breaks down acetylcholine in the synaptic cleft. Other clinical interventions focus on behavioral therapies like psychotherapy, sensory therapy, and cognitive exercises. Since Alzheimer’s disease appears to hijack the normal aging process, research into prevention is prevalent. Smoking, obesity, and cardiovascular problems may be risk factors for the disease, so treatments for those may also help to prevent Alzheimer’s disease. Some studies have shown that people who remain intellectually active by playing games, reading, playing musical instruments, and being socially active in later life have a reduced risk of developing the disease. Parkinson’s Disease Like Alzheimer’s disease, Parkinson’s disease is a neurodegenerative disease. It was first characterized by James Parkinson in 1817. Each year, 50,000-60,000 people in the United States are diagnosed with the disease. Parkinson’s disease causes the loss of dopamine neurons in the substantia nigra, a midbrain structure that regulates movement. Loss of these neurons causes many symptoms including tremor (shaking of fingers or a limb), slowed movement, speech changes, balance and posture problems, and rigid muscles. The combination of these symptoms often causes a characteristic slow hunched shuffling walk, illustrated in Figure. Patients with Parkinson’s disease can also exhibit psychological symptoms, such as dementia or emotional problems. Although some patients have a form of the disease known to be caused by a single mutation, for most patients the exact causes of Parkinson’s disease remain unknown: the disease likely results from a combination of genetic and environmental factors (similar to Alzheimer’s disease). Post-mortem analysis of brains from Parkinson’s patients shows the presence of Lewy bodies—abnormal protein clumps—in dopaminergic neurons. The prevalence of these Lewy bodies often correlates with the severity of the disease. There is no cure for Parkinson’s disease, and treatment is focused on easing symptoms. One of the most commonly prescribed drugs for Parkinson’s is L-DOPA, which is a chemical that is converted into dopamine by neurons in the brain. This conversion increases the overall level of dopamine neurotransmission and can help compensate for the loss of dopaminergic neurons in the substantia nigra. Other drugs work by inhibiting the enzyme that breaks down dopamine. Neurodevelopmental Disorders Neurodevelopmental disorders occur when the development of the nervous system is disturbed. There are several different classes of neurodevelopmental disorders. Some, like Down Syndrome, cause intellectual deficits. Others specifically affect communication, learning, or the motor system. Some disorders like autism spectrum disorder and attention deficit/hyperactivity disorder have complex symptoms. Autism Autism spectrum disorder (ASD) is a neurodevelopmental disorder. Its severity differs from person to person. Estimates for the prevalence of the disorder have changed rapidly in the past few decades. Current estimates suggest that one in 88 children will develop the disorder. ASD is four times more prevalent in males than females. Link to Learning This video discusses possible reasons why there has been a recent increase in the number of people diagnosed with autism. A characteristic symptom of ASD is impaired social skills. Children with autism may have difficulty making and maintaining eye contact and reading social cues. They also may have problems feeling empathy for others. Other symptoms of ASD include repetitive motor behaviors (such as rocking back and forth), preoccupation with specific subjects, strict adherence to certain rituals, and unusual language use. Up to 30 percent of patients with ASD develop epilepsy, and patients with some forms of the disorder (like Fragile X) also have intellectual disability. Because it is a spectrum disorder, other ASD patients are very functional and have good-to-excellent language skills. Many of these patients do not feel that they suffer from a disorder and instead think that their brains just process information differently. Except for some well-characterized, clearly genetic forms of autism (like Fragile X and Rett’s Syndrome), the causes of ASD are largely unknown. Variants of several genes correlate with the presence of ASD, but for any given patient, many different mutations in different genes may be required for the disease to develop. At a general level, ASD is thought to be a disease of “incorrect” wiring. Accordingly, brains of some ASD patients lack the same level of synaptic pruning that occurs in non-affected people. In the 1990s, a research paper linked autism to a common vaccine given to children. This paper was retracted when it was discovered that the author falsified data, and follow-up studies showed no connection between vaccines and autism. Treatment for autism usually combines behavioral therapies and interventions, along with medications to treat other disorders common to people with autism (depression, anxiety, obsessive compulsive disorder). Although early interventions can help mitigate the effects of the disease, there is currently no cure for ASD. Attention Deficit Hyperactivity Disorder (ADHD) Approximately three to five percent of children and adults are affected by attention deficit/hyperactivity disorder (ADHD). Like ASD, ADHD is more prevalent in males than females. Symptoms of the disorder include inattention (lack of focus), executive functioning difficulties, impulsivity, and hyperactivity beyond what is characteristic of the normal developmental stage. Some patients do not have the hyperactive component of symptoms and are diagnosed with a subtype of ADHD: attention deficit disorder (ADD). Many people with ADHD also show comorbitity, in that they develop secondary disorders in addition to ADHD. Examples include depression or obsessive compulsive disorder (OCD). Figure provides some statistics concerning comorbidity with ADHD. The cause of ADHD is unknown, although research points to a delay and dysfunction in the development of the prefrontal cortex and disturbances in neurotransmission. According to studies of twins, the disorder has a strong genetic component. There are several candidate genes that may contribute to the disorder, but no definitive links have been discovered. Environmental factors, including exposure to certain pesticides, may also contribute to the development of ADHD in some patients. Treatment for ADHD often involves behavioral therapies and the prescription of stimulant medications, which paradoxically cause a calming effect in these patients. Career Connection Neurologist Neurologists are physicians who specialize in disorders of the nervous system. They diagnose and treat disorders such as epilepsy, stroke, dementia, nervous system injuries, Parkinson’s disease, sleep disorders, and multiple sclerosis. Neurologists are medical doctors who have attended college, medical school, and completed three to four years of neurology residency. When examining a new patient, a neurologist takes a full medical history and performs a complete physical exam. The physical exam contains specific tasks that are used to determine what areas of the brain, spinal cord, or peripheral nervous system may be damaged. For example, to check whether the hypoglossal nerve is functioning correctly, the neurologist will ask the patient to move his or her tongue in different ways. If the patient does not have full control over tongue movements, then the hypoglossal nerve may be damaged or there may be a lesion in the brainstem where the cell bodies of these neurons reside (or there could be damage to the tongue muscle itself). Neurologists have other tools besides a physical exam they can use to diagnose particular problems in the nervous system. If the patient has had a seizure, for example, the neurologist can use electroencephalography (EEG), which involves taping electrodes to the scalp to record brain activity, to try to determine which brain regions are involved in the seizure. In suspected stroke patients, a neurologist can use a computerized tomography (CT) scan, which is a type of X-ray, to look for bleeding in the brain or a possible brain tumor. To treat patients with neurological problems, neurologists can prescribe medications or refer the patient to a neurosurgeon for surgery. Link to Learning This website allows you to see the different tests a neurologist might use to see what regions of the nervous system may be damaged in a patient. Mental Illnesses Mental illnesses are nervous system disorders that result in problems with thinking, mood, or relating with other people. These disorders are severe enough to affect a person’s quality of life and often make it difficult for people to perform the routine tasks of daily living. Debilitating mental disorders plague approximately 12.5 million Americans (about 1 in 17 people) at an annual cost of more than $300 billion. There are several types of mental disorders including schizophrenia, major depression, bipolar disorder, anxiety disorders and phobias, post-traumatic stress disorders, and obsessive-compulsive disorder (OCD), among others. The American Psychiatric Association publishes the Diagnostic and Statistical Manual of Mental Disorders (or DSM), which describes the symptoms required for a patient to be diagnosed with a particular mental disorder. Each newly released version of the DSM contains different symptoms and classifications as scientists learn more about these disorders, their causes, and how they relate to each other. A more detailed discussion of two mental illnesses—schizophrenia and major depression—is given below. Schizophrenia Schizophrenia is a serious and often debilitating mental illness affecting one percent of people in the United States. Symptoms of the disease include the inability to differentiate between reality and imagination, inappropriate and unregulated emotional responses, difficulty thinking, and problems with social situations. People with schizophrenia can suffer from hallucinations and hear voices; they may also suffer from delusions. Patients also have so-called “negative” symptoms like a flattened emotional state, loss of pleasure, and loss of basic drives. Many schizophrenic patients are diagnosed in their late adolescence or early 20s. The development of schizophrenia is thought to involve malfunctioning dopaminergic neurons and may also involve problems with glutamate signaling. Treatment for the disease usually requires antipsychotic medications that work by blocking dopamine receptors and decreasing dopamine neurotransmission in the brain. This decrease in dopamine can cause Parkinson’s disease-like symptoms in some patients. While some classes of antipsychotics can be quite effective at treating the disease, they are not a cure, and most patients must remain medicated for the rest of their lives. Depression Major depression affects approximately 6.7 percent of the adults in the United States each year and is one of the most common mental disorders. To be diagnosed with major depressive disorder, a person must have experienced a severely depressed mood lasting longer than two weeks along with other symptoms including a loss of enjoyment in activities that were previously enjoyed, changes in appetite and sleep schedules, difficulty concentrating, feelings of worthlessness, and suicidal thoughts. The exact causes of major depression are unknown and likely include both genetic and environmental risk factors. Some research supports the “classic monoamine hypothesis,” which suggests that depression is caused by a decrease in norepinephrine and serotonin neurotransmission. One argument against this hypothesis is the fact that some antidepressant medications cause an increase in norepinephrine and serotonin release within a few hours of beginning treatment—but clinical results of these medications are not seen until weeks later. This has led to alternative hypotheses: for example, dopamine may also be decreased in depressed patients, or it may actually be an increase in norepinephrine and serotonin that causes the disease, and antidepressants force a feedback loop that decreases this release. Treatments for depression include psychotherapy, electroconvulsive therapy, deep-brain stimulation, and prescription medications. There are several classes of antidepressant medications that work through different mechanisms. For example, monoamine oxidase inhibitors (MAO inhibitors) block the enzyme that degrades many neurotransmitters (including dopamine, serotonin, norepinephrine), resulting in increased neurotransmitter in the synaptic cleft. Selective serotonin reuptake inhibitors (SSRIs) block the reuptake of serotonin into the presynaptic neuron. This blockage results in an increase in serotonin in the synaptic cleft. Other types of drugs such as norepinephrine-dopamine reuptake inhibitors and norepinephrine-serotonin reuptake inhibitors are also used to treat depression. Other Neurological Disorders There are several other neurological disorders that cannot be easily placed in the above categories. These include chronic pain conditions, cancers of the nervous system, epilepsy disorders, and stroke. Epilepsy and stroke are discussed below. Epilepsy Estimates suggest that up to three percent of people in the United States will be diagnosed with epilepsy in their lifetime. While there are several different types of epilepsy, all are characterized by recurrent seizures. Epilepsy itself can be a symptom of a brain injury, disease, or other illness. For example, people who have intellectual disability or ASD can experience seizures, presumably because the developmental wiring malfunctions that caused their disorders also put them at risk for epilepsy. For many patients, however, the cause of their epilepsy is never identified and is likely to be a combination of genetic and environmental factors. Often, seizures can be controlled with anticonvulsant medications. However, for very severe cases, patients may undergo brain surgery to remove the brain area where seizures originate. Stroke A stroke results when blood fails to reach a portion of the brain for a long enough time to cause damage. Without the oxygen supplied by blood flow, neurons in this brain region die. This neuronal death can cause many different symptoms—depending on the brain area affected— including headache, muscle weakness or paralysis, speech disturbances, sensory problems, memory loss, and confusion. Stroke is often caused by blood clots and can also be caused by the bursting of a weak blood vessel. Strokes are extremely common and are the third most common cause of death in the United States. On average one person experiences a stroke every 40 seconds in the United States. Approximately 75 percent of strokes occur in people older than 65. Risk factors for stroke include high blood pressure, diabetes, high cholesterol, and a family history of stroke. Smoking doubles the risk of stroke. Because a stroke is a medical emergency, patients with symptoms of a stroke should immediately go to the emergency room, where they can receive drugs that will dissolve any clot that may have formed. These drugs will not work if the stroke was caused by a burst blood vessel or if the stroke occurred more than three hours before arriving at the hospital. Treatment following a stroke can include blood pressure medication (to prevent future strokes) and (sometimes intense) physical therapy. Section Summary Some general themes emerge from the sampling of nervous system disorders presented above. The causes for most disorders are not fully understood—at least not for all patients—and likely involve a combination of nature (genetic mutations that become risk factors) and nurture (emotional trauma, stress, hazardous chemical exposure). Because the causes have yet to be fully determined, treatment options are often lacking and only address symptoms. Review Questions Parkinson’s disease is a caused by the degeneration of neurons that release ________. - serotonin - dopamine - glutamate - norepinephrine Hint: B ________ medications are often used to treat patients with ADHD. - Tranquilizer - Antibiotic - Stimulant - Anti-seizure Hint: C Strokes are often caused by ________. - neurodegeneration - blood clots or burst blood vessels - seizures - viruses Hint: B Free Response What are the main symptoms of Alzheimer’s disease? Hint: Symptoms of Alzheimer’s disease include disruptive memory loss, confusion about time or place, difficulties planning or executing tasks, poor judgment, and personality changes. What are possible treatments for patients with major depression? Hint: Possible treatments for patients with major depression include psychotherapy and prescription medications. MAO inhibitor drugs inhibit the breakdown of certain neurotransmitters (including dopamine, serotonin, norepinephrine) in the synaptic cleft. SSRI medications inhibit the reuptake of serotonin into the presynaptic neuron.	oercommons	2025-03-18T00:36:07.500792	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15119/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15120/overview	Introduction In more advanced animals, the senses are constantly at work, making the animal aware of stimuli—such as light, or sound, or the presence of a chemical substance in the external environment—and monitoring information about the organism’s internal environment. All bilaterally symmetric animals have a sensory system, and the development of any species’ sensory system has been driven by natural selection; thus, sensory systems differ among species according to the demands of their environments. The shark, unlike most fish predators, is electrosensitive—that is, sensitive to electrical fields produced by other animals in its environment. While it is helpful to this underwater predator, electrosensitivity is a sense not found in most land animals.	oercommons	2025-03-18T00:36:07.519779	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15120/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15121/overview	Sensory Processes Overview By the end of this section, you will be able to: - Identify the general and special senses in humans - Describe three important steps in sensory perception - Explain the concept of just-noticeable difference in sensory perception Senses provide information about the body and its environment. Humans have five special senses: olfaction (smell), gustation (taste), equilibrium (balance and body position), vision, and hearing. Additionally, we possess general senses, also called somatosensation, which respond to stimuli like temperature, pain, pressure, and vibration. Vestibular sensation, which is an organism’s sense of spatial orientation and balance, proprioception (position of bones, joints, and muscles), and the sense of limb position that is used to track kinesthesia (limb movement) are part of somatosensation. Although the sensory systems associated with these senses are very different, all share a common function: to convert a stimulus (such as light, or sound, or the position of the body) into an electrical signal in the nervous system. This process is called sensory transduction. There are two broad types of cellular systems that perform sensory transduction. In one, a neuron works with a sensory receptor, a cell, or cell process that is specialized to engage with and detect a specific stimulus. Stimulation of the sensory receptor activates the associated afferent neuron, which carries information about the stimulus to the central nervous system. In the second type of sensory transduction, a sensory nerve ending responds to a stimulus in the internal or external environment: this neuron constitutes the sensory receptor. Free nerve endings can be stimulated by several different stimuli, thus showing little receptor specificity. For example, pain receptors in your gums and teeth may be stimulated by temperature changes, chemical stimulation, or pressure. Reception The first step in sensation is reception, which is the activation of sensory receptors by stimuli such as mechanical stimuli (being bent or squished, for example), chemicals, or temperature. The receptor can then respond to the stimuli. The region in space in which a given sensory receptor can respond to a stimulus, be it far away or in contact with the body, is that receptor’s receptive field. Think for a moment about the differences in receptive fields for the different senses. For the sense of touch, a stimulus must come into contact with body. For the sense of hearing, a stimulus can be a moderate distance away (some baleen whale sounds can propagate for many kilometers). For vision, a stimulus can be very far away; for example, the visual system perceives light from stars at enormous distances. Transduction The most fundamental function of a sensory system is the translation of a sensory signal to an electrical signal in the nervous system. This takes place at the sensory receptor, and the change in electrical potential that is produced is called the receptor potential. How is sensory input, such as pressure on the skin, changed to a receptor potential? In this example, a type of receptor called a mechanoreceptor (as shown in Figure) possesses specialized membranes that respond to pressure. Disturbance of these dendrites by compressing them or bending them opens gated ion channels in the plasma membrane of the sensory neuron, changing its electrical potential. Recall that in the nervous system, a positive change of a neuron’s electrical potential (also called the membrane potential), depolarizes the neuron. Receptor potentials are graded potentials: the magnitude of these graded (receptor) potentials varies with the strength of the stimulus. If the magnitude of depolarization is sufficient (that is, if membrane potential reaches a threshold), the neuron will fire an action potential. In most cases, the correct stimulus impinging on a sensory receptor will drive membrane potential in a positive direction, although for some receptors, such as those in the visual system, this is not always the case. Sensory receptors for different senses are very different from each other, and they are specialized according to the type of stimulus they sense: they have receptor specificity. For example, touch receptors, light receptors, and sound receptors are each activated by different stimuli. Touch receptors are not sensitive to light or sound; they are sensitive only to touch or pressure. However, stimuli may be combined at higher levels in the brain, as happens with olfaction, contributing to our sense of taste. Encoding and Transmission of Sensory Information Four aspects of sensory information are encoded by sensory systems: the type of stimulus, the location of the stimulus in the receptive field, the duration of the stimulus, and the relative intensity of the stimulus. Thus, action potentials transmitted over a sensory receptor’s afferent axons encode one type of stimulus, and this segregation of the senses is preserved in other sensory circuits. For example, auditory receptors transmit signals over their own dedicated system, and electrical activity in the axons of the auditory receptors will be interpreted by the brain as an auditory stimulus—a sound. The intensity of a stimulus is often encoded in the rate of action potentials produced by the sensory receptor. Thus, an intense stimulus will produce a more rapid train of action potentials, and reducing the stimulus will likewise slow the rate of production of action potentials. A second way in which intensity is encoded is by the number of receptors activated. An intense stimulus might initiate action potentials in a large number of adjacent receptors, while a less intense stimulus might stimulate fewer receptors. Integration of sensory information begins as soon as the information is received in the CNS, and the brain will further process incoming signals. Perception Perception is an individual’s interpretation of a sensation. Although perception relies on the activation of sensory receptors, perception happens not at the level of the sensory receptor, but at higher levels in the nervous system, in the brain. The brain distinguishes sensory stimuli through a sensory pathway: action potentials from sensory receptors travel along neurons that are dedicated to a particular stimulus. These neurons are dedicated to that particular stimulus and synapse with particular neurons in the brain or spinal cord. All sensory signals, except those from the olfactory system, are transmitted though the central nervous system and are routed to the thalamus and to the appropriate region of the cortex. Recall that the thalamus is a structure in the forebrain that serves as a clearinghouse and relay station for sensory (as well as motor) signals. When the sensory signal exits the thalamus, it is conducted to the specific area of the cortex (Figure) dedicated to processing that particular sense. How are neural signals interpreted? Interpretation of sensory signals between individuals of the same species is largely similar, owing to the inherited similarity of their nervous systems; however, there are some individual differences. A good example of this is individual tolerances to a painful stimulus, such as dental pain, which certainly differ. Scientific Method Connection Just-Noticeable DifferenceIt is easy to differentiate between a one-pound bag of rice and a two-pound bag of rice. There is a one-pound difference, and one bag is twice as heavy as the other. However, would it be as easy to differentiate between a 20- and a 21-pound bag? Question: What is the smallest detectible weight difference between a one-pound bag of rice and a larger bag? What is the smallest detectible difference between a 20-pound bag and a larger bag? In both cases, at what weights are the differences detected? This smallest detectible difference in stimuli is known as the just-noticeable difference (JND). Background: Research background literature on JND and on Weber’s Law, a description of a proposed mathematical relationship between the overall magnitude of the stimulus and the JND. You will be testing JND of different weights of rice in bags. Choose a convenient increment that is to be stepped through while testing. For example, you could choose 10 percent increments between one and two pounds (1.1, 1.2, 1.3, 1.4, and so on) or 20 percent increments (1.2, 1.4, 1.6, and 1.8). Hypothesis: Develop a hypothesis about JND in terms of percentage of the whole weight being tested (such as “the JND between the two small bags and between the two large bags is proportionally the same,” or “. . . is not proportionally the same.”) So, for the first hypothesis, if the JND between the one-pound bag and a larger bag is 0.2 pounds (that is, 20 percent; 1.0 pound feels the same as 1.1 pounds, but 1.0 pound feels less than 1.2 pounds), then the JND between the 20-pound bag and a larger bag will also be 20 percent. (So, 20 pounds feels the same as 22 pounds or 23 pounds, but 20 pounds feels less than 24 pounds.) Test the hypothesis: Enlist 24 participants, and split them into two groups of 12. To set up the demonstration, assuming a 10 percent increment was selected, have the first group be the one-pound group. As a counter-balancing measure against a systematic error, however, six of the first group will compare one pound to two pounds, and step down in weight (1.0 to 2.0, 1.0 to 1.9, and so on.), while the other six will step up (1.0 to 1.1, 1.0 to 1.2, and so on). Apply the same principle to the 20-pound group (20 to 40, 20 to 38, and so on, and 20 to 22, 20 to 24, and so on). Given the large difference between 20 and 40 pounds, you may wish to use 30 pounds as your larger weight. In any case, use two weights that are easily detectable as different. Record the observations: Record the data in a table similar to the table below. For the one-pound and 20-pound groups (base weights) record a plus sign (+) for each participant that detects a difference between the base weight and the step weight. Record a minus sign (-) for each participant that finds no difference. If one-tenth steps were not used, then replace the steps in the “Step Weight” columns with the step you are using. \| Results of JND Testing (+ = difference; – = no difference) \| \|\|\| \|---\|---\|---\|---\| \| Step Weight \| One pound \| 20 pounds \| Step Weight \| \| 1.1 \| 22 \| \|\| \| 1.2 \| 24 \| \|\| \| 1.3 \| 26 \| \|\| \| 1.4 \| 28 \| \|\| \| 1.5 \| 30 \| \|\| \| 1.6 \| 32 \| \|\| \| 1.7 \| 34 \| \|\| \| 1.8 \| 36 \| \|\| \| 1.9 \| 38 \| \|\| \| 2.0 \| 40 \| Analyze the data/report the results: What step weight did all participants find to be equal with one-pound base weight? What about the 20-pound group? Draw a conclusion: Did the data support the hypothesis? Are the final weights proportionally the same? If not, why not? Do the findings adhere to Weber’s Law? Weber’s Law states that the concept that a just-noticeable difference in a stimulus is proportional to the magnitude of the original stimulus. Section Summary A sensory activation occurs when a physical or chemical stimulus is processed into a neural signal (sensory transduction) by a sensory receptor. Perception is an individual interpretation of a sensation and is a brain function. Humans have special senses: olfaction, gustation, equilibrium, and hearing, plus the general senses of somatosensation. Sensory receptors are either specialized cells associated with sensory neurons or the specialized ends of sensory neurons that are a part of the peripheral nervous system, and they are used to receive information about the environment (internal or external). Each sensory receptor is modified for the type of stimulus it detects. For example, neither gustatory receptors nor auditory receptors are sensitive to light. Each sensory receptor is responsive to stimuli within a specific region in space, which is known as that receptor’s receptive field. The most fundamental function of a sensory system is the translation of a sensory signal to an electrical signal in the nervous system. All sensory signals, except those from the olfactory system, enter the central nervous system and are routed to the thalamus. When the sensory signal exits the thalamus, it is conducted to the specific area of the cortex dedicated to processing that particular sense. Review Questions Where does perception occur? - spinal cord - cerebral cortex - receptors - thalamus Hint: B If a person’s cold receptors no longer convert cold stimuli into sensory signals, that person has a problem with the process of ________. - reception - transmission - perception - transduction Hint: D After somatosensory transduction, the sensory signal travels through the brain as a(n) _____ signal. - electrical - pressure - optical - thermal Hint: A Free Response If a person sustains damage to axons leading from sensory receptors to the central nervous system, which step or steps of sensory perception will be affected? Hint: Transmission of sensory information from the receptor to the central nervous system will be impaired, and thus, perception of stimuli, which occurs in the brain, will be halted. In what way does the overall magnitude of a stimulus affect the just-noticeable difference in the perception of that stimulus? Hint: The just-noticeable difference is a fraction of the overall magnitude of the stimulus and seems to be a relatively fixed proportion (such as 10 percent) whether the stimulus is large (such as a very heavy object) or small (such as a very light object).	oercommons	2025-03-18T00:36:07.549620	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15121/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15122/overview	Somatosensation Overview By the end of this section, you will be able to: - Describe four important mechanoreceptors in human skin - Describe the topographical distribution of somatosensory receptors between glabrous and hairy skin - Explain why the perception of pain is subjective Somatosensation is a mixed sensory category and includes all sensation received from the skin and mucous membranes, as well from as the limbs and joints. Somatosensation is also known as tactile sense, or more familiarly, as the sense of touch. Somatosensation occurs all over the exterior of the body and at some interior locations as well. A variety of receptor types—embedded in the skin, mucous membranes, muscles, joints, internal organs, and cardiovascular system—play a role. Recall that the epidermis is the outermost layer of skin in mammals. It is relatively thin, is composed of keratin-filled cells, and has no blood supply. The epidermis serves as a barrier to water and to invasion by pathogens. Below this, the much thicker dermis contains blood vessels, sweat glands, hair follicles, lymph vessels, and lipid-secreting sebaceous glands (Figure). Below the epidermis and dermis is the subcutaneous tissue, or hypodermis, the fatty layer that contains blood vessels, connective tissue, and the axons of sensory neurons. The hypodermis, which holds about 50 percent of the body’s fat, attaches the dermis to the bone and muscle, and supplies nerves and blood vessels to the dermis. Somatosensory Receptors Sensory receptors are classified into five categories: mechanoreceptors, thermoreceptors, proprioceptors, pain receptors, and chemoreceptors. These categories are based on the nature of stimuli each receptor class transduces. What is commonly referred to as “touch” involves more than one kind of stimulus and more than one kind of receptor. Mechanoreceptors in the skin are described as encapsulated (that is, surrounded by a capsule) or unencapsulated (a group that includes free nerve endings). A free nerve ending, as its name implies, is an unencapsulated dendrite of a sensory neuron. Free nerve endings are the most common nerve endings in skin, and they extend into the middle of the epidermis. Free nerve endings are sensitive to painful stimuli, to hot and cold, and to light touch. They are slow to adjust to a stimulus and so are less sensitive to abrupt changes in stimulation. There are three classes of mechanoreceptors: tactile, proprioceptors, and baroreceptors. Mechanoreceptors sense stimuli due to physical deformation of their plasma membranes. They contain mechanically gated ion channels whose gates open or close in response to pressure, touch, stretching, and sound.” There are four primary tactile mechanoreceptors in human skin: Merkel’s disks, Meissner’s corpuscles, Ruffini endings, and Pacinian corpuscle; two are located toward the surface of the skin and two are located deeper. A fifth type of mechanoreceptor, Krause end bulbs, are found only in specialized regions. Merkel’s disks (shown in Figure) are found in the upper layers of skin near the base of the epidermis, both in skin that has hair and on glabrous skin, that is, the hairless skin found on the palms and fingers, the soles of the feet, and the lips of humans and other primates. Merkel’s disks are densely distributed in the fingertips and lips. They are slow-adapting, encapsulated nerve endings, and they respond to light touch. Light touch, also known as discriminative touch, is a light pressure that allows the location of a stimulus to be pinpointed. The receptive fields of Merkel’s disks are small with well-defined borders. That makes them finely sensitive to edges and they come into use in tasks such as typing on a keyboard. Art Connection Which of the following statements about mechanoreceptors is false? - Pacini corpuscles are found in both glabrous and hairy skin. - Merkel’s disks are abundant on the fingertips and lips. - Ruffini endings are encapsulated mechanoreceptors. - Meissner’s corpuscles extend into the lower dermis. Meissner’s corpuscles, (shown in Figure) also known as tactile corpuscles, are found in the upper dermis, but they project into the epidermis. They, too, are found primarily in the glabrous skin on the fingertips and eyelids. They respond to fine touch and pressure, but they also respond to low-frequency vibration or flutter. They are rapidly adapting, fluid-filled, encapsulated neurons with small, well-defined borders and are responsive to fine details. Like Merkel’s disks, Meissner’s corpuscles are not as plentiful in the palms as they are in the fingertips. Deeper in the epidermis, near the base, are Ruffini endings, which are also known as bulbous corpuscles. They are found in both glabrous and hairy skin. These are slow-adapting, encapsulated mechanoreceptors that detect skin stretch and deformations within joints, so they provide valuable feedback for gripping objects and controlling finger position and movement. Thus, they also contribute to proprioception and kinesthesia. Ruffini endings also detect warmth. Note that these warmth detectors are situated deeper in the skin than are the cold detectors. It is not surprising, then, that humans detect cold stimuli before they detect warm stimuli. Pacinian corpuscles (seen in Figure) are located deep in the dermis of both glabrous and hairy skin and are structurally similar to Meissner’s corpuscles; they are found in the bone periosteum, joint capsules, pancreas and other viscera, breast, and genitals. They are rapidly adapting mechanoreceptors that sense deep transient (but not prolonged) pressure and high-frequency vibration. Pacinian receptors detect pressure and vibration by being compressed, stimulating their internal dendrites. There are fewer Pacinian corpuscles and Ruffini endings in skin than there are Merkel’s disks and Meissner’s corpuscles. In proprioception, proprioceptive and kinesthetic signals travel through myelinated afferent neurons running from the spinal cord to the medulla. Neurons are not physically connected, but communicate via neurotransmitters secreted into synapses or “gaps” between communicating neurons. Once in the medulla, the neurons continue carrying the signals to the thalamus. Muscle spindles are stretch receptors that detect the amount of stretch, or lengthening of muscles. Related to these are Golgi tendon organs, which are tension receptors that detect the force of muscle contraction. Proprioceptive and kinesthetic signals come from limbs. Unconscious proprioceptive signals run from the spinal cord to the cerebellum, the brain region that coordinates muscle contraction, rather than to the thalamus, like most other sensory information. Barorecptors detect pressure changes in an organ. They are found in the walls of the carotid artery and the aorta where they monitor blood pressure, and in the lungs where they detect the degree of lung expansion. Stretch receptors are found at various sites in the digestive and urinary systems. In addition to these two types of deeper receptors, there are also rapidly adapting hair receptors, which are found on nerve endings that wrap around the base of hair follicles. There are a few types of hair receptors that detect slow and rapid hair movement, and they differ in their sensitivity to movement. Some hair receptors also detect skin deflection, and certain rapidly adapting hair receptors allow detection of stimuli that have not yet touched the skin. Integration of Signals from Mechanoreceptors The configuration of the different types of receptors working in concert in human skin results in a very refined sense of touch. The nociceptive receptors—those that detect pain—are located near the surface. Small, finely calibrated mechanoreceptors—Merkel’s disks and Meissner’s corpuscles—are located in the upper layers and can precisely localize even gentle touch. The large mechanoreceptors—Pacinian corpuscles and Ruffini endings—are located in the lower layers and respond to deeper touch. (Consider that the deep pressure that reaches those deeper receptors would not need to be finely localized.) Both the upper and lower layers of the skin hold rapidly and slowly adapting receptors. Both primary somatosensory cortex and secondary cortical areas are responsible for processing the complex picture of stimuli transmitted from the interplay of mechanoreceptors. Density of Mechanoreceptors The distribution of touch receptors in human skin is not consistent over the body. In humans, touch receptors are less dense in skin covered with any type of hair, such as the arms, legs, torso, and face. Touch receptors are denser in glabrous skin (the type found on human fingertips and lips, for example), which is typically more sensitive and is thicker than hairy skin (4 to 5 mm versus 2 to 3 mm). How is receptor density estimated in a human subject? The relative density of pressure receptors in different locations on the body can be demonstrated experimentally using a two-point discrimination test. In this demonstration, two sharp points, such as two thumbtacks, are brought into contact with the subject’s skin (though not hard enough to cause pain or break the skin). The subject reports if he or she feels one point or two points. If the two points are felt as one point, it can be inferred that the two points are both in the receptive field of a single sensory receptor. If two points are felt as two separate points, each is in the receptive field of two separate sensory receptors. The points could then be moved closer and re-tested until the subject reports feeling only one point, and the size of the receptive field of a single receptor could be estimated from that distance. Thermoreception In addition to Krause end bulbs that detect cold and Ruffini endings that detect warmth, there are different types of cold receptors on some free nerve endings: thermoreceptors, located in the dermis, skeletal muscles, liver, and hypothalamus, that are activated by different temperatures. Their pathways into the brain run from the spinal cord through the thalamus to the primary somatosensory cortex. Warmth and cold information from the face travels through one of the cranial nerves to the brain. You know from experience that a tolerably cold or hot stimulus can quickly progress to a much more intense stimulus that is no longer tolerable. Any stimulus that is too intense can be perceived as pain because temperature sensations are conducted along the same pathways that carry pain sensations Pain Pain is the name given to nociception, which is the neural processing of injurious stimuli in response to tissue damage. Pain is caused by true sources of injury, such as contact with a heat source that causes a thermal burn or contact with a corrosive chemical. But pain also can be caused by harmless stimuli that mimic the action of damaging stimuli, such as contact with capsaicins, the compounds that cause peppers to taste hot and which are used in self-defense pepper sprays and certain topical medications. Peppers taste “hot” because the protein receptors that bind capsaicin open the same calcium channels that are activated by warm receptors. Nociception starts at the sensory receptors, but pain, inasmuch as it is the perception of nociception, does not start until it is communicated to the brain. There are several nociceptive pathways to and through the brain. Most axons carrying nociceptive information into the brain from the spinal cord project to the thalamus (as do other sensory neurons) and the neural signal undergoes final processing in the primary somatosensory cortex. Interestingly, one nociceptive pathway projects not to the thalamus but directly to the hypothalamus in the forebrain, which modulates the cardiovascular and neuroendocrine functions of the autonomic nervous system. Recall that threatening—or painful—stimuli stimulate the sympathetic branch of the visceral sensory system, readying a fight-or-flight response. Link to Learning View this video that animates the five phases of nociceptive pain. Section Summary Somatosensation includes all sensation received from the skin and mucous membranes, as well as from the limbs and joints. Somatosensation occurs all over the exterior of the body and at some interior locations as well, and a variety of receptor types, embedded in the skin and mucous membranes, play a role. There are several types of specialized sensory receptors. Rapidly adapting free nerve endings detect nociception, hot and cold, and light touch. Slowly adapting, encapsulated Merkel’s disks are found in fingertips and lips, and respond to light touch. Meissner’s corpuscles, found in glabrous skin, are rapidly adapting, encapsulated receptors that detect touch, low-frequency vibration, and flutter. Ruffini endings are slowly adapting, encapsulated receptors that detect skin stretch, joint activity, and warmth. Hair receptors are rapidly adapting nerve endings wrapped around the base of hair follicles that detect hair movement and skin deflection. Finally, Pacinian corpuscles are encapsulated, rapidly adapting receptors that detect transient pressure and high-frequency vibration. Art Connections Figure Which of the following statements about mechanoreceptors is false? - Pacini corpuscles are found in both glabrous and hairy skin. - Merkel’s disks are abundant on the fingertips and lips. - Ruffini endings are encapsulated mechanoreceptors. - Meissner’s corpuscles extend into the lower dermis. Hint: Figure D Review Questions _____ are found only in _____ skin, and detect skin deflection. - Meissner’s corpuscles: hairy - Merkel’s disks: glabrous - hair receptors: hairy - Krause end bulbs: hairy Hint: B If you were to burn your epidermis, what receptor type would you most likely burn? - free nerve endings - Ruffini endings - Pacinian corpuscle - hair receptors Hint: A Free Response What can be inferred about the relative sizes of the areas of cortex that process signals from skin not densely innervated with sensory receptors and skin that is densely innervated with sensory receptors? Hint: The cortical areas serving skin that is densely innervated likely are larger than those serving skin that is less densely innervated.	oercommons	2025-03-18T00:36:07.579390	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15122/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15123/overview	Taste and Smell Overview By the end of this section, you will be able to: - Explain in what way smell and taste stimuli differ from other sensory stimuli - Identify the five primary tastes that can be distinguished by humans - Explain in anatomical terms why a dog’s sense of smell is more acute than a human’s Taste, also called gustation, and smell, also called olfaction, are the most interconnected senses in that both involve molecules of the stimulus entering the body and bonding to receptors. Smell lets an animal sense the presence of food or other animals—whether potential mates, predators, or prey—or other chemicals in the environment that can impact their survival. Similarly, the sense of taste allows animals to discriminate between types of foods. While the value of a sense of smell is obvious, what is the value of a sense of taste? Different tasting foods have different attributes, both helpful and harmful. For example, sweet-tasting substances tend to be highly caloric, which could be necessary for survival in lean times. Bitterness is associated with toxicity, and sourness is associated with spoiled food. Salty foods are valuable in maintaining homeostasis by helping the body retain water and by providing ions necessary for cells to function. Tastes and Odors Both taste and odor stimuli are molecules taken in from the environment. The primary tastes detected by humans are sweet, sour, bitter, salty and umami. The first four tastes need little explanation. The identification of umami as a fundamental taste occurred fairly recently—it was identified in 1908 by Japanese scientist Kikunae Ikeda while he worked with seaweed broth, but it was not widely accepted as a taste that could be physiologically distinguished until many years later. The taste of umami, also known as savoriness, is attributable to the taste of the amino acid L-glutamate. In fact, monosodium glutamate, or MSG, is often used in cooking to enhance the savory taste of certain foods. What is the adaptive value of being able to distinguish umami? Savory substances tend to be high in protein. All odors that we perceive are molecules in the air we breathe. If a substance does not release molecules into the air from its surface, it has no smell. And if a human or other animal does not have a receptor that recognizes a specific molecule, then that molecule has no smell. Humans have about 350 olfactory receptor subtypes that work in various combinations to allow us to sense about 10,000 different odors. Compare that to mice, for example, which have about 1,300 olfactory receptor types, and therefore probably sense more odors. Both odors and tastes involve molecules that stimulate specific chemoreceptors. Although humans commonly distinguish taste as one sense and smell as another, they work together to create the perception of flavor. A person’s perception of flavor is reduced if he or she has congested nasal passages. Reception and Transduction Odorants (odor molecules) enter the nose and dissolve in the olfactory epithelium, the mucosa at the back of the nasal cavity (as illustrated in Figure). The olfactory epithelium is a collection of specialized olfactory receptors in the back of the nasal cavity that spans an area about 5 cm2 in humans. Recall that sensory cells are neurons. An olfactory receptor, which is a dendrite of a specialized neuron, responds when it binds certain molecules inhaled from the environment by sending impulses directly to the olfactory bulb of the brain. Humans have about 12 million olfactory receptors, distributed among hundreds of different receptor types that respond to different odors. Twelve million seems like a large number of receptors, but compare that to other animals: rabbits have about 100 million, most dogs have about 1 billion, and bloodhounds—dogs selectively bred for their sense of smell—have about 4 billion. The overall size of the olfactory epithelium also differs between species, with that of bloodhounds, for example, being many times larger than that of humans. Olfactory neurons are bipolar neurons (neurons with two processes from the cell body). Each neuron has a single dendrite buried in the olfactory epithelium, and extending from this dendrite are 5 to 20 receptor-laden, hair-like cilia that trap odorant molecules. The sensory receptors on the cilia are proteins, and it is the variations in their amino acid chains that make the receptors sensitive to different odorants. Each olfactory sensory neuron has only one type of receptor on its cilia, and the receptors are specialized to detect specific odorants, so the bipolar neurons themselves are specialized. When an odorant binds with a receptor that recognizes it, the sensory neuron associated with the receptor is stimulated. Olfactory stimulation is the only sensory information that directly reaches the cerebral cortex, whereas other sensations are relayed through the thalamus. Evolution Connection PheromonesA pheromone is a chemical released by an animal that affects the behavior or physiology of animals of the same species. Pheromonal signals can have profound effects on animals that inhale them, but pheromones apparently are not consciously perceived in the same way as other odors. There are several different types of pheromones, which are released in urine or as glandular secretions. Certain pheromones are attractants to potential mates, others are repellants to potential competitors of the same sex, and still others play roles in mother-infant attachment. Some pheromones can also influence the timing of puberty, modify reproductive cycles, and even prevent embryonic implantation. While the roles of pheromones in many nonhuman species are important, pheromones have become less important in human behavior over evolutionary time compared to their importance to organisms with more limited behavioral repertoires. The vomeronasal organ (VNO, or Jacobson’s organ) is a tubular, fluid-filled, olfactory organ present in many vertebrate animals that sits adjacent to the nasal cavity. It is very sensitive to pheromones and is connected to the nasal cavity by a duct. When molecules dissolve in the mucosa of the nasal cavity, they then enter the VNO where the pheromone molecules among them bind with specialized pheromone receptors. Upon exposure to pheromones from their own species or others, many animals, including cats, may display the flehmen response (shown in Figure), a curling of the upper lip that helps pheromone molecules enter the VNO. Pheromonal signals are sent, not to the main olfactory bulb, but to a different neural structure that projects directly to the amygdala (recall that the amygdala is a brain center important in emotional reactions, such as fear). The pheromonal signal then continues to areas of the hypothalamus that are key to reproductive physiology and behavior. While some scientists assert that the VNO is apparently functionally vestigial in humans, even though there is a similar structure located near human nasal cavities, others are researching it as a possible functional system that may, for example, contribute to synchronization of menstrual cycles in women living in close proximity. Taste Detecting a taste (gustation) is fairly similar to detecting an odor (olfaction), given that both taste and smell rely on chemical receptors being stimulated by certain molecules. The primary organ of taste is the taste bud. A taste bud is a cluster of gustatory receptors (taste cells) that are located within the bumps on the tongue called papillae (singular: papilla) (illustrated in Figure). There are several structurally distinct papillae. Filiform papillae, which are located across the tongue, are tactile, providing friction that helps the tongue move substances, and contain no taste cells. In contrast, fungiform papillae, which are located mainly on the anterior two-thirds of the tongue, each contain one to eight taste buds and also have receptors for pressure and temperature. The large circumvallate papillae contain up to 100 taste buds and form a V near the posterior margin of the tongue. In addition to those two types of chemically and mechanically sensitive papillae are foliate papillae—leaf-like papillae located in parallel folds along the edges and toward the back of the tongue, as seen in the Figure micrograph. Foliate papillae contain about 1,300 taste buds within their folds. Finally, there are circumvallate papillae, which are wall-like papillae in the shape of an inverted “V” at the back of the tongue. Each of these papillae is surrounded by a groove and contains about 250 taste buds. Each taste bud’s taste cells are replaced every 10 to 14 days. These are elongated cells with hair-like processes called microvilli at the tips that extend into the taste bud pore (illustrate in Figure). Food molecules (tastants) are dissolved in saliva, and they bind with and stimulate the receptors on the microvilli. The receptors for tastants are located across the outer portion and front of the tongue, outside of the middle area where the filiform papillae are most prominent. In humans, there are five primary tastes, and each taste has only one corresponding type of receptor. Thus, like olfaction, each receptor is specific to its stimulus (tastant). Transduction of the five tastes happens through different mechanisms that reflect the molecular composition of the tastant. A salty tastant (containing NaCl) provides the sodium ions (Na+) that enter the taste neurons and excite them directly. Sour tastants are acids and belong to the thermoreceptor protein family. Binding of an acid or other sour-tasting molecule triggers a change in the ion channel and these increase hydrogen ion (H+) concentrations in the taste neurons, thus depolarizing them. Sweet, bitter, and umami tastants require a G-protein coupled receptor. These tastants bind to their respective receptors, thereby exciting the specialized neurons associated with them. Both tasting abilities and sense of smell change with age. In humans, the senses decline dramatically by age 50 and continue to decline. A child may find a food to be too spicy, whereas an elderly person may find the same food to be bland and unappetizing. Link to Learning View this animation that shows how the sense of taste works. Smell and Taste in the Brain Olfactory neurons project from the olfactory epithelium to the olfactory bulb as thin, unmyelinated axons. The olfactory bulb is composed of neural clusters called glomeruli, and each glomerulus receives signals from one type of olfactory receptor, so each glomerulus is specific to one odorant. From glomeruli, olfactory signals travel directly to the olfactory cortex and then to the frontal cortex and the thalamus. Recall that this is a different path from most other sensory information, which is sent directly to the thalamus before ending up in the cortex. Olfactory signals also travel directly to the amygdala, thereafter reaching the hypothalamus, thalamus, and frontal cortex. The last structure that olfactory signals directly travel to is a cortical center in the temporal lobe structure important in spatial, autobiographical, declarative, and episodic memories. Olfaction is finally processed by areas of the brain that deal with memory, emotions, reproduction, and thought. Taste neurons project from taste cells in the tongue, esophagus, and palate to the medulla, in the brainstem. From the medulla, taste signals travel to the thalamus and then to the primary gustatory cortex. Information from different regions of the tongue is segregated in the medulla, thalamus, and cortex. Section Summary There are five primary tastes in humans: sweet, sour, bitter, salty, and umami. Each taste has its own receptor type that responds only to that taste. Tastants enter the body and are dissolved in saliva. Taste cells are located within taste buds, which are found on three of the four types of papillae in the mouth. Regarding olfaction, there are many thousands of odorants, but humans detect only about 10,000. Like taste receptors, olfactory receptors are each responsive to only one odorant. Odorants dissolve in nasal mucosa, where they excite their corresponding olfactory sensory cells. When these cells detect an odorant, they send their signals to the main olfactory bulb and then to other locations in the brain, including the olfactory cortex. Review Questions Which of the following has the fewest taste receptors? - fungiform papillae - circumvallate papillae - foliate papillae - filiform papillae Hint: D How many different taste molecules do taste cells each detect? - one - five - ten - It depends on the spot on the tongue Hint: A Salty foods activate the taste cells by _____. - exciting the taste cell directly - causing hydrogen ions to enter the cell - causing sodium channels to close - binding directly to the receptors Hint: A All sensory signals except _____ travel to the _____ in the brain before the cerebral cortex. - vision; thalamus - olfaction; thalamus - vision; cranial nerves - olfaction; cranial nerves Hint: B Free Response From the perspective of the recipient of the signal, in what ways do pheromones differ from other odorants? Hint: Pheromones may not be consciously perceived, and pheromones can have direct physiological and behavioral effects on their recipients. What might be the effect on an animal of not being able to perceive taste? Hint: The animal might not be able to recognize the differences in food sources and thus might not be able to discriminate between spoiled food and safe food or between foods that contain necessary nutrients, such as proteins, and foods that do not.	oercommons	2025-03-18T00:36:07.609327	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15123/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15124/overview	Hearing and Vestibular Sensation Overview By the end of this section, you will be able to: - Describe the relationship of amplitude and frequency of a sound wave to attributes of sound - Trace the path of sound through the auditory system to the site of transduction of sound - Identify the structures of the vestibular system that respond to gravity Audition, or hearing, is important to humans and to other animals for many different interactions. It enables an organism to detect and receive information about danger, such as an approaching predator, and to participate in communal exchanges like those concerning territories or mating. On the other hand, although it is physically linked to the auditory system, the vestibular system is not involved in hearing. Instead, an animal’s vestibular system detects its own movement, both linear and angular acceleration and deceleration, and balance. Sound Auditory stimuli are sound waves, which are mechanical, pressure waves that move through a medium, such as air or water. There are no sound waves in a vacuum since there are no air molecules to move in waves. The speed of sound waves differs, based on altitude, temperature, and medium, but at sea level and a temperature of 20º C (68º F), sound waves travel in the air at about 343 meters per second. As is true for all waves, there are four main characteristics of a sound wave: frequency, wavelength, period, and amplitude. Frequency is the number of waves per unit of time, and in sound is heard as pitch. High-frequency (≥15.000Hz) sounds are higher-pitched (short wavelength) than low-frequency (long wavelengths; ≤100Hz) sounds. Frequency is measured in cycles per second, and for sound, the most commonly used unit is hertz (Hz), or cycles per second. Most humans can perceive sounds with frequencies between 30 and 20,000 Hz. Women are typically better at hearing high frequencies, but everyone’s ability to hear high frequencies decreases with age. Dogs detect up to about 40,000 Hz; cats, 60,000 Hz; bats, 100,000 Hz; and dolphins 150,000 Hz, and American shad (Alosa sapidissima), a fish, can hear 180,000 Hz. Those frequencies above the human range are called ultrasound. Amplitude, or the dimension of a wave from peak to trough, in sound is heard as volume and is illustrated in Figure. The sound waves of louder sounds have greater amplitude than those of softer sounds. For sound, volume is measured in decibels (dB). The softest sound that a human can hear is the zero point. Humans speak normally at 60 decibels. Reception of Sound In mammals, sound waves are collected by the external, cartilaginous part of the ear called the pinna, then travel through the auditory canal and cause vibration of the thin diaphragm called the tympanum or ear drum, the innermost part of the outer ear (illustrated in Figure). Interior to the tympanum is the middle ear. The middle ear holds three small bones called the ossicles, which transfer energy from the moving tympanum to the inner ear. The three ossicles are the malleus (also known as the hammer), the incus (the anvil), and stapes (the stirrup). The aptly named stapes looks very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in hearing. The malleus attaches at three points to the interior surface of the tympanic membrane. The incus attaches the malleus to the stapes. In humans, the stapes is not long enough to reach the tympanum. If we did not have the malleus and the incus, then the vibrations of the tympanum would never reach the inner ear. These bones also function to collect force and amplify sounds. The ear ossicles are homologous to bones in a fish mouth: the bones that support gills in fish are thought to be adapted for use in the vertebrate ear over evolutionary time. Many animals (frogs, reptiles, and birds, for example) use the stapes of the middle ear to transmit vibrations to the middle ear. Transduction of Sound Vibrating objects, such as vocal cords, create sound waves or pressure waves in the air. When these pressure waves reach the ear, the ear transduces this mechanical stimulus (pressure wave) into a nerve impulse (electrical signal) that the brain perceives as sound. The pressure waves strike the tympanum, causing it to vibrate. The mechanical energy from the moving tympanum transmits the vibrations to the three bones of the middle ear. The stapes transmits the vibrations to a thin diaphragm called the oval window, which is the outermost structure of the inner ear. The structures of the inner ear are found in the labyrinth, a bony, hollow structure that is the most interior portion of the ear. Here, the energy from the sound wave is transferred from the stapes through the flexible oval window and to the fluid of the cochlea. The vibrations of the oval window create pressure waves in the fluid (perilymph) inside the cochlea. The cochlea is a whorled structure, like the shell of a snail, and it contains receptors for transduction of the mechanical wave into an electrical signal (as illustrated in Figure). Inside the cochlea, the basilar membrane is a mechanical analyzer that runs the length of the cochlea, curling toward the cochlea’s center. The mechanical properties of the basilar membrane change along its length, such that it is thicker, tauter, and narrower at the outside of the whorl (where the cochlea is largest), and thinner, floppier, and broader toward the apex, or center, of the whorl (where the cochlea is smallest). Different regions of the basilar membrane vibrate according to the frequency of the sound wave conducted through the fluid in the cochlea. For these reasons, the fluid-filled cochlea detects different wave frequencies (pitches) at different regions of the membrane. When the sound waves in the cochlear fluid contact the basilar membrane, it flexes back and forth in a wave-like fashion. Above the basilar membrane is the tectorial membrane. Art Connection Cochlear implants can restore hearing in people who have a nonfunctional cochlear. The implant consists of a microphone that picks up sound. A speech processor selects sounds in the range of human speech, and a transmitter converts these sounds to electrical impulses, which are then sent to the auditory nerve. Which of the following types of hearing loss would not be restored by a cochlear implant? - Hearing loss resulting from absence or loss of hair cells in the organ of Corti. - Hearing loss resulting from an abnormal auditory nerve. - Hearing loss resulting from fracture of the cochlea. - Hearing loss resulting from damage to bones of the middle ear. The site of transduction is in the organ of Corti (spiral organ). It is composed of hair cells held in place above the basilar membrane like flowers projecting up from soil, with their exposed short, hair-like stereocilia contacting or embedded in the tectorial membrane above them. The inner hair cells are the primary auditory receptors and exist in a single row, numbering approximately 3,500. The stereocilia from inner hair cells extend into small dimples on the tectorial membrane’s lower surface. The outer hair cells are arranged in three or four rows. They number approximately 12,000, and they function to fine tune incoming sound waves. The longer stereocilia that project from the outer hair cells actually attach to the tectorial membrane. All of the stereocilia are mechanoreceptors, and when bent by vibrations they respond by opening a gated ion channel (refer to ). As a result, the hair cell membrane is depolarized, and a signal is transmitted to the chochlear nerve. Intensity (volume) of sound is determined by how many hair cells at a particular location are stimulated. The hair cells are arranged on the basilar membrane in an orderly way. The basilar membrane vibrates in different regions, according to the frequency of the sound waves impinging on it. Likewise, the hair cells that lay above it are most sensitive to a specific frequency of sound waves. Hair cells can respond to a small range of similar frequencies, but they require stimulation of greater intensity to fire at frequencies outside of their optimal range. The difference in response frequency between adjacent inner hair cells is about 0.2 percent. Compare that to adjacent piano strings, which are about six percent different. Place theory, which is the model for how biologists think pitch detection works in the human ear, states that high frequency sounds selectively vibrate the basilar membrane of the inner ear near the entrance port (the oval window). Lower frequencies travel farther along the membrane before causing appreciable excitation of the membrane. The basic pitch-determining mechanism is based on the location along the membrane where the hair cells are stimulated. The place theory is the first step toward an understanding of pitch perception. Considering the extreme pitch sensitivity of the human ear, it is thought that there must be some auditory “sharpening” mechanism to enhance the pitch resolution. When sound waves produce fluid waves inside the cochlea, the basilar membrane flexes, bending the stereocilia that attach to the tectorial membrane. Their bending results in action potentials in the hair cells, and auditory information travels along the neural endings of the bipolar neurons of the hair cells (collectively, the auditory nerve) to the brain. When the hairs bend, they release an excitatory neurotransmitter at a synapse with a sensory neuron, which then conducts action potentials to the central nervous system. The cochlear branch of the vestibulocochlear cranial nerve sends information on hearing. The auditory system is very refined, and there is some modulation or “sharpening” built in. The brain can send signals back to the cochlea, resulting in a change of length in the outer hair cells, sharpening or dampening the hair cells’ response to certain frequencies. Link to Learning Watch an animation of sound entering the outer ear, moving through the ear structure, stimulating cochlear nerve impulses, and eventually sending signals to the temporal lobe. Higher Processing The inner hair cells are most important for conveying auditory information to the brain. About 90 percent of the afferent neurons carry information from inner hair cells, with each hair cell synapsing with 10 or so neurons. Outer hair cells connect to only 10 percent of the afferent neurons, and each afferent neuron innervates many hair cells. The afferent, bipolar neurons that convey auditory information travel from the cochlea to the medulla, through the pons and midbrain in the brainstem, finally reaching the primary auditory cortex in the temporal lobe. Vestibular Information The stimuli associated with the vestibular system are linear acceleration (gravity) and angular acceleration and deceleration. Gravity, acceleration, and deceleration are detected by evaluating the inertia on receptive cells in the vestibular system. Gravity is detected through head position. Angular acceleration and deceleration are expressed through turning or tilting of the head. The vestibular system has some similarities with the auditory system. It utilizes hair cells just like the auditory system, but it excites them in different ways. There are five vestibular receptor organs in the inner ear: the utricle, the saccule, and three semicircular canals. Together, they make up what’s known as the vestibular labyrinth that is shown in Figure. The utricle and saccule respond to acceleration in a straight line, such as gravity. The roughly 30,000 hair cells in the utricle and 16,000 hair cells in the saccule lie below a gelatinous layer, with their stereocilia projecting into the gelatin. Embedded in this gelatin are calcium carbonate crystals—like tiny rocks. When the head is tilted, the crystals continue to be pulled straight down by gravity, but the new angle of the head causes the gelatin to shift, thereby bending the stereocilia. The bending of the stereocilia stimulates the neurons, and they signal to the brain that the head is tilted, allowing the maintenance of balance. It is the vestibular branch of the vestibulocochlear cranial nerve that deals with balance. The fluid-filled semicircular canals are tubular loops set at oblique angles. They are arranged in three spatial planes. The base of each canal has a swelling that contains a cluster of hair cells. The hairs project into a gelatinous cap called the cupula and monitor angular acceleration and deceleration from rotation. They would be stimulated by driving your car around a corner, turning your head, or falling forward. One canal lies horizontally, while the other two lie at about 45 degree angles to the horizontal axis, as illustrated in Figure. When the brain processes input from all three canals together, it can detect angular acceleration or deceleration in three dimensions. When the head turns, the fluid in the canals shifts, thereby bending stereocilia and sending signals to the brain. Upon cessation accelerating or decelerating—or just moving—the movement of the fluid within the canals slows or stops. For example, imagine holding a glass of water. When moving forward, water may splash backwards onto the hand, and when motion has stopped, water may splash forward onto the fingers. While in motion, the water settles in the glass and does not splash. Note that the canals are not sensitive to velocity itself, but to changes in velocity, so moving forward at 60mph with your eyes closed would not give the sensation of movement, but suddenly accelerating or braking would stimulate the receptors. Higher Processing Hair cells from the utricle, saccule, and semicircular canals also communicate through bipolar neurons to the cochlear nucleus in the medulla. Cochlear neurons send descending projections to the spinal cord and ascending projections to the pons, thalamus, and cerebellum. Connections to the cerebellum are important for coordinated movements. There are also projections to the temporal cortex, which account for feelings of dizziness; projections to autonomic nervous system areas in the brainstem, which account for motion sickness; and projections to the primary somatosensory cortex, which monitors subjective measurements of the external world and self-movement. People with lesions in the vestibular area of the somatosensory cortex see vertical objects in the world as being tilted. Finally, the vestibular signals project to certain optic muscles to coordinate eye and head movements. Link to Learning Click through this interactive tutorial to review the parts of the ear and how they function to process sound. Section Summary Audition is important for territory defense, predation, predator defense, and communal exchanges. The vestibular system, which is not auditory, detects linear acceleration and angular acceleration and deceleration. Both the auditory system and vestibular system use hair cells as their receptors. Auditory stimuli are sound waves. The sound wave energy reaches the outer ear (pinna, canal, tympanum), and vibrations of the tympanum send the energy to the middle ear. The middle ear bones shift and the stapes transfers mechanical energy to the oval window of the fluid-filled inner ear cochlea. Once in the cochlea, the energy causes the basilar membrane to flex, thereby bending the stereocilia on receptor hair cells. This activates the receptors, which send their auditory neural signals to the brain. The vestibular system has five parts that work together to provide the sense of direction, thus helping to maintain balance. The utricle and saccule measure head orientation: their calcium carbonate crystals shift when the head is tilted, thereby activating hair cells. The semicircular canals work similarly, such that when the head is turned, the fluid in the canals bends stereocilia on hair cells. The vestibular hair cells also send signals to the thalamus and to somatosensory cortex, but also to the cerebellum, the structure above the brainstem that plays a large role in timing and coordination of movement. Art Connections Figure Cochlear implants can restore hearing in people who have a nonfunctional cochlear. The implant consists of a microphone that picks up sound. A speech processor selects sounds in the range of human speech, and a transmitter converts these sounds to electrical impulses, which are then sent to the auditory nerve. Which of the following types of hearing loss would not be restored by a cochlear implant? - Hearing loss resulting from absence or loss of hair cells in the organ of Corti. - Hearing loss resulting from an abnormal auditory nerve. - Hearing loss resulting from fracture of the cochlea. - Hearing loss resulting from damage to bones of the middle ear. Hint: Figure B Review Questions In sound, pitch is measured in _____, and volume is measured in _____. - nanometers (nm); decibels (dB) - decibels (dB); nanometers (nm) - decibels (dB); hertz (Hz) - hertz (Hz); decibels (dB) Hint: D Auditory hair cells are indirectly anchored to the _____. - basilar membrane - oval window - tectorial membrane - ossicles Hint: A Which of the following are found both in the auditory system and the vestibular system? - basilar membrane - hair cells - semicircular canals - ossicles Hint: B Free Response How would a rise in altitude likely affect the speed of a sound transmitted through air? Why? Hint: The sound would slow down, because it is transmitted through the particles (gas) and there are fewer particles (lower density) at higher altitudes. How might being in a place with less gravity than Earth has (such as Earth’s moon) affect vestibular sensation, and why? Hint: Because vestibular sensation relies on gravity’s effects on tiny crystals in the inner ear, a situation of reduced gravity would likely impair vestibular sensation.	oercommons	2025-03-18T00:36:07.642817	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15124/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15125/overview	Vision Overview By the end of this section, you will be able to: - Explain how electromagnetic waves differs from sound waves - Trace the path of light through the eye to the point of the optic nerve - Explain tonic activity as it is manifested in photoreceptors in the retina Vision is the ability to detect light patterns from the outside environment and interpret them into images. Animals are bombarded with sensory information, and the sheer volume of visual information can be problematic. Fortunately, the visual systems of species have evolved to attend to the most-important stimuli. The importance of vision to humans is further substantiated by the fact that about one-third of the human cerebral cortex is dedicated to analyzing and perceiving visual information. Light As with auditory stimuli, light travels in waves. The compression waves that compose sound must travel in a medium—a gas, a liquid, or a solid. In contrast, light is composed of electromagnetic waves and needs no medium; light can travel in a vacuum (Figure). The behavior of light can be discussed in terms of the behavior of waves and also in terms of the behavior of the fundamental unit of light—a packet of electromagnetic radiation called a photon. A glance at the electromagnetic spectrum shows that visible light for humans is just a small slice of the entire spectrum, which includes radiation that we cannot see as light because it is below the frequency of visible red light and above the frequency of visible violet light. Certain variables are important when discussing perception of light. Wavelength (which varies inversely with frequency) manifests itself as hue. Light at the red end of the visible spectrum has longer wavelengths (and is lower frequency), while light at the violet end has shorter wavelengths (and is higher frequency). The wavelength of light is expressed in nanometers (nm); one nanometer is one billionth of a meter. Humans perceive light that ranges between approximately 380 nm and 740 nm. Some other animals, though, can detect wavelengths outside of the human range. For example, bees see near-ultraviolet light in order to locate nectar guides on flowers, and some non-avian reptiles sense infrared light (heat that prey gives off). Wave amplitude is perceived as luminous intensity, or brightness. The standard unit of intensity of light is the candela, which is approximately the luminous intensity of a one common candle. Light waves travel 299,792 km per second in a vacuum, (and somewhat slower in various media such as air and water), and those waves arrive at the eye as long (red), medium (green), and short (blue) waves. What is termed “white light” is light that is perceived as white by the human eye. This effect is produced by light that stimulates equally the color receptors in the human eye. The apparent color of an object is the color (or colors) that the object reflects. Thus a red object reflects the red wavelengths in mixed (white) light and absorbs all other wavelengths of light. Anatomy of the Eye The photoreceptive cells of the eye, where transduction of light to nervous impulses occurs, are located in the retina (shown in Figure) on the inner surface of the back of the eye. But light does not impinge on the retina unaltered. It passes through other layers that process it so that it can be interpreted by the retina (Figureb). The cornea, the front transparent layer of the eye, and the crystalline lens, a transparent convex structure behind the cornea, both refract (bend) light to focus the image on the retina. The iris, which is conspicuous as the colored part of the eye, is a circular muscular ring lying between the lens and cornea that regulates the amount of light entering the eye. In conditions of high ambient light, the iris contracts, reducing the size of the pupil at its center. In conditions of low light, the iris relaxes and the pupil enlarges. Art Connection Which of the following statements about the human eye is false? - Rods detect color, while cones detect only shades of gray. - When light enters the retina, it passes the ganglion cells and bipolar cells before reaching photoreceptors at the rear of the eye. - The iris adjusts the amount of light coming into the eye. - The cornea is a protective layer on the front of the eye. The main function of the lens is to focus light on the retina and fovea centralis. The lens is dynamic, focusing and re-focusing light as the eye rests on near and far objects in the visual field. The lens is operated by muscles that stretch it flat or allow it to thicken, changing the focal length of light coming through it to focus it sharply on the retina. With age comes the loss of the flexibility of the lens, and a form of farsightedness called presbyopia results. Presbyopia occurs because the image focuses behind the retina. Presbyopia is a deficit similar to a different type of farsightedness called hyperopia caused by an eyeball that is too short. For both defects, images in the distance are clear but images nearby are blurry. Myopia (nearsightedness) occurs when an eyeball is elongated and the image focus falls in front of the retina. In this case, images in the distance are blurry but images nearby are clear. There are two types of photoreceptors in the retina: rods and cones, named for their general appearance as illustrated in Figure. Rods are strongly photosensitive and are located in the outer edges of the retina. They detect dim light and are used primarily for peripheral and nighttime vision. Cones are weakly photosensitive and are located near the center of the retina. They respond to bright light, and their primary role is in daytime, color vision. The fovea is the region in the center back of the eye that is responsible for acute vision. The fovea has a high density of cones. When you bring your gaze to an object to examine it intently in bright light, the eyes orient so that the object’s image falls on the fovea. However, when looking at a star in the night sky or other object in dim light, the object can be better viewed by the peripheral vision because it is the rods at the edges of the retina, rather than the cones at the center, that operate better in low light. In humans, cones far outnumber rods in the fovea. Link to Learning Review the anatomical structure of the eye, clicking on each part to practice identification. Transduction of Light The rods and cones are the site of transduction of light to a neural signal. Both rods and cones contain photopigments. In vertebrates, the main photopigment, rhodopsin, has two main parts Figure): an opsin, which is a membrane protein (in the form of a cluster of α-helices that span the membrane), and retinal—a molecule that absorbs light. When light hits a photoreceptor, it causes a shape change in the retinal, altering its structure from a bent (cis) form of the molecule to its linear (trans) isomer. This isomerization of retinal activates the rhodopsin, starting a cascade of events that ends with the closing of Na+ channels in the membrane of the photoreceptor. Thus, unlike most other sensory neurons (which become depolarized by exposure to a stimulus) visual receptors become hyperpolarized and thus driven away from threshold (Figure). Trichromatic Coding There are three types of cones (with different photopsins), and they differ in the wavelength to which they are most responsive, as shown in Figure. Some cones are maximally responsive to short light waves of 420 nm, so they are called S cones (“S” for “short”); others respond maximally to waves of 530 nm (M cones, for “medium”); a third group responds maximally to light of longer wavelengths, at 560 nm (L, or “long” cones). With only one type of cone, color vision would not be possible, and a two-cone (dichromatic) system has limitations. Primates use a three-cone (trichromatic) system, resulting in full color vision. The color we perceive is a result of the ratio of activity of our three types of cones. The colors of the visual spectrum, running from long-wavelength light to short, are red (700 nm), orange (600 nm), yellow (565 nm), green (497 nm), blue (470 nm), indigo (450 nm), and violet (425 nm). Humans have very sensitive perception of color and can distinguish about 500 levels of brightness, 200 different hues, and 20 steps of saturation, or about 2 million distinct colors. Retinal Processing Visual signals leave the cones and rods, travel to the bipolar cells, and then to ganglion cells. A large degree of processing of visual information occurs in the retina itself, before visual information is sent to the brain. Photoreceptors in the retina continuously undergo tonic activity. That is, they are always slightly active even when not stimulated by light. In neurons that exhibit tonic activity, the absence of stimuli maintains a firing rate at a baseline; while some stimuli increase firing rate from the baseline, and other stimuli decrease firing rate. In the absence of light, the bipolar neurons that connect rods and cones to ganglion cells are continuously and actively inhibited by the rods and cones. Exposure of the retina to light hyperpolarizes the rods and cones and removes their inhibition of bipolar cells. The now active bipolar cells in turn stimulate the ganglion cells, which send action potentials along their axons (which leave the eye as the optic nerve). Thus, the visual system relies on change in retinal activity, rather than the absence or presence of activity, to encode visual signals for the brain. Sometimes horizontal cells carry signals from one rod or cone to other photoreceptors and to several bipolar cells. When a rod or cone stimulates a horizontal cell, the horizontal cell inhibits more distant photoreceptors and bipolar cells, creating lateral inhibition. This inhibition sharpens edges and enhances contrast in the images by making regions receiving light appear lighter and dark surroundings appear darker. Amacrine cells can distribute information from one bipolar cell to many ganglion cells. You can demonstrate this using an easy demonstration to “trick” your retina and brain about the colors you are observing in your visual field. Look fixedly at Figure for about 45 seconds. Then quickly shift your gaze to a sheet of blank white paper or a white wall. You should see an afterimage of the Norwegian flag in its correct colors. At this point, close your eyes for a moment, then reopen them, looking again at the white paper or wall; the afterimage of the flag should continue to appear as red, white, and blue. What causes this? According to an explanation called opponent process theory, as you gazed fixedly at the green, black, and yellow flag, your retinal ganglion cells that respond positively to green, black, and yellow increased their firing dramatically. When you shifted your gaze to the neutral white ground, these ganglion cells abruptly decreased their activity and the brain interpreted this abrupt downshift as if the ganglion cells were responding now to their “opponent” colors: red, white, and blue, respectively, in the visual field. Once the ganglion cells return to their baseline activity state, the false perception of color will disappear. Higher Processing The myelinated axons of ganglion cells make up the optic nerves. Within the nerves, different axons carry different qualities of the visual signal. Some axons constitute the magnocellular (big cell) pathway, which carries information about form, movement, depth, and differences in brightness. Other axons constitute the parvocellular (small cell) pathway, which carries information on color and fine detail. Some visual information projects directly back into the brain, while other information crosses to the opposite side of the brain. This crossing of optical pathways produces the distinctive optic chiasma (Greek, for “crossing”) found at the base of the brain and allows us to coordinate information from both eyes. Once in the brain, visual information is processed in several places, and its routes reflect the complexity and importance of visual information to humans and other animals. One route takes the signals to the thalamus, which serves as the routing station for all incoming sensory impulses except olfaction. In the thalamus, the magnocellular and parvocellular distinctions remain intact, and there are different layers of the thalamus dedicated to each. When visual signals leave the thalamus, they travel to the primary visual cortex at the rear of the brain. From the visual cortex, the visual signals travel in two directions. One stream that projects to the parietal lobe, in the side of the brain, carries magnocellular (“where”) information. A second stream projects to the temporal lobe and carries both magnocellular (“where”) and parvocellular (“what”) information. Another important visual route is a pathway from the retina to the superior colliculus in the midbrain, where eye movements are coordinated and integrated with auditory information. Finally, there is the pathway from the retina to the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN is a cluster of cells that is considered to be the body’s internal clock, which controls our circadian (day-long) cycle. The SCN sends information to the pineal gland, which is important in sleep/wake patterns and annual cycles. Link to Learning View this interactive presentation to review what you have learned about how vision functions. Section Summary Vision is the only photo responsive sense. Visible light travels in waves and is a very small slice of the electromagnetic radiation spectrum. Light waves differ based on their frequency (wavelength = hue) and amplitude (intensity = brightness). In the vertebrate retina, there are two types of light receptors (photoreceptors): cones and rods. Cones, which are the source of color vision, exist in three forms—L, M, and S—and they are differentially sensitive to different wavelengths. Cones are located in the retina, along with the dim-light, achromatic receptors (rods). Cones are found in the fovea, the central region of the retina, whereas rods are found in the peripheral regions of the retina. Visual signals travel from the eye over the axons of retinal ganglion cells, which make up the optic nerves. Ganglion cells come in several versions. Some ganglion cell axons carry information on form, movement, depth, and brightness, while other axons carry information on color and fine detail. Visual information is sent to the superior colliculi in the midbrain, where coordination of eye movements and integration of auditory information takes place. Visual information is also sent to the suprachiasmatic nucleus (SCN) of the hypothalamus, which plays a role in the circadian cycle. Art Connections Figure Which of the following statements about the human eye is false? - Rods detect color, while cones detect only shades of gray. - When light enters the retina, it passes the ganglion cells and bipolar cells before reaching photoreceptors at the rear of the eye. - The iris adjusts the amount of light coming into the eye. - The cornea is a protective layer on the front of the eye. Hint: Figure A Review Questions Why do people over 55 often need reading glasses? - Their cornea no longer focuses correctly. - Their lens no longer focuses correctly. - Their eyeball has elongated with age, causing images to focus in front of their retina. - Their retina has thinned with age, making vision more difficult. Hint: B Why is it easier to see images at night using peripheral, rather than the central, vision? - Cones are denser in the periphery of the retina. - Bipolar cells are denser in the periphery of the retina. - Rods are denser in the periphery of the retina. - The optic nerve exits at the periphery of the retina. Hint: C A person catching a ball must coordinate her head and eyes. What part of the brain is helping to do this? - hypothalamus - pineal gland - thalamus - superior colliculus Hint: D Free Response How could the pineal gland, the brain structure that plays a role in annual cycles, use visual information from the suprachiasmatic nucleus of the hypothalamus? Hint: The pineal gland could use length-of-day information to determine the time of year, for example. Day length is shorter in the winter than it is in the summer. For many animals and plants, photoperiod cues them to reproduce at a certain time of year. How is the relationship between photoreceptors and bipolar cells different from other sensory receptors and adjacent cells? Hint: The photoreceptors tonically inhibit the bipolar cells, and stimulation of the receptors turns this inhibition off, activating the bipolar cells.	oercommons	2025-03-18T00:36:07.676592	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15125/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15126/overview	Introduction An animal’s endocrine system controls body processes through the production, secretion, and regulation of hormones, which serve as chemical “messengers” functioning in cellular and organ activity and, ultimately, maintaining the body’s homeostasis. The endocrine system plays a role in growth, metabolism, and sexual development. In humans, common endocrine system diseases include thyroid disease and diabetes mellitus. In organisms that undergo metamorphosis, the process is controlled by the endocrine system. The transformation from tadpole to frog, for example, is complex and nuanced to adapt to specific environments and ecological circumstances.	oercommons	2025-03-18T00:36:07.694798	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15126/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15127/overview	Types of Hormones Overview By the end of this section, you will be able to: - List the different types of hormones - Explain their role in maintaining homeostasis Maintaining homeostasis within the body requires the coordination of many different systems and organs. Communication between neighboring cells, and between cells and tissues in distant parts of the body, occurs through the release of chemicals called hormones. Hormones are released into body fluids (usually blood) that carry these chemicals to their target cells. At the target cells, which are cells that have a receptor for a signal or ligand from a signal cell, the hormones elicit a response. The cells, tissues, and organs that secrete hormones make up the endocrine system. Examples of glands of the endocrine system include the adrenal glands, which produce hormones such as epinephrine and norepinephrine that regulate responses to stress, and the thyroid gland, which produces thyroid hormones that regulate metabolic rates. Although there are many different hormones in the human body, they can be divided into three classes based on their chemical structure: lipid-derived, amino acid-derived, and peptide (peptide and proteins) hormones. One of the key distinguishing features of lipid-derived hormones is that they can diffuse across plasma membranes whereas the amino acid-derived and peptide hormones cannot. Lipid-Derived Hormones (or Lipid-soluble Hormones) Most lipid hormones are derived from cholesterol and thus are structurally similar to it, as illustrated in Figure. The primary class of lipid hormones in humans is the steroid hormones. Chemically, these hormones are usually ketones or alcohols; their chemical names will end in “-ol” for alcohols or “-one” for ketones. Examples of steroid hormones include estradiol, which is an estrogen, or female sex hormone, and testosterone, which is an androgen, or male sex hormone. These two hormones are released by the female and male reproductive organs, respectively. Other steroid hormones include aldosterone and cortisol, which are released by the adrenal glands along with some other types of androgens. Steroid hormones are insoluble in water, and they are transported by transport proteins in blood. As a result, they remain in circulation longer than peptide hormones. For example, cortisol has a half-life of 60 to 90 minutes, while epinephrine, an amino acid derived-hormone, has a half-life of approximately one minute. Amino Acid-Derived Hormones The amino acid-derived hormones are relatively small molecules that are derived from the amino acids tyrosine and tryptophan, shown in Figure. If a hormone is amino acid-derived, its chemical name will end in “-ine”. Examples of amino acid-derived hormones include epinephrine and norepinephrine, which are synthesized in the medulla of the adrenal glands, and thyroxine, which is produced by the thyroid gland. The pineal gland in the brain makes and secretes melatonin which regulates sleep cycles. Peptide Hormones The structure of peptide hormones is that of a polypeptide chain (chain of amino acids). The peptide hormones include molecules that are short polypeptide chains, such as antidiuretic hormone and oxytocin produced in the brain and released into the blood in the posterior pituitary gland. This class also includes small proteins, like growth hormones produced by the pituitary, and large glycoproteins such as follicle-stimulating hormone produced by the pituitary. Figure illustrates these peptide hormones. Secreted peptides like insulin are stored within vesicles in the cells that synthesize them. They are then released in response to stimuli such as high blood glucose levels in the case of insulin. Amino acid-derived and polypeptide hormones are water-soluble and insoluble in lipids. These hormones cannot pass through plasma membranes of cells; therefore, their receptors are found on the surface of the target cells. Career Connection EndocrinologistAn endocrinologist is a medical doctor who specializes in treating disorders of the endocrine glands, hormone systems, and glucose and lipid metabolic pathways. An endocrine surgeon specializes in the surgical treatment of endocrine diseases and glands. Some of the diseases that are managed by endocrinologists: disorders of the pancreas (diabetes mellitus), disorders of the pituitary (gigantism, acromegaly, and pituitary dwarfism), disorders of the thyroid gland (goiter and Graves’ disease), and disorders of the adrenal glands (Cushing’s disease and Addison’s disease). Endocrinologists are required to assess patients and diagnose endocrine disorders through extensive use of laboratory tests. Many endocrine diseases are diagnosed using tests that stimulate or suppress endocrine organ functioning. Blood samples are then drawn to determine the effect of stimulating or suppressing an endocrine organ on the production of hormones. For example, to diagnose diabetes mellitus, patients are required to fast for 12 to 24 hours. They are then given a sugary drink, which stimulates the pancreas to produce insulin to decrease blood glucose levels. A blood sample is taken one to two hours after the sugar drink is consumed. If the pancreas is functioning properly, the blood glucose level will be within a normal range. Another example is the A1C test, which can be performed during blood screening. The A1C test measures average blood glucose levels over the past two to three months by examining how well the blood glucose is being managed over a long time. Once a disease has been diagnosed, endocrinologists can prescribe lifestyle changes and/or medications to treat the disease. Some cases of diabetes mellitus can be managed by exercise, weight loss, and a healthy diet; in other cases, medications may be required to enhance insulin release. If the disease cannot be controlled by these means, the endocrinologist may prescribe insulin injections. In addition to clinical practice, endocrinologists may also be involved in primary research and development activities. For example, ongoing islet transplant research is investigating how healthy pancreas islet cells may be transplanted into diabetic patients. Successful islet transplants may allow patients to stop taking insulin injections. Section Summary There are three basic types of hormones: lipid-derived, amino acid-derived, and peptide. Lipid-derived hormones are structurally similar to cholesterol and include steroid hormones such as estradiol and testosterone. Amino acid-derived hormones are relatively small molecules and include the adrenal hormones epinephrine and norepinephrine. Peptide hormones are polypeptide chains or proteins and include the pituitary hormones, antidiuretic hormone (vasopressin), and oxytocin. Review Questions A newly discovered hormone contains four amino acids linked together. Under which chemical class would this hormone be classified? - lipid-derived hormone - amino acid-derived hormone - peptide hormone - glycoprotein Hint: C Which class of hormones can diffuse through plasma membranes? - lipid-derived hormones - amino acid-derived hormones - peptide hormones - glycoprotein hormones Hint: A Free Response Although there are many different hormones in the human body, they can be divided into three classes based on their chemical structure. What are these classes and what is one factor that distinguishes them? Hint: Although there are many different hormones in the human body, they can be divided into three classes based on their chemical structure: lipid-derived, amino acid-derived, and peptide hormones. One of the key distinguishing features of the lipid-derived hormones is that they can diffuse across plasma membranes whereas the amino acid-derived and peptide hormones cannot. Where is insulin stored, and why would it be released? Hint: Secreted peptides such as insulin are stored within vesicles in the cells that synthesize them. They are then released in response to stimuli such as high blood glucose levels in the case of insulin.	oercommons	2025-03-18T00:36:07.718108	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15127/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15128/overview	How Hormones Work Overview By the end of this section, you will be able to: - Explain how hormones work - Discuss the role of different types of hormone receptors Hormones mediate changes in target cells by binding to specific hormone receptors. In this way, even though hormones circulate throughout the body and come into contact with many different cell types, they only affect cells that possess the necessary receptors. Receptors for a specific hormone may be found on many different cells or may be limited to a small number of specialized cells. For example, thyroid hormones act on many different tissue types, stimulating metabolic activity throughout the body. Cells can have many receptors for the same hormone but often also possess receptors for different types of hormones. The number of receptors that respond to a hormone determines the cell’s sensitivity to that hormone, and the resulting cellular response. Additionally, the number of receptors that respond to a hormone can change over time, resulting in increased or decreased cell sensitivity. In up-regulation, the number of receptors increases in response to rising hormone levels, making the cell more sensitive to the hormone and allowing for more cellular activity. When the number of receptors decreases in response to rising hormone levels, called down-regulation, cellular activity is reduced. Receptor binding alters cellular activity and results in an increase or decrease in normal body processes. Depending on the location of the protein receptor on the target cell and the chemical structure of the hormone, hormones can mediate changes directly by binding to intracellular hormone receptors and modulating gene transcription, or indirectly by binding to cell surface receptors and stimulating signaling pathways. Intracellular Hormone Receptors Lipid-derived (soluble) hormones such as steroid hormones diffuse across the membranes of the endocrine cell. Once outside the cell, they bind to transport proteins that keep them soluble in the bloodstream. At the target cell, the hormones are released from the carrier protein and diffuse across the lipid bilayer of the plasma membrane of cells. The steroid hormones pass through the plasma membrane of a target cell and adhere to intracellular receptors residing in the cytoplasm or in the nucleus. The cell signaling pathways induced by the steroid hormones regulate specific genes on the cell's DNA. The hormones and receptor complex act as transcription regulators by increasing or decreasing the synthesis of mRNA molecules of specific genes. This, in turn, determines the amount of corresponding protein that is synthesized by altering gene expression. This protein can be used either to change the structure of the cell or to produce enzymes that catalyze chemical reactions. In this way, the steroid hormone regulates specific cell processes as illustrated in Figure. Art Connection Heat shock proteins (HSP) are so named because they help refold misfolded proteins. In response to increased temperature (a “heat shock”), heat shock proteins are activated by release from the NR/HSP complex. At the same time, transcription of HSP genes is activated. Why do you think the cell responds to a heat shock by increasing the activity of proteins that help refold misfolded proteins? Other lipid-soluble hormones that are not steroid hormones, such as vitamin D and thyroxine, have receptors located in the nucleus. The hormones diffuse across both the plasma membrane and the nuclear envelope, then bind to receptors in the nucleus. The hormone-receptor complex stimulates transcription of specific genes. Plasma Membrane Hormone Receptors Amino acid derived hormones and polypeptide hormones are not lipid-derived (lipid-soluble) and therefore cannot diffuse through the plasma membrane of cells. Lipid insoluble hormones bind to receptors on the outer surface of the plasma membrane, via plasma membrane hormone receptors. Unlike steroid hormones, lipid insoluble hormones do not directly affect the target cell because they cannot enter the cell and act directly on DNA. Binding of these hormones to a cell surface receptor results in activation of a signaling pathway; this triggers intracellular activity and carries out the specific effects associated with the hormone. In this way, nothing passes through the cell membrane; the hormone that binds at the surface remains at the surface of the cell while the intracellular product remains inside the cell. The hormone that initiates the signaling pathway is called a first messenger, which activates a second messenger in the cytoplasm, as illustrated in Figure. One very important second messenger is cyclic AMP (cAMP). When a hormone binds to its membrane receptor, a G-protein that is associated with the receptor is activated; G-proteins are proteins separate from receptors that are found in the cell membrane. When a hormone is not bound to the receptor, the G-protein is inactive and is bound to guanosine diphosphate, or GDP. When a hormone binds to the receptor, the G-protein is activated by binding guanosine triphosphate, or GTP, in place of GDP. After binding, GTP is hydrolysed by the G-protein into GDP and becomes inactive. The activated G-protein in turn activates a membrane-bound enzyme called adenylyl cyclase. Adenylyl cyclase catalyzes the conversion of ATP to cAMP. cAMP, in turn, activates a group of proteins called protein kinases, which transfer a phosphate group from ATP to a substrate molecule in a process called phosphorylation. The phosphorylation of a substrate molecule changes its structural orientation, thereby activating it. These activated molecules can then mediate changes in cellular processes. The effect of a hormone is amplified as the signaling pathway progresses. The binding of a hormone at a single receptor causes the activation of many G-proteins, which activates adenylyl cyclase. Each molecule of adenylyl cyclase then triggers the formation of many molecules of cAMP. Further amplification occurs as protein kinases, once activated by cAMP, can catalyze many reactions. In this way, a small amount of hormone can trigger the formation of a large amount of cellular product. To stop hormone activity, cAMP is deactivated by the cytoplasmic enzyme phosphodiesterase, or PDE. PDE is always present in the cell and breaks down cAMP to control hormone activity, preventing overproduction of cellular products. The specific response of a cell to a lipid insoluble hormone depends on the type of receptors that are present on the cell membrane and the substrate molecules present in the cell cytoplasm. Cellular responses to hormone binding of a receptor include altering membrane permeability and metabolic pathways, stimulating synthesis of proteins and enzymes, and activating hormone release. Section Summary Hormones cause cellular changes by binding to receptors on target cells. The number of receptors on a target cell can increase or decrease in response to hormone activity. Hormones can affect cells directly through intracellular hormone receptors or indirectly through plasma membrane hormone receptors. Lipid-derived (soluble) hormones can enter the cell by diffusing across the plasma membrane and binding to DNA to regulate gene transcription and to change the cell’s activities by inducing production of proteins that affect, in general, the long-term structure and function of the cell. Lipid insoluble hormones bind to receptors on the plasma membrane surface and trigger a signaling pathway to change the cell’s activities by inducing production of various cell products that affect the cell in the short-term. The hormone is called a first messenger and the cellular component is called a second messenger. G-proteins activate the second messenger (cyclic AMP), triggering the cellular response. Response to hormone binding is amplified as the signaling pathway progresses. Cellular responses to hormones include the production of proteins and enzymes and altered membrane permeability. Art Connections Figure Heat shock proteins (HSP) are so named because they help refold mis-folded proteins. In response to increased temperature (a “heat shock”), heat shock proteins are activated by release from the NR/HSP complex. At the same time, transcription of HSP genes is activated. Why do you think the cell responds to a heat shock by increasing the activity of proteins that help refold misfolded proteins? Hint: Figure Proteins unfold, or denature, at higher temperatures. Review Questions A new antagonist molecule has been discovered that binds to and blocks plasma membrane receptors. What effect will this antagonist have on testosterone, a steroid hormone? - It will block testosterone from binding to its receptor. - It will block testosterone from activating cAMP signaling. - It will increase testosterone-mediated signaling. - It will not affect testosterone-mediated signaling. Hint: D What effect will a cAMP inhibitor have on a peptide hormone-mediated signaling pathway? - It will prevent the hormone from binding its receptor. - It will prevent activation of a G-protein. - It will prevent activation of adenylate cyclase. - It will prevent activation of protein kinases. Hint: D Free Response Name two important functions of hormone receptors. Hint: The number of receptors that respond to a hormone can change, resulting in increased or decreased cell sensitivity. The number of receptors can increase in response to rising hormone levels, called up-regulation, making the cell more sensitive to the hormone and allowing for more cellular activity. The number of receptors can also decrease in response to rising hormone levels, called down-regulation, leading to reduced cellular activity. How can hormones mediate changes? Hint: Depending on the location of the protein receptor on the target cell and the chemical structure of the hormone, hormones can mediate changes directly by binding to intracellular receptors and modulating gene transcription, or indirectly by binding to cell surface receptors and stimulating signaling pathways.	oercommons	2025-03-18T00:36:07.743347	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15128/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15129/overview	Regulation of Body Processes Overview By the end of this section, you will be able to: - Explain how hormones regulate the excretory system - Discuss the role of hormones in the reproductive system - Describe how hormones regulate metabolism - Explain the role of hormones in different diseases Hormones have a wide range of effects and modulate many different body processes. The key regulatory processes that will be examined here are those affecting the excretory system, the reproductive system, metabolism, blood calcium concentrations, growth, and the stress response. Hormonal Regulation of the Excretory System Maintaining a proper water balance in the body is important to avoid dehydration or over-hydration (hyponatremia). The water concentration of the body is monitored by osmoreceptors in the hypothalamus, which detect the concentration of electrolytes in the extracellular fluid. The concentration of electrolytes in the blood rises when there is water loss caused by excessive perspiration, inadequate water intake, or low blood volume due to blood loss. An increase in blood electrolyte levels results in a neuronal signal being sent from the osmoreceptors in hypothalamic nuclei. The pituitary gland has two components: anterior and posterior. The anterior pituitary is composed of glandular cells that secrete protein hormones. The posterior pituitary is an extension of the hypothalamus. It is composed largely of neurons that are continuous with the hypothalamus. The hypothalamus produces a polypeptide hormone known as antidiuretic hormone (ADH), which is transported to and released from the posterior pituitary gland. The principal action of ADH is to regulate the amount of water excreted by the kidneys. As ADH (which is also known as vasopressin) causes direct water reabsorption from the kidney tubules, salts and wastes are concentrated in what will eventually be excreted as urine. The hypothalamus controls the mechanisms of ADH secretion, either by regulating blood volume or the concentration of water in the blood. Dehydration or physiological stress can cause an increase of osmolarity above 300 mOsm/L, which in turn, raises ADH secretion and water will be retained, causing an increase in blood pressure. ADH travels in the bloodstream to the kidneys. Once at the kidneys, ADH changes the kidneys to become more permeable to water by temporarily inserting water channels, aquaporins, into the kidney tubules. Water moves out of the kidney tubules through the aquaporins, reducing urine volume. The water is reabsorbed into the capillaries lowering blood osmolarity back toward normal. As blood osmolarity decreases, a negative feedback mechanism reduces osmoreceptor activity in the hypothalamus, and ADH secretion is reduced. ADH release can be reduced by certain substances, including alcohol, which can cause increased urine production and dehydration. Chronic underproduction of ADH or a mutation in the ADH receptor results in diabetes insipidus. If the posterior pituitary does not release enough ADH, water cannot be retained by the kidneys and is lost as urine. This causes increased thirst, but water taken in is lost again and must be continually consumed. If the condition is not severe, dehydration may not occur, but severe cases can lead to electrolyte imbalances due to dehydration. Another hormone responsible for maintaining electrolyte concentrations in extracellular fluids is aldosterone, a steroid hormone that is produced by the adrenal cortex. In contrast to ADH, which promotes the reabsorption of water to maintain proper water balance, aldosterone maintains proper water balance by enhancing Na+ reabsorption and K+ secretion from extracellular fluid of the cells in kidney tubules. Because it is produced in the cortex of the adrenal gland and affects the concentrations of minerals Na+ and K+, aldosterone is referred to as a mineralocorticoid, a corticosteroid that affects ion and water balance. Aldosterone release is stimulated by a decrease in blood sodium levels, blood volume, or blood pressure, or an increase in blood potassium levels. It also prevents the loss of Na+ from sweat, saliva, and gastric juice. The reabsorption of Na+ also results in the osmotic reabsorption of water, which alters blood volume and blood pressure. Aldosterone production can be stimulated by low blood pressure, which triggers a sequence of chemical release, as illustrated in Figure. When blood pressure drops, the renin-angiotensin-aldosterone system (RAAS) is activated. Cells in the juxtaglomerular apparatus, which regulates the functions of the nephrons of the kidney, detect this and release renin. Renin, an enzyme, circulates in the blood and reacts with a plasma protein produced by the liver called angiotensinogen. When angiotensinogen is cleaved by renin, it produces angiotensin I, which is then converted into angiotensin II in the lungs. Angiotensin II functions as a hormone and then causes the release of the hormone aldosterone by the adrenal cortex, resulting in increased Na+ reabsorption, water retention, and an increase in blood pressure. Angiotensin II in addition to being a potent vasoconstrictor also causes an increase in ADH and increased thirst, both of which help to raise blood pressure. Hormonal Regulation of the Reproductive System Regulation of the reproductive system is a process that requires the action of hormones from the pituitary gland, the adrenal cortex, and the gonads. During puberty in both males and females, the hypothalamus produces gonadotropin-releasing hormone (GnRH), which stimulates the production and release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary gland. These hormones regulate the gonads (testes in males and ovaries in females) and therefore are called gonadotropins. In both males and females, FSH stimulates gamete production and LH stimulates production of hormones by the gonads. An increase in gonad hormone levels inhibits GnRH production through a negative feedback loop. Regulation of the Male Reproductive System In males, FSH stimulates the maturation of sperm cells. FSH production is inhibited by the hormone inhibin, which is released by the testes. LH stimulates production of the sex hormones (androgens) by the interstitial cells of the testes and therefore is also called interstitial cell-stimulating hormone. The most widely known androgen in males is testosterone. Testosterone promotes the production of sperm and masculine characteristics. The adrenal cortex also produces small amounts of testosterone precursor, although the role of this additional hormone production is not fully understood. Everyday Connection The Dangers of Synthetic Hormones Some athletes attempt to boost their performance by using artificial hormones that enhance muscle performance. Anabolic steroids, a form of the male sex hormone testosterone, are one of the most widely known performance-enhancing drugs. Steroids are used to help build muscle mass. Other hormones that are used to enhance athletic performance include erythropoietin, which triggers the production of red blood cells, and human growth hormone, which can help in building muscle mass. Most performance enhancing drugs are illegal for non-medical purposes. They are also banned by national and international governing bodies including the International Olympic Committee, the U.S. Olympic Committee, the National Collegiate Athletic Association, the Major League Baseball, and the National Football League. The side effects of synthetic hormones are often significant and non-reversible, and in some cases, fatal. Androgens produce several complications such as liver dysfunctions and liver tumors, prostate gland enlargement, difficulty urinating, premature closure of epiphyseal cartilages, testicular atrophy, infertility, and immune system depression. The physiological strain caused by these substances is often greater than what the body can handle, leading to unpredictable and dangerous effects and linking their use to heart attacks, strokes, and impaired cardiac function. Regulation of the Female Reproductive System In females, FSH stimulates development of egg cells, called ova, which develop in structures called follicles. Follicle cells produce the hormone inhibin, which inhibits FSH production. LH also plays a role in the development of ova, induction of ovulation, and stimulation of estradiol and progesterone production by the ovaries, as illustrated in Figure. Estradiol and progesterone are steroid hormones that prepare the body for pregnancy. Estradiol produces secondary sex characteristics in females, while both estradiol and progesterone regulate the menstrual cycle. In addition to producing FSH and LH, the anterior portion of the pituitary gland also produces the hormone prolactin (PRL) in females. Prolactin stimulates the production of milk by the mammary glands following childbirth. Prolactin levels are regulated by the hypothalamic hormones prolactin-releasing hormone (PRH) and prolactin-inhibiting hormone (PIH), which is now known to be dopamine. PRH stimulates the release of prolactin and PIH inhibits it. The posterior pituitary releases the hormone oxytocin, which stimulates uterine contractions during childbirth. The uterine smooth muscles are not very sensitive to oxytocin until late in pregnancy when the number of oxytocin receptors in the uterus peaks. Stretching of tissues in the uterus and cervix stimulates oxytocin release during childbirth. Contractions increase in intensity as blood levels of oxytocin rise via a positive feedback mechanism until the birth is complete. Oxytocin also stimulates the contraction of myoepithelial cells around the milk-producing mammary glands. As these cells contract, milk is forced from the secretory alveoli into milk ducts and is ejected from the breasts in milk ejection (“let-down”) reflex. Oxytocin release is stimulated by the suckling of an infant, which triggers the synthesis of oxytocin in the hypothalamus and its release into circulation at the posterior pituitary. Hormonal Regulation of Metabolism Blood glucose levels vary widely over the course of a day as periods of food consumption alternate with periods of fasting. Insulin and glucagon are the two hormones primarily responsible for maintaining homeostasis of blood glucose levels. Additional regulation is mediated by the thyroid hormones. Regulation of Blood Glucose Levels by Insulin and Glucagon Cells of the body require nutrients in order to function, and these nutrients are obtained through feeding. In order to manage nutrient intake, storing excess intake and utilizing reserves when necessary, the body uses hormones to moderate energy stores. Insulin is produced by the beta cells of the pancreas, which are stimulated to release insulin as blood glucose levels rise (for example, after a meal is consumed). Insulin lowers blood glucose levels by enhancing the rate of glucose uptake and utilization by target cells, which use glucose for ATP production. It also stimulates the liver to convert glucose to glycogen, which is then stored by cells for later use. Insulin also increases glucose transport into certain cells, such as muscle cells and the liver. This results from an insulin-mediated increase in the number of glucose transporter proteins in cell membranes, which remove glucose from circulation by facilitated diffusion. As insulin binds to its target cell via insulin receptors and signal transduction, it triggers the cell to incorporate glucose transport proteins into its membrane. This allows glucose to enter the cell, where it can be used as an energy source. However, this does not occur in all cells: some cells, including those in the kidneys and brain, can access glucose without the use of insulin. Insulin also stimulates the conversion of glucose to fat in adipocytes and the synthesis of proteins. These actions mediated by insulin cause blood glucose concentrations to fall, called a hypoglycemic “low sugar” effect, which inhibits further insulin release from beta cells through a negative feedback loop. Link to Learning This animation describe the role of insulin and the pancreas in diabetes. Impaired insulin function can lead to a condition called diabetes mellitus, the main symptoms of which are illustrated in Figure. This can be caused by low levels of insulin production by the beta cells of the pancreas, or by reduced sensitivity of tissue cells to insulin. This prevents glucose from being absorbed by cells, causing high levels of blood glucose, or hyperglycemia (high sugar). High blood glucose levels make it difficult for the kidneys to recover all the glucose from nascent urine, resulting in glucose being lost in urine. High glucose levels also result in less water being reabsorbed by the kidneys, causing high amounts of urine to be produced; this may result in dehydration. Over time, high blood glucose levels can cause nerve damage to the eyes and peripheral body tissues, as well as damage to the kidneys and cardiovascular system. Oversecretion of insulin can cause hypoglycemia, low blood glucose levels. This causes insufficient glucose availability to cells, often leading to muscle weakness, and can sometimes cause unconsciousness or death if left untreated. When blood glucose levels decline below normal levels, for example between meals or when glucose is utilized rapidly during exercise, the hormone glucagon is released from the alpha cells of the pancreas. Glucagon raises blood glucose levels, eliciting what is called a hyperglycemic effect, by stimulating the breakdown of glycogen to glucose in skeletal muscle cells and liver cells in a process called glycogenolysis. Glucose can then be utilized as energy by muscle cells and released into circulation by the liver cells. Glucagon also stimulates absorption of amino acids from the blood by the liver, which then converts them to glucose. This process of glucose synthesis is called gluconeogenesis. Glucagon also stimulates adipose cells to release fatty acids into the blood. These actions mediated by glucagon result in an increase in blood glucose levels to normal homeostatic levels. Rising blood glucose levels inhibit further glucagon release by the pancreas via a negative feedback mechanism. In this way, insulin and glucagon work together to maintain homeostatic glucose levels, as shown in Figure. Art Connection Pancreatic tumors may cause excess secretion of glucagon. Type I diabetes results from the failure of the pancreas to produce insulin. Which of the following statement about these two conditions is true? - A pancreatic tumor and type I diabetes will have the opposite effects on blood sugar levels. - A pancreatic tumor and type I diabetes will both cause hyperglycemia. - A pancreatic tumor and type I diabetes will both cause hypoglycemia. - Both pancreatic tumors and type I diabetes result in the inability of cells to take up glucose. Regulation of Blood Glucose Levels by Thyroid Hormones The basal metabolic rate, which is the amount of calories required by the body at rest, is determined by two hormones produced by the thyroid gland: thyroxine, also known as tetraiodothyronine or T4, and triiodothyronine, also known as T3. These hormones affect nearly every cell in the body except for the adult brain, uterus, testes, blood cells, and spleen. They are transported across the plasma membrane of target cells and bind to receptors on the mitochondria resulting in increased ATP production. In the nucleus, T3 and T4 activate genes involved in energy production and glucose oxidation. This results in increased rates of metabolism and body heat production, which is known as the hormone’s calorigenic effect. T3 and T4 release from the thyroid gland is stimulated by thyroid-stimulating hormone (TSH), which is produced by the anterior pituitary. TSH binding at the receptors of the follicle of the thyroid triggers the production of T3 and T4 from a glycoprotein called thyroglobulin. Thyroglobulin is present in the follicles of the thyroid, and is converted into thyroid hormones with the addition of iodine. Iodine is formed from iodide ions that are actively transported into the thyroid follicle from the bloodstream. A peroxidase enzyme then attaches the iodine to the tyrosine amino acid found in thyroglobulin. T3 has three iodine ions attached, while T4 has four iodine ions attached. T3 and T4 are then released into the bloodstream, with T4 being released in much greater amounts than T3. As T3 is more active than T4 and is responsible for most of the effects of thyroid hormones, tissues of the body convert T4 to T3 by the removal of an iodine ion. Most of the released T3 and T4 becomes attached to transport proteins in the bloodstream and is unable to cross the plasma membrane of cells. These protein-bound molecules are only released when blood levels of the unattached hormone begin to decline. In this way, a week’s worth of reserve hormone is maintained in the blood. Increased T3 and T4 levels in the blood inhibit the release of TSH, which results in lower T3 and T4 release from the thyroid. The follicular cells of the thyroid require iodides (anions of iodine) in order to synthesize T3 and T4. Iodides obtained from the diet are actively transported into follicle cells resulting in a concentration that is approximately 30 times higher than in blood. The typical diet in North America provides more iodine than required due to the addition of iodide to table salt. Inadequate iodine intake, which occurs in many developing countries, results in an inability to synthesize T3 and T4 hormones. The thyroid gland enlarges in a condition called goiter, which is caused by overproduction of TSH without the formation of thyroid hormone. Thyroglobulin is contained in a fluid called colloid, and TSH stimulation results in higher levels of colloid accumulation in the thyroid. In the absence of iodine, this is not converted to thyroid hormone, and colloid begins to accumulate more and more in the thyroid gland, leading to goiter. Disorders can arise from both the underproduction and overproduction of thyroid hormones. Hypothyroidism, underproduction of the thyroid hormones, can cause a low metabolic rate leading to weight gain, sensitivity to cold, and reduced mental activity, among other symptoms. In children, hypothyroidism can cause cretinism, which can lead to mental retardation and growth defects. Hyperthyroidism, the overproduction of thyroid hormones, can lead to an increased metabolic rate and its effects: weight loss, excess heat production, sweating, and an increased heart rate. Graves’ disease is one example of a hyperthyroid condition. Hormonal Control of Blood Calcium Levels Regulation of blood calcium concentrations is important for generation of muscle contractions and nerve impulses, which are electrically stimulated. If calcium levels get too high, membrane permeability to sodium decreases and membranes become less responsive. If calcium levels get too low, membrane permeability to sodium increases and convulsions or muscle spasms can result. Blood calcium levels are regulated by parathyroid hormone (PTH), which is produced by the parathyroid glands, as illustrated in Figure. PTH is released in response to low blood Ca2+ levels. PTH increases Ca2+ levels by targeting the skeleton, the kidneys, and the intestine. In the skeleton, PTH stimulates osteoclasts, which causes bone to be reabsorbed, releasing Ca2+ from bone into the blood. PTH also inhibits osteoblasts, reducing Ca2+ deposition in bone. In the intestines, PTH increases dietary Ca2+ absorption, and in the kidneys, PTH stimulates reabsorption of the CA2+. While PTH acts directly on the kidneys to increase Ca2+ reabsorption, its effects on the intestine are indirect. PTH triggers the formation of calcitriol, an active form of vitamin D, which acts on the intestines to increase absorption of dietary calcium. PTH release is inhibited by rising blood calcium levels. Hyperparathyroidism results from an overproduction of parathyroid hormone. This results in excessive calcium being removed from bones and introduced into blood circulation, producing structural weakness of the bones, which can lead to deformation and fractures, plus nervous system impairment due to high blood calcium levels. Hypoparathyroidism, the underproduction of PTH, results in extremely low levels of blood calcium, which causes impaired muscle function and may result in tetany (severe sustained muscle contraction). The hormone calcitonin, which is produced by the parafollicular or C cells of the thyroid, has the opposite effect on blood calcium levels as does PTH. Calcitonin decreases blood calcium levels by inhibiting osteoclasts, stimulating osteoblasts, and stimulating calcium excretion by the kidneys. This results in calcium being added to the bones to promote structural integrity. Calcitonin is most important in children (when it stimulates bone growth), during pregnancy (when it reduces maternal bone loss), and during prolonged starvation (because it reduces bone mass loss). In healthy nonpregnant, unstarved adults, the role of calcitonin is unclear. Hormonal Regulation of Growth Hormonal regulation is required for the growth and replication of most cells in the body. Growth hormone (GH), produced by the anterior portion of the pituitary gland, accelerates the rate of protein synthesis, particularly in skeletal muscle and bones. Growth hormone has direct and indirect mechanisms of action. The first direct action of GH is stimulation of triglyceride breakdown (lipolysis) and release into the blood by adipocytes. This results in a switch by most tissues from utilizing glucose as an energy source to utilizing fatty acids. This process is called a glucose-sparing effect. In another direct mechanism, GH stimulates glycogen breakdown in the liver; the glycogen is then released into the blood as glucose. Blood glucose levels increase as most tissues are utilizing fatty acids instead of glucose for their energy needs. The GH mediated increase in blood glucose levels is called a diabetogenic effect because it is similar to the high blood glucose levels seen in diabetes mellitus. The indirect mechanism of GH action is mediated by insulin-like growth factors (IGFs) or somatomedins, which are a family of growth-promoting proteins produced by the liver, which stimulates tissue growth. IGFs stimulate the uptake of amino acids from the blood, allowing the formation of new proteins, particularly in skeletal muscle cells, cartilage cells, and other target cells, as shown in Figure. This is especially important after a meal, when glucose and amino acid concentration levels are high in the blood. GH levels are regulated by two hormones produced by the hypothalamus. GH release is stimulated by growth hormone-releasing hormone (GHRH) and is inhibited by growth hormone-inhibiting hormone (GHIH), also called somatostatin. A balanced production of growth hormone is critical for proper development. Underproduction of GH in adults does not appear to cause any abnormalities, but in children it can result in pituitary dwarfism, in which growth is reduced. Pituitary dwarfism is characterized by symmetric body formation. In some cases, individuals are under 30 inches in height. Oversecretion of growth hormone can lead to gigantism in children, causing excessive growth. In some documented cases, individuals can reach heights of over eight feet. In adults, excessive GH can lead to acromegaly, a condition in which there is enlargement of bones in the face, hands, and feet that are still capable of growth. Hormonal Regulation of Stress When a threat or danger is perceived, the body responds by releasing hormones that will ready it for the “fight-or-flight” response. The effects of this response are familiar to anyone who has been in a stressful situation: increased heart rate, dry mouth, and hair standing up. Evolution Connection Fight-or-Flight ResponseInteractions of the endocrine hormones have evolved to ensure the body’s internal environment remains stable. Stressors are stimuli that disrupt homeostasis. The sympathetic division of the vertebrate autonomic nervous system has evolved the fight-or-flight response to counter stress-induced disruptions of homeostasis. In the initial alarm phase, the sympathetic nervous system stimulates an increase in energy levels through increased blood glucose levels. This prepares the body for physical activity that may be required to respond to stress: to either fight for survival or to flee from danger. However, some stresses, such as illness or injury, can last for a long time. Glycogen reserves, which provide energy in the short-term response to stress, are exhausted after several hours and cannot meet long-term energy needs. If glycogen reserves were the only energy source available, neural functioning could not be maintained once the reserves became depleted due to the nervous system’s high requirement for glucose. In this situation, the body has evolved a response to counter long-term stress through the actions of the glucocorticoids, which ensure that long-term energy requirements can be met. The glucocorticoids mobilize lipid and protein reserves, stimulate gluconeogenesis, conserve glucose for use by neural tissue, and stimulate the conservation of salts and water. The mechanisms to maintain homeostasis that are described here are those observed in the human body. However, the fight-or-flight response exists in some form in all vertebrates. The sympathetic nervous system regulates the stress response via the hypothalamus. Stressful stimuli cause the hypothalamus to signal the adrenal medulla (which mediates short-term stress responses) via nerve impulses, and the adrenal cortex, which mediates long-term stress responses, via the hormone adrenocorticotropic hormone (ACTH), which is produced by the anterior pituitary. Short-term Stress Response When presented with a stressful situation, the body responds by calling for the release of hormones that provide a burst of energy. The hormones epinephrine (also known as adrenaline) and norepinephrine (also known as noradrenaline) are released by the adrenal medulla. How do these hormones provide a burst of energy? Epinephrine and norepinephrine increase blood glucose levels by stimulating the liver and skeletal muscles to break down glycogen and by stimulating glucose release by liver cells. Additionally, these hormones increase oxygen availability to cells by increasing the heart rate and dilating the bronchioles. The hormones also prioritize body function by increasing blood supply to essential organs such as the heart, brain, and skeletal muscles, while restricting blood flow to organs not in immediate need, such as the skin, digestive system, and kidneys. Epinephrine and norepinephrine are collectively called catecholamines. Link to Learning Watch this Discovery Channel animation describing the flight-or-flight response. Long-term Stress Response Long-term stress response differs from short-term stress response. The body cannot sustain the bursts of energy mediated by epinephrine and norepinephrine for long times. Instead, other hormones come into play. In a long-term stress response, the hypothalamus triggers the release of ACTH from the anterior pituitary gland. The adrenal cortex is stimulated by ACTH to release steroid hormones called corticosteroids. Corticosteroids turn on transcription of certain genes in the nuclei of target cells. They change enzyme concentrations in the cytoplasm and affect cellular metabolism. There are two main corticosteroids: glucocorticoids such as cortisol, and mineralocorticoids such as aldosterone. These hormones target the breakdown of fat into fatty acids in the adipose tissue. The fatty acids are released into the bloodstream for other tissues to use for ATP production. The glucocorticoids primarily affect glucose metabolism by stimulating glucose synthesis. Glucocorticoids also have anti-inflammatory properties through inhibition of the immune system. For example, cortisone is used as an anti-inflammatory medication; however, it cannot be used long term as it increases susceptibility to disease due to its immune-suppressing effects. Mineralocorticoids function to regulate ion and water balance of the body. The hormone aldosterone stimulates the reabsorption of water and sodium ions in the kidney, which results in increased blood pressure and volume. Hypersecretion of glucocorticoids can cause a condition known as Cushing’s disease, characterized by a shifting of fat storage areas of the body. This can cause the accumulation of adipose tissue in the face and neck, and excessive glucose in the blood. Hyposecretion of the corticosteroids can cause Addison’s disease, which may result in bronzing of the skin, hypoglycemia, and low electrolyte levels in the blood. Section Summary Water levels in the body are controlled by antidiuretic hormone (ADH), which is produced in the hypothalamus and triggers the reabsorption of water by the kidneys. Underproduction of ADH can cause diabetes insipidus. Aldosterone, a hormone produced by the adrenal cortex of the kidneys, enhances Na+ reabsorption from the extracellular fluids and subsequent water reabsorption by diffusion. The renin-angiotensin-aldosterone system is one way that aldosterone release is controlled. The reproductive system is controlled by the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are produced by the pituitary gland. Gonadotropin release is controlled by the hypothalamic hormone gonadotropin-releasing hormone (GnRH). FSH stimulates the maturation of sperm cells in males and is inhibited by the hormone inhibin, while LH stimulates the production of the androgen testosterone. FSH stimulates egg maturation in females, while LH stimulates the production of estrogens and progesterone. Estrogens are a group of steroid hormones produced by the ovaries that trigger the development of secondary sex characteristics in females as well as control the maturation of the ova. In females, the pituitary also produces prolactin, which stimulates milk production after childbirth, and oxytocin, which stimulates uterine contraction during childbirth and milk let-down during suckling. Insulin is produced by the pancreas in response to rising blood glucose levels and allows cells to utilize blood glucose and store excess glucose for later use. Diabetes mellitus is caused by reduced insulin activity and causes high blood glucose levels, or hyperglycemia. Glucagon is released by the pancreas in response to low blood glucose levels and stimulates the breakdown of glycogen into glucose, which can be used by the body. The body’s basal metabolic rate is controlled by the thyroid hormones thyroxine (T4) and triiodothyronine (T3). The anterior pituitary produces thyroid stimulating hormone (TSH), which controls the release of T3 and T4 from the thyroid gland. Iodine is necessary in the production of thyroid hormone, and the lack of iodine can lead to a condition called goiter. Parathyroid hormone (PTH) is produced by the parathyroid glands in response to low blood Ca2+ levels. The parafollicular cells of the thyroid produce calcitonin, which reduces blood Ca2+ levels. Growth hormone (GH) is produced by the anterior pituitary and controls the growth rate of muscle and bone. GH action is indirectly mediated by insulin-like growth factors (IGFs). Short-term stress causes the hypothalamus to trigger the adrenal medulla to release epinephrine and norepinephrine, which trigger the fight or flight response. Long-term stress causes the hypothalamus to trigger the anterior pituitary to release adrenocorticotropic hormone (ACTH), which causes the release of corticosteroids, glucocorticoids, and mineralocorticoids, from the adrenal cortex. Art Connections Figure Pancreatic tumors may cause excess secretion of glucagon. Type I diabetes results from the failure of the pancreas to produce insulin. Which of the following statement about these two conditions is true? - A pancreatic tumor and type I diabetes will have the opposite effects on blood sugar levels. - A pancreatic tumor and type I diabetes will both cause hyperglycemia. - A pancreatic tumor and type I diabetes will both cause hypoglycemia. - Both pancreatic tumors and type I diabetes result in the inability of cells to take up glucose. Hint: Figure B Review Questions Drinking alcoholic beverages causes an increase in urine output. This most likely occurs because alcohol: - inhibits ADH release - stimulates ADH release - inhibits TSH release - stimulates TSH release Hint: A FSH and LH release from the anterior pituitary is stimulated by ________. - TSH - GnRH - T3 - PTH Hint: B What hormone is produced by beta cells of the pancreas? - T3 - glucagon - insulin - T4 Hint: C When blood calcium levels are low, PTH stimulates: - excretion of calcium from the kidneys - excretion of calcium from the intestines - osteoblasts - osteoclasts Hint: D Free Response Name and describe a function of one hormone produced by the anterior pituitary and one hormone produced by the posterior pituitary. Hint: In addition to producing FSH and LH, the anterior pituitary also produces the hormone prolactin (PRL) in females. Prolactin stimulates the production of milk by the mammary glands following childbirth. Prolactin levels are regulated by the hypothalamic hormones prolactin-releasing hormone (PRH) and prolactin-inhibiting hormone (PIH) which is now known to be dopamine. PRH stimulates the release of prolactin and PIH inhibits it. The posterior pituitary releases the hormone oxytocin, which stimulates contractions during childbirth. The uterine smooth muscles are not very sensitive to oxytocin until late in pregnancy when the number of oxytocin receptors in the uterus peaks. Stretching of tissues in the uterus and vagina stimulates oxytocin release in childbirth. Contractions increase in intensity as blood levels of oxytocin rise until the birth is complete. Describe one direct action of growth hormone (GH). Hint: Hormonal regulation is required for the growth and replication of most cells in the body. Growth hormone (GH), produced by the anterior pituitary, accelerates the rate of protein synthesis, particularly in skeletal muscles and bones. Growth hormone has direct and indirect mechanisms of action. The direct actions of GH include: 1) stimulation of fat breakdown (lipolysis) and release into the blood by adipocytes. This results in a switch by most tissues from utilizing glucose as an energy source to utilizing fatty acids. This process is called a glucose-sparing effect. 2) In the liver, GH stimulates glycogen breakdown, which is then released into the blood as glucose. Blood glucose levels increase as most tissues are utilizing fatty acids instead of glucose for their energy needs. The GH mediated increase in blood glucose levels is called a diabetogenic effect because it is similar to the high blood glucose levels seen in diabetes mellitus.	oercommons	2025-03-18T00:36:07.788228	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15129/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15130/overview	Regulation of Hormone Production Overview By the end of this section, you will be able to: - Explain how hormone production is regulated - Discuss the different stimuli that control hormone levels in the body Hormone production and release are primarily controlled by negative feedback. In negative feedback systems, a stimulus elicits the release of a substance; once the substance reaches a certain level, it sends a signal that stops further release of the substance. In this way, the concentration of hormones in blood is maintained within a narrow range. For example, the anterior pituitary signals the thyroid to release thyroid hormones. Increasing levels of these hormones in the blood then give feedback to the hypothalamus and anterior pituitary to inhibit further signaling to the thyroid gland, as illustrated in Figure. There are three mechanisms by which endocrine glands are stimulated to synthesize and release hormones: humoral stimuli, hormonal stimuli, and neural stimuli. Art Connection Hyperthyroidism is a condition in which the thyroid gland is overactive. Hypothyroidism is a condition in which the thyroid gland is underactive. Which of the conditions are the following two patients most likely to have? Patient A has symptoms including weight gain, cold sensitivity, low heart rate and fatigue. Patient B has symptoms including weight loss, profuse sweating, increased heart rate and difficulty sleeping. Humoral Stimuli The term “humoral” is derived from the term “humor,” which refers to bodily fluids such as blood. A humoral stimulus refers to the control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood. For example, a rise in blood glucose levels triggers the pancreatic release of insulin. Insulin causes blood glucose levels to drop, which signals the pancreas to stop producing insulin in a negative feedback loop. Hormonal Stimuli Hormonal stimuli refers to the release of a hormone in response to another hormone. A number of endocrine glands release hormones when stimulated by hormones released by other endocrine glands. For example, the hypothalamus produces hormones that stimulate the anterior portion of the pituitary gland. The anterior pituitary in turn releases hormones that regulate hormone production by other endocrine glands. The anterior pituitary releases the thyroid-stimulating hormone, which then stimulates the thyroid gland to produce the hormones T3 and T4. As blood concentrations of T3 and T4 rise, they inhibit both the pituitary and the hypothalamus in a negative feedback loop. Neural Stimuli In some cases, the nervous system directly stimulates endocrine glands to release hormones, which is referred to as neural stimuli. Recall that in a short-term stress response, the hormones epinephrine and norepinephrine are important for providing the bursts of energy required for the body to respond. Here, neuronal signaling from the sympathetic nervous system directly stimulates the adrenal medulla to release the hormones epinephrine and norepinephrine in response to stress. Section Summary Hormone levels are primarily controlled through negative feedback, in which rising levels of a hormone inhibit its further release. The three mechanisms of hormonal release are humoral stimuli, hormonal stimuli, and neural stimuli. Humoral stimuli refers to the control of hormonal release in response to changes in extracellular fluid levels or ion levels. Hormonal stimuli refers to the release of hormones in response to hormones released by other endocrine glands. Neural stimuli refers to the release of hormones in response to neural stimulation. Art Connections Figure Hyperthyroidism is a condition in which the thyroid gland is overactive. Hypothyroidism is a condition in which the thyroid gland is underactive. Which of the conditions are the following two patients most likely to have? Patient A has symptoms including weight gain, cold sensitivity, low heart rate and fatigue. Patient B has symptoms including weight loss, profuse sweating, increased heart rate and difficulty sleeping. Hint: Figure Patient A has symptoms associated with decreased metabolism, and may be suffering from hypothyroidism. Patient B has symptoms associated with increased metabolism, and may be suffering from hyperthyroidism. Review Questions A rise in blood glucose levels triggers release of insulin from the pancreas. This mechanism of hormone production is stimulated by: - humoral stimuli - hormonal stimuli - neural stimuli - negative stimuli Hint: A Which mechanism of hormonal stimulation would be affected if signaling and hormone release from the hypothalamus was blocked? - humoral and hormonal stimuli - hormonal and neural stimuli - neural and humoral stimuli - hormonal and negative stimuli Hint: B Free Response How is hormone production and release primarily controlled? Hint: Hormone production and release are primarily controlled by negative feedback. In negative feedback systems, a stimulus causes the release of a substance whose effects then inhibit further release. In this way, the concentration of hormones in blood is maintained within a narrow range. For example, the anterior pituitary signals the thyroid to release thyroid hormones. Increasing levels of these hormones in the blood then feed back to the hypothalamus and anterior pituitary to inhibit further signaling to the thyroid gland. Compare and contrast hormonal and humoral stimuli. Hint: The term humoral is derived from the term humor, which refers to bodily fluids such as blood. Humoral stimuli refer to the control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood. For example, a rise in blood glucose levels triggers the pancreatic release of insulin. Insulin causes blood glucose levels to drop, which signals the pancreas to stop producing insulin in a negative feedback loop. Hormonal stimuli refer to the release of a hormone in response to another hormone. A number of endocrine glands release hormones when stimulated by hormones released by other endocrine organs. For example, the hypothalamus produces hormones that stimulate the anterior pituitary. The anterior pituitary in turn releases hormones that regulate hormone production by other endocrine glands. For example, the anterior pituitary releases thyroid-stimulating hormone, which stimulates the thyroid gland to produce the hormones T3 and T4. As blood concentrations of T3 and T4 rise they inhibit both the pituitary and the hypothalamus in a negative feedback loop.	oercommons	2025-03-18T00:36:07.814322	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15130/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15131/overview	Endocrine Glands Overview By the end of this section, you will be able to: - Describe the role of different glands in the endocrine system - Explain how the different glands work together to maintain homeostasis Both the endocrine and nervous systems use chemical signals to communicate and regulate the body's physiology. The endocrine system releases hormones that act on target cells to regulate development, growth, energy metabolism, reproduction, and many behaviors. The nervous system releases neurotransmitters or neurohormones that regulate neurons, muscle cells, and endocrine cells. Because the neurons can regulate the release of hormones, the nervous and endocrine systems work in a coordinated manner to regulate the body's physiology. Hypothalamic-Pituitary Axis The hypothalamus in vertebrates integrates the endocrine and nervous systems. The hypothalamus is an endocrine organ located in the diencephalon of the brain. It receives input from the body and other brain areas and initiates endocrine responses to environmental changes. The hypothalamus acts as an endocrine organ, synthesizing hormones and transporting them along axons to the posterior pituitary gland. It synthesizes and secretes regulatory hormones that control the endocrine cells in the anterior pituitary gland. The hypothalamus contains autonomic centers that control endocrine cells in the adrenal medulla via neuronal control. The pituitary gland, sometimes called the hypophysis or “master gland” is located at the base of the brain in the sella turcica, a groove of the sphenoid bone of the skull, illustrated in Figure. It is attached to the hypothalamus via a stalk called the pituitary stalk (or infundibulum). The anterior portion of the pituitary gland is regulated by releasing or release-inhibiting hormones produced by the hypothalamus, and the posterior pituitary receives signals via neurosecretory cells to release hormones produced by the hypothalamus. The pituitary has two distinct regions—the anterior pituitary and the posterior pituitary—which between them secrete nine different peptide or protein hormones. The posterior lobe of the pituitary gland contains axons of the hypothalamic neurons. Anterior Pituitary The anterior pituitary gland, or adenohypophysis, is surrounded by a capillary network that extends from the hypothalamus, down along the infundibulum, and to the anterior pituitary. This capillary network is a part of the hypophyseal portal system that carries substances from the hypothalamus to the anterior pituitary and hormones from the anterior pituitary into the circulatory system. A portal system carries blood from one capillary network to another; therefore, the hypophyseal portal system allows hormones produced by the hypothalamus to be carried directly to the anterior pituitary without first entering the circulatory system. The anterior pituitary produces seven hormones: growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), melanin-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). Anterior pituitary hormones are sometimes referred to as tropic hormones, because they control the functioning of other organs. While these hormones are produced by the anterior pituitary, their production is controlled by regulatory hormones produced by the hypothalamus. These regulatory hormones can be releasing hormones or inhibiting hormones, causing more or less of the anterior pituitary hormones to be secreted. These travel from the hypothalamus through the hypophyseal portal system to the anterior pituitary where they exert their effect. Negative feedback then regulates how much of these regulatory hormones are released and how much anterior pituitary hormone is secreted. Posterior Pituitary The posterior pituitary is significantly different in structure from the anterior pituitary. It is a part of the brain, extending down from the hypothalamus, and contains mostly nerve fibers and neuroglial cells, which support axons that extend from the hypothalamus to the posterior pituitary. The posterior pituitary and the infundibulum together are referred to as the neurohypophysis. The hormones antidiuretic hormone (ADH), also known as vasopressin, and oxytocin are produced by neurons in the hypothalamus and transported within these axons along the infundibulum to the posterior pituitary. They are released into the circulatory system via neural signaling from the hypothalamus. These hormones are considered to be posterior pituitary hormones, even though they are produced by the hypothalamus, because that is where they are released into the circulatory system. The posterior pituitary itself does not produce hormones, but instead stores hormones produced by the hypothalamus and releases them into the blood stream. Thyroid Gland The thyroid gland is located in the neck, just below the larynx and in front of the trachea, as shown in Figure. It is a butterfly-shaped gland with two lobes that are connected by the isthmus. It has a dark red color due to its extensive vascular system. When the thyroid swells due to dysfunction, it can be felt under the skin of the neck. The thyroid gland is made up of many spherical thyroid follicles, which are lined with a simple cuboidal epithelium. These follicles contain a viscous fluid, called colloid, which stores the glycoprotein thyroglobulin, the precursor to the thyroid hormones. The follicles produce hormones that can be stored in the colloid or released into the surrounding capillary network for transport to the rest of the body via the circulatory system. Thyroid follicle cells synthesize the hormone thyroxine, which is also known as T4 because it contains four atoms of iodine, and triiodothyronine, also known as T3 because it contains three atoms of iodine. Follicle cells are stimulated to release stored T3 and T4 by thyroid stimulating hormone (TSH), which is produced by the anterior pituitary. These thyroid hormones increase the rates of mitochondrial ATP production. A third hormone, calcitonin, is produced by parafollicular cells of the thyroid either releasing hormones or inhibiting hormones. Calcitonin release is not controlled by TSH, but instead is released when calcium ion concentrations in the blood rise. Calcitonin functions to help regulate calcium concentrations in body fluids. It acts in the bones to inhibit osteoclast activity and in the kidneys to stimulate excretion of calcium. The combination of these two events lowers body fluid levels of calcium. Parathyroid Glands Most people have four parathyroid glands; however, the number can vary from two to six. These glands are located on the posterior surface of the thyroid gland, as shown in Figure. Normally, there is a superior gland and an inferior gland associated with each of the thyroid’s two lobes. Each parathyroid gland is covered by connective tissue and contains many secretory cells that are associated with a capillary network. The parathyroid glands produce parathyroid hormone (PTH). PTH increases blood calcium concentrations when calcium ion levels fall below normal. PTH (1) enhances reabsorption of Ca2+ by the kidneys, (2) stimulates osteoclast activity and inhibits osteoblast activity, and (3) it stimulates synthesis and secretion of calcitriol by the kidneys, which enhances Ca2+ absorption by the digestive system. PTH is produced by chief cells of the parathyroid. PTH and calcitonin work in opposition to one another to maintain homeostatic Ca2+ levels in body fluids. Another type of cells, oxyphil cells, exist in the parathyroid but their function is not known. These hormones encourage bone growth, muscle mass, and blood cell formation in children and women. Adrenal Glands The adrenal glands are associated with the kidneys; one gland is located on top of each kidney as illustrated in Figure. The adrenal glands consist of an outer adrenal cortex and an inner adrenal medulla. These regions secrete different hormones. Adrenal Cortex The adrenal cortex is made up of layers of epithelial cells and associated capillary networks. These layers form three distinct regions: an outer zona glomerulosa that produces mineralocorticoids, a middle zona fasciculata that produces glucocorticoids, and an inner zona reticularis that produces androgens. The main mineralocorticoid is aldosterone, which regulates the concentration of Na+ ions in urine, sweat, pancreas, and saliva. Aldosterone release from the adrenal cortex is stimulated by a decrease in blood concentrations of sodium ions, blood volume, or blood pressure, or by an increase in blood potassium levels. The three main glucocorticoids are cortisol, corticosterone, and cortisone. The glucocorticoids stimulate the synthesis of glucose and gluconeogenesis (converting a non-carbohydrate to glucose) by liver cells and they promote the release of fatty acids from adipose tissue. These hormones increase blood glucose levels to maintain levels within a normal range between meals. These hormones are secreted in response to ACTH and levels are regulated by negative feedback. Androgens are sex hormones that promote masculinity. They are produced in small amounts by the adrenal cortex in both males and females. They do not affect sexual characteristics and may supplement sex hormones released from the gonads. Adrenal Medulla The adrenal medulla contains large, irregularly shaped cells that are closely associated with blood vessels. These cells are innervated by preganglionic autonomic nerve fibers from the central nervous system. The adrenal medulla contains two types of secretory cells: one that produces epinephrine (adrenaline) and another that produces norepinephrine (noradrenaline). Epinephrine is the primary adrenal medulla hormone accounting for 75 to 80 percent of its secretions. Epinephrine and norepinephrine increase heart rate, breathing rate, cardiac muscle contractions, blood pressure, and blood glucose levels. They also accelerate the breakdown of glucose in skeletal muscles and stored fats in adipose tissue. The release of epinephrine and norepinephrine is stimulated by neural impulses from the sympathetic nervous system. Secretion of these hormones is stimulated by acetylcholine release from preganglionic sympathetic fibers innervating the adrenal medulla. These neural impulses originate from the hypothalamus in response to stress to prepare the body for the fight-or-flight response. Pancreas The pancreas, illustrated in Figure, is an elongated organ that is located between the stomach and the proximal portion of the small intestine. It contains both exocrine cells that excrete digestive enzymes and endocrine cells that release hormones. It is sometimes referred to as a heterocrine gland because it has both endocrine and exocrine functions. The endocrine cells of the pancreas form clusters called pancreatic islets or the islets of Langerhans, as visible in the micrograph shown in Figure. The pancreatic islets contain two primary cell types: alpha cells, which produce the hormone glucagon, and beta cells, which produce the hormone insulin. These hormones regulate blood glucose levels. As blood glucose levels decline, alpha cells release glucagon to raise the blood glucose levels by increasing rates of glycogen breakdown and glucose release by the liver. When blood glucose levels rise, such as after a meal, beta cells release insulin to lower blood glucose levels by increasing the rate of glucose uptake in most body cells, and by increasing glycogen synthesis in skeletal muscles and the liver. Together, glucagon and insulin regulate blood glucose levels. Pineal Gland The pineal gland produces melatonin. The rate of melatonin production is affected by the photoperiod. Collaterals from the visual pathways innervate the pineal gland. During the day photoperiod, little melatonin is produced; however, melatonin production increases during the dark photoperiod (night). In some mammals, melatonin has an inhibitory affect on reproductive functions by decreasing production and maturation of sperm, oocytes, and reproductive organs. Melatonin is an effective antioxidant, protecting the CNS from free radicals such as nitric oxide and hydrogen peroxide. Lastly, melatonin is involved in biological rhythms, particularly circadian rhythms such as the sleep-wake cycle and eating habits. Gonads The gonads—the male testes and female ovaries—produce steroid hormones. The testes produce androgens, testosterone being the most prominent, which allow for the development of secondary sex characteristics and the production of sperm cells. The ovaries produce estradiol and progesterone, which cause secondary sex characteristics and prepare the body for childbirth. \| Endocrine Glands and their Associated Hormones \| \|\| \|---\|---\|---\| \| Endocrine Gland \| Associated Hormones \| Effect \| \| Hypothalamus \| releasing and inhibiting hormones \| regulate hormone release from pituitary gland; produce oxytocin; produce uterine contractions and milk secretion in females \| \| antidiuretic hormone (ADH) \| water reabsorption from kidneys; vasoconstriction to increase blood pressure \| \| \| Pituitary (Anterior) \| growth hormone (GH) \| promotes growth of body tissues, protein synthesis; metabolic functions \| \| prolactin (PRL) \| promotes milk production \| \| \| thyroid stimulating hormone (TSH) \| stimulates thyroid hormone release \| \| \| adrenocorticotropic hormone (ACTH) \| stimulates hormone release by adrenal cortex, glucocorticoids \| \| \| follicle-stimulating hormone (FSH) \| stimulates gamete production (both ova and sperm); secretion of estradiol \| \| \| luteinizing hormone (LH) \| stimulates androgen production by gonads; ovulation, secretion of progesterone \| \| \| melanocyte-stimulating hormone (MSH) \| stimulates melanocytes of the skin increasing melanin pigment production. \| \| \| Pituitary (Posterior) \| antidiuretic hormone (ADH) \| stimulates water reabsorption by kidneys \| \| oxytocin \| stimulates uterine contractions during childbirth; milk ejection; stimulates ductus deferens and prostate gland contraction during emission \| \| \| Thyroid \| thyroxine, triiodothyronine \| stimulate and maintain metabolism; growth and development \| \| calcitonin \| reduces blood Ca2+ levels \| \| \| Parathyroid \| parathyroid hormone (PTH) \| increases blood Ca2+ levels \| \| Adrenal (Cortex) \| aldosterone \| increases blood Na+ levels; increase K+ secretion \| \| cortisol, corticosterone, cortisone \| increase blood glucose levels; anti-inflammatory effects \| \| \| Adrenal (Medulla) \| epinephrine, norepinephrine \| stimulate fight-or-flight response; increase blood gluclose levels; increase metabolic activities \| \| Pancreas \| insulin \| reduces blood glucose levels \| \| glucagon \| increases blood glucose levels \| \| \| Pineal gland \| melatonin \| regulates some biological rhythms and protects CNS from free radicals \| \| Testes \| androgens \| regulate, promote, increase or maintain sperm production; male secondary sexual characteristics \| \| Ovaries \| estrogen \| promotes uterine lining growth; female secondary sexual characteristics \| \| progestins \| promote and maintain uterine lining growth \| Organs with Secondary Endocrine Functions There are several organs whose primary functions are non-endocrine but that also possess endocrine functions. These include the heart, kidneys, intestines, thymus, gonads, and adipose tissue. The heart possesses endocrine cells in the walls of the atria that are specialized cardiac muscle cells. These cells release the hormone atrial natriuretic peptide (ANP) in response to increased blood volume. High blood volume causes the cells to be stretched, resulting in hormone release. ANP acts on the kidneys to reduce the reabsorption of Na+, causing Na+ and water to be excreted in the urine. ANP also reduces the amounts of renin released by the kidneys and aldosterone released by the adrenal cortex, further preventing the retention of water. In this way, ANP causes a reduction in blood volume and blood pressure, and reduces the concentration of Na+ in the blood. The gastrointestinal tract produces several hormones that aid in digestion. The endocrine cells are located in the mucosa of the GI tract throughout the stomach and small intestine. Some of the hormones produced include gastrin, secretin, and cholecystokinin, which are secreted in the presence of food, and some of which act on other organs such as the pancreas, gallbladder, and liver. They trigger the release of gastric juices, which help to break down and digest food in the GI tract. While the adrenal glands associated with the kidneys are major endocrine glands, the kidneys themselves also possess endocrine function. Renin is released in response to decreased blood volume or pressure and is part of the renin-angiotensin-aldosterone system that leads to the release of aldosterone. Aldosterone then causes the retention of Na+ and water, raising blood volume. The kidneys also release calcitriol, which aids in the absorption of Ca2+ and phosphate ions. Erythropoietin (EPO) is a protein hormone that triggers the formation of red blood cells in the bone marrow. EPO is released in response to low oxygen levels. Because red blood cells are oxygen carriers, increased production results in greater oxygen delivery throughout the body. EPO has been used by athletes to improve performance, as greater oxygen delivery to muscle cells allows for greater endurance. Because red blood cells increase the viscosity of blood, artificially high levels of EPO can cause severe health risks. The thymus is found behind the sternum; it is most prominent in infants, becoming smaller in size through adulthood. The thymus produces hormones referred to as thymosins, which contribute to the development of the immune response. Adipose tissue is a connective tissue found throughout the body. It produces the hormone leptin in response to food intake. Leptin increases the activity of anorexigenic neurons and decreases that of orexigenic neurons, producing a feeling of satiety after eating, thus affecting appetite and reducing the urge for further eating. Leptin is also associated with reproduction. It must be present for GnRH and gonadotropin synthesis to occur. Extremely thin females may enter puberty late; however, if adipose levels increase, more leptin will be produced, improving fertility. Section Summary The pituitary gland is located at the base of the brain and is attached to the hypothalamus by the infundibulum. The anterior pituitary receives products from the hypothalamus by the hypophyseal portal system and produces six hormones. The posterior pituitary is an extension of the brain and releases hormones (antidiuretic hormone and oxytocin) produced by the hypothalamus. The thyroid gland is located in the neck and is composed of two lobes connected by the isthmus. The thyroid is made up of follicle cells that produce the hormones thyroxine and triiodothyronine. Parafollicular cells of the thyroid produce calcitonin. The parathyroid glands lie on the posterior surface of the thyroid gland and produce parathyroid hormone. The adrenal glands are located on top of the kidneys and consist of the renal cortex and renal medulla. The adrenal cortex is the outer part of the adrenal gland and produces the corticosteroids, glucocorticoids, and mineralocorticoids. The adrenal medulla is the inner part of the adrenal gland and produces the catecholamines epinephrine and norepinephrine. The pancreas lies in the abdomen between the stomach and the small intestine. Clusters of endocrine cells in the pancreas form the islets of Langerhans, which are composed of alpha cells that release glucagon and beta cells that release insulin. Some organs possess endocrine activity as a secondary function but have another primary function. The heart produces the hormone atrial natriuretic peptide, which functions to reduce blood volume, pressure, and Na+ concentration. The gastrointestinal tract produces various hormones that aid in digestion. The kidneys produce renin, calcitriol, and erythropoietin. Adipose tissue produces leptin, which promotes satiety signals in the brain. Review Questions Which endocrine glands are associated with the kidneys? - thyroid glands - pituitary glands - adrenal glands - gonads Hint: C Which of the following hormones is not produced by the anterior pituitary? - oxytocin - growth hormone - prolactin - thyroid-stimulating hormone Hint: A Free Response What does aldosterone regulate, and how is it stimulated? Hint: The main mineralocorticoid is aldosterone, which regulates the concentration of ions in urine, sweat, and saliva. Aldosterone release from the adrenal cortex is stimulated by a decrease in blood concentrations of sodium ions, blood volume, or blood pressure, or an increase in blood potassium levels. The adrenal medulla contains two types of secretory cells, what are they and what are their functions? Hint: The adrenal medulla contains two types of secretory cells, one that produces epinephrine (adrenaline) and another that produces norepinephrine (noradrenaline). Epinephrine is the primary adrenal medulla hormone accounting for 75–80 percent of its secretions. Epinephrine and norepinephrine increase heart rate, breathing rate, cardiac muscle contractions, and blood glucose levels. They also accelerate the breakdown of glucose in skeletal muscles and stored fats in adipose tissue. The release of epinephrine and norepinephrine is stimulated by neural impulses from the sympathetic nervous system. These neural impulses originate from the hypothalamus in response to stress to prepare the body for the fight-or-flight response.	oercommons	2025-03-18T00:36:07.852036	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15131/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15132/overview	Introduction The muscular and skeletal systems provide support to the body and allow for a wide range of movement. The bones of the skeletal system protect the body’s internal organs and support the weight of the body. The muscles of the muscular system contract and pull on the bones, allowing for movements as diverse as standing, walking, running, and grasping items. Injury or disease affecting the musculoskeletal system can be very debilitating. In humans, the most common musculoskeletal diseases worldwide are caused by malnutrition. Ailments that affect the joints are also widespread, such as arthritis, which can make movement difficult and—in advanced cases—completely impair mobility. In severe cases in which the joint has suffered extensive damage, joint replacement surgery may be needed. Progress in the science of prosthesis design has resulted in the development of artificial joints, with joint replacement surgery in the hips and knees being the most common. Replacement joints for shoulders, elbows, and fingers are also available. Even with this progress, there is still room for improvement in the design of prostheses. The state-of-the-art prostheses have limited durability and therefore wear out quickly, particularly in young or active individuals. Current research is focused on the use of new materials, such as carbon fiber, that may make prostheses more durable.	oercommons	2025-03-18T00:36:07.871970	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15132/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15133/overview	Types of Skeletal Systems Overview By the end of this section, you will be able to: - Discuss the different types of skeletal systems - Explain the role of the human skeletal system - Compare and contrast different skeletal systems A skeletal system is necessary to support the body, protect internal organs, and allow for the movement of an organism. There are three different skeleton designs that fulfill these functions: hydrostatic skeleton, exoskeleton, and endoskeleton. Hydrostatic Skeleton A hydrostatic skeleton is a skeleton formed by a fluid-filled compartment within the body, called the coelom. The organs of the coelom are supported by the aqueous fluid, which also resists external compression. This compartment is under hydrostatic pressure because of the fluid and supports the other organs of the organism. This type of skeletal system is found in soft-bodied animals such as sea anemones, earthworms, Cnidaria, and other invertebrates (Figure). Movement in a hydrostatic skeleton is provided by muscles that surround the coelom. The muscles in a hydrostatic skeleton contract to change the shape of the coelom; the pressure of the fluid in the coelom produces movement. For example, earthworms move by waves of muscular contractions of the skeletal muscle of the body wall hydrostatic skeleton, called peristalsis, which alternately shorten and lengthen the body. Lengthening the body extends the anterior end of the organism. Most organisms have a mechanism to fix themselves in the substrate. Shortening the muscles then draws the posterior portion of the body forward. Although a hydrostatic skeleton is well-suited to invertebrate organisms such as earthworms and some aquatic organisms, it is not an efficient skeleton for terrestrial animals. Exoskeleton An exoskeleton is an external skeleton that consists of a hard encasement on the surface of an organism. For example, the shells of crabs and insects are exoskeletons (Figure). This skeleton type provides defence against predators, supports the body, and allows for movement through the contraction of attached muscles. As with vertebrates, muscles must cross a joint inside the exoskeleton. Shortening of the muscle changes the relationship of the two segments of the exoskeleton. Arthropods such as crabs and lobsters have exoskeletons that consist of 30–50 percent chitin, a polysaccharide derivative of glucose that is a strong but flexible material. Chitin is secreted by the epidermal cells. The exoskeleton is further strengthened by the addition of calcium carbonate in organisms such as the lobster. Because the exoskeleton is acellular, arthropods must periodically shed their exoskeletons because the exoskeleton does not grow as the organism grows. Endoskeleton An endoskeleton is a skeleton that consists of hard, mineralized structures located within the soft tissue of organisms. An example of a primitive endoskeletal structure is the spicules of sponges. The bones of vertebrates are composed of tissues, whereas sponges have no true tissues (Figure). Endoskeletons provide support for the body, protect internal organs, and allow for movement through contraction of muscles attached to the skeleton. The human skeleton is an endoskeleton that consists of 206 bones in the adult. It has five main functions: providing support to the body, storing minerals and lipids, producing blood cells, protecting internal organs, and allowing for movement. The skeletal system in vertebrates is divided into the axial skeleton (which consists of the skull, vertebral column, and rib cage), and the appendicular skeleton (which consists of the shoulders, limb bones, the pectoral girdle, and the pelvic girdle). Link to Learning Visit the interactive body site to build a virtual skeleton: select "skeleton" and click through the activity to place each bone. Human Axial Skeleton The axial skeleton forms the central axis of the body and includes the bones of the skull, ossicles of the middle ear, hyoid bone of the throat, vertebral column, and the thoracic cage (ribcage) (Figure). The function of the axial skeleton is to provide support and protection for the brain, the spinal cord, and the organs in the ventral body cavity. It provides a surface for the attachment of muscles that move the head, neck, and trunk, performs respiratory movements, and stabilizes parts of the appendicular skeleton. The Skull The bones of the skull support the structures of the face and protect the brain. The skull consists of 22 bones, which are divided into two categories: cranial bones and facial bones. The cranial bones are eight bones that form the cranial cavity, which encloses the brain and serves as an attachment site for the muscles of the head and neck. The eight cranial bones are the frontal bone, two parietal bones, two temporal bones, occipital bone, sphenoid bone, and the ethmoid bone. Although the bones developed separately in the embryo and fetus, in the adult, they are tightly fused with connective tissue and adjoining bones do not move (Figure). The auditory ossicles of the middle ear transmit sounds from the air as vibrations to the fluid-filled cochlea. The auditory ossicles consist of three bones each: the malleus, incus, and stapes. These are the smallest bones in the body and are unique to mammals. Fourteen facial bones form the face, provide cavities for the sense organs (eyes, mouth, and nose), protect the entrances to the digestive and respiratory tracts, and serve as attachment points for facial muscles. The 14 facial bones are the nasal bones, the maxillary bones, zygomatic bones, palatine, vomer, lacrimal bones, the inferior nasal conchae, and the mandible. All of these bones occur in pairs except for the mandible and the vomer (Figure). Although it is not found in the skull, the hyoid bone is considered a component of the axial skeleton. The hyoid bone lies below the mandible in the front of the neck. It acts as a movable base for the tongue and is connected to muscles of the jaw, larynx, and tongue. The mandible articulates with the base of the skull. The mandible controls the opening to the airway and gut. In animals with teeth, the mandible brings the surfaces of the teeth in contact with the maxillary teeth. The Vertebral Column The vertebral column, or spinal column, surrounds and protects the spinal cord, supports the head, and acts as an attachment point for the ribs and muscles of the back and neck. The adult vertebral column comprises 26 bones: the 24 vertebrae, the sacrum, and the coccyx bones. In the adult, the sacrum is typically composed of five vertebrae that fuse into one. The coccyx is typically 3–4 vertebrae that fuse into one. Around the age of 70, the sacrum and the coccyx may fuse together. We begin life with approximately 33 vertebrae, but as we grow, several vertebrae fuse together. The adult vertebrae are further divided into the 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae (Figure). Each vertebral body has a large hole in the center through which the nerves of the spinal cord pass. There is also a notch on each side through which the spinal nerves, which serve the body at that level, can exit from the spinal cord. The vertebral column is approximately 71 cm (28 inches) in adult male humans and is curved, which can be seen from a side view. The names of the spinal curves correspond to the region of the spine in which they occur. The thoracic and sacral curves are concave (curve inwards relative to the front of the body) and the cervical and lumbar curves are convex (curve outwards relative to the front of the body). The arched curvature of the vertebral column increases its strength and flexibility, allowing it to absorb shocks like a spring (Figure). Intervertebral discs composed of fibrous cartilage lie between adjacent vertebral bodies from the second cervical vertebra to the sacrum. Each disc is part of a joint that allows for some movement of the spine and acts as a cushion to absorb shocks from movements such as walking and running. Intervertebral discs also act as ligaments to bind vertebrae together. The inner part of discs, the nucleus pulposus, hardens as people age and becomes less elastic. This loss of elasticity diminishes its ability to absorb shocks. The Thoracic Cage The thoracic cage, also known as the ribcage, is the skeleton of the chest, and consists of the ribs, sternum, thoracic vertebrae, and costal cartilages (Figure). The thoracic cage encloses and protects the organs of the thoracic cavity, including the heart and lungs. It also provides support for the shoulder girdles and upper limbs, and serves as the attachment point for the diaphragm, muscles of the back, chest, neck, and shoulders. Changes in the volume of the thorax enable breathing. The sternum, or breastbone, is a long, flat bone located at the anterior of the chest. It is formed from three bones that fuse in the adult. The ribs are 12 pairs of long, curved bones that attach to the thoracic vertebrae and curve toward the front of the body, forming the ribcage. Costal cartilages connect the anterior ends of the ribs to the sternum, with the exception of rib pairs 11 and 12, which are free-floating ribs. Human Appendicular Skeleton The appendicular skeleton is composed of the bones of the upper limbs (which function to grasp and manipulate objects) and the lower limbs (which permit locomotion). It also includes the pectoral girdle, or shoulder girdle, that attaches the upper limbs to the body, and the pelvic girdle that attaches the lower limbs to the body (Figure). The Pectoral Girdle The pectoral girdle bones provide the points of attachment of the upper limbs to the axial skeleton. The human pectoral girdle consists of the clavicle (or collarbone) in the anterior, and the scapula (or shoulder blades) in the posterior (Figure). The clavicles are S-shaped bones that position the arms on the body. The clavicles lie horizontally across the front of the thorax (chest) just above the first rib. These bones are fairly fragile and are susceptible to fractures. For example, a fall with the arms outstretched causes the force to be transmitted to the clavicles, which can break if the force is excessive. The clavicle articulates with the sternum and the scapula. The scapulae are flat, triangular bones that are located at the back of the pectoral girdle. They support the muscles crossing the shoulder joint. A ridge, called the spine, runs across the back of the scapula and can easily be felt through the skin (Figure). The spine of the scapula is a good example of a bony protrusion that facilitates a broad area of attachment for muscles to bone. The Upper Limb The upper limb contains 30 bones in three regions: the arm (shoulder to elbow), the forearm (ulna and radius), and the wrist and hand (Figure). An articulation is any place at which two bones are joined. The humerus is the largest and longest bone of the upper limb and the only bone of the arm. It articulates with the scapula at the shoulder and with the forearm at the elbow. The forearm extends from the elbow to the wrist and consists of two bones: the ulna and the radius. The radius is located along the lateral (thumb) side of the forearm and articulates with the humerus at the elbow. The ulna is located on the medial aspect (pinky-finger side) of the forearm. It is longer than the radius. The ulna articulates with the humerus at the elbow. The radius and ulna also articulate with the carpal bones and with each other, which in vertebrates enables a variable degree of rotation of the carpus with respect to the long axis of the limb. The hand includes the eight bones of the carpus (wrist), the five bones of the metacarpus (palm), and the 14 bones of the phalanges (digits). Each digit consists of three phalanges, except for the thumb, when present, which has only two. The Pelvic Girdle The pelvic girdle attaches to the lower limbs of the axial skeleton. Because it is responsible for bearing the weight of the body and for locomotion, the pelvic girdle is securely attached to the axial skeleton by strong ligaments. It also has deep sockets with robust ligaments to securely attach the femur to the body. The pelvic girdle is further strengthened by two large hip bones. In adults, the hip bones, or coxal bones, are formed by the fusion of three pairs of bones: the ilium, ischium, and pubis. The pelvis joins together in the anterior of the body at a joint called the pubic symphysis and with the bones of the sacrum at the posterior of the body. The female pelvis is slightly different from the male pelvis. Over generations of evolution, females with a wider pubic angle and larger diameter pelvic canal reproduced more successfully. Therefore, their offspring also had pelvic anatomy that enabled successful childbirth (Figure). The Lower Limb The lower limb consists of the thigh, the leg, and the foot. The bones of the lower limb are the femur (thigh bone), patella (kneecap), tibia and fibula (bones of the leg), tarsals (bones of the ankle), and metatarsals and phalanges (bones of the foot) (Figure). The bones of the lower limbs are thicker and stronger than the bones of the upper limbs because of the need to support the entire weight of the body and the resulting forces from locomotion. In addition to evolutionary fitness, the bones of an individual will respond to forces exerted upon them. The femur, or thighbone, is the longest, heaviest, and strongest bone in the body. The femur and pelvis form the hip joint at the proximal end. At the distal end, the femur, tibia, and patella form the knee joint. The patella, or kneecap, is a triangular bone that lies anterior to the knee joint. The patella is embedded in the tendon of the femoral extensors (quadriceps). It improves knee extension by reducing friction. The tibia, or shinbone, is a large bone of the leg that is located directly below the knee. The tibia articulates with the femur at its proximal end, with the fibula and the tarsal bones at its distal end. It is the second largest bone in the human body and is responsible for transmitting the weight of the body from the femur to the foot. The fibula, or calf bone, parallels and articulates with the tibia. It does not articulate with the femur and does not bear weight. The fibula acts as a site for muscle attachment and forms the lateral part of the ankle joint. The tarsals are the seven bones of the ankle. The ankle transmits the weight of the body from the tibia and the fibula to the foot. The metatarsals are the five bones of the foot. The phalanges are the 14 bones of the toes. Each toe consists of three phalanges, except for the big toe that has only two (Figure). Variations exist in other species; for example, the horse’s metacarpals and metatarsals are oriented vertically and do not make contact with the substrate. Evolution Connection Evolution of Body Design for Locomotion on Land The transition of vertebrates onto land required a number of changes in body design, as movement on land presents a number of challenges for animals that are adapted to movement in water. The buoyancy of water provides a certain amount of lift, and a common form of movement by fish is lateral undulations of the entire body. This back and forth movement pushes the body against the water, creating forward movement. In most fish, the muscles of paired fins attach to girdles within the body, allowing for some control of locomotion. As certain fish began moving onto land, they retained their lateral undulation form of locomotion (anguilliform). However, instead of pushing against water, their fins or flippers became points of contact with the ground, around which they rotated their bodies. The effect of gravity and the lack of buoyancy on land meant that body weight was suspended on the limbs, leading to increased strengthening and ossification of the limbs. The effect of gravity also required changes to the axial skeleton. Lateral undulations of land animal vertebral columns cause torsional strain. A firmer, more ossified vertebral column became common in terrestrial tetrapods because it reduces strain while providing the strength needed to support the body’s weight. In later tetrapods, the vertebrae began allowing for vertical motion rather than lateral flexion. Another change in the axial skeleton was the loss of a direct attachment between the pectoral girdle and the head. This reduced the jarring to the head caused by the impact of the limbs on the ground. The vertebrae of the neck also evolved to allow movement of the head independently of the body. The appendicular skeleton of land animals is also different from aquatic animals. The shoulders attach to the pectoral girdle through muscles and connective tissue, thus reducing the jarring of the skull. Because of a lateral undulating vertebral column, in early tetrapods, the limbs were splayed out to the side and movement occurred by performing “push-ups.” The vertebrae of these animals had to move side-to-side in a similar manner to fish and reptiles. This type of motion requires large muscles to move the limbs toward the midline; it was almost like walking while doing push-ups, and it is not an efficient use of energy. Later tetrapods have their limbs placed under their bodies, so that each stride requires less force to move forward. This resulted in decreased adductor muscle size and an increased range of motion of the scapulae. This also restricts movement primarily to one plane, creating forward motion rather than moving the limbs upward as well as forward. The femur and humerus were also rotated, so that the ends of the limbs and digits were pointed forward, in the direction of motion, rather than out to the side. By placement underneath the body, limbs can swing forward like a pendulum to produce a stride that is more efficient for moving over land. Section Summary The three types of skeleton designs are hydrostatic skeletons, exoskeletons, and endoskeletons. A hydrostatic skeleton is formed by a fluid-filled compartment held under hydrostatic pressure; movement is created by the muscles producing pressure on the fluid. An exoskeleton is a hard external skeleton that protects the outer surface of an organism and enables movement through muscles attached on the inside. An endoskeleton is an internal skeleton composed of hard, mineralized tissue that also enables movement by attachment to muscles. The human skeleton is an endoskeleton that is composed of the axial and appendicular skeleton. The axial skeleton is composed of the bones of the skull, ossicles of the ear, hyoid bone, vertebral column, and ribcage. The skull consists of eight cranial bones and 14 facial bones. Six bones make up the ossicles of the middle ear, while the hyoid bone is located in the neck under the mandible. The vertebral column contains 26 bones, and it surrounds and protects the spinal cord. The thoracic cage consists of the sternum, ribs, thoracic vertebrae, and costal cartilages. The appendicular skeleton is made up of the limbs of the upper and lower limbs. The pectoral girdle is composed of the clavicles and the scapulae. The upper limb contains 30 bones in the arm, the forearm, and the hand. The pelvic girdle attaches the lower limbs to the axial skeleton. The lower limb includes the bones of the thigh, the leg, and the foot. Review Questions The forearm consists of the: - radius and ulna - radius and humerus - ulna and humerus - humerus and carpus Hint: A The pectoral girdle consists of the: - clavicle and sternum - sternum and scapula - clavicle and scapula - clavicle and coccyx Hint: C All of the following are groups of vertebrae except ________, which is a curvature. - thoracic - cervical - lumbar - pelvic Hint: D Which of these is a facial bone? - frontal - occipital - lacrimal - temporal Hint: C Free Response What are the major differences between the male pelvis and female pelvis that permit childbirth in females? Hint: The female pelvis is tilted forward and is wider, lighter, and shallower than the male pelvis. It is also has a pubic angle that is broader than the male pelvis. What are the major differences between the pelvic girdle and the pectoral girdle that allow the pelvic girdle to bear the weight of the body? Hint: The pelvic girdle is securely attached to the body by strong ligaments, unlike the pectoral girdle, which is sparingly attached to the ribcage. The sockets of the pelvic girdle are deep, allowing the femur to be more stable than the pectoral girdle, which has shallow sockets for the scapula. Most tetrapods have 75 percent of their weight on the front legs because the head and neck are so heavy; the advantage of the shoulder joint is more degrees of freedom in movement.	oercommons	2025-03-18T00:36:07.909965	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15133/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15134/overview	Bone Overview By the end of this section, you will be able to: - Classify the different types of bones in the skeleton - Explain the role of the different cell types in bone - Explain how bone forms during development Bone, or osseous tissue, is a connective tissue that constitutes the endoskeleton. It contains specialized cells and a matrix of mineral salts and collagen fibers. The mineral salts primarily include hydroxyapatite, a mineral formed from calcium phosphate. Calcification is the process of deposition of mineral salts on the collagen fiber matrix that crystallizes and hardens the tissue. The process of calcification only occurs in the presence of collagen fibers. The bones of the human skeleton are classified by their shape: long bones, short bones, flat bones, sutural bones, sesamoid bones, and irregular bones (Figure). Long bones are longer than they are wide and have a shaft and two ends. The diaphysis, or central shaft, contains bone marrow in a marrow cavity. The rounded ends, the epiphyses, are covered with articular cartilage and are filled with red bone marrow, which produces blood cells (Figure). Most of the limb bones are long bones—for example, the femur, tibia, ulna, and radius. Exceptions to this include the patella and the bones of the wrist and ankle. Short bones, or cuboidal bones, are bones that are the same width and length, giving them a cube-like shape. For example, the bones of the wrist (carpals) and ankle (tarsals) are short bones (Figure). Flat bones are thin and relatively broad bones that are found where extensive protection of organs is required or where broad surfaces of muscle attachment are required. Examples of flat bones are the sternum (breast bone), ribs, scapulae (shoulder blades), and the roof of the skull (Figure). Irregular bones are bones with complex shapes. These bones may have short, flat, notched, or ridged surfaces. Examples of irregular bones are the vertebrae, hip bones, and several skull bones. Sesamoid bones are small, flat bones and are shaped similarly to a sesame seed. The patellae are sesamoid bones (Figure). Sesamoid bones develop inside tendons and may be found near joints at the knees, hands, and feet. Sutural bones are small, flat, irregularly shaped bones. They may be found between the flat bones of the skull. They vary in number, shape, size, and position. Bone Tissue Bones are considered organs because they contain various types of tissue, such as blood, connective tissue, nerves, and bone tissue. Osteocytes, the living cells of bone tissue, form the mineral matrix of bones. There are two types of bone tissue: compact and spongy. Compact Bone Tissue Compact bone (or cortical bone) forms the hard external layer of all bones and surrounds the medullary cavity, or bone marrow. It provides protection and strength to bones. Compact bone tissue consists of units called osteons or Haversian systems. Osteons are cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi, which transport blood. They are aligned parallel to the long axis of the bone. Each osteon consists of lamellae, which are layers of compact matrix that surround a central canal called the Haversian canal. The Haversian canal (osteonic canal) contains the bone’s blood vessels and nerve fibers (Figure). Osteons in compact bone tissue are aligned in the same direction along lines of stress and help the bone resist bending or fracturing. Therefore, compact bone tissue is prominent in areas of bone at which stresses are applied in only a few directions. Art Connection Which of the following statements about bone tissue is false? - Compact bone tissue is made of cylindrical osteons that are aligned such that they travel the length of the bone. - Haversian canals contain blood vessels only. - Haversian canals contain blood vessels and nerve fibers. - Spongy tissue is found on the interior of the bone, and compact bone tissue is found on the exterior. Spongy Bone Tissue Whereas compact bone tissue forms the outer layer of all bones, spongy bone or cancellous bone forms the inner layer of all bones. Spongy bone tissue does not contain osteons that constitute compact bone tissue. Instead, it consists of trabeculae, which are lamellae that are arranged as rods or plates. Red bone marrow is found between the trabuculae. Blood vessels within this tissue deliver nutrients to osteocytes and remove waste. The red bone marrow of the femur and the interior of other large bones, such as the ileum, forms blood cells. Spongy bone reduces the density of bone and allows the ends of long bones to compress as the result of stresses applied to the bone. Spongy bone is prominent in areas of bones that are not heavily stressed or where stresses arrive from many directions. The epiphyses of bones, such as the neck of the femur, are subject to stress from many directions. Imagine laying a heavy framed picture flat on the floor. You could hold up one side of the picture with a toothpick if the toothpick was perpendicular to the floor and the picture. Now drill a hole and stick the toothpick into the wall to hang up the picture. In this case, the function of the toothpick is to transmit the downward pressure of the picture to the wall. The force on the picture is straight down to the floor, but the force on the toothpick is both the picture wire pulling down and the bottom of the hole in the wall pushing up. The toothpick will break off right at the wall. The neck of the femur is horizontal like the toothpick in the wall. The weight of the body pushes it down near the joint, but the vertical diaphysis of the femur pushes it up at the other end. The neck of the femur must be strong enough to transfer the downward force of the body weight horizontally to the vertical shaft of the femur (Figure). Link to Learning View micrographs of musculoskeletal tissues as you review the anatomy. Cell Types in Bones Bone consists of four types of cells: osteoblasts, osteoclasts, osteocytes, and osteoprogenitor cells. Osteoblasts are bone cells that are responsible for bone formation. Osteoblasts synthesize and secrete the organic part and inorganic part of the extracellular matrix of bone tissue, and collagen fibers. Osteoblasts become trapped in these secretions and differentiate into less active osteocytes. Osteoclasts are large bone cells with up to 50 nuclei. They remove bone structure by releasing lysosomal enzymes and acids that dissolve the bony matrix. These minerals, released from bones into the blood, help regulate calcium concentrations in body fluids. Bone may also be resorbed for remodeling, if the applied stresses have changed. Osteocytes are mature bone cells and are the main cells in bony connective tissue; these cells cannot divide. Osteocytes maintain normal bone structure by recycling the mineral salts in the bony matrix. Osteoprogenitor cells are squamous stem cells that divide to produce daughter cells that differentiate into osteoblasts. Osteoprogenitor cells are important in the repair of fractures. Development of Bone Ossification, or osteogenesis, is the process of bone formation by osteoblasts. Ossification is distinct from the process of calcification; whereas calcification takes place during the ossification of bones, it can also occur in other tissues. Ossification begins approximately six weeks after fertilization in an embryo. Before this time, the embryonic skeleton consists entirely of fibrous membranes and hyaline cartilage. The development of bone from fibrous membranes is called intramembranous ossification; development from hyaline cartilage is called endochondral ossification. Bone growth continues until approximately age 25. Bones can grow in thickness throughout life, but after age 25, ossification functions primarily in bone remodeling and repair. Intramembranous Ossification Intramembranous ossification is the process of bone development from fibrous membranes. It is involved in the formation of the flat bones of the skull, the mandible, and the clavicles. Ossification begins as mesenchymal cells form a template of the future bone. They then differentiate into osteoblasts at the ossification center. Osteoblasts secrete the extracellular matrix and deposit calcium, which hardens the matrix. The non-mineralized portion of the bone or osteoid continues to form around blood vessels, forming spongy bone. Connective tissue in the matrix differentiates into red bone marrow in the fetus. The spongy bone is remodeled into a thin layer of compact bone on the surface of the spongy bone. Endochondral Ossification Endochondral ossification is the process of bone development from hyaline cartilage. All of the bones of the body, except for the flat bones of the skull, mandible, and clavicles, are formed through endochondral ossification. In long bones, chondrocytes form a template of the hyaline cartilage diaphysis. Responding to complex developmental signals, the matrix begins to calcify. This calcification prevents diffusion of nutrients into the matrix, resulting in chondrocytes dying and the opening up of cavities in the diaphysis cartilage. Blood vessels invade the cavities, and osteoblasts and osteoclasts modify the calcified cartilage matrix into spongy bone. Osteoclasts then break down some of the spongy bone to create a marrow, or medullary, cavity in the center of the diaphysis. Dense, irregular connective tissue forms a sheath (periosteum) around the bones. The periosteum assists in attaching the bone to surrounding tissues, tendons, and ligaments. The bone continues to grow and elongate as the cartilage cells at the epiphyses divide. In the last stage of prenatal bone development, the centers of the epiphyses begin to calcify. Secondary ossification centers form in the epiphyses as blood vessels and osteoblasts enter these areas and convert hyaline cartilage into spongy bone. Until adolescence, hyaline cartilage persists at the epiphyseal plate (growth plate), which is the region between the diaphysis and epiphysis that is responsible for the lengthwise growth of long bones (Figure). Growth of Bone Long bones continue to lengthen, potentially until adolescence, through the addition of bone tissue at the epiphyseal plate. They also increase in width through appositional growth. Lengthening of Long Bones Chondrocytes on the epiphyseal side of the epiphyseal plate divide; one cell remains undifferentiated near the epiphysis, and one cell moves toward the diaphysis. The cells, which are pushed from the epiphysis, mature and are destroyed by calcification. This process replaces cartilage with bone on the diaphyseal side of the plate, resulting in a lengthening of the bone. Long bones stop growing at around the age of 18 in females and the age of 21 in males in a process called epiphyseal plate closure. During this process, cartilage cells stop dividing and all of the cartilage is replaced by bone. The epiphyseal plate fades, leaving a structure called the epiphyseal line or epiphyseal remnant, and the epiphysis and diaphysis fuse. Thickening of Long Bones Appositional growth is the increase in the diameter of bones by the addition of bony tissue at the surface of bones. Osteoblasts at the bone surface secrete bone matrix, and osteoclasts on the inner surface break down bone. The osteoblasts differentiate into osteocytes. A balance between these two processes allows the bone to thicken without becoming too heavy. Bone Remodeling and Repair Bone renewal continues after birth into adulthood. Bone remodeling is the replacement of old bone tissue by new bone tissue. It involves the processes of bone deposition by osteoblasts and bone resorption by osteoclasts. Normal bone growth requires vitamins D, C, and A, plus minerals such as calcium, phosphorous, and magnesium. Hormones such as parathyroid hormone, growth hormone, and calcitonin are also required for proper bone growth and maintenance. Bone turnover rates are quite high, with five to seven percent of bone mass being recycled every week. Differences in turnover rate exist in different areas of the skeleton and in different areas of a bone. For example, the bone in the head of the femur may be fully replaced every six months, whereas the bone along the shaft is altered much more slowly. Bone remodeling allows bones to adapt to stresses by becoming thicker and stronger when subjected to stress. Bones that are not subject to normal stress, for example when a limb is in a cast, will begin to lose mass. A fractured or broken bone undergoes repair through four stages: - Blood vessels in the broken bone tear and hemorrhage, resulting in the formation of clotted blood, or a hematoma, at the site of the break. The severed blood vessels at the broken ends of the bone are sealed by the clotting process, and bone cells that are deprived of nutrients begin to die. - Within days of the fracture, capillaries grow into the hematoma, and phagocytic cells begin to clear away the dead cells. Though fragments of the blood clot may remain, fibroblasts and osteoblasts enter the area and begin to reform bone. Fibroblasts produce collagen fibers that connect the broken bone ends, and osteoblasts start to form spongy bone. The repair tissue between the broken bone ends is called the fibrocartilaginous callus, as it is composed of both hyaline and fibrocartilage (Figure). Some bone spicules may also appear at this point. - The fibrocartilaginous callus is converted into a bony callus of spongy bone. It takes about two months for the broken bone ends to be firmly joined together after the fracture. This is similar to the endochondral formation of bone, as cartilage becomes ossified; osteoblasts, osteoclasts, and bone matrix are present. - The bony callus is then remodelled by osteoclasts and osteoblasts, with excess material on the exterior of the bone and within the medullary cavity being removed. Compact bone is added to create bone tissue that is similar to the original, unbroken bone. This remodeling can take many months, and the bone may remain uneven for years. Scientific Method Connection Decalcification of Bones Question: What effect does the removal of calcium and collagen have on bone structure? Background: Conduct a literature search on the role of calcium and collagen in maintaining bone structure. Conduct a literature search on diseases in which bone structure is compromised. Hypothesis: Develop a hypothesis that states predictions of the flexibility, strength, and mass of bones that have had the calcium and collagen components removed. Develop a hypothesis regarding the attempt to add calcium back to decalcified bones. Test the hypothesis: Test the prediction by removing calcium from chicken bones by placing them in a jar of vinegar for seven days. Test the hypothesis regarding adding calcium back to decalcified bone by placing the decalcified chicken bones into a jar of water with calcium supplements added. Test the prediction by denaturing the collagen from the bones by baking them at 250°C for three hours. Analyze the data: Create a table showing the changes in bone flexibility, strength, and mass in the three different environments. Report the results: Under which conditions was the bone most flexible? Under which conditions was the bone the strongest? Draw a conclusion: Did the results support or refute the hypothesis? How do the results observed in this experiment correspond to diseases that destroy bone tissue? Section Summary Bone, or osseous tissue, is connective tissue that includes specialized cells, mineral salts, and collagen fibers. The human skeleton can be divided into long bones, short bones, flat bones, and irregular bones. Compact bone tissue is composed of osteons and forms the external layer of all bones. Spongy bone tissue is composed of trabeculae and forms the inner part of all bones. Four types of cells compose bony tissue: osteocytes, osteoclasts, osteoprogenitor cells, and osteoblasts. Ossification is the process of bone formation by osteoblasts. Intramembranous ossification is the process of bone development from fibrous membranes. Endochondral ossification is the process of bone development from hyaline cartilage. Long bones lengthen as chondrocytes divide and secrete hyaline cartilage. Osteoblasts replace cartilage with bone. Appositional growth is the increase in the diameter of bones by the addition of bone tissue at the surface of bones. Bone remodeling involves the processes of bone deposition by osteoblasts and bone resorption by osteoclasts. Bone repair occurs in four stages and can take several months. Art Exercise FigureWhich of the following statements about bone tissue is false? - Compact bone tissue is made of cylindrical osteons that are aligned such that they travel the length of the bone. - Haversian canals contain blood vessels only. - Haversian canals contain blood vessels and nerve fibers. - Spongy tissue is found on the interior of the bone, and compact bone tissue is found on the exterior. Hint: Review Questions The Haversian canal: - is arranged as rods or plates - contains the bone’s blood vessels and nerve fibers - is responsible for the lengthwise growth of long bones - synthesizes and secretes matrix Hint: B The epiphyseal plate: - is arranged as rods or plates - contains the bone’s blood vessels and nerve fibers - is responsible for the lengthwise growth of long bones - synthesizes and secretes bone matrix Hint: C The cells responsible for bone resorption are ________. - osteoclasts - osteoblasts - fibroblasts - osteocytes Hint: A Compact bone is composed of ________. - trabeculae - compacted collagen - osteons - calcium phosphate only Hint: C Free Response What are the major differences between spongy bone and compact bone? Hint: Compact bone tissue forms the hard external layer of all bones and consists of osteons. Compact bone tissue is prominent in areas of bone at which stresses are applied in only a few directions. Spongy bone tissue forms the inner layer of all bones and consists of trabeculae. Spongy bone is prominent in areas of bones that are not heavily stressed or at which stresses arrive from many directions. What are the roles of osteoblasts, osteocytes, and osteoclasts? Hint: Osteocytes function in the exchange of nutrients and wastes with the blood. They also maintain normal bone structure by recycling the mineral salts in the bony matrix. Osteoclasts remove bone tissue by releasing lysosomal enzymes and acids that dissolve the bony matrix. Osteoblasts are bone cells that are responsible for bone formation.	oercommons	2025-03-18T00:36:07.948515	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15134/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15135/overview	Joints and Skeletal Movement Overview By the end of this section, you will be able to: - Classify the different types of joints on the basis of structure - Explain the role of joints in skeletal movement The point at which two or more bones meet is called a joint, or articulation. Joints are responsible for movement, such as the movement of limbs, and stability, such as the stability found in the bones of the skull. Classification of Joints on the Basis of Structure There are two ways to classify joints: on the basis of their structure or on the basis of their function. The structural classification divides joints into bony, fibrous, cartilaginous, and synovial joints depending on the material composing the joint and the presence or absence of a cavity in the joint. Fibrous Joints The bones of fibrous joints are held together by fibrous connective tissue. There is no cavity, or space, present between the bones and so most fibrous joints do not move at all, or are only capable of minor movements. There are three types of fibrous joints: sutures, syndesmoses, and gomphoses. Sutures are found only in the skull and possess short fibers of connective tissue that hold the skull bones tightly in place (Figure). Syndesmoses are joints in which the bones are connected by a band of connective tissue, allowing for more movement than in a suture. An example of a syndesmosis is the joint of the tibia and fibula in the ankle. The amount of movement in these types of joints is determined by the length of the connective tissue fibers. Gomphoses occur between teeth and their sockets; the term refers to the way the tooth fits into the socket like a peg (Figure). The tooth is connected to the socket by a connective tissue referred to as the periodontal ligament. Cartilaginous Joints Cartilaginous joints are joints in which the bones are connected by cartilage. There are two types of cartilaginous joints: synchondroses and symphyses. In a synchondrosis, the bones are joined by hyaline cartilage. Synchondroses are found in the epiphyseal plates of growing bones in children. In symphyses, hyaline cartilage covers the end of the bone but the connection between bones occurs through fibrocartilage. Symphyses are found at the joints between vertebrae. Either type of cartilaginous joint allows for very little movement. Synovial Joints Synovial joints are the only joints that have a space between the adjoining bones (Figure). This space is referred to as the synovial (or joint) cavity and is filled with synovial fluid. Synovial fluid lubricates the joint, reducing friction between the bones and allowing for greater movement. The ends of the bones are covered with articular cartilage, a hyaline cartilage, and the entire joint is surrounded by an articular capsule composed of connective tissue that allows movement of the joint while resisting dislocation. Articular capsules may also possess ligaments that hold the bones together. Synovial joints are capable of the greatest movement of the three structural joint types; however, the more mobile a joint, the weaker the joint. Knees, elbows, and shoulders are examples of synovial joints. Classification of Joints on the Basis of Function The functional classification divides joints into three categories: synarthroses, amphiarthroses, and diarthroses. A synarthrosis is a joint that is immovable. This includes sutures, gomphoses, and synchondroses. Amphiarthroses are joints that allow slight movement, including syndesmoses and symphyses. Diarthroses are joints that allow for free movement of the joint, as in synovial joints. Movement at Synovial Joints The wide range of movement allowed by synovial joints produces different types of movements. The movement of synovial joints can be classified as one of four different types: gliding, angular, rotational, or special movement. Gliding Movement Gliding movements occur as relatively flat bone surfaces move past each other. Gliding movements produce very little rotation or angular movement of the bones. The joints of the carpal and tarsal bones are examples of joints that produce gliding movements. Angular Movement Angular movements are produced when the angle between the bones of a joint changes. There are several different types of angular movements, including flexion, extension, hyperextension, abduction, adduction, and circumduction. Flexion, or bending, occurs when the angle between the bones decreases. Moving the forearm upward at the elbow or moving the wrist to move the hand toward the forearm are examples of flexion. Extension is the opposite of flexion in that the angle between the bones of a joint increases. Straightening a limb after flexion is an example of extension. Extension past the regular anatomical position is referred to as hyperextension. This includes moving the neck back to look upward, or bending the wrist so that the hand moves away from the forearm. Abduction occurs when a bone moves away from the midline of the body. Examples of abduction are moving the arms or legs laterally to lift them straight out to the side. Adduction is the movement of a bone toward the midline of the body. Movement of the limbs inward after abduction is an example of adduction. Circumduction is the movement of a limb in a circular motion, as in moving the arm in a circular motion. Rotational Movement Rotational movement is the movement of a bone as it rotates around its longitudinal axis. Rotation can be toward the midline of the body, which is referred to as medial rotation, or away from the midline of the body, which is referred to as lateral rotation. Movement of the head from side to side is an example of rotation. Special Movements Some movements that cannot be classified as gliding, angular, or rotational are called special movements. Inversion involves the soles of the feet moving inward, toward the midline of the body. Eversion is the opposite of inversion, movement of the sole of the foot outward, away from the midline of the body. Protraction is the anterior movement of a bone in the horizontal plane. Retraction occurs as a joint moves back into position after protraction. Protraction and retraction can be seen in the movement of the mandible as the jaw is thrust outwards and then back inwards. Elevation is the movement of a bone upward, such as when the shoulders are shrugged, lifting the scapulae. Depression is the opposite of elevation—movement downward of a bone, such as after the shoulders are shrugged and the scapulae return to their normal position from an elevated position. Dorsiflexion is a bending at the ankle such that the toes are lifted toward the knee. Plantar flexion is a bending at the ankle when the heel is lifted, such as when standing on the toes. Supination is the movement of the radius and ulna bones of the forearm so that the palm faces forward. Pronation is the opposite movement, in which the palm faces backward. Opposition is the movement of the thumb toward the fingers of the same hand, making it possible to grasp and hold objects. Types of Synovial Joints Synovial joints are further classified into six different categories on the basis of the shape and structure of the joint. The shape of the joint affects the type of movement permitted by the joint (Figure). These joints can be described as planar, hinge, pivot, condyloid, saddle, or ball-and-socket joints. Planar Joints Planar joints have bones with articulating surfaces that are flat or slightly curved faces. These joints allow for gliding movements, and so the joints are sometimes referred to as gliding joints. The range of motion is limited in these joints and does not involve rotation. Planar joints are found in the carpal bones in the hand and the tarsal bones of the foot, as well as between vertebrae (Figure). Hinge Joints In hinge joints, the slightly rounded end of one bone fits into the slightly hollow end of the other bone. In this way, one bone moves while the other remains stationary, like the hinge of a door. The elbow is an example of a hinge joint. The knee is sometimes classified as a modified hinge joint (Figure). Pivot Joints Pivot joints consist of the rounded end of one bone fitting into a ring formed by the other bone. This structure allows rotational movement, as the rounded bone moves around its own axis. An example of a pivot joint is the joint of the first and second vertebrae of the neck that allows the head to move back and forth (Figure). The joint of the wrist that allows the palm of the hand to be turned up and down is also a pivot joint. Condyloid Joints Condyloid joints consist of an oval-shaped end of one bone fitting into a similarly oval-shaped hollow of another bone (Figure). This is also sometimes called an ellipsoidal joint. This type of joint allows angular movement along two axes, as seen in the joints of the wrist and fingers, which can move both side to side and up and down. Saddle Joints Saddle joints are so named because the ends of each bone resemble a saddle, with concave and convex portions that fit together. Saddle joints allow angular movements similar to condyloid joints but with a greater range of motion. An example of a saddle joint is the thumb joint, which can move back and forth and up and down, but more freely than the wrist or fingers (Figure). Ball-and-Socket Joints Ball-and-socket joints possess a rounded, ball-like end of one bone fitting into a cuplike socket of another bone. This organization allows the greatest range of motion, as all movement types are possible in all directions. Examples of ball-and-socket joints are the shoulder and hip joints (Figure). Link to Learning Watch this animation showing the six types of synovial joints. Career Connection Rheumatologist Rheumatologists are medical doctors who specialize in the diagnosis and treatment of disorders of the joints, muscles, and bones. They diagnose and treat diseases such as arthritis, musculoskeletal disorders, osteoporosis, and autoimmune diseases such as ankylosing spondylitis and rheumatoid arthritis. Rheumatoid arthritis (RA) is an inflammatory disorder that primarily affects the synovial joints of the hands, feet, and cervical spine. Affected joints become swollen, stiff, and painful. Although it is known that RA is an autoimmune disease in which the body’s immune system mistakenly attacks healthy tissue, the cause of RA remains unknown. Immune cells from the blood enter joints and the synovium causing cartilage breakdown, swelling, and inflammation of the joint lining. Breakdown of cartilage causes bones to rub against each other causing pain. RA is more common in women than men and the age of onset is usually 40–50 years of age. Rheumatologists can diagnose RA on the basis of symptoms such as joint inflammation and pain, X-ray and MRI imaging, and blood tests. Arthrography is a type of medical imaging of joints that uses a contrast agent, such as a dye, that is opaque to X-rays. This allows the soft tissue structures of joints—such as cartilage, tendons, and ligaments—to be visualized. An arthrogram differs from a regular X-ray by showing the surface of soft tissues lining the joint in addition to joint bones. An arthrogram allows early degenerative changes in joint cartilage to be detected before bones become affected. There is currently no cure for RA; however, rheumatologists have a number of treatment options available. Early stages can be treated with rest of the affected joints by using a cane or by using joint splints that minimize inflammation. When inflammation has decreased, exercise can be used to strengthen the muscles that surround the joint and to maintain joint flexibility. If joint damage is more extensive, medications can be used to relieve pain and decrease inflammation. Anti-inflammatory drugs such as aspirin, topical pain relievers, and corticosteroid injections may be used. Surgery may be required in cases in which joint damage is severe. Section Summary The structural classification of joints divides them into bony, fibrous, cartilaginous, and synovial joints. The bones of fibrous joints are held together by fibrous connective tissue; the three types of fibrous joints are sutures, syndesomes, and gomphoses. Cartilaginous joints are joints in which the bones are connected by cartilage; the two types of cartilaginous joints are synchondroses and symphyses. Synovial joints are joints that have a space between the adjoining bones. The functional classification divides joints into three categories: synarthroses, amphiarthroses, and diarthroses. The movement of synovial joints can be classified as one of four different types: gliding, angular, rotational, or special movement. Gliding movements occur as relatively flat bone surfaces move past each other. Angular movements are produced when the angle between the bones of a joint changes. Rotational movement is the movement of a bone as it rotates around its own longitudinal axis. Special movements include inversion, eversion, protraction, retraction, elevation, depression, dorsiflexion, plantar flexion, supination, pronation, and opposition. Synovial joints are also classified into six different categories on the basis of the shape and structure of the joint: planar, hinge, pivot, condyloid, saddle, and ball-and-socket. Review Questions Synchondroses and symphyses are: - synovial joints - cartilaginous joints - fibrous joints - condyloid joints Hint: B The movement of bone away from the midline of the body is called ________. - circumduction - extension - adduction - abduction Hint: D Which of the following is not a characteristic of the synovial fluid? - lubrication - shock absorption - regulation of water balance in the joint - protection of articular cartilage Hint: C The elbow is an example of which type of joint? - hinge - pivot - saddle - gliding Hint: A Free Response What movements occur at the hip joint and knees as you bend down to touch your toes? Hint: The hip joint is flexed and the knees are extended. What movement(s) occur(s) at the scapulae when you shrug your shoulders? Hint: Elevation is the movement of a bone upward, such as when the shoulders are shrugged, lifting the scapulae. Depression is the downward movement of a bone, such as after the shoulders are shrugged and the scapulae return to their normal position from an elevated position.	oercommons	2025-03-18T00:36:07.982911	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15135/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15136/overview	Muscle Contraction and Locomotion Overview By the end of this section, you will be able to: - Classify the different types of muscle tissue - Explain the role of muscles in locomotion Muscle cells are specialized for contraction. Muscles allow for motions such as walking, and they also facilitate bodily processes such as respiration and digestion. The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle (Figure). Skeletal muscle tissue forms skeletal muscles, which attach to bones or skin and control locomotion and any movement that can be consciously controlled. Because it can be controlled by thought, skeletal muscle is also called voluntary muscle. Skeletal muscles are long and cylindrical in appearance; when viewed under a microscope, skeletal muscle tissue has a striped or striated appearance. The striations are caused by the regular arrangement of contractile proteins (actin and myosin). Actin is a globular contractile protein that interacts with myosin for muscle contraction. Skeletal muscle also has multiple nuclei present in a single cell. Smooth muscle tissue occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as the respiratory tract and blood vessels. Smooth muscle has no striations, is not under voluntary control, has only one nucleus per cell, is tapered at both ends, and is called involuntary muscle. Cardiac muscle tissue is only found in the heart, and cardiac contractions pump blood throughout the body and maintain blood pressure. Like skeletal muscle, cardiac muscle is striated, but unlike skeletal muscle, cardiac muscle cannot be consciously controlled and is called involuntary muscle. It has one nucleus per cell, is branched, and is distinguished by the presence of intercalated disks. Skeletal Muscle Fiber Structure Each skeletal muscle fiber is a skeletal muscle cell. These cells are incredibly large, with diameters of up to 100 µm and lengths of up to 30 cm. The plasma membrane of a skeletal muscle fiber is called the sarcolemma. The sarcolemma is the site of action potential conduction, which triggers muscle contraction. Within each muscle fiber are myofibrils—long cylindrical structures that lie parallel to the muscle fiber. Myofibrils run the entire length of the muscle fiber, and because they are only approximately 1.2 µm in diameter, hundreds to thousands can be found inside one muscle fiber. They attach to the sarcolemma at their ends, so that as myofibrils shorten, the entire muscle cell contracts (Figure). The striated appearance of skeletal muscle tissue is a result of repeating bands of the proteins actin and myosin that are present along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes the entire cell to appear striated or banded. Each I band has a dense line running vertically through the middle called a Z disc or Z line. The Z discs mark the border of units called sarcomeres, which are the functional units of skeletal muscle. One sarcomere is the space between two consecutive Z discs and contains one entire A band and two halves of an I band, one on either side of the A band. A myofibril is composed of many sarcomeres running along its length, and as the sarcomeres individually contract, the myofibrils and muscle cells shorten (Figure). Myofibrils are composed of smaller structures called myofilaments. There are two main types of filaments: thick filaments and thin filaments; each has different compositions and locations. Thick filaments occur only in the A band of a myofibril. Thin filaments attach to a protein in the Z disc called alpha-actinin and occur across the entire length of the I band and partway into the A band. The region at which thick and thin filaments overlap has a dense appearance, as there is little space between the filaments. Thin filaments do not extend all the way into the A bands, leaving a central region of the A band that only contains thick filaments. This central region of the A band looks slightly lighter than the rest of the A band and is called the H zone. The middle of the H zone has a vertical line called the M line, at which accessory proteins hold together thick filaments. Both the Z disc and the M line hold myofilaments in place to maintain the structural arrangement and layering of the myofibril. Myofibrils are connected to each other by intermediate, or desmin, filaments that attach to the Z disc. Thick and thin filaments are themselves composed of proteins. Thick filaments are composed of the protein myosin. The tail of a myosin molecule connects with other myosin molecules to form the central region of a thick filament near the M line, whereas the heads align on either side of the thick filament where the thin filaments overlap. The primary component of thin filaments is the actin protein. Two other components of the thin filament are tropomyosin and troponin. Actin has binding sites for myosin attachment. Strands of tropomyosin block the binding sites and prevent actin–myosin interactions when the muscles are at rest. Troponin consists of three globular subunits. One subunit binds to tropomyosin, one subunit binds to actin, and one subunit binds Ca2+ ions. Link to Learning View this animation showing the organization of muscle fibers. Sliding Filament Model of Contraction For a muscle cell to contract, the sarcomere must shorten. However, thick and thin filaments—the components of sarcomeres—do not shorten. Instead, they slide by one another, causing the sarcomere to shorten while the filaments remain the same length. The sliding filament theory of muscle contraction was developed to fit the differences observed in the named bands on the sarcomere at different degrees of muscle contraction and relaxation. The mechanism of contraction is the binding of myosin to actin, forming cross-bridges that generate filament movement (Figure). When a sarcomere shortens, some regions shorten whereas others stay the same length. A sarcomere is defined as the distance between two consecutive Z discs or Z lines; when a muscle contracts, the distance between the Z discs is reduced. The H zone—the central region of the A zone—contains only thick filaments and is shortened during contraction. The I band contains only thin filaments and also shortens. The A band does not shorten—it remains the same length—but A bands of different sarcomeres move closer together during contraction, eventually disappearing. Thin filaments are pulled by the thick filaments toward the center of the sarcomere until the Z discs approach the thick filaments. The zone of overlap, in which thin filaments and thick filaments occupy the same area, increases as the thin filaments move inward. ATP and Muscle Contraction The motion of muscle shortening occurs as myosin heads bind to actin and pull the actin inwards. This action requires energy, which is provided by ATP. Myosin binds to actin at a binding site on the globular actin protein. Myosin has another binding site for ATP at which enzymatic activity hydrolyzes ATP to ADP, releasing an inorganic phosphate molecule and energy. ATP binding causes myosin to release actin, allowing actin and myosin to detach from each other. After this happens, the newly bound ATP is converted to ADP and inorganic phosphate, Pi. The enzyme at the binding site on myosin is called ATPase. The energy released during ATP hydrolysis changes the angle of the myosin head into a “cocked” position. The myosin head is then in a position for further movement, possessing potential energy, but ADP and Pi are still attached. If actin binding sites are covered and unavailable, the myosin will remain in the high energy configuration with ATP hydrolyzed, but still attached. If the actin binding sites are uncovered, a cross-bridge will form; that is, the myosin head spans the distance between the actin and myosin molecules. Pi is then released, allowing myosin to expend the stored energy as a conformational change. The myosin head moves toward the M line, pulling the actin along with it. As the actin is pulled, the filaments move approximately 10 nm toward the M line. This movement is called the power stroke, as it is the step at which force is produced. As the actin is pulled toward the M line, the sarcomere shortens and the muscle contracts. When the myosin head is “cocked,” it contains energy and is in a high-energy configuration. This energy is expended as the myosin head moves through the power stroke; at the end of the power stroke, the myosin head is in a low-energy position. After the power stroke, ADP is released; however, the cross-bridge formed is still in place, and actin and myosin are bound together. ATP can then attach to myosin, which allows the cross-bridge cycle to start again and further muscle contraction can occur (Figure). Link to Learning Watch this video explaining how a muscle contraction is signaled. Art Connection Which of the following statements about muscle contraction is true? - The power stroke occurs when ATP is hydrolyzed to ADP and phosphate. - The power stroke occurs when ADP and phosphate dissociate from the myosin head. - The power stroke occurs when ADP and phosphate dissociate from the actin active site. - The power stroke occurs when Ca2+ binds the calcium head. Link to Learning View this animation of the cross-bridge muscle contraction. Regulatory Proteins When a muscle is in a resting state, actin and myosin are separated. To keep actin from binding to the active site on myosin, regulatory proteins block the molecular binding sites. Tropomyosin blocks myosin binding sites on actin molecules, preventing cross-bridge formation and preventing contraction in a muscle without nervous input. Troponin binds to tropomyosin and helps to position it on the actin molecule; it also binds calcium ions. To enable a muscle contraction, tropomyosin must change conformation, uncovering the myosin-binding site on an actin molecule and allowing cross-bridge formation. This can only happen in the presence of calcium, which is kept at extremely low concentrations in the sarcoplasm. If present, calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin binding sites on actin. Once the tropomyosin is removed, a cross-bridge can form between actin and myosin, triggering contraction. Cross-bridge cycling continues until Ca2+ ions and ATP are no longer available and tropomyosin again covers the binding sites on actin. Excitation–Contraction Coupling Excitation–contraction coupling is the link (transduction) between the action potential generated in the sarcolemma and the start of a muscle contraction. The trigger for calcium release from the sarcoplasmic reticulum into the sarcoplasm is a neural signal. Each skeletal muscle fiber is controlled by a motor neuron, which conducts signals from the brain or spinal cord to the muscle. The area of the sarcolemma on the muscle fiber that interacts with the neuron is called the motor end plate. The end of the neuron’s axon is called the synaptic terminal, and it does not actually contact the motor end plate. A small space called the synaptic cleft separates the synaptic terminal from the motor end plate. Electrical signals travel along the neuron’s axon, which branches through the muscle and connects to individual muscle fibers at a neuromuscular junction. The ability of cells to communicate electrically requires that the cells expend energy to create an electrical gradient across their cell membranes. This charge gradient is carried by ions, which are differentially distributed across the membrane. Each ion exerts an electrical influence and a concentration influence. Just as milk will eventually mix with coffee without the need to stir, ions also distribute themselves evenly, if they are permitted to do so. In this case, they are not permitted to return to an evenly mixed state. The sodium–potassium ATPase uses cellular energy to move K+ ions inside the cell and Na+ ions outside. This alone accumulates a small electrical charge, but a big concentration gradient. There is lots of K+ in the cell and lots of Na+ outside the cell. Potassium is able to leave the cell through K+ channels that are open 90% of the time, and it does. However, Na+ channels are rarely open, so Na+ remains outside the cell. When K+ leaves the cell, obeying its concentration gradient, that effectively leaves a negative charge behind. So at rest, there is a large concentration gradient for Na+ to enter the cell, and there is an accumulation of negative charges left behind in the cell. This is the resting membrane potential. Potential in this context means a separation of electrical charge that is capable of doing work. It is measured in volts, just like a battery. However, the transmembrane potential is considerably smaller (0.07 V); therefore, the small value is expressed as millivolts (mV) or 70 mV. Because the inside of a cell is negative compared with the outside, a minus sign signifies the excess of negative charges inside the cell, −70 mV. If an event changes the permeability of the membrane to Na+ ions, they will enter the cell. That will change the voltage. This is an electrical event, called an action potential, that can be used as a cellular signal. Communication occurs between nerves and muscles through neurotransmitters. Neuron action potentials cause the release of neurotransmitters from the synaptic terminal into the synaptic cleft, where they can then diffuse across the synaptic cleft and bind to a receptor molecule on the motor end plate. The motor end plate possesses junctional folds—folds in the sarcolemma that create a large surface area for the neurotransmitter to bind to receptors. The receptors are actually sodium channels that open to allow the passage of Na+ into the cell when they receive neurotransmitter signal. Acetylcholine (ACh) is a neurotransmitter released by motor neurons that binds to receptors in the motor end plate. Neurotransmitter release occurs when an action potential travels down the motor neuron’s axon, resulting in altered permeability of the synaptic terminal membrane and an influx of calcium. The Ca2+ ions allow synaptic vesicles to move to and bind with the presynaptic membrane (on the neuron), and release neurotransmitter from the vesicles into the synaptic cleft. Once released by the synaptic terminal, ACh diffuses across the synaptic cleft to the motor end plate, where it binds with ACh receptors. As a neurotransmitter binds, these ion channels open, and Na+ ions cross the membrane into the muscle cell. This reduces the voltage difference between the inside and outside of the cell, which is called depolarization. As ACh binds at the motor end plate, this depolarization is called an end-plate potential. The depolarization then spreads along the sarcolemma, creating an action potential as sodium channels adjacent to the initial depolarization site sense the change in voltage and open. The action potential moves across the entire cell, creating a wave of depolarization. ACh is broken down by the enzyme acetylcholinesterase (AChE) into acetyl and choline. AChE resides in the synaptic cleft, breaking down ACh so that it does not remain bound to ACh receptors, which would cause unwanted extended muscle contraction (Figure). Art Connection The deadly nerve gas Sarin irreversibly inhibits acetycholinesterase. What effect would Sarin have on muscle contraction? After depolarization, the membrane returns to its resting state. This is called repolarization, during which voltage-gated sodium channels close. Potassium channels continue at 90% conductance. Because the plasma membrane sodium–potassium ATPase always transports ions, the resting state (negatively charged inside relative to the outside) is restored. The period immediately following the transmission of an impulse in a nerve or muscle, in which a neuron or muscle cell regains its ability to transmit another impulse, is called the refractory period. During the refractory period, the membrane cannot generate another action potential. . The refractory period allows the voltage-sensitive ion channels to return to their resting configurations. The sodium potassium ATPase continually moves Na+ back out of the cell and K+ back into the cell, and the K+ leaks out leaving negative charge behind. Very quickly, the membrane repolarizes, so that it can again be depolarized. Control of Muscle Tension Neural control initiates the formation of actin–myosin cross-bridges, leading to the sarcomere shortening involved in muscle contraction. These contractions extend from the muscle fiber through connective tissue to pull on bones, causing skeletal movement. The pull exerted by a muscle is called tension, and the amount of force created by this tension can vary. This enables the same muscles to move very light objects and very heavy objects. In individual muscle fibers, the amount of tension produced depends on the cross-sectional area of the muscle fiber and the frequency of neural stimulation. The number of cross-bridges formed between actin and myosin determine the amount of tension that a muscle fiber can produce. Cross-bridges can only form where thick and thin filaments overlap, allowing myosin to bind to actin. If more cross-bridges are formed, more myosin will pull on actin, and more tension will be produced. The ideal length of a sarcomere during production of maximal tension occurs when thick and thin filaments overlap to the greatest degree. If a sarcomere at rest is stretched past an ideal resting length, thick and thin filaments do not overlap to the greatest degree, and fewer cross-bridges can form. This results in fewer myosin heads pulling on actin, and less tension is produced. As a sarcomere is shortened, the zone of overlap is reduced as the thin filaments reach the H zone, which is composed of myosin tails. Because it is myosin heads that form cross-bridges, actin will not bind to myosin in this zone, reducing the tension produced by this myofiber. If the sarcomere is shortened even more, thin filaments begin to overlap with each other—reducing cross-bridge formation even further, and producing even less tension. Conversely, if the sarcomere is stretched to the point at which thick and thin filaments do not overlap at all, no cross-bridges are formed and no tension is produced. This amount of stretching does not usually occur because accessory proteins, internal sensory nerves, and connective tissue oppose extreme stretching. The primary variable determining force production is the number of myofibers within the muscle that receive an action potential from the neuron that controls that fiber. When using the biceps to pick up a pencil, the motor cortex of the brain only signals a few neurons of the biceps, and only a few myofibers respond. In vertebrates, each myofiber responds fully if stimulated. When picking up a piano, the motor cortex signals all of the neurons in the biceps and every myofiber participates. This is close to the maximum force the muscle can produce. As mentioned above, increasing the frequency of action potentials (the number of signals per second) can increase the force a bit more, because the tropomyosin is flooded with calcium. Section Summary The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Skeleton muscle tissue is composed of sarcomeres, the functional units of muscle tissue. Muscle contraction occurs when sarcomeres shorten, as thick and thin filaments slide past each other, which is called the sliding filament model of muscle contraction. ATP provides the energy for cross-bridge formation and filament sliding. Regulatory proteins, such as troponin and tropomyosin, control cross-bridge formation. Excitation–contraction coupling transduces the electrical signal of the neuron, via acetylcholine, to an electrical signal on the muscle membrane, which initiates force production. The number of muscle fibers contracting determines how much force the whole muscle produces. Art Connections Figure Which of the following statements about muscle contraction is true? - The power stroke occurs when ATP is hydrolyzed to ADP and phosphate. - The power stroke occurs when ADP and phosphate dissociate from the myosin head. - The power stroke occurs when ADP and phosphate dissociate from the actin active site. - The power stroke occurs when Ca2+ binds the calcium head. Hint: Figure B Figure The deadly nerve gas Sarin irreversibly inhibits acetycholinesterase. What effect would Sarin have on muscle contraction? Hint: Figure In the presence of Sarin, acetycholine is not removed from the synapse, resulting in continuous stimulation of the muscle plasma membrane. At first, muscle activity is intense and uncontrolled, but the ion gradients dissipate, so electrical signals in the T-tubules are no longer possible. The result is paralysis, leading to death by asphyxiation. Review Questions In relaxed muscle, the myosin-binding site on actin is blocked by ________. - titin - troponin - myoglobin - tropomyosin Hint: D The cell membrane of a muscle fiber is called a ________. - myofibril - sarcolemma - sarcoplasm - myofilament Hint: B The muscle relaxes if no new nerve signal arrives. However the neurotransmitter from the previous stimulation is still present in the synapse. The activity of ________ helps to remove this neurotransmitter. - myosin - action potential - tropomyosin - acetylcholinesterase Hint: D The ability of a muscle to generate tension immediately after stimulation is dependent on: - myosin interaction with the M line - overlap of myosin and actin - actin attachments to the Z line - none of the above Hint: D Free Response How would muscle contractions be affected if ATP was completely depleted in a muscle fiber? Hint: Because ATP is required for myosin to release from actin, muscles would remain rigidly contracted until more ATP was available for the myosin cross-bridge release. This is why dead vertebrates undergo rigor mortis. What factors contribute to the amount of tension produced in an individual muscle fiber? Hint: The cross-sectional area, the length of the muscle fiber at rest, and the frequency of neural stimulation. What effect will low blood calcium have on neurons? What effect will low blood calcium have on skeletal muscles? Hint: Neurons will not be able to release neurotransmitter without calcium. Skeletal muscles have calcium stored and don’t need any from the outside.	oercommons	2025-03-18T00:36:08.023798	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15136/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15137/overview	Introduction Breathing is an involuntary event. How often a breath is taken and how much air is inhaled or exhaled are tightly regulated by the respiratory center in the brain. Humans, when they aren’t exerting themselves, breathe approximately 15 times per minute on average. Canines, like the dog in Figure, have a respiratory rate of about 15–30 breaths per minute. With every inhalation, air fills the lungs, and with every exhalation, air rushes back out. That air is doing more than just inflating and deflating the lungs in the chest cavity. The air contains oxygen that crosses the lung tissue, enters the bloodstream, and travels to organs and tissues. Oxygen (O2) enters the cells where it is used for metabolic reactions that produce ATP, a high-energy compound. At the same time, these reactions release carbon dioxide (CO2) as a by-product. CO2 is toxic and must be eliminated. Carbon dioxide exits the cells, enters the bloodstream, travels back to the lungs, and is expired out of the body during exhalation.	oercommons	2025-03-18T00:36:08.042257	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15137/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15138/overview	Systems of Gas Exchange Overview By the end of this section, you will be able to: - Describe the passage of air from the outside environment to the lungs - Explain how the lungs are protected from particulate matter The primary function of the respiratory system is to deliver oxygen to the cells of the body’s tissues and remove carbon dioxide, a cell waste product. The main structures of the human respiratory system are the nasal cavity, the trachea, and lungs. All aerobic organisms require oxygen to carry out their metabolic functions. Along the evolutionary tree, different organisms have devised different means of obtaining oxygen from the surrounding atmosphere. The environment in which the animal lives greatly determines how an animal respires. The complexity of the respiratory system is correlated with the size of the organism. As animal size increases, diffusion distances increase and the ratio of surface area to volume drops. In unicellular organisms, diffusion across the cell membrane is sufficient for supplying oxygen to the cell (Figure). Diffusion is a slow, passive transport process. In order for diffusion to be a feasible means of providing oxygen to the cell, the rate of oxygen uptake must match the rate of diffusion across the membrane. In other words, if the cell were very large or thick, diffusion would not be able to provide oxygen quickly enough to the inside of the cell. Therefore, dependence on diffusion as a means of obtaining oxygen and removing carbon dioxide remains feasible only for small organisms or those with highly-flattened bodies, such as many flatworms (Platyhelminthes). Larger organisms had to evolve specialized respiratory tissues, such as gills, lungs, and respiratory passages accompanied by complex circulatory systems, to transport oxygen throughout their entire body. Direct Diffusion For small multicellular organisms, diffusion across the outer membrane is sufficient to meet their oxygen needs. Gas exchange by direct diffusion across surface membranes is efficient for organisms less than 1 mm in diameter. In simple organisms, such as cnidarians and flatworms, every cell in the body is close to the external environment. Their cells are kept moist and gases diffuse quickly via direct diffusion. Flatworms are small, literally flat worms, which ‘breathe’ through diffusion across the outer membrane (Figure). The flat shape of these organisms increases the surface area for diffusion, ensuring that each cell within the body is close to the outer membrane surface and has access to oxygen. If the flatworm had a cylindrical body, then the cells in the center would not be able to get oxygen. Skin and Gills Earthworms and amphibians use their skin (integument) as a respiratory organ. A dense network of capillaries lies just below the skin and facilitates gas exchange between the external environment and the circulatory system. The respiratory surface must be kept moist in order for the gases to dissolve and diffuse across cell membranes. Organisms that live in water need to obtain oxygen from the water. Oxygen dissolves in water but at a lower concentration than in the atmosphere. The atmosphere has roughly 21 percent oxygen. In water, the oxygen concentration is much smaller than that. Fish and many other aquatic organisms have evolved gills to take up the dissolved oxygen from water (Figure). Gills are thin tissue filaments that are highly branched and folded. When water passes over the gills, the dissolved oxygen in water rapidly diffuses across the gills into the bloodstream. The circulatory system can then carry the oxygenated blood to the other parts of the body. In animals that contain coelomic fluid instead of blood, oxygen diffuses across the gill surfaces into the coelomic fluid. Gills are found in mollusks, annelids, and crustaceans. The folded surfaces of the gills provide a large surface area to ensure that the fish gets sufficient oxygen. Diffusion is a process in which material travels from regions of high concentration to low concentration until equilibrium is reached. In this case, blood with a low concentration of oxygen molecules circulates through the gills. The concentration of oxygen molecules in water is higher than the concentration of oxygen molecules in gills. As a result, oxygen molecules diffuse from water (high concentration) to blood (low concentration), as shown in Figure. Similarly, carbon dioxide molecules in the blood diffuse from the blood (high concentration) to water (low concentration). Tracheal Systems Insect respiration is independent of its circulatory system; therefore, the blood does not play a direct role in oxygen transport. Insects have a highly specialized type of respiratory system called the tracheal system, which consists of a network of small tubes that carries oxygen to the entire body. The tracheal system is the most direct and efficient respiratory system in active animals. The tubes in the tracheal system are made of a polymeric material called chitin. Insect bodies have openings, called spiracles, along the thorax and abdomen. These openings connect to the tubular network, allowing oxygen to pass into the body (Figure) and regulating the diffusion of CO2 and water vapor. Air enters and leaves the tracheal system through the spiracles. Some insects can ventilate the tracheal system with body movements. Mammalian Systems In mammals, pulmonary ventilation occurs via inhalation (breathing). During inhalation, air enters the body through the nasal cavity located just inside the nose (Figure). As air passes through the nasal cavity, the air is warmed to body temperature and humidified. The respiratory tract is coated with mucus to seal the tissues from direct contact with air. Mucus is high in water. As air crosses these surfaces of the mucous membranes, it picks up water. These processes help equilibrate the air to the body conditions, reducing any damage that cold, dry air can cause. Particulate matter that is floating in the air is removed in the nasal passages via mucus and cilia. The processes of warming, humidifying, and removing particles are important protective mechanisms that prevent damage to the trachea and lungs. Thus, inhalation serves several purposes in addition to bringing oxygen into the respiratory system. Art Connection Which of the following statements about the mammalian respiratory system is false? - When we breathe in, air travels from the pharynx to the trachea. - The bronchioles branch into bronchi. - Alveolar ducts connect to alveolar sacs. - Gas exchange between the lung and blood takes place in the alveolus. From the nasal cavity, air passes through the pharynx (throat) and the larynx (voice box), as it makes its way to the trachea (Figure). The main function of the trachea is to funnel the inhaled air to the lungs and the exhaled air back out of the body. The human trachea is a cylinder about 10 to 12 cm long and 2 cm in diameter that sits in front of the esophagus and extends from the larynx into the chest cavity where it divides into the two primary bronchi at the midthorax. It is made of incomplete rings of hyaline cartilage and smooth muscle (Figure). The trachea is lined with mucus-producing goblet cells and ciliated epithelia. The cilia propel foreign particles trapped in the mucus toward the pharynx. The cartilage provides strength and support to the trachea to keep the passage open. The smooth muscle can contract, decreasing the trachea’s diameter, which causes expired air to rush upwards from the lungs at a great force. The forced exhalation helps expel mucus when we cough. Smooth muscle can contract or relax, depending on stimuli from the external environment or the body’s nervous system. Lungs: Bronchi and Alveoli The end of the trachea bifurcates (divides) to the right and left lungs. The lungs are not identical. The right lung is larger and contains three lobes, whereas the smaller left lung contains two lobes (Figure). The muscular diaphragm, which facilitates breathing, is inferior to (below) the lungs and marks the end of the thoracic cavity. In the lungs, air is diverted into smaller and smaller passages, or bronchi. Air enters the lungs through the two primary (main) bronchi (singular: bronchus). Each bronchus divides into secondary bronchi, then into tertiary bronchi, which in turn divide, creating smaller and smaller diameter bronchioles as they split and spread through the lung. Like the trachea, the bronchi are made of cartilage and smooth muscle. At the bronchioles, the cartilage is replaced with elastic fibers. Bronchi are innervated by nerves of both the parasympathetic and sympathetic nervous systems that control muscle contraction (parasympathetic) or relaxation (sympathetic) in the bronchi and bronchioles, depending on the nervous system’s cues. In humans, bronchioles with a diameter smaller than 0.5 mm are the respiratory bronchioles. They lack cartilage and therefore rely on inhaled air to support their shape. As the passageways decrease in diameter, the relative amount of smooth muscle increases. The terminal bronchioles subdivide into microscopic branches called respiratory bronchioles. The respiratory bronchioles subdivide into several alveolar ducts. Numerous alveoli and alveolar sacs surround the alveolar ducts. The alveolar sacs resemble bunches of grapes tethered to the end of the bronchioles (Figure). In the acinar region, the alveolar ducts are attached to the end of each bronchiole. At the end of each duct are approximately 100 alveolar sacs, each containing 20 to 30 alveoli that are 200 to 300 microns in diameter. Gas exchange occurs only in alveoli. Alveoli are made of thin-walled parenchymal cells, typically one-cell thick, that look like tiny bubbles within the sacs. Alveoli are in direct contact with capillaries (one-cell thick) of the circulatory system. Such intimate contact ensures that oxygen will diffuse from alveoli into the blood and be distributed to the cells of the body. In addition, the carbon dioxide that was produced by cells as a waste product will diffuse from the blood into alveoli to be exhaled. The anatomical arrangement of capillaries and alveoli emphasizes the structural and functional relationship of the respiratory and circulatory systems. Because there are so many alveoli (~300 million per lung) within each alveolar sac and so many sacs at the end of each alveolar duct, the lungs have a sponge-like consistency. This organization produces a very large surface area that is available for gas exchange. The surface area of alveoli in the lungs is approximately 75 m2. This large surface area, combined with the thin-walled nature of the alveolar parenchymal cells, allows gases to easily diffuse across the cells. Link to Learning Watch the following video to review the respiratory system. Protective Mechanisms The air that organisms breathe contains particulate matter such as dust, dirt, viral particles, and bacteria that can damage the lungs or trigger allergic immune responses. The respiratory system contains several protective mechanisms to avoid problems or tissue damage. In the nasal cavity, hairs and mucus trap small particles, viruses, bacteria, dust, and dirt to prevent their entry. If particulates do make it beyond the nose, or enter through the mouth, the bronchi and bronchioles of the lungs also contain several protective devices. The lungs produce mucus—a sticky substance made of mucin, a complex glycoprotein, as well as salts and water—that traps particulates. The bronchi and bronchioles contain cilia, small hair-like projections that line the walls of the bronchi and bronchioles (Figure). These cilia beat in unison and move mucus and particles out of the bronchi and bronchioles back up to the throat where it is swallowed and eliminated via the esophagus. In humans, for example, tar and other substances in cigarette smoke destroy or paralyze the cilia, making the removal of particles more difficult. In addition, smoking causes the lungs to produce more mucus, which the damaged cilia are not able to move. This causes a persistent cough, as the lungs try to rid themselves of particulate matter, and makes smokers more susceptible to respiratory ailments. Section Summary Animal respiratory systems are designed to facilitate gas exchange. In mammals, air is warmed and humidified in the nasal cavity. Air then travels down the pharynx, through the trachea, and into the lungs. In the lungs, air passes through the branching bronchi, reaching the respiratory bronchioles, which house the first site of gas exchange. The respiratory bronchioles open into the alveolar ducts, alveolar sacs, and alveoli. Because there are so many alveoli and alveolar sacs in the lung, the surface area for gas exchange is very large. Several protective mechanisms are in place to prevent damage or infection. These include the hair and mucus in the nasal cavity that trap dust, dirt, and other particulate matter before they can enter the system. In the lungs, particles are trapped in a mucus layer and transported via cilia up to the esophageal opening at the top of the trachea to be swallowed. Figure Which of the following statements about the mammalian respiratory system is false? - When we breathe in, air travels from the pharynx to the trachea. - The bronchioles branch into bronchi. - Alveolar ducts connect to alveolar sacs. - Gas exchange between the lung and blood takes place in the alveolus. Hint: Figure B Review Questions The respiratory system ________. - provides body tissues with oxygen - provides body tissues with oxygen and carbon dioxide - establishes how many breaths are taken per minute - provides the body with carbon dioxide Hint: A Air is warmed and humidified in the nasal passages. This helps to ________. - ward off infection - decrease sensitivity during breathing - prevent damage to the lungs - all of the above Hint: C Which is the order of airflow during inhalation? - nasal cavity, trachea, larynx, bronchi, bronchioles, alveoli - nasal cavity, larynx, trachea, bronchi, bronchioles, alveoli - nasal cavity, larynx, trachea, bronchioles, bronchi, alveoli - nasal cavity, trachea, larynx, bronchi, bronchioles, alveoli Hint: B Free Response Describe the function of these terms and describe where they are located: main bronchus, trachea, alveoli, and acinus. Hint: The main bronchus is the conduit in the lung that funnels air to the airways where gas exchange occurs. The main bronchus attaches the lungs to the very end of the trachea where it bifurcates. The trachea is the cartilaginous structure that extends from the pharynx to the primary bronchi. It serves to funnel air to the lungs. The alveoli are the sites of gas exchange; they are located at the terminal regions of the lung and are attached to the respiratory bronchioles. The acinus is the structure in the lung where gas exchange occurs. How does the structure of alveoli maximize gas exchange? Hint: The sac-like structure of the alveoli increases their surface area. In addition, the alveoli are made of thin-walled parenchymal cells. These features allow gases to easily diffuse across the cells.	oercommons	2025-03-18T00:36:08.075741	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15138/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15139/overview	Gas Exchange across Respiratory Surfaces Overview By the end of this section, you will be able to: - Name and describe lung volumes and capacities - Understand how gas pressure influences how gases move into and out of the body The structure of the lung maximizes its surface area to increase gas diffusion. Because of the enormous number of alveoli (approximately 300 million in each human lung), the surface area of the lung is very large (75 m2). Having such a large surface area increases the amount of gas that can diffuse into and out of the lungs. Basic Principles of Gas Exchange Gas exchange during respiration occurs primarily through diffusion. Diffusion is a process in which transport is driven by a concentration gradient. Gas molecules move from a region of high concentration to a region of low concentration. Blood that is low in oxygen concentration and high in carbon dioxide concentration undergoes gas exchange with air in the lungs. The air in the lungs has a higher concentration of oxygen than that of oxygen-depleted blood and a lower concentration of carbon dioxide. This concentration gradient allows for gas exchange during respiration. Partial pressure is a measure of the concentration of the individual components in a mixture of gases. The total pressure exerted by the mixture is the sum of the partial pressures of the components in the mixture. The rate of diffusion of a gas is proportional to its partial pressure within the total gas mixture. This concept is discussed further in detail below. Lung Volumes and Capacities Different animals have different lung capacities based on their activities. Cheetahs have evolved a much higher lung capacity than humans; it helps provide oxygen to all the muscles in the body and allows them to run very fast. Elephants also have a high lung capacity. In this case, it is not because they run fast but because they have a large body and must be able to take up oxygen in accordance with their body size. Human lung size is determined by genetics, sex, and height. At maximal capacity, an average lung can hold almost six liters of air, but lungs do not usually operate at maximal capacity. Air in the lungs is measured in terms of lung volumes and lung capacities (Figure and Table). Volume measures the amount of air for one function (such as inhalation or exhalation). Capacity is any two or more volumes (for example, how much can be inhaled from the end of a maximal exhalation). \| Lung Volumes and Capacities (Avg Adult Male) \| \|\|\| \|---\|---\|---\|---\| \| Volume/Capacity \| Definition \| Volume (liters) \| Equations \| \| Tidal volume (TV) \| Amount of air inhaled during a normal breath \| 0.5 \| - \| \| Expiratory reserve volume (ERV) \| Amount of air that can be exhaled after a normal exhalation \| 1.2 \| - \| \| Inspiratory reserve volume (IRV) \| Amount of air that can be further inhaled after a normal inhalation \| 3.1 \| - \| \| Residual volume (RV) \| Air left in the lungs after a forced exhalation \| 1.2 \| - \| \| Vital capacity (VC) \| Maximum amount of air that can be moved in or out of the lungs in a single respiratory cycle \| 4.8 \| ERV+TV+IRV \| \| Inspiratory capacity (IC) \| Volume of air that can be inhaled in addition to a normal exhalation \| 3.6 \| TV+IRV \| \| Functional residual capacity (FRC) \| Volume of air remaining after a normal exhalation \| 2.4 \| ERV+RV \| \| Total lung capacity (TLC) \| Total volume of air in the lungs after a maximal inspiration \| 6.0 \| RV+ERV+TV+IRV \| \| Forced expiratory volume (FEV1) \| How much air can be forced out of the lungs over a specific time period, usually one second \| ~4.1 to 5.5 \| - \| The volume in the lung can be divided into four units: tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume. Tidal volume (TV) measures the amount of air that is inspired and expired during a normal breath. On average, this volume is around one-half liter, which is a little less than the capacity of a 20-ounce drink bottle. The expiratory reserve volume (ERV) is the additional amount of air that can be exhaled after a normal exhalation. It is the reserve amount that can be exhaled beyond what is normal. Conversely, the inspiratory reserve volume (IRV) is the additional amount of air that can be inhaled after a normal inhalation. The residual volume (RV) is the amount of air that is left after expiratory reserve volume is exhaled. The lungs are never completely empty: There is always some air left in the lungs after a maximal exhalation. If this residual volume did not exist and the lungs emptied completely, the lung tissues would stick together and the energy necessary to re-inflate the lung could be too great to overcome. Therefore, there is always some air remaining in the lungs. Residual volume is also important for preventing large fluctuations in respiratory gases (O2 and CO2). The residual volume is the only lung volume that cannot be measured directly because it is impossible to completely empty the lung of air. This volume can only be calculated rather than measured. Capacities are measurements of two or more volumes. The vital capacity (VC) measures the maximum amount of air that can be inhaled or exhaled during a respiratory cycle. It is the sum of the expiratory reserve volume, tidal volume, and inspiratory reserve volume. The inspiratory capacity (IC) is the amount of air that can be inhaled after the end of a normal expiration. It is, therefore, the sum of the tidal volume and inspiratory reserve volume. The functional residual capacity (FRC) includes the expiratory reserve volume and the residual volume. The FRC measures the amount of additional air that can be exhaled after a normal exhalation. Lastly, the total lung capacity (TLC) is a measurement of the total amount of air that the lung can hold. It is the sum of the residual volume, expiratory reserve volume, tidal volume, and inspiratory reserve volume. Lung volumes are measured by a technique called spirometry. An important measurement taken during spirometry is the forced expiratory volume (FEV), which measures how much air can be forced out of the lung over a specific period, usually one second (FEV1). In addition, the forced vital capacity (FVC), which is the total amount of air that can be forcibly exhaled, is measured. The ratio of these values (FEV1/FVC ratio) is used to diagnose lung diseases including asthma, emphysema, and fibrosis. If the FEV1/FVC ratio is high, the lungs are not compliant (meaning they are stiff and unable to bend properly), and the patient most likely has lung fibrosis. Patients exhale most of the lung volume very quickly. Conversely, when the FEV1/FVC ratio is low, there is resistance in the lung that is characteristic of asthma. In this instance, it is hard for the patient to get the air out of his or her lungs, and it takes a long time to reach the maximal exhalation volume. In either case, breathing is difficult and complications arise. Career Connection Respiratory Therapist Respiratory therapists or respiratory practitioners evaluate and treat patients with lung and cardiovascular diseases. They work as part of a medical team to develop treatment plans for patients. Respiratory therapists may treat premature babies with underdeveloped lungs, patients with chronic conditions such as asthma, or older patients suffering from lung disease such as emphysema and chronic obstructive pulmonary disease (COPD). They may operate advanced equipment such as compressed gas delivery systems, ventilators, blood gas analyzers, and resuscitators. Specialized programs to become a respiratory therapist generally lead to a bachelor’s degree with a respiratory therapist specialty. Because of a growing aging population, career opportunities as a respiratory therapist are expected to remain strong. Gas Pressure and Respiration The respiratory process can be better understood by examining the properties of gases. Gases move freely, but gas particles are constantly hitting the walls of their vessel, thereby producing gas pressure. Air is a mixture of gases, primarily nitrogen (N2; 78.6 percent), oxygen (O2; 20.9 percent), water vapor (H2O; 0.5 percent), and carbon dioxide (CO2; 0.04 percent). Each gas component of that mixture exerts a pressure. The pressure for an individual gas in the mixture is the partial pressure of that gas. Approximately 21 percent of atmospheric gas is oxygen. Carbon dioxide, however, is found in relatively small amounts, 0.04 percent. The partial pressure for oxygen is much greater than that of carbon dioxide. The partial pressure of any gas can be calculated by: Patm, the atmospheric pressure, is the sum of all of the partial pressures of the atmospheric gases added together, × (percent content in mixture). The pressure of the atmosphere at sea level is 760 mm Hg. Therefore, the partial pressure of oxygen is: and for carbon dioxide: At high altitudes, Patm decreases but concentration does not change; the partial pressure decrease is due to the reduction in Patm. When the air mixture reaches the lung, it has been humidified. The pressure of the water vapor in the lung does not change the pressure of the air, but it must be included in the partial pressure equation. For this calculation, the water pressure (47 mm Hg) is subtracted from the atmospheric pressure: and the partial pressure of oxygen is: These pressures determine the gas exchange, or the flow of gas, in the system. Oxygen and carbon dioxide will flow according to their pressure gradient from high to low. Therefore, understanding the partial pressure of each gas will aid in understanding how gases move in the respiratory system. Gas Exchange across the Alveoli In the body, oxygen is used by cells of the body’s tissues and carbon dioxide is produced as a waste product. The ratio of carbon dioxide production to oxygen consumption is the respiratory quotient (RQ). RQ varies between 0.7 and 1.0. If just glucose were used to fuel the body, the RQ would equal one. One mole of carbon dioxide would be produced for every mole of oxygen consumed. Glucose, however, is not the only fuel for the body. Protein and fat are also used as fuels for the body. Because of this, less carbon dioxide is produced than oxygen is consumed and the RQ is, on average, about 0.7 for fat and about 0.8 for protein. The RQ is used to calculate the partial pressure of oxygen in the alveolar spaces within the lung, the alveolar Above, the partial pressure of oxygen in the lungs was calculated to be 150 mm Hg. However, lungs never fully deflate with an exhalation; therefore, the inspired air mixes with this residual air and lowers the partial pressure of oxygen within the alveoli. This means that there is a lower concentration of oxygen in the lungs than is found in the air outside the body. Knowing the RQ, the partial pressure of oxygen in the alveoli can be calculated: With an RQ of 0.8 and a in the alveoli of 40 mm Hg, the alveolar is equal to: Notice that this pressure is less than the external air. Therefore, the oxygen will flow from the inspired air in the lung ( = 150 mm Hg) into the bloodstream ( = 100 mm Hg) (Figure). In the lungs, oxygen diffuses out of the alveoli and into the capillaries surrounding the alveoli. Oxygen (about 98 percent) binds reversibly to the respiratory pigment hemoglobin found in red blood cells (RBCs). RBCs carry oxygen to the tissues where oxygen dissociates from the hemoglobin and diffuses into the cells of the tissues. More specifically, alveolar is higher in the alveoli ( = 100 mm Hg) than blood (40 mm Hg) in the capillaries. Because this pressure gradient exists, oxygen diffuses down its pressure gradient, moving out of the alveoli and entering the blood of the capillaries where O2 binds to hemoglobin. At the same time, alveolar is lower = 40 mm Hg than blood = (45 mm Hg). CO2 diffuses down its pressure gradient, moving out of the capillaries and entering the alveoli. Oxygen and carbon dioxide move independently of each other; they diffuse down their own pressure gradients. As blood leaves the lungs through the pulmonary veins, the venous = 100 mm Hg, whereas the venous = 40 mm Hg. As blood enters the systemic capillaries, the blood will lose oxygen and gain carbon dioxide because of the pressure difference of the tissues and blood. In systemic capillaries, = 100 mm Hg, but in the tissue cells, = 40 mm Hg. This pressure gradient drives the diffusion of oxygen out of the capillaries and into the tissue cells. At the same time, blood = 40 mm Hg and systemic tissue = 45 mm Hg. The pressure gradient drives CO2 out of tissue cells and into the capillaries. The blood returning to the lungs through the pulmonary arteries has a venous = 40 mm Hg and a = 45 mm Hg. The blood enters the lung capillaries where the process of exchanging gases between the capillaries and alveoli begins again (Figure). Art Connection Which of the following statements is false? - In the tissues, drops as blood passes from the arteries to the veins, while increases. - Blood travels from the lungs to the heart to body tissues, then back to the heart, then the lungs. - Blood travels from the lungs to the heart to body tissues, then back to the lungs, then the heart. - is higher in air than in the lungs. In short, the change in partial pressure from the alveoli to the capillaries drives the oxygen into the tissues and the carbon dioxide into the blood from the tissues. The blood is then transported to the lungs where differences in pressure in the alveoli result in the movement of carbon dioxide out of the blood into the lungs, and oxygen into the blood. Link to Learning Watch this video to learn how to carry out spirometry. Section Summary The lungs can hold a large volume of air, but they are not usually filled to maximal capacity. Lung volume measurements include tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume. The sum of these equals the total lung capacity. Gas movement into or out of the lungs is dependent on the pressure of the gas. Air is a mixture of gases; therefore, the partial pressure of each gas can be calculated to determine how the gas will flow in the lung. The difference between the partial pressure of the gas in the air drives oxygen into the tissues and carbon dioxide out of the body. Art Connections Figure Which of the following statements is false? - In the tissues, drops as blood passes from the arteries to the veins, while increases. - Blood travels from the lungs to the heart to body tissues, then back to the heart, then the lungs. - Blood travels from the lungs to the heart to body tissues, then back to the lungs, then the heart. - is higher in air than in the lungs. Hint: Figure C Review Questions The inspiratory reserve volume measures the ________. - amount of air remaining in the lung after a maximal exhalation - amount of air that the lung holds - amount of air the can be further exhaled after a normal breath - amount of air that can be further inhaled after a normal breath Hint: D Of the following, which does not explain why the partial pressure of oxygen is lower in the lung than in the external air? - Air in the lung is humidified; therefore, water vapor pressure alters the pressure. - Carbon dioxide mixes with oxygen. - Oxygen is moved into the blood and is headed to the tissues. - Lungs exert a pressure on the air to reduce the oxygen pressure. Hint: D The total lung capacity is calculated using which of the following formulas? - residual volume + tidal volume + inspiratory reserve volume - residual volume + expiratory reserve volume + inspiratory reserve volume - expiratory reserve volume + tidal volume + inspiratory reserve volume - residual volume + expiratory reserve volume + tidal volume + inspiratory reserve volume Hint: D Free Response What does FEV1/FVC measure? What factors may affect FEV1/FVC? Hint: FEV1/FVC measures the forced expiratory volume in one second in relation to the total forced vital capacity (the total amount of air that is exhaled from the lung from a maximal inhalation). This ratio changes with alterations in lung function that arise from diseases such as fibrosis, asthma, and COPD. What is the reason for having residual volume in the lung? Hint: If all the air in the lung were exhaled, then opening the alveoli for the next inspiration would be very difficult. This is because the tissues would stick together. How can a decrease in the percent of oxygen in the air affect the movement of oxygen in the body? Hint: Oxygen moves from the lung to the bloodstream to the tissues according to the pressure gradient. This is measured as the partial pressure of oxygen. If the amount of oxygen drops in the inspired air, there would be reduced partial pressure. This would decrease the driving force that moves the oxygen into the blood and into the tissues. is also reduced at high elevations: at high elevations is lower than at sea level because the total atmospheric pressure is less than atmospheric pressure at sea level. If a patient has increased resistance in his or her lungs, how can this detected by a doctor? What does this mean? Hint: A doctor can detect a restrictive disease using spirometry. By detecting the rate at which air can be expelled from the lung, a diagnosis of fibrosis or another restrictive disease can be made.	oercommons	2025-03-18T00:36:08.116256	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15139/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15140/overview	Breathing Overview By the end of this section, you will be able to: - Describe how the structures of the lungs and thoracic cavity control the mechanics of breathing - Explain the importance of compliance and resistance in the lungs - Discuss problems that may arise due to a V/Q mismatch Mammalian lungs are located in the thoracic cavity where they are surrounded and protected by the rib cage, intercostal muscles, and bound by the chest wall. The bottom of the lungs is contained by the diaphragm, a skeletal muscle that facilitates breathing. Breathing requires the coordination of the lungs, the chest wall, and most importantly, the diaphragm. Types of Breathing Amphibians have evolved multiple ways of breathing. Young amphibians, like tadpoles, use gills to breathe, and they don’t leave the water. Some amphibians retain gills for life. As the tadpole grows, the gills disappear and lungs grow. These lungs are primitive and not as evolved as mammalian lungs. Adult amphibians are lacking or have a reduced diaphragm, so breathing via lungs is forced. The other means of breathing for amphibians is diffusion across the skin. To aid this diffusion, amphibian skin must remain moist. Birds face a unique challenge with respect to breathing: They fly. Flying consumes a great amount of energy; therefore, birds require a lot of oxygen to aid their metabolic processes. Birds have evolved a respiratory system that supplies them with the oxygen needed to enable flying. Similar to mammals, birds have lungs, which are organs specialized for gas exchange. Oxygenated air, taken in during inhalation, diffuses across the surface of the lungs into the bloodstream, and carbon dioxide diffuses from the blood into the lungs and expelled during exhalation. The details of breathing between birds and mammals differ substantially. In addition to lungs, birds have air sacs inside their body. Air flows in one direction from the posterior air sacs to the lungs and out of the anterior air sacs. The flow of air is in the opposite direction from blood flow, and gas exchange takes place much more efficiently. This type of breathing enables birds to obtain the requisite oxygen, even at higher altitudes where the oxygen concentration is low. This directionality of airflow requires two cycles of air intake and exhalation to completely get the air out of the lungs. Evolution Connection Avian Respiration Birds have evolved a respiratory system that enables them to fly. Flying is a high-energy process and requires a lot of oxygen. Furthermore, many birds fly in high altitudes where the concentration of oxygen in low. How did birds evolve a respiratory system that is so unique? Decades of research by paleontologists have shown that birds evolved from therapods, meat-eating dinosaurs (Figure). In fact, fossil evidence shows that meat-eating dinosaurs that lived more than 100 million years ago had a similar flow-through respiratory system with lungs and air sacs. Archaeopteryx and Xiaotingia, for example, were flying dinosaurs and are believed to be early precursors of birds. Most of us consider that dinosaurs are extinct. However, modern birds are descendants of avian dinosaurs. The respiratory system of modern birds has been evolving for hundreds of millions of years. All mammals have lungs that are the main organs for breathing. Lung capacity has evolved to support the animal’s activities. During inhalation, the lungs expand with air, and oxygen diffuses across the lung’s surface and enters the bloodstream. During exhalation, the lungs expel air and lung volume decreases. In the next few sections, the process of human breathing will be explained. The Mechanics of Human Breathing Boyle’s Law is the gas law that states that in a closed space, pressure and volume are inversely related. As volume decreases, pressure increases and vice versa (Figure). The relationship between gas pressure and volume helps to explain the mechanics of breathing. There is always a slightly negative pressure within the thoracic cavity, which aids in keeping the airways of the lungs open. During inhalation, volume increases as a result of contraction of the diaphragm, and pressure decreases (according to Boyle’s Law). This decrease of pressure in the thoracic cavity relative to the environment makes the cavity less than the atmosphere (Figurea). Because of this drop in pressure, air rushes into the respiratory passages. To increase the volume of the lungs, the chest wall expands. This results from the contraction of the intercostal muscles, the muscles that are connected to the rib cage. Lung volume expands because the diaphragm contracts and the intercostals muscles contract, thus expanding the thoracic cavity. This increase in the volume of the thoracic cavity lowers pressure compared to the atmosphere, so air rushes into the lungs, thus increasing its volume. The resulting increase in volume is largely attributed to an increase in alveolar space, because the bronchioles and bronchi are stiff structures that do not change in size. The chest wall expands out and away from the lungs. The lungs are elastic; therefore, when air fills the lungs, the elastic recoil within the tissues of the lung exerts pressure back toward the interior of the lungs. These outward and inward forces compete to inflate and deflate the lung with every breath. Upon exhalation, the lungs recoil to force the air out of the lungs, and the intercostal muscles relax, returning the chest wall back to its original position (Figureb). The diaphragm also relaxes and moves higher into the thoracic cavity. This increases the pressure within the thoracic cavity relative to the environment, and air rushes out of the lungs. The movement of air out of the lungs is a passive event. No muscles are contracting to expel the air. Each lung is surrounded by an invaginated sac. The layer of tissue that covers the lung and dips into spaces is called the visceral pleura. A second layer of parietal pleura lines the interior of the thorax (Figure). The space between these layers, the intrapleural space, contains a small amount of fluid that protects the tissue and reduces the friction generated from rubbing the tissue layers together as the lungs contract and relax. Pleurisy results when these layers of tissue become inflamed; it is painful because the inflammation increases the pressure within the thoracic cavity and reduces the volume of the lung. Link to Learning View how Boyle’s Law is related to breathing and watch a video on Boyle’s Law. The Work of Breathing The number of breaths per minute is the respiratory rate. On average, under non-exertion conditions, the human respiratory rate is 12–15 breaths/minute. The respiratory rate contributes to the alveolar ventilation, or how much air moves into and out of the alveoli. Alveolar ventilation prevents carbon dioxide buildup in the alveoli. There are two ways to keep the alveolar ventilation constant: increase the respiratory rate while decreasing the tidal volume of air per breath (shallow breathing), or decrease the respiratory rate while increasing the tidal volume per breath. In either case, the ventilation remains the same, but the work done and type of work needed are quite different. Both tidal volume and respiratory rate are closely regulated when oxygen demand increases. There are two types of work conducted during respiration, flow-resistive and elastic work. Flow-resistive refers to the work of the alveoli and tissues in the lung, whereas elastic work refers to the work of the intercostal muscles, chest wall, and diaphragm. Increasing the respiration rate increases the flow-resistive work of the airways and decreases the elastic work of the muscles. Decreasing the respiratory rate reverses the type of work required. Surfactant The air-tissue/water interface of the alveoli has a high surface tension. This surface tension is similar to the surface tension of water at the liquid-air interface of a water droplet that results in the bonding of the water molecules together. Surfactant is a complex mixture of phospholipids and lipoproteins that works to reduce the surface tension that exists between the alveoli tissue and the air found within the alveoli. By lowering the surface tension of the alveolar fluid, it reduces the tendency of alveoli to collapse. Surfactant works like a detergent to reduce the surface tension and allows for easier inflation of the airways. When a balloon is first inflated, it takes a large amount of effort to stretch the plastic and start to inflate the balloon. If a little bit of detergent was applied to the interior of the balloon, then the amount of effort or work needed to begin to inflate the balloon would decrease, and it would become much easier to start blowing up the balloon. This same principle applies to the airways. A small amount of surfactant to the airway tissues reduces the effort or work needed to inflate those airways. Babies born prematurely sometimes do not produce enough surfactant. As a result, they suffer from respiratory distress syndrome, because it requires more effort to inflate their lungs. Surfactant is also important for preventing collapse of small alveoli relative to large alveoli. Lung Resistance and Compliance Pulmonary diseases reduce the rate of gas exchange into and out of the lungs. Two main causes of decreased gas exchange are compliance (how elastic the lung is) and resistance (how much obstruction exists in the airways). A change in either can dramatically alter breathing and the ability to take in oxygen and release carbon dioxide. Examples of restrictive diseases are respiratory distress syndrome and pulmonary fibrosis. In both diseases, the airways are less compliant and they are stiff or fibrotic. There is a decrease in compliance because the lung tissue cannot bend and move. In these types of restrictive diseases, the intrapleural pressure is more positive and the airways collapse upon exhalation, which traps air in the lungs. Forced or functional vital capacity (FVC), which is the amount of air that can be forcibly exhaled after taking the deepest breath possible, is much lower than in normal patients, and the time it takes to exhale most of the air is greatly prolonged (Figure). A patient suffering from these diseases cannot exhale the normal amount of air. Obstructive diseases and conditions include emphysema, asthma, and pulmonary edema. In emphysema, which mostly arises from smoking tobacco, the walls of the alveoli are destroyed, decreasing the surface area for gas exchange. The overall compliance of the lungs is increased, because as the alveolar walls are damaged, lung elastic recoil decreases due to a loss of elastic fibers, and more air is trapped in the lungs at the end of exhalation. Asthma is a disease in which inflammation is triggered by environmental factors. Inflammation obstructs the airways. The obstruction may be due to edema (fluid accumulation), smooth muscle spasms in the walls of the bronchioles, increased mucus secretion, damage to the epithelia of the airways, or a combination of these events. Those with asthma or edema experience increased occlusion from increased inflammation of the airways. This tends to block the airways, preventing the proper movement of gases (Figure). Those with obstructive diseases have large volumes of air trapped after exhalation and breathe at a very high lung volume to compensate for the lack of airway recruitment. Dead Space: V/Q Mismatch Pulmonary circulation pressure is very low compared to that of the systemic circulation. It is also independent of cardiac output. This is because of a phenomenon called recruitment, which is the process of opening airways that normally remain closed when cardiac output increases. As cardiac output increases, the number of capillaries and arteries that are perfused (filled with blood) increases. These capillaries and arteries are not always in use but are ready if needed. At times, however, there is a mismatch between the amount of air (ventilation, V) and the amount of blood (perfusion, Q) in the lungs. This is referred to as ventilation/perfusion (V/Q) mismatch. There are two types of V/Q mismatch. Both produce dead space, regions of broken down or blocked lung tissue. Dead spaces can severely impact breathing, because they reduce the surface area available for gas diffusion. As a result, the amount of oxygen in the blood decreases, whereas the carbon dioxide level increases. Dead space is created when no ventilation and/or perfusion takes place. Anatomical dead space or anatomical shunt, arises from an anatomical failure, while physiological dead space or physiological shunt, arises from a functional impairment of the lung or arteries. An example of an anatomical shunt is the effect of gravity on the lungs. The lung is particularly susceptible to changes in the magnitude and direction of gravitational forces. When someone is standing or sitting upright, the pleural pressure gradient leads to increased ventilation further down in the lung. As a result, the intrapleural pressure is more negative at the base of the lung than at the top, and more air fills the bottom of the lung than the top. Likewise, it takes less energy to pump blood to the bottom of the lung than to the top when in a prone position. Perfusion of the lung is not uniform while standing or sitting. This is a result of hydrostatic forces combined with the effect of airway pressure. An anatomical shunt develops because the ventilation of the airways does not match the perfusion of the arteries surrounding those airways. As a result, the rate of gas exchange is reduced. Note that this does not occur when lying down, because in this position, gravity does not preferentially pull the bottom of the lung down. A physiological shunt can develop if there is infection or edema in the lung that obstructs an area. This will decrease ventilation but not affect perfusion; therefore, the V/Q ratio changes and gas exchange is affected. The lung can compensate for these mismatches in ventilation and perfusion. If ventilation is greater than perfusion, the arterioles dilate and the bronchioles constrict. This increases perfusion and reduces ventilation. Likewise, if ventilation is less than perfusion, the arterioles constrict and the bronchioles dilate to correct the imbalance. Link to Learning View the mechanics of breathing. Section Summary The structure of the lungs and thoracic cavity control the mechanics of breathing. Upon inspiration, the diaphragm contracts and lowers. The intercostal muscles contract and expand the chest wall outward. The intrapleural pressure drops, the lungs expand, and air is drawn into the airways. When exhaling, the intercostal muscles and diaphragm relax, returning the intrapleural pressure back to the resting state. The lungs recoil and airways close. The air passively exits the lung. There is high surface tension at the air-airway interface in the lung. Surfactant, a mixture of phospholipids and lipoproteins, acts like a detergent in the airways to reduce surface tension and allow for opening of the alveoli. Breathing and gas exchange are both altered by changes in the compliance and resistance of the lung. If the compliance of the lung decreases, as occurs in restrictive diseases like fibrosis, the airways stiffen and collapse upon exhalation. Air becomes trapped in the lungs, making breathing more difficult. If resistance increases, as happens with asthma or emphysema, the airways become obstructed, trapping air in the lungs and causing breathing to become difficult. Alterations in the ventilation of the airways or perfusion of the arteries can affect gas exchange. These changes in ventilation and perfusion, called V/Q mismatch, can arise from anatomical or physiological changes. Review Questions How would paralysis of the diaphragm alter inspiration? - It would prevent contraction of the intercostal muscles. - It would prevent inhalation because the intrapleural pressure would not change. - It would decrease the intrapleural pressure and allow more air to enter the lungs. - It would slow expiration because the lung would not relax. Hint: B Restrictive airway diseases ________. - increase the compliance of the lung - decrease the compliance of the lung - increase the lung volume - decrease the work of breathing Hint: B Alveolar ventilation remains constant when ________. - the respiratory rate is increased while the volume of air per breath is decreased - the respiratory rate and the volume of air per breath are increased - the respiratory rate is decreased while increasing the volume per breath - both a and c Hint: D Free Response How would increased airway resistance affect intrapleural pressure during inhalation? Hint: Increased airway resistance increases the volume and pressure in the lung; therefore, the intrapleural pressure would be less negative and breathing would be more difficult. Explain how a puncture to the thoracic cavity (from a knife wound, for instance) could alter the ability to inhale. Hint: A puncture to the thoracic cavity would equalize the pressure inside the thoracic cavity to the outside environment. For the lung to function properly, the intrapleural pressure must be negative. This is caused by the contraction of the diaphragm pulling the lungs down and drawing air into the lungs. When someone is standing, gravity stretches the bottom of the lung down toward the floor to a greater extent than the top of the lung. What implication could this have on the flow of air in the lungs? Where does gas exchange occur in the lungs? Hint: The lung is particularly susceptible to changes in the magnitude and direction of gravitational forces. When someone is standing or sitting upright, the pleural pressure gradient leads to increased ventilation further down in the lung.	oercommons	2025-03-18T00:36:08.150216	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15140/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15141/overview	Transport of Gases in Human Bodily Fluids Overview By the end of this section, you will be able to: - Describe how oxygen is bound to hemoglobin and transported to body tissues - Explain how carbon dioxide is transported from body tissues to the lungs Once the oxygen diffuses across the alveoli, it enters the bloodstream and is transported to the tissues where it is unloaded, and carbon dioxide diffuses out of the blood and into the alveoli to be expelled from the body. Although gas exchange is a continuous process, the oxygen and carbon dioxide are transported by different mechanisms. Transport of Oxygen in the Blood Although oxygen dissolves in blood, only a small amount of oxygen is transported this way. Only 1.5 percent of oxygen in the blood is dissolved directly into the blood itself. Most oxygen—98.5 percent—is bound to a protein called hemoglobin and carried to the tissues. Hemoglobin Hemoglobin, or Hb, is a protein molecule found in red blood cells (erythrocytes) made of four subunits: two alpha subunits and two beta subunits (Figure). Each subunit surrounds a central heme group that contains iron and binds one oxygen molecule, allowing each hemoglobin molecule to bind four oxygen molecules. Molecules with more oxygen bound to the heme groups are brighter red. As a result, oxygenated arterial blood where the Hb is carrying four oxygen molecules is bright red, while venous blood that is deoxygenated is darker red. It is easier to bind a second and third oxygen molecule to Hb than the first molecule. This is because the hemoglobin molecule changes its shape, or conformation, as oxygen binds. The fourth oxygen is then more difficult to bind. The binding of oxygen to hemoglobin can be plotted as a function of the partial pressure of oxygen in the blood (x-axis) versus the relative Hb-oxygen saturation (y-axis). The resulting graph—an oxygen dissociation curve—is sigmoidal, or S-shaped (Figure). As the partial pressure of oxygen increases, the hemoglobin becomes increasingly saturated with oxygen. Art Connection The kidneys are responsible for removing excess H+ ions from the blood. If the kidneys fail, what would happen to blood pH and to hemoglobin affinity for oxygen? Factors That Affect Oxygen Binding The oxygen-carrying capacity of hemoglobin determines how much oxygen is carried in the blood. In addition to , other environmental factors and diseases can affect oxygen carrying capacity and delivery. Carbon dioxide levels, blood pH, and body temperature affect oxygen-carrying capacity (Figure). When carbon dioxide is in the blood, it reacts with water to form bicarbonate and hydrogen ions (H+). As the level of carbon dioxide in the blood increases, more H+ is produced and the pH decreases. This increase in carbon dioxide and subsequent decrease in pH reduce the affinity of hemoglobin for oxygen. The oxygen dissociates from the Hb molecule, shifting the oxygen dissociation curve to the right. Therefore, more oxygen is needed to reach the same hemoglobin saturation level as when the pH was higher. A similar shift in the curve also results from an increase in body temperature. Increased temperature, such as from increased activity of skeletal muscle, causes the affinity of hemoglobin for oxygen to be reduced. Diseases like sickle cell anemia and thalassemia decrease the blood’s ability to deliver oxygen to tissues and its oxygen-carrying capacity. In sickle cell anemia, the shape of the red blood cell is crescent-shaped, elongated, and stiffened, reducing its ability to deliver oxygen (Figure). In this form, red blood cells cannot pass through the capillaries. This is painful when it occurs. Thalassemia is a rare genetic disease caused by a defect in either the alpha or the beta subunit of Hb. Patients with thalassemia produce a high number of red blood cells, but these cells have lower-than-normal levels of hemoglobin. Therefore, the oxygen-carrying capacity is diminished. Transport of Carbon Dioxide in the Blood Carbon dioxide molecules are transported in the blood from body tissues to the lungs by one of three methods: dissolution directly into the blood, binding to hemoglobin, or carried as a bicarbonate ion. Several properties of carbon dioxide in the blood affect its transport. First, carbon dioxide is more soluble in blood than oxygen. About 5 to 7 percent of all carbon dioxide is dissolved in the plasma. Second, carbon dioxide can bind to plasma proteins or can enter red blood cells and bind to hemoglobin. This form transports about 10 percent of the carbon dioxide. When carbon dioxide binds to hemoglobin, a molecule called carbaminohemoglobin is formed. Binding of carbon dioxide to hemoglobin is reversible. Therefore, when it reaches the lungs, the carbon dioxide can freely dissociate from the hemoglobin and be expelled from the body. Third, the majority of carbon dioxide molecules (85 percent) are carried as part of the bicarbonate buffer system. In this system, carbon dioxide diffuses into the red blood cells. Carbonic anhydrase (CA) within the red blood cells quickly converts the carbon dioxide into carbonic acid (H2CO3). Carbonic acid is an unstable intermediate molecule that immediately dissociates into bicarbonate ions and hydrogen (H+) ions. Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood down its concentration gradient. It also results in the production of H+ ions. If too much H+ is produced, it can alter blood pH. However, hemoglobin binds to the free H+ ions and thus limits shifts in pH. The newly synthesized bicarbonate ion is transported out of the red blood cell into the liquid component of the blood in exchange for a chloride ion (Cl-); this is called the chloride shift. When the blood reaches the lungs, the bicarbonate ion is transported back into the red blood cell in exchange for the chloride ion. The H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion. This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA. The carbon dioxide produced is expelled through the lungs during exhalation. The benefit of the bicarbonate buffer system is that carbon dioxide is “soaked up” into the blood with little change to the pH of the system. This is important because it takes only a small change in the overall pH of the body for severe injury or death to result. The presence of this bicarbonate buffer system also allows for people to travel and live at high altitudes: When the partial pressure of oxygen and carbon dioxide change at high altitudes, the bicarbonate buffer system adjusts to regulate carbon dioxide while maintaining the correct pH in the body. Carbon Monoxide Poisoning While carbon dioxide can readily associate and dissociate from hemoglobin, other molecules such as carbon monoxide (CO) cannot. Carbon monoxide has a greater affinity for hemoglobin than oxygen. Therefore, when carbon monoxide is present, it binds to hemoglobin preferentially over oxygen. As a result, oxygen cannot bind to hemoglobin, so very little oxygen is transported through the body (Figure). Carbon monoxide is a colorless, odorless gas and is therefore difficult to detect. It is produced by gas-powered vehicles and tools. Carbon monoxide can cause headaches, confusion, and nausea; long-term exposure can cause brain damage or death. Administering 100 percent (pure) oxygen is the usual treatment for carbon monoxide poisoning. Administration of pure oxygen speeds up the separation of carbon monoxide from hemoglobin. Section Summary Hemoglobin is a protein found in red blood cells that is comprised of two alpha and two beta subunits that surround an iron-containing heme group. Oxygen readily binds this heme group. The ability of oxygen to bind increases as more oxygen molecules are bound to heme. Disease states and altered conditions in the body can affect the binding ability of oxygen, and increase or decrease its ability to dissociate from hemoglobin. Carbon dioxide can be transported through the blood via three methods. It is dissolved directly in the blood, bound to plasma proteins or hemoglobin, or converted into bicarbonate. The majority of carbon dioxide is transported as part of the bicarbonate system. Carbon dioxide diffuses into red blood cells. Inside, carbonic anhydrase converts carbon dioxide into carbonic acid (H2CO3), which is subsequently hydrolyzed into bicarbonate and H+. The H+ ion binds to hemoglobin in red blood cells, and bicarbonate is transported out of the red blood cells in exchange for a chloride ion. This is called the chloride shift. Bicarbonate leaves the red blood cells and enters the blood plasma. In the lungs, bicarbonate is transported back into the red blood cells in exchange for chloride. The H+ dissociates from hemoglobin and combines with bicarbonate to form carbonic acid with the help of carbonic anhydrase, which further catalyzes the reaction to convert carbonic acid back into carbon dioxide and water. The carbon dioxide is then expelled from the lungs. Art Connections Review Questions Which of the following will NOT facilitate the transfer of oxygen to tissues? - decreased body temperature - decreased pH of the blood - increased carbon dioxide - increased exercise Hint: A The majority of carbon dioxide in the blood is transported by ________. - binding to hemoglobin - dissolution in the blood - conversion to bicarbonate - binding to plasma proteins Hint: C The majority of oxygen in the blood is transported by ________. - dissolution in the blood - being carried as bicarbonate ions - binding to blood plasma - binding to hemoglobin Hint: D Free Response What would happen if no carbonic anhydrase were present in red blood cells? Hint: Without carbonic anhydrase, carbon dioxide would not be hydrolyzed into carbonic acid or bicarbonate. Therefore, very little carbon dioxide (only 15 percent) would be transported in the blood away from the tissues. How does the administration of 100 percent oxygen save a patient from carbon monoxide poisoning? Why wouldn’t giving carbon dioxide work? Hint: Carbon monoxide has a higher affinity for hemoglobin than oxygen. This means that carbon monoxide will preferentially bind to hemoglobin over oxygen. Administration of 100 percent oxygen is an effective therapy because at that concentration, oxygen will displace the carbon monoxide from the hemoglobin.	oercommons	2025-03-18T00:36:08.179384	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15141/overview", "title": "Biology, Animal Structure and Function", "author": null }
https://oercommons.org/courseware/lesson/15142/overview	Introduction Most animals are complex multicellular organisms that require a mechanism for transporting nutrients throughout their bodies and removing waste products. The circulatory system has evolved over time from simple diffusion through cells in the early evolution of animals to a complex network of blood vessels that reach all parts of the human body. This extensive network supplies the cells, tissues, and organs with oxygen and nutrients, and removes carbon dioxide and waste, which are byproducts of respiration. At the core of the human circulatory system is the heart. The size of a clenched fist, the human heart is protected beneath the rib cage. Made of specialized and unique cardiac muscle, it pumps blood throughout the body and to the heart itself. Heart contractions are driven by intrinsic electrical impulses that the brain and endocrine hormones help to regulate. Understanding the heart’s basic anatomy and function is important to understanding the body’s circulatory and respiratory systems. Gas exchange is one essential function of the circulatory system. A circulatory system is not needed in organisms with no specialized respiratory organs because oxygen and carbon dioxide diffuse directly between their body tissues and the external environment. However, in organisms that possess lungs and gills, oxygen must be transported from these specialized respiratory organs to the body tissues via a circulatory system. Therefore, circulatory systems have had to evolve to accommodate the great diversity of body sizes and body types present among animals.	oercommons	2025-03-18T00:36:08.196713	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15142/overview", "title": "Biology, Animal Structure and Function", "author": null }

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