Human Systems and Homeostasis

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Q How does this ice climber hang on to his body temperature? This climber has to concentrate on every move—one slip could mean serious injury or even death. His body is working just as hard on the inside to provide energy and to maintain a stable body temperature. The climber’s clothes help prevent heat loss, while his body’s internal systems increase his body heat.

R E a d IN g T o o l b o x This reading tool can help you learn the material in the following pages.

USING LANGUAGE Your Turn Analogies Analogies compare words that have similar Use information found in the chapter to complete the relationships. You can write analogies with words or with following analogies. colons. For example, the analogy “up is related to down in 1. heart : pump :: kidney : _____ the same way that top is related to bottom” can be written 2. nervous system : nerves :: endocrine system : _____ “up : down :: top : bottom.” To answer an analogy problem, you must figure out how the words are related. In the example given, up is above down and top is above bottom.

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1.1 Human Biology 28.1

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Main Idea 10c Specialized cells function together in tissues, organs, organ systems, and the whole organism. Specialized, or differentiated, cells are only the first level of organization in a multicellular organism. Scientists organize multicellular structures into five basic levels, beginning with cells and moving to increasingly complex levels— tissues, organs, organ systems, and the whole organism. These five levels in the human body are shown in FIGURE 1.3.

1 Cells Each type of specialized cell has a particular structure and a chemical makeup that enable it to perform a specific task. Some cells in the lungs, for instance, are involved in the exchange of gases. Others secrete mucus that helps to trap foreign particles and to protect the lungs from pathogens, such as bacteria and viruses. 2 Tissues A group of similar cells that work together to perform a specialized function are known as tissue. The human body is made up of four general types of tissues. CONNECT TO • Epithelial tissue consists of protective sheets of tightly packed cells Digestion and connected by special junctions. The skin and the membranes that line Elimination the stomach, the lungs, and other organs are epithelial tissues. In addition to serving as a protective layer, epithelial tissue • Connective tissue serves to support, bind together, and protect other can absorb materials and secrete tissues and organs. Tendons, ligaments, bone, and cartilage are all special types of fluids. Your ability to digest food and connective tissues. eliminate waste depends in part • Muscle tissue is capable of contracting to produce movement. The on the specialized functions of human body contains skeletal, cardiac, and smooth muscle tissues. epithelial tissue, as you will learn in Digestive and • Nervous tissue transmits and receives impulses in response to Excretory Systems. stimuli, processes information, and regulates the body’s response to its environment. 3 Organs A group of tissues that carry out a specialized function of the body form an organ. For example, the lungs are composed of all four types of tissues. Muscle and connective tissues expand and contract the lungs. Nervous tissue sends and receives messages that help regulate gas exchange in the lungs and the rate at which a person breathes. Epithelial tissue forms the inner lining of the lungs. 4 Organ systems Two or more organs that work together to perform body functions form an organ system. The organ system that allows you to breathe includes not only the lungs but also the sinuses, the nasal passages, the pharynx, and the larynx (the voice box). Organ systems perform the most complex activities in the body. 5 Organism Together, the organ systems make up the entire organism. For you or any other organism to stay alive, all of the systems must interact and work together. As a result, anything that harms one organ or organ system will affect the health of the entire body.

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FIGURE 1.3 Five Levels of Organization Biology All levels of organization interact and work together to maintain the body’s health. HMDScience.com GO ONLINE Human Organ Systems 1 cELLs Epithelial lung cell These cells have tiny hairlike structures (cilia) at the top.

2 Tissues Epithelial lung tissue Cells with cilia are packed together in the lung’s inner lining. They act like a conveyor belt to move foreign particles and pathogens out of the lungs.

3 Organs Lungs The lungs are composed of four types of tissue. The lungs are the site where gases are exchanged.

4 Organ Systems Respiratory system This system includes the lungs, trachea, larynx, pharynx, sinuses, and nose. The nose and sinuses filter, moisten, and warm the air before it enters the lungs.

5 Organism Human The respiratory system is one of several organ systems that work together to keep the human body functioning properly.

CRITICAL How might a sinus infection affect the rest VIEWING of the respiratory system? 10c ((t) ©Photo Researchers, Inc.; (c) ©Dr. Willis/Getty Gladden ((t) Images ©Photo Inc.; Researchers, (c) ©Dr.

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FIGURE 1.4 major Organ Systems System Major Tissues and Organs primary function Circulatory heart, blood vessels, blood, lymph nodes, transports oxygen, nutrients, wastes; helps regulate body tem- lymphatic vessels perature; collects fluid lost from blood vessels and returns it to the circulatory system Digestive mouth, pharynx, esophagus, stomach, small⁄large breaks down and absorbs nutrients, salts, and water; eliminates intestines, pancreas, gallbladder, liver some wastes Endocrine hypothalamus, pituitary, thyroid, parathyroid, influences growth, development, metabolism; helps maintain adrenal glands, pancreas, ovaries, testes homeostasis Excretory skin, lungs, kidneys, bladder eliminates waste products; helps maintain homeostasis Immune white blood cells, thymus, spleen protects against disease; stores and generates white blood cells Integumentary skin, hair, nails, sweat and oil glands acts as a barrier against infection, injury, UV radiation; helps regulate body temperature Muscular skeletal, smooth, and cardiac muscles produces voluntary and involuntary movements; helps to cir- culate blood and move food through the digestive system Nervous brain, spinal cord, peripheral nerves regulates body’s response to changes in internal and external environment; processes information

Reproductive male: testes, penis, associated ducts and glands produces reproductive cells; in females, provides environment female: ovaries, fallopian tubes, uterus, vagina for embryo

Respiratory nose, sinuses, pharynx, larynx, trachea, lungs brings in O2 for cells; expels CO2 and water vapor Skeletal bones, cartilage, ligaments, tendons supports and protects vital organs; allows movement; stores minerals; serves as the site for red blood cell production

The major organ systems in the human body, including their main parts and primary functions, are listed in FIGURE 1.4. Keep in mind that all of the organs in these systems developed from specialized cells and tissues that arose from a single cell, the zygote. The major parts and functions of each organ system are examined in greater detail in the following chapters on human body systems. How do these complex organs and organ systems keep functioning and working together properly? As you will read in Section 2, the body has sophisti- cated mechanisms for maintaining a stable internal environment. Compare and Contrast How do tissues differ from organs and organ systems?

Self-check Online HMDScience.com 28.1 Formative Assessment GO ONLINE Reviewing main Ideas Critical thinking CONNECT TO 1. How does the process of cell 3. Apply What organ systems must Cell Cycle determination differ from the work together to bring oxygen to the 5. In the spring, tadpoles lose their process of cell differentiation? body’s cells? 10c tails as part of their life cycle. At a 2. Relate the levels of organization to 4. Predict A cell has undergone determina- certain stage in development, the each other and to the whole human tion to become an endocrine gland cell. human fetus acquires individual body system. 10c If it is transplanted to a leg muscle, what fingers and toes. What occurs in do you think will happen to this cell? some cells of both species to explain these changes?

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Biology IDEO Web V CLIP BIOLOGY Keep an Athlete Hypothermia Maintaining Homeostasis, Running Regulate a runner’s Learn about hypothermia and Skin Find out how sweat homeostasis to get her to its potentially life-threatening and goose bumps help your the end of a course in the consequences. Find out what body maintain homeostasis. best time without stopping. happens when you get so cold that homeostasis breaks down. (c) ©Michael Krasowitz/Getty Images

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28.2 Mechanisms of Homeostasis

4B, 10A, 11A KEY CONCEPT Homeostasis is the regulation and maintenance of the internal environment. VOCABULARY main ideas homeostasis Conditions within the body must remain within a narrow range. feedback Negative feedback loops are necessary for homeostasis. negative feedback positive feedback Connect to Your World The complex tissues, organs, and organ systems in your body must respond to a wide 4B investigate and explain cellular processes, including variety of conditions. For instance, during the summer, you might walk out of a cold, homeostasis, energy conversions, air-conditioned store into a stifling hot, summer day. Your body temperature has to transport of molecules, and synthesis of new molecules; 10A remain the same under both conditions in order for you to survive. In fact, your life describe the interactions that occur depends on your body’s ability to maintain the delicate balance of your internal among systems that perform the functions of regulation, nutrient chemistry. absorption, reproduction, and defense from injury or illness in animals; 11A describe the role of internal feedback mechanisms in the Main Idea 4B, 10A maintenance of homeostasis Conditions within the body must remain within a narrow range. During every moment of your life, trillions of chemical reactions are taking place in your body. The enzymes that control these reactions work best within a narrow range of conditions. One of these conditions is your internal body temperature, which should remain between 36.7°C and 37.1°C (98.2°F and 98.8°F). If it rises only a few degrees, you could easily die from overheating. At temperatures over 41°C (106°F), many enzymes stop functioning. If your internal temperature falls below 27°C (80°F), your heart may fail. Likewise, the levels of trace minerals in your body must stay within strict limits. For instance, if calcium levels are too high, you can slip into a coma. If they are too low, your heartbeat becomes irregular. Biology HMDScience.com You live in a constantly changing environment. Your body must cope not GO ONLINE only with temperature changes but also with pollution, infection, stress, and many other conditions. Every change is a challenge to your body. What keeps Keep an Athlete Running the human body from breaking down every time the internal or external environment changes? Homeostasis and the Internal Environment REA d i N G TO OLB ox Fortunately, the body has many control systems that keep its internal environ- VOCABULARY ment stable. Together, these control systems are responsible for maintaining The word homeostasis is homeostasis. Homeostasis (ho-mee-oh-STAY-sihs) is the regulation and formed from two Greek words: maintenance of the internal environment—temperature, fluids, salts, pH, homos, meaning “similar,” and nutrients, and gases—within the narrow ranges that support human life. Your stasis, meaning “standing” or “stopping.” internal control systems respond quickly to environmental change, whether from outside conditions or internal ones, as shown in Figure 2.1.

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Control Systems in the Body FIGURE 2.1 Homeostasis and Change Internal control systems require Control systems in the skin help reduce or conserve body heat. sensors, a control center, communication systems, and targets.

Sensors Sensors, also called above normal Blood flow to the receptors, gather information about pore skin increases. Tiny muscles conditions inside and outside of the expand the pores. body. In cold or hot weather, for Sweat glands instance, sensors in your skin and release water to sweat cool the body. nasal passages gather data about gland air temperatures. The body has normal temperature thousands of internal sensors and Pores and other specialized sensors that detect muscles are changes in the outside world. relaxed. Blood Control center A control center, often flow to the skin is normal. Sweat the brain, receives information from hair glands are not the sensors. It then compares this follicle active. muscle information to the set points, or ideal values, at which the body functions goose Blood flow to the below normal best. When conditions move above or bump skin decreases. below a set point, the control center Tiny muscles responds by sending messages contract the pores and the through a communication system. skin around Communication systems Communi- body hairs to cation is controlled by the nervous conserve heat. system and the endocrine system, which carry messages to all parts of Apply if the girl in cold temperature starts jogging, how would the the body. These messages, in the form control mechanisms in her skin respond as she runs? 4B, 10A of nerve impulses or hormones, tell targets in the body how to respond to internal or external changes. Biology VIDEO C Targets A target is any organ, tissue, or cell that changes its level of activity in LIP response to a message. For instance, in a cold environment, a message might HMDScience.com cause the muscles to start shivering to generate more body heat. GO ONLINE Explain Why is it so important to maintain homeostasis within the body? Maintaining Homeostasis, Skin 10A

Main Idea 4B, 10A, 11A Negative feedback loops are necessary for homeostasis. Sensors, control centers, communication systems, and targets work together in what is known as a feedback loop. Feedback is information from sensors that allows a control center to compare current conditions to a set of ideal values. In a feedback loop, information moves continuously among sensors, a control center, and a target. Most functions in the body are regulated by negative

(tr) Adamski ©Lori Peek/Getty Images; (cr) ©age fotostock/SuperStock; (br) ©Steve Mason/Photodisc Green/Getty Images feedback loops.

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Negative Feedback In negative feedback, a control system counteracts any change in the body that moves conditions above or below a set point. Negative feedback loops help maintain homeostasis. A thermostat is a good example of how a negative feedback loop works. A sensor in the thermostat continuously measures air temperature in a room. A control mechanism then compares the current room temperature to a set point, say 21°C (69.8°F). When the temperature falls below 21°C, the thermostat sends an electronic message that turns on the furnace. When the air temperature is at or just above 21°C, the thermostat sends another message that turns off the furnace. As a result, the room always stays within a few degrees of the desired temperature. CONNECT TO Negative feedback loops are the reason why you cannot hold your breath Biochemistry for a long time. The control systems involved in this feedback loop are shown in Figure 2.2. As you hold your breath, sensors in the circulatory and respira- As you read in Cells and Energy, cells require a constant supply tory systems send information to the brain stem, the body’s respiratory control of oxygen to maintain cell center. Sensors signal a gradual increase in carbon dioxide (CO2) and a metabolism. Oxygen is not decrease in oxygen (O ). The control center compares this information with stored in the human body in any 2 great amounts. Once oxygen the set points for these gases. When the change becomes too great, the control reserves have been used up, the center takes steps to counteract it. Messages are sent to the muscles of the body must have a fresh supply diaphragm and the rib cage to relax and then contract, forcing you to exhale of oxygen to prevent cell death. and then inhale deeply. At this point, you cannot stop these muscles from moving. You will continue to breathe rapidly and deeply until the gas levels return to their set points.

FIGURE 2.2 Negative Feedback Loop Negative feedback counteracts any change in the body that moves conditions away from a set point.

You inhale and hold your breath. When O2 /CO2 levels The O2 levels in the blood begin to are restored, normal decline and CO2 levels begin to rise. breathing resumes.

1 5

2 Sensors alert the brain stem as O /CO levels You continue to 2 2 move too far from the set inhale and exhale points. Messages are sent more deeply and 4 through the nervous and rapidly than nor- endocrine systems to the mal until O /CO 2 2 muscles of the diaphragm levels return to 3 and the rib cage. their set points.

The muscles of the diaphragm and the rib cage relax, forcing you to exhale. As the muscles contract, you inhale deeply.

Infer if you continued to breathe rapidly and deeply for too long in Step 4, how would this affect the negative feedback loop? 10A, 11A

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QUICKLAB Modeling 11A

Negative Feedback Loop MaterialS You can experience a negative feedback loop by doing a hardcover book at least 6" 3 9" simple demonstration. Problem How does a negative feedback loop work? Procedure 1. Balance the hardcover book on your head. 2. Walk 3 meters forward and backward—once with eyes open, then with eyes closed. Analyze and Conclude 1. Analyze Summarize the negative feedback loop that helped keep the book balanced on your head. How did closing your eyes affect your ability to balance the book? 2. Connect Describe the role of internal feedback mechanisms in the maintenance of homeostasis.

Positive Feedback Negative feedback loops maintain homeostasis by counteracting, or reversing, change to return conditions to their set points. In some cases, however, the body actually needs change to accomplish a specific task. In positive feedback, a control center uses information from sensors to increase the rate of change away from the set points. Though not as common in the body, this type of feedback is important whenever rapid change is needed. If you cut your finger, positive feedback mechanisms increase the rate of change in clotting factors in the blood until the wound is sealed. Once the injury heals, another positive feedback loop occurs as chemicals are released to dissolve the clot. Positive feedback also occurs in the release of certain growth hormones during puberty. Your body needs higher levels of these hormones to accomplish all of the changes that take place at this time. Infer Why are most of the functions of the body regulated by negative, rather than by positive, feedback mechanisms? 11A Self-check Online HMDScience.com 28.2 Formative Assessment GO ONLINE Reviewing Main Ideas Critical thinking CONNECT TO 1. A system to maintain homeostasis 3. Predict When a newborn baby Zoology must have at least four parts that nurses, the mother’s body is 5. Reptiles regulate their body function together. Name these stimulated to produce milk. What temperature by changing parts, and briefly explain what each would happen to the milk supply if their environment. A snake, one does. 4B the mother chose to bottle feed for instance, must lie in 2. What is the main difference rather than breast feed? Why? sunlight to warm its body. between the way negative feedback 4. Sequence Suppose you go on Mammals can regulate their and positive feedback loops regulate a long hike in hot weather. Describe internal environment to gain change in the body? a possible negative feedback loop or lose body heat. How 4B, 11A that would keep your body from might this ability give overheating. 4B, 11A mammals an advantage over reptiles?

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Figure 3.1 thermoregulation VOCABULARY whole system levels to each other andto the biological systems andrelate the analyze thelevels oforganization in injury orillness inanimals; 10C reproduction, anddefense from of regulation, nutrientabsorption, systems that perform thefunctions interactions that occur among from data; 10Adescribe the make inferences, andpredict trends order. at therighttimeandin every organ system doing itsjob Likewise, your life dependson the secret to apitcrew’s success. Unit 9:HumanBiolog 2Ganalyze, evaluate, 28.3

Precision teamwork is 2G, 10A, 10C y Interactions AmongSystems and places thedriver at serious risk. checking theengine.Ifanyone fails to doajobproperly, itaffects theentire team one memberjacks upthecar, others are changingthetires, infuel,and putting person hasaspecial role that mustbecoordinated withtheefforts oftheteam. As The momentaracecar infor pulls apitstop, thepitcrew springs into action. Each Connect to Your World KEY CONCEPT Each organEach system organ other affects systems.

mally. Adults bone lose mass, which means bones their break more easily. decreases. Without enough vitamin D, children’s bones do not develop nor- organ along path this fails to do its job, level the of vitamin body Dinthe body.in the two These minerals are essential for building strong bones. If any interacts with hormones that regulate amount the of calcium and phosphorus is converted into active vitamin D. another compound, Here, to kidneys. whichthe is carried then compound this to liver. the carried The liver changes inactive the form of vitamin Dinto form of vitamin D. As substance that presence inthe of ultraviolet light is changed into an inactive systemendocrine are for process necessary this as well. The skincontains a your body. You may not know that liver, the circulatory kidneys, system, and You may know that sunlight plays production inthe apart of vitamin Din Vitamin entire body. among organ systems means that what asingle affects organ system the affects oftype community regulated by feedback mechanisms. This interaction interact with one another. On alarger of all organ the scale, systems form a At its most is basic level, acommunity body the cells that of specialized hot or cold weather. organs are others, affecting as regulation inthe of your temperature body in substance such as vitamin D. In other you cases, are more aware that some systems is not always obvious—for example, produces body the when a messages impulses. and nerve The relationship among your organs and organ system must also coordinate with other organ systems through chemical your must body do its job. own special But for you to remain healthy, each Mai m

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Production Systems interact to maintain homeostasis. 10A, 10C 10A, Figure 3.2

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FIGURE 3.2 Vitamin D Production Each organ plays a critical role in the production of vitamin D.

UV light 1 UV light strikes the skin, producing an inactive form of vitamin D.

Inactive vitamin D circulates in the 2 Active vitamin D and blood to the liver, where it is changed 4 hormones regulate the into an intermediate compound. amount of calcium and phosphorus needed for 3 The intermediate compound is bone development. carried to the kidneys, where it is converted into active vitamin D. Identify Which organs are involved in the production of vitamin D?

Regulation of Body Temperature The process by which the body regulates its internal temperature under a variety CONNECT TO of conditions is known as thermoregulation (thur-moh-rehg-yoo-LAY- Animals shuhn). The most obvious organ systems involved in maintaining body tem- In A Closer Look at Amniotes, perature are the skin and muscles. You VISUAL VOCAB you learned that animals have sweat in hot weather and shiver when many ways of regulating their Thermoregulation maintains a you are cold. However, far more is going body temperatures. Some animals stable body temperature under a stay cool by panting, by being on than what you can see on the surface. variety of conditions, just as a active only at night, or by getting Thermoregulation requires the close thermostat regulates a furnace. Both rid of excess heat through their interaction of the respiratory, circula- mechanisms use feedback to keep body structures, such as large ears temperatures within set ranges. or thin skins. tory, nervous, and endocrine systems. control Sensors in the skin and blood vessels messages provide information about body tem- thermostat perature to a control center in the brain i furnace called the hypothalamus. The hypothal- n f o to target amus protects the body’s internal organs control by monitoring temperature. When the hypothalamus receives information that the temperature of the blood is rising, Web

it sends messages through the nervous and endocrine systems. These messages HMDScience.com activate the sweat glands, dilate, or widen, blood vessels in the skin, and GO ONLINE increase both heart and breathing rates. All of these activities carry heat away Hypothermia from the center of the body to the surface, where excess heat can escape. When the temperature of the blood falls too low, the hypothalamus sends another set of signals to the skin and to the muscular, respiratory, and circulatory systems. Blood vessels in the skin constrict, reducing blood flow to prevent loss of heat. Muscles in the skin contract around the pores, reducing their size. Rapid, small contractions of skeletal muscles cause shivering. The thyroid gland releases hormones that increase metabolism. All of these activities increase body heat production and reduce the loss of heat to the environment. Infer If a person’s circulatory system does not function well, how might thermoregulation in his or her body be affected? 10A

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Main Idea 10A A disruption of homeostasis can be harmful. Some changes may be too great or too rapid for your body to control through feedback mechanisms. Homeostasis can be disrupted for several reasons. • Sensors fail to detect changes in the internal or external environment. • Wrong messages may be sent or the correct ones fail to reach their targets. • Serious injuries can overwhelm the homeostatic mechanisms. • Viruses or bacteria can change the body’s internal chemistry. Disruption of homeostasis can begin in one organ or organ system and result in a chain reaction that affects other organs and organ systems. These effects can be harmful to your body over the short or long term. Short-Term Effects Short-term effects usually last a few days or weeks. For example, when a cold virus first enters your body, your immune system may not be able to prevent the virus from multiplying. As a result, you develop a sore throat, runny nose, and dry cough, and your muscles and joints become inflamed. However, within a few days, your body’s immune system begins to kill the virus and to restore homeostasis. Usually, there is no lasting harm to your body. FIGURE 3.3 Type 1 Diabetes Failure to control glucose levels affects the entire body. Long-Term Effects A long-term disruption of homeostasis, as in the case of diabetes, can cause more damage. Diabetes occurs when the body fails to control the amount of glucose circulating in the blood. 1 Pancreas cells are attacked Normal glucose control Glucose levels are by the immune system. controlled by two hormones—insulin and gluca- Insulin production decreases, and cells cannot remove gon—which are released by the pancreas. When glucose from the blood. glucose in the blood rises above a set point, beta cells in the pancreas release insulin. Insulin causes 2 Blood glucose levels rise. The kidneys excrete the excess cells to take in more glucose from the blood and glucose along with large causes the liver to store glucose as glycogen. When amounts of water. blood glucose levels fall below the set point, alpha 3 The body begins to use fat cells in the pancreas release glucagon. This hor- stored in the tissues as an pancreas energy source. As fat breaks mone stimulates the liver to break down stored fat down, the blood becomes glycogen into glucose and release it until levels in more acidic. the blood rise to the set point. 4 With changes in pH and fluid Type 1 and type 2 diabetes What if the pancreas balance, cell metabolism is impaired. Cells throughout fails to do its job? The result can be diabetes the body function poorly or mellitus, a condition in which the body can no kidneys die, affecting every organ longer regulate glucose levels. There are two types system. of diabetes. Type 1 occurs when the body’s immune system destroys the ability of beta cells Apply How might the to produce insulin. Type 2 is caused when insulin muscular system be affected production decreases or when insulin cannot by type 1 diabetes? 10c move glucose into cells.

828 Unit 9: Human Biology high glu co se Blood levels Blood

low 0 50 100 150 200 250 Time (min)

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n go ca glu Blood levels Blood low 0 50 100 150 200 250 DATA ANALYSIS 2G Time (min)

Interpreting Inverse Relationships Graph 1. insulin levels Graph 2. glucose levels Two variables are inversely related if an increase high high high in the value of one variable is associated with a glu gcluo csoe decrease in the value of the other variable. For se ins example, the level of insulin decreases the longer ulin a person exercises. Therefore, insulin levels have Blood levels Blood Blood levels Blood an inverse relationship with exercise time. The levels Blood low graphs at right show the levels of insulin, glucose, low low0 50 100 150 200 250 0 50 100 150 200 250 0 50 100 150 200 250 Time (min) and glucagon during moderate exercise over 250 Time (min) Time (min) minutes. Use the graphs to answer the questions. Graph 3. glucagon levels

high 1. Analyze Which variable(s) has/have an inverse relationship with time? high

n 2. Conclude What relationship exists between glucagon and the other o n ag o two variables (insulin and glucose)? Explain. c ag glu c glu Blood levels Blood Blood levels Blood low low0 50 100 150 200 250 0 50 100 150 200 250 Time (min) In type 1 diabetes, the failure of the pancreas sets up a destructive chain Time (min) reaction in other organ systems, as shown in Figure 3.3. As glucose builds up in the blood, the kidneys must remove it along with large amounts of water. high Also, since the body is unable to use glucose as an energy source, it must use high stored fat instead. As the fat breaks down, the blood becomes more acidic. Biology IDEO V ins C This altered pH disrupts the metabolism of the cells in every organ and every inusli LIP unlin system in the body. The long-term effects can result in heart disease, blindness, HMDScience.com Blood levels Blood nerve damage, kidney damage, and even coma and death. levels Blood GO ONLINE low lowDiabetes0 50 and 100 150the Immune 200 250 In type 2 diabetes, the pancreas cannot produce enough insulin, or the 0 50 100 150 200 250 System Time (min) insulin cannot be used to move glucose into the cells. As a result, blood Time (min) glucose levels rise, and the cells starve. Risk factors for developing type 2 diabetes include chronic obesity, a family history of diabetes, and aging. Connect Why might diabetes be a particular problem for an athlete?

Self-check Online HMDScience.com 28.3 Formative Assessment GO ONLINE Reviewing mAIN Ideas Critical thinking CONNECT TO 1. Why do the organ systems in the 3. Analyze Why would giving synthetic Evolution body need to work so closely insulin to people with type 1 diabetes 5. Some animals can store more together? 10c restore their glucose homeostasis? glucose—in the form of 2. Explain why a long-term disruption 4. Predict If you lived in Alaska for glycogen—in their bodies of homeostasis can often be more the whole year, what changes than can other animals. What damaging to the body than a might occur in your calcium and might be the evolutionary short-term disruption. phosphorus levels during the winter advantage of having these versus the summer? Explain. extra energy stores?

Chapter 28: Human Systems and Homeostasis 829 CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” Unit 830

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CHAPTER 28 TOOLBOXREADING

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thermoregula positive f feedback relates to what happensinafeedback loop. using amicrophone. Explain how this meaning of that loud squeal you sometimes hear whensomeone is signal putoutby anamplifier returns to itssource. It’s electrical Feedback engineering. occurs ofa whenpart The word term thermoregulation? “hot” or“warm.” How doesthismeaning relate to the word comes from theGreek thermos, whichmeans A thermos isacont based onthemeaning ofthese two parts. or “stopping.” Write abriefdefinitionofhomeostasis homos, meaning “similar,” andstasis, meaning “standing” The word this meaning relates to thedefinitionofalivingorgan. meaning “instrument”or“impl The word organ comes from theLatin word organum, negativ differenti determination organ s organ tissue

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the body’s homeo Give two examples ofwhat can happen to aperson if When glucos failur Explain how thefailure ofoneorgan can lead to the negative feedback loop? Explain your answer. decline. Isthisprocess anexample ofapositive ora hormones are released that cause theglucose levels to how each level relates to thenext usinganexample. Name each ofthelevels oforganization, anddescribe hands andfeet. both neededto develop suchstructures ashuman Briefly e what happensnext asthecells develop intheembryo? Once acel during theprocess ofdetermination? ty Embryonic stem cells have thepotential to become any the maintenanc Describe therole of internal feedback mechanismsin sensors work together to helpyou stay cool? On ahot day, how doyour body’s control center and conditions withinthenarr Your bodyhascontrol systems that keep itsinternal the lungs to well. function specialized cells intherespiratory system that enable enable themt Organs have manyspecialized cells andtissues that Humans are compo pe ofcell inthebody. What happensto these cells e ofother organs orofanentire organ system. HMDScience.com Interact 10 10C xplain how cell differentiation andcell death are a

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831 DO NOT EDIT--Changes must be made through “File info” CorrectionKey=B

Critical Thinking 23. Compare Explain how the cells in the human body Analyzing Data Interpret an Inverse Relationship might be similar to various building materials in The graph below shows the relationship between 10c a house. different types of energy yield during exercise. Use 24. Infer Scientists are investigating methods to use the graph to answer the next three questions. embryonic stem cells to repair any tissue in the human body. What characteristic of embryonic stem cells could EXERCISE AND ENERGY YIELD make this type of treatment possible? 100 aerobic 80 25. Analyze Review the chart of organ systems on the last energy yield page of Section 1. Identify some interconnections 60 between the immune system and the circulatory system. Percent 10c 40 anaerobic 26. Apply Describe which organ systems you think would 20 energy yield be involved in maintaining homeostasis when a person gives a major speech or presentation. Include what may 0 5 10 15 be happening within the person just before, during, and Time (min) after the speech. 10c 27. Explain For various specialized cells to work together, they must communicate with one another. Use the 33. Compare and Contrast Within what time period information you learned in the chapter Cell Structure does the greatest amount of change occur in both and Function about cell parts to describe how you think variables? a neuron might communicate with a muscle cell. 34. Analyze Which variable is inversely related to time? 28. Compare and Contrast Explain how the difference Explain. between negative and positive feedback makes negative feedback more effective in maintaining homeostasis in 35. Conclude What relationship do the two variables have the body. 11a to each other at the beginning and at the end of the exercise period? 29. Describe People with weak or damaged hearts often have trouble regulating their body temperatures in a hot or a cold environment. Explain why an impaired Making Connections heart might make a person less able to maintain 36. Communicate Blogs have become a popular form of homeostasis. 10A communicating personal experiences online. Think about the changes that occur in your body when you wake up Analyzing Visuals in the morning—changes in your heart rate, in your Use the diagram of the digestive system to answer the breathing, and in the movements of your arms and legs. next three questions. Describe in a blog entry some of the environmental and physical changes that you experience. Which organ 30. Analyze Why is this considered salivary systems seem to be involved? What feedback loops 10c an organ system? glands might be working to make sure such changes do not 10a, 11A 31. Infer How do you think the mouth become too great? nutrients released from food esophagus 37. Interpret Extreme sports test the limits of the human leave the digestive system and body. Describe one extreme condition, other than travel throughout the body? temperature, facing the ice climber in the photograph 10c stomach liver on the chapter opener. Explain how feedback mecha- 32. Relate When a person is sick nisms in the climber’s body can maintain homeostasis under the extreme condition you choose to describe. and is vomiting, how does 11a this condition affect the organ system and its ability to provide nutrients to intestines the body? 10c

832 Unit 9: Human Biology Biology End-of-Course Exam Practice

Record your answers on a separate piece of paper. 4B, 11B MULTIPLE CHOICE 4 No matter what the temperature is outside, the human body temperature stays relatively constant 2E at about 98.6°F. This is part of the body’s ability to 1 A group of scientists investigates how the blood maintain — pressure of students changes while taking an A osmoregulation exam. To properly control their experiment, the B homeostasis scientists must first select the appropriate C negative feedback loops equipment and measure the — D positive feedback loops A number of questions on the exam B students’ grade point averages 11A C temperature and humidity of the exam room 5 The kidneys filter wastes and excess salts from the D students’ blood pressure before the exam blood. If salt concentrations are low, negative feedback mechanisms would most likely — 2G, 11A A decrease the amount of salts removed 2 The hormone glucagon increases blood sugar B increase the amount of salts removed levels while the hormone insulin reduces blood C slow down overall kidney function sugar levels. When blood sugar becomes too high, what is most likely to happen to insulin and D increase the rate of kidney function glucagon levels for the body to maintain THINK THROUGH THE QUESTION homeostasis? Think about what the body needs to do to maintain A Insulin levels increase and glucagon levels homeostasis in this situation. Remember, the decrease. feedback mechanism should affect only salt B Insulin and glucagon levels remain the same. concentration. C Glucagon levels increase and insulin levels decrease. D Insulin and glucagon levels decrease. 10A 6 Which characteristic best fits in the overlapping 10A area of the Venn diagram below? 3 Why is it important that oxygen and carbon dioxide levels be closely regulated in the human body? excretory respiratory A Both gases are needed for the proper system system functioning of cell processes. B Oxygen is needed for cell processes and carbon A absorbs nutrients dioxide is a waste product. B brings in oxygen C Both gases are waste products that need to be removed from cells. C transports oxygen D The carbon and oxygen from the gases are D removes wastes needed to build new molecules.

Chapter 28: Human Systems and Homeostasis 833