Hormones and the Endocrine System

Hormones and the Endocrine System
Chapter 26 Hormones and the Endocrine System

Introduction In lions, the hormone testosterone promotes the development and maintenance of male traits including growth and maintenance of the mane and increased height and weight. © 2012 Pearson Education, Inc. 2

The Nature of Chemical Regulation The Vertebrate Endocrine System
Figure 26.0_1 Chapter 26: Big Ideas Hypothalamus The Nature of Chemical Regulation The Vertebrate Endocrine System Figure 26.0_1 Chapter 26: Big Ideas Hormones and Homeostasis 3

Figure 26.0_2 Figure 26.0_2 Phenotypic difference between the sexes (Panthera leo) 4

THE NATURE OF CHEMICAL REGULATION
THE NATURE OF CHEMICAL REGULATION Copyright © 2009 Pearson Education, Inc. 5

26.1 Chemical signals coordinate body functions
The endocrine system consists of all hormone-secreting cells and works with the nervous system in regulating body activities. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The nervous and endocrine systems coordinate and regulate most other systems of the body. You might consider comparing the speed and duration of each system’s response. The nervous system generally responds faster but for a shorter duration than the endocrine system. This helps to explain why it takes many minutes for a person to calm down after a very upsetting event. The hormones do not clear quickly from the systems. © 2012 Pearson Education, Inc. 6

The nervous system also communicates, regulates, and uses electrical signals via nerve cells. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The nervous and endocrine systems coordinate and regulate most other systems of the body. You might consider comparing the speed and duration of each system’s response. The nervous system generally responds faster but for a shorter duration than the endocrine system. This helps to explain why it takes many minutes for a person to calm down after a very upsetting event. The hormones do not clear quickly from the systems. © 2012 Pearson Education, Inc. 7

Comparing the endocrine and nervous systems The nervous system reacts faster. The responses of the endocrine system last longer. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The nervous and endocrine systems coordinate and regulate most other systems of the body. You might consider comparing the speed and duration of each system’s response. The nervous system generally responds faster but for a shorter duration than the endocrine system. This helps to explain why it takes many minutes for a person to calm down after a very upsetting event. The hormones do not clear quickly from the systems. © 2012 Pearson Education, Inc. 8

Hormones are chemical signals, produced by endocrine glands, usually carried in the blood, and responsible for specific changes in target cells. Hormones may also be released from specialized nerve cells called neurosecretory cells. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The nervous and endocrine systems coordinate and regulate most other systems of the body. You might consider comparing the speed and duration of each system’s response. The nervous system generally responds faster but for a shorter duration than the endocrine system. This helps to explain why it takes many minutes for a person to calm down after a very upsetting event. The hormones do not clear quickly from the systems. © 2012 Pearson Education, Inc. 9

Endocrine cell Hormone molecules
Figure 26.1A Secretory vesicles Endocrine cell Hormone molecules Blood vessel Figure 26.1A Hormone from an endocrine cell Target cell 10

Neurotransmitter molecules
Figure 26.1B Nerve cell Nerve signals Neurotransmitter molecules Figure 26.1B Neurotransmitter from a nerve cell Nerve cell 11

26.2 Hormones affect target cells using two main signaling mechanisms
Two major classes of molecules function as hormones in vertebrates. The first class includes hydrophilic (water-soluble), amino-acid-derived hormones. Among these are proteins, peptides, and amines. The second class of hormones are steroid hormones, which include small, hydrophobic molecules made from cholesterol. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal-transduction pathway. Pushing the doorbell, like a hormone binding to plasma-membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. © 2012 Pearson Education, Inc. 12

Hormone signaling involves three key events: reception, signal transduction, and response. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal-transduction pathway. Pushing the doorbell, like a hormone binding to plasma-membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. © 2012 Pearson Education, Inc. 13

An amino-acid-derived hormone binds to plasma-membrane receptors on target cells and initiates a signal transduction pathway. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal-transduction pathway. Pushing the doorbell, like a hormone binding to plasma-membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. Animation: Water-Soluble Hormone © 2012 Pearson Education, Inc. 14

Water-soluble hormone
Figure 26.2A_s1 Interstitial fluid Water-soluble hormone Receptor protein 1 Plasma membrane Target cell Figure 26.2A_s1 A hormone that binds a plasma membrane receptor (step 1) Nucleus 15

Figure 26.2A_s2 Interstitial fluid Water-soluble hormone Receptor protein 1 Plasma membrane Target cell 2 Signal transduction pathway Relay molecules Figure 26.2A_s2 A hormone that binds a plasma membrane receptor (step 2) Nucleus 16

Figure 26.2A_s3 Interstitial fluid Water-soluble hormone Receptor protein 1 Plasma membrane Target cell 2 Signal transduction pathway Relay molecules Figure 26.2A_s3 A hormone that binds a plasma membrane receptor (step 3) 3 Cellular responses Cytoplasmic response or Gene regulation Nucleus 17

A steroid hormone can diffuse through plasma membranes, bind to a receptor protein in the cytoplasm or nucleus, and form a hormone-receptor complex that carries out the transduction of the hormonal signal. Student Misconceptions and Concerns 1. Student comprehension of the two mechanisms by which hormones trigger changes in target cells relies upon a good understanding of cell membranes and basic cellular chemistry. If these subjects have not been taught recently in your course, consider giving students a brief refresher before distinguishing between these mechanisms. 2. Students might not appreciate the diverse ways in which coordination and communication are achieved between the body’s cells. Endocrine signals generally work like a radio transmitter, sending signals outward. Only target cells, like people with radios tuned to a particular frequency, will receive the signal. In contrast, the nervous system provides a direct, two-way connection between the sender and receiver, much more like a land-based telephone call. Teaching Tips The two mechanisms by which hormones trigger changes in target cells can be compared using this analogy. If a house is like a cell, ringing the doorbell and having someone answer it is like using a signal-transduction pathway. Pushing the doorbell, like a hormone binding to plasma-membrane receptors, causes an internal change. Using steroid hormones, on the other hand, is like walking up to the house, opening the door, and walking inside to deliver a message. Here the signal passes through the surface and into the interior of the home/cell to directly communicate the message. Animation: Lipid-Soluble Hormone © 2012 Pearson Education, Inc. 18

Interstitial fluid Steroid hormone Target cell Nucleus Figure 26.2B_s1
Figure 26.2B_s1 A hormone that binds an intracellular receptor (step 1) 19

Interstitial fluid Steroid hormone Target cell Receptor protein
Figure 26.2B_s2 Interstitial fluid Steroid hormone 1 Target cell 2 Receptor protein Nucleus Figure 26.2B_s2 A hormone that binds an intracellular receptor (step 2) 20

Hormone- receptor complex
Figure 26.2B_s3 Interstitial fluid Steroid hormone 1 Target cell 2 Receptor protein 3 Nucleus Hormone- receptor complex DNA Figure 26.2B_s3 A hormone that binds an intracellular receptor (step 3) 21

Cellular response: activation of a gene and synthesis of new protein
Figure 26.2B_s4 Interstitial fluid Steroid hormone 1 Target cell 2 Receptor protein 3 Nucleus Hormone- receptor complex DNA 4 Transcription Figure 26.2B_s4 A hormone that binds an intracellular receptor (step 4) mRNA New protein Cellular response: activation of a gene and synthesis of new protein 22

THE VERTEBRATE ENDOCRINE SYSTEM
THE VERTEBRATE ENDOCRINE SYSTEM © 2012 Pearson Education, Inc. 23

26.3 Overview: The vertebrate endocrine system consists of more than a dozen major glands
Some endocrine glands (such as the thyroid) primarily secrete hormones into the blood. Other glands (such as the pancreas) have endocrine and nonendocrine functions. Other organs (such as the stomach) are primarily nonendocrine but have some cells that secrete hormones. Student Misconceptions and Concerns Appreciating the precise actions of hormones requires a thorough understanding of the specificity of target cells. The fact that only certain target cells will respond to a given hormone signal allows hormones to be “broadcast” generally throughout the circulatory system without affecting every single cell. Teaching Tips Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the potential benefits and risks of human growth hormone injections in the elderly. © 2012 Pearson Education, Inc. 24

The following figure shows the locations of the major endocrine glands. Student Misconceptions and Concerns Appreciating the precise actions of hormones requires a thorough understanding of the specificity of target cells. The fact that only certain target cells will respond to a given hormone signal allows hormones to be “broadcast” generally throughout the circulatory system without affecting every single cell. Teaching Tips Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the potential benefits and risks of human growth hormone injections in the elderly. © 2012 Pearson Education, Inc. 25

Ovaries (female) Testes (male)
Figure 26.3 Hypothalamus Thyroid gland Pituitary gland Parathyroid glands (embedded within thyroid) Thymus Adrenal glands (atop kidneys) Pancreas Figure 26.3 The major endocrine glands in humans Ovaries (female) Testes (male) 26

The following table summarizes the main hormones produced by the major endocrine glands and indicates how they function and are controlled. Student Misconceptions and Concerns Appreciating the precise actions of hormones requires a thorough understanding of the specificity of target cells. The fact that only certain target cells will respond to a given hormone signal allows hormones to be “broadcast” generally throughout the circulatory system without affecting every single cell. Teaching Tips Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the potential benefits and risks of human growth hormone injections in the elderly. © 2012 Pearson Education, Inc. 27

Table 26.3 Table 26.3 Major Human Endocrine Glands and Some of Their Hormones 28

Table 26.3_1 Table 26.3_1 Major Human Endocrine Glands and Some of their Hormones (Part 1) 29

Table 26.3_2 Table 26.3_2 Major Human Endocrine Glands and Some of their Hormones (Part 2) 30

Two endocrine glands are not discussed further. The pineal gland is pea-sized, located near the center of the brain, and secretes melatonin, a hormone that links environmental light conditions with biological rhythms. The thymus gland lies above the heart, under the breastbone, and secretes a peptide that stimulates the development of T-cells. Student Misconceptions and Concerns Appreciating the precise actions of hormones requires a thorough understanding of the specificity of target cells. The fact that only certain target cells will respond to a given hormone signal allows hormones to be “broadcast” generally throughout the circulatory system without affecting every single cell. Teaching Tips Growth hormone levels typically decline as we age. Recent studies suggest that injections of engineered human growth hormone may promote muscle growth and decrease body fat. However, additional research is necessary to fully appreciate the potential benefits and risks of human growth hormone injections in the elderly. © 2012 Pearson Education, Inc. 31

26.4 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems The hypothalamus blurs the distinction between endocrine and nervous systems, receives input from nerves about the internal conditions of the body and the external environment, responds by sending out appropriate nervous or endocrine signals, and uses the pituitary gland to exert master control over the endocrine system. Student Misconceptions and Concerns The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. Although this is mentioned briefly in the text, consider emphasizing further the potential negative consequences of the abuse of these powerful hormones. The National Institute of Health provides additional details on its website at Teaching Tips 1. Morphine and other opiates bind to the same cell receptors that naturally bind endorphins, producing powerful pain-killing effects. 2. Students may not have carefully considered the benefits of pain. Consider emphasizing the adaptive nature of pain to your class. The authors note the risks of stopping pain in an injured part of the body. Based on this, challenge students to propose explanations as to why endorphins nonetheless evolved. © 2012 Pearson Education, Inc. 32

Brain Hypothalamus Posterior pituitary Anterior pituitary Bone
Figure 26.4A Brain Hypothalamus Figure 26.4A Location of the hypothalamus and pituitary Posterior pituitary Anterior pituitary Bone 33

26.4 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems The pituitary gland consists of two parts. The posterior pituitary is composed of nervous tissue, is an extension of the hypothalamus, and stores and secretes oxytocin and ADH, which are made in the hypothalamus. Student Misconceptions and Concerns The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. Although this is mentioned briefly in the text, consider emphasizing further the potential negative consequences of the abuse of these powerful hormones. The National Institute of Health provides additional details on its website at Teaching Tips 1. Morphine and other opiates bind to the same cell receptors that naturally bind endorphins, producing powerful pain-killing effects. 2. Students may not have carefully considered the benefits of pain. Consider emphasizing the adaptive nature of pain to your class. The authors note the risks of stopping pain in an injured part of the body. Based on this, challenge students to propose explanations as to why endorphins nonetheless evolved. © 2012 Pearson Education, Inc. 34

Uterine muscles Mammary glands
Figure 26.4B Hypothalamus Neurosecretory cell Hormone Posterior pituitary Anterior pituitary Blood vessel Figure 26.4B Hormones of the posterior pituitary Oxytocin ADH Uterine muscles Mammary glands Kidney tubules 35

Mammary glands (in mammals)
Figure 26.4C Neurosecretory cell of hypothalamus Blood vessel Releasing hormones from hypothalamus Endocrine cells of the anterior pituitary Figure 26.4C Hormones of the anterior pituitary Pituitary hormones TSH ACTH FSH and LH Prolactin (PRL) Growth hormone (GH) Endorphins Thyroid Adrenal cortex Testes or ovaries Mammary glands (in mammals) Entire body Pain receptors in the brain 36

Figure 26.4D Figure 26.4D Gigantism, caused by an excess of growth hormone during childhood 37

Anterior pituitary Thyroxine
Figure 26.4E Hypothalamus Inhibition TRH Anterior pituitary Inhibition TSH Figure 26.4E Control of thyroxine secretion Thyroid Thyroxine 38

26.4 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems The anterior pituitary synthesizes and secretes hormones that control the activity of other glands and is controlled by two types of hormones released from the hypothalamus: releasing hormones stimulate the anterior pituitary, and inhibiting hormones inhibit the anterior pituitary. Student Misconceptions and Concerns The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. Although this is mentioned briefly in the text, consider emphasizing further the potential negative consequences of the abuse of these powerful hormones. The National Institute of Health provides additional details on its website at Teaching Tips 1. Morphine and other opiates bind to the same cell receptors that naturally bind endorphins, producing powerful pain-killing effects. 2. Students may not have carefully considered the benefits of pain. Consider emphasizing the adaptive nature of pain to your class. The authors note the risks of stopping pain in an injured part of the body. Based on this, challenge students to propose explanations as to why endorphins nonetheless evolved. © 2012 Pearson Education, Inc. 39

26.4 The hypothalamus, which is closely tied to the pituitary, connects the nervous and endocrine systems Pituitary secretions include growth hormone (GH) that promotes protein synthesis and the use of body fat for energy metabolism, endorphins that function as natural painkillers, and TRH (TSH-releasing hormone) that stimulates the thyroid (another endocrine gland) to release thyroxine. Student Misconceptions and Concerns The abuse of growth hormones and steroids is of great concern in the world of professional and amateur sports. Although this is mentioned briefly in the text, consider emphasizing further the potential negative consequences of the abuse of these powerful hormones. The National Institute of Health provides additional details on its website at Teaching Tips 1. Morphine and other opiates bind to the same cell receptors that naturally bind endorphins, producing powerful pain-killing effects. 2. Students may not have carefully considered the benefits of pain. Consider emphasizing the adaptive nature of pain to your class. The authors note the risks of stopping pain in an injured part of the body. Based on this, challenge students to propose explanations as to why endorphins nonetheless evolved. © 2012 Pearson Education, Inc. 40

HORMONES AND HOMEOSTASIS
HORMONES AND HOMEOSTASIS © 2012 Pearson Education, Inc. 41

26.5 The thyroid regulates development and metabolism
The thyroid gland is located in the neck, just under the larynx (voice box). The thyroid gland produces two similar hormones, thyroxine (T4) and triiodothyronine (T3). These hormones regulate many aspects of metabolism, reproduction, and development. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips Hypothyroidism produces symptoms that are like turning down a furnace during a cold winter. When thyroid levels are low, cells produce ATP and heat at a slower rate, and the person feels colder and is more lethargic than others in the same room. This reminds students that aerobic respiration produces heat and ATP. Hyperthyroidism is just the opposite, with an overproduction of heat as the consequence. © 2012 Pearson Education, Inc. 42

Figure 26.5A Figure 26.5A The maturation of a tadpole (below) into an adult frog (above), as regulated by thyroid hormones 43

Figure 26.5A_1 Figure 26.5A_1 The maturation of a tadpole into an adult frog, as regulated by thyroid hormones (part 1) 44

Figure 26.5A_2 Figure 26.5A_2 The maturation of a tadpole into an adult frog, as regulated by thyroid hormones (part 2) 45

Thyroid imbalance can cause disease. Hyperthyroidism results from too much T4 and T3 in the blood, leads to high blood pressure, loss of weight, overheating, and irritability, and produces Graves’ disease. Hypothyroidism results from too little T4 and T3 in the blood and leads to low blood pressure, being overweight, and often feeling cold and lethargic. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips Hypothyroidism produces symptoms that are like turning down a furnace during a cold winter. When thyroid levels are low, cells produce ATP and heat at a slower rate, and the person feels colder and is more lethargic than others in the same room. This reminds students that aerobic respiration produces heat and ATP. Hyperthyroidism is just the opposite, with an overproduction of heat as the consequence. © 2012 Pearson Education, Inc. 46

Iodine deficiency can produce a goiter, an enlargement of the thyroid. In this condition, the thyroid gland cannot synthesize adequate amounts of T4 and T3, and the thyroid gland enlarges. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips Hypothyroidism produces symptoms that are like turning down a furnace during a cold winter. When thyroid levels are low, cells produce ATP and heat at a slower rate, and the person feels colder and is more lethargic than others in the same room. This reminds students that aerobic respiration produces heat and ATP. Hyperthyroidism is just the opposite, with an overproduction of heat as the consequence. © 2012 Pearson Education, Inc. 47

Figure 2.2A Figure 2.2A Goiter, a symptom of iodine deficiency, in a Burmese woman 48

Thyroid grows to form goiter
Figure 26.5B No inhibition Hypothalamus TRH No inhibition Anterior pituitary TSH Insufficient T4 and T3 produced No iodine Thyroid Figure 26.5B How iodine deficiency causes goiter Thyroid grows to form goiter 49

26.6 Hormones from the thyroid and parathyroid glands maintain calcium homeostasis
Blood calcium level is regulated by antagonistic hormones each working to oppose the actions of the other hormone: calcitonin, from the thyroid, lowers the calcium level in the blood, and parathyroid hormone (PTH), from the parathyroid glands, raises the calcium level in the blood. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips The use of calcitonin and parathyroid hormone to hold blood calcium levels steady is similar to the use of a heater and chiller on a fish tank or a furnace and air conditioner in a home to keep temperatures steady. The same analogy can be applied to the contrasting functions of insulin and glucagon. © 2012 Pearson Education, Inc. 50

Homeostasis: Normal blood calcium level (about 10 mg/100 mL)
Figure 26.6 8 7 Calcitonin Thyroid gland releases calcitonin Stimulates Ca2 deposition in bones Reduces Ca2 reabsorption in kidneys 9 6 Stimulus: Rising blood Ca2 level (imbalance) Blood Ca2 falls Ca2 level Homeostasis: Normal blood calcium level (about 10 mg/100 mL) Stimulus: Falling blood Ca2 level (imbalance) Ca2 level 1 Blood Ca2 rises 5 Figure 26.6 Calcium homeostasis Parathyroid glands release parathyroid hormone (PTH) Stimulates Ca2 release from bones 2 Parathyroid gland 3 PTH Increases Ca2 reabsorption in kidneys Active vitamin D Increases Ca2 uptake in intestines 4 51

Blood Ca2 rises Ca2 level Stimulus: Falling blood Ca2 level
Figure 26.6_1 Ca2 level Stimulus: Falling blood Ca2 level Homeostasis Ca2 level Blood Ca2 rises 1 5 Release of parathyroid hormone Ca2 release Figure 26.6_1 Calcium homeostasis (part 1) Active vitamin D 3 PTH Ca2 reabsorption 2 Ca2 uptake 4 52

Thyroid gland releases calcitonin
Figure 26.6_2 8 7 Calcitonin Thyroid gland releases calcitonin Stimulates Ca2 deposition Reduces Ca2 reabsorption 9 Stimulus: Rising blood Ca2 level 6 Ca2 level Blood Ca2 falls Figure 26.6_2 Calcium homeostasis (part 2) Homeostasis Ca2 level 53

26.7 Pancreatic hormones regulate blood glucose levels
The pancreas secretes two hormones that control blood glucose: insulin signals cells to use and store glucose, and glucagon causes cells to release stored glucose into the blood. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips 1. The use of calcitonin and parathyroid hormone to hold blood calcium levels steady is similar to the use of a heater and chiller on a fish tank or a furnace and air conditioner in a home to keep temperatures steady. The same analogy can be applied to the contrasting functions of insulin and glucagon. 2. Scientists are exploring the use of pancreatic cell transplants as a new source of insulin for patients with type 1 diabetes. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this subject is © 2012 Pearson Education, Inc. 54

Homeostasis: Normal blood glucose level (about 90 mg/100 mL)
Figure 26.7 Body cells take up more glucose Insulin 3 2 Beta cells of pancreas stimulated to release insulin into the blood 4 Blood glucose level declines to a set point; stimulus for insulin release diminishes Liver takes up glucose and stores it as glycogen 1 High blood glucose level Stimulus: Rising blood glucose level (e.g., after eating a carbohydrate-rich meal) Glucose level Homeostasis: Normal blood glucose level (about 90 mg/100 mL) Stimulus: Declining blood glucose level (e.g., after skipping a meal) Glucose level Figure 26.7 Glucose homeostasis 5 5 Low blood glucose level Blood glucose level rises to set point; stimulus for glucagon release diminishes 6 Alpha cells of pancreas stimulated to release glucagon into the blood 8 Liver breaks down glycogen and releases glucose to the blood 7 Glucagon 55

Body cells take up glucose Insulin
Figure 26.7_1 Body cells take up glucose Insulin 3 2 Beta cells of pancreas stimulated 4 Blood glucose declines; insulin release stimulus diminishes Liver takes up glucose; stores as glycogen 1 Stimulus: Rising blood glucose level Figure 26.7_1 Glucose homeostasis (part 1) Glucose level Homeostasis Glucose level 56

Glucose level Homeostasis Glucose level
Figure 26.7_2 Glucose level Homeostasis Glucose level Stimulus: Declining blood glucose level 5 8 Blood glucose rises; glucagon release stimulus decreases 6 Figure 26.7_2 Glucose homeostasis (part 2) Liver breaks down glycogen; glucose is released Alpha cells of pancreas stimulated 7 Glucagon 57

26.8 CONNECTION: Diabetes is a common endocrine disorder
Diabetes mellitus affects about 8% of the U.S. population and results from a lack of insulin or failure of cells to respond to insulin. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips Scientists are exploring the use of pancreatic cell transplants as a new source of insulin for patients with type 1 diabetes. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this subject is © 2012 Pearson Education, Inc. 58

There are three types of diabetes mellitus. 1. Type 1 (insulin-dependent) is an autoimmune disease caused by the destruction of insulin-producing cells. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips Scientists are exploring the use of pancreatic cell transplants as a new source of insulin for patients with type 1 diabetes. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this subject is © 2012 Pearson Education, Inc. 59

Type 2 (non-insulin-dependent) is caused by a reduced response to insulin, associated with being overweight and underactive, and the cause of more than 90% of diabetes. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips Scientists are exploring the use of pancreatic cell transplants as a new source of insulin for patients with type 1 diabetes. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this subject is © 2012 Pearson Education, Inc. 60

Gestational diabetes can affect any pregnant woman and lead to dangerously large babies, which can complicate delivery. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips Scientists are exploring the use of pancreatic cell transplants as a new source of insulin for patients with type 1 diabetes. Pancreatic cells may be derived from donors and/or modified from other cells using stem cell technology. One website devoted to this subject is © 2012 Pearson Education, Inc. 61

Figure 26.8A Figure 26.8A Testing glucose levels (above) and injecting human insulin (left) 62

Figure 26.8A_1 Figure 26.8A_1 Testing glucose levels and injecting human insulin (part 1) 63

Figure 26.8A_2 Figure 26.8A_2 Testing glucose levels and injecting human insulin (part 2) 64

Hours after glucose ingestion
Figure 26.8B 400 350 300 Diabetic 250 Blood glucose (mg/100 mL) 200 150 Healthy 100 50 Figure 26.8B Results of glucose tolerance tests 1 2 3 4 5 Hours after glucose ingestion 65

26.9 The adrenal glands mobilize responses to stress
The endocrine system includes two adrenal glands, sitting on top of each kidney. Each adrenal gland is made of two glands fused together, the adrenal medulla and adrenal cortex. Both glands secrete hormones that enable the body to respond to stress. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips The effects of the “fight-or-flight” response will likely last many minutes after the initial events that triggered the response. Telling such a person to calm down is unlikely to help. Instead, removing the person from the stimulus (if possible), engaging in mild exercise such as walking, and allowing many minutes of time will most likely reverse the condition. © 2012 Pearson Education, Inc. 66

Adrenal medulla Adrenal gland Adrenal cortex Kidney Figure 26.9_1
Figure 26.9_1 How the adrenal glands control our responses to stress (part 1) 67

Nerve signals from the hypothalamus stimulate the adrenal medulla to secrete epinephrine (adrenaline) and norepinephrine (noradrenaline). These hormones quickly trigger the “fight-or-flight” responses, which are short-term responses to stress. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips The effects of the “fight-or-flight” response will likely last many minutes after the initial events that triggered the response. Telling such a person to calm down is unlikely to help. Instead, removing the person from the stimulus (if possible), engaging in mild exercise such as walking, and allowing many minutes of time will most likely reverse the condition. © 2012 Pearson Education, Inc. 68

Figure 26.9 How the adrenal glands control our responses to stress
Adrenal medulla Stress Adrenal gland Nerve signals 1 Adrenal cortex Hypothalamus 3 Kidney Releasing hormone Cross section of spinal cord Anterior pituitary Nerve cell Blood vessel 4 Nerve cell ACTH 5 Adrenal medulla Adrenal cortex ACTH 2 Mineralocorticoids Glucocorticoids Epinephrine and norepinephrine Figure 26.9 How the adrenal glands control our responses to stress Short-term stress response Long-term stress response Mineralocorticoids Glucocorticoids 1. Glycogen broken down to glucose; increased blood glucose 1. Retention of sodium ions and water by kidneys 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 2. Increased blood volume and blood pressure 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity 2. Immune system may be suppressed 69

Stress Nerve signals Hypothalamus Releasing hormone Nerve cell
Figure 26.9_2 Stress Nerve signals 1 Hypothalamus 3 Releasing hormone Nerve cell Anterior pituitary Cross section of spinal cord Blood vessel 4 Nerve cell ACTH 5 Adrenal medulla Adrenal cortex Figure 26.9_2 How the adrenal glands control our responses to stress (part 2) ACTH 2 Glucocorticoids Mineralocorticoids Epinephrine and norepinephrine Short-term stress response Long-term stress response 70

Short-term stress response
Figure 26.9_3 Short-term stress response 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity Figure 26.9_3 How the adrenal glands control our responses to stress (part 3) 71

Adrenocorticotropic hormone (ACTH) from the pituitary causes the adrenal cortex to secrete glucocorticoids and mineralocorticoids. The effects of these hormones cause long-term responses to stress. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips The effects of the “fight-or-flight” response will likely last many minutes after the initial events that triggered the response. Telling such a person to calm down is unlikely to help. Instead, removing the person from the stimulus (if possible), engaging in mild exercise such as walking, and allowing many minutes of time will most likely reverse the condition. © 2012 Pearson Education, Inc. 72

Long-term stress response
Figure 26.9_4 Long-term stress response Mineralocorticoids Glucocorticoids 1. Retention of sodium ions and water by kidneys 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Increased blood volume and blood pressure 2. Immune system may be suppressed Figure 26.9_4 How the adrenal glands control our responses to stress (part 4) 73

26.10 The gonads secrete sex hormones
Steroid sex hormones affect growth, affect development, and regulate reproductive cycles and sexual behavior. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips In humans, differences in the concentrations of sex hormones decrease between the sexes throughout adulthood. Differences in secondary sexual characteristics such as muscle tone and hair growth may diminish as a natural part of aging. Students with interests in geriatrics may enjoy assignments or extra credit to investigate this topic. © 2012 Pearson Education, Inc. 74

Sex hormones include estrogens, which maintain the female reproductive system and promote the development of female characteristics, progestins, such as progesterone, which prepare and maintain the uterus to support a developing embryo, and androgens, such as testosterone, which stimulate the development and maintenance of the male reproductive system. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips In humans, differences in the concentrations of sex hormones decrease between the sexes throughout adulthood. Differences in secondary sexual characteristics such as muscle tone and hair growth may diminish as a natural part of aging. Students with interests in geriatrics may enjoy assignments or extra credit to investigate this topic. © 2012 Pearson Education, Inc. 75

Figure 26.10 Figure Male elephant seals in combat 76

The synthesis of sex hormones by the gonads is regulated by the hypothalamus and pituitary. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips In humans, differences in the concentrations of sex hormones decrease between the sexes throughout adulthood. Differences in secondary sexual characteristics such as muscle tone and hair growth may diminish as a natural part of aging. Students with interests in geriatrics may enjoy assignments or extra credit to investigate this topic. © 2012 Pearson Education, Inc. 77

26.11 EVOLUTION CONNECTION: A single hormone can perform a variety of functions in different animals
The peptide hormone prolactin (PRL) in humans stimulates mammary glands to grow and produce milk during late pregnancy. Suckling by a newborn stimulates further release of PRL. High PRL during nursing inhibits ovulation. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips The shifting functions of prolactin reflect the kind of “remodeling” frequently found in evolution. Typically, new structures and functions result from modifications of ancestral structures and functions. In this case, as reproductive strategies evolved, the functional significance of prolactin was remodeled. © 2012 Pearson Education, Inc. 78

Figure 26.11 Figure Suckling promotes prolactin production 79

26.11 EVOLUTION CONNECTION: A single hormone can perform a variety of functions in different animals
PRL has many roles unrelated to childbirth, suggesting that PRL is an ancient hormone diversified through evolution. In some nonhuman mammals, PRL stimulates nest building. In birds, PRL regulates fat metabolism and reproduction. In amphibians, PRL stimulates movement to water. In fish that migrate between salt and fresh water, PRL helps regulate salt and water balance. Student Misconceptions and Concerns 1. Many students struggle to remember the basic structures, functions, and locations of the major vertebrate organs. Understanding and remembering the specific control mechanisms are typically beyond their background knowledge entering a general biology college course. Students will appreciate any reminders or reference materials that help them to organize this information. 2. As the section title indicates, a central theme of endocrine function is the maintenance of homeostasis. Repeatedly framing the details of hormonal and glandular function in the context of homeostasis can increase levels of student comprehension. Teaching Tips The shifting functions of prolactin reflect the kind of “remodeling” frequently found in evolution. Typically, new structures and functions result from modifications of ancestral structures and functions. In this case, as reproductive strategies evolved, the functional significance of prolactin was remodeled. © 2012 Pearson Education, Inc. 80

You should now be able to
Explain how testosterone affects lions. Compare the mechanisms and functions of the endocrine and nervous systems. Distinguish between the two major classes of vertebrate hormones. Describe the different types and functions of vertebrate endocrine organs. © 2012 Pearson Education, Inc. 81

Describe the interrelationships between the hypothalamus and pituitary glands. Describe the functions of the thyroid and parathyroid glands. Explain how insulin and glucagon manage blood glucose levels. Describe the causes and symptoms of type 1 and type 2 diabetes and gestational diabetes. © 2012 Pearson Education, Inc. 82

Compare the functions of the adrenal gland hormones. Describe the three major types of sex hormones and their functions. Describe the diverse functions of prolactin in vertebrate groups and its evolutionary significance. © 2012 Pearson Education, Inc. 83

Water- soluble hormone Lipid- soluble hormone
Figure 26.UN01 Water- soluble hormone Lipid- soluble hormone Receptor protein in plasma membrane Receptor protein in cytoplasm Signal transduction pathway Cytoplasmic response Figure 26.UN01 Reviewing the Concepts, 26.2 Hormone receptor protein or Gene regulation Gene regulation 84

Hypothalamus: • Master control center of the endocrine system Brain
Figure 26.UN02 Hypothalamus: • Master control center of the endocrine system Brain Anterior pituitary: • Composed of endocrine tissue • Controlled by hypothalamus • Produces and secretes its own hormones Posterior pituitary: Composed of nervous tissue Figure 26.UN02 Reviewing the Concepts, 26.4 Stores and secretes hormones made by hypothalamus 85

Causes Releases Releases Causes Pancreas Glucose in blood Insulin
Figure 26.UN03 Glucose in blood Causes Insulin Releases Releases Causes Pancreas Glucose in blood Glucagon Figure 26.UN03 Reviewing the Concepts, 26.7 86

f. influences sleep/wake rhythms b. stimulates ovaries
Figure 26.UN04 1. thyroxine 4. insulin 7. PTH 2. epinephrine 5. melatonin 8. ADH 3. androgens 6. FSH Pineal gland Testes Parathyroid gland Adrenal medulla Pancreas Hypothalamus Anterior pituitary Thyroid gland Figure 26.UN04 Connecting the Concepts, questions 1–8 a. lowers blood glucose f. influences sleep/wake rhythms b. stimulates ovaries c. triggers fight-or-flight g. raises blood calcium level d. promotes male characteristics e. regulates metabolism h. boosts water retention 87

Hormones and the Endocrine System

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