1. PowerLecture: Chapter 15 The Endocrine System

2. Learning Objectives  Know the general mechanisms by which molecules integrate and control the various metabolic activities in organisms.  Understand how the neuro-endocrine center controls secretion rates of other endocrine glands and responses in nerves and muscles.  Know the major endocrine glands and their secretions.

3. Learning Objectives (cont’d)  Know how sugar levels are regulated by hormones.  Differentiate the modes of action of steroid and nonsteroid hormones.

4. Impacts/Issues Hormones in the Balance

5.  Arsenic may be an endocrine disrupter, especially of glucocorticoids. Glucocorticoids in turn regulate genes that protect against cancer. Glucocorticoids in turn regulate genes that protect against cancer. This may be the link between the consumption of arsenic in water supplies and increased rates of bladder, lung, and skin cancers. This may be the link between the consumption of arsenic in water supplies and increased rates of bladder, lung, and skin cancers.

6. Hormones in the Balance  Other endocrine disrupters are also coming under scrutiny. The herbicide atrazine has been widely used on crops and turf grasses. The herbicide atrazine has been widely used on crops and turf grasses. PCBs, used for many years as fluid insulation in electrical transformers, have been banned but still persist in the environment, where they are linked to reproductive disorders in humans and animals. PCBs, used for many years as fluid insulation in electrical transformers, have been banned but still persist in the environment, where they are linked to reproductive disorders in humans and animals.  Research is continuing on endocrine disrupters; the jury is still out.

7. Useful References for Impacts/Issues The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  EPA: Endocrine Disruptors Research Initiative  InfoTrac: New Report Points Up Growing Evidence of Endocrine Disrupters. European Report, May 4, 2006.

8. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu.  Some pesticides may disrupt hormone function in humans and other animals. Should they remain in use while researchers study their safety? a. No, they could be dangerous; until we know for sure, it is better to be safe than sorry. a. No, they could be dangerous; until we know for sure, it is better to be safe than sorry. b. Yes, banning them because of potential harm isn't fair; there should be solid evidence first. b. Yes, banning them because of potential harm isn't fair; there should be solid evidence first.

9. Useful References for How Would You Vote? The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  InfoTrac: Endocrine Disruption Study on Atrazine Disputed. Pesticide & Toxic Chemical News, Jan. 13, 2003.  Water Conserve 2.0: Chemical Affecting Frogs’ Sexuality; Males Are Acquiring Female Attributes after Exposure to a Common Weedkiller, Study Says

10. Section 1 The Endocrine System: Hormones

11.  Hormones are signaling molecules that are carried in the bloodstream. Signaling molecules are hormones and secretions that can bind to target cells and elicit in them a response. Signaling molecules are hormones and secretions that can bind to target cells and elicit in them a response. Hormones are secreted by endocrine glands, endocrine cells, and some neurons. Hormones are secreted by endocrine glands, endocrine cells, and some neurons. Local signaling molecules are released by some cells; these work only on nearby tissues. Local signaling molecules are released by some cells; these work only on nearby tissues. Pheromones are signaling molecules that have targets outside the body and which are used to integrate behaviors. Pheromones are signaling molecules that have targets outside the body and which are used to integrate behaviors.

12. The Endocrine System: Hormones  Hormone sources: The endocrine system. The sources of hormones (hormone producing glands, cells, and organs) may be collectively called the endocrine system. The sources of hormones (hormone producing glands, cells, and organs) may be collectively called the endocrine system. Endocrine sources and the nervous system function in highly interconnected ways. Endocrine sources and the nervous system function in highly interconnected ways.

13. The Endocrine System: Hormones  Hormones often interact. In an opposing interaction the effect of one hormone opposes the effect of another. In an opposing interaction the effect of one hormone opposes the effect of another. In a synergistic interaction the combined action of two or more hormones is necessary to produce the required effect on target cells. In a synergistic interaction the combined action of two or more hormones is necessary to produce the required effect on target cells. In a permissive interaction one hormone exerts its effect only when a target cell has been “primed” to respond by another hormone. In a permissive interaction one hormone exerts its effect only when a target cell has been “primed” to respond by another hormone.

14. Animation: Major Human Endocrine Glands CLICK TO PLAY

15. hypothalamus pituitary gland adrenal glands ovaries testes pineal gland thyroid gland parathyroid glands thymus gland pancreatic islets Fig. 15.1a, p. 271

16. Useful References for Section 1 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  InfoTrac: Review of the Endocrine System. Deirdre G. Bauer. MedSurg Nursing, Oct. 2005.

17. Section 2 Types of Hormones and Their Signals

18.  Hormones come in several chemical forms. Steroid hormones Steroid hormones are lipids made from cholesterol. Amine hormones are Amine hormones are modified amino acids. Peptide hormones are peptides of only a few amino acids. Peptide hormones are peptides of only a few amino acids. Protein hormones are longer chains of amino acids. Protein hormones are longer chains of amino acids.

19. Types of Hormones and Their Signals All hormones bind target cells; this signal is converted into a form that works in the cell to change activity. All hormones bind target cells; this signal is converted into a form that works in the cell to change activity. A target cell’s response to a hormone is dependent on two factors: A target cell’s response to a hormone is dependent on two factors: Different hormones activate different cellular response mechanisms.Different hormones activate different cellular response mechanisms. Not all cells have receptors for all hormones; the cells that respond are selected by means of the type of receptor they possess.Not all cells have receptors for all hormones; the cells that respond are selected by means of the type of receptor they possess.

20. Types of Hormones and Their Signals  Steroid hormones interact with cell DNA. Steroid hormones, such as estrogen and testosterone, are lipid-soluble and therefore cross plasma membranes readily. Steroid hormones, such as estrogen and testosterone, are lipid-soluble and therefore cross plasma membranes readily. Once inside the cell, they penetrate the nuclear membrane and bind to receptors in the nucleus, either turning on or turning off genes.Once inside the cell, they penetrate the nuclear membrane and bind to receptors in the nucleus, either turning on or turning off genes. Switching genes on or off changes the proteins that are made by the cell, thus effecting a response.Switching genes on or off changes the proteins that are made by the cell, thus effecting a response. Some steroid hormones bind receptors in the cell membrane and change membrane properties to affect change to the target cell’s function. Some steroid hormones bind receptors in the cell membrane and change membrane properties to affect change to the target cell’s function.

21. receptor hormone- receptor complex change in cell activity 1 A steroid hormone molecule moves from the blood into the fluid that bathes a target cell. Fig. 15.2a, p. 273 4 Now the hormone- receptor complex triggers gene activity in the DNA 5 In the cytoplasm, the resulting protein carries out the cell’s response to the hormone signal. 2 Being a lipid-soluable molecule, the steroid hormone diffuses across the target cell’s plasma membrane. 3 The hormone diffuses through the cytoplasm, then on through the nuclear envelope. Inside the nucleus, it will bind with a receptor molecule.

22. Video: Mechanism of a steroid hormone Video: Mechanism of a steroid hormone CLICK TO PLAY

23. Types of Hormones and Their Signals  Nonsteroid hormones act indirectly, by way of second messengers. Nonsteroid hormones include the amine, peptide, and protein hormones. Nonsteroid hormones include the amine, peptide, and protein hormones. Nonsteroid hormones cannot cross the plasma membrane of target cells, so they must first bind to a receptor on the plasma membrane. Nonsteroid hormones cannot cross the plasma membrane of target cells, so they must first bind to a receptor on the plasma membrane. Binding of the hormone to the receptor activates the receptor; it in turn stimulates the production of a second messenger, a small molecule that can relay signals in the cell.Binding of the hormone to the receptor activates the receptor; it in turn stimulates the production of a second messenger, a small molecule that can relay signals in the cell. Cyclic AMP (cyclic adenosine monophosphate) is one example of a second messenger.Cyclic AMP (cyclic adenosine monophosphate) is one example of a second messenger.

24. 1 A glucagon molecule diffuses from blood into the fluid that bathes the plasma membrane of a liver cell. ATP glucagon receptor at target cell’s membrane 3 The cyclic AMP now activates protein kinase A. 5 Protein kinase A also inhibits an enzyme required for glycogen synthesis. cyclic AMP + P i 4 Protein kinase A converts phosphorylase kinase to active form. This enzyme activates a different enzyme, which breaks down glycogen to its glucose monomers. 2 Glucagon binds with the receptor, and the binding activates adenylate cyclase. This enzyme catalyzes the formation of cyclic AMP inside the target cell. Fig. 15.2b, p. 273

25. Video: Mechanism of a peptide hormone Video: Mechanism of a peptide hormone CLICK TO PLAY

26. Useful References for Section 2 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  InfoTrac: Can PYY Cure Obesity? U.S. News & World Report, Sept. 15, 2003.

27. Section 3 The Hypothalamus and Pituitary Gland: Major Controllers

28. The Hypothalamus and Pituitary Gland  The hypothalamus and pituitary gland work jointly as the neural-endocrine control center. The hypothalamus is a portion of the brain that monitors internal organs and conditions. The hypothalamus is a portion of the brain that monitors internal organs and conditions. The pituitary is connected to the hypothalamus by a stalk. The pituitary is connected to the hypothalamus by a stalk. The posterior lobe consists of nervous tissue and releases two hormones made in the hypothalamus.The posterior lobe consists of nervous tissue and releases two hormones made in the hypothalamus. The anterior lobe makes and secretes hormones that control the activity of other endocrine glands.The anterior lobe makes and secretes hormones that control the activity of other endocrine glands.

29. hypothalamus pituitary stalk anterior lobe posterior lobe membrane around brain Fig. 15.1b, p. 271 optic chasma Location of the pituitary gland:

30. The Hypothalamus and Pituitary Gland  The posterior pituitary lobe produces ADH and oxytocin. Neurons in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin, which are released from axon endings in the capillary bed of the posterior lobe. Neurons in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin, which are released from axon endings in the capillary bed of the posterior lobe. ADH (or vasopressin) acts on the walls of kidney tubules to control the body’s water and solute levels by stimulating reabsorption. ADH (or vasopressin) acts on the walls of kidney tubules to control the body’s water and solute levels by stimulating reabsorption. Oxytocin triggers uterine muscle contractions to expel the fetus and acts on mammary glands to release milk. Oxytocin triggers uterine muscle contractions to expel the fetus and acts on mammary glands to release milk.

31. Animation: Posterior Pituitary Function CLICK TO PLAY

32. kidney nephrons mammary glands muscles in uterus wall ADH oxytocin Fig. 15.3, p. 274 a Secretory neurons in the hypothalamus synthesize ADH or oxytocin. b The ADH Oxytocin moves downward inside the axons of the secretory neurons and accumulates in the axon endings. c Action potentials trigger the release of these hormones, which enter blood capillaries in the posterior lobe of the pituitary. d The hormone molecules move into the general circulation.

33. The Hypothalamus and Pituitary Gland  The anterior pituitary lobe produces six other hormones. Corticotropin (ACTH) stimulates the adrenal cortex. Corticotropin (ACTH) stimulates the adrenal cortex. Thyrotropin (TSH) stimulates the thyroid gland. Thyrotropin (TSH) stimulates the thyroid gland. Follicle-stimulating hormone (FSH) causes ovarian follicle development and egg production. Follicle-stimulating hormone (FSH) causes ovarian follicle development and egg production.

34. The Hypothalamus and Pituitary Gland Luteinizing hormone (LH) also acts on the ovary to release an egg. Luteinizing hormone (LH) also acts on the ovary to release an egg. Prolactin (PRL) acts on the mammary glands to stimulate and sustain milk production. Prolactin (PRL) acts on the mammary glands to stimulate and sustain milk production. Somatotropin (STH), also known as growth hormone (GH), acts on body cells in general to promote growth. Somatotropin (STH), also known as growth hormone (GH), acts on body cells in general to promote growth. Most of these hormones are releasers that stimulate target cells to secrete other hormones; other hormones from the hypothalamus are inhibitors and block secretions. Most of these hormones are releasers that stimulate target cells to secrete other hormones; other hormones from the hypothalamus are inhibitors and block secretions.

35. Animation: Anterior Pituitary Function CLICK TO PLAY

36. Fig. 15.4, p. 275 ACTHTSHFSHLHPRLSTH(GH) adrenal glands thyroid gland testes in males, ovaries in females mammary glands a Cell bodies of different secretory neurons in the hypothalamus secrete releasing and inhibiting hormones. b The hormones are picked up by a capillary bed at the base of the hypothalamus. c The bloodstream delivers hormones to a capillary bed in the anterior lobe of pituitary. d Molecules of the releasing or inhibiting hormone diffuse out of capillaries and act on endocrine cells in the anterior lobe. e Hormones from anterior lobe cells enter small blood vessels that lead to the general circulation. most cells (growth-promoting effects)

38. Video: Hypothalamus and Pituitary CLICK TO PLAY

39. Useful References for Section 3 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  The Pituitary Society  InfoTrac: The Scent of Trust. Prevention, Oct. 2005.

40. Section 4 Factors That Influence Hormone Effects

41.  Problems with control mechanisms can result in skewed hormone signals. Endocrine glands in general only release small quantities of hormones and control the frequency of release to make sure there isn’t too much or too little hormone. Endocrine glands in general only release small quantities of hormones and control the frequency of release to make sure there isn’t too much or too little hormone. Factors That Influence Hormone Effects

42.  Abnormal quantities of hormones can lead to growth problems. Gigantism results from an Gigantism results from an oversecretion of growth hormone in childhood. Pituitary dwarfism Pituitary dwarfism results from an undersecretion of GH. Factors That Influence Hormone Effects Figures 15.5a and 15.14

43. Acromegaly is a condition resulting from an oversecretion of GH in adulthood leading to abnormal thickening of tissues. Acromegaly is a condition resulting from an oversecretion of GH in adulthood leading to abnormal thickening of tissues. Diabetes insipidus occurs when ADH secretions fall or stop, leading to dilute urine and the possibility of serious dehydration. Diabetes insipidus occurs when ADH secretions fall or stop, leading to dilute urine and the possibility of serious dehydration. Factors That Influence Hormone Effects Figure 15.5b

44.  Hormone interactions, feedback, and other factors also influence a hormone’s effects. At least four factors influence the effects of any given hormone. At least four factors influence the effects of any given hormone. Hormones often interact with one another.Hormones often interact with one another. Negative feedback mechanisms control secretion of hormones.Negative feedback mechanisms control secretion of hormones. Target cells may react differently to hormones at different times.Target cells may react differently to hormones at different times. Environmental cues can affect release of hormones.Environmental cues can affect release of hormones. Hormones throughout the body are affected in similar ways. Hormones throughout the body are affected in similar ways. Factors That Influence Hormone Effects

46. Video: Hormone Replacement Therapy  This video clip is available in CNN Today Videos for Anatomy & Physiology, 2003, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

47. Useful References for Section 4 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  InfoTrac: AcromegalyAna Pokrajac- Simeunovic and Peter Trainer. Chemist & Druggist, Nov. 19, 2005.  InfoTrac: Acromegaly. Ana Pokrajac- Simeunovic and Peter Trainer. Chemist & Druggist, Nov. 19, 2005.

48. Section 5 The Thymus, Thyroid, and Parathyroid Glands

49.  Thymus gland hormones aid immunity.  Thyroid hormones affect metabolism, growth, and development. The thyroid gland secretes thyroid hormone (TH), which has effects on metabolism, growth, and development; the thyroid gland also secretes calcitonin, which helps regulate calcium levels in the blood. The thyroid gland secretes thyroid hormone (TH), which has effects on metabolism, growth, and development; the thyroid gland also secretes calcitonin, which helps regulate calcium levels in the blood. The Thymus, Thyroid, and Parathyroid Glands

50. Fig. 15.6a, p. 278 thyroid cartilage (Adam’s apple) blood vessel thyroid gland trachea (windpipe)

51. Animation: Thyroid Hormone Action CLICK TO PLAY

52. Fig. 15.6b, p. 278 Stimulus Blood level of thyroid hormone falls below a set point. Hypothalamus Anterior Pituitary Thyroid Gland Rise in the blood level of thyroid hormone inhibits secretion of TRH and THS. Thyroid hormone is secreted. + TRH TSH Response

53. Fig. 15.6b, p. 278 Stimulus Blood level of thyroid hormone falls below a set point. Stepped Art TRH TSH Thyroid hormone is secreted. Thyroid Gland + Hypothalamus Anterior Pituitary Response – – Rise in the blood level of thyroid hormone inhibits secretion of TRH and TSH.

54. Iodine-deficient diets interfere with proper synthesis of thyroid hormones. Iodine-deficient diets interfere with proper synthesis of thyroid hormones. Simple goiter is an enlargementSimple goiter is an enlargement of one or both lobes of the thyroid gland in the neck; enlargement follows low blood levels of thyroid hormones (hypothyroidism). Graves disease and other forms ofGraves disease and other forms of hyperthyroidism result from too much thyroid hormone in the blood. Figure 15.7 The Thymus, Thyroid, and Parathyroid Glands

55.  PTH from the parathyroids is the main calcium regulator. Humans have four parathyroid Humans have four parathyroid glands, which secrete parathyroid hormone (PTH), the main regulator of blood calcium levels. More PTH is secreted when blood calcium levels drop below a certain point; less is secreted when calcium rises.More PTH is secreted when blood calcium levels drop below a certain point; less is secreted when calcium rises. Calcitonin contributes to processes that pull calcium out of the blood.Calcitonin contributes to processes that pull calcium out of the blood. The Thymus, Thyroid, and Parathyroid Glands

56. Fig. 15.8, p. 279 Decrease in calcium ion concentration in blood Parathyroid glands PTH stimulates Calcium ion level increases Osteoclasts release calcium ions from bone Kidney tubules increase calcium ion reabsorption Intestine increases calcium ion absorption

57. Fig. 15.8, p. 279 Decrease in calcium ion concentration in blood Osteoclasts release calcium ions from bone Kidney tubules Increase calcium ion reabsorption Intestine Increases calcium ion absorption Stepped Art Parathyroid glands PTH stimulates Calcium ion level increases

58. Rickets in children arises from a vitamin D deficient diet; vitamin D is needed to aid absorption of calcium from food. Rickets in children arises from a vitamin D deficient diet; vitamin D is needed to aid absorption of calcium from food. Hyperparathyroidism sees so much calcium being withdrawn from a person’s bones that the bone tissue is dangerously weakened. Hyperparathyroidism sees so much calcium being withdrawn from a person’s bones that the bone tissue is dangerously weakened. The Thymus, Thyroid, and Parathyroid Glands

59. Useful References for Section 5 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  The American Thyroid Association  InfoTrac: Primary Hyperparathyroidism (The Effective Physician). William E. Golden; Robert H. Hopkins. Internal Medicine News, Dec. 1, 2005.

60. Section 6 Adrenal Glands and Stress Responses

61.  The adrenal cortex produces glucocorticoids and mineralocorticoids. One adrenal gland is located on top of each kidney; the outer part of each gland is the adrenal cortex, the site of production for two major steroid hormones. One adrenal gland is located on top of each kidney; the outer part of each gland is the adrenal cortex, the site of production for two major steroid hormones.

62. Adrenal Glands and Stress Responses Glucocorticoids raise the level of glucose in the blood. Glucocorticoids raise the level of glucose in the blood. The main glucocorticoid, cortisol, is secreted when the body is stressed and blood sugar levels drop; cortisol promotes gluconeogenesis, a mechanism for making glucose from amino acids derived from protein breakdown.The main glucocorticoid, cortisol, is secreted when the body is stressed and blood sugar levels drop; cortisol promotes gluconeogenesis, a mechanism for making glucose from amino acids derived from protein breakdown. Cortisol also dampens the uptake of glucose from the blood, stimulates the breakdown of fats for energy, and suppresses inflammation.Cortisol also dampens the uptake of glucose from the blood, stimulates the breakdown of fats for energy, and suppresses inflammation. Hypoglycemia can result when the adrenal cortex makes too little cortisol; this results in chronically low glucose levels in the blood.Hypoglycemia can result when the adrenal cortex makes too little cortisol; this results in chronically low glucose levels in the blood.

63. Animation: Control of Cortisol Secretion CLICK TO PLAY

64. Hypothalamus Anterior Pituitary Adrenal Cortex CRH ACTH Cortisol is secreted, with these effects: a Blood level of cortisol falls below a set point adrenal cortex adrenal medulla kidney c Cell uptake of glucose from blood slows in many tissues, especially muscles (not the brain). d Proteins are broken down in many tissues, muscles especially. The amino acids are converted to glucose, and used in the assembly or repair of cell structures. e Fats in adipose tissue are broken down to fatty acids that enter blood as an alternative energy source, indirectly conserving glucose for the brain. Fig. 15.9, p. 281 Response b f Both the hypothalamus and pituitary detect rise in blood level of cortisol and slow its secretion. Stimulus

65. Adrenal Glands and Stress Responses Mineralocorticoids regulate the concentrations of minerals such as K + and Na + in the extracellular fluid; aldosterone is one example that works in the nephrons of the kidneys. Mineralocorticoids regulate the concentrations of minerals such as K + and Na + in the extracellular fluid; aldosterone is one example that works in the nephrons of the kidneys. The adrenal cortex also secretes sex hormones in the fetus and at puberty. The adrenal cortex also secretes sex hormones in the fetus and at puberty.

66. Adrenal Glands and Stress Responses  Hormones from the adrenal medulla help regulate blood circulation. The inner part of the adrenal gland, the adrenal medulla, secretes epinephrine and norepinephrine. The inner part of the adrenal gland, the adrenal medulla, secretes epinephrine and norepinephrine. Secretion by the adrenal medulla influences these molecules to behave like hormones to regulate blood circulation and carbohydrate use during stress. Secretion by the adrenal medulla influences these molecules to behave like hormones to regulate blood circulation and carbohydrate use during stress.

67. Adrenal Glands and Stress Responses  Long-term stress can damage health. Stress triggers the fight-flight response and the release of cortisol, epinephrine, and norepinephrine; constant release of these molecules can contribute to hypertension and cardiovascular disease. Stress triggers the fight-flight response and the release of cortisol, epinephrine, and norepinephrine; constant release of these molecules can contribute to hypertension and cardiovascular disease. Excess cortisol suppresses the immune system, making individuals susceptible to disease. Excess cortisol suppresses the immune system, making individuals susceptible to disease. Social connections for support and exercise for health can reduce the effects of stress. Social connections for support and exercise for health can reduce the effects of stress.

68. Video: Peanut Allergies  This video clip is available in CNN Today Videos for Anatomy & Physiology, 2004, Volume VIII. Instructors, contact your local sales representative to order this volume, while supplies last.

69. Useful References for Section 6 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  InfoTrac: Prenatal Exposure to Stress and Stress Hormones Influences Child Development. Elysia Poggi Davis; Curt A. Sandman. Infants & Young Children, July– Sept. 2006.

70. Section 7 The Pancreas: Regulating Blood Sugar

71.  The pancreas has both exocrine and endocrine functions; the endocrine cells are located in clusters called pancreatic islets.

72. Fig. 15.10, p. 282 stomach pancreas small intestine

73. The Pancreas: Regulating Blood Sugar  Each pancreatic islet secretes three hormones: Alpha cells secrete glucagon, which causes glycogen stored in the liver to be converted to glucose, which then enters the bloodstream.Alpha cells secrete glucagon, which causes glycogen stored in the liver to be converted to glucose, which then enters the bloodstream. Beta cells secrete insulin, which stimulates the uptake of glucose by liver, muscle, and adipose cells to reduce levels in the blood, especially after a meal.Beta cells secrete insulin, which stimulates the uptake of glucose by liver, muscle, and adipose cells to reduce levels in the blood, especially after a meal. Delta cells secrete somatostatin, which can inhibit the secretion of glucagon and insulin.Delta cells secrete somatostatin, which can inhibit the secretion of glucagon and insulin. Figure 15.9

74. Animation: Hormones and Glucose Metabolism CLICK TO PLAY

75. Fig. 15.10a, p. 282 Stimulus Increase in blood glucose Stimulus Decrease in blood glucose Body cells, especially in muscle and adipose tissue, take up and use more glucose. Cells in skeletal muscle and liver store glucose in the form of glycogen. Response Decrease in blood glucose Response Increase in blood glucose Cells in liver break down glycogen faster. The released glucose molecules enter blood. glucagoninsulin beta cellsalpha cells PANCREAS glucagoninsulin beta cellsalpha cells a e f b c gh i j + _ x d _ + x

76. Useful References for Section 7 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  Journal of the Pancreas  InfoTrac: Perfecting a ‘Pancreas’: Scientists Fine-Tune a Device to Be Used by Diabetics. Jamie Talan. Newsday, May 15, 2006.

77. Section 8 Disorders of Glucose Homeostasis

78.  Diabetes mellitus is a disease resulting from the secretion of too little insulin. Without insulin, cells can’t Without insulin, cells can’t remove glucose from the blood; the kidneys remove the excess in urine, creating imbalances in water-solute concentrations. Metabolic acidosis, a lower than optimal blood pH, can result because of this imbalance. Metabolic acidosis, a lower than optimal blood pH, can result because of this imbalance. Figure 15.11

79. Disorders of Glucose Homeostasis  In type 1 diabetes (also known as “juvenile-onset diabetes”) the insulin is no longer produced because the beta cells have been destroyed by an autoimmune response. Only about 1 in 10 diabetics have this form of diabetes. Only about 1 in 10 diabetics have this form of diabetes. Treatment is by insulin injection. Treatment is by insulin injection.

80. Disorders of Glucose Homeostasis  Type 2 diabetes is a global health crisis. In type 2 diabetes the insulin levels are near normal but the target cells cannot respond to the hormone. In type 2 diabetes the insulin levels are near normal but the target cells cannot respond to the hormone. Beta cells eventually break down and produce less and less insulin.Beta cells eventually break down and produce less and less insulin. Excess glucose in the blood damages capillaries.Excess glucose in the blood damages capillaries. Cardiovascular disease, stroke, heart attack, and other serious complications arise. Cardiovascular disease, stroke, heart attack, and other serious complications arise.

81. Disorders of Glucose Homeostasis  Metabolic syndrome is a warning sign. Prediabetes describes individuals with slightly elevated blood sugar levels that have an increased risk for developing type 2 diabetes; about 20 million Americans fall into this category and do not know it. Prediabetes describes individuals with slightly elevated blood sugar levels that have an increased risk for developing type 2 diabetes; about 20 million Americans fall into this category and do not know it.

82. Disorders of Glucose Homeostasis A composite of features collectively called metabolic syndrome also describe risk for diabetes; these features include: “apple shaped” waistline, elevated blood pressure, low levels of HDL, and elevated glucose and triglycerides. A composite of features collectively called metabolic syndrome also describe risk for diabetes; these features include: “apple shaped” waistline, elevated blood pressure, low levels of HDL, and elevated glucose and triglycerides. Type 2 diabetes can be controlled with a combination of improved diet, exercise, and sometimes drugs. Type 2 diabetes can be controlled with a combination of improved diet, exercise, and sometimes drugs.

84. Video: Gene Therapy for Diabetes  This video clip is available in CNN Today Videos for Genetics, 2005, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

85. Useful References for Section 8 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  American Diabetes Association  CDC: Diabetes  InfoTrac: Pancreas and Islet Transplantation in Type 1 Diabetes. Diabetes Care, April 2006.  InfoTrac: Preventing Diabetes. Kathy Doheny. Natural Health, April 2004.

86. Section 9 Some Final Examples of Integration and Control

87.  Light/dark cycles influence the pineal gland, which produces melatonin. Located in the brain, the pineal gland is a modification of a primitive “third eye” and is sensitive to light and seasonal influences; this gland secretes the hormone melatonin. Located in the brain, the pineal gland is a modification of a primitive “third eye” and is sensitive to light and seasonal influences; this gland secretes the hormone melatonin. Melatonin is secreted in the dark, and levels change with the seasons.Melatonin is secreted in the dark, and levels change with the seasons. The biological clock seems to tick in synchrony with day length and is apparently influenced by melatonin.The biological clock seems to tick in synchrony with day length and is apparently influenced by melatonin. Some Final Examples of Integration and Control

88. Seasonal affective disorder (SAD) affects persons during the winter and may result from an out-of-sync biological clock; melatonin makes it worse; exposure to intense light helps. Seasonal affective disorder (SAD) affects persons during the winter and may result from an out-of-sync biological clock; melatonin makes it worse; exposure to intense light helps. Melatonin levels may potentially be linked to the onset of puberty. Melatonin levels may potentially be linked to the onset of puberty. Some Final Examples of Integration and Control

89.  Hormones also are produced in the heart and GI tract. Atrial natriuretic peptide (ANP) produced by the heart atria regulates blood pressure. Atrial natriuretic peptide (ANP) produced by the heart atria regulates blood pressure. Gastrin and secretin from the GI tract stimulate release of stomach and intestinal secretions. Gastrin and secretin from the GI tract stimulate release of stomach and intestinal secretions. Some Final Examples of Integration and Control

90.  Prostaglandins have many effects. More than 16 prostaglandins have been identified in tissues throughout the body. More than 16 prostaglandins have been identified in tissues throughout the body. When stimulated by epinephrine and norepinephrine, prostaglandins cause smooth muscles in blood vessels to constrict or dilate.When stimulated by epinephrine and norepinephrine, prostaglandins cause smooth muscles in blood vessels to constrict or dilate. Allergic responses to dust and pollen may be aggravated by the effects of prostaglandins on airways in the lungs.Allergic responses to dust and pollen may be aggravated by the effects of prostaglandins on airways in the lungs. Prostaglandins have major effects on menstruation and childbirth. Prostaglandins have major effects on menstruation and childbirth. Some Final Examples of Integration and Control

91.  Growth factors influence cell division. Hormonelike proteins called growth factors influence growth by regulating the rate of cellular division. Hormonelike proteins called growth factors influence growth by regulating the rate of cellular division. Epidermal growth factorEpidermal growth factor (EGF) influences the growth of many cell types, as does insulinlike growth factor (IGF). Nerve growth factor (NGF)Nerve growth factor (NGF) promotes growth and survival of neurons in the developing embryo.

92. Some Final Examples of Integration and Control The current list of growth factors is expanding rapidly; many of these factors may have applications in medicine. The current list of growth factors is expanding rapidly; many of these factors may have applications in medicine.  Pheromones may be important communication molecules in humans. Pheromones are released outside of the body by several animals to serve as sex attractants, territory markers, and communication signals. Pheromones are released outside of the body by several animals to serve as sex attractants, territory markers, and communication signals. Recent studies suggest that humans also may communicate using pheromones. Recent studies suggest that humans also may communicate using pheromones.

93. Some Final Examples of Integration and Control  Are endocrine disrupters at work? Endocrine disrupters are proposed to be environmental substances that interfere with reproduction or development. Endocrine disrupters are proposed to be environmental substances that interfere with reproduction or development. Sperm counts in Sperm counts in males in Western countries declined about 40% between the years 1938 and 1990, possibly due to exposure to estrogens in the environment. Figure 15.13

94. Useful References for Section 9 The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.  National Research Center for Women & Families: Are Pretty Products Causing Early Puberty?  Howard Hughes Medical Institute: The Matters: Biological Clockworks  InfoTrac: Drug of Darkness: Can a Pineal Hormone Head Off Everything from Breast Cancer to Aging? Science News, May 13, 1995.  InfoTrac: The Chemistry of Love. Sanjay Gupta. Time, Feb. 18, 2002.

95. Video: Hormone-Induced Adjustments Video: Hormone-Induced Adjustments CLICK TO PLAY