Chapter 26 Hormones and the

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1 Chapter 6 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. PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey 01 PearsonEducation, Inc. Lecture by Edward J. Zalisko Figure 6.0_1 Chapter 6: Big Ideas Figure 6.0_ The Nature of Chemical Regulation The Vertebrate Endocrine System Hormones and Homeostasis 6.1 Chemical signals coordinate body functions THE NATURE OF CHEMICAL REGULATION The endocrine system consists of all hormone-secreting cells and works with the nervous system in regulating body activities. Copyright 009 Pearson Education, Inc.

2 6.1 Chemical signals coordinate body functions 6.1 Chemical signals coordinate body functions The nervous system also communicates, regulates, and uses electrical signals via nerve cells. Comparing the endocrine and nervous systems The nervous system reacts faster. The responses of the endocrine system last longer. 6.1 Chemical signals coordinate body functions 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. Figure 6.1A Secretory vesicles Hormone molecules Target cell Blood vessel Endocrine cell Figure 6.1B 6. Hormones affect target cells using two main signaling mechanisms Nerve cell Nerve signals Neurotransmitter molecules Nerve cell 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.

3 6. Hormones affect target cells using two main signaling mechanisms Hormone signaling involves three key events: reception, signal transduction, and 6. Hormones affect target cells using two main signaling mechanisms An amino-acid-derived hormone binds to plasma-membrane receptors on target cells and initiates a signal transduction pathway. response. Animation: Water-Soluble Hormone Figure 6.A_s3 Water-soluble hormone 1 Interstitial fluid Receptor protein 6. Hormones affect target cells using two main signaling mechanisms Target cell Plasma membrane A steroid hormone can diffuse through plasma membranes, Signal transduction pathway Relay bind to a receptor protein in the cytoplasm or nucleus, and molecules form a hormone-receptor complex that carries out the transduction of the hormonal signal. 3 Cellular responses Cytoplasmic response or Nucleus Gene regulation Animation: Lipid-Soluble Hormone Figure 6.B_s4 Steroid hormone Interstitial fluid 1 Target cell Receptor protein THE VERTEBRATE ENDOCRINE SYSTEM Nucleus 3 Hormonereceptor complex DNA 4 mrna Transcription New protein Cellular response: activation of a gene and synthesis of new protein

4 6.3 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. 6.3 Overview: The vertebrate endocrine system consists of more than a dozen major glands The following figure shows the locations of the major endocrine glands. 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. Figure 6.3 Thyroid gland Parathyroid glands (embedded within thyroid) Thymus glands (atop kidneys) Pancreas Pituitary gland 6.3 Overview: The vertebrate endocrine system consists of more than a dozen major glands The following table summarizes the main hormones produced by the major endocrine glands and indicates how they function and are controlled. Testes (male) Ovaries (female) Table 6.3_1 Table 6.3_

5 6.3 Overview: The vertebrate endocrine system consists of more than a dozen major glands 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. 6.4 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. Figure 6.4A Brain 6.4 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 Posterior pituitary Anterior pituitary Bone stores and secretes oxytocin and ADH, which are made in the hypothalamus. Figure 6.4B Figure 6.4C Neurosecretory cell of hypothalamus Hormone Posterior pituitary Neurosecretory cell Blood vessel Releasing hormones from hypothalamus Blood vessel Anterior pituitary Pituitary hormones Endocrine cells of the anterior pituitary Oxytocin ADH TSH ACTH FSH and LH Prolactin (PRL) Growth hormone (GH) Endorphins Uterine muscles Mammary glands Kidney tubules Thyroid cortex Testes or ovaries Mammary glands (in mammals) Entire body Pain receptors in the brain

6 Figure 6.4D Figure 6.4E Inhibition TRH Anterior pituitary Inhibition TSH Thyroid Thyroxine 6.4 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. 6.4 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. 6.5 The thyroid regulates development and metabolism HORMONES AND HOMEOSTASIS The thyroid gland is located in the neck, just under the larynx (voice box). The thyroid gland produces two similar hormones, thyroxine (T 4 ) and triiodothyronine (T 3 ). These hormones regulate many aspects of metabolism, reproduction, and development.

7 Figure 6.5A 6.5 The thyroid regulates development and metabolism Thyroid imbalance can cause disease. Hyperthyroidism results from too much T 4 and T 3 in the blood, leads to high blood pressure, loss of weight, overheating, and irritability, and produces Graves disease. Hypothyroidism results from too little T 4 and T 3 in the blood and leads to low blood pressure, being overweight, and often feeling cold and lethargic. 6.5 The thyroid regulates development and metabolism Figure.A Iodine deficiency can produce a goiter, an enlargement of the thyroid. In this condition, the thyroid gland cannot synthesize adequate amounts of T 4 and T 3, and the thyroid gland enlarges. Figure 6.5B No inhibition 6.6 Hormones from the thyroid and parathyroid glands maintain calcium homeostasis Anterior pituitary Thyroid TRH TSH No inhibition No iodine Insufficient T 4 and T 3 produced Blood calcium is regulated by antagonistic hormones each working to oppose the actions of the other hormone: calcitonin, from the thyroid, lowers the calcium in the blood, and parathyroid hormone (PTH), from the parathyroid glands, raises the calcium in the blood. Thyroid grows to form goiter

8 Figure Calcitonin Pancreatic hormones regulate blood glucose s 6 Thyroid gland Blood Ca rises releases calcitonin Stimulus: Rising blood Ca (imbalance) Ca Homeostasis: Normal blood calcium (about 10 mg/100 ml) Ca Stimulates Ca deposition in bones 9 Blood Ca falls Reduces Ca reabsorption in kidneys Stimulus: Falling blood Ca (imbalance) 1 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. 5 Stimulates Ca release from bones 3 PTH Parathyroid glands release parathyroid hormone (PTH) Parathyroid gland Increases Ca uptake in intestines Active vitamin D 4 Increases Ca reabsorption in kidneys Figure 6.7 Body cells Insulin take up more 3 glucose Beta cells of pancreas stimulated to release insulin into the blood Liver takes up glucose 1 High blood and stores it as glucose glycogen Stimulus: Rising blood glucose Glucose (e.g., after eating a carbohydrate-rich Homeostasis: Normal blood glucose meal) (about 90 mg/100 ml) Glucose 4 Blood glucose declines to a set point; stimulus for insulin release diminishes Stimulus: Declining blood glucose (e.g., after skipping a meal) 6.8 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. Blood glucose rises to set point; stimulus for glucagon release diminishes 8 Liver breaks down glycogen and releases glucose to the blood 7 Glucagon 5 Low blood glucose 6 Alpha cells of pancreas stimulated to release glucagon into the blood 6.8 CONNECTION: Diabetes is a common endocrine disorder There are three types of diabetes mellitus. 1. Type 1 (insulin-dependent) is an autoimmune disease caused by the destruction of insulin-producing cells. 6.8 CONNECTION: Diabetes is a common endocrine disorder. Type (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.

9 6.8 CONNECTION: Diabetes is a common endocrine disorder Figure 6.8A 3. Gestational diabetes can affect any pregnant woman and lead to dangerously large babies, which can complicate delivery. Figure 6.8B Blood glucose (mg/100 ml) Diabetic Healthy Hours after glucose ingestion 6.9 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. Figure 6.9_1 6.9 The adrenal glands mobilize responses to stress Kidney gland medulla cortex 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.

10 Figure 6.9 gland Kidney medulla cortex Cross section of spinal cord Nerve signals 1 Nerve cell Nerve cell 3 4 ACTH Stress Releasing hormone Anterior pituitary Blood vessel 6.9 The adrenal glands mobilize responses to stress Adrenocorticotropic hormone (ACTH) from the pituitary causes the adrenal cortex to secrete glucocorticoids and medulla ACTH 5 cortex mineralocorticoids. Epinephrine and norepinephrine Short-term stress response Mineralocorticoids Glucocorticoids Long-term stress response The effects of these hormones cause long-term responses to stress. 1. Glycogen broken down to glucose; increased blood glucose. Increased blood pressure 3. Increased breathing rate 4. Increasedmetabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity Mineralocorticoids 1. Retention of sodium ions and water by kidneys. Increased blood volume and blood pressure Glucocorticoids 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose. Immune system may be suppressed 6.10 The gonads secrete sex hormones 6.10 The gonads secrete sex hormones Steroid sex hormones affect growth, affect development, and regulate reproductive cycles and sexual behavior. 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. Figure The gonads secrete sex hormones The synthesis of sex hormones by the gonads is regulated by the hypothalamus and pituitary.

11 6.11 EVOLUTION CONNECTION: A single hormone can perform a variety of functions in different animals Figure 6.11 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 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. You should now be able to 1. Explain how testosterone affects lions.. Compare the mechanisms and functions of the endocrine and nervous systems. 3. Distinguish between the two major classes of vertebrate hormones. 4. Describe the different types and functions of vertebrate endocrine organs. You should now be able to You should now be able to 5. Describe the interrelationships between the hypothalamus and pituitary glands. 6. Describe the functions of the thyroid and parathyroid glands. 7. Explain how insulin and glucagon manage blood glucose s. 8. Describe the causes and symptoms of type 1 and type diabetes and gestational diabetes. 9. Compare the functions of the adrenal gland hormones. 10. Describe the three major types of sex hormones and their functions. 11. Describe the diverse functions of prolactin in vertebrate groups and its evolutionary significance.