Hormones and the Endocrine System Chapter 45

1. Hormones and the Endocrine SystemChapter 45

2. Overview: The Body’s Long-Distance Regulators • Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body • Hormones reach all parts of the body, but only target cells have receptors for that hormone

3. Coordination between endocrine and nervous systems • The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior • The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling.

4. Concept 45.1: Hormones and other signaling molecules bind to target receptors, triggering specific response pathways • Intercellular Communication • The ways that signals are transmitted between animal cells are classified by two criteria • The type of secreting cell • The route taken by the signal in reaching its target

5. Endocrine Signaling • Endocrine cells that release specific signaling molecules, which can travel long distances through the blood to reach all parts of the body. • Maintains homeostasis, mediates responses to stimuli, regulates growth and development Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

6. Paracrine and Autocrine Signaling • Paracrine signaling—target cells lie near the secreting cells • Autocrine signaling—target cell is also the secreting cell • Both use local regulators that travel short distances, reaching target cells by diffusion • Both play roles in regulating blood pressure, nervous system function, and reproduction Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. b. Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell.

7. Synaptic and Neuroendocrine Signaling • Synaptic signaling--neurons form specialized junctions with target cells, called synapses • At synapses, neurons secrete molecules called neurotransmitters that diffuse short distances and bind to receptors on target cells Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. b. Cells communicate over short distances by using local regulators that target cells in the vicinity of the emitting cell.

8. Synaptic and Neuroendocrine Signaling • Neuroendocrinesignaling--specialized neurosecretory cells secrete molecules (neurohormones) that travel to target cells via the bloodstream (e.g. vasopressin—essential to kidney function and water balance) Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

9. Signaling by Pheromones • Members of the same animal species sometimes communicate with pheromones, chemicals that are released into the environment • Pheromones serve many functions, including marking trails leading to food, defining territories, warning of predators, and attracting potential mates Essential knowledge 3.E.1: Individuals can act on information and communicate it to others. a. Organisms exchange information with each other in response to internal changes and external cues, which can change behavior. LO 3.42 The student is able to describe how organisms exchange information in response to internal changes or environmental cues.

10. Endocrine Tissues and Organs • Endocrine glands – endocrine cells grouped together in ductless organs • Secrete hormones directly into surrounding fluid • Exocrine glands – have ducts and secrete substances onto body surfaces or into cavities

11. Multiple Effects of Hormones • The same hormone may have different effects on target cells that have • Different receptors for the hormone • Different signal transduction pathways

12. Feedback Regulation • Negative feedback inhibits a response by reducing the initial stimulus, thus preventing excessive pathway activity Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point.

13. Feedback Regulation • Positive feedback reinforces a stimulus to produce an even greater response Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. b. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set-point. Amplification occurs when the stimulus is further activated which, in turn, initiates an additional response that produces system change.

14. Insulin and Glucagon: Control of Blood Glucose • Insulin produced by alpha cells of pancreatic islets • Reduces blood glucose levels by • Promoting the cellular uptake of glucose • Slowing glycogen breakdown in the liver • Promoting fat storage, not breakdown Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

15. Insulin and Glucagon: Control of Blood Glucose • Glucagon produced by beta cells of pancreatic islets • increases blood glucose levels by • Stimulating conversion of glycogen to glucose in the liver • Stimulating breakdown of fat and protein into glucose Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

16. Diabetes Mellitus • Caused by a deficiency of insulin or a decreased response to insulin in target tissues • It is marked by elevated blood glucose levels • Type 1 diabetes mellitus(insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells • Type 2 diabetes mellitus(non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. c. Alteration in the mechanisms of feedback often results in deleterious consequences.

17. Concept 45.3: The hypothalamus and pituitary are central to endocrine regulation • Endocrine pathways are subject to regulation by the nervous system, including the brain

18. Coordination of Endocrine and Nervous Systems in Vertebrates • The hypothalamus receives information from the nervous system and initiates responses through the endocrine system • Attached to the hypothalamus is the pituitary gland • Posterior pituitary - stores and secretes hormones that are made in the hypothalamus • Anterior pituitary - makes and releases hormones under regulation of the hypothalamus

19. Posterior Pituitary Hormones • The two hormones released from the posterior pituitary act directly on nonendocrine tissues • Oxytocin regulates milk secretion by the mammary glands • Antidiuretic hormone (ADH) regulates water uptake by the kidneys Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

20. Antidiuretic hormone (ADH) Ch. 44 • Eating a bag of salty pretzels decreases blood osmolarity • This triggers the release of ADH by posterior pituitary • ADHmakes kidneys retain more water and excrete more concentrated urine • Blood osmolarity increases, osmoreceptors in hypothalamus reduce ADH production • What do you think happens if you drink a large volume of water? Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms maintain dynamic homeostasis for a particular condition (variable) by regulating physiological processes, returning the changing condition back to its target set point.

21. Anterior Pituitary Hormones • Hormone production here is controlled by releasing and inhibiting hormones from the hypothalamus • For example, prolactin-releasing hormone from the hypothalamus stimulates the anterior pituitary to secrete prolactin (PRL), which has a role in milk production Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

22. Thyroid Regulation: A Hormone Cascade Pathway http://www.answering-christianity.com/thyroid_gland_1.jpg • The release of thyroid hormone results from a hormone cascade pathway involving the hypothalamus, anterior pituitary, and thyroid gland • Hormone cascade pathways typically involve negative feedback Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. a. Negative feedback mechanisms… Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

23. Disorders of Thyroid Function and Regulation • Hypothyroidism, too little thyroid function, can produce symptoms such as • Weight gain, lethargy, cold intolerance • Hyperthyroidism, excessive production of thyroid hormone, can lead to • High temperature, sweating, weight loss, irritability, and high blood pressure • Graves disease, a form of hyperthyroidism caused by autoimmunity, is typified by protruding eyes Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. c. Alteration in the mechanisms of feedback often results in deleterious consequences.

24. Malnutrition can alter thyroid function • Thyroid hormone refers to a pair of hormones • Triiodothyronin (T3), with three iodine atoms • Thyroxine (T4), with four iodine atoms • Insufficient dietary iodine causes pituitary to secrete TSH •  TSH levels lead to an enlarged thyroid gland, called a goiter Campbell, Reece, and Simon. (2007 ). Essential Biology with Physiology. Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. c. Alteration in the mechanisms of feedback often results in deleterious consequences.

25. Concept 45.4: Endocrine glands respond to diverse stimuli in regulating homeostasis, development, and behavior • Endocrine signaling regulates homeostasis, development, and behavior

26. Parathyroid Hormone and Vitamin D: Control of Blood Calcium • Two antagonistic hormones regulate the homeostasis of calcium (Ca2+) in the blood of mammals • Parathyroid hormone (PTH) is released by the parathyroid glands • Calcitonin is released by the thyroid gland Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

27. PTH increases the level of blood Ca2+ • PTH releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys • It also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food • Calcitonin decreases the level of blood Ca2+ • It stimulates Ca2+ deposition in bones and secretion by kidneys Essential knowledge 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes.

28. Adrenal Hormones: Response to Stress • The adrenal glands are adjacent to the kidneys • Each adrenal gland actually consists of two glands: the adrenal medulla (inner portion) and adrenal cortex (outer portion) http://biology-forums.com/gallery/14755_28_08_12_1_42_24_82281403.jpeg

29. Hormones from the Adrenal Medulla • The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline) • They are secreted in response to stress-activated impulses from the nervous system • They mediate various fight-or-flight responses

30. Short Term Stress • Epinephrine and norepinephrine • Trigger the release of glucose and fatty acids into the blood • Increase oxygen delivery to body cells • Direct blood toward heart, brain, and skeletal muscles and away from skin, digestive system, and kidneys • The release of epinephrine and norepinephrine occurs in response to involuntarynerve signals Essential knowledge 3.E.1: Individuals can act on information and communicate it to others. a. Organisms exchange information with each other in response to internal changes and external cues, which can change behavior.

31. Hormones from the Adrenal Cortex • The adrenal cortex releases a family of steroids called corticosteroids in response to stress • These hormones are triggered by a hormone cascade pathway via the hypothalamus and anterior pituitary (ACTH) • Humans produce two types of corticosteroids: glucocorticoids and mineralocorticoids

32. Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system • Mineralocorticoids, such as aldosterone, affect salt and water balance • The adrenal cortex also produces small amounts of steroid hormones that function as sex hormones Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

33. Gonadal Sex Hormones • The gonads, testes and ovaries, produce most of the sex hormones: androgens, estrogens, and progestins • All three sex hormones are found in both genders, but in significantly different proportions • Synthesis of the sex hormones is controlled by FSH and LH from the anterior pituitary

34. Testosterone • The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system (sperm production) • Testosterone causes an increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.

35. Estrogens and progestins • Estrogens, most importantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics • In mammals, progestins, which include progesterone, are primarily involved in preparing and maintaining the uterus Essential knowledge 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. c. Signals released by one cell type can travel long distances to target cells of another cell type.