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Chapter 26

Chapter 26. Chemical Regulation. Testosterone and Male Aggression: Is There a Link? Testosterone and other androgens develop and maintain male reproductive anatomy and secondary sexual characteristics Does testosterone promote aggressive behavior?

lesley-church
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Chapter 26

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  1. Chapter 26 Chemical Regulation

  2. Testosterone and Male Aggression: Is There a Link? • Testosterone and other androgens develop and maintain male reproductive anatomy and secondary sexual characteristics • Does testosterone promote aggressive behavior? • In male cichlid fish, androgen levels increase during territorial displays • The connection in humans is problematic • Hormones and other chemical signals enable organ systems to function cooperatively

  3. THE NATURE OF CHEMICAL REGULATION • 26.1 Chemical signals coordinate body functions • Hormones are chemical signals that communicate regulatory messages throughout the body • Secreted by endocrine glands that make up the endocrine system • Travel in the circulatory system to target cells • Local regulators secreted into interstitial fluid affect nearby target cells • Pheromones carry messages between different individuals of a species

  4. The endocrine system collaborates with the nervous system in controlling whole-body activities • Neurosecretory cells perform functions of both systems • Chemical neurotransmitters carry information from one nerve cell to another or to other cells

  5. LE 26-1a Secretory vesicles Blood vessel Target cell Endocrine cell Hormone molecules

  6. LE 26-1b Blood vessel Neuro- secretory cell Target cell Hormone molecules

  7. LE 26-1c Nerve cell Nerve signals Neuro- transmitter molecules Nerve cell

  8. 26.2 Hormones affect target cells by two main signaling mechanisms • Hormones are made of proteins, amines, or steroids • Hormone signaling involves three key events • Reception of the signal • Signal transduction • Response: change in target cell's behavior

  9. Water-soluble hormone mechanism • Hormone binds to receptor protein on target cell's plasma membrane • Activation of protein initiates signal transduction pathway • Final relay molecule activates protein that carries out cell's response • One hormone may trigger a variety of responses Animation: Water-Soluble Hormone

  10. LE 26-2a Water-soluble hormone (epinephrine) Receptor protein Target cell Plasma membrane Signal transduction pathway Relay molecules Glycogen Glucose Cellular response (in this example, glycogen breakdown)

  11. Steroid hormone mechanism • Hormone diffuses through plasma membrane of target cell • Binds to receptor protein in cytoplasm or nucleus, creating a complex that transduces the signal • Hormone-receptor complex attaches to specific site on cell's DNA • Binding to DNA stimulates transcription of genes into RNA, which is translated into proteins

  12. LE 26-2b Lipid-soluble hormone (testosterone) Target cell Receptor protein Hormone- receptor complex Nucleus DNA Transcription mRNA New protein Cellular response: activation of a gene and synthesis of new protein

  13. Animation: Lipid-Soluble Hormone

  14. THE VERTEBRATE ENDOCRINE SYSTEM • 26.3 Overview: The vertebrate endocrine system • The vertebrate endocrine system consists of more than a dozen glands • Glands can be endocrine specialists or have endocrine and nonendocrine function • Hormones can have a narrow or wide range of targets and effects • Only sex organs and cortex of adrenal gland produce steroid hormones • Most endocrine glands produce water-soluble hormones

  15. The pineal gland is an outgrowth of the brain • Secretes melatonin, affecting animal's daily and seasonal rhythms • Cues reproductive activity in mammals • The thymus gland plays an important role in the immune system • Stimulates development of T cells • Shrinks drastically at puberty

  16. LE 26-3 Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands (atop kidneys) Pancreas Ovary (female) Testes (male)

  17. 26.4 The hypothalamus, closely tied to the pituitary, connects the nervous and endocrine systems • The hypothalamus exerts master control over the endocrine system • Receives information from nerves about internal and external conditions • Uses the pituitary gland to relay directives to other glands • Releasing and inhibiting hormones from the hypothalamus control the pituitary

  18. LE 26-4a Brain Hypothalamus Posterior pituitary Anterior pituitary Bone

  19. The posterior pituitary is an extension of the hypothalamus • Stores and secretes hormones made in the hypothalamus • Oxytocin and antidiuretic hormone (ADH) • The anterior pituitary is composed mostly of glandular tissue • Synthesizes and secretes its own hormones • TSH, ACTH, FSH, LH, growth hormone, prolactin, and endorphins

  20. LE 26-4b Hypothalamus Hormone Neurosecretory cell Posterior pituitary Anterior pituitary Blood vessel Oxytocin ADH Uterine muscles Mammary glands Kidney tubules

  21. LE 26-4c Neurosecretory cell Blood vessel Releasing hormones from hypothalamus Endocrine cells of the anterior pituitary Pituitary hormones TSH ACTH Endorphins FSH and LH Growth hormone (GH) Prolactin (PRL) Thyroid Adrenal cortex Mammary glands (in mammals) Entire body Testes or ovaries Pain receptors in the brain

  22. The hypothalamus acts through the anterior pituitary to direct activity of the thyroid gland • Hypothalamus produces TRH • TRH stimulates anterior pituitary to produce TSH • TSH influences thyroid to release thyroxine • Controlled by a negative-feedback mechanism

  23. LE 26-4d Hypothalamus Inhibition TRH Anterior pituitary Inhibition TSH Thyroid Thyroxine

  24. Other critical pituitary hormones • Growth hormone (GH) promotes protein synthesis and use of fat for energy • Too much or too little leads to various human disorders • Prolactin (PRL) has many different effects in different species • Endorphins are the body's natural painkillers

  25. HORMONES AND HOMEOSTASIS • 26.5 The thyroid regulates development and metabolism • Thyroid hormones affect virtually all the tissues of vertebrates • Thyroid gland produces T4 (thyroxine) and T3 • Play crucial roles in development and maturation • In mammals, thyroid hormones maintain normal blood pressure, heart rate, muscle tone, and digestive and reproductive functions

  26. Hyperthyroidism • Excess T4 and T3 in the blood • Most common result is Graves disease • Hypothyroidism • Insufficient amounts of T4 and T3 • Can result from defective thyroid gland or insufficient iodine in diet • Can lead to cretinism and goiter • Negative feedback maintains homeostatic levels of T4 and T3

  27. LE 26-5b No inhibition Hypothalamus TRH No inhibition Anterior pituitary TSH Insufficient T4 and T3 produced No iodine Thyroid Thyroid grows to form goiter

  28. 26.6 Hormones from the thyroid and parathyroids maintain calcium homeostasis • Blood calcium levels are regulated by two antagonistic hormones • Calcitonin from the thyroid • Parathyroid hormone (PTH) from the four parathyroid glands • Feedback systems keep calcium levels near the homeostatic set point • Failure can have drastic effects on the body

  29. LE 26-6 Calcitonin Thyroid gland releases calcitonin Stimulates Ca2+ deposition in bones Reduces Ca2+ uptake in kidneys Blood Ca2+ falls Stimulus: Rising blood Ca2+ level (imbalance) Homeostasis: Normal blood calcium level (about 10 mg/100mL) Stimulus: Falling blood Ca2+ level (imbalance) Blood Ca2+ rises Active vitamin D Parathyroid glands release parathyroid hormone (PTH) Parathyroid gland Stimulates Ca2+ release from bones Increases Ca2+ uptake in kidneys Increases Ca2+ uptake in intestines PTH

  30. 26.7 Pancreatic hormones regulate blood glucose levels • The pancreas secretes two antagonistic hormones critical in regulating the body's energy supply • Insulin signals cells to use and store glucose • Glucagon causes cells to release stored glucose into the blood

  31. Negative feedback manages the amount of glucose circulating in blood versus amount stored as glycogen

  32. LE 26-7 Body cells take up more glucose Insulin Beta cells of pancreas stimulated to release insulin into the blood Blood glucose level declines to a set point; stimulus for insulin release diminishes Liver takes up glucose and stores it as glycogen High blood glucose level Stimulus: Rising blood glucose level (e.g, after eating a carbohydrate-rich meal) Homeostasis: Normal blood glucose level (about 90 mg/100 mL) Stimulus: Declining blood glucose level (e.g., after skipping a meal) Blood glucose level rises to set point; stimulus for glucagon release diminishes Alpha cells of pancreas stimulated to release glucagon into the blood Liver breaks down glycogen and releases glucose to the blood Glucagon

  33. CONNECTION • 26.8 Diabetes is a common endocrine disorder • In diabetes mellitus, body cells are unable to absorb glucose from the blood • Results from a lack of insulin or a failure of cells to respond to it • Cells burn fats or protein as fuel • Glucose remains in the blood, is excreted in urine • Can be a life-threatening disease

  34. Type 1 (insulin-dependent) diabetes is an autoimmune disease • Usually develops in childhood • Pancreas does not produce enough insulin • Treated by injections of insulin • Type 2 (non-insulin-dependent) diabetes is usually associated with being overweight • Characterized by deficiency of insulin or reduced responsiveness of target cells • Treated by diet and lifestyle changes

  35. Diabetes can be detected by a glucose tolerance test

  36. LE 26-8 400 350 300 Diabetic 250 Blood glucose (mg/100mL) 200 150 Normal 100 50 0 1 2 0 1 2 3 4 5 Hours after glucose ingestion

  37. 26.9 The adrenal glands mobilize responses to stress • Adrenal glands atop the kidneys are actually two glands fused together • The adrenal medulla ensures rapid, short-term response to stress • Responds to nerve signals from the hypothalamus

  38. Produces fight-or-flight hormones epinephrine and norepinephrine • Mobilize glucose • Increase blood pressure, breathing, and metabolic rates • Change blood-flow patterns

  39. The adrenal cortex provides a slower, longer lasting response to stress • Responds to endocrine signals: ACTH from the pituitary • Secretes corticosteroids • Glucocorticoids act mainly on salt and water balance • Mineralocorticoids mobilize cellular fuel

  40. CONNECTION • 26.10 Glucocorticoids offer relief from pain, but not without serious risks • Glucocorticoids relieve inflammation and pain • Often prescribed for athletic injuries • Can mask injury and suppress immunity • Increase risk of diabetes, eye problems, bone fractures • Former basketball player Bill Walton has drawn attention to the dangers

  41. Table 45.1 • Major human endocrine glands and some of their hormones

  42. Table 45.1

  43. 26.11 The gonads secrete sex hormones • Estrogens, progestins, and androgens are steroid sex hormones • Produced by the gonads in response to signals from the hypothalamus and pituitary • Both males and females have all three hormones in different proportions

  44. Females have a high ratio of estrogens to androgens • Estrogens stimulate development of female characteristics and maintenance of reproductive system • Progestins prepare and maintain uterus to support an embryo • Males have a high ratio of androgens to estrogen • Androgens stimulate development of male characteristics and maintenance of reproductive system • Testosterone is the main androgen

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