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CHAPTER 26 Chemical Regulation

CHAPTER 26 Chemical Regulation. Testosterone and Male Aggression. Testosterone and other male hormones seem to be related to aggressive behavior in some species

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CHAPTER 26 Chemical Regulation

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  1. CHAPTER 26Chemical Regulation

  2. Testosterone and Male Aggression • Testosterone and other male hormones seem to be related to aggressive behavior in some species • In the fish species Oreochromis mossambicus, elevated levels have been found in the males that engage in, or even just observe, territorial battles

  3. But scientists have demonstrated a correlation between testosterone levels and competition • Research has concluded that high levels of testosterone in human males does not lead directly to higher levels of violent aggression

  4. The overarching role of hormones is to coordinate activities in different parts of the body • Hormones regulate energy use, metabolism, and growth • Hormones and other chemicals also maintain homeostasis

  5. THE NATURE OF CHEMICAL REGULATION 26.1 Chemical signals coordinate body functions • Endocrine glands and neurosecretory cells secrete hormones • Hormones are chemical signals that are carried by the blood and cause specific changes in target cells • All hormone-secreting cells constitute the endocrine system • It works with the nervous system to regulate body activities

  6. Hormone from an endocrine cell Secretoryvesicles Bloodvessel Targetcell ENDOCRINE CELL Hormonemolecules Figure 26.1A

  7. Hormone from a neurosecretory cell Bloodvessel NEUROSECRETORYCELL Targetcell Hormonemolecules Figure 26.1B

  8. Neurotransmitters • Prostoglandins • Local regulators produce changes in cells NERVECELL Nervesignals Neurotransmittermolecules Nerve cell Figure 26.1C

  9. 26.2 Hormones affect target cells by two main signaling mechanisms • Most hormones derived from amino acids bind to receptor proteins in the target-cell plasma membrane • They initiate signal-transduction pathways that cause changes inside the target cell

  10. Hormone (epinephrine) RECEPTORPROTEIN 1 2 Plasmamembrane TARGETCELL (2)The receptor protein activates a signal-transduction pathway in the cell (1)A hormone binds to a receptor protein in the plasma membrane Signal-transductionpathway Relaymolecules 3 (3)A series of relay molecules transmits the signal to a protein that carries out the cell’s response Glycogen Glucogen Cellular response(in this example, glycogen breakdown) Figure 26.2A

  11. Steroidhormone 1 TARGETCELL 2 Receptorprotein • Steroid hormones bind to intracellular receptors • The steroid-receptor complex binds to DNA, turning specific genes on or off 3 Hormone-receptorcomplex NUCLEUS DNA 4 Transcription mRNA • In this example, a new protein is synthesized Newprotein Cellular response:activation of a geneand synthesis ofnew protein Figure 26.2B

  12. THE VERTEBRATE ENDOCRINE SYSTEM 26.3 Overview: The vertebrate endocrine system • The vertebrate endocrine system consists of more than a dozen glands • The glands secrete more than 50 hormones • Only the sex glands and the adrenal cortex secrete steroids • The remaining glands secrete nonsteroid hormones

  13. Hypothalamus Pineal gland Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands(atop kidneys) Pancreas Ovary (female) Testis (male) Figure 26.3

  14. Table 26.3

  15. Table 26.3, part 2

  16. 26.4 The hypothalamus, closely tied to the pituitary, connects the nervous and endocrine systems • The hypothalamus is the master control center of the endocrine system • It regulates the posterior and anterior pituitary gland Brain Hypothalamus Posterior pituitary Bone Anterior pituitary Figure 26.4A

  17. Composed of nervous tissue • Stores and secretes hormones made in the hypothalamus • Anterior pituitary • Composed of glandular tissue • Exerts control over the anterior pituitary by secreting releasing hormones or inhibiting hormones • Posterior pituitary

  18. Homeostasis is maintained by negative-feedback mechanisms coupled with environmental cues Hypothalamus TRH Inhibition Anterior pituitary TSH Thyroid Thyroxine Figure 26.4B

  19. 26.5 The hypothalamus and pituitary have multiple endocrine functions • Neurosecretory cells extending from the hypothalamus into the posterior pituitary • synthesize oxytocin and antidiuretic hormone (ADH) • transmit nerve signals that trigger oxytocin and ADH release from the posterior pituitary

  20. Hypothalamus Neurosecretorycell Hormone Posteriorpituitary Bloodvessel Anteriorpituitary Oxytocin ADH Uterine muscles Mammary glands Kidney tubules Figure 26.5A

  21. Releasing and inhibiting hormones secreted by the hypothalamus control the anterior pituitary • The brain and anterior pituitary also produce endorphins

  22. Neurosecretorycell Blood vessel Releasing hormonesfrom hypothalamus Endocrine cells ofthe anterior pituitary Pituitary hormones TSH ACTH FSHandLH Growthhormone(GH) Prolactin(PRL) Endorphins Thyroid Adrenalcortex Testes or ovaries Entirebody Mammary Glands(in mammals) Painreceptorsin the brain Figure 26.5B

  23. HORMONES AND HOMEOSTASIS 26.6 The thyroid regulates development and metabolism • The thyroid gland produces two amine hormones • T4 and T3 • These regulate development and metabolism • Negative feedback maintains homeostatic levels of T4 and T3 in the blood

  24. Thyroid imbalance can cause cretinism, metabolic disorders, and goiter No inhibition Hypothalamus TRH Anteriorpituitary TSH InsufficientT4 and T3produced No iodine Thyroid Thyroid growsto form goiter Figure 26.6A, B

  25. 26.7 Hormones from the thyroid and parathyroids maintain calcium homeostasis • Blood calcium level is regulated by a tightly balanced antagonism between • calcitonin from the thyroid • parathyroid hormone from the parathyroid glands

  26. Calcitonin Thyroidglandreleasescalcitonin • Calcium homeostasis StimulatesCa2+ depositionin bones ReducesCa2+ uptakein kidneys STIMULUS:Risingblood Ca2+level (imbalance) Homeostasis: Normal bloodcalcium level (about 10 mg/100 mL) STIMULUS:Fallingblood Ca2+ level(imbalance) Activevitamin D Parathyroidglandsrelease parathyroidhormone (PTH) Parathyroidgland StimulatesCa2+ releasefrom bones IncreasesCa2+ uptakein kidneys IncreasesCa2+ uptakein intestines PTH Figure 26.7

  27. 26.8 Pancreatic hormones manage cellular fuel • Blood glucose levels are controlled by two antagonistic hormones secreted by the pancreas • Insulin signals cells to use and store glucose as glycogen • Glucagon signals cells to release stored glucose into the blood

  28. Bodycellstake up moreglucose Insulin Beta cellsof pancreas stimulatedto release insulin intothe blood • Glucose homeostasis Liver takesup glucoseand stores it asglycogen Blood glucose leveldeclines to a set point;stimulus for insulinrelease diminishes High bloodglucose level STIMULUS:Rising blood glucoselevel (e.g., after eatinga carbohydrate-richmeal) Homeostasis: Normal blood glucose level(about 90 mg/100 mL) STIMULUS:Declining bloodglucose level(e.g., afterskipping a meal) Blood glucose levelrises to set point;stimulus for glucagonrelease diminishes Alphacells ofpancreas stimulatedto release glucagoninto the blood Liverbreaks downglycogen and releases glucoseto the blood Glucagon Figure 26.8

  29. 26.9 Connection: Diabetes is a common endocrine disorder • Diabetes mellitus is a serious hormonal disease • Body cells are unable to absorb glucose from the blood • There are two types of diabetes

  30. Autoimmune disease in which pancreatic beta cells are destroyed and thus not enough insulin is produced • Often develops before age 15 • Patient requires insulin supplement, often by injection • Type I (insulin-dependent) diabetes

  31. Pancreatic cells function properly and there are sufficient amounts of insulin produced • Body cells fail to respond to insulin • Accounts for 90% of diabetes cases in the United States • Associated with obesity • Often develops after age 40 • Manageable • Type II (non-insulin-dependent) diabetes

  32. The diagnostic test for diabetes is a glucose-tolerance test Diabetic Normal Figure 26.9

  33. 26.10 The adrenal glands mobilize responses to stress • Hormones from the adrenal glands help maintain homeostasis when the body is stressed • Adrenal medulla • Nervous signals from the hypothalamus stimulate secretion of epinephrine and norepinephrine • These quickly trigger the fight or flight response

  34. Chemical signals (ACTH) stimulate secretion of corticosteroids, including glucocorticoids and mineralocorticoids • Corticosteroids boost blood pressure and energy in response to long-term stress • Adrenal cortex

  35. Adrenalmedulla STRESS Nervesignals Adrenalgland • How the adrenal glands control our responses to stress Adrenalcortex Hypothalamus Releasing hormone Kidney Nervecell Anterior pituitary Spinal cord (cross section) Blood vessel ACTH Nervecell Adrenal cortex Adrenalmedulla ACTH Epinephrine andnorepinephrine Glucocorticoids Mineralocorticoids SHORT-TERM STRESS RESPONSE LONG-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 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Immune system may be suppressed Figure 26.10

  36. 26.11 Connection: Glucocorticoids offer relief from pain, but not without serious risks • Athletes often take glucocorticoids • They relieve pain and inflammation • But they also mask the injury and suppress immunity • Example: cortisone Figure 26.11

  37. 26.12 The gonads secrete sex hormones • The gonads secrete sex hormones • Secretion is controlled by the hypothalamus and the pituitary • The steroid hormones are found in both sexes but in different proportions • estrogens • progestins • androgens

  38. maintain the female reproductive system • stimulate the development of female characteristics • Estrogen and progestins

  39. In male elephant seals, androgens account for bodies weighing 2 tons or more, a thick hide, and aggressive behavior • Androgens, such as testosterone, trigger the development of male characteristics Figure 26.12

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