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  1. Endocrine Control Chapter 31

  2. An Orchestra of Hormones • Hormones influence the growth, development, and reproductive cycles of nearly all animals • They influence behavior, physical appearance, and well-being

  3. Hormones • Secreted by endocrine glands, endocrine cells, and certain neurons • Animal hormones travel through the bloodstream to nonadjacent target cells

  4. Other Signaling Molecules • Neurotransmitters • Local signaling molecules • Pheromones

  5. Discovery of Hormones (1) • Bayliss and Starling wanted to know what triggers secretion of pancreatic juices into canine gut • Was it nerves or something else? • Severed nerves to dog’s upper intestine; left blood vessels intact

  6. Discovery of Hormones (2) • Results - Even with nerves severed, pancreas still secreted alkaline solution into intestine • Conclusion - The nervous system was not stimulating the pancreatic response, some other substance was the trigger

  7. Endocrine System hypothalamus pituitary gland

  8. Responses to Hormones Vary • Different hormones activate different responses in the same target cell • Not all types of cells respond to a particular hormone

  9. Two Main Hormone Types • Steroid hormones • Derived from cholesterol • Estrogens, progestins, androgens (such as testosterone), cortisol, aldosterone • Peptide hormones • Peptides, proteins, or glycoproteins • Glucagon, ADH, oxytocin, TRH, insulin, somatotropin, prolactin, FSH, LH, TSH

  10. Steroid Hormone Action • Most diffuse across the plasma membrane and bind to a receptor • Hormone-receptor complex acts in nucleus to inhibit or enhance transcription

  11. Steroid Hormones hormone • Most diffuse across the plasma membrane and bind to a receptor • Hormone-receptor complex acts in nucleus to inhibit or enhance transcription receptor hormone-receptor complex gene product

  12. Peptide Hormone glucagon • Hormone binds to a receptor at cell surface • Binding triggers a change in activity of enzymes inside the cell glucagon receptor cyclic AMP + Pi ATP cAMP activates protein kinase A Protein kinase A converts phosphorylase kinase to active form and inhibits an enzyme required for glucagon synthesis.

  13. The Hypothalamus • Region in the forebrain • Contains hormone-secreting cells • Interacts with pituitary

  14. Pituitary Gland • Pea-size gland at base of hypothalamus • Two lobes: • Posterior lobe stores and secretes hormones that were synthesized in the hypothalamus • Anterior lobe produces and secretes its own hormones

  15. Posterior Lobe

  16. Anterior Pituitary ACTH TSH FSH LH PR L STH (GH) (growth-promoting effects) adrenal glands thyroid gland testes in males ovaries in females mammary glands

  17. Normal Hormone Production • Generally, the body produces only very small amounts of hormones • To isolate 1 milligram of TRH, researchers dissected 7 metric tons of hypothalamic tissue

  18. Abnormal Somatotropin Output • Gigantism results from overproduction of STH during childhood • Pituitary dwarfism results from underproduction of STH during childhood • Acromegaly results from overproduction of STH during adulthood

  19. Effects and Control of Hormone Secretion • Hormones often interact • Negative feedback mechanisms often control secretion • Environmental cues may mediate secretion

  20. Feedback Mechanisms • Negative feedback • An increase in concentration of a hormone triggers activities that inhibit further secretion • Positive feedback • An increase in concentration of a hormone triggers activities that stimulate further secretion

  21. Negative Feedback: Adrenal Gland

  22. Control of Cortisol Secretion (1) • Hypothalamus senses decline in glucose and secretes a releasing hormone (CRH) • CRH stimulates anterior pituitary to secrete ACTH • ACTH acts on the adrenal cortex to stimulate cortisol secretion

  23. Control of Cortisol Secretion (2) • Cortisol secretion • Inhibits blood glucose uptake by muscle and other tissues • Causes breakdown of proteins to amino acids and conversion to glucose • Causes degradation of adipose tissue to fatty acids for use as energy source

  24. Control of Cortisol Secretion (3) • Decrease in glucose uptake and release of glucose from protein breakdown causes blood glucose level to rise • Hypothalamus and anterior pituitary detect the increase and decrease secretion of CRH and ACTH • Adrenal cortex decreases cortisol secretion

  25. Localized Feedback in Adrenal Medulla • Norepinephrine secreted by neurons in the medulla accumulates in the synaptic gap • Some molecules bind to receptors on the axon endings that secreted them • This prevents further secretion of norepinephrine by that axon

  26. Thyroid Gland Disorders • Goiter • Hyperthyroidism • Hypothyroidism

  27. Calcium Regulation • Parathyroid hormone (PTH) is the main regulator of calcium in the blood • It is secreted when calcium levels drop • PTH causes bone cells to digest bone tissue and release calcium • PTH also stimulates calcium reabsorption by the kidneys and absorption by the gut

  28. Local Signaling Molecules • Prostaglandins • Produced and secreted in response to local changes • Sixteen types with a variety of effects • Growth factors • Affect cell division rates in tissues

  29. Control of Glucose Metabolism insulin Glucose uptake Glucose to glycogen Glucose falls Glucose is absorbed Cells use glucose Glucose rises Glycogen to glucose glucagon

  30. Diabetes Mellitis • Disease in which excess glucose accumulates in blood, then urine • Effects include • Excessive urination • Constant thirst • Weight loss • Ketone formation and acid-base imbalances

  31. Two Types of Diabetes • Type 1 • Autoimmune disease • Usually appears in childhood • Treated with insulin injections • Type 2 • Target cells don’t respond • Usually appears in adults • Treated with diet, drugs

  32. The Pineal Gland • Photosensitive gland embedded in brain • In the absence of light, secretes melatonin • Controls seasonal sexual behavior in many animals • Affects the human biological clock • May also play a role in human puberty and in seasonal affective disorder

  33. Deformed Frogs • The number of deformed frogs is increasing worldwide • One factor may be water pollutants that interfere with thyroid function • In one study, frogs from polluted water developed normally when they were given extra thyroid hormones

  34. Control of Molting • In arthropods, molting is controlled by the steroid hormone ecdysone • In crustaceans, molting glands produce and store this hormone • Hormone-secreting neurons control its release • The neurons respond to environmental cues

  35. Control of Molting