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Hormonal Responses to Exercise

Powers, Chapter 5. Hormonal Responses to Exercise. Neuroendocrinology 神經內分泌學. Sense information, organize appropriate responses, deliver messages to proper organs or tissues Endocrine glands 腺體 release hormones directly into the blood

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Hormonal Responses to Exercise

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  1. Powers, Chapter 5 Hormonal Responses to Exercise

  2. Neuroendocrinology 神經內分泌學 • Sense information, organize appropriate responses, deliver messages to proper organs or tissues • Endocrine glands 腺體 release hormones directly into the blood • Hormones alter the activity of tissues that possess receptors to which the hormone can bind • The plasma hormone concentration determines the magnitude of the effect at the tissue level

  3. Blood Hormone Concentration Determined by: • Rate of secretion of hormone from endocrine gland • Rate of metabolism or excretion of hormone • Quantity of transport protein • Changes in plasma volume

  4. Control of Hormone Secretion • Rate of insulin secretion from the pancreas is dependent on: • Magnitude of input • Stimulatory vs. inhibitory

  5. Factors That Influence the Secretion of Hormones

  6. Hormone-Receptor Interactions • Trigger events at the cell • Magnitude of effect dependent on: • Concentration of the hormone • Number of receptors on the cell • Affinity of the receptor for the hormone • Down-regulation of receptor number • decreased when exposed to chronically elevated hormone concentrations • Up-regulation of receptor number • Chronic exposure to low hormone concentrations

  7. Hormone-Receptor Interactions • Hormones bring about effects by: • Altering membrane transport • Stimulating DNA to increase protein synthesis • Activating second messengers • Cyclic AMP(cAMP) • Ca++ • Inositol triphosphate • Diacylglycerol

  8. Mechanism by Which Steroid Hormones Act on Target Cells

  9. The Cyclic AMP “Second Messenger” Mechanism

  10. Ca++ and Phospholipase C Second Messenger Systems

  11. Hormones: Regulation and Action • Hormones are secreted from endocrine glands • Hypothalamus 下視丘 and pituitary glands腦下垂體 • Thyroid 甲狀腺 and parathyroid glands 副甲狀腺 • Adrenal glands (adrenal medulla and adrenal cortex) 腎上腺 • Pancreas 胰臟 • Testes 睪丸 and Ovaries卵巢

  12. Hypothalamus • Controls activity of the anterior and posterior pituitary glands • Influenced by positive and negative input

  13. Positive and Negative Input to the Hypothalamus

  14. Anterior Pituitary Gland腦下垂體前葉

  15. Growth Hormone 生長激素 • Secreted from the anterior pituitary gland • Essential for normal growth • Stimulates protein synthesis and long bone growth • Increases during exercise • Mobilizes fatty acids from adipose tissue • Aids in the maintenance of blood glucose

  16. Posterior Pituitary Gland腦下垂體後葉 • Secretes antidiuretic hormone (ADH)抗利尿激素 • Reduces water loss from the body to maintain plasma volume • Stimulated by: • High plasma osmolality and low plasma volume due to sweating • Exercise

  17. Change in the Plasma ADH Concentration During Exercise

  18. Thyroid Gland • Triiodothyronine (T3) & thyroxine (T4) 甲狀腺素 • Important in maintaining metabolic rate and allowing full effect of other hormones • Calcitonin抑鈣素, 降血鈣素 • Regulation of plasma Ca++ • Parathyroid Hormone 副甲狀腺素 • Also involved in plasma Ca++ regulation

  19. Adrenal Gland • Adrenal medulla 腎上腺髓質 • Secretes catecholamines:Epinephrine 腎上腺素and norepinephrine 正腎上腺素 • Adrenal cortex腎上腺皮質 • Secretes steroid hormones:Mineralcorticoids礦物性皮質素, glucocorticoids糖皮質素

  20. Adrenal Medulla • Part of the sympathetic nervous system • Secrete catecholamines • Epinephrine (E) and norepinephrine (NE) • Bind to receptors on effector organs • Alpha () and beta () receptors • Bring about changes in cellular activity via second messengers

  21. Response to Catecholamines: Role of Receptor Type

  22. Adrenal Cortex • Mineralcorticoids (aldosterone醛固酮) • Promote reabsorption of Na+ and K+ in kidney, Involved in maintaining plasma Na+ and K+ • Part of the renin-angiotensin-aldosterone system of blood pressure regulation

  23. Adrenal Cortex • Glucocorticoids (Cortisol) 可體松 • Stimulated by exercise and long-term fasting • Promotes the use of free fatty acids as fuel • Stimulates glucose synthesis • Promotes protein breakdown for gluconeogenesis and tissue repair

  24. Pancreas Insulin 胰島素 • Secreted by the  cells of the islets of Langerhans • Promotes the storage of glucose, amino acids, and fats • Diabetes mellitus is characterized as a lack of insulin (Type 1) or a lack of insulin receptors (Type 2) • Results in high blood glucose levels • Considered a significant health risk Glucagon升糖激素 • Released from the  cells of the islets of Langerhans • Promotes the mobilization of fatty acids and glucose

  25. Testes • Release testosterone 睪固酮 • Anabolic steroid • Promotes tissue (muscle) building • Performance enhancement • Androgenic steroid • Promotes masculine characteristics

  26. Estrogen 女性荷爾蒙 • Establish and maintain reproductive function • Levels vary throughout the menstrual cycle

  27. Muscle Glycogen Utilization • Breakdown of muscle glycogen is under dual control • Epinephrine-cyclic AMP • Fig 5.13, 5.14 • Ca++-calmodulin • Delivery of glucose parallels activation of muscle contraction • Glycogenolysis can still occur in presence of -blocking agent • Propranolol, fig 5.15

  28. Control of Glycogenolysis

  29. Muscle Glycogen Utilization • Glycogen breakdown is related to exercise intensity • High-intensity exercise results in greater and more rapid glycogen depletion

  30. Plasma Epinephrine Concentration During Exercise

  31. Maintenance of Plasma Glucose During Exercise • Mobilization of glucose from liver glycogen stores • Mobilization of FFA (free fatty acid 游離脂肪酸) from adipose tissue • Spares blood glucose • Gluconeogenesis from amino acids, lactic acid, and glycerol • Blocking the entry of glucose into cells • Forces use of FFA as a fuel

  32. Blood Glucose Homeostasis During Exercise • Permissive and slow-acting hormones • Thyroxine 甲狀腺素 • Cortisol • Growth hormone • Act in a permissive manner to support actions of other hormones

  33. Cortisol • Stimulates FFA mobilization from adipose tissue • Mobilizes amino acids for gluconeogenesis • Blocks entry of glucose into cells

  34. Plasma Cortisol During Exercise • At low intensity:↓plasma cortisol • At high intensity:↑plasma cortisol

  35. Growth Hormone • Important in the maintenance of plasma glucose • ↓ glucose uptake, ↑FFA mobilization, ↑gluconeogenesis

  36. Growth Hormone During Exercise:Trained vs. Untrained

  37. Growth Hormone During Exercise:Effect of Intensity

  38. Blood Glucose Homeostasis During Exercise • Fast-acting hormones • Norepinephrine and epinephrine • Insulin and glucagon • Maintain plasma glucose • Increasing liver glucose mobilization • Increased levels of plasma FFA • Decreasing glucose uptake • Increasing gluconeogenesis

  39. Role of Catecholamines in Substrate Mobilization

  40. Epinephrine & Norepinephrine During Ex • Increase linearly during exercise • Favor the mobilization of FFA and maintenance of plasma glucose

  41. Epinephrine & Norepinephrine Following Training • Decreased plasma levels in response to exercise bout • Parallels reduction in glucose mobilization • Physical training, stimulates the sympathetic nervous system, increases the capacity to respond to extreme challenges

  42. Plasma Catecholamines During Exercise Following Training

  43. Effect of Insulin and Glucagon on FFA Uptake and Oxidation

  44. Insulin During Exercise • Plasma insulin decreases during exercise • Prevents rapid uptake of plasma glucose • Favors mobilization of glucose and FFA

  45. Effect of Training on Plasma Insulin During Exercise

  46. Effect of Training on Plasma Glucagon 升糖激素 During Exercise

  47. Control of Insulin and Glucagon Secretion During Exercise

  48. Effect of SNS 交感神經系統on Substrate Mobilization

  49. Hormonal Responses to Exercise

  50. Free Fatty Acid Mobilization During Exercise • FFA mobilization decreases during heavy exercise • This occurs in spite of persisting hormonal stimulation for FFA mobilization • Could be due to high levels of lactic acid • Promotes resynthesis of triglycerides

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