Hormonal control and responses

1. Hormonal control and responses

2. Types of Hormones • Amino acid derivatives • epinephrine, serotonin, melotonin • Protein • insulin, parathyroid hormone, growth hormone • Steroids • derived from cholesterol • sex hormones, mineralocorticoids, prostaglandins

3. Hormone-receptor interaction • Some hormones circulate to all tissues, but only act on some • receptor must be present for effect to occur • eg thyroid stimulating hormone only exerts an effect on the thyroid • conversely some hormones work on virtually all tissues (insulin)

4. Blood Hormone Concentration • the effect of a hormone related to concentration in blood (to a point) • Concentration affected by 4 factors • rate of hormone secretion • rate of metabolism or excretion • transport proteins • plasma volume (affected by exercise)

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

6. Factors That Influence the Secretion of Hormones

7. Mechanisms of Hormone Action • alteration of membrane transport (insulin) • stimulation of DNA synthesis (testosterone, estrogen) • activation of “second messengers” • hormone doesn’t enter the cell

8. Relationship of Hypothalamus, Pituitary and Target Glands

9. The Hypothalamus is the “Master Gland” • the hypothalamus controls the pituitary in two ways • the hypothalamus can release “releasing hormones” • releasing hormones act on anterior pituitary (TSH, ACTH, GH) • neurons originating in the hypothalamus act on posterior pituitary (ADH)

10. Positive and Negative Input to the Hypothalamus (Growth Hormone)

11. Growth Hormone • uptake of amino acids and protein synthesis • opposes insulin • reduces use of plasma glucose • increases gluconeogenesis • mobilizes FFA

12. Antidiuretic Hormone (ADH) • causes resorbtion of H2O to maintain fluid • stimulated by two factors • high plasma osmolality (sweating) • low plasma volume (loss of blood, exercise)

13. Intensity vs. Plasma ADH

14. The Adrenal Glands • Medulla • secretes epinephrine (E) and norepinephrine (NE) • Cortex • secretes mineralocorticoids, glucocorticoids

15. Response to Catecholamines: Role of Receptor Type

17. Aldosterone (Mineralocorticoid) • regulates K+ and Na+ concentrations • controls resorbtion in the kidney • involved in thirst response

18. Intensity vs. Mineralocorticoid Response

19. Actions promotes breakdown of tissue protein (inhibits protein synthesis) mobilizes FFA from adipose stimulates gluconeogenesis blocks entry of glucose into tissues (increases fat utilization) Involved in adaptation response to stress (exercise) Cortisol

20. Control of Cortisol Secretion

21. Insulin aids in transport of glucose into cells stimulated when blood sugar increases (storage of glucose, amino acids and fat) inhibited during exercise Glucagon opposite effect of insulin stimulated by low blood glucose mobilizes glucose and fatty acids Pancreas

22. Sex Hormones • testosterone • elevated during short-term high intensity exercise • levels typically lower in endurance trained individuals

23. Estrogen • promotes higher levels of fat metabolism ? • chronic endurance training may suppress E2 (amenorrhea)

24. glycogen metabolism controlled by epinephrine (cAMP) and intracellular Ca++ (calmodulin) from sarcoplasmic reticulum epinephrine increases rapidly with intense exercise adrenergic blockade glycogen depleted only in exercising muscles Ca++ faster than cAMP and more specific Muscle Glycogen Utilization

25. Blood Glucose Homeostasis During Exercise • mobilization of glucose from liver glycogen stores • mobilization of plasma FFA from adipose tissue to spare plasma glucose • synthesis of new glucose in the liver (gluconeogenesis) from AA, La, and glycerol • blocking of glucose entry into cells to force the substitution of FFA as a fuel

26. Slow Acting Hormones • Thyroxine • allows other hormones (eg epinephrine) to exert effect • Cortisol • GH

27. Cortisol and Maintenance of Plasma Glucose

28. At low intensity, cortisol decreases- at high intensity it increases

29. Growth Hormone Effects During Exercise

30. Growth Hormone During Exercise • Combine amino acids and glycerol to make glucose in the liver • Breaks down triglycerides (fat) in the adipose tissue to make FFA available • Blocks entry of glucose into the cell • All of these go to maintain blood glucose

31. Plasma GH Response vs. Intensity

32. GH Response in Runners vs. Controls (Runners have improved response)

33. catecholamines (epinephrine and norepinephrine) N primarily neurotransmitter at synapse E primarily plasma hormone insulin glucagon Fast Acting Hormones

34. Effects of Catecholamines during Exercise

35. Catecholamines (adrenergic) During Exercise • Break down glycogen in liver to free glucose available • Break down triglycerides in the adipose tissue to make FFA available • Block entry of glucose into the cell

36. Catecholamine Response during Prolonged Exercise

37. Insulin (storage) vs. Glucagon (mobilization)

38. Insulin Levels Reduced during Moderate to Intense Exercise

39. Endurance Training Attenuates Insulin Response at Given Workload

40. Reduced Glucagon Response after Endurance Training

41. Take home… • Almost all of the hormonal responses will be attenuated with endurance training • Exception-growth hormone

42. increased utilization of FFA as fuel substrate decreased reliance on plasma glucose therefore decreased reliance on liver glycogen Glucagon Response Reduced after Endurance Training Because…

43. Remember • -adrenergic… inhibition • -adrenergic… excitation

44. Adrenergic Control of Pancreatic Hormones

45. Effect of Increased Sympathetic Activity on Fuel Utilization

46. increased blood flow to exercising tissues increased metabolism causes gradient (diabetics) increased # s of glucose transporter at membrane (diabetics) Glucose Uptake by Cells can Increase 7-25 Fold During Exercise. How?

47. General Hormonal Responses to Graded or Prolonged Exercise

48. Lactic Acid Inhibits FFA Release from Adipose Tissue (Means?)