Chapter 5: Hormonal Responses to Exercise

1. Chapter 5:Hormonal Responses to Exercise EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 5th edition Scott K. Powers & Edward T. Howley Presentation revised and updated by TK Koesterer, Ph.D., ATC Humboldt State University

2. Neuroendocrinology Endocrine glands 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

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. 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

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

9. Mechanism of Steroid Hormones

10. Cyclic AMP�Second Messenger� Mechanism

11. Other Second Messenger, Systems

12. Hormones: Regulation and Action Hormones are secreted from endocrine glands Hypothalamus and pituitary glands Thyroid and parathyroid glands Adrenal glands Pancreas Testes and Ovaries

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

14. Anterior Pituitary Gland

15. Growth Hormone 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 by increasing gluconeogenesis

16. Posterior Pituitary Gland Secretes antidiuretic hormone (ADH) or vasopressin Reduces water loss from the body to maintain plasma volume Stimulated by: High plasma osmolality and low plasma volume due to sweating - Exercise

18. Change in the Plasma ADH Concentration During Exercise

19. Thyroid Gland Triiodothyronine (T3) & thyroxine (T4) Important in maintaining metabolic rate and allowing full effect of other hormones Incr. glucose uptake by cells; incr. FFA usage T3 6-12 hours; T4 2-3 days; inc. w/ex. Calcitonin Regulation of plasma Ca++ incr. blood Ca++ = Incr. calcitonin release, blocks release of Ca++ from bones; Decreases with exercise Parathyroid Hormone Primary plasma Ca++ regulation When blood Ca++ is low, get incr. in Para. H. which stimulates kidneys to reabsorb Ca++ & incr. SI absorption Incr. w/ exercise

20. Adrenal Medulla Secretes catacholamines (Epinephrine and Norepinephrine) Increases HR, Glycogenolysis, Lypolysis, blocks Glucose entry into cells (glucose maint.)

21. Adrenal Cortex Mineralocorticoids (aldosterone) Maintain plasma Na+ and K+ Regulation of blood pressure

22. AldosteroneRenin - Angiotensin system

23. Change in Mineralcorticoids During Exercise

24. Adrenal Cortex Glucocorticoids (Cortisol) Stimulated by exercise and long-term fasting and stress Promotes the use of free fatty acids as fuel and decr. Glucose into cells Stimulates glucose synthesis, liver Promotes protein breakdown for gluconeogenesis and tissue repair Glucose Maint.

25. Pancreas Secretes digestive enzymes and bicarbonate into small intestine Releases Insulin - Promotes the storage of glucose, amino acids, and fats Glucagon - Promotes the mobilization of fatty acids and glucose. Increases glycogenolysis and gluconeogenesis

26. Muscle Glycogen Utilization Breakdown of muscle glycogen is under dual control Epinephrine-cyclic AMP Ca2+-calmodulin Delivery of glycogen parallels activation of muscle contraction Glycogenolysis � breakdown of glycogen

27. Control of Glycogenolysis

28. Muscle Glycogen Utilization Glycogenolysis is related to exercise intensity High-intensity of exercise results in greater and more rapid glycogen depletion Plasma epinephrine is a powerful simulator of glycogenolysis High-intensity of exercise results in greater increases in plasma epinephrine

29. Glycogen Depletion During Exercise

30. Epinephrine Concentration During Exercise

31. Maintenance of Plasma Glucose During Exercise Mobilization of glucose from liver glycogen stores Mobilization of FFA 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 T4 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 decreases At high intensity plasma cortisol increases

35. Changes in Plasma Cortisol During Exercise

36. Growth Hormone Important in the maintenance of plasma glucose Decreases glucose uptake Increases FFA mobilization Enhances gluconeogenesis

37. Growth Hormone in the Maintenance of Plasma Glucose

38. Growth Hormone During Exercise:Effect of Intensity

39. Growth Hormone During Exercise:Trained vs. Untrained

40. 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

41. Role of Catecholamines in Substrate Mobilization

42. Epinephrine & Norepinephrine During Exercise Increase linearly during exercise Favor the mobilization of FFA and maintenance of plasma glucose

43. Change in Plasma Catecholamines During Exercise

44. Plasma Catecholamines During Exercise Following Training

45. Effects of Insulin & Glucagon

46. Insulin During Exercise Plasma insulin decreases during exercise Prevents rapid uptake of plasma glucose Favors mobilization of liver glucose and lipid FFA Trained subjects during exercise More rapid decrease in plasma insulin Increase in plasma glucagon

47. Changes in Plasma Insulin During Exercise

48. Effect of Training on Plasma Insulin During Exercise

49. Effect of Training on Plasma Glucagon During Exercise

50. Effect of SNS on Substrate Mobilization

51. Hormonal Responses to Exercise

52. Hormonal Responses to Exercise

53. Free Fatty Acid Mobilization During Heavy Exercise FFA mobilization decreases during heavy exercise This occurs in spite of persisting hormonal stimulation for FFA mobilization May be due to high levels of lactic acid Promotes resynthesis of triglycerides Inadequate blood flow to adipose tissue Insufficient transporter for FFA in plasma

54. Effect of Lactic Acid on FFA Mobilization