1. Hormonal Responses to Exercise
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 Adrenal cortex 腎上腺皮質
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
Effect of E/NE
Membrane-bound enzyme
Intracellular mediator
Effects on Various Tissues 1
E=NE
Adenylate cyclase
 cAMP
 Heart rate
 Glycogenolysis
 Lipolysis 2
E>>>NE
 Bronchodilation
 Vasodilation 1
ENE
Phospholipase C
 Ca++
 Phosphodiesterase
 Vasoconstriction 2
cAMP
Opposes action of 1 & 2 receptors

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 Androgenic 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

51. Effect of Lactic Acid on FFA Mobilization