1. Chapter 5 Hormonal Responses to Exercise
EXERCISE PHYSIOLOGY
Theory and Application to Fitness and Performance, 6th edition
Scott K. Powers & Edward T. Howley

2. Neuroendocrinology Neuroendocrine system Endocrine glands Hormones
Endocrine system releases hormones
Nervous system uses neurotransmitters
Endocrine glands
Release hormones directly into the blood
Hormones
Alter the activity of tissues that possess receptors to which the hormone can bind

3. Blood Hormone Concentration
The free plasma hormone concentration determines the magnitude of the effect at the tissue level
Determined by:
Rate of secretion of hormone from endocrine gland
Magnitude of input
Stimulatory vs. inhibitory input
Rate of metabolism or excretion of hormone
At the receptor and by the liver and kidneys
Quantity of transport protein
Steroid hormones
Changes in plasma volume

4. Factors That Influence the Secretion of Hormones
Figure 5.1

5. Hormone-Receptor Interactions
Hormone affect only tissue with specific receptors
Magnitude of effect dependent on:
Concentration of the hormone
Number of receptors on the cell
Affinity of the receptor for the hormone
Downregulation
Decrease in receptor number in response to high concentration of hormone
Upregulation
Increase in receptor number in response to low concentration of hormone

6. Mechanisms of Hormone Action
Altering membrane transport
Insulin
Stimulating DNA to increase protein synthesis
Steroid hormones
Activating second messengers via G protein
Cyclic AMP
Ca+2
Inositol triphosphate
Diacylglycerol

7. Mechanism of Steroid Hormone Action
Figure 5.2

8. Cyclic AMP “Second Messenger” Mechanism
Figure 5.3

9. Calcium and Phospholipase C Second Messenger Mechanisms
Figure 5.4

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

11. Hypothalamus and Pituitary Gland
Controls secretions from pituitary gland
Anterior Pituitary Gland
Adrenocorticotropic hormone (ACTH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Melanocyte-stimulating hormone (MSH)
Thyroid-stimulating hormone (TSH)
Growth hormone (GH)
Prolactin
Posterior Pituitary Gland
Oxytocin
Antidiuretic hormone (ADH)

12. Hormones Released From the Anterior Pituitary Gland
Figure 5.5

13. Growth Hormone Secreted from the anterior pituitary gland
Stimulates release of insulin-like growth factors (IGFs)
Essential growth of all tissues
Amino acid uptake and protein synthesis
Long bone growth
Spares plasma glucose
Reduces the use of plasma glucose
Increases gluconeogenesis
Mobilizes fatty acids from adipose tissue

14. The Influence of the Hypothalamus on Growth Hormone Secretion
Figure 5.6

15. Antidiuretic Hormone
Reduces water loss from the body to maintain plasma volume
Favors the reabsorption of water from the kidney
Stimulated by:
High plasma osmolality and low plasma volume
Due to sweat loss without water replacement

16. Change in Plasma ADH Concentration During Exercise
Figure 5.7

17. Thyroid Gland Stimulated by TSH
Triiodothyronine (T3) and thyroxine (T4)
Maintenance of metabolic rate
Allowing the full effect of other hormones
Calcitonin
Regulation of plasma Ca+2
Parathyroid Hormone
Primary hormone in plasma Ca+2 regulation

18. Adrenal Medulla Secretes the catecholamines
Epinephrine (E) and norepinephrine (NE)
Bind to adrenergic receptors
Alpha ()
Beta ()
Effects depend on hormone used and receptor type

19. Adrenal Cortex Aldosterone (mineralcorticoid)
Control of Na+ reabsorption and K+ secretion
Na+/H2O balance
Regulation of blood volume and blood pressure
Part of renin-angiotensin-aldosterone system
Stimulated by:
Increased K+ concentration
Decreased plasma volume

20. Change in Renin, Angiotensin II, and Aldosterone During Exercise
Figure 5.8

21. Adrenal Cortex Cortisol (glucocorticoid)
Promotes protein breakdown for gluconeogenesis and tissue repair
Stimulates FFA mobilization
Stimulates glucose synthesis
Blocks uptake of glucose into cells
Promotes the use of free fatty acids as fuel
Stimulated by:
Stress, via ACTH
Exercise

22. Control of Cortisol Secretion
Figure 5.9

23. Pancreas Both exocrine and endocrine functions Secretes:
Insulin (from b cells)
Promotes the storage of glucose, amino acids, and fats
Glucagon (from a cells)
Promotes the mobilization of fatty acids and glucose
Somatostatin (from d cells)
Controls rate of entry of nutrients into the circulation
Digestive enzymes and bicarbonate
Into the small intestine

24. Testes and Ovaries Testosterone Estrogen Released from testes
Anabolic steroid
Promotes tissue (muscle) building
Performance enhancement
Androgenic steroid
Promotes masculine characteristics
Estrogen
Released from ovaries
Establish and maintain reproductive function
Levels vary throughout the menstrual cycle

25. Control of Testosterone Secretion
Figure 5.10

26. Control of Estrogen Secretion
Figure 5.11

27. Change in FSH, LH, Progesterone, and Estradiol During Exercise
Figure 5.12

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
Figure 5.13

30. Plasma Epinephrine Concentration During Exercise
Figure 5.14

31. Control of Muscle Glycogen Utilization
Breakdown of muscle glycogen is under dual control
Epinephrine-cyclic AMP
Via b-adrenergic receptors
Ca+2-calmodulin
Enhanced during exercise due to Ca+2 release from sarcoplasmic reticulum
Evidence for role of Ca+2-calmodulin in glycogenolysis
Propranolol (b-receptor blocker) has no effect on muscle glycogen utilization

32. Control of Glycogenolysis
Figure 5.16

33. Changes in Muscle Glycogen Before and After Propranolol Administration
Figure 5.15

34. Blood Glucose Homeostasis During Exercise
Plasma glucose maintained through four processes:
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
Controlled by hormones
Permissive or slow-acting
Fast-acting

35. Permissive and Slow-Acting Hormones
Thyroid hormones
Act in a permissive manner to support actions of other hormones
Cortisol and growth hormone
Stimulate FFA mobilization from adipose tissue
Enhance gluconeogenesis in the liver
Decrease the rate of glucose utilization by cells

36. Role of Cortisol in the Maintenance of Blood Glucose
Figure 5.17

37. Changes in Plasma Cortisol During Exercise
Figure 5.18

38. Role of Growth Hormone in the Maintenance of Plasma Glucose
Figure 5.19

39. Changes in Plasma Growth Hormone During Exercise
Figure 5.20

40. Fast-Acting Hormones Epinephrine and norepinephrine
Maintain blood glucose during exercise
Muscle glycogen mobilization
Increasing liver glucose mobilization
Increasing FFA mobilization
Interfere with glucose uptake
Plasma E and NE increase during exercise
Decreased plasma E and NE following training

41. Role of Catecholamines in Substrate Mobilization
Figure 5.21

42. Change in Plasma Epinephrine and Norepinephrine During Exercise
Figure 5.22

43. Plasma Catecholamines Responses to Exercise Following Training
Figure 5.23

44. Fast-Acting Hormones Insulin Glucagon
Uptake and storage of glucose and FFA
Plasma concentration decreases during exercise
Decreased insulin response following training
Glucagon
Mobilization of glucose and FFA fuels
Plasma concentration increases during exercise
Decreased response following training
Insulin and glucagon secretion influenced by catecholamines

45. Effects of Insulin and Glucagon
Figure 5.24

46. Changes in Plasma Insulin During Exercise
Figure 5.25

47. Changes in Plasma Glucagon During Exercise
Figure 5.26

48. Effect of Epinephrine and Norepinephrine on Insulin and Glucagon Secretion
Figure 5.27

49. Effect of the SNS on Substrate Mobilization
Figure 5.28

50. Summary of the Hormonal Responses to Exercise
Figure 5.29

51. Hormone-Substrate Interaction
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 albumin to transport FFA in plasma

52. Changes in Plasma FFA Due to Lactic Acid
Figure 5.30

53. Effect of Lactic Acid on FFA Mobilization
Figure 5.30