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HORMONAL REGULATION OF EXERCISE

C HAPTER 5. C HAPTER 5. HORMONAL REGULATION OF EXERCISE. HORMONAL REGULATION OF EXERCISE. Learning Objectives. w Learn the role of your endocrine system in maintaining homeostasis in the body during rest and during acute physical activity.

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HORMONAL REGULATION OF EXERCISE

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  1. CHAPTER 5 CHAPTER 5 HORMONAL REGULATIONOF EXERCISE HORMONAL REGULATIONOF EXERCISE

  2. Learning Objectives w Learn the role of your endocrine system in maintaining homeostasis in the body during rest and during acute physical activity. w Learn the difference between steroid and nonsteroid hormones and their actions within the body. w Discover the roles of hormones in regulating fat and carbohydrate metabolism. w Find out how hormones help keep your fluid levels in check and prevent dehydration.

  3. ENDOCRINE ORGANS

  4. Steroid Hormones w Lipid soluble w Diffuse through cell membranes; receptors located within cell w Chemical structure is derived from or is similar to cholesterol w Secreted by adrenal cortex, ovaries, testes, placenta

  5. Nonsteroid Hormones w Nonlipid soluble w Cannot diffuse through cell membranes; receptors located on cell membrane w Two types: amino acid derivatives and protein or peptide hormones

  6. Nonsteroid Hormones w Hormones travel in the blood to their specific target organs. w Receptors are specific to hormones such that only the correct hormone will "fit" in the correct receptor. w Each cell has 2,000 to 10,000 specific receptors.

  7. ACTION OF A STEROID HORMONE

  8. ACTION OF A NONSTEROID HORMONE

  9. Control of Hormone Release w Plasma levels of specific hormones fluctuate. w Secretion is regulated by a negative feedback system. w Cells can also alter their number of hormone receptors via down- or up-regulation.

  10. Alteration in Number of Receptors Down-regulation—Decrease in number of cell receptors; less hormone can bind to the cell and higher concentrations of the hormone remain in the blood plasma Up-regulation—Increase in number of cell receptors; more hormone can bind to the cell and lower concentrations of the hormone remain in the blood plasma

  11. w Steroid hormones pass through cell membranes and bind to receptors within the cell. They synthesize protein via a process called direct gene activation. (continued) Key Points Nature of Hormones w Hormones are classified into steroidal types (lipid soluble and formed from cholesterol) or nonsteroidal types (nonlipid soluble and formed from amino acids, peptides, or proteins). w Hormones are secreted in the blood and travel to sites where they exert an effect on only those target cells that have receptors specific to that hormone.

  12. Key Points Nature of Hormones w Nonsteroid hormones bind to receptors on the cell membrane, which triggers a second messenger within the cell, which in turn triggers numerous cellular processes. w A negative feedback system regulates the release of most hormones. w The number of receptors on a cell can change the cell's sensitivity to hormones. Up-regulation is the increase of receptors and down-regulation is the decrease in receptors.

  13. THE PITUITARY GLAND

  14. Anterior lobe Posterior lobe w Growth hormone (GH) w Antidiuretic hormone (ADH) w Prolactin (PRL) w Oxytocin w 4 hormones that affect other endocrine glands Hormones of the Pituitary Gland

  15. HOW ADH CONSERVES BODY WATER

  16. Growth Hormone w Promotes muscle growth and hypertrophy by facilitating amino acid transport w Directly stimulates fat metabolism (lipolysis) w Levels are elevated during aerobic exercise in proportion to exercise intensity

  17. Triiodothyronine (T3) and Thyroxine (T4) w Increase protein and enzyme synthesis w Increase size and number of mitochondria in cells w Promote rapid cellular uptake of glucose w Enhance glycolysis and glycogenesis w Increase FFA availability for oxidation Calcitonin w Metabolizes calcium Hormones of the Thyroid Gland

  18. Did You Know…? The parathyroid gland produces parathyroid hormone (PTH), which regulates plasma calcium concentration and plasma phosphate by targeting the bones, intestines, and kidneys.

  19. Hormones of the Adrenal Medulla w Catecholamines—epinephrine and norepinephrine w Stimulated by sympathetic nervous system to prepare you for immediate action w Increase rate and force of heart contraction, blood pressure, and respiration w Increase metabolic rate, glycogenolysis, and release of glucose and FFA into blood w Force more blood to go to the skeletal muscles through vasodilation and vasoconstriction of specific vessels

  20. Mineralocorticoids w Maintain electrolyte balance in extracellular fluids w Include aldosterone Glucocorticoids w Maintain consistent plasma glucose levels between meals w Include cortisol Gonadocorticoids w Released in addition to those released by reproductive organs but in lesser amounts w Include androgens, estrogens, and progesterones Hormones of the Adrenal Cortex

  21. BLOOD CONCENTRATION CHANGES OF EPINEPHRINE AND NOREPINEPHRINE

  22. Hormones of the Pancreas Insulin—secreted when plasma glucose levels are elevated (hyperglycemia) Glucagon—secreted when plasma glucose concentrations are below normal (hypoglycemia)

  23. PLASMA GLUCAGON AND TRAINING

  24. PLASMA INSULIN AND TRAINING

  25. PLASMA GLUCOSE AND TRAINING

  26. Reproductive Hormones w Androgens (i.e., testosterone) w Estrogens w Progesterone

  27. Did You Know…? Though not a major endocrine organ, the kidneys produce a hormone called erythropoietin, which regulates red blood cell (erythrocyte) production by stimulating bone marrow cells. This hormone is important in our adaptation to training and to altitude due to the oxygen-carrying capacity of red blood cells.

  28. Hormones Increasing Glucose Metabolism w Glucagon w Epinephrine w Norepinephrine w Cortisol

  29. BLOOD GLUCOSE LEVELS

  30. PLASMA LEVELS OF HORMONES

  31. PLASMA LEVELS OF GLUCOSE AND INSULIN

  32. Did You Know…? When carbohydrate reserves are low, the hormones accelerate the oxidation of fats to ensure your muscles get the energy they need. The rate of fat breakdown into FFA and glycerol may partly determine the rate at which muscles use fat as a fuel source during exercise.

  33. Hormones Increasing Fat Metabolism w Cortisol w Epinephrine w Norepinephrine w Growth hormone

  34. PLASMA LEVELS OF FFA AND CORTISOL

  35. PLASMA LEVELS OF EPINEPHRINE, NOREPINEPHRINE, GH, AND FFA

  36. w Glucose levels decline during prolonged exercise, indicating that exercise facilitates insulin action so that less is required during exercise than at rest. (continued) Key Points Hormones, Metabolism, and Energy w Glucagon, epinephrine, norepinephrine, and cortisol help promote glycogenolysis and gluconeogenesis, thus increasing plasma glucose levels when needed. w Insulin facilitates glucose transport to the muscle fibers.

  37. Key Points Hormones, Metabolism, and Energy w When carbohydrate reserves are low, cortisol, epinephrine, norepinephrine, and growth hormone facilitate fat oxidation. w Cortisol accelerates lipolysis, releasing FFAs into the blood so they can be taken up by the cells and used for energy production. w Cortisol levels peak and return to near normal levels during prolonged exercise. When this happens, the catecholamines and GH take over cortisol's role in releasing FFAs into the blood.

  38. Hormones and Fluid and Electrolyte Balance Aldosterone—Released by the adrenal cortex in response to decreased blood pressure; promotes sodium reabsorption in kidneys and to increase plasma volume. Anitdiuretic hormone (ADH)—Released by the posterior pituitary in response to increased blood osmolarity; promotes water conservation by increasing plasma volume.

  39. THE RENIN-ANGIOTENSIN MECHANISM

  40. PLASMA VOLUME AND ALDOSTERONE

  41. Did You Know…? Following the initial drop, plasma volume remains relatively constant throughout exercise due to 1. The actions of aldosterone and ADH, 2. Water returning from the exercising muscles to the blood, and 3. The increase in amount of water produced by metabolic oxidation within muscles.

  42. Postexercise Fluid Balance Fluid loss from the blood results in hemoconcentration—a concentration of the particles of the blood. Hemodilution, on the other hand, is a dilution of the constituents of the blood caused by gains in fluid to the blood.

  43. PLASMA VOLUME CHANGES

  44. w Angiotensin II increases peripheral arterial resistance, which increases blood pressure and triggers the release of aldosterone. (continued) Key Points Hormones and Fluid Balance w Aldosterone and ADH are the two primary hormones involved in regulating fluid balance. w When plasma volume or blood pressure decrease, the kidneys produce renin that eventually converts to angiotensin II.

  45. Key Points Hormones and Fluid Balance w Aldosterone promotes sodium reabsorption in the kidneys, which in turn causes water retention, thus increasing the plasma volume. w ADH is released in response to increased plasma osmolarity and acts on the kidneys to promote water conservation. w Plasma volume increases, which results in dilution of the plasma solutes and blood osmolarity decreases.

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