Hormonal Control During Exercise Endocrine Glands and Their

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Hormonal Control During Exercise

Hormonal Control During Exercise

Endocrine Glands and Their Hormones • Several endocrine glands in body; each may produce

Endocrine Glands and Their Hormones • Several endocrine glands in body; each may produce more than one hormone • Hormones regulate physiological variables during exercise

Hormonal Regulation of Metabolism During Exercise • Major endocrine glands responsible for metabolic regulation

Hormonal Regulation of Metabolism During Exercise • Major endocrine glands responsible for metabolic regulation – – Anterior pituitary gland Thyroid gland Adrenal gland Pancreas • Hormones released by these glands affect metabolism of carbohydrate and fat during exercise

Endocrine Regulation of Metabolism: Anterior Pituitary Gland • Pituitary gland attached to inferior hypothalamus

Endocrine Regulation of Metabolism: Anterior Pituitary Gland • Pituitary gland attached to inferior hypothalamus • Three lobes: anterior, intermediate, posterior • Secretes hormones in response to hypothalamic hormone factors – Releasing factors, inhibiting factors – Exercise secretion of all anterior pituitary hormones

Endocrine Regulation of Metabolism: Anterior Pituitary Gland • Releases growth hormone (GH) – –

Endocrine Regulation of Metabolism: Anterior Pituitary Gland • Releases growth hormone (GH) – – Potent anabolic hormone Builds tissues, organs Promotes muscle growth (hypertrophy) Stimulates fat metabolism • GH release proportional to exercise intensity

Endocrine Regulation of Metabolism: Thyroid Gland • Secretes triiodothyronine (T 3), thyroxine (T 4)

Endocrine Regulation of Metabolism: Thyroid Gland • Secretes triiodothyronine (T 3), thyroxine (T 4) • T 3 and T 4 lead to increases in – – – Metabolic rate of all tissues Protein synthesis Number and size of mitochondria Glucose uptake by cells Rate of glycolysis, gluconeogenesis FFA mobilization

Endocrine Regulation of Metabolism: Thyroid Gland • Anterior pituitary releases thyrotropin – Also called

Endocrine Regulation of Metabolism: Thyroid Gland • Anterior pituitary releases thyrotropin – Also called thyroid-stimulating hormone (TSH) – Travels to thyroid, stimulates T 3 and T 4 • Exercise increases TSH release – Short term: T 4 (delayed release) – Prolonged exercise: T 4 constant, T 3

Endocrine Regulation of Metabolism: Adrenal Medulla • Releases catecholamines (fight or flight) – Epinephrine

Endocrine Regulation of Metabolism: Adrenal Medulla • Releases catecholamines (fight or flight) – Epinephrine 80%, norepinephrine 20% – Exercise sympathetic nervous system epinephrine and norepinephrine • Catecholamine release increases – Heart rate, contractile force, blood pressure – Glycogenolysis, FFA – Blood flow to skeletal muscle

Endocrine Regulation of Metabolism: Adrenal Cortex • Releases corticosteroids – Glucocorticoids – Also, mineralocorticoids,

Endocrine Regulation of Metabolism: Adrenal Cortex • Releases corticosteroids – Glucocorticoids – Also, mineralocorticoids, gonadocorticoids • Major glucocorticoid: cortisol – Gluconeogenesis – FFA mobilization, protein catabolism – Anti-inflammatory, anti-immune

Endocrine Regulation of Metabolism: Pancreas • Insulin: lowers blood glucose – Counters hyperglycemia, opposes

Endocrine Regulation of Metabolism: Pancreas • Insulin: lowers blood glucose – Counters hyperglycemia, opposes glucagon – Glucose transport into cells – Synthesis of glycogen, protein, fat – Inhibits gluconeogenesis • Glucagon: raises blood glucose – Counters hypoglycemia, opposes insulin – Glycogenolysis, gluconeogenesis

Regulation of Carbohydrate Metabolism During Exercise • Glucose must be available to tissues •

Regulation of Carbohydrate Metabolism During Exercise • Glucose must be available to tissues • Glycogenolysis (glycogen glucose) • Gluconeogenesis (FFAs, protein glucose)

Regulation of Carbohydrate Metabolism During Exercise • Adequate glucose during exercise requires – Glucose

Regulation of Carbohydrate Metabolism During Exercise • Adequate glucose during exercise requires – Glucose release by liver – Glucose uptake by muscles • Hormones that circulating glucose – – Glucagon Epinephrine Norepinephrine Cortisol

Regulation of Carbohydrate Metabolism During Exercise • Circulating glucose during exercise also affected by

Regulation of Carbohydrate Metabolism During Exercise • Circulating glucose during exercise also affected by – GH: FFA mobilization, cellular glucose uptake – T 3, T 4: glucose catabolism and fat metabolism • Amount of glucose released from liver depends on exercise intensity, duration

Regulation of Carbohydrate Metabolism During Exercise • As exercise intensity increases – Catecholamine release

Regulation of Carbohydrate Metabolism During Exercise • As exercise intensity increases – Catecholamine release – Glycogenolysis rate (liver, muscles) – Muscle glycogen used before liver glycogen • As exercise duration increases – More liver glycogen utilized – Muscle glucose uptake liver glucose release – As glycogen stores , glucagon levels

Figure 4. 4

Figure 4. 4

Regulation of Carbohydrate Metabolism During Exercise • Glucose mobilization only half the story •

Regulation of Carbohydrate Metabolism During Exercise • Glucose mobilization only half the story • Insulin: enables glucose uptake in muscle • During exercise – Insulin concentrations – Cellular insulin sensitivity – More glucose uptake into cells, use less insulin

Figure 4. 5

Figure 4. 5

Regulation of Fat Metabolism Exercise During • FFA mobilization and fat metabolism critical to

Regulation of Fat Metabolism Exercise During • FFA mobilization and fat metabolism critical to endurance exercise performance – Glycogen depleted, need fat energy substrates – In response, hormones accelerate fat breakdown (lipolysis) • Triglycerides FFAs + glycerol – Fat stored as triglycerides in adipose tissue – Broken down into FFAs, transported to muscle – Rate of triglyceride breakdown into FFAs may determine rate of cellular fat metabolism

Regulation of Fat Metabolism Exercise • Lipolysis stimulated by – – – (Decreased) insulin

Regulation of Fat Metabolism Exercise • Lipolysis stimulated by – – – (Decreased) insulin Epinephrine Norepinephrine Cortisol GH • Stimulate lipolysis via lipase During

Hormonal Regulation of Fluid and Electrolytes During Exercise • During exercise, plasma volume ,

Hormonal Regulation of Fluid and Electrolytes During Exercise • During exercise, plasma volume , causing – Hydrostatic pressure, tissue osmotic pressure – Plasma water content via sweating – Heart strain, blood pressure • Hormones correct fluid imbalances – Posterior pituitary gland – Adrenal cortex – Kidneys

Hormonal Regulation of Fluid and Electrolytes: Posterior Pituitary • Posterior pituitary – Secretes antidiuretic

Hormonal Regulation of Fluid and Electrolytes: Posterior Pituitary • Posterior pituitary – Secretes antidiuretic hormone (ADH), oxytocin – Produced in hypothalamus, travels to posterior pituitary – Secreted upon neural signal from hypothalamus • Only ADH involved with exercise – Water reabsorption at kidneys – Less water in urine, antidiuresis

Hormonal Regulation of Fluid and Electrolytes: Posterior Pituitary • Stimuli for ADH release –

Hormonal Regulation of Fluid and Electrolytes: Posterior Pituitary • Stimuli for ADH release – Plasma volume = hemoconcentration = osmolality – Osmolality stimulates osmoreceptors in hypothalamus • ADH released, increasing water retention by kidneys • Minimizes water loss, severe dehydration

Hormonal Regulation of Fluid and Electrolytes: Adrenal Cortex • Adrenal cortex – Secretes mineralocorticoids

Hormonal Regulation of Fluid and Electrolytes: Adrenal Cortex • Adrenal cortex – Secretes mineralocorticoids – Major mineralocorticoid: aldosterone • Aldosterone effects – Na+ retention by kidneys – Na+ retention water retention via osmosis – Na+ retention K+ excretion

Hormonal Regulation of Fluid and Electrolytes: Adrenal Cortex • Stimuli for aldosterone release –

Hormonal Regulation of Fluid and Electrolytes: Adrenal Cortex • Stimuli for aldosterone release – Plasma Na+ – Blood volume, blood pressure – Plasma K+ • Also indirectly stimulated by blood volume, blood pressure in kidneys

Hormonal Regulation of Fluid and Electrolytes: Kidneys • Kidneys – Target tissue for ADH,

Hormonal Regulation of Fluid and Electrolytes: Kidneys • Kidneys – Target tissue for ADH, aldosterone – Secrete erythropoietin (EPO), renin • EPO – Low blood O 2 in kidneys EPO release – Stimulates red blood cell production – Critical for adaptation to training, altitude

Hormonal Regulation of Fluid and Electrolytes: Kidneys • Stimulus for renin (enzyme) release –

Hormonal Regulation of Fluid and Electrolytes: Kidneys • Stimulus for renin (enzyme) release – Blood volume, blood pressure – Sympathetic nervous system impulses • Renin-angiotensin-aldosterone mechanism – Renin: converts angiotensinogen angiotensin I – ACE: converts angiotensin II – Angiotensin II stimulates aldosterone release

Figure 4. 8

Figure 4. 8

Figure 4. 9

Figure 4. 9

Hormonal Regulation of Fluid and Electrolytes: Osmolality • Osmolality – Measure of concentration of

Hormonal Regulation of Fluid and Electrolytes: Osmolality • Osmolality – Measure of concentration of dissolved particles (proteins, ions, etc. ) in body fluid compartments – Normal value: ~300 m. Osm/kg • Osmolality and osmosis – If compartment osmolality , water drawn in – If compartment osmolality , water drawn out

Hormonal Regulation of Fluid and Electrolytes: Osmolality • Aldosterone and osmosis – Na+ retention

Hormonal Regulation of Fluid and Electrolytes: Osmolality • Aldosterone and osmosis – Na+ retention osmolality – Osmolality water retention – Where Na+ moves, water follows • Osmotic water movement minimizes loss of plasma volume, maintains blood pressure

Hormonal Regulation of Fluid and Electrolytes: Osmolality • ADH, aldosterone effects persist for 12

Hormonal Regulation of Fluid and Electrolytes: Osmolality • ADH, aldosterone effects persist for 12 to 48 h after exercise • Prolonged Na+ retention abnormally high [Na+] after exercise – Water follows Na+ – Prolonged rehydration effects