hormonal control exercise

Hormonal Control
During Exercise

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
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–
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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
• 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)
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–
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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 (T3), thyroxine (T4)
• T3 and T4 lead to increases in
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–
–

–
–
–

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 thyroid-stimulating hormone (TSH)
– Travels to thyroid, stimulates T3 and T4

• Exercise increases TSH release
– Short term: T4  (delayed release)
– Prolonged exercise: T4 constant, T3 

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, 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 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
• Glycogenolysis (glycogen  glucose)

• Gluconeogenesis (FFAs, protein  glucose)

Regulation of Carbohydrate
Metabolism During Exercise
• Adequate glucose during exercise requires
– Glucose release by liver
– Glucose uptake by muscles

• Hormones that  circulating glucose
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–
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Glucagon
Epinephrine
Norepinephrine
Cortisol

Regulation of Carbohydrate

Metabolism During Exercise
• Circulating glucose during exercise also
affected by
– GH:  FFA mobilization,  cellular glucose uptake
– T3, T4:  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 
– 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

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

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
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(Decreased) insulin
Epinephrine
Norepinephrine
Cortisol
GH

• Stimulate lipolysis via lipase

During

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 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
–  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
– 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
–  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, aldosterone
– Secrete erythropoietin (EPO), renin

• EPO
– Low blood O2 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
–  Blood volume,  blood pressure
– Sympathetic nervous system impulses

• Renin-angiotensin-aldosterone mechanism
– Renin: converts angiotensinogen  angiotensin I
– ACE: converts angiotensin I  angiotensin II
– Angiotensin II stimulates aldosterone release

Figure 4.8

Figure 4.9

Hormonal Regulation of Fluid and
Electrolytes: Osmolality
• Osmolality
– Measure of concentration of dissolved particles
(proteins, ions, etc.) in body fluid compartments
– Normal value: ~300 mOsm/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   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 to 48
h after exercise
• Prolonged Na+ retention  abnormally high
[Na+] after exercise
– Water follows Na+
– Prolonged rehydration effects