• Facilitates glucose transport into cells (via increased number of GLUT-4)
• Enhances synthesis of glycogen, protein, fat
Relationship between glucose and insulin:
Changes in plasma concentrations of glucose and insulin during prolonged cycling at
65% to 70% of VO2. Note the gradual decline in insulin throughout the exercise,
suggesting an increased sensitivity to insulin during prolonged effort.
Pancreas lowers BG by:
Glucagon → Raises blood glucose
• Produced by alpha cells in the pancreas
• Counters hypoglycemia
• Promotes glycogenolysis, gluconeogenesis
Changes in hormone concentration during exercise:
,Changes (as a percentage of preexercise values) in plasma concentrations of
epinephrine, norepinephrine, glucagon, cortisol, and glucose during 3 hrs of cycling at
65% VO2.
Hormonal regulation of fluid and electrolytes:
During exercise, plasma volume decreases (decreases the viscosity of blood, makes
pumping easier on heart)
• Sweating (water, Na+, K+, Cl-)
• Plasma water decreases
• Decreased performance
• Increased strain on the heart
Hormones correct fluid imbalances by:
Memorize diagram in Ch. 4
posterior pituitary gland
Secretes antidiuretic hormone (ADH) and oxytocin
• Neural signal from hypothalamus stimulates posterior pituitary to release
• Decreased plasma volume = increased osmolality
antidiuretic hormone (ADH)
Only ADH is involved with exercise.
• Increase water reabsorption at kidneys
• Less water in urine
ADH is released, increasing water retention
• At the kidney
, • Minimizes water loss
osmolality
• Measure of concentration of dissolved particles (e.g., proteins, ions) in body fluid
compartments
• Osmolarity stimulates osmoreceptors in hypothalamus
• Osmotic water movement minimizes loss of plasma volume, maintains blood pressure
Osmolarity and water retention:
• If compartment osmolality increases, water is drawn in
• If compartment osmolality decreases, water is drawn out
• Creatine in muscle increases water content
adrenal cortex
Stimulates aldosterone release.
• Outermost layer secretes mineralocorticoids
• Decreased plasma Na+
• Decreased blood volume, blood pressure
• Increased plasma K+
aldosterone
• Increases Na+ retention by kidneys → increase in water retention
• Maintains blood volume/electrolyte
• Causes increased K+ excretion
• Na+ retention leads to increased osmolality → leads to increased water retention
Where Na+ moves, water follows
kidneys
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