Ex Phys Lecture 5

Endocrine system characteristics

Influences metabolic activity via hormones released into the blood to target tissues. Slower response than nervous system but longer-lasting effects.

Main effects of hormonal regulation during exercise

Maintain optimal blood glucose levels; provide active tissues with energy substrates during/after exercise; replenish stored energy levels.

Endocrine system pathway components

Host organs/glands (pituitary, thyroid, adrenal, pancreas); Chemical messengers (insulin, GH, T3/T4); Target/receptor organs with specific protein receptors.

Factors affecting hormone effects

Hormone concentration, rate of release, receptor number, and affinity.

Down-regulation vs. Up-regulation of receptors

Down-regulation = # of receptors decrease (desensitization/untrained); Up-regulation = # of receptors increase (sensitization/training).

Steroid vs. Non-steroid hormones

Steroid: Derived from cholesterol, lipid-soluble, passes directly into cells. Non-steroid: Cannot enter cells, binds to cell membrane receptors and uses cAMP.

Growth Hormone (GH) functions & doping effects

Causes protein synthesis, lipolysis, inhibits glucose uptake (blocks insulin). Doping helps maintain lean mass/lower fat but can cause heart enlargement over time.

Anti-Diuretic Hormone (ADH) function

Water retention. Osmoreceptors sense dehydration, pituitary releases ADH, kidneys reabsorb water back into bloodstream to stabilize blood volume.

Thyroid Gland (T3/T4) functions

Increases cAMP, cell metabolism rate, lipid/glucose usage for ATP, heart rate, contractility, and metabolic rate; increases during exercise.

Adrenal Medulla vs. Adrenal Cortex hormones

Medulla (SNS): Norepinephrine, Epinephrine (glycogenolysis, liver glucose release, lipolysis, "fight-or-flight"). Cortex: Cortisol and Aldosterone.

Renin-Angiotensin-Aldosterone System (RAAS) steps

Dehydration -> decreased BP -> kidneys release renin -> converts angiotensinogen to Angiotensin I -> ACE converts to Angiotensin II -> stimulates aldosterone & vasoconstriction -> Na+ reabsorbed.

Growth Hormone summary

Source: Pituitary | Use: Proteins, inhibits glucose uptake, lipolysis | Exercise effect: Same.

Antidiuretic Hormone (ADH) summary

Source: Pituitary | Use: Kidneys reabsorb water | Exercise effect: Water retention.

T3/T4 summary

Source: Thyroid | Use: Increase cAMP, metabolism, HR, contractility | Exercise effect: Increase metabolic rate, HR, contractility.

Epinephrine / Norepinephrine summary

Source: Adrenal Medulla | Use: Glycogenolysis, liver glucose release, lipolysis | Exercise effect: Inhibits glucose uptake, increases gluconeogenesis, lipolysis, HR, contractility.

Cortisol summary

Source: Adrenal Cortex | Use: Gluconeogenesis, glycogenolysis, protein breakdown, lipolysis | Exercise effect: Same.

Aldosterone summary

Source: Adrenal Cortex | Use: Kidneys retain Na+, water follows | Exercise effect: Water retention.

Glucagon summary

Source: Pancreas (Alpha) | Use: Increases liver glucose release, blood glucose, amino acid/FFA uptake | Exercise effect: Glycogenolysis, lipolysis, rises during exercise.

Insulin summary

Source: Pancreas (Beta) | Use: Increases tissue uptake of glucose, FFA, amino acids, lowers blood glucose | Exercise effect: Removes blood glucose, FFA, amino acids.

Erythropoietin summary

Source: Kidneys | Use: Regulates blood cell production via bone marrow | Exercise effect: No big difference (doping context).