Hormonal Responses to Exercise Chapter 5

Neuroendocrinology Endocrine Glands –Release messengers: hormones Hormones –Circulate in blood –Affect tissue with receptors –Concentration affects action –Inactivated or metabolized

Neuroendocrinology Hormone-Receptor Interaction –Receptor Concentration Down regulation Up-regulation –Receptor Blocking

Neuroendocrinology Mechanisms of Action –Alter membrane transport –Stimulate DNA for protein synthesis –Activate “Second Messengers” Examples: Hormones and Exercise

Hormones and Exercise Insulin –Beta cells in Pancreas –Responds to high blood glucose (hyperglycemia) –Alter membrane transport of glucose –Stimulates glucose uptake (blood to cells) Muscle cells – can only “fill” so much Adipose cells – unlimited “filling” Other cells – liver, etc.

Hormones and Exercise Diabetes Mellitus –Type I (Juvenile Onset – Insulin Dependent) Non-functioning Beta cells – no insulin Chronic hyperglycemia results in: –Poor circulation –Neuropathy –Limb loss –Blindness –Hypertension Need an exogenous source of insulin - injection

Hormones and Exercise Diabetes Mellitus –Type II (NIDDM) Functioning Beta cells High CHO / calorie diet Plenty of insulin – in fact, too much? Chronic hyperinsulinemia results in: –Down-regulation of receptors –Poor insulin sensitivity** –Hyperglycemia and its effects

Hormones and Exercise During Exercise –Glucose availability increases - glycogenolysis –Insulin production decreases –M. cell need for energy increases –Increased glucose transport occurs without insulin –Transport of gluc. & FFA into M. cells increases –Transport of gluc. & FFA into other cells decreases –Energy available for M. contraction

Hormones and Exercise Effect of Exercise on NIDDM Diabetes –During Ex. Transports glucose into cell without insulin –Result of Ex. (after ex.) Increases sensitivity of m. cells to insulin –Up-regulation of receptors occurs Improves (reverses) Type II

Hormones and Exercise Glucagon –Alpha cells of pancreas –Mobilizes glucose from liver –Mobilizes FFA from adipose –Makes substrates available when blood levels are low

Hormones and Exercise Cortisol –Adrenal cortex –Stimulates FFA and AA mobilization –Decreases rate of glucose utilization –Used for energy regulation and tissue repair

Hormones and Exercise “Sparing Glucose” –Muscle glycogen = limited fuel source –Use fat instead –Put glucose in blood –Make more glucose “gluconeogenesis” (Cs from AA) Cori cycle (Cs from lactate)

Hormones and Exercise Growth Hormone (GH) –Pituitary gland –Stimulates tissue protein synthesis & bone growth –Increases during exercise for energy regulation –Do exercisers grow bigger? –Should I take this to grow bigger?

Hormones and Exercise Testosterone –From testes and ovaries (anterior pituitary) –Anabolic and androgenic effect –Stimulates protein synthesis Negative affects? Balance

Questions?

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