Endocrine System and Endocrine System and ExerciseExercise

Glucose uptake increases during Glucose uptake increases during exerciseexercise

Release from kidneys, gut, and liverRelease from kidneys, gut, and liver Make new from 3-carbon molecules (LA, Make new from 3-carbon molecules (LA,

pyr., glycerol, and alanine, LA most pyr., glycerol, and alanine, LA most important)important)

Deliver alternative substrates to the active Deliver alternative substrates to the active tissue (FAs, triglycerides, lactate, aa tissue (FAs, triglycerides, lactate, aa leucine)leucine)

Increased glucose causes insulin Increased glucose causes insulin levels to riselevels to rise

Insulin AntagonistsInsulin Antagonists

Insulin stimulates glycogen storage, epi and Insulin stimulates glycogen storage, epi and glucagon stimulate glycogen breakdownglucagon stimulate glycogen breakdown

Insulin stimulates protein synthesis Insulin stimulates protein synthesis Leptin is an anabolic hormone that promotes Leptin is an anabolic hormone that promotes

use of energyuse of energy Cortisol promotes catabolism and release of Cortisol promotes catabolism and release of

aa’s from muscle into bloodaa’s from muscle into blood

InsulinInsulin

LeptinLeptin

Energy StorageEnergy Storage

Energy DissipationEnergy Dissipation

FFAFFA CarbohydratesCarbohydrates

Feed-forward controlFeed-forward control

When exercising, catacholamine-mediated When exercising, catacholamine-mediated stimulation of hepatic glucose production stimulation of hepatic glucose production (why?)(why?)

HormonesHormones

Chemical messengersChemical messengers Generalized in action an circulate widelyGeneralized in action an circulate widely Some specific, localized effect (ACH)Some specific, localized effect (ACH) Norepi is both local and generalNorepi is both local and general

Two types of hormones:Two types of hormones:

Steroid: produced by the adrenal cortex and Steroid: produced by the adrenal cortex and gonads, made from cholesterolgonads, made from cholesterol

Polypeptides: aka small proteins, derived Polypeptides: aka small proteins, derived from aa’s in other endocrine glandsfrom aa’s in other endocrine glands

Action:Action:

Usually bind on specific sites on target Usually bind on specific sites on target tissue, binding can:tissue, binding can:

Affect permeabilityAffect permeability Activate an enzyme or enzyme systemActivate an enzyme or enzyme system Activate genetic apparatus to manufacture Activate genetic apparatus to manufacture

intracellular proteins or other substratesintracellular proteins or other substrates Increase secretatory activityIncrease secretatory activity

cyclic AMP (cAMP)cyclic AMP (cAMP)

Many hormones, when bind to a tissue form Many hormones, when bind to a tissue form cAMPcAMP

cAMP activates many systemscAMP activates many systems Second messengerSecond messenger

Low intensity exerciseLow intensity exercise

Little effect on hormone levelsLittle effect on hormone levels >50% VO>50% VO22max see elevation in max see elevation in

catecholaminescatecholamines Why? Why? With training, lowerWith training, lower Moderate exercise, the same or enhanced Moderate exercise, the same or enhanced

responseresponse Why?Why?

Insulin and glucagon: immediate Insulin and glucagon: immediate control of blood glucosecontrol of blood glucose

Insulin stimulates uptake, glycogen and fat Insulin stimulates uptake, glycogen and fat synthesissynthesis

Glucagon, secreted when blood levels are Glucagon, secreted when blood levels are low, acting to raise those levels low, acting to raise those levels

Two effects:Two effects:– Enhance glycogenolysisEnhance glycogenolysis– Increase glycogenolysis (indirectly stimulating Increase glycogenolysis (indirectly stimulating

beta oxidation)beta oxidation)

Liver’s role in stabilizing blood Liver’s role in stabilizing blood glucose levels glucose levels

HGP is considered representative of HGP is considered representative of glucose productionglucose production

Critical for overall homeostasisCritical for overall homeostasis Levels are high, storeLevels are high, store Levels are low, releaseLevels are low, release