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Lecture 42
Energy Balance
Term | Definition |
---|---|
Energy Input | Energy in ingested food.digested food energy trapped in atp phosphate bonds Atp used to drive physiological func |
Energy Output | external work used to move objects or the body.internal work:posture;shivering;internal activities.needed for life:ion pumping,heart pumping,synthesis etc.all activities ultimately becoming heat |
Basal Metabolic Rate | BMR=energy/time-calories/day.2000cal/day are 2000 kilo cal/day |
Neutral Balance | energy input=energy output,food energy=external work + internal work + heat |
Positive Balance | energy input > energy output.energy stored in adipose tissue,weight gain. |
Negative Balance | energy input < energy output.weight loss,first from adipose tissue,then from muscle |
Hypothalamic Control of Intake | hypothalamus integrates mult. signal matching feeding to energy needs. balance of hunger and satiety. |
Neuropeptide Y | released by h+,stimulates appetite. |
Melanocortins | released by h+,suppress appetite.NPY and MC's after brain activities that control food intake. |
Leptins | secreted by adipose tissue-proportional to tg storage in adipose inc. fat stores signals satiety by releasing leptins.leptins dec NPY and inc MC's |
Digestive System Appetite Control | hormones from the GI tract control hypothalamic release. |
Ghrelin/PYY3-36 | ghrelin rises before eating,stimulates appetite and falls after eating-inc NPY release PPY released during meals and signals satiety |
CCK | the release of cck signals satiety before digestion has occured-stop eating before the new calories available.stimulating cck w/ fat or protein early in eating may control food intake amount |
Social Control | social context:family meals,habits,stress,loneliness,distraction etc. caloric intake often strongly influenced by outside factors obesity: dec excercise BMR,biochem differences,habit,hormonal differences etc.inc morbibity + mortality. anorexia-K+imbalance |
Temperature Regulation | 98.6 F=37 C.convulsions at 106:death from protein dencturation at 110.core temp is regulated:shell variable |
Heat Balance | balance of input and output.internal heat must be removed.mult heat exchange mechanisms |
Heat Exchange | radiation of electromagnetic waves:sun,fireplace.conduction:transfer by contact from warm-cold.convection:air/water currents inc transfer.evaporation of water from skin removes heat.sweat inc evaporation,dripping doesnt.fitness dec sweat salt content |
Heat Production | muscle contraction,shivering is contraction w/o work,all heat.BMR gets lower limit of heat production. |
Response to Cold | hypothalamus thermoreceptors control responses.dec skin blood flow-goosebumps ineffective.human adaptation-movement,clothing,outside sources. |
Response to Heat | inc skin blood flow inc sweating,adaptation.fever:wbc's release endogenous pyrogen,reset hypothalamus.asprin blocks prostaglandin production |