PSL 250

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PSL 250
2013-12-08 13:52:48
PSL L42 Energy Balance
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  1. Energy Input
    • energy in ingested food
    • digested food energy trapped in ATP phosphate bonds
    • ATP used to drive physiological functions
  2. Energy Output
    • External work used to move objects or the body
    • Internal work: posture; shivering (makes heat); internal activities needed for life: ion pumping (Na-K), heart pumping, synthesis, etc.
    • All activities ultimately become heat
  3. BMR: Basal Metabolic Rate
    • BMR= Energy/ Time---calories/day
    • 2,000 Calories/day are 2,000kilocalories (kcal)/day
  4. Neutral Balance
    • Energy input= energy output
    • food energy= external work+internal work+heat
  5. Positive Balance
    • energy input > energy output
    • energy stored in adipose tissue, weight gain
    • 3,500 kcal in 1 lb adipose tissue
  6. Negative Balance
    • Energy input < energy output
    • weight loss, first from adipose tissue, then from muscle
  7. Hypothalamic Control of Intake
    • Hypothalamus integrates multiple signals matching feeding to energy needs
    • Balance of hunger and satiety
  8. walk 1 mile extra per day for a year
    lose 10lbs

    • burn 100 calories- same amount in a large cookie
    • add 3500 more calories per year gain 10lbs
  9. Neuropeptide Y
    Released by HT (hypothalamus), Stimulates appetite
  10. Melanocortins
    • Released by HT (hypothalamus), suppresses- appetite
    • NPY and MC's alter brain activities that control food intake
  11. Leptins
    • Secreted adipose tissue- proportional to TG (triglycerides) storage in adipose
    • Increasing fat stores signals satiety by releasing leptins
    • Leptins decrease NPY and increase MC"s
    • only released after digesting a meal
    • carbs leave first, then proteins, then fats
  12. Digestive System Appetite Control
    Hormones from the GI tract control hypothalamic release
  13. Ghrelin/ PYY3-36
    • Ghrelin rises before eating, stimulates appetite, and falls after eating- increases NPY release
    • PPY released during meals and signals satiety
  14. CCK
    • the release of CCK signals satiety before digestion has occurred, stop eating before the new calories available
    • stimulating CCK with fat or protein early in eating may control food intake amount
  15. Social control
    • social context: family meals, habits, stress, loneliness, distration, etc.
    • caloric intake often strongly influenced by outside factors
    • Obesity: decreased exercise, BMR, biochem differences, habit, hormonal differences, etc.- increase morbidity and motrality
    • anorexia nervosa- psychological start- K+ imbalance
  16. Temperature Regulation
    • 98.6F= 36C
    • Convulsions at 106; death from protein denaturation at 110
    • core temperature is regulated; shell variable
  17. heat balance
    • balance of input and output
    • internal heat must be removed
    • multiple heat exchange mechaisms
  18. heat exchange
    • radiation by electromagnetic waves; sun, fireplace
    • conductions; transfer by contact from warm to cold
    • convection; air/water currents increase transfer
    • evaporation of water from skin removes heat
  19. heat productions
    • muscle contraction: shivering is contraction without work, all heat
    • BMR sets lower limit of heat production
  20. Responses to cold
    • hypothalamus thermoreceptors control responses
    • decreased skin blood flow- goosebumps ineffective
    • human adaptation- movement, clothing, outside sources
    • windchill takes away heat from bareskin
    • bundle up- dead air zones
  21. responses to heat
    • increased skin blood flow, increased sweating, adaptation
    • Fever: WBC's release endogenous pyrogen, reset hypothalamus
    • aspirin blocks prostaglandin production