ExPhys exam 4

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dvdromm
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290504
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ExPhys exam 4
Updated:
2014-12-03 16:31:40
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ExPhys exam
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ExPhys exam 4
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ExPhys exam 4
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  1. Means by which heat can be produced and gained by the body
    • Voluntary
    • -Exercise = 70–80% energy expenditure appears as heat
    • Involuntary
    • -Shivering = Increases heat production by ~5x
    • -Action of hormones
    • Thyroxine
    • Catecholamines
    • Called nonshivering thermogenesis
  2. Means of heat loss
    • Radiation
    • Transfer of heat via infrared rays
    • Like a grill
    • 60% heat loss at rest
    • Can be a method of heat gain
    • Conduction
    • Heat loss due to contact with another surface
    • Example: cold towel
    • Convection
    • Heat transferred to air or water
    • Heated molecules are moved away
    • Example: a fan pushing air past skin
    • Evaporation
    • Heat from skin converts water (sweat) to water vapor
    • Requires vapor pressure gradient between skin and air
  3. Explain role of temp and humidity on sweat evaporation
    • Sweat evaporation requires a vapor pressure gradient between skin and air
    • Evaporation rate depends on:
    • - Temp and relative humidity
    • -conductive currents around the body
    • -amount of skin surface exposed
    • 25% of heat loss at rest
  4. How much heat is lost through sweat evaporation
    • 0.58 kcal heat / ml of sweat evaporated
    • 1L sweat = loss of 580 kcal
    • 1L = 1 Kilogram
  5. Describe the changes in HR and blood flow during prolonged constant load exercise in hot/humid environment
    • a. constant work rate,
    • prolonged exercise
    • (1) CO maintained (CO = HR x SV)
    • (2) SV decreases but HR increases to compensate
    • (3) cardiovascular drift - due to rising body temperature
    • (a) due to skin vasodilation & dehydration
    • (b) both decrease venous return which reduces SV
    • if hot/humid environments - response is exaggerated
  6. hypothalamus and response to temperature
    • Anterior hypothalamus
    • -Responds to increased core temperature
    • -Commencement of sweating
    • -=Increased evaporative heat loss
    • -Increased skin blood flow
    • -=Allows increased heat loss
    • Posterior hypothalamus
    • -Responds to decreased core temperature
    • -Shivering and increased norepinephrine release
    • -=Increased heat production
    • -Decreased skin blood flow
    • -=Decreased heat loss
  7. Acclimitization to cold
    • more heat, less shivering
    • • increase thyroid hormone, moresensitive to NE, uncoupled ox-phos
    • • more leptin, increase SNS activity
    • • more adipose tissue (insulation)
    • • less heat loss in hands in feet
    • • intermittent peripheral vasodilation
    • • habituation (more pain tolerance)
    • • better sleep
  8. Acclimitization to heat
    • Plasma Volume
    • Earlier onset of sweating
    • Osmolality of sweat
    • Muscle glycogenolysis
  9. cross sectional vs. longitudinal training studies
    • Cross-sectional Studies
    • Compare groups (sedentary vs runners) that differ in physical activity level on some variable (VO2max, CO, HR, strength).
    • Looks at differences.

    • Longitudinal Training Studies
    • Examines the changes that occur over the
    • course of a training program.
    • Looks at changes, and rate of change
    • Problems: cost/length. attrition. age-period confound
  10. symptoms of overt-training 6
    • decrease in performance
    • loss of body weight
    • chronic fatigue
    • increased number of infections
    • psychological staleness
    • elevated heart rate and blood lactate levels during exercise
  11. go over aerobic training effects

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