Comparative Vertebrate Physiology
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Comparative Vertebrate Physiology
Temperature regulation
Temperature regulation O2 consumption depends on temperature
Heat production At rest
70 - 80% from organs 20 - 30% from skeletal muscle
During exercise Skeletal muscle produces 30 - 40X more heat
than rest of body
Control of heat Metabolism plus heat transfer
Heat transfer
Conduction Transfer of heat from physical contact
Convection Transfer of heat by warming a layer of air or
water. Replacement of layer increases heat transfer
Heat transfer Radiation
Transfer of infrared rays (thermal heat) 50% of heat transfer
Evaporation Liquid turning into a gas transfers heat Lungs and skin
Thermal strategies Based on stability of body temperature
Homeotherms (birds, mammals) Poikilotherms (fish, amphibians, reptiles)
Thermal strategies Based on ability to produce heat
Endotherms (birds and mammals) Ectotherms (fish, amphibians, reptiles)
Thermal strategy summary
Thermal strategy
Heterothermy Temporal (monotremes) Regional (fish)
Heat production
1. Vasoconstriction of cutaneous vessels Restrict blood flow to the core Short vs. long term (frostbite)
Heat production 2. Increase metabolic rate
Norepinephrine from sympathetic fibers
3. Thyroxine release
Hypothalamus
thyrotropin releasinghormone (TRH)
anterior pituitary
thyroid stimulatinghormone (TSH)
thyroid gland metabolic rate
Heat production 4. Shivering
As a last resort Involuntary muscle contraction
5. Behavioral Huddling
Heat loss 1. Vasodilation
Increase loss via heat transfer
2. Perspiration If dry it’s efficient, if not it’s inefficient
3. Behavior
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