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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 anterior pituitary thyrotropin releasing hormone (TRH) thyroid gland thyroid stimulating hormone (TSH) metabolic rate Heat production 4. Shivering As a last resort Involuntary muscle contraction 5. Behavioral Huddling Heat loss 1. Vasodilation 2. Perspiration Increase loss via heat transfer If dry it’s efficient, if not it’s inefficient 3. Behavior