Comparative Vertebrate Physiology Temperature regulation

Temperature regulation O2 consumption depends on temperature

Heat production At rest During exercise 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 Convection 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 Evaporation 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 3. Thyroxine release Norepinephrine from sympathetic fibers 3. Thyroxine release

Heat production 4. Shivering 5. Behavioral As a last resort Involuntary muscle contraction 5. Behavioral Huddling

Heat loss 1. Vasodilation 2. Perspiration 3. Behavior Increase loss via heat transfer 2. Perspiration If dry it’s efficient, if not it’s inefficient 3. Behavior