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