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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