Ch.10 Thermal Regulation

What are the four heat-transfer mechanisms?

Conduction, convection, radiation, and evaporation.

What is conduction?

Heat transfer through direct contact or a stationary material.

What is convection?

Heat transfer by moving air or water.

What is radiation?

Heat exchange through electromagnetic emission and absorption.

Why does evaporation cool an animal?

Vaporization consumes latent heat from the body.

How does wind increase heat loss?

It removes the insulating boundary layer and raises convection.

Endotherm versus ectotherm?

Primarily metabolic heat versus environmental heat for body temperature.

Homeotherm versus poikilotherm?

Relatively stable versus variable body temperature.

What is the thermoneutral zone?

Ambient range where resting endotherms maintain temperature at minimal MR.

What happens below the lower critical temperature?

Endotherms increase heat production to offset heat loss.

What happens above the upper critical temperature?

Evaporative cooling and other heat-loss mechanisms increase.

What is shivering thermogenesis?

Heat produced by repeated skeletal-muscle contraction.

How does brown-fat UCP1 generate heat?

Uncouples mitochondrial proton flow from ATP synthesis.

What is Q10?

Rate at T divided by rate at T−10°C.

What does acclimation mean?

Physiological adjustment under controlled environmental conditions.

What does acclimatization mean?

Physiological adjustment under natural environmental conditions.

What is a thermal performance optimum?

Temperature where measured physiological performance peaks.

What is the pejus range?

Temperatures beyond optimum where performance declines.

How can ectotherms behaviorally thermoregulate?

Move among sun, shade, water depths, or other microhabitats.

How do cryoprotectants aid cold survival?

Reduce freezing damage and improve tolerance of low temperatures.

What is the simplified endotherm heat-balance equation?

MR = C(Tb − Ta) = (Tb − Ta)/I.

How are conductance and insulation related?

Conductance C = 1/insulation I.

What is countercurrent heat exchange?

Opposite-flow blood vessels transfer heat and limit heat loss.

What is regional endothermy in tuna?

Countercurrent exchangers retain heat in active tissues.

How does hibernation save energy?

Torpor lowers temperature, ventilation, heart rate, and metabolism.

Why can a heat lamp raise frog MR but lower mouse MR?

Warming speeds frog reactions but can reduce cold mouse thermogenesis.