THERMAL PHYSIOLOGY

This includes adaptations in face of environmental challenges.

Heat fluxes

(Body Temperature, TB)

Metabolism

Main source of thermal energy
in the heat balance equation.

Conduction

Direct transfer of heat between two substances in contact with each other.

Heat flows from a region of ↑ temperature to
a region of lower temperature.

Rate depend on:
• area of physical contact
• different temperature
• thermal conductive properties

Convection

The heat is being carried from one point to another by a moving substance.

Exchanged depend on:
• thermal gradient
• rate of flow the fluid
• the conductivity of the fluid

Radiation

Transfer of thermal energy in the form of light waves, as exemplified by the heat we receive from the sun.

All bodies, including mammals, emit heat by radiation.

Evaporation

Water molecules absorb thermal energy from
an object when making the transition from
liquid to vapor.

Magnitude of heat loss depend on volume of
H2O and its heat of vaporization.

Thermal zone

Upper critical zone

Metabolic rate ↑ to induced a physiological
response to prevent overheating.

(Hyperthermia)

Lower critical zone

Metabolic rate ↑ to induced heat production.

(Hyphothermia)

Thermoneutral zone

Metabolic rate is minimal
(basal metabolic rate).

To investigate the biological
implications of temperature to the
function of living organisms.

Thermal strategies

Ectotherm

Rely mainly on external energy source.

Endotherm

Rely heavily on metabolic energy.

Poikilotherm

Body temperature varies directly with
environmental temperature.

Homeotherm

Maintain relatively constant
internal environmental.

Thermoregulation

Behavioral response

Surface area/
volume

Physiological
response

Insulation

Sweating

Shivering

Muscle contraction --> increase heat production.

Non-shivering

Metabolism --> increase heat production.

Circulating Adaptation

Vasolidation

Vasocontriction

Countercurrent Exchange

Heat production may happen as a by-product of metabolic processes.

The inefficient part of molecular transformations that causes part of the energy not to be used for work, but instead, lost as heat.

Thermal energy will not be transferred when there is thermal equilibrium.

Thermogenesis

An endothermic organism struggles in face of a colder-than-desirable ambient.