3 Flashcards
(15 cards)
Homeotherm
Organism that maintains its body temperature at a constant level, usually above that of the environment, by its metabolic activity. 37 degrees
Thermal gradient from body core to skin surface
Ideal 4 C
In extreme cold, could be as much as 20 C
Shivering increases heat production
By 5
Conduction
Heat loss due to contact with another surface.
High energy molecules bumping into low energy molecules.
Convection
Heat transferred to air or water.
This is because hot air is less dense (lighter) than cold air, so the each temperature of air moves towards the opposite temperature.
Radiation
Transfer of heat via infrared waves.
Requires a temperature gradient.
60% of heat lost at rest.
Evaporation
Heat from skin coverts sweat to water vapour.
Requires a vapour pressure gradient.
25% heat lost at rest.
1 L sweat = 580kcal lost
Most important during exercise. Hot/humid environment bad to exercise in.
Non-shivering thermogenesis
Action of hormones (like thyroxine) increase body temperature
Physiological response to heat load
Heat load. Sensed by thermal receptors in body’s skin and core. They signal the anterior hypothalamus which regulates cooling. The hypothalamus initiates vasodilation, which brings blood to the surface to cool, and sweating.
Physiological responses to cold stress
Cold. Sensed by receptors in body’s skin and core. They signal the posterior hypothalamus which initiates shivering, vasoconstriction, and hormone release.
VO2 is linearly proportional to
Body temperature
Major ways heat is lost in cold environment
Convective and radiative heat loss
Major ways heat is lost in hot environment
Evaporative heat loss
Dehydration of _% of body weight can impair performance
1-2%
What acclimation occurs from exercising in a hot environment?
Inc. plasma volume. Sweat sooner, sweat more. Dec. in sodium and chloride losses in sweat.
