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Regulation

SUN
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Solar radiation

Evaporation (sweat) Evaporation (respiration)

Convection and radiation

Convection
Radiation

Ground thermal radiation

Ground conduction

Figure 5.4: Thermoregulatory mechanism

and adrenaline stimulate higher metabolic Shivering: This is an involuntary contraction
rates to produce more warmth. Metabolism of skeletal muscles that generates heat.
is mostly carried out by the liver and skeletal The rapid muscle movements increases
muscles. The increased activity of adrenal, metabolic activity, producing heat that
thyroid and pituitary glands results into helps raise and maintain the body’s internal
secretion of hormones. These hormones temperature in exposure to cold conditions.
help to increase the body metabolic rate.
Additional heat produced in the body as Vasoconstriction: Blood vessels near
a result of increased metabolic rate raises the skin constrict, reducing blood flow
body temperature to the required level. to the surface. This minimizes heat loss
Increased metabolic rate of the body by directing warm blood to the body’s
requires increased food consumption. This core. Most of the blood passes beneath
is the reason why animals in cold climates the insulating layer of subcutaneous
require a larger amount of food compared fats, therefore little heat is lost to the
to those in hot climates. environment. See Figure 5.5.

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