What are the physiological responses to cold? Discuss.

PHYSIOLOGICAL RESPONSES TO COLD

When there is a fall in the environmental temperature, a drop in animal's body temperature is prevented by a reduction in heat loss by physical regulation. When this physical regulation becomes insignificant to maintain the body temperature heat production will be increased as a line of defense by means of chemical regulation.

Reduction in heat loss

Behavioral response

• A reduction of heat loss is brought by adoption of posture such as curled up position of animals at rest. So that the surface area exposed to cold will be reduced.

Increased fur insulation

• In case of prolonged cold exposure, the animals will develop increased fur growth and subcutaneous fat as a means of increasing peripheral insulation.

Piloerection

• It occurs to reduce the insulation value of hair or fur. In this process the hairs become more erect and is brought about by the erector pili muscle of the hair follicle.

Circulatory Adjustments

• When exposed to cold vasoconstriction occurs in the skin and superficial tissues mediated by the vasoconstrictor nerves there by reducing the heat loss in 2 ways:
• Vasoconstriction decreases the peripheral blood flow causing a drop in skin temperature there by reducing the temperature gradient between the skin and the environment.
• It increases the functional insulation of the skin because of reduction in convected heat loss of the perfusing blood.
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