Responses of Animals to Cold
The decrease in environmental temperature activates thermogenic activities, which prevents the decline in Tc in homeotherms. The regulatory responses are elicited against the drop in body temperature by reduction of heat loss via insulation.
When this regulation is inefficient in restoring Tc, metabolic increment as chemical regulation is intensified to protect the body temperature. Animals reduce the heat loss by changing the posture, intensifying insulation properties of fur via piloerection and increasing fur growth and subcutaneous fat deposition. Vasoconstriction occurs at the extremities of the animals once the environmental temperature drops. The vasoconstriction reduces blood flow to skin and periphery resulting in reduction in temperature which neutralizes or reduces the temperature gradient between the skin and the environment. Further, the functional insulation of the skin is increased due to reduction in the convectional heat loss by decreased blood supply to skin. In addition, the sensory receptors transmit signals of lower temperature to the CNS which primarily induces the peripheral vasoconstriction. Moreover, the close arrangement of arteries and veins assists in the heat conservation where cold venous blood is transported centrally alongside to warm arterial blood from periphery. The continuous heat exchange between the returning venous blood is warmed, and the arterial blood is cooled which effectively reduces heat losses by countercurrent heat exchange mechanism in cold environment.28.17
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