it is liable to lose heat energy but this can be counteracted in a number of ways;h It could raise the hairs into a more vertical position by the contraction of the erector pili muscles. Air can then be trapped in the spaces between the hairs and, being a poor conductor of heat, it serves as an insulatory layer round the animal. This is an involuntary response brought about by the nervous system.h The arterioles leading to the superficial capillaries constrict and as a result blood flow to the surface of the skin is greatly reduced (vasoconstriction). This is brought about by the sympathetic nervous system and is useful in uncovered regions such as the ears where the surface-volume ratio is particularly large and so particularly susceptible to cold.h The metabolic rate can be increased therefore heating the inside of the body. A general increase in the metabolic rate is brought about by the hormones adrenaline and thyroxin which are produced in large amount during cold conditions. There is then a general increase in muscle tone, which is then followed by spasmodic contractions (shivering)The response to high temperature is basically the reverse of the above processes; i.e h Hairs lie flat against the bodyh The arterioles dialate (vasodialation) allowing blood to flow back to the surface of the skin so heat can be lost by diffusion.h Sweating occurs and the evaporation of the water from the skin cools the skin and blood.h Panting occurs. In some animals there are no sweat glands except in the pads of the paws. Thus they pant which speeds up evaporation from the lungs, pharynx and other moist areas helping to cool blood.h Metabolic rate decreases, so less energy is generated by the bodyArctic Polar Bears (Thalarctos maritimus)Polar bears have successfully adapted to one of the world's most inhospitable climates, and remain active throughout the harsh winter. They are found on the sea ice of the Arctic throughout the North Polar basin.The ...
