The name for constancy ofthe internal environment is homeostasis the body must reguiate many body systems and processes to keep innerconditions stable thetemperature nucleus in the hypothalamus controls heat loss and production by the body through the skin overheating causes an increased blood flow from the blood vessels to radiate heat and causes sweating though the sweat glands. To lose heat a fall in body temperature constricts the surface blood vessels stops sweating and makes the erector muscles contract causing the hairs, to stand on end trapping air as an insulating layer additional heat can be produced by shivering.
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Body movement can also be homeostatic. a hot person may spread out arms and legs to increase heat loss; a cold person curls up to reduce the areas of the body lossing warmth.
