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temperature regulationThe process by which body temperature is maintained within narrow limits. Blood temperature is monitored in the hypothalamus of the brain. A drop in temperature prompts closure of the skin blood vessels and shivering; a rise in temperature results in skin flushing and sweating so that heat may be lost by radiation and evaporation. In fevers, the hypothalamic thermostat is set high and shivering and skin vessel closure raise the temperature.
temperature regulationthe maintenance of body temperature at a steady level. This occurs to some extent in all vertebrates and many invertebrates, but applies particularly to HOMOIOTHERMS. In humans, a constantbody temperature of 36.9 °C is maintained, and this is the optimum temperature for normal metabolic reactions involving enzymes.
Various mechanisms bring about temperature regulation. In mammals and birds, hair and feathers trap air which acts as insulation. Sweating acts as a cooling mechanism, and animals in cooler climates have a smaller surface area/volume ratio (see BERGMANN'S RULE). Subcutaneous fat also acts as an insulation; superficial blood vessels constrict in response to cold and dilate in warm conditions, so taking blood away from the skin surface when it is cold and to the skin surface when warm. The centre for controlling body temperature lies in the HYPOTHALAMUS.
Plants also control their temperature and keep cool by transpiration, losing the latent heat of EVAPORATION. On the loss of too much water they wilt, but this results in their leaves being moved (by drooping) from the direct rays of the sun so that in effect they remain cooled until sunset.