Many living organisms maintain internal temperature within narrow limits in spite of changing internal and external conditions that tend to cause it to deviate. Humans and other higher vertebrates are homeotherms, organisms capable of regulating core temperature within narrow limits through physiological (e.g., sweating, shivering) and behavioral changes driven by thermal discomfort. Poikilothermic animals such as reptiles exhibit greater variation in temperature and primarily use behavioral (e.g., voluntarily moving to a more temperate environment), rather than less well-developed physiological, thermoregulatory responses. With the exception of sweating in humans, heat loss and heat production effector mechanisms serve other functions as well (e.g., muscles used in shivering are used for voluntary movement), and in both homeotherms and poikilotherms strict adherence to temperature regulation can be set aside for brief periods in favor of other activities. The temperature of circulating blood in humans is not homogeneous, and deep body temperatures vary with the site of measurement. For example, in humans rectal temperature tends to be 0.5–0.7°C higher than oral and axillary temperatures.
KeywordsMalignant Hyperthermia Narrow Limit Control System Temperature Thermal Discomfort Deep Body Temperature
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