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Skin temperature is the temperature of the outermost surface of the body. Normal human skin temperature on the trunk of the body varies between 33.5 and 36.9 °C (92.3 and 98.4 °F), though the skin's temperature is lower over protruding parts, like the nose, and higher over muscles and active organs. [ 1 ]
Simplified control circuit of human thermoregulation. [8]The core temperature of a human is regulated and stabilized primarily by the hypothalamus, a region of the brain linking the endocrine system to the nervous system, [9] and more specifically by the anterior hypothalamic nucleus and the adjacent preoptic area regions of the hypothalamus.
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, thus avoiding the need for internal thermoregulation.
When the core temperature falls, the blood supply to the skin is reduced by intense vasoconstriction. [18] The blood flow to the limbs (which have a large surface area) is similarly reduced and returned to the trunk via the deep veins which lie alongside the arteries (forming venae comitantes).
The ambient temperature of the body directly affects blood flow through microvasculature. Changes in temperature affect the viscosity of blood and the surface tension. Surface tension decreases with increasing temperature, decreasing the minimum flow rate (see Surface tension). The decrease in minimum flow rate by higher temperatures allows ...
An early morning temperature higher than 37.3 °C (99.1 °F) or a late afternoon temperature higher than 37.7 °C (99.9 °F) is normally considered a fever, assuming that the temperature is elevated due to a change in the hypothalamus's setpoint. [15]
The human body always works to remain in homeostasis. One form of homeostasis is thermoregulation. Body temperature varies in every individual, but the average internal temperature is 37.0 °C (98.6 °F). [1] Sufficient stress from extreme external temperature may cause injury or death if it exceeds the ability of the body to thermoregulate.
Deaths due to hypothermia have played an important role in many wars. [1] The term is from Greek ῠ̔πο (ypo), meaning "under", and θέρμη (thérmē), meaning "heat". The opposite of hypothermia is hyperthermia, an increased body temperature due to failed thermoregulation. [7] [8]