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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.
As in other mammals, human thermoregulation is an important aspect of homeostasis. In thermoregulation, body heat is generated mostly in the deep organs, especially the liver, brain, and heart, and in contraction of skeletal muscles. [1] Humans have been able to adapt to a great diversity of climates, including hot humid and hot arid.
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] Lower thresholds are sometimes appropriate for elderly people. [15]
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.
The human body maintains a core body temperature at around 37 °C or 98.6 °F through mechanisms controlled by the thermoregulatory center within the hypothalamus.When the body is exposed to high ambient temperatures, intense physical exertion, or both, the thermoregulatory center will initiate several processes to dissipate more heat: [9] [11] [12]
Heat stroke occurs when thermoregulation is overwhelmed by a combination of excessive metabolic production of heat (exertion), excessive heat in the physical environment, and insufficient or impaired heat loss, resulting in an abnormally high body temperature.
This is comparable to a common incandescent light-bulb. However, adult humans can produce in excess of 1,000 W (1.3 hp) of heat energy during strenuous exercise. [8] Hence, if the body were perfectly insulated, core temperature would continue to increase until lethal core temperatures were achieved.
An ectotherm (from the Greek ἐκτός (ektós) "outside" and θερμός (thermós) "heat"), more commonly referred to as a "cold-blooded animal", [1] is an animal in which internal physiological sources of heat, such as blood, are of relatively small or of quite negligible importance in controlling body temperature. [2]