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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.
Sweating occurs when the ambient air temperature is above 35 °C (95 °F) [dubious – discuss] and the body fails to return to the normal internal temperature. [18] The evaporation of the sweat helps cool the blood beneath the skin. It is limited by the amount of water available in the body, which can cause dehydration. [5]
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 rate of heat loss from the human body is a function of subcutaneous fat thickness, but metabolic heat production is not accurately predictable, which is a limitation on predicting the lowest water temperature in which a stable thermal balance can be reached, with or without a given external insulation.
Thermoreceptors of the skin sense the temperature of water. A thermoreceptor is a non-specialised sense receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range.
Thermogenesis is the process of heat production in organisms.It occurs in all warm-blooded animals, and also in a few species of thermogenic plants such as the Eastern skunk cabbage, the Voodoo lily (Sauromatum venosum), and the giant water lilies of the genus Victoria.
The resting human body generates about two-thirds of its heat through metabolism in internal organs in the thorax and abdomen, as well as in the brain. The brain generates about 16% of the total heat produced by the body. [8] Heat loss is a major threat to smaller creatures, as they have a larger ratio of surface area to volume.
Homeothermy [b] maintains a stable internal body temperature regardless of external influence and temperatures. The stable internal temperature is often higher than the immediate environment. The opposite is poikilothermy. The only known living homeotherms are mammals and birds, as well as one lizard, the Argentine black and white tegu.