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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]
Heat is lost from the body in proportion to the amount of exposed skin. [289] [290] The head accounts for around 7–9% of the body's surface, and studies have shown that having one's head submerged in cold water only causes a person to lose 10% more heat overall. [291] [medical citation needed]
Although heat has a negative impact on the health of the entire population, some factors may increase the risk of adverse outcomes. [31] People who are at an increased risk of dying from heat exposure include the elderly, young children, those who have low socioeconomic status or pre-existing diseases. [ 31 ]
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.
Surface heat loss may be reduced by insulation of the body surface. Heat is produced internally by metabolic processes and may be supplied from external sources by active heating of the body surface or the breathing gas. [2] Radiation heat loss is usually trivial due to small temperature differences, conduction and convection are the major ...
The principles of heat transfer in engineering systems can be applied to the human body to determine how the body transfers heat. Heat is produced in the body by the continuous metabolism of nutrients which provides energy for the systems of the body. [43]
Until the body temperature is raised to near-normal levels: Types: Primary hypothermia: caused by exposure to a cold environment; Secondary hypothermia: caused by an underlying pathology that prevents the body from generating enough core heat. Causes: Mainly exposure to cold weather and cold water immersion: Risk factors