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Humidity affects thermoregulation by limiting sweat evaporation and thus heat loss. [6] Humans cannot survive prolonged exposure to a wet-bulb temperature above 35 °C (95 °F). Such a temperature used to be thought not to occur on Earth's surface but has been recorded in some parts of the Indus Valley and Persian Gulf.
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 honey bee, for example, does so by contracting antagonistic flight muscles without moving its wings (see insect thermoregulation). [18] [19] [20] This form of thermogenesis is, however, only efficient above a certain temperature threshold, and below about 9–14 °C (48–57 °F), the honey bee reverts to ectothermy. [19] [20] [21]
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. [1] A high concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidity affects rate of evaporation of water. [ 2 ]
It can show postural changes where it changes its body shape or moves and exposes different areas to the sun/shade, and through radiation, convection and conduction, heat exchange occurs. Vasomotor responses allow control of the flow of blood between the periphery and the core to control heat loss from the surface of the body.
Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate. It is usually caused by prolonged exposure to high temperatures. The heat-regulating mechanisms of the body eventually become overwhelmed and unable to deal effectively with the heat, causing the body temperature to climb uncontrollably.
When understanding the concept of shivering it is important to understand the human physiological responses to cold exposure. There are many reactions that humans have to the cold such as “cutaneous vasoconstriction and shivering thermogenesis” these processes “decrease heat loss and increase metabolic heat production”.