Our skin is endowed with both cold and warmth receptors.
There are more cold receptors than warmth receptors. Therefore peripheral
detection of temperature mainly concerns detecting cool and cold instead of
warm temperatures. When the skin is chilled over the entire body immediate
reflex effects are involved to increase the temperature of the body. The two
important effects are providing a strong stimulus to cause shivering, with
resultant increase in the rate of body heat production and promoting skin
vasoconstriction to diminish the transfer of body heat to the skin.
The effects of hypothermia depend on whether there is whole
body exposure or exposure of only body parts. When the whole body is exposed,
metabolic processes; particularly in the brain and medullary centres slow down,
causing death, before apparent changes in the cells or local reactions will
occur in the parts of the body.
When only parts of the body gets exposed to very chill
temperature, the local reactions begin to appear. These reactions are chilling
and freezing of cells and tissues leading to frost bite. The injury is in two
ways. (1) Crystallisation of the intra and extra-cellular water causing
physical dislocation within the cells, which is the direct effect. (2) The
indirect effects are exerted by circulatory changes. Depending on the rate at
which the temperature drops and the duration of the temperature, slowly
developing chilling may induce vasoconstriction and increased permeability,
leading to oedematous changes. This results in the dryness of the body skin and
also lips.
When the drop in temperature persists for a long time
atrophy and fibrosis may follow, which result in permanent circulatory
impairment as well as tissue damage. Often gangrene follows thawing and the
frostbitten areas are lost. This we often experience in the lips by the
appearance of infarction necrosis of affected areas even after the temperature
begins to return towards normal. Courtesy : The Hindu
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