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How does the body regulate its temperature, and how does it then fight a fever?

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How does the body regulate its temperature, and how does it then fight a fever? 5th March 2000 Body temperature is regulated by the hypothalamus, a small but vital region of the brain situated below the two thalami and above the pituitary gland. The anterior portion of the hypothalamus controls heat loss by means of peripheral vasodilatation and sweating when the body temperature is above the normal set point. The posterior portion is responsible for conserving heat when the body temperature falls, producing peripheral vasoconstriction and shivering. The hypothalamus is the central component of several neural feedback loops that monitor body temperature and bring about changes to maintain the temperature within an optimum range. Thermoreceptors are present in the hypothalamus, skin, respiratory system, and digestive system. These receptors monitor temperature and enable the hypothalamus to initiate appropriate responses. ...read more.


As a result, the amount of heat being lost from the skin surface falls and body heat is conserved. A decrease in sympathetic tone produces the opposite effect: the blood vessels dilate and skin blood flow increases, increasing heat dissipation. The degree of sympathetic tone that exists is governed by information sent from the hypothalamus to the vasomotor centre, a specialised area within the brainstem. fever Fever (pyrexia) occurs when the body temperature is maintained at an above-normal level. There can be various causes: infection, inflammation, dehydration, and abnormalities in the brain. Chemical signals that induce fever are called pyrogens. They can originate from infectious pathogens, in which case they are referred to as exogenous pyrogens, and from activated cells of the immune system - endogenous pyrogens. These signals change the hypothalamic set point for body temperature and raise it by several degrees, apparently by increasing the production of prostaglandins in the hypothalamus. ...read more.


When the level of circulating pyrogens falls, either because the infection has been overcome or because the inflammatory process has been resolved, the hypothalamic set point returns to its normal level. The person feels hot, becomes flushed and warm to the touch, and sweats profusely. Excess body heat is dispersed until the body temperature returns to its normal level. It is thought that fever helps the body's defence mechanisms to deal with problems such as infection and tissue damage. However, if the body temperature rises above 41 - 42 � C for any length of time, cells within the body are damaged and the functioning of vital organs such as the heart, brain, liver and kidneys can be affected. Several antipyretic drugs, for example aspirin, are available and can be given to control a potentially damaging fever. These drugs appear to act by reducing prostaglandin production and allowing the hypothalamic set point to return to normal. ...read more.

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