Why Does the Body Temperature Rise During Fever?

Normal body temperature fluctuates between 97°F (36.1°C) and 100°F (37.8°C), with the average being 98.6°F (37°C). When our body temperature rises above 98.6°F, we call it fever. Our normal body temperature is maintained by a certain part of the brain called the “anterior hypothalamus”. This region functions like a thermostat, registering the body temperature. The nervous system constantly relays information about the body’s temperature to the thermostat, which in turn activates different physical responses, designed to cool or warm the body, depending on the circumstances, in order to maintain the body temperature at a normal set point.

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Fevers are primarily caused by viral or bacterial infections. So, when an infection occurs, fever-inducing agents called pyrogens are released in the bloodstream, either by the body’s immune system or by the invading cells. The pyrogens trigger the resetting of the thermostat at a higher level and we thus register a higher body temperature during fever.

To reach a higher temperature from the normal body temperature, the body moves blood to the warmer interior, increasing the metabolic rate, and inducing shivering — that often accompanies a fever and is caused by these movements of blood to the body’s core, leaving the surface and the extremities cold. Once the higher temperature is achieved, the shivering and chills stop. Again, when the infection is overcome or drugs such as aspirin or acetaminophen are taken, the thermostat resets to normal (98.6°F) and the body’s cooling mechanisms send the blood back to the surface and sweating occurs.

We often panic when we have high temperature or fever. However, fever is an important component of our immune system. Actually, the immune system chemicals, that react with the fever-inducing agent and trigger the resetting of the thermostat, increase the production of cells that fight off the invading bacteria or viruses. Higher temperatures also inhibit the growth of some bacteria, accelerating the chemical reactions that help the body cells to repair themselves. In addition, the increased heart rate that may accompany the changes in blood circulation also speeds up the arrival of white blood cells to the site of infection to fight with the invaders.

Sources: The Telewgraph (Kolkata, India)

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