Why does the body become hot when we have fever?

Answer 1

Remember getting a cut on your hand and it swelling up? That inflammation is a local response of the body to the injury. There are, however, systemic, or body-wide responses; one of the most important is fever, defined as an abnormally high body temperature >37° degrees Celsius (98.6° degrees Fahrenheit.) the most common cause of fever is infection from bacteria (we respond to their toxins) and/or viruses. Body temperature is controlled by a part of the brain called the hypothalamus. The hypothalamus is sometimes called the body’s thermostat and it is normally set at 98.6° degrees Fahrenheit. (Here it is going to get a little complicated, but I’ll try to keep it to a minimum.) When we are infected with, for example, a bacterium, our body’s phagocytes ingest the bacteria. This, as you might have guessed, is a good thing. Unfortunately, there is a chemical structure (the lipopolysaccharide component of the bacteria) that causes the phagocyte to release a chemical messenger called cytokine interleukin~1; think of this as an instant message (IM). When this interleukin~1 reaches the hypothalamus it tells the hypothalamus to release prostaglandins that reset the thermostat at a higher temperature, thus causing fever. So it’s bacteria being eaten by a phagocyte that releases a chemical that causes the fever. Let’s assume that we are infected with a pathogen that raises our temp to 102.2 degrees °F, a moderate grade fever. To adjust to the new thermostat setting the body responds with blood vessel constriction an increased rate of metabolism and shivering, all of which raise the body temperature. Even though we are getting hotter, however, the skin remains cold and we get a chill. I am reminded of the old medical adage that the surest sign you’re getting hot is when you’re feeling cold. When the temperature reaches the thermostat’s setting, the chill disappears. Our body will maintain a 102.2° F temp until that instant messenger is gone and no more unsupervised little bacteria are running around causing trouble. As the infection subsides, heat losing actions like vasodilation and sweating go into operation. The skin becomes warm and we being to sweat. People think they are getting hotter; they are actually returning to a normal temp. Medically speaking this is known as the crisis point of the fever. Fever is good up to a certain point. It draws more T cells to help and intensifies the effect of interferons which combat viruses. Expiration happens when a patient gets to hot; normally 110-114 °F. Hope this clears up some stuff for you. Thanks.

Answer 2

Theoretically, fever has been conserved during evolution because of its advantage for host defense. There are certainly some important immunological reactions that are sped up by temperature, and some pathogens with strict temperature preferences could be hindered. The overall conclusion seems to be that both aggressive treatment of fever and too little fever control can be detrimental. This depends on the clinical situation, so careful assessment is needed.

Answer 3

Fever occurs due to the destruction of the heat losing center in the hypothalamus and so the heat gaining and conservation centere is the only working so body temprature rises leading to fever.

Answer 4

when your body is invaded by an antigen (eg a virus or bacteria) your specialised phagocytes (specialised immune cells) release antibodies which merges with each antigen to form an antigen-antibody complex. this is then engulfed by the phagocytes, and broken down by enzymes. as all this is happening, your phagocytes release molecules called endogenous pyrogens. these are sent to the part of the brain called the hypothalamus which acts sort of like a thermostat for the body. the molecules will raise the so-called 'normal' temperature such that it is higher than your current temperature. hence your brain will sense that you are feeling 'cold', because it is below the new 'normal' temperature.