There are substances which when injected into the bloodstream to cause chain reactions that lead to increased body temperature and changes in the processes of thermoregulation in the body. This condition is called fever, and substances that cause it are called pyrogens (from the Greek. piros - fire, heat, and genes - generating, producing).
Pyrogens are endogenous (produced in the body) and exogenous (enter the body from the outside). Exogenous pyrogens are components of cell membranes of microbes and toxins and waste products of these microbes. Exogenous pyrogens induce an increase in body temperature not in themselves but indirectly, inducing the formation of endogenous pyrogens.
Endogenous pyrogens are formed in lymphocytes (mainly monocytes and macrophages). These include interleukins, interferons, the decay products of steroid hormones, cytokines and other substances.
Endogenous pyrogens, in turn, affect the temperature of the body, acting on the center of thermoregulation in the hypothalamus - the Department of brain. Under the action of pyrogens, the hypothalamus begins to perceive normal body temperature as low, and the point of permanent supported by the body temperature is shifted up. This occurs by changing the ratio of heat production and heat transfer. Interestingly, in the adult human, reduced heat dissipation, and in newborns in which the processes of thermoregulation haven't "adjusted"on the contrary, increases the production of heat. The first way is much better as it does not increase the costs of energy: the body just begins to give into the environment less heat. This is achieved by contraction of the peripheral vessels, reducing blood flow to peripheral tissues and decreased sweating. The skin is pale, the skin temperature decreases. As a result, we feel the chills - cold feeling: it triggers the receptors that respond to cold and send a signal to the hypothalamus. The hypothalamus, in turn, sends a signal to the cerebral cortex, which is responsible for our conscious behavior. Feeling the chill, we try to move less, bundle up, and thus further reduce heat transfer. In addition, when the chills we begin to tremble. Shiver is a small muscle contractions that result in body temperature also increases.
Raising thus the body temperature to the new set point, the body holds it: the heat production and heat dissipation balance each other, and further increase in temperature does not occur. And thermoregulation occurs by the same mechanisms that operate in the norm. When this skin vessels dilate, pallor, tremors and chills disappear and the skin becomes hot to the touch. We begin to feel the heat.
Fever lasts until the body remain endogenous pyrogens or until we artificially will not lower the temperature by drugs or by other means. After the termination of pyrogens on thermoregulation center mounting point is lowered to normal levels. And then the hypothalamus begins to perceive the temperature as high. He immediately takes action: sends a signal to the expansion of dermal vessels and profuse sweating. Active heat dissipation. It lasts as long as the temperature does not return to normal value.
Why is this happening and what should the temperature rise? Fever appears always when the permeation of the causative agents of acute infectious diseases. It is believed that the increased body temperature - this part of the measures taken by the body to destroy the source of infection. But we need to honestly acknowledge that the role of increasing temperature of the body in fighting infection are not fully established. It is believed that the self-heating body
first,it activates all the processes in it, including protective reactions (speed increases production of antibodies and interferon - internal antiviral agents, is activated neutralization of toxins in the liver, and increases the excretion of urine, and with it the toxins),
and secondly,it prevents the growth of harmful microorganisms and causes their death.
When you need to bring the temperature down with acute infectious diseases? Doctors advise to take antipyretics, if she starts to "outrageous" for 38-38,5 degrees, because in these values greatly increases the load on the heart and lungs, and at higher values there is a direct threat to life. In the first months of life the temperature is above 38 degrees is dangerous as it increases the risk of seizures and damage to the nervous system.
If you feel much worse at lower temperatures (37-37 .5°C), also we should not delay with receiving funds from fever. But sometimes (especially in young children)that the mercury thermometer has gone beyond the point of 38 degrees, and the child feels quite normal: plays, runs. In this case, create an additional burden on the liver is also useless.
In short, the signal to the reception febrifuge should be not so much the thermometer reading as a condition of the body. In General, adults can not reduce the temperature if the numbers on the thermometer below to 38.5 degrees, and children below 38.
Did you know that...
Why extreme elevation of the temperature on the thermometers - 42°C? Because at this temperature begins denaturation (clotting) of blood proteins. A similar process occurs when cooking eggs: transparent gelatinous egg white becomes white and thick. In addition, at this temperature, the brain starts the metabolism. This condition is already incompatible with life, that is deadly.