Why Do We Get Fever When We Are Sick_ The Actual Mechanism Behind Fever _Pathophysiology Of Fever

Fever is probably the most common symptom of all, and every single person experiences a fever at least once in a while. So, in this video we will see the mechanism behind fever.
To understand this, let’s recall the normal temperature regulation first. Humans are referred to as homeotherms, meaning that they are able to maintain their body temperature at a constant range of 98 to 98.6 Fahrenheits, or 36.6 to 37 in Celsius. This critical range is called the temperature set point in humans. Hypothalamus is the principal thermoregulator in our body. It regulates the temperature set point within this constant range by maintaining a balance between heat producing and heat losing mechanisms.
Fluctuations in the temperature are detected by peripheral thermoreceptors, which include the Ruffini endings, Kraus end bulbs, and free nerve endings, and central thermoreceptors, which are in the central nervous system and internal organs. These receptors then send signals to the hypothalamus, which in turn activates either heat generating mechanisms, or heat losing mechanisms to bring the body temperature to normal.
When the body temperature is elevated, it is detected by the hypothalamus, and it activates heat losing mechanisms to get rid of excess heat, and at the same time, it inhibits heat producing mechanisms in the body. Heat losing mechanisms include increased blood supply to the skin, which increases heat loss through radiation. And increased sweating. When sweat evaporates, it absorbs heat from the skin, which helps lower the body temperature. To prevent excess heat from generated, hypothalamus also reduces the metabolic rate within the body. As a result, cellular functioning will be much slower than normal.
When the body temperature is reduced, hypothalamus activates heat producing mechanisms, and inhibits heat losing mechanisms. Blood supply to the skin will be reduced, so the heat loss through radiation is minimal. And body hair gets straighten, which helps keep a static airflow near the body surface. This helps to reduce heat loss through convection. Additionally, hypothalamus may induce shivering, which helps generate some excess heat. And the metabolic rate will also be increased.
Fever is actually a symptom, rather than a disease. It is a condition where the body temperature is persistently elevated than the normal level. Bacterial and viral infections are the commonest causes for fever. Other than that, allergic reactions. Certain drugs. Post operative status. Certain cancers, especially renal cell carcinoma. Alcohol withdrawal. Blood transfusions. And pancreatitis can also induce fever.
In stressful conditions like infection, body produces large amounts of cytokines, specifically tumor necrosis factor, interleukins 1 and 6. These cytokines act on the hypothalamus, and they elevate the temperature set point to a level higher than the normal. Now the hypothalamus tries to get the body temperature up to that point. To do so, it activates heat producing mechanisms, and inhibits heat losing mechanisms. Ultimately, the body temperature will be increased, resulting in fever. this is the actual mechanisms of fever. in addition to cytokines, certain bacterial products, and toxins can also induce fever. these substances are collectively known as pyrogens. Finally, certain brain abnormalities such as brain tumors and trauma can cause direct effects on the hypothalamus, which also can lead to fever.

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