What is a normal body temperature?
Historians have credited Dr Carl Wunderlich, a nineteenth-century German physician, as developing the concept that 37C or 98.6F is a normal temperature for the human body, he felt this temperature had clinical significance. Although there are modern critiques of his analysis of the raw data, 37C or 98.6F remains an established set point.
A set point is an operating level in an adaptive control system. Set points are selected by the brain around which something cycles in order to function optimally.
Temperature cycles. It cycles around thermal set points. During the day, a normal body temperature is 37C or 98.6F and can rise above or descend below depending on internal or external factors. For example, the body might be dealing with something, an invasion or pathogen, which may require the immune system to operate hot or even cooler for a while. Fluctuations may occur because there is a circadian influence, or cycling can occur because of external environmental influences, bitter cold or extreme heat.
Normal body temperature, as a correctly selected set point, will enable the temperature to return to 37C or 98.6F when the event that is causing alteration returns to normal. An example being when a fever has passed, the immune system has done its job and the brain then tells the body the event is over and homeostasis can be resumed the temperature resumes to cycling around 37C or 98.6F.
At night, the brain drops the set point to 36.3C or 97.34F. The temperature then cycles around this lower set point during sleep.
What is a low body temperature?
A low body temperature is any temperature below 37C or 98.6F. This may have a variety of causal factors.
External or internal environments. It may well be that some internal pathogens or organs need to be dealt with by the immune systems at lower operating temperatures for a while and so the brain, the central management control system, will allow the temperature to drop to a lower set point during this period. When the job is done, the brain brings the set point back to 'normal' and the temperature rises.
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