The starting point in any homeostasis is the identification of its set or the normal point. The set point of human body temperature is taken as 37°C, which is also called the normal or core body temperature. The core body temperature refers to the temperature of the combined portion of the trunk, head and upper part of arms and legs. The body temperature otherwise is not uniform throughout.
- The surface skin temperature is usually lowest but it varies considerably due to a variety of external and internal conditions.
- The armpit usually records 1 degree less than the temperature inside the mouth.
- The anal temperature is 1 degree higher than the core body temperature. In very young children, the clinical thermometer is placed inside the anus and the temperature recorded is reduced by one degree to assess if the child is having any fever.
- For all practical purposes, the oral (mouth) temperature is taken as normal body temperature, which is usually 37°C (±0.5).
Whenever the core body temperature departs from the normal, the body takes corrective measures. For example:
- If the temperature falls, there is increased heat production in the body along with prevention of heat loss.
- If body temperature rises, there is cooling to give out excess heat.
Mechanism of Thermoregulation
The principal heat-regulating centre is located in the hypothalamus, a part of the forebrain. This part acts like a thermostat.
When the body has to face cooling below the normal temperature, it switches on or speeds up the heat-producing processes and simultaneously shuts off the heat-losing ones. When the body faces overheating during summer or after intense physical exercise, it accelerates the cooling process and switches off the heat- producing ones.