Thermoregulation : Nursing

Thermoregulation is the body’s ability to balance between heat gain and heat loss, thus maintaining a stable internal temperature of around 36 to 37.5° C or 96.8 to 99.5° F. This range is considered normal body temperature but it’s actually the average across the population. Normal body temperature can vary depending on the time of day, age of the individual, activity level, and many other factors. This normal body temperature is maintained by four mechanisms: neural and vascular control; heat production; heat loss; and behavioral control.

Okay, let’s discuss the physiology of these four mechanisms, starting with neural and vascular control. If we zoom into the brain, there's a region called hypothalamus. The hypothalamus acts like a thermometer. It has thermoreceptors that monitor the body’s internal, or core, temperature; and it also receives information about the peripheral temperature from the thermoreceptors in the skin.

Now, the hypothalamus is also the body’s thermostat, because it controls the internal temperature “set point” and when the core temperature deviates from the set point, the hypothalamus will signal the rest of the body to increase or decrease the body temperature and bring it back to the set point. So, on a hot summer day, the hypothalamus senses the core body temperature is getting too high and responds by initiating mechanisms like sweating and dilating skin blood vessels, resulting in body heat loss. On the flip side, on a cold winter day, the hypothalamus senses that the core body temperature is getting too low, and in turn, activates mechanisms like shivering which generates heat, and vasoconstriction in the skin that prevents heat loss.

Now normally the set point is 36 to 37.5° C or 96.8 to 99.5 °F; however, when the person has a fever, the hypothalamus can adjust the thermostat, raising the set point to a higher temperature. The body responds by increasing the core temperature to the new set point, which is helpful for fighting off infections.

The next mechanism is heat production, which is a result of internal metabolic processes that produce heat as a byproduct. All tissues in the body produce heat, but a major source of heat production comes from the muscles through voluntary movements like exercising, and involuntary movements like shivering. In neonates, heat production can happen without muscle activity, called non-shivering thermogenesis. This is because they have a higher percentage of “brown fat” than adults, which is more effective at generating heat.