Homeostasis maintains the body’s internal conditions at relatively constant levels. Maintaining stable conditions within our body allows cells and processes to function properly.
The control of our internal body temperature is called thermoregulation. The normal human body temperature is 37°C, which is the temperature that enzymes in the body work best.
If the temperature falls below 37°C, enzyme activity slows down
If the temperature rises above 37°C, enzymes can denature
The hypothalamus in the brain controls the processes that warm us up and cool us down. Scientists call the hypothalamus the thermoregulatory centre. It basically acts as the body’s thermostat.
The thermoregulatory centre contains receptors, called thermoreceptors, that are sensitive to the temperature of the blood. The skin also contains thermoreceptors and sends nervous impulses to the thermoregulatory centre.
Responses to Changes in Temperature
Response to an increase in temperature
When the body temperature gets too high (e.g. when exercising):
Blood vessels that supply the capillaries near the skin dilate, which means they get wider and this is known as vasodilation. This results in increased blood flow through the skin, leading to more thermal energy being lost to the surroundings.
Sweat glands excrete sweat onto the skin’s surface. The skin uses energy from the body to evaporate the sweat, which cools the body.
Response to a decrease in temperature
When the body temperature gets too low:
Blood vessels that supply the capillaries near the skin constrict and this is known as vasoconstriction. It means that less blood will flow through the skin, so less thermal energy will be lost to the surroundings.
Effector muscles contract, causing our hair to stand upright. As a result, the hairs trap a small layer of insulating air, reducing the heat loss through our skin.
Our skeletal muscles undergo rapid, automatic contractions (shivering). This action requires a lot of energy from respiration. The chemical reactions involved in this process release a lot of heat energy, which warms the body.