Control of body temperature and physiological responses to extremes of temperature

Body temperature is controlled by the thermoregulatory centre located in the hypothalamus in the brain.
The thermoregulatory centre receives information about the body’s temperature from two sets of peripheral thermoreceptors in the skin and the blood temperature in the brain.
When the body temperature rises above the ideal temperature, physiological responses for heat loss are activated.
When the body temperature drops below the ideal temperature, physiological responses for heat conservation and heat production are activated.
The ideal human body temperature is considered to be around 37 degrees Celsius.

The skin’s blood vessels dilate in response to warm temperatures, a process known as vasodilation, which allows more blood to flow through the skin and lose heat to the environment.
Sweat glands produce sweat, which evaporates from the skin surface, using heat energy from the body, thus cooling the body down.
Behavioural responses like removing clothing, moving to a cooler environment, and drinking water, also aid in cooling the body.

In cold temperatures, peripheral blood vessels constrict, a process called vasoconstriction, decreasing blood flow near the skin surface and reducing heat loss to the environment.
Shivering is a response to cold, in which muscles involuntarily contract and relax rapidly to produce heat.
The hairs on the skin also stand up to trap a layer of air, which insulates the body, known as piloerection.
Behavioural responses like adding layers of clothing, moving to a warmer environment, and consuming warm food or drinks, help in conserving warmth and increasing body temperature.

Extreme heat may potentially trigger hyperthermia or heat stroke, leading to symptoms like dizziness, confusion, convulsions, or even unconsciousness.
Extreme cold may potentially trigger hypothermia, leading to symptoms like shivering, numbness, loss of coordination, and in severe cases, a decrease in heart and respiration rates.
In both scenarios, it is crucial to move the individual to an environment with normal temperature, hydrate them, and seek immediate medical attention.