We are in a season of extreme heat in much of the United States. One of the reasons we can survive this heat is because of the human cooling system. The heat release system design built into our bodies is extraordinarily efficient and superior to other forms of life.
Our body’s internal temperature depends on the climate, what our clothing consists of, and how active we are. The human cooling system to prevent overheating begins with receptors in our skin that sense when a person begins to overheat. When those receptors send a warning signal to the brain, the brain’s hypothalamus signals eccrine glands in the skin to release sweat.
The skin can release up to three pounds (1360 grams) of sweat in an hour. As the sweat evaporates, it removes 540 calories per gram of water evaporated (778 BTUs per pound of water) from the body. Meanwhile, blood vessels dilate, sending more blood to the capillaries in the skin, taking heat away from the body’s core and radiating it away from the skin’s surface. Finally, the person’s breath carries away whatever excess heat is left.
One of the main reasons humans can exist everywhere on the planet is the design of our bodies and the human cooling system that enables us to handle heat and cold. This design reminds us of the words of the psalmist, “I praise you, God, because I am fearfully and wonderfully made; your works are wonderful, I know that full well” (Psalms 139:14).
— John N. Clayton © 2021
Reference: National Geographic July 2021, page 60.