Sweating to Keep Cool

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While our air conditioners are working hard to cool our homes in the record high heat waves sweeping the U.S. this summer, our bodies are working just as hard to keep cool.

Our bodies work to maintain internal organ and tissue temperature at a relatively constant value between 96.8 and 100.4 degrees F. Body temperature regulation is controlled by a homeostatic feedback system. When skin and central thermoreceptors detect an increase in temperature above 100.4 degrees F, they send a signal to the brain. This signal causes reactions, such as sweating, to either minimize the body’s temperature increase or help lower body temperature to the desired range.  

The response to cool ourselves is slow and requires a certain core temperature to be reached. However, once activated, sweating and heat loss continue until our body temperature cools or max cooling efforts are met. This entire feedback process is determined mainly by our deep body temperature in our internal organs, but our skin temperature can also contribute to the response time. For example, if our skin is warm, it can increase the speed that sweating and cooling effects start.  

Sweating is an important function to regulate temperature and is just one of the ways our body responds to an increase in temperature. Where does the sweat come from?   We have specific glands that produce sweat. There are three main types of sweat glands:

  • Eccrine glands are the largest of the sweat glands—we have between 2 and 4 million of them—and are primarily responsible for sweating and temperature regulation.
  • Apocrine glands do not start functioning until puberty. They are larger and open up to hair follicles rather than the skin surface. In many species, apocrine glands are thought to be a scent gland, playing a role in body odor.
  • Apoeccrine glands develop between the ages of 8 and 14 and share properties of both eccrine and apocrine glands.

The amount of sweat our eccrine glands produce in response to a temperature increase depends on the number of glands we have and secretion rate per gland—more glands result in more sweat. The initial stimulation of sweating recruits glands rapidly, then the rate that sweat is produced increases slowly and steadily. Dehydration will slow the sweating response, so it’s important to stay hydrated in the heat to prevent overheating.    

Sweating is often given a bad rap for making us sticky, stinky and generally uncomfortable. But the next time you’re sweaty, remember how hard our bodies work to help us stay as cool as the proverbial cucumber.    

Casey Derella, PhD, is a postdoctoral associate in the Department of Kinesiology at the University of Virginia. Her research interests primarily focuses on how sex and disease alter the microcirculation and skeletal muscle, contributing to cardiovascular disease.

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