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The word homeostasis comes from the Latin roots homeo, meaning similar, and stasis, meaning condition. Homeostasis is the ability of the body to keep everything in balance. It’s important for the body to always monitor what is going on, correcting functions that are out of balance and bringing them back to normal. Homeostasis and regulation of the body’s internal environment are key principles of normal physiology.

The body uses homeostasis to monitor and regulate its always-changing internal environment. The body then coordinates responses to minimize any imbalances. Here’s an example: On a hot, sunny day, the thermostat in your brain (an area known as the hypothalamus) can sense that you are getting warmer and will activate ways to keep your body cool. This includes increasing the blood flow to your arms and legs to release heat through your skin. You’ll also sweat more, which cools you off when the water evaporates off your skin. You might also decide to remove some of your clothing, spend some time in the shade and drink water.

Homeostasis also controls levels in the body of water, salt, oxygen and carbon dioxide. And it controls the pressure and volume of bodily fluids. Special circumstances—like exercise, pregnancy and traveling to a high altitude—can change the body’s condition. However, in these situations, homeostasis activates physiological controls to make sure the body keeps functioning normally even when it’s faced with unusual or new demands. This is called “compensation.” When compensation fails, the body isn’t able to regulate itself. This often leads to illness or disease, including cancer, autoimmune disorders and cell death. External factors, including toxins, trauma, bacteria and viruses, can also disrupt the body’s balance.

So pay attention to how you feel. If you’re healthy and your body is functioning normally, you’ll know that your body’s homeostatic control systems are working well.

Barb Goodman, PhD, FAPS, is a professor of physiology at the University of South Dakota.