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Author(s): Wade Haaland

What is Homeostasis?

Homeostasis is a term that refers to constancy in a system. To physiologists, homeostasis means "maintaining a constant internal environment." 

The internal environment usually is thought of as the extra-cellular fluid (ECF) that constantly bathes the cells, providing nutrients and carrying away wastes. If a system is in homeostasis, it is in its normal, or resting, state. If disturbances disrupt the normal state, the system will act to restore the normal state. For example, a person who is standing still has a normal resting respiratory rate. If that person runs as fast as he/she can for 30 seconds, his/her respiratory rate will increase to meet the body's demand for oxygen. During the run, the body uses more oxygen than it does when it is standing still. To maintain homeostasis, the respiratory rate increases to meet the increased demand. Furthermore, when the person returns to a resting state, the respiratory rate eventually will return to a normal rate because of the decreased demand for oxygen.