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FUNCTION OF THE HEART
The heart’s duties are much broader than simply pumping blood continuously throughout life. The heart must also respond to changes in the body’s demand for oxygen. The heart works very differently during sleep, for example, than in the middle of a 5-km (3-mi) run. Moreover, the heart and the rest of the circulatory system can respond almost instantaneously to shifting situations—when a person stands up or lies down, for example, or when a person is faced with a potentially dangerous situation. |
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