The heart is a muscular organ that serves as a pump, sending blood to every part of the body. The heart is always at work, even while you sleep. If your heart were to stop for any length of time, you couldn’t live, but that doesn’t mean the heart never rests.
Each “heartbeat” consists of a contracting and relaxing of the heart
muscles. When the heart contracts, it pumps blood through the blood vessels; when it relaxes, it draws blood in.
The heart beats about once every second, but the heartbeat itself lasts for less than 4/5 of a second. For the remainder of the time (1/5), the heart rests. Since the heart beats about 100,000 times daily, that means that your heart actually rests for more than five hours each day!
Your heart pumps about seven quarts of blood per minute, and more than 10,000 quarts each day, which means that in an average lifetime, your heart will pump more than 250 million quarts of blood.