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Matters of the heart have baffled humans since the dawn of time, with sonnets and entire books devoted to the meaning of love. Now scientists are finding that the blood pump in your chest is just as complex. You can't live or love without it. Find out the sappy scoop on the heart, including how sex and laughter are indeed good for it, and how bad news really can break it. -- Jeanna Bryner

Weighing in at 10 ounces, the blood-filled muscle called the heart has become the universal symbol of love. The Greeks believed the heart was the seat of the spirit, the Chinese associated it with the center for happiness and the Egyptians thought the emotions and intellect arose from the heart. No one is sure the exact origin of the love association, however. One idea is that the heart got its "love mark" in the ancient Greek city of Cyrene, now in modern-day Libya. The colony was known for a plant called Silphium, with heart-shaped seed pods. Silphium had medicinal properties, and possibly also was used as an herbal contraceptive.

Alas, a broken heart can cause one to swoon. A breakup with a loved one or news of a family death literally can lead to broken hearts in the form of heightened risk for heart attack, studies have shown. Such trauma can also trigger the release of stress hormones into the bloodstream that temporarily "stun" the heart. The resulting symptoms mimic those of a heart attack - chest pain and shortness of breath - but this type of achy heart can bounce back in days with some TLC and rest.

In under a minute, your heart can pump blood to every cell in your body. And over the course of a day, about 100,000 heart beats shuttle 2,000 gallons of oxygen-rich blood many times through about 60,000 miles of branching blood vessels that link together the cells of our organs and body parts. That's a hefty job for a fist-sized muscle.