The heart is a pumping system which intakes deoxygenated blood through the veins, delivering it to the lungs for oxygenation and then pumping it into the various arteries to be transmitted to where it is needed throughout the body for energy. 

The heart is about the size of a fist but delivers a more powerful punch. Luckily for us, it contains a buffer zone to decrease its force or we would be shaken by every beat. This buffer zone also protects the heart from outside injury and keeps it from scraping against the chest wall. 

In some instances, nightmares can seem so real that the heart will pound in fear. In one study, the heart rate of the sleeper was timed at 150 beats per minute. Myth has it that the heart is the seat of the emotions, but it is, instead, a pump to circulate the blood throughout the body and only contributes to the emotions by sending oxygenated blood to our brain cells; so, if you want to gain someone's affection, you may have to ask Cupid to shoot them through the head rather than the heart. An arrow through the heart (or through the head, for that matter) would stop all bodily functions. The Medical Dictionary reports that the heart beats more than 2.5 billion times in an average lifetime. Isn't that "thumping"?