The human heart is really easy to understand--it's just muscles and shit. Plenty of people understand the human heart. It's really not that complicated. After all, it's only function is to pump blood throughout the body. But all of that being said, it is one of the most amazing pumps known to man. I think what you mean is about the emotional parts of the human brain.

Emotions involve the entire body, but only the brain is essential. If you had no brain, you would have no emotions. We do need both reason and emotion for thinking and decision-making. They get put together in the brain.

Neuro-scientists have observed that the brain often "fires" a signal to act before the person makes a conscious decision to act, and cite this as evidence that we do not really make our own decisions. Wouldn't neuro-scientists, of all people, recognize that a person is one whole being, not just our conscious mind? Decisions may be made below the level of conscious intellect; they are still your decisions.