About the functions of a heart, there are many similarities between the traditional Chinese medical science and the Western medical science.
In the traditional Chinese medical science, a heart has two main physiological functions.
The first one is to control blood and vessels. A heart impulses blood to circulate and carry nutritive substances to every part of the whole body. The motivity of a heart is called “Qi” (气) which is the smallest basic element of a body. A heart also can convert nutritive substances, Qi and body fluid into blood. A heart can control the dilating and constricting of vessels for keeping the normal circulation of blood.
The second one is to keep mental activity. In fact, ancient Westerners also thought a heart controlled the mental activity of a person. So in the English language, there are many phrases such as “at heart”, “by heart”, “broken heart”, “do one's heart good”, “gain one's heart” which are used to describe mental activity. Keeping mental activity is related to the formation of blood. Blood nourishes mental activity. So if the blood is deficient, the mental activity will be affected badly such as insomnia and neuroses.
Because a heart controls blood and vessels, the status of the heart can be showed via the appearance of the face and the tongue. So a healthy person has a florid complexion and the color of his tongue is also florid. An anemic patient has a pallid look and the color of his tongue is also pallid and a little thin. If the vessels are not unobstructed, the blood will be stagnated, and then the face will be a little bluish and purplish, and the tongue has not only such color but also petechiae. If the heart has a fire which is described as a heated (nearly excitability and irritability but not pyrexia) pathological condition, the face will be red, and the tongue even has small ulcers. If the heart can’t keep mental activity well, the tongue also can’t work well, and the person will be stammering, lisping or even aphemic.
The feeling of joy is related to the heart. If the Qi of the heart is ample, the heart can work well, and the person feels delighted and optimistic. But if the Qi of the heart is lacking, the person will have an emotional slump and feel languid.
The formation of sweat is also related to the heart. Body fluid is the source of sweat. Body fluid and blood nourish each other. So there is a word “Sweat and blood have the same source”. If blood is deficient, body fluid will be lacking, and then the formation of sweat will be reduced. If perspiring is in excess, the body fluid will be seriously lost, and the blood of the heart will be much reduced too, so the heart will palpitate and the person will feel panicky. Reciprocally, if a person is excessively nervous or feels terrified, the heart won’t regulate normally the formation and excretion of sweat, and then the body will perspire very much.
According to the theory of the traditional Chinese medical science, an important pathological cause of acute myocardial infarction is the sudden heavy loss of the heart’s Yang-Qi (阳气), which functions are propelling and warming. So blood can’t be impulsed by the heart, and the excretion of sweat loses control. The patient will be suffering from shock with a pallid face and he is damp with cold sweat.
In the traditional Chinese medical science, the methods of treating mental diseases and neuroses are to regulate the functions of the heart. Though the truth is that the brain keeps mental activity, the traditional methods of regulating the heart are still very effective. Nowadays some foreign scientists found that, the character and temperament of a person who has a transplanted heart is not his past nature but the character and temperament of the original owner of the heart. So the functions of a heart are really mysterious.