In Western medicine, it is described as controlling the circulation or "governing blood and blood vessels". In Chinese medicine, the heart has a few more attributes that can seem quite alien to Westerners.
For example, it is said that it can be:
In Chinese medicine theory, the health of the heart is mirrored in the face, because the heart has close association with blood vessels. If heart Qi is strong, the complexion is ruddy and healthy, whereas if the Qi is weak then the face will be pale.
The heart is also closely associated with the tongue in the five element model. So, the Chinese believe that taste is a reflection of heart Qi vitality.
Depending on the heart's energy (Qi), the blood will be vigorous and the person healthy and full of life.
This is a similar to other traditional medical theories - including Ayurveda and ancient Egyptian belief - in which the heart is closely associated with the soul and emotions.
In Chinese medicine, it is the heart, rather than the brain, that controls the "mental activities" (i.e. a wide range of thought processes, perception, mental health, and behaviour). The brain is regarded simply as a system for receiving and storing information and so has no real involvement in thought processes.
Therefore, mental disorders are believed to be caused by some sort of damage to the heart, rather than the brain. Remedies that are traditionally said to "calm the spirit" are often ones which, in Western terms, we would use to regulate heart activity.
The heart is also associated with the emotion "joy". This is not entirely the pleasant emotion it seems: in traditional, conservative Chinese society, "joy" can also mean unruly or inappropriate behaviour.
