Qi is the essential substance that makes up the body and maintains various physiological activities. Qi in different viscera and organs functions differently. Generally speaking, there are five physiological functions of qi.

Qi is the motivation of the physiological functions of all the viscera and organs in the body. The propelling function of qi can stimulate and maintain the physiological functions of the viscera and other organs. That is why qi is called the root of life. Qi in different viscera and organs functions differently. For example, kidney-qi promotes the development of the body and reproduction, transform water and receive lung-qi; heart-qi promotes blood circulation; lung-qi governs respiration and regulates water passage; spleen-qi promotes digestion and absorption of food and commands blood; liver-qi regulates various functions by smoothing the activity of qi. Weakness of qi in promotion will lead to hypo function of the viscera and other organs and cause various deficiency problems.

Qi warms the body and is the source of heat energy in the body. It is very important in maintaining normal body temperature and ensuring the physiological functions of all the viscera and organs. Since qi can warm the body, it is similar to yang in nature. So the kind of qi that warms the body is called "yang-qi". All the five zang-organs have yang-qi respectively. For example, heart-yang warms and dredges blood vessels to promote blood circulation; 

Lung-yang warms and nourishes skin and muscular interstices, preventing exogenous pathogenic factors from invading the body; spleen-yang warms and transforms food and water, promoting digestion and absorption; liver-yang steams and fumigates qi, promoting qi transformation in the five zang-organs and the six fu-organs; kidney-yang warms life-gate, stimulates reproduction and transforms water. If the warming function of qi is weakened, it will lead to stagnation of internal cold, unsmooth circulation of qi and blood and devitalization of the visceral functions.

Qi can protect the body, resisting the invasion of various pathogenic factors and preventing disease. As to pathogenic factors, the kind of qi that protects the body is called "healthy qi" or "genuine qi". Healthy qi functions to protect the whole body against the invasion of pathogenic factors and, after the invasion of pathogenic factors into the body or onset of disease, to fight against the pathogenic factors to promote healing of disease. If the protecting function of qi is weakened, it mainly leads to decline of body resistance and susceptibility of the body to invasion of pathogenic factors.

Fixation of qi means that qi can astringe and control liquid substances, such as blood, body fluid and sperm, to prevent them from losing. To be specific, qi fixating blood means that qi keeps blood to flow inside "the vessels and prevent it from flowing out of the vessels; qi fixating sweat, urine and saliva means that qi controls the secretion and excretion of these liquids so as to restrict the excretion and prevent loss; qi fixating sperm means that qi balances sex function and prevents seminal emission. Besides defecation and location of the viscera are under the influence of the fixating function of qi. If the fixating function of qi is weakened, it will lead to loss of blood, body fluid and sperm. The weakness of the qi fixation may also lead to protracted diarrhea, incontinence of urine and stool as well as proctoptosis and hysteroptosis.

Qi-transformation means changes caused by the movement of qi, which is the essential cause of the conception, development, growth and decline of life. Life activities concerned with @transformation can be divided into three categories. Firstly, through food and respiration the body absorbs nutrients from the external world and transforms them into essence, qi, blood and body fluid essential to the body. 

Secondly, inter-promotion among the refined substances (essence, qi, blood and body fluid etc.) is the process of automatic regulation, improvement and balance of life. Thirdly, waste substance and turbid qi are excreted out of the body in the process of life. If qi-transformation is weakened, the whole process of life will be in disorder or decline, leading to various diseases. The declination of qi-transformation even leads to death.