Pain is an unpleasant subjective sensory and emotional experience associated with tissue injury or potential injury, and is a complex physiological and psychological activity. When various injurious stimuli act on the organism to a certain extent, they can cause the release of some analgesic substances from the injured site, such as histamine, bradykinin, 5-hydroxytryptamine, acetylcholine, H+, K+, prostaglandins, etc. These substances act on the nociceptors in the skin and other tissues to produce nociceptive impulses and rapidly conduct along the afferent nerves to the spinal cord, up through the thalamus tracts of the spinal cord and the spinal cord reticulum, and then transmit to the thalamus, and then project to the cerebral cortex to cause pain sensation. If acute pain is not treated timely and effectively, structural changes can occur centrally and locally, transforming it into chronic pain. Different parts of the pain characteristics, onset time, the degree of pain, accompanied by different symptoms, can also be accompanied by increased blood pressure, heart rate, out of the end of the cold, loss of appetite, lack of concentration, can not work normally, so the body has pain, must not endure.