The central nervous system consists of the brain and the spinal cord, of which the brain is divided into three parts: the cerebrum, cerebellum, and brainstem, and the spinal cord is divided into five parts: cervical, thoracic, lumbar, sacral, and caudal medullas. The cerebrum mainly controls a person’s random movements and collects sensory signals from the nerves, in addition to being closely linked to the person’s memory, emotions and other mental activities. The cerebellum mainly maintains the body’s balance and keeps the body in good posture. The brainstem contains important neural nuclei and reticular formation, and its main role is to maintain a person’s state of arousal. The brainstem is the center of human life and controls human breathing and heartbeat. The spinal cord is a direct continuation of the brainstem, and its main physiological roles are the conduction of nerve signals, the control of urination and defecation, and basic physiological reflexes. There are sympathetic neurons in the lateral horns of the spinal cord that can control the activities of the internal organs of a person, and the common diseases of the central nervous system include encephalitis, hydrocephalus, cerebral hemorrhage, cerebral infarction, and spinal cord cavernous diseases.