The nervous system is the hub that connects all tissues and organs of the body and plays a leading role in regulating the physiological activities and functions of the body. The central nervous system includes the brain and spinal cord, and the peripheral nervous system includes the cerebral nerves and spinal nerves. I. Central nervous system The central nervous system is the main part of the human nervous system, which can receive incoming information from all over the body and integrate and process it for transmission or storage, with the characteristics of coordination and integration, consisting of two parts, the spinal cord and the brain: 1. 2, the brain: is the main part of the central nervous system, consisting of telencephalon, mesencephalon and brainstem, cerebellum, located within the cranial cavity, can control all the volitional activities of the body. The peripheral nervous system refers to all nerve structures other than the brain and spinal cord, including peripheral nerves, neuromuscular junction, and muscles. The peripheral nerves are roughly divided into three major parts: 1. Brain nerves: there are 12 pairs, such as olfactory nerve, optic nerve, motoneurotic nerve, trigeminal nerve, and the talocrural nerve. Each pair of cerebral nerves can perform their own physiological functions, and if they are damaged, they will cause a series of discomfort; 2, spinal nerves: a total of 31 pairs, consisting of 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of caudal nerves. If the human body is injured in the process of movement, it will often accumulate spinal nerves and thus cause symptoms such as sensory and motor disorders; 3, autonomic nerves: mainly composed of sympathetic and parasympathetic nerves: (1) sympathetic nerves: can innervate the abdominal viscera, smooth muscle of glands and heart vessels, etc., and can also regulate the functional activities of the above tissues and organs. Stimulation of the sympathetic nerve causes increased heart rate, increased contractility of the heart muscle, hyper-metabolism, dilated pupils, and vasoconstriction of the abdominal viscera and peripheral skin vessels; (2) parasympathetic nerve: stimulation may cause increased gastrointestinal motility, slowed heart rate, narrowed pupils, increased glandular secretion, and relaxation of the sphincter. Most of the tissues and organs in the body are under the dual innervation of sympathetic and parasympathetic nerves, which are managed by the cerebral cortex to coordinate and promote visceral activities.