The vagus nerve is the tenth pair of cerebral nerves and is a mixed nerve that can send several branches in the abdomen, thorax and neck, innervating the neck, organs in the thoracic cavity and most of the organs in the abdominal cavity. It can regulate the three systems of respiration, circulation and digestion by conducting sensory impulses in organs and organs and controlling the activities of cardiac muscles, smooth muscles and glands. In simple terms, it governs the functions of swallowing, breathing, heartbeat, and digestion. The vagus nerve contains four types of fibers, which are involved in somatomotor, somatosensory, visceral motor and visceral sensory. Somatomotor fibers: Somatomotor fibers mainly innervate the skeletal muscles of the pharynx and are characterized by random movements; 2. Somatosensory fibers: Somatosensory fibers come from pseudomonopolar neurons in the spinal ganglia, whose central protrusions form the posterior roots of the spinal nerves into the spinal cord and peripheral protrusions into the spinal nerves distributed in the skin, skeletal muscles, tendons and joints. They transmit the superficial sensory (pain, temperature sensation, etc.) of the skin and the deep sensory (kinesthesia, position sensation, etc.) impulses of the muscles, tendons and joints to the center; 3. Visceral motor parasympathetic fibers: they are the main component of the vagus nerve and are distributed in the trachea, bronchi, heart, lungs and other intrathoracic organs as well as in the abdominal organs such as the liver, kidneys, spleen, pancreas, adrenal glands, and the digestive duct between the stomach and the transverse colon, and can regulate the activities of the above organs; 4. Visceral sensory fibers: Visceral sensory fibers are mainly responsible for conducting sensory impulses in the viscera of the thoracic and abdominal cavities. If the main trunk of the vagus nerve is damaged, discomfort reactions such as nausea, vomiting, increased heart rate or deep and slow breathing will occur, and if paralysis of the pharyngeal muscle occurs, symptoms such as speech difficulty, swallowing disorder and hoarseness will occur.