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:''For the musician known as Somatic, see Hahn Rowe.'' The somatic nervous system (SoNS or voluntary nervous system) is the part of the peripheral nervous system associated with skeletal muscle voluntary control of body movements. The SoNS consists of afferent nerves and efferent nerves. Afferent nerves are responsible for relaying sensation from the body to the central nervous system (CNS); efferent nerves are responsible for sending out commands from the CNS to the body, stimulating muscle contraction; they include all the non-sensory neurons connected with skeletal muscles and skin. The ''a-'' of ''afferent'' and the ''e-'' of ''efferent'' correspond to the prefixes ''ad-'' (to, toward) and ''ex-'' (out of). == Parts of somatic nervous system == There are 43 segments of nerves in the human body. With each segment, there is a pair of sensory and motor nerves. In the body, 31 segments of nerves are in the spinal cord and 12 are in the brain stem. Besides these, thousands of association nerves are also present in the body. Thus somatic nervous system consists of three parts: * Spinal nerves: They are peripheral nerves that carry sensory information into and motor commands out of the spinal cord. * Cranial nerves: They are the nerve fibers that carry information into and out of the brain stem. They include smell, vision, eye, eye muscles, mouth, taste, ear, neck, shoulders, and tongue. * Interneurons (association nerves): These nerves integrate sensory input and motor output, numbering thousands. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Somatic nervous system」の詳細全文を読む スポンサード リンク
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