The somatic system is the part of the peripheral nervous system that is responsible for carrying motor and sensory information both to and from the central nervous system. This system is made up of nerves that connect to the skin, sensory organs and all skeletal muscles. The system is responsible for nearly all voluntary muscle movements as well as for processing sensory information that arrives via external stimuli including hearing, touch and sight.
Parts of the Somatic Nervous System
The somatic nervous system derives its name from the Greek word soma, which means "body." The somatic nervous system contains two major types of neurons: sensory neurons (or afferent neurons) that carry information from the nerves to the central nervous system, and motor neurons (or efferent neurons) that carry information from the brain and spinal cord to muscle fibers throughout the body.
The neurons of the somatic nervous system project from the central nervous system directly into the muscles and sensory organs. The system is a direct path with synapses to connect nearby neurons. The body of the neuron is located in the CNS, and the axon then projects and terminates in the skin, sense organs or muscles. Electrochemical impulses then travel along the axon to the brain or spinal cord.
Reflex Arcs and the Somatic Nervous System
In addition to controlling voluntary muscles movements, the somatic nervous system is also associated with involuntary movements known as reflex arcs. During a reflex arc, muscles move involuntarily without input from the brain. This occurs when a nerve pathway connects directly to the spinal cord. Some examples of reflex arcs include jerking your hand back after accidentally touching a hot pan or an involuntary knee jerk when your doctor taps on your knee.
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Nervous system. (2001). Body Guide. A.D.A.M. Found online at http://www.besthealth.com/besthealth/bodyguide/reftext/html/nerv_sys_fin.html#pns
Somatic nervous system. (2007). Dorlands Medical Dictionary. Merck & Co., Inc.