Description

The part of the peripheral nervous system in association with the control of voluntary body movements through skeletal muscles is known as somatic nervous system (SNS). The SNS is made of nerves known as afferent nerves and motor nerves. Afferent nerves do the relaying of sensation within the body, to the central nervous system while, the stimulus of sensation, which are accountable for sending out the commands from the central nervous system to the muscle responding to the stimulus helping in contraction of muscles is done by efferent nerves. The neurons linked with skin and skeletal muscles are also non-sensory neurons.

The nerves, which are present in the somatic nervous system are differentiated by their presence in a specific location, which can either be in the spinal region or the head. The sending and receiving or relaying of information from various muscle nerves of the body till the central nervous system or from the brain stem to the periphery are done by 12 pairs of cranial nerves. The use of these nerves is mainly for the movement of the tongue, neck region and the head. The sensory information relayed from the periphery to the spinal cord and muscle movement commands from the spinal cord till the skeletal muscles are done through the 31 pairs of spinal nerves which are present for sensing and relaying of information.

The most notable factor is that acetylcholine, which is a neurotransmitter excites or increases the effect in somatic nervous system whereas in autonomic nervous system, which is responsible for the involuntary movements has an inhibitory effect.

Functions

The voluntary muscles of the body and the system, which is responsible for voluntary movement of reflex arcs are entirely controlled by the somatic nervous system. The path through which the transmission of neural signals occur are directly associated with a series of cell bodies in the upper part of motor neurons also known as upper motor neuron. The stimulus generated from the precentral gyrus is transmitted through upper motor neurons to the corticospinal tract, with the help of axons to regulate the voluntary movement of the skeletal muscles. The stimulus generated travels using upper motor neurons through the ventral horn present in the spinal cord, which is then received by the alpha motor neurons sensory receptor, which are large lower motor neurons present in the spinal cord and brainstem.

A neural circuit, which develops an automatic connection in between sensory inputs and motor input is called a reflex arc. These circuits are of different nature of complexity, which function in transmission of reflexes like immediate withdrawal of hands on connection with a hot object whereas knee jerk also known as patellar reflex occurs  by tapping the patellar tendon  which helps in ordinary behavior. The basic function of the somatic nervous system is establishing a connection in accordance with the external stimulus based on which the internal responses occur to cope with the changes occurring outside in the environment that helps in  the establishment of a neural link between the body muscle fibers and the central nervous system.