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Somatic Nervous System

Leena Palande Apr 17, 2019
The communication network in our body comprises brain, spinal cord, and peripheral and motor nerve fibers. We will enlighten you about the functions and disorders of the somatic nervous system.
The working of our bodily systems is really amazing. The nervous system is the most important system in our body, and it is divided into the central and peripheral nervous system. The former consists of the brain and spinal cord, and the latter is further divided into two major parts - the somatic nervous system (SNS) and the autonomic nervous system (ANS).
The autonomic nervous system is further subdivided into sympathetic and parasympathetic nervous systems. A third division, the enteric nervous system is also sometimes taken into consideration, while studying the parts of the nervous system.
The SNS is made up of peripheral nerve fibers that send sensory information to the central nervous system and motor nerve fibers that send information to the skeletal muscle. Its main functions are to control voluntary movements of your body and help you feel through all your senses.
The brain and the spinal cord are connected to the skeletal muscles and the external receptors are connected with the nerves that belong to the SNS. This is the system that helps you feel the touch, smell, sight, taste, and sound.


  • The peripheral nervous system, consisting of the SNS and the ANS, is made up of the nerves that lie under the skin and the nerves that are spread everywhere else.
  • Both these systems mostly operate automatically.
  • The nerves belonging to SNS control voluntary body movements.
  • It is observed that these somatic nerves, which sense external stimuli, function automatically even in event of a coma.
  • This system is responsible for the functioning of all sensory organs including the eyes, ears, tongue, and skin.
  • It controls the working of the skeletal muscles and the muscles attached to the bone, which are used for voluntary movements.
  • During any movement, this system carries impulses from the brain to the muscle to be moved.
  • In its sensory capacity, it carries impulses from the sensory organ to the brain.
  • Thus, there exist two types of neurons - the afferent and the efferent.
  • The impulses from the sense organs are carried to the central nervous system by afferent or sensory neurons, and the impulses from the central nervous system are transmitted to the muscles by efferent or motor neurons.
  • Neurons, which comprise the SNS emerge from the brain or spinal cord, reach the muscle or sense organ directly.
  • Their cell body (the soma) is situated in the brain or spinal cord, and the axons (long nerve filaments) travel to or from the cell body ending in the muscle, skin, or sense organ.
  • They carry electrochemical impulses along with them.
  • The average adult brain contains about 100 billion neurons.


  • The disorders of this system include diseases of the nerve roots, ganglia (a mass of nerve tissue or a group of neurons), sensory, and motor nerves.
  • A functional disorder and/or abnormal change that occurs in any region of the peripheral nervous system is called a neuropathy.
  • If neuropathy involves only one nerve, it is called a mononeuropathy, and if it involves several nerves, it is referred to as mononeuropathy multiplex or polyneuropathy.
The most common SNS disorders are:

Neuritis: Inflammation of a peripheral or cranial nerve.

Cranial Nerve Diseases: Disorders and diseases of the cranial nerves, which are 12 in number and basically run the head as well as help to regulate the organs of the thoracic and abdominal cavities.
Cranial Nerve Neoplasms: These disorders mainly consist of benign or cancerous growth in cranial nerve tissues. For instance, acoustic neuroma, optic nerve glioma, optic nerve meningioma.
Diabetic Neuropathies : Peripheral and cranial nerve disorders associated with diabetes are common. For instance, the common condition associated with diabetic neuropathy includes third nerve palsy, which affects the oculomotor nerve.
Myasthenia Gravis : Myasthenia gravis disease or neuromuscular junction disease occurs, when the body generates an immune system attack against its own skeletal muscles. It affects the transmission of the nerve impulses to the muscle at the neuromuscular junction.
Trigeminal Neuralgia : This is the most common neuralgia, which affects the fifth cranial (trigeminal) nerve. Trigeminal neuralgia causes episodes of severe, stabbing, electric shock-like pain in the areas of the face, where the branches of the nerve are distributed, i.e., lips, eyes, nose, scalp, forehead, upper jaw, and lower jaw.
Brachial Plexus Neuropathies: The disorders of the peripheral nerve components of the brachial plexus, which consist of a group of lower neck and upper back spinal nerves that are responsible for communications with the arm, forearm and hand, can result in local pain, muscle weakness, and decreased sensation in the upper extremity.
The nervous system is a vast topic. The information about the somatic nervous system given here is a short summary, as the human nervous system, which includes the brain, spinal cord, ten billion neurons, and uncountable interneural connections, is possibly the single most complex object in the entire cosmos.
Disclaimer: This is for informative purposes only, and should not be used as a replacement for expert medical advice.