What Is the Somatic Nervous System?

Table of ContentsView AllTable of ContentsLocationFunctionPartsSomatic vs. AutonomicDiseasesSigns of ProblemsTreatmentsPrevention

Table of ContentsView All

View All

Table of Contents

Location

Function

Parts

Somatic vs. Autonomic

Diseases

Signs of Problems

Treatments

Prevention

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The somatic nervous system is part of theperipheral nervous systemand plays a role in voluntary movements and sensory processing.

The somatic nervous system carries motor and sensory signals to and from the central nervous system (CNS). Because of this bodily system, we are able to control our physical movements and process four of thefive senses—smell, sound, taste, and touch.

Learn more about the somatic nervous system, including its location, function, and parts. We also provide a few examples of how the somatic nervous system works, as well as how it is different from the autonomic nervous system.

Somatic Nervous System Location

The somatic nervous system includes all of the nerves that extend from the brain and spinal cord. It does not include the brain and spinal column themselves, both of which are part of thecentral nervous system. There are two types of somatic nerves: cranial and spinal.

Cranial Nerves

The somatic nerves that extend from the brain are known ascranial nervesand are located on the back of the head and neck.There are 12 pairs of cranial nerves in total, each of which splits to carry signals between both sides of the brain and body. These nerves are often involved in neuromuscular disorders.

Spinal Nerves

The somatic nerves that extend from the spinal column are known asspinal nerves. There are 31 pairs of spinal nerves. Eight come from the cervical portion of the spine, 12 are in the thoracic region, both the lumbar and sacral regions have five spinal nerves, and one is near the tailbone. A disease or injury in any of these areas can result in a loss of sensation and function below that area.

Somatic Nervous System Function

If you’re wondering what the somatic system does, it has two basic functions:

How exactly does this complex system work? Answering this question requires a closer look at its key parts.

Parts of the Somatic Nervous System

The term somatic is drawn from the Greek wordsoma, which means “body.” This is appropriate considering that it is this system that transmits information back and forth between the CNS and the rest of the body.

The somatic nervous system contains two main types ofneurons(nerve cells):

The neurons that make up the somatic nervous system project outward from the CNS and connect directly to the muscles of the body. They carry signals from muscles and sensory organs back to the central nervous system.

The body of the neuron is located in the CNS and theaxon(a portion of the neuron that carries nerve impulses away from the cell body) projects and terminates in the skin, sensory organs, or muscles.

Other components of the somatic nervous system include:

Reflex Arcs

Reflex arcs include sensory nerves that carry signals to the spinal cord, often connect with interneurons there, then immediately transmit signals down the motor neurons to the muscles that triggered the reflex.

During a reflex, muscles move involuntarily without input from the brain; you don’t have to think about doing these things. This occurs when a nerve pathway connects directly to the spinal cord. Examples of reflex actions include:

Reflex arcs that impact the organs are calledautonomic reflex arcswhile those that affect the muscles are referred to assomatic reflex arcs.

Somatic vs. Autonomic Nervous Systems

The somatic and autonomic nervous systems are both parts of the peripheral nervous system, which allows thebrainand spinal cord to receive and send information to other areas of the body. However, they have different functions.

Somatic Nervous SystemConnects CNS with muscles and skinControls voluntary movementsAutonomic Nervous SystemConnects CNS with visceral organsRegulates involuntary body processes

Somatic Nervous SystemConnects CNS with muscles and skinControls voluntary movements

Connects CNS with muscles and skin

Controls voluntary movements

Autonomic Nervous SystemConnects CNS with visceral organsRegulates involuntary body processes

Connects CNS with visceral organs

Regulates involuntary body processes

The somatic nervous system connects the central nervous system with the body’s muscles and skin. Its primary function is to control voluntary movements and reflex arcs, while also helping us process the senses of touch, sound, taste, and smell.

An example of a somatic system function is if you are out for a jog in the park one brisk winter morning and as you run, you step on a patch of slick ice. Once your foot starts to slip, your somatic nervous system carries a message to the muscles in your legs, enabling you to catch yourself and avoid a fall.

In comparison, theautonomic nervous systemconnects the CNS with visceral organs (heart, stomach, etc.) This system regulates a variety of involuntary body processes, some of which include heartbeat, blood flow, breathing, body temperature, and emotion response.

Diseases of the Somatic Nervous System

Somatic nervous system diseases are those that impact the peripheral nerves outside of the brain and spinal cord. Diseases that impact the peripheral nerve fibers of the somatic nervous system can cause what is known as peripheral neuropathy.

Other somatic nervous system diseases include:

Several additional factors can ultimately lead to damage to the somatic nervous system, thus impacting its function. Among them are certain medications,exposure to toxins, and infections such as shingles, Lyme disease, andHIV.

What Is Stiff-Person Syndrome (SPS)?

Signs of Somatic Nervous System Problems

The symptoms experienced with a somatic nervous system issue can vary depending on whether the damage is to the motor nerves (which control movement) or sensory nerves (which affect the senses).

Signs of motor nerve damage include:

If there is damage to the sensory system, the following symptoms may exist:

Treatments for Somatic Nervous System Conditions

Treatments used for somatic nervous system issues range from taking medication or doing physical therapy to needing nerve ablation or surgery. Other options include acupuncture, transcutaneous electrical nerve stimulation (TENS), and using devices or equipment to assist with the physical movement process.

Healthcare professionals who specialize in treating somatic nervous system issues include:

If you suspect that you may have a somatic nervous system issue, your healthcare provider can help determine whether an issue exists and/or refer you to a specialist in the neurology field for diagnosis and treatment.

Preventing Peripheral Neuropathy

While diseases that impact the somatic nervous system are not always preventable, there are lifestyle changes you can make that may help prevent peripheral neuropathy.

Some strategies that may help include:

It is also essential to treat chronic health conditions such as diabetes, which may play a role in the onset of peripheral neuropathy.

How the Peripheral Nervous System Works

8 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tawfik EA, Walker FO, Cartwright MS. Neuromuscular ultrasound of cranial nerves.J Clin Neurol. 2015;11(2):109-121. doi:10.3988/jcn.2015.11.2.109American Association of Neurological Surgeons.Anatomy of the spine and peripheral nervous system.Cuevas J.The somatic nervous system.Reference Module in Biomedical Sciences. 2015:B9780128012383054000. doi:10.1016/B978-0-12-801238-3.05364-2Cleveland Clinic.Somatic nervous system.Dorland.Dorland’s Illustrated Medical Dictionary.Cleveland Clinic.Neuropathy (peripheral neuropathy).National Institute of Neurological Disorders and Stroke.Peripheral neuropathy fact sheet.Cleveland Clinic.Neuropathy (peripheral neuropathy): Prevention.Additional ReadingCleveland Clinic.Somatic nervous system.Ganong WF.Review of Medical Physiology.Somatic nervous system.Dorland’s Illustrated Medical Dictionary.

8 Sources

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tawfik EA, Walker FO, Cartwright MS. Neuromuscular ultrasound of cranial nerves.J Clin Neurol. 2015;11(2):109-121. doi:10.3988/jcn.2015.11.2.109American Association of Neurological Surgeons.Anatomy of the spine and peripheral nervous system.Cuevas J.The somatic nervous system.Reference Module in Biomedical Sciences. 2015:B9780128012383054000. doi:10.1016/B978-0-12-801238-3.05364-2Cleveland Clinic.Somatic nervous system.Dorland.Dorland’s Illustrated Medical Dictionary.Cleveland Clinic.Neuropathy (peripheral neuropathy).National Institute of Neurological Disorders and Stroke.Peripheral neuropathy fact sheet.Cleveland Clinic.Neuropathy (peripheral neuropathy): Prevention.Additional ReadingCleveland Clinic.Somatic nervous system.Ganong WF.Review of Medical Physiology.Somatic nervous system.Dorland’s Illustrated Medical Dictionary.

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Tawfik EA, Walker FO, Cartwright MS. Neuromuscular ultrasound of cranial nerves.J Clin Neurol. 2015;11(2):109-121. doi:10.3988/jcn.2015.11.2.109American Association of Neurological Surgeons.Anatomy of the spine and peripheral nervous system.Cuevas J.The somatic nervous system.Reference Module in Biomedical Sciences. 2015:B9780128012383054000. doi:10.1016/B978-0-12-801238-3.05364-2Cleveland Clinic.Somatic nervous system.Dorland.Dorland’s Illustrated Medical Dictionary.Cleveland Clinic.Neuropathy (peripheral neuropathy).National Institute of Neurological Disorders and Stroke.Peripheral neuropathy fact sheet.Cleveland Clinic.Neuropathy (peripheral neuropathy): Prevention.

Tawfik EA, Walker FO, Cartwright MS. Neuromuscular ultrasound of cranial nerves.J Clin Neurol. 2015;11(2):109-121. doi:10.3988/jcn.2015.11.2.109

American Association of Neurological Surgeons.Anatomy of the spine and peripheral nervous system.

Cuevas J.The somatic nervous system.Reference Module in Biomedical Sciences. 2015:B9780128012383054000. doi:10.1016/B978-0-12-801238-3.05364-2

Cleveland Clinic.Somatic nervous system.

Dorland.Dorland’s Illustrated Medical Dictionary.

Cleveland Clinic.Neuropathy (peripheral neuropathy).

National Institute of Neurological Disorders and Stroke.Peripheral neuropathy fact sheet.

Cleveland Clinic.Neuropathy (peripheral neuropathy): Prevention.

Cleveland Clinic.Somatic nervous system.Ganong WF.Review of Medical Physiology.Somatic nervous system.Dorland’s Illustrated Medical Dictionary.

Ganong WF.Review of Medical Physiology.

Somatic nervous system.Dorland’s Illustrated Medical Dictionary.

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