The sensory and motor neurons that connect the central nervous system to the rest of the body

• Overview
• Function
• Anatomy
• Conditions and Disorders
• Care

Overview

What are nerves?

Nerves are like cables that carry electrical impulses between your brain and the rest of your body. These impulses help you feel sensations and move your muscles. They also maintain certain autonomic functions like breathing, sweating or digesting food.

Nerve cells are also called neurons. Neurons are present all over your body, especially in your brain and spinal cord. Nerves, together with your brain and spinal cord, are the foundation of your nervous system. Most of the time when doctors use the term “nerve,” they’re referring to the part of your nervous system outside of your brain and spinal cord. This is called your peripheral nervous system.

What are the types of nerves?

You have two main types of nerves:

• Sensory nerves carry signals to your brain to help you touch, taste, smell and see.
• Motor nerves carry signals to your muscles or glands to help you move and function.

You also have two main groups of nerves branching out from your brain and spinal cord:

• Cranial nerves: These 12 nerve pairs originate in your brain and extend through your face, head and neck. Cranial nerves can have sensory functions, motor functions or both. For example, cranial nerves help you make facial expressions, move your eyes and process smells.
• Spinal nerves: You have 31 pairs of spinal nerves branching out from your spinal cord. These nerves can provide sensory function, motor function or both. For example, spinal nerves may carry sensations from your joints and muscles to your spinal cord. Spinal nerves also control some of your reflexes or involuntary responses, such as pulling your hand away from a hot stove.

Function

What is the purpose of nerves?

Nerves send electrical signals from one part of your body to another. These signals control your:

• Voluntary movement.
• Senses (touch, pain, feeling hot or cold, vibration, hearing, sense of balance, taste, smell and sight).
• Blood pressure.
• Breathing.
• Digestion.
• Heart rate.
• Stress response.

How do nerves function with the rest of the nervous system?

Your nerves help the two parts of your nervous system communicate with each other:

• Your peripheral nervous system is the network of nerves that transmit (carry) signals from all over your body to your spinal cord, which is part of your central nervous system.
• Your central nervous system is your brain and spinal cord. It receives and interprets nerve signals from your peripheral nervous system. Your brain integrates these messages (inputs) to inform everything you do, including how you move, feel, behave and think. Some reactions are reflexive, happening below the level of consciousness, like moving your hand away from a hot stove.

When a nerve sends an electrical impulse:

1. The signal travels down the axon, the “wiring” connection of the nerve.
2. The message converts to a chemical signal at the end of the nerve called the axon hillock.
3. The chemical releases molecules called neurotransmitters, into a space that bridges the space between one neuron to another. These bridges are called synapses.
4. The neurotransmitter binds to a receptor on the muscle or connecting neuron and converts to another electrical signal.
5. Electrical signals travel up the length of that next neuron.
6. The process repeats until the message reaches its target.

Anatomy

Where are your nerves located?

Many nerves start in your spinal cord and some even from your brain. They extend throughout your body, including in your:

• Arms, including your ulnar nerve, median nerve, radial nerve and axillary nerve.
• Chest and abdomen, including your vagus nerve and phrenic nerve.
• Face, including your facial nerve, trigeminal nerve and optic nerve.
• Legs, including your sciatic nerve, femoral nerve, tibial nerve, obturator nerve and sural nerve.
• Pelvis, including your pudendal nerve.

What is the structure of the nerves?

Your nerves are made up of:

• Axons, cord-like groups of fibers in the center of your nerve.
• Dendrites, branches that carry electrical impulses.
• Endoneurium, a layer of connective tissue surrounding axons.
• Perineurium, a layer of connective tissue that surrounds groups of axons called fascicles.
• Epineurium, a layer of connective tissue that covers the outer surface of your nerve.

In your brain, cells called oligodendrocytes surround axons. Outside of your central nervous system (brain and spinal cord), cells called Schwann cells surround the axons.

Both oligodendrocytes and Schwann cells contain a fatty tissue called myelin. Myelin surrounds the axons in a layered sheath (coating). The myelin sheath is like the insulation around electrical wiring. If it gets damaged, your nerves can’t send electrical signals as quickly. Sometimes, they stop sending electrical signals completely.

Conditions and Disorders

What conditions and disorders affect the nerves?

Some conditions affect how well your nerves send signals. If damage or injury interferes with nerve signals, you may develop a neurological condition.

Common conditions that affect the nerves include:

• Peripheral neuropathy: Damage to your peripheral nerves (nerves outside of your brain and spinal cord).
• Sciatica: Pain that affects the nerve roots in your lower back, or your sciatic nerve, the nerve that runs from your lower back down the backs of both legs.

Care

How can I keep my nerves healthy?

You can keep your nerves and entire nervous system healthier by adopting healthy habits, like:

• Avoid tobacco or quit smoking.
• Eat a nutritious diet full of whole grains, healthy fats, lean protein, fruits and vegetables.
• Limit alcohol intake.
• Manage health conditions that can affect your nerves, such as diabetes.
• Reduce stress with healthy coping techniques such as meditation or exercise.
• Sleep at least seven to eight hours each night.
• Stay hydrated by drinking plenty of water and other fluids.

What else should I ask my doctor about my nerves?

You may also ask your healthcare provider:

• How do I know if I’m having nerve pain?
• What’s the most likely cause of nerve pain?
• What tests can I have to check the health of my nerves?
• What treatments can improve my nervous system health?
• How can I prevent nerve problems from returning?

A note from Cleveland Clinic

Your nerves run throughout your whole body. They connect your brain and spinal cord with other parts of your body so you can move and feel sensations. They also control many of your body’s “automatic” functions, such as breathing or digesting food. You can improve the health of your entire nervous system by practicing healthy habits, like eating nutritious foods and exercising regularly.

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