Merck Manual

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Quick Facts

The Spinal Cord

By

The Manual's Editorial Staff

Last full review/revision Jun 2020| Content last modified Jun 2020
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What is the spinal cord?

The spinal cord is a long tube made up of nerves that goes from the brain down your back through the hollow center of your spine.

  • The spinal cord is like a thick electrical cable that carries messages back and forth between your brain and your body

  • Just like the skull protects your brain, the spine protects your spinal cord, which is very delicate

  • The spinal cord carries signals from the brain that tell your body what to do, such as moving your arms or legs

  • The spinal cord also carries signals to the brain from your body such as what you're touching or where it hurts

  • Reflexes (such as pulling your hand away from a hot stove) happen in the spinal cord without the brain being involved

  • If your spinal cord is damaged, you usually lose the ability to move or feel part of your body

How does the spinal cord work?

Nerve cells in the brain send messages down your spinal cord. Other nerves in your spinal cord receive these messages and send them on to your body through one of the spinal nerves.

Nerve cells in the spinal cord have nerve fibers running all over your body that are connected to sense receptors. For example, there are sense receptors in your skin for touch and pain. Anything that triggers those receptors, such as a needle poke, sends a signal up nerve fibers to your spinal cord. Other nerve cells in your spinal cord carry that signal to your brain where you feel pain.

How the Spine Is Organized

A column of bones called vertebrae make up the spine (spinal column). The vertebrae protect the spinal cord, a long, fragile structure contained in the spinal canal, which runs through the center of the spine. Between the vertebrae are disks composed of cartilage, which help cushion the spine and give it some flexibility.

Like the brain, the spinal cord is covered by three layers of tissue (meninges).

How the Spine Is Organized

Spinal nerves: Emerging from the spinal cord between the vertebrae are 31 pairs of spinal nerves. Each nerve emerges in two short branches (roots):

  • One at the front (motor or anterior root) of the spinal cord

  • One at the back (sensory or posterior root) of the spinal cord

The motor roots carry commands from the brain and spinal cord to other parts of the body, particularly to skeletal muscles.

The sensory roots carry information to the brain from other parts of the body.

Cauda equina: The spinal cord ends about three fourths of the way down the spine, but a bundle of nerves extends beyond the cord. This bundle is called the cauda equina because it resembles a horse’s tail. The cauda equina carries nerve impulses to and from the legs.

What are spinal nerves?

Spinal nerves are medium-sized nerves that connect your spinal cord to smaller nerves that travel to different parts of your body. There are 31 pairs of spinal nerves that enter and exit the spinal cord in the spaces between your vertebrae.

Each spinal nerve runs from a specific part of the spinal cord to a specific area of your body. So, for example, if you touch a specific spot on your skin, you feel it because of the message sent to your brain by one specific spinal nerve.

What can go wrong with the spinal cord?

Many problems can affect your spinal cord, including:

  • Injuries

  • Cancer that has spread to your spine can push on the spinal cord and damage it

  • Loss of spinal cord nerve cells from diseases like multiple sclerosis or a blocked blood supply

Once nerve cells in the spinal cord die, they can't grow back. So damage to the spinal cord is usually permanent.

If your spinal cord is damaged, your symptoms depend on where the damage occurred. For example, if the spinal cord is damaged in your lower back, you may lose movement and sensation in your legs but still be able to use your arms. But if the spinal cord is damaged in your neck, both your arms and legs may be affected. If the spinal cord is damaged high in your neck, you may not be able to breathe. You can lose control of your bladder and bowels and lose sexual function regardless of where your spinal cord is damaged.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version

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