Structure

Spinal cord

Also called Medulla spinalis

The body's main information highway, and home to lightning-fast reflexes.

The spinal cord lit up in a 3D model of the human brain

The spinal cord is a long, soft bundle of nerve tissue that runs from the base of the brain down inside your backbone. It carries messages between the brain and the body in both directions. It also handles some reflexes on its own, like yanking your hand off a hot stove before you even feel the pain. In adults it is roughly 40 to 45 cm long, and 31 pairs of spinal nerves branch out from it.

Where it is

Inside the backbone, running from the base of the skull down to about the top of the lower back, where it tapers to a point. Below that, a bundle of nerve roots carries on down.

What it does

A two-way highway

Commands flow down from the brain to the muscles, while touch, pain and body-position signals flow up.

Reflexes

Some responses, like the knee-jerk or pulling away from pain, are handled right in the cord for extra speed.

Walking rhythms

Circuits in the cord seem able to produce basic rhythmic stepping movements, though how much this happens in humans is still debated.

Body upkeep

It helps control the bladder, bowels, sweating and blood vessels.

Think of it as a thick data cable running down your back, with 31 pairs of branch lines reaching every part of the body.

Works with

Medulla oblongataAt the base of the skull, the spinal cord merges into the medulla.
Corticospinal tractThis main movement pathway carries commands from the cortex down the cord.
Motor neuronMotor neurons in the cord send fibers out to every muscle below the neck.
Primary somatosensory cortexTouch and body-position signals travel up the cord and eventually reach this touch-sensing cortex.
CerebellumIt keeps the cerebellum constantly updated on where your limbs are.
Raphe nucleiSerotonin fibers from the raphe nuclei run down the cord to help turn pain down.

When it goes wrong

Spinal cord injury

Damage can cause loss of movement and feeling below the injury. The higher the injury, the more of the body is affected, and a neck injury can affect both arms and legs.

ALS (motor neuron disease)

In ALS, the motor neurons in the spinal cord and brain slowly die, causing muscle weakness that spreads over time.

For learning only, not medical advice. If you have a health concern, talk to a doctor.

Surprising facts

The cord is shorter than the backbone. It ends near the top of the lower back, so doctors can safely take a sample of spinal fluid from lower down without touching it.
The bundle of nerve roots below the end of the cord is called the cauda equina, Latin for "horse's tail".
You have 8 pairs of spinal nerves in your neck, but only 7 neck bones.

By the numbers

42 to 45 cmLength in men (39 to 43 cm in women)

31 pairsSpinal nerves

About 1 cmThickness

Where the name comes from

"Spinal" comes from the Latin "spina", which first meant "thorn" and later "backbone". In Latin the cord is called medulla spinalis, "spinal marrow".

Quick quiz

3 questions. Your answers are saved and come back in your daily review.

Which of these is a job of the spinal cord?
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A two-way highway. Commands flow down from the brain to the muscles, while touch, pain and body-position signals flow up.
The spinal cord is part of which larger structure?
Show the answer
Brainstem. It belongs to the brainstem.
Which part fits this description? "Like a thick data cable running down your back, with 31 pairs of branch lines reaching every part of the body."
Show the answer
Spinal cord. It is the spinal cord. The body's main information highway, and home to lightning-fast reflexes.

Sources

Neuroanatomy, Spinal Cord Morphology, StatPearls, NCBI Bookshelf
Neuroanatomy, Spinal Cord, StatPearls, NCBI Bookshelf
Physiology, Spinal Cord, StatPearls, NCBI Bookshelf

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