Like a slender, fragile vine made of highly sensitive tissue and a billion neurons, your spinal cord is like a living extension of your brain running through your spine. It’s also one of the most important parts of the human body. It serves no less of a function than connecting your brain to your body and sending out all the vital nerve signals that allow you to do everything from picking up a pen to walking across a room. Here are 15 nervy facts about this amazing body part.

1. YOUR SPINAL CORD IS PART OF THE CENTRAL NERVOUS SYSTEM.

The brain and the spinal cord make up the central nervous system. The brain is in charge of thoughts, interpretations of the external environment through our senses, and our physical movements. The spinal cord is the main source of communication between the body and the brain. This is why spinal cord injuries disrupt information between the brain and other body parts.

2. IT'S LIKE THE INTERNET OF NERVE SIGNALS.

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The spinal cord is not one unified cord, actually, but a bundle of nerves sending and receiving a vast amount of signals from all over the body. It starts at the base of your brain, runs down the backbone, and terminates between your first and second lumbar vertebrae, in the low back.

Not only does the spinal cord act as the route for all nerve signals traveling between the brain and the body, but many receptors for pain and other stimulus communicate with the spinal cord through peripheral nerves. These small fibrous nerves are all over the body and send constant communication from all over the body to the brain. The spinal cord is a central hub of nerve signals.

3. IT FUNCTIONS INDEPENDENTLY OF THE BRAIN.

The spinal cord does not take all commands from the brain. It is able to send signals directly to the muscles when necessary.

4. IT CONTROLS VOLUNTARY AND INVOLUNTARY MOVEMENT OF THE MUSCLES.

The spinal cord is responsible for passing along the nerve signals that control not only voluntary movements like picking up a spoon or opening a door, but the involuntary movements (those made without your conscious decision) of the diaphragm, bowels, and bladder.

5. IT'S SMALLER THAN YOU THINK.

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You might assume that the spinal cord is very thick, since it serves such an important function in the human body. However, it gets its job done in a small amount of physical space, from between nearly .4 to almost .6 inches in diameter.

6. THE BRAIN AND THE SPINAL CORD BOTH HAVE GRAY AND WHITE MATTER, JUST IN DIFFERENT PLACES.

The brain and the spinal cord contain the same essential material, but organize them differently. In the brain, the gray matter comprises the outer portion of the brain’s physical material. In the spinal cord, the gray matter hangs out in the inner part of the cord. Gray matter is an accumulation of neurons that deal with either motor or sensory function. White matter contains the wiring for communication between the brain and other structures.

7. IT STOPS GROWING ONCE YOU TURN FIVE.

The spinal cord undergoes a lot of growth in your first four to five years, up to about 16 or 20 inches long, but from then on, it’s done. Your body keeps growing around the spinal column, which stays exactly as long as it was when you reached the age of five.

8. YOUR SPINAL CORD HAS A MEMORY FOR PAIN.

When you experience an instance of great pain—you stub your toe incredibly hard, for example, or even break it—the neurons in your spinal cord will carry signals more easily to the nerves in your injured toe for several days, making the toe feel more sensitive. This is the result of a molecule thought to be the precursor to memory, known as PKMzeta. Your spinal cord is especially sensitive to this molecule and “records” instances of pain as a result.

9. YOUR SPINAL CORD PASSES THROUGH 33 INDIVIDUAL VERTEBRAE.

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Between all those bony vertebrae stacked one on top of the other along your spine are tiny spaces just big enough for your slender spinal cord to traverse through.

10. THE HUMAN SPINAL CORD IS DIVIDED INTO 31 DIFFERENT SEGMENTS.

Each segment has many sets of nerves that exit the spinal cord: eight cervical, 12 thoracic, five lumbar, five sacral, and one coccygeal nerve.

11. DAMAGE TO THE SPINAL CORD CAN CAUSE PARALYSIS.

When the spinal cord is severed at any point due to injury, a number of resulting forms of paralysis can occur.

Complete: When almost all sensory feeling and ability to control movement are lost below the spinal cord injury.

Incomplete: When you still have some motor or sensory function below the injury.

Other terms used are: Quadriplegia or tetraplegia, which means your arms, hands, trunk, legs, and pelvic organs are all affected by your spinal cord injury; and paraplegia, which means paralysis extends to all or part of the trunk, legs and pelvic organs. About 58 percent of spinal cord injured individuals are considered paraplegic and about 42 percent quadriplegic [PDF].

12. YOU NEED YOUR SPINAL CORD IN ORDER TO SWEAT.

In spinal cord injuries resulting in quadriplegia, the spinal cord no longer can transmit the signals from your brain to your sweat glands. Thus, people with this kind of injury must be cooled down manually with cool water or air conditioning.

13. A SPINAL TAP CAN COME WITH A NASTY HEADACHE.

The medical procedure may be essential, but the mockumentary is more entertaining. Image credit: Kevin Dooley, via Flickr // CC BY 2.0

For people who require a spinal tap—where a large needle is inserted into the spinal cord to remove fluid for medical tests—a very common side effect is a wretched headache that scientists can’t fully explain. One theory is that cerebrospinal fluid continues to leak out of the tiny hole left by the puncture, and the fluid volume loss somehow triggers the headache, though at this time, the mechanism for the headache is still not understood.

14. STEM CELL TREATMENTS MAY REPAIR SPINAL CORD INJURIES.

Studies have shown stem cell treatments have reparative effects on injured spinal cords, and in certain cases of spinal cord injury, may reverse paralysis. Stem cells can replace the nerve cells that have died; generate new supporting cells to reform myelin and stimulate re-growth of damaged axons; protect cells at the injury site from further damage; and prevent spread of injury by suppressing harmful inflammation.

15. TECHNOLOGY ALLOWS PARALYZED PEOPLE TO REGAIN MOVEMENT IN THEIR LIMBS.

From electrical implants to new ways of rerouting brain signals, researchers are pressing the boundaries of technology and working on fascinating new ways to help people with spinal cord injuries regain function, paving the way for a cyborg revolution in which machines do the work of malfunctioning body parts.