Spinal Cord Anatomy

Your brain and spinal cord make up the central nervous system, the nerves that run from the spine and supply the rest of your body are called the peripheral nervous system.

Central Nervous system = Brain and Spinal Cord

Peripheral nervous system = nerves that run from the spine into your arms, legs and trunk

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spinal cord shown away from the spinal canalSpinal Cord and Nerve Roots

The spinal cord carries nerve impulses or 'messages' from your brain which is your 'control centre' , to your limbs and organs and back again.

The spinal cord starts at the brain and runs encircled by the vertebrae, in a bony channel called the spinal canal , all the way down your back. diagram of human spine - cauda equinaThis means the cord is safely enclosed by the bony protective spine.

The spinal cord actually ends quite high up in the back - at about the level of the second lumbar vertebra, but it does continue in a looser bundle of nerve roots, called the cauda equina, all the way down to the sacrum.

There is a space on each side between each vertebra, that allows a nerve, called a nerve root, to leave the spinal cord. This space is called the foramen.

These nerve roots join together to form single large nerves, including the well known sciatic nerve (unfairly blamed for lots of back pain) which runs down the back of your leg, and the often forgotten femoral nerve which runs down the front.

The spine is a strong, beautifully designed structure that allows movement whilst at the same time protecting the spinal cord. It is not fragile or vulnerable. Very few people with back pain have major problems with the actual structure of their spines.

Image on the left Mikael Häggström via Wikimedia Commons

 

diagram of the entire nervous system showing tye spinal cord and the nerve roots

By Persian Poet Gal (Own work) [Public domain], via Wikimedia Commons

When looked at in cross section,or sliced sideways, the spinal cord shows two distinct areas. A darker gray central area which is butterfly shaped, this is surrounded by a whiter area.  The central area contains tissue called gray matter, and this is made up of the main bodies of each of the nerve cells.

diagram of a cross section of the spinal cord showing the greay and white matter

Michal Komorniczak (Medulla_spinalis) via Wikimedia Commons

 

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When you are looking at the butterfly shape the top two wings are called the dorsal (posterior) horns and the bottom two are called the ventral (anterior) horns.

The dorsal horns are very interesting to us as they are responsible for managing the sensory information from the body. This includes touch, pressure, movement etc. This is the area where your nervous system starts interpreting signals from your body and this area can become over sensitised when you have chronic pain.

diagrma of a nerve showing the grey cell body and the white myelin sheath on the nerve axonThe whiter outer area of the butterfly shape is made up of myelinated axons. Axons are the parts of the nerve that carry the transmitted nerve impulse back and forth to the nerve cell body and the the brain.They are whitish in colour because they are covered in a myelin sheath, this sheath is a little like an insulator, or pipe lagging, which helps speed up the transmission of nerve impulses. These axons run up and down the length of the spinal cord.

Different areas of the spinal cord deal with different sorts of nerve impulses. These are called tracts and If you have a spinal cord injury the symptoms you will get will depend on which part of the spinal cord tract is injured.

For example the white area between the two dorsal horns at the top consists of tracts that send messages to the brain about pressure, touch and position sense.

Lower back pain rarely involves damage to the spinal cord. However, changes to the processing of information through the cord are very important in our understanding of back pain as increased sensitivity in the central nervous system is one of the major problems in chronic pain.

Lower Back Pain Toolkit Home Page

 

01-Feb-2013

 

 

 

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