Spinal Cord

The spinal cord is part of the central nervous system. It runs from the medulla oblongata down the back, inside the vertebral column, which protects it. It is also surrounded by protective membranes (the meninges) and cerebrospinal fluid.The spinal cord has two jobs: it carries impulses between the brain and the rest of the body, and it coordinates simple spinal reflexes without involving the brain.In cross-section the cord has a central core of grey matter, shaped roughly like a butterfly or the letter H. Grey matter contains neurone cell bodies, dendrites, relay neurones and synapses, and has little myelin. Around it is white matter, made of myelinated axons running up and down the cord; the myelin makes it look white. A narrow central canal filled with cerebrospinal fluid runs through the middle.Pairs of spinal nerves leave the cord between the vertebrae, one on each side. Each spinal nerve joins the cord by two roots:• the dorsal root (towards the back) carries sensory neurones into the cord. It has a swelling, the dorsal root ganglion, which contains the cell bodies of the sensory neurones.
• the ventral root (towards the front) carries motor neurones out of the cord. Their cell bodies are in the grey matter.Because sensory information enters dorsally and motor instructions leave ventrally, damage to one root affects only sensation or only movement.