Structure and function of the spinal cord
The spinal cord lies in the canal formed by the vertebrae; in adults it is a cord-shaped organ 40–45 cm long and thinner than a finger (about 1 cm). A narrow canal runs through its centre. In a cut, the grey matter in the middle looks like the letter “H” or a butterfly – these are neuron bodies; the white matter around it consists of the long processes of neurons (nerve tracts). Thirty-one pairs of mixed nerves leave the spinal cord: each forms from a dorsal root (sensory fibres) and a ventral root (motor fibres) joining. Nerve centres in the grey matter provide the spinal cord’s reflex function: the knee reflex, pulling a hand away, urination and others. White matter performs conduction: impulses go up to the brain and from the brain down to organs. The brain controls spinal reflexes. If the spine or spinal cord is injured, movement and feeling below the injury may be lost, so a person who has fallen badly should not be moved and 103 should be called.
Spinal cord section model: draw a circle on paper, a butterfly-shaped grey matter inside, white outside; label the dorsal and ventral roots as sensory and motor.