Spinal cord is the continuation of medulla oblongata. It is in fact a tubular bundle of nerves. It starts from brain stem and extend to lower back. Like brain, spinal cord is also covered by meninges. The vertebral column surrounds and protects spinal cord.
Size
Spinal cord is roughly 40cm long and about as wide as your thumb for most of its length.
Structure
The outer region of spinal cord is made of white matter (containing myelinated axons). The central region is butterfly shaped that surrounds the central canal. It is made of grey matter (containing neuron cell bodies).
Spinal Nerves
31 pairs of spinal nerves arise along spinal cord. These are "mixed" nerves because each contains axons of both sensory and motor neurons. At the point where a spinal nerve arises from spinal cord, there are two roots of spinal nerve. Both roots unite and form one mixed spinal nerve. Figure 12.4
• The dorsal root contains sensory axons and a"ganglion where cell bodies are located.
• The ventral,root contains axons of motor neurons.
Functions
Spinal cord performs two main functions:
1)It serves as a link between body parts and brain. Spinal cord transmits nerve impulses from body parts to brain and from brain to body parts.
2) Spinal cord also acts as a coordinator, responsible for some simple reflexes.