Divisions of the Nervous System

What is the Central Nervous System?

The central nervous system is made up of the brain and the spinal cord, and is the body's processing centre. The brain and the spinal cord are very soft and delicate structures which require protection. They are protected by three structures. Bone The bones of the skull enclose the brain. The spinal cord is enclosed in the spinal canal that is formed by vertebrae. This protects the CNS from physical damage, i.e. knocks and bumps. Cerebrospinal Fluid The brain and spinal cord are surrounded by a fluid called cerebrospinal fluid (CFS), and it acts as a shock absorber. The CSF also supplies nutrients and removes waste. Meninges The meninges are membranes made up of connective tissue which covers the inside of the bones of the CNS; it both produces and contains cerebrospinal fluid. The meninges have three layers.

1. Pia mater (inner layer); contains many blood vessels, sticks closely to the brain and spinal cord

2. Arachnoid (middle layer); has a web-like appearance, is thin but waterproof

3. Dura mater (outer layer); durable, touch, double layer, sticking closely to the brain