03.02.3 Nervous tissue

Nervous tissue makes up the brain, spinal cord and nerves. It is made up of two types of cells. Nerve cells or neurons relay information through electrical signalling and support cells (glial cells) protect andnourish the neurons.

Neurons are made up of a cell body and a long process called an axon (Figure 3.5). The cell body houses the nucleus and other organelles, and it is also where the electrical impulses are initiated.Axons are long structures (up to 1m long) which carry the electrical signal to the target cell. Dendrites receive the signal from communicating neurons (see section 1.1).

The best known glial cells are Schwann cells. They wrap around axons and act as electrical insulators (like insulation tape around an electric wire). Schwann cells are effective insulators because of the fattymaterial they produce, called myelin.

Figure 3.5 A typical neuron showing the axon and myelin sheath (Copyright, QUT)