4. What is ‘grey matter’?
You can think of the brain as being a bit like a telephone network. The bodies of the brain cells are the callers, sending and receiving the signals, and the axons are the wires, linking the network together. Like real wires, brain cell axons transmit signals using electricity. To stop the signals getting crossed and to help the messages move faster, the axons have insulation. Known as myelin sheaths, this insulation contains layers of white-coloured fat, visible inside the brain as ‘white matter’. The bodies of the cells don’t have this insulation, so they appear grey.