Introduction to the brain

The brain is the body’s most complex organ. It is made up of many folds (called gyri) and grooves (called fissures or sulci, depending on their size). This wrinkly outer bit of brain that we see and typically think of when we envisage a brain is called the cerebral cortex (or cerebrum). We also have a walnut-looking ‘mass’ of brain at the base of our cerebral cortex at the back, this is known as the cerebellum.

Together with the spinal cord, the brain makes up the central nervous system (CNS), the processing centre of the body.

You might hear bits of the brain (or spinal cord) described as grey matter and white matter. We’ll focus on the brain here.

Grey matter makes up around 40% of the brain and white matter makes up around 60% of the brain. In the simplest terms, grey matter deals with information processing and white matter facilitates this processing by helping nerve signals get around the brain.

It can be helpful to think about these two types of matter using the example of a house’s lighting system. White matter is the insulation (myelin sheath) around the wiring (neurons) of the brain, that helps the signals travel more quickly and efficiently, connecting up different wires in order to produce light (cognitive functioning).

Grey matter is the ends of the wires (high concentrations of neuronal bodies, axon endings and dendrites) that the white matter helps to connect up. Due to this connectivity the grey matter can process lots of information. These are the areas that we commonly associate with producing the cognitive functions (the cerebral cortex and the cerebellum, for example).