Transcript

Processing and transmission of signals in the brain are both carried out by neurons. These vary greatly in size and shape but all consist of three structures – an input set of fibres, the dendrites, that receive signals, a cell body and an output, the axon, that carries the signal to other cells.

The functional anatomy of the brain is determined by the connections between the axons and the dendrites. These are called the synapses.

Signals flow through the synapses from the axons to the dendrites. The neuron responds to these multiple inputs – with the right set of inputs it fires, sending a pulse or action potential on to other neurons. These other neurons can in turn signal to other cells, resulting in information processing throughout the nervous system.

In the first few years of life, the neurons in the cortex develop rapidly in complexity. This development is guided by signals from the genes and from the environment. As the synapses proliferate and strengthen selectively, they form the neural systems that enable us to carry out the whole range of human functions. This process of synaptic change, which goes on throughout life, is known as plasticity.

The networks that are built up connect neurons locally and across the brain. The end result is staggering in its complexity. In the adult brain, the average neuron is connected to 10 to 20,000 other neurons.

The speed of the networks increases too as electrically insulating glial cells form round the long axons that connect different parts of the cortex. This process is known as myelination. It is the myelin that makes the white matter white.

The brain’s development is governed by feedback. We interact with our surroundings – with repeated exposure, neural systems are activated. Networks that are used frequently are strengthened and refined. Networks that are not used disappear. Through this mechanism, the brain becomes more effective in processing information.

Our understanding of the brain’s networks is still very limited but functional imaging methods are beginning to allow us to see the networks and the activity within them.