The Structure and Function of Sensory, Relay and Motor Neurons
The nervous system is composed of specialised cells called neurons. The neurons form pathways in the brain and throughout the body by being connected to one another by synapses.
There are about 100 billion neurons or nerve cells in the average nervous system. Neurons vary in size and shape. The neurons are specialised for communication whether this is between other neurons or with other organs in the body such as the heart or stomach.
There are three main neurons, all of which have different roles to play — Sensory, Relay and Motor Neuron.
|Structure||WHAT IS IT?|
|Cell body||This includes a nucleus which contains the genetic material (chromosomes) of the cell. Surrounding the nucleus are other components that are essential for the functioning of the whole neuron. This is what gives the brain its grey colour (“grey matter”).|
|Axon||This is a long extension from the cell body and can be up to a meter in length. Usually has two or more branches, called collateral branches.|
|Myelin sheath||This insulates or protects the axon from external influences that might affect transmission of the nerve impulse. This is what gives the brain it’s white colour (“white matter”).|
|Terminal button||Sends signals to an adjacent cell (another neuron, a muscle cell etc). This is how information is passed between neurons through electrical impulses.|
|Dendrite||Receives nerve impulses or signals from adjacent neurons.This is how information is passed between neurons through electrical impulses.|
The Three Main Types of Neurons