What is the structure and function of a nerve cell?

Nerve cells serve an important function in our bodies to relay information as electrical signals from the periphery to the central nervous system. Nerve cells are also called 'neurons' and can be as long as 3 feet. Nerve cells are composed of tiny branches called dendrons which branch into further even smaller extensions called dendrites. They also have a nucleus surrounded by cytoplasm, a cell membrane and an axon. The axon is a long fibre that is coated or insulated in a fatty sheath made out of a substance called myelin. This insulation is what adapts the neuron to carry electrical impulses from one place in the body to another. Neurons work by responding to a stimulus (a change in the environment) that is detected by receptors. There are three main types of neurons- sensory, relay and motor. Once a stimulus is detected, electrical impulses are first sent along the sensory neuron to the central nervous system (CNS). It is then transferred to a relay neuron (also known as an interneuron) which helps pass the information between the sensory neuron and the CNS. These relay neurons can also then pass the information back to a nerve cell known as a motor neuron. Motor neurons carry the electrical impulse to effectors. Effectors are muscles or glands that produce a response. An example of this process can be shown by how the eye responds to light. Light is the stimulus, detected by light receptors called rods and cones. The amount of light entering the eye is then controlled by the muscles of the iris (the effectors).