A nerve is composed of a bundle of fibres that are surrounded by layers of tissue and fat and present throughout the body. Mixed nerves are those nerves that carry both the sensory and motor nerves. Electrical impulses are transformed from the central nervous system to the muscles of the body. They contain both sensory and motor fibres.

Reflex action is an involuntary action in response to a stimulus that is controlled by the spinal cord together with the medulla oblongata. The nerve pathway that takes place in a reflex action is called a reflex arc. Autonomic and somatic are the two types of reflex arcs. Some important components of reflex arc are receptor organs, sensory neurons, nerve centre, interneurons, motor neurons, and effectors.