In vertebrates, such as humans, the nervous system consists of two main components: the central nervous system and the peripheral nervous system, as noted by Inner Body. The brain and spinal cord make up the CNS, and the PNS includes the sensory neurons and nerves that link the CNS to other parts of the body. The main function of the nervous system is to transmit nerve signals throughout the body to coordinate its movement and various other activities.
The nervous system consists of neurons and glial cells, which are types of specialized cells that are around neurons. The body contains billions of neurons, which are nerve cells that receive and transmit electrochemical signals within the body. A neuron consists of a cell body with a nucleus, dendrites and axons. Dendrites are branch-like extensions of the neurons that receive electrical messages and transmit them to the cell body. Axons are long fibers that transmit information away from the cell body.
There are sensory and motor neurons. Sensory neurons react to certain stimuli, which include light and sound, and send neural signals to the CNS for processing. Motor neurons in the CNS send signals to muscles and glands in the body. The function of nerves, which consist of bundles of axons, is to carry information in the form of nerve impulses between the CNS and other areas of the body. For example, the optic nerve is a cranial nerve that transmits information through electrical impulses from the eye's retina to the brain for processing, notes Healthline.