The PNS connects the nerve cells of the brain and the spinal cord to the rest of the body. The basic unit of the PNS is the neuron or nerve cell. Axons conduct impulses away from the cell body. They carry impulses between the cell body and nerve terminals or receptors in the muscles, skin, or internal organs. Axons are covered by a myelin sheath composed of a white, lipid material, which acts as an insulator for the conduction of impulses.
Neurons are the basic anatomical and functional unit of the nervous system.
The junction between one neuron and the next is called the synapse. It is here that excitatory or inhibitory chemicals are released for impulses to be transmitted. The twelve pairs of cranial nerves are numbered in Roman numerals. This numeration is in relation to a descending order of how the nerves attach to the CNS in the brain. Also deals with chewing and jaw reflexes.