Nerve impulses are propagated (transmitted) along the entire length of an axon in a process called continuous conduction. To transmit nerve impulses faster, some axons are partially coated with myelin sheaths. These sheaths are composed of cell membranes from Schwann cells, a type of supporting cell outside the CNS. Nodes of Ranvier (short intervals of exposed axon) occur between myelin sheaths. Impulses moving along myelinated axons jump from node to node. This method of nerve impulse transmission is saltatory conduction.