Nodes of Ranvier are known as the gaps (about 1 micrometer in diameter) formed between myelin sheath cells along axons or nerve fibers.
Several vertebrate axons are surrounded by a myelin sheath allowing rapid and efficient saltatory propagation of action potentials. The contacts between neurons and glial cells display a very high level of spatial and temporal organization in myelinated fibers. The myelinating glial cells, oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS), are wrapped around the axon, leaving the axolemma relatively uncovered at regularly spaced nodes of Ranvier.The internodal glial membranes are fused to form compact myelin, whereas the cytoplasm-filled paranodal loops of myelinating cells are spirally rolled up around the axon at both sides of the nodes. This organization demands a tight developmental control and the formation of a variety of specialized zones of contact between different areas