Editing Node of Ranvier (section)

==Overview==
[[File:Neuron.svg|thumb|upright=1.2|Node of Ranvier in the [[peripheral nervous system]]]]
The nodes are primarily composed of sodium and potassium voltage-gated ion channels; [[Cell adhesion molecule|CAMs]] such as neurofascin-186 and [[NRCAM|NrCAM]]; and cytoskeletal adaptor proteins such as [[Ankyrin|ankyrin-G]] and [[Spectrin|spectrinβIV]].<ref>{{cite journal |last1=Poliak, Peles |first1=S, E |title=The local differentiation of myelinated axons at nodes of Ranvier |journal=Nat Rev Neurosci |date=2003 |volume=4 |issue=12 |pages=968–980 |doi=10.1038/nrn1253 |pmid=14682359 }}</ref>
Many vertebrate axons are surrounded by a myelin sheath, allowing rapid and efficient [[Saltatory conduction|saltatory ("jumping") 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 the 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 wrapped 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 of the myelinating cell membrane. Each node of Ranvier is flanked by paranodal regions where helicoidally wrapped glial loops are attached to the axonal membrane by a septate-like junction.

The segment between nodes of Ranvier is termed as the [[Internodal segment|internode]], and its outermost part that is in contact with paranodes is referred to as the juxtaparanodal region. The nodes are encapsulated by [[Microvillus|microvilli]] stemming from the outer aspect of the [[Schwann cell]] membrane in the PNS, or by perinodal extensions from [[astrocytes]] in the CNS.