text: The nodes of Ranvier Na+/Ca2+ exchangers and high density of voltage-gated Na+ channels that generate action potentials.  A sodium channel consists of a pore-forming α subunit and two accessory β subunits, which anchor the channel to extra-cellular and intra-cellular components.  The nodes of Ranvier in the central and peripheral nervous systems mostly consist of αNaV1.6 and β1 subunits. The extra-cellular region of β subunits can associate with itself and other proteins, such as tenascin R and the cell-adhesion molecules neurofascin and contactin.  Contactin is also present at nodes in the CNS and interaction with this molecule enhances the surface expression of Na+ channels. 
  Ankyrin has been found to be bounded to βIV spectrin, a spectrin isoform enriched at nodes of Ranvier and axon initial segments.   The PNS nodes are surrounded by Schwann cell microvilli, which contain ERMs and EBP50 that may provide a connection to actin microfilaments. Several extracellular matrix proteins are enriched at nodes of Ranvier, including tenascin-R, Bral-1, and proteoglycan NG2, as well as phosphacan and versican V2. At CNS nodes, the axonal proteins also include contactin; however, Schwann cell microvilli are replaced by astrocyte perinodal extensions.