Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na) through a cell's plasma membrane. They are classified according to the trigger that opens the channel for such ions, i.e. either a voltage-change ("Voltage-gated", "voltage-sensitive", or "voltage-dependent" sodium channel also called "VGSCs" or "Nav channel") or a binding of a substance (a ligand) to the channel (ligand-gated sodium channels).