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).

are voltage-gated sodium channels always open?
no