Question: are voltage-gated sodium channels always open

Answer: No, 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).