379701 IGERS Saka Why is the threshold for firing an action potential around-40 mV? O A. Patch-clamp experiments have shown that the driving force for sodium is the largest at -40 mv -40 mV is the voltage at which the four pore loops that make up the selectivity filter change their three-dimensional configuration At this voltage sodium ions start leaving the cell because the inside of the cell is no longer negative enough to keep them inside At this voltage the selectivity fiter of voltage-gated sodium channels switch from being selective to potassium to being selective to sodium E.-40 mV is the voltage at which the voltage sensor of voltage-gated sodium channels move の hp