what is the threshold needed for an action potential
A stimulus is received by the dendrites of a nerve cell. This causes the Na+ channels to open. If the opening is sufficient to drive the interior potential from -70 mV up to -55 mV, the process continues. Having reached the action threshold, more Na+ channels (sometimes called voltage-gated channels) open. The Na+ influx drives the interior of the cell membrane up to about +30 mV.