Action potential will only be fired when the memebrane potential is above the threshold level.
This follows the all-none -principle.
No matter the strenght of stimulus if the magnitride is not upto the threshold level,No action potential will.be generated.
An example is the flushing of water closet or lavoratory.No mater one tried to flush,if the water in the closet does not fill up to the threshold for flushing,,to propel flushing. not flushing will take place.
