What is the all or nothing response of an action potential?
All or nothing response of an action potential (AP), refers
simply to the fact that an AP will either occur, or not. There is
no gradient, no half APs or double APs. The only option is AP, or
no AP. Like in computer binary, the response is either 1 (an AP) or
0 (no AP).
All the factors trying to induce (or inhibit) an action
potential (i.e other action potentials, EPSPs and IPSPs) add up
(summate) at the axon hillock, (aka the trigger zone). Here, if the
stimulation is big enough an action potential will occur. If the
stimulation is not big enough, no action potential occurs.