As already mentioned, each neuron can have many synapses.
Therefore, the potential changes that occur in it depend on the net effect of
all synapses. Certain synapses may produce inhibitory effects and others may
produce stimulatory effects. What happens in the postsynaptic neuron depends on
which effect is predominant.
For example, if action potentials arrive rapidly in a synapse that
has a stimulatory effect, the potential in the postsynaptic neuron may reach
threshold quickly and produce an action potential. At the same time, if action
potentials arrive in a synapse that produces an inhibitory effect, the
postsynaptic membrane will be-come hyperpolarized, making it difficult for
action potential to be generated. This mechanism of inte-grating the effects of
two or more neurons by the postsynaptic neuron is known as summation.