A postsynaptic neuron has three presynaptic inputs - from neurons X, Y and Z. When X, Y, and Z are stimulated simultaneously, the postsynaptic neuron reaches threshold and undergoes an action potential. What is this process called?
Presynaptic neurons release chemical signals called neurotransmitters into the synaptic cleft in order to trigger graded potentials in the postsynaptic neuron. Some neurotransmitters produce excitatory post-synaptic potentials, whereas other neurotransmitters generate inhibitory post-synaptic potentials. Summation refers to the process that determines whether an action potential is generated by the combined effects of excitatory and/or inhibitory signals. The summation can be temporal or spatial regarding the number of cells communicating with the neuron. Temporal summation occurs when a presynaptic terminal is stimulated repeatedly in rapid succession. On the other hand, spatial summation occurs when excitatory potentials fire from different presynaptic neurons.
