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?

Summation

Explanation:

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.