When two excitatory postsynaptic potentials (EPSPs) occur at a single synapse so rapidly in succession that the postsynaptic neu
ron's membrane potential has not returned to the resting potential before the second EPSP arrives, the EPSPs add together, producing A. spatial summation
B. temporal summation
C. tetanus
D. the refractory state
Temporal summation occurs when stimuli are applied to the same axon in rapid succession. These back to back stimuli cause overlapping EPSPs that sum. Temporal summation requires the buildup of neurotransmitter released by a single presynaptic end bulb two or more times in rapid succession that does not allow the postsynaptic neuron's membrane potential to return to the resting potential. The resultant postsynaptic potentials sum. A typical EPSP lasts about 15 msec. Therefore, temporal summation occurs when the second release of neurotransmitters occurs soon after the first one so that the postsynaptic neuron does not acquire resting potential.
