Define temporal summation in neuronal synapses.

Define temporal summation in neuronal synapses.

• A. The integration of postsynaptic potentials from multiple presynaptic neurons at different locations on the postsynaptic neuron
• B. The accumulation of postsynaptic potentials arriving in quick succession from the same presynaptic neuron, reaching threshold
• C. The spread of action potentials along the axon
• D. The release of neurotransmitters from multiple neurons at once

Answer: (B)

Temporal summation is the accumulation of postsynaptic potentials arriving in quick succession from the same presynaptic neuron, allowing the membrane potential to reach the threshold for firing an action potential. Each EPSP adds to the residual depolarization before it fully decays; when the interval between arrivals is short relative to the membrane’s time constant, the EPSPs overlap and sum in time. If enough depolarization builds up, voltage-gated channels open and an action potential is triggered. This differs from spatial summation, where inputs from different presynaptic neurons at different synapses combine. The other options describe propagation along the axon or simultaneous release from multiple neurons, not the rapid, repeated input from a single neuron that defines temporal summation.

Temporal summation is the accumulation of postsynaptic potentials arriving in quick succession from the same presynaptic neuron, allowing the membrane potential to reach the threshold for firing an action potential. Each EPSP adds to the residual depolarization before it fully decays; when the interval between arrivals is short relative to the membrane’s time constant, the EPSPs overlap and sum in time. If enough depolarization builds up, voltage-gated channels open and an action potential is triggered. This differs from spatial summation, where inputs from different presynaptic neurons at different synapses combine. The other options describe propagation along the axon or simultaneous release from multiple neurons, not the rapid, repeated input from a single neuron that defines temporal summation.