Temporal summation is defined as

Temporal summation is defined as

• A. Increasing the frequency of firing of excitatory terminals
• B. Summation of inputs from multiple terminals
• C. Inhibition over time
• D. Simultaneous activation of many terminals

Answer: (D)

Temporal summation is about how a neuron sums inputs that arrive in rapid succession from the same presynaptic source. When an excitatory terminal fires repeatedly, each EPSP is brief; if another EPSP arrives before the previous one has decayed, their depolarizations overlap and add together. With a high enough frequency of input, the overlapping EPSPs can bring the membrane potential to the threshold and trigger an action potential. This is different from summation from multiple terminals at once, which is spatial summation—inputs from different presynaptic neurons summing at the same time. So, the idea that temporal summation depends on increasing the firing rate of excitatory terminals best captures the concept. Inhibition over time is not about summing excitatory inputs, and simultaneous activation of many terminals describes spatial rather than temporal integration.

Temporal summation is about how a neuron sums inputs that arrive in rapid succession from the same presynaptic source. When an excitatory terminal fires repeatedly, each EPSP is brief; if another EPSP arrives before the previous one has decayed, their depolarizations overlap and add together. With a high enough frequency of input, the overlapping EPSPs can bring the membrane potential to the threshold and trigger an action potential. This is different from summation from multiple terminals at once, which is spatial summation—inputs from different presynaptic neurons summing at the same time. So, the idea that temporal summation depends on increasing the firing rate of excitatory terminals best captures the concept. Inhibition over time is not about summing excitatory inputs, and simultaneous activation of many terminals describes spatial rather than temporal integration.