Which term describes summation when subthreshold stimuli from the same axon are repeated?

Which term describes summation when subthreshold stimuli from the same axon are repeated?

• A. Temporal summation
• B. Spatial summation
• C. Positive feedback
• D. Negative feedback

Answer: (A)

The key idea is how signals add up over time on a neuron. When subthreshold inputs arrive from the same axon repeatedly, each tiny depolarization lasts for a short time. If another input comes while the first is still partially decaying, their effects overlap and sum, pushing the membrane potential closer to the threshold. If stimuli come in rapid succession, this temporal overlap can reach threshold and trigger an action potential. That timing-based addition of responses from the same location is temporal summation. If inputs came from different locations on the neuron at the same time, that would be spatial summation, which is not what this item describes. Positive and negative feedback refer to how activity is amplified or damped in a circuit, not to the way postsynaptic potentials summate in time.

The key idea is how signals add up over time on a neuron. When subthreshold inputs arrive from the same axon repeatedly, each tiny depolarization lasts for a short time. If another input comes while the first is still partially decaying, their effects overlap and sum, pushing the membrane potential closer to the threshold. If stimuli come in rapid succession, this temporal overlap can reach threshold and trigger an action potential. That timing-based addition of responses from the same location is temporal summation.

If inputs came from different locations on the neuron at the same time, that would be spatial summation, which is not what this item describes. Positive and negative feedback refer to how activity is amplified or damped in a circuit, not to the way postsynaptic potentials summate in time.