Spatial summation is described as

• A. When multiple sub stimuli converge on one cell body simultaneously
• B. When a single neuron is stimulated repeatedly
• C. When inputs converge on separate neurons
• D. When a stimulus fails to reach threshold

Answer: (A)

Spatial summation happens when several subthreshold inputs from different presynaptic neurons arrive at the same postsynaptic neuron at roughly the same time and their effects add up on the postsynaptic membrane. If the combined depolarization reaches the threshold, an action potential is produced. This is different from temporal summation, where a single presynaptic neuron fires rapidly so its successive inputs accumulate over time. It also wouldn’t involve inputs spreading to separate neurons, which wouldn’t summate at one cell. The described situation—multiple subthreshold signals converging on one neuron at once—best illustrates spatial summation.