Nightingale Physiology Practice Test

Spatial summation happens when inputs from several presynaptic neurons converge onto one postsynaptic neuron and their postsynaptic potentials add up at the same place on the cell. If multiple terminals release neurotransmitter at the same time, the resulting excitatory or inhibitory signals combine at the dendrites and near the axon hillock, influencing whether the neuron reaches threshold to fire. The key idea is summation across space: many different synapses contributing to the overall membrane potential of a single neuron. This is different from temporal summation, where rapid firing at a single synapse over time builds up the postsynaptic effect. While spatial summation can involve excitatory inputs, it’s not limited to inhibitory synapses only. The option describes exactly the convergence of neurotransmitter release from several presynaptic knobs onto one postsynaptic neuron, which captures this spatial integration.