Spatial summation is defined as

Spatial summation is defined as

• A. Increasing the frequency of firing of a single terminal
• B. Excitation of many terminals at the same time
• C. Inhibition of multiple terminals
• D. Summation over time intervals

Answer: (B)

Spatial summation occurs when many excitatory inputs from different presynaptic terminals arrive at the postsynaptic neuron at roughly the same moment. Each input produces a small depolarization (an excitatory postsynaptic potential). If several of these depolarizations occur together, they add up at the postsynaptic membrane, increasing the chance that the membrane potential reaches the threshold to trigger an action potential. This contrasts with temporal summation, where rapid firing from a single terminal causes successive EPSPs to accumulate over time. The idea behind spatial summation is that the neuron integrates inputs from multiple sources, and when enough simultaneous excitatory signals are present, the neuron fires. Inhibitory inputs would oppose this accumulation, reducing the likelihood of reaching threshold. The effectiveness also depends on where the inputs are located, since closer inputs to the soma or axon hillock have a larger influence due to less attenuation.

Spatial summation occurs when many excitatory inputs from different presynaptic terminals arrive at the postsynaptic neuron at roughly the same moment. Each input produces a small depolarization (an excitatory postsynaptic potential). If several of these depolarizations occur together, they add up at the postsynaptic membrane, increasing the chance that the membrane potential reaches the threshold to trigger an action potential. This contrasts with temporal summation, where rapid firing from a single terminal causes successive EPSPs to accumulate over time. The idea behind spatial summation is that the neuron integrates inputs from multiple sources, and when enough simultaneous excitatory signals are present, the neuron fires. Inhibitory inputs would oppose this accumulation, reducing the likelihood of reaching threshold. The effectiveness also depends on where the inputs are located, since closer inputs to the soma or axon hillock have a larger influence due to less attenuation.