Define and differentiate synaptic integration: spatial vs temporal summation; how inputs shape output.

Define and differentiate synaptic integration: spatial vs temporal summation; how inputs shape output.

• A. Spatial summation combines inputs from different synapses to increase depolarization.
• B. Temporal summation combines rapid inputs from the same synapse; Inhibition has no effect.
• C. Inhibition always enhances the chance of reaching threshold.
• D. Spatial summation integrates inputs across different synapses; temporal summation integrates rapid inputs from the same synapse; inhibition reduces the probability of reaching threshold; net effect determines AP generation.

Answer: (D)

Neurons decide whether to fire by summing all incoming signals at the cell body. Spatial summation means inputs arriving at different synapses on the dendritic tree add together at the soma to produce a larger or smaller net change in membrane potential. Temporal summation is when rapid, repeated inputs from the same synapse occur close in time, causing their postsynaptic potentials to overlap and sum before they decay, which can push the membrane toward threshold even if a single input wouldn’t. Inhibitory inputs shift the balance by hyperpolarizing the membrane or shunting current, making it harder for depolarizations to reach threshold. The axon hillock integrates these signals, and the overall net effect determines whether an action potential is generated. So spatial summation integrates inputs across different synapses, temporal summation adds rapid inputs from the same synapse, inhibition reduces the probability of reaching threshold, and the combined effects set the likelihood of firing.

Neurons decide whether to fire by summing all incoming signals at the cell body. Spatial summation means inputs arriving at different synapses on the dendritic tree add together at the soma to produce a larger or smaller net change in membrane potential. Temporal summation is when rapid, repeated inputs from the same synapse occur close in time, causing their postsynaptic potentials to overlap and sum before they decay, which can push the membrane toward threshold even if a single input wouldn’t. Inhibitory inputs shift the balance by hyperpolarizing the membrane or shunting current, making it harder for depolarizations to reach threshold. The axon hillock integrates these signals, and the overall net effect determines whether an action potential is generated.

So spatial summation integrates inputs across different synapses, temporal summation adds rapid inputs from the same synapse, inhibition reduces the probability of reaching threshold, and the combined effects set the likelihood of firing.