Define spatial summation in neuronal synapses.

Define spatial summation in neuronal synapses.

• A. The accumulation of postsynaptic potentials arriving in quick succession from the same presynaptic neuron
• B. The summation of excitatory postsynaptic potentials at the same location
• C. The integration of postsynaptic potentials from multiple presynaptic neurons at different locations on the postsynaptic neuron
• D. The decay of signals from a single presynaptic neuron

Answer: (C)

Spatial summation is the integration of postsynaptic potentials arriving from multiple presynaptic neurons at different locations on the postsynaptic neuron. Each synapse generates an EPSP or IPSP locally on the dendritic tree; these potentials spread passively and attenuate as they travel toward the soma. When several PSPs arrive around the same time from different spots, their electrical effects add up at the axon hillock. If the total depolarization reaches the threshold, an action potential is fired. Proximal inputs near the soma have a larger impact than distal ones due to less attenuation. This differs from temporal summation, where rapid successive PSPs from the same presynaptic neuron add up in time. Inhibition can also shape the outcome by offsetting excitation.

Spatial summation is the integration of postsynaptic potentials arriving from multiple presynaptic neurons at different locations on the postsynaptic neuron. Each synapse generates an EPSP or IPSP locally on the dendritic tree; these potentials spread passively and attenuate as they travel toward the soma. When several PSPs arrive around the same time from different spots, their electrical effects add up at the axon hillock. If the total depolarization reaches the threshold, an action potential is fired. Proximal inputs near the soma have a larger impact than distal ones due to less attenuation. This differs from temporal summation, where rapid successive PSPs from the same presynaptic neuron add up in time. Inhibition can also shape the outcome by offsetting excitation.