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This is called spatial summation and is complemented by temporal summation, wherein successive releases of transmitter from one synapse will cause progressive polarization change as long as the presynaptic changes occur faster than the decay rate of the membrane potential changes in the postsynaptic neuron. [4]
Spatial summation occurs when postsynaptic potentials from adjacent synapses on the cell occur simultaneously and add together. An action potential occurs when the summated EPSPs, minus the summated IPSPs, in an area of membrane reach the cell's threshold potential.
The two ways that synaptic potentials can add up to potentially form an action potential are spatial summation and temporal summation. [5] Spatial summation refers to several excitatory stimuli from different synapses converging on the same postsynaptic neuron at the same time to reach the threshold needed to reach an action potential. Temporal ...
Postsynaptic potentials undergo spatial and temporal summation due to their graded nature. [9] Spatial summation: When inputs are received simultaneously at nearby synapses, their postsynaptic potentials combine. Multiple excitatory inputs combine resulting in greater membrane depolarization (more positive).
Electrotonic potentials can sum spatially or temporally. Spatial summation is the combination of multiple sources of ion influx (multiple channels within a dendrite, or channels within multiple dendrites), whereas temporal summation is a gradual increase in overall charge due to repeated influxes in the same location. Because the ionic charge ...
A similar process occurs in retrograde neurotransmission, where the dendrites of the postsynaptic neuron release retrograde neurotransmitters (e.g., endocannabinoids; synthesized in response to a rise in intracellular calcium levels) that signal through receptors that are located on the axon terminal of the presynaptic neuron, mainly at ...
The summation of these three EPSPs generates an action potential. In neuroscience , an excitatory postsynaptic potential ( EPSP ) is a postsynaptic potential that makes the postsynaptic neuron more likely to fire an action potential .
Fig. 1: Spatial and temporal summation.Two EPSPs innervated in rapid succession sum to produce a larger EPSP, or an action potential in the postsynaptic cell. Coincidence detection relies on separate inputs converging on a common target.