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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 ...
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 ...
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 enters in one location and dissipates to others, losing ...
The greater the value of the length constant, the further the potential will travel. A large length constant can contribute to spatial summation—the electrical addition of one potential with potentials from adjacent areas of the cell. The length constant can be defined as: = +
If multiple synapses are simultaneously activated, dendritic spikes may be formed through spatial summation. Spatial summation involves the addition of multiple input signals resulting in a larger signal and possibly a dendritic spike. Hippocampal CA1 neurons have been shown to produce reliable dendritic spike propagation through spatial ...
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).