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Summation, which includes both spatial summation and temporal summation, is the process that determines whether or not an action potential will be generated by the combined effects of excitatory and inhibitory signals, both from multiple simultaneous inputs (spatial summation), and from repeated inputs (temporal summation).
Temporal summation: When a single synapse inputs that are close together in time, their potentials are also added together. Thus, if a neuron receives an excitatory postsynaptic potential, and then the presynaptic neuron fires again, creating another EPSP, then the membrane of the postsynaptic cell is depolarized by the total sum of all the ...
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.
Central sensitization of the dorsal horn neurons that is evoked from C fiber activity is responsible for temporal summation of "second pain" (TSSP). [15] This event is called 'windup' and relies on a frequency greater or equal to 0.33 Hz of the stimulus. [15] Windup is associated with chronic pain and central sensitization. [15]
Examples of graded potentials. Graded potentials are changes in membrane potential that vary according to the size of the stimulus, as opposed to being all-or-none.They include diverse potentials such as receptor potentials, electrotonic potentials, subthreshold membrane potential oscillations, slow-wave potential, pacemaker potentials, and synaptic potentials.
Therefore, in order to achieve threshold and generate an action potential, the postsynaptic neuron has the capacity to add up all of the incoming EPSPs based on the mechanism of summation, which can occur in time and space. Temporal summation occurs when a particular synapse is stimulated at a high frequency, which causes the postsynaptic ...
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.
Medial temporal lobe structures such as the uncus, the parahippocampal gyrus and the hippocampal formation, are also intimately related to the incisura. The principal vascular structures coursing along the middle incisural space are the posterior cerebral artery and the superior cerebellar artery which pass around the brainstem, parallel to the ...