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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).
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.
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.
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 ...
Normal functioning of the central nervous system entails a summation of synaptic inputs made largely onto a neuron's dendritic tree. These local graded potentials, which are primarily associated with external stimuli, reach the axonal initial segment and build until they manage to reach the threshold value. [ 5 ]
General depiction of a motor unit, consisting of a motor neuron innervating a group of muscle fibers. Motor unit recruitment is the activation of additional motor units to accomplish an increase in contractile strength in a muscle. [1]
Summation can be achieved in two ways: [30] frequency summation and multiple fiber summation. In frequency summation, the force exerted by the skeletal muscle is controlled by varying the frequency at which action potentials are sent to muscle fibers. Action potentials do not arrive at muscles synchronously, and, during a contraction, some ...
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: = +