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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 muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. [ 2 ] [ 3 ] When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract.
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 ...
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 motor unit recruitment, or rate coding, deals with the frequency of activation of muscle fiber contractions. Consecutive stimulation on the motor unit fibers from the alpha motor neuron causes the muscle to twitch more frequently until the twitches "fuse" temporally.
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
A fused tetanic contraction is the strongest single-unit twitch in contraction. [6] When tetanized, the contracting tension in the muscle remains constant in a steady state. This is the maximal possible contraction. [3] During tetanic contractions, muscles can shorten, lengthen or remain constant length. [7]
All movements, e.g. touching your nose, require motor neurons to fire action potentials that results in contraction of muscles. In humans, ~150,000 motor neurons control the contraction of ~600 muscles. To produce movements, a subset of 600 muscles must contract in a temporally precise pattern to produce the right force at the right time. [6]