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An action potential occurs when the membrane potential of a specific cell rapidly rises and falls. [1] This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of excitable cells, which include animal cells like neurons and muscle cells, as well as some plant cells.
A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. B. Actual recordings of action potentials are often distorted compared to the schematic view because of variations in electrophysiological techniques used to make the recording.
The magnitude of the action potential set up in any single nerve fibre is independent of the strength of the exciting stimulus, provided the latter is adequate. An electrical stimulus below threshold strength fails to elicit a propagated spike potential. If it is of threshold strength or over, a spike (a nervous impulse) of maximum magnitude is ...
In Greek, the root rhe translates to "current or flow", and basi means "bottom or foundation": thus the rheobase is the minimum current that will produce an action potential or muscle contraction. Rheobase can be best understood in the context of the strength-duration relationship (Fig. 1). [2]
Once the action potential has finished in the neuromuscular junction, the used acetylcholine is cleared out of the synaptic cleft by the enzyme acetylcholinesterase. Several diseases and problems can be caused by the inability of enzymes to clear away the neurotransmitters from the synaptic cleft leading to continued action potential propagation.
The signal is a short electrical pulse called action potential or 'spike'. Fig 2. Time course of neuronal action potential ("spike"). Note that the amplitude and the exact shape of the action potential can vary according to the exact experimental technique used for acquiring the signal.
Figure FHN: To mimick the action potential, the FitzHugh–Nagumo model and its relatives use a function g(V) with negative differential resistance (a negative slope on the I vs. V plot). For comparison, a normal resistor would have a positive slope, by Ohm's law I = GV, where the conductance G is the inverse of resistance G=1/R.
Alike individual action potentials, CAP waveforms are typically biphasic presenting a negative and positive peak. The morphological attributes of the CAP (amplitude, spread, latency) depend on various factors including electrode placement, stimulus intensity, number of fibers recruited, the synchronization of action potentials, and conduction ...