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An action potential occurs when the membrane potential of a ... One consequence of the decreasing action potential duration is that the fidelity of the signal can be ...
The slope of phase 0 on the action potential waveform (see figure 2) represents the maximum rate of voltage change of the cardiac action potential and is known as dV/dt max. In pacemaker cells (e.g. sinoatrial node cells ), however, the increase in membrane voltage is mainly due to activation of L-type calcium channels.
After initiation of an action potential, the refractory period is defined two ways: The absolute refractory period coincides with nearly the entire duration of the action potential. In neurons, it is caused by the inactivation of the voltage-gated sodium channels that originally opened to depolarize the membrane. These channels remain ...
Afterhyperpolarization, or AHP, is the hyperpolarizing phase of a neuron's action potential where the cell's membrane potential falls below the normal resting potential. This is also commonly referred to as an action potential's undershoot phase. AHPs have been segregated into "fast", "medium", and "slow" components that appear to have distinct ...
Image of a myocardial action potential. Effective refractory period in green. In electrocardiography, during a cardiac cycle, once an action potential is initiated, there is a period of time that a new action potential cannot be initiated.
The prolongation of the action potential duration and refractory period, combined with the maintenance of normal conduction velocity, prevent re-entrant arrhythmias. (The re-entrant rhythm is less likely to interact with tissue that has become refractory).
The strength-duration time constant (chronaxie) and rheobase are parameters that describe the strength-duration curve—the curve that relates the intensity of a threshold stimulus to its duration. As the duration of a test stimulus increases, the strength of the current required to activate a single fiber action potential decreases.
The threshold potential is the potential an excitable cell membrane, such as a myocyte, must reach in order to induce an action potential. [6] This depolarization is caused by very small net inward currents of calcium ions across the cell membrane, which gives rise to the action potential.