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Repolarization usually takes several milliseconds. [1] Repolarization is a stage of an action potential in which the cell experiences a decrease of voltage due to the efflux of potassium (K +) ions along its electrochemical gradient. This phase occurs after the cell reaches its highest voltage from depolarization.
Unlike in muscle, repolarization occurs at a slow rate (100 ms). This prevents the heart from undergoing sustained contractions because it forces the refractory period and cardiac action potential firing to be of the same length of time. Repolarization depends on the charges of ions and their flow across membranes.
During repolarization, the sodium channels begin to become inactivated, causing a net efflux of potassium ions. This causes the membrane potential to drop down to its resting membrane potential of -100mV. Hyperpolarization occurs because the slow-acting potassium channels take longer to deactivate, so the membrane overshoots the resting ...
Schematic of an electrophysiological recording of an action potential, showing the various phases that occur as the voltage wave passes a point on a cell membrane.The afterhyperpolarisation is one of the processes that contribute to the refractory period.
The exact function of potassium channels have not quite been revealed, but it is known that they may contribute to the rapid repolarization of the action potentials or play a vital role in buffering the potassium ions at the nodes.
In other words, because the membrane potential inside the axon becomes increasingly negative relative to the outside of the membrane, a stronger stimulus will be required to reach the threshold voltage, and thus, initiate another action potential. This period is the relative refractory period.
In the process of depolarization, the negative internal charge of the cell temporarily becomes more positive (less negative). This shift from a negative to a more positive membrane potential occurs during several processes, including an action potential. During an action potential, the depolarization is so large that the potential difference ...
Ventricular contraction occurs between ventricular depolarization and repolarization. During this time, there is no movement of charge, so no deflection is created on the ECG. This results in the flat ST segment after the S wave. [70] Frames 24–28 in the animation depict repolarization of the ventricles.