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Depolarization is essential to the function of many cells, communication between cells, and the overall physiology of an organism. Action potential in a neuron, showing depolarization, in which the cell's internal charge becomes less negative (more positive), and repolarization, where the internal charge returns to a more negative value.
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.
(A brief chemical gradient driven efflux of Na+ through the connexon at peak depolarization causes the conduction of cell to cell depolarization, not potassium.) [27] These connections allow for the rapid conduction of the action potential throughout the heart and are responsible for allowing all of the cells in the atria to contract together ...
A typical action potential begins at the axon hillock [41] with a sufficiently strong depolarization, e.g., a stimulus that increases V m. This depolarization is often caused by the injection of extra sodium cations into the cell; these cations can come from a wide variety of sources, such as chemical synapses, sensory neurons or pacemaker ...
repolarization of the heart toward the positive electrode produces a negative deflection; repolarization of the heart away from the positive electrode produces a positive deflection; Thus, the overall direction of depolarization and repolarization produces positive or negative deflection on each lead's trace.
Repolarization of the ventricle happens in the opposite direction of depolarization and is negative current, signifying the relaxation of the cardiac muscle of the ventricles. But this negative flow causes a positive T wave; although the cell becomes more negatively charged, the net effect is in the positive direction, and the ECG reports this ...
Depolarization propagates through cardiac muscle very rapidly. Cells of the ventricles contract nearly simultaneously. The action potentials of cardiac muscle are unusually sustained. This prevents premature relaxation, maintaining initial contraction until the entire myocardium has had time to depolarize and contract. Absence of tetany.
The larger the stimulus, the greater the depolarization, or attempt to reach threshold. The task of depolarization requires several key steps that rely on anatomical factors of the cell. The ion conductances involved depend on the membrane potential and also the time after the membrane potential changes. [6]