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Afterdepolarization
Afterdepolarizations are abnormal depolarizations of cardiac myocytes that interrupt phase 2, phase 3, or phase 4 of the cardiac action potential in the electrical conduction system of the heart. Afterdepolarizations may lead to cardiac arrhythmias.
== Early afterdepolarizations ==
Early afterdepolarizations (EADs) occur with abnormal depolarization during phase 2 or phase 3, and are caused by an increase in the frequency of abortive action potentials before normal repolarization is completed. Phase 2 may be interrupted due to augmented opening of calcium channels, while phase 3 interruptions are due to the opening of sodium channels. Early afterdepolarizations can result in torsades de pointes, tachycardia, and other arrhythmias.〔Cranefield, PF: The Conduction of the Cardiac Impulse. New York, Future Publishing Co. 1975〕
Afterhyperpolarizations can also occur in cortical pyramidal neurons. There, they typically follow an action potential and are mediated by voltage gated sodium or chloride channels. This phenomenon requires potassium channels to close quickly to limit repolarization. It is responsible for the difference between regular spiking and intrinsically bursting pyramidal neurons.〔Nelson Spruston, "Pyramidal Neurons: dendritic structure and synaptic integration", 2008. Nature Reviews. Neuroscience.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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