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Usage of the term "depolarization" in biology differs from its use in physics, where it refers to situations in which any form of polarity ( i.e. the presence of any electrical charge, whether positive or negative) changes to a value of zero. Depolarization is sometimes referred to as "hypopolarization" [1] [2] (as opposed to hyperpolarization).
This is the depolarization phase. When the membrane potential reaches the threshold potential (around -20 to -50 mV), the cell begins to rapidly depolarise (become more positive). [16] This is mainly due to the flow of Ca 2+ through L-type calcium channels, which are now fully open. During this stage, T-type calcium channels and HCN channels ...
(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 ...
While the maintenance of ventilation/perfusion ratio during regional obstruction of airflow is beneficial, HPV can be detrimental during global alveolar hypoxia which occurs with exposure to high altitude, where HPV causes a significant increase in total pulmonary vascular resistance, and pulmonary arterial pressure, potentially leading to ...
The budding yeast, Saccharomyces cerevisiae, is a model system for eukaryotic biology in which many of the fundamental elements of polarity development have been elucidated. Yeast cells share many features of cell polarity with other organisms, but feature fewer protein components.
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.
Contraction of heart muscle cells requires depolarization and repolarization of their cell membranes. Movement of ions across cell membranes causes these events. The cardiac conduction system (and AV node part of it) coordinates myocyte mechanical activity.
This is followed by a hyperpolarization-activated "sag" current that contributes to slowly depolarizing the membrane potential. An inward Ca 2+ current through T-type calcium channels is the last phase, and the main current responsible for the large transient depolarization. This overrides the other currents once T-type channels are activated.