For other uses, see Depolarization (disambiguation).
In biology, depolarization or hypopolarization[1][2] is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. 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.
Most cells in higher organisms maintain an internal environment that is negatively charged relative to the cell's exterior. This difference in charge is called the cell's membrane potential. 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 across the cell membrane briefly reverses polarity, with the inside of the cell becoming positively charged.
The change in charge typically occurs due to an influx of sodium ions into a cell, although it can be mediated by an influx of any kind of cation or efflux of any kind of anion. The opposite of a depolarization is called a hyperpolarization.
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).
^ abZuckerman, Marvin (May 31, 1991). Psychobiology of Personality. Cambridge University Press. ISBN 9780521359429.
^ abGorsuch, Joseph W. (January 1, 1993). Environmental Toxicology and Risk Assessment: 2nd volume. ASTM International. ISBN 9780803114852.
any kind of anion. The opposite of a depolarization is called a hyperpolarization. Usage of the term "depolarization" in biology differs from its use in...
an ECG: The P wave, which represents depolarization of the atria. The QRS complex, which represents depolarization of the ventricles. The T wave, which...
A depolarizer or depolariser, in electrochemistry, according to an IUPAC definition, is a synonym of electroactive substance, i.e., a substance which...
or spreading depolarization (SD) is a wave of electrophysiological hyperactivity followed by a wave of inhibition. Spreading depolarization describes a...
stimulus, there is an efflux of Chloride from the cell, resulting in depolarization of the cell. This causes the GDPs. Once the KCC2 expression is relatively...
perpendicular, would have a depolarization ratio of 1/10 = 0.1, which corresponds to a highly polarized band. The value of the depolarization ratio of a Raman band...
wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120...
A quantum depolarizing channel is a model for quantum noise in quantum systems. The d {\displaystyle d} -dimensional depolarizing channel can be viewed...
larger the stimulus, the greater the depolarization, or attempt to reach threshold. The task of depolarization requires several key steps that rely on...
a Ca2+ mediated depolarization, which causes voltage gated Na+ channels to open, resulting in action potentials. This depolarization is followed by a...
Anoxic depolarization is a progressive and uncontrollable depolarization of neurons during stroke or brain ischemia in which there is an inadequate supply...
will be decreased as opposed to increased. Possibly resulting from the depolarization of the S4 segments and the little time given for inactivation. For long...
pacemaker phase, or slow diastolic depolarization or phase 4. The duration of this slow diastolic depolarization (pacemaker phase) thus governs the cardiac...
enable them to locally depolarize adjacent cells. Gap junctions allow the passage of positive cations from the depolarization of the pacemaker cell to...
that continuously cycle through depolarization- and repolarization phases. However, not every cycle reaches depolarization threshold and thus an action potential...
specific cell rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types...
complex, and the sinus rhythm therefore gives rise to the whole heart's depolarization. Exceptions to this include complete heart block and certain ventricular...
whereby losing their net alignment and thus the material become depolarized. This depolarization can be measured if the material is sandwiched between two ohmic...
efflux of Na+ through the connexon at peak depolarization causes the conduction of cell to cell depolarization, not potassium.) These connections allow...
ions entering the cell cause the depolarization characteristic of an action potential. Like skeletal muscle, depolarization causes the opening of voltage-gated...
displacement of the hair bundle, resulting in depolarization or hyperpolarization of the hair cell. The depolarization of the hair cells in both instances causes...
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