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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.
Hyperpolarization is a change in a cell's membrane potential that makes it more negative. Cells typically have a negative resting potential, with neuronal action potentials depolarizing the membrane. Cells typically have a negative resting potential, with neuronal action potentials depolarizing the membrane.
Previously, electrophysiological studies have provided the evidence that there is a Ca 2+-mediated depolarization, which causes voltage-gated Na + channels to open, resulting in action potentials. This depolarization is followed by a period of hyperpolarization mediated by Ca 2+-dependent K + channels or GABA-activated Cl − influx. [citation ...
This depolarization is called an EPSP, or an excitatory postsynaptic potential, and the hyperpolarization is called an IPSP, or an inhibitory postsynaptic potential. The only influences that neurons can have on one another are excitation, inhibition, and—through modulatory transmitters—biasing one another's excitability.
Threshold decrease is evident during extensive depolarization, and threshold increase is evident with extensive hyperpolarization. With hyperpolarization, there is an increase in the resistance of the internodal membrane due to closure of potassium channels, and the resulting plot "fans out".
The initial influx of calcium ions also poses a small cellular depolarization, causing the voltage-gated ion channels to open and allowing full depolarization to be propagated by chloride ions. Some plants (e.g. Dionaea muscipula ) use sodium-gated channels to operate plant movements and "count" stimulation events to determine if a threshold ...
Depolarization increases the Na + current through the persistent channels, resulting in a lower rheobase; hyperpolarization has the opposite effect. The strength-duration time constant increases with demyelination, as the exposed membrane is enlarged by inclusion of paranodal and internodal membrane.
This change in charge, voltage, and membrane potential generates an electrical signal referred to as an action potential. Action potentials are used for communication between neurons within nervous tissue. [4] Graph showing the depolarization, repolarization, and hyperpolarization of an action potential.