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How does ion movement across a cell membrane create or stop electrical impulses?

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Electrical impulses, or action potentials, are generated and regulated by the movement of charged ions across the cell membrane through specialized ion channels.

Generating Impulses

Cells maintain a resting potential where the interior is negatively charged relative to the exterior. When a stimulus occurs, sodium channels open, allowing sodium ions to flow into the cell. This influx makes the interior less negative, a process known as depolarization. If the membrane potential reaches a specific threshold, sodium channels open fully, causing a rapid surge of positive charge that creates the action potential.12

Stopping Impulses

To stop the impulse and return the cell to its resting state, the membrane undergoes repolarization:
* Sodium Channel Closure: The sodium channels close, halting the influx of positive charge.2
* Potassium Efflux: Potassium channels open, allowing positively charged potassium ions to diffuse out of the cell, which restores the negative internal charge.12
* Active Restoration: Ion pumps eventually reset the original ion concentrations, preparing the cell for future signaling.32

Various chemical agents and toxins can modulate these channels, either inhibiting or prolonging these electrical events.4