threshold potential
Quick Summary
The threshold potential is a critical level of electrical charge in biology, specifically within nerve and muscle cells. It represents the point at which a cell's membrane, which normally maintains a negative charge internally (the resting potential), becomes sufficiently depolarized to trigger an action potential.
When a stimulus causes positive ions, primarily sodium, to enter the cell, the internal charge becomes less negative. If this influx reaches the threshold potential (around -60 mV), it triggers the rapid opening of more sodium channels, causing a surge of sodium ions into the cell. This rapid influx reverses the membrane's polarity, creating the electrical signal known as the action potential, which is essential for transmitting nerve impulses and muscle contractions.12
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