critical membrane potential

The critical membrane potential, often referred to as the threshold potential, is a physiological concept crucial for the functioning of excitable cells like neurons and muscle cells. It represents a specific level of electrical potential across the cell membrane that, if reached, triggers a significant event, such as the generation of an action potential.12

Before reaching this threshold, the cell membrane maintains a resting potential, typically around -60 to -75 millivolts, with the interior of the cell being negatively charged relative to the exterior. When a stimulus causes the membrane potential to become less negative, a process called depolarization occurs. If this depolarization reaches the threshold potential (around -58 mV), voltage-gated sodium channels open, leading to a rapid influx of sodium ions. This influx causes a dramatic reversal of polarity, creating an action potential, which is the electrical signal that allows for nerve impulse transmission or muscle contraction. If the membrane potential becomes even more negative than the resting potential, it is termed hyperpolarization.34125