What occurs when a cell reaches threshold potential?

When a cell reaches threshold potential, it initiates a significant physiological event known as an action potential. The threshold potential represents a critical level of depolarization that a neuron or muscle cell must achieve for an action potential to occur. This depolarization is typically a result of the opening of voltage-gated sodium channels, allowing sodium ions to rush into the cell. As the membrane potential becomes more positive, it triggers a rapid and substantial change in the membrane potential, leading to the propagation of an electrical signal along the neuron or muscle fiber. This rapid depolarization is essential for communication in the nervous system and for muscle contraction.

In contrast, resting potential refers to the state of the cell before it is stimulated and is not associated with action potential generation. The hyperpolarized state occurs after an action potential, where the membrane potential becomes more negative than the resting potential due to potassium channels still being open. Negative charge in this context typically describes the resting state or hyperpolarization, which does not occur at the moment threshold is reached. Thus, reaching threshold potential is the crucial activation point that results in the generation of an action potential.