What is the term for the occurrence when a stimulus causes the axon membrane to depolarize to a certain level?

The term that refers to the occurrence when a stimulus causes the axon membrane to depolarize to a certain level is known as threshold potential. This is a critical point in the process of generating an action potential in neurons. When a stimulus reaches the neuron's membrane and depolarizes it to the threshold level, typically around -55 mV, it initiates an all-or-nothing response, leading to an action potential.

At this threshold, voltage-gated sodium channels open, allowing sodium ions to rush into the cell, further depolarizing the membrane and resulting in the rapid spike seen in an action potential. Without reaching this threshold potential, the neuron would not fire, making it a crucial element in neuronal signaling.

Resting potential refers to the stable, negative charge of the neuron when it is not transmitting a signal. Membrane potential is a more general term that describes the voltage difference across a cell’s membrane, encompassing both resting and action potentials. The action potential itself is the result of exceeding the threshold potential, but the term specifically describing the level of depolarization required to trigger it is the threshold potential.