Which of the following is true regarding action potentials compared to local potentials?

When discussing action potentials in comparison to local potentials, it's important to understand their fundamental characteristics. Action potentials are indeed characterized as being irreversible, meaning that once they are initiated, they will propagate down the axon without stopping or reversing back. This is due to the opening of voltage-gated sodium channels which lead to the rapid depolarization of the membrane.

In contrast, local potentials can vary in magnitude and often decay over distance, meaning they can become weaker as they travel along the neuron and may not always lead to an action potential if the threshold is not met. The graded nature of local potentials indicates that they can vary in strength depending on the stimulus, whereas action potentials have a consistent amplitude once initiated.

Thus, the defining feature that makes action potentials distinctly different from local potentials is their irreversible nature, ensuring that once the threshold potential is reached, the process of depolarization and repolarization will continue to completion without reversal.