Describe the events that must occur to generate an AP. Relate the sequence of changes in permeability to changes in the ion channels, and explain why the AP is an all-or-none phenomenon.

Video transcript

Everyone. Let's take a look at this question together which of the following best describes the all or non principle of the action potential. Is it answer choice? A, the strength of the action potential is directly proportional to the strength of the stimulus. Answer. Choice B the duration of the action potential is directly proportional to the strength of the stimulus. Answer. Choice C the magnitude and duration of the action potential are always the same regardless of the strength of the stimulus or answer choice D the magnitude of the action potential decreases as it propagates down the axon. Let's work this problem out together to try to figure out which of the following answer choices best describes the all or non principle of the action potential. So in order to solve this question, we have to recall what we know about the all or non principle of the action potential. And we note that the all or non principle refers to the fact that once that threshold stimulus is reached, the action potential will always have the same magnitude and duration, no matter the strength of the stimulus that initiated it. Which means that if the stimulus goes beyond that threshold, the action potential will still have the same magnitude and duration. However, if the stimulus goes below that threshold, there will be no action potential because the stimulus has to reach that threshold in order for the action potential to be generated. And if the stimulus is below that threshold, no action potential will be generated. So looking at our answer choices, which one best describes this principle, well, since the action potential will always have the same magnitude and duration, no matter the strength of the stimulus after that threshold. So answer choice C, the magnitude and duration of the action potential are always the same regardless of the strength of the stimulus is the correct answer. Since the strength and duration of the action potential are not proportional to the strength of the stimulus and the magnitude of the action potential does not decrease as it propagates down the axon leaving us with answer choice C which is the correct answer. I hope you found this video to be helpful. Thank you and goodbye.