00:01
This question is asking us to identify which of the things on this list will block nerve signals.
00:09
They pose this in the context of anesthetics, but the problem doesn't necessarily have to be specific to that.
00:16
It's just a good exercise in thinking about how these different things work.
00:21
The first thing we'll do is just remind ourselves of what a normal or an untreated neuron might look like.
00:30
So we know that before there's any stimulation, this neuron will be at its rusting potential.
00:39
With some stimulus, there'll be a small increase in voltage due to the influx of sodium ions.
00:47
And this is the beginning of depolarization.
00:49
And once this reaches some critical threshold, all of the voltage -gated sodium ions will open, allowing even more sodium ions into the cell, which will cause a huge spike in potential.
01:08
Okay.
01:10
At this point, potassium e -flux will begin, so potassium ions will leave the cell, repolarizing the membrane.
01:20
There'll be a little overshoot before it comes back to its resting potential.
01:26
Okay.
01:27
So with that in mind, let's think about what each of these kinds of drugs would do.
01:36
So we'll just have very similar graphs for all of them.
01:39
We'll have voltage versus time.
01:43
And this is just to help us think through this problem.
01:46
So the first kind is for a, one that prevents the opening of voltage -gated sodium channels.
01:54
So if we can't depolarize the membrane, we'd basically be stuck hovering around resting potential.
02:06
There may be some slight increases just due to perhaps there's a very strong stimulus or a physical stimulation of this nerve, but it really won't be able to completely depolarize and have an action potential.
02:25
So this is actually a perfect choice for what they're looking for...