PALJ@laccd.edu: Welcome back to this final section on the introductory to the nervous system and in this portion we are going to look at what is happening when I say an action potential travels down the axon. Okay. Did you remember to clock. When I said action. PALJ@laccd.edu: Okay, so PALJ@laccd.edu: In order to understand what happens, we have to understand what the axon looks like before that impulse reaches it so PALJ@laccd.edu: That axon is resting PALJ@laccd.edu: I hope you're not down. Al
right, so when its resting doing nothing. And this one, the red part is showing the cytoplasm, or the XO plaza inside the axon. The yellow part is showing the phosphor lifted. PALJ@laccd.edu: And the blue part is showing the fluid that's outside the PALJ@laccd.edu: So let's start with what looks what's going on on the outside of the axon outside the axon. We have a very high content of sodium so na is sodium and there's lots of sodium molecules and each of them has a plus one charge. So there's
a very positive charge out there. PALJ@laccd.edu: Then we have the plasma membrane. And so the plaza members of fossil lifted by layer. And do you see all these yellow things that kind of look like manholes going through. Okay, so what they are is PALJ@laccd.edu: They are different kind of channels and each channel. PALJ@laccd.edu: Is voltage gays. So when the voltage comes down. These are going to be opening them up and we have one channel that's going to be for sodium. We have a different chan
nel for potassium. We have a channel for calcium. We're going to be talking about the sodium and potassium channels today. PALJ@laccd.edu: And then the purple structure is a different type PALJ@laccd.edu: Of trans mural protein. And this one is going to be a sodium, potassium PALJ@laccd.edu: Where it's going to be moving potassium back into the cell and sodium back out of the cell. And that will require ATP because that's active transport. PALJ@laccd.edu: So let's look. Finally at what's going o
n inside the accent. PALJ@laccd.edu: Inside the axon. We have a lot of potassium. Very little. So outside the axon. We have a lot of sodium PALJ@laccd.edu: And inside the axon. We also have a lot of negatively charged particles which are very close to the plasma membrane. Now we have a lot more positively charged particles outside the axon and inside the axon, it is relatively negative by comparison. PALJ@laccd.edu: So that we say the charges are not even if we were to measure the Millie voltage
outside and set that as zero, the plasma membrane and inside PALJ@laccd.edu: The axon would measure a negative number. So it's negatively charged in there. So we say it is polarized. The inside of the axon is more negative than outside the neuron is PALJ@laccd.edu: Getting back to that sodium potassium pump represented by that purple structure going through the plasma membrane. PALJ@laccd.edu: This is working to keep that in balance. It is pumping sodium out, which means it's pumping it up the
concentration graded and it's pumping potassium in. PALJ@laccd.edu: Which is also going up the concentration gradient. Okay, now it's not a one to one. It's a three to two. But we don't need to know that. PALJ@laccd.edu: I just realized it's maintaining the polarity and is keeping the sodium outside the cell, which is where we want it. And the potassium inside the cell, which is where we want it. And so this process is after transport for both movements. PALJ@laccd.edu: Right now, what's gonna h
appen is PALJ@laccd.edu: That's right action. PALJ@laccd.edu: So if we have an impulse that reaches a threshold, then what's going to happen is deep polarization and here's how it happens. The sodium gates open PALJ@laccd.edu: Where it was sodium. It was outside the cell. So what's going to happen to it. It's going to rush down on its concentration gradient, and it's going to pour into the cell, bringing PALJ@laccd.edu: Positive charges with it so that negativity inside the cell is not going to
stay as negative. And that's where the word D polarization comes from. So here is showing the sodium gates opening and sodium rushing into the cell. PALJ@laccd.edu: All right, then what's going to happen is, next we are going to PALJ@laccd.edu: Close the sodium gates and we're going to have open potassium gates. Okay, so PALJ@laccd.edu: Sodium can no longer come in, even if there's still more of it out. It can't come in anymore because the sodium dates close but now the but the potassium gates o
pen. So what's potassium going to do PALJ@laccd.edu: That's right. There were some more insights. So it's going to work its way outside. And so it's going to be bringing positive charges outside the cell, thereby making inside the axon negative again, which is a process known as re polarization PALJ@laccd.edu: So then the potassium gates going to close. PALJ@laccd.edu: Where's the sodium. That's right. It's inside the cell where we want it outside the cell, whereas the potassium outside the cell
where do we want it inside the cell. So they're in the wrong places. So what's going to happen next. PALJ@laccd.edu: The sodium potassium pump is going to become active again is gone to pump sodium out, it's going to bring potassium and it's not going to be changing the net charges. PALJ@laccd.edu: Now this entire sequence for one area. So t mobile. So you were saying closes potassium opens, but has rushes out and then the sodium potassium pump that whole thing takes three milliseconds. PALJ@la
ccd.edu: But here's how it does not work. It does not work in one little area, we have this opening PALJ@laccd.edu: And then we made some nice and we have this and this one is no it doesn't work like that at all. It's self propagating. So the first place we have this sales force your hand. Okay. And then when this goes to this. The next era area is like this. PALJ@laccd.edu: Well, this one was like this and then as soon as the sentence rushed in here, then it's going to be down here. So this con
version here. Meanwhile, potassium, searching out there. Meanwhile, over here we have the sodium potassium pump every so the whole thing cell propagates going down. PALJ@laccd.edu: As you can see it traveling down so PALJ@laccd.edu: Going back to what we learned before we started with action potential shorting in the axon hillock. PALJ@laccd.edu: traveling down the axon. Now when you say traveling down the axon using certain ketchup. And so the merchants in potassium potassium rushes out. So tha
t's a PALJ@laccd.edu: New study back in potassium, sodium back at potassium back in and you need to do that. The whole life until it reaches the PALJ@laccd.edu: Accenture model, specifically the terminal hutong workhouses an influx of calcium, which causes synaptic vessels veiled with PALJ@laccd.edu: neural transmitters to undergo so psychosis into the snap to class where they are looking for their receptors on the post synaptic sale and once we are done with the introduction. PALJ@laccd.edu: Th
ank you so much. I know this is a difficult section, but hopefully we broke it down nice and simple. So you could get it off all and I will see you soon. And thank you for all your hard work in this class. I really appreciate
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