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BIOL 2301 Human Anatomy & Physiology I - BIOL2301_lecture13_1005
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00:03 All right, you move. that was loud. Let's go back
00:07 that. OK, there we Um Thank you for braving this horrible
00:15 storm. Yeah. If, if like me, as you're walking across
00:19 , you saw a big puddle, avoided it and you went around it
00:23 stepped it up your deeper puddle. I've got two wet socks and I
00:27 like a cat that has paper bags its feet. I just wanna do
00:31 the whole time. What we're gonna today is we're gonna talk about the
00:34 potential. I promise you this, is a, again, this is
00:38 uh uh more of an abstract thing we're kind of dealing with. Um
00:42 I'm gonna hopefully try to make this uh with a couple of visuals and
00:47 , uh some class participation things, really what we're trying to deal with
00:51 is a long term signal. So we're talking about an action potential,
00:56 usually think about a neuron, but doesn't just occur in neurons. It
00:59 also occur in muscle cells. And idea is is that you're going to
01:03 a signal at the cell and you're send the signal along the length of
01:08 axon. So some distance away, that you can tell that into the
01:13 to release a chemical message, that the purpose of the action potential.
01:18 for example, if we were looking a cell and this happened to be
01:21 the cell body is, this is SOMA and over there it is the
01:25 terminal, then the distance that you're to send that message is going to
01:29 along the entire length. All So it is a very, very
01:35 , very fast, very big signal travels the length of the cell that
01:40 its purpose. All right. And can measure it again when you see
01:44 graphs like this, you got to what am I doing? I'm sticking
01:47 probe into the cell at a specific . And I'm asking what kind of
01:51 is taking place at this location relative where I'm comparing it to. All
01:57 . So if I was a probe I was sticking it into the cell
02:01 this point, what we're doing is asking over time what's going on at
02:05 particular point and you can see there's nothing going on and then there's
02:09 and then there's big change and then big change again in the opposite
02:13 And then we have this kind of little dip thing before we go back
02:16 normal. So the bottom of the is time the up and down why
02:22 is gonna be the change in And so what we're doing is we're
02:25 from uh from resting membrane potential, sort of change is occurring at this
02:30 location? All right now, with to an action potential, an action
02:36 is always, always, always under circumstance that we're looking at here.
02:40 this is a neuronal action potential. are different action potentials in different
02:44 But when we're talking about a what we're saying is that it will
02:48 have a very rapid change in membrane that is 100 millivolts. So you
02:53 see here we're starting at minus 70 going all the way up to plus
02:57 . Now, those values aren't particularly . But what I'm trying to get
03:01 to understand here is that there is response that occurs that is always going
03:04 happen. And so what it does it follows this rule called the all
03:08 none rule. The all R nun says either you're gonna get an action
03:13 or you're not. So if you stimulating a cell that is going to
03:18 , if you're gonna get an action , it will go all the way
03:21 to 30 and then it'll come back and we're gonna learn why that
03:25 right? But if you don't give a strong enough stimulation that it will
03:30 result in an action potential and you get anything at all. It will
03:34 return back to rest. Now, emphasize this, I'm gonna say something
03:38 little controversial to wake you up. action potential is like pregnancy you either
03:46 or you are not, there is in between. So there's not a
03:50 of action potential just like there's not kind of pregnancy. Ok? I
03:56 say virginity, but I figured that a little bit too early in the
04:00 . Yeah. All right. the reason this happens is because what
04:07 have, we're going to have channels are going to open and close in
04:12 to changes in the membrane potential. these are voltage gated channels. And
04:16 we have already learned about there being that are found on the surface of
04:20 cell. We've talked about, there voltage gated channels and Ligo gated channels
04:25 we've talked about leak channels. So we're doing now is we're kind of
04:29 in here on these voltage gated channels asking where are they and what are
04:33 doing? And so what's gonna happen is when a cell is stimulated,
04:38 going to start opening up voltage gated in a specific fashion in a specific
04:43 to see this detrimental growth. Um uh basically uh grow and then it's
04:50 fall away and then once you get , it's going to, it's going
04:54 go in a non detrimental fashion. detrimental means that it has different
04:59 In other words, it's going to up and slowly come down. It
05:02 do that. It just climbs up it goes down. Now, the
05:05 that I want to do this and going to start here, we're going
05:07 probably do this about 30 times in class just so it comes in is
05:11 going to do the wave. You what the wave is, right?
05:15 been to sporting events. You guys looking at me like, I don't
05:20 , wave is a lot of especially after a couple of beers.
05:23 right, eight o'clock in the Not so much. But what we're
05:28 do is I'm gonna get a stimulus you don't have to stand up,
05:30 just do your hands. OK? we're gonna do the wave. And
05:33 an a potential is basically an influx an e flux of ions moving along
05:39 length of the cell. Remember from stom all the way down to the
05:42 terminal uh ends. And so if were to do the wave, we
05:50 not too, too cool for Come on guys. All right,
05:52 do it again, right. We're fun. We look at that and
05:56 you watch the wave just travels, ? So once the wave starts,
05:59 goes now a long time ago, , my wife is an Aggie and
06:06 went to the uh, sorry, the Cotton Bowl. It was
06:10 uh, Sugar Bowl in New Now, I went to school in
06:12 Orleans. So this was a big . Happened to be the year that
06:15 lane went undefeated. So I was , really excited because I was gonna
06:18 in New Orleans to watch a football on TV. While we went to
06:22 Sugar Bowl to go watch the Aggies to Ohio State like 40 million to
06:26 or something ridiculous. All right. what was cool about the game is
06:30 one? The Sugar Bowl was full two, they have three decks and
06:35 all three decks, they were doing wave on the top deck and the
06:39 deck, it was going one direction the middle deck, it was going
06:41 other direction and it kept going for fourth quarter. Damn Buckeyes. They
06:45 just so, yeah, you ever ? All right. So once you
06:51 a wave, typically that wave continues until something interrupts it. Right.
06:57 so that's true here with an action . Well, it's gonna go until
07:01 interrupted, erupts it. And really thing that's gonna interrupt it is the
07:05 that are going to be found in terminal end. All right. So
07:08 gonna ignore that for right now. gonna walk through it. So,
07:11 we like to do is we like show you, um, the different
07:16 here of an action potential. All . So the first thing I want
07:19 point out here before we do anything do you see how the artist here
07:23 put a bunch of zebra lines on , on your graph? What that
07:28 zebra you're doing is they're trying to your eyes to focus in on these
07:32 areas. But obviously, the thing you really should be looking for is
07:36 are there changes taking place on the graph? All right. So I'm
07:44 actually see if I have a black so that you guys can see in
07:46 back. I think I do. right, let's hope one of these
07:49 works. So when you have an potential, it starts off flat and
07:54 it starts curving upward and then it upward and then it comes back down
07:58 it does something along those lines. you can kind of see there's a
08:01 there, there's a real change there's a change up top.
08:05 there's a change over here and then a change over there and you can
08:08 that they're kind of represented up there that graph. And those are the
08:13 that you should be asking yourself whenever see a change on a graph,
08:16 must have happened. Slope, Do you remember taking that way back
08:21 you're learning your draw the lines or doing the, the Parabolas and stuff
08:26 that? All right, those are numbers and they're just mathematical equations.
08:30 that's really what they're doing. They're at a certain point, the number
08:33 you plug in causes a change in shape of that line. And so
08:38 you have to ask yourself is when doing this action potential, why is
08:41 line changing? Because if you can that question, you're gonna see why
08:46 getting an action potential here. All . So what we're looking at here
08:52 we're looking at a series of All right. So you're gonna see
08:57 and then you're gonna see rep to point where we actually rep polarize too
09:02 . And so we get a polarization then we're going to re polarize to
09:07 back to rest. All right. the things that are responsible for this
09:12 going to be voltage gated sodium channels voltage gated potassium channels. Now we
09:18 know in the membrane. Do we leak channels? Everyone nod your head
09:22 say yes, yes, we And which, which uh leak channel
09:26 we have more of potassium? All . So we have a lot more
09:31 channels than we have sodium channels. that's why we start down there at
09:35 70. OK. So that's kind the first thing. And then what
09:39 little graph is showing you is basically story we're going to tell you.
09:42 all the stuff underneath is telling you channel is opening when. So at
09:46 very end if you want to come and look at this to help remind
09:49 as you're studying, what's going on this is a good way to
09:52 But what I want to do here I want to deal with these depolarizations
09:56 this rep polarization, what's gonna be here? So I said sodium is
10:00 to be the first one. So depo is gonna be the opening of
10:04 voltage gated sodium channels. All And the rep polarization is going to
10:08 the result of a closing those channels B opening up potassium channels,
10:14 So these are not leak channels, are the voltage gated channels. So
10:19 we're doing is we have the doors . They're just shut. What we're
10:22 is we're opening and closing them at times. So the first one I
10:27 to deal with is the weird All right, this is the voltage
10:30 sodium channel. If you look at , what it's going to show you
10:33 that it actually has two different It's not doing a good job of
10:38 either. So I thought this was better picture. All right, I'm
10:40 be your voltage gated sodium channel. have two gates. See my two
10:43 . I got a gate over here a gate over here. All
10:45 I've got a gate that's closed and gates that that's open. If I
10:49 two gates, that means I have states All right. My first state
10:53 a closed but capable of opening See nothing can pass through me because
10:58 gates closed, right? If I'm open, that gate is going to
11:02 wide. And so now things can through me. All right. But
11:06 moment that I open, this is moment that I begin shutting this,
11:10 is the second gate. It's an gate. So we call the first
11:13 , an activation gate. We call second one, an inactivation gate.
11:17 what happens is, is I'm here my first state closed but capable of
11:21 my second state once I'm stimulated is , I begin shutting that inactivation
11:27 And so my third state is I have to be reset. So
11:31 incapable of opening and I have to all the way around to the other
11:35 . I can't go back through that stage. So I go stage one
11:39 stage two to stage three and I to reset again all the way back
11:43 here. At stage one, I go 12321 that doesn't work right?
11:48 close, open, closed, incapable opening. Now, I can be
11:56 again. All right, I'm still . All right now, because of
12:02 three states, there's only a short of time that I'm allowing sodium in
12:07 inactivation gate is like one of these here. If I open this
12:13 hopefully the alarm will go off. you see how it shuts on its
12:18 ? Right. That's kind of what hinge is like on that inactivation
12:23 It's just an automatic closure. It's kind of like, oh, I'm
12:26 to go ahead and close up because been told because of the change in
12:30 shape of the molecule to cause this of me to come closed. So
12:35 an automatic response. There is no stimulation of the channel, it's
12:41 capable of opening open. Now, closed, incapable of opening, going
12:45 those three gates. The second one the voltage gated potassium channel. That's
12:50 . It's just one gate. So I have one gate, I have
12:52 states, I'm open, I'm right? So I'm not stimulated,
12:56 closed. I should do it like . I'm stimulated, I'm open and
12:59 I close back up again. So an easy one. That's, that's
13:03 akin to what you're used to thinking . All right. So what we're
13:07 with here is we're dealing with these channels on top of the leak channels
13:13 we've already talked about on top of uh A TP A that's gonna be
13:18 as well. So what we're gonna is we're just gonna walk through this
13:22 here. We are at rest. this is a state of rest.
13:24 what I'm doing. Risking me brain at minus 70. All right.
13:30 what was going on here? at this time, it would help
13:34 this was actually turned on. So here at this time, the only
13:40 that we have that are open are leak channels. So the voltage gated
13:44 channels are closed but capable of opening potassium channels which are voltage gated are
13:51 and they can be opened if they're . But we have leak channels and
13:55 leak channels that we have are both and sodium channels. We have more
13:59 channels and sodium channels. So at , we're just cruising along at minus
14:03 . All we've got to do is got to just somehow get us stimulated
14:08 we're going to do anything. So is normal now where we are and
14:12 we're gonna be spending, our time on the neuron. We're gonna be
14:15 the Axon Hili. Do you remember the Axon Hili was? Do I
14:20 to draw the picture of the axon the neuron real quick? Yeah.
14:25 . Right. If you had to where the Axon Hili was, where
14:30 you think it is near, near Axon? It says in the
14:37 right. So if you draw yourself neuron, there's your neuron, the
14:44 right here, that's the Axon It's basically the base of the axon
14:51 it travels out. OK. So we're gonna be focusing is we're gonna
14:56 focusing here when we're producing an action . But where do we receive signals
15:02 which part of the neuron. Do receive signals, the dendrites? So
15:06 gonna see them up here and, the SOMA, that's the most common
15:11 that doesn't mean that you can't signal the Axon Hili or the Axon.
15:14 we, you got to think in of this is the receiving part,
15:17 the sending part. So here, we're gonna see is in the dendrites
15:23 on the stoma, we're gonna get sort of triggering event, right?
15:27 , chemical binds up to a receptor a channel, a ligand gate channel
15:33 open up. Now that uh uh is a graded potential. What we
15:40 about on Tuesday and that thing is small ripple. Remember it's like a
15:46 splash and then it kind of moves . So if, for example,
15:52 stimulating right here, that ripple is to travel a certain distance away and
15:57 out. If it's over here, going to travel a distance and it's
16:00 die out and so on and so , right? And so remember how
16:03 talked about EP SPS and we talked IP SPS and we said we get
16:07 sum them up together and we get SPS. Do you remember that?
16:10 a GPS P makes basically makes an or adding up excitatory signals, makes
16:15 bigger and bigger. So what would is I would have a whole bunch
16:19 these and if I can get a enough wave, that big enough wave
16:22 going to make its way here to Axon. Hi. All right.
16:27 , what are we talking about when talk about waves? Just the movement
16:30 ions. If I can get ions through the cell towards the Axion
16:35 what I can do is I can that as a change in memory
16:41 right? So you can think about like this if I throw a rock
16:45 the pond and I create a wave it just goes a short distance
16:50 right? If I throw a bigger in the pond, I get a
16:54 wave. No one's doing the Yeah, that's a different type of
17:02 , right? But you can imagine kind of ripple away, right?
17:05 remember what do we want, we the action potential that goes the whole
17:09 . All right. So the triggering results in a membrane potential change as
17:14 function of the GP SPS. And that, that ripple effect, that
17:20 P works its way towards that Hi, what it's gonna do is
17:25 not going to encounter um leak Now, what we're gonna do is
17:29 gonna find voltage gated channels. All . And which type of voltage gated
17:36 , sodium and potassium channels? All . So what's gonna happen is,
17:42 we're going to open a couple of voltage gated channels? All right.
17:47 if I open up a voltage gated channels sodium comes in what happens to
17:51 cell and sodium comes in hyperpolarize, or nothing depolarize. You got to
17:58 those things together. Remember we said influx equals depolarization. So I get
18:04 if I'm getting depolarization, which is , right? So my triggering event
18:09 excitation. So it's depolarization and it's its way forward and I now open
18:14 a voltage gated sodium channel. I going to get more depolarization because more
18:19 comes in. If more sodium comes , I get more depolarization which results
18:25 the opening of more voltage gated If I open up more voltage gated
18:30 , what happens further, more If I get more depolarization, I'm
18:39 open up more or basically, I'm more sodium to come in which results
18:43 more depolarization, which opens up more channels which opens, results in more
18:49 . See what we have here is have a cycle, right? It's
18:53 positive feedback loop. It's taking the , dropping it on the hill and
18:58 it bigger and bigger and bigger. so that's what we're seeing. And
19:03 you look at the graph, you've this type of curve before I get
19:08 little bit of a of a triggering which results in greater depolarization, which
19:13 in greater depolarization, which results in depolarization and so on. You see
19:18 do we have here? That's why seeing that curve is because of
19:24 It's a geometric growth because each time get a depolarization that makes it to
19:30 , I'm opening up those channels in to the depolarization, which results in
19:35 channels being open, which results in depolarization. That is that big cycle
19:41 you're seeing there. Now, on graph, you can see we have
19:46 dotted line. All right. This line is called the threshold. All
19:51 . Now this is a chicken and statement. All right. You
19:55 which came first? Did the threshold first or did we reach the
20:00 All right, the truth is, the threshold represents the point when all
20:05 voltage gated channels have been opened. right, it's not some magic number
20:11 all of a sudden we reached So now threshold has been reached.
20:14 actually identified says, oh, we keep hitting this thing and so
20:17 everything is going forward. But if look at what's going on here,
20:21 really, oh, it's not the that we're reaching. It's the number
20:24 channels that we're opening and all the or the number of channels we're opening
20:28 all OK. So once I open all the channels and a threshold has
20:36 reached, I now have an action . All right. Now, really
20:42 we're saying here is at this here's my dotted line, there's my
20:48 at that point right there. That when I've reached threshold, that is
20:54 I've opened up. All my voltage sodium channels. And what I've done
20:57 this point is I've now flipped the of the cell. Put this in
21:04 for you. When we had the channels, we had sodium leak channels
21:09 we had potassium leak channels which which leak channel. We have more of
21:13 about how much again, it's a number. So about 20 to 1
21:18 what, what, what we see books will talk about it being 50
21:21 1. Some will talk about being to 1. But what we're gonna
21:25 now is because we have these voltage sodium channels, more and more sodium
21:31 . So that we flip the the opposite direction no longer does potassium
21:38 the influx. Instead we're going to with sodium influx. It's almost a
21:44 difference. So you can think about like this, it's like a floodgate
21:47 sodium coming in and I'm using hyperbole . It's not really a floodgate.
21:51 , it's just that we flipped it . And so as a result,
21:55 we have sodium coming in faster than is leaving by an incredibly large
22:01 So how much sodium do we want get inside the cell? When will
22:04 sodium stop moving into the cell? you remember the number by chance?
22:10 again, not 100 millivolts. That's this is going to that, that's
22:15 difference in change. But remember we that equilibrium potential, we did the
22:18 and I said you don't need to the numbers, but some of you
22:21 anyway, I was just trying to if anyone did it. No
22:23 OK. So remember we said that equilibrium potential for potassium was around minus
22:28 then we said that the equilibrium potential sodium was around plus 60. And
22:32 had that long bar and we kind put the thing. Do you remember
22:36 ? Now? I mean, you'll be able to go. Yeah,
22:39 still see that right. So there keep moving pota or sodium into the
22:46 until equilibrium is met for sodium which at plus 60. Do we get
22:51 plus 60? Take a look at graph. Do we get a plus
22:56 ? No. So something must have because you see we're having this influx
23:02 sodium and then all of a sudden , it stops and switches directions.
23:11 something must have happened? What type channels are involved? Voltage gated sodium
23:19 ? And what do we say about voltage gated sodium channels closed capable of
23:24 open and then they closed. So slam shut. So sodium can't come
23:34 . So we basically return it back its original state. All right.
23:39 , if nothing else were to our graph would do something like
23:44 It's not gonna do this but it be like, oh OK. I
23:47 here to this top. And so what I would do is I would
23:50 return back to normal. But you see does the graph do that?
23:55 , it shoots right back down the direction. So why does that
24:01 All right. Now, most textbooks do a real good job of explaining
24:09 . They're like, oh at this now, all the voltage gated potassium
24:13 open up. We remember we have around. So they're opening up.
24:17 so at that peak, that's when begin opening. And so that's going
24:20 be the result of the rep So again, we flip it back
24:24 other direction. So we're now shooting down towards the potassium equilibrium potential.
24:29 what is that potassium equilibrium potential? just told you to go, we're
24:35 to it. We're running, running, running, running and we're
24:37 to get down there. But we're never gonna get there. All
24:40 . Now, here's the truth, stimulation that opens up the voltage gated
24:46 channels, right? The thing that right here is the same stimulation that
24:52 opening up the voltage gated potassium The difference is that voltage gated sodium
24:57 open up right here. But the gated potassium channels open over here,
25:04 just slower doors. They're like your that you tell a joke to,
25:09 ? And they kind of stare at for a second before they start laughing
25:12 it takes a little while before they getting it All right. Do you
25:16 that friend or are you the Right. So really what we're doing
25:24 we're opening up both channels here. the sodium one open at this point
25:28 it takes a little bit of Remember because the graph is time before
25:32 voltage gated potassium channels open. It happened to coincide when the sodium channels
25:39 and the potassium channels open. And a result now what we're doing is
25:44 getting this massive repolarization event, potassium rushes into the cell. We're moving
25:50 minus 90. But these chat these , they're just like the door we
25:54 opened. So when I've opened the , it's gonna slowly close back.
25:59 so it's going to do so, it does so in such a way
26:02 it doesn't stop at the resting potential , what it does is it
26:10 You can see here, I'm over . So at this point right
26:14 I begin shutting those voltage gated potassium . Now, the vated sodium channels
26:21 already closed and they're going through the of resetting themselves during this period of
26:27 , that takes a little bit of as well. But you can see
26:30 shutting here. And so look at the curve slowly changes, right?
26:35 changing because I have less and less potassium channels open. And by the
26:40 I get to the bottom, they're closed. And so now we've returned
26:44 cell back to its normal state where just a bunch of leak channels that
26:48 open. And not only do we a bunch of leak channels open,
26:51 we also have sodium potassium a pumps man, we screwed up everything.
26:55 got too much sodium inside. We have enough potassium inside. It's too
27:00 outside. So what we're going to is we're going to start moving things
27:02 again to where they started and that the cell to return back to the
27:07 potential. So this is a little showing you what's going on with regard
27:16 the voltage gated sodium channel, You can see here, I'm at
27:23 here, I'm opened, right? I'm slowly climbing that threshold, they're
27:27 open. And what I'm doing is slowly beginning to close. And by
27:31 time I get to the top boom I'm now closed with the voltage gated
27:35 channel. And at the same that's where I'm going to open up
27:39 voltage gated potassium channels. And I've mentioned this slide, the hyper polarization
27:47 . All right. What did I say when we're in that little pink
27:53 , the voltage gated potassium channels are . So you're slowing down the rate
27:58 your, of your repolarization. Oops overshot it. I'm now hyper polarized
28:04 more potassium is leaving the cell than normally would those channels eventually all
28:09 And now I have too much potassium too much sodium inside. I use
28:15 pumps and I'm starting to move everything to normal. And so there,
28:20 coming back up to reach that resting , which is back to the light
28:24 or whatever color that is. All . So this is representing the movement
28:31 the A TP A. So I you're sitting there going, wait a
28:36 . I'm not sure I get all stuff. Ken. Think about the
28:40 . What is the first change that place? This is again playing mouse
28:44 . It's A then B then C D I'm opening up voltage gated sodium
28:49 . I'm getting a great potential that in and reaches the axon helix.
28:53 that can happen that causes this rise the point where I'm getting this positive
28:59 . Now, I got all my gated sodium channels open massive depolarization
29:04 They close shut. That's the same I open up the voltage gated potassium
29:08 . I'm now getting repolarization, they extra time to shut down. So
29:13 I do is I hyperpolarize for this period. Now all the voltage gated
29:17 channels are closed and now I'm pumping back so that I can get things
29:23 to rest. Not as hard right , let's do that wave again.
29:33 right. And I want to show why you can use the wave to
29:36 you see this stuff because your arms just like the graph, right?
29:40 watch what happens here? Let's do wave. So you guys are some
29:45 you are still too cool for school . You're good that you can do
29:49 . Now, what I want you do in Seaworld Shamoo Splash zone.
29:54 right. I want you to talk these two and when I say
29:57 whatever point of the wave you're you stopped in that point.
30:01 But I want everybody to watch them you're doing the wave. Ready,
30:06 stop. All right. Keep your where they are, right? So
30:11 here, what are your, what your hands doing going up or
30:14 They're going down, what's going over ? They're going up, what's coming
30:18 ? Over here? You're going up you're kind of going up. You
30:21 are waiting until you're waiting. look at the graph, look at
30:26 you are on the graph. Because remember this is a graph over
30:30 , right? So if you're putting hands down, where are you on
30:33 graph? You're on the back right? Where are you with
30:39 If you're putting your hands up, put your hand back up.
30:43 where are you? If your hands up, you're at the top and
30:47 where are you? If you're just , you're on that side,
30:51 You can put your hands down. the way you need to look at
30:54 graph is to remember, I'm watching oh I'm going up over time and
30:59 I'm coming back down, over So that's the beginning, right?
31:03 going up and now I'm coming back and so you can keep looking at
31:08 , not so much as a scary blip that's colorized. Instead, think
31:14 it as what is happening in terms the movement of ions back and forth
31:20 if my hands represent those ion OK? It would be awesome if
31:25 guys do that in the middle of exam, proctors will be right on
31:29 of you the whole time. what are they doing? All
31:33 please don't do anything that's good and you in trouble. The thing is
31:38 that when we look at that action , it is being propagated just like
31:42 was propagated in here. All how did you know it was time
31:45 you to put your hand? What watch the person next to you,
31:49 the in front of you. And what you're doing is as, as
31:54 , as a classroom is you are and moving and propagating that action
32:01 which is the wave because the person to you started right before you.
32:07 so that's what propagation and action potential . It starts at the Axon Hillock
32:12 it begins to be propagated forward. when we look at this wave,
32:16 we're basically saying is, oh, I'm watching at a specific point,
32:21 seeing that graph, but at each is its own little graph. So
32:25 can put all the graphs together. basically what I'd see is I'd see
32:28 wave working its way down. It's when we look at this little graph
32:33 , it's just that single point on uh on the Axon, we're just
32:39 at that one little pot spot. why I said focus on these people
32:42 we're doing it because that's just what graph is doing, right? It's
32:46 saying here, I'm just looking at spot. All right. So when
32:51 propagate it's going the entire length and is sequential and it's non detrimental,
32:57 it doesn't die over here. even though they're like, I'm
33:02 they're still doing the wave the same that the wave was occurring that was
33:06 here. Would you agree? I mean, granted there are some
33:09 you who are doing this, that's the wave. That's just really
33:13 Dancing, right? See when I it, you can start seeing
33:20 All right. So this is the opening of the voltage gated sodium channels
33:27 by the sequential closing of the potassium . And so what that means is
33:32 that on the back side of the that the wave cannot go the opposite
33:38 ? Why? Well, remember we voltage gated sodium channels and they have
33:43 states state, one closed but capable opening state, two open state,
33:49 closed, incapable of opening. So are forced in one direction because on
33:56 back side, you're always gonna have vulture gated sodium channels going through the
34:01 of resetting themselves. So unlike a potential, which is just an opening
34:06 closing of a channel that has one , it can ripple in any
34:10 And action potential always has to go one direction. All right. So
34:16 means if we start over there, can't turn around and go back.
34:21 has to go all the way in direction. The place we start Axon
34:30 where we're headed is the action or terminal. Now, the thing is
34:37 the greater potential, we describe that and duration is empowered or encoded in
34:46 strength and the duration of the greatest . Right? Remember little poke,
34:51 stimulation or little greater potential. Big big greater potential. And again,
34:56 not accurate, but it's a good to be able to see it.
35:00 . So the stronger stimulus, the the response action potentials, it's an
35:06 or no response. Right. So much of the language of action
35:13 has to be done in the frequency action. All right, it can't
35:19 done in making a bigger action, action potentials do not sum like graded
35:24 do. It's either you got it you didn't. It's a binary.
35:29 a yes or no. Oh How we ensure the yes or the no
35:35 how do we show, you create this, this environment so that
35:39 only um just this, this yes no. And this is what the
35:45 period is. All right. So refractory period, by definition is a
35:49 of time where there is a period rest or a period of nothing
35:53 That's, that's by its definition. you may have heard refractory period in
35:57 areas. So with regard to the potential, it is the period of
36:01 in which you cannot produce. the truth is, is our refractory
36:07 is divided into two halves. We what is called an absolute refractory
36:11 which means never, never, never any circumstances ever period. The end
36:16 you ever have another action potential stimulated this period of time? And then
36:20 have relative refractory period like, maybe if you have a strong enough
36:24 , you can have an action potential this period of time. So absolute
36:29 ever ever relative, as long as stimulus is strong enough. All
36:36 And so what I wanna do is want to just kind of briefly explain
36:39 . All right. Um I'm just to see if my slides actually.
36:44 . It doesn't, it just stays . All right. With regard to
36:47 absolute refractory period, the absolute refractory occurs. I'm just gonna use this
36:52 it's not marked up there. It occurs during this period of time to
36:57 about right. Here. All somewhere in there someplace. So during
37:02 period of time, you cannot get action potential. It might even include
37:07 . All right. So this would absolute. All right. And then
37:12 relative is gonna be this, all . And so that means both areas
37:18 your period of that's we refer to a refractory period. All right.
37:22 why absolute? All right, if open up all my voltage gated
37:28 can I stimulate the opening of more gated sodium channels? No, thank
37:34 . That, that was like a . Let me just log that to
37:37 . And I'm gonna let you dig sucker right out of the park.
37:40 . So if I can't stimulate the of more voltage gated, can't produce
37:46 bigger or more of an action In other words, if I have
37:50 stimulation that occurs, that results in a potential forming, I can't create
37:55 one immediately right after it to have happen. I'm gonna show this to
38:00 . Ready. Here comes splash I'm gonna, I'm gonna, I'm
38:08 do this. I want you to the for me ready. Just these
38:13 watch them. Ready. Go, , go, go, go,
38:18 . Can you keep up? You keep up, can you right?
38:22 the a in order to produce an potential, what do you have to
38:25 ? You have to go all the up and you have to come all
38:27 way down. That's the, that's wave, right? Like I
38:29 this is not the way this is wave. So if you're getting a
38:33 , you're going here and another stimulation along, you can't start all over
38:37 , you're already going on your way . All right. So the action
38:42 here, the absolute refractory period represents period of time where I've already opened
38:46 all my volt educated channels. I open up any more of them.
38:49 can't start a new group of There are none to do so.
38:53 once you get a stimulation, you to go through that whole process before
38:57 comes back. All right, we're to the other side. All
39:03 on this side, what have I with my vated sodium channels? They're
39:09 ? Are they able to able to yet? So if I stimulate
39:13 are they gonna open? No, have to reset themselves. On the
39:17 side, the volt gated sodium channels closed, but there's not any amount
39:21 work that I can do to convince to open up again. They have
39:24 go through their whole cycle to get . So the absolute refractory period represents
39:30 different things going on here. On front side, all my channels have
39:34 opened. I can't do any opening further on the backside. All my
39:39 are closed and they have to be . So I cannot get another action
39:42 during that period of time. That's absolute refractory period, relative refractory
39:48 OK. Now, as we're starting get more towards this direction, so
39:53 we're starting to get around here, when I begin resetting my voltage gated
39:57 channels. So they're now in stage again, they're closed capable of
40:02 But the problem is is I've actually resting membrane potential. Why have I
40:08 that? What's allowing me to go direction open potassium channels? Right?
40:14 my vulture potassium channels are open. now what I'm doing is in order
40:18 me to get back up here to the e of the potassium, I
40:24 to have a really strong stimulation to , right? So I need something
40:31 to reach a threshold. So really I'm saying is I need to have
40:37 channels open so that I can get to threshold. And I'm trying to
40:42 the opposite flow or the the in outflow of the potassium. So during
40:47 period of time, when my voltage sodium channels are beginning to reset
40:52 I could get one, I just to do more to get there.
40:57 in this particular case, over the difference between the rest and threshold
41:02 about minus 55 millivolts mathematically sorry, is minus 55. So it's about
41:08 millivolts, right? So over that's 15 millivolts. But down over
41:12 , this might be 20 or 25 and so I have to overcome that
41:18 distance. I can do it. just need a pretty big stimulation to
41:22 that happen. Now, why do we need this? Well,
41:27 the way that we encode information and potentials is in frequency and in
41:33 And so what we can do is I have say a muscle that needs
41:36 contract, I don't just send one potential, I send a whole bunch
41:40 them and the closer together they are an indicator of the strength of the
41:47 . So if you have an action that's being sent like this on a
41:51 basis, I want to say I want a stronger signal. I
41:57 have a period of time that I affect, but I have other periods
42:03 time between them that I can affect I can bring them closer and closer
42:07 till they're actually stacked on top of other. And that's probably not so
42:11 right now. But I wanted you understand that it exists for a
42:16 I'm gonna, I'm gonna switch gears just for a second. Think about
42:19 heart because we've been talking about right? And that's where we're gonna
42:22 as neurons. I want to think your heart, your heart has an
42:25 potential, right? If your action got really, really close together,
42:30 would happen to your heart? So heart goes th th th th th
42:34 , thump, thump. So as action potentials get closer, what happens
42:37 the contraction of your, of your ? Th th th, th,
42:41 , th, th, th, , th th, imagine if they
42:44 too close. What would happen? you want that to happen?
42:50 Right. The pumping action of the is maintained because they have very long
42:56 periods. And that means that they get up next to each other,
43:00 a skeletal muscle doesn't have their, refractory periods are just as long as
43:05 action potentials. Um This is the you have to actually see the
43:09 But can I sustain a contraction in arm? Yeah. Right.
43:16 Let's make, let's watch Dr Wayne himself. How long do you think
43:22 can hold this out? All So is my arm contracting here?
43:28 , it's also contracting in other parts my body. Yeah, if I
43:31 this too long. Right. But just a sustained contraction. It's a
43:37 of a series of action potentials that really, really close together to tell
43:40 the most contract and maintain contraction. right. So the refractor period there
43:46 there to ensure that there is space that these things don't stack on top
43:51 each other. They encode strength as as duration, unlike greater potential would
43:58 on top of each other. So this is basically trying to say is
44:05 , it limits the frequency of the potential. So basically the a,
44:09 action potential moves and then what happens the place where it used to be
44:15 it's reset itself can ensure that you get another action potential. Now,
44:21 could try to do waves really, fast. We wanna try to do
44:23 really fast. It, it doesn't work out. Can you visualize
44:30 Yeah. OK. All right. , action potentials are fast. All
44:37 . It's, it's the idea here that they're moving along the length of
44:42 terminal to get a signal from one of the cell to the other
44:45 very quickly and, and they they move the speed of electrical
44:49 So it's just as it moves The thing is, is that we
44:53 increase or decrease the speed based on factors. All right, the first
44:58 is how thick is the axon that traveling down? What's its diameter?
45:04 big? Um Our big or large have less resistance. So there's less
45:12 to ion flow, less resistance to flow means that the Axion potential can
45:16 faster. All right, if I really, really tiny axons, then
45:20 gonna move slower. So big equals , tiny equals slow. All
45:25 Now, would you say that many the signals in your body are pretty
45:29 ? So you want them to get the two points pretty quickly?
45:32 All right. So you can imagine you want is a whole bunch of
45:35 , thick fat axons, but the big, thick fat fat axons you
45:41 , the more space you're gonna need your body, which means you're gonna
45:43 to become larger, which means your are going to have to become
45:47 which means your body is going to to become larger. And you can
45:49 there's a problem in this because it's never ending cycle of getting bigger,
45:53 , bigger, bigger, bigger, ? So second way it has to
45:58 with what we wrap around the it's called myelin. If you have
46:03 presence, presence around the axon, it does is it increases the rate
46:08 transmission because it covers up portions of axon that forces the action potential,
46:15 ions to only enter in at very points. So the Axion potential travels
46:21 . Now, usually what I like do when I do this is I
46:24 to uh demonstrate this, but let's kind of first look at what the
46:28 is. So we've talked about these types of cells already. We we
46:33 mentioned, we said look, there these glial cells, do you remember
46:36 cells way back in the beginning? . So there's two types of glial
46:40 that are, that are responsible for . We have the oligodendrocyte that's located
46:45 the central nervous system. So brain spinal cord and that's what you're looking
46:49 here. Um In this little you can see here is the cell
46:54 of the oligodendrocyte and it has these . These are the dendrites. These
46:59 of what they do is they go they wrap themselves multiple times around the
47:05 . And in between those wrappings, have this little tiny space. So
47:11 wrapping is what is referred to as myelin sheath. In the um peripheral
47:17 system, we have Schwan cells which now being called neuro limo sites,
47:23 ? The same thing again, it on who's teaching your class. You
47:26 probably know both of them. So , neuroma sites. So here what
47:30 have is we have a single cell this is what this picture is demonstrating
47:34 and it's down here. So that wraps itself around multiple times around the
47:39 and basically creates an an insulating So the axon is incapable of interacting
47:46 the myelin to with the surrounding extracellular . It's only in between the cells
47:53 there is an interaction and the distance those cells, right? I
47:59 the distance between the these these blank is just far enough so that the
48:05 potential can reach it. All they're not too far, otherwise they'd
48:09 useless and they're not too close because wouldn't be solving the problem that we're
48:13 to do. We're trying to get action potential to jump from point to
48:17 to point. So these two things going to speed up the action potential
48:24 and the uh myelination. Now, we're looking at here is that little
48:31 space and this is an easier way see it again. This is a
48:33 cartoon showing you the AGA site. usually wrap themselves around 20 to 40
48:38 100 they rather a large number of . And so that's what this is
48:42 to represent. It's like, look, see it's not just one
48:44 . And what you can see is can see this little tiny space in
48:47 here. Those are the neuroma Little tiny space in between the little
48:52 space is where the action is taking . And it has a special
48:56 we call it the node of named the guy that discovered it. Note
49:01 ram. So action potentials are jumping node of Ranvier to node of
49:06 They're not jumping from myelin to My is the installation. The note
49:12 Ranvier is where the action is All right. So here's a better
49:16 . It is trying to show you here, I'm covering up. So
49:20 is happening in this space. This where depolarization is taking place. And
49:24 I'm gonna do is my action potential basically jumping from here to there to
49:28 to there. OK? No, take a look at this propagation.
49:44 on, I like racing. So wanna let you know, I usually
49:51 someone come up here and race me year I, I had a student
49:54 I had like five classes and we very familiar and so I said we're
49:58 race and then what she did was pushed me over and beat me.
50:02 push me over. All right. what we're gonna do is we're going
50:05 race from here to the other just like, right over there.
50:10 right. I want you to walk . Ok. Come right. All
50:18 . So on your mark, get go. Now you're just taunting
50:26 Ok. That's good. All Do you see him walking?
50:33 You can sit down what you wanna it again? You wanna beat me
50:36 ? Make you feel better and he's shit. All right. Why did
50:40 beat me when we, when we ? He was, he was taking
50:45 strides, right? So did we the same distance? Actually, he
50:50 further than he needed to. But , we covered the same distance.
50:52 we covered the same distance, But how did I cover the
50:57 I covered the entire distance by literally toe heel, toe heel,
51:02 So this is the way that I walking when he was walking. He
51:05 taking normal strides. And so he's doing this. Is he covering the
51:10 surface of the, the floor? taking jumps or leaps doesn't seem like
51:19 because it's like how we walk, ? But what he's doing is he's
51:23 taking a jump over that small space his two steps. All right.
51:28 so what myelination does, it allows to jump over portions of the
51:35 which is why it speeds you All right. So what we're looking
51:39 here when we're describing this type of action potentials are propagated are moving along
51:46 length of the axon. And they to cover the distance of that
51:50 If they're going to be covering the length of the axon where there's no
51:55 in place, they're closed channels all the entire length. And so what
52:00 have here is a type of propagation called contiguous. Some books will say
52:05 continuous. And so I think both are now acceptable. So why is
52:09 continuous? Because you have to do entire length without skipping any portion of
52:13 axon? All right, it's pretty . All right. But we also
52:19 saltatory Salto literally means to jump And so revier to not to,
52:28 to over and over. And so you have two axons of the same
52:38 , the speed Pakistan would be All you're doing is skipping over
52:50 So that's what we're kind of looking here. So here again, just
52:53 to show you here, it is . That was the to to heal
52:56 . So you can see the entire of the cell is undergoing the depolarization
53:02 the repolarization along its length. So why it's slow. It's just doing
53:07 little bit the whole plasm membrane with . What am I doing? I'm
53:14 over, I'm going from the Axon jump over the myelin. Not of
53:18 beer. Not to ran beer. , to ran beer, not to
53:21 beer. No, to ran All right. I'm skipping over the
53:25 because it prevents the move or the exchange between the extracellular fluid and the
53:34 . This is just the same All right, showing that same
53:40 These are far enough apart. So when this depolarizes, it causes depolarization
53:46 . So that you get that depolarization the same thing, you can't go
53:51 . Why refractory periods, you can't backwards. Why refractory periods. All
54:03 . Now what happens here? There's lot of benefits. So it's not
54:06 faster. I mean, it is times faster. So that means you
54:10 keep your, your axons really, tiny, which is good. But
54:14 other thing is that you end up less energy and your body is all
54:17 less energy. So this is much your advantage. OK. So does
54:24 kind of make sense? So, far what we have is we have
54:26 action potential that's different than a graded . Graded potentials are the things that
54:32 in the stimulation or, or creating action potentials at the Axion,
54:37 That's what we saw, we saw the information cause of the action potential
54:43 be formed forms of the axon Then it's going to move down the
54:47 the act or the axon by the and closing of voltage gated sodium
54:51 opening and closing of the voltage gated channels, right? Repolarization, hyper
54:59 , repolarization. And it does so quickly when we look at those graphs
55:05 I'm just gonna hop back real quick wrong direction. When you look at
55:12 graphs, they don't show you the scale. All right, they just
55:18 it's time. And in fact, one doesn't even say it's time.
55:22 I know it does actually, it show the time scale. Do you
55:24 up there milliseconds? So the length time from the front to the back
55:28 of that is four milliseconds. So that perspective. Think about a
55:33 Now divide that second into 1000. right, that's a millisecond. So
55:40 can imagine in a second, you have, well, there's four
55:44 So you could have 250 action potentials a second. That's impressive. All
55:54 . Last a little bit here. questions about this so far? Because
56:03 I wanna do is I wanna tie we've learned together. I wanna take
56:07 stuff about the greater potentials. I to take the action potentials and I
56:11 to put this into the frame of of this is what's going on in
56:14 neurons. This is what's going on your muscles. All right.
56:17 most of the focus here will be , right? But is going
56:23 All right, just slightly differently. , first off, we get down
56:26 the axon terminal and what we're doing we're not jumping that action potential from
56:31 sending cell to the receiving cell. , what we're doing is we're sending
56:35 signal to that terminal end over here say, hey, we need you
56:39 tell the next cell through chemicals that supposed to fire or not fire,
56:45 ? The message doesn't matter at this . Typically, when we said we're
56:49 to excite the next cell in, it. If I'm inhibiting the
56:55 then I'm producing an IP sp in next cell, right? We talk
56:59 IP SPS, right? So what doing is we're just sending a
57:04 So the a a potential format of axon hili, it goes down the
57:07 of the axon goes down to the . The terminal's job is to release
57:11 chemical message. All right. So what we're looking at. We call
57:15 a chemical synapse. All right, serving as the signal to tell the
57:20 cell what to do. And so we're gonna do is we're going to
57:23 a response in the next cell. is the, the cell that's sending
57:27 referred to as the presynaptic cell. , the interaction between the two cells
57:32 referred to as the synapse. And the receiving cell of the postsynaptic
57:38 So now we come back full circle I excite the postsynaptic cell, I
57:42 an EPSP right? And exci post . If I'm exciting the postsynaptic cell
57:50 creating inside that receiving cell. An sp. Yeah. So this is
57:59 going on down at the terminal I keep pointing down here because you're
58:02 terminal end, right? So here have, here's your synaptic knob,
58:07 ? This is your receiving cells. that's your postsynaptic cell. You can
58:10 the vesicles are in here. You imagine I'm opening, closing what type
58:14 channels, voltage gated sodium channels and gated potassium channels. So when we
58:23 down to the axon terminal, we just bounce that and then come all
58:28 way back the other direction. Instead we have in the terminal end is
58:32 have a different type of voltage gated . We have a voltage gated calcium
58:37 . All right. So the receiving is responding to the ax potential because
58:42 using the same language depolarization. We're bringing in sodium to have that
58:48 Keep going. Instead, we're allowing into the cell so that it can
58:54 that cell to move that vesicle holding chemical message, the neurotransmitter and
59:00 hey, you need to move up the surface and release that signal.
59:06 ax potential travels down. Next we have voltage gated calcium channels,
59:12 ax potential results in the opening of voltage gated calcium channel, calcium floods
59:16 the axon terminal. The calcium is signal that tells the vesicle to open
59:22 . So it opens up, it neurotransmitter into the synaptic cleft. So
59:27 what the little diamonds represent are the . And they don't know where to
59:31 . They're just following the rules of . So they out they go and
59:36 , these two, the distance between two things is almost nothing. I
59:41 , remember we talked about the, not touching you again, right?
59:43 that's kind of what's going on And then what we're going to do
59:47 that neurotransmitter then binds to a receptor the postsynaptic cell. If the neurotransmitter
59:53 excitatory, it's gonna open up that or open up that channel and you're
59:58 have sodium flow in. If it's neurotransmitter, it's gonna open up that
60:03 and potassium is gonna flow out. when I have sodium flow into the
60:08 , what's happening over here in this , what do I get? Epsp
60:15 ? And if, if potassium flows , what do I get an IPO
60:19 SP and it's hyper polarization. All . So you see what we're doing
60:23 ? It's just simply starting where it's going back to where we
60:28 we chose to start with the EP and the IP sp. So a
60:34 potential results in if it's an excitatory potential and if it's strong enough,
60:39 results in the production of an action of the Axion heli, which then
60:43 down the length of the cell and the release of neurotransmitter that is then
60:47 by another cell which is then stimulated either produce an EPSP or an IP
60:53 . So the key thing here to about EP SPS and IP SP is
60:55 they are occurring in the receiving They're not part of the, the
61:00 portion. They're on the receiving Ok. Now, I want you
61:10 imagine for a moment you're walking across as you do, I've seen you
61:15 do it. You're looking down at phone and everyone's really frustrated because everyone's
61:20 to leave the garage at the same and they turn four lanes into two
61:24 , right? We've all experienced It's lots of fun and they're still
61:27 construction in both directions. So it's fun to get out of there between
61:31 , but you're walking across the street you hear this blaring of a horn
61:35 you look up and you see this or this bus coming at you.
61:40 do you do? How long did take you to do it?
61:44 she said move. That's a good . You move. You don't just
61:47 at it but a lot of they just, they freeze right
61:52 I'm, I'm creating this scenario because want you to focus in on the
61:56 here, right? You freeze Because your brain is in a moment
62:00 indecision. You're like, what do do? In this case? The
62:03 is that's really what's going on? I jump? Do I duck?
62:07 I run? You don't know you're just, that's what's going
62:11 But part of your decision process is at all your options and that's kind
62:15 why your brain is in the midst freezing. It's like, OK,
62:19 I do this? And so it's information. Do I do that?
62:23 so you can imagine in this network decision makers have multiple cells,
62:29 Let's just say there are four cells are. So, I mean,
62:34 many synapse? Two synapse? Three ? All right. So four
62:43 there'd be three synapses between them, of those synapses. Remember what are
62:48 doing? We're taking neurotransmitter and we're it out and it's just floating around
62:53 . I don't know where I'm supposed go. I'm just gonna go
62:55 there's where I bind and it binds . And so this path between the
63:00 cells, which is not very small a synaptic delay. All right,
63:05 it takes time for the neurotransmitter to from point A to point B.
63:09 the more neurons you have in a , the more synaptic delay you
63:15 right. So if I have three , that's gonna be, have a
63:20 delay than if I had two which would be a greater delay than
63:24 I had one synapse. So for , for example, right? You
63:30 , to reflex, if I take baseball throw at you, what are
63:32 gonna do? You're gonna catch See. So you're gonna duck
63:35 you're gonna catch, right? But , that's a reflex, right?
63:39 don't wanna have to think. well, there's baseball coming up my
63:42 . Hm. I don't know, should I do about this?
63:45 Because by the time you become you're being in the head, synaptic
63:52 is what occurs, the more neurons invite into the process. Ok.
64:00 it takes about 0.3 to 0.5 milliseconds a signal to go between cells.
64:07 you can imagine this can be pretty if you have 10 50 100 neurons
64:12 the process, it starts taking its . All right, what's important about
64:25 particular picture is first, don't memorize , right? I don't want you
64:29 memorize the picture because these are very neurotransmitters. And I'm not going that
64:34 with you guys. But why I this picture is because it actually demonstrates
64:38 we're trying to learn here whenever you a cell, right? So if
64:43 release a neurotransmitter out of the snap the synaptic cleft stimulate that cell as
64:50 as the neuro transmit. So, potentials are supposed to be just be
64:55 notes. Hey, I want you turn on or hey, I want
64:58 to turn off, they're not meant sit there and constantly send that
65:03 Remember, action potentials are very, brief. And so if I want
65:08 keep stimulating the cell, I'm gonna a lot of action potentials. So
65:12 every time I release a neurotransmitter, need to remove that neurotransmitter from
65:18 that environment. I've got to terminate signals, terminate the message and there
65:22 different ways that we do it. so what we have in this little
65:26 here are the seven primary groups of . And what that, what each
65:30 these do is they show each of four ways to terminate. So the
65:34 one that was ever discovered was this is the enzymatic destruction. And so
65:38 just presume this is how it all and that's what's being demonstrated over
65:42 So this is a Coiner neuron, releasing Aceta Colline. You will know
65:46 Aceta Col. It is like the . All right. This is what
65:51 your muscles. It plays an important in the nervous system. It's all
65:55 the place, but it's primarily in is, is how we learn about
66:00 . And so what we found out when we release that neurotransmitter, there
66:04 an enzyme that sits in that synaptic and it's like the worst game of
66:08 Rover that you've ever seen. You remember playing Red Rover? You didn't
66:13 Red Rover. Oh, we gotta outside and do that right now.
66:17 . Yeah, it would be a of fun. So let me explain
66:19 Red Rover is. Basically you get lines of kids and what they
66:23 This is a kamikaze run to decapitate , right? So yeah, it
66:28 it awesome. It was, it great. So what you do is
66:31 up and you say Red Rover, Rover, let Lucy come over and
66:33 Lucy looks over there a little OK. I've got to do this
66:37 so she tries to find the weakest between two people and everybody is holding
66:42 like this. And so you're basically to grip it and you run over
66:45 fast as you can and you try break through the line. If you
66:49 a nice strong line, you're gonna on that poor kid and really just
66:54 horrible things. It's awesome. And other, if you're strong enough,
66:57 gonna cause a lot of bruising on arms. It is great. Let
67:03 like to know and pe was we had recess. Did you guys
67:07 recess growing up? Are you Because I look at my kids,
67:11 don't know how to play football because don't play football. They didn't do
67:14 , they didn't hurt each other. mean, you know, I
67:17 you see those memes about growing up Gin Xers and how um how life
67:22 much more dangerous. That is not exaggeration. I mean, we did
67:26 have seat, I didn't have a belt required in my car until I
67:29 18 years old. Yeah, we fun. I told you I rode
67:37 bike off a roof into a swimming . No, you, no,
67:43 was fun. Am I dead? . Got a couple of scars on
67:49 chin. Didn't get from that. fell off a cliff. But that's
67:52 story for another day. Anyway. that enzyme is sitting in the cleft
67:58 Red Rover, red Rover, let come over and so it through and
68:03 the enzymes in there going chop you , chop you up, chop you
68:06 , chop you up, chop you . And so you're destroying the uh
68:10 just as it's being released. Only small portion of the neurotransmitter makes it
68:14 second way. Well, I'm not over that line. I'm just gonna
68:18 over here. So you can diffuse of the snap the cliff and then
68:21 other enzymes gonna deal with you a bit later. You know, you
68:24 to get rid of the neurotransmitter. if you're not in the cliff,
68:27 can't stimulate the cell. So that's way you can terminate, you can
68:31 up, there could be uptake by neuron. So um these all show
68:35 kind of the uptake right here. can see how they are all showing
68:39 here it is, it's been released in you go and So, what
68:41 doing is you're basically releasing your but you already have things that can
68:45 pick it up and destroy it or it. So, what you're doing
68:48 you're, again, you're removing the from that particular cleft. And the
68:55 , and this is being demonstrated up is there can be other cells uh
68:59 the synapse. And typically, you think about it like this. A
69:03 is basically two cells talking to each like, so, so see,
69:08 , we're not really touching even though touching and then you can add another
69:11 coming along and basically wrapping the and that there are uptaking the other neurotrans
69:19 take uptaking those neurotransmitters and either destroying or recycling them. And that's what
69:24 is trying to show you are these cells um that are around the
69:30 But the big point here is as as I have neurotransmitter in the
69:34 I'm going to be stimulating the next down the line. So I want
69:37 get rid of that as fast as can. I just want a quick
69:41 . And so these four different means the way that I do it.
69:45 , it doesn't matter which one which I'm, I'm not gonna ask
69:48 , what does the Colleen do? is this? Um That's not so
69:53 . The last little bit here is with the actual neurotransmitters. Um
69:59 neurotransmitter simply is the chemical signal. just a fancy word. We use
70:04 brain transmitter. It's basically a signal two cells. So they're acting in
70:10 Perrin fashion. All right. But can also stimulate yourself. That would
70:14 acri but we're not gonna really talk that. We are working in
70:18 in the context of the neuro of synapse. And the truth is,
70:22 these are like the big families, there are hundreds of different neuro
70:27 And so the family is the first , is the sea of Coleman,
70:32 one discovered and they were so we finally figured out how neurons talk
70:36 muscles. And so this is going be the way that all neurons talk
70:40 each other and it just happened to the only one that did it.
70:43 there's no relative to Aceto Cole. it's its own old class. But
70:47 can see up here we have You've heard of CTA Cola means you
70:51 not have heard the big name, you've heard of the specific ones.
70:54 you heard of dopamine? Ok. you heard of Adrenaline? Ok.
70:59 adrenaline has another name. It's called and that's what's up there. The
71:03 I that's Epinephrine. So Adrenaline you've of. And so that's a Cine
71:08 then uh Epinephrine has a cousin, called Norine. Um And so that's
71:13 Cine as well. Um Serotonin, heard of serotonin? Have you ever
71:17 of histamine? Yeah. You normally I hit the B, the B
71:21 B all blocked up, right? , but it is an actual
71:26 So, these are what are called monoamine. What you have done is
71:29 take an amino acid and you've modified , you actually have a acid
71:38 Ok. Glutamate as, or amino . Gaba is a, and
71:49 we've learned about a T PB that energy, but it's also a
71:57 . It gets cut A MP, also a transmitter. There are gasses
72:03 your brain use. These are called or the gas emitters. And so
72:07 heard of nitric oxide, that's when go and get the gas, the
72:11 gas, you know, laughing carbon monoxide and hydrogen sulfide. These
72:18 gasses that are used in very, small amounts to tell cells what to
72:21 . It's weird, you know, would, who would have thought um
72:26 also small molecules, small uh these are the peptides. So there's
72:30 whole bunch of different ones. The that you're probably most familiar with up
72:34 is the endorphins, right? So heard that word. Um these are
72:39 small peptides that are used in signaling pain. For example, typically,
72:43 are gonna be secreted with other ones then there are the econo which uh
72:47 , it's just a large family of that play signaling as signaling molecules.
72:53 really what I wanna do is just these particular ones out. So,
72:57 , the, this is one, see if it's up here. I
73:00 . Yeah. There it is. you, if you want to look
73:02 , see what it looks like it be excitatory inhibitory depending upon where you
73:06 it. All right. So this not uncommon. It's gonna be.
73:10 sort of role does it play? you'll see something that's excitatory, something
73:13 inhibitory. This is one where it play both roles. It's both in
73:17 central and peripheral nervous system. And I mentioned, it's not related to
73:21 others. We're gonna see it when talk about the neuromuscular junction, um
73:26 acids, uh The specific ones are and asperate. These two are both
73:31 . Why glutamate is so important? of your synapses in your brain use
73:36 . All right. So you may heard of dopamine, but glutamate is
73:39 big boy Gaba and glycine are So if glutamate is excitatory, you
73:46 it, you get Gaba. So excitatory inhibitory. And then finally,
73:49 mono means um these are, are be synthesizes from amino acids. And
73:54 if you look up here uh finally . So if you look at the
73:58 right up here, that's tyrosine in orange one. So the tyro and
74:04 we've done is we've done small modifications how you get the mono means.
74:09 up there, you can see you can see Norine, you can
74:12 epinephrine all you've done is you've just some slight modifications to that original amino
74:18 . And that is that neurotransmitter so you're on the last slide ya before
74:26 get up and leave though. And do this slide. Let me make
74:29 quick announcement and then, um uh we can go. All right,
74:35 electrical synapse does exist 99.9% of the we're going to be looking at are
74:40 to be chemical synapses. The stuff we just described a neurotransmitter between two
74:46 , but electrical synapses occur as There is no synaptic delay when you
74:51 an electrical synapse because there's no space you have to travel between literally the
74:56 being sent between the cells. So using a gap junction where the signal
75:01 from one cell to the next over over and over again. The,
75:05 key example of this, of of an electrical synapse and it's not
75:09 only place, but it's the muscles the heart, they're all interconnected with
75:13 other. So what you're doing to the contraction in the heart is the
75:16 potential is sent from cell to cell cell to cell to cell very,
75:19 quickly. And that's why you get overall excitation. You will also see
75:25 communication. Whereas a normal a potential a potential travels only in one
75:31 you are going to have a presynaptic and you have a postsynaptic cell,
75:34 not sending signals back and forth like , it's only going in one
75:39 All right, that being said, a very, very quick announcement.
75:42 , um, our exam is on . Right. There are a couple
75:47 people that still haven't signed up for exam for a slot. You need
75:50 do so, but I want you know if you see a date other
75:54 Tuesday the 10th, don't sign up that date. Your date is Tuesday
75:59 10th. All right. If you up on a date that's not Tuesday
76:04 10th, they're gonna, they might you in but there'll be no exam
76:07 you. All right. So I'm letting you guys know because this happened
76:10 a couple of makeup exams where they're , oh, I have, I
76:14 three dates up there and so they up and it caused lots of
76:17 So only on the date that we've assigned you sign up for it.
76:24 . Uh-huh, why aren't you
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