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BIOL 2301 Human Anatomy & Physiology I - 2301_lecture13_1006
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00:05 Alright, good morning. You all like some of us are less awake
00:09 normal thursday mornings are kind of aren't they? Yeah, Yeah,
00:16 think they are all right. Hopefully I'll be able to wake you up
00:20 little bit. Alright, what we're do is we're gonna talk about some
00:23 stuff. Action potentials. Yeah. it says in the name it's exciting
00:28 . It's not exciting at all. right. We talked about on
00:34 we talked about greater potentials and great or changes the membrane potential,
00:38 We talked about what a membrane potential just the difference in charge on either
00:42 of the membrane. So, we ways that we change this. The
00:45 way was a great potential where we up channels and islands were allowed to
00:49 through and they kind of leaked in kind of moved along a very,
00:54 short distance and caused a small change or outside really inside the stuff that
00:59 kind of interested in. So, Alright, action potentials are a little
01:03 different. These are going to be distance signals. All right. And
01:09 think there's a really, really easy or a good way to demonstrate one
01:13 these and I just want to go how to define them first and we'll
01:17 an example and then we'll walk through see how it's done. Alright,
01:20 , first off this is gonna be at the initial segment. I realized
01:24 I looked at the slide this it's like, oh look, it
01:27 have a picture of a neuron. where's the initial segment to remind
01:30 Remember this is the initial segment right . The axon hillock. Alright,
01:34 when you you can just draw a of a neuron or just say axon
01:37 . Alright. So, that's where are gonna be starting from. And
01:40 what's gonna happen is we're gonna open channels and we're going to create this
01:44 brief, very rapid, very large in the membrane potential where the inside
01:49 the cell, which was at minus is going to completely reverse itself and
01:53 100 of positive 100 million volts Right? So, it's gonna you
01:57 see it goes all the way up about plus 30. That's 100 fold
02:01 before it reverses itself and comes right down again. Alright, So,
02:07 event when you're looking at a graph this. Look at first what the
02:13 different arms of the graph are. , we have here is we have
02:17 . It's really miller volts. And over here we have seconds, really
02:22 . All right, so, we're volts over time. But what we're
02:25 doing here is we're looking at just small portion of the membrane.
02:29 So, this would be like if guys were on the membrane, I'm
02:32 sitting here staring at one spot asking going on here? And you're saying
02:36 time, I see the membrane change potential and then it goes back to
02:41 ? All right. So, it's wave that you're taking a picture of
02:44 a specific time. If you're looking like this or you can say over
02:49 , this is what that wave looks . It's like, oh, there
02:52 comes and there it goes. So when you see the graph,
02:57 panic about it. And the other I'd point out, when you're looking
03:00 a graph like this is notice that where changes are taking place in this
03:05 instance, the artist has actually drawn to show you where there's change.
03:10 you're not always gonna see that very . You'll just see a line doing
03:14 . So, whenever you see a like that, the first question you
03:17 you, you should be asking is , where do I see change?
03:20 when I see the line changing that means something is interesting is
03:24 So, that's what we're gonna be on is where those little lines change
03:29 . And we're gonna ask the question just a moment, what's happening at
03:32 points to allow this thing to do it's doing. All right.
03:36 what we say is that when we producing an action potential, it moves
03:39 a non detrimental fashion, which is fancy way for saying is once you
03:43 one, it looks exactly the same the entire time of its existence.
03:47 we looked at a greater potential right the opening, it was really,
03:51 high. So there's a massive But as you move further and further
03:55 , it got smaller and smaller and . So that would be detrimental.
04:00 . So non detrimental would be where initiated. I get this big response
04:04 then the entire length that stays the same size. So, it has
04:10 really unique feature of this non detrimental propagation. All right now, why
04:17 is happening is gonna be because of gated channels. We're gonna look at
04:20 . And then the other thing that point out here is that it follows
04:24 all or nothing law. Alright. what that means is that you are
04:30 you create enough membrane potential change to through that this term. It says
04:37 point at which we begin an action . Then you're gonna get an action
04:41 and there's nothing you can do to it. But if you can't reach
04:44 threshold, you won't get one. is where I shock everybody and wake
04:49 up first place. So, when see things like all or none
04:52 This is like virginity. See I'm waking you guys up, you're
04:56 , what? He's going to talk bad things now. Yeah,
05:01 You either are or you aren't. is no in between. All
05:06 You don't like that one. We'll a different one pregnancy. You either
05:11 or you aren't. There is no of pregnant. Okay, All or
05:16 . This is a binary system. either gonna get an action potential or
05:20 won't. All right. So, you see action potential, it's not
05:24 a greater potential where you have a weak action potential, you either get
05:28 action potential or you don't have one potential. You can have a tiny
05:31 potential. You can have a huge potential. Alright. So, this
05:35 the key feature of an action potential to wake your butts up. Besides
05:42 to controversial things. I just all right, we're gonna imagine you
05:47 are a cell. You are an and the axon goes that way.
05:50 right here is the initial segment. you ever done the wave? You
05:54 what the wave is, right? don't know you know how to do
05:57 . Alright. See I am a . Don't I look like a
06:04 right? I do. And see it still is gonna do is gonna
06:08 the initial segment to produce an action . Once an action potential is
06:12 it's like a wave. And watch happens when we produce a wave.
06:16 what happens over there? They're not do it. And then we're gonna
06:18 it a couple of times. Watch . Here we go, Oh,
06:20 guys suck. Big time. See barely you you are not following
06:25 or none rule. You're like, a greater potential now and act potential
06:29 we are all doing this and we're keep doing until we get it right
06:32 . We don't have to stand up that's way too much. We're not
06:36 cool for school. Especially you guys there sitting there. He's not gonna
06:39 me not doing it. I see who doesn't do it and I mark
06:41 down in my grade book. I all your names. Yeah.
06:46 Ready. Here we go, look that. And you see that once
06:50 wave starts it goes a couple of ago and I say a couple years
06:54 , a long time before you were , I went to the Sugar
06:58 Watch uh texas A and M lose Ohio State. So it was a
07:02 time ago. My wife's gonna g why we went. And anyway,
07:07 Bowl has or the Sugar Bowl has tiers. The Superdome 123 tiers.
07:11 had three waves going one on the tier, one in the middle tier
07:16 they're going in opposite directions. And the top tier had one going back
07:20 original direction. And so this was on over and over and over again
07:24 it didn't stop until Ohio State It was crazy. Alright. So
07:28 went around like eight times wild. right. And what you just saw
07:32 we did that that way is that did the exact same thing except for
07:37 people who go for school and they want to be here. We all
07:40 this. You guys suck. I it's 8:30 AM, wake up,
07:46 is your coffee ready? Here we , look at that and it just
07:51 , Oh no I saw over there little this thing over here going
07:55 that's not the wave, that's a dance. Look at me, I'm
07:59 dance right? This is the way hand goes, all the way up
08:04 its peak, can't go any And then it comes right back down
08:06 , doesn't it? And how did know it was your turn to
08:10 You watch the person next year? like okay is it my turn,
08:13 turn and let me see what you . That's what you just did and
08:17 what's going on here. Okay, what we said is that we are
08:22 a specific point now we're gonna do wave again, but we're all gonna
08:26 right here, okay? You know the wave comes? You know what
08:30 supposed to do, Right? So gonna signal when it starts. But
08:32 watch right here. Ready, go everything. You gotta wait your
08:39 Alright, let's try it, let's it again. Alright ready? But
08:43 all watching here, ready to Did you see did he do everything
08:47 you guys did? Right? So you were looking at this if that
08:50 that you're looking at there is your , you can see it's sitting down
08:54 and then it's like okay, it's turn and then it comes back down
08:57 . Do you see how it does right up there. So that's what's
09:01 on with this action potential. It's a result of these ions moving back
09:06 forth. And so what we wanna , you gotta figure out where to
09:09 my stuff. What we wanna do I want to ask the question
09:12 Alright, that's what we want to with, is the how we know
09:17 it is, we can see But how's it doing now? The
09:21 this occurs is first off is the hillock region. Let's go back right
09:29 region right here, the axon hillock going to be stimulated via graded
09:35 Alright, so remember what we did we stimulated, you know, received
09:40 sort of input, some sort of that causes a greater potential, that
09:44 potential created a deep polarization that then depreciated over distance. But if you
09:51 get that greater potential arrive at the potential or at the axon hillock or
09:56 initial segment, what you can do you can start causing a deep polarization
10:00 going to result in this larger All right now, the reason it
10:05 happen is because here we have voltage channels. What causes voltage gated channels
10:10 open, Oh it says in the voltage, what kind of voltage
10:19 Right? So when I adjust or the membrane potential, I'm changing the
10:26 around that voltage gated channel. That is responding to that change in ion
10:37 it. And so it's going to or close. So there's two of
10:41 . So, what we're gonna see we're gonna see a deep polarization.
10:44 is the result of the opening of sodium channels. Alright. So,
10:48 voltage gated sodium channels. So that be this stage right here.
10:53 over here on this side, this the result that re polarization as a
10:57 of the closing of those voltage gated channels and the opening of voltage gated
11:04 channels. Right? So, we're be dealing with these two major groups
11:10 channels. Now, remember when we describing this through describing the cell?
11:16 gonna drive me nuts all day. right. Remember when we're describing the
11:20 , we said that we have leak and we have voltage gated channels.
11:23 depending upon where they're located, results membrane potential changes of interest. And
11:29 now what we're doing is we're focusing on these particular areas where these voltage
11:34 channels are gonna be located. so everywhere you have leak channels and
11:40 at the axon hillock and along the of the axis is voltage gated channels
11:44 gonna. Now the first voltage gated , voltage gated sodium channel. It's
11:49 It's a little weird. Alright. of having one gate, it has
11:54 gates. That's what this is trying show you here. Alright. It's
11:58 a very good job of showing you two gates. In fact, it
12:02 show it at all. I'll be voltage gated channel for you. All
12:05 , So here I've got one gate I've got another gate. All
12:09 I have If I have two that means I can be in three
12:12 configurations. I'm in the first the initial state which is a closed
12:17 but capable of opening. Alright, here I am, I'm closed.
12:22 can't pass through me. Right? so I'm closed. But I'm capable
12:26 opening when I get stimulated changed. know, in other words, the
12:31 around me changes. I can open first gate and now I'm in my
12:35 configuration. Note gate number one is open gate number two is still
12:40 So I'm in the open state. the moment I open this first
12:46 the second gate begins to close. now I'm in my third state and
12:51 in my clothes but incapable of being state. And so it has to
12:55 . And I got to go and reconfigured back into that original state.
12:59 right, so you don't go state open state or state a close
13:04 Be open state. C closed and go back to open again. You
13:08 to go all the way back to first closed state. So close but
13:12 of opening open. Closed, incapable opening. And then re modified to
13:17 closed but capable of opening. There's intermediate between those those two in
13:23 All right. So, those three in order for ions to pass through
13:32 both those gates need to be And it's done for a very,
13:34 short period of time between the two states. The too close states.
13:40 right. So, it's kind of weird voltage gated channel because it has
13:43 two gates, potassium gated channels are and simple because they're just like everything
13:48 . They're just basically one set of . And so if you have one
13:51 of gates, that means they're open they're closed. Right? And so
13:55 , what's gonna open them change in membrane potential around it. That's gonna
13:58 up with the voltage gated potassium channel over a period of time it closes
14:03 again. Now, in order to these things, we're gonna have to
14:11 at a little bit about timing because , remember what our graph is?
14:14 graph is miller volts versus time. so the question we have to ask
14:19 , alright, what's going on during different moments. And so what we're
14:24 do is we're gonna focus here on blue area which is the period of
14:27 . Right? So right now, sitting here when we before we started
14:31 the wave, your arms were at . And so we're asking, what
14:34 the state of these channels and the at the time? Well, remember
14:39 always have leak channels. What's the of the leak channel Always open?
14:43 , you got ions going in and and is maintaining that membrane potential at
14:47 . What are the voltage gated channels like right now at rest? They're
14:52 closed, so nothing's going through So, remember when we were looking
14:56 the leak channels, what was the roughly between potassium channels and sodium leak
15:02 ? In other words, what was permeability? Lots of potassium? Very
15:07 sodium. And your book said it's ratio of 20 to 1 or 25
15:12 1 other books I've seen. It's high as 75 to 1. But
15:15 get the sense is like lots of channels, very few sodium channels.
15:19 potassium is moving out faster than sodium moving in And that drives that membrane
15:24 down to -70 and that's why we there. Alright, so both types
15:29 channels of the voltage gated channels are but they're all closed. So,
15:32 only movement we see our through those channels and you can see those questions
15:36 asked you, they're always on the . I'm asking the questions right?
15:41 a trick. Right. So, can always look up there and find
15:44 answer. All right. So, our state at rest. So,
15:48 established what every cell is doing while waiting to be stimulated. It just
15:52 of like or every neuron is kind like whatever what's going on. This
15:55 the state I'm in. All So, what we want to do
15:59 ask the question, What is the actually at the axon hillock?
16:04 Remember we stimulated the cell someplace around dendrites or on the soma. And
16:09 caused a greater potential. Which is wave that dies down over the
16:14 But if that wave can reach the hillock, remember what does the wave
16:19 ? It represents ions moving and finding partners. Right? And so,
16:25 ions that haven't found their partners are the membrane potential change. And
16:31 if you have ions that are moving they find their way into the axon
16:35 , you've changed the membrane potential at axon hillock. And what's located the
16:40 hillock, voltage gated channels, voltage channels open up to changes in membrane
16:49 . All right. So, if have a greater potential that can have
16:55 greater that can reach the axon that's gonna be a membrane potential change
16:59 the axon hillock. That membrane potential is gonna cause voltage gated channels to
17:06 up. Alright, so, I from the close to the open state
17:11 start flowing in with ions flow. what happens to the membrane potential?
17:15 changes it de polarizes. Which means have more membrane potential change, which
17:22 more voltage gated sodium channels to Which causes more sodium to come
17:28 which causes more voltage gated sodium channels open. Which causes more sodium to
17:33 in until all the voltage gated channels open. This is a positive feedback
17:37 . When we talk about feedback loops you're like, why do I have
17:40 know this stuff? You must be the it must be on the
17:43 That's all I have to know. we're gonna see this over and over
17:46 . So here where we see that change where we go here were flat
17:52 all of a sudden now we're starting climb up. What we're doing is
17:55 watching that feedback loop cycle. We off with a couple of voltage gated
17:59 channels opening. Then that results in which results in more, which results
18:03 more and look at what happens. get this geometric growth. And then
18:08 this point at the very end of region where we reach threshold threshold is
18:15 point where all those voltage gated channels open. And so now we can't
18:20 anymore. So we have reached a where all the sodium is rushing
18:24 And what we've done is we've now the the permeability of the cell.
18:31 at rest permeability favored potassium or sodium . So now I've opened up a
18:39 bunch of vultures gated sodium channels. permeability is flipped. It now favors
18:44 . So that moves us to the stage. So here we've reached that
18:50 where all those channels are open. they're open and they're now allowing flow
18:56 go through them ions to flow And so we see those massive influx
19:00 sodium which causes a massive depressurization Now, when I described this,
19:06 I said, this is about a difference now. So we went from
19:10 a 20-fold difference the other direction and flipped it the other way.
19:14 It's it's just it's just favors sodium . So the inside sales gonna be
19:19 . And we're doing we're gonna rush , rush up and you can start
19:22 out here at the top. Something happening because I should be going in
19:26 What? Let me see if you remember equilibrium potentials. What point would
19:31 stop moving into the cell? Do guys remember about plus 61?
19:36 But look, we stopped here plus . So, something must have
19:41 What what do you think happened? about the channel. How many gates
19:47 the channel? Have to. So first channel opened. What's gonna
19:53 Next. 2nd channel closes. now, this is something that you
20:01 envision because you've been through automatic Right? I mean, this is
20:06 auto door. It's being held in opening, right or it's held
20:10 But look at this, it closes its own If I open it
20:22 Yeah, that's like a voltage gated it opens and it's time to close
20:32 our graph is voltage over time. so what we're gonna see here at
20:39 top this point right there where we we hit that peak. That's the
20:45 when all those voltage gated channels close these remember these are voltage gated sodium
20:51 . But dr wayne you say, you say there is voltage gated potassium
20:54 ? Yes, we'll get to them just a second. So that rise
20:58 deep polarization is a function of the of and and keeping those voltage gated
21:04 channels open for a very brief period time. It's a timed event.
21:10 what they do is they open? then this thing slowly closes. Kind
21:15 like that door slowly closed. And when they close sodium can't come
21:20 Now all things being equal, if had nothing else, it's just we
21:25 have this type of channel then our on the backside. There would be
21:29 polarization but it would take a long would be like that. It would
21:34 get back because what we'd be using we'd be using pumps to pump all
21:38 sodium back out again. But that's what we see. What do we
21:41 in the graph, which direction does go down and it goes down
21:47 doesn't it? So this is a of that second voltage gated channel of
21:52 channel. So the re polarization is the voltage gated sodium channels closing.
21:59 it no longer dominates. And the of the voltage gated potassium channels.
22:05 , the truth is, is the for both of these events is right
22:10 . All right. So, we at that point what we call thresholds
22:16 all the voltage gated sodium channels are and so they go shooting up at
22:20 same point is when all the voltage potassium channels are triggered as well.
22:26 thing is that voltage gated potassium channels like your friend that you tell jokes
22:30 , that doesn't get stuff right? the ones that kind of stare at
22:33 for a second before they go, , now I get the joke right
22:38 , Your slow friend. Do you a slow friend? I have lots
22:42 slow friends. All right. So vaulted potassium channels aren't opening until that
22:52 of time passes. So they're stimulated . But this is when they
22:57 Just kind of moving along this line here or you could say from here
23:00 there. But at this point, timing is perfect and it's perfect because
23:06 shutting one voltage gated channel closed while up the other and that's what causes
23:12 massive re polarization process. And so ladies help me with the color
23:20 Is it lavender? You gotta you be more, you got to be
23:27 to these colors, otherwise I'm just call it purple lavender. Okay,
23:33 . I'm getting three nods up here the front. Alright, so that's
23:37 . What's that color then, Okay, just gotta make sure,
23:41 if I just say purple and purple will just be like, yeah,
23:44 purple. And you guys will be . Alright, Ladies will be
23:49 guys will be like, yep, that's perfect for me. Lavender region
23:55 here represents that period when those voltage potassium channels are open. And so
24:01 seeing this massive re polarization but remember slow channels, It took them a
24:06 time to open. It's gonna take a long time to close. All
24:13 , now, this is where I'm ask a question and this is kind
24:17 a personal question, Have you ever driving really, really fast on a
24:21 and you see that yellow light and just kind of take a couple of
24:24 to respond to it, right? you're like, I don't know what
24:27 do here, you just kind of , well maybe I'll be able to
24:29 through it and then you're like, , it's red and you slam on
24:32 brakes and you kind of slide into intersection looking at people you ever done
24:36 . Please don't hit me. Alright, that's kind of what the
24:41 potassium channels doing, right? It's a slow responder. And so what
24:45 does is it doesn't just stop here rest. It just keeps on
24:49 Alright. And it keeps allowing potassium leave the cell even though we've gone
24:56 thresh or past resting potential now, are we trying to go the inside
25:01 cell if if we have more potassium open, what is our equilibrium
25:07 guys remember negative 89 negative 90 if around that area are good.
25:13 we're trying to shoot all the way there till we reach equilibrium, but
25:17 never gonna get there because those channels eventually close. And so, what
25:21 seeing now, if I uh get , I guess. I don't do
25:27 here, hold on. Oh, me see. No, I
25:30 I do. So this is hyper . I'm just gonna skip over that
25:34 for a second. So, that's what this region is. This represents
25:37 period of hyper polarization as a function those voltage gated potassium channels being open
25:44 a little bit time. A little too long. Alright, But it's
25:48 that much. It's really just creates little dip. And then the sodium
25:52 phds, Wait, wait, no, no. You need to
25:54 back over here. You need to over there and it starts pumping and
25:56 things back to normal. All And so, you can see during
26:00 period of time, I'm slowly returning down to rest and that's what we
26:04 over here. Is that that period rest again now, During all of
26:08 , notice what we've done is we've a channel that was closed and opened
26:12 and then it closed again. And during that period of time we're going
26:16 have to be resetting everything and then other channel opened and then it
26:22 Right? And so now we're basically ions back into their place.
26:27 during this period of time, we two major events that are going to
26:31 around that peak. And that peak simply shows you the the change in
26:41 potential and how many ions were moving and forth. Alright. So that's
26:46 all this is. And this kind shows you again that voltage gated
26:50 So, this is showing you the channel, what's going on? Um
26:54 know, you can see closed opening . It's open now, closed
27:00 So, I guess there's the two activation. There's an activation gate
27:09 Let's go back to our wave. right. So, when we started
27:13 the wave, what did we We had something that triggered it.
27:18 . And then our hands went Right? So, what's going on
27:23 my hands going up? What's Which one's voltage gated sodium channels?
27:30 gotta make sure we have the voltage part in there because remember there are
27:34 of different channels in it. And trigger is a change of membrane
27:38 So, this is the voltage gated channels going up and then this is
27:46 voltage gated potassium channels? Yes. , so that's what's going on
27:52 remember? It's a So, if think of this being a membrane all
28:00 way down this portion of the membrane it's going through an action potential when
28:05 at its peak has allowed sodium to in, which is now stimulating this
28:11 which is triggering it to start And as the sodium comes in is
28:16 to initial initiate a triggering over So, the propagation is a result
28:22 all those ions flowing in. And what ends up happening is we get
28:26 wave of sodium moving through and moving the length of the cell. That's
28:34 action potential propagates itself and why it at that same height the entire
28:41 That kind of makes sense. So, when we triggered it,
28:46 was enough to get that positive feedback to work its way all the way
28:51 the entire length of the axon. that's what you're seeing here.
28:56 So, in the little cartoon this saying, look, this is that
28:59 set. Well, really you can showing in the middle of the axon
29:03 . But this is saying this is deep polarization and then the next region
29:08 stimulated cause it to de polarize. on the back side we're now getting
29:15 ization now we're gonna do the wave more time. But when I say
29:21 , put your hand leave your hands they are. Okay, So it's
29:24 that you guys are gonna be But you watch all right, so
29:27 ready? We're gonna trigger it. ? Go stop. All right,
29:33 , you can see here this is where the peak is, right as
29:37 going on over here, this is front side. Oh I see you
29:40 your hands down and put it back . I'm just here. But you
29:43 see this is where it's about to and over here. This is where
29:48 starting to come down, isn't Right? So what's happened is is
29:52 looking at the peak of that picture you know, I freeze framed
29:55 Right? So what you're doing is looking here at it going up and
30:01 this side, that's where it's going . That makes sense. So when
30:05 looking at the graph, this is drive me nuts. When you're looking
30:10 that graph, you just need to about it. What am I
30:14 I'm looking at a freeze frame at particular location or I'm looking at a
30:19 location asking what's going on over And I'm actually asking where am I
30:24 that period of time now, who I pick on? Which which person
30:35 pick on him. Alright, he's do action potentials as I stimulate
30:41 Alright, I want you to watch . Okay, So every time I
30:44 you do a wave. Okay. ? Gotta go faster, you're so
30:52 of sync, you're just right, a point, right? Where you
30:56 that? And you can't start another potential. Right? You have to
30:59 your whole wave as you're going All right. And that's true for
31:02 membrane as well. What we have we talk about this is the term
31:06 use is called a refractory period. the period of time in which another
31:10 potential can't occur. Alright, so you're going up, I can't initiate
31:17 action potential, can I? Because already going up? And as you're
31:20 down, I can't initiate another action because you have to go through a
31:25 of resetting before another one can So with action potentials there not like
31:32 potential? Remember, we could do a greater potential. Could I take
31:34 greater potential and put another greater potential top of that? What do we
31:38 that summation? Right. Action potentials no summation. They are an all
31:44 nothing event. Right? You're either to get the full one or you're
31:48 gonna get one at all. if you get the full one,
31:51 can't add more to it. the reason for this is because on
31:55 front end you have all the votes channels opened. If I've opened up
32:00 the votes educated channels. Can I up anymore? Not a trick
32:04 The answer is no. Right? I've opened everything, we have everything
32:10 . So, I can't make a action potential if I've already opened up
32:15 the voltage gated sodium channels. okay. So, when you look
32:22 a refractory period, what we have we have two different halves to
32:26 Alright. The first half is referred as the relative refractory period. And
32:30 relative refractory period refers to this light and most of this purple area,
32:36 all of it, but most of . All right. And what this
32:40 is that period of time when I've up all my voltage gated sodium channels
32:45 I can't open up anymore. So can't stimulate another action potential during that
32:49 of time. The other half of absolute refractory period. That period of
32:53 when all my voltage gated sodium channels closed, Right? And I've opened
33:00 some vulture gated potassium channels. If in that close but incapable of
33:04 can I stimulate to start up another potential? So, if this is
33:08 clothes capable openings, I'm in this . Can I open up anymore?
33:13 , I have to go back and to reset, remember? So there's
33:16 three stages closed, but capable of . Open closed, incapable of
33:22 Notice the term they're incapable. I make those terms up just to make
33:26 guys confused. That's to describe the . So, if I try to
33:30 a channel that's closed, but incapable opening. Can I open it.
33:34 . It says so, in the incapable of opening. So those two
33:39 prevent me from having another action And that means we're in that absolute
33:46 period. So it represents that green about half of this purple, right
33:51 here, and then what we have the rest is the relative refractory
33:57 The relative refractory period means, I can stimulate it maybe. And
34:04 what would allow me to do Well, first off, I'm gonna
34:08 voltage gated sodium channels closed, but of them are gonna be capable of
34:12 up, right. In other they've gone through the reset process and
34:17 I can now open them. But also have to be able to overcome
34:21 potassium that's leaving. Right? So I may have some lingering potassium channels
34:27 , there's not enough to prevent me getting an action potential. Now,
34:31 easiest place to see this would be down here, at the bottom of
34:34 this trough in the hyper polarization. , if I'm at the bottom of
34:40 hyper polarization, you can imagine I'm have a couple of potassium channels still
34:44 , but I'm not gonna have a of them open. There's still enough
34:48 gets me below my resting membrane But if I start opening up voltage
34:53 channels, is it possible, do think for me to get up here
34:57 threshold. What do you think? . Right. And the answer is
35:03 , maybe I just have to have strong enough stimulus to cause more and
35:08 voltage gated sodium channels to allow enough to have me reach that point where
35:13 those channels open up. So in in that relative period that's where a
35:20 event has to be stronger. But can result in an action potential because
35:26 are things that can be opened and are channels that can be overcome or
35:32 influx of potassium or out flux of can be overcome. So refractory periods
35:41 there to ensure that action potentials can't . They're there to ensure that all
35:48 none response. And what it it allows us to use action potentials
35:53 a mechanism to code information. so again, this is time you
36:00 what the units are there for the m stands for milliseconds. The length
36:09 an action potential from this point there that point there is about 4:00
36:15 All right. So that's not a big period of time. What we've
36:20 here is we've taken an execution. kind of stretched it out on the
36:23 . So you can see it if were looking at it on a
36:26 that was, you know, a . It would be a line.
36:31 what you see is that action potential rather spread far apart. So it
36:34 you room to bring action potentials fairly together. How do I know when
36:40 hurts more than something else? I increased the number of action potentials in
36:45 period of time. I code um in the number of action potentials that
36:53 being sent when I'm dealing with magnitude greater potentials. How do I encode
36:58 in a greater potential, bigger graded ? Do you remember that magnitude and
37:07 are encoded in the graded potential action , duration and magnitude are going to
37:13 encoded by the number of action All right, so, coming back
37:22 this little picture here. So right at those purple spots, would that
37:28 a relative or a absolute refractory What do you think? Absolute I
37:35 the right answer absolute okay, back on this side. What do you
37:39 relative or absolute relative? And so can imagine I can have another action
37:46 following this one right here. Even though the picture of the
37:49 could I have another action potential moving , Could I have sodium flowing in
37:53 area right here? What do you ? You don't think so?
37:58 it looks like it's already returned back normal. So, I'd say,
38:03 , okay, let's go back and at the picture again. If this
38:06 here represents this right here, then means this area right here is not
38:16 . Come on. Stupid thing is this right there. It's already
38:21 So again, let's go back to wave. I'm just gonna do it
38:25 you because I know you're cool for . If I've done this, can
38:31 do another wave? Yeah, I've it. Yeah. So, I
38:36 keep doing this right. I can't this. But I saw over there
38:42 , Right, this is my If I come all the way up
38:47 come all the way down, I'm to do that next wave, I
38:50 do it this time and I can around and wait. I can do
38:54 this time right close together. But the key thing is is that
39:01 have to bring myself back down and polarize before I'm able to do it
39:07 . Alright, that relative refractory period I'm coming right down and I'm now
39:12 near the bottom. Oh yeah, can go again. That helpful.
39:17 make a little bit of sense kind sort of. Okay, so,
39:25 you're looking at a membrane, when I get another action potential? Once
39:29 first action potential has passed, I get another one started there. That's
39:35 idea. All right. Yes. right. So, if we're looking
39:44 this graph, it's not showing it here. If I had to
39:47 So, we know that this sodium rushing in all the sodium channels are
39:51 . So that's always absolute. Always always when you're dealing with potassium,
39:56 first half of the potassium is more less absolute. Okay. It's just
40:01 you start getting towards the end of potassium area, that's when you're getting
40:06 relative. Now, whatever you have potentials are gonna have refractory period.
40:14 cells have different types of action potentials gonna have different types of refractory
40:19 So for example, even though we talked about, I'm just gonna use
40:22 as an example. Think about your . Do you think your heart has
40:25 refractory period? Yeah, it has write because it's electrical, it produces
40:29 potential. What's interesting is that the period is as long as the action
40:34 and this causes your heart to behave a very specific way. How does
40:38 heart beat? Thump, thump, , thump. Right. So basically
40:46 contraction is the length of an action . So that the refractory period allows
40:52 go through a full contraction relaxation Anyone here want their hearts to go
40:57 this? No, that would be bad thing. So the muscle itself
41:04 the refractory built in for the length the contraction so that you can actually
41:08 the pump action of the heart kind Cool. All right now, that's
41:13 a visual representation. Okay, how fast do action potentials travel?
41:22 , that can be pretty fast. dependent upon two different factors. What
41:26 the diameter of the fiber that you're at? In other words, how
41:30 is that acts on And this one does that accident have Myelin or
41:34 All right now to help you understand . It helps to be an
41:39 And I know that very few of are audio files, you know,
41:42 audio file is right? Someone who music or sound, you know,
41:47 mean, I'm sure many of you like music, but you guys all
41:50 to those little tiny crappy little You know, what you need is
41:53 need a system, you know, an amplifier and big speakers and I
42:00 something. You put them in your and you sit beside me.
42:05 I don't like that. But if do that, do we have anyone
42:08 built speakers built sound systems like Anyone here, brother? Okay.
42:13 if you look on the back of speakers, what type of wires are
42:18 big big thick wires? Right? makes sense. The thicker the
42:24 the less resistance, the less the greater the current, the greater
42:29 current, the better the sound, least in the case of speakers.
42:34 right, this is true for all , thick wires better than small
42:38 Less resistance so current. Remember what talking about when we're talking about action
42:43 . Talking about the movement of ions of ions are currents. Alright.
42:50 you ever wonder why you have to physics to when you're planning on going
42:53 the medical profession is so that you understand the simple concept of electrical
42:58 That's really all this is to introduce to some concepts of electrical conductivity and
43:05 . And that's what your neurons are . They're conducting electricity along their lengths
43:09 , like wires. All right. sometimes you need to create a signal
43:17 really, really fast. Which means have to create a really big wire
43:22 you have a finite space. Would agree you have a finite space inside
43:26 ? Yeah. So, you can if I wanted to make a bigger
43:29 inside me, what would I have do is that I have to make
43:32 bigger meat. And then by baking bigger me, I'd have to have
43:35 bigger wire. Which would mean I'd to have a bigger me. Which
43:38 a bigger wire, which is a me and a bigger one. And
43:40 see the problem. Alright, this is where Myelin comes into
43:44 And what Myelin does is it allows to skip parts of the wire.
43:50 right. And what we're doing here , well, let me first just
43:53 of show you what Myelin is. , so, we've mentioned the maybe
43:58 haven't mentioned these cells yet. I remember with you guys. All
44:01 So, well, Myelin is simply cell. It's either gonna be the
44:08 inside or Schwann cell or the site the central nervous system. Is that
44:11 nervous of the peripheral nervous system. what these cells do is they wrap
44:15 membranes around the axon. And they seclude or exclude a portion of that
44:23 from the surrounding environment. And so going to see a better picture
44:27 But you can kind of see how wraps itself around literally 50 to 100
44:31 . This would be an example of Schwann cell. All good inter site
44:35 do the same thing. But you see here here's the cell body and
44:38 actually extends multiple extensions outward to wrap . So it's actually wrapping hundreds of
44:47 here. This axon is surrounded by , many, many different um neural
44:53 . Now, what we've done here we've created an area of insulation.
44:58 right. So there's this this region the axon that is no longer exposed
45:04 the surrounding environment. And so when have current remember current is the exchange
45:10 ions from the surrounding environment to the inside that axon. So, what
45:15 means is there are areas where I'm having exchange. So what's actually going
45:22 ? There we go. We can it a little bit better.
45:26 so again, this down here is cells Schwann cells or lymphocytes up
45:31 This would be all good vendor But you can see it does the
45:34 thing on the axon, they have little regions that are exposed to the
45:39 environment. This is a better This little region that's exposed. It's
45:45 the node of Ranveer. And it's that the action potentials are taking
45:50 All right. The distance between Note Ranveer to Note of Ranveer is just
45:56 enough that an action potential here which that inflow of sodium is enough to
46:04 that next area. If the if the Myelin was too long,
46:09 you wouldn't be able to get the potential in the next one.
46:12 it's the right distance. So that next area is stimulated. Now to
46:18 clear because I know some of you're miss this. The note of Ranveer
46:22 the space between the Myelin. It not the Myelin. Okay, this
46:27 the note of Ranveer. Not that's just Myelin, Myelin is the
46:33 . And so that you can visualize . I want you to imagine for
46:37 moment me making a gate, In terms of distance, what's the
46:41 In terms of my step? This would be like a normal step
46:45 me. Would you agree roughly that's walking that be a normal step.
46:50 covering a certain distance. I'm leaving between each foot when I do
46:55 This would not be a normal Right. I mean, if I
46:58 like this, it's really hard for to actually create enough force to make
47:03 put more energy and effort into So that would be kind of the
47:09 thing. If they're too far you're not really gonna get action
47:13 So that's why I was trying to at is that the action potentials are
47:17 to reach the next area very, easily. All right. So when
47:25 look at propagation, right, what you said, propagation is simply the
47:28 of action action potential down the length the axon. Right? What we're
47:35 is we can use one of two . Remember we said we don't have
47:38 have Mayan. What does Myelin increases speed, right? So I
47:44 have an axon where I don't have island and I can just basically move
47:48 its length. And when we move the length of an axon where there
47:51 no my island, we have to every little step. It's kind of
47:55 when we're doing the way everything, one of you in theory was doing
48:01 wave. Right? So it's like then here, then here, then
48:05 , then here then here and all way down the length. Right?
48:08 would be like contiguous or continuous. way you can you can use All
48:14 . And so that would be like walking across the floor, toe to
48:20 , right? In order to get one side or the other. If
48:23 walking toe to heel, I'm covering entire length of the floor,
48:29 So that would be continuous. And that's what the top one that we're
48:33 at kind of looks like there's no . So there doesn't there doesn't see
48:37 the second type is salvatori. Salvatori where the action potential leaps or jumps
48:45 node of Ranveer to know to And literally the word salvatori means to
48:51 . Alright. It's salvatore with an . Not with A Y. And
48:54 is to jump latin. And so we're doing. And you can see
48:59 the bottom picture here, I'm getting action potential here, which spreads causes
49:06 opening of the sodium channels, which the second action potential, which spreads
49:10 causes the opening of the sodium which creates the next one. And
49:13 would be like me walking across the like So Right, I'm skipping over
49:20 of the membrane that are being protected the Myelin. So this would be
49:24 fast. So, again, this just a closer view of what we
49:30 saw conduction along the entire length. doesn't skip a portion at all.
49:34 covers every single solitary millimeter of the . That was fun. We'll see
49:43 we can get right back to where was the end. Yeah, see
49:50 works just fast. There we Stop that. Just trying to do
49:54 again. Oh, I think the stuck. Alright, let's try that
50:05 . I think that's where we Okay, so I should Yeah,
50:10 still recording that. That's okay. right. With salvatore, you can
50:19 in this picture how we're just going . No to Ranveer to know to
50:23 over and over again. All So here this will be if you
50:32 the same size uh fiber, make I don't have it. Maybe it
50:37 on the next one. If you the same size fiber do continues versus
50:44 . That the five the signal in in the one that's my eliminated would
50:49 about 75 times faster. And not is it about 70 times five times
50:55 , you're not moving as many ions your ions are now concentrated at very
50:59 locations. So you're using less And so this becomes advantageous for the
51:05 because it enables you to create very quick action potentials. Now looking at
51:13 time here, this is we're actually pretty quick. So, let me
51:16 I'd like to just demonstrate this to . And I'm just gonna show Come
51:22 . We're gonna Yeah. What? don't think you can beat me?
51:29 do you think you think she can me? That's all right. You
51:33 to stretch it out first? You're good. All right.
51:36 what we're gonna do is we're gonna up to the bench. All
51:38 So, what I need to do I need to walk normally. Can
51:41 do that? Alright, I did one year. And the person I
51:44 up as someone I knew who she me. Don't push me. I
51:51 you're gonna win without cheating. All . All right. You're gonna walk
51:56 . I'm gonna walk toe to and I'm just gonna demonstrate that jump
52:02 portions of the carpet by walking Gonna go faster. Ready.
52:07 good sir. Go All right. think that was a fluke. I
52:19 a No. We're gonna do this . I'm gonna get it.
52:27 It's kind of early mark. Get go. She cruised to a
52:36 didn't she? Do you see how you can see, can you see
52:39 salvatori. It's faster. She didn't to do any effort. And she
52:44 literally stepping over just portion of the that I had to step on.
52:49 this is why this is advantageous. , when there are signals that the
52:53 system wants to do. Thank you participating. Yeah. Uh When there
52:58 signals that the brain needs to make , it's gonna use this type of
53:04 ation or fibers that are Myelin ated increase its signal. So, you
53:09 imagine when we're looking at size of and we'll see this a little bit
53:15 . When you have thick fibers with elimination. Those must be pretty important
53:18 that you want to send quickly. right. When you have little itsy
53:21 tiny fibers that have been on my that are gonna be pretty slow.
53:25 so they're going to be not as as signals. That kind of makes
53:29 . Alright. Alright. So, understand when you're looking at these,
53:36 know, contiguous or continuous versus south what that means and understand.
53:41 Please understand the difference between myelin and of Ranveer. Don't confuse the
53:46 I guarantee someone's gonna do that. when we started this whole thing on
53:55 we showed the picture of two Remember they kind of look like this
53:59 neuron with its axon coming down terminating another axon and then that signal goes
54:05 . Right. And so what I do is I want to focus that
54:10 that we just looked at has just an action potential. Action potential travels
54:14 the way down to the axon What is going on at the axon
54:18 ? Why should we care about all stuff? Well the purpose of the
54:22 , the action potential is to create signal from the soma to that distant
54:28 of that axon to tell it to a neurotransmitter. It's not there to
54:33 the next six cell what to The action potential is an internal signal
54:37 one side of the cell to the . That kind of makes sense.
54:41 ? So in other words, when have an action potential in me,
54:44 action potential doesn't leap to the next . When I produce a graded potential
54:49 the cell, I'm not moving electrical From one cell to the next.
54:54 only occurs during electrical synapses of which are less than 1% of those of
54:58 the synapses in your body. Less 1% of them are like that.
55:01 heart is a place where you see types of electrical synapses because all the
55:06 are interconnected by gap junctions. What we're dealing with here is we're
55:10 with two cells that are very, close to each other. All
55:13 And so what we're gonna do is gonna send a chemical signal between the
55:17 . And so, what that action does it serves as a way to
55:21 that signal that it received and its and then create an electrical signal along
55:28 length to tell itself to release a at the far end. Alright.
55:34 that's where that synapses and that's where are now. So, if you
55:38 at this, this is where we come. We've sent the action potential
55:41 and we're now down here at the end over on this side, That's
55:46 we started. So we've kind of around the loop. This would be
55:50 post synaptic cell where you're either looking the dendrite, the soma. So
55:54 I'm doing is I'm telling another cell respond to the chemical and produce a
55:59 potential. That kind of makes So we kind of did a chicken
56:03 egg which came first and we just of worked our way around because it
56:07 matter where we start. We could started at the actual potential and gotten
56:10 graded potential. But I think it's to go the other direction.
56:15 In other words, the first cell stimulated to release to create a signal
56:24 first cell created an action potential that all the way down to the second
56:29 . That's at the second cell I'm . I'm receiving a chemical message that's
56:34 to create a greater potential that can lead to another action potential that can
56:38 go on to a third cell. where we are. All right.
56:43 , we're interested in asking the question the neurotransmitters. What are they?
56:46 do we do that? It is , really basic. Alright. So
56:51 the initial segment I'm producing an action . What are the channels that I
56:56 to create an action potential potential? me, voltage gated sodium and potassium
57:04 they're opening, closing, opening, , opening, closing, opening,
57:06 all the way down. Right? then I get to the synaptic end
57:09 synaptic or the axon terminal and there's more voltage gated sodium potassium channels.
57:15 I'm still moving ions back and forth . Now I have new channels voltage
57:20 calcium channel. So see entire I've created an action potential. The
57:25 of the action potential is to cause calcium channels to open when the calcium
57:30 open. What that does allows calcium the selma calcium serves as a signal
57:36 those vesicles. Now do you remember that first unit we talked about vesicles
57:41 exocet. Oh sis And we said mechanism that we use is we use
57:46 to cause them to merge with the and release their content. And that's
57:49 we're doing here. Is that calcium which is already in position to merge
57:54 the membrane released its content. And content is the neurotransmitter. That's just
57:59 name of the chemical that neurons release tell the next cell what to
58:03 And so that neurotransmitter is released into synaptic cleft. Once it's released into
58:10 synaptic cleft it's gonna diffuse to where less neurotransmitter. So that means it
58:15 pretty much go anywhere. But the is that it will travel across that
58:20 cleft and bind to a receptor on opposite side on the post synaptic
58:26 So this would be the pre synaptic that's the post synaptic cell. This
58:31 collectively referred to as the synapse. neurotransmitter binds the one that makes the
58:37 binds to its channel causes that channel open. And if it's a channel
58:43 allows sodium to come in then that is going to produce an E.
58:48 . S. P. If that opens up and allows potassium to leave
58:53 chlorine to move in that's gonna be I. P. S.
58:58 You see what we've done? We've back around. All right So this
59:06 how we started the whole process in particular case. Right So act potential
59:14 in the opening of calcium channels. vultures calcium channels allow calcium and which
59:19 cause excessive doses of the neurotransmitter neurotransmitter across the class, opens up the
59:25 ? That's the signal for the next to be stimulated. That is the
59:30 because anne PSP or an I. . S. P. Depending upon
59:33 type of channel it is now. long does it take to get across
59:44 ? About 0.32 point five milliseconds. so you can imagine for each time
59:49 signaling between two cells there's a small and we call this a synaptic
59:54 Your brain is full of many many neurons in which there are many many
59:59 synapses. And so the more you to process the greater the delay there's
60:03 be because you're basically sending a signal each of those cells and this is
60:07 exaggeration. It's just the way that can visualize it. Have you been
60:10 in the street and someone honks at and you kind of stare at them
60:13 a second. You're like I don't what to do. Your brain is
60:16 your brain is kind of like Alright. That's not what's going on
60:19 . But you can think about it oh that must be synaptic delay or
60:22 got to process all these different things figure out. Do I get out
60:25 the way I do I just sit and stare at them you know?
60:28 I get in a fight with the . You know there's all these different
60:31 that are going on. Alright. you're processing information. So the more
60:37 your pathway is, the longer the delay is because it just becomes an
60:42 effect. Right? So for each , just add 0.5 milliseconds to the
60:48 it takes to process information. Getting of this thing. All right.
61:01 slide has a lot of information in image and I don't need you to
61:05 the image. Please do not memorize image. All right. What I
61:09 to talk about here is how do turn things off? Alright, so
61:13 neuro transmitter has been now been excessive doses goes binds to its receptor
61:18 of the channel to open. As as that neuro transmitters around it will
61:24 to open up that channel and we want that to happen. We don't
61:28 a channel to remain open for an period of time. We wanted to
61:31 a very, very brief, very quick stimulation that moves and goes off
61:36 disappears. So, what we're looking in this picture here are the seven
61:41 types of of neuro transmitters, transmitters how they're being released. And you
61:46 need to memorize them. Don't It's what it does. It just
61:49 you as an example that they all of use the same mechanisms. So
61:53 we wanna do is we want to . That's the term you end the
61:58 . So how do we go about it? Well, the most the
62:02 one that was actually discovered, I'm gonna say it's the most common way
62:04 if you look at this, you'll that it's not the first thing is
62:07 we're gonna have enzyme down here in synapse. So we say we're going
62:10 destroy the neurotransmitter as a it's being . It's already present. It's like
62:15 most dangerous game of red rover Right? You have your pre synaptic
62:20 , your post synaptic cell. You a bunch of enzymes on the
62:23 They're sitting there ready to chew The neurotransmitter is being released, neurotransmitter
62:27 released. It's like sprint across to into its channel. The enzyme sitting
62:31 going to chew you up before you get there. All right, So
62:35 one place where we see this is the very first one that was ever
62:39 . So acetylcholine is that neurotransmitter nestor race is the enzyme. And
62:45 everyone presumed this is how it all because like it was the first one
62:49 . So, they start looking for . None of the others have this
62:53 of mechanism. So, this is one mechanism, but it's one of
62:57 most common types of of uh So this is gonna be a system
63:05 you see very often just because of commonality. Alright, the second,
63:10 is not shown in any of these is diffusion. So, remember I'm
63:14 out. And so I'm not being to that receptor instead. I'm just
63:22 of floating wherever their stuff. And I could conceivably just float out of
63:27 synapse and if I'm floating on the there's not gonna be channels or receptors
63:32 I can activate. So I don't anything. So simply by wandering away
63:37 a means of termination. It's efficient , but it is one.
63:43 and then something else will destroy you the way. Another type is by
63:48 . All right. And so if look at all these pictures, you
63:51 see there's little arrows pointing up, , this is that neuron itself up
63:56 its own neurotransmitter. And what you're here is basically a recycling. So
64:00 idea here is, oh, I've this stuff but I have things that
64:04 gather up any excess or anything that find in the synapse, I can
64:09 it up, destroy it myself or it in some sort of way.
64:15 neuron itself that released its chemical is for removing its chemical. And then
64:22 or fourthly, you have other cells this is kind of a good one
64:25 kind of see here, you can that we have like astrocytes that are
64:30 around the uh the synapse And it's for all cells they have astrocytes around
64:37 and on them they may have receptors well that don't get stimulated by the
64:41 but are responsible for gathering up that removing it from the synapse so that
64:47 synapse can be stopped very very quickly then it will either break the materials
64:52 and recycle it or it will send materials back to the neuron for
64:58 So while you don't need to know specific, you can see that every
65:02 one of these kind of uses these of mechanisms and all you're doing is
65:08 basically telling that particular synapse is I you to respond quickly and be done
65:13 I want to be able to send signals. I don't want you to
65:15 stuck in an on state all the . I need you to be on
65:19 off on and off as quick as can get you. How we
65:28 How does it feel? Okay. it feel hard or is it it
65:34 goes fast? Sorry. Maybe it's caffeine I had this morning took a
65:39 of caffeine this morning to get Mhm. All right. Any questions
65:47 mean I know you guys are looking the clock going, when is he
65:48 shut up? You know? So kind of motivates me to is I
65:53 get through it all. Alright, talk about neurotransmitters there's no question.
65:59 talk about neurotransmitters again. This can like you have to memorize a whole
66:03 of stuff and you really don't. just trying to show you there's lots
66:05 different types of neurotransmitters, there's about are the neurotransmitters, simply a chemical
66:10 . That's all it is. There's 100 different identified neurotransmitters in the
66:15 Um There's probably more as we go . Um we learn new ones,
66:20 this is this is one that's been of identified most recently, are the
66:24 . So you guys heard of nitric , right, when you go to
66:27 dentist and they give you the the and you're like, you know,
66:31 that's not the only one. Carbon is actually a neurotransmitter. You
66:35 the one that if you um it basically binds to hemoglobin irreversibly,
66:40 now you can't carry oxygen, so terrible. But your cells can actually
66:44 it as a neurotransmitter. And this hydrogen sulfide, that's another gas
66:49 Uh If you don't know, hydrogen is that stuff that makes eggs
66:53 you know, it's like yeah, cells use hydrogen sulfide as a gas
66:58 . But anyway, so the point all these different types of chemicals
67:01 I'm just trying to show you there's variety of different types of neurotransmitters.
67:05 follow different categories. The very first that was discovered, as I pointed
67:09 . The last side was the seat colon a ch is how it's
67:13 And so they discovered this and they like really excited that we understand,
67:18 to each other and so we're gonna and look and see if there are
67:20 other molecules, like a set of and they were not. And so
67:25 was like okay so what do we ? And then they started discovering the
67:28 ones. So there was all this of this idea like you know because
67:33 molecules matched themselves. You know if like find one that means you probably
67:37 a whole family of different types of . So you see the calling was
67:40 this weird one that stands out. used almost everywhere. All right.
67:45 the nervous system, it's between the muscular junction is what makes your muscles
67:50 , right? When you tell your to move, you're using locally.
67:54 right. But it's it stands on own so it falls on its own
67:58 . It's kind of weird right Then have things like the mono means and
68:01 you've heard of these, have you of serotonin? You heard that one
68:06 chart of histamine? But you probably of it. I mean what happens
68:09 I get all stuffy and idea to a histamine? Right. But it's
68:13 it's a neurotransmitter. Alright. Heard ? Maybe not heard of cata cola
68:18 ? But have you heard of Yeah. Have you heard of
68:22 Have you heard of nor epinephrine? . See you have you just don't
68:27 it maybe let me change the Have you ever heard of adrenaline?
68:31 , so adrenaline and its cousin is adrenaline that's epinephrine and norepinephrine. Those
68:36 their names. So those three molecules are collectively the cata cola means they
68:42 into this category called the mono And what the mono amine is you
68:46 right here we start off with with amino acid and we just modify it
68:51 and that's how we end up with different molecules of the cata cola means
68:54 an example. Um tyrosine is another where we where we it's not
69:00 Uh timing is another one where we a bunch of modifications trip to
69:04 here's another one where we do a of modifications. Alright, so then
69:08 have some specific amino acids but dr . I thought amino acids were what
69:12 made proteins with. Yes, uses amino acids as a neurotransmitter. So
69:20 see these. You've probably heard of , glutamate and aspartame are specifically those
69:27 acids and they serve as that google is a specific amino acid. Gaba
69:32 just a modification of glutamate, slight A T P. What do you
69:38 a teepee for energy? Yet? it is. Once again A and
69:42 and A T. P serve as as well. So a lot of
69:48 molecules have multiple responsibilities. I mentioned gasses, we have peptides. Um
69:54 probably heard of uh the opioids, probably more familiar with these things that
69:58 not supposed to take illegal drugs that of things but you are familiar
70:03 I'm sure endorphins, you heard of , right? Endorphins. Our endogenous
70:10 . Your body uses it to protect against pain. Right? So when
70:15 hurt yourself, your body releases endorphins help soothe you as an analgesic.
70:21 . We also have a bunch of that also serve. So basically when
70:25 looking at new york transmitter, they under these different classes. Now
70:29 you don't need to memorize these. will see these again. You will
70:34 these again. You will see a of choline a lot. All
70:37 But you don't need to memorize them . Alright. I don't need your
70:40 rise structure. Please don't memorize When we come back to them and
70:44 introduced to them again. We'll start a little bit more about them for
70:48 . Just understand there's lots of different . You should just kind of know
70:52 in the back of your head and should know that these other ones
70:56 Alright. But we didn't describe what do yet, have we?
71:00 All right, well, I guess we go. That's alright. So
71:07 I said, the state of calling is one of the more common
71:10 This can be a neurotransmitter that both excitatory or inhibitory in nature.
71:16 So what does that mean? It under certain conditions it's gonna excite cells
71:21 other conditions going to inhibit cells. what it's doing is binding to channels
71:25 are gonna be either allow sodium to into the cell or it's gonna allow
71:30 to come out of the cell. right, amino acids. As I
71:35 , we have excitatory ones, Glutamate aspartame. I think those are easy
71:39 remember because they're the two that really of stand out as as as amino
71:44 with that eight at the end, just have to remember. Glycerine is
71:48 inhibitory one and Gaba is also the inhibitory. So, the two the
71:53 that stand out as being the big acids and then glycerin is one that
71:57 sound like the other two. it's the inhibitory one is how I
72:00 it. And then I mentioned all already. Those are the biogenic amines
72:04 the mono means. Alright, my slide, wow. Alright. So
72:12 that we've talked about up to this has been dealing with what are called
72:17 synapses and what we're gonna be looking over the next two units after this
72:22 , which is on Tuesday, if didn't know right after this test,
72:26 we're gonna do is we're gonna do two lectures of the muscles and then
72:29 else is gonna be the nervous All right. And so, What
72:34 gonna be looking at is we're gonna looking at chemical synapses, 99% of
72:40 the synapses in the body or chemical . So you'll see action potentials that
72:46 in the release of a neurotransmitter that a post synaptic cell that produces a
72:51 potential which will then cause stimulation. other cell. About 1% of the
72:59 have electrical synapses. There are some that use electrical synapses, but we're
73:04 kind of ignoring them because they're so and far between. When you see
73:08 synapses, typically this is gonna be cardiac muscle and smooth muscle. And
73:12 you don't really get to deal with muscle all that much until A.
73:16 P. Two. And we're gonna you to the ideas of smooth muscle
73:20 one of these muscle lectures, but not going to dive down deep because
73:24 is really stuff. You see when talking about the digestive system, the
73:28 system and so on, and so . That would be like your blood
73:31 . All right. But here, we see with an electrical synapses that
73:35 two cells are connected to each other gap junctions. So, when we're
73:40 at at the chemical synapse are the cells touching each other? No,
73:44 separated by a space a gap right . Playing the I'm not touching you
73:49 . You remember the I'm not touching game when you're when you're a
73:52 I'm not touching you. They're very close together. All right.
73:57 they're connected with each other. That they're acting in unison. All
74:01 There's no synaptic delay. So the are basically as one cell d polarizes
74:06 the cells begin to de polarize. . And the signal it can be
74:12 , meaning it's not necessarily going in direction, it can go in both
74:16 , whereas when you're dealing with the synapse, you're basically moving from one
74:21 down the line in one direction. , guys, that's the weekend,
74:26 guess. So, remember test on . Don't show up here, go
74:30 A's and I'll see you on
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