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BIOL 2301 Human Anatomy & Physiology I - 2103_lecture12_0301
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00:02 Good morning, everybody. Yeah. right. So, today is first
00:08 need to remind you, we have test next Tuesday, right? And
00:11 after next Tuesday. Then we have class, Which sucks because spring break
00:16 on friday. Mm hmm. I'm about the spring break party. Not
00:23 that one day in there that we have to come in and pay attention
00:28 we're going to do. Um If been, if you've been paying attention
00:31 have been following things, the natural of things would be like we learned
00:34 the skeleton, then we learned about . And then we learned that skeleton
00:38 there to help with locomotion in some . And so the next natural thing
00:42 be muscles, But it's not. the reason it's not is because we
00:48 to understand the mechanics of communication between that use electrical and chemical signaling
00:58 And muscles need to do that. other words, you can't make your
01:01 work unless there are um, ions to change the membrane potentials and which
01:09 the muscles to contract yada, yada yada. So, unfortunately,
01:14 next two lectures are the two most lectures. You'll get over the course
01:20 the semester. All right. And not gonna pretend like this is fun
01:24 . It might be for one or of you. All right. But
01:27 the rest of y'all, you're not sit here and go, this is
01:30 . It's physiology. I don't Just tell me how muscle works.
01:35 tell me how a neuron works. . So you've got to just kind
01:40 shut that down and just kind of with this for a second. All
01:45 , The second thing I'd say is because it's abstract, it can be
01:49 to understand. So, let me you guys when you were reading this
01:52 , then it makes sense to Yeah, I've seen it's just gonna
01:57 one head is going Yeah, I I got it. Alright,
02:00 understanding that there's a complexity here that can do that is going to kind
02:05 drag you down. So if it's and it's a little complex, that's
02:09 be where we're gonna be. We're have an aversion to it, and
02:13 gonna say hopefully this won't be on exam, right? Because that's what
02:18 do. I will just tell you my exams are designed around my
02:23 right? You already know this. 50 questions. We have six
02:27 that means there's roughly eight questions per . Alright, I don't sit there
02:32 go, well, you know, don't care if they know this stuff
02:34 actually go through and I was here's this lecture. These are the
02:37 that I have talked about. Let ask a question from each of these
02:41 and that's what the test look Oh, you mean if I study
02:45 ? Yeah. Alright. So, we're gonna do is we're gonna look
02:49 this question of, how do cells using electrical potentials and all starts with
02:57 review of stuff that we've already talked . So, this is what this
03:01 . Is basically saying, look, already learned that a cell is a
03:04 and that in that compartment what we're to do is we're going to have
03:08 concentrations of an ion relative to the of that compartment. Alright. And
03:14 we have things that aren't even what those things that I don't even want
03:17 do, they want to become Right. So, there's this idea
03:23 equilibrium that wants to occur naturally between there is this equilibrium. All
03:31 That's your chemistry slash physics lesson for day. All right. So,
03:36 plasma membrane is that barrier that creates compartment And that unequal distribution creates this
03:45 that wants to create equilibrium. So, that's our first step.
03:50 we're gonna see a lot of pictures graphs like this on it. And
03:55 going to point out that there's nothing to memorize. It's the concept that
03:59 important. Okay. And if there's there's a number that I want you
04:02 learn, I'll say learn this All right. But for right
04:06 the idea here is don't memorize these . You can see though that there's
04:12 differences. Can you see the big ? Yeah, like, right
04:16 for sodium, there's a tenfold difference sodium on the inside versus the
04:21 So, there's lots of sodium on outside. Very little sodium on the
04:24 . So, sodium wants to move the cell. Okay, that's number
04:30 . Now, the membrane itself remember semi permeable, meaning it's not going
04:36 allow things that have charges through So, what we have to do
04:39 we have to have a door to the charges to move between those two
04:44 . Alright. And so this is the purpose of an ion channel
04:48 It's the door. Alright. They're in terms of what they're going to
04:53 to pass through them right there, meaning that all you got to do
04:57 open the door and things are going move in the direction of their
05:03 They're going to move from an area high concentration and area of low concentration
05:06 far. I've taught you nothing have I? All right,
05:11 Now, there are two types of that we are interested in today.
05:15 right. The ligand gated now in channel, this is where you have
05:23 like a door that can exist neither open or the closed state.
05:28 When it's open, things can pass when it's closed. That gate doesn't
05:32 for things to pass through. leak channels are really gated channels,
05:40 we don't call them gated channels, channels are channels that are in a
05:45 state of openness. So things can pass through all the time. That
05:50 , there is a leak channel. that door ever closed? Never.
05:56 . It's always in an open So we could refer to that door
05:59 there, that passageway as a leak . So they're always going to be
06:05 . And there it's showing you here modality, their voltage gated meaning that
06:09 thing that causes them to open is change in the membrane potential. That's
06:14 lot of big words, we're not worry about that just right yet.
06:16 basically what it's saying is that because that membrane potential because of our around
06:21 , it's always in an open state because it's in an open state,
06:24 can move back and forth naturally without sort of stimulation. Okay,
06:32 So when we talk about gated channels general, the ones that are most
06:39 to us under the when we talk muscles and we talk about neurons are
06:43 to be these two types right The ligand gated and the voltage gated
06:48 we said, is where we have sort of message, some sort of
06:51 signals. Something physical that comes along literally binds to that channel and when
06:58 binds to it's like putting a key a lock and that gate opens up
07:02 allows things to pass through. And once you remove that leg in that
07:06 closes back up. All right, voltage gated, on the other hand
07:11 a whole bunch of charges around. so when you change the charge around
07:17 channel, just like the ligand, going to cause the gate to open
07:22 close depending upon which type of voltage channel you're looking at. But for
07:26 purposes we're gonna say it's going to up. And when you open it
07:29 , that allows things to pass All right. And so, how
07:32 this do this? It's you I mean it's not magic or
07:36 basically, if you look at the acids, you see all the different
07:39 . So when you change the charges some that's already charged, it changes
07:43 interaction when I took my jacket off minute ago, my whole shirt was
07:48 staticky because it's you know, basically and it's stuck to my body in
07:53 , uncomfortable ways, right? Because charge that had been built up by
07:58 jacket and the shirt was then transferred from my shirt to my body,
08:03 would be kind of an example. , there's just a change in
08:09 All right. So, when we're about membrane potentials, we're talking about
08:15 plasma membrane that's impermeable to ions with ions on either side with gates that
08:22 be opened or closed depending upon whether not their voltage or ligand,
08:27 And in some cases they are leak , which means that they're always
08:33 Now. Generally speaking, if you at any cell in the body,
08:38 statements are true. Okay. if you're looking at this going I
08:42 understand whenever you see a bracket around ion that refers to a concentration.
08:48 right. So, it's basically telling how much is there. Alright,
08:52 generally speaking and here are the values you want to compare and see does
08:56 , Am I seeing what I'm seeing there? It says if you look
09:00 potassium, the concentration of potassium inside cell is going to be greater than
09:05 concentration of potassium on the outside of cell. When that happens, that
09:09 that potassium is gonna naturally leave through channels from inside the cell to outside
09:16 cell. Alright, so potassium is leaking out of the cell. All
09:23 . The opposite is true for there's more sodium outside the cell then
09:27 inside. So sodium is naturally leaking the cell through legal channels. Chlorine
09:34 another island which we have lots of there's more chlorine on the outside than
09:39 is inside. So chlorine would naturally to move from the outside of the
09:44 to the inside of the cell. lastly when we're dealing with calcium,
09:48 , there's more calcium on the outside on the inside. So calcium naturally
09:52 to leak into a cell. Now pointing all these things out because as
09:57 go through not just in this but in a and p.
10:00 When you start talking about the heart when you start talking about all these
10:04 , these all the cells that you're at have the same sort of behavior
10:09 gonna be focusing on these two for most part. But these will come
10:13 later. And if you just want kind of look and see what those
10:17 are again, don't memorize the You can kind of see Oh
10:20 look on the outside over here. lots relative to their There's a tenfold
10:24 . So I can see why sodium go from the outside of the cell
10:27 the inside of the cell if you some absolute numbers. Now, here's
10:34 you already know. We've not talked it yet, but it's important to
10:39 , right? When you're dealing with , ions have charges. All
10:45 ions of the same charge repel each , ions of similar charges are attracted
10:52 one another. That's not anything Right? Hopefully. You learned that
10:56 long time ago in Earth Science and grade right now, with that in
11:02 , if you think about your body your body electrically charged. In other
11:08 , if you went and touch would you electrocute them? No.
11:14 right. You do not. You're number of positive and negative ions in
11:18 body are equally matched. All So you're electrically neutral. But where
11:25 ions are are not exactly creating electrical . Alright, There's an uneven
11:33 And so what happens is because we this uneven distribution of ions that means
11:39 there are electrical gradients just like there chemical gradients. So, when we
11:43 that there's lots of sodium on the of the cell and very little sodium
11:47 the inside of the cell. That's chemical gradient, right? sodium wants
11:52 move into the cell. But you look at it from a different perspective
11:55 you can say, okay, I a bunch of positive charges on the
11:59 of the cell, and I have positive charges on the inside of the
12:02 . When I'm just looking at So, those positive charges want to
12:06 inside the cell and every time a charge moves, it leaves behind a
12:13 charge. All right. Because there's that it's attracted to and so,
12:19 basically attracted to a negative charge. , if you're having this disequilibrium,
12:24 you're basically saying is when there's less charges over here, that's the equivalent
12:29 saying there's lots of negative charge over . And so they're moving to where
12:35 negative charges. But each time they're , that means you're creating a negative
12:40 on the other side. Does that of makes sense? Okay. All
12:46 . So, the electrical gradient as as the chemical gradient become important.
12:53 , I want to just back up slide again. Alright, I want
12:55 just show you what we have What type of ion? Is that
12:59 or negative positive. What type of is that Positive? What about that
13:04 ? And what about that one It's actually two positives, right,
13:08 you can see the valence here. that whole chemistry thing that we're just
13:11 of ignoring. Right? But if look at this and we said,
13:14 a second, I've got sodium and , right? And they're dis
13:19 And so I've got lots of sodium here. I got a lot of
13:21 over here all of a sudden. I'm looking at different positive ions but
13:25 don't care what the ion is. we care about is the charge.
13:29 so now you're looking at differences just virtue of the concentrations. Now that's
13:35 little bit more confusing. So you think about it. Like this
13:37 I have a lot of sodium ions here, I have a lot of
13:41 ions over here, I've got very sodium ions over here. I got
13:45 little very few potassium ions over but the absolute numbers of all those
13:51 would be the number of positive ions they're probably not equal. So,
13:55 a disequilibrium in terms of the number ions, you're not asking the question
14:00 what I am, Is there you're what is the charge? All
14:03 So, when we're talking about electrical were not considering what the ion
14:07 we're just considering its charge. if you see how I said this
14:11 get a little bit confusing here. looking at eyes and there. You're
14:15 doing that glaze where it's like I see what he's saying. But hopefully
14:19 show you here in just a second that means. All right. A
14:25 of colors up there. Alright, we're talking about here or what this
14:31 is trying to show you is showing those relationships Now I'm gonna give a
14:36 example that I give every semester because think it's understandable but it's a dumb
14:42 . You ready in Houston? Over bel air, not bel air over
14:47 River Oaks. There are two high that sit side by side to one
14:52 . Alright. We have a private school ST john's very big school and
14:56 next door we have Lamar high Another very big school. All right
15:01 , literally side by side, they're by a little tiny offense. All
15:07 . Now, you can imagine at high school that there are couples.
15:12 you agree with that? Alright. can imagine they're doing all the things
15:16 couples do. They look at each with goo goo eyes and they say
15:19 things to each other and they hang all day holding hands. Can you
15:24 them? Yeah, they're the same that you rolled your eyes at in
15:27 school when you were in high All right. And you can imagine
15:31 ST john's there is the exact same that there are couples opposites attracted to
15:37 another's doing the goo goo eyes I love you, I love you
15:42 . You know, doing all that stuff that makes us all uncomfortable and
15:46 us roll our eyes at these But also you can imagine at these
15:51 that there are uncoupled individuals. And you look at this picture, that's
15:57 of what's going on up here over this side, you can see the
16:03 sodium couples with chlorine. They're very happy, they're holding hands.
16:06 giving each other goo goo eyes all . But you can see that there's
16:10 some uncoupled stuff. There's even some couples that's because remember we said there's
16:16 uneven concentration. So every now and you might see a potassium which is
16:20 positive charge attracted to a chlorine, is a negative charge on the inside
16:24 the cell. It's kind of the thing. We have these positive
16:29 These potassium ions are all over the and they're attracted to this big giant
16:33 And you're sitting there going through your if you came in, you'd
16:36 I don't know what that is. an an ionic secular protein,
16:40 It's a protein that has lots of charges to it. Alright, so
16:44 how they bounce themselves out. And that again, it's the same sort
16:48 thing. They're doing the goo goo and you can kind of see there's
16:51 trying to demonstrate that there's major pairings and then every now and then you
16:56 see a sodium and it might pair . But you can see that this
16:59 charge doesn't have enough positive charges inside cell. So you could basically say
17:04 a whole bunch of uncoupled negative charges the cell. So you can imagine
17:11 you didn't know this. Um There to be a time when you had
17:14 was called an open campus lunch. think they stopped doing that in an
17:19 campus lunches. You could eat anywhere campus or you could actually leave
17:22 But let's pretend for a moment or high schools you have an open campus
17:25 and you can eat anywhere on the of the campus. And so all
17:29 cute couples come outside, right? you can imagine there holding their hands
17:33 that little sack lunches, giving each the goo goo eyes and they sit
17:37 and then you have the sad All right, the ones that aren't
17:42 and they're sitting there with their saddle sandwiches. They're walking outside and they're
17:47 it on this side and then they up and across the fence they see
17:55 UNP aired charge and what do they ? They're attracted to them,
18:00 And so they start walking up to fence and they hang out at the
18:05 and then on the other side, negative charges are doing the same
18:08 They're like and they come up over up against the fence. Now,
18:14 can't get together why? Because of fence. And that's what we have
18:19 . That's what the plasma membrane It's like the fence. And so
18:23 negative charges accumulate around the plasma The plasma membrane itself doesn't have a
18:30 . Right? The plasma membrane just in between them and said, you
18:33 can't get together right now, if look hard enough, they might find
18:37 leak channel and then they just kind walk through the leak channel.
18:42 So that's what the purpose of that channel is, is to allow ions
18:46 move across that barrier to find their . Okay, so all we're asking
18:55 which way are we going? And are we attracted to? All right
19:01 , the membrane potential, when you that word is simply the differences between
19:07 positive charges on one side and really we say is the positive charges on
19:12 other side. But you can think it as the accumulation of negative charges
19:16 the other side. All right. , that that membrane potential it refers
19:21 the potential energy. And it's saying big of a difference is it?
19:25 bigger the difference, the more energy have stored up the smaller the
19:28 the less energy I have. But still potential energy. Things can move
19:33 there is a path through which that can move. So, when you
19:38 that term, that's what it refers . All right. No matter what
19:45 you look at in the body, a membrane potential. There is a
19:49 of charges on the inside and on outside of the cell. But its
19:54 and muscle cells that take advantage of difference in charge. Right? If
20:00 potential energy, I can convert potential into kinetic energy and I can use
20:08 that energy to do things and you think about a mussel. What does
20:12 muscle do? A muscle causes And so, I'm using potential energy
20:17 the form of these differences in ions create activity in the muscles to cause
20:23 . All right. And the same is true of neurons were using it
20:27 a different way to send signals. right. So, when you think
20:33 that word, that's what it's referring . All right. So, don't
20:37 the language confuse you now. The we measure this difference is we do
20:43 like this. We use a volt and we stick a probe inside the
20:46 and we stick a probe on the of the cell and it's looking at
20:49 difference in charge between those two Alright? So, if you see
20:54 negative value on your volt meter, what that's telling you, is that
20:59 inside of the cell has more negative than the outside. Alright. In
21:04 words, less positive charges. The way you can say that.
21:08 And the converse would be true that inside of the cell has more positive
21:12 and on the outside then you'd have plus value. All right. And
21:17 you're gonna see we're gonna be talking lot about this this membrane potential in
21:22 for example, of having a $70 volt membrane potential. And so all
21:29 just telling us that there's more positive on the outside than on the
21:33 Or as we said, less positive or negative charge on the inside.
21:38 all It means. It's just it's the difference. Okay, So our
21:44 are small. So, we measure miller volts. All right. And
21:48 measurement remember his potential energy. if it's potential, that means its
21:52 to do work now for the scary slides. All right. And I
22:02 these scary slides because some of you going to see these equations down here
22:06 immediately your brain freezes up and my God, what have I gotten
22:09 into? Alright. There are some and some professors who will spend hours
22:16 about this equation. All right. am not that professor, you're
22:22 thank goodness, But we do need know what it is. Alright.
22:25 called the nursed equation and what that equation does. It allows us to
22:30 what the like Excuse me, the potential is for an ion again,
22:36 bunch of different words what an equilibrium is. If you look at the
22:40 , it tells you, it says energy necessary to reach a balance between
22:45 two sides of a membrane for a ion. All right. And so
22:51 it really does is ask the what's the difference between the two
22:55 Now? Remember what I said, said you didn't need to memorize any
22:57 these values. Right. So that's news. The second thing is you
23:02 not have to do math in my . I like that. Yeah,
23:08 say that to every day. It's thinking but physiologists have to define
23:12 And so this is what the guy sat there and did his little nerd
23:17 and figured out how to measure these . And basically this is the equation
23:21 came up with. And really if look at this and again, I
23:24 want you to memorize the equation. don't even want you to memorize like
23:28 does it say? It basically says at the concentration. If I compare
23:31 outside of the inside and do all math with it, I can determine
23:36 or how much energy is necessary to balance what the membrane potential would be
23:42 all I have is this one ion when balance occurred what it would look
23:47 . Alright, so just does the . And so just use the example
23:51 of I'm gonna use sodium, the relative to the inside is tenfold.
23:56 it would be 150 divided by which is 10. The log of
23:59 is one. Right? So one 61 is 61 Z refers to the
24:09 . And so sodium has a valence one because one plus charge. And
24:12 61 divided by one is one. our answer would be 61 And you
24:17 see there is a positive number. basically what it says is that in
24:22 for me to reach balance the difference the positive and the negative is so
24:27 that basically 61 million volts would be change or the difference between the two
24:33 when both sides were equal. that's all it's saying is where balance
24:39 occurred, that's the difference in And you can do this for every
24:44 ion that we care about. Now this this little graph shows three,
24:49 are a lot of ions in the and you can do each and every
24:53 of them. But we're not Alright, and the reason I bring
24:59 up is because we can use these to help us calculate what the membrane
25:06 is supposed to be for a And that's what the next slide
25:10 And if you read through the book came across this equation is called the
25:13 Hodgkin Katz equation and it says look not just each of the individual ions
25:20 . It also matters what their relative is. And again you don't need
25:26 memorize the equation. I'm not going do the math here because Right.
25:31 you can see it's basically saying, , I'm going to take into consideration
25:35 ion that can be passing across the . All right. And in this
25:41 I just showed you three of them our little graph only shows three of
25:44 . As I mentioned, there's a of ions. Alright, But what
25:50 focusing in on is going to be value right there. That's permeability.
25:55 refers to the ability of something being to go back and forth across the
26:00 and it's dependent upon the actual number channels that are available. So,
26:06 I don't like your book. What did here is they used a value
26:10 one and then they did fractions fractions very helpful. So, let's kind
26:14 convert these two right here. to get this number right here to
26:18 , what do I need to multiply . Buy two. Get one
26:23 No, No, a little higher . Mhm. 25. That's
26:34 Yeah. Multiply Not at multiply. , if I multiply this number by
26:40 to get one, what does this become? If I multiply by
26:43 25. So, what that tells so that we can understand what's going
26:47 . When I'm dealing with probability. says for everyone ion that crosses over
26:52 membrane. 25 potassium ions pass across membrane. All right. That's what
27:00 value represents. And so every ion different permeability because there's a different number
27:06 channels for that specific ion. So we said sodium wants to go
27:12 the cell. There's only one sodium channel. Alright, so sodium goes
27:18 the cells. I said ha I one into the cell and the potassium
27:21 has 25 league channels and sell but I got 25 going out.
27:27 you see what we have here? have an imbalance in terms of movement
27:31 that imbalance in terms of movement has effect on the membrane potential. Which
27:36 what we used. That's why that is in that equation to tell you
27:40 degree of effect. All right. every one of these has an effect
27:46 the membrane. Now, we're keeping and we're going to talk about that
27:51 more. But we're going to look at this graph. So, way
27:55 here, we said, here's the equation. We calculated the equilibrium potentials
28:01 ions. Just pretend. Yeah, course we did. We did all
28:03 math because we're incredible math nerds. just died here. I knew this
28:08 going to happen. That's why you be prepared. All right, test
28:32 we go. All right. we did all our calculation to get
28:36 our equilibrium potential for all our different . Right? So, there's our
28:41 potentials. They're shown on the graph the equilibrium potential potassium equilibrium potential for
28:46 , equilibrium potential for sodium, you on this graph, they're way far
28:51 . So, what it's basically saying in order for sodium stop moving across
28:56 membrane, I have to measure the of the cell as being at plus
29:01 . If I wanted to stop tasi into the cell or out of the
29:05 , the inside the cell must become . All right. And then if
29:10 actually go and measure There's my actual membrane potential at -70. Now,
29:18 is that -70 if I go back here, remember all of these things
29:22 an effect. And what becomes most is the degree of permeability? All
29:30 , now we go back to a example, something that you guys can
29:33 . You've all been to a sporting At least one in your life.
29:37 want you to think about a football . Could be a basketball game.
29:40 matter. But when you have a filled with 40,000 fans at halftime,
29:45 gets up out of the stands, down to the bathrooms. Right
29:50 is it a problem going to the now in out Easy peasy. Lemon
29:56 , Sorry, that was kind of pun. Um Ladies getting in the
30:02 , there's a problem. Yes, mean, you might get back to
30:07 seat at the in the in the of the fourth quarter, if you're
30:10 . Right? It's because I'm going give away the story guys, it's
30:15 guys P and troughs. Alright you each have your individual stalls so
30:21 are like 17 stalls in the bathroom you have to wait your turn.
30:25 pee in a trough. Basically we in there and we go shoulder,
30:28 , we stare straight into our We don't make eye contact, we
30:31 talk with anybody, we just go to our business, take a step
30:35 , go wash your hands and We go, How many people can
30:38 put out a trough? 1 2 . Thank you. So we get
30:43 and out very quickly. So what would say then using that terrible example
30:48 that the degree of bathroom permeability favors , Would you agree? Right,
30:58 can move more people in and out the bathroom than women can move in
31:02 out of the bathroom because of their designs. All right. And so
31:07 permeability kind of dictates the movement and what's going on here when it comes
31:13 um the cell, if we have potassium channels then we have sodium channels
31:22 that is going to have a greater on the resting membrane potential. That
31:27 sense. In other words, if can move more sodium than I can
31:31 potassium or sorry if I can move potassium and I can move sodium then
31:34 resting membrane potential is gonna look a like the equilibrium potential for potassium and
31:40 like the equilibrium potential for sodium. if you go look at that
31:45 where is the resting memory potentials over -70. Whereas equilibrium potential for potassium
31:53 . And we're about sodium plus But they're not the exact same.
32:00 ? So we're not quite at -90 we're nowhere near plus 60. So
32:05 means potassium is always going to be . That means sodium is always going
32:09 be moving because we never reach that . That membrane potential that would stop
32:15 movement of potassium or stop the movement sodium. So sodium is always going
32:22 potassium is always going out and we a mechanism to ensure that those ions
32:27 have left will then be moved back place. And if you consider all
32:32 those, the equilibrium for potassium, equilibrium for sodium plus all the other
32:37 were ignoring. Plus you think about active transport of pushing sodium back into
32:43 out of the cell and potassium back the cell, which is that sodium
32:48 80 P A. S. Then why we end up with This voltage
32:55 -70, that's what it all And why do I talk about
33:01 Why did I just spend how much ? 30 minutes talking about this?
33:09 one is because when I was sitting your seats and the professor started talking
33:14 voltages and -70 and I sat there , what the hell is this number
33:19 why does it exist? And he explained it. Right. So,
33:24 nothing worse in this world than being something and not understanding why.
33:28 So that's the reason why that voltage looking at there is dependent upon which
33:34 are moving And their relative permeability is number one. All right. And
33:41 number two. See? Yeah, have it up there. Is that
33:46 , What this all represents is the that govern how we maintain this
33:55 And if that potential is how neurons . And is that potential is how
34:01 work. We should probably kind of our minds around it just a little
34:06 . All right. So all this says what I just told you a
34:11 ago, the -70 creates a Right? So that you still have
34:17 leaking out. There's more potassium leaking than their sodium leaking in The
34:23 cellular proteins are too big. They do anything. So, they're stuck
34:26 the inside. They're creating a larger charge. That's what's being left
34:31 That negative charge is attractive to the that can leak in sodium wants to
34:37 in because there's more sodium on the . So that's the direction it wants
34:40 go. And then when sodium leaks chlorine goes, hey, wait a
34:43 . I was hanging out with And so it kind of follows along
34:51 then once things start going that you would think that we'd eventually reach
34:55 . But then we have this pump says no, no, no,
34:58 , no, you're not where you're to be. I'm gonna put you
35:00 back out here and you're supposed to right in there and it keeps this
35:03 going So that you're always stuck at -7. So I'm gonna pause
35:11 That is the complex part. Any questions And trust me, there's
35:16 such thing as a dumb question about . This is the part that most
35:22 get lost on and it's and it's understandable because it's not what you're
35:27 Yes, sir, that's correct. right, yes. Right. So
35:55 that, let's let's ignore the pump a second. All right, eventually
36:01 you're gonna do is you're going to a point. Alright, so,
36:04 the pump, the sodium is on outside, sodium is on the inside
36:08 this. So what's gonna end up is you're going to keep moving while
36:11 trying to get to this point of , Right? So that would be
36:15 sodium potassium, it's gonna try to the same thing, but equilibrium is
36:20 those specific values, right? So inside of the cell would have to
36:25 plus 61 before sodium would stop So sodium is gonna keep going and
36:30 fact, what would happen, instead it reaching equilibrium, it would start
36:33 like this. That's right. You're literally stuck in a state of
36:41 but the balance there and I'm gonna those two words. You're the state
36:45 imbalance or state of is what we it is a constant flux. And
36:51 in other words, things are always to be moving, but they're static
36:56 that state of constant moving. All . I saw a hand up
37:00 Yes, ma'am. That's correct. , if if things would stop
37:14 this is this is this is kind hyperbole, then that is a representation
37:20 death. Alright. In other when when nothing moves any further,
37:25 no action. There's no energy. a state of death. Alright.
37:29 the cell, you know? does that equal to death? Or
37:33 that come? You know, That's question. But But the idea is
37:38 we have this thing that's at its point and all we gotta do now
37:44 this is a potential. It tells that I could then use that potential
37:49 do something. So, all this that we've talked about here is describing
37:54 I put this cell and I'm just do a physical thing where I'm tipped
37:59 all I gotta do is Give it nudge one way or the other and
38:02 going to cause some sort of energy if that makes sense? All
38:11 Anyone else. All right. what's the take home in all of
38:16 ? Well, in essence, we potential energy that we're going to use
38:20 that it's these ions being out of that allows us to have this
38:26 All right. But me just saying once your brains are gonna go
38:31 Okay, So, let's see how works. We're gonna use the neuron
38:36 our example, right? Because if can learn neurons, you've learned
38:39 Because neurons are like, what we've for years and years and years and
38:43 . All right. And you're But I want to learn muscles because
38:46 makes the most sense, and I , but that's just not how we
38:49 it. All right. So, is a neuron, Alright. It's
38:54 basic functional structure of the nervous So, when you think neural
38:58 this is what we're gonna be focusing . Even though by number they're not
39:02 most numerous part of nervous tissue. . It's an excitable cell, meaning
39:08 it has is that it's going to able to transmit electrical signals.
39:12 when we say transmit electrical signals, we're referring to Is moving an electrical
39:17 from one side of the cell to other. Alright. When you get
39:21 to the end of the cell, when you're going to do a chemical
39:24 . So, a neuron talks to cell through a chemical means, But
39:30 sends a signal across its length by electrical means. Now, why is
39:36 important? Well, your neurons in brain are actually fairly small. But
39:42 are neurons that leave the central nervous , your brain, or your spinal
39:47 , for example, that are as as your limbs. Right? So
39:51 I want to get my pinky to , I have a neuron that begins
39:55 here in my spinal cord that travels entire length of my arm, plus
40:00 short distance of my back. So the length of a single cell.
40:04 a pretty big sell. And if want to wiggle that, I need
40:08 get that signal there quickly into an signal is the fastest means through which
40:13 can make that happen. So that's these electrical signals become very, very
40:19 . All right now, again, has all that made possible because they
40:25 the pumps and we have channels. just like we just described. There's
40:29 channels. There's voltage gated channels. going to be ligand gated channels and
40:32 are pumps that are involved. And going to be basically having different concentrations
40:38 are going to open and close depending our needs. And that's the probably
40:42 difficult part about this is what's All right. And then when we
40:46 down to the base, when we the electrical signal that electrical signals used
40:50 tell the end that terminal end to a chemical signal. They're very,
40:55 long lived. In other words, start producing them during embryonic development and
41:00 they are formed, they stick around your entire life. For the most
41:05 , they are a mid topic meaning with few exceptions, they do not
41:10 . So what you have is what get. All right. Mhm.
41:14 going to be absolutist there. Although it's not entirely true. All
41:19 . But it's not like your skin it's like, oh, I damaged
41:22 nervous tissue. Oh, I'll just new neurons. That's not what's going
41:25 happen. All right. They also of the amount of work that they
41:31 , their very, very metabolic meaning use up a lot of oxygen and
41:35 lot of glucose. So, structurally cell has some parts to it.
41:42 have the body. All right. is what is referred to as the
41:47 . The cytoplasm within that is referred as the pair carry on within their
41:54 going to have all the cellular machinery we've all learned about. But because
41:59 were neurons. And because you had naming things uh they didn't at the
42:04 didn't understand that all cells have the same parts. And so they named
42:08 differently. And so, very you'll see things called missile bodies.
42:12 missile body are the ribosomes. And reason we point this out is because
42:16 the protein making machinery is going to located up here in the soma or
42:21 cell body. So, within the of carry on is where you're gonna
42:24 the ribosomes or the missile bodies. right. You can see in our
42:28 cartoon, I'm just gonna focus on one. But it's true for any
42:32 . And you have these little Alright. Some extensions are referred to
42:37 dendrites. One extension is gonna be to as an axon. The nomenclature
42:42 , generally speaking, is that you information via the dendrites. You send
42:47 via the axon. All right. go into more detail in the next
42:53 about what that means. All we're going to point this out
42:58 but we'll come back and repeat this a little bit later when we do
43:01 nervous system again. Is that when have a bunch of neurons clustered together
43:06 you're really focusing here on the cell . So, if you have a
43:09 bunch of cell bodies clustered together in central nervous system, we refer to
43:13 as a nuclei. Not to be with the nucleus. Right. And
43:18 they're found in the peripheral nervous they're referred to as a ganglia.
43:22 right. So, when you hear terms and you're talking about the nervous
43:26 , they're just saying this is where cell bodies, a whole bunch of
43:29 are located. Oh, look, guess I do have more information on
43:35 . All right. So, the processes dendrites. Well, let me
43:41 to this here with regard to the nervous system, the axons, these
43:45 fibers that are traveling. They basically processes as they travel. They are
43:50 between one point in the next. refer to it as a tract.
43:54 then if you're in the peripheral nervous , when you're looking at these processes
43:57 these axons, they're bundled together and travel Between one point in the
44:01 That's what we refer to as a . So, very often you'll see
44:06 question I'll ask on an exam will are there any nerves in the central
44:10 system? And immediately your brain will . Of course there is. And
44:13 answer is no nerves are specific to peripheral nervous system and the central nervous
44:21 it's called attract. Alright, so nerves in the central nervous system
44:28 And I mentioned we have the dendrites the axon dendrites are typically receptive.
44:34 typically have more uh lots of Although there's gonna be some cases where
44:39 not. Also, if you look a cell, if you see like
44:43 one has 12345 dendrites, if you at another cell and had 20
44:47 you'd say, Aha, it has greater receptive field or is able to
44:52 more input. So basically the more have, the more information you're capable
44:57 receiving. So what they do is take incoming information and they send it
45:03 the cell body. All right. , you can see here, the
45:06 arrows are showing you, I'm sending towards the cell body here. And
45:10 type of information that's being uh sent an electrical signal. And we refer
45:16 this type of electrical signal as a potential. And that's what the rest
45:21 the class is going to be talking is what is the greatest potential
45:27 on the other hand, is if have one, you only have
45:32 Alright, there are some cells that just dendrites. And so those are
45:38 little bit more complex. So we kind of ignore man a mp.
45:42 typically you'll see an axon is fairly and it's fairly large and has some
45:47 to it. The place where the originates kind of is a bulge.
45:52 it's the point of origin called the hillock. All right. The axon
45:59 can actually divide. So it can along and it can split. And
46:02 it splits, we refer to the as collaterals because there's more than one
46:08 at this point. But it's it as a single point. So,
46:12 signal goes down. It may split those. And then when you get
46:16 to the bottom, you'll see more . And so here you can see
46:20 branches, several branches. Those are Teledyne. Andrea. And what that
46:25 is many branches. And then at very end of the television, you
46:30 these little tiny bulges at the end referred to as the axon terminals.
46:36 it's so it's at the axon terminal , right there. That's where you're
46:40 see the interaction between one neuron and cell it's trying to influence.
46:48 So you might also see the Terps knob. So this area is referred
46:54 as the synapse. I have an . So at the end of the
47:04 , that's when we see chemical. correct. So what we'll see um
47:10 at this point right here, this where we're gonna be releasing chemicals for
47:15 represent this cell telling that cell what do. All right. The pink
47:21 right here is supposed to represent this cell. So this is cell number
47:24 . This would be cell number Cell number one. Cell number
47:28 Or for focusing in on it. you can have neurons committing with other
47:33 neurons or they can be communicating with that can be communicating with glands.
47:38 can communicate with many different types of . So, it's never like fully
47:44 electric. That is correct. So question is will ever be fully
47:49 Alright, so, we've got to a distinction here which I'm just going
47:52 do for the sake of of this but it won't come back until
47:56 is that some neurons will communicate with cells electrically. But there has to
48:02 a gap junction between the two. ? So that does happen. But
48:06 a rare thing, most of the that we're gonna be looking at are
48:10 to be communicating via chemical signaling. what they're doing is this is my
48:16 Andrea going down to the next there's my axon terminal. I'm releasing
48:22 from here and it's directly affecting the that I'm communicating with. Which like
48:29 ones are electric. So um they're few and far between. The best
48:35 of electrical, of electrical, of connection would be actually looking at muscle
48:41 specifically looking at cardiac muscle. But are neurons in the brain that do
48:46 these type of electrical connections which we ignore because it just complicates things for
48:51 . Yeah. Where the collateral. . So in this picture there's not
48:57 not one being shown. So what could say is imagine this fiber coming
49:02 this axon and then it's splitting and over here and then there's another another
49:07 over there. Alright, so that's a collateral is. Just think what
49:11 collateral mean? It goes off to side. So it's just another extension
49:15 another branch. So it allows this cell. So what you can imagine
49:20 artist, what the artist is trying do in the picture is to demonstrate
49:23 most simple model we can explore, ? But you can also imagine that
49:29 one neuron is not just talking to neuron. That's a terrible chain.
49:34 ? It would be better if that was talking to say several 1000 other
49:37 . So that's why you'd expect to other extensions, other collaterals, But
49:43 only have one axon. So you're gonna see three axons coming off the
49:47 body. You only see one But that one axon can then split
49:52 its path. Anyone else. Um have tracks that we have nerves tracks
50:04 in the nervous system and the nerves peripheral. Alright, So, same
50:13 . No. Yes and no. right. And I'm I'm trying not
50:18 uh to throw you off on this now because that's really what the last
50:23 is going to be about. All . Because we haven't talked to anyone
50:26 , know what the peripheral nervous system . Very central nervous is one person
50:29 three people. Okay. The rest you are sitting there going words that
50:34 mean anything to me just right now that's okay because we haven't learned about
50:38 yet. Alright. So, so want to kind of stand away from
50:42 . What I want to just kind do is say All right,
50:45 when I have axons bundled together, from one point to the next,
50:50 bundling refers to something specific in one and something else in another location.
50:58 , that's what the track to the represents is just the movement of ions
51:02 not iron, but axons along a . Okay. All right. What
51:10 the next one here have? All . So, when we talk about
51:14 axon, this is the conducting All right. So, what we're
51:18 is we're saying we're sending a signal the cell body down to the acts
51:24 terminals. Alright. The axon itself not have any initial bodies. It
51:29 have a Golgi apparatus. That means proteins that are found in the axon
51:34 created and made or does up here the cell body. Okay,
51:42 a lot of work is being done the cell body. The accident itself
51:45 have stuff in there, but it's making it. So, that means
51:49 I have something I want to release here, I had to have made
51:53 up there, yep, That's number secondly, we have special names for
52:00 cytoplasm and the axon because again, wanted to be special and wanted to
52:05 one more thing for you to It's called axa plasm. Alright,
52:09 , if you see a word that a lot like another word that you've
52:12 before and you're talking about a specific . Just think, okay, some
52:17 , 40 or 50 years ago named something special because it was just a
52:21 cell. Alright, that's an example this, The axa plasm. And
52:26 the plasma membrane instead of calling it plasma lemma, or or you
52:31 apply the membrane. It's called the Emma. Thank you very much.
52:36 vocabulary award to memorize. All So, ax. So, just
52:41 to an axon now, as I , if you're making things up here
52:49 they need to get down here, you need to be able to transport
52:53 . And so there is different types transport. Alright, So if I'm
52:59 towards the axon terminal, it's called . If I'm going back, it's
53:05 retrograde and that's kind of easy to when I go back in time or
53:09 to a, you know, a restaurant that's like, oh, I
53:12 know, medieval castle, that's It would probably be in the 80s
53:19 . Retroviruses reverse. It's going backwards wrong direction. Alright, So anterograde
53:26 this direction, retrograde, is that ? And what we say is there's
53:30 speeds. All right. We have referred to as facts, axonal transport
53:34 why I mention this is so that can now visualize those motor proteins.
53:39 here I've got vesicles and mitochondria and and you can see I'm transporting them
53:44 those pathways using those motor proteins and energy. So, that allows me
53:49 speed things down there and I can about 400 per day. How much
53:53 a millimeter? It's a bit see this. Right? But if I
53:57 100 of them, it's like 300 of them is a yard or
54:00 meter. No, sorry, it's of them is a meter.
54:05 so, basically I can move this in a day moving, moving
54:10 That's that's what's considered fast. So can all of a sudden say,
54:14 now I kinda understand why I want cells to use electrical signaling because it's
54:18 lot faster to get things going. then we also have slow and this
54:22 both both directions. You can I can go there showing you
54:25 there's one, there's other but then have the slow axonal transport and this
54:29 where it's going to be moving back this direction or sorry, it's the
54:34 direction. All right. And this basically sitting and moving with the,
54:39 the cytoplasm, with the ectoplasm, way you can visualize this is like
54:43 in an inner tube and going Have you ever been tubing? You
54:46 what tubing is set in an inner ? Have your favorite drink? We're
54:50 going to pretend like it's non Alright? And then you get the
54:53 tube and what do you do? go with the flow? Alright.
54:56 just kind of move along and it's and it's boring and you get horribly
55:01 and you regret making the trip and what's going on here. It's just
55:05 , very slow. All right. again, you can see speed.
55:10 why is it important? Well, want to use energy to get things
55:13 where they need to go quickly. is another important vocabulary lesson because we're
55:26 to use these terms a lot and this is going to do is going
55:30 force you to go back to third when you first learned the number
55:32 Do you remember the number line? right. So and if this is
55:37 in this direction for you, what that? Not zero, but it
55:43 be positive or negative negative and then direction would be positive. All
55:49 So in terms of terminology when I at zero, I am what is
55:54 to be in neutral state. anytime I move off of zero,
55:58 matter how far I move. If move this far off of zero,
56:01 I move all the way that direction have become polarized, right? I
56:06 be extremely polarized or can be sort polarized but I'm still polarized.
56:11 So if you're not zero, if measure A charge between two points using
56:18 volt meter, your polarized. It doesn't matter if you move in
56:23 direction. If I move this direction polarized. If I'm over here at
56:27 and I move this direction that's That's polarized. Okay, so far
56:32 with me. All right. So just gonna minus 10 plus 10.
56:36 matter polarized. If I become more I'm moving further away from zero.
56:45 zero was way over there? I at -10. Now I'm like
56:49 Alright. So I'm more polarized. we call that hyper polarized.
56:55 If I'm at -10 and I become polarized and move towards zero have become
57:01 porous de polarized. Right? So , starting at zero, I'm
57:08 If I move away from zero, become Polarized. If I move further
57:14 from zero hyper polarized, if I back to uh my my initial polarized
57:22 , I have a new term I've polarized, right? And then if
57:28 move closer to zero, I am polarized. And if I move back
57:31 my original polarized state, I've re again, that makes sense. It
57:36 matter if I go this direction. here am I getting neutral. So
57:39 I go over here I am If I become more I'm if I
57:46 back to my original polarized state, polarized. If I become less
57:52 I'm d polarized. Alright, so key thing here is understanding where you're
57:58 from Alright, when we look at cell at rest, it has a
58:01 potential of minus 70. Is it or? No, It's polarized because
58:06 -70, it's not zero. So if you look at a
58:12 A neuron is at -70, it's a polarized state. If I become
58:17 polarized, which way am I going move? All right? If zero
58:23 over there. So I'm going to this direction. I'm deep polarizing.
58:28 right. And something's happening, I've my state. So something must be
58:33 . And then when I returned back my polarized state, I'm re
58:37 I'm now back at rest And that's of confusing, isn't it? Because
58:42 thinking, oh well ref would be . No, by starting point is
58:47 . Now, another thing I can is I can go this direction.
58:49 am I doing now? I am with h hyper polarizing. I've moved
58:57 from zero. Alright, so notice the terms refer to it refers
59:01 Where do I start to begin Right? So if I'm over
59:05 I'm polarized. If I become more , I'm moving further from my from
59:11 from neutral. And if I'm d I'm getting close to zero.
59:16 one of the weird ones here is this is neutral and I'm over here
59:21 my polarized state, I can de as I move back towards zero.
59:27 if I passed zero I don't change nomenclature. I just call it deep
59:33 because because it'd be weird to okay, now I'm re polarizing or
59:38 because you're just continuing moving and then I returned back it's just re polarized
59:44 what I say this because we're going learn about action potentials where that
59:48 he says if I keep moving if , if I just keep moving.
59:52 right now notice here down here in bottom. All right here, I've
59:57 deep polarization of hyper polarization. So we have cells that are sitting at
60:03 70. Alright, that's a neuron we say d polarized. What we're
60:07 saying is that the inside of the which started off as negative is it's
60:12 negative. That means there's positive ions in. So what we say there's
60:16 net inward flow of positive violence. , now which I on, do
60:22 remember? I'm just saying do you which ion moves into cells?
60:25 sodium? Good. Alright. When hyper polarized. Alright. So if
60:30 start off polarizing you become hyper that means the inside of the cell
60:35 becoming more negative. Alright, well think okay, well that means chlorine
60:39 coming in and you'd be right, chlorine doesn't move on its own.
60:42 dependent upon other ions to tell it to go. So what I on
60:48 move in order to become more negative . Right? So remember we said
60:53 potassium leaves, it leaves behind a ion So when potassium is leaving,
60:56 becoming more and more hyper polarized now the resting state, you're not hyper
61:04 or d polarizing. You're at And so you've already established that
61:08 So we're referring to hyper or deep . We've got to be changing one
61:13 of all the stuff we've already talked . Are we changing equilibrium potentials?
61:20 , that's just a that's a fact life. So what's the one thing
61:23 can change. That was part of equation that I pointed and spent the
61:29 slide talking about, that's right. the permeability. That's like you
61:35 Right, just nod your head Of course. That's exactly what I
61:38 . Permeability. All right, you're stuck in line at the
61:44 It goes around the stadium six How can we increase the rate of
61:49 moving into the bathroom? What what be the one thing that we could
61:54 if it was magic and we could whatever we wanted to More stalls.
61:59 . That's all you gotta do, the permeability instead of there being 17
62:03 . Let's make 34. We double rate of permeability. Let's put 170
62:09 as a tenfold increase in the Does that make sense? So,
62:15 we're talking about hyper polarization and deep , we're changing permeability. That's going
62:21 be the key thing. All So change the membrane potential result in
62:26 signals. That is a key That's what we've been trying to build
62:29 to. Alright, So, if have the membrane potential, which is
62:33 resting potential, that's potential energy, we're saying is that if we want
62:37 create an electrical signal, we have do anything that's gonna change that permeability
62:43 anything that's gonna alter the ion Well, we're not really gonna be
62:47 ion concentration. We're not dumping extra in your body or extra potassium in
62:51 body. That's not gonna happen. . So, really the one thing
62:54 we can really change is that And we've already talked about the
63:01 the channels are either existing in a state or an open state. If
63:05 closed, it's not permissible. But I open it got an increase in
63:12 . So, that's what we're gonna working with. So, there's two
63:14 of changes. We have graded This is what we're going to see
63:18 in the cell body in a Alright. Great potential allows for short
63:25 electrical signals. The action potential, is what we're going to spend thursday
63:29 about is for long distance signaling their different types of signals that are going
63:34 be occurring here. Alright, with regard to greater potential, this
63:38 a local change in potential. has different degrees of magnitude, which
63:42 fancy word for saying it can be or small. All right. It
63:47 be one in Millersville change it could a 20 million will change.
63:50 changes in magnitude hits the term Right? So, one thing is
63:55 it has differences and change. Um , the example I use here is
64:01 10 fold changes of five full The other thing, it doesn't
64:04 It can be not doesn't matter. can be a positive change or a
64:09 change. It can be a deep or hyper polarization and so, what's
64:13 happen is usually there's some sort of event. So, what this is
64:16 to show you here is saying at point is when I opened up a
64:20 and when I open up this it happened to be a sodium
64:23 And when sodium came rushing in, gonna happen is I'm going to see
64:27 massive change right there. I'm gonna lots and lots of sodium Russian and
64:33 what it's gonna do is just as we open up the gate at that
64:36 school, when that uncoupled uh partner through that gate there, like so
64:43 uncoupled people. I'm hanging out with now and the next one's going,
64:47 , I'm hanging out with you And so what they're doing is they're
64:50 to partner up and so what you're is you're changing the difference in charge
64:55 those ions are coming in and coupling . But in that immediate circle they're
65:00 to get all the coupling taken care . And so now the islands have
65:03 travel further and further and further And so at the site of
65:08 that's where you're going to see the change. But as you move further
65:12 further away, there's gonna be less less and less. All right,
65:16 can't visualize that picture of this. I take a rock and throw it
65:20 a pool, write a nice calm , what's going to happen where that
65:26 hits, I'm gonna get a splash ? And then I'm gonna get
65:31 the highest ripples are going to be to splash. Now they move further
65:34 further and further away, there's going be less of a ripple,
65:38 And you can imagine infinite pool eventually gonna get to a point where there's
65:41 ripple. Does that make sense? . And that's what's going on here
65:47 the greatest potential. I have the change at the site of where the
65:53 the triggering event occurred. And as move further and further away, that
65:57 is going to get weaker and weaker weaker, or that energy change is
66:01 to get weaker and weaker. So greatest potential represents that energy wave as
66:09 traveling from the site of triggering further . So this is the greater
66:15 It has varying degrees of magnitude and degrees of duration. Alright, magnitude
66:20 strength. So the bigger the bigger stimulus, the bigger the bigger the
66:29 response. Alright, again, stupid . This is not how your body
66:33 , but just go with me. I have a needle in my hand
66:36 I go to you, you oh, that kind of hurts,
66:40 , but if I took a running and then jammed that needle into your
66:45 , would you experience greater pain? , varying degrees of magnitude, bigger
66:50 , bigger response? Alright, so a greater potential, that's not how
66:54 body works, but I'm trying to help you visualize that. Alright,
66:59 it's the same sort of thing if stimulate a cell and I create a
67:03 stimulus versus a small stimulus, I'm get varying degrees of a response in
67:07 cell. The other thing that's is that the longer I stimulate,
67:13 longer the duration integrated potential. So, you can see there is
67:17 correlation the bigger the stimulus, the the response. The longer the
67:21 the longer the response. And this true for greater potentials. All
67:28 It's a magnitude and duration. as I said, the potential decreases
67:34 intensity. And the reason for that because of that pairing, basically you
67:39 lots of sodium here that's able to up. So lots of sodium going
67:42 . But as you move further and away, there's less sodium traveling further
67:45 further away. So, you see changes. All right. So,
67:52 is gonna be the most sodium over would be less sodium. So,
67:55 seeing a membrane potential change that would very large. But as you move
67:58 away from the site of origin, less and less. And that's why
68:01 use that ripple as an example, I throw a rock into a
68:05 I get a big splash, but splash doesn't stay the same height all
68:09 way as that ripple moves further and away from the site of origin,
68:12 gets smaller and smaller and smaller because the case of the pool it's meeting
68:18 , Right? The water is resisting . That wave of energy. All
68:25 . So, with regard to to greater potential. This is not a
68:29 long signal. It can only travel short distance. So here you can
68:34 here's the big response, but it travels a short distance away.
68:38 if I wanted to travel further, type of greater potential do I
68:42 I need a bigger one, don't ? All right. And we're going
68:45 say, well, why do I to go further? We'll see here
68:47 just a second. This is just to show you this. So,
68:53 showing here here I've stimulated and just in a in a pool, the
68:59 goes in all different directions. It's traveling in one direction. So,
69:02 trying to show you here if look great potential is going the wrong direction
69:06 the dendrite, it's not gonna do . But in this direction, you
69:09 see this is how big of a you see here. But at this
69:12 you can see it's a little bit by here. It's there. It's
69:15 little bit smaller. So it doesn't this particular stimulus doesn't go very very
69:20 . It only went right to there that's kind of a useless tiny stimulus
69:24 didn't do much of anything. But each stimulus is small then well,
69:35 haven't gotten there yet. Alright, , we have special names for greater
69:39 . This is where we get into apple alphabet soup of stuff. So
69:42 . P. S. P. for excitatory post synaptic potential. All
69:50 . Signatory means that it is a . It's stimulating the cell. Post
69:55 refers to which sell your stimulating. what it's saying here is saying if
70:00 is the pre synaptic cell, this here represents the synapse, this would
70:06 the post synaptic cell. So the we're looking at is what happens when
70:10 of these little ions or not. on one of these little chemicals opens
70:14 one of these channels were going to a response in this cell. And
70:19 if it is a channel that opens and allows sodium to come in,
70:23 what we're going to see is sodium in. And so we're gonna see
70:26 deep polarization. We're gonna see We're gonna become less negative than we
70:32 before. So, instead of being here at -70 and saying, Okay
70:36 become more negative. We're going to moving this direction. So, that's
70:41 . We're moving towards zero. and if you measured it here,
70:45 are down here at -70 up here be zero. You can see we're
70:49 up like so so this is the of sodium into a cell is basically
70:57 . It's excitatory it's creating this P. S. P.
71:02 one APSP is very small. And again values. Don't matter.
71:08 you can just say it's not enough create a massive response in the
71:13 It's like again, it's like me me with that needle. It's a
71:16 tiny thing. All right, so not enough to cause us to really
71:23 um further from this resting potential and this will make sense in just
71:29 The other type of greater potential is . And what we're basically saying at
71:33 point is that we're moving further from . Alright, so again, if
71:37 over here at -70 if we open a channel that allows potassium to leave
71:42 allow chlorine to come in, then gonna move further and further away from
71:46 . So we're moving further and further from excitation. So that's why it's
71:51 to as inhibitory. So I PSP inhibitory. Post synaptic potential. I
71:56 . And it's the same sort of . What we're doing is we're at
71:59 we're moving further away from some sort action. And again, these are
72:04 , very small stimulations but it's a stimulation. I love this picture,
72:12 down here because what this shows you how the nervous system actually works because
72:18 our pictures keep showing you it's one plus another cell and they're talking to
72:22 other. But this is showing you purple thing right here is the post
72:26 cell. All these little blue things the axon terminals of thousands of different
72:35 . All right now, let me this perspective. This example doesn't work
72:38 much. The older I get, younger you guys get, the worst
72:41 example becomes alright. But back in day there was this thing called facebook
72:48 you can get on Facebook and you have a pole, right? So
72:52 can ask all 4000 of your closest , right? Say um I am
72:58 this person and I want to know or not I should break up with
73:00 or not. And so all your friends can then now vote whether or
73:05 you can break up with them or together. And so you ask all
73:09 closest 4000 friends, some of them gonna say by all means break up
73:13 you know, some are gonna say , no, you guys are great
73:16 . You should stick together. And really what you need is just 50
73:20 one, right? 50% plus And then you're gonna do whatever they
73:23 . So, you can imagine some are gonna tell, you know,
73:26 an inhibition. Someone you're going to yes, right? And presuming that
73:31 those votes were equal depending on which is higher. That's the way you're
73:35 go and what you're producing here, you were a cell, like a
73:39 and receiving all these signals, all signals summarized together is called the
73:44 P. S. P. The post synaptic potential. All right.
73:49 basically just the sum of all the PS. And the I PS
73:53 Now having said that eps and eps not equal individually PS PS and other
73:59 PSR not equal. Some cells are to produce stronger signals than other cells
74:04 they're not equally weighted. So you to just think in terms of grand
74:08 synaptic potential is the sum of everything it's not everything is not equal in
74:13 of the summary and there's two different that we can sum things up.
74:16 is what we refer to as temporal and something we refer to as spatial
74:21 . Alright. So if some nation to I'm going to count up all
74:24 e p. S. P. and how big they are. So
74:26 are big. Some are small and look at all their values and I
74:29 up all my I. P. . P. S. Some are
74:31 and some are small and they keep their values whichever Pushes me in whichever
74:36 . So if I'm in -70 if grand post synaptic potential pushes me this
74:40 then I d polarized the cell. the grand post synaptic that grand post
74:45 potentials push me this way I hope polarized the cell I'm moving further away
74:50 excitation but it's the sum of all the votes is really kind of what
74:55 is. Alright so how do we them up? Alright so the term
75:00 and temporal spatial refers to space temporal to time. Okay Both of them
75:07 a temporal component to them. Both them have a time component but we're
75:10 to kind of see this. So we're dealing with spatial we're dealing with
75:13 two or more axons terminating on a and communicating at the same time.
75:23 , so that's the time component that going to kind of ignore but the
75:26 thing here is two or more. , so let's say I am an
75:31 and my clap represents an ep sp a very loud sound is it?
75:37 mean it's it's loud enough but not to do anything to the cells but
75:41 two of us were to clap it's little bit louder. If three of
75:47 were to clap. If four of were to collapse, you got
75:55 Yeah. 123. And if all us were to clap. 123,
76:02 a louder sound. Alright, that's example of spatial summation. Different axons
76:10 at the same time releasing a chemical at the same time, stimulating a
76:15 at the same time, each producing own PSP PSP at the same time
76:21 them all up bigger signal. That summation temporal summation is a lot harder
76:28 demonstrate with a clap, it's one , one acts on releasing its material
76:36 the receiving neuron the post synaptic So if again my clap represents me
76:42 any PSP. Here's the PSP and let's say I stimulated again I produced
76:48 one and then a little bit later another one. You can see those
76:52 far apart. They don't create a sound. It's just their own individual
76:56 . But imagine if I could clap fast That they become one big giant
77:03 . So I'm sorry it's just not happen. But watch. Yeah I
77:11 do it fast enough. But imagine I could get that small little bit
77:15 time in between each of those so together that sounds like one big giant
77:19 . That would be temporal summation. so what this is trying to say
77:24 I'm releasing so much chemical that there's an opportunity for the receiving cell to
77:29 . And so they're just responding constantly that chemical. So they're creating a
77:34 and greater G. P. P. Okay no cancelation simply is
77:40 when two or more cells are responding sending a signal but one is positive
77:46 ones and you know once excitatory ones . So if this one is excited
77:50 bring this one is inhibitory and let's they're the same magnitude they cancel each
77:55 out. All right that was the slide. How common is cancelation.
78:06 It's it's so the question is how is cancelation? It's as common as
78:10 two eps being produced. So excitation inhibition are occurring all the time.
78:16 you can imagine uh you know you're different types of input. So one
78:22 of input may be telling you something or another type that another type of
78:26 might be telling you something negative. stupid. Examples, you're trying to
78:31 the street and you're trying to decide I go or do I stay?
78:34 so different types of input? Good . Thank you. Sometimes they hit
78:40 . I miss also. Yes. remember, just remember if you haven't
78:50 up for the exam, probably want do so. Yeah. Oh,
78:59
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