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BIOL 2301 Human Anatomy & Physiology I - BIOL2301_lecture12_1003
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00:01 All right, y'all, everyone else wet socks. Yeah, it
00:07 doesn't it? I gotta walk around them for an hour and a
00:10 You just get to soak in All right, today is a uh
00:15 interesting day when it comes to the that we're gonna be covering. Um
00:21 the button I want to push. and I say interesting in the sense
00:24 a lot of the stuff that we're to do here at the front end
00:26 very conceptual. And so it can confusing if you're sitting here uh trying
00:32 memorize stuff. What we're trying to here is trying to understand conceptually what
00:37 going on at the level of the . So what we're gonna be doing
00:40 we're gonna ask a question first, do we form and create resting membrane
00:46 and then answer the question and including is the resting membrane potential? All
00:52 . Now, if you have taken class and you've talked about this and
00:56 makes sense, you're great. You're steps ahead of everybody else, but
01:00 speaking, this is where we see lot of stumbling and I'm not saying
01:03 to scare you. I'm just saying alert that if you're like, I'm
01:06 getting it, just raise your hand say, I'm not getting it and
01:08 try to, we'll try to get on the same page. All
01:11 This is not one of those things it's like everyone gets it the first
01:14 and it's like, yeah, let's moving. Ok. Second thing we're
01:17 do is we're, we're doing this what we're going to be working our
01:21 into over the next couple of units we're going to be starting to look
01:24 excitable cells. All right. So cells include muscles and neurons. And
01:28 fact, we're going to talk about today and their structure. So we're
01:31 to kind of dip our toe in conceptual stuff, kind of move away
01:36 it so that we can kind of in, into, into juices for
01:38 little bit. And then we're going talk about the neuron and then when
01:41 come back on Thursday, we will dealing with some conceptual stuff. All
01:47 . Um So this is very heavy today. All right. So I'm
01:51 warning you right now. And so we're looking at here is stuff that
01:55 talked about already. I mean, the sense that we've talked about
01:59 right? We've taken a space and say, look, we're dividing one
02:02 from another and whenever we divide there's a reason for that division and
02:07 purpose for this division here is so we can create these unique environments with
02:12 concentration of ions either inside the cell both inside and outside the cell.
02:18 so there are some conditions that we to understand when it comes to
02:22 There we go. First off, platinum membrane is semi permeable. All
02:26 . So now we're going to start these words we've been using and start
02:30 applying them. All right. So does it mean that it's semi
02:33 Well, we are in permeable as plas membrane, we're impermeable to charge
02:38 . And so that's where our mind going to be today is really talking
02:42 these ions. So if you're an , you cannot pass through the lipid
02:48 , just like you can't pass through wall, you have to have some
02:53 of pathway to it through it. how do you get through the
02:56 What do you need doors? All . And so that's what our semi
03:02 is resulting from, is the presence channels or pumps in the plasma
03:08 So we allow things to pass through we want them to. All
03:14 now, we're not gonna talk about and other things to which to which
03:17 membrane is permeable. We're only concerning today with the ions. All
03:21 Now, the second thing we've talked briefly is look, there's this unequal
03:26 of ions in body, there's ion that differ between both the inside of
03:32 cell and the outside of the And this is a chart right
03:35 which I don't want you to but I want you to become familiar
03:39 . Right. In other words, you see that and go?
03:42 yeah, I can see the numbers different when I look either inside the
03:45 or outside the cell. Could you that? Yeah. OK. So
03:49 gonna see a lot of math Here's the good news. We don't
03:53 to do the math. Yeah, know it. Thank you.
03:56 if you were reading the book, saw equations and you're like,
03:59 what have I got myself into? right, the truth is, is
04:04 physiologists, this is like sitting in jacuzzi drinking your favorite drinks,
04:10 It's like, oh there's math and get to explain things. All
04:15 For freshman level biology classes. This like torture. And so I don't
04:21 it's important for you to actually be to do the math, but you
04:25 need to understand what the math Does that make sense? So I'm
04:30 gonna give you an equation on the and say do the math because
04:36 All right. So first off what is trying to show you visually is
04:40 represented up here, you can see unequal distribution. And so because there's
04:46 unequal distribution, ions are going to in the direction or want to move
04:50 the direction where there is less of particular ion. So you can see
04:54 , we can see CASI wants to out of the cell, sodium wants
04:57 move into the cell. Calcium wants move into the cell. And this
05:00 a general way your body works. no matter where you look, this
05:05 going to be true with very few . All right, there are some
05:10 in the body. We don't have learn them. OK. So ions
05:15 going to do this in a passive , meaning there is nothing driving them
05:20 than the natural physical laws that govern moving down a concentration gradient.
05:27 So we're not pumping these things. potassium is desperate to move out and
05:33 equilibrium. All right. So if ever took chemistry and you hear that
05:38 over and over again, equilibrium, , equilibrium, all we're doing is
05:40 trying to create balance in the All right, we've got lots
05:45 We're gonna move down until there's We're never going to allow it to
05:49 though. All right, some other , the greater the concentration, the
05:55 the, the the flux or the the movement. Now, this is
05:59 concept we've already talked about. We look if there's already very similar,
06:03 low similarities or similarities. So there's slope, then the movement is
06:07 very slow. But if we make really, really steep. The slope
06:10 steep, then things move fast. so what that's telling you is if
06:14 is a steep slope, so you see here 100 and 50 to
06:17 that's a steep slope, right? 100 and 50 millimoles over here,
06:22 four over here. That's gonna be , very quick. This is even
06:26 . You could see that team. calcium wants to run in and
06:31 this is less than that. So moves faster than sodium. Calcium moves
06:36 than, than all of them. right, if they were allowed to
06:39 , if there were, if there nothing blocking them, they would just
06:43 to reach those equilibrium as quickly as . But if this just, I'm
06:47 up a number, if this was and this was 2.4 it'd be a
06:51 slower, right? That kind of sense because there's not much of a
06:55 there. Now, you gotta press button. All right. Now,
07:01 order for things to pass through, need doors. And so this is
07:03 channels come in. All right. these are proteins found in the
07:09 So they're membrane proteins by definition, ? And they're the ones that
07:14 they are the doors in the wall the cell. All right. And
07:19 different kinds, right? We have that are open all the time we
07:24 these leak channels because they're leaky, let things just go through. We
07:30 gated channels, gated channels between the states are being open and closed.
07:34 truth is leak channels which are open gated channels, but they're always in
07:38 open state. So we just we ignore them and just basically say
07:43 passed through, all right. But gated channels, one that has to
07:47 something that causes that gate to open close. Now these channels are going
07:51 be selective in what they will allow pass through. Um I don't have
07:56 really good example, other than just , you go to a restroom and
07:59 says on the door of men or the door of women and then you
08:03 that I can't, I can't go a woman's restroom, not allowed.
08:06 that's kind of the same thing If it's a potassium channel, it
08:10 allows potassium to go through it. it's sodium channel, only sodium is
08:13 to go through it. If it's cat ion channel, only positively charged
08:16 can go through it. If it's anionic channel, only anions can go
08:20 it. So they're very selective as what they'll allow to pass through
08:24 right? So the permeability is allowed these types of channels, but they're
08:32 . And so what we're allowing is to be dependent upon which channels are
08:38 . And then of course, we to ask the question, how do
08:42 open them all right now, with to these gated channels, the two
08:47 types that you're going to experience over next couple of weeks are these two
08:51 lion gated channel, the voltage gated . And so all this is just
08:55 you is what is the key that the door? All right. So
08:59 are just some sort of binding All right, you can just,
09:03 , it's long, it's the key goes into the keyhole and turns it
09:08 opens the gate. All right. so once the gates open things can
09:12 through. All right, these can found either inside the cell or outside
09:16 cell. Um We're not gonna really with that question right now, but
09:20 really dealing with the, the And when we say inside the
09:24 we can see them on things like sarcoplasm reticulum. All right, which
09:28 be a type of endoplasm reticulum. see these a little bit later.
09:32 right, voltage gated channels. On other hand, are a little bit
09:36 different and something you have to kind wrap your mind around it. All
09:40 . And so part of this is , OK, I'm understand something in
09:44 to understand this right now. So haven't talked about membrane potentials yet.
09:48 what I want you to imagine is there is a concentration ions that sit
09:52 the plasma membrane, they're attracted to other, but they can't reach each
09:57 So if we change the numbers of attracted ions to each other, what
10:01 doing is we're changing the membrane Now, if I just said
10:05 good to you just say, it's go good for right now.
10:08 let me try to wrap my mind this. If I have a particular
10:12 around this molecule right here, the gate you can see here here is
10:16 charges and I change that concentration of . What that does is because of
10:22 the arrangement of the amino acids on channel, it's going to change the
10:28 of the channel and cause it to . So if I make it more
10:32 or say more negative around that then the the channel itself causes itself
10:36 become open. All right. So depended upon charge to open these
10:43 This is easy to understand, I . Keys, right? Keys are
10:49 . This is about electrical charge. if there is a change in the
10:55 potential, these open or close, ? So far, are you guys
11:04 me? OK. All right, wanna make sure. All right.
11:10 here again, we're not memorizing Remember I said, I don't want
11:14 to memorize this chart, but we to understand it conceptually. All
11:18 So generally speaking, when we look ions, there are some rules that
11:24 need to follow with regard to There's always more. See I said
11:29 did an absolute there. And I know, this almost always, almost
11:33 there is more potassium inside the cell outside the cell. So if that's
11:37 , then what you're going to see potassium is always again, will most
11:42 be leaving the cell passively. All . So basically what we're, what
11:47 learning right now is more potassium inside . Potassium leaf cells that's called an
11:51 flux. All right. The second important. So these two are the
11:57 boys. When we're talking about we're really talking about potassium and
12:01 With regard to sodium, we have lot of sodium on the outside of
12:05 cell and very little sodium on the of the cell. So sodium actively
12:10 into the cell. This is All right. So we have potassium
12:14 flux, we have sodium influx and the other two, we don't really
12:19 ourselves with so much, but we to understand that they're there. So
12:22 with regard to chlorine, there's more on the outside than on the
12:26 It's so it's gonna move um And then with calcium, there's more
12:30 on the outside than there is So it's gonna move inward. So
12:34 this goes back to Sesame Street One of these things is not like
12:39 others. So remember the one that's like the others and all the others
12:43 the opposite, right? So potassium to go out of cells, all
12:47 others want to go in the cells far. So good. Yeah,
12:51 telling you everything you need to You learned Sesame Street. If you
12:54 out on Sesame Street, you are behind in your education. All
13:02 Other things you already know. Do know that charges that are the same
13:06 repelled from each other? Yes. . Good. And you know that
13:12 that are different are attracted towards each ? All right. So because we
13:19 the uneven distribution, the way you think about it, if I have
13:24 of positive charges over here and very positive charges over here, I also
13:28 not just dealing with concentration, I'm with charge. So what we're saying
13:33 over here, I have lots of charge. I have lots of negative
13:39 , right? So the there's an to draw positive charges where there's negative
13:45 . And the way we think about movement of ions is we're usually thinking
13:48 terms of positive charges and where they're where you don't usually think about the
13:52 charges, right? So the idea is that there's not just a chemical
13:58 like we saw over here, there also an electrical gradient. All
14:04 So if I have lots of positive the outside and very few positive on
14:08 inside, then positive chargers are gonna to move inward to the cell down
14:13 electrical gradient. OK. Now notice didn't describe anything other than the
14:19 We didn't say which ions were We're just simply asking the question,
14:23 it positively charged or is it negatively ? And these two things together positive
14:29 , negative charges? So the electral and the chemical gradient are working in
14:35 to determine the movement of these And this is the problem that comes
14:41 . It's like what now I've got deal with both of these things at
14:43 same time. Yes. It's like and listening to music, both things
14:49 can do at the same time, ? Please say yes. OK.
14:53 right. Now, so if ions gonna be permeable and they're being transfer
15:00 being transported across the membrane, then charge distribution across the membrane is has
15:04 potential to change. OK. So other words, we're separating out
15:13 we're making different concentrations of them, have charges and that difference in charge
15:19 be changed by just simply moving the around. And what we're dealing with
15:24 is in essence, we're creating All right. In other words,
15:29 have established potential energy to allow things happen. So if we move ions
15:36 , we're basically storing up energy for cells to do work. And that
15:43 simply what the membrane potential is. , this is where I try to
15:49 it easy for you. OK? you look at this picture up here
15:52 a moment and I want you to around do you see on the outside
15:55 the cell? What do you see whole bunch of sodium and a whole
15:57 of chlorine? Right? Are they to each other? Positive and negative
16:03 ? Sodium chloride is called salt. right, see table salt. So
16:08 know that one? OK. On inside of the cell, we have
16:11 strange letter A minus and a minus not a grade. It's an actual
16:16 cellular protein. Anionic means negatively It's a cellular protein. They're
16:22 they can't move anywhere but what's attracted negative charges, positive charges, which
16:27 the ion that we have the most inside cells. You can just look
16:31 the picture, what's the K potassium ? All right. So in a
16:37 cell, in a normal environment, is kind of what it looks like
16:40 the cell. You have a lot sodium and some chlorine that's attracted to
16:44 . And so they basically neutralize each . And on the inside of the
16:47 , you have potassium which is attracted the negative charges of the anions or
16:51 cellular proteins. But if you look there also, you see a whole
16:55 of things that are not attached to , right? You can see up
16:59 to the membrane, we have a bunch of sodium lined up on the
17:02 . Do you see that? And see over here we have a whole
17:05 of ox cellular proteins that are lined against the membrane. All right.
17:09 , this is a scenario I want paint here in this city. This
17:12 the only city I've ever seen this . But it's probably true. In
17:14 words, we have high schools that next right, right next to each
17:19 . Have you, did you know ? I mean, like a leaf
17:21 like two high schools right next right downtown in River Oaks. You
17:26 Lamar right next door to Episcopal High . Right? I know Klein has
17:30 couple of high schools right next to other. And these are just the
17:34 I know off the top of my because I've had to go to football
17:37 there. Right. You can imagine these schools inside each of the individual
17:43 that are next door to each other there are couples when you were in
17:46 school. Were there couples? Ok. So you can imagine.
17:50 these couples are attracted to each other they spend all their time together,
17:53 they? Right. They walk down halls holding hands and making googly
17:58 Right? And then one goes to bathroom and the other one stands outside
18:03 for them to come back. Does this sound like high school?
18:06 . Ok. Yeah. For good bad. Right. We just just
18:11 with me. All right. Now can imagine also in these high schools
18:17 there are people who are not coupled right now. For the sake of
18:23 discussion here, we need to I'm gonna talk about heterosexual couples because
18:27 need opposites. All right. So you, if this is offensive to
18:33 , I'm sorry, welcome to the . All right. So let's imagine
18:40 these campuses that they have an open policy on campus, you can eat
18:46 on campus you want to. I know this doesn't happen. But
18:50 just imagine. Ok, and between two schools, you have a fence
18:54 goes in between them to define the properties, right? And so at
18:58 time, everyone comes rushing out because one wants to eat inside the building
19:03 let's escape its prison and they go . And so what do the couples
19:08 ? They sit together and they're like the googly eyes and sharing their peanut
19:11 jelly sandwiches and you know, all weird stuff. But you can imagine
19:16 either side. So if you have the schools, you have the couples
19:19 here and the couples who are But then you also have the sad
19:22 , the ones that don't have a , right? And so they come
19:26 with their little brown bag and they're little sad. But between the
19:31 we have this chain link fence and do they do is they come out
19:34 they look and they see across the something that's not coupled, right?
19:42 so what do they do. They , they smile and then over here
19:48 sad and turn and smile and then wander towards the fence. Yes.
20:02 , are these couples, these non couples? Are they together?
20:07 Why? What's between them fence? that's what we have here. We
20:14 a cell membrane that's acting like the . We have charges that are attracted
20:19 each other because positive, negative charges attracted to each other, but they're
20:23 kept apart, right? It's a tale right now. These couples,
20:31 we get them together? Yes. open the doors? Right. So
20:37 that fence, there's got to be gate someplace. If we can open
20:39 the gate, then they're going to start flooding through and they're going to
20:42 up and everything's going to be hunky . All right. So what we've
20:46 described here didn't like that example. just shook her head going. Oh
20:51 goodness. All right. All So what we have here in this
20:55 example here is a resting membrane The resting membrane potential is the attraction
21:00 those opposite charges on either side of membrane. Notice the membrane itself has
21:06 charge, right? The membrane doesn't . It's just in the way it
21:11 preventing those two ions together. All . So what we have is we
21:17 a membrane potential. Well, why we call it a potential?
21:20 this is potential energy. Could they together? What did we say?
21:24 . So there is potential energy. is creating the energy or the operation
21:30 that membrane? It's saying you're 22 can't come together. But if I
21:34 out of the way out of the , that's OK. So it's called
21:41 because of that, it's something that happen, but it's not. All
21:48 , if we open up a whatever gates available, right, if
21:52 open up a gate, we're gonna , this would be the type of
21:57 that we're gonna be looking at in of creating electrical current. All
22:02 So when we talk about muscles and talk about uh um neurons, we're
22:07 about opening and closing gates so that ions which are no that want to
22:13 together that they can. All So that's really what we're dealing
22:18 Here is the resting membrane potential is the potential a cell has as a
22:23 of the separation of those charges, excited cell takes advantage of that resting
22:30 opens up the gates and allows for . Now, we can measure this
22:35 we can use a volt meter to this. And the way that we
22:37 the measuring is we're comparing something versus else. And so our frame of
22:42 when we're measuring is always going to on the outside of the cell,
22:45 is the inside of the cell relative the outside of the cell? That's
22:50 99.9% of the time is what you're . OK. So what we have
22:55 we have a reference electrode and what doing is you're sticking something inside the
22:58 and it's saying what's going on inside cell relative to that? All
23:03 So if that charge that you read the volt meter is negative, what
23:07 it tell you about the inside of cell? There are more or less
23:12 charges more. OK? And if was positive more charges, all
23:19 So when we're talking about these cells we're saying, oh, they have
23:23 minus 70 rest mli resting brain What we're saying is that the inside
23:29 the cell is more negative than the of the cell by negative 70 mil
23:33 by 70 millivolts. That's really that's what would just say. All
23:38 , and we can calculate that All right, we can use,
23:42 can actually go and calculate a whole of fun things. All right.
23:45 this is where that math comes in we said we're not gonna do
23:47 But I'm gonna explain a little bit what this is. Now, if
23:53 look at an individual cell or an ion, ignore all the other
23:58 So you can imagine we have so different ions in our, in our
24:02 . But the ones that we were with were there was four that I
24:05 you potassium sodium and then chlorine All right. But really, the
24:10 two are the big ones. And we ignored everyone but one, so
24:14 look at potassium and we measure how potassium is on the inside and how
24:17 potassium is on the outside, we use this equation called the nert
24:21 So you can see the ratio here versus N. So if there's
24:26 if there's more on the outside versus , then you'd expect this to
24:29 if it's a log, it would a positive number. If, if
24:33 the in the outside is, or , if the inside is greater than
24:37 outside, then it would be a number. Because if you're doing a
24:41 and what you can do is you figure out mathematically using that equation,
24:45 is the point where ions would move and then get to that point where
24:50 would stop moving? All right. what point would equilibrium be reached?
24:55 would be the charge where equilibrium would reached? Now, if you're sitting
24:59 going wait a second. I don't what you're saying here because first you
25:02 stuck on the equation up here because was big and scary. But the
25:06 you're asking is OK, I want move ions into the cell, but
25:10 going to be a point where an is going to go in and saying
25:13 too many of these ions here. more attracted to the outside, I'm
25:17 back to the outside and then it'd like, well, I'm not happy
25:20 here because there's too many of the . It's that one last ion.
25:23 it basically keeps going back and forth and out. That's the question,
25:26 do I reach equilibrium? So this what this equation is describing. And
25:31 ion in your body can be calculated upon what its concentration is both inside
25:37 outside using that equation. And then just do the math and you come
25:41 with the number. Now, if look at this, this again,
25:45 memorize the list, right? But want to kind of see what we're
25:49 here. All right. So for , potassium will move out of the
25:54 until the inside of the cell is minus 90 millivolts. In other
25:58 going back to this picture, potassium move out of the cell over and
26:02 again, leaving behind negative charges which , which are those anionic cellular proteins
26:07 the point where find that almost minus then the inside of the cell becomes
26:14 to it again. And so it goes back in and then sits there
26:16 balance. That kind of makes right? Yes. OK.
26:25 sodium would move into the cell and just talking about sodium by itself,
26:29 would move into the cell until it behind chlorine until the inside of the
26:35 becomes positive. 60 again, you go and look at the equation.
26:39 could do the math if you wanted . But there it is, it's
26:41 positive 60. All right. And once it gets around positive 60 it
26:46 moving. Chlorine, you could do same thing. Chlorine would move into
26:49 cell until the inside of the cell minus 60. All right. So
26:54 of the individual cells or sorry, of the individual ions has its own
26:58 potential. But how many ions did talk about? Four? You can
27:08 three, I'll take three. All , we start with four and there
27:12 other ions involved. So you can't look at the effect of one
27:17 right? All the ions have this on the inside versus the outside of
27:23 cell. And so we can actually out what the membrane potential is with
27:29 horrible equation called the Goldman Hodgkins Now again, we're not gonna be
27:35 math. I'm just explaining what it and what you're doing. What this
27:38 is very similar to the nerds equation it asks the question is, can
27:42 calculate out the membrane potential of the if I know the concentrations? And
27:49 know the permeability, what permeability, what's permeability? Well, permeability just
27:55 the question is, how readily does move across the membrane? Now,
27:58 don't like this particular chart that they us because they gave us a frame
28:02 reference for potassium as big one. so both sodium and chlorine are fractions
28:08 one. That's a terrible way to stuff. It's much easier to find
28:11 lowest number and make that one and look at the ones relative to
28:15 And so you'd see that I'm just use sodium versus potassium. So that
28:21 this is saying here, if you at that ratio one to 0.04 that's
28:24 potassium has a 25 fold greater permeability sodium. All right. Next example
28:34 guys ever been to a football Ladies? Have you been to a
28:38 game? Ok. It's half You need to go to the
28:42 All right, when you get back your seats about the fourth quarter,
28:52 so many people? But there's, actually more guys at a football game
28:56 and we can get in and out the bathroom quickly. Why have you
29:00 wondered this question? All right I'm gonna give away our secrets.
29:04 that ok? All right ladies, have stalls where you can do your
29:10 , guys have troughs. All And what that means is a trough
29:14 usually about 10 15 ft long. what we do is we walk in
29:18 and in this trough we go in it's like, OK, I gotta
29:21 my business. You go up, don't look at it, no eye
29:24 , you look straight forward, you your business And so if there's like
29:27 people in the bathroom, you're on of the trough. But the more
29:30 more people you get, the closer closer you get to it literally shoulder
29:34 shoulder. So this is why we talk or do anything, we just
29:38 and do our business. So with to the movement of people through
29:44 what would you say is permeability? you think men have greater permeability in
29:50 bathroom than women do? Yeah, could have 40 stalls in a
29:56 right? But if we have two that can each accommodate 15 people,
30:01 ? I mean we're doing 30 people that. We don't have to wait
30:05 someone to come out of a stall that's why we move so much quicker
30:09 a bathroom. All right, it's easy thing to kind of understand if
30:13 think along those lines, right? how many doors are there for
30:19 And what this is basically saying is potassium has 25 doors for every one
30:25 of sodium. So for every 25 that go out of the cell,
30:30 many sodium go into the cell? doors? How many potassium move
30:40 25 and the ratio is 25 to . So how many sodium are gonna
30:45 in the opposite direction? One? right. So what this is telling
30:50 is that when we look at a potential, the greater the permeability,
30:56 greater the effect that ion has on membrane potential. So in looking at
31:04 and understanding that concept that the greater permeability relative for that ion has the
31:10 uh effect on the membrane potential, on has the greatest effect. Looking
31:15 this potassium, right. So potassium the most profound effect on where the
31:23 membrane potential will be. Right. it was potassium by itself, I'm
31:28 go back a slide. Actually, don't need to. It's right up
31:31 . If potassium was the only the resting membrane potential for a cell
31:36 be minus 90 if sodium was by and there were no other ions in
31:42 body, the resting membrane potential for cell would be plus 60 plus 61
31:48 fine chloride. What would it be 66? But because we have all
31:56 ions, they all have their effect the cell so far, so good
32:02 the greatest effect is going to be by the one with the greatest
32:07 So which one has the greatest So what do you think the membrane
32:12 looks like if you had to? mean, if you read the
32:15 you know the answer already, But what do you think it looks
32:19 ? Do you think it looks like 90 or you think it looks like
32:21 61 or do you think it you know, well, ignore the
32:25 because I said those two are the ones. What do you think the
32:28 of the cell is more like minus or is it more like plus 60
32:32 , more like minus 90? All . So when we go and look
32:38 the cell here we are, here's resting membrane potential. How do we
32:43 there? This is the whole reason teach this because when I sat in
32:47 seat, someone said inside of minus 70 it's the presence of the ions
32:52 the equilibrium potentials. And then they talking and everyone else is in the
32:56 going huh I don't want you to doing. Huh huh. Is
33:01 All right. So how that equation equation right there. That's how we
33:09 that number that minus 70. And can go me too. We can
33:13 take that volt meter and stick it there and go oh look the inside
33:16 the cell is minus five minus OK. So we can calculate it
33:21 we can measure it and they which means our math is good.
33:26 right. So the greater the the greater the effect. And you
33:32 see right over here the resting membrane is minus 70. This has the
33:37 permeability. So we're a lot like chlorine is a lot close too,
33:44 you can see that it's right So there's very little movement of
33:47 It's kind of already balanced because of presence of the resting membrane potential.
33:52 right. Now, here we Again, we're gonna put all this
33:58 together. All right, minus 70 our resting membrane potential. This is
34:04 we say. If a cell is doing anything, it's sitting there twiddling
34:07 thumbs waiting to be told what to . The resting membrane potential is minus
34:12 . The inside of the cell is 70. The outside is zero.
34:15 right, that the the ratio the of reference but is potassium and
34:26 You can look at the picture I don't even use this foot is
34:28 and equilibrium. So what do you do? It wants to move outside
34:33 the cell until the inside the outside the sorry, it wants to move
34:36 of the cell until the inside of cell is minus 90. All
34:42 So membrane potential doesn't create equilibrium. still having potassium leave the cell.
34:49 is sodium moving into the cell. . When will sodium stop moving into
34:54 cell when it reaches plus 61. the resting membrane potential creates a state
35:02 the ions aren't stopping the move or not, they're not stopping, they're
35:07 flowing. So you can imagine I've got my ions right here is
35:11 the some membrane potassium moving out sodium moving in. So they're just trying
35:16 reach their membrane potential or reach their potential, but they're not able
35:21 But every time sodium moves in, , that's taking a sodium from the
35:25 . We don't want that. And we need to move the things back
35:28 where they started. So we have pump in place and it says,
35:30 , I'm going to put you back you go. So even though we
35:34 this constant leaking of ions, this flow, this constant flux, we're
35:41 moving away from minus 70 we're pumping ions to where they need to go
35:46 that we can keep this going on . The energy in your body,
35:52 A TP that you, that you is primarily ensuring this happens. You
35:58 I'm wasting all this A TP just kind of, it's not a waste
36:07 the ions want to move and we something at rest. What did we
36:12 that a membrane potential? And when have potential energy, what does that
36:21 ? You can do something with OK. And that's the goal here
36:27 we're establishing potential energy in our bodies our cells to do things. And
36:34 the cool part. Now getting there a little bit hard. All
36:38 So the key thing is the things want you to walk away from
36:42 All right cells have a membrane You can calculate it out. It's
36:47 on the degree of permeability and it's upon how the concentrations of those ions
36:55 can do the math to figure it . But we're not gonna we could
37:00 reasons. All right. But the thing here is the ions are always
37:05 mo are always in flux, they're moving down there. Electrochemical gradient is
37:12 word that we're using here. Equilibrium is when your electrochemical gradient has
37:19 that balance, that e equilibrium And those I keep flipping slides because
37:26 keep forgetting I have it that your potential for potassium. That's your equilibrium
37:31 for sodium. There's your resting membrane . OK. Mhm mhm Need for
37:45 space. So permeability. Oh So uh the sorry the which is based
37:54 the availability of the number of All right. So let's just use
37:59 doors as an example of a How many people can fit out that
38:05 ? Just say two, right? right, and two out there.
38:08 the rate at which people could leave room would be four at a
38:12 right? So the permeability for this is like four people, right?
38:17 do I want if I want to permeability? What do I need to
38:21 more doors? All right. So see now if the doors are closed
38:26 this, I can't pass through So I have to have something that
38:29 the door. All right. And the idea here is what we're gonna
38:32 working with. All right. So gonna come back to this. I
38:37 you to soak in this idea of and their purpose and where they come
38:43 . All right, that's our starting . What we're gonna do now is
38:46 gonna move back into the anatomy and gonna deal with the question of
38:51 All right, the neurons, neurons the cells of the nervous system.
38:57 , they're the functional cell of the system, not the only cell of
39:01 nervous system. They're the quarterback there this is the cell we give all
39:04 attention to. All right, they really do their thing unless they have
39:09 cells around them. But we're when we get to the nervous
39:12 we'll deal with it. All So first off, this is an
39:15 cell, just like a muscle cell are excitable. What that means is
39:19 transmitting electrical signals along their length. right. Now, usually when we
39:25 about neurons, we talk about this and people think that this excitability is
39:31 on here between the two cells. not what's going on. All
39:34 what we're talking about is we're talking conduction of electrical signals from one side
39:38 the cell to the other neurons can really, really small like they are
39:42 the brain and stuff or they can really long. And I think I've
39:46 mentioned we have neurons that originate in spinal cord that travel the length of
39:50 arm or the length of your So they can be 2 3 ft
39:54 , they're very, very long And the idea here is I'm conducting
39:59 very quickly along the length of the so I can get quick responses.
40:04 . It's like passing a note except you have an internet connection, a
40:09 connection. All right. Now, we're doing is we're sending these electrical
40:15 from one part of the body to other. Um, we're going to
40:19 that this is gonna happen because of presence of these uh membrane proteins,
40:24 channels as well as pumps and um relative concentrations in where they're found with
40:31 to the cells. Once you make , you have them for life,
40:35 have incredible longevity. All right. the neurons that make up your nervous
40:39 right now where the neurons you were with, which is really cool.
40:43 will your entire lifetime, they're meaning they don't go through mitotic cycles
40:50 most cells do. Once you create neuron you, for the most part
40:53 stuck with what you got. There some exceptions to the rules more than
40:57 usually let on. But I want to just think in terms of what
41:00 , what you're going, what you . Ok. That's not 100%
41:05 But I just want you to think way, ok, they're highly,
41:09 metabolic when we think about consuming you know, consuming energy, oxygen
41:15 glucose. We don't, we kind this is how your body works.
41:19 the truth is that the glucose that consume is sent almost exclusively to your
41:24 . The oxygen that you consume is going to be consumed by all your
41:28 . But your brain makes a huge on this stuff. All right,
41:34 just getting better out there. the nervous system in neurons were um
41:50 we first started talking about cells, said, hey, these are the
41:53 that all cells have. But in early days of histology and, and
42:01 , they didn't understand this concept. mean, they, they knew that
42:04 cells had stuff. But if you in the nervous system, you gave
42:08 nervous system special names and all the , special names. And when you
42:12 worked in the muscles, you did same thing. And so there's language
42:15 kind of goes with this, the system and neurons that we just have
42:19 kind of pick up and go So the cytoplasm of a neuron is
42:24 the Peron. They portion that's doing the work. This is where you
42:31 all the cellular machinery is going to in the pair. Carry on the
42:37 body has a name. We usually to it as the soma that's
42:42 that's really what it means. But the same thing. I mean,
42:45 you think of a cell that has cell body, that's, that's
42:47 it's, it's a major component. within the para carry on. That's
42:51 all the work of the cell is done. So this is where your
42:55 partic is um this is where the are located. This is where the
42:59 located, et cetera, et et cetera. The guy who found
43:03 ribosomes in the uh neurons. His name was Niel and he had found
43:08 special stain that worked and they were ribosome, but they got a special
43:12 , they call Niel bodies. All , you can see if you look
43:18 your neuron that it kind of looks a star in this particular case.
43:21 this is just the artist's rendition. all have different neurons have different shapes
43:25 appearances. But these extensions, these are called dendrites. All right.
43:34 I have up there, Axon as axon is a type of dendrite.
43:38 is simply a word that means And so it kind of looks like
43:41 branches. And so the dendrites you see are the smaller ones and the
43:48 which is a dendrite, which happens be a larger one and they actually
43:51 different functionality. Typically, when we dendrite, we we're referring to an
43:57 that receives another cell. All So they're kind of on the receiving
44:01 . Whereas the axon always on the end. When you are in the
44:13 system, you will see these body together in a variety of different
44:20 right? It's primarily located in gray when we're looking at the central nervous
44:24 . But where you see them is these clusters and call these clusters
44:32 So you can just think when you a nucleus, not a nucleus,
44:35 nuclei or a nucleus of cell it's basically just a bunch of cell
44:42 that are clustered together that are processing together in the peripheral nervous system.
44:47 central nervous system is your brain and spinal cord, peripheral nervous system is
44:51 else. We don't call them We give them a special name,
44:54 call them ganglia, but they're essentially same thing. It's just cell
44:58 a whole bunch of these jammed together a, in a specific location and
45:04 processing information together. So with regard the neural processes, I've already
45:12 we have the dendrites. This is receiving end the axon. This is
45:16 long one here that is gonna be sending side in terms of where this
45:20 . This region right here is called ax axon hili. The axon heli
45:25 important because it's from this location that action potential is going to be
45:31 The action poten potential is the electrical that's gonna travel along the length of
45:37 axon. Now, the axon itself divide. So it's not, it's
45:42 not one little strand that just it can actually split into multiple strands
45:46 go in different places when you have axon split. Those are called
45:51 In other words, they're branches on the Axon um when you get down
45:55 the very end. So this stuff down here or this stuff right
45:59 those are called Telo Indri. And at the very tips of the telo
46:04 that you're in close a position right to the next cell and that's what's
46:08 to be forming the synapse. So very end of the telo indri are
46:14 the synaptic knobs. All right. these are just language things and the
46:20 way to remember it is just draw a, a really bad picture of
46:25 um axon or sorry of a, a neuron. So this is how
46:29 do it just, you know, then, and then just start gaming
46:34 parts. So that would be like dendrite, right? And you
46:37 there's your nucleus missile bodies, Axon Axon, et cetera, et
46:45 et cetera. Doesn't have to take lot of effort to draw it.
46:49 right. Now, I have a , dendrites are predominantly gonna be producing
46:58 potentials and then the axon is what's be producing an action potential. We're
47:04 talk a little bit about greater Today, we're gonna serve action potentials
47:08 Thursday. All right. But these types of electrical signals that are being
47:13 in response to the opening of these that we just talked about.
47:18 the axons when they travel together, you're in the central nervous system,
47:22 call it a tract. And if out in the peripheral nervous system,
47:27 call it a nerve. All you have no nerves in the central
47:32 system, you only have tracks. . So the axon is the most
47:41 thing that we're going to be spending time on. And I say most
47:44 because we just kind of generally focus , right? So this is the
47:49 region of the neuron. This is you think of a nerve impulse or
47:52 action potential, this is where it's . It basically takes a signal from
47:56 cell body and transmits it down to synaptic terminal, right? It does
48:01 have any of the machinery of the . The axon lacks all that
48:06 Instead, its sole function is to sure that that signal travels down.
48:11 have a special name for the We call it axoplasm because reasons,
48:19 . The plasm membrane, not a Lima, it's an axolemma. Thank
48:25 again, neuroscientists. All right. , here you can see this is
48:30 to represent the cell body down That's the synapse. This is supposed
48:34 represent the axon. So we are to be signaling from the synapse.
48:40 that means you're gonna have to have molecules that are going to have to
48:43 found there because we're not sending an signal between cells. We're sending a
48:48 signal between cells. But I don't the chemicals anywhere except for the cell
48:53 . So if I'm going to send chemicals from my Axon terminal and I
48:58 them up in the cell body, have to transport them. And so
49:01 have transport. We have two All right. Retrograde would mean retro
49:08 backwards. So it's going from the back to the cell body. So
49:13 is forward. All right. So I'm moving materials from the cell
49:18 it's anterograde. Now, we have different speeds at which things can
49:23 We have fast or slow, We're talking about 400 millimeters per
49:29 All right. So think about a um a millimeter, how big
49:34 is and then you multiply it by , you now have a centimeter and
49:39 multiply that by 40 and you're looking like this far. So that's how
49:46 right? You can, you can by fast axonal travel. Now,
49:52 are you doing that? Well, have those motor proteins. Remember those
49:56 carry vesicles. So what we do we make up our chemicals, we
50:00 them in vesicles and we strap them the backs of the motor proteins and
50:03 travel down intermediate filaments all the way . So that this is what this
50:07 trying to show you and we deliver vesicles down to the axon terminal.
50:11 they can be released, the chemicals from those vesicles with regard to the
50:17 axonal. It's much much slower 0.1 three millimeters per day can picture that
50:22 millimeter multiply by three or divide by . Whichever you want to do this
50:27 or kin to more kin to you in a, in an inner tube
50:33 a on a slow moving river just in the sights. Make sure you
50:39 your drink with you, OK? just kind of floats around going.
50:43 ? This is kind of cool. , uh typically you're gonna see this
50:47 the interior grade. If you're moving and forwards, you're most likely doing
50:53 Axonal language. OK? So if haven't figured this out by now,
51:04 of the stuff in the early classes you take are language classes. Have
51:08 noticed this? If you're in a class, you're learning a new
51:11 you're in a Kim class, you're a new language, mathematics, new
51:16 , right? And so this is of those places where we are really
51:21 with a new language. All But what we're gonna do is we're
51:24 flash back to third grade. You remember third grade. Do you remember
51:28 lines in third grade? I, think that's the year that they start
51:34 number lines, right? So you a number line, I'm sitting on
51:37 right now over there. That would the negatives over there. That would
51:41 positives if I'm sitting on zero, am neutral, right? Would you
51:47 agree? All Right. OK. I move off zero in either
51:51 I become polarized. OK. Does make sense? So, if I'm
51:57 here, I become polarized. If come back to zero, I'm
52:02 If I or not polarized, if move this direction, I'm polarized.
52:06 I come back to zero, I no longer polarized. If I move
52:09 here, what am I polarized? doesn't matter how big if I'm not
52:16 . right? If I'm not I'm polarized. All right. So
52:20 the first thing you need to take polarization means I am not neutral.
52:24 am not equal to zero. Now, we already learned that the
52:29 of the cell is minus 70. I'm just gonna go over here to
52:32 70. What am I? I'm ? Great. So the inside of
52:39 cell is polarized because it's at minus . All right. If I become
52:45 polarized, which way am I going move that way? Right. All
52:51 . So becoming more polarized is called polarization. OK. If I return
52:59 to my polarized state, my original point, I have re polarized.
53:06 if I become less polarized, I'm towards zero right way over there,
53:11 less polarized than I was before. I'm becoming depolarized. All right.
53:17 then I remove, go back from depolarized state back to my original polarized
53:21 . I am polarized once again. . Now we're just gonna flip the
53:28 here. I am. I'm at 60. All right, polarized or
53:35 polarized. If I become more I'm moving in which direction? There
53:41 go. OK. So I have polarized. And if I return back
53:48 my original polarized state, and if go over here I am and then
53:54 return back. Excellent. All this language becomes very important because this
54:00 the language of the nervous system. talking about depolarization. You'll see the
54:04 depolarizes the cell depolarizes over and over over again. And you need to
54:08 what am I doing is I'm approaching . I'm moving away from a polarized
54:12 of minus 70 I'm moving towards In the case of the action
54:17 we do something really, really I depolarize. So here I'm at
54:21 70 I depolarize and I go and cross over zero and now I'm going
54:26 direction to plus 30. I don't my language because my starting point was
54:33 minus 70. All right, I'm all the way over to here.
54:37 just cut across zero doesn't mean I my language. And then when I
54:42 back, it's still called rep OK. So generally speaking,
54:52 it's general if we have an inward of positive ions into the cell,
54:57 what it refers to. We're calling a depolarization because the cell becomes less
55:03 on the inside. Remember all those cellular proteins that we're waiting for a
55:08 . They're like, please please come here. I want to eat lunch
55:11 you, right? If I can positive ions to flow into the
55:15 I'm depolarizing. I'm becoming less negative I was. OK? If I
55:22 positive ions because remember notice we're not about flow of negative ions, but
55:26 I have a flow of positive ions of the cell, I'm leaving behind
55:31 anions and so the inside of the becomes more negative. That's hyper
55:40 Are we good with that good with language? OK. All right.
55:45 changes in the membrane potential will result an electrical signaling. And again,
55:50 electrical signaling is going to be recurring the cell. It's not going to
55:53 occurring between the cells. Right. very few cases where we're going to
55:58 electrical synapses when we talk about the and a MP two, that will
56:01 an example of an electrical synapse. of the synapses we're looking at in
56:05 body are chemical in nature. So the electrical activity that we're looking at
56:09 going to be occurring within a cell . All right. So there are
56:14 different types of, of electrical two different types of potential changes,
56:19 graded potential, which is what we're to talk about right now. These
56:21 short distance signals, the action On the other hand, is a
56:25 distance signal, we said a couple minutes ago, I don't know if
56:29 caught it. Dendrite primarily deal in language of graded potentials. Action potentials
56:36 reserved primarily for the axon. All . And it's not a reserve,
56:42 because of the presence of the right being in those particular places. That's
56:47 what it boils down to. All . Now, anything that is going
56:52 change the membrane of the permeability for ion will result in electrical change,
56:57 that alters the ion concentration on either of that membrane is going to cause
57:03 change in that membrane potential. So that potential change. And so when
57:08 talking about membrane potentials, we're talking , here's our baseline. And then
57:13 sort of changes are we occurring? it gonna be a short distance signal
57:17 is it going to be this long signal? And so the question we're
57:20 is if it's one of those what's causing it when it comes to
57:25 greater potential? All right. So we are, we're looking at the
57:29 of a cell or it could be dendrite if you'd like if that makes
57:32 easier for you. And you can here, what I've done is I've
57:35 some sort of chemical that has caused channel to open. So imagine for
57:41 moment, those ions stuck on either of the membrane looking at each other
57:49 . And if I open the what's it going to do, I'm
57:53 go through the gate and I'm gonna my partner. Right. That's what's
57:58 on. And you can imagine what the change that occurs nearest where the
58:04 is. So, imagine you have ions lined up on either side of
58:08 gate, desperate to go through. I open up the gate, they're
58:11 go flooding through very, very aren't they? So you're gonna see
58:14 greatest movement nearest where it opens and can measure that. So just underneath
58:21 that channel is opening is where you're see the greatest potential change, but
58:27 gonna find their partner pretty quickly. so they're not gonna move from that
58:31 . The further away I move, fewer ions moving away or moving
58:35 right? So if I, let's say I have a whole bunch right
58:40 , then the next one that comes has to move over here to find
58:43 partner. And then it's gonna be you move further and further along,
58:47 gonna be fewer ions who are partner . And so the further and further
58:52 you or the lower the membrane potential . Have you ever thrown rocks in
59:03 ? Yes. I mean, it's you see a smooth glassy surface,
59:05 got to disturb it, right? if you get a little tiny pebble
59:11 that, right, you get a tiny splash. It's not a big
59:16 , a little splash, but that's site where you're gonna have the largest
59:20 . But the ripple that's formed is gonna be as big as the big
59:23 splash? No, it's smaller and further and further it moves away from
59:27 site of origin, the smaller the gets until it dies away. That
59:32 of makes sense. That's what's happening is the biggest splash. The biggest
59:37 and potential change is where that stimulus and the further and further away you
59:44 from it, the smaller and smaller change becomes OK. So it dies
59:51 . So one of the conditions of potentials is that it is a small
59:58 that dies out over a short OK. Now, these changes can
60:07 in one or two different directions. I open up a channel that allows
60:10 into the cell, I'll get a . If I open up a channel
60:14 allows potassium to leave, I will a hyper polarization. OK. That
60:20 of makes sense, right? So case it can happen because neither of
60:24 two ions are in equilibrium. What do I have up here? Um
60:30 thing I'd point out is that this go very far. So like I
60:34 , it's a ripple, it only a very, very short distance away
60:37 the site of origin. Another thing membrane potential or grated potentials have is
60:43 they have different magnitudes and durations. a direct correlation right now.
60:49 I'm just going to give you an here, this is not a description
60:52 a greater potential. If I take little tiny needle and I come up
60:56 go to you, you'll feel it ? But it probably won't be too
61:01 . Right. So you'd go out then you'd be mad at me.
61:05 right. So you can imagine very small, but I can take
61:08 same needle and I can go. . So I'm now increasing the magnitude
61:16 behind how I'm sticking you? So would it hurt more?
61:21 Now, let's say I come over and I grab that needle just
61:24 And I take a running start and jam it into, would it be
61:32 stronger stimulus? Would you get a response? Yes, a very angry
61:37 response. What you're looking at up is that here, we're looking in
61:44 of the strength of the stimulus. this is magnitude. So you can
61:49 here, this one is a tiny . This one is a little bit
61:53 . This one's even bigger and the in the greater potential is I have
61:56 small grade of potential. I have bigger one and I have an even
61:59 one. So magnitude matters, the the stimulus, the greater the greater
62:06 duration is also true. It's coded that potential. So what we're doing
62:12 we're opening up the channel, we're , how long do we keep the
62:14 open? So again, going back the needle, let's just say we're
62:18 the low. I just do it . You barely feel it right.
62:23 time in which the simul occurs is short, but I could go and
62:27 it there for a little bit and pull it away. So the duration
62:30 that pain would be longer and then could do it again softly, but
62:34 it there for even longer. So that would be coated in the
62:40 of the graded potential. And this doesn't do this because these are all
62:44 same length. All right. So is strength, duration is time.
62:50 those two things are encoded in the of the graded potential. We've already
62:59 this, that they're short lived, only last as long as those ions
63:03 find their partner. So at the of stimulation, we'll get something large
63:07 then they die out. All this is the better way to see
63:14 . All right. So you can here, I'm creating a depolarization.
63:20 here, if I measured it, I had a little thing to
63:22 you'd see that I've got this really strong signal. But as I
63:28 further and further away, that signal weaker and weaker, it rippled,
63:32 died away. All right. So potentials are very short lived, they
63:39 a short distance before they die Now, if I am opening channels
63:47 allow the inside of the cell to more positive. So remember this is
63:53 in the cell, I've received a inside the cell. I'm creating this
63:57 potential. If it's a depolarization, the inside of the cell to become
64:01 positive, it's an excitatory potential. right. So, depolarization is
64:07 We give it a name. It's , it's a postsynaptic potential. So
64:12 has four letters epsp, it's how abbreviate it. But let me just
64:16 the word down. Excitatory refers to depolarization event. Postsynaptic. It tells
64:20 it's the receiving cell. All I'm the cell that is receiving the
64:25 and it's a membrane potential change. where the potential comes from. All
64:29 . So typically this is a local of sodium. I'm starting to get
64:33 about this thing. All right. typically, this is the opening of
64:37 channels, small sodium, moving into cell. The opposite would be the
64:42 sp. What happens to the It becomes hyper polarized. In this
64:49 , what we're doing is we're doing of two things. Typically, we're
64:52 up a potassium channel. So potassium out of the cell. So it
64:56 a potassium eat flux. So the of the cell becomes more negative.
65:00 also cases where you can open up chlorine channel and chlorine channels or chlorine
65:04 into the cell causing it to become negative. All right. But that's
65:08 little bit rarer. But again, sort of principle here. What am
65:12 doing is I'm allowing ions to If, if it's potassium, it
65:16 out. If it's chlorine, it in causing the cell to become
65:20 it's moving away from threshold, it hyper polarizing. And so we call
65:26 an I PSP inhibitory postsynaptic potential. , why do I care guys on
65:37 media? Ok. Have you ever or given a poll on social
65:44 Let's say you're dating somebody and you ask 4000 of your closest friends,
65:50 or not you should break up with person, right? Well, that's
65:54 follows you, right? All your friends. Yeah. Yeah. So
65:58 put it up there, say, I break up with this person?
66:03 so your 4000 closest friends are going give you their very strong opinions of
66:07 or no, right? And you're do whatever they say because social media
66:12 always right. Thank you for giving that look. That's, that's,
66:16 brings joy to my heart. She at me and she was like,
66:19 . Yeah, good. All So let's say now you're a neuron
66:27 you have your 4000 closest friends talking you see the picture that purple thing
66:34 the middle, that is the cell of a neuron. All those little
66:39 things are the axon terminals terminating on neuron. This is how many neurons
66:45 telling that cell what to do. so if these, some of these
66:49 are going to be sending positive do it. Some of these are
66:54 send negative signals, don't do And then you're going to do the
66:58 is going to respond to all the that it's receiving. So here you
67:04 , you send out your pole two later, you get the signal that
67:08 yes, break up with the guy the gal. And what do you
67:13 ? You respond? You have produced excitation. If the signal comes back
67:19 says no, don't, don't do so foolish. Don't listen to people
67:22 social media. Then you're like, OK. Well, I shouldn't have
67:25 out the poll in the first And so you don't, that would
67:28 inhibition. You're not allowing it to and that's what's going on. Each
67:32 these signals are sending some sort of or each of these neurons sending some
67:37 of signal that results in the That would be a ex excitation or
67:42 in an IP sp inside the cell would be negative. So you got
67:46 ones and you have negative ones and fighting it all out and they
67:50 because you have different magnitudes, you're have different variations in terms of how
67:56 affect the cell. And if you up all the EP SPS, it
68:00 up all the IP SPS and their magnitudes, you get some sort of
68:05 , either I'll get a depolarization or get inhibition So we call this
68:12 the summation of all of these different , the grand postsynaptic potential. All
68:19 , that's the GPS P. It means all the signals that I
68:23 All right. And the way that works is that there is different types
68:28 summation. We have temporal summation, have spatial summation and we have
68:33 All right. So temporal summation, you see hear the word temporal,
68:37 does that sound like? What do think of when you hear temporal
68:41 That's what we're looking for. And if you're spatial it means space.
68:45 right. Now, I'm just gonna you now, spatial summation has a
68:49 component in it. All right. it has to do with look at
68:54 definition you'll see. All right. I think our first one here is
68:58 . Yes. All right. So it is the simultaneous. So simultaneously
69:03 at the same time. All that's the keyword there firing of more
69:08 one uh I have the word a up there. But basically let's just
69:15 it a signal for right now. the idea here is I'm just going
69:19 give you an example. So you see here it's in the middle
69:22 So here I have a signal that the depolarization. Here is another signal
69:29 causes depolarization. You can imagine you see I have two signals coming here
69:35 the same time. So when both those are being triggered at the same
69:39 , it will make them bigger. , this is an easy thing to
69:43 . Um You don't have anything in hand. So I'm gonna clap.
69:46 want you to hear how loud my is. OK. So just wait
69:49 me. Is that a loud Kind of sort of? All
69:53 Now you clap. So, just him that I appreciate the enthusiasm
70:00 we're gonna have something where the whole does something a little bit later.
70:02 do it again. All right. now watch the two of us
70:07 123. Is it louder? OK. So that would be an
70:12 of spatial summation. He has his magnitude. I have my own
70:16 but our magnitude together creates a greater . So if we're both EP SPS
70:22 , we'd create a larger GPS P is the sum of the two EP
70:27 . OK. That's what that's So it's basically suing two or
70:31 Do you all want to do it ? Do you want to all clap
70:33 ? Do they make you feel Yeah. OK. Let's do
70:36 Seeing that a lot more fun. . So you can imagine that would
70:40 a really big signal. All temporal summation is a little bit harder
70:45 , to describe using the same But the idea here is you have
70:49 neuron and the frequency at which it's a signal. Increases so that they're
70:55 and closer together. So again, I was clapping, you know,
70:58 not a very loud one. But I started doing this, I never
71:04 an opportunity for sound to stop ceasing between them. Right. And so
71:09 signal gets bigger and bigger and it grows on itself. So one
71:12 the things that we can do with greater potential is that we can add
71:15 together. All right, with regard cancellation. All we're doing now is
71:21 taking an Epsp and an IP SP we're just adding them, adding them
71:26 . So I'm just making up a , let's say one causes a positive
71:30 mobile volt change, depolarization. One a negative five polar or five millivolt
71:35 . So plus five plus negative five that's cancellation. But yes, we're
71:46 get there. It's, it's, terminology, it really kind of works
71:49 action potentials. The way you can about this is if I have um
71:56 different magnitudes, I'm just summing them together. So if I had plus
72:00 and minus five, I would have a cancellation, right? Even though
72:04 not a complete cancel, but they're against each other. And so that's
72:09 a cancellation is. It basically, results in that the two things eliminating
72:15 . Was that my last slide? was my life like, all
72:18 So before we walk out of we need to take this home and
72:23 we come back on Thursday, we're use these terms, this idea,
72:27 greater potentials to result in understanding what action potential is. So, if
72:33 not understanding stuff, either read or me or come by my office.
72:38 talk about these things. All I don't want you to be sitting
72:41 in the dark. Have a great . Stay dry,
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