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BIOL 2301 Human Anatomy & Physiology I - BIOL2301 lecture12_0227
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00:02 All right, good morning y'all. , let's see if we can just
00:05 of sum up what's coming up. have an exam next week,
00:09 All right. Sorry. It's, gonna be on Thursday. So right
00:12 spring break, um, I will let you know right now, we
00:15 have class on Tuesday before, but class will not be the material in
00:20 class will not be on the All right, the way the schedule
00:24 this year is I, I had figure out which was the best way
00:28 do it. And I'd rather you take the exam right before spring break
00:32 opposed to come to class and basically it off completely and I couldn't put
00:36 . I wanted to give you guys day off, but there was no
00:39 day after spring break. So, we'll have this class and next class
00:44 be on the exam and the next will be the next unit, but
00:48 don't get tested until Thursday. Does make sense? I'll say it again
00:53 Thursday and probably again on Tuesday, just for our sake. And
00:59 um, I'm not gonna promise you is a great day. All
01:02 This is the material that most people through. All right. And the
01:07 I'm not doing this to scare ok, I'm just, you
01:09 kind of putting your brains like, , if I don't get it the
01:13 time, that's not surprising. All , that's, that's how you kind
01:16 approach this. All right. And we're gonna talk about today is we're
01:19 talk about electrical potentials and this is theoretical stuff, but it's not visual
01:25 , right? This is not stuff can look down at the body and
01:27 look, I can see that All right, because these are ions
01:32 back and forth across membranes. And we go through this whole process of
01:37 all this stuff is so that you understand what's happening in a muscle cell
01:41 what's happening in a neuron, which all the rest of this semester.
01:46 right. So everything we talk about the next two classes really kind of
01:51 up and prepare us for all the that's coming in the next two
01:55 All right. So it's very physiologically . All right. And so some
02:00 these things will make sense and, really what I want you to do
02:04 as we're going through it, I want you to get trapped in the
02:06 . All right, because that's usually happens. We see big words and
02:09 words, words. We've never seen then we go, ah, I
02:12 understand it but you've been to And so, you know, things
02:17 things roll downhill. Right. I , that's a simple thing and that's
02:20 of what we're looking at are things downhill. All right. So,
02:24 , if the language gets a little confusing, just say, wait,
02:26 , wait, wait, wait. you talk to me as if I
02:28 a two year old and ill will of back it up and try to
02:31 it more simplified to make it And so that's where we're going
02:36 It's all going to be about greater and action potentials over the next few
02:40 . So today we're going to really of deal with greater potentials. See
02:43 already a word where it's like, don't know what that word means and
02:45 an action potential. All right. as we go through, I'll just
02:49 of break it all down. All . So the first thing, what
02:52 gonna do is I want you to about a cell. All right.
02:54 that's what they're looking at here We have our little cell should make
02:58 I did hit. Yeah, we recording. All right. And what
03:01 already know about cells is that we a plasma brain that has a,
03:05 permeable state that it is what we refer to as being semi permeable.
03:09 we talked about already about there being so that the inside of the cell
03:13 different from the outside of the So, so far nothing new,
03:17 ? Everyone should not, they're gonna . No, that all makes
03:19 All right, the thing is, what we have that makes the inside
03:24 the outside of the cell particularly unique regard to electrical potentials is that the
03:30 concentrations are different, both inside and the cell. Now, you're gonna
03:35 these numbers over and over again. you think you have to memorize the
03:38 ? No, you do not have memorize the numbers. Is it helpful
03:41 memorize the numbers? Not so Maybe if you stay in the
03:44 it might be helpful. But the here is like, look if I
03:48 out or inside the cell, I've a lot more potassium than on the
03:52 of the cell. All right. the same is true for the sodium
03:55 in the opposite direction. I have lot more sodium on the outside than
03:58 have on the inside. And so of this, we have these unique
04:04 and the behavior of ions just like else that has different concentrations is things
04:10 to move in a direction that goes an area of high concentration to an
04:14 of low concentration. All right. so this is what we were when
04:19 say there's a concentration gradient, that's we're referring to is that there's more
04:24 something on one side of the membrane on the other. And those,
04:27 ions want to move until there's but there will never be equilibrium.
04:32 right, because the mechanics of the of the machinery of the cell and
04:36 the chemistry and stuff like that will allow it to happen. And so
04:40 always going to be in this state unequal distribution. All right.
04:45 when ions move, they're gonna do passively, you do not have to
04:49 energy into the system, right? I put a ball on the top
04:53 a hill, the ball is gonna . There's nothing I could do to
04:55 that ball from rolling other than putting to prevent it from rolling,
04:59 It's just gonna go and that's what ions wanna do is they want to
05:02 down the hill. And so you see here uh those two that I
05:06 out are the big ones that we're focus on. All right, but
05:09 doesn't mean that there aren't other So like calcium, you can see
05:12 a huge uh gradient that favors movement the cell. You can see your
05:16 has a, a greater concentration outside inside. All right. But for
05:21 now, we're, we're not going focus on those Zs. We just
05:24 to understand that principle. Now, said plasma membranes are impermeable, generally
05:31 to ions because uh you need to some sort of mechanism to cross that
05:35 , right. The ions want to where water is. The plasma membranes
05:39 made up of lipids, lipids and uh ions don't mix. So
05:43 the ions are just going to stay whatever environment they, whether it's outside
05:47 cell or inside the cell. But you give them a doorway, then
05:52 will move. And so that's where focusing next is we're saying. all
05:56 , well, there are channels. right. And what are these
06:00 Well, we've already talked about There are two basic types of
06:04 There are gated channels. They are ones that have the doors and the
06:08 open and close. And we have channels and leak channels are really gated
06:13 that have doors that are always in open state. All right. So
06:16 , they do have the gate, just stuck. And so a leak
06:21 is something that is always open and ions can pass through freely in a
06:26 channel, they're closed. And so has to come along and open up
06:30 channel. All right. But doesn't if I have high ion concentration in
06:37 and low ion concentration in there, what's gonna happen is the ions are
06:40 flow as long as that gates open when the gates closed, they can't
06:43 through but they want to go And that's really what all this stuff
06:46 telling you. So an ion channel a membrane protein if you don't
06:50 And it's what allows get passage of through. Now, we're gonna spend
06:54 of our time talking about gated But I want you to understand that
06:58 channels do exist. And if you a leak channel, that means anything
07:01 that particular ion type can flow This is like if that door was
07:05 , anything um that could fit through door is gonna fit through the
07:08 right? Mosquito Hawks guys getting tired the mosquito Hawks. Yet those,
07:13 big, big ass moss mosquito looking . I'm so tired of those
07:18 Be sitting around all the ones hit in the face. There's one right
07:22 , see that the door let it . All right, it's gonna land
07:28 on top of your nope missed All right. So le channels allow
07:33 to pass through. They, it, they're always open. But
07:36 we're going to focus on are the primary types of gated channels. We're
07:40 to come back to leak channels because are important. All right. So
07:43 two primary types and there are more these, but these are the two
07:46 types that we're dealing with today. have the lien gated channel and these
07:52 easy to understand. We've talked about before. We have some sort of
07:55 that comes along and binds the channel is the key to open the gate
07:59 gate opens up and ions are allowed pass through. And so you can
08:02 we state we exist in a closed an open state. The one where
08:06 gonna be primarily focused though is here the voltage gated channel and, and
08:12 with the voltage gated channel, we're looking at something that binds to the
08:17 . Instead, it's responding to the of ions inside and outside the cell
08:24 that channel. All right. So opens in response to a charge,
08:30 ? So if it becomes more positive more negative, and then we're not
08:33 to describe which one does which. the idea here is when that charge
08:37 around the cell, the ions or , the the the the channel itself
08:43 actually change shape. And that's what the gate to open. So if
08:47 change the ion concentrations, voltage gated open and allow ions to move,
08:54 causes more ionic change, it's kind a positive feedback loop. It's very
09:01 . All right. But the key is that voltage gated channels are opened
09:04 the presence or changes in ion OK. Now, this is where
09:10 going to spend most of our not today, but tomorrow. All
09:15 . And when you talk about muscles you talk about cells, we're really
09:18 a lot with these voltage gated All right. Now, here are
09:23 rules that you have to know. I said you don't need to know
09:25 numbers, right? I said that do not need to know the
09:29 Yeah, but you do need to which side has more. OK?
09:35 so with regard to the first these are tattooed to your body.
09:39 you're into tattooing, this is you caffeine on your body, tattoo this
09:43 your body. This is one of important things. There is more potassium
09:48 the cell than outside the cell. right, almost in every case in
09:53 body. This is true. So that means is is that when
09:57 when you're talking about potassium ions, ions are going to move out of
10:02 cell and into the external environment. right. So potassium flux is always
10:09 of the cell. And again, are some exceptions to that rule,
10:12 we're not learning the exceptions today. right. So potassium almost always,
10:18 , always is from inside the cell outside the cell. That's the direction
10:22 flux. All right. So that's a little, little greater than
10:26 It's supposed to be an arrow. just too lazy to to click in
10:30 Asy sign. All right, with to sodium, there's always more sodium
10:37 the cell than inside the cell. if I open up ion gated
10:41 what's gonna happen is ion flows into cell? All right. So that's
10:47 always, always, always, there's few exceptions to that rule when it
10:52 to chlorine, there is so much chlorine outside the cell than inside the
10:56 . So chlorine is going to move the cell. And then finally,
11:01 , there's so much more calcium outside cell than inside the cell. So
11:05 you open up calcium channel, calcium into the cell, all right.
11:09 , there's some really weird stuff in . But when we get to the
11:12 and start talking about calcium, you'll why this is true, almost invariably
11:17 . All right. So there is to be questions, I promise you
11:21 are going to be on the They are going to say,
11:23 which direction is flux for this particular ? All right. And so when
11:27 hear the word flux, it's just which direction is it moving? All
11:30 . It's, again, it's that language stuff that you should become aware
11:34 . All right. And this is true in almost every situation so
11:42 No one has raised their hand and , well, why? Oh,
11:44 it is. Let's see, like do. Yeah, you'd say in
11:54 direction would potassium flow as, or way would, which way is potassium
11:59 ? And you and your choices would something like potassium flux is uh out
12:04 the cell. It's gonna be, usually gonna be along that language out
12:07 the cell, into the cell, sort of thing. Yeah, I'm
12:10 gonna try to be tricky. Uh huh. Yes, sir.
12:15 huh. We're not gonna go there uh so uh all right,
12:21 Everyone put down your pencils. Do write this down like in the
12:25 we have two different types of fluids the interstitial fluid and the intracellular fluid
12:31 flipped. So it's backwards. And it's like, trust me, if
12:37 is some place in the body where can be an exception to the
12:39 I guarantee there's gonna be one. that's the example where there is an
12:43 to the rule, but we are gonna learn it today. Excellent.
12:48 right, not learning that today. almost always. So you can just
12:52 ahead and put your brain always, good enough. All right.
12:55 here's something you guys already know, ? You already know opposites attract and
13:01 rappel. OK. That's that is for all sorts of ions,
13:06 If I have a positive charge in negative charge, they will push
13:09 right? If I have two negative , if you've done this with
13:13 you try to push them together, repel and they try to move away
13:16 each other. Same thing with two of a magnet, they move away
13:20 each other. And this is true ions. And so while we have
13:24 concentration gradients, right, so we lots of sodium over here, a
13:29 sodium over here is going to move its gradient. But we have to
13:33 consider charge. When we're looking at movement of ions, see a positively
13:38 ion is attracted to a negatively charged . And so it moves from positive
13:43 negative, right? But every time ion moves it's carrying its charge with
13:47 . So as positive charges move along gradients, they're making that gradient balance
13:54 along charge. And so what will up happening is if you have,
13:58 you can think like this, I lots of positive, very few
14:01 don't think about positive negative. But think in terms of the number of
14:04 as I have lots of positives over and very few positives, what will
14:07 is is you will start reaching an and now you'll start repelling positive
14:13 All right. So when we look ion movement, we don't just consider
14:19 ion, we have to consider the . And this is what is referred
14:22 as the electrical chemical gradient. So things matter. And when we look
14:27 a cell, let's see if I a uh yeah. So we're talking
14:33 that's the charge thing I just All right. So we have both
14:36 concentration gradient which is this stuff. have an electrical gradient which is this
14:42 and then together they are causing the of ions and the consideration of those
14:49 of ions together. And so this what it looks like in a
14:54 In a very simple model. You're that didn't look simple to me.
14:59 right. So let's kind of look this. So you can see here
15:03 our plasma membrane, plasma, plasma is made up of phospholipids. Phospholipids
15:09 no bearing in this. Other than , they're a barrier, right?
15:12 not attracted to, they are not , they're not doing anything to the
15:17 . They just simply sit between the environments, right? So membranes are
15:24 , they're just in the way they're chaperones at a dance, keeping the
15:27 apart. OK. So you can't each other, right? 6 ft
15:33 the outside of the cell. We sodium, we have chlorine, sodium
15:36 chlorine. One's positive, one's negative is positive, chlorine is negative.
15:40 what do they do? Are they to each other? Of course,
15:44 are right? But they're also in watery environment. So they dissociated but
15:48 positive and negative charges are attracted to other on the inside of cells.
15:53 have lots and lots of potassium. can see that you can also see
15:55 have some sodium and chlorine too. what this picture is trying to show
15:58 . Its relative concentrations. Potassium is charged. It's attracted to negative ions
16:03 well. What are the negative ions are inside cells? Well inside the
16:08 , we have lots and lots of and those proteins have negative charges associated
16:12 them. We call them anionic cellular . See the big long scary
16:17 It just means negatively charged proteins. those negative charges are what keeps potassium
16:22 and, or, or, or up. All right. And so
16:25 what you see in this side over is like, here's that cellular protein
16:29 the potassium is like, yeah, attracted to that negative charge. So
16:31 just gonna go hang out with All right. Now, what I'm
16:36 do is I'm gonna describe something to have this all make some clear
16:43 All right, what you're looking at is similar to what you see between
16:48 high schools that are next to each . Have you ever heard of high
16:51 next to each other? If if you are on the west side
16:54 town, a leaf had two high that are next to each other.
16:56 you've gone towards the center part of , there's two high schools next to
16:59 other. It's Lamar and I think Episcopal. I can't remember if they're
17:03 to each other and they're around the because it's just easy to buy a
17:06 plot of land and put two schools next to each other. And you
17:09 imagine in these schools that there are who hook up, right? Did
17:12 know people in high school who were , did you date in high
17:16 Please nod your head and say yes, I did. And so
17:19 was attracted to somebody. How about ? Were you attracted? Do you
17:22 to hang out with them? All . So that's kind of what we're
17:25 here is we're seeing. Although that's strange when you see four of them
17:28 . But you can kind of see , it's like, yeah, I've
17:30 positive charges and negative charges and they together in a high school. I
17:34 guys, girls, please just bear me if you're, we're thinking heterosexual
17:38 , opposites attract, right? they, they like to hang out
17:42 each other. All right. And can imagine at lunchtime, you
17:46 couples like to hang out and look other in the eyes and do go
17:49 gaga faces, right? Like they at each other longingly. I love
17:54 . I love you. I love . I love you. It doesn't
17:57 anything, it's just learning how to social, right? And so you
18:01 imagine it, both high schools have but also in those high schools.
18:05 you have people who are single? you know people in high school who
18:10 single? But did they want to coupled with somebody? Maybe you were
18:15 of those people? Right? But , there's not enough of that going
18:20 . And so you can imagine on campuses next to each other, they
18:24 a fence between the two sort of that you see the fence and let's
18:29 for a moment that instead of lunch stuck in a prison cafeteria, I
18:33 , just a cafeteria that you can anywhere on campus. Right? You
18:36 go outside and so you can go and have lunch underneath that oak tree
18:40 deal with your allergies. And you imagine that everyone going out to lunch
18:45 sitting there and so the couples are there holding hands and doing their little
18:49 bags, smoochy faces. And then have the people who are solo and
18:54 and they walk outside with their little , they walk outside and they look
19:00 that little fence and what do they across the fence? There's something I'm
19:07 to and they turn and look and can imagine on the other campus a
19:11 sad sack looks outside and sees cross fence, something it's attracted to.
19:17 , what are they gonna do? they just gonna keep living their sad
19:20 life? No, they're gonna start towards the fence and they're going to
19:24 through the fence at each other and gonna go, I found you.
19:31 found you, but we're stuck apart of the stupid fence. But that's
19:37 you can see here, right? mean, you see the non paired
19:41 has found a negative charge but it get to it because the fence is
19:45 the way. And so what you're here is the build up of ionic
19:50 around the membrane. All right. , could they get together? Is
19:55 a possibility that this could happen. everyone's dream come true? Right?
20:00 is like a rom rom com, ? Could this happen? Yeah,
20:04 not here. Yes. Yes. we gotta do is open up that
20:06 , right? And then if you up the gate, then that ion
20:10 flow through. So there is a , isn't there? All right.
20:15 , what we're talking about here is potential energy. All right. And
20:19 made this stupid little story up just that you could picture what's actually the
20:23 are doing. Ions are not They're just attracted to a a negative
20:27 . That's because you're always talking positive negative, the positive charge wants to
20:31 inside the cell because there's negative charges . And also because there's a lot
20:35 missing sodium on the inside of the . So it wants to move in
20:38 it can't. So it accumulate it's the surrounding the fence, the
20:44 And so what you can do is can measure the difference between the
20:49 the freely available positive charges and the of positive charges over here right around
20:54 membrane, that's the membrane potential. when you're reading in the book going
20:58 potential, and it's like, oh is really scary word and I don't
21:00 what it means. All it's saying look, we know how many free
21:03 are available and the difference between this and that side, that's the membrane
21:09 it's the potential energy in that And we can measure it in a
21:14 , very simple way. All we can get a volt meter.
21:17 right. And this is what this is trying to show you. It
21:19 , look if we stick an electrode the cell, an electrode outside the
21:23 , we can measure the difference between two charges. And it's going to
21:26 out in terms of number of And in this case, because there's
21:30 few of them or so there's so of them, we measure it in
21:33 volts. That's what this is. like, hey, I'm measuring the
21:38 of the potential between the inside and outside of the cell. All
21:42 if it's a negative value, what seeing here is that the inside of
21:46 cell has more negative charge in the of the cell. And if it's
21:50 positive value, then you just say more positive charges on the inside of
21:54 cell relative to the outside of the . And so every time you look
21:59 these numbers, you're going to see sort of value, it's going to
22:02 negative something because the inside of the has all these anionic cellular proteins that
22:07 haven't matched up yet. And that's it's always more negative come, it's
22:12 the only reason we're gonna just really all the reasons why it is in
22:17 a moment. All right. So membrane potential is simply the difference in
22:23 between the ions on the inside of cell relative to the outside of the
22:28 , not all the ions are right? Because some of the ions
22:31 have their partners. And so they're participating, right, a positive negative
22:36 are are canceling each other out. these are just the free ions that
22:39 available to interact. And so when look at a cell and say this
22:44 the charge, that's what we're referring . This, this difference in charge
22:49 that membrane. Now, physiologists like do math. Do you guys like
22:56 do math? Good. That's a answer. No, I don't like
22:59 do math either. My daughter came to me yesterday and she started throwing
23:03 this trigonometry that I hadn't done in 30 some odd years and said,
23:07 , how do I do this I'm like, I have no
23:09 It has left my brain 20 years , right. Last time I had
23:14 do math was like CALC two in . I mean, other than simple
23:20 . Yeah, I'm, I'm All right. You're not gonna have
23:23 do math on the exam. All , you're not gonna have, you
23:26 this horrible equation down here. Do have to memorize that equation?
23:31 All right. I'm showing it to because it shows you that there are
23:34 principles involved. All right. And you look at an equation like
23:38 Rather than having to do the you can actually see a relationship.
23:41 there a relationship between ions on the and on the inside? The answer
23:47 be yes. If you ever see ratio, which that's what that
23:50 there is a relationship between them. . And what you could do is
23:55 this was my upper level physiology you'd be able to say,
23:58 oh I see that relationship. I plug it in here. So I
24:02 actually do a calculation to determine the concentration inside and outside. I
24:07 I can figure that out fairly quickly understand the directional flow. All
24:12 you're not going to have to do . But what we're looking at here
24:15 what is called the Nernst equation named the guy who discovered it. All
24:19 . And basically what it says, says look um ions are have different
24:26 and there's also an electrical difference between , these ions. And we have
24:30 these different types of ions. And I know the concentration of the ions
24:33 the outside of the cell, on inside of the cell, I can
24:36 the point when ions stop moving. I open up a channel. All
24:42 , I can find the point of based on its electrical charge. All
24:47 . And so that's what this little does. It says, hey,
24:50 I know the outside and the I can look at that ratio and
24:53 can throw it into this equation if know the valence and then what's going
24:56 happen is I'm going to get the of equilibrium. So what that means
24:59 every time an ion moves, remember carrying with it, it's charged.
25:03 we got something moving down its concentration . And as I'm moving down my
25:07 gradient, the electrical gradient is going the opposite direction and there's gonna be
25:12 point where those two things crisscross And balance occurs. And so what
25:17 would the example would be is if I cross that threshold,
25:21 I'm gonna get to the point where , I've created an imbalance and so
25:25 wanna go back the other direction. so I'm now kind of sitting here
25:28 that state where I'm going back and , back and forth and that's the
25:32 . All right. So the Nernst helps us to find the voltage,
25:38 membrane potential where that particular ion stops . In other words, flexing in
25:46 directions is the same. All that's the equilibrium. All right.
25:52 that make sense so far? All right. Let's go to the
25:58 here and then I'll try to explain in opposite directions, not necessarily
26:06 they're in opposite directions, right? think about it if I'm moving in
26:11 direction because of concentration, right? I have a charge when I move
26:15 here, that attraction to move this has decreased. And so there's a
26:22 where as I keep decreasing, decreasing decreasing, I'm gonna get a point
26:27 equilibrium. That's what it's trying to . OK. Um Another way you
26:32 do this is um just trying to of a real simple model here.
26:40 I always want to come back to and girls. All right, is
26:43 OK? Can I stick with the and girls model? All right,
26:46 going to a party? There's uh we're gonna talk to the guys for
26:49 second. So ladies just bear with guys. You're going to a party
26:53 there's 20 girls for every guy. you excited? You? Yeah,
26:57 , you're ready to go to that , right? Because the odds of
27:00 actually meeting somebody is pretty good, ? It's like 20 to 1,
27:04 ? That's awesome. Right? But it starts changing, right? When
27:09 becomes equal, then everyone's gonna have partner. You just got to presume
27:13 it's everyone's gonna be happy, So everyone's gonna have a partner.
27:16 if I switch it the opposite what's gonna happen? Guys are not
27:19 want to go to that party Are they same sort of deal?
27:23 that help at all? Probably Yeah, I know. OK.
27:30 each ion has its own equilibrium right? Because remember all these values
27:37 all the values the same over No. So if the values aren't
27:41 same. That mean the math isn't be the same and you can see
27:44 they come up with different numbers. when do ions, when does potassium
27:49 flowing out of the cell? So is the question to ask is like
27:52 potassium flows out of the cell, what point does potassium stop flowing out
27:56 the cell? Well, when I a membrane potential of minus 89 potassium
28:01 not going to flow out of the anymore. Oh OK. Well,
28:04 about sodium? Well, sodium wants flow into the cell and it will
28:08 flowing into the cell until the inside the cell becomes positive. 60
28:12 It's really 61 millivolts. But you what I'm saying here and it's
28:15 oh well, what about chlorine? , chlorine basically will flow into the
28:20 until the inside of the cell is 66. And again, these are
28:24 determined mathematically and you can go and it and it matches up,
28:29 But that's really what this is And again, do the numbers matter
28:32 I see the look on your face , oh my goodness, I gotta
28:33 numbers. Do the numbers matter right . No, it's just telling you
28:38 there is a point where flow All right. That's what it's telling
28:43 is. There's a point that's a num, it's a value, it's
28:46 , it's electrical value, a voltage says this ion will stop moving when
28:52 membrane potential reaches this. Now this all theoretical. What you just told
28:58 that this is what happened. it's all theoretical. Why is it
29:01 ? Because how many ions exist at same time in the cell? The
29:06 should be all of them and each them have their own equilibrium potential.
29:11 you can see are these two values same? No. So is potassium
29:16 gonna be moving? Yes. And gonna cause the change in terms of
29:22 . And so what happens is sodium never be able to reach its equilibrium
29:27 , right? Because that's gonna force to start moving and they're all moving
29:31 the same time, they're trying to balance between all of these ions because
29:37 all working together, right? Which the crazy part. So there is
29:42 actual mathematical equation to figure this stupid out. You ready for the ugly
29:47 again? Do you have to memorize ? No, no. OK.
29:51 is the ugly one right here. called the Goldman Hodgkin Ks equation.
29:56 you can look and see why I want you to memorize it right?
29:59 is a lot of stuff there. right. But basically it says
30:01 we have to consider all the ions and oh by the way, it's
30:04 just the ions that are present, how permeable the membrane is to this
30:12 . Well, what is permeability? , permeability refers to the number of
30:16 that are available to that particular Now, here's another stupid example to
30:21 you understand this. You all been a sporting event, let's just use
30:24 football game because they're big and there's of people at them. All
30:27 I been to a sporting event. gone to the bathroom at a sporting
30:32 ? Ladies. Have you gone to bathroom at the sporting event? How
30:36 did it take? You? Let's it's half time you decide it's time
30:38 go to the bathroom. How long it take you to get in and
30:41 of the bathroom forever? You're back at the middle of the third
30:47 right? But guys, how long it take for us to go to
30:49 bathroom? You go down, go the bathroom, come back up and
30:53 know a couple of minutes. No deal, right? Why? All
30:58 . Now we're gonna talk about some that go on in the bathrooms,
31:02 bathrooms in particular versus women's bathrooms. right, ladies, if you don't
31:06 , men typically have in their troughs. All right, we have
31:12 shared bathroom experience is the best way put it. Ok. In other
31:17 , we have these long things when have to go to the bathroom,
31:21 a reason we don't have lines is we don't have to go into our
31:24 individual stall, right? We don't our own toilets we have this
31:30 So if one person goes in, got this 10 ft long trough that
31:33 get to pee in. That's easy . And at half time when you
31:37 4000 people going to the bathroom at same time, guys, what do
31:40 do? We walk in there, our eyes forward. We look at
31:43 wall, we do our business, to shoulder and then we get out
31:46 , we go wash our hands and get out. That's why it's so
31:49 . We don't have to wait for stall to become free, right?
31:54 , whereas a woman's restroom may be to accommodate 20 women at once and
31:58 restroom can accommodate 100 people at So what would we say about the
32:04 restroom versus the women's restroom? It more permeable or really more minimal in
32:10 case for restroom use, right? that's the same thing as what permeability
32:15 . It's basically saying, hey, many ions are you allowed to pass
32:20 at any given moment? If I more ion channels for say potassium,
32:26 has a greater permeability, the membrane a greater permeability to pa potassium than
32:31 does for sodium. Does that make ? Right. So if I have
32:36 gate for sodium and 10 gate for , who's going to have the greater
32:39 on the membrane should say potassium? that's how it is in the
32:46 And this is what this chart is to show you and we'll go over
32:49 so I can actually circle it. right. Now, the, the
32:53 of this book or whoever drew this did a crappy job because the worst
32:58 you can do is when you're comparing is having fractions in your comparison.
33:03 let's turn these fractions into whole So if this were one, I'd
33:10 to multiply this by 25 to get value. So in essence, what
33:15 is saying is I for every one here, I have 25 potassium
33:21 So for every sodium that passes across membrane, I have 25 channels that
33:28 potassium to pass through. So for one sodium, 25 potassium ions
33:36 So which one has the greater Potassium? So potassium has a massive
33:43 . And we have to consider that what Goldman Hodgkin casts all those
33:47 Those are the, the permeability uh factors. And so again, you
33:52 have to memorize, you don't have do the number. But let's take
33:54 look down here at this graph. right. Now, here's a number
33:59 don't have to memorize, but you're see it enough times that you probably
34:02 remember it forever. All right, membrane potential of a neuron is measured
34:09 minus 70 millivolts. OK. Stick the two things you look in there
34:15 say, oh, that's minus 70 right, minus 70 millivolts where does
34:19 come from? Where does that minus come from? Well, potassium is
34:23 , sodium is moving, chlorine is , calcium is moving. All these
34:26 are moving. But the two that the biggest movers are the sodium and
34:29 potassium, potassium has a greater So it's gonna have a greater effect
34:36 membrane potential. What was the equilibrium of potassium? You can look up
34:42 ? It's way over here minus What was the membrane potential of
34:48 Yeah, way over there. This a 25 fold greater effect. So
34:53 what it does to membrane potential. pulls it way way down and it
34:57 a lot like potassium's equilibrium potential, it? It's not the same,
35:01 it's a lot like it. All . Now, if potassium were to
35:06 out of the cell and reach minus the inside of the cell would get
35:10 90 if potassium would stop moving, it can never reach minus 90 because
35:14 is moving in and it's pulling it up towards plus 61. But it
35:21 such a little effect that this is as far as we can get.
35:25 so when we're looking at that what we're looking at is the effect
35:28 the ions moving back and forth across membrane. And where is it settling
35:34 ? Where's that balance between the sodium the potassium, moving the chlorine,
35:39 the calcium moving and all the other that we're not considering. Well,
35:43 right there and that's where that resting potential comes from. OK. Did
35:53 tell you this was hard and kind confusing. Yeah. So what we're
35:58 with here is a value. You're see it over and over again.
36:03 gonna hear the term here. We a cell resting at minus 70
36:07 Why does it rest at minus 70 ? Because that is the value where
36:13 those ions effects cause the cell to in balance. That's what the word
36:20 . OK. It's at equilibrium. , does potassium stop moving here?
36:27 . Does sodium stop moving? So are they in equilibrium? If
36:32 answer is no, for both of ? Are they in equilibrium?
36:36 So you can imagine there's moving and moving and eventually over time, the
36:41 would find its equilibrium. Potassium would its equilibrium and everything would just basically
36:45 moving via concentrations. But we have other thing that's working right.
36:50 do you guys remember us talking about sodium potassium A TP A pumps?
36:54 you remember me mentioning those long, time ago? This is in that
36:58 unit and you're like, OK, is he telling me this another thing
37:01 memorize? Great. Now all the I talk about are important at some
37:04 . All right, I don't just things out there to be mean.
37:07 right, those pumps are there just a pump on a boat is
37:12 If water gets in the boat, gonna happen to the boat it's gonna
37:16 . So how do you keep the out of the boat? You have
37:18 pumps and those bilge pumps sit there go. Ok, let's pump the
37:21 back out of the boat. And what the sodium potassium A TP A
37:24 does. See it takes that sodium moving into the cell and says,
37:27 , no, no, I don't you here. I'm gonna pump you
37:30 out and I'm gonna put you back you started. And uh by
37:33 by the way, um this potassium just left, I want it back
37:36 the cell. So I'm bringing the back in. So what we're doing
37:40 we're moving sodium and potassium back where started and they move back down their
37:46 and then you grab them and you them back and they just keep doing
37:48 . And so we're finding a point equilibrium for all of these things through
37:53 different systems. And so all the in your body have this sort of
37:58 that's going on. There is every in your body has a resting membrane
38:05 . Every cell has this imbalance, cell is constantly moving ions to ensure
38:11 this is happening to that, that inside of the cell is remaining constant
38:16 to the outside of the cell. it's the muscles and the nerves that
38:22 advantage of this system to create electrical . The reason you're able to move
38:30 because your cells take advantage of the of ions and create contractions. The
38:35 you're able to understand the words that coming out of my mouth for the
38:38 part is because of the electrical activity these cells using these mechanisms. Good
38:55 . Mhm That yeah. So this this is a a homeostatic example what
39:01 just described. So there there is basically what you say is you have
39:05 body that's an open system. All , again, I'm getting all wonky
39:08 technical clear, it's called an open because I got stuff always leaving,
39:12 I'm always adding things in and so a point where it's like it's just
39:15 constant, right? So the example you often see is a bucket being
39:21 with water and the water is not up because there's a hole in the
39:24 allowing water to leave at the same . And so the resting membrane potential
39:29 is similar to that. It's not but it's similar to that. And
39:33 is it similar? Well, because though I have ions moving both in
39:37 out, I'm also having a system moving things back to where they
39:42 So while things are following the rules equilibrium constant, right? This idea
39:48 oh I'm going to move down my gradient, right? I'm attracted to
39:54 that's oppositely charged my electrical gradient. though those things are true, I
40:00 to consider every ion doing those Right. But on top of
40:05 I have something that's saying every time of my ions moves, I'm going
40:09 start moving them back and that's what lasts a little bit here. So
40:13 we have a membrane potential at minus is because of the equilibrium uh constants
40:18 the equilibrium potentials for all of those plus this pump system. And we're
40:24 take advantage of this. And that's the next half of this lecture is
40:29 . Plus the next lecture is on we use it. All right.
40:35 I'm gonna pause for a moment. you guys mold this for a second
40:39 ask me anything you want, like or not we're gonna win the national
40:42 . There you go. Yes. the pump itself is the way to
40:55 that the system doesn't stop and slow . All right. So imagine you
41:00 have this pump would sodium keep moving its gradient until there's a concentration
41:07 It would, it would try, mean, they would find it would
41:09 a point of, of balance in of concentration, the the electrical potential
41:14 change, it would probably shift a bit around here someplace. But potassium
41:18 to move out of the cell until found kind of a balance for
41:22 And the answer is yes. And what you're doing here is you're preventing
41:25 from happening. All right, you're, you're allowing another mechanism,
41:31 pump to come along and say, , I know at some point you
41:34 find equilibrium. I'm never gonna let get there. I'm gonna just keep
41:38 you back so that we keep the flowing. That's the idea. That
41:44 be a good way to think about . Say, say that again.
41:53 . OK. Question. What's the of the leak channels? Well,
41:56 leak channel is what allows these ions move freely? All right. So
42:01 talked about the gated channels. We , we didn't even mention but everything
42:05 just looked at in terms of these that allow these ions to pass through
42:09 now are always open, always open are called leak channels. So you're
42:15 at potassium leak channels and you're looking sodium leak channels, the ratio of
42:20 is 25 to 1. In this , I've read other texts that refer
42:23 being between 5075 to 1. So can see the massive effect potassium has
42:29 why it pulls this membrane down so ? All right. Why is it
42:33 rest at this point? It's because has such a massive effect? All
42:39 , that's the idea here. Any questions? Did I make it
42:46 Did I make it clear as mud did I, did I, did
42:50 make it clearer than it was when read about it. Let me answer
42:55 question. 123. So you won and then three. Go ahead.
43:00 do you need the leak channels? if you didn't have flow, then
43:04 have nothing to take advantage of. you'll see why here in a little
43:06 . OK. That's really gonna be about tomorrow's lecture than anything else.
43:11 leak channels are there because you have have the the ability of an ion
43:14 move and create this great internet or this sort of membrane potential in the
43:19 place. All right, you're CRE what, what did I say a
43:23 potential was it's potential energy. All . Now this is, this
43:28 I know this is a far not everyone's taken physics and, and
43:30 know for sure that not everyone, of you have been taken college
43:33 but in high school, did you physics? Did you learn about potential
43:37 versus kinetic energy? Other than three in the front that are shaking their
43:42 up and down back in the Did you guys learn about potential energy
43:45 kinetic energy? OK. Potential energy energy that you can use,
43:50 It's stored energy. Kinetic energy is in motion. See, there we
43:56 . Check mark, we got that can move on. All right.
43:59 what we're doing is we're creating potential , something that we can use for
44:03 activity of these cells later. Next , essentially the degree that very good
44:13 . That might be a way that phrase it on the test. He
44:16 . So what you're saying is that greater the um greater the permeability,
44:20 greater the effect that ion has on membrane potential. The answer is
44:25 All right. So the greater the , the greater the effect that that
44:31 ion has on that membrane potential. . We're going to see this in
44:38 tomorrow for sure. All right, gonna see how we start manipulating these
44:43 a little, little bit, a bit later. I said tomorrow.
44:46 you know Thursday. Yes. so the mi minus 70 is always
45:06 . That's the balance between all of , right? So this is where
45:10 cell is at. But if you at potassium, where does it want
45:14 go? It wants to go So potassium will always move until it
45:18 this point. But you never reach point because you're always stuck here.
45:22 make sure I'm pointing at the right . All right. What about
45:25 Chlorine is always moving, right? it's trying to get here, but
45:30 stuck over there. Now, which moves faster do you think if you
45:34 to, if you had to do rate of diffusion, right? And
45:38 that we've never talked about rates of other than concentration gradients. But what
45:42 you think? Does this move faster slower than this one. This one
45:54 faster than this one. It moves . It has less to go.
46:00 . That's, that's the way you think about. It's like if I'm
46:02 at near stoplight, I'm gonna be of going slow. Right. Because
46:06 don't have that far to go. if I'm far away I'm still
46:10 Right. I mean, I know Texas, we're gonna speed right up
46:13 the stoplight. But what about this ? It wants to go really
46:18 right? It's trying desperately but it go fast. Why can't it go
46:21 ? Because it doesn't have the right , but it really wants to get
46:26 . I got a long way to . Any other questions about membrane
46:35 Uh huh. Go ahead. this is good. The two,
46:39 average and that's exactly what this does what this equation, right? I
46:46 , you look at that and you see there's a lot of letters in
46:49 but what is this showing you? just gonna point here the permeability times
46:54 concentration, permeability, times the So you can see here how this
47:00 weight to it based on that Again, we don't have to do
47:04 math. You don't know, need know the equation. I'm not gonna
47:07 you, I just wanted to show the relationship. OK. There are
47:13 out there even in the community colleges make you memorize this and do
47:18 It's just mean, I don't think important enough. You know, if
47:22 a physiologist, it becomes important. right, I'm gonna move. So
47:27 want you to put in your brain now. OK. I'm dealing with
47:31 potentials. All right. That's, the thing I want you to hold
47:34 to right now. And what we're do is we're gonna shift back to
47:38 . All right, we're gonna come to this in just a second.
47:41 right. So what I wanna do I want to look at a
47:43 So the neuron is the fa cell is the functional cell of the nervous
47:49 . This is where we're gonna spin of the rest of these lectures on
47:52 talking about neurons. So we should of understand what they are. All
47:55 . So this is what we refer as being an excitable cell. It's
47:58 to take that membrane potential that every has. So remember, everyone has
48:02 own membrane potential. They're not all 70 neurons are minus 70. And
48:06 it's going to do is it's going use that membrane potential to be able
48:10 change it, manipulate it so that can produce electrical impulses. Now,
48:16 often you'll hear people talk about use electrical impulses to talk to each
48:19 . And that's not necessarily true. a way to think about it,
48:22 it's not necessarily true. What you think about is that neurons can be
48:26 , very long cells. They're also , very small cells, but they
48:28 be very long cells. And what doing is you're sending an electrical impulse
48:34 the length of the cell from one of the cell to the other so
48:38 you can then communicate to the next through a chemical message. All
48:42 So the electrical signal is along its . So here is the body of
48:46 cell, this is the next So the electrical signal goes along here
48:51 then here is where you're gonna release chemical. But we still refer to
48:55 as electrical signaling. It's not entirely . All right. But what we're
49:00 is that electrical signal is a function the change in that membrane potential.
49:05 right. So these cells live in long period of time. Basically,
49:11 neurons that you're born with are the that you die with. All
49:15 there's very few new neurons that are throughout your lifetime. I mean,
49:19 early on during development. Yes. as you age, what you have
49:24 what you have. All right. are a mitotic. When you ever
49:28 a, at the beginning of the it means not right. So they're
49:31 mitotic cells, they are not actively . So that's why I'm saying once
49:37 born with them, you more or have what you have. All
49:41 they're also highly metabolic meaning they are all the time and they are consuming
49:48 part, primarily oxygen and glucose. reason you have such a huge need
49:52 the fuel that you have is because these types of cells. All
49:58 So these are the cells of the system. Now, we need to
50:01 there's, there's some language that goes this. I'm just going to let
50:05 know right now, very early on didn't understand that every cell had the
50:09 pieces parts. And so what they is they discover a new cell type
50:12 they would start naming things and give special names and they didn't understand.
50:17 yeah, this is just the cell . This is just this. And
50:20 these names are terminology that have stuck the nervous system because of when those
50:26 were discovered. So with the the cyto the cytoplasm. So the
50:31 inside there is called the Pericar All right. So just need to
50:36 about this. This is where all organelles are located. So basically all
50:39 machinery of the cell are located in Pericar on which is located in the
50:43 or cell body of the neuron. right. So you can see
50:49 soma cell body, this would be material inside is the pericar on the
50:55 . Got a special name because a who was doing research on the neuron
50:59 found this stain that actually caused the to pop. And then create a
51:03 tiny Granules and they're like, look, and they call them Nel
51:06 . They're ribosomes. All right. when you see a Nile body,
51:10 what you should think. Ok. the ribosomes and all the cellular machinery
51:13 located in the cell body. that's where I expect them to
51:16 And then what you have is you a bunch of extensions that come off
51:22 cell body. There's two different All right, these are called dendrites
51:26 axons. Collectively, you can refer them as dendrite. Dendrite literally means
51:32 like a tree branch. All So that's why they named them the
51:35 they are. But one and the are functionally different from each other.
51:39 when you see different names, you , oh yeah, it has a
51:42 name because it has a different All right. Now, typically,
51:49 you're gonna find is neurons are gonna found in clusters. All right,
51:52 cell bodies are gonna be grouped together the axons are typically gonna be grouped
51:56 and they're traveling into and those axons gonna be traveling into particular directions.
52:00 get to that in a moment. when I'm looking at the cell
52:03 a clump of cell bodies together in central nervous system, which is your
52:09 and your spinal cord are referred to a nuclei. All right, that's
52:14 nucleus like what we have here, it's the same word. So,
52:18 just a cluster of those cells. when you're out in the peripheral nervous
52:21 , so everything outside of your brain your spinal cord, we're gonna refer
52:25 these clusters of cell bodies as All right. So gangly and nuclear
52:31 the same thing. They're just located different places. So they have unique
52:36 for where they're, where they're When we go to these processes,
52:42 grouped together dendrites, when you're looking one of them, right? So
52:48 one right here is the axon, axon is the sending branch. So
52:54 are sent from the cell body The axon, the dendrites are the
53:01 branches. So when information is received other cells, they are received from
53:05 dendrites. So dendrites take messages or signals, send them to the cell
53:12 and from the cell body down and through the axon. Now, when
53:18 take a group of these axons and moving together, they're usually again clump
53:23 and they're moving in the, in same direction in the peripheral nervous
53:27 we call those nerves. All But in the central nervous system,
53:32 don't have any nerves, there are nerves in the central nervous system,
53:36 call them tracks. All right. when you hear nerve, don't think
53:42 inside my brain or my spinal I'm outside. And when I hear
53:46 , oh, I'm inside the central system, but it's the same
53:50 It's the groups of axons moving in same direction. The cell body has
53:57 point where it becomes the axon that called the axon Hillock. You'll see
54:04 , it's called the trigger zone. right. So when we're talking about
54:08 potentials, this is where our focus gonna be. This is where we
54:13 the action potential. And you're sitting going, I don't know, an
54:17 potential is, that's fine. We'll to that in, in uh in
54:21 lecture. All right, I'm pointing out now. So the Axon Hillock
54:25 where the signal, the action potential produced. Moving down the axon,
54:31 axon is not just a single line single extension, it can actually branch
54:37 it branches. We refer to the as a collateral. All right.
54:41 this one doesn't show a collateral and at the very bottom, you're gonna
54:46 that axon split and become a bunch little tiny fingers. These are called
54:52 TDRI and at the base of the , that's where we have the axon
54:58 . The other name for the axon is the synaptic knob. So here
55:03 are just looking a little bit closer you can see this uh for the
55:07 and why we distinguish this. So the cellular machinery is gonna be locating
55:11 cell body. There are no uh machinery inside the axon itself. All
55:18 . So the axon is very specific terms of its functionality. All
55:23 It is specific in conducting electrical signals its length. All right.
55:29 if I was the cell body and arm was an axon, its sole
55:33 is to send signals from here down my fingers, which would be the
55:39 . All right, we don't receive direction we send. That's the only
55:43 that this does. All right, cytoplasm inside the axon no different than
55:52 cytoplasm or the pericar on in the body, right? It's still the
55:55 fluid and the same ions, et , et cetera. But we give
55:58 a special name, we call it axoplasm. Great muscles have their own
56:03 for their stuff too. And it makes you mad. All right,
56:06 axoplasm. And then the plasma you'll sometimes see people refer to it
56:10 the axolemma. That's just the fancy saying plasma membrane of the axon.
56:15 right. So terrible cartoon. But demonstrates what we're trying to get to
56:24 , what we have. Here's our body. This is all the machinery
56:27 that's making all the things that the makes. The way the cell talks
56:30 one cell to the next is gonna through a chemical message, right?
56:34 all the chemical messages that the axon making is being made in the cell
56:40 . But the way that I'm talking that next cell is way down here
56:44 the axon terminals. So I have get that message that chemical down
56:50 And so we use a form of to do so. So we have
56:56 skeletal elements, elements inside there. if I'm moving materials from the cell
57:01 , I'm gonna be moving them through usually. And what I'm gonna do
57:05 I'm gonna move them towards that synaptic in the TDRI and the,
57:11 the, the type of, of we refer to when we're moving towards
57:16 Axon terminal is called anterograde transport. right. So that's what we're seeing
57:23 here if I'm moving back to the body. So materials that I pick
57:27 at the Axon terminal, I'm going transport back to be processed. This
57:32 be retrograde transport. Now there are different speeds. We can do it
57:38 or we can do it slow fast about 400 millimeters per day. So
57:43 about how big a millimeter is take 400 of them, right? So
57:50 centimeter would be 10 or it would 100 I'm doing that wrong. It's
57:55 millimeters and then you take 10 of or 100 of those that would be
57:59 a meter. So you know, hun 4 m, right? Is
58:02 is that am I am I accurate ? Yes. No. Ok.
58:07 making sure cent is 100. So about 4 4 m per
58:12 So that seemed pretty fast. How are you? Are you bigger than
58:16 m? How long is your entire ? If you're 6 ft, roughly
58:24 m. So, in about half day, you can move something from
58:28 brain down to your big toe. right. So not particularly fast,
58:34 it's faster. But look at slow to three millimeters per day. That
58:42 . No, no, it's gonna forever. The difference here is like
58:45 getting on a, on a little tube and just sitting on a river
58:48 letting it take you wherever you want go. The other one is
58:51 They're using uh A TP and motor and that's what they're trying to show
58:55 here. See a little motor little motor proteins carrying things around.
58:59 if it's fast, you have energy invested in moving it quickly. If
59:04 slow, no energy question. fast, slow. All right,
59:13 is real slow, fast, relatively . OK. Does that make sense
59:20 far in terms of structure? Could draw yourself a neuron and label the
59:27 ? I mean, maybe not this second. But could you do that
59:28 the next 24 hours? The answer be. Yes. All right.
59:34 . Yes, ma'am. Oh So , this, you're asking a very
59:43 question that I didn't really kind of . So when we're talking about the
59:47 message, so the question is, neurotransmitter, I've read, I read
59:51 word neurotransmitter. What the hell are talking about? Doctor Wayne? More
59:54 less what you just said. So, the chemical message that a
59:59 is producing is called a neurotransmitter. way that a neurotransmitter gets to the
60:05 where it can be released has to through a method of delivery. All
60:09 . So, all we're doing is saying if this is where I'm releasing
60:13 , but I'm making it here, do I get the neurotransmitter to
60:18 Well, I'm going to carry it a vesicle and I'm gonna move it
60:21 and I'm gonna set it down here there. So we're not talking about
60:24 neurotransmitter itself being released from the We're just talking about how do I
60:28 the neurotransmitter to the place where it's to get the get released?
60:48 So you're asking a really good right? And again said, wait
60:53 minute, I've got all these messages all these signals I have to make
60:57 this is as fast as it is this enough? Is really what
61:01 saying? Right. And the answer yes, because you're not releasing a
61:05 of chemical at any given time, producing much, much more and storing
61:09 away for that particular release. so you're not, you have more
61:15 storage at the end of your, your axons to release that chemical message
61:22 you actually need. So you're only a couple of molecules at a
61:26 Chemical messaging is incredibly powerful, which why it's very highly controlled. And
61:33 you're not gonna run out, think , think about how many times your
61:38 are firing just right now listening to , but your brain doesn't explode and
61:44 don't just pass out or anything. brain is able to keep up because
61:48 only a couple of neurotransmitter molecules that using at any given moment and is
61:53 this every single solitary millisecond milliseconds, ? Millions upon millions of synapses are
62:03 right now to tell you to tell what to do. Yep.
62:26 Question is so any sort of small of this transfer system can screw things
62:32 ? Oh Yeah. Like I you guys are walking miracles. You
62:41 a system that is in perfect This is why you guys are in
62:45 class and why you all wanna go this profession or into a profession of
62:50 . Because you can already see, got all these crazy systems. We're
62:55 even toe deep in this stuff yet you can already see if this goes
63:01 . You mean the cells start messing ? Uh huh Yeah, let's learn
63:07 language. OK. Um Talking we're using some terminology and this is
63:17 so that we're all on the same . I could just re repeat them
63:22 you, but I want you to this. You remember back in third
63:24 when you started working on number remember the number lines had the line
63:29 in both directions, zero in the . All right. So if you're
63:33 me, which direction is this positive negative? That's negative over here is
63:37 . OK. So if I'm sitting my, on my, on my
63:42 , right? My number line I'm zero, I'm neutral. OK.
63:46 has no polarity to it. But I step off of zero in either
63:51 , I have polarity, right? if I go over here to minus
63:56 , I have polarity. If I over here to plus one, I
63:59 polarity, if I go way over to plus 100 or plus 1000 or
64:03 1 million or in the opposite So anything that's not zero, it's
64:09 makes sense. So I'm gonna become for you. All right, I'm
64:19 just go over here since we gonna over here in the world of
64:21 I'm gonna be negative right now. here I am standing at minus
64:25 So am I polar? Yes. all your cells because they have a
64:30 potential of something other than zero, already exist in a polar state.
64:35 right. Now, if I become negative, what have I become,
64:41 become more polar, right? If go back over here, I'm still
64:46 at my minus 70 I'm still And if I move in this direction
64:52 have still polar, aren't I? am I more polar or less polar
64:55 I started? If this is where started. I'm less. All
64:59 So I'm gonna come back to my state. If I move in this
65:04 , I've become less polar. I d polarized. OK. So the
65:11 D polar means become less polar than were. When you started, when
65:15 returned back to my polarized state, have re polarized. All right.
65:22 if I become more polarized than when started, I have hyper polarized.
65:28 , given that I'm living over here the land of negative. This is
65:31 most of our language exists. All . But if I started way over
65:39 , what do you think? Plus ? Does that look like? Plus
65:42 ? So if I move this what have I done? I've
65:46 I've been less po and I'm, I move back to my polarized
65:49 I've rep polarized. And if I over here, I've hyper polarized because
65:54 started off polar. All right. , this language is consistent and you
66:00 see what I've done is I'm the graph shows you up and down positive
66:04 and so on and so forth. one place where this gets all kind
66:07 weird and screwed up and it's gonna when we deal with the action potential
66:10 you start off polarized and you depolarize you cross over zero and you go
66:16 the way up to plus 30 then go back again, we don't change
66:19 language just because, because we crossed zero because it's all in one single
66:23 . So what we're gonna see is we're gonna depolarize and we cross over
66:27 , we still depolarize because it's the motion and then we're gonna stop and
66:31 we're gonna return back and that would repolarization. OK? So just use
66:36 language as, as you see, like, oh I start off
66:39 I'm gonna depolarize or I'm gonna You just gotta remember which direction am
66:43 moving? Am I becoming more more negative, more positive than I
66:49 or did I get less of what started? And that's where you use
66:52 language now because we're gonna be living the land of negative. Typically,
66:57 is what you're gonna see a net flow of positive ions. So let's
67:03 if anyone was paying attention which ion a is positively charged and flows into
67:08 cell. Sodium good. So a inward flow of positive ions results in
67:14 . So when sodium flows into the , we call it depolarization, a
67:18 outward flow. Notice they're never right? It's never negative ions,
67:22 net outward flow of positive ions. one did that? Potassium results in
67:28 polarization. All right. So those are gonna be things you're gonna see
67:33 and over and over again as we through the next two lectures and then
67:38 beyond, we're gonna say and we the polarization and blah, blah,
67:42 . And you got to connect those to what we're seeing. All
67:46 So if, if this is just draw it out for you just
67:49 the little graph and say, here I'm going up so I've started
67:51 polarized. What do I do? , here I'm depolarizing. Here.
67:54 coming down, I'm rep polarizing. draw it out so you can visualize
67:59 . Now, coming back to our here, we're back to that membrane
68:04 , membrane potentials. It's just the we're going to see over and over
68:08 . A change in the membrane potential a result in a change in its
68:11 state. All right, it's going result in an electrical signal in neurons
68:16 muscles. All right. So if can change the permeability of the
68:20 remember, we said permeability matters. we change that permeability, we're going
68:24 change membrane potential because we're no longer that balance, we're now switching the
68:31 out. So we're going to move towards where the equilibrium potential for potassium
68:36 or we're gonna move towards equilibrium potential or for um sodium because those are
68:41 two major ones. Anything that alters ion concentration again, going back to
68:46 Hodgkins cats. If I change those concentrations, if I go back and
68:50 at those formulas that talked about those , if I change the ratios that's
68:54 to have an effect. Well, can think about this look if I
68:58 a slope like this and I go certain speed down the slope, if
69:01 change the slope, am I going go faster? Yeah. All
69:05 So it's gonna have an effect. both those two things which are in
69:09 equations that I showed you, which don't have to memorize, they have
69:13 effect on the membrane potential. So times kinds of potential changes. And
69:19 here we're getting into that language, have a graded potential and we have
69:23 action potential. Again, notice what potential stands for. Talks about the
69:28 potential. What type of poten? have a graded potential. When you
69:31 the word graded, it means it different heights, right? So it's
69:37 grade. So graded potentials deal with changes. And so these types of
69:44 potentials, we're gonna go through them here in just a moment are going
69:47 deal with short term signals, very distances. So if I think about
69:53 cell like a neuron, it's gonna across a very small portion of the
69:58 . But then we have the action , the action potential long distance
70:01 That's when I have a very long like the neurons that traveled down the
70:06 of my arm from my spinal cord go to my pinky to cause it
70:10 wiggle. That signal is a very signal. And that's where I'm going
70:14 use the axon. And I'm gonna an electrical signal that travels the length
70:18 that axon. And that's what tomorrow's is on is going to be on
70:22 action potential. So I want to here on the graded potential. So
70:27 we are, we're looking at a , we're looking at the neuron cell
70:30 . Can you tell we're on the cell body? See the dendrite,
70:34 dendrite, the dendrite, we're down . Do you see all that?
70:39 . And so what this is showing says, look here, I have
70:42 neuron releasing a chemical message and that message is binding to a channel.
70:49 this would be what type of gated ligand gated channel, right? We
70:55 ligand is where you have a And so what that's gonna do is
70:58 gonna open up the channel and this channel happens to be uh a sodium
71:04 . So when I open up the channel, what's sodium gonna want to
71:08 wants to go in, right? we said with sodium, sodium wants
71:11 move in the cells. And so open up the channel, sodium rushes
71:14 and starts looking for that partner. like where is that negative charge that
71:18 looking for? And so you can where do I have the most
71:21 Where do I have the most positive ? Free sodium is right here where
71:25 coming in. But as I move from that opening, I'm starting to
71:29 partners. And so the free sodium available gets less and less and less
71:34 . The further and further I move . So if I were to graph
71:37 out, what I would see is , I have the greatest amount of
71:42 in terms of charge right underneath where gate is open. And the further
71:46 away, that charge diminishes and then becomes like the rest of the cell
71:52 falls away. So again, I you to picture, remember the the
71:57 I used is you have somebody with brown bag looking through the gate,
72:02 gate opens. What am I looking ? I'm looking for my partner.
72:05 once I find that partner, I'm longer looking for a partner, all
72:10 little arrows are representing lonely sodiums still to find a partner as they flow
72:16 from the gate. And so a uh sorry graded potential has characteristic to
72:25 . All right, it's a very small change. It has a
72:29 degree of magnitude. Magnitude is just term that means it has a certain
72:35 to it. You guys remember despicable , right? Vector I commit crimes
72:42 magnitude and direction. That's what a is. Magnitude is just simply
72:48 So here varying magnitude. So this just an example, the 10 millivolts
72:55 here, five millivolts change. It be a depolarization or hyper polarization is
72:59 depolarization. What kind of ion is ? Sodium or potassium sodium, if
73:07 a hyper polarization, it would be . And we're also gonna learn it
73:11 also be chlorine. But for right , just that, all right,
73:16 great potential is gonna be due to sort of triggering event. A triggering
73:20 simply means opening up a channel. that's what we see here. We've
73:24 up a channel to allow sodium to in the magnitude and the duration of
73:30 greater potential is going to be directly to the magnitude and the duration of
73:34 stimulus. All right. Now, is just an example. This is
73:37 how it really happens in the Imagine I have a needle in my
73:43 and if I come up to you go poop, would you feel it
73:47 I poked you with the needle Yeah. Would it have a
73:52 Yeah, very small one, Because magnitude of strength, right?
73:56 about duration if I went poop? duration? Right. So far?
74:01 . What if I went like Would it have a greater magnitude?
74:06 have a greater duration in terms of pain? Yeah. OK. Now
74:10 me taking a running start and then in you greater magnitude, greater
74:18 Yeah, greater potentials have both those based on the stimulus itself.
74:27 everything I just showed described there, are not greater potentials. That's just
74:31 of duration of magnitude. All So the stronger the triggering event.
74:36 you can see here here is the event, the stronger it is the
74:40 the magnitude of the greater potential. isn't showing duration. But you can
74:44 if duration was in this direction, this was longer, then this would
74:47 longer. Ok. Second thing, decrease in intensity as they go further
74:55 further away. We've already described why they found their partner. When they
74:58 their partner, they die out You can visualize this. Think about
75:02 little rock that you're throwing into a pond. If I throw a rock
75:05 the pond, does it make a ? Doesn't make a splash?
75:10 So think about it, a little rock, a little tiny rock makes
75:12 little small splash. It creates a and that ripple moves away and eventually
75:16 out, the bigger the pond you'd see it dying out, right?
75:20 I took a big giant rock, it make a bigger ripple, make
75:23 bigger splash and a bigger ripple? it would take longer for that thing
75:26 die out, but eventually it would out. Now, in a
75:29 the dying out is a result of resistance of the water to the force
75:33 causing the water to move here. because of the partnering of those positive
75:37 or negative ions to their opposite All right. So that's why it
75:42 out. So greater potentials have an that dies out over distance. And
75:51 they are very short lived. All . They come and they go,
75:57 don't have a duration to them. , the only duration that they're limited
76:01 is based on the stimulus itself. are we doing on time? We're
76:05 46. All right. Um This just the same slide and it's just
76:10 to show you here with, if were to measure it. So here
76:12 can see the stimulation, notice that doesn't have a particular direction it goes
76:16 all directions, just kind of like rock being thrown into the pond,
76:20 travels in all these different directions. here you could say, look at
76:23 big it is here like the big splash. But as I move further
76:26 further away, it dies out over . So if I want to get
76:31 really, really far, what kind stimulation should I have a big one
76:34 a small one? A big OK. Good. We have two
76:42 types of potentials here. And what looking at is we're looking at the
76:46 cell. All right. So you see in our little picture up
76:49 we have two cells, we have that's sending one that is receiving.
76:52 we're looking at the greater potential here the receiving cell, I opened
76:56 I released my chemical message I received . And so what's going to happen
77:00 if that signal is excitatory opens up that allows for sodium to rush into
77:05 cell, then I'm going to get positive depolarization, right. I'm going
77:09 depolarize. And so this type of is referred to as excitatory, post
77:15 potentials. When you see all those stuck together, each one means something
77:19 . It's a depolarization, post the interaction between those two cells is
77:25 a synapse. And so it's on receiving side, post synaptic on the
77:29 side and then the potentials again, just referring to that it's a graded
77:34 . All right. So when you this, what you're looking at is
77:37 looking at sodium rushing into the cell always. So sodium moves into the
77:41 and potassium is not moving out of cell. So that's why you see
77:45 depolarization and then ultimate rep polarization. ep SPS are depolarizations. So what
77:51 you think IP SPS are inhibitory postsynaptic ? They're hyper polarization. And here
77:58 we're doing is we're opening up either potassium channel or a chlorine channel.
78:02 I'm opening up a potassium channel, is rushing out when I'm opening up
78:05 chlorine channel. Basically, things are of staying in balance. And so
78:08 don't really see a lot of stuff on. But what you're seeing now
78:12 you're seeing a hyper polarization in the . So inhibitory postsynaptic potentials are moving
78:20 and further away from what we're going call threshold. Basically, the cell
78:24 becoming hyper polarized. It's just the . Now, at any given time
78:29 cell is being talked to. So a neuron and you can see in
78:33 neuron, we have lots of cells to it. You see all those
78:36 there, the cell is purple. the little blue things are synapses.
78:40 what we have here is we have lot of cells that are sending
78:45 some of them are positive, some them are negative. It's like going
78:48 to your social media of choice and up a poll and asking all your
78:51 , for example, hey, I'm this person. Should I break up
78:55 them? And all 4000 of your friends, right? Because every one
78:58 those followers are friends are gonna give their really honest opinion about whether or
79:03 you should break up or stay And at the end of the
79:07 you're going to look at that poll you're going to make a decision based
79:09 what they tell you. You're gonna up all the pluses and you're gonna
79:13 up all the minuses. And that's essence what the next type of a
79:17 is. It's called a grand post potential. The GPS P, the
79:22 P is the sum of those EP and the IP SPS and excitatory and
79:27 inhibitory post synaptic potentials. Now they have varying degrees of magnitude. So
79:32 are going to be really, really . Some are gonna be really
79:34 both excitatory as well as inhibitory. in the end, you're going to
79:38 the membrane potential to some degree. it's the sum of those potentials that
79:45 that tell the cell what it should next. And so when we're looking
79:50 the cell, this is where we're to be focusing and saying,
79:54 what is that GPS P that is result of stimulation here? Is it
79:58 excited or is the cell being told to fire? And if the cell
80:02 being excited, then it's going to its own signal to talk to the
80:06 cell. So the process that we're to go through to do these are
80:12 of summation. And when we come on Thursday, this is where we're
80:16 to start, we're going to look the different types of GP SPS,
80:19 we produce these GP SPS and ultimately to produce the action potential. All
80:25 . So you guys, I will you on uh Thursday. Hopefully,
80:30 stuff made sense
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