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BIOL 3324 Human Physiology - 3324_lecture06_0908
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00:05 All right folks, let's see if can get this bad boy started.
00:12 only have a million slides to go . Lots of information to go
00:16 We have a test on Tuesday. panicking, dogs and cats are sleeping
00:22 mayhem. Just a reminder. All . So we do know test is
00:29 . You should have uh got your of slots already if you didn't do
00:34 yet. Well, you're probably panicking this point. Just ask one of
00:36 friends, how do I do Um I would remind you also that
00:40 are extra credits in the class. guys know about this? I think
00:42 mentioned this on, you know, the first day of class.
00:46 so extra credit. There's always an credit that opens up before an
00:49 There'll always be an extra credit that up after the exam. I probably
00:53 go into details of how it So at six p.m. On monday until
00:59 a.m. On Tuesday there's an opportunity for extra credit. All it is is
01:04 series of questions and ask you, takes you like five minutes. Are
01:07 prepared to take the exam and and answer them for yourself? I don't
01:12 at the answers, right? It's a self assessment to see have I
01:16 the work to prepare myself for the ? What am I comfortable with?
01:19 am I not comfortable with? That of thing and then you just get
01:22 done. I'm telling you this you might want to write it
01:24 put it, put an alarm in system because I guarantee you a quarter
01:27 you're gonna forget about it. And you'll be all mad, can't you
01:30 it up for me now? And it's like, no, no,
01:32 four before the exam. Alright. about six p.m. I think it's six
01:36 On monday. It opens closes at a.m. On on Tuesday before the
01:42 The second half, hold on. second half opens up after exam about
01:47 week after. All right. And reason it's a week after because there
01:50 be some late exams or something. it asks the question right now that
01:53 looked at your exam or you've seen grades and you've gone over your
01:58 think about how you answer the first , you know, were you
02:02 Were you prepared in this area? blah blah. And I'm not looking
02:06 this. I don't know. And don't care. I'm asking have you
02:11 assessed because the most important thing in for an exam is being aware of
02:16 you should know and what you don't and knowing how well prepared your because
02:20 face it, we all do right? It's like I've studied,
02:22 studied I've studied a lot last but if you like those areas that
02:26 kind of hard and you're like, , maybe you want to ask me
02:29 about this and we kind of lie ourselves and like, hopefully I won't
02:32 any questions. I guarantee there will questions. All right. Just just
02:37 saying that in your head like the test fairy comes along and goes one
02:42 of the exam is gonna be That's not true. It just feels
02:45 that. All right. So, just letting you know this is this
02:48 and the first half is worth 2.5 . The second half is worth 2.5
02:53 . That's five points onto your test . Oh yeah. So it's worth
03:00 time. So, you can think this way if you take your test
03:03 and you do all of them at end of the semester, you've added
03:07 points to your overall test average, ? That's pretty cool. That's
03:12 That's that's a lot. Alright, I'm just gonna remind you of that
03:16 . I had a hand back there then here love to. No.
03:24 remember on test days, no you show up here, you'll be
03:28 puppy. Alright, so don't ever up to class on test days.
03:35 don't you don't get any practice Our practice, they're there to show
03:41 how I write questions. So you're going 100% blind. The credit is
03:46 the extra credit. Extra credit is assessing that. There's one before,
03:54 ? One before monday six PM closes AM Tuesday morning. Second one after
04:01 test, it opens up like a later? I'll announce that one when
04:04 happens. So don't worry about that just yet. Okay, It's all
04:09 blackboard. Right? And it'll take like five minutes of your life.
04:13 take it seriously. Don't think of as points. Think of it as
04:15 assessment. You're getting points for doing . That's the bonus. Alright,
04:21 , all right, today, we're up everything we talked about today is
04:26 be on the exam. Everything that fail to talk about is still gonna
04:30 on the exam. So, I get through this stuff now. It's
04:33 that hard. What we're gonna do we're gonna talk about action potentials.
04:36 from max potential we're gonna move to and from synapses. We're gonna just
04:39 about generically what's going on with regard the synapse. All right. And
04:44 , what we're looking at a pier the board is basically the change in
04:50 permeability for sodium potassium. Now, do I talk about that? Why
04:53 I bring this up? What do have to show you this graph?
04:58 remember we established already that there is certain permeability for sodium and a certain
05:04 for potassium on ourselves. Right. guys remember the permeability for everyone.
05:08 . How many roughly, Roughly? different books, say 25. Some
05:13 75. Does't matter. But what shows you is this black line represents
05:17 action potential. We practice the action . Remember that we all did the
05:20 and it was really cool and It was the best class you ever
05:23 . And what this is showing you that over the course of that action
05:27 , what we're doing is we're changing for sodium potassium. And the question
05:31 how and what is this ultimately Right? Why do I even care
05:36 this action potential? All right. , when you change potentials, what
05:42 means is that we're gonna be seeing in those proteins that are going to
05:48 for the propagation of an electrical signal the length of the cell. To
05:53 change in the cell. That's that's whole purpose. Alright, well,
05:58 change we'll get to that? All . So, the first thing I
06:01 to point out is that the channels we're dealing with here are not leak
06:05 . Like we've been talking about those the gates that are always open.
06:08 talking about voltage gated channels. I my phone up there so, I
06:11 know what a voltage gated channel. responds to this change in potential.
06:17 , as ions move through, that's the surrounding environment around those channels.
06:23 then those channels are going to change in response to the change in the
06:28 that are around them and that's what them to open and close.
06:32 a voltage gated channel. There are types that we are interested in.
06:34 we're talking about action potential. We're at the uh sodium voltage gated channel
06:40 we're gonna be looking at the I say voltage gated sodium channel. We're
06:42 be looking at a voltage gated potassium . So here this is the picture
06:47 the voltage gated sodium channels. You look at the picture, you can
06:49 at me. If you look at , you'll remember this on the exam
06:52 think what an idiot he looks Alright, so I'm a voltage gated
06:55 channel. I have two gates. gate number one. Gate number
07:00 Gate number one is the activation gate , number two is the inactivation
07:05 There are three states as a result there being two gates. The first
07:09 is a closed but capable of opening . So my activation gate is
07:14 My activation gate is open, nothing pass through me. I get stimulated
07:20 open as a result of the change the environment around me and that's gonna
07:23 my activation gate to open. Now open and things can throw through.
07:28 the moment that I open, this the moment I begin closing my inactivation
07:33 and it's a little slower. So one opens up quite fast. This
07:37 closes slowly. Now I'm in my state. So first date was
07:42 capable of opening. Second state is . Third state closed, incapable of
07:49 . I have to go all the back to the beginning and I can't
07:52 it magically. So you just have pretend like I do it magically.
07:55 one goes back here. This one back there and there's no intermediate between
08:00 . Right? So you can think like this step A, you
08:03 step your face a close but capable opening. Step be open, step
08:08 . Close but incapable of opening. have to go all the way back
08:12 the step again. I can't go to B. B. Does not
08:15 between are going the backwards direction. it's A B. C. Abc
08:21 repeat. Alright, so once the gate closes, I have to reset
08:29 I can open up again. that's a sodium gate voltage gated sodium
08:34 is the tricky one of the two potassium channels are easy. One gate
08:42 gate. How many stages do I to? What are the two states
08:46 and close? Yeah, there you . Alright, so that's voltage gated
08:51 channels, but think about voltage gated channels that they're a little bit wonky
08:55 the sense that they're a little bit . They're like your friend, you
08:58 the one that you tell jokes They stare at you for a little
09:01 before they get the joke. Don't that person. There we go.
09:07 what I'm waiting for. The All right, so what we're gonna
09:11 is we're gonna walk through the potential you see a graph like this?
09:14 for changes in the graph. so look at the black line.
09:18 questions. Where does the line change ? When you see that? That
09:22 something must have happened. Right. lot of people look at graphs and
09:26 panic. We are not those people people go to A and M.
09:29 are Cougars and if your post back fun of you because you're Nagy.
09:36 right. In the first stage, we're looking at is we're looking at
09:40 the arrow is in our little picture . So, we're looking at the
09:42 potential. What's going on at the potential? Well, we have the
09:46 potassium 88 pes pump pumping. We the leak channels open because their leak
09:52 and so we have sodium going in everyone that goes in, we have
09:57 potassium going out. Everything is good normal and perfect. Right. So
10:02 that that we've talked about already is . But those voltage gated channels do
10:07 are not open. So, as as the cell is concerned, everything
10:11 being managed through these things. Right . All right there there in the
10:16 the in the cell membrane, but not open. Right? The voltage
10:20 sodium or the voltage gated potassium Alright, So where the arrow
10:24 Now, you see it's moved there's change that's taken place here.
10:28 what's happened here is we've stimulated the . Alright. So whatever it was
10:33 stimulated the cell opened up channels to sodium to come into the cell.
10:38 this particular case, when sodium comes the cell, the cell begins to
10:43 polarized, right? It becomes more than it was before, which causes
10:48 environment around voltage gated channels to slightly . So if I'm opening up a
10:55 that allows sodium to come in cause polarization that might destabilize or basically,
11:01 cause one of these voltage gated sodium to open up. If I open
11:05 a voltage gated sodium channel, sodium into the cell. If sodium comes
11:09 the cell, I. D. more, which will cause nearby voltage
11:15 sodium channels to open, which causes sodium to come into the cell,
11:18 causes more voltage gated sodium channels to . And you see what we have
11:22 is a positive feedback loop. So what you're looking at here at
11:27 initial state is when we've had some of stimulus act to the point where
11:33 have a wave of sodium come all way down to the axon hillock and
11:38 axon hillock has now become slightly d , which leads to more deep polarization
11:42 more deep polarization polarization as a function the opening of those voltage gated sodium
11:48 . So sodium comes in and eventually going to happen is you're going to
11:52 this feedback loop that's going to cause to rise and rise and rise and
11:56 very, very quickly. So, what they're trying to show you here
11:59 , that blue line that you see I drew there represents something called the
12:05 . Alright, now, threshold is representation of something happening. All
12:11 When we say threshold, we say this point we have met the point
12:16 we will continue on and now the potential will occur to its completeness.
12:22 , remember how did I describe an potential on Tuesday? It's like it's
12:27 virginity. You either are or you . Right? So, if you
12:31 reach threshold, you aren't an action . If you do reach threshold,
12:39 are an action potential. Okay, the truth is, is that that
12:44 is just a line that was identified when this happens. Okay, It's
12:50 like every cell goes well, this my threshold here. And so,
12:53 you meet that. What threshold actually is the point where all those voltage
12:58 sodium channels are open. Alright, , once you've opened up all the
13:02 gated sodium channels, you have now uh the permeability, sodium now dominates
13:08 permeability. It's almost 1000 fold greater the potassium permeability. So now it's
13:15 for every 1000 molecules of sodium going one molecule of potassium is leaving.
13:22 how big of a difference is it . And so, what you see
13:26 is sodium is starting to rush in what we're doing is we're now moving
13:30 . We're deep polarizing to the point we're trying to get way up here
13:34 plus 60, right? Because that's equal equilibrium potential for potassium. Excuse
13:39 . For sodium. Right? So nothing else were to get in the
13:44 and this was the state of the , we would just keep shooting up
13:47 we hit plus 60 and then we equilibrium and everything would be hunky
13:50 But obviously that's not what happens. see what happens, we cap out
13:56 there. So something must have something gotten away. What do you
14:01 ? Got in the way? Question. Mhm. It's different for
14:09 cells. But remember it's not, reached the threshold. Ergo I now
14:13 gonna be an action potential. It's the line that marks when I've reached
14:17 certain something certain has happened inside the . Ergo I will write And
14:23 part of this was is, you , experimentation that was taking place when
14:27 just measuring voltage all over the And so they're like, what happens
14:31 I bump it up plus one? happens if I bump bump it up
14:34 two and so on and so And eventually like, oh if I
14:37 it up to this minus 55 I an action potential. And so that's
14:41 threshold and then what you do is kind of got oh well the reason
14:45 that now that we have the ability find out is because these channels
14:50 Alright, so the threshold was discovered but then the rationale or the reason
14:55 it um uh defined why it's Okay, so I'm gonna come back
15:02 the question. What do you think at that point? Right there.
15:07 gates close. Remember three states I'm . I'm open. sodium is rushing
15:13 and this is a little slower and it closes. Now. If you
15:18 at the graph a little bit more , you'll notice that down here,
15:21 have time and over here we have . And so really what this is
15:25 a graph over time. Right? so it's asking a question, what's
15:29 over time? Well over time I'm a channel and then over time I'm
15:35 that same channel. And so the between that point and that point right
15:41 , that 0.0.0.5 milliseconds is how long takes between opening and closing the
15:47 But if that's all that happened, all I did was close the
15:51 then we would slowly return back to and we don't we completely reverse and
15:57 the other direction. Why do you ? And it actually says up there
16:01 the graph potassium So remember our good friend, the slow one, the
16:07 that didn't get the joke right? one you said here's a joke and
16:11 kind of stare at you for a . That's when they get the
16:15 See both potassium channel voltage gated potassium voltage gated sodium channel are stimulated simultaneously
16:22 channels fast. It opens up quickly then it slowly closes over that half
16:26 millisecond. Which is, I grand scheme of things. That's very
16:29 time, right? But it takes half a millisecond for the potassium channel
16:34 respond. And so what you end with is basically two phases. You
16:39 a rapid deep polarization phase as a of sodium dominating. Slam the door
16:45 and now we have rapid re polarization a result of opening up the potassium
16:50 . Yeah, it's just how it's it's built. You know, it's
16:57 it's just because I'm sure if we to a bio chemist or physicist,
17:00 would probably tell us why. But a biologist and reasons okay. But
17:05 a good question. And it's a question that you could probably investigate.
17:08 has to do with the structure of protein, but in essence the gate
17:12 slower. Right? The reason, don't know. So, what we
17:18 as a function of that at this right here is simply the opening of
17:26 potassium channels while simultaneously the closing of sodium channels. And remember these are
17:31 voltage gated, these are not the channels. So it's all bolt
17:35 And so those voltage gated channels stay again for a brief period of
17:40 And so where that arrow is That shows you that point where those
17:46 begin to close and see and look what happens to the slope. The
17:49 is like, okay, now I'm down but because they close as slowly
17:54 they open, you overshoot the resting . It's kind of like when we
18:00 on our brakes, when the light from yellow to orange, right before
18:04 turns to red, don't your lights orange yellow to orange and there's
18:12 Yeah, my lights turn yellow to . That's why I'm always constantly accelerating
18:18 the I'm just teasing you guys when an aggressive driver, there's a color
18:27 yellow and red, it's orange. right. And so when I'm speeding
18:32 and it's like, oh no, have to and I slam on my
18:35 and what do I do? I sliding into the intersection, waving at
18:38 people as I go and then I accelerate again. Right? So that's
18:43 of what's going on here is we're the door shut but they're all not
18:47 at the same time. Some are open, some are partially open and
18:50 why you see this overshoot here. , so this is where rest would
18:56 . Right? So you can see getting a slight overshoot. Yes
19:04 Well, no, no. So threshold is about -55. Alright,
19:10 remember the equilibrium potential, if all if it was only potassium or
19:14 only sodium equilibrium potential would be up plus 60. And that's what we're
19:18 to get right, but we don't have sodium, what else do we
19:23 ? And what else do we have ? What else do we have
19:27 What else do we have? You just just start adding up every one
19:31 ever learned about from the dawn of . Alright. So really what we're
19:36 at here, what are the ones actually have an effect the two that
19:39 the major effect our sodium and And so we're looking at the dance
19:42 those two things. So if nothing were to happen, if all it
19:46 was potassium channels all staying open, shoot down about -90. But we
19:50 see that happening because we have leak right for sodium. And so all
19:55 thing balances out, trying to get to the -70 eventually, which we
20:00 we can calculate that, but we're gonna for this class. I love
20:03 not gonna as Alright, so you can start off resting resting.
20:08 I stimulate open up some voltage gated channels right on that stimulus. That
20:14 more to open up more to open through a positive feedback loop to all
20:17 them are open up. That's when read threshold threshold, I'm now rushing
20:21 towards plus 60. But those gates shut. I'm now here about plus
20:27 potassium channels open Now I'm shooting back while the while I'm trying to return
20:32 to rest those those slowly closed. so I overshoot. And now I'm
20:37 here in the state of hyper It's a transient hyper polarization again.
20:43 at the time from the beginning to end of this thing. We're looking
20:46 four milliseconds. Alright, that's a short period of time. Right?
20:53 , you can imagine this is replacing for repeating itself very, very
20:58 So this transient hyper polarization results in period of time where I'm sitting below
21:06 . Have you guys ever seen this ? Refractory period? Maybe.
21:10 a refractory period is defined as a in which something can't work because things
21:16 to be repaired replaced returned back to . All right. And so with
21:23 to an action potential, the refractory , there's actually this broad period
21:27 look, things haven't returned back to yet. So, I can't quite
21:31 an action potential during this period of . So, we have right
21:35 you can see there's the actual potential then the two shaded areas represent this
21:38 where things can't happen. All right we have an absolute refractory period where
21:45 says under no circumstances can I produce action potential. Now, why would
21:51 be true if I've opened up all sodium channels? All my voltage gated
21:55 channels, is there any amount of that can result to me opening up
22:00 sodium channels? No. So under circumstances when all my channels are
22:06 I can't open any other channels and they're in that close but incapable of
22:10 state, is there any amount of that's going to cause them to open
22:13 ? No. So during that period time when those voltage gated sodium channels
22:18 either completely all open or they're in stage of close but incapable incapable of
22:24 . I can't stimulate my neuron to an action potential. So the absolute
22:31 period says you cannot get another action during this period of time. The
22:38 refractory period on the other hand, , well, you know, um
22:42 voltage gated sodium channels are repairing themselves returning back to their original state so
22:49 could stimulate them. But in order get there you have to overcome a
22:55 deficit that you're now currently in. remember I've got potassium coming into the
23:02 faster than normal, right? Faster the normal 1 to 50 ratio.
23:08 just make up a number 1 to . Right? So I have to
23:12 that voltage deficit to get back to point where I can open up and
23:17 sodium dominate. So, there's a of time when my sodium channels have
23:23 kind of reset themselves but they can't a strong enough sodium influx to overcome
23:28 potassium influx. They can but I to give it a stronger signal to
23:33 so. And that would be in relative refractory period. All right.
23:39 wayne. Fine. So why should care? Well, refractory periods are
23:45 the cells separate out action potentials. . Action potentials are always the same
23:52 . The same height. Right? saw they all go to plus
23:55 When you started at one side it the entire length without reducing its
24:01 Right? So how would I ever a stronger signal? If I can't
24:06 a stronger action potential how many I ? So what I can do is
24:13 can increase the rate at which a fires and that's an indication of an
24:20 in strength of whatever the stimulus So, having a refractory period limits
24:26 I can fire. Now again, we look at this, it was
24:30 ? Four milliseconds. So you can a cell firing at a rate like
24:36 , right? There's a there's a in there. So what I can
24:40 is I can increase the rate until can get them as close together until
24:46 now. But butting up against my refractory period. Now, just to
24:51 this one more time. Let's clap clap. It is fun.
24:54 What? Let's see how fast we clap. Can you make one noise
24:59 your pants? No, if you your hands together, they don't make
25:02 , do they? So, it's I can only clap as fast as
25:06 body will allow me and that's like refractory period. There's only so much
25:11 make a clap. I mean, can try to do that. It's
25:13 not a loud clap. So refractory limits frequency of an action potential.
25:20 so you can as you see answers up around the board. Um If
25:26 want to if I want to show of the signal, I'm willing to
25:33 the number of action potentials that are to be traveling. All right,
25:40 let's come back to this. Do understand the steps of an act
25:47 Right? What's happening at each of little arrows? Do we understand the
25:52 of this hyper polarization and why? why we have to point it
25:57 Has to do with this. Right . It's an area where I can
26:01 get an action potential but I have have a stronger signal to get
26:05 That makes sense right after. To it in the language of other
26:10 I have to create enough voltage to the -55 threshold even though that's a
26:16 way of saying it. Right, okay back there people in the front
26:22 nodding their heads and I can't trust . You know these are the
26:26 They're the ones like give me the . I was the back row person
26:31 this is how I sat the entire . Are we good? You ready
26:37 race me? I'm gonna need you race me today. Race. We're
26:41 race that. Cool. Alright. , well not just yet, we're
26:45 you're gonna have to stretch. I . All right now action potentials are
26:55 . We saw that when we did wave, right? We start the
26:58 , it just goes right, so a conduction. And so when you
27:02 about this, remember when we're looking this, remember what you said is
27:05 it's like having a probe at a point in the cell and asking what's
27:09 over time in that particular cell or particular point of the cell. So
27:14 you're looking at this, it's oh, that's when the hands go
27:17 . That's when the hands go Right? But this is occurring over
27:21 entire length. So what you have imagine is that that wave is moving
27:26 the length of the cell and so can actually measured at different points and
27:30 conduction is going to be propagated in perpetual fashion until there's nothing left.
27:36 other words, there's no voltage gated over at this end to allow for
27:40 continued propagation. Alright. In other , what causes these? This is
27:45 potential keep happening is because along the length of that axon are voltage gated
27:51 and potassium channels. So as long you have that along the length of
27:55 distances you're going, you're going to that action potential going on forever.
28:00 kind of makes sense. Right. so that means as that action potential
28:05 . So you can imagine here it . I'm not gonna make you guys
28:07 your hands but as the acts potentials , let's say right here at this
28:11 , we're at the peak of the potential over here, we're coming
28:15 Right? So here this would be refractory period, wouldn't it? Because
28:21 they're coming down, this is not wave right here. This is kind
28:24 really bad dancing, right? But wave is I go up, I
28:29 my peak, I come all the back down and now I can complete
28:33 process all over again and that's what action potential is. There's no kind
28:37 this is not, this is this is bad buddy. I don't
28:42 , I don't know anything about bad . Bad bunny to me is just
28:46 cream. That's gone off blue I don't Yeah, what's that?
28:55 That's a good question. So if action potential is the question is can
28:59 action potential be stopped? So if action potential simply is the movement of
29:04 through those channels, voltage gated how could you stop an action potential
29:10 the channel so that they can't Right. So there's a question I
29:14 ask on an exam and says, , given what I just told you
29:19 the period behind the period that's following here is a region in refraction.
29:25 ? So this is the front, is you waiting for that action potential
29:28 . You know that's you're watching This is where the potential is.
29:33 is where it was the refractory So if you have to action potentials
29:38 towards each other, this would be hypothetical. This does not happen in
29:41 body at all under any circumstances. if you have an action potential going
29:45 way and action potential going that way the same axon, what happens when
29:48 meet this is what I hear. very quiet. Go ahead. You
29:59 got your hand up, let's hear bellow it loudly. That's exactly
30:07 Alright. I'll say what he said I could hear them. So when
30:10 come into contact with each other, one is going to come into contact
30:13 that refractory period. This one is to come into contact with this one's
30:17 period. And really, what is refractory period? It's simply the point
30:21 all the channels are open. So I can't open any other channels,
30:24 can't make the actual potential go any . So they basically come and
30:29 Right? So the idea here, thing that's the take home is an
30:33 potential isn't just a wave of something we see a pretty picture of it
30:39 the movement of ions as a result the opening and closing of channels.
30:45 if I can't open channels any it isn't going anywhere. There's no
30:51 movement. It's stuck. So, answer your question again. Stopped.
30:59 . And that's what this is trying show you. All right. As
31:05 potential is traveling is traveling along the of the membrane. And as long
31:09 there are voltage gated channels, it's going to move along and move along
31:12 chug and cover the entire length of axon. All right. That's a
31:17 of work because you have to move lot of ions. All right.
31:21 got a time out here. There's lot of hyperbole and what I'm
31:24 Alright, really? We're talking about few ions moving back and forth cause
31:28 changes. But when I say ions of islands. It's it really paints
31:32 picture, doesn't it? And that's I wanted to paint the picture.
31:37 this kind of shows you that Alright. And so that kind of
31:41 along the length of basically me walking the hill. Right? So as
31:46 as there's voltage gated channels, I'm gonna keep moving and moving until there
31:49 none. The problem is this is of slow. Do you see me
31:54 , is that kind of slow kind So we want to speed things up
32:00 ways. You can speed up a . Alright. In terms of an
32:05 potential one, you can give that , more volume. Right? More
32:12 speeds up an ax potential in Or what you can do is you
32:16 basically cover up and insulate portions of axon and force the action potential to
32:22 over sections of the axon. how do I do that?
32:28 this is where my allen comes Alright, so contiguous is kind of
32:32 we've been describing basically every little solitary millimeter. Whatever you want to
32:37 A micrometer is basically covered in these gated channels. So the action potential
32:44 moves very very slowly along the No, Myelin, when my allen
32:48 along, what you do is you these regions that are insulated away from
32:56 uh external environment. So all your gated channels are located in these
33:01 These are called nodes of Ranveer. , Myelin is not the note of
33:07 . The note of Ranveer is the that's opened up. And so what
33:10 now have is you have a concentration the voltage gated channels in these little
33:15 spaces. And the length of the is as long as it needs to
33:20 in order for this to be stimulated to still allow for stimulation to occur
33:25 there again. Let's take a look walking for a moment. All
33:31 Walk a normal gate. Is me over portions of the floor.
33:37 You see that there are portions of floor. I'm not stepping on if
33:42 go toe to heel a lot All right, but I'm covering the
33:47 floor. This is what would be the other where I'm stepping the other
33:55 I'm stepping like. So that's All right. Now notice my gates
34:01 very long. Am I doing Because that would really suck. Look
34:05 that man create my balance. So a point where it becomes too
34:11 Right? And that's kind of the thing here. The distance from here
34:15 here is goldilocks, just right. goldilocks three bears. Remember?
34:33 so, so remember in this what we have is we have water
34:36 the inside, water on the outside ions can move both in and out
34:40 the cell. Right? When you're about a wire, they're not gonna
34:44 over insulated areas because the ions aren't out into the air and then
34:50 Right? So it's a little bit if you're thinking in terms of an
34:55 like the body versus an environment like electrical structure. All right. But
35:02 same principles are gonna apply anyone Well, I mean, I know
35:06 listening to music on their little I know, their earbuds and stuff.
35:11 are there any audio files here? mean true audiophiles, you know like
35:15 got your you got your stereo you got your big speakers. So
35:19 wires that you go to your speaker that they're not all wifi and
35:23 Are they thin wires. Are they wires? Okay. Generally speaking now
35:31 . Why less resistance conduct better? that's the reason. And the same
35:40 is true in the body big thick conduct better than little. Itsy bitsy
35:48 axons. Alright, They have more tiny ones have more resistance to
35:53 Yeah, pick up that. I my electric guitar. Right? It
36:06 seems like right. But if you . So the other way you can
36:11 about this is like so you go and buy a cheap, you
36:15 stereo system, you know, back the day, you can go buy
36:17 cheap one and they give you the attached and they give you these little
36:20 thin like they're like thread thin And then you can melt those like
36:28 plus their crappy aluminum or something like . But, you know, if
36:32 have a good stereo system, good system, you're gonna get yourself those
36:35 thick monster wires, right? You . So the Myelin is like is
36:49 . You can't there there is no . Sorry. There is no contact
36:54 the environment. So the only place the internal portion of the cell can
36:58 with the external portion is through that membrane that's exposed. And this is
37:11 we can see that. Yeah, . You would think so. But
37:18 all information that have the same equal ? No. All right. And
37:24 give you an example here, Anyone ever been hit by a baseball bat
37:27 a baseball? Lots of fun. . So, that first time you
37:31 hit sharp pain, right? It's of important to know you've you've been
37:36 hard, Right? And so you that really sharp pain. But then
37:40 pain lingers for a while, And now you're starting to get these
37:46 pain, right, damage has Just let you know, quit using
37:50 part, Right? That's what pain . Pain is not necessarily just weakness
37:54 your body. Some people got that . People who workout pain is your
38:00 telling you you've caused damage. You doing this, you're gonna die.
38:04 is also why working out hurts. . So, this is a better
38:13 of what that is. So, can see here, you can see
38:18 voltage gated channels associated affiliated with these membranes, right there. Only
38:24 So, what you're doing is you're an influx of sodium that, you
38:28 , it travels from the site. like we saw with that greater potential
38:31 it's going to look for its matching , but it can travel just far
38:36 to start stimulating the opening of those gated channels in this point. And
38:41 , enough to cause it to reach threshold of an open. So,
38:45 , you get this massive influx of and that just keeps happening over and
38:49 again. So it's just like moving potential forward except you're just not covering
38:56 entire ground. Let's get up here race. I want to just prove
39:02 Now, you be nice to I had a student a couple of
39:06 ago said, let's race. She a soccer player. I had her
39:09 like four classes, so she knew . So the first thing she does
39:11 she pushes me like you're gonna beat . I'm not gonna I'm not putting
39:16 in a position to lose. All . I want you were gonna race
39:19 the other side of the benches here you're gonna walk normally without pushing me
39:26 I'm gonna go toe to toe and gonna see who goes there. First
39:30 , get set, go, come , go. Do you see what's
39:39 ? Because he's walked over space. moved faster. So for the same
39:47 can sit down. Thanks. I race you back. But I
39:50 you're Yeah, he's gonna beat me . And that's it was pretty
39:54 right? So, so you can for axon of two similar size of
40:00 exact same size one that has my results in a faster signal than one
40:05 does not. Okay, now the option is I can again, I
40:10 expand out and make my axon But you can imagine I have a
40:14 space in my body. If I have my Ellen, I would just
40:17 making all my other axons bigger, means I have to make my body
40:20 , which means I have to make axons bigger, which means I have
40:22 make my body bigger. You see just causes this endless loop of can't
40:27 . So, my allen is the to solve the problem of speeding up
40:32 potentials for certain signals. Yeah, my allen is remember we have two
40:43 cells, I'm trying to find a where I'm not looking directly in the
40:46 at you. Myelin is two different in the in the central nervous
40:51 We have the Alexandra site, So it's just a cell and then
40:55 the outside and the peripheral nervous system have this other cell called the neural
40:59 or the Schwann cell. And what of them are doing is they're taking
41:03 the case of the Schwann cell which easier to describe. The cell is
41:07 wrapping itself and flattening itself and wrapping the the acts on multiple times.
41:13 it creates these multiple layers of fat that's what plasma membrane is.
41:17 And basically just creating this massive fat so that the extra cellular fluid doesn't
41:23 into contact with the axon at that point, all that interest is very
41:27 . The difference is is that you're your cytoplasm out and you're wrapping around
41:31 axons. So the soma. The body comes sits in a particular location
41:37 it's just portions of yourself. But does the exact same thing multiple
41:41 We're talking 50 to 100 times around axon and that's what this is trying
41:45 show you. These are Schwann cells you can see up there. The
41:48 insight. Alright so it's basically a insulation is lack of better term.
41:56 what? Yeah go ahead. Oh . So you've heard of multiple
42:06 autoimmune disease against my alan which causes breakdown of the myelin sheath which causes
42:13 neurons that that would normally have fast action and stuff like that are now
42:19 . So people who have M. . Aren't able to control their body
42:23 way that the brain wants them So that would be an example of
42:29 . So what I wanna do is I want to shift a little bit
42:32 we know what an action potential is we still don't know why we have
42:35 . Right? And what I wanna is I want to get to
42:38 But before we talk about the synapses really interested I want to understand there
42:42 what are referred to as electoral electrical . So what we have here is
42:46 have two cells are connected to each by a series of of connections and
42:50 we can have these gap junctions allow the ions to pass through the
42:54 So reciprocal synapses where the current moves both directions right? So it basically
43:00 going like this. So some will going in this direction. Sorry someone
43:05 in this direction, Some will be out I guess this is the picture
43:07 here, that kind of shows that . And then the other direction.
43:11 it's reciprocal and then rectifying basically you're looking at gating mechanisms and so there's
43:16 current that basically causes it to go of in one direction. So,
43:20 idea is that the flow occurs because have ions actually leaving the cell and
43:26 being picked up by the cell that was coming from. And so it
43:30 this kind of how your heart Alright. It uses these types of
43:35 . And so we have electrical synapses regard to the cells of the
43:40 Right? The cardiac muscle cells. right. But you can also have
43:46 in the nervous system but we don't talk about them all the time because
43:49 just not that common. The thing interested in is what we would call
43:52 chemical synapse. All right now, chemical synapse is what you find down
43:58 at the Teledyne dri, at the bottom of that neuron that we started
44:02 . And so you can see what's here in the little red letter with
44:05 little tiny lightning bolts everywhere. Is action potential. That potential is opening
44:11 voltage gated sodium channels, followed by opening of the voltage gated potassium
44:15 And the closing of the voltage gated channels and it's just gonna keep going
44:18 we get down here. And what have is we lose the voltage gated
44:23 and potassium channels instead. What we now is a voltage gated calcium
44:29 Why calcium? Well, calcium tends serve generally speaking in a lot of
44:34 places as a signaling molecule. And we're trying to do is since we're
44:38 storing up calcium like we do in fibers instead, we're just gonna take
44:42 from the environment and allowed to come in the cell to serve as a
44:46 molecule. Alright, so the current a chemical synapse is not coming down
44:52 then jumping over to the next Like we see over here because these
44:56 directly connected. Instead, we have space that we're going to send chemicals
45:02 one cell to the next. We some terms that we use here this
45:06 the sending sele where the synapse where that knob is. That's called the
45:11 synaptic cell. So the one on opposite side of that space which is
45:16 the synapse is the post synaptic See how clever this is,
45:21 And what we're gonna do is that potential travels down causes the opening there
45:27 is right there. The opening of calcium channel. And when that calcium
45:31 flooding in it goes to that vesicles we talked about the vesicles big already
45:38 up and ready to go because of snares. It basically signals to the
45:42 . It says okay, time to your stuff. And so at that
45:47 in that space, those vesicles open and merge with the plasma membrane release
45:51 neurotransmitter. The neurotransmitter is then going cross over that space. And presumably
45:58 it is a synapse, there's a on the other side for that neurotransmitter
46:03 is going to cause that channel that channel to open up. Which is
46:08 to allow sodium or potassium to move that channel, sodium and potassium
46:13 If it's chlorine it would be in and then we're going to stimulate the
46:18 cell in in the line. So see we have here we have an
46:23 signal that travels the length of the to get down to the very end
46:27 the cell to cause the release of chemical. So this is why it's
46:32 chemical synapse. Now this signal is directional. The signal is going this
46:38 from pre to post. It's not ever go post to pre. This
46:41 not a two way street. It's one way street. If this cell
46:45 to signal with that cell, it's to have to work through its axon
46:48 go back the other direction. And the accent would go that direction.
46:54 this is our synaptic vessels testicle. me, You can see what am
46:58 doing. I make them through the like I make them everywhere else.
47:01 transport him down using that uh anterograde of transport. I take them down
47:06 the end and I storm there until signal comes. So all this stuff
47:10 independent of that electrical signaling. It's of the action potential. The purpose
47:15 the action potentials just caused the release . It is to remind you,
47:21 vesicles are complex, that calcium is allows me to go from a staged
47:28 ready to release to that release I'll see him. So, it's
47:33 a reminder of why we talked Don't worry about Monk 18. That
47:37 me and me being hopefully a couple years ago. Oh, they'll learn
47:41 the names of all these proteins. worry. I love this picture because
47:46 is a really good demonstration of a this is the neuro muscular junction.
47:52 , so down here we have a up here we have a neuron,
47:56 is the terminal end of the We call this the neuro muscular
48:00 And you can see all the little speck looking things. Those are acetylcholine
48:06 , their channels, their sodium channels are dependent upon acetylcholine to bind to
48:12 . All right, Colleen binds sodium into the cell because of the cell
48:18 polarize because the muscle to contract through lot of other steps that we're not
48:22 to go into over here. It's showing you how you're lining up all
48:26 vesicles they're lined up and ready to . All you gotta do send that
48:31 down the action potential travels causes calcium come in, calcium comes in?
48:37 causes that vesicles to open up the blue dots. Acetylcholine. Acetylcholine goes
48:43 and switch receptor cause deep polarization in post synaptic cell in this case the
48:49 . Yeah. Mhm. No no . So that's a fair question because
49:00 does get very very confusing because this very similar to like the mouse trap
49:04 like A. B. C. . So the actual pencil comes down
49:09 the terminal end of the pre synaptic at the terminal end of that pre
49:15 cell. We have voltage gated calcium . So what I'm doing is I'm
49:18 a lot of calcium into the pre cell that calcium serves as a signal
49:24 open up the vesicles to allow the to be released to act on the
49:28 synaptic cell. Alright and then what dealing here with here is a channel
49:33 opens up that allows sodium to come or potassium to go out and we'll
49:37 to that in just a second. you read? I don't know
49:41 that was tough. Yeah and and is tough. Alright so you just
49:46 like this step one pre synaptic cell potentials traveling along the length of the
49:50 gets down to the end of the that's called the Teledyne area or the
49:54 terminal or the synaptic knob. Any those names will pop up in your
49:58 your reading at the synaptic knob. gonna see voltage gated calcium channels.
50:05 the action potential is there to stimulate opening of that calcium channel? When
50:10 channels open calcium channels, calcium comes to the pre synaptic cell. When
50:17 comes into the pre synaptic cell, stimulates the vesicles merging with the plasma
50:23 at the synapse released by neurotransmitter. , when I released my neurotransmitter neurotransmitter
50:30 is working across the synapse to find receptor at the receptor. That receptor
50:37 a channel. We don't care what of channel is right now. Right
50:40 be a sodium channel, potassium chlorine channel, whatever it causes the
50:45 of the channel. And when you up the channel, that ion is
50:48 start moving through whichever type of ion is and it's going to cause change
50:53 change in that receiving cell, the synaptic cell. So if it's sodium
50:57 gonna cause what type of change? polarization. If it's potassium it's gonna
51:02 hyper polarization polarization is returning back to the same thing. But it would
51:07 the same sort of thing if I'm polarized, I'm going to re
51:11 Right, that makes sense. the current is for biologists by as
51:18 as biologists are concerned, the current the movement of positive ions to an
51:22 where there's less positive ions. Which really confusing because does that mean there's
51:26 negative ions, not necessarily, it's moving positive ions to where there's less
51:31 them. If you talk to a , they may have a different
51:34 If dr physicist, they'll laugh at and then they'll say no,
51:37 no biologists are idiots. That's All right. I'm a dad.
51:44 I have to talk about this in way that dad's talked about this.
51:47 you ever walked into a room, a light on, turn on the
51:50 , walked out of the room, the light on what your dad
51:53 Turn off the dang light. I'm it clean. I do this 30
51:57 a day. You know, are raised in a barn? You
52:01 no turn off the light. Well everything you turn on in the
52:04 you always have to turn off. it'll just keep going. Consider your
52:08 . Look at your life and imagine the electronics that you have. If
52:12 always on all the time everywhere. how stressful that would be right?
52:20 just the lights, everything that's what go on inside a cell. So
52:25 that you turn on has to be off inside a cell. And so
52:27 a termination for this signal, So when that neurotransmitter gets released by
52:34 neuron, what it's doing is it's that next cell to do something.
52:38 so you want that signal to be and quick so that cell knows what
52:42 do and then it's done doing what does. So there are a lot
52:45 different ways that we can turn off signal. Alright. In other
52:49 how do we kill that? That , that chemical synapse the first type
52:56 enzymatic destruction. Do not memorize this here. These are just examples.
53:01 . Enzymatic destruction was the first one because it was with acetylcholine and what
53:06 have found in the synaptic space, ? That synaptic cleft, we found
53:11 set of colonist race. So as as the silicone is released, there's
53:15 an enzyme there sitting there playing chop chop chop chop as it's being
53:20 it's kind of like the world's deadliest of red rover, right? If
53:24 an enzyme and you're quick enough you get across if not you're doomed.
53:28 ? That's # one. There's also all floating all over the place.
53:32 the second thing is that you can away, right? Because remember as
53:37 as a as a neurotransmitter as a molecule, you're looking for your
53:41 So if all your receptors are concentrated the synaptic cleft, that's where the
53:45 should be done. So if I away, I can't do the signal
53:49 then you have enzymes that are gonna , you're not supposed to be here
53:51 chop chopping away you go. So the two most common, you
53:57 also be taken in by a Alright, so that you can see
54:01 in this picture right there and there there and there and there and they're
54:05 trying to show you neurons play a in taking up their own neuro transmitter
54:09 hear what they're doing is they're saying , no, we're gonna let go
54:12 you, but we're also going to you up and we're gonna destroy you
54:14 we're gonna reuse you. And so would be another way. And
54:19 and this one shows it best. here, it says, look surrounding
54:23 will have other types of cells, just the receiving cell. And we
54:27 have these cells that have ways to these these signaling molecules and we'll break
54:33 down or reprocess them and then we'll them back to the neuron as
54:38 So you can take them the other . But the big picture here,
54:44 the four different ways that you can this is that you want to terminate
54:49 signal very quickly. You want the to send the signal and be done
54:56 it so that the responding cell produces immediate response to that. Alright,
55:04 makes sense. Yeah. Uh That probably no, they're probably not.
55:10 can't tell you for sure because I know. But my guess is
55:14 that they would all be at different . Yes. So what you do
55:24 you find for what we're talking about destruction were saying right here, within
55:28 context of the synapse, really only colon ergic ones are the ones that
55:31 know of that actually have enzymes that that role. And it's just because
55:35 all over the place, you Colin ergic uh synapses, man,
55:40 construction is just distracting in it. , but so that was one of
55:45 like the first discovered, and very what we do is the most common
55:48 is the first one discovered is like is gonna be like this and then
55:52 is like it at all. And kind of the case here. Um
55:56 we just have so many of so that's where it's gonna be,
55:58 gonna be in the synaptic cleft. . And then circulate are generic enzymes
56:03 are looking for things that shouldn't be . So as I mentioned at the
56:12 , one of two things can happen I have a channel that is open
56:15 sodium, I get the polarization if have a so if I have a
56:21 that's for, say potassium, I get hyper polarization. So depending on
56:26 type of channels I'm gonna have a type of synapse. Right? So
56:30 example, I have excitatory synapses. , we've got these really, really
56:34 names. And when you when you these names at the synapse, what
56:37 referring to is what's going on now the post synaptic cell. Alright.
56:43 if I release the neurotransmitter and it up a uh sodium channel. What
56:50 gonna get is a potential in that synaptic cell that is excitatory it's gonna
56:56 deep polarization. So we call that the excitatory where is it happening post
57:04 cell And it's a change in the . And that's where the name comes
57:08 Sony PSP. Because that's much easier excitatory post synaptic potential. I'm gonna
57:15 on all of you guys saying that now. E. P.
57:20 P. S. Are graded Alright. They're occurring in that receiving
57:26 and so I'm producing a greater What do we know about graded
57:30 They very magnitude. What does that ? That means if I have a
57:36 signal I'm gonna get a strong I'll get a strong E.
57:39 S. P. If I have small signal I'll get a small
57:43 All right. They don't have refractory . What that means is if I
57:48 have a refractory period and a greater , that means I can take a
57:51 potential and have another greater potential stack top of another one stack on top
57:55 it. So in other words I make big strong graded potentials in an
58:00 way. Refractory period to prevent that happening. Because I can't get action
58:06 close enough together to get them to on each other and action potential is
58:09 all response. Yeah one. So take a look at the picture.
58:24 up here that is our action It's causing the release of calcium which
58:31 the vesicles to merge which causes release neurotransmitter. The neurotransmitter binds to its
58:37 , opens a channel and causes a potential change which would be the
58:43 P. S. P. There go. So do you see where
58:45 is? It's located in this cell potentials up here, E.
58:49 S. P. Is being produced the receiving cell. Alright. So
58:54 could be an excitatory synapse resulting in PSP. Alright so the E.
59:01 . S. P. Is the ? Okay. The last thing is
59:05 it can be summed which is what saying here. Alright, so this
59:07 just showing you varying magnitude. Can vary in terms of their length as
59:15 ? Yeah. Right. Because they have refractory periods. So I'm just
59:19 use a really really bad example. if I came up to you and
59:23 you with a needle right, let's pretend that that results in a greater
59:28 . So a little poke would be a right and then you can imagine
59:32 take that needle and poke you for long time and I'd be like
59:37 so there's length and then I can a running start with that needle and
59:41 it into your arm and what would get? Very very tall response?
59:46 , bigger magnitude now, greater potentials come from being stabbed by a needle
59:53 that would be an example of stimulus you a response. Okay.
60:06 Hey Yeah so you're you're you're catching language that I screwed up there.
60:13 calcium is allowed into the cell. right. So what we'll see a
60:18 bit later is we're going to talk calcium being stored up in cells.
60:22 that's probably where I tripped with the . Calcium is released from the
60:26 But that's not what's going on It's going into the cell because because
60:30 is no storage of calcium inside the muscle cells. Okay. Okay.
60:42 . P. S. P. . Are the opposite of E.
60:46 . S. P. S. . The channel is going to be
60:49 potassium to move out of the cell it causes hyper polarization. So we're
60:55 further away from threshold. Okay now both of these things can be some
61:01 have the same characteristics. Just one causing the polarization ones causing hyper
61:08 Why I want to show you this here which I think is a really
61:11 cartoon is that this shows you the of a neuron. You can see
61:16 the dendrites have kind of been And all these little blue dots are
61:23 the axon terminals of other axons. each axon I'm sorry each neuron is
61:30 association with other axons, thousands of and so you can imagine that some
61:35 them are sending signals that are resulting E. P. S.
61:38 S. Some of our sending signals are resulting in I. P.
61:41 . P. S. And so you have to do as a neuron
61:44 you are opening and closing channels and you have sodium coming in and potassium
61:50 . And if you have a strong signal that is able to wash all
61:53 way to the axon terminal or not the axon hillock, then you can
61:59 an action potential. So graded potentials used to create action potentials in subsequent
62:07 , right? So you can imagine I'm stimulating the cell up here,
62:11 it creates a strong enough graded that wave would work its way
62:16 remember how it's kind of like a and it kind of you know,
62:19 strength along the way. If it's enough over here to get down here
62:23 cause deep polarization, you can get action potential. Let's say along the
62:27 you open up A I. S. P. Or you create
62:29 I. P. S. Here. You might actually be able
62:31 inhibit so the some of the P. S. P.
62:35 And the I. P. P. S. If you count
62:37 magnitudes like plus minus plus five minus . Whatever you can actually add them
62:44 and you get this potential change that refer to as the grand post synaptic
62:53 . So for you math geeks, . P. S. P.
62:56 equally PS PS plus I. S. P. S where I
62:59 PS are negative and E. S. P. S are positive
63:02 now, all you gotta do is add them up. And if you
63:04 enough to get you above threshold, you go to an action potential.
63:08 this type of of summation. There's different types. One is temporal,
63:12 is spatial. All right. And what this slide is. Trying to
63:16 you. So, I want to you here. So, up here
63:19 where we're measuring and this is where getting this chart. Okay, that's
63:22 membrane potential Over here, we're measuring the axon hillock. So we're asking
63:27 are we getting at the axon So you can see action potentials there
63:30 then down here is just at the , What do we see going
63:33 Okay, so in this first one have a single uh axon resulting in
63:39 E. P. S. There you go. You can see
63:41 E. P. S. But you can see that that
63:44 P. S. P is not strong. And so by the time
63:47 that signal gets down here to the hillock, if we measure it
63:50 you can see that we don't get threshold. No threshold. No action
63:56 . Right, that's easy. If I don't get threshold, no
64:00 potentials here, I'm doing spatial Name says two things. Two or
64:07 uh E. P. S. . S. Uh realize should say
64:15 neurons firing at the same time on receiving cell. Alright, two or
64:20 . Right so do it like this my one signal is a clap.
64:26 when the both of us clap Is it louder? Yeah so there's
64:31 summation right of sound. That's kind the same thing too at the same
64:35 . And so here you see when both fire at the same time,
64:38 get a stronger E. P. . P. Up here. When
64:41 get down and look at the axon I get action potentials. I'm over
64:45 threshold. Why do I get two them? I happen to be over
64:48 threshold for a period of time. results in two. That's what the
64:53 is showing you. So that that is if I get two X potentials
64:57 gonna keep traveling along the length and why I get them down here.
65:02 if I get three? Well they're give you bigger ones. I get
65:05 action potentials and get more action potential the line. So you see here
65:08 is encoded in the number of action that are being sent. Right okay
65:14 what about temporal temporal is one action one neuron firing multiple times? In
65:21 and closer secession. Right? Because graded potentials can be additive acts potentials
65:27 . So if I have one action firing like this right, each one
65:32 those is going to result in an . P. S. P.
65:34 goes up and then comes down. if I bring those things closer together
65:39 length of time that that greater potential up and comes down doesn't change.
65:42 goes up and by the time it's down the next one is causing it
65:46 go up, I'm adding on top it and then the next on top
65:48 that. And that's what you see is the post synaptic potential is going
65:54 and higher and higher because these are enough together to get us there,
65:58 gets us over threshold. So we a series of action potentials. So
66:02 summation is a single neuron firing multiple in succession. So it's a time
66:08 . Whereas this is the number of being fired at the same time resulting
66:14 the downstream response. So post synaptic always occurring inside the post synaptic
66:19 you're asking how am I acting on ? Post synaptic cell cancelation is also
66:28 occur. So, if you have ep sp and an I.
66:30 S. P, let's just say are the same magnitude. So if
66:33 the same magnitude plus five and minus equals so, nothing happened.
66:38 So in essence this one's causing sodium come into this was causing potassium to
66:41 out. It's at the same So I get no response. That's
66:45 you see there. All right. it's basically E. P.
66:49 P. S. I. S. P. S of some
66:51 the magnitudes basically canceling each other, a type of spatial summation. So
66:59 are lots of different types of So we tend to think in terms
67:03 axons acting on dendrites or axons acting cell bodies. So that would be
67:09 O. Is telling you what's attaching to what it's attached to is the
67:12 half. So axon dendritic access Those are the two most common
67:17 There's even um some that are called . So ax sonic, so that's
67:21 the axon is just acting directly on on the action itself. So it's
67:27 the opening of voltage gated channels nearby where the actual stimulus is taking
67:33 So remember you're always acting on a gated channel which allows for the sodium
67:38 potassium to move. Which will then immediate effect on the surrounding voltage gated
67:44 . Whereas here you have to travel you get to the voltage gated
67:49 there's some weirder ones, not just one, you can have dentro somatic
67:53 dendritic, don't worry about them, pop up over time. They exist
67:59 it tells you it's dendrite down dendrite on soma, so on and
68:03 forth. Axons size matters right? same thing because the dendrites faster the
68:16 , right? Smaller than dendrite. more resistance you have, the harder
68:21 is for the signal to move That's simply the same thing,
68:25 So there's an attenuation and this is trying to show you look in the
68:28 dendrite versus the fat dendrite you get same E. P. S.
68:32 . The same result. But because have resistance you get a lower signal
68:37 the axon hillock. Whereas here you a stronger signal that results in the
68:42 potential branching. No it's actually to size. So so branching. This
68:51 a good question that someone came up branching. Uh Just gives you more
68:55 for interaction between cells. Right? what you're looking at is the dendrite
69:02 , is it a bigger dendrite or it a smaller dendrite? And they
69:06 change their size. Which is weird ? They will. That's one of
69:11 ways that neurons modify signaling between themselves they change the shapes of their dendrites
69:17 their axons as needed. Which is confusing Now much of the rest of
69:25 stuff has to do with I should here since About 10 minutes.
69:30 I might be able to do Alright. That information in in these
69:36 neuronal pools can be both divergent or can be focused. And what it
69:41 to be divergent is like a signal out to lots of different things.
69:45 right. So an example of of would be for example if I saw
69:51 bear charging at me my system would basically say hey uh increase heart rate
69:57 rate. Uh Make those muscles start faster as you run. Breathe
70:02 So all this stuff. So it's acting on multiple things. Multiple
70:06 right? Whereas focused is like, , I'm just focusing on this one
70:10 thing. I'm turning this thing on this thing. Alright, so,
70:15 that's kind of what what that actually of refers to. So they can
70:20 confined or they can spread out One of the things that point out
70:26 neurons in the pathway, the more are, the greater the number of
70:30 and the longer it takes to transmit and this is what is referred to
70:35 delay. Wait, I always remember even though this is not true.
70:39 don't take this is true, is I'm walking across the street and that
70:43 honks at me as it's slamming on brakes and I sit there and go
70:46 because my brain is trying to figure what to do. It's trying to
70:50 all those synapses and that's why I'm . That's not what's really going
70:53 But you can think of it along lines. There are a lot of
70:58 types of neurotransmitters. About 100 of . You have to memorize all these
71:04 how they call clarity and stuff like . Just teasing. We don't do
71:09 here. What I want to point here is they're all classified by
71:14 The first one was the seat of . That was the first one to
71:16 . And everyone was all excited because we understood what neurotransmitters were like and
71:21 of course it's in its own class by itself. We have the mono
71:27 this group you're familiar with. Cata means epinephrine, norepinephrine and dopamine.
71:31 heard of those right? If not gonna become familiar with them but you
71:35 see they're all over here um they formed from tryptophan, serotonin histamines
71:41 Um They're all part of this class this modification of amino acids that have
71:46 modified. We actually use amino acids like glutamate and Spartak and slicing.
71:51 are neurotransmitters, right, modification of to Gaba, the pureeing A.
71:57 P. And A. T. . Your entire life you've been told
72:00 are molecules of energy yet they're also molecules. The more you learn,
72:09 more you learn that you don't know right. Um Gas is nitric
72:15 carbon monoxide, which apparently kills you it doesn't because it's a signaling molecule
72:20 then hydrogen sulfide. That's the thing makes egg smell icky alright, that's
72:25 signaling molecule. These are called the um there's a name for me it's
72:30 the gas summers and I'm I know butchering it right now because I haven't
72:34 about it. We got peptides that serve as signaling molecules we've gotta
72:37 annoyed that serve as signaling molecules as . So there's all these different
72:43 The ones I want you to the ones I want you to take
72:46 today and say these are things that see Colleen, it's excitatory inhibitory.
72:51 found everywhere. It's found in the muscular junction. It's one of those
72:56 you'll see over and over again. right, it falls into its own
73:00 category. I need you to know two excitatory glutamate and appetite and then
73:05 two that are inhibitory Gaba and you know? So you just have
73:10 kind of memorize those two. And generally speaking you should know the cata
73:15 means as the biogenic amines but we'll with with what they are and who
73:18 are like dopamine is like one of most common types of neurotransmitters out
73:23 So, knowing that that it's a cola mean that it plays roles in
73:27 nervous system as a very important one important Histamine and serotonin, you probably
73:34 of histamine when you get all hopped . But it's actually it's another
73:42 I want to throw this up here we've talked about signaling pathways and I
73:46 you to understand that you know, not a one for one for
73:50 So this is an example of a a divergent pathway alright where we can
73:55 through multiple different types of receptors get sorts of unique responses. So here's
74:00 , it can act through an alpha receptor and alpha two receptor beta
74:04 It has different g proteins coupled with different types of receptors. And you
74:09 all sorts of weird responses. These just trying to show you currents.
74:13 I can affect potassium currents can affect currents. There's all sorts of strange
74:20 that can happen by acting through the receptor depending upon which one I come
74:26 contact with. So this is what think about when it's divergent convergent
74:31 Look I'm gonna get the same response I'm using different types of neurotransmitters and
74:36 have different types of receptors. So cell may have its unique receptor ligand
74:43 but the end result of these is same pathway which just makes things
74:50 Yeah. So are they uh modular ? What do you mean? Do
75:04 modulate other things, pardon? So what that means is that it can
75:18 either way. And so I'd have kind of see what the question looks
75:21 or what the statement was in So when I hear modulation it means
75:26 that kind of feedback and changes the that two cells interact with each
75:32 And so you know like epinephrine and do not behave that way. I
75:38 they act as a neurotransmitter and in cases they act as hormones. They
75:44 some very strange interesting stuff. So I hear a word module modulation that's
75:49 I think of is that they're acting a neuro modulator and that's not the
75:53 here. Yeah. So just that exist and that we're gonna deal with
75:59 later. So they're gonna pop up and over again. So right so
76:03 now it's just there's a class of that are made from amino acids,
76:09 biogenic amines and they're all over the and they're gonna you're gonna see these
76:14 in particular over and over again. not gonna talk a lot about
76:17 But if you go I know someone was saying they were taking doctors at
76:20 class. I can't remember. it's like dopamine like every other word
76:25 of his mouth. Not yet. . It will be yeah. Was
76:30 every other word out of his Yeah, it's everywhere. So there's
76:36 particular activating system in your brain. heard it described as like a sprinkler
76:41 that just spreads dopamine. Oh What do I have like three
76:54 four minutes. Okay. I might able to do this. Alright.
76:58 synaptic inhibition facilitation. That's a fancy for saying I have an actual ax
77:04 uh synapse. Alright. And what saying here is what I'm doing.
77:09 synaptic inhibition. I have a neuron inhibitory that's riff that is blocking the
77:15 along that axon terminal so you can here I've got a cell that's been
77:19 , it's releasing neurotransmitter neurotransmitter. But I have an inhibitory neurotransmitter or an
77:25 neuron that's blocking it. So I'm getting a response in the target
77:29 So pre synaptic, there's our I'm blocking at the pre synaptic axon
77:35 preventing activity from happening? Alright, gonna switch it on you. There's
77:38 a picture up here that is now , this is not activated. So
77:43 is not releasing neurotransmitters, this is releasing neurotransmitters. What would that be
77:48 if this is excitatory? It'll be that, causing release the neurotransmitter stimulating
77:54 cell. So that would be pre facilitation. Alright so the idea here
78:01 I'm not acting through the entire I can target where I want activity
78:05 occur. Right? So if I'm these three right. I could say
78:12 two things are turned on but this over here is turned off because I'm
78:16 the activity between that interaction. That's pre synaptic refers to. A neuro
78:25 simply changes the behavior through two cells I think I might be answering your
78:30 now. Alright, neuromodulation. You imagine the relationship between two cells is
78:36 the number the amount of neurotransmitter I'm released versus the amount of receptors able
78:40 respond to that neurotransmitter. Alright, you think of any sort of
78:45 Right there is interaction. If I to increase that interaction. What what
78:49 are two things that I can do receptors or more neurotransmitters? If I
78:57 to reduce that interaction. What do do? Less neurotransmitter or less
79:05 So what a neuro modulator is is molecule released by a neuron either pre
79:11 or pro synaptic that changes that So I could be a pre synaptic
79:16 that releases a neuro modulator that increases number of receptors in which case now
79:21 increased the activity between those two I get a stronger response just using
79:27 same amount of neurotransmitter. Alright, a neuro modulator changes the relationship between
79:35 cells. Alright. It modulates the between the two through the neurotransmitters.
79:41 . Or the receptors? Alright. what that slide all said. That's
79:46 just lots of words. Just say two things that you guys figured out
79:49 those are pictures to show you. fast transmission, don't worry about
79:58 It's the last little bit I think more slides. Yeah tropic versus meta
80:04 basically says, look, neuro transmitter is going to act through receptor that
80:09 is going to open up a channel it's gonna activate a pathway. If
80:14 a channel, what type of channel we? What type of reaction do
80:16 have I? On a tropical meta . On a tropic? Yeah,
80:20 you go. If it's meta what am I doing? I'm acting
80:23 a pathway? Right so meta tropic are very very quick and short
80:28 On a tropic or even faster and lived. I'm basically creating that sort
80:33 environment. So this is just trying show you that here we have a
80:40 acting through a g protein, Look what it can do, I can
80:43 and open up a channel. I act and open up an enzyme and
80:47 through a pathway I can act and up a channel indirectly. So there's
80:51 lot of different things that I could . All right. But ultimately this
80:58 what we normally see neuro modulators and well that's not just neuromodulation, but
81:04 neurotransmitters can do unique things last little here is just trying to show you
81:09 with this particular channel and then I'm gonna go through this stuff, but
81:15 you want me to I mean, got people out here that want to
81:18 in, you're like what you want want want me want me to tell
81:24 . Oh my goodness, I got lot of slides. Alright, the
81:27 of the last three sides is just with that neuromodulation and just just some
81:33 definitions, it's like two slides worth stuff. Test Tuesday, we don't
81:40 here. I will have office hours Tuesday if you're desperate. I have
81:45 quick
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