| 00:01 | and you? All right guys. what do we have on Tuesday? |
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| 00:14 | . An exam because you aren't as as a freshman. I asked |
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| 00:19 | Hey, what's coming up? They an exam on thursday next week. |
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| 00:21 | up coming up thursday? Like an ? I'm like, all right. |
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| 00:25 | enthusiasm. You're like exam. All . So do you show up here |
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| 00:32 | exam day? You show up here the classroom? No. What do |
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| 00:37 | do? Go take good acosta, your exam whatever time you selected. |
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| 00:42 | where you go. You don't need come here. I'm not going to |
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| 00:44 | here. So don't bother showing If you do, you're gonna be |
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| 00:47 | and lonely. All right. That's one. So, if you haven't |
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| 00:51 | your body, if you don't hear , well, you don't have to |
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| 00:53 | your hand if you've never taken a at CASA, which is quite possible |
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| 00:57 | this group. Even if you've been since freshman, right, they need |
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| 01:01 | have a biometric. So what that is you go over to cost a |
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| 01:04 | time. Do it like today. over there, show them your |
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| 01:10 | I've heard from students that they're not driver's licenses anymore. They want student |
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| 01:16 | . I don't know if that's 100% . Students sometimes lie. They |
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| 01:21 | Okay. So they accept driver's Maybe the person who is working the |
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| 01:24 | for the other person just said, don't trust that. You know that |
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| 01:27 | driver's license doesn't look real Even so says you're 26 DQ'd joke. |
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| 01:38 | That's number one. All right. just go over there and get your |
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| 01:41 | done. I think they still do biometric person I talked to this |
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| 01:45 | So they're only doing that at They're not doing it over here at |
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| 01:47 | C b b C b D whatever classroom CBB and I don't know |
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| 01:51 | Agnes Arnold. I think you just up so I'm useless when it comes |
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| 01:55 | this type of information. All So, that's number one. Number |
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| 01:59 | , We have class Thursday, but the Tuesday following this is September |
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| 02:05 | . So the Tuesday following, I not be here in town. We |
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| 02:09 | not have class. Okay. I'll out an email reminder to say we're |
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| 02:12 | going to be here. You're still for the information. I will post |
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| 02:16 | lecture from a previous semester that you go and listen to and be bored |
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| 02:20 | pretend like you're in class some of you might want to just fall asleep |
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| 02:23 | you're listening to it. All So, but just to let you |
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| 02:28 | , we won't be meeting that All right. So today, we're |
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| 02:31 | to finish up everything you need to about the test, but were afraid |
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| 02:33 | ask. That sounds good. You where that comes from. That's a |
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| 02:39 | from the 60s. Don't worry about . All right. Where we left |
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| 02:45 | ? We were talking about exponential. that X potentials. What do we |
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| 02:48 | ? We were doing the wave. want to do the wave again? |
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| 02:50 | cause it's fun. No, you're looking at me like, I don't |
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| 02:53 | to do it. See, they want to start. All right. |
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| 02:58 | need a bigger stimulus. I Ready. We're gonna do it. |
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| 03:02 | got to do it. We just do wake you up. Okay, |
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| 03:10 | . See that was the way that went through. That was like an |
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| 03:12 | potential. Alright, remember exponential. looking at a specific point in time |
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| 03:17 | that. We're just asking at a a particular point what's happening over |
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| 03:22 | And so basically we're doing is we're the change of membrane potential when you're |
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| 03:27 | with action potentials. You have something called a refractory period of refractory period |
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| 03:31 | is the period of time in which action potential cannot be produced. All |
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| 03:38 | . So, with regard to our cartoon up here, you can see |
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| 03:41 | there are two different parts to the period There's one that's called the absolute |
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| 03:46 | period. That's where you drink vodka . That is a that's a |
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| 03:51 | That's a funny absolut vodka. Thank you. Thanks. See, |
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| 03:55 | least we get one laugh if I get one laugh. Two, |
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| 04:02 | There we go. Then. See that means we're paying attention? |
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| 04:06 | Factor period is a period of time which under no circumstance will you ever |
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| 04:10 | an action potential then we have the refractory period? I'm not gonna throw |
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| 04:14 | in here relative refractory period is the of time where in an action potential |
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| 04:20 | be produced. But under only certain . All right. And if you |
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| 04:25 | at the picture up there, you see the absolute refractory period encompasses a |
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| 04:30 | of time where we're going through a polarization and we're coming back down the |
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| 04:34 | polarization. And so the reason we have a refract or why we have |
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| 04:38 | refractory period, why we can't produce action potential is because during the deep |
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| 04:43 | period, remember what we said? had two different gates. We had |
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| 04:46 | voltage sodium gate. We had a potassium gated channel. The voltage voltage |
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| 04:51 | gate voltage, sodium gate voltage gated channels. In the words all backwards |
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| 04:56 | , voltage gated sodium channel. Remember two gates. First gate was the |
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| 05:02 | gate. The second gate was the gate. And so again, if |
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| 05:06 | am the channel, here's my activation , it's closed. I'm stimulated. |
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| 05:10 | open ions are flowing through and then my inactivation gate is going on during |
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| 05:16 | period of deep polarization we said. I know it's hard to remember because |
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| 05:20 | the last six minutes of class and when you all turn into zombies, |
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| 05:24 | we said that we're opening up all voltage gated sodium channels. Right? |
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| 05:30 | if I've opened up all the voltage sodium channels. Is there any amount |
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| 05:33 | stimulation that can open any more? , that's good. That's not a |
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| 05:39 | question. Right. It sounds like trick question, but it's not if |
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| 05:43 | opened them all, can I open ? The answer is no. |
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| 05:47 | I can't stimulate and create more voltage I've already done everything I can so |
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| 05:54 | can't stimulate any further action potentials because nothing there to stimulate to open. |
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| 06:00 | right. So that's the first So in looking at this on the |
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| 06:03 | up from here to here, I've done everything. I possibly can when |
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| 06:07 | hit that peak. That's when that gate is closed right now. Can |
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| 06:13 | force that an activation gate open based what I taught you on Tuesday? |
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| 06:19 | . So no matter what type of I do, that gate is |
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| 06:22 | It has to go all the way and reset itself to the original |
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| 06:27 | So it doesn't matter how much I . I can't open that channel so |
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| 06:31 | can't get during that re polarization of . I can't get those channels to |
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| 06:36 | . I have to wait till they before I can do anything. So |
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| 06:40 | other half of the absolute refractory period during that period of time when I'm |
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| 06:45 | the inactivated state incapable of opening. be reset. All right. And |
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| 06:51 | there's that boundary where I flip over the relative refractory period. Now I've |
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| 06:56 | a couple of sodium channels they've reset ? Right, and I've got more |
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| 07:01 | are in the process of resetting All right. So, during the |
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| 07:06 | refractory period, I can stimulate in hopes that maybe I'll get those things |
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| 07:10 | . But there's one problem. right here at this boundary right here |
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| 07:15 | they're doing the purple. Remember at point here, is when I open |
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| 07:19 | the potassium channels, remember their slow slow friend, they're still open as |
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| 07:24 | start transitioning over here. And I have to create a strong enough |
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| 07:30 | to overcome the hyper polarization that those are causing. In other words, |
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| 07:38 | I'm going downward, I might be to open up some sodium channels. |
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| 07:42 | there's so many more potassium channels that I'm not going to be able to |
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| 07:46 | any change. But as those potassium begin to close, and now I |
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| 07:52 | these available sodium channels. Now, a possibility for me being able to |
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| 07:57 | them. Now. Usually, what talking about, we're talking about down |
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| 08:00 | now, where is this? This our resting potential. Right? |
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| 08:04 | I'm in a hyper polarized state If takes 15 million volts to open up |
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| 08:09 | voltage gated sodium channels at rest and down here Is 15 million volts going |
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| 08:16 | be enough to get those channels to that hyper or that deep polarization and |
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| 08:21 | like the answer right there. Now, I don't know if this |
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| 08:24 | is down here, let's just say 20. So, I need a |
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| 08:28 | stimulus. Something that causes a 20 volt change to get those that system |
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| 08:34 | . So I reached that threshold. all my sodium channels are opening so |
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| 08:37 | can get that spike again. So refractory period limits when I can do |
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| 08:43 | potentials. Now, I'm going to this because again, Seaworld, Shamu |
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| 08:50 | them. Right, you want to with me today? She's like, |
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| 08:54 | , sure, fine. She's got lot of stuff in her lap so |
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| 08:57 | gotta put that over there. it doesn't break anything here. Let's |
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| 09:00 | do that. All right, We're to make her do the wave. |
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| 09:05 | her ready? I'm gonna clap. gonna do away. So, that's |
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| 09:09 | you gotta do ready? I am again. You see the problem |
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| 09:17 | She's not doing the wave anymore. she doing? She's dancing right? |
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| 09:23 | not missed. She's missing those Right? She's just playing. Please |
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| 09:28 | me catch up, please. I don't want to look like a |
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| 09:31 | in the class. Thank you for along the right, So, what's |
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| 09:35 | here is only at those points where goes all the way up and comes |
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| 09:38 | the way back down. Has she through an action potential when her hands |
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| 09:43 | down here someplace she's ready to be to do it again. Right? |
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| 09:47 | this is not the wave, This is hey ho mm can you |
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| 09:54 | ? I don't dance, Right? kind of what's going on, Is |
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| 09:59 | ? It's saying no, no, , you can't do go up there |
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| 10:02 | just maintain it. You can't go and go back up. That's not |
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| 10:06 | action potential. Now, I told the physical reasons why you can't So |
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| 10:10 | we're expecting is to come all the back down before we get another |
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| 10:14 | Now, what none of these charts showing you is a period of time |
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| 10:18 | which this is taking. So that length across the bottom, there's roughly |
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| 10:22 | 4:00. These are really, really responsiveness, right? So you can |
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| 10:29 | I can produce an action potential very quickly relative to what we call |
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| 10:36 | . Right? I can produce in second. I can produce how many |
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| 10:42 | action potentials. Judges do the right? For milliseconds times 2 50 |
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| 10:47 | one second do that, right? looking at all the people who've taken |
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| 10:52 | in the last year and they're all at me like I should know. |
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| 10:56 | think that's right. All right. , you can produce a lot of |
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| 10:59 | potentials in a second time, But you can't produce an infinite |
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| 11:04 | You're limited to how many action potentials can produce. And so what we're |
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| 11:09 | here is we're coding the frequency of potentials. Alright, now action potentials |
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| 11:17 | gonna be conducted around along the just like the like what we |
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| 11:21 | right? with the wave right? conducts and what it's doing, it's |
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| 11:25 | from uh basically it's covering the entire of the axon. So it's going |
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| 11:32 | section to section two section. There's skipping, it's just it's hitting every |
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| 11:36 | . The example I want to use is like if I were walking across |
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| 11:40 | stage and I'm doing it toe to , there's not a portion of the |
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| 11:44 | that my feet do not cover, ? So this is what normal conduction |
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| 11:50 | like. All right. It only over a small portion. And what |
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| 11:53 | doing is you're asking really? It's like a wave of of things moving |
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| 11:58 | at what you're doing is you're counting this point, what is the difference |
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| 12:01 | charge that's occurring? So I don't you to picture like like the surface |
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| 12:06 | doing something weird like what we just . It's really just looking at |
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| 12:10 | But what we're saying here is that deep polarization is progressing forward because as |
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| 12:16 | . D polarize here, ions flow right? And so there are channels |
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| 12:23 | the front end as you're going down axon that becomes stimulated open which then |
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| 12:29 | more ions to flow in which causes deep polarization. And it's kind of |
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| 12:34 | you watching the person next to you okay now it's my turn to de |
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| 12:38 | and then it finished the action and on the backside that's where the refractory |
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| 12:45 | is Right. Because what did we at in this picture over here? |
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| 12:51 | this is just a point on the that we're measuring the difference in our |
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| 12:57 | in the membrane potential. So you imagine the action potential is traveling from |
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| 13:05 | to point to point to point to to point all the way down the |
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| 13:08 | of the accident. Does that kind makes sense? All right. That |
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| 13:12 | sense. Over here. They all . So that means you have to |
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| 13:16 | . Right Because if you don't, you're going on there going on, |
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| 13:19 | got a smart side in the dump and that's not gonna work, we'll |
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| 13:22 | to make sure of. So this a localized event that is expanded from |
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| 13:31 | to point to point. So it's series of local events all in a |
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| 13:35 | along the lane. Now that action once it's triggered, it's just going |
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| 13:40 | keep going until there's no channels to up. All right. So when |
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| 13:45 | started at the axon hillock, it all the way the terminal and it |
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| 13:49 | at the terminal because there are no voltage gated sodium channels for it to |
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| 13:54 | . Otherwise it keeps trying to go . I don't know where it go |
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| 13:57 | that point. Now it does. in two ways. So the one |
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| 14:01 | just looked at is what is called or contiguous. And I kind of |
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| 14:05 | looking this up because I've always seen all our textbooks contiguous. And then |
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| 14:10 | read someplace continuous. I'm like, they got that wrong. And I |
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| 14:14 | looking it was like no, so or continuous, meaning all in a |
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| 14:21 | , just as we saw it spreads the entire length. The entire structure |
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| 14:26 | . Now this will occur when the doesn't have any myelin wrapped around |
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| 14:30 | All right. So basically you just nothing but acts on uh plasma |
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| 14:37 | axle Emma. And so you're basically polarizing the whole thing. The other |
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| 14:42 | is salvatori. Salvatori means to And so what we're doing now is |
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| 14:46 | jumping over the length of the So what the my island does, |
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| 14:51 | serves as an insulator and prevents the Emma from actually coming into contact with |
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| 14:58 | surrounding extra cellular fluid. And so can't have action potentials wherever you have |
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| 15:03 | island. You can only have action where there is no violence. All |
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| 15:06 | , these are called nodes of rand . And so what happens is an |
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| 15:10 | potentials produce here. And it causes deep polarization and the ions this next |
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| 15:17 | is close enough that the ions can and cause deep polarization there created the |
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| 15:21 | action potential and so on down the . Now, if you want to |
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| 15:25 | this picture me walking across the Right? I'm literally missing portions of |
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| 15:32 | stage as I walk, right? not actually jumping and I'm not going |
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| 15:37 | do that because I'm sure I look . Right? So here that's kind |
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| 15:44 | like toe to toe covering the whole here, skipping portions now, why |
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| 15:48 | I want to do salvatori? Why I want that over the other? |
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| 15:53 | reason is that sell territory conduction allows the actual potential to conduct faster. |
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| 15:59 | right now, there's a whole lot stuff in here with regard to the |
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| 16:03 | of an action potential. To things you need to be concerned with. |
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| 16:07 | thicker the or the greater the diameter the axon. The faster and action |
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| 16:15 | able to travel. You can think it in terms of resistance and there's |
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| 16:19 | whole bunch of physics and math that involved in this. But basically fatter |
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| 16:23 | allow for less resistance. So you greater conduction that easy to remember. |
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| 16:29 | wires, lots of resistance. Poor , That's easy. Right? |
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| 16:36 | you can imagine I have signals that need to get from my big toe |
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| 16:39 | to my brain and back down again , very quickly. All right. |
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| 16:43 | I don't need to be fast. , you can imagine if all I |
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| 16:46 | to work with were diameters, I have some fat neurons or fat fat |
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| 16:52 | on my neurons and I'd have thin , neurons that had very small |
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| 16:56 | But if I have a fat acts like that, would my body have |
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| 17:00 | be bigger? Yeah, I'd have accommodate that. And I don't have |
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| 17:04 | one neuron, I've got thousands upon . Right? And so you can |
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| 17:08 | my body would have to be bigger my body was bigger. Which is |
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| 17:12 | of sad because it's already pretty Right then I would have to have |
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| 17:17 | and bigger neurons. Which would mean bigger body. Which means bigger |
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| 17:20 | Bigger body, bigger neurons. You it's a never ending cycle. |
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| 17:24 | So to fix that problem, we up with that we didn't come up |
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| 17:29 | but the thing that developed was my . All right. So my ALAN |
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| 17:35 | you to keep a small diameter but be able to conduct quicker. It |
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| 17:41 | allows for conductance Relative to a accent the same diameter. About a 50 |
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| 17:47 | increase in conductance speeds. All So that means you can have small |
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| 17:54 | that are insulated so you don't have get a bigger body. Yes |
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| 17:58 | Turn Which my depends on the signal is being transmitted. All right. |
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| 18:05 | we haven't talked about neurons particularly. fact we won't today. Uh That's |
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| 18:11 | the next unit is like okay, sort of axons or what sort of |
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| 18:15 | do we have? And what do do? But you can think about |
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| 18:18 | in these terms just drill generic ones signals that the brain needs to know |
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| 18:22 | away. You need to be An important signals Not so fast. |
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| 18:27 | ? So if you stepped on a , it's probably a good thing to |
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| 18:30 | your foot up so you want a signals. But if you're standing on |
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| 18:34 | , it's going to be slow It's probably not needs to be quite |
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| 18:38 | fast. I couldn't hear you, , sort of, not really. |
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| 18:50 | going to be applied to say but not okay. And I'll get |
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| 18:53 | that just a moment. All Because I'm gonna I'm gonna distinguish between |
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| 18:57 | we're gonna be talking about synapses And that's really what your question |
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| 19:00 | What about the electrical and chemical and is this important? Yeah. All |
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| 19:09 | . It actually does not. So what's interesting and there's there's a lot |
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| 19:14 | work that's been done on on, my island in terms of how it |
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| 19:17 | and stuff. But basically what it is it produces a mile and sheet |
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| 19:22 | just wide enough so that each note rand beers close enough, that one |
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| 19:27 | stimulate the one next to it, ? So you might be able to |
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| 19:30 | an extra micron and totally screw everything . So, so those cells, |
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| 19:36 | in this particular case, these are cells, they are are situating themselves |
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| 19:41 | such a way. So that that is is exactly what you need to |
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| 19:47 | and you slow down the process too , You kill it. So it's |
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| 19:51 | specific. So that's all this thing talks about, it consumes less energy |
|
| 19:57 | well. So you're not sitting there to pump everything and I want to |
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| 20:00 | real uh not real clear, but kind of clarify something here. In |
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| 20:05 | of my descriptions. I use a of hyperbole, right? I |
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| 20:09 | ions are rushing out, right, you hear me say that term? |
|
| 20:12 | that gives you an impression like thousands thousands of molecules are moving. And |
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| 20:16 | truth is an action potential, you have one or two molecules moving across |
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| 20:19 | membrane. It's it's not a lot , but I'm not gonna ask you |
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| 20:23 | , how many molecules are moving across membrane. The idea here is that |
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| 20:26 | doesn't take a lot of ions to these action potentials. But you can |
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| 20:31 | if you're producing X potentials all the , you know, eventually you're going |
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| 20:35 | start getting an imbalance. And so need to have your sodium potassium pump |
|
| 20:39 | , no, no, go back where you started, Right? So |
|
| 20:42 | energy involved in all of these And so if you have no my |
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| 20:47 | that's occurring across the entire length. there's more ions moving. But when |
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| 20:51 | put my Ellen, there's fewer spots you're actually moving the ion so there's |
|
| 20:56 | need to do more pumping, let's to pump house that, I'll do |
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| 21:01 | . So it's an energy saving process you haven't learned this symbology yet anything |
|
| 21:07 | energy saving equals good right now, just in the body. If the |
|
| 21:13 | can find a more efficient way to something, it will and use |
|
| 21:16 | So, just as a general All . So, let me be 100% |
|
| 21:21 | here because some people do get That's the note of Ranveer. That's |
|
| 21:26 | all the activity is happening. This not the note of Ranveer. This |
|
| 21:30 | a mile and she this is what's and nothing is happening here. You're |
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| 21:35 | over the mile and sheet to the Ranveer. Notre Ranveer to note of |
|
| 21:40 | . Okay. Some people get those sometimes and I don't want you to |
|
| 21:45 | those people. All right. Moving the electrical synapses. We're gonna be |
|
| 21:50 | at synapses next. That's what we're of spending the rest of this lecture |
|
| 21:54 | is the synapse. How do cells to each other? We've already talked |
|
| 21:57 | lot about those, but we're looking specifically at the synapse. Alright, |
|
| 22:01 | a type of perricone response. All . We have two different types of |
|
| 22:05 | . We have electrical synapses. This where I'll mention them once and we |
|
| 22:08 | never talk about him ever again. because All right. We spend all |
|
| 22:12 | time talking about the other one. chemical synapse electrical synapses exist in one |
|
| 22:16 | two forms. What is called a or what it's called is uh a |
|
| 22:22 | . So down here below this is reciprocal synapse. So, you can |
|
| 22:26 | what they're showing you here is ions in this direction, ions flowing in |
|
| 22:30 | direction. So, there's reciprocation from to cell. They're giving equal amounts |
|
| 22:36 | ions. All right. So, would be an example of a reciprocal |
|
| 22:41 | . Current moves in both directions, efficacy or equal efficiency. All |
|
| 22:45 | up there at the top. That's rectifying synapse. So, you can |
|
| 22:49 | the flow is in one direction. right. And then there are channels |
|
| 22:53 | they're not showing that allows those ions escape out of the cells. You |
|
| 22:56 | have a pump on the other cell pumps it back in and it creates |
|
| 22:59 | gradient that is always flowing in one . All right. So, basically |
|
| 23:04 | action potential is moving in one direction what is trying to do now, |
|
| 23:08 | these are supposed to be the same , but ignore that that era is |
|
| 23:12 | ? I just think that shows a example of of these two things. |
|
| 23:16 | , rectifying it in one direction. is in both directions. All |
|
| 23:21 | So, these exists cells uses as means of talking to each other. |
|
| 23:26 | see this in the cardiac system. see them in smooth muscles. That's |
|
| 23:30 | all we're going to say about We're more interested in the chemical |
|
| 23:35 | All right. And the reason we're in the chemical synapses because this is |
|
| 23:38 | neurons talk to other selves, including . This is how neurons tell muscle |
|
| 23:45 | to work as well. All And so the chemical synapse is basically |
|
| 23:50 | happens with the action potential once it down to the axon tournament. |
|
| 23:54 | that's what we're looking at here. there's the axon terminal. You can |
|
| 23:58 | the little lightning bolt, shiny things there. That's supposed to be the |
|
| 24:02 | potential. Six explosions, I don't . Mm. All right. And |
|
| 24:08 | happens is is that we're sending that potential from the axon hillock down to |
|
| 24:13 | axon terminal to tell the axon terminal release chemicals to stimulate the next |
|
| 24:19 | That's the whole purpose of an action . Alright, remember neurons can be |
|
| 24:24 | long. I mentioned the one of big toe up to my spinal |
|
| 24:27 | that's a long cell. That's like long, Right? And so, |
|
| 24:31 | I'm trying to do is I'm trying stimulate from the spinal cord to tell |
|
| 24:36 | big toe to do something. And , to make that signal fast, |
|
| 24:40 | use the electrical thing to go the . And then when I get to |
|
| 24:43 | distance to the destination, I can the chemical and get a quick |
|
| 24:48 | Right? I don't have to send chemicals in the blood stream and let |
|
| 24:51 | wander around my body for 30 minutes it finally finds my big toe to |
|
| 24:54 | , Oh, by the way, might want to move that. |
|
| 25:03 | here. Okay, so you're you're . But I want to make sure |
|
| 25:08 | we understand the language. Electrical signaling cell to cell in that last slide |
|
| 25:14 | cell to cell, right with regard the action potential. It's signaling from |
|
| 25:19 | side of the cell to the Right? So it's like I start |
|
| 25:23 | signal over here, it travels the and finishes over here. It doesn't |
|
| 25:29 | from cell to cell. And so one of the key things that we |
|
| 25:32 | to understand that with regard to electrical . We're talking about cell signaling to |
|
| 25:36 | cells. So it's not an electrical when we're dealing with the synapse, |
|
| 25:41 | electrical portion is to make the signal the cell traveled a long distance. |
|
| 25:47 | makes sense. Okay. And it's often, you know, if you |
|
| 25:51 | a young teacher who's teaching mp for first time, they start talking about |
|
| 25:55 | and electrical signalling and they're getting it because yes, there's an electrical component |
|
| 26:00 | it, but it's not the cell the electrical signals. It's doing a |
|
| 26:04 | signal. Okay, so you can down here this right here is what |
|
| 26:10 | called the synaptic clip. This relationship these two cells is what is the |
|
| 26:16 | . So what's happening is that action stuff happens causes release of neuro transmitter |
|
| 26:23 | chemical to stimulate the next cell. right, bye. Binding those receptors |
|
| 26:28 | the synapse. Okay, so I'm kind of jumping around here, just |
|
| 26:34 | that you can kind of see the picture. Big picture kind of |
|
| 26:37 | So the synapses simply the release of chemical signal from a sending sell to |
|
| 26:42 | receiving cell and then we give names those things to sell. That is |
|
| 26:46 | is called this pre synaptic cell, , that's complicated. And the one |
|
| 26:51 | receiving is called the post synaptic C We are biologists already. This |
|
| 26:57 | easy mode. All right now we're moving in the same direction. It's |
|
| 27:04 | directional. All right, so the potential which causes that neurotransmitter, that |
|
| 27:11 | is moving from the pre synaptic cell to the post synaptic cell one |
|
| 27:16 | You're not going the other direction. . Mhm. So the action potential |
|
| 27:23 | serves as a signal to get this flowing. When the chemical gets to |
|
| 27:30 | other side. It produces a graded . That's why we define those |
|
| 27:37 | So, action potential up there. happens causes neurotransmitter to be released, |
|
| 27:43 | binds its receptor causes uh the opening a channel which causes deep polarization in |
|
| 27:49 | cell. I'm getting a grated potential here. Okay. Different than an |
|
| 27:56 | potential as we defined. So where we get the neurotransmitter? Well, |
|
| 28:04 | found in synaptic vessels where the synaptic come from. It comes from the |
|
| 28:08 | body. They're transported via the secular knows a specific type anterograde, remember |
|
| 28:16 | grade moves it downward. And what do is we start the vesicles down |
|
| 28:20 | in the axon terminal. And so basically always producing neurotransmitter producing these vesicles |
|
| 28:28 | those vesicles down to the end over and they're sitting there waiting for that |
|
| 28:33 | potential to cause them to open and their materials. Mhm. Okay. |
|
| 28:44 | question is is the movement of the independent of the action potential? |
|
| 28:48 | Remember we talked about regulatory excretion or . Right so I'm constantly making neuro |
|
| 28:55 | , constantly packing packaging it up constantly it down to the axon terminal when |
|
| 29:02 | gets released is dependent upon the action . Okay excellent. Now. Oh |
|
| 29:09 | goodness. Big words in all complicated . All right. What I want |
|
| 29:14 | to take from this picture right All right. Is using those |
|
| 29:19 | Remember we talked about the the stairs the T snares? Right? That |
|
| 29:22 | snare. And that T snare allows vesicles to a line up right there |
|
| 29:27 | the synaptic end, right at the synaptic membrane. And look it's ready |
|
| 29:33 | go. So from here look at , it is already ready to already |
|
| 29:39 | to go. But it ain't leaving out. It's not allowing it to |
|
| 29:43 | . Why? Well because there's a that prevents it from happening. The |
|
| 29:49 | . Snaring the T. Snare basically up the situation so that vehicle is |
|
| 29:53 | to go. But we need a to cause that vesicles to merge with |
|
| 30:00 | plasma membrane. All right. That in is saying no. So we |
|
| 30:07 | to get rid of complex in. , what do we do we bring |
|
| 30:10 | calcium? How do I bring in ? Mm Well, I have this |
|
| 30:15 | potential that is being sent down the of the axon. Opening up these |
|
| 30:20 | gated sodium channels. It arrives at axon terminal. No more voltage gated |
|
| 30:27 | channels. Instead we have voltage gated channels. All right. So the |
|
| 30:34 | potential disappears, Right? Because the channels and the potassium channels are what |
|
| 30:39 | for the the conduction of the action . But it's a signal. And |
|
| 30:45 | that signal is there to open up channels, calcium channels open up calcium |
|
| 30:51 | into the axon terminal. What does do? The magic gets rid of |
|
| 30:57 | complex and molecule kicks out and says away. And now we get merging |
|
| 31:02 | the membrane. You're a transmitter gets . He is showing you here is |
|
| 31:07 | calcium coming in over here. The gets released. And then the uh |
|
| 31:13 | snares basically disassociate and are recycled. so then you bring the next testicle |
|
| 31:19 | place and it's ready to go. , it's a calcium signal that becomes |
|
| 31:26 | . And the calcium comes in because action potential is the message in the |
|
| 31:33 | to cause that channel to open. just that those channels are specifically located |
|
| 31:38 | the terminal end. That makes Now, I want to show you |
|
| 31:42 | picture showing you how this all Well, not how it works, |
|
| 31:47 | what you can imagine it looks like right here is your neuromuscular junction to |
|
| 31:53 | my muscle contract like. So I not produced one action potential. I |
|
| 32:01 | thousands upon thousands of action potentials. right. A muscle contraction is only |
|
| 32:08 | . When I stopped sending action the muscles relaxes. It's not that |
|
| 32:14 | . But I want you to just of picture that's kind of what it's |
|
| 32:17 | stimulate muscle contracts, remove the muscle relaxes. Okay, so what |
|
| 32:22 | means is that when I'm stimulating I'm exponentials in the thousands and look at |
|
| 32:29 | all those vesicles are lined up all up at the pre snapped again. |
|
| 32:36 | what's on the post synaptic side. would be called a your mustard |
|
| 32:41 | This is the motor in plate has special name but it's still the synaptic |
|
| 32:45 | . It's still the synaptic junctions. still the post synaptic cell. And |
|
| 32:50 | at all those green things. What the green things? They're the |
|
| 32:55 | the little blue things. That's the in the neuromuscular junction. That's |
|
| 32:59 | Acetylcholine is ready to go so that can get a contraction right? And |
|
| 33:06 | always making aceto calling because you never when you're going to call on that |
|
| 33:10 | to contract. That makes sense? , ma'am dinner special. Yeah. |
|
| 33:20 | it is. So the question is are the neurotransmitter specialist or is it |
|
| 33:24 | like a random bunch of molecules That's more or less. The answer |
|
| 33:29 | their specialist, their unique to the that's released. Human. That's where |
|
| 33:32 | going to go. We're going to by the end of the class that |
|
| 33:35 | are hundreds of different neurotransmitters. You've to memorize every single one of them |
|
| 33:38 | all the conditions under which they're being . No, thank you. You're |
|
| 33:43 | because you know, I'm lying right , but I'm gonna show you which |
|
| 33:47 | are important. Right? And so idea here is that each neuron produces |
|
| 33:52 | own neurotransmitters and those Oh, neurotransmitters to their own specific receptors and create |
|
| 33:58 | expectation or inhibition at the synapse, on which neurotransmitter you're looking at. |
|
| 34:04 | . So it's not just a It's actually very well organized. And |
|
| 34:08 | say that from a perspective of someone ago, that's kind of complicated. |
|
| 34:13 | right. Now, when you walk a room, do whatever business you |
|
| 34:21 | is you leave the room, what you supposed to do? Turn off |
|
| 34:25 | lights good. Your father taught you . Right, You turn off the |
|
| 34:31 | everything you turn on, you must off my Children still have not learned |
|
| 34:36 | and it drives me nuts. They on my computer play Minecraft. I |
|
| 34:40 | in there. Minecraft is still open they leave the computer. It's like |
|
| 34:44 | do know creeper is going to blow up? They don't care. All |
|
| 34:49 | , whatever. So that principle is principle that you can carry in a |
|
| 34:55 | . Anything that you turn on is to be turned off. There's already |
|
| 34:58 | system in place for every step that activated to be inactivated. All |
|
| 35:03 | And so when you send neuro transmitter the sin apps, we've got to |
|
| 35:08 | that you're a transmitter because we don't it hanging around causing problems. A |
|
| 35:12 | transmitter is a very quick rapid um to create change in the next |
|
| 35:18 | So we want to clear that synapse as quick as possible so that when |
|
| 35:21 | next signal comes along, we know going to happen. All right. |
|
| 35:25 | we can we're telling the cell what do. And so termination you almost |
|
| 35:28 | me fall right, termination can have of different for different ways. All |
|
| 35:33 | . First enzymatic destruction. All Now, all of these can be |
|
| 35:39 | or none of them can be It's just kind of a mishmash. |
|
| 35:41 | actually found this picture which is actually cool. You don't need to memorize |
|
| 35:45 | of it. It just demonstrates all different ones. And it actually shows |
|
| 35:48 | specific neurotransmitters or for specific neurons which they prefer to use. All |
|
| 35:54 | So the first one systematic destruction and like what the city Colin Colin gets |
|
| 35:59 | into the into the synaptic cleft and out there in the synaptic cleft already |
|
| 36:03 | enzyme called acetylcholinesterase that's there to destroy city Colin. So it's like the |
|
| 36:09 | game of red rover that you could ever imagine. You guys know what |
|
| 36:13 | rubber is. You're looking at me no red rover for those of you |
|
| 36:18 | didn't grow up playing red rover, have two sides, you have side |
|
| 36:22 | you have side B one side screams rover. Red rover. Let and |
|
| 36:25 | you name somebody, come over. let us see the Colleen come |
|
| 36:28 | Acetylcholine comes running across. It has break through the line and if they |
|
| 36:33 | then they get to grab someone and it to the other side or something |
|
| 36:35 | that. I can't remember the fun was you get to run into |
|
| 36:38 | All right? So, I want to imagine in that game taking |
|
| 36:44 | really angry pit bulls and putting them the middle so that when you run |
|
| 36:47 | the angry pit bull attacks you so can't get across, that's what the |
|
| 36:52 | is designed to do. It basically chewing up the neurotransmitter before it has |
|
| 36:57 | chance to get to the other So it actually reduces the availability so |
|
| 37:00 | the signal is shorter lived. So you're basically chopping everything up as |
|
| 37:05 | as it's leaving the cell. That's enzymatic destruction. Number two, the |
|
| 37:10 | , none of these things show But you can imagine um just kind |
|
| 37:13 | going into the synaptic collecting going, know, I don't have to go |
|
| 37:16 | in particular. I'm not driven or don't have to go that way. |
|
| 37:20 | can wander over here and I can out of synaptic cleft and not do |
|
| 37:24 | and then an enzyme comes along and me up and gets rid of |
|
| 37:27 | Right? So the fusion from the is another thing that can happen. |
|
| 37:30 | can be taken in by a neuron so here the uptake is in the |
|
| 37:35 | direction. So any of these, can look at it like here I'm |
|
| 37:37 | released. You can see the hair a little receptors like I'm being taken |
|
| 37:41 | and what can happen is I can be destroyed or recycled. When I |
|
| 37:44 | recycle it means put into another vesicles I can be released again destroyed means |
|
| 37:48 | up, sent back up to the to the cell body recycled or repackage |
|
| 37:54 | rebuilt and then sent right back down . All right. And you'll |
|
| 37:58 | look at how many of these systems that. This one does. This |
|
| 38:02 | does this one does this one this this one they all do. |
|
| 38:07 | The only one that doesn't is the that's a Colin ergic. In other |
|
| 38:13 | , the one that has the enzymatic . Guess which one we discovered |
|
| 38:18 | If you had to guess which the one that's not like all the |
|
| 38:24 | Colleen that was like the first neuron figured out and we just figured everyone |
|
| 38:28 | going to be just like that one not a single one has. |
|
| 38:33 | Mhm mm. It's the worst. but that's what we get for. |
|
| 38:38 | at muscles first and then the other which is a little weirder, is |
|
| 38:42 | we see here in the glutamate, glutamine energy. The energy is at |
|
| 38:48 | end. Right. And basically what have is you have astrocytes and other |
|
| 38:52 | that are always kind of surrounding these . And in this particular case the |
|
| 38:56 | sites can take up the neurotransmitter, it down and then send the parts |
|
| 39:01 | onto the neuron. All right so basically serves as a way to cleanse |
|
| 39:06 | clear out um the cells so four ways but you don't have to know |
|
| 39:12 | one does which that's not so All right. But the whole point |
|
| 39:17 | is why am I clearing it out I can get another signal right |
|
| 39:22 | Yes ma'am. Yeah I have no . S. S. R. |
|
| 39:36 | . Oh see you're asking now drug and I don't know those. I |
|
| 39:42 | no. See this is this is . You you want to see the |
|
| 39:44 | of my knowledge just started asking me about like drugs pathogens I can tell |
|
| 39:50 | about parasites that's about it. Yeah prejudice. Yeah. Right so |
|
| 40:00 | is good. So would the signal to grow or would it still be |
|
| 40:04 | . Yes. Right. And so idea here is your clearing it so |
|
| 40:08 | you can keep this consistent thing. if you're if you're allowing the neurotransmitters |
|
| 40:12 | around for a very long period of then you're either gonna inappropriately stimulate the |
|
| 40:18 | for a longer period of time. you can create stronger responses in the |
|
| 40:22 | . All right. So you can in a pathogenic environment if I'm not |
|
| 40:27 | up or destroying neurotransmitter, I'm inappropriately the next cell too long or too |
|
| 40:34 | . But in a non pathogenic what I can do is I can |
|
| 40:38 | or modulate how that neuron is responding the signal that I'm that I'm |
|
| 40:44 | So it serves as a mechanism of . If I can modulate or moderate |
|
| 40:49 | much I'm leaving behind and we'll talk that towards the end of the lecture |
|
| 40:54 | . That's a good observation. I don't. 11. Yeah. |
|
| 41:06 | . Why do you how do you it happens? Yeah. And I'm |
|
| 41:11 | doing this. Put you on the . But it's something that you guys |
|
| 41:14 | already learned. All right, you're , damn it. I should have |
|
| 41:23 | Close, but you're you're you're Right, So what you're doing is |
|
| 41:29 | that you are responding in a negative . In other words, what would |
|
| 41:33 | is oh there's so much neurotransmitter always stimulated. So the response in the |
|
| 41:38 | cell is let me remove receptors so can get back to a normal |
|
| 41:45 | Right. So the idea here is my normal response is is uh let's |
|
| 41:50 | say 10 receptors, €10 transmitters. I'm keeping your transmitter around. So |
|
| 41:55 | of getting a 10-10 responsible. Getting a 20 receptor responsible, then I |
|
| 41:59 | have what I'm doing. So I get back to my normal responsiveness. |
|
| 42:04 | right. So, it's what is down regulation you're down regulation you're down |
|
| 42:09 | the presence of the receptor to get normal response. You would. All |
|
| 42:14 | . So, you're less um sensitive guess tubes to the you're trying to |
|
| 42:23 | back to a state of normal sensitivity becoming less sensitive is really because you're |
|
| 42:28 | currently you're more sensitive to the What's that? Uh The answer is |
|
| 42:37 | , but and I'm not going to into the but but I mean over |
|
| 42:40 | periods of time you you basically habituate a normalized response. That's what you |
|
| 42:47 | a normalized response. Normally your body return back to that. But does |
|
| 42:52 | always no in question. Okay, saw the hand and yeah. So |
|
| 42:59 | dangerous if you like scratch your head something because I'm looking for those types |
|
| 43:02 | queues to grab my attention. Did have a question to now thought of |
|
| 43:08 | else? All right. All So, we're okay with termination. |
|
| 43:12 | right. So, we're moving now the next cell. What is the |
|
| 43:17 | synaptic cell Alright. And remember, producing a greater potential in that |
|
| 43:21 | And there's one of two types of we can get we can get excitation |
|
| 43:25 | we can get inhibition I guess we no response but excitation or inhibition. |
|
| 43:33 | . And so you can imagine if neurotransmitter is being released. What's happening |
|
| 43:38 | you guys remember these things right we saw them. These are the |
|
| 43:41 | potentials. It's how much are we ? If a lot of neurotransmitters released |
|
| 43:46 | say a little bit you get a greater potential of a little bit |
|
| 43:49 | you know? So on and so . So the potential that you're producing |
|
| 43:53 | the post synaptic cell is causing a polarization. Now, what type of |
|
| 43:59 | ? How do we know it's Well, what we're doing is we're |
|
| 44:02 | non specific cat ion channels. All . And so in this particular |
|
| 44:06 | what you're doing is you're getting a of sodium moving in very little potassium |
|
| 44:10 | out. And so you're getting that polarization. So excitatory neurotransmitters cause deep |
|
| 44:17 | in the post synaptic cell. And call those great potentials. Are you |
|
| 44:22 | for this excitatory? Post synaptic Now, the first time you receive |
|
| 44:29 | you're like a big word. Lots lots of stuff. So excited story |
|
| 44:33 | you? It's a deep polarization. is it happening? Post synaptic |
|
| 44:37 | And it's a potential. It's a potential. That's where the name comes |
|
| 44:40 | . So that's an E. S. P. So because it's |
|
| 44:43 | greater potential that means it can vary magnitude in accordance with the magnitude of |
|
| 44:49 | stimulus, stronger stimulations, stronger graded . Longer stimulations. Longer potentials. |
|
| 44:58 | ? There's no refractory period. Where we see refractory periods? Action |
|
| 45:04 | We don't see them with greater Right. And the unique thing about |
|
| 45:10 | potentials is that you can sum them . All right. So with an |
|
| 45:15 | potential, it's an all or none . Right? With a refractory |
|
| 45:18 | That means you get one. It goes to the same height that travels |
|
| 45:22 | exact same way all the way across membrane. And you can't get another |
|
| 45:27 | because of the refractory period. it's a one and done thing. |
|
| 45:30 | ? Yes. Right. So the the cell remember the inside the cell |
|
| 45:38 | negative. And what you're doing is you de polarize, you're becoming less |
|
| 45:43 | . All right. So how less ? Well, depends on how much |
|
| 45:47 | . Right? We can use some . Numbers five million volts 10 million |
|
| 45:52 | . 15 million volts. You something like that. Not very |
|
| 45:56 | All right. So, I can an excitatory potential and I can take |
|
| 46:02 | one and add them on top each and get a bigger one. That's |
|
| 46:06 | we mean when we some because there's refractory period. That means you can |
|
| 46:10 | them on top of each other and going to talk about this and just |
|
| 46:12 | go ahead. So remember. So vultures keeps this is a really good |
|
| 46:22 | because we're kind of running through all stuff. We really kind of ignored |
|
| 46:25 | the voltage gated sodium channels are You have the strongest concentration of voltage |
|
| 46:31 | sodium channels at the axon hillock. everywhere. But you have a high |
|
| 46:37 | there. All right. And then next highest concentrations along the length of |
|
| 46:41 | axon. Which would make sense because where the extra chances are occurring. |
|
| 46:44 | right, so, and we're gonna a chicken and egg thing here, |
|
| 46:48 | is very frustrating when you're trying to this stuff. If I'm producing grated |
|
| 46:53 | that are causing deep polarization, remember like a ripple in a pond. |
|
| 46:57 | so I'm doing this say at a , that ripple is going to move |
|
| 47:02 | the axon hillock. And so if can get enough of those channels to |
|
| 47:07 | up at the axon hillock, that's I produce the action potential. Now |
|
| 47:11 | do have these on the cell body not with a great number of |
|
| 47:15 | Right? So you can get kind a semi boost as you're going |
|
| 47:19 | But not a real boost. Everyone with the PS PS. Oh I |
|
| 47:26 | alphabet soup time. E. S. P excitatory post synaptic |
|
| 47:32 | So if I have an excitatory I must have an inhibitory one and |
|
| 47:36 | exactly the same thing. The difference is that I'm not opening cat ion |
|
| 47:41 | instead, I'm either opening up a channel. No, that's non specific |
|
| 47:47 | what I'm doing is I'm opening up channel. Chlorine channels get a little |
|
| 47:50 | confusing because their equilibrium potential is at 70 million volts. And if your |
|
| 47:56 | already at minus 70 million volts, I open up a chlorine channel does |
|
| 47:59 | move? No, there's no But if the membrane potential is ST |
|
| 48:07 | is chlorine going to move. so chlorine can be an inhibitory ion |
|
| 48:14 | after you've moved away from resting membrane in neurons. Other cells have different |
|
| 48:20 | memory potentials. potassium channels. On other hand, what we're trying to |
|
| 48:24 | if we open up a potassium potassium is desperate to escape from the |
|
| 48:28 | , isn't it? So, if rushes out, what's going to happen |
|
| 48:32 | the membrane potential, deep polarization is towards zero, becoming less negative potassium |
|
| 48:39 | out is more negative. Right? getting a hyper polarization. So, |
|
| 48:45 | name again here is inhibitory post synaptic . Just like the excitatory post post |
|
| 48:51 | potential. It varies in magnitude. no refractory period. I can sum |
|
| 48:55 | . All right, It's just a of movement in terms of resting membrane |
|
| 48:59 | . More negative. Further away from . Deep polarization. Excitatory post potential |
|
| 49:06 | less negative. Moving towards threshold to that action potential. Now, I |
|
| 49:12 | they could be summed this is going fall short. How many guys still |
|
| 49:18 | facebook accounts, anyone? Okay, a couple of you. All |
|
| 49:22 | Let's pretend we're gonna put a poll facebook. We're going to ask all |
|
| 49:26 | of our friends are very close right? Whether or not you should |
|
| 49:31 | up with your significant of it because always know better than you. |
|
| 49:36 | So you put out there to all 4000 friends, should I break |
|
| 49:40 | And this includes your significant other who now probably voting in favour of |
|
| 49:44 | Right? Should I break up with significant other and all 4000 of your |
|
| 49:48 | respond? Some of them say of you should. Others say no, |
|
| 49:54 | . They're the best thing that's ever to you because you're still on |
|
| 49:58 | Right? And so in the end look at the end of the pole |
|
| 50:01 | whichever is the majority. That's what gonna do makes sense so far. |
|
| 50:08 | grand post synaptic potential is like the . So in our little picture |
|
| 50:14 | what we have is we have a and it has a whole bunch of |
|
| 50:18 | tiny feet touching it. Those are terminals. The light blue is the |
|
| 50:22 | terminals. The purple is the post cell to all those light blue pre |
|
| 50:28 | cells, some of those cells are epa are are sending excitatory signals. |
|
| 50:33 | of those cells are sending inhibitory That means underneath each of those that |
|
| 50:37 | sending and receiving on the receiving You're producing E P. S. |
|
| 50:40 | . S. And I P. . P. S. If |
|
| 50:42 | P. S. P. S you less negative and I PS PS |
|
| 50:45 | you more negative. All you gotta is some up which is which And |
|
| 50:49 | in the grand scheme of things you're figure out do I move closer or |
|
| 50:52 | I move further away in response to of these signals? So the sum |
|
| 50:59 | all those E. P. P. S. And I PS |
|
| 51:01 | is called the G. P. . P. The grand got to |
|
| 51:04 | it with that big the grand post potential. All right. So in |
|
| 51:10 | words these neurons are not being stimulated one cell or two cells but thousands |
|
| 51:18 | cells. And so when a neuron producing an action potential it's in response |
|
| 51:23 | all the different cells that are talking it. Okay that are sending these |
|
| 51:29 | inhibitory signals. All right now we this through the process of summation. |
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| 51:36 | I said there's that word summation and have two different types temporal and spatial |
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| 51:43 | when you hear the word temper. do you think of time and |
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| 51:48 | So, time and space. I'm to help you out man. I |
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| 51:55 | am. Mhm. You need me I could come in here with like |
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| 51:59 | nerf gun sometimes just start shooting at . I know it's hard it's hard |
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| 52:05 | be in these seats, especially after year of being in a seat at |
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| 52:08 | where you could turn off your camera walk away. I know I taught |
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| 52:13 | that. Just press the button. the recording go walk away. What |
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| 52:20 | mean? Teachers do that to Uh . All right. So here's the |
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| 52:28 | types of summations. Alright, I'm gonna I'll show you what this |
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| 52:32 | I'll show you when it's spatial here what happens with no summation. |
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| 52:36 | this is our ground framework. So here we are producing some sort |
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| 52:41 | E. P. S. Alright, so all of these look |
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| 52:44 | they're gonna be E P S. . S. All right. |
|
| 52:46 | you can see I'm seeing a deep , but I don't That's what it's |
|
| 52:51 | and big, but over distance, it kind of dies down. |
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| 52:54 | here's it's showing you threshold at the hillock and look that uh E P |
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| 52:59 | . P is not strong enough to us to threshold. So we don't |
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| 53:02 | an action potential. So, you see an action potential down here in |
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| 53:06 | acts on All right. So, just looking at three different points what's |
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| 53:10 | at the dendrite. What's happening at axon hillock. Do we get the |
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| 53:13 | to know and what does it look when we do? Okay, here |
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| 53:17 | spatial summation. Alright, so spatial is when you have two or more |
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| 53:25 | firing at the same time. now notice there's a time component to |
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| 53:32 | at the same time? All So to demonstrate this and this will |
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| 53:37 | you up since you're going to be guinea pig. Now I'm going to |
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| 53:40 | once, listen to how loud it . Now we're gonna clap together. |
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| 53:44 | how much louder you see? The clap, the louder it gets. |
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| 53:49 | right. And that's kind of what summation is doing. Its allowing for |
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| 53:52 | additive effect at that particular thing. that's what you see here, we've |
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| 53:57 | two of these neurons firing at the time, produces a larger mps P |
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| 54:04 | at the axon hillock that PSP is large enough to reach threshold. So |
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| 54:08 | do I get it? I Boom, boom to action potentials. |
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| 54:11 | action potentials are carried forward through the Now, why do I get two |
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| 54:17 | potentials? Because I'm above threshold for period of time where the refractory period |
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| 54:22 | up, goes down and then it up and down again. And then |
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| 54:25 | the time that second refractory period is , I'm below threshold again. |
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| 54:30 | so the number of action potentials depends how long I'm above threshold. |
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| 54:35 | so here I get a larger Look if I throw in a third |
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| 54:39 | , I'm over the threshold for a period of time. So I get |
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| 54:43 | action potentials. So what does this you? It tells you I hope |
|
| 54:48 | you're seeing. Is that the stronger stimulation, the more action potentials I |
|
| 54:54 | . So the strength of a stimulus encoded in the number of action potential |
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| 55:01 | . Did you see that strength of potentials are not in the height of |
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| 55:08 | action potential, It's in the number action potentials that produce. Right, |
|
| 55:13 | gonna talk about muscles when we get and I'm gonna lift up things in |
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| 55:17 | room because that's what I like I'd like to show you how strong |
|
| 55:20 | am. Yes. Right. And going to lift up a pin versus |
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| 55:25 | chair, say muscle. But I'm to do different things because I'm recruiting |
|
| 55:32 | producing more action potentials to produce greater , temporal summation. On the other |
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| 55:39 | , is one neuron not to one where the firing of that neuron occurs |
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| 55:46 | greater frequency. So the action potential so the so the stimulation occurs with |
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| 55:52 | frequency. Now I'm gonna clap. only myself because there's only one of |
|
| 55:56 | , right? So that's not very , that's not very loud. That's |
|
| 56:01 | very loud. But when I start them closer and closer together, if |
|
| 56:04 | could go faster and be one very loud sound, right, there's no |
|
| 56:10 | in between. And so if there no rest in between, you can |
|
| 56:13 | to go back to your example, I'm releasing neuro transmitter with greater |
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| 56:18 | So there's more neuro transmitter inside the , there's more neuro transmitter inside the |
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| 56:24 | . I'm going to slowly move my up until finally I'm maintaining above threshold |
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| 56:31 | I can get a series of action that are then carried down the |
|
| 56:37 | So you see what we're doing here in the pre synaptic cell we're |
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| 56:42 | And we have actual potential that result post synaptic cell responsive graded potentials that |
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| 56:48 | they're strong enough will result at least this case because we're dealing with a |
|
| 56:52 | , another action potential that then results the release of uh neurotransmitter in the |
|
| 56:57 | cell so and so on. So just communicating from cell to cell to |
|
| 57:00 | . What to happen. That kind makes sense. Mhm. Now if |
|
| 57:06 | have a negative signal right? If have an inhibitory signal, what am |
|
| 57:10 | doing? Well I'm just canceling it . So we just give it a |
|
| 57:14 | name called cancellation instead of some asian I take an excitatory post synaptic potential |
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| 57:20 | five million volts. And at the time specially some eight right special summation |
|
| 57:26 | an I. P. S. . Of negative five plus five plus |
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| 57:29 | five equals zero. So my grand potential is zero. No change Plus |
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| 57:41 | -10 -5 million volts. I'm going get a hyper polarization. So and |
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| 57:46 | on. That's what cancellation is just fancy word for just saying the simultaneous |
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| 57:51 | of E. P. S. P. S. P. |
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| 57:52 | So that I do not reach threshold I don't get an action potential. |
|
| 57:57 | of the cells downstream are going to . Now there are lots of different |
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| 58:01 | of synapses. The ones that were common when we just looked at our |
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| 58:05 | example accident heretic. So here's your . You can imagine that would be |
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| 58:10 | riddick. There's what are called access or spiciness. So as we've got |
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| 58:16 | looking at neurons, we start noticing they have these little raised areas and |
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| 58:20 | kind of like synapses. They're like is a place where that synapse is |
|
| 58:24 | to occur. And so you have axon and that little spine so that |
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| 58:29 | have this direct connection as opposed to generic dendritic one. We also have |
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| 58:35 | synapses. We have access somatic So they're found all over the place |
|
| 58:39 | those are the normal ones and then some really weird ones. So you |
|
| 58:43 | have an accent on an ax on there. That would be Axl Jack |
|
| 58:47 | , right? You can have a on a dendrite which would be |
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| 58:50 | Dendritic or you can have a dendrite a on a cell body which would |
|
| 58:54 | dangerous. Somatic. So these do . They're just not really common and |
|
| 58:58 | don't ever talk about them. They're that cousin that you don't ever want |
|
| 59:03 | mention. All right, dendrites can attenuate a signal, right? We |
|
| 59:10 | about accidents being wider diameter or smaller . Well, if I want to |
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| 59:16 | or change a response, all I do is change diameter and a dendrite |
|
| 59:22 | dendrites faster signal. So it's There's no resistance. So, great |
|
| 59:27 | move easier. If I make a tiny thin dendrite then it's harder. |
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| 59:31 | more resistance. So I get a response. So neurons can modulate or |
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| 59:38 | signaling simply in terms of their And the problem is that it affects |
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| 59:46 | happening at the axon hillock and that's this is showing us. Like look |
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| 59:50 | little itsy bitsy tiny dendrite thick same size signal differing response here. |
|
| 59:55 | get an axe potential here. I . Now your neurons are going to |
|
| 60:02 | found in what are called neuronal What's in the Ronald pool, Junior |
|
| 60:08 | ? We're all hanging out together. guess we call those gangs. |
|
| 60:15 | you're not in a gang. Just trying to wake you up, |
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| 60:21 | , throw things at you but you'd sue the school and I'd get in |
|
| 60:27 | . All right. Now, a is simply a group of cells that |
|
| 60:31 | together. So when you're in a group that's kind of like a neuronal |
|
| 60:37 | kind of Not at all. All . So, typically I can be |
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| 60:44 | focus, which means that neuron, though it's in a pool is specifically |
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| 60:49 | on a specific group of cells within pool. All right. And so |
|
| 60:53 | sending signals in a specific direction. types of bulls. Well, I'm |
|
| 60:58 | really so particular to who I'm talking . And so that would be a |
|
| 61:03 | . And so you can imagine for example, I have a neuron |
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| 61:07 | is sending information up to the optic of the brain saying you're honest, |
|
| 61:11 | that same neuron has branches that go to the oral regions of the |
|
| 61:15 | Different ones go to this memory. the idea is that I'm just sending |
|
| 61:19 | in all sorts of different areas. ? So not quite so local. |
|
| 61:23 | really more widespread. So there's different . Now, each neuron is restricted |
|
| 61:30 | they only have a specific number of sources. They have a specific number |
|
| 61:33 | output sources. So, a single to a neuron isn't going to go |
|
| 61:37 | . All right. It's going to going to specific locations, but they're |
|
| 61:41 | , very narrowly focused or it can broadly focused is what I'm trying to |
|
| 61:44 | out of here. All right. other thing is that the more neurons |
|
| 61:50 | having a pathway, the more synapses have more synapses, you have more |
|
| 61:53 | delay, there is going to So that means it's going to take |
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| 61:57 | to process information. So in very complex pools. Things are going to |
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| 62:03 | longer to process versus very simple Where things are basically very few. |
|
| 62:09 | this is a joke. So just with me. It's like when you |
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| 62:12 | out into the street and someone's honking you or maybe you're honking at somebody |
|
| 62:17 | they stop and they stare at you their brain is kind of like, |
|
| 62:19 | don't know what to do. Have ever had that happen? Right? |
|
| 62:23 | like I'm stuck. Well just think it as you're having a difficult time |
|
| 62:30 | because you have to go through every in the brain before you recognize that |
|
| 62:34 | you shouldn't be standing in the middle the street and you should probably take |
|
| 62:37 | steps forward maybe, especially in front my car because I got places to |
|
| 62:46 | . You're going to learn over the of the semester. I'm a completely |
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| 62:51 | person in my car. You think a good question? I don't know |
|
| 63:01 | answer to that. I mean I I really don't. I mean I |
|
| 63:05 | that there is variation within those but there's probably a lot of similarities |
|
| 63:11 | that there's not a lot of So in other words you might be |
|
| 63:16 | is a dopamine pathway. So dopamine stimulate other cells are dopamine, but |
|
| 63:20 | there might be a divergence out of . So that you're now stimulating in |
|
| 63:24 | with a different type of neurotransmitter, that I don't know the answer |
|
| 63:29 | That's a good question. It's a question. Oh speaking of neurotransmitters, |
|
| 63:33 | talk about neurotransmitters. All right, is the fun, scary slide, |
|
| 63:39 | ? It says look uh transmitted by is simply the chemical that's being released |
|
| 63:44 | in these perricone fashions uh by a so that it can act on those |
|
| 63:50 | synaptic cells. Now, neuro transmitter act in an autocrat fashion in an |
|
| 63:55 | way. In other words, you're to have an axon terminal that comes |
|
| 63:58 | and bends back onto that cell and that sell directly. So that would |
|
| 64:02 | autocratic. But we're really just going kind of focus on perricone pathway. |
|
| 64:07 | going to act always at the you're always going to elicit a rapid |
|
| 64:11 | , release the neurotransmitter because an immediate , quick response. Lots and lots |
|
| 64:17 | neurotransmitters. These are the basic And as I said, the very |
|
| 64:22 | one ever discovered was a set of . And they were like, |
|
| 64:25 | we discovered how neurons talk to each and they started looking for more neurotransmitters |
|
| 64:30 | none of them fall into the same as a seat of Colleen, none |
|
| 64:33 | them look like a seed of None of them behave like casino |
|
| 64:37 | Very frustrating when you think you've discovered like that. All right. |
|
| 64:42 | we got the mono means some of names should be familiar to the catacombs |
|
| 64:45 | you may not know, but you do know dopamine. You probably do |
|
| 64:48 | epinephrine serotonin. You've probably heard of . You've probably heard of hit the |
|
| 64:53 | is what you think you have the histamine, those that all stopped |
|
| 64:57 | Right. You know that one. fact the history. Histamine is a |
|
| 65:05 | that some cells in the immune system Also not just here in the north |
|
| 65:11 | an inflammatory, it promotes inflammation amino . You changed Glutamate and expert |
|
| 65:22 | You should know. Gabba is a of glutamate. Listen, you should |
|
| 65:25 | as well the puritans, I mean when back in freshman biology you learned |
|
| 65:31 | 80 p. And it's like energy the cell. And you're like, |
|
| 65:34 | , I got this. And now like no, it does other |
|
| 65:38 | And it's like it's like learning that pilgrims about the pilgrims in flight first |
|
| 65:43 | and then realizing they weren't the first in the U. S. You're |
|
| 65:47 | , really? Why can't you teach about Jamestown? When I was in |
|
| 65:51 | grade and said, I mean we wear that stupid hat and the white |
|
| 65:56 | . The dickie, you don't know today they make you do that. |
|
| 66:05 | . Did they let you learn about in first grade? Some of your |
|
| 66:09 | on I don't know. Jamestown is right. Never mind. Nitric cost |
|
| 66:17 | . These are the gases gases we them? Um ah gas it |
|
| 66:25 | So they're not neurotransmitters that we've technically gas emitters, but nitric oxide, |
|
| 66:30 | monoxide, hydrogen sulfide. These are molecules. You know what hydrogen sulfide |
|
| 66:37 | like. Yes, you do rotten and it is a chemical that your |
|
| 66:43 | uses to signal. Not everywhere. just a very specific type of |
|
| 66:48 | There are peptides. Usually these are be Costa created some of the |
|
| 66:53 | These are the cost annoyed that we about. They can be as |
|
| 66:57 | And this is just the short Right. But we want to focus |
|
| 67:01 | on even a shorter list. Um we want to do is we |
|
| 67:04 | all right, Colleen, santa Colin right here. That's what it looks |
|
| 67:08 | . Uh you ever wonder why you're organic chemistry? So you can look |
|
| 67:11 | pictures like this and go, I saw that in organic chemistry |
|
| 67:14 | That's a ring structure. All And basically it's everywhere. It's its |
|
| 67:20 | special category because nothing else looks like . It can be excitatory or inhibitory |
|
| 67:26 | on what system you're looking at when dealing with the muscle system musculature. |
|
| 67:31 | right. So the neuromuscular junction. , always, always, always under |
|
| 67:35 | circumstance. No exceptional rule. Okay, when we look at the |
|
| 67:42 | and parasympathetic systems, we'll see a of Colleen goes both ways. Amino |
|
| 67:49 | . We already know the protein building the two that are excitatory glutamate and |
|
| 67:53 | irritate. That should be easy to in with eight and then the inhibitory |
|
| 67:57 | gathered glassy. All right. It's one of those things. You just |
|
| 68:01 | and you go with it for the of your life. Then we have |
|
| 68:04 | biogenic amines. All right. These amino acids. What we've done chop |
|
| 68:08 | the car box select group. So is histamine serotonin epinephrine, norepinephrine |
|
| 68:13 | These all fall into that last Alright. The biogenic amines. |
|
| 68:18 | these are the ones we need to . All right. one way that's |
|
| 68:27 | what we've learned in terms of submission cancellation. One way we can regulate |
|
| 68:32 | is through pre synaptic inhibition or Now again, the words mean something |
|
| 68:38 | pre synaptic means occurring in the pre cell. And what are we |
|
| 68:42 | I'm either inhibiting or facilitating that cell doing the opposite of what it's supposed |
|
| 68:49 | be doing is really all right. , I'm gonna try to paint a |
|
| 68:53 | . What we're looking at. This is inhibition but it could be |
|
| 68:56 | You can see here, I've got neurons producing an action potential. The |
|
| 69:00 | travels down different uh branches of this on and stimulates three different cells. |
|
| 69:07 | the top one showing you that it's being stimulated. Right? But you |
|
| 69:10 | imagine that's what's going on. So can stimulate three different cells. One |
|
| 69:14 | easy mode with pre synaptic inhibition. have a different neuron having an axe |
|
| 69:21 | all Exxon IQ synapse, right happens be here at the axon terminal. |
|
| 69:27 | is an inhibitory neurons. It's releasing neurotransmitter. And so what it's doing |
|
| 69:33 | it's inhibiting that particular acts on terminal prevent it from actually producing Euro |
|
| 69:42 | So, the pre synaptic cell is inhibited at that particular location so that |
|
| 69:48 | inhibiting the response up here in the when we turn it into facilitation for |
|
| 69:56 | so that you can see this. excitatory neurons, no actual potential. |
|
| 70:01 | of these cells are being stimulated. . I have a pre synaptic cell |
|
| 70:06 | here that is not inhibitory but is excitatory. It's releasing its excitatory |
|
| 70:13 | That means this particular branch is being . So it's producing Euro transmitter. |
|
| 70:20 | what's happening in the target self a ? The other two cells they're not |
|
| 70:26 | stimulated, Right? Because this is stimulating at that particular location. |
|
| 70:33 | this is one way that we can responses. It's not like it's an |
|
| 70:38 | or none thing. If I can a neuron, I can regulate anywhere |
|
| 70:43 | its length, china. Cool. right, So this is not cancellation |
|
| 70:52 | this is not summation. That's one the key things to take away from |
|
| 70:58 | neuro modulators on the other hand, kind of like neuro transmitters, but |
|
| 71:04 | they stick around a little bit And what they do is they modulate |
|
| 71:08 | response. So this sort of goes to what the question was earlier is |
|
| 71:13 | ? Well, if I have lots neurotransmitter in in the space? Am |
|
| 71:18 | going to get a bigger response? answer is yes. All right. |
|
| 71:21 | how do I do this? I modulate the responsiveness of either the post |
|
| 71:27 | cell or the pre synaptic cell. right, so this is what I |
|
| 71:31 | you to picture. All right. can facilitate or inhibit facilitate. Makes |
|
| 71:35 | up. So how can I If I want to make a bigger |
|
| 71:39 | I produce, I can either release neuro transmitter. Right? So that's |
|
| 71:44 | for a longer period of time so can get a bigger response or I |
|
| 71:47 | release the normal amount of neuro transmitter I stimulate the post synaptic cell to |
|
| 71:53 | more receptors in place. So basically of there being one receptor for one |
|
| 71:59 | there's two receptors. So I got choice of where I can go and |
|
| 72:02 | a bigger response. I've facilitated the . That kind of makes sense |
|
| 72:07 | I can do the same thing. can I can inhibit at the pre |
|
| 72:10 | cell or modulate the pre synaptic I can modulate the post synaptic cell |
|
| 72:14 | a negative way. And if the synaptic cell is releasing neuro transmitter how |
|
| 72:19 | I inhibit at the pre synaptic What would be the way I could |
|
| 72:21 | that? It's up there on the always I've what do you think? |
|
| 72:27 | can reduce the amount of neurotransmitter being ? Less neurotransmitter. Less of |
|
| 72:32 | What's the other way on a reduced of receptors? Less fewer receptors. |
|
| 72:38 | chance of response occurring? Right. gonna probably refer back over and over |
|
| 72:45 | back to kindergarten games. Do you ever play um musical chairs? The |
|
| 72:51 | behind musical chairs is fewer chairs and . Right? So how do I |
|
| 72:57 | it so that everybody wins? Put chairs? All right. How do |
|
| 73:01 | make it so that everybody loses take chairs. Right. Or the opposite |
|
| 73:07 | if I have a static number of , I reduce the number of |
|
| 73:11 | Right? So you see I can can muck with either one of those |
|
| 73:15 | facilitate or inhibit the responsiveness. I The worst type of musical chairs was |
|
| 73:20 | they had like four people in one . Right? I mean it was |
|
| 73:25 | enough with two people, one chair they're all nudging each other. But |
|
| 73:28 | they're like, okay, we're taking two chairs, you have four people |
|
| 73:31 | and they're just like really one chair . I'm gonna have to beat up |
|
| 73:35 | other people to get that candy bar whatever it is with or Yeah, |
|
| 73:40 | typically neuromodulation is going to be these . So we're actually doing this through |
|
| 73:44 | protein coupled receptors were basically changing this through g protein coupled receptors. |
|
| 73:50 | in terms of responsiveness, right? get fast transmission versus slow transmission. |
|
| 73:57 | we're looking at this in terms of versus modulation, which is long periods |
|
| 74:02 | time. Right, so this up is neuro transmitters, right? You |
|
| 74:05 | see neurotransmitter neurotransmitter and then everything else of falls in between. Finally get |
|
| 74:10 | to neuromodulation? Here's how we see things. I wanna tropic when you |
|
| 74:17 | the word diana tropic means ions are . And so what we're doing is |
|
| 74:21 | opening up a channel. So here's neurotransmitter opens up a channel. I |
|
| 74:24 | deep polarization. Is that faster? ions flowing? It's fast. It's |
|
| 74:32 | . It's very fast. Right? of action potentials are action potentials |
|
| 74:36 | Yes. Right. So to get X potential I'm gonna have a fast |
|
| 74:41 | . So the greater potential whenever I'm with electricity and ion flowing current |
|
| 74:46 | meta tropical on the other hand deals signal transaction a bunch of proteins. |
|
| 74:53 | is that gonna be fast or slow to the first one? It's gonna |
|
| 74:57 | slower. Right. I've got to this on and I got to turn |
|
| 74:59 | on and I got to turn this and then turn this one and I'm |
|
| 75:01 | get some sort of effect. So slower, relatively speaking. But this |
|
| 75:06 | a very short response. This is longer lived response. All right. |
|
| 75:10 | so this is an example of g coupled receptors um acting. So here |
|
| 75:15 | our diana tropic. Right, so I am neurotransmitter open up a |
|
| 75:19 | I'm comes through. Men in the still can open up channels. It's |
|
| 75:23 | a delayed response. So here we g protein coupled receptor turning on G |
|
| 75:27 | turning on. Admiral cyclist turns on campy turns on protein can you say |
|
| 75:32 | turns on a whole bunch of stuff ultimately results in phosphor relation. Opening |
|
| 75:35 | that channel islands flow through you mean went through all those steps to open |
|
| 75:40 | a channel. Yes but you did other stuff along the way. |
|
| 75:45 | so meta tropic responses can result in opening of a channel. Look |
|
| 75:49 | gamma beta subunit opens up a channel . So they have to go through |
|
| 75:53 | those steps to get there. But you're doing is you're activating an opening |
|
| 75:57 | . Getting an idea tropic response or about uh bit of a tropic |
|
| 76:02 | Thank you very much. You So there are different ways that you |
|
| 76:06 | do this. Glutamate channels are an of this. So we have some |
|
| 76:12 | are meta tropic gprs, they're actually in glue. So you'll see |
|
| 76:16 | They'll say meta tropic glutamate receptors, are always producing E. P. |
|
| 76:22 | . P. S. All these there's a whole bunch of ionic |
|
| 76:25 | A tropic pathways we have the So here you can see AMp A |
|
| 76:30 | basically a cat ion channel. Glutamate along bind that opens up sodium comes |
|
| 76:35 | potassium kind of tries to leave but sodium comes in normal. Alright. |
|
| 76:40 | what's interesting is that we also have receptors NMDA receptors aren't open even under |
|
| 76:48 | stimulation. Right? You need glutamate they still don't open. You need |
|
| 76:52 | of the receptors available for them to . And so what happens is you |
|
| 76:56 | up the amp a receptor uh that comes in causes deep polarization which causes |
|
| 77:03 | to get kicked out. So now have an open channel and now you |
|
| 77:06 | Iran's moving through. So you get much more much different response. It's |
|
| 77:11 | slower response than you start because you to go through those two steps. |
|
| 77:15 | you have a different type ionic. now you have a modulated response. |
|
| 77:19 | cells have kind of receptors, but , it's sort of the same sort |
|
| 77:23 | idea here is that we just have channel that opens up and allows for |
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| 77:27 | polarization of the cell cells can also plastic when you see the word plastic |
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| 77:34 | changes and I know I'm running out time. Everything that's going to be |
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| 77:38 | the math last three sides on the . So either I stop or you |
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| 77:42 | and you can leave, I don't . Right, no one's coming in |
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| 77:46 | this class. So I've got you you need to leave to go to |
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| 77:49 | class really, Honestly, you had hand up question. No, |
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| 77:53 | Okay. Just stretching because I'm keeping too long. Right? So with |
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| 77:58 | to plasticity, plasticity means capable of or in response to different stimuli. |
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| 78:04 | so in this particular case right here is trying to show you look if |
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| 78:08 | give a low frequency stimulus, then gonna open up some calcium channels. |
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| 78:11 | get some neuro transmitter? I'll get small response out of that particular |
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| 78:18 | But if I stimulate the cell uh a much much stronger signal, I |
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| 78:25 | a different response with lots of action , different neurotransmitters, more calcium going |
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| 78:30 | the cells so on and so So cells can change their responsiveness depending |
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| 78:36 | the type of stimulation that they're Mhm. So there are different |
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| 78:42 | We can they have different names depending how they change. So we have |
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| 78:48 | and potentially a shin. This is you some facilitation you can see here |
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| 78:52 | helping to produce more action potentials. ation would be after the fact you |
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| 78:58 | the action potentials. Depression and Can give you the example of situations |
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| 79:04 | funny. The first experiments that we're in a situation where uh banana slugs |
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| 79:10 | sea slugs, not bananas. You , sea slug is picture of that |
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| 79:15 | ugly thing that you find early in morning, crawling in Houston across your |
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| 79:19 | , right? Take that expanded out big, make it that big. |
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| 79:24 | it has very fat neurons because there's milo nation. And so what they |
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| 79:28 | do Is it go up because it those little in 10 eyes and you |
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| 79:33 | a probe because you never hit him a stick. You hit him with |
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| 79:36 | probe and they'd whack that lie. do you think that slug would do |
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| 79:39 | that? I and they stick it and then what do you do? |
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| 79:45 | it again. Slowly stick it Whack it again and eventually the slug |
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| 79:52 | realizing okay this is my life now so now it doesn't ever stick. |
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| 79:57 | a little idea. It's habituated and holding that I stock in. All |
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| 80:02 | . That's an example of habituation. so neuron responds like okay this is |
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| 80:07 | is always happening now. So I'm longer going to respond the way that |
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| 80:11 | note that I normally do. All . So that's what we're referring to |
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| 80:15 | little bit earlier. Last slide. term depression potentially. Ation. All |
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| 80:21 | . This is how we learn in information is through potentiality shin. |
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| 80:27 | Long term memory. So this is trying to show you what is |
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| 80:30 | Long term potential nation is basically when get we have that relationship between the |
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| 80:37 | synaptic and post synaptic cell. Remember said a certain amount of neurotransmitters being |
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| 80:41 | . A certain amount of receptors there long term means we're changing that relationship |
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| 80:47 | term. All right. So in words I might change how much neurotransmitters |
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| 80:52 | released from the pre synaptic cell and maintain that for just make up months |
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| 81:00 | . Right. Change number of receptors number of receptors so I can have |
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| 81:07 | long term potential Haitian depression would just the opposite. I'm taking out neurotransmitter |
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| 81:13 | ? Last neurotransmitter over long time, periods of time or I'm reducing the |
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| 81:18 | of receptors on the post synaptic cell long periods of time. So now |
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| 81:23 | relationship between these neurons is different than it began. And this is how |
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| 81:30 | interactions in our brains change. How able to store up memory, how |
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| 81:34 | able to create new actions and interactions the individual cells. Is they change |
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| 81:40 | they talk to each other? It's always going to be the same. |
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| 81:44 | a little bit of neuro transmitter. increasing and decreasing. Makes sense. |
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| 81:49 | I kept you over three minutes. apologize, examines on Tuesday go kick |
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| 81:54 | butt. Remember always big party. said yeah it's a cake. I |
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| 82:00 | money set aside already and it's gonna good because I don't drink swill |
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| 82:07 | Yeah. Mhm mm. |
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