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BIOL 2301 Human Anatomy & Physiology I - 2301_lecture09_0617
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00:01 So we'll see whether or not a to make that horrible, horrible
00:06 It's actually kind of cool what they're . They're redoing the entire room putting
00:13 on either side. So, the in the back I think see whatever's
00:17 here. I'm not really certain. But they looked at me like we're
00:21 sorry. Um All right, so is kind of an interesting day in
00:27 of what we're going to be I say, interesting in the sense
00:31 um we're dealing with some concepts that that are kind of difficult to
00:37 but I think are really as not hard as we make it out to
00:42 . All right. And so what gonna be looking at today, we're
00:44 be looking at how we turn those potentials into actual functional uh forms of
00:52 that the cell can use to create mechanisms. Okay. And so we're
00:57 be looking at what are called graded and action potentials. And if you've
01:00 a biologic one class, you've probably these before and you're probably like,
01:03 this sucks. And I don't want learn this stuff, blah blah
01:06 That's normal. All right. I'm try to make it a little bit
01:09 and hopefully it'll help you remember, you understand what's going on. But
01:13 to doing that, what I wanna is I want to first talk about
01:15 neuron as an example cell that uses types of electrical signaling. Alright.
01:22 , first off I want, what want to understand is that neurons are
01:26 be a multiple different sizes. We have little itsy bitsy tiny neurons that
01:30 incredibly microscopic and very, very Or we can have neurons that literally
01:34 from your nervous system out through your , down to your furthest extremity.
01:40 . So they can be incredibly long they can be incredibly small. And
01:44 as a result they need to be to communicate from one side of the
01:48 to the other in order to be to transmit signals between two different or
01:54 say three cells. So, if have cell number one, Cell number
01:56 , Cell number three, to get signal from cell number one to cell
01:59 two. And then the cell number and cell number three you say being
02:02 in your pinky, it has to a very long distance and it would
02:07 a really, really long time to throw a chemical out in the blood
02:10 have that chemical take its sweet time your body. It takes about five
02:14 for a chemical to move completely through body and hopefully find that one cell
02:18 you want to talk to. what we're going to see here is
02:20 a neuron is designed to send electrical through themselves very, very quickly.
02:28 right. And so this is why able to get a response, say
02:32 a muscle or even in a gland that signal begins in the nervous
02:39 Alright, So the neuron we've kind seen them a little bit right?
02:45 said nervous system, two types of , neurons and glial cells. Here's
02:49 neuron is the functional structure of the system. That is the cell that
02:53 all the heavy lifting. It's the of the system. Alright. So
02:57 an excitable cell and that means it and transmits electrical signals along its
03:02 Its job is detect some sort of that it receives and then its job
03:07 in the process that signal and then really transducer and then process it so
03:13 some sort of response can be And so when I say they're conducting
03:18 signals, they're not doing electrical They're using these membrane potentials and the
03:24 signals that they can create to send their own length. And then what's
03:28 to happen is is so, for , down here here we got cell
03:32 one here, Cell number two at end of the cell. That's when
03:36 electrical signal arrives. And it causes release of a chemical signal that then
03:41 received by that next cell transducer and in another electrical signal along the length
03:47 the cell. Alright, so notice electrical signaling is occurring between cell to
03:52 . It's occurring within the cell All right now these cells Basically,
03:59 they're created, they live your entire . Now that 100% true.
04:07 there are cells that do And then are cells that can be created new
04:10 then their cells that do die away stuff right? But they're incredibly long
04:15 there. Amy topic meaning once you them they don't keep multiplying and
04:19 So they don't go through the replicated that you see. For example in
04:24 cells, they're highly, highly They typically are the primary source through
04:30 our oxygen and glucose get consumed. really when I say glucose, if
04:35 really dive deep into the into the you'll find that it's not actually glucose
04:39 we keep it simple and we're just say glucose. So when you think
04:43 the food in the air, I the brain which has millions upon billions
04:48 these cells if not more. It's the primary consumer of these two primary
04:56 nutrients that your body seeks. The one being the muscle being another big
05:02 . Alright. Of the oxygen. gonna be one of those days.
05:08 , let's see. There we Alright, so we're gonna see this
05:14 . Also when we look at muscles when they first started looking at these
05:19 , these cells, no one really that all cells had all the same
05:23 . And so they started naming the as they discovered them and then later
05:27 like, oh well everything has the parts. But we didn't change the
05:30 because you know when you're special you to think you're special or keep yourself
05:34 . So, we've got a couple names here. The side of plasma
05:36 called the pair of carry on. , so that's going to be up
05:40 inside the Soma. That's the cell . All right. The ribosomes in
05:47 are called missile bodies named after the who figured out the stain that caused
05:51 to pop up. Alright. There no central. So that's kind of
05:55 unique. But why would you need if you're not going through mitosis?
05:59 right. You'll see along the outside there's a whole bunch of different
06:06 Alright. Some of the processes are to as dendrites, some of the
06:10 are referred to as axons. If have an axon, you only have
06:14 . You can have many many different . All right. When you find
06:19 cell bodies and clusters which you will the central nervous system, they have
06:23 special name form. We call them . Not to be confused with plural
06:28 nucleus. Alright. It's just a of those cells or really the cell
06:35 . When you're on the peripheral nervous and I know you don't know the
06:38 between central and peripheral nervous system That's gonna be the next unit.
06:42 , So, when you're in the nervous system, I should just define
06:46 . Central nervous system is your brain your spinal cord peripheral nervous system is
06:50 else. Alright in the peripheral nervous , clusters of these cell bodies are
06:54 to as ganglia. Right? You'll a little bit later and I'll point
07:00 to you is that there's a structure the basil nuclear in the central nervous
07:04 , but the old name for it basil ganglia. So it's like someone
07:10 said, no, no, we've to separate these two things out.
07:13 , So anyway, whenever you see lot of these together, the cluster
07:17 one of those two names, Kyla saying a gaggle of geese,
07:23 A murder of crows, you it's called a murder. Mhm.
07:28 right, So let's talk about these . These axons and dendrites.
07:34 So they're going to extend from the body. If you're in the central
07:38 system. Whenever you see bundles of , these processes moving together, you
07:45 to them as tracks. So you along a track. If you see
07:49 of these processes in the peripheral nervous , you call them nerves. Here's
07:54 fun little question. You can see it's on my test or someplace
07:58 Can you find nerves in the central system? The answer is no.
08:02 are no nerves in the central nervous . All right. You're like,
08:06 a second. Aren't nerves and nervous go together. Yes, they
08:09 But nerves are found in the periphery the peripheral nervous system, Alright.
08:14 called Tracks in the central nervous It's one of those b. S
08:18 questions, I'm gonna put a trick to see if you're paying attention is
08:23 your nomenclature. Alright, so what these different types of processes?
08:27 we have dendrites. So these are of dendrites right here. These
08:32 Alright. Dendrites are typically the receptive on a neuron. Alright, so
08:40 you'll see is you'll typically find receptors some sort that are found someplace on
08:46 dendrites and their job is to receive from the surrounding environment, whether it
08:52 another cell or something in the extra fluid. So, in essence,
08:58 can think of it when they show errors. I'm taking messages and I'm
09:03 them to to or towards the cell . Alright. Now, still bodies
09:08 also receive messages but we're talking about here. All right, so,
09:12 they're gonna use in terms of when get stimulated, they're going to produce
09:17 change in the membrane potential called a potential. All right, we'll get
09:22 that in just a minute, graded . Not action potentials. The axon
09:29 the sending process. Not all cells an axon very, very often you
09:35 see in the central nervous system cells just have nothing but dendrites.
09:40 We're not gonna worry about that. going to use this as our
09:43 So we have the receiving process is have the sending process. The sending
09:49 is always called the axon. The begins at a structure called the axon
09:56 . It distinguishes itself by the presence the type of receptors that are found
10:00 or in that area. Alright. then from the axon hillock you travel
10:06 and you're going to go to the where you're going to see a series
10:09 Teledyne Andrea sometimes we just refer to as acts on terminals. All
10:15 So that's what you see down are those Teledyne bria at the very
10:20 of each of those Teledyne area. where you see the synaptic knob.
10:25 right. So it's basically the bulb kind of is tied in and it
10:28 of bulges out. We'll deal with moment. So, that's what you'd
10:33 . That would be the synaptic knob there. Now, what this picture
10:37 show is that these acts songs can divide. So, you can imagine
10:41 , instead of focusing on that one come this way, you can imagine
10:44 a branch that comes off and that's referred to as a collateral.
10:48 I could have a single neuron send a single axon that splits and then
10:53 of those splits then talks to a cell. Alright, so this is
10:57 way for me to expand the cells which I'm speaking to. Right?
11:03 a collateral simply is just a Now we're always gonna keep it
11:09 We're always gonna have a picture that pretty much like this where it's gonna
11:11 a bunch of dendrites and then a axon and you're talking to one cell
11:15 to make our lives easy. All . So the action is the conducting
11:22 , as we said, structurally, doesn't have the same material that you
11:26 in the soma. There's not gonna any missile bodies. There's gonna not
11:29 be any Golgi apparatus is it's basically any proteins that you're gonna find in
11:34 axon is going to be produced up the soma. Now again, we
11:40 things differently here. So we called fluid or the materials inside the axon
11:46 the axa plasm. I'll probably call cytoplasm because it's just easy. But
11:51 what they refer to it. And plasma membrane is instead of calling the
11:55 lemma. That's another term for the membrane. They call it the axle
12:00 . So they are special because you , reasons. Now if you go
12:09 a neuron, what you're gonna see you're going to see a series of
12:13 of skeletal elements and those elements allow materials to move back and forth.
12:17 you guys did eventually go watch that video right on on blackboard, the
12:22 video where it showed the inside of cell and you got to see the
12:26 doing all that fun stuff or that of selling the the keynesians and dining
12:31 all that. Well, this is example where you'd see something like this
12:35 what we're talking about is moving material and forth. So, remember we
12:41 at and we suggested, or I that we have electrical signals that are
12:46 things to be told to be released here. But all the materials inside
12:52 neuron are being made up here. I'm releasing things from down here,
12:56 gotta get down there. And the type of transport that we
12:59 which is called um neuronal transporting is going to be uh anterograde, meaning
13:05 moving towards this region where the synapse going to be found, or it
13:10 be moving retrograde, which is moving back up towards the cell body.
13:15 , if I'm interrogated what I'm doing I'm delivering things that will ultimately be
13:19 down here. So, for I might move vesicles and store the
13:24 down here so that when it's time signal, I have something that can
13:27 released, right? But there's gonna be times where I pick up things
13:32 at the synaptic knob, Things that to be processed, broken down,
13:38 recycled. And what I'm gonna do I'm gonna transport it back. The
13:41 direction to where all the cellular machinery anterograde Is typically very fast, they
13:50 fast external transport. So you're moving 400 a day. If you want
13:54 kind of figure out what that that's about 40% of a meter.
13:58 big is a meter? Three, ? It's about three ft.
14:03 figure out where three ft is about there. So, you can move
14:08 about that far in a day with . Axonal transport. Now, if
14:15 talking about little tiny cell, no deal. But if you're talking about
14:18 very long cell, you imagine you to be making tons and tons of
14:22 to get that material down to where needs to go. So, this
14:26 X only, you can go either , but typically what you're doing is
14:30 um you're trying to get things down . The other type is the slow
14:34 and this is more like you getting an inner tube and going down like
14:37 frio river. You know, if ever have anyone done that, have
14:41 done the tubing? Right? Get tube one for the beer one for
14:45 . You get you get in the and you just kind of like sit
14:49 you just kind of move like It's like I'm not making any
14:53 Oh, look, waterfall. Right. That's what slow axonal is
15:00 about. All right. You're not the machinery to drive you.
15:05 you're not using a T. And the and the motor proteins to
15:08 materials here. It's more just moving the flow of the axa plasm.
15:14 , so, with that in when we talk about the things that
15:17 gonna be talking about. I want to envision there's a neuron. All
15:21 . This idea, I've got the body, I got these dendrites,
15:24 got this ax on. And what gonna do now is we're gonna ask
15:28 question based on the stuff that we yesterday. Remember we learned all these
15:32 these channels, right? These these and close these open gated channels.
15:38 closed gated channels are the ones that capable of opening and closing. We've
15:41 these differences in chemicals on either What we're gonna do now is we're
15:45 ask the question of how we can those materials moved back from fourth.
15:51 before we do that, we gotta a little bit of language down.
15:54 right. We're going to jump back third grade in a number line.
15:58 you remember number lines in 3rd grade they got the arrows pointing both
16:02 You have negative numbers over here, positive numbers over here, zero in
16:06 middle. Okay. If I'm sitting my zero, I am considered to
16:11 neutral or non polarized. Right? moment I move off, zero is
16:18 moment I become polarized. So, I move 100 spaces that way I'm
16:24 . If I move 1/10 of a off zero, I'm still polarized.
16:28 no longer zero. So anything other zero is considered polarized. Doesn't matter
16:34 way you go on the number Now, the reason I'm talking about
16:37 lines is because remember we said if stick a probe in a cell we're
16:41 to measure the difference of that cell inside of the cell relative to the
16:45 fluid. So the inside of the most often is minus something. So
16:52 going to be polarized in that It's gonna be polarized in the direction
16:57 you normally think of numbers. So here I am at zero.
17:03 polarizing over here and now I'm sitting some number that's negative. I'm in
17:09 polarized state. I'm gonna scooch over little bit. That's gonna get in
17:14 way. All right now, If is over there, If I move
17:20 zero I'm becoming more or less Less. Right? I'm moving back
17:27 that neutral state. When we become polarized, we are deep polarizing.
17:33 I returned back to my original polarized , I have re polarized right?
17:40 I'm already polarized over here. And if I move this direction, I've
17:45 more polarized than I was before. ? So when that happens I've hyper
17:52 . And then of course if I back to my original polarized state,
17:56 re polarized once again so notice re and moving to the original polarized
18:01 D polarizing is moving towards zero. polarizing is moving away from zero.
18:07 you can do the same thing in positive direction. If I'm starting at
18:11 and I move away from zero. I'm polarized as I move back towards
18:16 , I'm d polarizing as I move towards my original polarized state. I've
18:21 polarized. If I moved further away zero I'm hyper polarized. Same rules
18:27 . You just need to know which you're moving. All right. And
18:31 words are important because we're gonna be to cells as D polarizing and hyper
18:35 over and over and over again. . So we need to know that
18:38 starting off polarized. And what are doing? We're asking the questions were
18:43 If we're d polarizing. If I'm , I'm becoming more and more positive
18:48 negative if I'm negative over here. I'm polarized if I'm adding more and
18:53 positive charge and my d polarizing or hyper polarizing de polarizing. Alright.
19:01 if I have positive ions moving into cell, the inside of the cell
19:04 becoming more positive or negative positive. . You guys got this. Don't
19:11 the language confuse you. All So this is a restatement from
19:19 Remember we said we have membrane Membrane potentials are the result of the
19:24 of the islands on either side of membrane. It has nothing to do
19:27 the actual charge of the membrane because don't have charges. And we said
19:31 that membrane potential is also dependent upon the so I'm blanking on the word
19:38 looking for right now permeability. Sorry had to pee in my head but
19:41 couldn't get past that. All And the permeability. Right.
19:45 we talked about those two things. and number of ions. Alright.
19:51 any time we change one of those states, what we're going to do
19:54 we're going to change the membrane Remember potential is a steady state or
19:59 equilibrium that's reached as a result of two states right now. Is that
20:04 Hodgkin Katz equation that we kind of at freaked out and said we're not
20:08 to talk about it. Right. , there are two types of potential
20:12 . So, if we're talking about membrane, there's two types. We
20:14 the graded potentials. Graded potentials are distance signals. All right. There
20:20 that occur in the cell that are , very small. They travel only
20:25 short distance from the side of An action potential on the other
20:29 is a long distance signal. you can think about that axon.
20:33 trying to send a signal along the of that full axon. So,
20:37 two different signal types are going to used in different ways. And we're
20:41 focus first on the greater potential because can use grated potentials to create action
20:49 . You're gonna see lots of pictures are very, very weird looking.
20:53 , So, what I want you see here is we have a channel
20:58 there. Alright. It's some sort gated channel in this case. Let's
21:02 call it a ligand gated channel. , So something has to come along
21:05 bind to that channel. All And what we're saying is when something
21:09 and binds onto that channel, it the channel to open up when that
21:12 opens up. Have we changed the of the cell? If I open
21:17 the door, have I changed the of the room? Yes.
21:19 if I open up a channel, changed permeability and as a result,
21:23 of a specific type of iron can on through. So, a greater
21:28 is a local change in membrane potential has different or varying degrees of
21:35 varying degrees of magnitude means different depending on how many channels I open
21:40 and it can change the membrane potential a certain degree that that magnitude.
21:46 . So, in this particular what it's saying is, look,
21:48 opened up the channel that allows sodium commence a sodium starts coming in and
21:53 I had a probe at that I would see that the membrane potential
21:56 was starting down here, climbs dramatically that source. Now, I want
22:01 to imagine for a moment that example I used a stupid example of those
22:06 schools, side by side with the staring through the fence at each
22:09 Remember they're attracted to each other. , if you were to open a
22:12 in the fence, what are people do? They're gonna go through and
22:16 gonna find that partner. All And so when they couple up,
22:20 you've done, if you've changed the between the two charges on those
22:24 Right. Every couple that forms results a loss in the the difference in
22:31 . Right. So, you can the closer I am to the
22:35 the more couples that are being But if you're further away from the
22:39 of the gate, you've got a time before someone matches up with
22:43 And so the further you are away the gate, the less change that
22:47 going to see, right, You have a partner over there, but
22:52 have to walk all the way down the gate and come back all the
22:54 over here. And by the time get to you, that gate may
22:57 closed. Right? And maybe they never be able to get to
23:02 All right. So, what we're have is some sort of specialized triggering
23:08 . Typically, this is going to some sort of chemically gated channel.
23:13 ? So there's gonna be ligand gated it's gonna open up that ion
23:16 that ion channel. If it's a channel that allows sodium to come
23:21 you're gonna get a deep polarization. if that channel is, say a
23:26 channel, we have more potassium inside cell, it's gonna travel outwards.
23:30 , you're gonna end up with a polarization instead of this going this
23:35 This would go that direction. That of makes sense. Yeah. All
23:42 , typically, and what we see that these are mostly sodium gated
23:48 sorry, gated sodium channels would be correct term. All right.
23:54 we're just seeing a deep polarization at site. And as you move further
23:59 further away, it's less and less less of a deep polarization as a
24:03 of charges coming in and saying I am causing that deep polarization.
24:10 charge hasn't made it that far And that's why you see the
24:14 Now way you can visualize this, get to this in just seconds.
24:19 you can visualize this. Have you thrown a rock into a pond or
24:23 pool? Right. And if you a small rock or even a big
24:27 and just throw it, it's gonna and where it hits. You get
24:30 big splash, right? And then get a ripple that moves slowly
24:35 That ripple is biggest near where the was. But as that ripple moves
24:40 as a result of resistance, which not what we're looking at here.
24:44 ripple gets smaller and smaller and smaller it travels away and eventually, if
24:47 have an infinitely large pool, you eventually lose the ripple. All
24:52 So, it's kind of the same you can think of a greater potential
24:55 basically I'm making a big splash and that ripple away from the splash dies
25:01 . Okay, Now, greater potentials a magnitude and duration that are the
25:08 of the triggering event in english. that means is the bigger the
25:13 the bigger the response, the longer stimulus, the longer the response.
25:18 , so it's trying to show you . Um Here's the stimulus. It's
25:21 small stimulus. So I got a response here. I have a bigger
25:26 . I'm getting a bigger deep I'm getting a bigger response. Here's
25:30 third stimulus even bigger than the one it. And the other thing that
25:34 could do, see if I can a pen out here fast enough to
25:39 this. If I had a stimulation lasted a long time, see this
25:52 in time then the response would be as high but it was sorry,
25:57 keep going for a long time. , the the stimulus length or the
26:04 would be longer. All right. , time and duration are dependent upon
26:11 triggering events in a graded potential. right, that's the key thing.
26:16 potential, time and duration or duration magnitude. Excuse me not. Time
26:20 duration, duration and magnitude are dependent the triggering events, duration and
26:27 Now, if you need uh an of that, if I poked you
26:31 , it wouldn't hurt. You you'd be like, okay, that
26:34 . But if I took my finger dug it in your arm for a
26:36 , you'd be like Yeah, it And it's lasting a long time,
26:41 would be an example of of how can think about duration and magnitude.
26:47 , when I poke you, that's causing a greater potential. Greater potentials
26:51 the opening of that little tiny channel allowing ions to come through for a
26:55 bit so far. You guys with , Okay, we've already mentioned this
27:06 potential. They decrease in intensity with travel. And there's lots of reasons
27:10 this. As I mentioned when I opened up, I have lots of
27:15 rushing through that's gonna allow as those that sodium rushes through. That's gonna
27:21 me from that, that lower And it's basically saying, hey,
27:26 I'm here. So that positive charge the negative charge. And so what
27:31 gonna see is going to see a deep polarization. But as those sodium
27:35 eaten up here, in other they match up with that negative
27:39 There's gonna be fewer and fewer sodium are able to make it further and
27:43 away. And so as a you don't see the same degree of
27:47 polarization. Alright, so it's the of the sodium partnering with those negative
27:54 that are causing that massive deep polarization . All right, there is some
28:02 in there. Another stuff but the here is that I'm not able to
28:06 or join up with the partner. , the other thing is the greater
28:10 is very, very short lived, ? It's dependent upon as we said
28:14 . How long those channels remain So if I gotta Ligon that comes
28:18 and binds that channel, that's going be in microseconds. It basically binds
28:22 and it gets kicked out. But the period of time that it gets
28:24 , it opens up ions po through then it shuts back up again.
28:29 . It's kind of like this, come along, you open the
28:33 things sneak in and the door Nothing come in any further short
28:41 All right. This also shows you same thing. So, here we're
28:50 here's where that stimulation is taking We can go and measure and
28:55 It's really, really high deep But as that signal ripples away,
29:00 going to see smaller and smaller ripples notice it goes in all directions,
29:05 ? It's basically wherever I create that , the ripples move away from that
29:11 . So it's even traveling away from cell body uselessly. It's not supposed
29:15 go that direction, but nothing That prevents it from doing so.
29:20 you can imagine this signal right here really strong but by the time it
29:23 to the Soma, it's not very at all. So, we have
29:30 terms for these types of graded This is where the alphabet soup comes
29:37 . We have E. P. . P. S. And
29:38 P. S. P. And G. P. S.
29:40 . S. Huh? Not as as sounds. Alright. E PSP
29:47 for the post synaptic. So, going to learn what the synapses here
29:53 a little bit. So it's on post synaptic side. So it's on
29:56 receiving cell and then the last Is potential. Excitatory post synaptic
30:04 That's the abbreviation. Which would you write ups pr excitatory post synaptic
30:10 That's why scientists make abbreviations, Because the PSP is easier.
30:16 So whenever you have an E. . S. P, what you're
30:19 is you are opening up usually a channel. Now notice here I say
30:25 a chemically gated cat ion channel. the truth is, some of these
30:29 aren't as specific as we like to . All right. And so,
30:33 don't want you to get caught up it. But when you open up
30:35 cat ion channel, some potassium but mostly it's sodium coming in.
30:40 right. But I just want you think about the sodium. So,
30:43 E. P. S. S. Are are made, that
30:46 the result of Alright, Sony PSP cause E. P. S.
30:50 . Is the result of the opening a sodium channel that sodium then comes
30:57 the cell causes a rapid deep That channel closes and all that sodium
31:03 up. Then you return back to back to rest. All right.
31:08 it's a small deep polarization event. like taking a pebble and dropping it
31:13 the water and you're getting a little in a little bit of a
31:17 All right now, the thing is want bigger signals if we want to
31:23 the cell. So this one little right here and getting one little tiny
31:29 is probably not going to be strong to get that deep polarization to get
31:34 action potential in the cell. we're going to have to do something
31:39 that. Now again, we greater potential can have different magnitudes.
31:43 can have big ones and you have ones, but generally speaking, they're
31:46 very large. To begin with, I. P. S.
31:51 Is just the opposite. It's an post synaptic potential. Again, it's
31:56 by the opening of a gated not the I mean, it's the
32:01 of it's not it doesn't make So, what we do is we
32:05 up a channel that channel is going either allow potassium to go out of
32:09 cell or chlorine to go into the and as potassium leaves, that makes
32:13 inside of the cell more negative. so, what you see is you
32:16 a dip away from the resting membrane and it's just like what we saw
32:21 the PSP, the differences which type iron is moving. Alright.
32:27 again, this should say insufficient cause Well, it's it's insufficient kind of
32:33 polarization. In fact, what it does. So ignore this sentence.
32:37 it really does, it moves you and further away from the ability to
32:41 an action potential. That's the better . There's the danger of why we
32:45 copy and paste stuff. Okay? if you look at the slide,
32:49 just copy paste, copy paste, paste. All right. Again.
32:58 what do we do? How do get a cell to reach this threshold
33:03 produce a signal that we call an potential? Well, what we do
33:08 we add them up. All ready for the dumbest example on the
33:13 . I'm so glad. Let's say get on your form of social media
33:19 in the day. I used to able to say facebook but no one
33:21 facebook anymore. So pick your Alright? And let's say you asked
33:26 group of 1000 friends, all, of your very very close friends who
33:30 you. Right? And you look, I'm dating this person and
33:35 need to know whether or not I break up with them. So you
33:38 out that poll, Right? And say, hey um do I break
33:42 this person? I'm sure the person on the pole and he's gonna or
33:45 gonna say yeah, we're breaking But anyway, just ignore that for
33:48 moment and say okay, so your friends answer the call. You
33:54 some of them say yeah, by means break up the other ones.
33:57 no no give them a chance. ? And what you do is you
34:01 up all the sum of all those responses And whatever that is greater is
34:08 thing you're gonna do. That's kind what neurons do. The difference is
34:13 looking at the magnitudes of these eps the magnitudes of the hips and their
34:19 them up. So if you have lot of eps that's going to be
34:23 lot of deep polarization, maybe one strong enough to cause a cell to
34:27 polarize and ultimately result in an action . But if you have a whole
34:33 of I PS PS that's going to the other direction. So they basically
34:36 the E. P. S. . S. And basically move you
34:39 from threshold so you can't produce an potential. And so the sum of
34:44 the E. P. S. . S. And the I.
34:45 PS at a given moment is referred as the G. P.
34:50 P. The grand post synaptic So it's a summary right? So
34:57 can see in this little cartoon up because this is really kind of what
35:00 neuron looks like. This is the body. And all those little blue
35:04 represent axons from other neurons and that there would be the synapse. So
35:10 purple cell here in the middle is one that's the post synaptic cell it's
35:14 one receiving signals from all those little synapses. Some of these are going
35:18 be sending signals that cause E. . S. P. S.
35:21 of them are gonna be sending signals cause I PS ps if a cartoon
35:24 better, that's a little bit Green means go, red means
35:29 right? And if if given all being equal, if each of our
35:32 the same magnitude, all you gotta is some up in whichever is the
35:36 that gets you to threshold. If occurs then you fire but if you
35:40 reach threshold, nothing happens. The potential dies and you don't create a
35:49 . So the way we do this of summation which is in essence what
35:54 gps a gps P is. It's summation of the sum of all these
35:59 is a result of one of two types of summations. It's either going
36:03 be temporal or spatial. When you the word temporal, what do you
36:07 of? Please don't say that little of that bone time. Good.
36:12 then when you hear um spatial, do you think of? So it's
36:16 and space? Yeah, it's all . E No, no, it's
36:20 than that. Alright, so what gonna do, we're gonna do a
36:22 bit of an example here just to of prove this point. Alright so
36:26 different types of some nations and then other where you have E.
36:29 S. P. S. And . P. F. P.
36:31 . They cancel each other out. we just call that cancelation. But
36:35 . So, I'll start with spatial , spatial summation is when you have
36:40 or more um pre synaptic inputs sending signal. All right. So,
36:48 idea here is like I've got these and those firing at the same
36:55 Right? So spatial means how many we get going at the same
37:01 Look, see if I make a ? Not a very loud clap,
37:06 if you and I clap Ready? 2 3. Ready? All of
37:13 . 123. Now more of us . See it gets louder and
37:19 See how you play the game with . I'll wake you up. I
37:22 . Alright, that's spatial. We're all at the same point, we're
37:27 different parts of the room, but adding that clap together makes a bigger
37:32 bigger sound. Think of it in of magnitude, right? The greater
37:36 magnitude of all those E. S. P. S summed up
37:39 gives me this big giant G. . S. P. That's enough
37:42 get me the threshold I can produce action potential. All right, this
37:47 harder to show his temporal summation. , here what we're doing is we're
37:51 at a single uh neuron or really single input. And what they're doing
37:57 so let's just say I'm firing on regular basis. See I'm just doing
38:02 , right? But what's happening is each of those collapse. There's a
38:06 a gap. So the amount of that's being produced actually climbs and diminishes
38:11 and diminishes. Right? So with summation, what you're gonna do is
38:15 going to decrease the amount of time each of those deep polarization. So
38:21 you're trying to do is you're trying bring um these things closer together so
38:26 this one never gets an opportunity to to rest. So here it is
38:30 it doesn't get to go to So the next one goes up on
38:32 of it. And when I reach boom I get that big old action
38:37 . So I'm gonna just try to you and trust me I cannot do
38:40 with my hand. I'm not fast . All right. But if I
38:51 right, the sounds are getting closer closer together so eventually you can think
38:55 it. If I could go fast that I never have an opportunity to
38:58 even a pause. It just becomes large sound. All right. I
39:03 do that obviously. But that's what summation is like. This is one
39:07 that's firing successively so that you get and more E. P.
39:12 P. S. That never have opportunity to come back to that
39:16 So they kind of build on each there becoming larger and larger as a
39:21 unit. And as I mentioned cancelation simply an E P. S.
39:26 an I. P. S coming so you don't get anything. And
39:30 again presuming equal magnitude not all VPs and PS PS has the same
39:35 I could have a big magnitude of PSP and a small magnitude I
39:39 It just brings the sum. Makes slightly smaller. That kind of makes
39:45 that the G P. S. would respond in the back there and
39:48 over here. Yeah. Yes, . So special would be multiple
39:55 So you can look it up at picture right here and you can see
39:57 lots of different inputs. Right? mean over here I've got uh and
40:02 that results in I. P. . P. Over here I've got
40:05 inputs that results in the E S. P. S. Here's
40:07 more E P S. P. over there. And so, what
40:09 can imagine is if they're simultaneously firing , right, that means they're creating
40:15 change in the membrane potential together. the sum of their parts becomes
40:21 Now notice does spatial have a time ? Yeah, it does at the
40:27 time. Alright. But what we're is that you and I together make
40:33 bigger noise then you and I apart P. S. P.
40:42 What do you think? Right, make you can move further and further
40:46 from threshold. So, if this threshold and we haven't really defined what
40:51 is. It's the point where an potential is produced. All right.
40:55 , if I have a whole bunch I PS PS this would go
40:58 right, That would go down. in terms of spatial it would be
41:02 down. So I'm really far away from threshold, I have to overcome
41:06 lot to bring myself up to threshold . Why do I care about
41:12 It has to do with the action . Right. And then we had
41:15 there special and that's absolutely correct. . So the term summation just refers
41:26 the additive effect of the type of potential you're looking at. So if
41:31 greater potentials are of the same right? E p s P R
41:34 P S B, then we refer it being spatial or temporal summation.
41:39 if there are different types, we call it cancelation. It's not necessarily
41:46 faster effect. What it is is it's a it would be a similar
41:51 because if the effect is producing an potential, anything that brings me to
41:55 threshold. Right. So with sorry, temporal, what I'm doing
41:59 I'm bringing the stimulation closer together from single actually right from a single
42:07 And so if that brings me to , boom, I get my action
42:10 , if two or more uh inputs in me coming up to threshold,
42:15 get an action potential. There's no here. It's just when do I
42:20 to there? If I get to , that's action potential? Just telling
42:29 where the input is? Sorry? think about like this. Alright.
42:33 part of this is hard to explain we don't understand the neural networks.
42:36 right. So you can think of brain as being a whole bunch of
42:39 talking to other cells, right? it's not just like the cartoons we
42:44 where it's like one cell, one . It was more like that other
42:48 where every cell is like this where getting thousands of inputs and then you're
42:53 out thousands of inputs. Right? you're talking to a whole bunch of
42:57 cells. So the idea here is the context of those networks, I'm
43:03 to get input or stimuli that tells what to do to the next
43:10 And so you're at well, why I care about what the next cell
43:13 ? What if the next cell is this this chemical, this hormone,
43:18 next cell might be tell this muscle move right? Um Ready for another
43:23 example because I mean because when I you a dumb example, it's not
43:27 in the sense that I'm telling you it works. But it gives you
43:31 idea, Alright? You're walking across street because you're reading your phone because
43:36 what you all do. Right? you hear this honk massive honk and
43:42 hear screeching of brakes? you look and you see a bus coming at
43:46 , what do you do? Are sure? Most of you do this
43:52 ? And the reason I'm saying you that is because you're now getting multiple
43:58 inputs and your brain is trying to what to do. Most of us
44:03 freeze under those circumstances because we don't whether to run, duck,
44:07 yell, you know, whatever it , Right? And that's why we
44:11 hit by the bus. Right? what you can think of here is
44:17 processing as a result of all the inputs. And so each action that
44:21 brain is doing is receiving these kinds inputs. Well, I say it's
44:26 dumb examples because that's not how your works. It's just you know,
44:31 is receiving a whole bunch of but you don't freeze because it's
44:35 you know, too much input. trying to figure out what to do
44:40 kind of answer the question kind of , kind of It's not a question
44:44 and then there. Okay, so now all we're dealing with is potential
44:51 , right? So remember all the we expended was was moving the ions
44:56 the place where they don't want to and that was that pump action,
44:59 ? So we're pumping and pumping the out of the cell. We're pumping
45:03 into the cell. So we're expending there. And so energy is being
45:08 up. And every time we open one of those gates, then those
45:11 move. And that's again kinetic You're expending the energy that you stored
45:16 . All right. And so we're use that now to create a
45:20 So, notice what we've done here we've only created local signals,
45:23 It's a signal that says from the , I'm trying to get to the
45:27 , that's all I'm trying to or might be, I'm on the
45:29 and I'm trying to get to the hillock and really, that's where we're
45:32 to send the signals ultimately to the hillock. Okay. But it's a
45:36 eye, you're like, wait a , you're talking energy potential. What
45:39 its potential energy that we're gonna use create kinetic energy, which is then
45:44 to result in this this long distance . Yeah, Well, so,
45:56 not in in the sense that we're at it. Right. I
45:59 cause whenever we draw this, we kind of draw the this uh you
46:04 , this membrane and we say, , here's a here's a channel here
46:06 here's a channel there. And what say is their spatial. Alright.
46:10 if you only have one channel, say, well, there's temporal,
46:14 that's not the best way to kind approach this. What you can really
46:17 kind of say is when I'm receiving from two or more sources. I'm
46:21 spatial when I'm receiving input from a source and the signals are going faster
46:27 faster. I'm probably getting a temporal . Alright. And so when would
46:32 see this? Well at any given ? Right. Well I'll just use
46:36 any given moment. But you're right your your blood vessels receive input from
46:41 sympathetic neurons and it's basically determining the of of dilation of those different um
46:50 those blood vessels. If I increase rate of sympathetic response, what that's
46:56 to do is cause vaso constriction when reduce the signal it causes visa
47:04 Now notice this isn't lots of One nerve doing that. One
47:08 So that would be an example of temporal response. I'm increasing the input
47:12 a single neuron and how fast it's to cause that result. That would
47:17 an example of temporal. Right. that help a little bit? So
47:22 just I mean again we're looking at little thing, we're not looking at
47:26 whole system, the whole system would everything going off at once, that's
47:31 bunch of different neurons but that's not spatial either. And I don't want
47:35 go into why? All right, with that in mind with what we've
47:41 described, what I wanna do is want to switch gears, how we
47:45 on time. Oh good. Look can take a small break when we
47:51 back. What I wanna do is want to take this idea of the
47:53 potential and I want to convert it the action potential and because I'm afraid
48:00 not gonna we're gonna run out of . Let's just take a five minute
48:02 . Okay. Get up stretch, to the bathroom, Go tell the
48:07 next door, you can drill on wall about five minutes. Okay.
48:28 Sam. Alright. So what we're do now is we're going to move
48:32 from the grated potential and what we're do is we're gonna look at action
48:38 . Alright, So I told you two different types. This is a
48:41 type of signaling that occurs within these . So you'll see them in
48:46 This is what we're gonna be focusing . But this also occurs in muscle
48:49 . So they're not specific to their specific too excitable cells. All
48:55 , so, the way that this is where you where we're gonna be
48:59 is we're going to look at the hillock and if we can get that
49:04 hillock to reach threshold, what we're is we're opening up a whole bunch
49:08 channels that allows a whole bunch of to Russia in the cell that causes
49:13 massive deep polarization event, and this deep polarization event is what we refer
49:19 as an all or nothing event. either have it or you don't.
49:23 right. And so I use the just so that it becomes 100%
49:28 Alright, you're either a virgin or are not a virgin, there is
49:33 kind of a virgin. All That's an action potential. You either
49:38 an action potential or you are not action potential. You can't be a
49:43 of action potential. Okay. There's there's no two ways about it.
49:49 right. And so, what an potential is is a large change in
49:53 membrane potential. So, you're gonna 100 million volt change. You go
49:57 -70 all the way up to plus . All right. And then what's
50:01 happen is once you get that plus , then you completely reverse course and
50:07 return back to threshold. And we're to see that there's some weird stuff
50:11 going on. The reason this happens that what we're doing is we're gonna
50:17 opening not ligand gated channels. Like see primarily with the with the graded
50:22 . But we're making a response to membrane potential changes. And we're opening
50:29 gated channels. Alright, So, greater the channel, the greater potentials
50:33 opening up channels and allowing ions to in or out. That causes the
50:39 or the aerial um changes in membrane . And if you have voltage gated
50:45 there, those channels are then going open resulting in this. All
50:51 Now, what we see on these . And you know, I don't
50:55 how much anyone's ever emphasized how important is to read a graph. Because
50:59 you look at a graph and you're to read a graph, you can
51:01 can discern so much information. And what this graph is showing you is
51:06 volts. So, potentials. This on this side and then on this
51:10 that's time. And so what you're doing is you're looking at a portion
51:14 the membrane and you're staring just at membrane and you're asking what's going on
51:20 time. And the time was actually small, 10 milliseconds. All
51:24 And so, what I want to here is I want you to understand
51:27 we're asking for uh say, let's look at that membrane and see
51:32 happening there. But also let's take step back and look at what this
51:36 potentials doing. So just like a potential. You throw a rock in
51:39 pool and you get that ripple that away from the from the side of
51:43 and action potentials away that once created along the length of the cell.
51:49 right. But it's the same process occurring over and over and over again
51:53 what we refer to as a non fashion, meaning it gets no bigger
51:57 it gets no smaller. Now, best example for this is to think
52:02 the wave that we do at sporting . Have you ever done the
52:06 The wave is fun. Right. . In fact, we're gonna do
52:11 wave, Yeah. And your grade on it. Mhm. Alright.
52:19 real simple, Right? You get stimulus and if you don't know the
52:22 it is. That's when you you have to stand up. Just we're
52:25 doing the arm things. Okay? when I signal, we're just gonna
52:29 the way we're gonna start over We end over there. I don't
52:31 to tell you anything else. So if we do the wave,
52:38 guys think you're too cool for Let's try this again. We're going
52:42 see here's a stimulus. We're gonna the wave. I see that middle
52:48 over there. Everyone's gonna do Right? Let's try it again.
52:58 ? That's that's that's like bad Alright. But you saw that once
53:03 started the wave, it traveled at given speed, right? And it
53:09 and it wasn't like it changed. just did the same except for the
53:13 thing over here. Alright, So what this is. But the difference
53:17 is we're focusing in on a single . Now, we're all going to
53:21 the wave one more time. But , while you're doing the wave,
53:24 want you to watch her. Remember told you this is sea world,
53:27 Shamu You're in the splash zone. . Ready? Everyone's gonna watch her
53:33 we do the wave. Ready. . What did her arms do?
53:39 started low, They went up. reached a peak and then they came
53:45 down, Her arms started going up she saw these arms already here,
53:51 arms started going up when her arms coming down and you probably saw that
53:55 the periphery as you're watching her you know this because you did the
53:58 too, and that's how you know was your turn. But if you
54:01 at this picture, what you just , there was the exact same thing
54:05 just watching her. It's basically saying is the start and look, arms
54:09 going up. Something tells it to up the arms, go up,
54:13 reach their peak and then they come down and they come back down to
54:18 . So we're watching a single So when you look at a
54:21 what you're looking at is a single on the cell. And you're asking
54:25 sort of membrane changes or potential changes occurring at that one point. So
54:32 that in mind, what we're gonna is we're gonna dissect this. And
54:35 already done it for you in this , They're basically saying look for where
54:38 occur. So it's basically saying nothing's on, something's going on there.
54:42 we're gonna see a slight climb and going on there. So that's when
54:46 go up to here and then there's change. So we come down here
54:48 they've color coded it all for So whenever you're looking at a
54:52 look for where the changes occur. you see a change occurring on the
54:55 , something happened. Right. I that's that's an obvious statement but you'd
54:58 surprised how many people fail to understand concept. So let's look and see
55:05 going on here. Why do we these different changes? Just making sure
55:10 this is moving forward? All So the action potential begins at the
55:17 hillock. Alright. And so everything doing here is starting there. But
55:20 we started it's going to travel along length of the axon just as we
55:24 . Now, the primary reason for is a result of a deep polarizing
55:29 . P. S. P. remember if I'm signaling through the dendrites
55:32 telling those dendrites d polarized polarized polarized I get that deep polarization signal if
55:38 long enough or strong enough and big and it rise at the axon
55:42 It's going to start stimulating voltage gated inside the axon hillock. And I
55:48 the reason we named the axon hillock because it distinguishes itself by having thousands
55:54 thousands of voltage gated sodium channels. that's one of our first players is
56:01 voltage gated sodium channel. There's also gated potassium channels there. All
56:07 And so what happens if I get big enough G. P.
56:09 P. I'm going to stimulate those to open. I'm also gonna stimulate
56:14 channels to open. But there's an in which this happens now. The
56:19 polarization event is a function of the gated sodium channel. Lots of sodium
56:25 in that causes deep polarization. That make sense. So that's why I
56:30 this uptick the re polarization, why goes down as a result of those
56:35 gated sodium channels opening and the other gated sodium channels. I say sodium
56:42 voltage gated potassium channels opening and the gated sodium channels closing closing. Now
56:49 understand this let's take a quick I know this is not your favorite
56:53 of anatomy physiology but this is to you understand a voltage gated sodium channel
56:59 weird. It has two gates. you have one gate but here we
57:04 two gates. One gate is called activation gate. That one of the
57:07 gates called the inactivation gate. And you exist in these three states as
57:12 result of these two different gates. initial state is closed but you're capable
57:17 opening. Alright so if this is activation gate and this is my inactivation
57:22 . Here's my activation gate. It's a closed state, my inactivation gates
57:25 an open state. And so that's first condition. My first state I
57:30 stimulated open. My activation gate ions can pass through me. But
57:35 moment I open this gate is the that this gate begins to shut.
57:39 I limit the number of ions that allowed to pass through. So,
57:42 go from a closed state to an state. I feel like a cheerleader
57:47 , an open state to a closed . But this close state doesn't reverse
57:52 like that. It basically closes. I have to go through this weird
57:55 where I stay closed. So I from state a closed state. Be
58:01 to the state C. Which is but not capable of opening. And
58:04 have to go all the way back here without coming through that.
58:08 I go A B C A B . That's how I work. All
58:12 . So, to get from here there takes a little bit of time
58:15 is going to become important in a . All right. So, that's
58:19 voltage gated sodium channel, voltage gated channels are typical. They have one
58:25 . So, you have two states open. You're closed the end.
58:29 . Yes, that's I am. exactly what I'm gonna do. All
58:36 , But you understand now. so, we have this weird channel
58:39 has three states. We have one that has two states open and
58:43 All right, so back to where are at rest at rest. We're
58:48 gonna walk through and you're gonna see these channels work. So, here
58:50 am at rest. So, remember our channels or in ourselves we have
58:56 channels. We have sodium channels. channels. What's the ratio of potassium
59:02 channels to sodium channels, you guys ? Not 1 - five is much
59:08 . Yeah, 1-25 and it can as high as 1-75. But I'm
59:12 that what I was looking for there big. Alright. There's lots of
59:16 channels. Not a lot of sodium . We have the pumps in
59:20 The inside of the cell is more than it is positive. sodium is
59:23 in a little bit, but more is leaking out. That's our current
59:27 . So, that's how we get at rest. All right. The
59:31 gated channels are in a closed state both in both instances. So not
59:35 don't have any sort of effect on membrane at this point because there's no
59:40 through these particular channels. Alright. there it is. There's the number
59:46 times more. Here's a hint. never ask questions. Alright.
59:52 that's our that's our state at All right, then we get a
59:57 . All right. So, what we're talking about is something stimulates
60:01 cell causes a greater potential that greater ripples away from the site of
60:07 And if it's strong enough, what gonna do is it's gonna reach the
60:11 hillock so that G. P. . P. Arrives at the axon
60:14 and as a result, that's going change the membrane potential at the axon
60:20 . If I change the membrane potential the axon Hillock, that's going to
60:23 a couple of voltage gated sodium channels open up. If I open up
60:28 voltage gated sodium channels, what comes the cell? Not a trick question
60:33 like asking who's buried in Grant's Who's buried in Grant's tomb?
60:43 Well, you could have been whatever heard, you could have said the
60:45 thing. Right. Right. If open up a voltage gated sodium
60:49 what comes into the cell sodium when comes to the cell? What happens
60:54 the cell? It d polarizes which the membrane The membrane potential change.
60:59 I get a membrane potential change, gonna cause the opening of more vulture
61:03 sodium channels which causes more sodium to in, which causes more voltage gated
61:07 to open, which causes more We have a positive feedback loop
61:13 So the triggering event results in deep which causes the opening of these
61:17 which causes more sodium to come which causes more deep polarization.
61:21 what we're doing is we see go this low state and all of a
61:25 we start going higher and higher and because we're amplifying the amount of sodium
61:30 into the cell, massive flow of . Now, at this point we're
61:39 reach threshold threshold is represented by the line. Now we can think of
61:45 as being the point at which we've an action potential. And that would
61:49 right. And that's fine. But threshold is more a marker of when
61:54 occurred rather than something I'm trying to if that makes sense. All
62:00 In other words, threshold basically marks point where the action potential begins.
62:05 not the point at which an action you reach this and you're gonna get
62:09 action potential. All right, It's it's it's kind of backwards.
62:13 essence, threshold represents the point when opened up all the voltage gated sodium
62:19 . So, when you open up the both educated sodium channels, whole
62:22 of sodium is rushing into the All right. And so what you've
62:26 done is you've reversed permeability. So, at rest permeability. Favorite
62:32 moving out of the cell. So, basically potassium is flowing out
62:36 cell when you open up all these gated sodium channels. Now, sodium
62:39 rushing into the cell and that's why see this massive deep polarization and it
62:45 up And that's why you're shooting towards 30. Now we mentioned, and
62:49 told you don't need to memorize this . There's an equilibrium potential for
62:53 That equilibrium potential for sodium is plus sodium will continue to rush into the
62:58 until it reaches plus 60, but doesn't it stops at plus 30.
63:03 , this is where the voltage gated come into play. Alright.
63:08 what we had is we're opening up the channels. Boom. So,
63:12 me is rushing in and our activation is slowly closing and then it slams
63:18 . Nothing come in anymore. The where that happens is when the inside
63:23 the cell becomes plus 30. Now which came first, Was it the
63:30 that was reached or was it that gate closed? What do you think
63:35 the gate closed? Right, because want to keep going until I get
63:38 60 but the gate closed, sodium come anymore. We're full. We're
63:42 . We're slamming the door shut on . Now notice this is a timing
63:46 . Everything that we're going to talk here is about timing, right?
63:50 we're really asking what's happening over I open the gate. The gate
63:54 shuts. All right, and that's has me reached that threshold or that
63:59 that threshold, that peak now, nothing else were to happen.
64:04 what happened is I would slowly move because I got the pumps going
64:08 I told you sodium you're supposed to over there. I'm gonna keep pushing
64:11 out and potassium, I'm gonna pull back in and eventually we'd slowly come
64:15 down and eventually get back to our point. But that's not what
64:19 We reverse and we go the opposite now before we get to our opposite
64:23 , I'll be happy to answer the . Yeah, shoulder. Uh
64:30 Alright, so the word threshold just the point at which is how we
64:34 Is that point where we begin the potential. Alright, that's all it
64:38 means. So muscle cells have different than neurons which have different thresholds and
64:43 cardiac muscle cells. So on and forth. So everyone has different resting
64:47 . Everyone has different thresholds. And you memorize them. If you have
64:52 know them or you just kind of , okay, I'll learn it for
64:54 one test and move on. We're there and then there so go
65:05 So the gate closes and you're at . So that peak represents the point
65:09 the gate closes. All right, that's what you're seeing and you're
65:13 You hit that point and it's just I can't get any further. So
65:15 can kind of see that the gates open up on the front end are
65:18 probably close before the ones on the end open up. So that's why
65:22 kind of see the peak. Kind do this. I'm kind of coming
65:25 the stop, right? So when get to the absolute tip top of
65:29 apex, that's when it's basically saying shut every one of these gates and
65:34 is no longer rushing, rushing into cell, then we go here and
65:37 we go back over there. Right. When that Yeah, that's
65:50 , it's actually So yeah, so represents the point where I've opened up
65:54 the volt educated channels over here if can just get a couple of those
65:59 start opening, I can create that or I can get that, I
66:02 get that feedback loop occurring. So here, let's just say open
66:08 two channels. Two channels results in results in 88. Results 16.
66:12 , what you're seeing is you're seeing slow climb and then ultimately you'll get
66:16 a point where you get a massive . Right? So, if that
66:25 , if if I don't start that means migrated potential didn't reach the
66:31 hillock. It died out before it got there. So, remember that
66:37 , it's dependent on the strength of ripple. It's that duration and the
66:42 the magnitude isn't strong enough to reach axon hillock. I can't initiate this
66:48 through to get to that threshold or open up those voltage gated channels.
66:58 . Okay. Same reason this door when I open it. Is there
67:06 telling? There's Why did that Why does that close? Let's take
67:12 look. Mhm. It's it's a . Right? So, this is
67:22 gate that's a real good. This this is where the questioning part.
67:25 is where biochemistry gets real interesting and , Right. It's like why does
67:28 do it? It's because structurally that's it works. It looks like a
67:33 and when you change the shape, stopper goes in and moves into
67:37 but it takes a little bit of to do. So just like that
67:39 takes a little bit of time to after you open it. Yeah.
67:49 report re polarization is moving back to you originate, hyper polarization means moving
67:55 from where you originated. So in words, moving further away from
68:00 Well, we're going to see this just a moment because I know that
68:03 graph has a hyper polarization state. right. Yeah. So this is
68:12 now. Well, so, we're . And then we started deep polarization
68:18 then we continued deep polarization. And where we are at the top.
68:23 , we're d polarizing because we move and further away from zero. You're
68:27 , wait a second, but We passed zero. Mhm resting and
68:36 , but we'll see. Alright. , if I haven't answered your question
68:40 four slides, I'm hoping it's gonna three slides, but I'm giving myself
68:43 cushion. And you say you didn't my question and you suck. Just
68:46 cut. You can see it in brain. Don't say that.
68:50 All right. So, we're at peak. All right. We've closed
68:55 voltage gated channels, voltage gated sodium , but we're not slowly drifting
69:00 We're rapidly drifting down. And the we rapidly drift down why we re
69:06 is a function of two things. first is we close those channels,
69:10 we kind of mentioned. But the . So the second is the opening
69:15 the voltage gated potassium channels. do you have that friend that you
69:20 tell a joke to and they kind stare at you for a minute before
69:24 start laughing, takes a while to it. That is the voltage gated
69:28 channel. Alright. It is told open at the exact same time.
69:34 that reaching that threshold is the threshold both the voltage gated channels for the
69:40 channel and the potassium channel potassium That takes a while to kind of
69:44 it. Oh, you wanted me open? Okay. And so it's
69:48 that peak is when that thing opens again it's a mechanism thing but it's
69:54 about timing so I'm told here, I don't open until about there,
70:00 should say from here to there. so two things are occurring at the
70:04 of that, of that um right, we're closing the voltage gated
70:10 channels so no sodium can come in we're also opening up the voltage gated
70:15 channel so that we can rapidly return to original state and that's what that
70:20 polarization is. So all this light stuff represents the re polarization.
70:26 So potassium rushes out of the we can go for that plus 30
70:30 back down to that -70. But it's slow to open, it's also
70:34 to close and because it's slow to , we kind of overshoot where we
70:42 trying to stop, kind of like on your brakes when you kind of
70:46 make that decision, like, it is a yellow light and I
70:48 shouldn't go through it. But you're 70 miles an hour and you kind
70:51 slide up to the that's what's going here and you're going into the
70:56 And so is he all right? , this is just a slide to
71:02 of show you what we're describing here regard to those channels. Right?
71:08 the voltage gated sodium channel, you have to focus. It just kinda
71:12 you visualize what's going on there. , getting to the state of hyper
71:17 . So the voltage gated uh channels open and they kind of remain
71:22 but some of them begin shutting and begin shutting and then they stop right
71:26 there. And then what we're gonna is at that point they're all closed
71:30 gated sodium channels have been closed, resetting themselves, voltage gated potassium channels
71:34 closed. And now the 80 ph , wait, wait, wait,
71:38 out of whack here, let me moving things back again and that allows
71:41 to return back to here and now back at rest again. So hyper
71:45 is a result of the remaining voltage potassium channels being open and trying to
71:51 back to their close state and then out of. So this is this
71:56 be hyper polarization there and then going direction That would be re polarization?
72:03 we've got deep polarization re polarization, polarization polarization and then you're now back
72:11 rest long. Does this whole That's four milliseconds? No one
72:20 wow, supposed to go. okay. Do it again. Thank
72:29 . All right. Now, we've seen that this action potential. This
72:35 is propagated just like a wave is we do it. So it starts
72:39 at the axon hillock. It moves the area next to the axon hillock
72:42 moves to the next area which moves the next area and so on.
72:45 it keeps doing that. It doesn't its height because every single time you're
72:49 up all the channels, right? why you're able to get the same
72:54 the entire way. That's why it diminishes because the concentration of those channels
72:59 constant from the axon hill all the down the axon. And so it's
73:04 sequentially opening these channels and then closing channels, results in the action potential
73:11 . And that's why it looks like wave rolling into the beach. The
73:15 being the synapse. This scares me death that we're gonna run out of
73:23 . Okay. got 30 minutes three . Good. All right now,
73:31 a time wherein a new action potential be produced. We refer to that
73:36 the refractory period? Alright? So going to try to demonstrate a refractory
73:44 . Who wants to be my guinea this time? She's like, I
73:48 want to do it again. We'll on him. Alright. You
73:56 You're gonna be my action potential. watch him every time I stimulate you
74:01 do a full action potential. All , that means you gotta take your
74:04 off. You gotta be ready. faster. Come on, keep up
74:10 me. See, I'm clapping faster get his hands up. Right?
74:15 , he's actually missing an opportunity to an action potential. So, we've
74:20 into a refractory period. Alright, , the refractory period basically is a
74:25 comes in. But all those mechanisms we just described are ongoing and so
74:31 can't interrupt them and I can't increase . For example, if I'm over
74:37 , I've opened up all my voltage sodium channels. So, if I
74:40 the cell again, can I open more voltage gated sodium channels?
74:44 I've already I've already reached that So there's no amount of stimulation that
74:48 make me produce a bigger or a or a new action potential cause I'm
74:53 doing it. I have to wait everything goes through and gets reset.
74:59 right over here, for example, will have the voltage gated sodium channels
75:06 that third state. They're closed but haven't reset themselves. They're incapable of
75:11 . So no amount of stimulation? can do can overcome that,
75:17 I have to wait until all process ? But when I'm over here I
75:23 now start opening up those voltage gated channels but I have to overcome Some
75:29 those voltage gated potassium channels are still . So this type of stimulation that
75:34 me from -7 to -55, that's 15 million volts. I can overcome
75:39 no sweat. But if I'm down and I've got voltage gated potassium channels
75:44 , I have to produce more Right? I have to produce more
75:49 to get me to the point where overcoming all those sodium channels.
75:54 And that's really what what this refractory refers to. It's basically the state
75:59 those channels are going to dictate whether not I can move forward or not
76:03 those areas where I can't do anything all. We refer to that as
76:06 absolute refractory period, complete completely So, if I get a
76:12 if I'm in that absolute period which really from here to about right
76:17 I can't get anything to happen. not gonna be another action potential.
76:22 ? But in the relative refractory period that period, I can overcome the
76:28 of things. Right? So, already have alter gated sodium channels available
76:32 I might have some that are inactive I still have some that are that
76:36 able to be stimulated at this Right? I still have potassium channels
76:41 are open. But if I can enough sodium channels open. I can
76:45 the amount of potassium coming going out the amount of sodium coming in.
76:49 that might be enough for me to the cell. Alright, I just
76:54 to put a little bit more energy more work into it to make that
76:58 . So the refractory period limits the of action potentials that I can
77:06 Yeah. So, you can think it like this that on an individual
77:15 you can produce multiple action potentials in row. Remember I described for a
77:19 , the blood vessels being dilated and . So, that's a result of
77:23 number of action potentials I'm producing. ? I can speed up the rate
77:27 action potentials because they're far apart and can slow down the rate of action
77:32 , make them further apart. But becomes a point where I can't push
77:36 so close together that they stack on other because of this refractory period.
77:40 you can think of on an individual basis. Yes, this is
77:42 But also all sorts of cells are this simultaneously. Okay, so by
77:51 time the refractory period has moved. right, So, this is trying
77:54 show you here is the front Here's the back hand. So,
77:57 is basically trying to show you the period. I can now create a
78:02 here to produce another action potential. I can start one. But I
78:07 to wait for that period to All right. And so these refractory
78:12 are what limits the number of action . The number of signals that you
78:16 do along a neuron, depending on type of cell. Just like
78:22 Refractory periods are different in different types cells, action potentials move um at
78:35 specific rate dependent upon the size of cell that you're looking at. There's
78:39 two things that can actually affect the . The first is the diameter of
78:43 fiber. You can think of a very much like you would think of
78:51 wire. Alright, So there's resistance that wire. There's there's only so
78:56 sodium and potassium that can be inside particular cell. Alright. And so
79:03 you have a very very small you end up with something that has
79:07 of resistance. If you have a wire, you have less resistance for
79:12 of you guys who build stereos. already know which type of wire do
79:15 want to use when I'm building a ? Small thin wire or big thick
79:20 . What do you think? if you've ever been to the
79:23 they have a special name for that of wire when you buy it.
79:25 called monster wire. You know that's great marketing ploy. Get the big
79:30 . The big wire makes big Right. Well, that's gonna be
79:35 . True as well in the Alright. The larger the diameter,
79:39 faster the signal. All right, don't get as much resistance. All
79:45 now you can imagine if I want get a signal say from my brain
79:49 to my big toe and I want get it really, really fast.
79:52 I gotta do is just make the bigger and bigger and bigger. But
79:54 bigger I make the wire the bigger have to make my legs are
79:56 I make my legs are bigger. to make my body. The bigger
79:58 make my body, the bigger have make my neuron, the bigger make
80:00 neuron, the fat I have to . And you can see it becomes
80:03 endless cycle of getting bigger and bigger bigger and while I can accomplish
80:07 just fine with food, I'm not do that for my neurons right?
80:12 , what I'm gonna do is I'm use a different mechanism. It's called
80:15 Nation. And what Myelin Myelin Nation . It allows me to insulate portions
80:21 that neuron so that I can then my signal. So right now when
80:28 dealing with a neuron that doesn't have Ellen, that action potential travels the
80:33 length of the cell. But when get my alan, what I can
80:38 is I can skip over sections and allows me to speed up the rate
80:43 which that action potential travels and I'll this here just shortly. Alright,
80:48 the Myelin is going to be dependent one of two types of glial cells
80:51 depending on where you are. So the central nervous system the glial cell
80:55 we use is called A knowledge a site. We'll come and talk about
80:58 even further in unit two. If in the peripheral nervous system, you
81:03 everywhere else in the body that you're call those neural insights and the reason
81:09 mentioned them is just because structurally they very very different. Right? So
81:13 in the peripheral nervous system, the lymphocyte basically each individual neural insight wraps
81:18 around an axon and creates these Myelin . So each one of those represents
81:23 individual cell. But in the central system and all the good inter site
81:27 off to the side sends out a bunch of processes. All right.
81:31 we set a process that's called a . And so Allah go means many
81:35 processed cell. So here's the cell they're sending out a process and you
81:40 see it's my eliminating multiple cells. , sir. Sorry. Never.
81:58 . Why? I'm sorry. I missed the first half of that.
82:04 again it has to it has to with the distance in the room.
82:07 know. So if you want the or the signal, the signal only
82:20 the length of the axon. So once we produce an action potential is
82:24 to travel the length of that So once you start the axon hillock
82:28 going to go all the way down the tele Andrea and then once it
82:32 to the tele ginger it's going to something which we're hopefully going to get
82:35 here shortly. Alright. But I'm to get to we're still in motion
82:41 to the end of the cell. so that's kind of the flow
82:49 Well neuron has a lifespan. It's the lifespan of your entire life.
82:53 ? We remember how we define the at the beginning. A neuron is
82:57 topic. So once you create it basically you are done making them and
83:02 they don't reproduce themselves. And even I say that there is some untruth
83:08 that there are cells that can actually new neurons. But generally speaking,
83:12 you create that neuron that neuron is going to replicate itself, it is
83:15 it is. And so if it it's dead. Alright. So as
83:20 as you have neurons they're gonna be to produce these particular signals and they're
83:25 to last for the distance that they and you can produce those signals for
83:29 entire length of your life. That of makes sense. Okay now there
83:35 some probably I can guarantee you there's exceptions to that rule. But for
83:40 purposes we're going to stick to Don't go back. I'm going to
83:50 it this way. Yes. There is a population of cells.
83:55 look at them a little bit later can serve as neural stem cells.
83:58 generally speaking, we don't replace our cells. Generally speaking. All
84:04 so here's those Myelin sheaths. You can see what they do is
84:09 you take a cell and you wrap or a portion of a cell and
84:12 wrap it multiple times around the And so what you do is you
84:16 insulated a portion of the cell. you look you can see in between
84:20 of the individual cells. There's a or here's the individual cells. This
84:25 the the points of the Allah God site. And so now you don't
84:32 interaction with that cell with the external . Except that those little tiny
84:37 those little tiny points are called the of Ranveer. Alright, so here
84:43 that's the node that's a node. so now what we have is we
84:46 an action potential that doesn't travel along the myelin is. It travels between
84:50 the myelin is. So the length that Myelin sheath is far enough so
84:56 um are there close enough together? that actually potential can stimulate the point
85:00 the other side of that Myelin But long enough to actually speed up
85:04 process is really kind of what we're at here. So this is kind
85:08 a better way. You can kind see it here. Here's yellow Gajendra
85:11 . Here's the mural in a You can see that little space.
85:14 note of ranveer where the little red are. This is a little bit
85:17 closer look, you can see here's axon. This portion of the axon
85:22 the only part that's in contact with extra cellular fluid. So this is
85:25 only place where an action potential can . So an action potential instead of
85:30 along length, it leaps over these parts and so you go, you
85:37 faster. All right now the types propagation that exist, there's two different
85:46 . One is called continuous or depending on which book you look
85:50 The other type is called salvatori. is real simple. That's like me
85:55 toe to heel the distance to get the axon hillock to the axon
85:59 The wall is gonna be the Whether I walk toe to heel,
86:03 . I walked to the hill, covering the entire distance of the
86:08 Okay, if I come over here walk with my normal gate, I'm
86:14 over portions of the floor, same , but which one's faster. The
86:20 one? If I'm walking toe to , I have to slow myself down
86:24 make sure I cover the entire But I'm walking with my normal
86:28 I move a lot faster and that's this propagation speeds things up. I'm
86:33 over portions of the axon. I'm forced to skip over it through the
86:39 tutorial. Alright, so again I'm moving along the entire length stimulating
86:45 opening closing channels along the entire length the cell. It's a it's a
86:49 process than when I skip over portions the of the axon. Now one
86:57 the mistakes that most students make is they see the word Myelin, they
87:00 that the action potential is jumping from sheath to Myelin sheath. No that's
87:06 . You're jumping between the Myelin sheath from node to node to node.
87:11 here's a note of Ranveer. Note Ranveer. Note of Ranveer Note of
87:14 along the way. Alright. The salvatori comes from jump salt tar so
87:22 literally jumping over the Myelin and this just another picture of that. You
87:26 see again, I'm doing all my potential stuff here at this note of
87:31 , those neurons come in cause deep causes that to fire, causes deep
87:37 and so on. And you all same rules still apply. You still
87:41 refractory periods, you're still moving along you're moving along faster As much as
87:47 times faster than you would if you have the myelin the other benefit of
87:51 is that it consumes less energy. I have to reset everything and move
87:56 along the entire length that costs more . More pumps are needed to move
88:01 materials back. But if I have only in specific locations, then I'm
88:06 to use less energy because I'm only ions back and forth in those hill
88:17 . So this action potential which started the axon hillock in response to graded
88:22 . So you can kind of see we started. We produce any PSP
88:27 E. P. S. S. And I. P.
88:28 . P. S. Some of up together, we get G.
88:30 . S. P. S. G P. S. P is
88:32 enough. It comes down to the hillock that axon hillock is stimulated to
88:37 that deep polarization, the deep polarization or results in an action potential that
88:43 travels along the length of that whether it's my eliminated or annihilated.
88:47 it finally gets down to that And really what we're doing is we're
88:52 an internal signal to tell that cell release a signal to stimulate the next
88:58 on the line. So what we're is we're now down here at the
89:03 knob. And what we're trying to is we're trying to tell the cell
89:07 release a neurotransmitter, a chemical signal tell that other cell on the other
89:13 of that synapse to respond to whatever chemical is that we're releasing that
89:19 So you can say the sending signal a synapse. And this is a
89:26 where those two cells are in communication each other. The sending signals,
89:31 pre synaptic cell. The space here referred to as a synaptic cleft.
89:36 relationship as a synapse, the receiving is the post synaptic cell. Now
89:41 we come way back over here and making my E. P.
89:45 P. S. And my P. S. P.
89:46 What does the P. S. for? Post synaptic? So in
89:51 post synaptic cell I've responded to another . So I've produced an E.
89:57 . S. P. Or an . P. S. P.
89:59 this receiving cell. So it's kind a chicken and egg thing.
90:03 So we started down here in the above and we came all the way
90:08 this in that cell to get to pre synaptic side. So here we
90:16 , here's our pre synaptic cell. our post synaptic cell. This little
90:21 represents the action potential action potential as result of the opening of voltage gated
90:26 channels. Then the opening of the gated potassium channel. You get your
90:30 polarization, you get your re polarization you get down to the synaptic knob
90:35 you lose the voltage gated sodium potassium . They're replaced by a different type
90:41 volts educated channel. These are the gated calcium channels. Now, calcium
90:46 the body is often used as a molecule. And so what we're doing
90:52 that action potential is coming down to synaptic Nagy to create a signal that
90:57 to release that neurotransmitter. So the we release neurotransmitters of action potential comes
91:02 results in the opening because it ruins membrane potential change is causing the opening
91:08 voltage gated calcium channels, calcium floods the cell. And if you go
91:13 back to that lecture on the snares the snaps and I showed you that
91:16 , really complex picture, I don't memorize this. So maybe you
91:19 just skipped over the slide. If go and look at that slide,
91:21 shows you the calcium and what it's . The calcium comes in, binds
91:26 that complex on those vesicles that causes vesicles to open and that results in
91:32 release of that neurotransmitter again all the and there aren't important it's here action
91:39 , opening voltage gated channels, voltage channel allows calcium to flow. And
91:43 no more action potential calcium flows causes vesicles to open the neurotransmitters released
91:50 by simple diffusion goes out of that and then just kind of scatters
91:56 Some of that neurotransmitter is going to across that cleft and it's going to
92:01 up to ligand gated channels. And it binds up that leg and gated
92:05 , what happens to that channel it . And so that's going to cause
92:10 , not neurotransmitters ions to move into out of the cell, some of
92:15 going to float away, some of gonna get chewed up, there's all
92:18 of different ways or different things that happen to the neurotransmitter. But
92:24 if we can get that neuro transmitter bind to that channel, we've now
92:29 a signal to that next cell. telling that signal how to behave the
92:35 it takes for that neurotransmitter to move the pre synaptic cell of the post
92:40 cell Takes about .32.5 seconds. So that time is referred to as the
92:46 delay. So you can imagine from to there about half, half a
92:51 . If I have a chain of cells in a row to get the
92:55 from the first cell to the last , you're gonna have synaptic delay between
92:59 of those cells. So you just the number of cells or the number
93:01 synapses and multiply it by that delay that tells you how long it takes
93:06 to get that signal across all sorts things. So, here you are
93:10 the crosswalk with that bus bearing down you, honking their horn, the
93:13 screeching. You can now see why takes a little bit of time for
93:17 to respond because you've got all sorts systems sending all sorts of signals and
93:21 each of those cells. There's a delay. So you're just kind of
93:25 an input at this point before you your decision for everything type of
93:37 We have, we turn things on we turn things off. Right?
93:41 once you turn something on, you have to turn it off,
93:45 is the dad response, right? walk in the room, you use
93:48 light when you leave, turn off light, I'm gonna leave off the
93:52 you turn off the light, You open the refrigerator, you close
93:57 refrigerator, you release a neurotransmitter, got to clean up your neurotransmitter.
94:02 so there's different ways that we clean the neuro transmitter so that that signal
94:08 get maintained because as long as neuro is in that synaptic cleft it will
94:14 stimulating that next cell. And these of signals that we're looking at are
94:19 to be very very quick neural signals supposed to be like, I want
94:23 to do this. It's not like want you to do this and keep
94:26 this. If that's gonna happen, keep sending the signal. So what
94:31 doing is we're gonna clean it Now. The temptation will be to
94:36 this slide. Please do not memorize slide. This is from a very
94:39 complex journal that summarizes all the different of neurons and neurotransmitters and how they
94:45 stuff I picked this out because it shows the four ways to terminate a
94:49 . The first one is the easiest is the first one we discovered it
94:52 called enzymatic destruction. So we looked a muscle neuromuscular junction, acetylcholine is
94:59 and there's an enzyme in that junction the seat of colonist race and what
95:02 does is as soon as you release acetylcholine which is the neurotransmitter, it
95:06 there and chops things up and so a little bit is able to get
95:10 the receptors on the other side. like the most dangerous game of red
95:15 that could ever exist, neurotransmitters sprinting across the synaptic cleft and the
95:20 sitting there just showing things up as goes along. This is really the
95:23 place where you see in dramatic But was the first one discovered?
95:27 thing that can happen is that the can just kind of float out and
95:31 away, in which case it will another enzyme which will come along and
95:34 it up. But in essence if neurotransmitter isn't in the isn't in that
95:39 , you can't stimulate the cell. diffusion is a perfectly good way to
95:43 sure that the signal doesn't occur. diffusion. The neurons can uptake uh
95:49 neurotransmitters. So that's what these little are just kind of showing you.
95:52 , I can I can take it myself. The other thing that can
95:55 is you can have nearby cells including post synaptic cell astrocytes, any cells
96:01 are surrounding it can also take that up and when you take it up
96:04 can either destroy it or you can it, repackage it and recycle
96:08 So if you're taking it up yourself what they're seeing here, it's like
96:11 I've taken it up and I'm gonna it and I'm gonna send it back
96:14 again. Alright. But if I it up in this cell, I'm
96:17 gonna destroy it. But the ultimate here in terms of termination is to
96:22 neurotransmitter from the synapse. So the is terminated so that a signal is
96:27 brief and very specific for when that you sent it. Now there's a
96:34 of different neurotransmitters. There's about 100 them that have been identified so
96:39 You don't need to memorize them You don't even need to know all
96:41 shapes of them. Alright. I'm gonna point out a couple to you
96:45 that you're aware of what they look . How many slides do have?
96:49 three. Four. Okay. Alright. I'm doing good then.
96:55 wanted to get you out a little because I know you want to go
96:57 out about your tests. All But basically they're acting in that fashion
97:03 the synaptic clefts and so the first that was ever discovered, this is
97:05 you should know is acetylcholine. You don't even know its structure and
97:09 don't think it's right up there. right, you don't even know But
97:12 was the first one discovered. And everyone was like when they first discovered
97:15 this is what neurotransmitters look like. so they start looking for things that
97:18 like acetylcholine and nothing existed, But it's a very common neurotransmitter.
97:24 . We have the mono amines. so some of these you may have
97:27 of, have you heard of serotonin ? Yeah. Have you heard of
97:31 ? Yeah. Have you heard of ? Yeah, you probably when you
97:35 history you think might know that but just another of these mono means that
97:41 used as a signaling molecule, epinephrine norepinephrine. That's adrenaline and adrenaline.
97:46 these are examples of neurotransmitters. Some acids are used as neurotransmitters. So
97:53 and aspartame. It should sound Glycerine should sound familiar. Gaba is
97:57 modification of glutamate. So these are signaling molecules some of the puritans can
98:03 ATP we think of as being that molecule, but ATP is also used
98:09 a neurotransmitter in some cells, nitric . That's laughing gas. No,
98:16 not nitric oxide. But basically laughing is in 02 nitric oxide, carbon
98:23 , hydrogen sulfide. These are gasses your brain uses as neurotransmitters kind of
98:30 and there's a whole bunch of peptides probably heard of endorphins. Um But
98:35 a couple of others in there. And then there's some lipids that can
98:38 used as well as neurotransmitters. So point in this is that there's these
98:44 one that group that group and that are probably ones that you'll probably come
98:48 with all the rest of them. probably just like, okay, good
98:52 . Alright, But there are different . Different molecules that sells used for
98:58 and that's kind of what I've I've here are the ones that you typically
99:06 final slide and we're done. So we've been describing over the last
99:11 maybe a day and a half is form of chemical signaling and how we
99:16 chemical signals. All right, So have this actual potential greater potential as
99:21 way to send a signal over a distance in a cell to ultimately result
99:26 a chemical signal. But there are types of electrical signaling that take
99:31 We've seen this slide before about electrical , even though we've talked about chemical
99:36 and we're gonna spend most of our talking about chemical signaling moving forward is
99:40 are neurons that are connected to each by gap junctions and use electrical
99:45 And so those action potentials and greater that we've just described basically are passed
99:50 cell to cell directly and can be as a form of communication.
99:57 So I throw that out there less a Oh, let me just throw
100:01 monkey wrench in it. Just what really trying to tell you is that
100:04 learned of a mechanism that's really, common, but it's not the only
100:09 . And so it'll come along at point, bite you in the past
100:15 . I don't know anyway, that's . We have an exam on
100:19 Yeah. What do we have on night? Extra credit. See,
100:23 just want to make sure I'm not email you and remind you this
100:26 So put it in your phones and whatnot. I have an
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