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0:03
Alexandria Reynolds: Okay, so for today, we are going to talk about the action potential.
0:12
Alexandria Reynolds: So last class we covered all about neurons and basic functions of cells okay now we're going to extend this information to Chapter two to learn more about actual and what happens when the cell actually fighters, as we were talking about in the laboratory.
0:37
Alexandria Reynolds: Is everybody Okay, with the lighting, should I turn one down I don't want to turn them both down, because then they can't see me.
0:45
one.
0:58
Alexandria Reynolds: Okay, so everybody i'm on Can you see the slideshow fine can hear me okay me thumbs up Thank you guys okay.
1:08
Alexandria Reynolds: So let's talk about the action potential.
1:12
Alexandria Reynolds: There is a lot of chemistry in this there's a lot of biology in this, but i'm going to try to do it in a simple way so that everybody's on board, he doesn't you know, maybe not necessarily have biology. Alexandria Reynolds: i'm going to try to do this as best I can do you have questions you can always ask them, but here we go alright.
1:33
Alexandria Reynolds: So let's first talk a little bit about.
1:37
Alexandria Reynolds: Chemistry and how it works with the cells in the brain Okay, so when.
1:45
Alexandria Reynolds: We.
1:47
Alexandria Reynolds: Look at how the cell communicate.
1:52
Alexandria Reynolds: We have to first understand how the cell is made up in terms of electrical components Okay, and then that will then help us understand how the action potential or self firing works electrically speak.
2:13
Alexandria Reynolds: So we're going to talk about two kinds of movement okay one and.
2:24
Alexandria Reynolds: One is called electrostatic pressure which we refer to the electrical gradient and one is diffusion through concentration gradient okay.
2:35
Alexandria Reynolds: So we're going to talk about how the cells book inside and outside the cell walls are made up of different electrical Adams and how the movement of those atoms and of the.
2:52
Alexandria Reynolds: liquid determines of what fate that selling okay so it's accomplished through to process electrical gradient and concentration gradients right. Alexandria Reynolds: So electrical gradient is the same concept as using MAC so anybody played with magnets as a kid or maybe even if you have access to a magnet you're gonna play with it right okay you take opposite ends and what do you do when you put them together.
3:24
Alexandria Reynolds: The opposite polar polar ice maggots what do they do when you bring them closer together.
3:29
Alexandria Reynolds: Their traffic right they'll go and they'll still go together what happens if you have two different polarities and you put them together.
3:40
Alexandria Reynolds: They push each other away, they were put repel each other right so when we talk about electrical gradient, this is the same process there Adam real positive we charged in atoms that are negatively charged and those were the opposite chargers wait there's no record.
3:58
Those have the same So if you know I said it right right when I say that right it out opposite and.
4:04
Alexandria Reynolds: Now I got myself questioning good.
4:07
Alexandria Reynolds: So the same idea happened with electrical gradient hey those particles with opposite charges so if you have a positively charged Adam and negatively charged data. Alexandria Reynolds: they're going to attract each other and they're going to want to get you know the same area okay.
4:26
Alexandria Reynolds: Those atomic particles that are negatively charged for example they're going to repel each other, you have other atoms are positively charged the same charge they're going to repel each other.
4:38
Alexandria Reynolds: And so, if you have.
4:42
Alexandria Reynolds: A liquid Okay, and you have electrically charged molecules in that liquid you're going to see that all the ones that are the same chart are going to repel each other and move away from each other versus if you have obviously charge they're going to bunch together that.
5:03
Alexandria Reynolds: kind of like when you put salt mixture into water you're going to see it disperse differently based off of the electrical. Alexandria Reynolds: Adams within the makeup of the salt in comparison to the water Okay, and it distributes differently throughout the word idea is to be balanced right, so the whole thing will eventually and now it's up.
5:28
Alexandria Reynolds: When we talk about concentration gradients case, this is a different concept concentration gradient is when you see higher. Alexandria Reynolds: concentrations of something moving through out of liquid to an area of lower concentration, what happens if you take a cup of water and you drop a drop of food coloring and.
5:57
Alexandria Reynolds: what's going to happen to the football.
6:01
Alexandria Reynolds: it's good to disperse out and eventually what is that cup of water gonna look like.
6:09
Alexandria Reynolds: it's going to look like the color that you dropped in so let's say you have a drop of blue food coloring. Alexandria Reynolds: Okay, when you see it hit the water it's going to be super concentrated and very blue. Alexandria Reynolds: Right now you're going to see it start to disperse throughout the water and spreading itself out to areas that don't have food coloring.
6:31
Alexandria Reynolds: So that eventually the whole thing will be a lighter shade because it's all dispersed completely into that liquid area that makes sense. Alexandria Reynolds: So your brain and the cells and molecules myself all work with both of these processes to stay regularly back. Alexandria Reynolds: And we see that these processes jump in when we start to see changes in the concentrations of the atoms and other molecules in the brain.
7:09
Alexandria Reynolds: That everybody, good evening so far and understand the difference between electrical gradient and concentration gradient everybody understand that right.
7:22
Now.
7:24
Alexandria Reynolds: In the brain.
7:26
You have.
7:29
Alexandria Reynolds: This many with.
7:35
Alexandria Reynolds: You guys follow, along with the.
7:38
Alexandria Reynolds: slides should be able to see the top menu there very good okay.
7:43
Alexandria Reynolds: So in the brain we have flu Okay, we have extracellular fluid that's outside of the cell and we have intracellular fluid that's inside of the cell okay extra being out in troubling it.
8:01
Alexandria Reynolds: These concentrations of fluid okay contain different island.
8:08
Alexandria Reynolds: Some of the most the biggest concentrations are sodium or na plus right okay so i'm going to probably refer to almost all of these five their like their actual chemical name.
8:27
Alexandria Reynolds: symbol so just make sure that you know if you keep forgetting to write it on the side of your notes.
8:35
Alexandria Reynolds: notice that sodium is have what church.
8:40
Alexandria Reynolds: Was it high potassium.
8:44
And the brain has what church.
8:47
Alexandria Reynolds: Positive and chloride, and the brain has a witcher.
8:52
Alexandria Reynolds: neck so it's important to understand that these different molecules have different.
9:03
Alexandria Reynolds: um chargers okay that's going to play into importance, a little bit later as we start to talk about the the. Matthew Holding: Actual charges.
9:17
Alexandria Reynolds: Also, besides these on molecules are different sizes and we're going to get to that in a few minutes to why that's important, so the the ions. Alexandria Reynolds: sodium potassium and corn and other ones like large protein molecules move in and around the cell according to those those principles that we just talked to that electrical gradients and concentration gradient Okay, they move according to diffusion.
9:47
Alexandria Reynolds: we're going to talk about specifically how it does that in and of itself.
9:52
Alexandria Reynolds: When you see movements of these ions across the whole cell membrane hey we're going to see.
10:01
Alexandria Reynolds: The action potential.
10:03
Alexandria Reynolds: And the action potential is the firing of the cell.
10:09
Alexandria Reynolds: For when I say that a cell of neurons firing I am saying that it is displaying an action potential.
10:20
Alexandria Reynolds: So those are two terms of going to use interchange so I might say when you see the action potential and, I might say what the cell fire they mean the same thing okay good everybody knows or did most people are familiar with.
10:35
Alexandria Reynolds: find a sword on gas at I just trying to judge what how how how much you guys are coming back so any questions so far, trying to go through this kind of slowly so that everybody can have the same sort of foundation everybody did I going too slow.
10:53
Alexandria Reynolds: to catch it says like now I just go slow okay now.
10:58
Alexandria Reynolds: Remember, probably back when we learn science and maybe six or seventh grade we talk, maybe even later I don't know I have zero capacity of understanding science now in relation to grades.
11:11
Alexandria Reynolds: You guys remember, we talked the thing oh resting potential Okay, a resting potential of something okay just sitting there waiting to be us back.
11:21
Alexandria Reynolds: So in the membrane of a cell, we have something called a resting potential and it's six out about a negative 70 milligrams so the resting state of the cell is actually negative.
11:36
Alexandria Reynolds: it's a negative truck okay so.
11:42
Alexandria Reynolds: Why negative seven okay.
11:47
Alexandria Reynolds: And you're looking at different books of bio psychology and physiological psychology and all the other names that you can call it. Alexandria Reynolds: You may say see slight variations of negative 70 negative 70 is the number that we've kind of settled on for teaching purposes, because of experiments done on different neural.
12:12
Alexandria Reynolds: So if you go into this field, you might find that different neurons have different resting potentials.
12:19
Alexandria Reynolds: And it might vary, you might see something negative 1560 they all sit on a negative level but we're going to sit settle with negative 70 So if I asked you like on a task, what is the resting potential of a cell what's the answer.
12:38
Alexandria Reynolds: Negative 70 mil okay negative 70 below so.
12:45
Alexandria Reynolds: How we come to determine this particular number is there a series of experiments.
12:53
Alexandria Reynolds: And we've been able to identify this by using a recording electrode and a giant squid so and i'll go over how that's been done.
13:05
Alexandria Reynolds: How is it that resting potential is maintain, first of all diffusion a lesser static pressure okay so electrical gradient concentration gradient all factors in there. Alexandria Reynolds: And the fact that there is leakage of certain ions across the cell membrane to keep it at a negative 70 okay so there's more negative ions we didn't sell.
13:35
Alexandria Reynolds: For it because it had a negative resting potential and we're going to go into what those are and how they move and how that changes the nature of the stuff that so we did so far, yes.
13:52
Alexandria Reynolds: Why does the number very it depends on the cell the kind of where it is in the brain it depends on the species because. Alexandria Reynolds: Everything that we really are facing the teaching staff offers up with giant squid so um so there's a little bit of variation based on speaking, but generally speaking it's a pretty you know negative level.
14:13
Alexandria Reynolds: And also, you know everything that we teach in neuroscience is like based on the study that we did 50 years ago.
14:20
Alexandria Reynolds: And it's been replicated and you know we're we're pretty confident of it but we're always learning new things about the brain. Alexandria Reynolds: So you guys might somebody in here might be like super into neuroscience of going to Grad school and learn why was taught this way but there's a lot of exceptions to the rule and it's just based off of what we're gathering and learning about so.
14:45
Alexandria Reynolds: Okay, good question any other questions.
14:48
Alexandria Reynolds: Everybody good so far we're going at a good pace this stuff can be kind of happy, so I want to kind of walk us through that because we're building up our knowledge and then i'm going to pay him hit you with actual potential okay alright so let's look at this real quick.
15:03
Alexandria Reynolds: So this is the cell membrane Okay, so this is the cell membrane Okay, this is what makes up the outer portion of the cell. Alexandria Reynolds: So at the outside of the numbering business, the actual outside of the cell Okay, so this is all that fluid that's sitting outside in between each cell right here is the barrier and then here we have the inside of the cell.
15:31
Alexandria Reynolds: So, this would be all the intracellular fluid and components within itself you're basically looking at inside the cell and here's the so here.
15:41
Alexandria Reynolds: Outside the cell and that's outside of the so memory everybody gets a phone now outside of the cell what you're going to see is there's a high concentration of core I didn't tsuneo at a relatively low concentration of potassium.
16:02
Alexandria Reynolds: And notice that the sizes of the molecules here are the size of the box represents like the concentration of them Okay, so you have a lot of chloride, and a lot of sodium.
16:15
Alexandria Reynolds: And that in high concentration is processing on the outside of the cell.
16:21
Alexandria Reynolds: So using electrostatic pressure fusion, it is maintaining these ions in the extracellular fluid.
16:32
Alexandria Reynolds: Low concentration of attacks, you know sit outside of the cell.
16:37
Alexandria Reynolds: It is more positive right everybody see that outside the souls were positive, because you have a high concentration of sodium. Alexandria Reynolds: And you have a low concentration of potassium but that's going to outweigh how much core is there, so it's going to maintain a positive charge outside of the stuff everybody's got so far.
16:59
Alexandria Reynolds: Now inside of the cell, we have a large concentration of large we call them large proteins, which is a negative charge a.
17:10
Alexandria Reynolds: And then we have a large concentration of potassium, which is a positive charge large, small concentration of chloride more concentration of Sony.
17:22
Alexandria Reynolds: Here, this the large proteins and the amount of chloride okay also lead to it being a more negative charge inside sitting at that negative seven you know Okay, and again the forces of electrical static pressure and diffusion are keeping that those molecules in place.
17:48
Alexandria Reynolds: Large proteins cannot get through the cell membrane because the molecular size is too big, they cannot really go back to that.
18:03
Alexandria Reynolds: or we're going to talk about pumps and how things move through here.
18:10
Now.
18:13
Alexandria Reynolds: inside of the cell is mostly potassium outside of the cell is mostly sodium and core now what is so important.
18:27
So.
18:29
Alexandria Reynolds: Okay, this is kind of gross.
18:33
Alexandria Reynolds: But if you were to lick the solution i'm excited to sell.
18:40
Well, we do.
18:43
Alexandria Reynolds: Have a salty right Okay, so if this helps you remember that all the fluid outside of the cell is made up of sodium and chloride, and that, together, gives a salt right.
18:59
Alexandria Reynolds: And that taste salty Okay, that if you were to with the outside of the cell, it would taste the salt I don't suggest it, but if you were giving out.
19:11
Alexandria Reynolds: Concentration gradient allows for these ions to stay in place.
19:18
Alexandria Reynolds: happy and being excited itself into the inside the cell and sodium court outside of itself.
19:26
Alexandria Reynolds: A letter static pressure explains why the inside of the cell sits at this negative 70 miles because potassium and.
19:36
Alexandria Reynolds: sodium wants to stay inside of the cell.
19:42
Alexandria Reynolds: And chloride, which is negatively charged wants to get out of the cell and away from all this potassium and sodium because it is opposite the charge. Alexandria Reynolds: Everybody understand football, so these two processes are explaining why the inside of the cell sits at a negative 70 high because the core ideas continuously trying to escape.
20:08
Alexandria Reynolds: And the concentration gradient is maintaining the cell voltage inside and outside of the cell as well, now there.
20:20
God.
20:28
OK.
20:31
Alexandria Reynolds: OK, so the question is off topic, but i'll attempt to answer the question is, if you were to lick the outside of our brain, would it be considered cannibalism. Alexandria Reynolds: and very odd question but i'll take a stab at it no pun intended i'm i'm pretty positive that cannibalism by definition is the consumption.
20:52
Alexandria Reynolds: of human flesh.
20:55
Alexandria Reynolds: So I think if you look at you're good and you're not considered a cannibal unless you're somehow getting some of that justin.
21:07
Alexandria Reynolds: very odd.
21:09
Alexandria Reynolds: answer.
21:11
Alexandria Reynolds: First time i've had that question now is why is the brain exposed.
21:19
Alexandria Reynolds: I don't know and perhaps the fact that you expose it might start to teeter you over to the cannibalism realm I don't know, but I believe it's actually a very interesting question did I answer her question.
21:34
Alexandria Reynolds: I do not.
21:36
Alexandria Reynolds: advise any kind of licking or consuming of human flesh.
21:42
Alexandria Reynolds: Just my disclaimer everybody's aware okay so Finally, there has to be a balance of concentration gradient electric static pressure in order to keep it all balanced in.
21:57
Alexandria Reynolds: A homeostatic right.
22:03
Now.
22:05
Alexandria Reynolds: let's talk about how we maintain the status OK, so the topics is sodium potassium transporters. Alexandria Reynolds: So the sodium potassium transporters help to keep the cell at its resting membrane potential of negative 70 mobile Okay, because it's constantly pushing sodium. Alexandria Reynolds: Out of the cell and pushing potassium back in now remember these are different concentrations of the two Okay, and how we're able to maintain.
22:41
Alexandria Reynolds: The bounce and so you look at the the figure okay here number one you see that an ATP as adenosine transporter train for protein. Alexandria Reynolds: which we won't really get into right now or later, but ATP is what we use for energy in the south and it requires this process of transport.
23:03
Alexandria Reynolds: requires energy, so this is why we're going to see ATP being included in this process, because without it, you can't function so can't work, so what you're going to see this process working here we have step one.
23:19
Alexandria Reynolds: Three sodium ions and an ATP being a.
23:26
Transport it through this particular case for the ATP is going to bind to allow us to actually give an energy to the best okay.
23:35
Alexandria Reynolds: That number two okay we're going to see the ATP change shape to allow for it to process to get the energy that it needs. Alexandria Reynolds: To send these three potassium i'm excuse me, these three sodium ions out of the cell hey remember is inside of the cell we're throwing these bad boys out okay so three sodium get pumped out.
24:01
Alexandria Reynolds: With the use of of ATP right now you're going to see that the shape change of the transporter pump that is allowing the sodium to. Alexandria Reynolds: push out of the cell but also enables the potassium to buy OK, so the three sodium get booted out and then the two potassium is allowed to bind change shape again and push that into the cell so for every three sodium molecules that the self pushes outside it brings in to potassium.
24:48
Alexandria Reynolds: Now, what does that do to the charge if we're pushing out three positively charged molecule and only accepting to positively charged molecules in what is this doing to the cell inside the cell charge was.
25:06
it's it's keeping it negative.
25:09
Alexandria Reynolds: Because it's dumping out, not all the positive but is dumping out more positive than is taking it don't make sense.
25:18
Alexandria Reynolds: Everybody got that Okay, so these very specific sodium potassium transporters are allowing.
25:29
Alexandria Reynolds: me to throw out with the use of ATP changes the shape of the transporter.
25:38
Via.
25:40
help.
25:42
Alexandria Reynolds: In a while to sodium to bind to fix it to tap into by three sodium go out to passing.
25:51
Alexandria Reynolds: back and allows it to come inside this up, I know I keep switching it, but you guys see it on the thing and how right yeah.
26:01
Alexandria Reynolds: Excellent another cannibals and watching here.
26:09
Alexandria Reynolds: Because we get we can actually with this this.
26:12
Alexandria Reynolds: And you can measure the concentrations and you can measure how much is going in and out, so we can actually take a snapshot of this and different level and be able to to to tag this is.
26:26
This person.
26:28
that's.
26:30
Alexandria Reynolds: All right, any other questions are we good.
26:34
Alexandria Reynolds: Now this process is going to keep repeating and cycling through maintaining that resting potential so.
26:43
Now.
26:47
Alexandria Reynolds: let's talk about Ion okay so.
26:52
Alexandria Reynolds: There are proteins that are embedded.
26:56
In the cell membrane wall.
27:01
Alexandria Reynolds: That can allow certain ions to leave an errand and remember.
27:09
Alexandria Reynolds: that the whole point of this is to keep cells at a resting potential negative 17 goals and phil is ready for the action potential to send the electrical signal for.
27:23
Alexandria Reynolds: The first step of the action potential is the opening of the sodium channels to allow for a change in charge of the inside of the stuff.
27:38
Now.
27:40
Alexandria Reynolds: transmitter receptors are these are chemical receptors.
27:46
Alexandria Reynolds: actually contains the cloud for quicker function and faster distribution of electrical signal and it not necessarily the signal is faster the reactions faster okay.
28:00
Alexandria Reynolds: So we're going to talk about to voltage feed and chemical live and eat it i'm a types of.
28:09
hours a day.
28:12
Alexandria Reynolds: or so we good so far, this is a really nice visual here, this is an Ion channel that's close not accepting any eye on this one I hears oh man right and that's allowing for the change in molecular distribution.
28:30
Alexandria Reynolds: So, in order for us to make conclusions about what an actual potential is and how it works okay i'm gonna just very briefly describe the process of how we look at this and how we studied. Alexandria Reynolds: sort of big science So what do you need to learn about the neuron obviously you need to start with a Sally the neuron.
28:55
Alexandria Reynolds: You need some way to measure electrical current in the neurons to be able to actually test this and you need an Ionic solution to store this in so that you can basically replicates what you're seeing brain, so this particular experiment is done with a squid giant Axa not a giant squid.
29:17
Alexandria Reynolds: squid giant X and the way that it's worded deception very particular this actually is it large enough that you don't need a highly powerful microscope to use this why they use, specifically the giant accent, and then you need the ability to be able to record.
29:35
Alexandria Reynolds: The process and you also need stimulating electrodes in order to again follow the process, the actual potential for this is what the setup looks like.
29:47
it's actually.
29:49
Alexandria Reynolds: really interesting to see this so you're seeing that we have petri dish with the defiance squared X in here. Alexandria Reynolds: And then we have the volt meter so that you can actually test to see what voltages we have the wire electro that's placed in this saltwater solution and then we're able to conduct the electricity, this is actually put into the action itself.
30:16
Alexandria Reynolds: Then we have a simulator and then we have the ability to report it.
30:21
This here is basically where we record the electrical impulse.
30:28
Alexandria Reynolds: And then we're able to determine at the resting state and then we're able to determine an actual potential what the voltage change is what it looks like a cross the X factor for that car, we would do this and allow.
30:46
um.
30:47
Alexandria Reynolds: So there have been good, you know you can you can take neurons out of the bridge screen and you can.
30:58
Alexandria Reynolds: You can serve them.
31:01
Alexandria Reynolds: there's so much smaller that it's hard to get a good idea of of what this looks like.
31:10
Alexandria Reynolds: A lot of what we do with this week called translational research is we make assumptions, we say well.
31:17
Alexandria Reynolds: The structure is the same or identical the process appears to be identical when observing it and other factions.
31:27
Alexandria Reynolds: So that's kind of like taking what we know, building on it based off of these kinds of experiments. Alexandria Reynolds: If you take sensation and perception with me you'll see that we do the same sort of thing with animal work and looking at things like the visual system. Alexandria Reynolds: of hearing things like that these experiments are done with a brain as close as we can get to the human brain, which is usually non human primates.
31:52
Alexandria Reynolds: and looking at the structures and the makeup and saying well, these are basically identical so you take the information that you learn there can you apply it to the human brain. Alexandria Reynolds: So we're taking what we learn our larger scale and applying it to the same cell structure as a human and saying this is how it works that make sense.
32:14
Alexandria Reynolds: Any other questions.
32:18
Alexandria Reynolds: All right.
32:20
So.
32:23
Alexandria Reynolds: What did we learn from doing these experiments on on a switch jocks okay so we've learned that the resting potential is a different charge. Alexandria Reynolds: When the neuron is at rest versus when it's active okay so we're running we're settling on that negative 70 bills being the resting state and then that the inside of the shark cell is charged negatively in comparison to the outside of cells, the positive charge.
32:57
Alexandria Reynolds: Any stimulants that elicits an action potential tool.
33:04
Alexandria Reynolds: which we call a sufficient stimulus that crosses that threshold is caused by the movement of those positively charged ions the potassium. Alexandria Reynolds: And sodium, we know that the action is what carries the electrical impulse to the end of neuron and we know that the change in the membranes potential in charge happens as it moves down that.
33:33
Alexandria Reynolds: Okay, so you actually see it changed from a negative 17 novels to a positive charge as it moves that electrical impulse down the hacks hi I have a YouTube video on here it's a.
33:50
Alexandria Reynolds: Like a not a cartoon but it's like a computer graphic what electrical impulse probably looks like anything with brain so that's just a neat way to kind of visualize how we do that.
34:06
Alexandria Reynolds: Has anybody been able to access the self service human anatomy APP yet.
34:12
Alexandria Reynolds: Is it on there excellent so you guys now have access to the human anatomy APP it's called human anatomy atlas. Alexandria Reynolds: It should be able to be installed from self service if you don't see it, let me know, but you should it should be able to see it, because if you're enrolled in the class.
34:30
Alexandria Reynolds: We won't be messing with that yet because we can't look at molecular stuff on it, if you only look at kind of big big brain stuff but we'll we'll be using that in class probably next week or the week after.
34:43
Okay.
34:45
Alexandria Reynolds: Any questions so far.
34:47
Alexandria Reynolds: Okay, all right.
34:50
Alexandria Reynolds: Now let's look at what the action potential looks like honest autograph okay so.
34:59
Alexandria Reynolds: When you chain.
35:03
Alexandria Reynolds: Inside of a cell and negative charge to a more positive charge right you're changing.
35:16
Alexandria Reynolds: When you change the charge you're basically causing it to engage in an electrical stimulation.
35:26
Alexandria Reynolds: That.
35:28
Alexandria Reynolds: That follows all the way down the accent of the cell in next step, stimulate the next cell.
35:37
Alexandria Reynolds: And if it's strong enough signal to the next cell, it will then potentially cause the next one as well depends on where it's attached to the cell in excel.
35:49
Alexandria Reynolds: And what the other cell is do okay so we're going to talk about that here in a minute here's what it looks like on a graph So this is the threshold, so this is right here, this is this right here is the resting state.
36:06
Alexandria Reynolds: So, if you look at where the cursor is pointed here okay everyone states of the cell is sitting at a negative 70 mil okay this cell is just sitting there minding his own business nothing's happening it's just resting OK now another cells i'm.
36:26
connections.
36:29
Alexandria Reynolds: Possibly connected on to the cells, then dry or so body.
36:34
Alexandria Reynolds: is sending a signal to the cell saying hey wake up.
36:41
Alexandria Reynolds: What we're seeing.
36:45
Is.
36:49
Alexandria Reynolds: winning.
36:52
Alexandria Reynolds: So we got ahead that's it no see that Okay, we got hit number one it's nothing that number two did nothing with number three is it nothing still maintaining its resting states so each time this cell gets hit it's charged shane olu.
37:15
Alexandria Reynolds: So, each time it gets hits.
37:18
Alexandria Reynolds: charge are starting to make this sell a little bit more.
37:27
Alexandria Reynolds: So number one changes it from negative 72 maybe like.
37:35
Alexandria Reynolds: A negative 65 Okay, but that's not enough for the cell to respond by then another hit no.
37:47
Alexandria Reynolds: Over stimulation more sodium and potassium.
37:52
Alexandria Reynolds: is for it to hit a certain threshold in this case and, again, this is something that you might see the number change a little bit based on the book. Alexandria Reynolds: And this case, the negative sap the negative 60 and the threshold of excitation so when it hits when the chart changes from negative 17 and this graph in this case the negative 60 it starts the process of the action potential.
38:25
Alexandria Reynolds: Once the process starts once the threshold is pit it's an all or nothing everything starts to work he doesn't need any more stimulation it doesn't need any more signaling any more messages the cell takes over from this point okay.
38:49
Now we're starting to see.
38:53
Alexandria Reynolds: I am flood the cell positively charged ions flood the cell so every cell was at a negative 70 minding its own business it got enough stimulation to drop it to a negative 60 okay.
39:10
Alexandria Reynolds: To increase.
39:12
Alexandria Reynolds: Right, what happens to the charge yeah positively charged ions rush to sell.
39:24
This this all become more positive or more Nick.
39:30
Alexandria Reynolds: It becomes more positive so if it's sitting in a negative resting state of negative, so it gets simulation to set it at a negative 16 becoming more positive, which are. Alexandria Reynolds: Now, in his for threshold and all of a sudden, potassium rushes now it's going to change the charge of the inside of the cell, to be more positive In fact it happened so fast and there's so many I on the Russian it become positive which.
40:05
Alexandria Reynolds: is zero So it goes from the resting state of negative 72 the threshold of negative 16.
40:16
Alexandria Reynolds: hits the switch now it's going to Russian to hit a positive 40 so it's going to get so positively charged but it's actually going to call the inside, to now.
40:28
There may see that.
40:30
Alexandria Reynolds: So certain.
40:38
Alexandria Reynolds: And the p.
40:41
Alexandria Reynolds: bars for.
40:45
Alexandria Reynolds: high, but if I were to ask you what a P positive charge that the cell membrane gets to the number.
40:56
Alexandria Reynolds: Two, what is your answer.
40:59
Alexandria Reynolds: What.
41:02
Alexandria Reynolds: It at home to if you want to answer as well as positive force very good, positive 40 so.
41:12
Alexandria Reynolds: Once I hit that peak positive charge hey once it hits the peak positive charge, it will then.
41:22
Alexandria Reynolds: it's Max and start pushing out that pause those positive vibe.
41:28
Alexandria Reynolds: So it's good to push out because of.
41:31
Alexandria Reynolds: What happened to get started to sell it good to pushing out all the positive item.
41:40
Alexandria Reynolds: So now become.
41:43
Alexandria Reynolds: More night exactly so now the cells becoming more negative.
41:50
Alexandria Reynolds: Right.
41:51
Alexandria Reynolds: And then.
41:54
Alexandria Reynolds: And hits the resting state again and negative seven.
41:59
Alexandria Reynolds: But this process, remember, we all talked about regulation from your circulation it actually overshoot and this process of hyper polarization and actually.
42:12
Alexandria Reynolds: dips below even more the negative 70 and hits about negative 80 or so and it's got to kind of.
42:23
Alexandria Reynolds: regulate itself back to negative seven.
42:27
Alexandria Reynolds: And during this process of hyper polarization hey it does not have the ability to fire again it's kind of regulate itself.
42:38
And we'll talk about this in just a second.
42:41
Alexandria Reynolds: Does everybody see that.
42:47
Alexandria Reynolds: As the cell gets the simulation going to change from a negative 70 hit the threshold to negative 60 or so. Alexandria Reynolds: that's going to start the process it's going to it's going to change its its charge to a negative 240 and then it's going to dip down all the way below. Alexandria Reynolds: Negative 70, and that is going to be upgraded again and now, at this point it's ready to go to to fire again, and this whole thing takes about three milliseconds.
43:20
And it fires over and over and over again.
43:23
Yes.
43:32
Alexandria Reynolds: yeah we're I have another graph that and so that all dogs like get.
43:39
Alexandria Reynolds: over any questions so far are we good.
43:43
I should have another draft that that actually has three terms on it so.
43:48
Alexandria Reynolds: I don't i'm going to put that in there because it's really easy to tell the difference.
43:55
alright.
43:57
So here.
43:59
Alexandria Reynolds: Is the steps here are the steps each points all right.
44:10
Alexandria Reynolds: Alright, so we're at negative 70 the threshold of negative 60 is it at this point the sodium channels open and then study and search the flood the cell. Alexandria Reynolds: And then step to the potassium channels are going to flood the cell so First, we have the sodium channels opening that's going to start getting it to more positive charge.
44:33
Alexandria Reynolds: Right after that task sam's gonna open up continuing to make the inside the cell are positive, and here the pig is next. Alexandria Reynolds: Now the sodium channels are refractory they can't do anything right now they're kind of second is refractory state.
44:50
Alexandria Reynolds: So no more sodium enters the cell so, then that means that the cell can't become more positive because it's not accepting it anymore positively charged ions, then what we see is that potassium is so that pete is hits potassium will start leaving itself.
45:08
Alexandria Reynolds: And we have at the met the the potential starts to go to rest level this step here, we, the potassium channels are closing sodium channels for resetting but in the process of the sodium channels resetting it's going to dip a bit below.
45:26
Alexandria Reynolds: And then those extra potassium cells ions excuse me, are going to then diffuse and get back to the negative 70.
45:36
Alexandria Reynolds: Back everybody good so far, and here again here are the different steps here, this is step one with the channels opening here's the refractory period where it's closed, and then the sodium channels are there.
45:51
Alexandria Reynolds: That allows for us to do it over and over and over again until you die okay any questions about that so far.
46:00
yeah.
46:02
Alexandria Reynolds: See, we have read polarization hyper polarization the polarization and I thought I had a table in here that should only.
46:11
i'm gonna have i'm gonna have to go back.
46:14
Okay.
46:17
Alexandria Reynolds: When it comes to refractory period Okay, there are two types of refractory periods that occur after an action potential happens.
46:27
Alexandria Reynolds: So we have an absolute refractory period where the cell is essentially halted for just about a half a millisecond where it can't do anything else okay.
46:43
Alexandria Reynolds: How many of you have ever flushed the toilet.
46:47
Alexandria Reynolds: And then realized that you probably need to watch it again, for whatever reason, right and you tried to do the little flusher and it just like to anybody ever experienced that night.
47:04
Alexandria Reynolds: What that toilet is still.
47:07
Alexandria Reynolds: His experience experiencing an outstanding refractory period, what has to happen to the toilet for it to be able to flush again.
47:20
Alexandria Reynolds: It has to fill back up with water in the back right so in the process of it feeling that water that's what's going to happen okay you're just gonna have to sit there and watch right. Alexandria Reynolds: And then, once the toilets ready and filled back up water, then when you push the flat, you know when you when what is that called.
47:43
Alexandria Reynolds: flusher handle right what to do the handle of the toilet it's gonna flush again same process with the with the neuron. Alexandria Reynolds: It goes through this absolute record period where it cannot fire again it just physically can't and why do you think we should have an absolute refractory period for our reasons.
48:05
Alexandria Reynolds: Why is the support.
48:10
Alexandria Reynolds: It needs time to rest absolutely what happens if a brain cell can't read.
48:23
Alexandria Reynolds: What if it can't go back to homeostasis what happened for itself.
48:31
i'm hearing some mobile.
48:33
Alexandria Reynolds: It burns out is essentially a contract what happens to fried cells, they thought right exactly.
48:43
Alexandria Reynolds: So when you have cells that are firing too often and not experiencing this absolute refractory period essentially what you're having is you're you're burning yourself and that's not a good thing that's not a healthy cell Okay, you can actually see this happen with conditions like.
49:01
epilepsy.
49:03
Alexandria Reynolds: epilepsy is when you have excessive firing of neurons that's not good for your brain not good for your brain to have the success of firing and areas that aren't supposed to be firing.
49:16
Alexandria Reynolds: Right, and that is not.
49:19
Alexandria Reynolds: that's not going to be conducive to a healthy set of cells for your brain.
49:24
Alexandria Reynolds: Now we also have a relative period, which we call the relative refractory period where it's unlikely that the south can.
49:34
Alexandria Reynolds: Fire again, it can happen, but there is a period of time where it isn't a resting period where it normally does sell fire.
49:46
Alexandria Reynolds: And what drives, these are the opening and closing of the of the sodium channels say so in cases where we have close close up cannot channel we can't have that Russia positive ions and therefore it will not allow for it to change in charge to allow for natural essential to.
50:06
Alexandria Reynolds: Any questions about that yes.
50:13
Alexandria Reynolds: that's a good question, so what sells have the absolute worst is a relative of refractory period. Alexandria Reynolds: I want to say I don't know the answer off the top of my head I don't know if it's always sell specific I think it's more sometimes location, specific and I think it's based off of some motors, which reflect themselves.
50:35
Alexandria Reynolds: I think we might cover this a little bit later, but I can't think off the top of my head. J.P. Stallard: When having one or the. Alexandria Reynolds: Other it's more of like there's a period of time right before the absolute period where there's the refractory and then a period after this you know saying.
50:52
So um that's probably a better explanation of the two together, then sells itself yeah.
51:00
Any other questions yeah.
51:07
Alexandria Reynolds: What causes the change in the status of the positive versus negative, so the whole thing starts with a stimulation from another cell. Alexandria Reynolds: So and we're going to get to that so you'll see so the exchange of information from cell the cell is chemical that chemical message could say fire or don't fire.
51:30
Alexandria Reynolds: When enough message is received that stimulation will will signal the cell, to have an electrical impulse and that's where the solid.
51:39
Alexandria Reynolds: And we're going to talk specifically about what is enough, and what were wearing wearing his order to get the process started okay all right any other questions about refractory period or the process and of itself, are we all good so far.
51:57
Alexandria Reynolds: just give me a thumbs up if you're following along.
52:02
Alexandria Reynolds: yay Thank you guys all right now very important feature of the action potential is something called the all or none well. Alexandria Reynolds: Once the action potential begins, once it is trigger it goes down the length of the accident it either happens or. Alexandria Reynolds: You don't have a partial action potential we don't have a great action potential we don't have a sort of kind of action potential we either have messages sent or the message is not set.
52:36
Alexandria Reynolds: One of the other all or none other happens or doesn't happen now, we do have something called the rate law and that's about intensity of the stimulus and that can change the rate. Alexandria Reynolds: And variation of fire, so the rate law is not doesn't fire or not necessarily or how fast fires, the rate lock is what's the firings.
53:06
back or.
53:10
Alexandria Reynolds: Well, but it's not.
53:14
Alexandria Reynolds: Like how strong each one is it's the rate.
53:19
and frequency.
53:21
Alexandria Reynolds: Of the fire that's the right one day so variations and intensity how fast and how quickly, are they from back to back, as well as variation great i'll be accident so in terms of fire okay so.
53:42
Alexandria Reynolds: Here we see.
53:46
a shorter period.
53:50
versus.
53:52
Alexandria Reynolds: longer period.
53:55
Alexandria Reynolds: of actual fire that makes sense.
53:58
Alexandria Reynolds: And that is taken through the.
54:04
giant.
54:05
axl rose good.
54:08
back any questions so far we good.
54:12
Alexandria Reynolds: All right.
54:13
Alexandria Reynolds: Now.
54:16
Alexandria Reynolds: we've talked about this a little bit before, but this is where we're going to explain how this works with the myelin sheath.
54:22
Alexandria Reynolds: Action potentials are regenerate down the length of the accent so as it hooks from know to know we're seeing those ions move.
54:36
Alexandria Reynolds: In the membrane of the accident continuously to allow for that electrical impulse to continue down the length of the axis. Alexandria Reynolds: So what you're seeing here is that the sodium and potassium channels open along the length of the accent okay I open open open open.
55:00
Alexandria Reynolds: Here here here here over here here here here here here and in each section of the expose the accent okay we're seeing this process repeat and we call us a regeneration because we're essentially recreating the actual potential at each open spots.
55:18
Alexandria Reynolds: Because.
55:20
Alexandria Reynolds: The myelination occurs in my wedding Friday tissue here is going to change the conduction Okay, and it can't do it in that particular spot so he's got to regenerate and jump nodes at every point of the nodes are ready for here.
55:40
Alexandria Reynolds: These nodes around va allow for the electrical impulse to continue to regenerate until it hits the end of the APP okay.
55:51
Alexandria Reynolds: So the myelination or the myelin sheath are going to increase the speed of conduct conduction and allow it to go faster.
56:02
Alexandria Reynolds: From those mode right there salvatori conduction.
56:06
Alexandria Reynolds: So at this point there are fewer sodium and potassium channels that have to open at each node allowing for faster conduction if we had no my one cheese imagine this.
56:23
Alexandria Reynolds: We have no my one sheet that would mean that every sodium and potassium pump.
56:30
Alexandria Reynolds: And channel a one the entire way.
56:34
Alexandria Reynolds: His job would have to be open, open open.
56:40
Alexandria Reynolds: That would take a long time and it's not smooth and if we have a disruption that's going to cause a problem for that electrical impulse to go down the length of the acid. Alexandria Reynolds: However, if we only have sections of sodium potassium channels, but have to open at any given time it's going to allow for faster processing of those Ion movements to allow for faster conduction download like the bx now.
57:13
Alexandria Reynolds: vs Evan Evan Evan Evan Evan Evan Evan Evan Evan Evan Evan you see how that changes how fast that message just from note to note if we're like I mean i'm i'm gonna i'm gonna have it open versus.
57:27
Alexandria Reynolds: So the myelin sheath are giving us the opportunity to cover the cell in such a way that speeds that electrical impulse up from node to node that makes sense, the rosina.
57:43
Alexandria Reynolds: Any questions at home so everybody see what how the myelin sheath work to live for less surface area of the nodes of Ram va to requires a steady potassium channels to open.
57:56
Along goal.
58:00
Alexandria Reynolds: So to summarize, all of this together.
58:04
Alexandria Reynolds: The activation of a neuro on.
58:09
Alexandria Reynolds: Through the signal from another cell and enough stimulation occurs to cause an actual potential to have.
58:17
Alexandria Reynolds: The action potential that propagate down the length of the accident jumping from know to note of the nodes around da to the end of the civil what happens now, when it gets.
58:31
Alexandria Reynolds: So the cell is got this electrical impulse that runs throughout it now it's going to hit the end of the cell and then release the chemicals to send a message to the next cell, whether or not to fire and what kind of chemicals, for it to release if it does.
58:52
Alexandria Reynolds: That so it's a complex message of what the next cells job.
59:00
Alexandria Reynolds: And the kind of cell and the location of the cell it's going to give us information as to what kind of chemicals that sells producing and synthesizing. Alexandria Reynolds: And what message is getting sent from point people back so it's going to depend on what kind of sell it is going to depend on what kind of chemicals and synthesizing to determine what that message is going to be and then we'll come.
59:25
Alexandria Reynolds: back that so if we look at this right here, this is a sending sell this is the terminal but.
59:33
Alexandria Reynolds: Here we have the micro tutorials that's coming from the accent.
59:37
Alexandria Reynolds: And then we have different ways that the Chemicals can be transported and synthesize whether the cell body, whether they get transported to the accident. Alexandria Reynolds: Or whether there's synthesized and housed here in the terminal buttons, this is the receiving end, this is the dendritic cell body here the post synaptic area where it's going to then receive the chemicals from that action potential message.
1:00:03
everybody gets.
1:00:05
The same clear.
1:00:08
Alexandria Reynolds: Then we're going to go over this process and how cells.
1:00:15
get this information, what they do.
1:00:18
Everybody good so far.
1:00:21
Alexandria Reynolds: My have will do one last slide and then we'll end for today and i'll OK, so the very.
1:00:30
Alexandria Reynolds: crux of this, why do we care about the actual potential and then sending a signal the Salomon itself has stuffy our true potential.
1:00:40
Alexandria Reynolds: Now, what does it do.
1:00:43
Alexandria Reynolds: The next cell has to determine if it's going to also fire an actual potential, but it takes the information from the previous cell to determine okay.
1:00:53
Alexandria Reynolds: So, in order to receive information and chemicals, it has to have the ability to have receptors to accept the kinds of molecular shapes that the cell is trying to give to.
1:01:08
Alexandria Reynolds: So here we have the terminal button of oneself.
1:01:14
Alexandria Reynolds: The den greider cell body of the receiving sell high So the message has been sent, and this electrical impulse has activated the cell the actual potential occurred, now we have these chemicals to relay another message, so this right here the priests genetic memory.
1:01:36
Alexandria Reynolds: It contains testicles are stacks that contain chemicals notice neurotransmitters neurotransmitters are things like dopamine serotonin see to cali calling, these are all different kinds of.
1:01:52
Alexandria Reynolds: Chemicals right and then here we have the synaptic cleft or synaptic gap.
1:02:02
Alexandria Reynolds: Which is essentially a very, very tiny open area not physically attached itself it's an open area physical space between neurons where the chemicals then get sort of exchange.
1:02:17
Alexandria Reynolds: And then, finally, you have the post synaptic receiving end, and this has receptors that are designed to take in very specific chemical structures. Alexandria Reynolds: So if you have a cell that's giving it doesn't mean you have to have a doberman nergis receptor to accept that chemical message, like a lock and key so think of the chemical like docu me as the key.
1:02:47
Alexandria Reynolds: And the law would be the receptors that are on the cell they got a lot into place in order for it to take that information. Alexandria Reynolds: back so next time we will talk about specifically the best schools and how the chemicals are general synthesize within the cell where there's synthesize and all that does anybody have any questions about the material.
1:03:15
Alexandria Reynolds: Everybody good okay at home is anybody have any questions about the material.
1:03:22
Alexandria Reynolds: Alright i'm going to go ahead and end the recording.
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