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BIOL 2301 Human Anatomy & Physiology I - 2103_lecture21_0414
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00:05 All right. So, what you're at up here, I think there's
00:10 slides in a row. There might five slides from your previous lecture that
00:15 kind of skipped over. And I when I did this, um probably
00:20 move them in. The slides for all and I moved them together because
00:26 makes sense together. Do that kind makes sense. So if you don't
00:29 them in front of you, don't . I don't think the notes are
00:34 or the the information here is particularly or anything that you have to
00:38 oh no, I've got to find . All right, and what we're
00:40 do, there's a couple of things gonna look at today first, we're
00:43 to just kind of deal with these of dealing with um how signals are
00:50 or magnified and organized. Not but modulated. That's kind of the
00:55 thing they should take like 5, minutes maybe. Then what we're gonna
00:58 is we're gonna then jump in and gonna look at these somatic sensory
01:02 ones that kind of referred to um I gotta remember today's thursday two on
01:07 , and and we're gonna look at they're organized and then we're gonna jump
01:11 the eyes and we're gonna look at structure of the eye and what a
01:16 bit of its organization. And then come back after the weekend. Then
01:21 going to look at the physiology, the I actually processes information. So
01:27 kind of the order in which we're today. So like like I
01:30 the first five slides may seem like did they come from? So,
01:37 of them are going to like the look kind of stuff that you've seen
01:41 . So, our starting point here how do the neurons code signal
01:46 And we've talked about this, we said, look, when you're dealing
01:50 a signal, right, we're producing greater potential up here in the cell
01:55 that if it's strong enough and reaches axon hillock, it's going to produce
01:59 potentials. So, you remember That's that's review. And so that's
02:03 this kind of showing here up This is the stimulus that's being
02:07 So, remember when we're talking about , the bottom line represents off the
02:11 line up here represents represents on And the line that's vertical going up and
02:17 kind of tells you how intense it . So this is smaller than
02:21 which is smaller than that. And this is not very intense. This
02:24 more intensive. There's lots or very . Right? That's how we're looking
02:28 the picture. And so it says , when we have this low
02:32 we don't produce a very strong graded . The greater potential is is really
02:38 of weak. It's not enough to the threshold. So because it doesn't
02:41 threshold, you don't get action potentials the length of the neuron, that's
02:45 what that first picture is showing But over here it's saying,
02:48 all right, so here we're getting little bit more intensity. And so
02:52 going to produce a stronger receptor What is a greater potential? And
02:57 that greater potential is enough to get threshold. Which produces action potentials that
03:02 travel down the length that results in release of a neurotransmitter. Okay,
03:07 far so good. And then lastly , look, but when the intensity
03:10 even greater, what's going to happen we get a greater potential greater potential
03:15 there are great potentials will have a equivalent to or similar to the magnitude
03:21 the stimulus. So that's going to an even greater period of of potential
03:29 above threshold, which results in a frequency of action potentials. Now,
03:35 you're looking at these lines going to like an action potential that I've seen
03:38 , remember when we're looking at an potential is over a graph that was
03:42 milliseconds. And what they were doing there stretching it out. And what
03:46 doing in this picture is they're saying you're recording like say over a
03:50 this is kind of what an action looks like it looks like a line
03:53 us. And so there's this long between action potentials here that look long
03:58 us. But relative to that. we can see that there's more action
04:02 in between there. Right. And the reason we have a full action
04:06 because of what unique feature about an potential starts with an R. And
04:11 ended the period. Refractory period. ? So that allows us to go
04:19 and then back off. Right. the actual potential. And then you
04:21 that period of time where it's kind a rest and then you get another
04:24 . And so what they're saying is you're getting more and more and
04:27 So here's the here's the image. want you to picture picture and need
04:30 picture. A needle picked up the morning still and if I barely touch
04:37 with the needle that's what it's You're not even gonna feel it.
04:41 . But if I come up to and go you know you might like
04:45 you feel it and then imagine me a running start and to handing a
04:49 into your arm as hard as I . Well there you go, that's
04:52 third one. So there's an example how we encode intensity when it comes
04:58 the senses or when we're talking about sensory information. Alright. It's encoded
05:05 the frequency of the action potentials. the greater the stimulus it goes through
05:12 that process. Okay. Greater the or is greater than magnitude. That
05:16 greater magnitude greater potentials which means more above threshold which means more action
05:22 That's what all this stuff is telling . But that's not the only way
05:26 we can encode strength and greatness, ? Because there's a point where you
05:31 produce more action potentials. Mhm. the in a particular region, wherever
05:43 receptors are again, we're kind of about touch but this is kind of
05:47 for other things as well. Is you can imagine that there are multitudes
05:52 receptors. Alright. Would you agree that? Like if I was looking
05:56 my skin, we already said there's of a receptor range, you
05:59 or receptive field but you know, can have really, really small receptive
06:04 right next to each other. And the greater the stimulus, the greater
06:08 that I'm going to start stimulating more more receptors outside of that original
06:13 And that's what this is kind of you. It's like look here is
06:16 range of whatever system we're looking What happens is is that that first
06:21 becomes activated and as it's becoming activated can see now the second one becomes
06:27 because they have an overlap. And then as you keep going up
06:32 the third one does. And so of the reason we can determine or
06:36 or detect uh intensity is because we more and more and more receptors into
06:46 signal that's being sent forward. So can imagine one neuron is doing this
06:52 and then you can imagine two neurons doing this and three neurons. So
06:55 the first neuron as the signal gets and stronger like this. In the
07:00 one it's like this and then the one it's like this. And all
07:03 these signals are being sent forward to into into the central nervous system so
07:10 your perception then or your brain understands signal is becoming greater and greater and
07:16 . So the signal is encoded as by the frequency of the action
07:22 And it's also encoded by the number receptors that have been recruited during that
07:29 . That's number two. All So that's a twofold. That's what
07:34 is basically saying right there. Twofold that we detect intensity right now to
07:42 signals. One of the ways that are modulated before they even get into
07:48 central nervous system is through a process lateral inhibition. All right. And
07:54 the easy way to think about you know, or to demonstrate to
07:58 is get your pen right? And if you look at your pen that
08:03 using right now, you have a end and you have a blunt
08:06 right? If you touch yourself with pokey and and just kind of go
08:09 here, you can feel that it's single point, right? But if
08:12 turn it over that point becomes not single point, it's now a broader
08:17 , right? You kind of see So with lateral inhibition. What I
08:23 you to picture is the pokey Alright? If you take that pokey
08:26 and you look at it when you touch it, you see that's touching
08:29 single point. But as you push stylist end further down, you'll see
08:34 the indentation in your skin becomes right? And so what's happening is
08:40 does your brain know where that actual is? All right. And it
08:45 to do with the intensities that were describing. So at the point of
08:50 that would be point B in our cartoon up here. Alright. And
08:55 we increase the intensity, remember, recruiting outwards from that original point of
09:00 . But the strong stimulus as it's down produces action potentials that are going
09:05 travel along collaterals. So you can here's the pathway pathway for B.
09:10 for a pathway for C. And C. Are just areas outside
09:14 B. And what it's saying is as I'm moving that signal up to
09:19 nervous system here, I have collaterals serve to innovate the pathways on the
09:27 pathways and what they are, they're . They're basically, when I release
09:32 neurotransmitter, they inhibit the the signal this particular neuron is trying to
09:39 And so what happens is is it for an image for your nervous system
09:45 only the middle area is being stimulated it's not receiving the signals from A
09:49 C. In other words, you're telling you to I know you're being
09:55 but you're not as stimulated as I , so don't even bother sending the
09:59 upwards, I'm the important signal. so that signal goes up to the
10:03 , the brain says, oh that's stimulation is taking place. Alright,
10:08 it creates this larger contrast. So is what you're receiving up here,
10:15 ? That's what it would look So here's the greater intensity A and
10:19 lesser intensity, relatively speaking. But it arrives up at the level of
10:23 central nervous system really up at the , what it's basically saying is,
10:28 , here's B. It looks much bigger than it actually was,
10:31 what I've done is I've decreased or the surrounding signals. So I get
10:37 greater contrast and the brain perceives the of something large. Alright now
10:45 you can go back and think about a little stylist that I was showing
10:48 alright, when I poked myself, can see how I get that indentation
10:53 you can kind of see there. when I poked myself this direction,
10:57 kind of this broader structure that's poking exact same area that's being stimulated in
11:01 first place here, it feels thick , it feels pokey, right?
11:06 the reason it feels so pokey, though I'm stimulating the same areas is
11:10 result of lateral inhibition. Hello? . No, that's it, You
11:31 understanding exactly what I'm saying, so just repeat what he said, which
11:36 a repetition of what I said. stimulation in the center of this field
11:42 producing the largest signal. And as result of that, that signal inhibits
11:47 surrounding signals which are also being But they're being they're being downplayed or
11:54 . They're the reason why it's called inhibition because it's outside the central
12:01 And as a result, what you up here, right with the central
12:06 system perceives is not all of that , it's only the one that's the
12:12 point of stimulation because of that All right now, it doesn't just
12:17 in touch. Alright, this is for a lot of systems. All
12:22 , we're gonna be looking a little later at bipolar cells in the
12:25 And that's one of the ways bipolar work basically. One gets turned on
12:30 the other one gets inhibited turned off that's how your eyes can perceive the
12:35 before information ever even gets to the nervous system contrast. And what would
12:41 contrast would be light versus dark. example, in these areas, you
12:44 see the darker areas. So darker look dark, lighter areas look
12:49 And it's a function of this mechanism here called lateral inhibition. All right
12:59 , there's a term that we And this is I probably was a
13:04 that was in the other one. not it's a few slides forward in
13:07 particular section might be right after. might be right before the eye stuff
13:13 this slide because like I said I move things around cause I think they
13:16 better together. All right, so what we said is that when we're
13:20 at receptors, receptors respond to a signal, you can't put light up
13:27 a olfactory receptor and stimulated. every receptor has its own modality.
13:33 . And so what we say has particular stimulus for example. Alright.
13:37 so again by those same rules that just use, you know, the
13:42 has to cause a cell to reached . So there's a greater potential that's
13:46 to be produced. That greater potential referred to as a receptor potential.
13:50 if that greater potential results in reaching than what we've done is we've changed
13:56 modality. We've gone from whatever we're to that action potential and that action
14:03 is what allows the signal or the nervous system to understand what's going
14:08 And so it's the number of action that are being ascent the code that
14:14 the central nervous system to understand one . But two. Because of your
14:21 your detecting a specific signal through a receptor. The central nervous system knows
14:26 I get a signal from this particular , that means it's this type of
14:31 . Alright. So if I'm getting signal from my eye then it knows
14:35 I'm receiving light from this particular region my eye which means I'm seeing light
14:42 just say for example right over okay, if my nose is stimulated
14:47 receptors, a specific receptors get I'm detecting strawberry, How's that?
14:53 not really strawberry, but you get idea. Okay now we've talked about
15:02 and physic adaptation. This picture is and physic, right? But what
15:07 want to point out here is that is something that occurs at the level
15:13 the receptor as well as the level the central nervous system. Alright,
15:18 receptor, if it's constantly bombarded over over and over again, what will
15:23 is it recognizes that it's that it's overstimulated and so what it will do
15:30 it will create a mechanism or use mechanism to prevent overstimulation. One of
15:36 ways that it can do is so it's a cell for example, if
15:39 has lots of receptors, one of things it can do is it can
15:42 the number of receptors. Alright, if I have 100 receptors and I'm
15:48 being overstimulated, like well maybe I need that many receptors, let me
15:51 half of them away. So now have 50 receptors, so to get
15:54 same level of intensity, I have you know, really kind of overstimulate
15:59 cell. All right now what this , it allows us to adapt to
16:05 the particular stimulus actually is. And are different ways of adaptation that we're
16:11 gonna go into right now, but example that is an adaptation that we
16:15 to think about is like going from light area to a dark area.
16:20 , that's not adaptation. That's basically of the ways that our eyes determines
16:24 much how much light is getting into eyes. But an example of adaptation
16:30 be remember we talked about hot spicy and we all like hot spicy food
16:35 for people who like I'm not gonna about it, but it's like I
16:38 eat hotter and hotter and hotter In other words, as if I'm
16:43 eating spicy food. My body adapts this idea of like, oh everything
16:47 have has something spicy in it. , I have reduced the number of
16:51 . And so in order for me stimulate those receptors, I've got to
16:55 even more spicy goodness in my That's kind of a terrible example.
17:00 of sort of makes sense. All , so understand that the systems and
17:08 and adjust themselves through this process of . All right. So I told
17:15 it'd be about five or 10 So how good was I was?
17:19 17. Mhm. What are you to do? All right.
17:24 now what we're gonna do is we're to deal with these somatic sensory
17:27 So, when you hear the word sensory, remember Samantha's body sensory refers
17:31 basically tactile or touch. So, they're basically saying is where we're receiving
17:37 information from the from our body. right. So, we have uh
17:43 is an ascending pathway, meaning it from our body up to the central
17:48 system. So this is a ferret . This is information going from the
17:53 into the central nervous system. All . We sometimes um we're going to
18:00 it up into one of two ways can think of it in terms of
18:04 from below the neck. If it's below the neck, that means it's
18:07 to use spinal nerves, right? if it's above this point, that
18:13 you're gonna be using cranial nerves. right. So, pretty straightforward.
18:18 right. In terms of how we're this up, there's two major pathways
18:24 names. One is called the dorsal pathway, and it has another name
18:29 we're going to see in just a or the intro lateral pathway. All
18:34 . Now, if you pause and at this for a second, dorsal
18:38 also posterior and the other one is and lateral. Do you see what
18:45 got here? Basically, there's the parts of the white matter and that's
18:50 of the things you need to remember we're dealing with pathways we're dealing with
18:53 tracks or the white matter. do you guys see that?
19:00 So, the dorsal pathway, the column pathway deals primarily with fine touch
19:07 or appropriate reception. Alright, your of your body in space, the
19:12 . Collateral pathways primarily deal with pain or temperature. Now, are they
19:18 to that? No, but that's The primary information. Alright, so
19:24 that means is is the dorsal just to below the neck or just above
19:28 neck? What do you think? , that's good. No, that
19:33 the dorsal pathway has an above the and has a portion that's below the
19:36 . What about entro lateral that just or the other? No.
19:42 it's going to have an above neck below neck portion to it.
19:47 so what our starting point is is to be really? How do we
19:52 these in general? All right. , it doesn't matter which the matter
19:56 pathway. You have? All somatic pathways? I should be careful because
20:01 always an exception to the rule. generally speaking, there are three neurons
20:06 these pathways. Alright, so we're up and we call them 1st,
20:10 and 3rd order. You might read . Primary secondary and tertiary neurons.
20:16 , I even have up their tertiary if you look. But first order
20:21 order third order. If my starting is is in the periphery and my
20:26 point is in the cns which one going to be first order periphery or
20:30 P and s All right. Which going to be 3rd order cns or
20:36 cns. And where do you think second order is going to be between
20:41 two? That makes sense, Okay. So let's see first order
20:47 . The receptor is going to be on the first order neuron. All
20:52 . So, it's either going to closely associated with or it's going to
20:55 a part of like we were describing . Okay. On Tuesday.
21:02 it's job that receptor is to take stimulus, turn it into an action
21:06 and then conduct that signal inward. right. When we described um the
21:13 nerve we talked about information coming in information and sending information that first neuron
21:20 into the spinal cord. Remember, in the spinal cord itself. Body
21:25 located out in that dorsal ganglion. so there that's what that's representing.
21:32 where the dorsal ganglia would be out the periphery. All right. If
21:38 a cranial nerve, that's not where going to be. It's going to
21:40 in a cranial nerve, nuclei. right. So, understand information.
21:46 it's spinal nerve, it's going to in that language. Now, the
21:50 order neuron is going to project to secondary or second order neuron. Second
21:56 neuron is going to be found in central nervous system. All right.
22:01 , you can see here second order we're going to see it's going to
22:05 either up here in the brain stem it's going to be down here in
22:10 spinal cord? All right. And is it going to be in the
22:14 cord, the dorsal or posterior Remember we said when that when that
22:19 comes in? When we looked at gray matter, we said it terminates
22:22 there in that dorsal horn. So is an example of it terminating in
22:27 dorsal horn, right there. But some of them won't. They'll be
22:32 to the brain stem if you're originating you're not a spinal nerve. Look
22:36 you're gonna be a cranial nerve, where that nuclei is going to be
22:39 or nucleus. Now the second order you can see here whether it begins
22:45 the brain stem or if it begins here in the spinal cord is going
22:50 terminate up in the thalamus. All . So the third order neuron always
22:55 in the thalamus. What's the purpose the thalamus sort of sort information?
23:01 does that information need to go? right. So you can see I'm
23:05 somatic sensory information. We know where wants to go. It needs to
23:09 to the somatic sensory cortex but it to go to the thalamus first.
23:13 . Now, at some point it deca state and remember what it
23:18 It means cross. So here we see it's coming in on I guess
23:23 your case it's going to be on left hand side and it's devastating here
23:27 the right hand side here. You see I've entered it on the left
23:30 . I've gone all the way up the brain stem and then I'm devastating
23:33 to the right hand side. so if it's projected to the
23:43 we're dealing with this conscious sensations now are a portion and we're not going
23:48 dive into them, but some of may be going straight to the cerebellum
23:51 you're dealing with appropriate exception. In words, the position of your body
23:55 space. You do not need to aware of where my body is in
23:58 , but your brain needs to know it can tell your brain how to
24:02 about right? So that's why it's sent to the cerebellum. Remember the
24:06 was all about processing information in terms movement, so knowing where everything
24:12 it becomes important, so appropriate. goes to the cerebellum. Finally,
24:18 order neuron cell bodies over here in thalamus. So that's the red
24:22 That's going to go onto this sensory cortex and the parietal lobe.
24:28 one outside the body, into the , two from the spinal cord or
24:34 brain stand up to the thalamus, from the thalamus to the semantics century
24:41 . And that is every one of pathways with the exception of those weird
24:44 that are going to the cerebellum now look at the specific pathways. You'll
24:52 that I break them down. secondary and tertiary or 1st,
24:56 3rd order. All right. We , the dorsal deals primarily with fine
25:02 and appropriate reception. All right. has another name, remember I
25:07 when you look at the names, names tell you where they're going.
25:11 they are called the dorsal column, meniscal system or pathway. All
25:16 Which is a very, very long . But you're gonna see why
25:19 Alright. So, with regard to , these are my eliminated. All
25:23 . They're traveling up through that dorsal in the white matter of the of
25:31 spinal cord. Alright, so cell bodies are in the dorsal
25:37 They're going to enter into that dorsal column. The physically dorsal physically and
25:44 go into two different structures. If coming from the lower body, you're
25:49 to enter into this region called the is Godzilla's. Now, if you
25:54 when we were looking at the brain , there was a location we named
25:59 the brain stem that wasn't marked in picture. Remember that? It was
26:03 the nucleus Godzillas and had a friend the nucleus status. And this is
26:12 pathway that leads to that nuclei. , so the secular priscilla's meticulous
26:22 They're just tracks that travel up to particular location to those nucleus Godzilla's nucleus
26:29 . Alright, those that's what That's organ of the second neuron. All
26:33 . So, you have to lower it starts with a G. The
26:38 body starts with the sea. Now, here I say, it
26:41 Samantha Topi We've already talked about this basically as fibers enter in what they
26:46 . The ones that are closest to body are nearest to the medial
26:50 The ones that are higher up are lateral. And that's all this is
26:53 saying. And so you can see in the pathway, you know,
26:58 is lower, so it's going to on the medial side. This is
27:00 , It stays lateral. All So the brain stem is where we're
27:05 to see declaration and then you're gonna in from the nucleus. Godzilla's or
27:12 into the medial meniscus that's going to . That's just a pathway that projects
27:17 up to the thalamus. So, you see where the name comes
27:20 It goes up the dorsal column via the nucleus priscilla. Sir kenyatta's then
27:26 the medial limb. Discus up to thalamus from the thalamus to the primary
27:31 cortex. Alright. And what are doing? Fine and touch or appropriate
27:36 ? Where does purpose reception primarily go ? So it's not going up here
27:40 the thalamus. Now, there's a of big names in there and it's
27:47 easier to just map it out. 1231 facility A vesicular kenyatta's facts,
27:56 that just stopping to do this. always gotta stop and pause,
28:05 vesicular kenyatta's vesicular priscilla's. Alright, figure out which one you put that
28:12 one number to begin in nucleus priscilla's kenyatta's via the medial meniscal pathway.
28:18 thalamus, tada magic. What you're find touch some appropriate reception. The
28:29 lateral. All right. So again the pathway is going to be
28:34 All right, they're gonna be in white matter. They're going to be
28:37 the anterior um particularly or the lateral . Where are those? If you
28:43 remember if we're looking So up that would be the dorsal particularly.
28:49 would be the lateral funicular. And here those are the anterior funicular.
28:55 , just basically saying relatively to the matter. Where am I? I'm
29:00 it. I'm in front of I'm behind it and to the side
29:02 it. Alright, so the name tells you Antero lateral, so I'm
29:06 to be on the front of it I'm gonna be on the side of
29:09 system. The other name makes it easier spinal thalamic pathway. Were you
29:15 spinal cord? Where are you going there? Alright again. What are
29:20 conducting? Pain and temperature primarily. still have violated fibers but there might
29:25 some annihilated fibers involved. Okay, it's sending information is not so important
29:31 the information being sent along my element . three chains. 1,
29:36 3 where the cell bodies located dorsal . Okay, what are we going
29:43 use in terms of the second order . Alright, so we come
29:46 we go in through the dorsal horn I'm in the lateral pathway notice called
29:51 lateral spinal thalamic tract. Alright, here I am I'm going and I'm
29:56 I'm exiting out and I'm now in lateral pathway. Alright, if I'm
30:02 and using anterior pathway, that's the body, so I'm gonna do the
30:06 thing, I'm gonna come in and gonna go out through the anterior side
30:09 I'm gonna stay on the anterior side I'm just going to travel my way
30:14 all the way up to The Thalamus that's where the 3rd order neuron is
30:19 to be. All right. So primary neuron comes into the dorsal
30:24 . Second order neuron deck associates at level of spinal cord travels up and
30:30 terminates on the third order neuron in thalamus. And those are your two
30:39 sensory pathways? Alright, dorsal column the internal lateral pathway. So
30:50 Big words. Yeah. So the of the class, what we're going
31:00 do and and and just to be what we're gonna do is we're now
31:05 with sensory input sensory information. So things we just looked at kind of
31:09 up the sense of touch and pain temperature, all the stuff that we
31:14 about on Tuesday. So we've kind wrap that up and what we're doing
31:17 is we're moving into these areas of special senses? Alright. Special senses
31:22 think are kind of interesting. How my I work? How does my
31:24 work? How does my taste buds ? Why does coffee taste yucky or
31:29 , depending. Right. And so gonna start with the I. And
31:33 we're gonna just kind of work through rest of them and then at the
31:36 of the unit, we're gonna deal the autonomic nervous system and we're going
31:40 deal with the pathways, the motor that come back out again.
31:44 So, we still have pathways to with. But I think doing this
31:47 of makes things a little bit And so, if your eye,
31:52 you're not familiar with your eye, right, that's your eye. It's
31:57 spherical. It's not 100% spherical. right. It's in the orbit of
32:02 skull. So, you know that . It's surrounded by a whole bunch
32:05 fat which you can't see. Thank . Alright. And there's three
32:11 And so you can see up what we've done is we've divided these
32:13 that we have the fibers tunic, the outside layers. Then we have
32:16 kind of middle vascular tunic. So can see this is where the blood
32:20 are gonna be. Right. This kind of the meaty layers. And
32:23 finally, internally we have the which is kind of the the nervous
32:28 layer. Alright, that's the easy to think about it. All
32:32 So the tunic is What covers So we have the square and the
32:37 . We're gonna break all this stuff . The vascular tunic has these different
32:40 the irish. You've probably heard that . But these the silly everybody in
32:44 car ride, you probably have All right. And then the nervous
32:47 , the retina, That's the easy . You've heard that before. Optic
32:51 . You've probably heard that. And it's the retina. In the optic
32:53 . You can see this is nervous . But before we get into the
33:00 and its structures and what they we need to understand what it's
33:04 All right. And I encourage you go onto Wikipedia and look up visible
33:09 and you'll see this picture right This is supposed to be an animated
33:13 . But it doesn't work that way power point. So, it's a
33:18 , flat looking thing. And you've heard probably at some point if you
33:22 physical science way back in 8th grade if you actually have taken physics,
33:26 probably explored visible light a little bit physics to at the college level.
33:31 think in high school, you do the second semester. And what they
33:35 is they talk about light and oh, light is both a particle
33:38 a wave. You've heard that, ? It moves as if it were
33:41 wave and it does. But what's is that the wave is not like
33:46 wave if you take a rope and it, right, the wave is
33:50 different. It actually has to wave that are associated with it. One
33:54 is an electrical field, one that's magnetic field. And if you again
33:58 you go on the Wikipedia and watch video or watch that little gift,
34:01 get mesmerized because these two things are in unison. They don't work
34:07 One is going up while the other is going down. And so it's
34:10 kind of this like I said, can stare at it for a little
34:16 , help you go to sleep at . All right. So, it's
34:20 unique waveform very different than what we the way I like to think about
34:27 and the way I like to think light and photons altogether because they're basically
34:33 of energy. Right? So a photon can stimulate a molecule and pop
34:40 an electron. It's basically it's a and particle. And so these represent
34:45 . And if you look at the of visible light right here, what
34:50 talking about here is strength of In other words, what is the
34:55 of this light which is a representation energy? All right, visible
35:01 Is this small, a portion of entire uh spectrum of electromagnetic radiation?
35:09 right. So, we only see what we what we say what our
35:13 can detect. In other words, eyes are receptors that only detect a
35:17 sliver of electromagnetic radiation. So, have radiation detectors in our heads.
35:25 right. And so that's what you're with. And what they do is
35:27 represent wavelength. And so the wavelength basically just the distance between two wave
35:33 , peaks as you are going in direction. The wavelength increases in terms
35:38 distance. Right? That's wavelength. over here, you have short
35:43 All right. So, you have energy basically there, causing the wave
35:46 go like this up and down. then as you move further and further
35:49 than the wavelengths get weaker and weaker weaker. In terms of energy.
35:56 you get bombarded with gamma rays, happens to you? You become the
36:02 ? That's right glad some people are attention. Right? When you go
36:06 the dentist, do they give you big old giant apron? Put it
36:10 your body, protect your gonads. really what they're there for. Whether
36:14 male or female is there to protect gonads? Got to make sure mutations
36:18 take place in the gonads. we're going to cover you with lead
36:21 the lead can absorb the energy from x rays. Where are your cell
36:26 ? Do you guys know? I mean five G? Right,
36:31 scary stuff. Where's five G. you think it's over here? Tell
36:35 when to stop someplace in there. . Five jeeps, microwave. What
36:49 you do with your microwave? You water with it. That's its
36:54 That's an energy wavelength to boil water your food. That's what it
36:58 Is it heats that. That's how get the heating up. All
37:01 So, you can see here, know, our eyes actually detect something
37:05 has greater energy than our phones. right. But there's a lot of
37:10 . There's a lot of wavelength except . Alright, so, we're detecting
37:16 energy with our eyes and it also an amplitude amplitude is the height of
37:21 wavelength, right? Basically, it's height height between this right here.
37:26 the trough. And the top of wave and amplitude just represents intensity.
37:33 , So intensity is like bright light not bright light. Right?
37:38 right now, if you go is this bright light? Yeah,
37:41 kind of walk out there and here it very bright? No. So
37:45 would say is the amplitude, even you're using the same wavelength amplitude can
37:51 . Does that make sense? but like I said, if you
37:55 and watch this thing you're gonna look and go, man, it's even
37:57 complex. Yes. It's more complex I'm just describing. So the purpose
38:02 the eye then is to detect that of energy that photon that is moving
38:09 a specific wavelength and those colors that detect represent different energy forms that are
38:15 detected by the receptors in our Now as an organism. We are
38:24 heavily dependent upon sight and this is a slam against people who have vision
38:29 Alright. But we are an organism basically live by sight. Look at
38:34 our eyes are located on our They're right in the front, the
38:39 of which is we are predators as . We need to see our
38:43 We put there we have bifocal vision we can understand depth and we basically
38:48 our eyes to hunt and to get we want right? So they're right
38:54 in the front as a result we to protect our eyes. And so
38:58 a bunch of structures that do So for example you don't think of
39:02 eyebrows as being protective but they are natural sweatbands for your eyes when you
39:10 water drips down your forehead hits that on your orbital ridge and the water
39:15 moves out to the side and away your eyes for the most part.
39:21 . Not always. I've had water , my eyes just like you have
39:25 right. But it's a pretty good . And look at how your eyebrows
39:29 . Next time you go look in mirror, look at the shape of
39:31 eyebrows. Alright. They are literally little tiny peaks like little tiny roofs
39:36 they're like this and that's why the kind of goes outward. But it
39:40 can go down the nose. Alright spend a lot of time. Ladies
39:46 your lashes look beautiful because one batting eyes at guys is something makes us
39:50 , oh it does right. But are there to prevent large foreign objects
39:57 contacting the surface of the eye, your eyelash and watch what happens you
40:04 close your eyes. All right. mean if you're trying real hard like
40:08 can do that. No, but you let me do it, watch
40:11 happens do you really want me to ? Yeah, mm hmm. Before
40:22 touching someone else's eyelash? That All right. So, I knew
40:30 was gonna happen today. So the is is that the eyelashes there to
40:36 particles in the air and to move away from your eyes. That is
40:41 purpose. Okay. Third structure up your eyelids. They have a special
40:48 called the palpa bray, papa bray there to protect your eyes? They
40:52 basically the shutters of your eyes. have one that's up and one that's
40:55 the bottom. So that's the upper the lower. All right. And
40:59 actually are not just little pieces of , There's actually stuff to them.
41:04 muscles inside. Alright. There's Uh if you've ever had uh kind
41:09 that cyst sitting on the end of eyelid that's really just basically a blocked
41:14 , you know? So if you add heat to it if you have
41:16 little baby, this happens all the . You just add a little warm
41:19 and a rag and it will help the skin around it and usually allow
41:24 to squeeze that goo out of So there's two glands. The
41:28 Um I don't think I have the one listed up here, but the
41:31 plans. These are the ones on edge right here where the eyelashes lashes
41:36 located and those basically are there to c. Bum which sits on the
41:42 of the eyelids so that your lack secretion is a fancy word for your
41:48 . Stay on the surface of your . Right? So basically you're like
41:53 like a wax lip, you know there And basically the tears just stay
41:59 the surface and wash over the surface opposed to just dripping everywhere across your
42:04 . All right. I just like use this word because it just sounds
42:09 sake or uncle? Your uncle. , the car uncle is that little
42:16 right there. It's where the eye hanging out right in the morning when
42:20 wake up and you're like, I eye boogers and I got to get
42:23 of them. Right? That's your uncle. Right? Oh, there
42:29 a salary gland there. Okay, the conjunctivitis is this structure here.
42:37 can see it's on the back of palpa bray. Yeah, folds on
42:41 . That's called the for next. whenever you're structure kind of bends on
42:45 . The point where it bends is the for next. And what it
42:47 it comes and it goes over the of the eye. Except over the
42:53 cornea is going to be in the and then it continues along. So
42:56 all it's all over in the front this and it continues over here.
43:00 can think of like this, it's a shrink wrap uh structure that protects
43:05 surface of the eye. Alright? basically wherever you have the white of
43:09 eye that you can see. That's all right. And then it goes
43:14 and behind the eyelids. So it creates a seal between the external environment
43:19 the internal environment around your eye. right. So in other words,
43:24 you poke through that you're now inside body all right, you can see
43:28 fat and stuff behind it. So the ocular part is the part
43:33 attached to the skull era. The part is part on the back of
43:37 eyelid. Now they're goblet cells goblet cells produce mucus so that's helping
43:44 the eye. It's not incredibly And the reason it's not incredibly tight
43:49 because if it was then you couldn't your eyes so it's just tight enough
43:53 that it doesn't bunch up. But allows you to keep your eyes moving
43:57 , it has lots of nerves in you ever touched your eye kind of
44:02 weird if something touches your eye, be like there's something in my
44:06 right? And it's highly vascular Alright. So if you looked at
44:10 eyes and seen it all bloodshot. right. That's in that conjunctivitis.
44:17 you've heard of the term conjunctivitis, an infection of that surface structure and
44:24 causes your eyes turn of red. right. Key thing here it doesn't
44:30 the cornea. The cornea is So you can think of the cornea
44:35 the the the the clear portion through light is gonna be passing through.
44:41 so you can think of the cornea kind of being the safe space and
44:44 it's kind of like a skirt that from the cornea up and around over
44:49 back of the eyelids. So all things are protecting physically protecting. But
44:56 way that we protect as through the ball fluids. Orla Kimmel's secretions.
45:01 right. This is a fancy word tears. There's all sorts of stuff
45:04 here. Alright. The key one want to point out here is life
45:09 licenses. I'm is one of your natural antibacterial enzymes. All right.
45:17 you can imagine it's being in your because this is now wet warm
45:22 What wants to live in wet warm bacteria. It's also a place where
45:27 produce a lot of I. A. I. G.
45:30 Is a antibody that your body is generic antibody that your body produces to
45:35 infection. And so your tears have lot of I. G. And
45:38 lot of his life's assignment. All . But you're lacma gland sits on
45:43 outside over here. Now when you up where your tears fall primarily kind
45:49 over here. Right So what you see here is kind of the general
45:53 . And it's because the lack formal through which tears are removed from the
45:59 of the eye are found near the Ocurre uncle. Okay so lack of
46:08 glands out here on the outer It's constantly producing fluid. These lacquer
46:13 fluids at a kind of a constant . That fluid is being pushed over
46:18 surface of the eye has all this stuff in it to make sure that
46:23 washing debris and particles and bacteria and things killing it off and and removing
46:29 . And then what you have is have these little tiny structures called the
46:34 to basically little tiny holes. So have one on the bottom. You
46:38 actually go and see these. These these are not microscopic. You can
46:41 look in the mirror and just kind looking and you can see they're sitting
46:44 there on the bottom one on the and there's a little tiny canal called
46:48 curriculum that then connects to the lack ball sack which is part of the
46:52 lacquer Donald duck. And so you see the flow of tears would be
46:56 through the puncture through the through the down through the lateral stack and out
47:01 the nasal cavity. Now to help visualize this, think about when you
47:07 right? What happens right? Because you're crying you're producing more legible
47:17 a lot of it, you're producing much that it just flows out over
47:21 edges of your eyes. But you're pushing it down and through the pump
47:26 through the curriculum into the lacquer mail and down through the lateral duck.
47:30 it goes into your nasal cavity. you just have extra water in your
47:33 cavity dripping around. And boy we when things are dripping in our nasal
47:37 don't we? That's when you get so you can kind of see the
47:44 . So this is another way the protects itself. There are a series
47:50 external muscles called the extrinsic eye muscles memorize the names. But you can
47:56 the rectus means up and down. one on top, one on bottom
48:00 , that side to side or not to side, it's kind of at
48:03 angle and then here you can see rectus and that's gonna be lateral
48:09 Alright I'm not gonna ask you the of these. Please do not memorize
48:12 . But my goal here is to you is that you are capable of
48:17 your eyes because we have muscles attached the surface of the eye,
48:23 If you look forward and then just put your eyes over there
48:27 look at that person to left. their trouble. All right. Now
48:31 at the person at the right there trouble But don't let them know that
48:34 looking at him, right? I know what you're doing. You're
48:38 rolling your eyes at me, See that's because of those muscles right
48:45 . These are attached to the skull . The white of your Yeah,
48:50 wonder. Oh, mm hmm. , so let me go back
48:57 So, whenever you're talking about what happens is you're squeezing the
49:01 right? So any fluid on the of your eye has to go
49:05 And if you have too much and trying to push it towards the punk
49:10 then it's just gonna go wherever it , right. It also happens when
49:14 watch really, really sappy commercials, always asked why are you crying during
49:20 commercial? Because I have emotions You'll understand when you get older.
49:30 sorry. All right. So, said there's three layers. We have
49:34 tunic. We have the Alright, tunic consists of the square in the
49:39 . Alright, the square, that's white of your eye. The
49:42 that's the clear stuff right in the , right? And you can kinda
49:45 go in the mirror and take a at it and you'll see Oh
49:47 I can see got this kind of bump on the surface of my eye
49:52 corny and so everything else back That's clara. The school era is
49:56 with the dura matter. So you're matter basically is what forms That's clara
50:03 of neat. All right now we're gonna go in the development. I
50:07 even know if your chapter does but what's interesting is how the I actually
50:11 . It's like a structure that develops the inside out. It basically kind
50:15 like goes out and then pops out like this. So it makes sense
50:21 this is kind of why that would um um Dura matter. Alright.
50:27 what is what his purpose is clear ? I shape. That's why you
50:30 a round or spherical. I it your eye. It's really really
50:34 You know? Just like the door tough and it serves as a point
50:37 attachment for those extrinsic muscles. All . So when you think whites of
50:42 eyes, that's the square that I see. But that goes all the
50:45 around the eye. The cornea is we're kind of interested in. Its
50:51 tissue. It is not dead Alright. It's just happens to be
50:55 vascular Alright. So it gets its nutrients from um a little bit from
51:01 tears but not so much. It's from the fluid that sits behind the
51:06 . So you can see there's this space but this is an epithelium very
51:11 alive. Alright, transparent. Its is to allow for light to pass
51:16 the eye. Are receptors for light gonna be located here in the retina
51:21 we'll get to that in a little . All right. The other thing
51:24 it does because of its structure and it's just a different material is that
51:29 light hits it and it's opaque or opaque, it's translucent or transparent.
51:34 translucent transparent, light will hit it it will bend. Alright. That's
51:39 refraction. So the first thing that cornea is doing is it's bending
51:44 And what we're trying to do, trying to bend light so it reaches
51:47 very specific point in the back of eye. When we get to the
51:52 tunic, there are three parts to . Alright, corduroy tell your body
51:57 , iris is what you're most familiar but let's just kind of walk through
52:01 core. Oid you can see is the way around the eye.
52:04 It's basically the vascular layer. This where the blood vessels are. All
52:08 . So you can think of this as being kind of connective tissue that
52:13 and then what we're doing is we're the vasculature underneath that protective layer and
52:18 is what's providing the nutrients to the that are in the new neural layer
52:22 the retina as well as the nutrients the cells that are in this in
52:26 uh fibrous tunic outside. So kind the meat of the sandwich as it
52:33 . All right. And so as come around, you can see we've
52:36 it's better shown right up here we this large structure that formed from the
52:42 . It's called the silly everybody. everybody has a couple of things to
52:46 has muscles and has these processes. processes are just kind of out
52:51 What they do is they produce what called the acquis humor. The humor
52:55 is released and it comes out of space. We're gonna learn about this
52:59 the second and then it kind of outward, fills in the space behind
53:03 cornea and then ultimately empties out in way. So this is where the
53:09 of the cornea are going to get nutrients is from the humor. We'll
53:14 back to it a second. Look the flow. We also have the
53:18 muscles ancillary muscles. There's a type smooth muscle that this is, what
53:23 stuff represents is distinct from the iris the purpose of these, as you
53:28 see they're attached to these ligaments. ligaments are attached to the lens.
53:34 when the muscles contract, they pull the ligaments. And when you pull
53:38 the ligaments, you pull on the and you change the shape of the
53:43 . Alright, so this is what's to allow for what we call
53:48 Being able to see far or Okay. So the celery muscles found
53:54 the silly everybody play a role in . Again, that's something we're going
53:59 talk about in just a minute. last structure is the iris. And
54:03 , this is a bunch of smooth . It's actually interesting. It's a
54:07 that has pigment in it, you ? So when you look at somebody
54:10 say, oh you have such beautiful , right? What you're looking at
54:14 a muscle that has pigment embedded in . And there's actually two different groups
54:18 them. Alright. And what these is when they contract and relax that
54:22 changing the size of the hole through light passes into the eye.
54:30 So the iris is allowing not The the iris allows the amount of
54:37 in the lens which we're going to with in a bit, is what
54:40 with focus. All right. So think yeah, we're going a little
54:48 deeper into this. All right. , there's two muscles there were sphincter
54:53 . We have a dilator muscle. even tell you where they're located their
54:56 of the pupil. So, when look at somebody, how many guys
55:01 had an eye exam? I I can look around and see the
55:03 who wore glasses, but those aren't glasses. Have you ever had eye
55:07 . Alright, what do they Is they take this big old
55:10 right? And they say look forward , they dilate your eyes. So
55:13 muscles don't work, right? So you're this and then what they do
55:16 they shine a light into your eye your pupil. Now when you look
55:20 somebody you see that little black circle actually you looking into their eye,
55:26 just can't see anything in there. like looking into a dark closet because
55:31 your deep dark secrets are in there it makes it all dark. No
55:35 because light is not reflected back at . And so it's dark when you
55:40 at a pupil it's dark because the that's going in never comes back
55:45 Okay. So how do we open close the whole what we're doing is
55:51 changing the size of these two The sphincter muscle is a circular
55:57 Alright? It's p parasympathetic, innovated its contract. I'll. So what
56:01 does is when it contracts it makes hole smaller, what makes a little
56:08 less light goes in. So when bright, this is the one that's
56:12 to be contracting this one's gonna be during that period of time. Now
56:18 there's very little light you want to able to see you need to get
56:22 light into the eye. And so you're gonna do is you want
56:25 So these muscles contract these relaxed, is sympathetic in nature. And what
56:30 is is these are radial in And so what they do when they
56:34 they pull the relaxing circular muscle And so now you have a bigger
56:39 through which light passes. It's still in there because light doesn't escape.
56:45 right. But this is how we how much light is going in and
56:50 . So right now, if you at somebody you can see in
56:53 it's a little bit darker. So have your eyes are a little bit
56:56 dilated. Go outside for like 10 and go look at someone's eyes and
57:00 pupils are like these little itsy bitsy tiny dots, right? Because of
57:05 amount of light that's available. the lens. So, if the
57:12 determines the amount of light going in out of the pupil. Or that
57:16 hole is called the pupil. So the pupil just represents the whole
57:22 , so the lens adjust the size the hole and then that light going
57:26 the pupil. The first thing that's to come into contact with as a
57:30 is the lens. Remember we said lens plays a role in focusing
57:34 All right. And so it's the , how we're gonna focus. So
57:38 what I said we want to get light that's coming into our eyes focused
57:42 here at this little tiny spot at back of our I that doesn't mean
57:45 the only spot that has receptors that's we want the light focused. All
57:49 . And so what we're gonna do we're gonna change the shape of this
57:52 depending upon when we're looking now. is kind of a concept that's a
57:56 bit wonky to understand. So, want you to think about these muscles
58:00 wrapped around a circle. All And so when that muscle contracts,
58:05 it's gonna do is remember it's contracting from the lens itself and it's pulling
58:12 the ligaments, right? When it on the ligaments, it makes the
58:16 thinner. And what that does is when you I'm doing this wrong.
58:22 , I did it wrong. I it backwards time out. Mm.
58:26 hate when I do that when it what it does, it contracts
58:32 Doesn't contract backwards, it contracts And so when it contracts forward,
58:38 happening is it's not actually pulling on ligament anymore. So, normally,
58:43 you think about is when you think a muscle contracting, it can pulls
58:46 a ligament making the ligament or tendon , right? Or the ligament
58:51 And that's not what's going on It's the opposite. So when the
58:55 are going around this round structure, it contracts it contracts this way and
58:58 loosens the ligament. And when you the ligament, you're no longer pulling
59:02 the lens. The lens relaxes and fact. And that allows you to
59:07 things near which is like they're trying show you the watch. All
59:10 So look down at your device or piece of paper in front of
59:14 That would be your muscle being Okay? Now, when your muscle
59:22 right, it falls backwards away from lens and when it falls away from
59:26 lens it pulls on the ligaments. the ligament really really tight, which
59:30 the lens pulled and it gets really thin. And this is your
59:35 view now. How do I remember ? So you saw how I kind
59:38 like, oh wait a second. got it all backwards. How do
59:40 remember this? Think about what happens you're tired? Do you have real
59:48 look when you're tired now, you of get that three mile stare
59:52 don't you? So you can think when my muscles relaxed and I'm
59:57 my lens is getting really tight and why I have that long stare.
60:03 my farsightedness. And you can do really is that people are back.
60:07 easier like the interesting look up, can see how quickly you can accommodate
60:12 really interesting. And this is not in accommodation. Your eyes actually scans
60:17 about 30 times per second. So actually when you look at something you
60:22 just kind of look at it. like You do that about 30,000 times
60:26 second, which is pretty impressive how information you're inputting into your eyes.
60:32 accommodation is simply the process of changing lens from near sighted view too far
60:39 view and it's simply the contraction of muscles. When I'm working hard.
60:45 have to think about what I'm looking the rights and here I am nearsighted
60:49 my muscles are relaxed. That's my . Easy way to remember that.
60:58 , I deal with the question of real quick. Just simply put refraction
61:02 the bending of light when light hits different substance, the light travels through
61:07 at a different speed. All And so what happens is when that
61:11 it changes the speed of light so moves or bends as a result.
61:16 I love the picture. And you you've you've seen that. It's like
61:19 looking at your drink and you see straw and you're like kind of that
61:23 . So this is what is going with your eyes. Light hits these
61:27 transparent structures. They're going to be Now the shape of a lens matters
61:33 if you have a concave lens. ? So the concave lenses, one
61:37 the right, right, that's going cause light to bend away from the
61:41 point, you know? But we a lens that is convex and as
61:46 can see it bends towards the focal . And so I've been pointing out
61:50 focal point over and over on your . So what we have is we
61:53 structure that is trying to bend the towards this focal point in the back
61:58 your eye. Alright Called the So if you think about the
62:05 the eye, you have a you have fluid right filled with Aquarius
62:11 . You have a lens, And then you have another cavity filled
62:15 another liquid. And so each of bend the eye or bend the light
62:20 a little bit to get to that . So the two cavities of the
62:26 . Alright, We have the anterior . We have the posterior cavity.
62:30 just put ourselves in perspective because he the lens. This would be the
62:34 everybody. Alright, so this is the celery muscle is, This is
62:39 we're producing the uh acquis humor and flowing out above the lens and out
62:47 around the iris and then it's emptying in a structure that's located within the
62:53 itself. I don't know. I listed up here. I don't think
62:56 do. All right, but it's best name ever. So, we
63:00 have to note for the test, it's just one of those trivial pursuit
63:04 the way that acquires humor leaves the to a structure called the canal of
63:10 named after somebody I had a hard growing up. I think Slim isn't
63:18 awesome. So the canal of Not the list of there.
63:23 Anyway, you can see we have chambers in the anterior. So here's
63:27 anterior chamber that sits right behind the cornea, just in front of the
63:33 posterior chamber is right behind the just in front of the lens in
63:37 posterior cavity. This is where we're to find vitreous humor. Vitreous humor
63:43 more of a gel. You don't a lot of it new. So
63:47 always kind of making a quick That's why it's flowing when it,
63:51 it gets, when you get proteins in the aqueous humor, That's when
63:56 um it kind of gets gummed up it stops flowing out through the canal
63:59 slim. And that's the, so happens when my brain turns off cataracts
64:13 was looking for? That's a cataract is that kind of gumming up and
64:19 proteins accumulating and becoming more opaque. vitreous humor, it's just kind
64:25 is what it is and it just of sits there, it helps to
64:28 the shape of the eye so that kind of creates this positive pressure outward
64:33 of create that rounded nous or that nous. Um it's still transparent so
64:38 allows I like to be transferred to through it. Have you ever noticed
64:42 little tiny floaties in your eyes when looking at stuff like something like it's
64:46 hard right now, but if you're at a white piece of paper,
64:48 like, oh yeah, and you of try to focus on and it
64:50 of goes up and you keep following . So those are basically um dead
64:56 that are actually sitting in the vitreous . And so what's happening is light
65:00 hitting it. And so you're detecting the light refracting or bouncing off one
65:07 these structures. And that's why you that little tiny floating, they're just
65:16 , look this is just showing you different refraction, right? So what
65:21 light gets bent, bent, bent it comes and as you're bending
65:25 what you're doing is you're moving it the phobia centralist. We haven't talked
65:32 the retina yet, we're about to there. But all structures within the
65:37 , there are a bunch of light . But where we want light focus
65:43 directly behind the lens. This is our greatest acuity is whenever we see
65:50 , notice what we do is we our head or turn our eyes to
65:53 in on it because it gives us greatest security in terms of what we're
65:58 at. So if I'm looking I can see all the way out
66:01 , this is my peripheral vision, can see my fingers wiggling,
66:05 Everyone's a little bit different. You play that game right, You
66:09 But out over here things aren't quite clear, I can kind of detect
66:13 there are people out here, but I see movement, what do I
66:16 is I turn my head and my right? Because that's where my greatest
66:21 . So, that's what we're trying do is we're trying to send light
66:25 that phobia central is because that's where security is gonna be. So,
66:30 leads us to that last structure of retina. All right. Outer tunic
66:35 middle layer vascular also have some muscles it. Help us to focus
66:40 And finally what we're doing is we're light and we're sending it to this
66:44 here. So, I want you envision what we're looking at.
66:48 here light is coming through the cornea the lens and is moving back here
66:52 a phobia centralist. So, we're to show you here. Here's the
66:56 coming into the retina. So there's be layers and layers of cells.
67:01 this, right here is the last cell on the retina, and here's
67:05 cornea. Our receptor cells are going be right here. All right,
67:12 , light passes through cells to get the receptor cells. So, our
67:19 layers, the first layer is a layer. All right, This is
67:24 outermost layer. So, this is one nearest asteroid. Alright. Called
67:29 pigment epithelium. Alright, It's a layer where you have pigments. When
67:34 hits a pigment, what does that do? It absorbs the light.
67:38 , when you look into somebody's what do you see the darkness of
67:42 souls. Right? No, that's it. You don't see anything because
67:46 light is bouncing back out. It's absorbed by this pigmented layer. Now
67:50 is valuable because you don't want light around because you're receptor cells are basically
67:56 this cell right here is detecting light a specific location. And so if
68:01 is bouncing around the inside of your it's telling your brain light is being
68:04 from that particular location over there, example. Right? So if it
68:09 from over here and bounced around and hit that your brain wouldn't know what
68:13 do with that light. So the epithelium absorbs light so that the neural
68:19 the receptor cells can detect light from specific location. The other thing that
68:26 provides vitamin A, vitamin A. going to see in just a little
68:30 vitamin A. Is this kind of um long chain structure with these ring
68:35 structures at the end. If you vitamin A directly in half, you
68:39 up with this molecule called retinol Not O. L. A.
68:44 . Retinol is going to be important terms of detecting light. So it
68:51 the molecule that is like receiving. what vitamin A. Is the neural
68:56 . There's all these different layers. you can see we have a flood
68:59 pigment later we have these other layers are along these neurons and what they
69:04 is they help to transducers that light into a signal and they actually pre
69:10 that signal along the way. this is the layer that's gonna be
69:14 and we're gonna be processing information before even gets sent up through the optic
69:19 to the visual cortex. So, are these layers? All right.
69:25 gonna work our way from the retinal epithelium. So, there's a pigmented
69:29 . All this stuff is a neural . We start here with photo receptor
69:33 . Because well, they're the most there. What the text like it
69:38 in the name photo receptor light Alright, there are two types of
69:44 and cones. Their job is to the light energy into that signal that's
69:49 ultimately be sent up to the All right now they generate because these
69:55 are so small, they don't generate potentials. They generate graded potentials.
69:59 graded potentials are strong enough to produce chemical message that's going to be sent
70:05 . The next layer of cells are the bipolar cells called bipolar cells.
70:09 they are literally bipolar cells. Here's cell body. There is one
70:13 There's the other side, bipolar. , very, very original name.
70:18 right. Now, what we have is we're going to see that the
70:22 of cells are going to be decreasing we move towards the brain. I'm
70:26 make up a number let's say we a million photo receptor cells. The
70:30 of bipolar cells is, for 100,000. Alright. So, we're
70:35 the number of cells. So what doing is we're going to start seeing
70:39 towards the brain And then what we're do is remove the gate land sales
70:43 even fewer. So again if it a million might be 100,000, might
70:47 10,000. Just making up numbers. . So there's fewer cells. Their
70:52 is to take information from multiple receptor and help to um uh process that
71:01 so that the brain can perceive what actually getting. So it modulates the
71:06 that's being received at the level of receptor. These two also generate graded
71:13 . And what they're doing is they're onto the third level of cells,
71:15 ganglion cells that's yellow ones. so these are the tertiary cell that's
71:21 to be sent on into the nervous . Alright. And what they do
71:25 they actually produce action potentials because they a further distance, the axons of
71:33 ganglion cells converge and form the optic . Alright so the optic nerve is
71:39 to be the one that travels onto thalamus. There are two other layers
71:44 cells we see right here we have horizontal cell and over here we have
71:47 endocrine cells. So you can see horizontal cell sits kind of between the
71:51 receptor and the bipolar cell, they modulate signals. Alright. So not
71:56 are you getting modulation because of convergence the horizontal cells and the immigrant cells
72:01 saying, you know what? I this information needs to be processed even
72:06 . And so it helps helps to how that signal is moving forward.
72:10 , so they integrate information. So horizontal between the photo receptors and the
72:16 cells are between the bipolar and ganglion . So even before light information leaves
72:23 i it's already been processed kind of . one example would be contrast,
72:33 versus dark. Right? You look this up here and you're going that's
72:37 versus that down there, that's But this looks a lot darker to
72:41 than it actually is because your brain that's light, that's dark. I
72:45 to create that contrast. So the better understands light versus dark here.
72:51 just an example of one of the that it does. You ever seen
72:57 optical illusions of like the checkerboard, black and the white and then it's
73:01 you know, it's like over here which color is the same. It's
73:04 they have some gray and you're like , well this gray over here is
73:08 obviously great because there's a shadow but like no it's actually the same color
73:11 the black. That would be an of it being modulated. I used
73:15 show a whole bunch of optical illusions here just to show you what they're
73:19 brain is doing, your book talks this and I just wanted to mention
73:26 . Alright. You may get a on this just because it's interesting.
73:30 don't know. I'm internalize it, guess. Alright, so we have
73:36 are called photosensitive ganglion cells. All . So, we have the photo
73:41 cells. We have bipolar cells. have ganglion cells. Alright, information
73:45 from here this direction and onto the nervous system. The photosensitive ganglion cells
73:50 in this category of cells over That that that third group of
73:55 he says the name ganglion cells, they're photosensitive, meaning they actually respond
74:02 light. All right. And what photo sets of ganglion cells do is
74:08 help your internal circadian clock. It tells your eyes. They respond specifically
74:15 blue light and they will tell your whether or not light is present or
74:20 brain whether or not light is You guys have a hard time going
74:26 sleep when you've been on your phones a long time. I don't
74:30 you're a liar. I mean, can go on and see this like
74:38 absorbent uh shields and stuff for your your computers and stuff because the blue
74:44 stimulates this and it mucks with your rhythm. It's one of the reasons
74:48 we have such a hard time sleeping because we have all these false blue
74:53 that we put right into our brains brain cell. It's the middle of
74:57 day. Middle of the day. of the day. All right.
75:02 also helps to regulate pupil size, size, pupil size. It also
75:06 to regulate the amount of melatonin. you can already see circadian rhythm.
75:12 . What are we doing? We're our internal clocks Now. I remember
75:16 would be driving in and I would this commercial all the time and I'm
75:19 gonna remember the name of it. there's a condition in blind people where
75:24 circadian rhythm basically starts modifying over the today. And I kind of talked
75:30 that. You can do that in and mice. It's because our internal
75:32 really runs it like 23 hours. so we don't you know, we
75:37 we kind of shift naturally a person can't see because they have a failure
75:43 the photo receptor cells. Right. cells are functional and so what's happening
75:50 their system is being modified and modulated this. It's really kind of
75:56 So their brains still detect light. just they don't detect light to
76:02 That kinda makes sense. Yeah. other ones that we already mentioned are
76:06 pigmented epithelial cells uh they these are ones that make up that uh that
76:14 layer and as I sit said already the other one, they basically capture
76:18 the photons. All right, So I want to focus, I'm just
76:26 to see how much time we have . None. All right. I'll
76:31 here because if I don't stop then dress. It doesn't make
76:37 All right. So when we come on Tuesday, we're gonna learn how
76:41 eye works. Gonna be a lot fun,
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