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BIOL 3324 Human Physiology - BIOL3324_lecture10_0926
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00:04 All right, I think this is we left off is this where we
00:07 off? OK. So we're going just quickly run through some ideas before
00:12 jump into the eye. The first we're going to deal with here are
00:16 receptive fields. And so this is concept that basically describes the range in
00:22 a receptor can detect information. All . And so typically, you'll see
00:27 picture like this look, the receptive is blah blah blah and it is
00:31 some touch thing, but receptive fields applicable to every type of receptor,
00:37 . So for example, we're going see here in the with the with
00:41 to vision that there is a specific in which the receptor is able to
00:46 light, right? So it's not about touch. Uh Typically a receptive
00:53 is associated with a primary sensory All right. So what that means
00:58 is if you have a neuron that a single dendrite that then spreads and
01:04 a tree of dendrites at the you now have a very large receptive
01:08 or if your dendrite is just this little thing. And terminates and it
01:12 a very small receptive field. So is, uh, it covers the
01:17 in which the, the receiving into cell is associated. And so when
01:22 were looking on, uh, right, Thursday, when we're looking
01:27 Thursday, we're looking at the PAC we're looking at Merkel disk, we
01:31 looking at Ronis core puzzles and all different misers core puzzles, right?
01:37 so what we saw is we saw simple ones. So small, simple
01:42 are going to have very small receptive , right? But then you have
01:45 like the ruins and the me and uh Pacinian which are wrapped in connective
01:52 that actually spread out the area in information can be received. And so
01:57 would be larger fields. The second is that about receptor fields is that
02:01 can have overlapping receptive fields. And the idea is is now you're you're
02:05 two different cells and the strength of signals from those two cells then is
02:10 to be interpreted by the nervous system determine the location of that particular
02:16 Now, we can have some fun this like so for example, on
02:18 palms of your hands, if we're about touch, you have very,
02:21 small receptive fields which would make I need to know what it
02:24 I'm touching what its characteristics are so and so forth. So having lots
02:28 receptors and lots of small, tiny gives me a greater sense of what
02:34 is. I'm actually engaged in, like on the back of my
02:38 totally unnecessary for me to know So I have very large receptive fields
02:44 this is something you can test at just or heck you can test it
02:47 if you want to grab two pins , or, or some sort of
02:52 . And what you can do just your arm is you can touch one
02:55 say here and then get the other and march it up your arm without
03:00 at it. And then you know person that you're doing this to
03:03 All right, tell me when you the one sensation and a single
03:09 So you need to have two, need to have two pins doing it
03:12 . So the idea is, is can feel the one touching and then
03:15 can feel the other one here. as I march this up, when
03:18 I get one sensation? And so on your arm, you'll notice that
03:22 distance between those two points is actually large and that shows you that you
03:26 these large overlapping fields that base or a large field. So that when
03:31 migrate from one field to the you're now within this larger encompassed
03:36 but you do it on your hands you have to get really, really
03:39 . I mean, before you almost touching two things because the fields are
03:43 small, right? It's just a little party trick you can play,
03:48 . So receptive fields are, are this, they can be large,
03:51 can be small, they overlap and are sending information so that your brain
03:56 interpret what's actually going on here. again, it's not limited to
04:00 We're going to see this in a bunch of different areas. And in
04:03 , when we're looking at vision we're going to see these receptive fields
04:06 I'm going to try to describe them such a way. That's something that's
04:09 to something that's hopefully not so Another type of receptor we mentioned,
04:16 talked about no c acceptor, no acceptor are those types of receptors that
04:20 noxious information, things that can be to cells. All right. So
04:25 all sorts of things that can damage , right? You could probably come
04:29 with a list of things that you do to damage your cells,
04:32 So here I've got an example, , right? You can tear a
04:36 , you can poke a cell, can rip a cell. So uh
04:39 what we're looking at is we're looking pressure changes. Um and, and
04:44 damage through mechanical means, you can a cell, you can freeze a
04:48 , right? So thermo receptors are something that we can do.
04:52 Um The joke I always do talk here is, I mean, since
04:56 all done chemistry lab at this Right. Everyone should be nodding their
05:00 . Of course, anyone here ever spill like an acid on yourself in
05:05 ? Yeah. I, I destroyed favorite shirt. Hydros or sulfuric
05:09 you know, and didn't even know I washed the shirt because after it
05:13 in the water just went, turned into sweats cheese. It was
05:16 sad. But hydrochloric acid so on so forth. This type, this
05:20 a good example of a chemical damaging cell. But we have other types
05:23 chemicals that can damage cells as Uh And then, so when we
05:27 about no C section, you can very specific types of receptors that are
05:31 specific to the type of damage that . But then we also have things
05:35 are polymodal which can detect all sorts different things. Um And because it's
05:41 broad and because it's so complex, just want to keep this simple and
05:45 say no C acceptor is detect things can damage cells. But here what
05:49 want to point out and this is this picture is kind of showing you
05:51 there are a variety of different types chemicals that can be used to modulate
05:57 types of receptors and are used as mechanisms for these receptors. All
06:02 So we can lower the activation Have you ever noticed that when you
06:06 a bruise, for example, just that area, you can get pain
06:09 lot quicker, right? So that's you're doing is you're modulating the mechanical
06:14 threshold so that it responds quicker to lower pressures as an example. All
06:23 , I guess the opposite would be who can walk on potholes and pretend
06:27 they don't feel it. Um they do but they don't respond. So
06:35 I want to kind of show you is a generic way to kind of
06:39 at these things, right? information that's causing damage to your cell
06:44 our cells are probably considered to be important. Wouldn't you agree? Like
06:48 you put your hand on a it's important to know that your hand
06:51 on the stove. So you don't your, the tissue, right?
06:56 . So what we see here is are different types of receptors identified primarily
07:01 size and primarily through the degree of , right? And so they've been
07:06 and so we can see three of classifications here. Alpha beta, alpha
07:10 and C fibers. All right. gene and generically speaking, what we've
07:15 here is we've, we've broken it in terms of fast signals versus slow
07:19 . And so you can see with alpha betas, for example, alpha
07:22 are very, very large relative to other two and they have myelination.
07:27 you'd expect those types of signals to wicked fast. Right. So this
07:32 the type of information where you're hey, we need to get this
07:38 up quick. Now, up to CNS quickly. Now here this is
07:45 of the no acceptor are going to using this, but this is primarily
07:50 to be like mechanical damage. So if I step on attack type
07:54 the next group are called the eight . So the eight delta you can
07:59 is significantly smaller, but they have myelination. So it's still fast but
08:03 not like wicked fast. Right? here, um, fast pain.
08:09 anyone here ever been hit by a ? Isn't that a lot of
08:13 No, anyone else? Baseball? about, um, oh, I
08:19 know, like a tennis racket, baseball bat, something like that.
08:23 sort of club, small stick had sibling stick up behind you and hit
08:27 with something hard. Ok. The that you get from that is what
08:32 immediate. It's sharp and you're right. That's this all right at
08:40 A Deltas. All right. after you've been hit, you get
08:45 pain, that throbbing pain. The that reminds you that you've been hit
08:49 flu, flu, flu, flump, flump, right. That's
08:55 C fiber. Ok. The C is significantly slower. Why it's even
09:02 than the A's? And it lacks myelination. Now up here, I've
09:07 cold and stuff like this, but is what we would think in terms
09:10 the slow pain, this image may helpful, maybe not. Um But
09:15 idea just shows you the speed at information comes. So the first response
09:20 be like a sharp, quick response you are getting yourself reflexively away.
09:27 that slow continual signal is to let know that damage has occurred. So
09:32 trying to avoid using that, that . So like if you twist your
09:38 sharp pain and then you're, you , protecting it because every time you
09:43 it hurts, that would be the if that makes sense. So
09:57 this is, it's just the it's, I mean, again,
10:01 notice here that what this is it's mostly just mechanical stimulation. So
10:07 only some no C section. So of your sensory input coming throughout your
10:13 is using the A betas when we're about. No C there are
10:19 but most of it's down here in A delta. That's what I was
10:22 to get at all right, to those two. Now, we also
10:28 ways to suppress pain because what is ? If you had to define
10:34 If you had to say what is ? What is pain? You usually
10:38 someone who is an athlete answer to , leaving your body. No,
10:46 , no, it's not. We sleep in your body. Now,
10:48 is it if you had, why would you experience pain? What
10:53 the purpose of pain, something's So don't use it. Right.
11:01 in essence what it is. It's weakness leaving in the body. It's
11:04 body saying you've been damaged. If keep doing what you're doing, we're
11:08 die or you're going to permanently All right. I like the
11:13 Like, because I like to think running and you get that runner's
11:16 you know, the cramps and stuff then what is it? It's like
11:19 gonna die, you're gonna die and body's right, you're gonna die.
11:22 stop running. Go home. Watch . All right. There is a
11:29 of different levels to analgesia. All . And this does not cover
11:35 And this, this is a really kind of summary of the different types
11:39 analgesics that we have in the body that we could use where they
11:43 So local anesthetics basically prevent signals from forward. Um But you also have
11:49 like opioids and stuff that basically block signals, right? So what we
11:54 here is is what we're trying to when we talk about analgesia is just
11:57 the suppression of the pain response. the pain response, remember, you
12:02 actually still be receiving it. You don't care. I mean there are
12:05 drugs like codeine that does that. like, yeah, it still
12:08 But yeah, what do I Right? But other types will actually
12:13 the sending of the signals All This is uh an example would be
12:17 the endorphins that you produce. All , these are endogenous endorphins. How
12:22 here? This is uh we, , we're gonna get personal today.
12:25 how many of you like spicy I mean, love it. I
12:28 like it's like I can't wait for peppers. One person. You,
12:33 and me, we got, we a party. All right. I'm
12:35 ghost pepper person. I love being ghost peppers. All right. And
12:40 of you are looking at me like uh salt. We're pushing limits.
12:44 right. And salt is not spicy the way. But anyway, black
12:49 . How's that? All right. , what's happening when you're eating spicy
12:54 is you are actually activating thermo It's a chemical that's binding to a
13:00 , not in an inappropriate way, in doing so it gives you the
13:04 of heat. Body says pain because what we do when we get the
13:09 like, oh, this is too and that's when you start reaching for
13:12 water and everything else. And that work. Don't use water. Anything
13:16 fats in it. Fats are how get rid of heat just letting you
13:19 . All right. So what you is you, you try to reduce
13:23 pain and then that pain sticks around so your body says, I don't
13:27 , I gotta deal with this So I'm gonna release endorphins endorphin is
13:32 opiate. All right. And it through those opiate receptors and it relieves
13:37 pain and gives you a euphoric sensation then your body starts craving the euphoric
13:47 . So, what do we Eat spicier food? So, why
13:52 I eat ghost peppers? Because I'm the king of opiate addiction. All
14:00 . Start off with the simple, stuff. Jalapenos, pickled, work
14:05 way up to real peppers. Work way through the Asian foods, ghost
14:12 . Bring it Trinidad Scorpions. It's real stuff. All right.
14:20 what they're doing is they're uh basically a role in presynaptic inhibition. You
14:25 remember that what that term means. have a terminal end and instead of
14:32 releasing its neurotransmitter, what we're doing we're blocking at that particular location,
14:37 though the signal and an action potential coming down, it's blocking the signal
14:42 release the neurotransmitter. So the cell still stimulated. It's just not able
14:46 send the signal forward. OK. how uh anesthetics analgesia, particularly the
14:54 work another sensation. Have you guys that you're uh right side up and
14:59 of upside down? Yeah, you, you, yes, I'm
15:06 making sure because you could quite possibly upside down right now and you don't
15:10 it. Proprioception is your, is body understanding its position of the head
15:15 space. All right. That's the term here. All right. So
15:21 you are like have you ever done uh three dimensional um ring ride?
15:28 have one at Chema. There's one the Natural Science Museum. If you
15:31 to spring break, usually they'll have of those things. So after a
15:34 of tequilas, you, it looks an adventure. You know, you
15:41 got to get out more. Just my freshman the same thing. You
15:45 doing. Fun thing. Fun this . No. Have you seen
15:48 No, no. Get off your phones. Get out and experience the
15:53 . There's nothing more fun than getting rings going in three different directions and
15:57 afterwards. Ok? Maybe not. the idea here is, you
16:04 your right side up because your head its right side up. Here's a
16:08 one. When you were a Did you ever lay down on the
16:11 go round one person? No. ? Why didn't know they could most
16:18 take merry go rounds away because they're and scary. Oh my goodness.
16:24 . But you lay down in a go round, put your head towards
16:26 center and you don't really feel movement that much. But if you
16:28 flip yourself around, what do you like? Vomiting is the, is
16:33 answer? Right? Because you're going see here in two lectures that our
16:39 is being maintained by a couple of so that we understand where our position
16:46 . Have you ever tilted your This way, see, I'm watching
16:49 head tilt your head that way, how the world doesn't change all that
16:52 because your head or, you oh, I'm tilting. So I
16:56 to adjust my frame of reference, ? That's just an example. All
17:01 . So there are structures in, our muscles and in our ligaments
17:08 in our tendons, not our ligaments are responsible for giving us an understanding
17:12 the position of the rest of our in space. All right. So
17:18 since you guys don't ever get out much, but maybe you've heard of
17:23 , you know, there's something called sobriety exam. Have you heard of
17:29 a sobri you've heard of this? . So there are many different types
17:33 sobriety exams. One of them is they get a person to stand out
17:38 and touch their nose. How come can touch my nose like this with
17:43 eyes closed? Well, yeah, true. I'm not drunk. But
17:49 I was sober, how is this different than being drunk? Why can
17:52 do this? Because my muscles know my nose is. They know the
17:59 where they are in space. Why can't do it while you've been drinking
18:03 because you are impaired. And so , your awareness of your position in
18:10 has been altered, right? That's it's such a, it's such a
18:14 exam to, to administer the two of interest are the Golgi tin and
18:20 muscle spindle. All right, they're different. Goldie tendon is gonna be
18:25 the tendon. It's looking at the of stretch and, uh, in
18:29 tendon and determining how much force a is actually making, with regard to
18:34 muscle spindle, it's actually determined the of the muscle relative to the amount
18:38 stretch that's being produced. Now, sitting there going, well, I'm
18:42 sure if I understand this. So like to use an example. I
18:44 it's a little bit easier. ma'am. Mhm After you drink.
18:56 , so she's asking about the head . I don't know why those
19:00 but it's probably again, the I don't know what specifically it's
19:05 If you don't know what the spins that you don't want them just telling
19:10 lots of experience. OK. But it happens? I don't know.
19:16 . All right. This is slightly but not so much. All
19:23 So what I want you to think when you look at a muscle is
19:26 for every group of fibers that is muscle group, what you're gonna have
19:30 with is a receptor called the muscle fiber. All right. And its
19:34 is to determine the degree of stretch to intent. All right. So
19:39 gonna give you the example and I'm see if this helps you understand what
19:43 doing. All right. So inside muscle group, well, let's say
19:47 the outside, we have what we to as the extrafusal muscles. These
19:50 the muscles that are doing the work . There's still muscle fibers that are
19:55 in the work, but there are few and they're wrapped around them are
19:59 sensory receptors detecting how much stretch is on inside that, that intrafusal
20:05 So outside doing the work inside doing detecting. OK. That's what we're
20:10 , dealing with here. All let's say I am holding my arm
20:16 like so, all right. So have the intent of maintaining my arm
20:20 out. Like so and if you to put a £10 book in my
20:24 , what would happen, my arm go downward. So no longer is
20:28 intent matching the degree of stretch, muscles are being overstretched relative to the
20:33 of work that I want them to . So what do I have to
20:35 is I have to create greater contraction reduce the amount of stretch to bring
20:40 arm back up again. I used bring in a £12 book. I
20:43 to demonstrate this in class, but £12 book sucks. All right.
20:48 you can see here intent is being , right? Or you have this
20:53 . So you know how much stretch want to put into that muscle,
20:57 when you apply a greater load, the amount of stretch that you're doing
21:01 not enough So you have to contract bring it back up into position.
21:05 only way you know is if your being overstretched, you need a receptor
21:09 do that. That's what the muscle does. Does that make sense?
21:16 . So, muscle spindle on the of each muscle are tendons. All
21:23 . When a muscle pulls on a , the muscle is not pulling directly
21:27 the bol bone, it's pulling on connective tissue attached to the bone,
21:31 is this tendon. So you can of it. Muscle to tendon,
21:35 to bone. Ok. So that's a muscle is more or less
21:39 It's pulling on a tendon, the tendon is pulling on the bone that
21:43 the bone to move right. we again describe we're gonna put our
21:49 out, we're gonna put books on hands, right? Let's say you
21:54 a gun to my head and say you drop these books, I get
21:57 shoot you. So I have Now, don't I? So we're
22:01 to stack books, right? So first book comes on down, it
22:05 up, it comes again, Because muscle spindle add the next book
22:10 , it goes up again, This is just a normal response as
22:13 keep adding book. But eventually we're to get to the point where the
22:16 of books I can hold in my is greater than the amount of stretch
22:20 that muscle can maintain. In other , I'm overworking the muscle. And
22:25 I overwork a muscle, one of things a muscle is gonna do because
22:28 is meat, right? It is tissue, it will tear and does
22:33 body want its muscles to tear? . Ok. So this is where
22:37 Golgi tendon comes in. It's looking not the muscle and the amount of
22:42 that the muscle is doing, it's at the amount of stress inside the
22:46 when the stress on the tendon becomes great. In other words, when
22:50 start stretching that tendon, which has little bit of give in it and
22:53 starts stretching more and more and That's a sign that you're going to
22:57 damaging either the tendon or the muscle . So what do we do?
23:01 going to send an inhibitory signal through sensor receptor back to that muscle fiber
23:06 say no more firing. And so am I going to do? The
23:12 relaxes and then I get shot? . Now, the shooting portion here
23:19 just to show you that I'm not up, it's I have no control
23:23 it. The Golgi tendon is protecting body from being overstressed or overworked and
23:30 doing so by detecting where the muscle doing the work in the tendon,
23:35 in the muscle itself. Ok? that kind of make sense? Kind
23:42 sort of? All right, let's about something a little bit more
23:49 How many people planning on optometry? ? All right, good.
23:55 you guys are gonna spend four years about what we're going to spend an
23:59 and a half, maybe. All , the eye is complex. We're
24:08 even going to scratch the surface. have a question. I don't be
24:11 , she said maybe a molecule. . What's up? How many slides
24:21 ? Uh-huh. Honestly, I don't when I was growing up, they
24:27 me it was lactic acid build It's a lie. It's not lactic
24:31 my side. Well, so it's, it's the idea here is
24:37 we're, it's the one of the that the cells are, are
24:40 the muscle is trying to protect the again saying, hey, we
24:44 we are lacking oxygen, but it's see what you'd expect is that if
24:47 lacking oxygen, what we would do we fall into the glycolic pattern.
24:51 so this is where they claim that was lactic acid. But when they
24:55 to see lactic acid causes the same , it does not do that.
24:58 it's not lactic acid build up, it is something in the cycle of
25:02 out of oxygen to. But we know what it is or I don't
25:06 , I don't know what it OK. All right. So first
25:13 , uh your part of your homework is to look up on Wikipedia.
25:17 image right here. Just go to light waves or electromagnetic radiation, you'll
25:21 this picture right here. And the I want you to do that because
25:24 is a movable GIF, right? not a GIF, right? Graphics
25:33 , right? And what it does it's gonna show you what a wavelength
25:36 like. See when we think of , we think of what we learned
25:39 back when, where it was just nice little sine wave or cosine
25:42 whichever, and you kind of did little thing. Um And we will
25:46 that type of wave when we talk the sound but light or Electromatic electromagnetic
25:51 , which light is a very small of actually has two components to
25:56 All right, you can see it two wave functions along two different
26:00 So we have an electrical field and have a magnetic field and I can't
26:04 it. And unless you've taken physics they've done a really good job of
26:07 it, you're gonna sit there and kind of nod your head and say
26:09 . But if you go and look this as it's moving, you're just
26:12 be first, you'll be mesmerized, for about three or four minutes because
26:15 really cool. The, the two are doing that I can't do it
26:18 my hands, but they're both moving , which is really, really
26:24 But this also helps you to understand we're not dealing with something very,
26:28 basic. All right, we're dealing something a little bit more heavy,
26:31 complex. And so light you can is within a large spectrum of electromagnetic
26:38 . You've learned this way back when learned Roy GB, you remember Roy
26:42 Bi? Yeah. OK. We wavelength, we have amplitudes, wavelength
26:48 to the degree of energy that's All right, that's one of the
26:53 ways to think about this. Whenever dealing with wave forms, you're dealing
26:56 amounts of energy. All right. second part is amplitude, amplitude refers
27:01 intensity, intensity and energy are two things. So you can have a
27:07 of light, right? Of a wavelength, let's just say green and
27:12 can have bright green light or you have really, really dim green
27:15 right? One's intensity, one is other is wavelength here. Now what's
27:22 cool about this? If you think this is that we do detect electromagnetic
27:27 , right? Because that is the field. We talked a little bit
27:31 how other creatures can detect specific waveforms this range, right? So
27:40 it's just the types of receptors we are tuned specifically to this small little
27:47 . We got to do a little of anatomy to understand what the eye
27:49 doing. And I apologize for this there's lots of anatomy. All
27:57 So the first thing you point off the eye is almost round. It's
28:00 entirely round, but it's near Uh You can see we have three
28:04 areas of interest right on the We have the sclera and the
28:09 the sclera is the white of of your eye. So when you
28:12 at somebody, you see the whites their eyes, you're looking at sclera
28:15 then if you look carefully, you'll that it actually rises up and there
28:19 this clear structure of living tissue. cells are very much alive. They
28:22 happen to be clear. This is the cornea. All right. So
28:27 is one layer, the cornea or , the sla itself is actually connective
28:37 . It continues and extends as part the covering or the uh dura of
28:43 optic nerve. I just want to of point that out now underlying
28:47 And you can see here, I know if, yeah, it's not
28:50 represented uh see the little pink that's the red. It kind of comes
28:55 like that. There's a pink there it comes underneath there. So this
28:59 the middle layer. This is your , your sill area body and your
29:02 . All right. So it's three that are derived from the same uh
29:06 materials. The choroid is the bloody . All right, this is the
29:13 . So this provides the nutrients out the square and the cornea and inward
29:17 the inner layer, we have the , the iris, you're familiar with
29:22 the iris is the muscle that regulates amount of light that enters into an
29:26 . It's also the thing when you at somebody and you see and you
29:29 my what beautiful eyes you have and talking about the color of their eyes
29:33 whatever, that's what we're referring This is a muscle that's pigmented,
29:38 is kind of cool. All And then we have this weird
29:42 You can see it over here that look like kind of like scales
29:45 It's just again, uh artist This is the ciliary muscle or the
29:50 body. It has two functions. , it plays a role in accommodation
29:54 looking far and near. That's what is. The second thing that it
29:58 , it produces the fluids of the anterior cavities of the eye, the
30:05 um uh humor, the layer that interested in is the inner layer.
30:11 is what's marked in red. This the retina, the retina has two
30:17 . The first part is the outer . So remember when we're talking outer
30:21 inner, we're talking moving into the . So the outermost part is the
30:27 directly next to the choroid. The layer is a pigmented layer again.
30:32 you ever looked deep into somebody's I mean, like you're on a
30:39 , you know, they're looking right into your eyes. You, you're
30:44 the same thing you're giving each What eyes, right? And you're
30:47 like, I'm just lost in the dark of your eyes. There was
30:53 never said that you guys got to out. I'm telling you that's gonna
30:57 the theme today. Put down my and get out. All right,
31:02 when you look into someone's dark you are actually looking into their
31:09 The thing is is that when light in like a roach motel, it
31:13 come out so your eyes look right? I've seen glasses,
31:19 glasses, glasses, the rest of who don't have glasses? Have you
31:22 had an eye exam? Right. do they do? They get that
31:27 old shiny light? Right? It's put you in the little chin
31:31 right? And then what do they ? They, they dilate your eyes
31:35 so that it sucks because you can't anything and then they blind you with
31:38 horrible light. It's actually not a bright light. It's just, there's
31:42 a lot of it, right? what they're doing is they're shining a
31:45 into the eye and they're using a bit of, of some sort of
31:51 so that they can look in with light at the same time because when
31:54 goes in, it travels through the layers which are going to be where
31:59 receptors are and they light doesn't bounce out because if they did, then
32:04 wouldn't be able to understand the world you because light would be coming from
32:07 wrong directions. Instead it hits this layer and that light gets a sore
32:13 . And of course, you learned back when you learned about Roy G
32:17 is not the absence of light black light. And that's why the insides
32:23 your eyes look black. That's why have dark pupils. OK. So
32:30 iris is the color, the pupil the middle is literally the space traveling
32:36 into the body, the cavity of eye. All right. Now you
32:42 see here. Also, we have lens, we have two different uh
32:46 back here. This is vitreous Vitreous humor is more like gel.
32:50 goo it doesn't actually change all that over the course of your life
32:54 But every now and then you'll have cell flake off and end up floating
32:58 in your eye. And so if ever had flo, I don't know
33:01 you might call them, but you , you see that thing and you're
33:03 , I'm gonna watch that and then just kind of does this in your
33:06 . You've done that. That is floating in the Vitria humor. There's
33:10 you can do to get rid It's basically light is hitting it and
33:13 it funny and that's why you can it and the front of the eye
33:20 produced by the ciliary bodies, Is aqueous humor. So there is
33:24 division here. Aqueous humor washes over around the, the iris and then
33:32 into the anterior chamber. So this nutrients and materials that keep the front
33:37 of the eye alive. So, other words, in order for your
33:40 to be alive, it needs to the nutrients. This is where it's
33:43 from and then we get to come the best name ever in anatomy.
33:48 right. See that little dot Right , there's one over there too.
33:53 is how acre humor leaves the It's called the canal of slim.
33:59 don't need to memorize it. You even need to know it. It's
34:01 a fun word to say slim, it. Canal of slim named after
34:09 guy who discovered it. Poor Right? When you have glaucoma,
34:17 happening is, is that the canal slim gets blocked up and then the
34:22 accumulate in the aqueous humor and you another goo like substance that then can't
34:27 leaving. That's gonna include the So I don't know what they're gonna
34:32 it when you get to optometry school they're taking away all the eponymous
34:37 So it might be the, the of aqueous humor. Who, who
34:42 ? But you will always remember Canal of slim quick answer. Say
34:52 . Oh yeah. All right. she's asking the question about the
34:56 All right. And how you pronounce . It doesn't matter. There's I
35:00 think I've told you guys, I'm a member of a, of
35:03 , uh uh just an organization. a Human Anatomy and physio Physiological
35:09 And we have every year, one the main uh authors on one of
35:14 textbooks gives a lecture on how to words because we all pronounce everything
35:19 And he does it in such a that it feels like a game show
35:22 doesn't make you feel so stupid. it's like here's this word, how
35:26 you pronounce it? And he pronounces the four different ways that it could
35:29 be pronounce. And everyone raises their and then every one of us is
35:32 when he shows us the fifth So it's awesome. But what is
35:36 conjunctive of what does it do? right. Basically what it is is
35:38 layer of connective tiss you sow that have something that protects the back of
35:43 eye from the front of your In other words, the external environment
35:46 the internal environment, right? It's so tight that it covers the
35:51 you know, like flat, it's like a skirt, like a billowy
35:57 , it's tight around the waist. it goes right up next to the
36:01 , but then it kind of loosens because if it didn't loosen out,
36:05 could never do this. I don't if you could see what I was
36:10 my eyes, right. Moving my back and forth, right?
36:13 if they're all taught, you can't your eyes. So the idea is
36:16 it has a certain degree of freedom what it does is it wraps up
36:20 underneath the eyelid and goes about halfway behind the eye and then it comes
36:23 around again and then forms on the side of the eyelids and um,
36:28 all sides. So that's what it . And then, so when you
36:32 conjunctivitis, so what is it? , it's an infection, right?
36:39 basically, you have a bacterial infection that causes inflammation. So all the
36:43 vessels which are not located uh specifically the conjunctiva, but they're located uh
36:50 back, that's they all get a and puffy and then you have red
36:52 and everyone thinks you're scary and gross you are all right. So the
37:01 of all these structures that you're looking here is to bend the light to
37:05 very specific location on the retina where have the highest concentration of photoreceptors.
37:11 right. And so really what we're to do is we're trying to get
37:13 down to uh what is called the . Do I have a listed up
37:17 ? I don't. So I think the last one, see if I
37:21 that on the last one. So down here in the phobia,
37:24 ? So what we're doing is each these have a certain degree of refraction
37:28 them. And so you don't even to memorize numbers or anything like
37:32 But what you can imagine is if light is coming at you, you
37:35 , more or less straight, then you need to do is you need
37:38 bend that light so that its focal comes to that back part of the
37:42 where the phobia is located. So of the bending is going to be
37:46 place in the cornea. But each these layers, because there's fluid,
37:50 know, which is primarily water, other stuff is going to cause bending
37:53 well. So all of them working causes the bending. The lens itself
37:58 plays a really, really important role to direct light specifically to the phobia
38:05 upon where you are looking. So has to do with how light waves
38:09 moving out in the environment. So further you are away, the more
38:14 is going straight, but the closer are to the light source, the
38:17 the light is actually kind of So you have to stretch.
38:21 I see the kind of the brow does that make sense. Well,
38:25 got to think of it in terms like all the light waves are going
38:28 all different directions all the time, ? But in order for them to
38:31 off something and travel to me, had to travel straight at some
38:35 the further something is away the more it had to be to get to
38:39 . Right. In other words, it's a mile away and it's off
38:42 0.01 degrees, it's gonna bypass Right. But if it's like on
38:47 piece of paper here and it's reflecting , 0.1 degrees is not going to
38:50 that big of a deal because the waves are going to be more,
38:54 more freedom. There's not a a long distance for that, that
38:57 to travel. So what we need do is when we are looking either
39:02 or far, we need to refocus light back to the phobia to where
39:06 needs to be. And this is is this process of accommodation.
39:10 the way this works, it has do with the muscles, the intrinsic
39:13 of the eye, not the I just threw two words at
39:16 What do they mean? What does mean inside extrinsic? It would mean
39:22 . So intrinsic are the ciliary All right, the extrinsic would be
39:29 muscles that make your eyes wiggle right and let you look up and
39:32 , left and right while keeping your straight. Ok. So what we
39:37 here is we have a muscle, sill muscles are are spherical muscles,
39:42 wrap around the eye. So when contract what they do, so imagine
39:48 , they fall forward, right? when they relax, ah they fall
39:55 , kind of makes sense. So I have the muscles contracting, I'm
39:59 , I can't squeeze the eyes. I have to move to where I
40:02 move. And that means I'm moving when I'm relaxing. Uh Now attached
40:07 the Siller muscles are a series of , muscles and ligaments go together.
40:12 right. And these ligaments are attached the lens. The lens has a
40:17 shape. When I pull on the , I make the lens thinner and
40:23 . When I relax on the the lens gets squatter and fatter.
40:29 so light is going to be bent under those two circumstancess. Ok.
40:34 what this is trying to show you thin and, and long versus the
40:38 . Ok. Now, this is you have to think a little
40:42 right? When the muscles contract, fall forward, right? When they
40:47 forward, do the ligaments get tight loose, they get loose.
40:53 So I'm contracting the muscle, the falls forward. So the ligaments
40:57 ah, can they get loose? . And then when I relax the
41:05 they fall back, what happens is ligaments they get stretched, they get
41:11 . All right. So which one , which farsightedness when I see far
41:17 , near side is when I can near, right. So which one
41:20 responsible for which? Well, when are relaxed, you have a resting
41:27 . And so what you can see things far away. All right.
41:30 other words, accommodation occurs so that can see distance wise when I am
41:36 those muscles, I can see things . All right. Now, how
41:40 I remember this? All right, , you come up whatever way you
41:46 to, to remember something, I up with the dumb ways,
41:50 That make me remember stuff. Have ever been so tired that you're just
41:54 off in the distance? Right? like, uh, I'm just
41:58 I'm just relaxing. I'm relaxing my and so I've got the three mile
42:04 . So my eyes are relaxed. see far away. And when I'm
42:11 and reading and stuff like that and start getting that headache. It's because
42:14 working those muscles so hard because I'm at stuff really close. Right?
42:23 when I'm stretching the ligaments, when being pulled, that's when I'm doing
42:30 , that's why I remember it. . Did I do that backwards?
42:35 think I just did that backwards. , muscles are relaxed. No,
42:39 did it right. Muscles are When muscles are contracted, the ligaments
42:43 loose is what I meant to So I did get it backwards.
42:47 gonna say it one more time. no one is confused. And so
42:50 can say I taught you correctly when muscles are relaxed. I see far
42:59 ligaments are tight. The, the lens gets uh thinner. So when
43:06 muscles relax, I can see far when my muscles are contracted, that's
43:11 hard work. So now the ligaments relaxed. I can see near this
43:16 the process of accommodation moving between the and you can try this. All
43:20 . Look at something right in front you. Like look, look in
43:23 of you and then look at the , look down, look at the
43:25 , look at how quickly you You see that in that wild.
43:32 . What's really interesting is your eye actually, I think processes,
43:37 like it's something like 20,000 frames per . So it actually is going around
43:42 room and looking at all the different like that quickly, your brain can't
43:48 that fast, your eye can. it's something ridiculous like that. So
43:54 we understand the lens? What its is near sightedness, farsightedness. All
43:59 . And then in terms of the when the muscles are relaxed, far
44:03 the muscles are contracted near iris is than the lens, right? The
44:15 controls the amount of light going into eye. All right. It's sympathetically
44:21 . There are two muscles here. have a sphincter muscle when you think
44:25 sphincters, which please don't think of . That was a joke.
44:32 I know the look on her face what no sphincter muscles, what do
44:36 do? They contract, right? body actually has seven sphincters in a
44:41 in the digestive system and we'll talk about them when we get there.
44:45 right. But once I contract that muscle, how do I get it
44:49 relax again? Well, I have have a radio muscle that pulls the
44:53 back. All right. So, two muscles here are the sphincter and
44:57 dilator. All right. And they sympathetically regulated. Uh, the sphincter
45:04 the circular one parasympathetic. Um, then the dilator is the sympathetic.
45:09 do you remember which one is, , or which one is a
45:12 which time wind sympathetically stimulated? All . So think about um, you're
45:18 along, I grew up in the , you can do it here.
45:21 But if you're walking along and you a rattlesnake because you do hear that
45:25 the desert, what do you Do you want to know where that
45:28 is before you take another step, you? So not only does your
45:31 rate go up? Not does your go up? Not only does
45:33 um, your respiratory rate go but your eyes dilate and let more
45:38 in so that you're more aware of surroundings. So that's how I remember
45:41 is dilation. OK? I never on this. I just throw this
45:53 here to just show you um, you're wearing glasses, I know you
45:58 my stories. I had perfect eyesight the, until I was 45 years
46:04 , never wore glasses. It this is for the, the four
46:11 you are planning on optometry school. carefully. So here I was,
46:15 couldn't read my, my kid's medicine . I'm like, doing everything I
46:21 to read this thing. So I'm like, ok, I'm going to
46:23 optometrist, find out what's going She tells me, you know,
46:28 have a stigmatism. 45 years Never worn glasses in my life.
46:33 like stigmatism. How do I possibly a stigmatism? This is the lesson
46:41 old. That is what she told . Do not tell someone they're
46:50 No, but no, I'm still . My brain still feels like I'm
46:57 college and I'm surrounded by all y'all if you guys don't have fun.
47:03 , but anyway, so if you with near sightedness, far sightedness,
47:08 reason is is that we're not able focus the light where it needs to
47:14 . You can see where the focal is. And so remember because we're
47:17 light waves and the eyes have changed in these particular cases, the stigmatism
47:23 sucks whatever, right? What we is we're putting glasses another layer to
47:28 the light so that it hits the point. So the goal of the
47:34 is to get light to the to get it to the retina and
47:39 retina is where all the action takes . So all that anatomy I just
47:43 you and what was going on? goal is to get the light where
47:47 needs to be right. So light going to travel through the cornea,
47:52 the aqueous humor, through the through the uh the vitreous humor.
47:56 it's gonna work its way right down the retina and that light is gonna
48:01 the retina. And what it's gonna is it's gonna pass through multiple layers
48:06 cells to get to the photoreceptor So the retina has those two
48:14 the first layer that you're going to if you are coming through the cornea
48:19 the back of the eye would be neural layer. And then if that
48:23 doesn't hit the right cell, then it's gonna do is it's going to
48:26 and get absorbed in the pigmented So they then go bouncing around the
48:30 of your eye, confusing your brain to what you're looking at. All
48:34 . The other advantage that the pigmented has is that if light decides to
48:39 through the sclera is light gonna make to the pigmented layers or not pigmented
48:47 to the photoreceptors. The answer is , because it's basically like putting blackout
48:52 all the way around the inside of eye. So light will either hit
48:57 it needs to hit or it will absorbed. Now in looking at
49:04 that's not all it does. So importance of the pigmented layer is literally
49:09 create that blackout shade. But the thing that it does, it is
49:12 takes vitamin A and turns it into chemical that your eyes need. You've
49:18 heard eat carrots. It's good for eyes because there's lots of vitamin A
49:22 carrots. Well, what we're doing vitamin A, is this long chain
49:27 or it looks like a fat, probably not a fat, but at
49:30 ends are two phenol chains or two rings, you cleave it directly in
49:37 and you get two retinol molecules and the retinol that your eyes care
49:42 That's what it wants. All So we're going to get that
49:48 The neural layers has multiple layers of that are located in the eye.
49:55 , the photoreceptors are the only receptors here, kind of the rest of
50:00 cells in there are responsible for modifying modulating the signal before it ever leaves
50:06 eye. So the information, the information that you're receiving is actually preprocessing
50:13 it ever leaves the eye, which really kind of cool. So we
50:18 three major groups of cells and then have two groups of cells that sit
50:23 between them. And we're going to from the in or from the outermost
50:29 the innermost. All right. So going to from next to the pigmented
50:34 and we're going to go up to , where the Vitria humor sits.
50:38 right. So the first layer is photoreceptor cells. This is where all
50:41 action is at this, these are sexy cells. These are the ones
50:44 get all the attention because without you don't see, OK, there
50:49 two different types. We have rods we have cones. Why are rods
50:52 rods? They're shaped like a Why is a cone called a
50:56 Because it looks like a cone? . We're all on the same
51:00 Their job is to receive light energy turn it into a greater potential.
51:05 that greater potential results in the release neurotransmitter that is then released on to
51:09 next group of cells called the bipolar . They're bipolar, not because they're
51:14 and sad. There's two dendrites. is axonal, one is dendritic,
51:21 ? So you can see here here the receiving side, there's the cell
51:24 , there's the axonal side, all . But again, these aren't particularly
51:28 cells. So they're not really they're just extensions. And so they
51:33 produce graded potentials and that greater potential in the release of a neurotransmitter that
51:38 a on the next group of These are the gang cells. All
51:43 . So these are the true These are the cells when we talk
51:48 that first order neuron, this is first order neuron that we're that we're
51:51 kind of dealing with. Here. represent a single ganglion cell represents a
51:57 field in the eye, right? what this suggests when I say that
52:03 that, that single in that single is going to have many bipolar cells
52:09 each of those bipolar cells should have different types of receptor cells or there's
52:14 potential for that. All right. all the light that's coming in is
52:20 to stimulate ganglion cells. Time this is an important time out.
52:27 going to use some hyperbole and I'm to be simplifying things significantly to understand
52:34 eye. All right, because very you'll see bipolar cells paired together,
52:40 see ganglion cells paired together so that have one that's on and one that's
52:44 . And so you might have one and one off bipolar cell on a
52:48 gangle cell which might be the on it might be the off. So
52:53 a lot of stuff going on in all the different cells. So we're
52:56 the most simple model we can to this stuff. We're going to say
53:01 cell activates a bipolar cell which activates ganglion cell and keep it that
53:08 OK. When we describe this in the bipolar cell and photoreceptor cells,
53:14 have modulator cells, these modulator cells called horizontal cells because they are
53:22 right? And that's what they're trying show you here. So their job
53:25 to modulate the signals going between those cells. We also have up here
53:31 the bipolar cells and the ganglion Another group of modulating cells, these
53:35 the amrine cells So already you can here is I've got things that are
53:41 how two cells are talking to each in the eye. And then if
53:47 told you how complicated, like I said, there's some complications even within
53:51 of the layers, there's modulation that's there as well. Just as an
53:56 . Do you guys remember the black , blue dress uh thing couple,
54:00 , right. What was it, it really a black dress or was
54:02 a blue dress? I just want see if we can start a
54:08 So part of that, of how perceive those images is a result of
54:14 that was going on in the eye the level of the eye kind of
54:18 . All right, before we go , let's deal with the photoreceptor
54:25 All right, this is where all action is, this is what we're
54:27 in. This is why you're taking class. OK. What we have
54:31 is we have the visual spectrum. right. And what this is showing
54:35 in this particular thing is you can the wavelength of that electromagnetic radiation and
54:41 can see on the on the y here is the relative absorbent which you
54:45 interpret to mean the amount of All right. So how active are
54:51 cells relative to this particular uh amount electromagnetic radiation or this particular wavelength?
55:00 for example, I'm just gonna use rod that you can see in
55:05 So you can see the rod is black one, the rod is stimulated
55:09 light waves are between about starting around . Uh um Sorry, what,
55:16 am I looking at here? It's nanometers. I had milliseconds stuck in
55:21 head and it was not going to away. All right. So about
55:24 nanometers, right? And you can it's about 40% active, right?
55:30 over time when you get back to it's really active. In other
55:35 if I give it a light that's at 500 nanometers, that receptor
55:41 goes absolutely bananas. It's at most , it can possibly be. But
55:45 I give it a wavelength at around it's only about 40% active. And
55:49 you can see the range in which active. So this entire range I
55:54 activate to varying degrees. And this true for all the different types of
56:00 cells that you have, right? you probably have heard these photoreceptor cells
56:06 being the red, the blue and green. Have you ever heard those
56:08 ? Red cones, blue cones, cones. Have you heard that?
56:13 right. Those terms are incredibly bad because you can see here. Um
56:21 just use green for the example. green, what type of cell is
56:26 at green? Well, the S is stimulated at green. Um so
56:34 the L cone, so is the cone and so is Roop or the
56:42 . So it's a terrible terminology that came up, but it was
56:49 easy way to kind of say, yeah, these are low watt light
56:52 , these are high light wave, are medium light wave and that's what
56:56 S and the M and the L for, right? It's super mid
57:00 low frequency. So you can see , that would be blue. So
57:07 are tighter bands out here low, are longer wavelengths. And so that
57:14 be where you're, where you're getting um these numbers. Do you guys
57:20 you'd need to bother to memorize them all? Of course, not the
57:28 here is that your walkway takeaway from is that the different types of cones
57:35 there are three cones and the the , the receptor that are found in
57:41 , all are stimulated across a wide of, of wavelengths, right?
57:48 each have AAA range and they have within that range. So they can
57:56 maximally stimulated or minimally stimulated. The thing that, that, that you
58:01 take away from this is that when look at color, color is not
58:06 the stimulation of a single receptor. , look at green. How many
58:11 those receptors did we say were being at, at this color green?
58:16 this beautiful hunter green. I don't what color it is right, all
58:19 them. But notice here, the is only simulated at 20%.
58:23 We're 50% there. We're gonna just that at 70%. And then the
58:28 don't participate in color at all. it's the combination of all three of
58:32 receptors and the degree of stimulation that rise to our perception of color.
58:46 to see I see kind of a in the room. Pink is
58:51 is a good one. But you know what pink is. Can you
58:54 pink up on that color chart in ? Roy B. Roy G?
59:01 do you think? No, but you see pink? Are you aware
59:04 what pink is? There's a maroon there? Do you see maroon on
59:08 ? No, it's not Roy Why can we perceive these colors?
59:14 because there's modulation in this and if ever played with Photoshop, right?
59:19 can do cmyk or the R GB you can adjust the colors to get
59:24 what you want. It's because there range within this. You're not just
59:29 eight colors. In fact, let just ask a thing right now because
59:32 know how much love I go off tangents, right? How many colors
59:35 you think humans can perceive? Throw numbers at me? You're all gonna
59:42 wrong. So just throw a number me. Huh? A billion.
59:47 is definitely wrong. Huh? That's how many guys can identify.
59:53 , we're closer to eight Roy GB , black and white. That's about
59:58 . What do you have? No ladies, you guys know
60:03 you know, 500 colors of right? 3000. I heard what
60:11 million keep going. Billion was way much. We're closer to about 14
60:19 colors that we can actually perceive. we have names for them all?
60:24 you work for Sherwin Williams probably do , but for the most of
60:28 we can be satisfied with just that's , that's blue. Ladies, you
60:32 , the different colors distinguishing between the colors of blue, like corn,
60:37 and, and navy and whatever that . What color is that? Aqua
60:47 ? See what color is that purple there? Huh? Lilac. Do
60:56 see that lilac? See they what color is that? What color
60:59 your sweatshirt? What would you call purple? So the other thing is
61:07 can actually uh perceive greater colors than can. It's actually one of those
61:13 that you guys have now with regard the eye in regard to the
61:19 So we have a retina think of retina as being a globe. You're
61:22 at the inside of a globe. what we're gonna do is we're gonna
61:24 it out for you. All And what we're doing is if you
61:28 at that retina, you'll notice that you are on the edges of that
61:32 because it doesn't come all the way . Remember, lights coming in this
61:35 on the edges of that retina, have a greater concentration. In
61:39 you almost have almost exclusively rods. as you move towards that Phobia,
61:44 is right behind the, the right behind the lens, that phobia
61:50 where you're going to see the largest of these cones. And that's what
61:55 little map is just trying to show . It's like over here, purple
61:59 the rods and then the green represents cones. And so look at how
62:03 cones are just jam packed inside the . All right. And what this
62:08 is it provides you greater acuity because two things. One you're using uh
62:15 cone instead of rod, which we'll to in a second. But the
62:17 reason is that we have a uh lack of convergence in, in the
62:23 phobia. What this means is that you look at a photo receptor cell
62:28 the phobia photoreceptor cell, a single cell might be only associated with a
62:33 bipolar cell, which is only associated a single ganglion cell and they're jammed
62:39 in there like that, which means every time a light particle hits a
62:43 cell, it's hitting a very, small receptive field. But over here
62:47 the edges, right, we'll have rods, there might be some cones
62:52 there, but it's mostly rods. what you'll have is I'm getting,
62:55 making up numbers here. So just with me. You may have for
62:59 ganglion cell, you may have 10 100 bipolar cells and then for each
63:03 those bipolar cells, 10 to 100 cells. So over here on the
63:11 , you don't have a lot of , right? Instead what you have
63:15 you're having very, very large receptive . So if light hits over here
63:20 over here, you're still getting the activation of a ganglion cell. Now
63:25 show this to you, I want to look at whatever it is that
63:27 writing on or whatever it is that reading and I don't want you to
63:30 your eyes, but I want you focus on a single word. Is
63:34 nice and crystal clear to you? say yes, if it's not,
63:36 need to go see your optometrist. , but notice you see how it's
63:40 , keep looking at that. Don't your eyes wander, but notice how
63:45 you kind of pull your vision back let yourself kind of see around that
63:49 , it's kind of fuzzy. And you want to do is desperately move
63:52 eye to go look at that, ? So what you're seeing here is
63:57 light enters your eye, it goes to the phobia. And so where
64:01 is coming straight into the eye, going to this high concentration to give
64:04 this acuity but surrounding that you don't acuity. You don't need all you
64:09 to know is a generic thing of going on. So, out in
64:12 periphery, it's a little bit But if you need, if you
64:15 something moving or something feels like danger maybe grabs your attention, what do
64:19 do? You turn your head and your eye to the thing that you're
64:24 at. So when we read, not, you know, keeping our
64:27 fixed and just kind of letting the absorb in, we're actually moving our
64:31 to the thing that we're actually looking and we're directing uh light to that
64:37 . So we have a high concentration photoreceptor cells specifically cones at the
64:45 There is very little convergence, So in other words, it's 1
64:49 1 to 1 almost in the And so it gives us a high
64:54 of acuity. Whereas on the we have high convergence and we don't
65:01 that high density of cones, we more rods. Now I throw this
65:06 up here. This is almost um helpful because I know that not every
65:10 of you has a video file, it kind of gives you a sense
65:13 what I was just describing here. I grew up with Standard, actually
65:16 less than Standard Def. Standard Def 480. It used to be the
65:20 , used to be 2 40. if you watch like shows on Nick
65:23 night, if they still do um They're really, really bad,
65:28 ? What is full HD in terms number of pixels, do you guys
65:32 ? So, so you, you bought in the hype 7
65:35 That's, that is true. 7 is acceptable high def but the true
65:39 is 10 80. Anyone who sells less is lying to you in
65:44 All right. But it's pretty right? You can see that versus
65:46 very clear. It's a difference of times the number of pixels just in
65:51 vertical, but it's actually significantly And then if you really bought into
65:55 48 or the four K, that's 2000, right? See again,
66:00 you see the marketing here? Four . No, no, no.
66:03 two K 1,002,000, but it's much clearer and this is how your
66:10 is interpreting information. This would be phobia. This is moving away from
66:14 phobia and this is out on the . That's the degree of acuity because
66:18 you have here is not large receptive . You have see bitsy tiny receptive
66:25 in the phobia. Yes, ma'am. Excuse me. Say
66:37 that's honestly, I've never been asked question. So I don't know.
66:40 suspicion is that you're probably trying to your extrinsic muscles to strain your eyes
66:45 such a way to adjust the amount light that's getting in. I don't
66:49 . I'm, I'm a wild spitball there. So don't, don't,
66:53 , don't have any idea. All , this is a nice little way
67:00 kind of do the compare and contrast I think is kind of important
67:03 Right. So, in terms of , there's only one type of
67:06 there's three different types of codes, S MLS. All right. Which
67:10 at different wavelengths a lot. What their shape or shapes or feature should
67:14 pretty obvious. Rod vs cone. is their role in color vision?
67:18 , rods have no role in color cones play a role in color
67:23 right? Because they're the ones that responding to the different wavelengths together.
67:28 rod just kind of do everything in of sensitivity, rods are significantly more
67:34 to light energy than cones. Are play a role in us seeing in
67:39 dark. And in fact, if give them too much light, they
67:41 out and they stop working. All . So right now, your vision
67:46 predominant, being determined right now by because we're in a bright space.
67:52 the rods have been bleached out. so they've basically been turned off,
67:55 the cones they're very active and that's everything is visible right now. So
68:01 terms of sensitivity, rods are very , a single pig or a single
68:07 of light can activate a rod but it takes much, much more
68:12 and much more photons to do the thing for a cone. Anyone here
68:16 to drive to the university this morning 6 36 45. Yeah. Isn't
68:19 a lot of fun? Did you how it was really, really
68:22 And over time things become less right. That's not just a function
68:26 the light being available. It's because eyes are modifying themselves. Going from
68:30 is called scotopic vision to photoop moving from rod vision to cone
68:36 right? In terms of acuity cones not play a major role in acuity
68:41 do not again, think about If you wake up in the middle
68:44 the night and you move around your , you can see light coming in
68:47 the shades or through the curtains a bit, but not enough to light
68:50 the room. You can see that pile of stuff that you left over
68:53 might be laundry, it might be monster, you're not quite sure,
68:57 ? But it's there and you can it and you can step around
68:59 So the idea is that you can a sense of shape, a sense
69:03 presence of things with rod vision, vision, but not so much clear
69:09 . So scotopic photo topic, scotopic night vision, photoop is day
69:14 That's what those two terms. So topic would be cones in terms of
69:19 . We already said rods play a role in convergence. They're around on
69:22 periphery cones, they're very, very convergence. And finally, in terms
69:27 concentration cones are found primarily in the . As you move away from the
69:32 , there's less and less cones, and more rods ready for a little
69:40 of fun signal transduction. Anything new ? No. All right. So
69:45 just gonna walk through the players. was actually the very first signal transduction
69:50 discovered, which is kind of So much of the nomenclature you see
69:54 is a function of this was the time it was discovered. So we
69:57 things special names and then realized it over and over and over again.
70:01 , what we're looking at here is have a G protein coupled receptor,
70:05 it's a unique G protein coupled All right. So this is the
70:10 uh uh the rin. So rhodopsin found in um uh rods and then
70:17 is found in cones. All But it's an opsin molecule. And
70:22 this is a G protein coupled receptor associated with that G protein coupled receptor
70:27 its ligand. The ligand is already . The difference is that the ligand
70:32 shape in the presence of light. that's what we're going to be looking
70:37 . Here's our G protein, we call it translucent. Great name it
70:43 light energy into a chemical signal. G protein is responsible for activating phospho
70:52 . All right. So what does dira do? Phosphorus takes cyclic GMP
70:56 it into GMP. It basically breaks cyclical molecule. Where do we get
71:02 cyclic GMP from? Well, we gate cycle. This is just always
71:06 , it's always producing cyclic GMP. there's lots of cyclic GMP inside the
71:12 . And then why we have cyclic P is, well, we have
71:15 receptor or these channels that are associated these structures, whether they're on the
71:20 of the cell, on the cone whether you're inside the rod, it
71:24 these discs that look like pancakes. can see here these little discs,
71:28 where they're located. Actually, that's better view right down there. They're
71:31 with that. And so when cyclic is around, they bind to these
71:35 and they open up the channel. sodium comes into the cell. When
71:39 comes into the cell, what What's the word we use? It's
71:45 . All right. Now, this the stuff that we're gonna be dealing
71:51 . So we're gonna come back and to these. But before we start
71:54 with this process and all the steps the mouse trap uh process, let's
71:59 understand this is a concept we haven't before, but we should have covered
72:03 because we need to understand that no whenever you're dealing with channels and stuff
72:07 you have current flowing into a cell has to be something that removes the
72:12 back out. So the current continues flow. That kind of makes
72:15 In other words, if sodium is , if those channels here are always
72:19 , sodium is always going to rush the cell until it reaches equilibrium.
72:23 there's going to be a point where equilibrium is going to be reached.
72:27 don't want that to ever happen. so what we have is we have
72:31 series of channels, potassium channels that us to move potassium out and create
72:38 flow. And then we have pumps place that are always making sure everything
72:41 moving back and forth. So in dark under normal circumstances, in our
72:47 cells, we always have the cyclic channels open or the cyclic nucleotide gated
72:53 open. Sodium is always flowing into cell. All right, sodium is
72:57 flowing in the cell. We get of the sodium by pumping it
72:59 But in doing so we pump potassium right uh oh too much potassium.
73:04 we have these channels to allow This is the dark current. So
73:08 in the dark, your cells are . Now, when I think of
73:15 , I don't know about you and answer the question in just a second
73:19 I think of de polarization, I of activation, don't you? So
73:23 the dark my cells are depolarized. my cells are active uh-oh and it
73:31 it weird, but it's more energy and I will show you in a
73:36 . Yes, ma'am. Ok. just, you're asking a whole can
73:44 worms. I don't know the answer . That's ok. Just, just
73:47 showing people that I'm dumb. it's good. All right.
73:49 no, no, it's good. . You need to know that.
73:52 can't know everything when people go Why do they go blind? Is
73:55 question? And the answer is, don't know. It could be,
73:58 could be at the level of the , it could be level at the
74:01 of the optic nerve. It could at the level of the geniculate
74:05 It could be at the level of brain itself. There's all sorts of
74:11 . So, I don't know, it's good. Right. Aren't you
74:15 ? I don't know stuff? So, remember with cataracts, that
74:21 the aqueous humor not being able to out of the, um, of
74:26 anterior cavity. And so what happens I said glaucoma didn't, I,
74:30 so bad. It's cataracts, cataracts the Anno glaucoma cataracts. See,
74:36 start talking, my brain goes one . And what happens is you get
74:39 gunk this goo and basically it sits there. What you have to do
74:43 you have to slice up the, cornea and then you have to pull
74:46 stuff out because it doesn't have a to drain out. That's what the
74:50 is. Huh? Yes. Yes. The question was, if
74:59 remember, doesn't it come back Yes. But it takes time.
75:02 . Cataracts don't just pop up. , they accumulate over time. All
75:07 . So, what we have here we have a cell that is depolarizing
75:12 the dark and releasing neurotransmitter on the cell. So, what is it
75:15 to the bipolar cell? Is it the bipolar cell? Yes, it
75:20 . So that's our first, that's first frame of reference. Our photoreceptor
75:24 are active. They're depolarized, they releasing neurotransmitter and they're stimulating a bipolar
75:29 . All right. But why can see in the dark? Well,
75:32 has to do with what's actually going here. So let me just show
75:36 here. This is our photo This is our opsin molecule is our
75:40 . You can see retinol here. exists in two states relates or it
75:45 bound to the sin molecule in the cyst form. So it has a
75:49 that's bent and then it, I'm inside this, this receptor light comes
75:55 and is summarizes that tail. Do ever wonder why I take organic
76:00 That right there, those three words used sis trans and isomerize. So
76:06 you know what am I doing? twisting the tail. The tail is
76:09 straight that causes the change in the of the photo pigment. Photo pigment
76:13 now no longer in the original I've activated the receptor. So light
76:17 activating a receptor. And what it's to do is it's going to cause
76:21 chain of events that are going to in the hyper polarization of the photoreceptor
76:28 . So this is just kind of you what it's doing, right?
76:30 when light comes along, I turn into the transform, the transform now
76:35 activated the option, the option is to go through a process of re
76:40 itself so that it can be received again. But what we've done is
76:44 activated this molecule. This option I love just throwing this up here
76:47 to show you how little we actually about in this class. So this
76:51 actually the process called the retinoid Do not under any circumstances. Try
76:56 remember any of this stuff. I not going to ask you a question
76:59 this. I'm just showing you to you all the different strips that go
77:03 just to get that s form that into the transform back to the S
77:09 because once it turns into cyst, can't do any or once it turns
77:12 trans, you can't do anything to . All right, here's the visual
77:16 pathway. See what we got We got light coming in light is
77:19 to change that from cyst to When that happens, we activate
77:24 When transduce is activated, it takes uh GTP and it was bound to
77:31 . It replaces it with GTP that alpha subunit goes and activates phosphor
77:37 phosphor Dira activates, it starts taking GMP and gobbling it up and turning
77:42 back into cyclic or into regular So what I'm doing is I'm reducing
77:47 amount of available cyclic GMP P. there's less cyclic GP, there's less
77:53 bind up to those channels. And there's less to bind up to the
77:57 , what do the channels do they up? If the channels are
78:01 does sodium go into the cell? ? If the sodium doesn't go into
78:05 cell, the cell stops depolarizing and hyper polarizes. So the cell
78:11 If the cell stops, it's no releasing neurotransmitter. If I'm no longer
78:15 neurotransmitter, I'm no longer stimulating the cell. But I still don't understand
78:20 I see. Well, you need understand what type of neurotransmitter you're being
78:24 here in the dark, the neurotransmitter being released. So you already understand
78:30 steps here. The neurotransmitter you're being , you're releasing is an inhibitory
78:35 And what you're doing is that photoreceptor when it's not stimulated is telling the
78:40 cell do not fire, it's preventing from becoming active because it, this
78:47 , is being prevented from being The gangly on cell downstream doesn't produce
78:53 potentials. So it does not send signal to your brain to say you
78:57 seeing light. But when light comes , we are no longer releasing
79:05 we hyper polarized, right? If no longer releasing neurotransmitter, the bipolar
79:10 is no longer inhibited. Its natural is to release a neurotransmitter. In
79:15 words, it naturally depolarizes, starts neurotransmitter. When it releases a neurotransmitter
79:20 activates the action or the gang the gangland cell fires and it tells
79:26 brain you're seeing light. Well, doesn't it do it? Like I
79:30 it to do it, which is see light and you activate the cell
79:32 things happen. Well, the thing , is that in the light versus
79:39 day or sorry, day versus there's more light in your life than
79:43 is darkness, right? We tend live in areas where there's more
79:49 So you actually use less energy over course of a life span. If
79:55 doing it this way, when you're things around, there's ways to modulate
80:05 , this is what these two slides about. And really what I want
80:09 just say is that the system that have here that we described here is
80:15 a binary system, it's not on . OK. What we have is
80:19 have other molecules like G cap and job is to modulate. So that
80:25 of going on and off, what have is you have varying degrees of
80:30 and off, right, you're balancing towards the middle, dependent upon whether
80:36 not the light or dark is there the level of the receptors we also
80:42 because we use um for example, was just trying to see it not
80:46 up here there, it is co calmodulin binds up calcium and calcium is
80:51 one that's playing a role in both these things. They're the ones that
80:55 the the gate. So the gate not just opened and closed, it's
81:00 open, more open, more most open. And so what you
81:06 do now is you're not transitioning so from here to there, you're transitioning
81:12 here to here. So you can the degree of hyper polarization and depolarization
81:19 upon the cell. So you can respond to the presence of light.
81:24 we get back, we'll just finish up. We already talked about color
81:27 , talked a little bit about So two little slides before we get
81:31 the air is just fine and just case you don't know, remember you
81:40 be signing up for the test which next Thursday, not this Thursday,
81:45 Thursday. No. So it
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