| 00:06 | I guess I had just never I . I paused it right after I |
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| 00:11 | it. Okay. Well in theory working now. All right. So |
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| 00:19 | I want to do is I want talk about the eye and we're gonna |
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| 00:23 | through structure first and then we're gonna through function. Right? The eye |
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| 00:27 | a very very complex structure. It's spherical. It's not exactly spherical. |
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| 00:33 | in the orbit of the of the or of the skull. Excuse |
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| 00:36 | Around it. You're gonna see fat cushions in place. And there are |
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| 00:40 | basic layers that we're gonna need to with. All right. The outer |
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| 00:43 | referred to as the fibrous tunic. concludes two structures called the square in |
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| 00:47 | cornea. Then we go into the so that middle layer, the sandwich |
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| 00:52 | . This is the vascular tunic. where all the vasculature is. It's |
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| 00:56 | you're gonna find the iris facility. the core oid. We're gonna talk |
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| 00:59 | what each of these do. And finally the interesting layer, the inner |
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| 01:03 | is the retina. The retina is neural layer. This is what the |
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| 01:07 | light. Alright, so there's two in there, there's the pigmented layer |
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| 01:10 | then there is the neural layer where actual receptor cells are located. It |
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| 01:17 | if I actually Alright, so before go on I need you to understand |
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| 01:22 | little bit about visible light. It's of the electromagnetic spectrum. We've already |
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| 01:26 | this at the front end where we you know there are other organisms that |
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| 01:30 | detect outside of this visible spectrum. for example, you got UV light |
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| 01:36 | infrared, which different organisms can We're kind of stuck in this small |
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| 01:41 | band of visible light that we can with our eyes. Excuse me. |
|
| 01:48 | this picture does not do it But when we think about light waves |
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| 01:52 | electromagnetic radiation, we see that it in ways. These are photons, |
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| 01:56 | of energy that uh move in a like fashion. I want you to |
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| 02:01 | to Wikipedia and just look up electromagnetic or visible light. And you're gonna |
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| 02:07 | this image here. That is actually gift. And it's basically moving. |
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| 02:12 | what you have is these waves are to oscillate back and forth wires. |
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| 02:17 | waves in a different plane are oscillating well and I can't describe it. |
|
| 02:23 | don't understand it. It's something that's based. But the wave is different |
|
| 02:28 | just taking a rope and snapping Alright, So there's two aspects to |
|
| 02:32 | . There's both an electrical and a field that are part of this |
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| 02:36 | And so what I want you to about when you look at visible |
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| 02:39 | when you see these things, what looking at and this is true in |
|
| 02:43 | . Maybe not so true in Alright. But in biology think of |
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| 02:47 | , those wavelengths as representing a packet energy. Right? So as the |
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| 02:54 | changes, you're changing the energy of photon. All right now, the |
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| 03:00 | represents the intensity when you're talking about . Alright, so different wavelengths are |
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| 03:05 | give you different uh spectrums when you about amplitude, how tall it |
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| 03:12 | You're talking about intensity. So again light right there is very intense. |
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| 03:16 | means it just has a high amplitude like not so intense and has a |
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| 03:21 | amplitude, so bright light versus um you know, dim light would be |
|
| 03:28 | . And when we're talking about uh height, what we're doing is we're |
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| 03:33 | the peak versus the trough and it's distance in there that represents amplitude. |
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| 03:42 | eye protects itself. Alright, you eyebrows. Eyebrows actually serve as a |
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| 03:48 | , like a headband to cause sweat drip away from the eyes. If |
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| 03:52 | go look at the shape of your , you're gonna see it's kind of |
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| 03:54 | a widow's peak like this. And basically pushes um uh sorry, sweat |
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| 04:01 | the midline or from to the lateral . We have eyelashes. Eyelashes are |
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| 04:06 | fans that keep dirt and dust away our eyes. It says go |
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| 04:10 | Right? All right. Lastly, have the eyelids themselves. These are |
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| 04:16 | big old shields that basically cover up protect the eyes. We have a |
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| 04:20 | from. They call them palpable They have this fibrous core plus some |
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| 04:24 | and there's glands in there, all of fun stuff. Um And what |
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| 04:29 | do is there's two of them and they open and close, that's gonna |
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| 04:33 | light to come in. But when close them basically you're protecting and covering |
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| 04:37 | the front of the eye. All . If you look at the eye |
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| 04:42 | so that space is just referred to a palpable fisher. So when your |
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| 04:45 | are open that's just a wide. widened the palpable fridge fisher. When |
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| 04:49 | close your eyes you've sealed them. right. We've talked about the space |
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| 04:53 | right here. That is called the Mulcair uncle. I don't know if |
|
| 04:57 | remember me talking at the beginning of semester because I said let's all say |
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| 05:00 | word car uncle. It's kinda like uncle, your uncle. I don't |
|
| 05:03 | why words that end with Uncle Sam . They just do all right. |
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| 05:08 | that's where we're gonna get this gritty matter when you wake up. I |
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| 05:12 | know what you call it sleep. know what I think my parents taught |
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| 05:16 | to call it. Don't remember at point. All right covering the eye |
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| 05:22 | a protective layer of tissue called the , basically a stratified screaming epithelium. |
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| 05:28 | can see it here. This little line that comes up and comes around |
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| 05:33 | what it does is it creates a between the external environment and the internal |
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| 05:38 | of your body. Alright. And covers over the square a of the |
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| 05:43 | but it does not cover the So on this side on the backside |
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| 05:48 | the eyelid, it's called the palpable . When it's attached to the eye |
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| 05:54 | , it's referred to as the ocular you bend over something that's referred to |
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| 05:58 | a foreign X. So that would the for next right there. All |
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| 06:02 | now there are goblet cells in there helps to moisten the i uh there |
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| 06:08 | some vasculature that's located there that helps the nutrients to the eye on the |
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| 06:14 | . It's loose enough that you can your eye around. It's not gonna |
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| 06:16 | tight. Like like um saran wrap if it was tight then you wouldn't |
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| 06:21 | able to move your eyes even though have muscles to move them. So |
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| 06:24 | just loose enough so that you can your eyes around and keep them |
|
| 06:28 | Did you guys get to dissect an in the lab? Are you gonna |
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| 06:32 | that today? All right. When comes you're gonna see basically going to |
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| 06:35 | corner and you're gonna see that skirt a conjunctivitis kind of sitting off the |
|
| 06:39 | , right? Because when they cut eyes you leave a portion of that |
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| 06:43 | associated with it. Alright, so is highly, highly innovative, highly |
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| 06:48 | arised. And then of course when get an infection of the conjunctivitis, |
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| 06:53 | gonna happen is those blood vessels And then so you end up with |
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| 06:57 | pinkish looking eyes, it's basically that's the conjunctivitis, not actually in the |
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| 07:03 | itself. So again, does not the cornea because you want light to |
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| 07:09 | less layers as possible to get through . So, tears are a way |
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| 07:14 | your eyes are protected. So it's just those physical structure that protected. |
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| 07:19 | this this tears that the lacquer Now your lack gland is not located |
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| 07:25 | . It's actually located on the lateral of your eye. And what you're |
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| 07:29 | is you're leaking those fluids, you're producing them secreted them. And what |
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| 07:34 | do is they go and travel over surface of the eye towards the |
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| 07:38 | Uncle and at the core. What you're gonna see is there's gonna |
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| 07:42 | two little tiny canals that are going form on either side of the |
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| 07:47 | Uncle. And the opening is called punk to all right. The canals |
|
| 07:51 | are called curriculum because they're little tiny . And what they do is they |
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| 07:55 | into the lacquer mail sack. And where the tears go and they empty |
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| 07:58 | into the nasal cavity. Now, do we know? And can remember |
|
| 08:02 | ? Think about when you cry, happens your tears fall. But they |
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| 08:07 | still keep going across the surface of eye and they get into your nose |
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| 08:10 | you start making those horrible noises right the water drips down the inside of |
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| 08:16 | nasal cavity right now. You also from those glands that are found on |
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| 08:22 | edges of your pal pobre, they're pretty. They produce kind of this |
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| 08:27 | this oil. And so it keeps tears from just rolling off your |
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| 08:31 | It keeps them on the surface and by the palpa bray of the |
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| 08:38 | So you're always producing this stuff and a little tiny thin layer of water |
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| 08:43 | , a lot of lot of proteins well as some bats as well. |
|
| 08:52 | . Why do we cry? I I don't know the answer to why |
|
| 08:57 | is an emotional response. I don't man. I don't know. It's |
|
| 09:04 | don't know why it's attached to That's a really good question. I'm |
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| 09:07 | there's an answer. I've just never it. Um What I would say |
|
| 09:12 | like I said there are other proteins there. So like the structure that |
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| 09:17 | most of the I. G. . In your body are the lack |
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| 09:19 | your glands. What is Ig immunoglobulin basically an antibody and what it does |
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| 09:24 | binds up to bacteria, bacteria What do they like? Warm and |
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| 09:29 | And what are your tears? Yeah sweet sweet things to eat and |
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| 09:35 | Right. Especially the tears of my . No no but bacteria like to |
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| 09:40 | into that. And so there's lots I g a lots of antibacterials that |
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| 09:44 | there to kill and destroy the Huh? So pink eye is an |
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| 09:50 | of the conjunctivitis. Right? So why the eyes get all pink because |
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| 09:55 | the blood vessels dilate. Now it's than just conjunctivitis. But it's but |
|
| 10:00 | similar to that's the same thing you're on the surface. Not just in |
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| 10:06 | tears. Tears move very very quickly think about when you get something in |
|
| 10:09 | eye. What do you do? eyes start watering little bit more and |
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| 10:13 | get enough and it pops it off out. Yeah. Sure. Everything |
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| 10:22 | stress for me. Mhm. What's website that that came from? It's |
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| 10:38 | . Yeah. Oh if it's from grenade. You know that's why you |
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| 10:45 | the guardians called the grenade because they're for their misspellings cancer in C. |
|
| 10:53 | . I. Pub med. That's first place you should go see tears |
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| 10:57 | or lack of your glands and emotional . See if there's anything that pops |
|
| 11:02 | . Um We talked about the extrinsic muscles. Again, I'm not interested |
|
| 11:06 | memorizing them but just know that in to have your eyes move around, |
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| 11:09 | gonna be eye muscles attached to the surface. All right. They're attached |
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| 11:15 | that fiber tunic. The fiber tunic the square in the cornea. So |
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| 11:20 | you say the whites of somebody's you're talking about this clara. |
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| 11:24 | It's basically continuous with the Durham So you can imagine very very tough |
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| 11:29 | to break through provides eye shape protects eye and it serves as an |
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| 11:34 | The cornea is the interesting structure? . It's a vascular but it's still |
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| 11:40 | tissue. So it gets its nutrients the Lakmal secretions on the front end |
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| 11:45 | on the back end by uh the humor that's going to be secreted on |
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| 11:51 | side. All right now, what does this clear living tissue allows for |
|
| 11:58 | to pass in. And what we're try to do is we're gonna try |
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| 12:01 | get light to that retina. so this is the first structure. |
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| 12:05 | because it has this compound back what it's gonna do is it's gonna |
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| 12:09 | bending light and pushing it towards. just gonna point it right here to |
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| 12:14 | structure in the back. That's not only place where the receptor cells are |
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| 12:18 | . But this is the central This is the phobia of the |
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| 12:22 | The densest concentration of those receptors are to be located. The next layer |
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| 12:30 | is the vascular tunic. Alright, we have square cornea, scleral protective |
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| 12:34 | allows light in. All right, vascular tunic has three parts. This |
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| 12:38 | where the intrinsic muscles of the eyes located. Alright, so the core |
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| 12:44 | is basically all this stuff going around edges. That's where all the blood |
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| 12:47 | are. This is what provides nutrients the school era as well as to |
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| 12:50 | retina. So it's the it's the where all the nutrients are coming |
|
| 12:58 | All right, the meat of the . All right. There's also a |
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| 13:01 | bunch of melanocytes in there, The are there to absorb light. |
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| 13:05 | when light enters in, it doesn't traveling through Similarly light can't penetrate through |
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| 13:13 | square. I mean it can but doesn't penetrate very deep because the melanocytes |
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| 13:18 | there to absorb light as best as . So that really there's only one |
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| 13:21 | to get light into the center of eye to the retina is that's through |
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| 13:26 | cornea, ultimately through the lens, through your pupil. This structure here |
|
| 13:35 | referred to as the silly everybody. two things in there. Alright, |
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| 13:39 | have the celery processes and again, just these kind of little extensions hanging |
|
| 13:43 | . They produce the acquis humor. humor is going to roll into this |
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| 13:49 | up and around the lens and into area that sits just underneath the |
|
| 13:57 | All right. I like saying this . So just say it with |
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| 14:01 | See that little tiny dot right that represents the exit point for that |
|
| 14:06 | humor because you're constantly using it. that's where that eggs out. That |
|
| 14:10 | tiny canal it's called. You don't know this. I'm not going to |
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| 14:14 | you. It's just a fun The canal of slim named after the |
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| 14:19 | who discovered it. Say slim. . See that a fun fun |
|
| 14:24 | And now you can answer a trivial question or bar trivia. It's the |
|
| 14:28 | of slim. All right. We have muscles. These are the intrinsic |
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| 14:34 | muscles as well as the muscles of irish. But we're going to focus |
|
| 14:37 | on these intrinsic muscles. Salieri Their job, they're attached to a |
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| 14:42 | of ligaments. They're associated with the . So, you can imagine what |
|
| 14:46 | doing is they're pulling on ligaments that on the lens and change the shape |
|
| 14:49 | the lens while we're focusing on Lastly, we have the iris iris |
|
| 14:55 | a bunch of smooth muscle. Its is to determine or to not |
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| 15:00 | but allow the right amount of light the center of the eye. |
|
| 15:06 | so smooth muscles. There's two of . They're one. I think the |
|
| 15:10 | slide one that's going to cause be tile in nature. One that's radial |
|
| 15:15 | nature. So, the contract I is the sphincter, right? When |
|
| 15:21 | contracts. That's parasympathetic. What it's do is it's gonna make the hole |
|
| 15:27 | less light. So parasympathetic stimulation causes light to intern to the eye. |
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| 15:34 | dilator pupil based causes the eye to . Makes the pupil lighter or are |
|
| 15:42 | and so more light is able to into the eye. Now, go |
|
| 15:49 | and ask your question here. Any like, make the muscle relax |
|
| 15:57 | . Yeah, it's like, oh , man, it's cool. |
|
| 16:02 | Right. So, basically you're interfering their ability to to contract. All |
|
| 16:08 | , now you guys see, I'll to your question. See the big |
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| 16:12 | black hole. Right? See the the little black hole. Right. |
|
| 16:17 | you're doing when you're looking at the is you're actually looking into a person's |
|
| 16:23 | , it's not a surface. You're looking beyond the lens and looking into |
|
| 16:28 | eye. The difference is is that is not bouncing back at you? |
|
| 16:32 | you don't see anything. It's like into a dark closet. Light goes |
|
| 16:36 | but doesn't come back out. All . So, when someone looks |
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| 16:40 | deep into your soul, that's where looking into your deep deep eyes where |
|
| 16:45 | light doesn't come back. No. we'll get to that in just a |
|
| 16:54 | . Alright. And it kind of of talked we've kind of talked about |
|
| 16:57 | being able to see way out here being kind of fuzzy. Right? |
|
| 17:01 | has to do with those receptive But what that means is there's Or |
|
| 17:05 | receptor cells that are detecting light that me to have that broad field of |
|
| 17:13 | . That makes that makes sense. . All right. So, the |
|
| 17:22 | is a transparent structure. It's again up of living cells. All |
|
| 17:27 | And it's shaped determines the degree of . That's going to be found in |
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| 17:33 | ligaments. All right now, remember dealing with the spherical structure here. |
|
| 17:38 | . The celery muscles are on that structure. So when those muscles contract |
|
| 17:45 | they do as they pull away. , they pull away from where they |
|
| 17:51 | Because Right, when I contract them this direction, when I relax, |
|
| 17:54 | fall forward. Okay, make sure going to double check to make sure |
|
| 17:59 | saying no, no I said it . My mistake. See this is |
|
| 18:05 | I have to double check. It's to get these two things backwards. |
|
| 18:08 | . So when they relax, what do is they go and when they |
|
| 18:14 | they move forward, they move towards lens. All right now what they're |
|
| 18:19 | , remember they're attached to those the ligaments attached to the lens. |
|
| 18:22 | when I'm relaxing, what I'm gonna is I fall back and I pull |
|
| 18:27 | the ligament harder, right? So like I'm relaxing but I'm taking the |
|
| 18:30 | with me, I'm going to contract I go the other direction and so |
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| 18:35 | I'm contracting the ligaments gets loose, I relax, the ligaments get tight |
|
| 18:41 | that's going to change the shape of lens. Now, what you're doing |
|
| 18:46 | you're changing the degree of focus for lens basically farsightedness versus nearsighted Now, |
|
| 18:52 | is what I do remember this is easy way to remember it when I |
|
| 18:55 | relaxed. I kind of zone don't I? My eyes go out |
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| 19:00 | focus and I'm looking off into the so when my muscles are relaxing |
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| 19:07 | I am farsighted. But when I'm my muscles are moved forward, I'm |
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| 19:13 | focusing in close, that's how I which one does, which Okay, |
|
| 19:20 | though I said it backwards before I at Mhm. Okay. Right now |
|
| 19:27 | process of changing the shape of the is called accommodation. All right, |
|
| 19:35 | are contracted, ligaments are loose. , muscles are relaxed, ligaments are |
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| 19:42 | , lens is stretched. I'm now far away. Switching between those two |
|
| 19:48 | what we refer to as accommodation. we mentioned the term refraction. The |
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| 19:53 | we talked about refraction is because light being bent every time it goes through |
|
| 19:57 | structure of a different substance. So now air is moving, light is |
|
| 20:03 | through air but when light hits a or you know, water or |
|
| 20:09 | that light is going to change speed then it's gonna refract and move at |
|
| 20:14 | different angle than it was initially. so every structure that light needs to |
|
| 20:20 | through is going to change its speed its direction. And so our eyes |
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| 20:25 | shaped to make sure that we're going take advantage of that bending. |
|
| 20:31 | when you go through a substance that concave, right, what's gonna happen |
|
| 20:39 | uh So here in the middle, gonna happen is you basically reflect light |
|
| 20:43 | or refract light away from the focal . Now, obviously our eyes aren't |
|
| 20:48 | this instead. What we have is lenses and everything else are our convex |
|
| 20:55 | nature, they're thick in the So what happens when light comes |
|
| 20:58 | It gets bent towards the focal Now, if you've taken physics, |
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| 21:02 | got to learn that in physics to optics. Yay, All right. |
|
| 21:08 | our eyes are going to take advantage this so that we can get light |
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| 21:12 | the focal point. The focal point that structure called the phobia in the |
|
| 21:17 | of the retina. Now there are of the eye. This is that |
|
| 21:23 | behind the lens of the posterior The space in front of the lens |
|
| 21:26 | referred to as the anterior cavity. in the posterior cavity is filled with |
|
| 21:31 | goo like substance of gelatinous fluid called humor purpose is primarily to hold the |
|
| 21:37 | of the eye. Your eye is hollow. It has a chewy center |
|
| 21:41 | a, I don't know, fruit or something like that. I don't |
|
| 21:45 | , you don't want to bite into . It'll squeeze out all the gooey |
|
| 21:48 | . All right. It is ah or less, you know, lacking |
|
| 21:57 | substance in its when light travels through , it doesn't, that light doesn't |
|
| 22:01 | anything That is also not 100% Have you ever seen floaters? You |
|
| 22:07 | , if you look at something like a clear wall and you see |
|
| 22:09 | thing isn't that is that frustrating. . And you try to focus on |
|
| 22:13 | . What does it do? That's actually dead cells that have flaked |
|
| 22:19 | the walls of the retina Sitting in vitreous humor and so light is reflecting |
|
| 22:24 | that and creating that unique shape. , you can't Yeah. Sorry. |
|
| 22:32 | know, I actually can see a vessel in one of my eyes because |
|
| 22:37 | something very similar. And my my also told me I have an eye |
|
| 22:42 | which I don't know what that You know? But she's she's going |
|
| 22:46 | watch it I guess. You going to turn into a horrible tumor |
|
| 22:51 | of my eye or something. I know. That's because think since I |
|
| 23:02 | Mhm. Four. Really? Starring on my he's gone, |
|
| 23:21 | I don't know. I mean that's know, again, you're entering into |
|
| 23:25 | realm of doctor Wayne going, I know. You know, I mean |
|
| 23:29 | it went away pretty quickly then It may not have also been when |
|
| 23:33 | think of scars, we think of wounds. It is probably fairly |
|
| 23:39 | right? It's enough to interfere with , right? Because as light hits |
|
| 23:45 | , even if they're small, it create massive differences. So what appeared |
|
| 23:50 | be big for your eye was actually small, relatively speaking. So that's |
|
| 23:56 | what it is. But I'm repairing quickly. I don't know. |
|
| 24:02 | so in the anterior chamber we have acquis humor. So the remember is |
|
| 24:09 | by the silly everybody's what it It flows over the front of the |
|
| 24:15 | passes out on the other side of iris empties out into that anterior |
|
| 24:20 | And then remember the exit point. that canal of slim which again I'm |
|
| 24:25 | gonna ask you what the exit point but its purpose there is to provide |
|
| 24:28 | nutrients to the cells um Of that oh just as the tears do on |
|
| 24:34 | front side, that's what it does the backside, I just show this |
|
| 24:38 | show you how much bending of light , right? So basically light gets |
|
| 24:43 | , you know multiple times. And what you're doing is you're bending each |
|
| 24:47 | you pass through a different layer so pass through the cornea, you bend |
|
| 24:51 | go through the Equus humor, you it, go through the lens, |
|
| 24:53 | it go through the vitreous humor, bend it again. And ultimately what |
|
| 24:57 | is is that you're bending light to . What is called the phobia centrales |
|
| 25:02 | this is the place of highest density cone cells. That is one of |
|
| 25:07 | types of receptor cells that we Moving into the retina. We said |
|
| 25:14 | are two layers, We have the layer which were really interested in and |
|
| 25:18 | have a pigmented layer. So what want you to do, don't you |
|
| 25:21 | where we are, light is coming this direction, right? So you |
|
| 25:24 | , So what it's gonna do is gonna first come into contact with the |
|
| 25:28 | layers and there's multiple layers of cells that neuro layer. The last layer |
|
| 25:33 | comes into contact with is the pigmented . Alright. And the purpose of |
|
| 25:37 | pigmented layer is very simple. It light. So, the idea |
|
| 25:41 | light comes through. If it doesn't anything, it will hit that pigmented |
|
| 25:46 | and it gets absorbed. It doesn't back or bounce around the inside of |
|
| 25:49 | eye. It basically eliminates stray um . All right. The neural layer |
|
| 25:59 | of photo receptor cells and a series neurons that are responsible for pre processing |
|
| 26:05 | before it gets up to the nervous or the central nervous system. And |
|
| 26:10 | these photo receptor cells that we're most in and their job is to transducer |
|
| 26:15 | light energy. Those photons into the that our brain then interprets as what |
|
| 26:21 | seeing. Alright. So, action are gonna be developed through this |
|
| 26:27 | Now. The names of the We're gonna start down here, the |
|
| 26:29 | nearest the pigmented layer. All These are called the photo receptor |
|
| 26:33 | There's two different types. There's rods there's cones. Why do you think |
|
| 26:37 | called rods and cones? There's See how simple am P is. |
|
| 26:42 | at the name. Okay, I it. And then we have bipolar |
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| 26:46 | . Why are they called bipolar They're bipolar in shape. That's why |
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| 26:51 | called that. They're the two there's cells in the body that are bipolar |
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| 26:54 | shape. We've already seen both of today. The first one was the |
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| 26:58 | receptor cell. Right. That was bipolar cell had cell bodies. And |
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| 27:02 | on either side. One being an 100. Here's the other one. |
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| 27:06 | right. And then this is another of bipolar cell. You can see |
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| 27:09 | has extension. The third is the cell. All right. Now, |
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| 27:13 | you look at these, their cells not very large. So they don't |
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| 27:17 | action potentials. They produce a greater that cause the release of a neurotransmitter |
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| 27:21 | stimulates the next cell that caused the of neurotransmitters through graded potentials which then |
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| 27:26 | the cells. And they are the that produce the action potential. See |
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| 27:30 | gangland cells, their axons are converging they're forming the optic nerve. So |
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| 27:36 | retina, which is basically all the of your eye is filled with these |
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| 27:41 | of cells. And then we have types of cells that sit in between |
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| 27:45 | . There are horizontal cells episode between photo receptor cells. The bipolar |
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| 27:49 | Their job is to modulate the signaling takes place between those cells. And |
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| 27:54 | we have a macron cells and these modulate signals between the bipolar cells and |
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| 27:59 | cells. But their role in understanding is very, very complex. So |
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| 28:04 | just going to say that they're Okay. Right, well, so |
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| 28:15 | will happen is if it hits a receptor cell then it's gonna stop |
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| 28:19 | But let's say it somehow sneaks all way through. Hits that photo or |
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| 28:23 | that pigment itself then instead of it back out. That would be |
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| 28:27 | Instead of going through that would not helpful. So it gets absorbed |
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| 28:32 | So the pigment is there to not it. It's to absorb it to |
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| 28:37 | the energy and make the inside of eye black. Yeah. So what |
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| 28:47 | do is you steam well. So happens is you stimulate the sound in |
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| 28:49 | signal that's being produced right? Not light but the signal then returns back |
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| 28:55 | . Yep. All right so there's types of cells called photo ganglion ICC |
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| 29:03 | . So they're ganglion cells. There these types of cells and I mentioned |
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| 29:07 | because they are light sensitive in other they respond to light but they don't |
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| 29:12 | you to see light. They don't you to see things they're responsive to |
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| 29:17 | . Which means when light hits them create action potentials and then the brain |
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| 29:21 | those action potentials. To help us that really it deals with our internal |
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| 29:30 | is really kind of it deals with circadian clock. So you can be |
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| 29:34 | blind right? But you know time day and you know whether or not |
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| 29:42 | light out because you have these P. G. C. |
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| 29:50 | You also have that retinal pigmented epithelium we talked about is there contained melanin |
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| 29:55 | absorb light. That's what allows the not to bounce around the inside of |
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| 29:59 | eyes. They also serve a second which is historic vitamin A. And |
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| 30:06 | they do is they also help cycle um uh one of the chemicals necessary |
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| 30:14 | the eyes to be able to process . So retina neural layer receives |
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| 30:27 | turns that into an action potential pigmented gonna absorb light. Does other things |
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| 30:34 | are important with regard to producing that potential to sell? That's most important |
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| 30:39 | this case is going to be the receptor cells. And what we're going |
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| 30:43 | see that the photo receptor cells play major role in converging information towards the |
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| 30:50 | cells. Now, I'm just gonna a little hyperbole in math here to |
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| 30:53 | you understand or help you understand for ganglion cell, I'm making up a |
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| 30:58 | every gangland cell. There's going to multiple bipolar cells. Right? And |
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| 31:02 | every bipolar style there's gonna be multiples photo receptor cells. Right? So |
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| 31:09 | visual receptive fields are dependent upon the of photoreceptors that are associated with that |
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| 31:16 | cell. That kind of makes Yes, now, kind of sort |
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| 31:22 | So if you had to give me message, you are all connected to |
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| 31:25 | , right, It doesn't matter who the message. As long as you |
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| 31:29 | it to me. Right, and I'm the ganglion cell, you guys |
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| 31:33 | the photo receptors. Right, stimulate there. I can stimulate up |
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| 31:37 | I get the message that's kind of that works. We'll see this a |
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| 31:41 | bit better. All right, the rods and the cones, the |
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| 31:45 | , there's one type cones. There's types uh you can see in terms |
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| 31:49 | structure, they're very different. What have in the rod cells is you |
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| 31:52 | a series of uh and the artist a poor job of this. They're |
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| 31:57 | pancake like structure sitting in there. , these discs, they're called membrane |
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| 32:01 | disks. Uh In essence, what do is you just have that |
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| 32:07 | I hate that everything is over on side. I gotta remember that. |
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| 32:10 | , what you do is you take rod and what you have is you |
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| 32:14 | a series of discs inside there. , when we're focusing on what it's |
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| 32:17 | this is what we're kind of focusing is on those discs. When you're |
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| 32:20 | with the cone, the cone is differently what it does. Instead, |
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| 32:25 | membrane kind of does this so you have the membrane bound disks. |
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| 32:30 | you have the membrane itself behaving like membrane bound disk and that's where all |
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| 32:36 | activity is going to be taking Now, what I've done here is |
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| 32:40 | tried to separate these things out to these compare contrast. Alright, |
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| 32:45 | when you're looking at the retina, , I remember the retina is on |
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| 32:48 | on a globe like structure, spherical . And what I want you to |
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| 32:51 | is I want you to imagine taking spherical structure and I want you to |
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| 32:54 | it out. Alright, so in middle, that would be the bull's |
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| 32:59 | of the dartboard. Okay, that be the phobia centrales, right? |
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| 33:03 | if I'm at the phobia central is where the greatest concentration of cones are |
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| 33:08 | . But as you move further and away, you're gonna see more and |
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| 33:13 | rod cells and less and less cone . Okay, that's the first |
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| 33:19 | In terms of the concentrations, there's of more rod cells than there are |
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| 33:25 | cells. Almost tenfold difference. All , Rod cells are responsible for night |
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| 33:32 | and when I say night vision and can't see in the dark, but |
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| 33:35 | can kind of see in the right? When there's a little bit |
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| 33:40 | light, they respond to very, low levels of photons that excites a |
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| 33:46 | sell very easily. You don't need lot of photons to do it. |
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| 33:49 | so that kind of gives us a of shape and structure that's around us |
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| 33:53 | give us clarity. It just kind , we can kind of see |
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| 34:00 | right? So what we say is they have high sensitivity but very low |
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| 34:08 | with regard to cone cells, there's be three different types and what they're |
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| 34:11 | . They're responsible for us seeing in light. So in day vision, |
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| 34:17 | ? It takes a lot of photons excite a cone And when you do |
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| 34:22 | basically you get really, really high and the reason you get high acuity |
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| 34:26 | also because of their density and the of cone cells associated with an individual |
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| 34:32 | , it's almost a 1-1 ratio which talk about. And that's what I |
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| 34:36 | here. Is that last one? here there's a high degree of convergent |
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| 34:41 | . Alright, so you can think it like this when I'm looking at |
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| 34:44 | cells, I'm gonna draw this So if I have a bunch of |
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| 34:50 | cells, I can have a whole of rod cells and cone cell. |
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| 34:54 | cell. Rod cells. Right? these rod cells can converge onto a |
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| 35:00 | cell and then those can converge onto single ganglion cell. So my receptive |
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| 35:06 | for that ganglion. Now is this thing. If I stimulate that rod |
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| 35:10 | , I'm gonna be stimulating that If I stimulate that rod cell, |
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| 35:13 | stimulating that ganglion cell, right? they're all connected, they're all on |
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| 35:18 | same field. This cone, on other hand, is has a very |
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| 35:25 | degree of convergence. That cone cell converge on a bipolar cell which will |
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| 35:30 | converge on a single ganglion cell. ? So I can only stimulate that |
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| 35:38 | to stimulate that ganglion, right? I have another consul over here, |
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| 35:45 | cone cell only stimulates that one All right, But if I get |
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| 35:50 | whole bunch of cone cells that are that low degree of convergence jammed up |
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| 35:56 | . That's very similar to having whole of. Well, I'll show you |
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| 36:03 | , hopefully this will make sense. be easier if I show you. |
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| 36:08 | , this kind of shows you the of the eye here, we flattened |
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| 36:12 | out. So here on the periphery have a lot of the blue, |
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| 36:19 | is representing the rod cells, the represent the cone cell. So in |
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| 36:23 | phobia you can see lots and lots lots and lots of cone cells. |
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| 36:27 | so if you looked at it, it out and say look here, |
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| 36:30 | got lots and lots of rods. then all of a sudden when I |
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| 36:32 | to the phobia, nothing, almost rods, only cones. And then |
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| 36:37 | here on the periphery there's very little and then again, moving outward lots |
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| 36:41 | lots of rods. So again, want you to look forward for a |
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| 36:45 | for me and I want you to at the periphery, you know, |
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| 36:48 | over here, is it well focused here? No, you can see |
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| 36:54 | happening, but you don't see things focused, right? So light is |
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| 36:59 | in and hitting rod cells over here the periphery, but it's not giving |
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| 37:03 | a high degree of acuity. It's kind of saying, yeah, |
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| 37:05 | there's something over there. And if want to have greater acuity, what |
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| 37:09 | I do is I turn my head focus my light onto that phobia. |
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| 37:14 | whatever it is, I'm looking at now comes into uh becomes very, |
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| 37:19 | cute. All right. So, phobia centrales is the region within this |
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| 37:27 | area. So you guys who cares darts? All right. So, |
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| 37:32 | have the bull's eye. And what you have inside the bull's eye? |
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| 37:38 | it called? Alright, you guys played darts, then you've seen |
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| 37:43 | you've thrown darts, but you're playing . That central thing is called the |
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| 37:47 | eye. The one that's in the center is the double bull's eye. |
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| 37:51 | worth double points. Mhm. You to go out and play some |
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| 37:56 | See this is your homework. Now out to a bar, learn about |
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| 38:04 | , right? Play some darts. . The macula, sorry, the |
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| 38:09 | Lutetia is like the bull's eye. phobia centralizes like the double bull's eye |
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| 38:16 | right inside the back. So that's all the light is trying to be |
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| 38:20 | . That would be what the light looking like. So, what this |
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| 38:27 | trying to show you here is how eyes adjust in different levels of |
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| 38:34 | Now, these are pictures. So they're trying to represent something. So |
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| 38:41 | it's light out right when there's more available. What happens is is that |
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| 38:48 | photons overwhelm the rod cells and they bleach out. They turn off in |
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| 38:55 | . And so now only the cones active and they're the ones that allow |
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| 38:58 | to see things with a high degree acuity. This is what we refer |
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| 39:02 | as foe topic vision. So things clear, we can detect colors really |
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| 39:07 | , we can see details clearly, ? But when there's low light |
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| 39:13 | there's not enough photons to stimulate the cells. You're now dependent upon the |
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| 39:17 | . Some cones might be turned on allows you to kind of see a |
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| 39:21 | bit of color but not quite a right? You can see different degrees |
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| 39:26 | light and dark, but you really determine color. This is scco topic |
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| 39:32 | . So this is predominantly through the . All right. And you've you've |
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| 39:38 | this, you know when it becomes , like right now like 8:30 |
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| 39:42 | when things start getting dark, Things get harder to see right now |
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| 39:46 | because you don't have enough light to the cones. And so the rods |
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| 39:50 | now starting to take over your Your moving from topic to topic when |
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| 39:54 | begins getting light in the morning, happens is you go from a scope |
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| 39:58 | tufo topic vision and this has to this adaptation. This idea that when |
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| 40:04 | is around cones are able to adapt respond very very quickly. But rods |
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| 40:11 | , they basically get bleached out very . It takes a long time to |
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| 40:15 | ready to start responding to light, do I want to say about this |
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| 40:27 | ? Mhm bipolar cells, what do want to say about this? So |
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| 40:35 | way that I described it earlier, said, look, we have got |
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| 40:38 | bipolar cell that's associated with a photo cell or bipolar cell? Multiple photo |
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| 40:44 | cells. The truth is, is very often you'll see two bipolar cells |
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| 40:49 | with one cell. And depending upon field, you know where that cell |
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| 40:55 | within the total field, it's going determine the response of which bipolar cell |
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| 41:00 | turned on or gets turned off. right. So the idea here is |
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| 41:05 | bipolar cells are modulating responses before it to the ganglion cell. And what |
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| 41:10 | image is trying to show you here there's an on and off pathway. |
|
| 41:17 | if you look at our our network , we have cells that are in |
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| 41:22 | center and we have cells that are on the outside you see that. |
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| 41:27 | these would be our outside those would . So, you can imagine that |
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| 41:32 | each of these cells, there's another cell that's associated with them and another |
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| 41:40 | cell. So depending upon which cell being stimulated. So if light hits |
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| 41:46 | here, It might stimulate this bipolar pathway in that one. So you're |
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| 41:52 | you're telling your brain light is hitting outside of this photo receptor or this |
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| 41:57 | field. But if it hits then what it's going to do is |
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| 42:01 | going to stimulate the other pathway and off the other one. I want |
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| 42:05 | to think formal about. Just look somebody and look at the light reflecting |
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| 42:08 | their forehead or their face or their , right? That's going to be |
|
| 42:13 | center when light is being in the of something and reflecting outward. It |
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| 42:17 | a sense of three dimensions, doesn't ? So part of that understanding three |
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| 42:23 | is not just our binocular vision, how light is hitting different receptive fields |
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| 42:28 | where it's done and that processing is place at the level of the bipolar |
|
| 42:35 | . You guys remember that, that meme that came out two years ago |
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| 42:38 | the dress. You're right, The yellow, the black, whatever we |
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| 42:45 | a group of bipolar cells that are when blue light hits versus yellow |
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| 42:51 | And so it's like, is it ? Is it yellow? So if |
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| 42:54 | blue, the blue bipolar cells turn the yellow bipolar cells turn off. |
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| 42:59 | yellow light hits the yellow polar bipolar turn off. So one of the |
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| 43:03 | that we distinguish colors is which pathways turned on. Alright, so the |
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| 43:08 | here with the bipolar cells is that starting to pre process information based upon |
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| 43:14 | light is hitting within the context of receptive field. All right, So |
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| 43:21 | information. So this tries to show that receptive field again, what I |
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| 43:26 | trying to demonstrate here is that the the receptive field, the more cells |
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| 43:30 | going to have. So here's the cell The ganglion cell represents the size |
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| 43:34 | represents the receptive field. So it matter if I hit here or hit |
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| 43:40 | . I'm stimulating that gangland style, ? The only way I'm gonna stimulate |
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| 43:45 | ganglion cells if I hit this So if I have a whole bunch |
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| 43:48 | these very, very close together, can have really, really acute |
|
| 43:53 | All right. Let me show you you guys familiar with TVs? You're |
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| 44:00 | familiar TVs you guys familiar with? games, eight bit video games, |
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| 44:04 | bit video games, 16 bit 32 . You know, people are going |
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| 44:09 | what? Alright, video games made the eighties look like garbage, |
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| 44:13 | Compared to Call of Duty and all four K. Stuff that you can |
|
| 44:17 | away with. Now. Right. are more acute versus less acute. |
|
| 44:23 | , this is standard death. This what I grew up with. I |
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| 44:27 | grow up with black and white. grew up with this. Alright. |
|
| 44:30 | from back there. Can you tell that is? Can you tell what |
|
| 44:34 | that is? Yeah, it's basically a mountain back there. There's a |
|
| 44:37 | . Gotta gotta gotta Standard definition says you didn't know is that there are |
|
| 44:43 | pixels from the top of that picture the bottom of that picture right |
|
| 44:47 | All right. So this is a size, right? So it doesn't |
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| 44:52 | which I'm looking at right there, the distance is two ft, there's |
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| 44:57 | pixels. So those pixels are fairly relative to the full death. High |
|
| 45:01 | is how many pixels? 10, . Right, so that means there's |
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| 45:07 | pixels from the top of that picture the bottom. So those pixels are |
|
| 45:10 | than those pixels 4K. What do think that means? It's me it's |
|
| 45:16 | to mean 4000. But yeah, the standard as you're doing 21 |
|
| 45:19 | It's stupid. Right? But is picture clearer than that picture? |
|
| 45:25 | because there's more pixels from top to from here to there, there's more |
|
| 45:29 | from here to there. I than than this one. And what's |
|
| 45:33 | here is you're jamming in tinier and things. So you get greater and |
|
| 45:38 | acuity. Alright, so we talk cones, What we have is we |
|
| 45:43 | more cells that are jammed close And each of those cells, each |
|
| 45:47 | those cones are associated with one ganglion . So if I stimulate that one |
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| 45:52 | cell, I'm only I'm or that photo receptor, I'm only uh stimulating |
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| 45:57 | one ganglion cell downstream. But if have a large receptive field, |
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| 46:03 | That means it doesn't matter where in receptive field, I'm going to have |
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| 46:07 | security because it doesn't matter if the hits over here over there, I'm |
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| 46:11 | stimulating the same cell. So it me like, oh, lights coming |
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| 46:15 | over there someplace. And so when looking out over here, when you're |
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| 46:19 | at the periphery, that's why it's of fuzzy, right? But when |
|
| 46:23 | look at directly at light coming into phobia where you have that high concentration |
|
| 46:29 | cones, that's why you get high of acuity. When we come |
|
| 46:43 | I'm just gonna skip over the slide we kind of already talked about |
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| 46:47 | When we come back, we're going deal with how the eye turns light |
|
| 46:55 | a message. The take home of last little bit, which I know |
|
| 46:59 | very, very confusing stuff because it's of dense, right? The idea |
|
| 47:03 | is how does the I manage to things clear for me, right, |
|
| 47:10 | by basically focusing the light on an where there's lots and lots of these |
|
| 47:15 | going down to the ganglion cell. have fun dissecting your I just |
|
| 47:20 | it might squirt out at you if press on |
|
