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BIOL 2301 Human Anatomy & Physiology I - BIOL2301_lecture15_0629
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00:04 All right, it's nine o'clock. guys ready to learn how polite of
00:11 sure teach us. OK. Um today, what we're gonna do is
00:17 gonna cover three parts, well, two full uh uh systems when it
00:23 to the special senses. And then we're gonna do is we're gonna kind
00:26 go through most of the eye. we're gonna start with the question of
00:30 . How does smell work? Then gonna ask the question, how does
00:34 work? And then we're gonna go deal with how does this, what
00:38 the structures of the eye? We're gonna quite get to, how does
00:42 eye actually put it all together so you can see? Um I
00:47 maybe we will get up there, I think that my lecture is actually
00:52 up for the two hours. So see. So, um these are
00:56 of my most fun lectures. I think, I mean, where
00:59 have the most fun because I can down rabbit trails big time on this
01:03 . And so what we're looking at is just kind of that overview and
01:08 can kind of see here, what we have? We are smelling
01:11 right? We're smelling people, people , don't do that in an in
01:18 elevator. People don't like that. then we have smelling things that are
01:26 , right? And that's really what is for. It's a sense of
01:29 . When you hear olfaction, sense smell, what we're looking for is
01:32 are detecting our environment or sampling our by looking at the chemicals in our
01:37 to help us understand what's around In other words, help us to
01:41 food, help us to identify other . Have you noticed people have unique
01:45 like your bow, your your I guess is what you guys call
01:49 bay. It's a see, it to be a bow but then someone
01:52 baby and then they got it smaller now we might as well just call
01:56 other bees, right? But they . Here's something crazy. All
02:03 women, ladies, your sense of is a million times greater than the
02:09 of smell of a male. All , just it's been proven scientifically where
02:13 like they've done a compare and contrast large cohorts. And it's like
02:19 this is like the limit where a can smell and women can smell a
02:22 times more fine or, or diluted . Women can identify their babies by
02:32 . I can barely, I I know that the kids smell,
02:36 know, but they're all teenage So, you know, that's not
02:41 hard thing. So we can identify and then we use this to help
02:46 danger. Right? And again, example I'm using here is food.
02:50 think of all the things like if smell natural gas, like if you
02:54 across the street before they started doing this work here on some mornings,
02:58 would actually smell stuff coming out of sewer and it would be like this
03:02 not a safe, safe thing. , I don't, this is
03:06 All right. Now, the thing , is despite how good our sense
03:10 smell is, it is not as as, or developed as other
03:13 We're pretty much aware that dogs can anything if you've watched enough TV shows
03:18 stuff like dogs can actually smell cancer, you know, it's
03:24 And again, what are they They're probably smelling the byproducts of chemicals
03:29 these cells are putting off or whatever pathogen is putting off? Right.
03:33 just in much, much, much dilute concentrations than we'd be able to
03:37 able to detect. All right. with that in mind, what is
03:43 that we're actually using? So, the nasal cavity, we have this
03:50 , this area that is called the epithelium. It is not your entire
03:54 cavity. In this picture, you kind of see where it's located.
03:58 here is your NARE won't point to NA that's the hole in your
04:04 That's not your nar, that's the you got two nares, right?
04:08 of you pierce your nares or not nail, your septum, right?
04:12 notice here's the na you see, the nasal concho that we talked about
04:17 turbinates. And what happens is, the olfactory epithelium is located in the
04:23 regions of the nasal cavity. So really high up here. And you
04:29 this because when you're walking around, say you're, you're walking on campus
04:33 you smell one of the smell, of those food trucks. What do
04:36 do? You go? Oh, nice. There you go. You
04:40 the air up high into that olfactory . So you can get a better
04:45 of what it is that you're right? You're pulling it back up
04:49 this. Now, here, what have is we have three basic cell
04:53 that we're interested in. All the, the most important cell,
04:57 one that was like, ok, it, we wouldn't be working is
05:01 olfactory receptor cell. Well, you'll it abbreviated some places orc. All
05:06 . This is an a neuron. here it is the little yellow thing
05:10 here. That's the olfactory. Um making sure I'm turned on. All
05:16 . So this is the olfactory epithelial . It is the thing responsible for
05:20 odors surrounding it. You'll have support and then you'll also see these stem
05:25 these basal cells is what they're referred often. And the basal cells can
05:30 rise to the olfactory receptor cells can give rise to the supporting cells.
05:35 the thing is is that these the or CS are not permanent,
05:40 actually have like a very short They're not the most shortest lifespan.
05:46 as far as neurons are concerned, are actually replaced quite frequently about every
05:50 months, roughly And then not shown is that you could also see that
05:56 going to be structures that are the glands produce mucus. So do
06:00 supporting cells, they produce mucus that cover and protect the olfactory receptor
06:06 But we're going to focus in on orc for a little bit. It's
06:09 bipolar neuron. What do we mean bipolar, bipolar neurons have a central
06:15 ? They have one dendrite, one , hence bipolar, right? And
06:21 can see here that the axon extends and it's going to join other axons
06:27 it's going to form what are called olfactory nerves. You remember how we
06:30 that nerves are plural here. So olfactory nerves are just a series of
06:35 axons from these olfactory receptor cells. the other end, we have the
06:41 . And so here you can see dendrite comes down, then it spreads
06:44 and it has these little tiny And if you were to look at
06:46 under the microscope or for for Instead of like this cartoon, it
06:51 of looks like a green onion, ? Are you guys familiar with green
06:57 ? Yeah. Ok. Bulb on bottom? A little tiny, like
07:01 on the bottom. And that's kind what you got here. You got
07:03 little tiny roots and it's here on olfactory hells hairs that are out in
07:09 the surface of the olfactory epithelium. are where the actual receptors are that
07:16 the chemicals. Now, this is by a layer of mucus. We'll
07:21 about the mucus in a moment, we refer to these little tiny,
07:25 structures as the olfactory hairs. That's the receptors are going to be
07:28 So you can imagine hundreds of thousands little tiny receptors out there.
07:32 each of these cells, these olfactory cells detect only one type of
07:40 All right. So in other like I'm just going to make it
07:43 . Let's say that the the smell cherry is one chemical, right?
07:48 not, but let's pretend it Then this particular cell can only detect
07:55 that that particular chemical, right? then you'll have other hundreds of thousands
08:00 cells and each one of them are to detect their own chemical.
08:05 So if you're have strawberry, that cannot, that chemical cannot bind with
08:12 receptors on this cell. So this will never be activated. It's only
08:16 that can activate this, that makes . Ok. Now, we have
08:21 of thousands of these cells and each these cells have hundreds of thousands of
08:27 . The chemical that the receptor that that receptor is referred to as an
08:34 and an odor is made up of of odorant. Ok. So far
08:41 you with me? Kind of sort ? All right. So we're backing
08:50 a little bit here. You see olfactory receptor cells Here is its axon
08:55 goes in, it joins up with axons of other cells. These axons
09:02 are joining up together are all from cells that detect the same chemical and
09:07 go up join up together form that nerve. And what they do is
09:12 enter into this larger structure. The that I said looks like the end
09:17 a toothbrush, that's the olfactory And within the olfactory bulb, we
09:22 these structures that are roundish in nature they're called the glome, that singular
09:29 , sorry glome, singular glomeruli is of which there are thousands. So
09:35 you can see a Glaus, all . And really the glomeruli is just
09:38 structure. It's not like we're going create a bulb and then we're going
09:41 put things in it. It's basically because of the way that things are
09:45 . And so it creates this roundish structure. And here is the synapse
09:51 the olfactory receptor cell and the second neuron, which are called the mitral
10:00 and the tufted cells. All So here you can see there's my
10:06 terminal synapse with the next uh dendrites the mitral cells. And that's where
10:13 get that brownish shape. And each these glomeruli represent a place where that
10:20 smell is being processed, that particular is being processed. So again,
10:25 have two up here, I've already you two smells cherries and strawberries,
10:29 are distinct. That one detects cherry these three check, detect cherry.
10:34 three detect strawberry. So when you cherry, this glama is activated,
10:39 mitral cell is activated that when you to smell strawberry, then this Glaus
10:45 activated. So that mitral cell is . So that kind of makes
10:49 The idea is is that we're preprocessing in the olfactory bulb. All
10:56 So remember how the thalamus processes information goes here, information goes there.
11:00 glomus is playing that role of processing before it gets to the olfactory cortex
11:07 you can actually identify the smell. right. Now, where does this
11:12 go? So what we're going to is we're going to form the olfactory
11:16 from the mitral cells that goes So remember how when we looked at
11:20 olfactory nerves from the, from the side, it kind of looked like
11:25 . We said here and then here's toothbrush looking thing. Maybe it looks
11:28 like a Q tip to you But pointing out at you, those
11:34 all the olfactory nerves. But what is moving down, that's that olfactory
11:39 and those are the axons of the cells. Ok. So this structure
11:46 here represents all those mitral cells going to the olfactory cortex. Now,
11:55 fibers are gonna project to the hypothalamus the amygdala. All right, this
12:00 part of the limbic system. What the limbic system for? What's
12:07 Export memory, emotion? OK. and emotion. All right. So
12:16 , you guys like going to Are there things that you smell that
12:20 you happy? Yeah. OK. you see what we're doing here?
12:26 ? We send stuff to the limbic so we can attach smell to emotion
12:34 now. I like to focus on . Perfume. Doesn't do much for
12:38 . All right. So when I chocolate, for example, what does
12:44 make me? It makes me right? When I smell fish,
12:50 don't like fish. I grew up the desert. I don't eat
12:54 You know, because desert the only we had were catfish out of the
12:58 Grande. You eat catfish on the Grand? No. You know my
13:04 forced me to eat the food. of the food that your mom used
13:06 force you to eat that you just not eat. Now, right?
13:09 you smell that cooking, does it you happy? No. What does
13:12 make you make you sad, makes grumpy. All right. Again,
13:18 . All right. So that signal there attaching emotion to smell.
13:27 Here, what we're doing is we're to the olfactory cortex. So over
13:32 course of your life, you learn right? You smell something and someone
13:36 you this is blank, right? is a flower. This is what
13:41 smells like. This is what a smells like. This is what whatever
13:44 like. And so that stuff goes the cortex and you encode that into
13:51 cortex. So that when you smell again, you know what you're
13:56 right? Does everyone here know what smells like? Can you can you
14:01 in your brain right now what barbecue like? Does it make you
14:05 It makes me happy. All but I can picture I can smell
14:11 . I I can, I can what that smell is because I've experienced
14:16 . It makes me happy. And that information is stored in the
14:22 Notice where the information is not doesn't go to the thalamus. So
14:28 is something that doesn't get sorted to different parts. It literally goes to
14:32 two places that it needs to So the system is pretty basic and
14:41 olfactory receptor cell, right? That's receptor. It has little tiny hairs
14:45 the hairs. That's where the actual receptors are located. We travel up
14:52 axon into the glomeruli, that's found the olfactory bulb, we synapse with
14:57 second order neuron, which is called mitral cell or a tufted cell.
15:00 two different types and then that information sent on to the cortex or to
15:06 limbic system pretty straightforward, right? . So what is an odor?
15:12 right. The things that I'm What are they? Well, first
15:17 , lots and lots of different Do you guys know what an in
15:20 file is? Have you ever heard word in a file? You know
15:26 one is? You probably just never the word. All right, I
15:30 you to picture a person holding a of wine. You picture him and
15:37 did that person do with that glass wine and then stick their nose in
15:45 glass and, ah, I get of currents. A little bit of
15:54 , some oaky cherries, some a little bit of mouse. If
16:08 get mouse or horse in the you know, and Eno File is
16:12 is wine. I know you're used vino, but Eno is wine file
16:18 . All right. And I use as an example because wine is a
16:24 chemical mixture. And what does a phi do? They try to get
16:31 sense of what all the different chemicals and trying to see what that overall
16:36 is and really what they're doing is just detecting the unique little molecules that
16:42 or you know that that activate the , that smell like things that they're
16:47 with, right? So it's like you smell a perfume, what do
16:50 do? You sit there and it like and then you roses as an
16:56 , smells like peaches or orange Notice what you say smells like,
17:02 ? Because there's specific chemicals that are to specific receptors that are being
17:08 All right. So the molecules that up a smell and there are hundreds
17:14 thousands of millions of molecules in everything you smell are called the odorant.
17:20 an odor consists of many molecules which called odorant. Now, in order
17:25 you to be able to detect an , it has to have two characteristics
17:29 it. The first is that it to be volatile. When you hear
17:32 , you probably think explosive, but not what volatile means. It means
17:35 vaporizes easily. All right. So I took a drop of perfume and
17:42 it on the table here, it quickly evaporate and go out into the
17:48 atmosphere and eventually that smell would push way backwards to as it diffuses out
17:54 the space, the air around Ok. So that's why perfume works
17:58 because it's volatile, it's vaporizes This picture I hope demonstrates that,
18:06 about when we say someone is right? What do we do?
18:09 give them stink lines because the odor away from the the subject. The
18:16 thing that that substance needs is that needs to be water soluble.
18:22 the reason for that is because remember, we said we had all
18:25 support cells and they're producing mucus and overlaying those little tiny olfactory hairs of
18:30 olfactory receptor cells, right? So basically you have this thin coating of
18:36 on the inside of your olfactory uh top of the olfactory epithelium mucus is
18:43 plus protein and that protein is called . There are different mucin proteins.
18:49 so basically what you're doing is you're the matrix of proteins that are being
18:53 are holding water in a place and serve as a protective barrier to capture
18:58 large things. You know, because kind of sticky. You've probably all
19:02 that mucus is kind of sticky, ? If you pick your nose booger
19:06 kind of sticky, I know none us pick our nose. We're all
19:09 that, right. You know. , we've all done it.
19:14 So the idea here is that in for you to be able to detect
19:19 odorant, it has to be able travel through that thin layer of
19:24 So it needs to be water If it's fat soluble, it's not
19:27 to penetrate that water barrier. All . So it needs to be sufficiently
19:33 soluble to be able to penetrate through . So we've already mentioned this when
19:38 detect an odor Right. Our yes, ma'am. Go ahead.
19:45 . It's because of the stuff that out of the oil. It's not
19:50 fat itself. It's the material that's the fat. So. Yes.
20:03 . Yep. Yep. So, you're buying your essential oils or if
20:06 go out and buy, um, oil or anything else that has those
20:10 smells, that's exactly what's going Yeah, you can make your own
20:15 , you know that, right? can buy, for example, I
20:18 , so for cooking, you can like just like olive oil and you
20:22 start dropping stuff into it. It's of like you can make, it's
20:25 an infusion, right? You can infused alcohols, you can make confused
20:30 , all that fun stuff. You learn that it's really good stuff.
20:34 right. Good question. All So normally when you breathe, so
20:42 we can see when you breathe, moving air like soap. That doesn't
20:46 air isn't getting up there. It's that the air for the most part
20:50 you're breathing in and out are staying low in the nasal cavity. But
20:54 of the air when it hits those , it rolls and works its way
21:00 . And so this is when you , when you're just breathing, you
21:04 of get a hint of a smell that's when you kind of stop and
21:07 do that deeper breathing, which is am I smelling? And that's when
21:11 pulling it up. So now what doing is you're forcibly pulling the air
21:16 now, when it hits those So con, right, what it
21:20 is it causes the air to become . And so that exposes more air
21:25 the epithelium itself. So that, know, if there is a,
21:29 it's basically allowing more odorant to come contact with that epithelium just by turning
21:36 over and over and over. And so that's how we get it
21:42 here. But normal breathing is down . And then the odorant is going
21:47 diffuse through that really, really thin of mucus. And then there are
21:54 binding proteins that help chaperone deodorants to they need to go, which is
22:01 of cool if you think about So that means there are these proteins
22:04 kind of say, oh look, , you're something I can, I
22:07 bind you. So I'm just gonna you to receptors and hopefully, I
22:12 help you find the receptor that you . Now, it's not as,
22:16 simple as that, it's much more , but the idea is that there's
22:19 chaperoning that takes place. And so you get to your receptor, that's
22:24 you detect it. And then there molecules that then help to remove those
22:30 from their receptor so that you can off the receptor and make it available
22:35 do them. All right. So idea here is just simply put normal
22:41 . I'm not really pushing things up the olfactory epithelium. It's when I
22:46 in deep debt, I really get . Now, if you dive down
22:52 and you look at these hair you're going to see the receptors and
22:56 is what it is. It's a protein coupled receptor. Um So this
23:00 stuff, stuff that you've already seen these receptors are, are associated with
23:06 proteins. The G proteins themselves are G ALPH. So for olf,
23:12 olfaction and these receptors, there are of different genes that make thousands of
23:22 types of receptors that have different sorts affinities towards different sorts of chemicals.
23:29 , if you recall going back three ago, that's a long time
23:34 Imagining in a fall semester or spring , I'm teaching this, you have
23:37 think back to like nine weeks 10 weeks ago. Remember when we
23:40 talking about G protein couple receptors right? And I said there are
23:45 upon thousands of these, well, of the thousands upon thousands are just
23:49 of this stupid structure right here. ? I think there are something like
23:53 to 5000 different genes that make different of receptors in your nose.
24:01 I think that's not going to be important. I'm not gonna ask you
24:04 many genes are there, right? I'm not really interested in this whole
24:08 for you. All right. But wanted to show you how this
24:11 So in essence, what happens is odorant comes along, it activates a
24:15 protein which activates a cycles which produces A and P cyclic A and P
24:22 to a channel causes the channel open which causes calcium to flow in and
24:28 to flow in. And when you charge ions come into a cell,
24:32 do we call that depolarization? So how we activate the cell. It's
24:37 here's the switch to turn on the . OK. So there's nothing here
24:43 different. This is why I kind tell you over and over again.
24:47 about the big picture, learn the when it's important. OK? So
24:52 is a pathway that you should already familiar with, right? And I'm
24:56 , I honestly, I'm not gonna you. So what, what is
25:00 enzyme that's responsible? I just want to see this because it's something that
25:03 seen before and we're gonna see it tomorrow. All right. So it's
25:09 a pattern that you should become aware here. This little graph is a
25:22 bit more complicated. And again, want you to just kind of conceptually
25:26 what's going on here. I don't you to try to memorize the
25:30 All right. So you got all the sonic. All right. You
25:34 that you have the the the different of syrups to make the 40 billion
25:38 flavors that they describe, right? want you to imagine five of the
25:44 . So what's the red syrup? say strawberry? OK. She's going
25:50 strawberry. What were you thinking? doesn't matter? Cherry strawberry,
25:57 She said strawberry first said strawberry. the yellow lemon? What's the blue
26:05 ? What's the green, green And then what's the purple?
26:10 OK. So no blue coconut, cherry this time. I'm good with
26:14 . All right. What this is you is in this, in this
26:18 , what we're trying to describe is we're able to detect all the different
26:23 of smells that exist in the All right. So there are not
26:27 five smells and like I said, have 1000 some odd genes. So
26:32 I said, about 5000 genes, genes, there are not four or
26:36 different smells in the universe. You with me on that, right?
26:40 , we could say there's probably an number. It's probably not truly
26:44 but it approaches infinite relative to the of receptors that we have. But
26:49 pretend for them that we have five receptors which we described strawberry,
26:56 blueberry, green, apple, and . I got them all.
27:01 Let's pretend that there are seven different in the universe. OK? And
27:08 want to detect them. All Now, notice odor A combined to
27:17 odor B combined A strawberry odors D a strawberry, the circle represents is
27:22 strong it binds. So it's its , how much it likes it,
27:28 ? So, odor A binds really to strawberry odor b less so odor
27:36 even less. So, and the ones don't bind at all. But
27:40 A also binds to lemon weekly. also binds to blueberry a little bit
27:46 strong than the lemon, not at to green apple and very little to
27:53 . So to detect odor, a activate four different receptors and you activate
28:01 four receptors at different strengths. So it's the combination of which receptors
28:09 bind to and the degree of So you can imagine when I bind
28:15 this, I'm really activating this cell I bind to this one, I'm
28:21 activating that cell all that much. it's the combination of those four and
28:26 lack of that one that gives me the sense of smell or that sense
28:32 that odor. All right. what do we want to call that
28:36 ? We'll just call it strawberry Ok. So when I smell strawberry
28:46 , I'm activating five receptors when even though this one's not being
28:50 being activated, zero. So that's I'm saying activated, right? And
28:55 you can see that every odor or odorant has its own profile. And
29:01 now seven to the fifth power is number of combinations we can have just
29:08 this chart. That's a lot, ? And then because each one is
29:15 a binary, it's not an on . It's, there's a very then
29:18 even creates an even larger profile. is why when you smell a
29:25 for example, you can pick up sorts of different unique combinations,
29:30 Or you smell food in a right? That first picture of them
29:41 up that plate of food and smelling . What you're doing is you're smelling
29:44 those different combinations and you're activating different of receptors and creating unique sorts of
29:50 in the olfactory epithelium, which then a unique pattern of activation in
29:56 in the gust sorry, the olfactory and that's when your brain goes.
30:00 what I'm smelling is blank. That's it all works. It's really,
30:06 complicated and we're keeping it as simple we possibly can here. All
30:12 So this is what they say. that pattern that starts here in the
30:17 creates a pattern in the glomery the pattern in the glomery li makes
30:21 all the way down to the And that's what gives you that
30:24 that pattern is with us is what you perception of smell. So this
30:31 trying to visualize that. And we've got color coding here.
30:36 green and blue. And if you're green or if you're yeah, red
30:39 , color blindness is a terrible But you know, I I find
30:43 but you can see here, here's the reds. So they're all smelling
30:47 . Here's all the green, they're lime or they detect lime. Here's
30:50 the blue, they detect blueberry. can see that they're kind of scattered
30:54 the truth is, is that the epithelium is less scattered and more
30:58 So it's like there's this profile that at one end and kind of changes
31:02 it moves along along the direct along length of the epithelium. But notice
31:08 all the green go to the uh uh glomeruli, all the blue
31:11 to the blue glome, all the go to the red Glaus. And
31:15 here, what we're doing is we're uh modifying a smell. So
31:20 I asked the question, did you , have you ever been to,
31:23 um Sonic? And you can imagine the summer they're making lots of
31:28 aren't they? And so they're just there pushing things in there. And
31:31 what may happen is they may squirt flavor in and as they're moving it
31:35 , they might actually pass it underneath else and a drop of a different
31:41 might actually get into your drink, ? And that syrup smell you could
31:49 detect, but it's so small relative the other ones that while a molecule
31:54 come along and activate the blueberry, you got was a strawberry in the
32:00 and your brain says, wait a . Um I may have gotten one
32:04 fire. Well, you know That's nothing relative to this. So
32:07 gonna do that lateral inhibition thing and gonna just pretend like it's not
32:11 I'm going to depress or inhibit that going forward. So I can focus
32:17 the smells that are actually truly So the mitral cells and the tufted
32:25 in the glomeruli modulate the signals that coming up into the glomeruli from the
32:33 receptor cells. So it's that first of modification and regulation that is taking
32:40 here. And we've already said So this is nothing new,
32:47 Cerebral cortex, that's the conscious perception smell. I smell blank,
32:54 So when you think cortex, that's your conscious awareness, limbic system,
32:59 . What's your visceral reaction to the ? If it's a smell of something
33:05 like chocolate, what's a visceral If you were smelling fresh brownies,
33:12 would, what would you do Would you start salivating? Would your
33:18 say feed me? Yeah. OK. So that would be an
33:23 of a visceral response. All What does the Amygdala do?
33:28 Oh I recognize that order. You , that's the smell of blank to
33:33 day. I can still remember the of my girlfriend in high school's
33:39 She always wore Lauren. So it Ralph Lauren Lauren if I smell
33:43 which they don't make it anymore. if I smell it's like immediately it's
33:48 , I think of her and that like years ago, you know,
33:54 ruled the earth pterodactyls, you was so much fun. All
34:05 Any question about a action, easy, I hope. Ok.
34:14 is a fancy word for the sense taste. So, olfaction gustation are
34:19 related here. We're dealing with chemical . So, so far olfaction and
34:24 are dealing with chemo receptors. All here, what we're doing is we're
34:29 to figure out what's in the food the drink that we're putting into our
34:32 . What are we consuming? And doesn't taste all that good. Gustation
34:38 really work unless olfaction is involved. right, you probably notice this when
34:45 sick and your nose all stocked up doesn't taste all that good, does
34:49 ? And the reason it doesn't taste that good is not because you're
34:52 It's because you can smell it. like, here's the chicken soup.
34:59 . I can't smell it. It's . I guess I'll eat it
35:03 It makes me feel good. Usually I teach this class around 11
35:18 a MP. I teach the human class around noon. So we get
35:22 stare at this picture for a little because it's just mean. All
35:30 Oh, I've been wondering why it worked. It's just because I don't
35:33 the antenna. Such an idiot. right. So the gustatory system is
35:44 found on the tongue. Ok. the tongue. You have these little
35:49 structures called paille. All right. I want you to go home or
35:54 can take your phone out and take picture of your tongue if you want
35:56 . But go, look in the and go, ah, and look
35:59 your tongue. All right. And see all the little tiny bumps on
36:03 tongue. And those are the those aren't taste buds. They're the
36:06 on the paille. Certain papilla have buds. All right. And it's
36:12 the taste buds. And here you see this is a structure of a
36:16 bud. It kind of looks like onion, doesn't it? Yeah.
36:21 notice onions seem to be the theme far this morning. All right.
36:27 the taste bud, we have cells those cells are called the gustatory
36:32 And these are the structures that detect taste, the chemicals that make up
36:39 , the, the food and materials you eat. It's what we actually
36:43 . All right. So the gustatory is the taste receptor cell and it's
36:51 the bump. It's, here's the inside the taste bud inside the taste
36:56 . That's where that little cell is located. Now, what we're gonna
37:00 is we're gonna look at the different of pali. First is the,
37:05 me see which one I wanna do . 1st, 1st 1, I
37:08 do the fill of forms. This is the filiform. That's the
37:14 . Filiform is the stuff that you all over your tongue. Now,
37:18 you're brave enough and you want to your tongue right now, you can
37:20 it. You're gonna, ah, you feel that your tongue is kind
37:23 rough, right? If you have dog or a cat when the dog
37:26 you. Right. Does it feel ? A little bit? No,
37:32 little bit. Yeah. I you feel the bumps to it,
37:35 ? Cats, they're even, they're even more and you can see
37:40 what it kind of looks like. . It's full. I mean,
37:43 means threadlike and it's not really It's more like a series of fingers
37:49 the purpose of this. They're very short, they're very spiky and
37:52 found all over the anterior two thirds your tongue. Like I said,
37:55 you go look at your tongue, literally covered in these types of
38:00 All right. They don't have any buds. Their job is to detect
38:06 in food and to manipulate food. right. Now, to envision
38:11 think about an ice cream cone. . Start licking that ice cream
38:16 right. The ice cream needs to raked off the cone and onto your
38:22 and that's what these little things They serve as little tiny rakes to
38:25 the food. All right. Think a cat drinking milk or a dog
38:29 water. How do they drink they dip their tongue in, if
38:35 watch it in slow motion, they kind of create a little bit of
38:37 bowl shape. But really what they're is if they don't create that bowl
38:42 , just dipping their tongue directly into fluid, it, it gets caught
38:47 in these little tiny grooves and stuff that allows them to bring the fluid
38:51 their mouth. All right. So its job is to grab things.
39:00 don't have a smooth tongue, you a rough tongue, the first type
39:05 taste bud. And again, you go and look at your tongue and
39:08 will see these, they are visible to the is the first type
39:13 paille is the first is the All right. Now, the
39:18 they're all over the place. So can see in a little cartoon they've
39:22 bumps and they're just kind of scattered . All right. And if you
39:26 look at your tongue, you'll see . It's like, look at the
39:29 , you'll see these bumps all over place. All right. Now,
39:33 surface part is rough, not this , but you can see it sits
39:38 there, but between them, they these grooves. So it's basically this
39:43 that is, has kind of the groove and it's in the walls of
39:47 grooves where you're gonna find. Um , I'm sorry, I I'm,
39:58 not even talking about the right I'm I'm talking about the fungi
40:02 My brain just turned off and I saw this over here not well
40:05 with humans. All right. These the weird ones. These don't
40:08 You don't have them anymore. They work for you anymore. Ok.
40:12 are the ones that the kids All right. So if you were
40:14 grab someone's tongue, stick out your , see, I'll wake you
40:20 All right. If you grab someone's and pull really hard, don't do
40:24 . They don't like that way over on the sides are these little tiny
40:30 . They're not slits, they're just of grooves that sit on the side
40:33 the tongue right about here. All . And it's these structures that are
40:38 foliate. Again, structural wise, kind of look like these buttons,
40:42 the grooves, that's where those uh little taste buds are actually located and
40:48 gonna find out all the taste buds located in the grooves. All
40:52 but not particularly well developed in This is where you primarily see them
40:56 infancy. So when little kids are to discover the world around them,
40:59 putting everything in their mouth, like everything. That's what they're doing is
41:04 out what's food and stuff. So those taste buds that are particularly active
41:08 , but over time they become less . This is the page where I'm
41:13 about the fungi forms. All So again, you look at your
41:16 . Here we have the little tiny everywhere, the little tiny dots
41:20 These are the fungi forms. I reflect that they're up there. All
41:25 , fungi form. Sounds like mushroom , fungi. So, mushroom are
41:30 like. And so they look like button mushrooms. And if you go
41:34 , look at someone and go, , you'll see the dots all over
41:36 tongues. Ok. Here, the buds are showing them up on the
41:41 . Um, they are about 300 you count them up on the
41:45 um, they're just found on on the anterior portion of it,
41:50 there's not a lot of taste buds , there's enough so that you can
41:54 things going on. But really, not the most active taste buds.
41:58 most active taste buds are the weird . All right. So, remember
42:02 I said you can pull on someone's , but you really can't pull their
42:05 very far out. And the reason that is because sorry, that little
42:12 right there, clip that thing and can pull your tongue out a little
42:14 further, please don't do that. right. But if you are able
42:20 have someone relax their jaw and pull tongue out, you'd see that the
42:24 one third is covered in these Do you see the tonsils way up
42:29 ? Those aren't the tonsils on the that you get removed. If you
42:33 , you know, an infection, are called bi lingual tonsils and they're
42:37 as part of your immune system. you see how the tongue, the
42:42 thir two thirds and the lateral third differently structured. And there's kind of
42:46 boundary you see in the boundary, these, these button like structures.
42:51 you see them there? About 12 them, those are called the circum
42:56 uh pail. And this is where have the greatest majority of receptors.
43:03 rather big in structure. I they're not like this but I
43:07 relative to little tiny dots, they're structurally, they're very large.
43:10 look at the pictures over there, can see them stand out here,
43:14 can see all these taste buds in grooves. All right. And they
43:18 this kind of inverted V function. is where the greatest concentration of the
43:23 buds are located. This is what a major portion and this makes the
43:27 sense. If something tastes bad, you want to swallow it? You
43:32 , like if it's like a I don't know, like a slimy
43:36 booger of a, of a uh . I know there are people in
43:42 who like oysters but uh like I , oysters. Yeah, they're living
43:51 in my mind. I ate one in New Orleans. They made
43:58 I'm going to that story later So those are where your taste buds
44:03 located. So circum valid creates that between the front and the half of
44:07 tongue. Those are where the greatest are. You have a couple that
44:12 over here in the foliate. They're quite so active. You have them
44:15 the surface of your tongue and the form and then you have the,
44:18 no taste buds in all the fill forms. When you get to the
44:22 bud, this is what you're looking here. All right, here's the
44:27 epithelium, surface epithelium goes down and . And what you have is a
44:33 tiny opening and in that little tiny , that taste bud is opened up
44:37 the external environment. OK? That's a taste pore. So this allows
44:43 the gustatory cells to actually be exposed the the environment of the oral
44:52 Now, we're trying to detect those chemicals are going to be dissolved
44:58 the saliva, the water of your , plus other stuff. There's water
45:02 other stuff. And it's this water when you dissolve it in there,
45:07 what allows the chemicals to actually be around your mouth to be able to
45:11 all the taste buds. Now, terms of the structure, as I
45:14 , it's kind of this onion like . You can see here, we
45:17 basal cells. Um I think this trying to, you know, it's
45:21 receptor cell, let's see what we here. Uh They're trying to say
45:24 a basal cell, whatever, So we got basal cells. Um
45:28 are the stem cells that give rise the other cells. We have these
45:31 cells, they're kind of like the cells that we saw in the olfactory
45:35 , they're there to support and provide and to make sure that the cells
45:40 functioning correctly. Um And then we the nerve fibers, the nerve fibers
45:44 in and actually uh terminate on. the gustatory cells themselves are not
45:52 I don't think they're neurons. I'm to remember. No. Yes.
45:55 nerve fibers are coming up to the cells. All right. And you're
46:00 familiar with this is that these cells stick around very long at all.
46:04 you ever burned your mouth, coffee, doing something stupid?
46:11 OK. You know how when you , burn your mouth, everything tastes
46:14 metal for a couple of days, ? It's like, it's like you've
46:18 licking pennies, right? But it take that long for you to lose
46:23 sense of licking penny flavor, It's because the cells that you damaged
46:27 removed and they're replaced by cells that functional. All right, the mouth
46:34 a comp incredibly um active environment. right. Think of all the things
46:40 you eat that damage the inside of mouth. You know, here eat
46:45 Doritos. Yeah, I mean, mentioned those because those are the two
46:50 chips ever. Right. I have you ever eaten a Dorito so
46:55 that you actually swallowed it wrong or had it in your mouth and it
47:00 this way and you the top of mouth, right? Your palate.
47:05 just that, that's just the simple . All right. You put burning
47:10 , burning tea, burning soup, . We do all sorts of horrible
47:18 and our mouth has to serve as gateway to all those dangerous things that
47:24 put in our mouth and it has protect us from that stuff. But
47:28 also has to repair itself when we in the dangerous things. And so
47:32 taste buds replace themselves rather frequently in of the types of gustatory cells.
47:38 is not a neuron, this is specialized neuroepithelium. All right,
47:45 It's just an epithelium that's derived from tissue. All right. Again,
47:50 have the dendritic endings that form these hairs. So the cartoon doesn't do
47:55 justice. But you can kind of if I had a little taste
47:58 the surface of the cells kind of up into and out of that taste
48:02 to detect the surrounding environment. It's where you're gonna find all the receptors
48:07 there are four basic types of All right, we have the type
48:12 cell type, one cells detect sodium . So this is what detects
48:20 Type two cells are the most populous of cell. There are many different
48:25 of them. Some of them would sweet, some detect bitter and some
48:31 Umami. All right. When I started teaching this class, I didn't
48:36 how to pronounce that word. I it your mommy. So that's an
48:41 way to remember. Dr Wayne is idiot. Doesn't know how to pronounce
48:45 . Do you know where Umami comes ? What language Japanese? And it
48:51 savory, savory. All right. are a type of G protein coupled
48:58 . We'll get to that in a . Type three, the text.
49:02 and then the type four kind of as that basal stem cell and so
49:06 , it can replace all the All right. So really, these
49:10 the active ones that you're most, you want to be most familiar
49:14 right? In terms of the So what we're gonna do is those
49:19 cells, right are in contact with nerves, those nerve fibers or those
49:23 form two different nerves, facial all right, facial nerve is responsible
49:29 the anterior portion and the glossopharyngeal is for the latter third, does that
49:35 of makes sense? We talked about facial nerve being a sensory neuron.
49:40 it detects the the stuff on the and then the latter third will
49:45 that's the throat. All right, also have ran nerve number 10,
49:50 is a little bit further down. I mentioned that only because while I
49:54 that the taste receptors are located on tongue. They're actually also located down
49:57 the esophagus. We actually have taste in our stomach. You know,
50:02 there they don't send signals back up the brain to tell us what we're
50:05 . They send signals to other places guys been listening to like Ozy about
50:11 in the news or anything, been about that, right? It's
50:15 it's a uh G LP one. always get this wrong. I think
50:19 an agonist. I may be It might be an antagonist. All
50:23 . But the idea is that sugar your stomach signals your body to prepare
50:27 sugars to enter into your body. one of the mechanisms it uses is
50:31 G LP one molecule. It basically regulates the uh insulin production so that
50:37 can pull sugars into your cells. right. So these receptors aren't just
50:42 taste, they're found in other places well. And the stomach is one
50:45 the places. And so I'm just to show you it's like, oh
50:47 , they innervate other things. All . So really this is what I'm
50:51 in facial nerve and Glossop. All , they're gonna predict uh project to
50:57 mela, then go to second order project to the thalamus. So,
51:01 far does this sound any different than we learned yesterday? All right.
51:05 primary neuron to a secondary neuron, neuron terminates in the thalamus. And
51:10 here we're going to have that third neuron, that tertiary neuron, tertiary
51:15 goes to the cortical gustatory area, gustatory cortex. So it sends
51:21 it sends signals to the place where remember what tastes are. All
51:25 Where else is it gonna go? gonna go to the hypothalamus. It's
51:29 go to the limbic system. Why hypothalamus, why the limbic system?
51:36 , do things taste good to Do things taste bad to you?
51:40 right. So that's our dimension. what it is that we're eating.
51:44 you ready to show you how dumb am? You like hearing how dumb
51:48 are? So it's important to know we are not gods, just mostly
51:52 . We're, we're Demi gods if believe that. No. All
51:58 So on Fridays me, Doctor some of you may have taken Doctor
52:02 , Doctor Morano. Doctor Farmer, uh Doctor Gifford, we go to
52:07 , we talk about students and how they are and how you're all perfect
52:10 every single solitary way, we talk all sorts of fun stuff. And
52:14 day, Doctor Cheek shows up late she's like, I'm so sorry,
52:18 late. I was out in front the library, one of the red
52:21 hawks had caught a squirrel and had ripped it apart and was eating
52:24 in front of the library and everyone around watching it and I said the
52:27 thing ever. I said, I never understand how, like a bird
52:33 prey or any other, you wild animal can eat something that's totally
52:37 like that because I'm an idiot. you ever thought about that?
52:42 oh, you're eating, like, pulling a squirrel apart and you're eating
52:45 intestines and you're eating the, the and all that stuff and it's just
52:49 , this is like high heaven for , right? And I'm sitting there
52:53 probably like you're thinking grossest thing Right? And she looked at me
53:00 of the same way that I would if someone asked me a dumb question
53:03 said something dumb. She says, know, better than that you teach
53:06 stuff is because they have receptors that detecting the materials that that thing is
53:13 up of, which is basically proteins fats and all sorts of things and
53:18 that protein and all that fat is signals to the hypothalamus saying,
53:25 you're getting what you need in order survive, you're happy about it.
53:30 that's what we do. We've just used to cooking food, right?
53:37 because we're humans, but we would the same thing if I'm sitting there
53:41 protein. Right? Sushi lovers. . OK. What is that?
53:46 that something you cook? No, mean, there's things that are cooked
53:50 it but you know, that's a fish. You can eat a raw
53:54 . Sounds gross because you haven't done . Maybe have and don't like
53:59 I, I'm not a sushi All right. So, the behavioral
54:04 associated with taste and smell are also to be responsive here. All
54:09 So, in other words, what your response to food when you
54:14 Food doesn't make you happy and make smile. Maybe, uh, when
54:19 eat something like ice cream, you stop. Right. Sugar good.
54:26 behavioral. So, anyway, so the idea here. It's just first
54:31 , second or third order. It do anything different than we've already
54:35 Now, let's get to the fun . All right. There are five
54:39 tastes. When I was sitting in shoes, there were four primary
54:42 By the time you're my age, was going to be probably six or
54:46 . All right, we just define once we find receptors. All
54:50 But for the longest time we said are four. Now, there are
54:54 . All right. So what are , what are the five?
54:56 first is salty? All right What we're doing is we detect salty
55:02 we detect any sort of chemical All right. So in this,
55:07 have table salt, which is sodium , but there's all sorts of
55:13 right? That we can have anything potassium. Um Anything that's basically found
55:18 that first column can be a All right. But what are examples
55:22 salty things? Right? I mean these look like salty snacks? Do
55:26 crave salty snacks sometimes? Yeah, you crave salty snacks, why do
55:30 think that is? What do you your body needs and need salt?
55:36 ? So, but that's all it's . It's binding to and activating uh
55:41 a channel. And then so now actually getting sodium to come into the
55:45 . All right. Sour think of that are sour name, things that
55:50 sour. Say again. Lemons. right. So lemons are. What
55:57 of fruit? Citrus? Ok. why are they sour citric acid?
56:03 ? Something out. That's sour sour kids. That's great. What's sour
56:09 kids? Why? Sour patch kids ? It has lots of citric acid
56:14 it has something else in it. and salt. True. But that's
56:20 , the salty and the sweet. right. Look upon the board.
56:25 do you see up there? What's there on the top? Hm.
56:33 . So, but what I, , what's up there? Yeah,
56:36 pickled pickled stuff. You pickle There's a lot of things to pickle
56:41 . But basically what we're using is , which is acetic acid. That's
56:47 what makes our pets kids and, warhead sour citric acid and acetic
56:52 Pickle juice. Pickle juice. All . So there's two sours right
56:59 but we could go through a whole of other sours. But those are
57:01 two easy ones. They don't make stomach stomachs, hurt, sour is
57:05 function of free protons. If you've enough time around chemistry and biology,
57:11 know, the free protons are the sign of acids. Basically, an
57:15 is something that releases a proton. right, the proton binds to and
57:21 a potassium channel. All right. what happens is, so, here's
57:26 potassium channel. It's proton binds to and that causes potassium to no longer
57:32 the cell. When the potassium can't the cell, it no longer can
57:36 it depolarizes. And that's a signal you detect sour. So salty,
57:43 said was type one. These are type threes. Notice I put these
57:46 because they're very specific, they only one particular flavor. So down there
57:50 the bottom, just to remind there's your citrus, a citric acid
57:54 there on the top, there's your . So pickled whatever they are.
57:58 acetic acid. Here's just a picture show you what the type ones and
58:03 threes do in very, very generic . Again, I'm not gonna abuse
58:07 with this stuff. You just understand it is. I'm doing.
58:11 detects salts, potassium or sorry, , detects protons. That's what you're
58:20 . Then we have sweet and umami . What we're looking for is
58:27 All right, we're looking for a configuration of glucose. What this glucose
58:32 . It binds to a receptor. actually called a fly trap receptor.
58:36 I think I show a picture of a little bit later. I
58:38 like a cartoon picture of it. is the G protein coupled receptor.
58:41 the glucose shape binds to that it activates and causes the cell to
58:47 . It's through a series of All right. Now, this is
58:51 type two cell and I'm just trying show you things that are sweet.
58:55 they're sweet up there. What makes brownie sweet? It's the sugar.
59:01 not the chocolate, right? What the uh fruit tart sweet? Apart
59:06 the sugar that you add to Fructose? Well, it's not
59:10 It's, it is. Um, is uh fructose but it's basically the
59:17 than that it's, but that's what shooting for. It's, it's the
59:21 like glucose. All right. Um here use the yellow packets in their
59:29 . The, no. See, guys are all good. You're all
59:34 using high fructose corn syrup at this . Um Yeah. Uh as pertains
59:40 pink packet, the yellow packet. away from now. They've actually discovered
59:44 it actually does DNA damage. yeah. Stay away from the stay
59:49 from. That's bad news. I've, I, it's like within
59:54 last month, last 22 months, like it actually affects you at the
59:59 level. DNA level. So I won't be surprised if they remove
60:03 from the market. All right. why, why was Sulo such a
60:08 deal? All right. Well, is glucose and fructose. Boy,
60:17 having a bad day today. All . But what you're doing here is
60:22 has that glucose configuration and, but not glucose, right? It has
60:28 alcohol to it. They've had an alcohol. So it can't be broken
60:32 by the enzymes that are in your . So you get the sense of
60:38 , but you don't get the calories you don't break down the sugar
60:46 Right? Stevia, you guys familiar Stevia? All right. It's another
60:54 , alcohol. All right. It's in a tree but it, we
60:58 have enzymes that break it down. , I think 100 times more sweet
61:03 sucrose. I can't remember how they it, but it has that sweet
61:08 but it can't be broken down. you don't get the calories. All
61:11 . There's still calories there, but can't do anything with them.
61:15 they're unattainable but they're sweet because they the right shape. Umami is triggered
61:24 amino acids. All right. In , it's the amino acid glutamate.
61:31 right. And what this does, gives that savory sense. Since I
61:35 a steak. If you're a tough. That's what you're looking
61:41 All right here again, activating G coupled receptor. It's a type two
61:45 cascades through a second messenger system. here use monosodium glutamate. Yeah.
61:55 . So notice it has two things there. Monosodium. So it gives
61:59 the saltiness. But what does it to the food? Makes it more
62:05 , makes it pop, doesn't All right? Because what you're activating
62:11 these receptors as well? It gives the sense of savory. All
62:16 Makes vegetables taste good. Here's the one. Bitter, bitter. What
62:30 bitter? Well, basically what we're is detecting alkaloids. Now, I
62:33 you to look up here because I see what alkaloids are. Let's see
62:37 we can recognize what each of these represent. What's up there? What
62:43 chocolate? Where does it come Trees? Cocoa, from trees.
62:50 that? Where did that come Yeah. Huh. From the
62:57 Yeah, it's, it's a It's actually from the mustard plant.
63:00 related to, let's see, radishes, Brussels sprouts, broccoli,
63:05 . These are called the, uh, cruciferous vegetables. It actually
63:09 from one plant that has been mutated time through, you know, crop
63:16 . So, it's all the same with different mutations that give rise to
63:21 florets and the broccoli and the cauliflower give rise to weird little leafs.
63:27 if you like cabbage, you it's the same thing, you
63:31 radishes, they actually tried to cross things. It's really funny because they
63:35 to cross a cabbage with a You know, again, it's the
63:39 plant. It's just trying to get features. So they were hoping they
63:42 the root of the radish and the of the cabbage and what they got
63:45 the head of the radish and the of the cabbage. So,
63:50 um, anyone here like Brussel Yeah. Ok. Good.
63:54 I'm just letting you know they've actually cross breeding Brussels sprouts there. Brussels
63:59 . There's, there's a couple of varieties. There's a slow growing
64:03 tasty one and a fast growing horrible tasting one when I grew
64:09 That's what was served by everybody. , Brussels sprouts are like the evil
64:12 that's trying to kill you right They've actually bred and figured out how
64:18 do it. So they now have Brussels sprouts that can grow fast
64:22 and so what you're seeing now is and more Brussels sprouts served in restaurants
64:25 other things because they actually taste which is weird. All right.
64:31 this? Not alcohol? It's What's in beer that is in common
64:40 cocoa, which comes from Brussels sprouts comes from mustard plants. What's in
64:50 hops? What is hops? Anyone what hops is? What's that?
64:57 , wheat is a grass and so can use wheat, we can use
65:01 , we can use all sorts of to make beer. No, but
65:05 , you're thinking you, you're you're, they're tall and what they
65:09 . They're vines. All right. what a hops plant is. But
65:13 they're doing. So I always like find out how much you guys know
65:16 this is not a ha ha. guys are stupid because I'm not surprised
65:20 don't know what hops is. Hops a vine that produces a flower.
65:25 what you do is you take that as it's about to bud and you
65:31 it in beer to preserve beer. has a bitter taste to it.
65:37 had baking chocolate. Did you ever into your mom's pantry when you were
65:42 kid and came across the chocolate? , oh, baker chocolate? I
65:47 my mom is holding out. I , you like a snake of Pete
65:51 then it's like worst flavor ever. mentioned the Brussel sprouts. It's a
66:00 that's trying to kill you. So provides a bitterness to the beer.
66:08 bitter? What is, why do all have this thing? Well,
66:13 has to do with this up The alkaloid. All right, an
66:17 is a chemical that a plant It's not solely this. An alkaloid
66:22 an alkaline chemical, right? it's saying it's, it's a alkaline
66:27 opposed to acidic, but an alkaloid a chemical that plants produce to protect
66:33 from being eaten or destroyed. All . So for example, nicotine is
66:42 alkaloid, it's produced by the tobacco to prevent the tobacco worms from eating
66:47 tobacco plant. It's a defense mechanism if we give you too much
66:52 it will kill you. All Musin muscarine is a chemical produced by
67:00 . It's the toxin that kills All right. It's a very bitter
67:07 , cocoa. If you give it a dog, what does it
67:11 Makes it sick? Or it can the dog? Right? Why?
67:16 the dog has receptors that when bound the chemicals in cocoa cause that poor
67:24 to become sick and die mustard. . Every one of those cruciferous vegetables
67:35 bitter. What's it telling? You eat me, go eat bacon
67:43 right? No, no, that's why it's there some bitter things
67:49 an appeal to us, right? it's because it's, you know,
67:55 , it provides dimension. But ultimately that bitterness is, is a signal
67:59 that plant saying I'm a danger to . But we can find ways to
68:05 it add dimension and make things taste . If you don't like beer,
68:10 ok. You can focus on your sprout or your chocolate. All
68:14 Now, there are hundreds of different of bitter receptors because there's 100 things
68:23 there that are trying to kill Right? You know, they tell
68:27 , you know, you go out the woods, what are you're supposed
68:29 do? Don't eat the berries. don't know what that is. Don't
68:33 that mushroom. You don't know what is. Why? Well, probably
68:36 try to kill you. How do find out? I taste it?
68:43 taste it. Do not put food your mouth that you don't know what
68:46 is. Our ancestors did that all us. Go find a book.
68:52 right. Anyway, so that's why have so many of these types of
68:56 . They G protein couple receptor type , they're there to protect us and
69:00 just happens to be to detect those . But some of the bidders things
69:05 really dangerous to us. They just dimension and this is just trying to
69:09 you those receptors in the pathways. if you're curious what it looks
69:13 alright, notice I have a big thing here. Do not memorize anything
69:17 this slide. I want to point out to you just to show you
69:20 biology is still in the infancy. was a paper that was produced,
69:24 think in like 2010, maybe 2011 they finally identified the actual receptor responsible
69:30 saltiness. But we've known for since early 19 hundreds, the four flavors
69:36 knew bitter, sweet, sour, umami was something that was the Japanese
69:43 said, hey, wait a there's a different receptor that detects this
69:47 and they identified it. But look when these were discovered the actual
69:53 4001, 2002, 2006, That wasn't that long ago,
70:03 That's within your lifetime for some of . And it's quite possible that there's
70:10 types of taste receptors. You guys sodas. Yeah, pop rocks.
70:17 you guys ever do pop rocks. . Some of you, if you
70:20 know what pop rock is, it's candy has carbon dioxide in it.
70:23 in your mouth. It's awesome. in the day they were myths.
70:29 one kid died, no one died pop rocks. They just made really
70:37 noises with their mouth. All there is a receptor mouth car four
70:43 . It detects carbon dioxide and the it detects carbon dioxide is because sometimes
70:47 put food in their mouth that isn't um I don't wanna use the word
70:52 , but you know that has bacteria it and the bacteria is byproduct of
70:58 metabolic cycles is produce carbon dioxide. if you put something in your mouth
71:02 fizzy and you feel that fizzy, an indication that you're probably eating something
71:08 has, you know, bacteria in . It's kind of a indicator and
71:13 . It's like something that's not supposed be carbonated. You know, remember
71:15 first time you had a soda, was kind of like this is
71:19 right? And then after a while were like, OK, this is
71:20 of cool. Now you drink his cloths, right? You know,
71:25 was weird because your body has created mechanism to detect that sort of carbon
71:32 . Now, I can tell you story, but I'm running out of
71:34 . I looked at the clock and spending too much time. Yeah.
71:42 the nitrogen. Um, it's, , it's that fuzziness and I don't
71:46 if there is an actual nitrogen I mean, they've been doing that
71:49 years that, in fact, most the British ales and stuff like
71:52 they, they use that nitrogen cartridge mimic what it's like to actually pump
71:57 carbon dioxide. There is actually being by the organism that is producing the
72:03 . Right. So it's like the in there is producing that as a
72:07 . So, but the nitrogen cartridge just a way to mimic and to
72:11 that cool foam layer guys like Mm Cheese good. You like ice
72:19 , ice cream good. You know you like those things because they're
72:24 right? Fatty meat is awesome. you noticed that everyone tries to make
72:27 eat lean meat, lean meat doesn't good flavor. Fatty meat is what
72:30 awesome. You know, bacon, , winner brisket. Oh Cannot wait
72:37 Independence Day, brisket Day, There are probably fat receptors in your
72:44 . We've actually discovered some of but I don't know if they're actually
72:48 in the mouth. We do know they are fat fatty acid receptors and
72:52 probably the reason you like those is your body uses fat as its dominant
72:58 of energy. We eat fat because more energy per unit gram than any
73:07 food that you can consume. And what your body uses to actually feed
73:13 muscles, feed everything else you've been it's glucose, glucose is for the
73:18 . Glucose is the, the royal . Everyone else gets fat, which
73:25 even better. Last thing you don't to know anything about. But I
73:29 to point this out. I want to be smarter than everybody else in
73:31 universe. Is that ok? You're to be the smartest people cool with
73:35 . Ok? This is more a pursuit thing, but you will probably
73:38 to a class where someone who doesn't anything about the mouth is teaching
73:41 And what they'll tell you is oh look around the mouth, you're
73:44 to see that your receptors are located different areas. OK? Which is
73:50 , right? In 19 01, German published the paper on the discovery
73:55 where the taste buds were and of , it was published in German and
74:01 translated it and he said that the buds are located in the places that
74:04 just described to you right back in back, the circum valley over here
74:08 the side, see over here on sides and then all over the surface
74:13 the tongue. And they pointed out where they're, where they're generally
74:17 But it got mistranslated mean that the senses of taste are located in these
74:24 areas and you know this to be lie. All right. I
74:27 intuitively, you should be able to No, this doesn't make sense to
74:30 . If you take something that has dimensions to it, sweet,
74:34 bitter, all those things and put in your mouth. If you roll
74:36 around your mouth, does it change flavor? No, it doesn't.
74:41 , you just get all of the at the same time. What he
74:45 really saying is that these are the you can see up there. There's
74:50 Silicon Valley, there's the foley, the fungi form. These are the
74:54 and it's within these taste buds is have all the different types of taste
75:00 . So just make sure you understand and when someone tells you this,
75:04 look at them and say, you know what you're talking about.
75:11 Gustatory, pretty straightforward. Hm. right, let's get to the
75:21 All right. Now, we're not the full eye today. I think
75:23 gave you slides through the full but I don't know why I do
75:28 . It's just don't fix my I guess. All right. What
75:32 the I and when, what does guy do helps you see it's responsible
75:41 vision? Ok. So that's kind what our focus is here is how
75:45 we go about being able to detect light around us or detect the world
75:51 us? All right, this is spherical structure. It's found in the
75:55 , right? It's surrounded by fat kind of holds it in place and
75:59 has three basic layers to it that see here, we have the fibrous
76:03 , the vascular tunic and the We're gonna walk through these and we're
76:06 to spend time tomorrow. Really talking this. OK. This is where
76:11 the action is at is in the . All right, the fibrous tunic
76:15 the sclera and the cornea, the . Um I'm, I'm gonna get
76:18 this in just a second. Is white stuff. The cornea is the
76:21 stuff in the front. The vascular is what you can't really see,
76:25 it does have your iris. So that's the, the colored
76:29 That's your iris. It's muscle, ciliary bodies and the choroid and then
76:34 nervous uh tunic, that's the final of the retina. That's the optic
76:39 and the structures of the retina in . Visible light is weird. All
76:45 . It is a portion of the spectrum it moves. Um So you
76:49 to think in terms of radiation. your eyes detect electromagnetic radiation. All
76:55 . So here, what we're dealing is we're dealing with packets of
76:59 These are photons, photons travel in , but they don't move in waves
77:03 you think of. It's not like this, right. I pulled this
77:07 from Wikipedia. It's actually a GIF moves. So I encourage you to
77:12 do. So this wave is moving this, but it has at 90
77:17 a secondary wave which is the magnetic and they move opposite each other.
77:23 if you looked at this thing, of these things would be moving
77:27 It is the weirdest thing I can't it move. If I could,
77:29 would me describing it is not but it's not a simple way.
77:33 like, oh look, here's a and let me snap the rope.
77:39 . Very strange. Now, what wavelength, wavelength is the difference distance
77:44 those two wave peaks? So in , what we say is that this
77:48 energy, right? It's an easy to think about that. So it's
77:53 amount of energy that is creating this wave form. So the waves are
77:57 apart, that's less energy when the are close together, that's lots of
78:02 , right? It also has Amplitude represents intensity, intensity and energy
78:08 not the same thing. OK. means the number of waves that are
78:13 at you, right? So a room means you have a lot of
78:20 , a dark room, few So that's intensity. So amplitude is
78:29 by the height from here to OK? From the trough to the
78:36 of the wave that would be your eyes are protected. We talked
78:45 little bit about this when we talked touching your eye, right? E
78:51 . All right. So first we have the eyebrows, where are
78:54 eyebrows, right? These if you and look at them are there to
79:02 your eyes from the sweat that drips from your forehead. And in Houston
79:06 probably experienced it at least once. . If you look at the shape
79:09 your eyebrows notice what they do, either kind of do this up down
79:13 or they kind of do this down . Very rarely do. They just
79:17 that direction. But what they're doing they're pushing water to the medium,
79:22 ? So if you go to the , what you're doing is you're pushing
79:25 down to your nose so that the doesn't go into your eyes. If
79:28 has you up down, then you're it to the median as well as
79:31 the lateral sides. All right, have eyelashes where your eyelashes, they're
79:37 the tip, right? And you those things and man, those are
79:40 triggers, they make your eyes just shut. All right. They extend
79:44 the margins, you can see out from the margins and what they do
79:47 they prevent large foreign objects. So of your finger, that's a large
79:53 object or dust and other things from to the surface. So when you
80:00 , what you're doing is two things actually moving tears, but you're also
80:03 air movement, airflow to push dust and basically sweep it away by doing
80:09 . We have the eyelids which have fun name. The Palpa Bray,
80:13 eyelids you have an upper one and lower one. So, superior,
80:17 , there, uh have a fibrous in them. There's some muscles in
80:20 , there's glands in them. Uh can see that little hairs point out
80:24 are the eyelashes. So there are glands that come out through the
80:28 I mean, through that follicle, there's also glands, um, that
80:32 those structures as well if you've ever a cyst on your eye,
80:37 That's a clogged Melton Gland. I had a student once who came to
80:42 and she's like, I can't take test today. I'm like, why
80:45 was like wearing her hat down. was talking like this said,
80:48 what's going on? She said, got, got one of these uh
80:51 know, assists. And I well, let's take a look at
80:53 . She looked up and I'm oh, it was, it
80:57 it was, it was big. was like, I'm going to go
81:01 the doctor this afternoon. I man, that's just rough. All
81:06 . So we got these meal boum . What they do is they,
81:09 produce a sea bum, the sea just sits right here on the
81:14 And what that does is it creates wax dam so that tears can't just
81:19 over the edges right now. If produce enough tears, are they gonna
81:23 over the edges? Yes. You , but normally your tears don't just
81:28 of randomly go out your eye, go in a particular direction,
81:33 So the space between the two it's called the pray fissure. Um
81:38 then lastly, um I like saying word because I just like the like
81:42 just like peduncle car. It's just , right? So this little thing
81:47 here in the middle where the yuck the yucky stuff is, that's your
81:54 . Ok. It's the lacrimal Typically this is where you'll see a
82:02 particulate found upon waking. What did call it when you grew up?
82:07 it sleep? Do you have something ? I go. No, no
82:12 , no one has a name for . You just call it, you
82:16 it crust. I think my mom them sleepers. I don't know.
82:20 right, you've heard of the Have you heard of that? Have
82:25 ever had heard of? I have , right? That's an infection of
82:29 conjunctiva. And this is just a epithelium that covers the surface of the
82:33 . You guys in the labs? you guys getting the dissect an
82:36 A sheep's eye? No cows. think it's usually a cow's eye,
82:41 think is what they do. And they come to you, there'll be
82:43 big old cow's eye and you'll see conjunctiva. It basically just sits on
82:47 surface and it, it, it surround the entire eye. It's only
82:52 frontal surface of it. So the . And so in the cartoon,
82:58 can see it here. So the is attached to the back of the
83:04 , right? The palpa bray, folds on itself or it folds is
83:08 the fornix and it comes forward and before it gets to the cornea.
83:13 it doesn't actually cover the cornea because would just be another layer of something
83:16 have to get to. But what does is it creates a barrier.
83:20 see there is no getting into behind eye, you have to break through
83:25 conjunctiva to get there and it's not tight because if it was tight,
83:29 your eyes couldn't move around. So has this looseness to it so that
83:33 can move your eyes around. All , so highly innervated, highly
83:40 it provides the nutrients um to the , that's the white part of your
83:45 . And if you get infected, happens is the blood vessels they
83:49 So you get red eye or pink is another one that you see.
83:54 that's really just the blood vessels, dilating and inflaming the lacrimal of
84:04 This is where your lacrimal gland So it says out here on the
84:11 tears are made, they flow over surface of the eye. It lubricates
84:15 surface of the eye. It washes um the hurt and the pain,
84:20 , it washes away. Um things kind of settle on the eye it
84:25 of all sorts of antibacterials. It IG A in it, which is
84:30 antibody. Uh One of the antibacterials lyme. So if you've ever heard
84:35 lyme, this is structure produces the lysozyme um in your body and actually
84:41 coats the eyes of that bacteria don't and live in the tears. If
84:47 look closely again, you can go the mirror and you can see these
84:50 , they're not particularly small. You these two openings, they're called the
84:54 and they open up into these little duct Jews and then the duct jules
84:59 up into the lacrimal sac, which actually internal right here. OK.
85:04 what happens is the tears wash over surface of the eye. They enter
85:08 these little tiny puncta into the duct into the lacrimal sac and then it
85:14 down through the nasal lacrimal duct and out into the nasal cavity.
85:18 think about that good cry that you've recently, right? Have you had
85:23 good cry right lately? Pulled out movie, that, that movie and
85:27 the Ben and Jerry's and yeah, the good ugly cry, it has
85:32 be the ugly cry. It can't be the sad cry when you're doing
85:36 ugly cry. What is one of things that you do all the
85:44 Right? You haven't had an ugly lately. Have you? OK.
85:50 till after the fourth exam. I ? Mhm. I'm just teasing.
85:59 just love putting pressure on you Right. That snottiness is not because
86:07 producing more snot. It's because those are being produced more and they're going
86:13 that lacrimal duct and they're emptying out , and so you're actually doing the
86:19 of the teardrops. I don't I don't know why we, the
86:29 is why do we cry when we're because it makes you, I don't
86:33 . I have no idea. Makes feel better. I don't know.
86:38 It's, it's a really good I don't have an answer for
86:43 Maybe I should look that up and out. But I'm not gonna,
86:49 write it down and say, why we cry and then go look it
86:52 , you just google it and, trust me, the first three websites
86:57 hit are gonna be women that don't what they're talking about. Actually just
87:01 I is where you want to Uh Purposes of crying right now.
87:07 we're doing when we blink is we're , we're always producing tears and tiers
87:13 actually there, there are papers written this, on what's in tears.
87:17 , there's three layers of it. actually there's fats in it, there's
87:21 in it and there's other materials and actually create different layers. But the
87:26 here is just that all I'm doing I'm creating a protective barrier. So
87:32 protect our eyes with the eyebrows, eyelids, the palpa bray, we
87:37 the conjunctiva, we have tears. expect your report tomorrow. You can
87:45 up something because I'll just go. , that's really interesting. Just make
87:48 that it's not really, really fantastical I'll probably tell another class. We
87:55 the extrinsic eye muscles. The extrinsic muscles are muscles that are actually attached
88:00 the fibrous layer, the fibrous tunic the outside. So that's why they're
88:04 , they're not intrinsic. Um They you with regard to eye movement and
88:09 stability in the eye. I'm not to ask you which one does,
88:13 ? All right. But you can it's not particularly hard in terms of
88:16 nomenclature. Rectus is, you it's telling you the direction,
88:22 lateral, inferior, you know, oblique tells you it's pulling at it
88:30 an angle. So the nomenclature tells what the muscle actually does and how
88:37 pulling. And so you can see they're positioned. All right, but
88:42 don't need to know the names of muscles and what they do. So
88:46 don't need to know. Yay. . So fibrous tunic, we have
88:50 square of the corner of the square the light of your eye. It
88:53 continuous with the dura matter. It shape, protects and attachment for those
88:59 muscles. So that's what your whites for. All right, they're
89:05 The cornea on the other hand is portion in the front, it's
89:09 it's convex, it is consists of cells. All right. So these
89:15 cells that you can see through, are avascular. So you don't want
89:21 vessels to go through those structures because would interfere with the passage of
89:27 Instead, they are going to be nutrients from the lacrimal gland, which
89:31 on the front side and the aqueous , which is on the back
89:35 So we'll see that aqueous humor is in this area right here.
89:40 So lacrimal would be on the front . What else do I have up
89:43 ? Oh, basically allows light to through and it helps to refract the
89:47 . So it bends it. That's the outside. Very boring.
89:52 particularly interesting, moving into the more structures. Here, we have the
89:56 tunic three parts I mentioned them The choroid, the ciliary by the
90:00 , the iris is the colored portion the eye. It is smooth
90:04 the purpose of which is to constrict or relax, allowing the passage of
90:10 passed or into the eye. So you can see the muscle, this
90:15 the iris. It's not the it's the muscle that determines the amount
90:22 light that passes through the point that passing through is called the pupil,
90:26 we'll get to in just a All right, colored smooth muscle around
90:33 inside of the eye is a layer vascular tissue. This is the
90:38 It is what provides the nutrients to materials on the inside the retina.
90:45 is also contained within it. A bunch of melanocytes. The purpose of
90:51 is to produce melanin. What does do melanin is a pigment that absorbs
90:56 ? So when light comes in, doesn't keep going through, it stops
91:03 the choroid through that pigmented layer. right, it serves as a black
91:10 . Have you ever looked into someone's , like deep into their eyes,
91:15 for their soul? What did you ? Blackness, darkness right next
91:24 go look, go look deep in eyes and tell me if you see
91:28 . No. The reason for that because all the light is being
91:31 It's like looking into a dark closet doesn't bounce out, it just gets
91:39 . We also have the ciliary ciliary bodies are here and here there's
91:42 bunch of stuff going on with the bodies. Here, we have a
91:46 , the muscles are attached to a . These are called the suspensory ligaments
91:50 are attached to the lens so we contract and relax the ligaments which are
91:54 to change the shape of the We also have the ciliary processes.
91:58 not really well defined in here. the idea here is these structures in
92:02 produce a fluid called that aqueous The aqueous humor flows outward between the
92:08 and the iris and out into this called the anterior cavity and then will
92:16 out through these little tiny holes that not labeled for you right there.
92:19 just gonna tell you what they are because it's the best word in
92:25 These are called the canal of named after the guy who discovered
92:31 which is like the worst last name . But they, the canal of
92:36 . Ok. We'll get to that a bit. So here we can
92:39 the iris again. There's your right? You can see the hole
92:44 formed inside the musculature. That's your . All right. It's simply the
92:50 . There are two muscles here that up the iris. We have a
92:53 and we have a dilator and it tells you sphincter, pupil dilator,
92:57 , the sphincter is the circular one it contracts what it does is it
93:02 the pupil to get smaller. This under parasympathetic regulation. The word parasympathetic
93:09 sympathetic mean nothing to you right Unless you know about the autonomic nervous
93:13 already. If you don't know anything it, we will know about the
93:16 nervous system on the last day of , right? But parasympathetic innervation,
93:21 radial nerves or sorry muscles make the dilate. All right. This is
93:29 sympathetic innovation. The lens is So light passes through the cornea through
93:39 aqueous humor through the pupil, which not just a space, there's nothing
93:43 . And then it passes into that and each of these structures are responsible
93:48 refracting light refraction is what's going to the light to the location in the
93:53 of the eye. The lens does the work. This never changes
93:58 It's the lens that changes shape and changes shape because we have muscles,
94:03 muscles that are attached to ligaments which attached to the lens. If I
94:08 at something far away, what's gonna is that the muscles become relaxed.
94:15 , these muscles are around just like I are, I is, I
94:22 just like the eye is round, sure I get my English.
94:26 Right. So here's your pupil, ? The muscles surround the eye,
94:32 know, like this. So when relax, what they do is they
94:36 like you do. And so they away and what they do is when
94:41 moving away from that, that pupil from that lens, they pull the
94:47 and they make the lens stretch And so the lens gets thinner and
94:54 how you see things far away. far sightedness, right? When you're
95:01 really, really hard on something, muscles contract, right? You're looking
95:06 your things down, you're looking the contract and so again, they contract
95:09 what they do is they fall forward they're contracting forward and that causes the
95:14 to loosen up and that causes the to not be stretched. This way
95:19 causes it to collapse so it becomes . This is what allows you to
95:25 near side of things. Now, do I remember which one is?
95:29 ? Have you ever just like zoned ? I'm looking around the room and
95:32 seeing a couple of you already zoned . Have you ever zoned out?
95:35 , what, what does it look you're doing? Staring in the
95:40 looking far away, far away from . I am not here. That's
95:45 I'm relaxed and I'm zoned out. looking far away. That is how
95:50 remember it. OK. When I'm , think about when you're reading something
95:57 tired you get, right? Because just like focused, right? It
96:03 a lot of work. So when looking at things close by working
96:08 really hard, this process of moving far side and near side and you
96:13 do this real quick. Look, down at your paper, look up
96:15 me, look at me, look, look down, look
96:18 you see how easy, I you just, you, it doesn't
96:21 effort to focus really quickly, does ? This is accommodation. That's what
96:26 process is. Now with regard to , what are we doing here?
96:30 just bending light so that it hits focal point. All right. So
96:35 can see that light when it hits objects, light bends because the speed
96:41 which it's traveling through the thing slows and changes direction. So if you've
96:45 looked at something, you see something this where the, like the,
96:48 pencil in this case, I don't why they put a pencil, not
96:50 straw, you know, but you see there's, it looks like
96:56 right? Like two different objects. that's because when that light hits that
97:01 , it bends, called refraction and changes the direction of the light.
97:05 we're taking advantage, our eyes take of this uh feature of substances and
97:13 light does when it change, you , changing direction and we can direct
97:17 light to a focal point. if we have something that is
97:23 the light passing through the convex item go to a focal point beyond the
97:28 . Whereas if you have a concave , the light is bent away from
97:32 . And so if it reflects that focal point would be like in
97:36 front. So this is why when look at satellite dishes, because you're
97:40 with the reflection, the satellite has of that little thing that sticks up
97:44 the front, right? You actually what your receiver is or you're bouncing
97:48 outwards like that. So this is your eyes do. It's focusing the
97:53 to a point behind the lens and point is going to be in the
97:59 of the eye. And I'll just back and show you see here,
98:01 back over here. If you look closely. If you see the
98:04 little divot, see a little bit it. That's where we're trying to
98:09 the light. We'll get to that a moment. We have a couple
98:13 cavities. Cavities are not holes in teeth. That's another, that's another
98:18 . I think they're called Karen's. can't remember exactly not Karen's.
98:25 All right. So, here's your , there's your cornea, right?
98:31 can see the iris, right? the cavity behind that's called the post
98:36 cavity, the cavity here, that's anterior cavity. The whole thing is
98:44 . So the poster cavity is filled vitreous humor. It's more like a
98:48 , it doesn't really change all that , so much over the course of
98:51 lifetime. You don't make new stuff it than there are cells. Um
98:55 you ever had like a, a , a floaty or something in your
98:59 ? And you, like, you to stare at it, you're
99:01 wait a second and, and then just kind of in your eyes kind
99:04 go with it. All right. , those are dead cells that have
99:08 off the inside of the posterior cavity floating in the Vitria humor. And
99:13 it's actually light is hitting it and reflecting and going a different way.
99:18 it looks like there's something there and is, it's just, you can't
99:22 on it because it's beyond your All right. But it's clear and
99:28 job is to hold the retina against choroid. So it basically puts an
99:34 pressure, keeping the retina in So the retina would be the little
99:41 layer, the red layer here. your choroid. So it pushes up
99:45 direction to hold that in place. here ever suffered from a detached retina
99:51 . Don't get a detached retina. bad. Painful, makes you vomit
99:57 your brain can't understand like what you're when the retinas been folded or
100:04 If you can have folded retinas, would be even worse. Yeah,
100:08 all sorts of horrible things. Don't any of those things as, as
100:12 you can avoid that. Don't do . All right, the anterior cavity
100:17 said here is the s area Remember what we're doing is we're making
100:21 fluid, the fluid rolls around the and then flows into this area and
100:26 out the canal of slim. So of this is the anterior cavity,
100:30 portion behind the iris is called the chamber. That's where you're going to
100:33 the ciliary bodies. The anterior chamber to where you're flowing. That would
100:37 where the canal of slim is It's providing the nutrients, it's producing
100:43 aqueous humor, aqueous humor is more , it's flowing, you're always making
100:48 , um it provides the nutrients for living cells of the cornea. Um
101:00 don't memorize numbers over here. Um this just shows you is how the
101:05 actually refracted through all these different So light hits the cornea, it
101:12 , goes through the a humor it hits the lens, refracts goes through
101:16 vireo humor. It refracts each of things in turn refract and modify the
101:22 of light. And what we're doing we're pushing that light to a focal
101:26 and that focal point is back here the back of the retina,
101:30 So the rumor, the internal side a retina, the focal point is
101:34 the Phobia central. So that's the point. So when we're modifying the
101:40 of the lens, what we're doing we're changing how those light waves and
101:45 they're coming from and how they are to get to that phobia when things
101:49 out of focus, that means you're hitting your focal point just right.
101:58 here we are in the retina. are we doing on time? Just
102:03 sure here. OK. 42 we'll how far we go. All
102:09 So with the retina, we have layers, we have out here next
102:14 the choroid. So here's a choroid is called the retinal pigmented epithelium.
102:19 we have melanin in the choroid which light. But we also have this
102:24 layer whose job is to absorb So light comes in, as we
102:30 through the cornea through the lens and to the here. So light is
102:34 traveling through multiple layers of cell, are the neural layers. And if
102:39 doesn't get absorbed here in the neural , we have this barrier to absorb
102:45 . So that neural or that pigmented . And then if somehow light gets
102:49 that the choroid will pick that up neural layers is where the activity is
102:55 , particularly here in the photoreceptor So we're going to go through layers
103:00 neurons to get to the photoreceptor These are the ones that absorb the
103:05 and turn it into a signal that then be sent back out through the
103:10 nerve to the brain to understand what signals mean, what those photon,
103:15 that light means. So it's here the photoreceptor cells that light energy is
103:23 into those action potentials. So what the five layers here um that you
103:29 know I'm just going to work from outside in. So notice light comes
103:34 direction, here's the choroid, remember choroid is outside, then we have
103:38 retinal layer, then this would be the Vitria humor is. So we
103:43 the photoreceptor cells, photoreceptor cells. can see there are two types,
103:47 are rods and cones named for their . Rods are rodlike cones or cone
103:52 very complicated stuff. These are responsible absorbing light and turning that light energy
104:01 a signal, right. They produce type of graded potential. What they
104:06 is they stimulate the next cell in pathway. Very complicated name here.
104:12 are called bipolar cells because they are bipolar, right? It's not because
104:18 are manic bipolar cells are fewer in than the photoreceptor cells. So what
104:27 doing is we're going to see this as we move downward. All
104:32 And what they do is they are processing information, they're already modulating signals
104:41 then those bipolar cells are going to onto ganglion cells. They're going to
104:46 greater potentials as well. See, aren't very big cells. So this
104:49 going to produce a greater potential. produces a greater potential. It stimulates
104:53 gangland cells of which there are So I'm just going to make up
104:56 . Let's pretend there are hundreds of cells, then there are tens of
105:00 cells and then there'd be like one on which the 10 bipolar cells.
105:05 you can see that convergence, they action potentials, their axons collectively form
105:12 optic nerve. And it's those action that they produce that are going to
105:18 to the visual cortex and allow us perceive what we're seeing. And then
105:22 between, we have horizontal cells and have acri cells and these are
105:27 So they are stimulated by these cells they change the responsiveness in the layer
105:33 follows. So here the photoreceptor cells sending signals to the bipolar cells.
105:38 horizontal cells are modifying the responsiveness of bipolar cells to the photoreceptor cells.
105:46 , the AOC cells are doing the thing. So this is part of
105:50 processing is taking place in the eye because of the relationships and those uh
105:57 cells in between the horizon and the . There are other cells in there
106:02 well. We talked about the retinal , epithelium already they are responsible for
106:07 photons. But the other thing that do is they recycle and process vitamin
106:12 . Vitamin A is going to be or it's really cleaved in half.
106:16 it produces this molecule called retinol retinol how you see it's the molecule that
106:21 you to absorb light molecules. So are going to process it there inside
106:26 pigmented epithelium. The other type of is a ganglion cell. So it's
106:32 like this type of cell over And I mentioned them because they're just
106:37 of interesting, they're called um IP . They're photosensitive ganglion cells are not
106:43 , bipolar cells are not photosensitive. cells are photosensitive. They're the ones
106:50 detect the light. But when we these, these IP G CS,
106:58 the photosensitive ganglion cells, they do light, they contain this molecule called
107:07 and they don't actually tell your brain you're seeing. What they do is
107:10 tell you when light is present. they actually signal the parts of your
107:15 that help you understand the time of . All right. So they play
107:21 role in your circadian clock. They your pupil size. People who are
107:27 , have active photosensitive gangling cells. they know how to respond to the
107:34 , but they don't actually respond to it. Our friend Melatonin, when
107:42 I release my tonin, when I it's getting dark and it's time to
107:45 to sleep. So that's what these do. So I just want to
107:49 out it's not just all about there's other stuff there as well.
107:57 right, I'm gonna get through the and the cones here just real
108:02 Um, and I think I'll probably there because we have like a lot
108:08 I'm talking really slow, but like I said, I get really
108:11 about this stuff. It's fun. interesting. Now, you know
108:14 how you, why perfume smells nice you. You know why fish tastes
108:20 . All right. So with the and the cones, with photoreceptor
108:23 there's two basic types of rods and cones and they're unique in what they
108:27 , right? They both detect but they detect light in different ways
108:31 they detect light at different times. , rods, there's one type of
108:36 cells, you can see its shape here versus the cone, right?
108:39 you can see the outer cone or , not the outer cone, the
108:42 region, the outer segment is basically series of the artist didn't do a
108:47 job. Of here, it looks a series of pancakes stacked on
108:50 So you can imagine the cell And inside there you have these little
108:54 discs that are stacked one on top each other. And it's here is
108:59 the actual reception of light is actually . Now, where they're located,
109:04 you think of your retina, So if this is the back of
109:08 eye, your retina kind of goes this, right? Notice it doesn't
109:11 the front, it's only kind of back where you're gonna find these cones
109:16 predominantly around the edges. You're not find them back here in the
109:20 you'll find them along the edges that further away you get from the Phobia
109:24 , the more rod you have the cones you have and you have tons
109:30 them, hundreds of millions per Their job is primarily responsible for vision
109:36 dim light. So you notice how night time you can kind of see
109:41 , but you can't really clearly see item. It's because of these and
109:45 reason is they respond to few they become really excited very quickly.
109:51 too many photons you overwhelm them and kind of turn off, they don't
109:55 off, but they become overwhelmed, bleach out and that's when the cones
109:59 over. So they don't do a job of distinguishing color. They give
110:03 your night vision, right? The thing they do is they have a
110:08 degree of convergence, which means you hundreds of these converging on bipolar
110:13 So think of like if I have bipolar cell, there may be 100
110:20 . And so if I stimulate a that's way over here and a rod
110:23 way over here, they give the same signal. So this is why
110:28 night vision is kind of blurry because don't get good clarity of image with
110:34 to cones. There's three different Each of them is sensitive to a
110:39 type of wavelength of light. So gives rise to our color vision.
110:43 is the type of vision we use the daytime. Look around the
110:46 Can you see clearly and see colors is everything nice and crystal clear?
110:51 . All right, structurally, it's here. What happens is is that
110:56 cone is basically the plasma membrane folding itself and behaving like what we saw
111:01 here. But it's differently structured. far fewer of them, about 3
111:06 10 million, but they're focused in Phobia. So there's they're highly,
111:11 concentrated where light is directly going. so it is responsible for our vision
111:18 wherever we have bright light, it more photons to activate these types of
111:24 , right? So you don't use when it's dark, they only become
111:29 when there's lots of photons. And that happens, your cones are being
111:32 of shut down. Whereas the rod sorry, the rodger is being shut
111:36 , but the cones are kind of over. And the thing about them
111:41 that they have a low degree of . The better way to think about
111:46 is in the Phobia, you'll have cone and it's attached to one bipolar
111:52 . So out here on the you don't, you have lots of
111:56 rods. So you get fuzzy Remember how we were doing that
112:00 At the fuzzy images over here on edge, I can see stuff going
112:03 , but I can't see clearly what is. I have to turn my
112:06 to look at it and that's when can see the details. So where
112:10 is directly in front of me, where I have the highest concentration of
112:14 . So I get really, really imaging. That's where the clarity comes
112:18 . When we come back, we're break those things down and see what
112:21 that means. So sorry, I over, I kept talking, it
112:25 keeps going. We're gonna do this we're gonna do smell tomorrow or not
112:31 , hearing and balance tomorrow. We're almost done guys. Isn't that
112:42 ? Or are you gonna miss You're gonna miss me. Thank
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