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BIOL 4315 Neuroscience Tue Th 4-5.30pm - Neuroscience Lecture 15 CNS II and the Eye
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00:02 This is lecture 15 of neuroscience. quiz is scheduled for this Friday.
00:12 today we will continue talking about the N S. We ended, we
00:18 the cranial nerves. Last time, gonna ask you to know factory optic
00:26 motor tri the cochlea and Vegas norms particular, their number, their
00:37 And uh what what they do. in particular, we talked about ocular
00:41 is the movement optic nerve is information the retina and we'll talk about it
00:47 early as well. But the material covered today will now be on your
00:52 . So this is all of the on the head and neck, right
00:56 the movement of the tongue. Everything everything below the neck is processed through
01:01 spinal cord. The spinal cord is into cervical. So you have seven
01:07 vertebra associated with each vertebra. You a nerve, the spinal nerve that
01:14 out of the vertebra. Uh you thoracic 12 thoracic vertebra. So,
01:21 one through t 12 and 12 thoracic . You have eight cervical nerves,
01:26 thoracic nerves lumber, one through five five lumber nerves and then saro vertebra
01:35 saro nerves. As you can some of the features of the anatomy
01:40 that spinal cord proper actually terminates about two, number three, L
01:48 L three vertebrae, he and from point on it spreads into what is
01:54 to as ana ana equestrian for ho called a for tail. So it
02:02 like horses tail, but the fibers no longer is one continuous proper spinal
02:09 . So these has some uh um significance because if you uh have to
02:20 super spinal fluid and do a spinal , the spinal tap will typically be
02:26 below where the proper matter of the cord is and try to be inserted
02:31 between the fibers to sample the suva fluid. And uh in some applications
02:39 uh anesthesia. So sub uh subdural during the process of birthing to take
02:47 the pain from the uh thoracic part lower parts of the body.
02:55 spinal cord, as we discussed will dorsal root ganglia cell bringing in the
03:02 element into the dorsal part. We know there are inhibitor into neurons
03:07 And then the other component of each nerve will be the motor outputs that
03:12 out of the ventral side of the cord and will comprise a single bundle
03:19 will be the spinal cord, the and the motor fibers. As you
03:23 see the spinal cord sort of looks a uh either a butterfly or some
03:31 of a creature with horns. So are referred to as dorsal horns on
03:36 dorsal side. And this is the matter. This is where the Somas
03:40 neurons are, the white matter surrounding gray matter and surrounding the dorsal horns
03:46 the ventral horns. This white matter ascending and descending pathways. So the
03:53 uh ascending pathways, dorsal columns here the back and then you have other
04:00 , lateral ventral ventral columns that will traveling descending uh pathways from the higher
04:08 up into the spinal cord. So then you have all of the
04:13 meninges that will be protecting the spinal major ascending sensory pathways, dorsal
04:21 That means all of this amount of information, sensor information from the body
04:27 into the spinal cord will ascend through dorsal column nuclei. And then there
04:33 also pathways that are ascending that come spine, spinal thalamic into thalamus,
04:40 thalamic pathways. Also ascending. for descending paths, there are multiple
04:46 many descending pathways that basically descend from parts of the brain into the spinal
04:53 , corticospinal rubrospinal medullary, reticular spinal , tectospinal trac fact, I'm not
05:01 ask you to know these, but important to understand that each one of
05:05 fiber bundles within the spinal cord is for carrying information, descending information from
05:13 centers of the brain. So, it's coming from cortex, it's
05:17 If it's coming from, it's tetu , if it's coming from vestibular
05:24 vestibular spinal projections. And uh at point, if you advance into like
05:31 professional health care education, uh graduate or medical degrees, in particular,
05:38 might be questions, for example, the injury may occur along the spinal
05:44 and uh what function may be So, obviously, an injury to
05:49 dorsal side of the spinal cord will sensor information or the ability to perceive
05:56 from the body because the ascending pathways gonna be injured in some way.
06:02 , if that injury takes place in different region, obviously, it would
06:07 to different functions like from the tectum would be impaired from the spine or
06:11 the Sibu apparatus. And therefore, would affect the gate and the balance
06:17 a person. Uh uh So these are specific, especially the descending
06:25 autonomic nervous system, visceral peripheral nervous . We don't have time to talk
06:30 it, but we have some time talk about imaging the brain and in
06:34 , imaging the brain in the clinical . So most of the time when
06:39 go into a doctor's office, we all very familiar with x-rays. When
06:46 go to the dentist's office, you x-rays or you go to uh
06:51 They ask you to do x-rays if have a um swelling and uh and
06:56 you sprang your ankle, you typically an x-ray first before you do anything
07:01 but so we all get familiar with and x-rays are alot two dimensional
07:10 Uh Although these days they're becoming three and the three dimensional or multidimensional x-rays
07:19 referred to as computer tomography or C scans. So you will hear about
07:25 T scans. Now, C T can be done on any part of
07:29 body. We are focusing of course the brain because we study C N
07:33 and we are most interested and not the static imaging techniques but the imaging
07:42 activity in the brain. So, which is magnetic resonance imaging, which
07:49 based on hydrogen atoms. It doesn't x-ray, it gives you in some
07:55 more detail, but it is still static image and it can be used
08:03 identify different changes x-rays in particular in skeletal structures in the bones fractures in
08:10 bones, uh C T S, can identify different masses in the
08:16 uh dysfunctions, uh potentially fluid, up, build up and Maria can
08:23 the same but there's no x-ray used . However, the brain is active
08:31 we strive to understand activity in the . And so therefore to image the
08:38 of the brain, we have to functional imaging techniques. Two of those
08:44 pets or posit emission tomography, pet and F MRI or functional mag Magnetic
08:54 imaging. So you can have two of MRI S. You can have
08:59 , a regular MRI which is not image the function, but it's gonna
09:03 the tissues and the bones and you a functional MRI which is actually gonna
09:10 you something about. In this brain activity when neurons are active and
09:17 particular, when specific regions of the are active, that are processing uh
09:23 functions or performing specific functions, those will demand more oxygen and will demand
09:33 metabolic supplies and then more food They're, they're if they're active
09:41 regions of the brain, they will more blood flow. So the more
09:47 the brain region, there's going to more regional blood flow to that
09:52 And there's going to be an increased of the active neuronal populations. So
09:59 you have a very intense visual that means that there's going to be
10:04 blood flow into the occipital lobe where visual cortex is located and there's going
10:10 be more metabolism in that area of brain compared to other parts of the
10:15 and neurons consume glucose. And this the main source of uh kind of
10:21 food intake. If you may, is based uh on the magnetic resonance
10:29 the magnetic spin, it's somewhat based the quantum physics of an atom taking
10:37 different orientation or a spin. You're for a hydrogen atom that has one
10:44 , it can be in either high or low energy state. Now,
10:49 frequency at which the state low state absorb energy and now become high state
10:59 or high energy state is called resonant . So that's where the frequency in
11:04 f the frequency uh uh uh functional resonance imaging. The resonance part is
11:14 frequency resonating at certain frequency radio waves emitted by protons. And those are
11:23 captured by these quite sophisticated uh Now, for F MRI, you're
11:34 magnets, so there will be very magnets and F MRI in particular is
11:41 going to concentrate for our purposes on and de oxyhemoglobin ratio. Hemoglobin carries
11:52 in the blood. The more demand is for that blood, the more
11:57 are active, the more they're going use up the oxygen, those regions
12:00 are more active are gonna contain more the deoxygenated ratio wise or more deoxy
12:08 compared to oxyhemoglobin. In both you have to, if you're imaging
12:17 brain, you have to enter and the coil, it could be a
12:22 coil like that or it could be photon uh electromagnetic radiation uh detector coils
12:32 positron emission tomography. These are not easy procedures. It is easier to
12:41 an x-ray or three dimensional x-ray C scan done on your head. Uh
12:47 it is harder when it comes to scans and F MRI S because of
12:53 magnet because of the coils because of uh spatial confinement, that one has
13:01 put their head inside this machine and on how long or what area or
13:10 tasks the person is performing when they're imaging their brain activity or if they're
13:16 pathological activity, even with regular this is a, a challenging
13:23 Uh uh Some uh people get really and kind of stay inside kind of
13:31 this dark tube with the glasses Uh and other people handle it very
13:38 . Some people have to be It's a difficult procedure for Children.
13:43 having a child stay still. Um their head go in to one of
13:49 coils. Uh In addition, if talking about positron emission, tomography,
13:57 emission tomography requires injection of radioactive OK. And radioactive solution is what's
14:07 to help expose basically the activity protons electrons and will admit electromagnetic radiation.
14:17 coils in the pet scan will pick this electromagnetic radiation. And in this
14:22 , we're looking at glucose consumption for purposes. So two deoxy glucose,
14:28 D G in particular. But so you do a pet procedure or any
14:35 of the body, but the head particular too is you get injected with
14:43 material and you literally become radioactive and cannot even sit in the presence of
14:53 person for about an hour or so you are radioactive and it takes time
15:03 your metabolism, your kidneys and the to take care of these radioactive uh
15:12 materials So that you're no longer So, basically you have to get
15:18 injection, you have to wait for 45 minutes for a pet scan to
15:22 hour. Then you have to undergo of, about, depending on how
15:28 what is being done. Half an to an hour in a scan.
15:32 , it's not, it's not easy it's challenging for Children. Yeah.
15:37 radioactive solutions. Um, of like, it's not necessarily the best
15:41 , it's probably very bad. So would it affect someone who is a
15:47 patient who tends to get a lot pet scans? Uh There's a limit
15:53 how many x-rays and how many scans can do a year. I don't
15:57 the exact specifics and they may vary patient to patient depending on their ability
16:03 undergo these procedures. And you're correct a person who has compromised uh
16:09 compromised kidney function may not be able undergo these uh these imaging procedures.
16:16 typically, you know, you would that not really to see how,
16:20 neurons are active in the brain. would do that if you have,
16:25 know, advanced stages of cancer like , which are the most common type
16:31 cancers, they stem from glia in brain. So yes, you
16:35 you would do that, that kind a um imaging. But you would
16:41 to consider, you'd have to consider about the age of the patient,
16:47 the number of scans they may have that year. Their kidney and liver
16:52 typically gets checked also before they do , any of this. So,
16:58 . So it um there's so many uh interested in that. And why
17:06 you use, why do we use scan? Actually, it's a really
17:18 question, but I, I read it last semester. It was because
17:22 was interested in comparison between it. , you typically uh when you do
17:31 of the time when you do pet for medical procedures, you also are
17:35 imaging activity of the cells. But I'm saying is these two techniques are
17:41 only techniques pet scan and F MRI will show you and reveal the functional
17:47 and the active areas in the Those are the only two techniques that
17:51 can use it. Pet scanning F R R. Now, why would
17:55 do one over the other? So say pat over MRI but not imaging
18:03 . Sometimes you have to do two to really get to the real answer
18:09 diagnosis. You're trying to let's say out if that person may have a
18:16 four cancer in their brain, real , you're gonna do multiple tests.
18:24 pet will reveal areas that are that show more inflammation. OK.
18:31 you may reveal that you know, than, than using uh MRI ultimately
18:42 patients that have very serious conditions and these kind of imaging. They will
18:48 C T scan and they will probably MRI as well. Now, if
18:53 are going to uh image the patient of the activity. So, epilepsy
19:00 seizures, they may do F MRI see what the source of seizure is
19:06 the seizure starts in the brain, . So different patients, different
19:12 You will use uh pet or MRI F MRI or pet scan for activity
19:20 , you use it if you want activity. In this case for the
19:24 neuronal imaging. So this shows for , one that neurons uh in the
19:31 brain were stimulated with some, let's visual stimulus or maybe auditory stimulus,
19:36 more likely visual because there's a lot activity in the occipital area. This
19:41 during stimulation and these hotspots, red basically are like heat maps that indicate
19:49 activity of neuronal populations in these specific of the brain. They're called the
19:54 maps of activity. And this is control where that patient is maybe not
20:01 a visual task, but it is given. Now, you can take
20:06 brain activity map that you obtained during stimulus and brain activity map that you
20:14 in control conditions. You can subtract tube, the image and the activity
20:19 subtract and it will show you the . So here it's showing the difference
20:24 there is a lot of activity in particular region. But so uh once
20:33 , these are really good techniques to activity. Now they're non invasive except
20:41 pet scan, it's invasive that you injected with radioactive with the area.
20:48 But they're also limited the things that discussed in experimental neuroscience such as visualizing
20:57 neurons, patching individual neurons looking at fluctuations and individual synapses resolution or study
21:06 images at different levels. In experimental , from a single molecule level to
21:12 cell, single dendrite, we can single neuron, we can image small
21:17 , we can image large circuit, can image experimentally but clinically, you're
21:24 because you kind of just open a brain or you are limited because you
21:30 non-invasive techniques too. And the limitation is that you don't get as much
21:37 either the temporal in time or spatial space resolution of whatever you're imaging.
21:46 these techniques they will not allow you get to single cell level. You
21:51 be lucky if they will allow you get to square millimeter level. And
21:56 know that within these uh square you will have hundreds if not thousands
22:03 tens of thousands of active neurons. there's also some delay because they're very
22:10 uh processors and computers that are hooked to these coils that pick up the
22:15 . So it's not as fast. you don't get as good of a
22:20 temporal resolution as we call spatial and , temporal and time spatial temple
22:26 But these are non-invasive techniques. And give us a glimpse of what is
22:29 in the brain. What kind of is happening in the brain.
22:34 this century, I hope we'll see noninvasive clinical imaging technique that can actually
22:41 in to hopefully a level of one a few cells in space. And
22:47 would go to be a huge, , huge accomplishment. If in the
22:52 , you can image at the scales we're talking about in experimental neuroscience noninvasively
22:59 these techniques. If you can detect neuron activity, using these techniques that
23:05 would be amazing. And hopefully some you will come up with some of
23:09 inventions or ideas for those inventions in future. So that's a little bit
23:14 the imaging and this actually concludes our N S uh study and section and
23:22 we're gonna move into the eye and the visual system. And uh when
23:30 talk about the visual system, it's whole system. Um it's a system
23:37 it is comprised of the retina. comprised of elements in the thalamus such
23:44 lateral geniculate nucleus and it has areas the occipital lobe and well beyond the
23:51 lobe that we discuss like association areas are sending and processing that information through
23:58 broader cortical areas. So a system something like a visual system, it's
24:03 that is multiple organs. And for sensory system, you have to have
24:08 sensory organ and the sensory organ. this case is the retina which is
24:15 in the back of your eye. is what captures the light. This
24:18 what transduce or changes the light that in the photos of light into an
24:24 signal, electrochemical signal. And it us to stimulate the cells in the
24:32 and in the cortex eventually generating an of the visual stimuli that we have
24:39 full complete picture of the visual So there's this German term gestal configuration
24:48 form and we form this overall view of form. What we see represents
24:56 of objects. Obviously black chair wide , its properties of object and organization
25:10 sensations by the brain. So why we see Only with 400 nm to
25:20 nm? Weird ones a lot. it be nice to see infrared or
25:27 V? Some animals can see and, and, and, and
25:32 exist uh in these different frequencies, wave lengths, we can only perceive
25:42 nm. We have a certain organization the retina. There's a circuit in
25:48 L G M, there's a circuit the primary visual cortex, there's a
25:54 . So we are limited by what how we're built. Three dimensional experiences
26:03 formed from two dimensional images by organizing into a stable pattern in your style
26:10 is constant despite variation and the information . So let's think about that.
26:23 doesn't work works. So what, is that? What is this thing
26:45 ? It can be many things, most of you would think that it's
26:48 sort of a cube, right? most of you can see three dimensions
26:53 those. But you make these three from two dimensions because a dot or
27:00 line on the board is two But our mind tells us that this
27:06 , this looks like a box, know, it has like you can
27:10 something in here, maybe there's a here. And most of you see
27:15 most of you don't see flat two , this is a two dimensional square
27:22 connected to another two dimensional. And there's another thing here, we actually
27:26 these things together. We learned how do this. The brain makes certain
27:32 about what is to be seen in world expectations that seem to derive in
27:37 from experience and in part from built visual wiring. So the built in
27:44 visual wiring is one thing that is . But what you expose to what
27:48 see in life as you develop is different story. And uh all of
27:55 are very different in how we perceive see things. And let's even uh
28:01 an example of art. Some people stand abstract art, other people love
28:07 art. Why is that? you know, maybe you are in
28:13 environment where you are surrounded by realistic or you were not surrounded by
28:19 you don't care for it. some abstract art, some cubes and
28:23 don't make any sense to you. don't see a value in it and
28:27 You have a neighbor who just paid for an abstract painting by Joan Miro
28:35 somebody like that. And you don't how they would, why would they
28:40 do that? So, so we things right? It's that we value
28:45 differently too. We react to things when we see things, you
28:51 Um so there is a wiring component is rigid that will study the circuit
28:57 the connectivity, but there is an component, how we grow up,
29:02 we see things, what is accepted see what is not accepted to
29:07 Uh and how, what we see influences how we behave and what we
29:15 . Uh It's a very powerful sense us, a sense of vision,
29:20 also group things. So I'm talking have this ambiguous pattern, what we
29:25 . And if I ask you, do you see here? Most of
29:30 will say, I see these uh a arrangement of blue and yellow and
29:39 and yellow lines in this column like . And I said, what do
29:45 see here? You were saying? , now I see these yellow and
29:49 dots and kind of the lines and layer like. And that is a
29:57 of similarity So we tend to group together and we say, oh because
30:02 are blue dots, therefore, they're together part of the same blue
30:07 That's similarity, they're very similar. therefore these similar yellow dots are all
30:12 be a part of this yellow Now, what if that is not
30:17 ? And the whatever whoever drew this or an artist will say,
30:23 it's actually blue, yellow, yellow, blue, yellow. This
30:31 my intent. Most of us will , well, why didn't you separate
30:36 more of my space or something like ? So I could see that when
30:40 comes to this principle of proximity, if you move these two blue circles
30:48 together, OK. Here they now the columns, if you move them
30:54 apart, they now form the This is closely together the columns further
31:00 the lines. So this is the . So we also assign on similarity
31:07 proximity of proximity, um certain uh that we perceive things. Basically we
31:16 . We, we, we have uh principles that govern our uh vision
31:23 in his readings. And uh this doesn't work like that one too if
31:30 see it, but it's very famous most of you have probably seen
31:34 but I sometimes draw it on the and when you draw it on the
31:38 , then it's hard to believe that is really the same. So I
31:46 have like a something to draw and , OK, well, this is
31:54 big thing but I'm gonna use So I'm gonna put, look,
31:59 nowhere to go for me. I'm , this is actually perfect. I'm
32:03 go right here and it stops this glass, it stops me
32:08 right? And I'm gonna go right it and make sure that the glass
32:14 , you see this blue line fits the glass boundaries. So, and
32:19 gonna draw this line, the same . So these two lines are identical
32:25 LA, what I mean? 0.0 minus, right? But I got
32:33 call in life. But if I this, I should probably do
32:50 these arrows can be in the, I can even make these shorter than
32:57 arrows on top. And now most you, if you didn't know that
33:01 used this same distance here if you know that and you were asked,
33:09 these arrows the same length, is line the same length? And you
33:16 say, I probably think this is and that's because of how it appears
33:24 . So there are, there are very basic uh illusions that we don't
33:31 think about it, but they're everywhere us. These kind of things visually
33:36 we think, oh, it's about same distance and it's not, you
33:40 , it's a little bit off when come closer, it's really off,
33:43 know, so, and sometimes it's same, but you have a different
33:51 intersecting with that same object in the space and it makes that object look
33:57 bigger or much smaller. So, know, the interior designers,
34:02 they should take the Neocortex with six and they're the ones that really like
34:07 , you know, play with perspectives different rooms and how different pieces of
34:13 can make the room look smaller or , but the same amount of
34:18 So this is all a part of now, if you have a person
34:23 further down, you probably wouldn't think this person is really small or maybe
34:30 wouldn't even think that this chair appears . But you would think that that
34:34 chairs are probably the same size. just that person is further away.
34:39 it appears smaller. It's not like you were to move that person,
34:43 person wouldn't be really tiny shrink, that person appears small. But you
34:50 say if somebody told you. is that person in the back?
34:53 kind of a like tiny fairytale See now it's just further away,
35:01 we understand that. So somebody moves from us. We don't think they
35:04 shrunk in size and became really like little ants far away. And
35:09 they grew again as they came closer us. This is the two faces
35:17 the vas very famous. This is faces in the vas this yellow fish
35:22 green frogs. Uh a lot of illusions once you see them, once
35:27 very easy to recognize them again. we learn them pretty quickly, but
35:30 are very complex. And there are three dimensional illusions. And there are
35:35 that not only create three dimensions, also create movement Within the two
35:45 So it's, it's, it's uh really interesting how that is achieved also
35:50 you can not only just see illusion see from two dimensions, three
35:55 but you can also see a movement three dimensions. So when we talk
36:00 uh light, when we talk about , amplitude, frequency wavelength is determined
36:08 how frequency was the frequency 400 versus nanometers and amplitude is uh The how
36:18 the light is. So when you , for example, to shop for
36:22 flashlight, when you're going camping, will tell you oh this has 300
36:28 or this has 600 lumens. So the intensity of the light.
36:33 It's the amplitude of of the of wavelength is the intensity, it can
36:38 more intense or less intense, but can be the same wavelength, it
36:41 be the same color. So uh of you may have learned Roy GB
36:47 700 down Roy GB, red, , yellow, green indigo uh violence
37:00 you have ultraviolet, you have x-rays radar broadcast bands, but this is
37:07 we see and the light has other . It can get reflected off the
37:13 , it can get absorbed into the or can get restored or bent as
37:22 crosses from different media such as between and water. So it can
37:28 And that's what happens a little bit it comes from air and it encounters
37:33 medium, which is the eye and have the cornia here, they have
37:39 eyeball, the pupil here, they the sclera and the iris rounding the
37:45 , all of the light is gonna into the pupil. Uh and that
37:52 from the retina as we discussed is to get processed by retinal circus,
37:59 later by thalamic circuits and finally by primary visual cortical circus. And that's
38:05 we study over the next two or lectures. Yes, how they call
38:10 blind per like, oh color you a little bit of eye.
38:18 let's talk about the anatomy of the . And then we'll get to the
38:23 and the mixing. So the anatomy the eye have the pupil. This
38:31 the lens, the lens will focus image of the light that comes into
38:35 pupil will focus on the back of eyeball which has the retina. The
38:41 is filled with victorious humor which gives a shape. It's a a solution
38:47 aqueous humor in the front that gives new nutrients and it can be affected
38:52 conditions like glaucoma, for example, lack of alu humor and uh build
38:58 uh of uh of abnormal tissue uh the lens in the back, directly
39:07 in the back of the pupil in center of Avia. And this area
39:13 you learn is responsible for the highest vision or the highest kind of a
39:20 vision that we have. Now, retinal fibers from retinal ganglion cells are
39:27 to exit out of the retina to is called the optic disc, also
39:32 as the blind spot where it forms optic nerve. And that optic nerve
39:38 cranial nerve two. So there's two nerve twos, there's left and right
39:45 nerves and uh they will form the of the fibers that project into the
39:53 out of the retina. This is light is done in such a way
40:00 it will stimulate the phobia with highest resolution not the light enters in such
40:06 way that it is uh when we on direct image or we want to
40:12 something with greater detail, the light be striking this area in the
40:19 So in the back of the you have the circuit, a part
40:24 that circuit, you have photo bipolar sauce and retinal ganglion sauce.
40:30 the light is going to pass through cells and the photo transduction it's going
40:35 take place at the level of the receptors retina. As we discussed as
40:42 of the central nervous system. If remember it came off of that optic
40:46 and optic uh cup during the early , this is the direction of light
40:53 . So light is going to come into the it's gonna get directed.
40:58 the retina is gonna go and start at first with the photo op photo
41:06 are gonna get connected to bipolar Bipolar cells are connected to retinal ganglion
41:13 . The retinal gang cells will form fibers of the optic nerve of the
41:19 nerve two. And in between affecting communication between photoreceptor bipolar cells and retinal
41:27 cells of two kinds of cells, cells and amrine cells. And this
41:33 the retinal circuit. So this is initially the image information is being processed
41:40 light information coming into the eye in back of the retina gets processed.
41:47 lens has these uh muscles and these that allow for when they contract to
42:01 the lens fatter or flatter, And depending on where the image is
42:10 you're looking at far. one may a flatter lens for it to focus
42:16 the retina. Once the image comes , your muscles and ligaments are going
42:22 adjust, making the lens fatter and refocusing and keeping the image focused on
42:31 back of the eyeball on the So if you have perfect vision,
42:38 tropia. In the cases of your image is being focused at a
42:46 which would correspond beyond where the retina are located, making things blurry.
42:55 the adjustment would be to have a or hyperopia correction which is convex.
43:10 , for myopia, it's the The lens is focusing the image where
43:17 would be ahead of the retina, making that image of the flower appear
43:23 . And so the correction would be con Cave lens, OK, concave
43:32 or concave lens that will repos that directly on the back of the right
43:39 computer conca and combat all the This is the principle behind the
43:45 right? So farsightedness, nearsightedness plus minus. This is the principle that
43:51 behind the, uh, lenses that put in your eyes, which basically
43:57 or proper improper focus, either farsightedness nearsightedness. Yes. Um, about
44:08 eye color? I can't answer that not be able to talk about
44:13 It's a good question. I like eye colors. So, what part
44:20 the eye exactly, um, attribute like the? It's, well,
44:29 , it's, it's the lens, the lens you could have,
44:32 problems that are related to cornia too will affect the vision. But most
44:35 most of the time it's the lens most of the correction is glasses.
44:40 . Yeah. Yes. What about other, there's people that I used
44:49 be like that and then it all downhill. Um, yeah. Better
44:59 2020. Yeah. I know some can, can see more detail and
45:05 , um it may have to not necessarily with the shape of the
45:10 , it may have to do with size of the pupil, maybe the
45:13 of the phobia a specific area. it's a, it's also a good
45:19 . Uh anatomically, I'm not sure it is in people that are better
45:23 a normal vision, you know, the for the eye color, you
45:27 , it has to do with the . But um it's also as genetic
45:34 you know, the eye color, ? There's a genetic component, there's
45:37 pigmentation expression component. Uh And um , so I love it. So
45:44 have them as a father and people tried explaining to like that academia,
45:51 things I never fully understood it. what is it in terms of like
45:56 like what is wrong essentially with the where ST so what are your
46:02 Basically whenever people ask me if my are first seen close or far
46:08 I just say like, oh, just can't like see like it's like
46:13 yeah. So it's a so it's can affect in both directions. The
46:17 also sometimes is associated with the movement the eyes too. That's a little
46:22 different, I would say. So uh it has to potentially to do
46:33 the inability to adjust your lungs and may have to do the these ligaments
46:39 the muscles that are necessary to contract adjust the lungs properly and,
46:45 and, and so, uh in lot of cases, it has to
46:51 with the thickness of the lungs. has to do, maybe it's not
46:57 the thickness that perfect all along the . And there might be areas that
47:02 uh kind of all like more fatter more flatter in other cases, you
47:10 , so all of these components could to it. Um, Now there
47:16 these glasses and there's this technology that saw that apparently allow you to,
47:23 do a lenses, it allow you change and a and adjust to either
47:31 or far, you may wanna uh into it. I just saw some
47:37 some description of it or something like . So OK, so basically for
47:43 , it's like the image is not , that's what it is like it
47:47 , I can see it right without glasses, but it just I I
47:50 have to like look into it and it's like sharp. So it's just
47:56 the potentially, yeah, potentially, you have have to have the because
48:08 me that's how I understand. But know, you can, this is
48:13 simple description but there can be more things that, that you know,
48:18 I'm not accounting for. But all these things, the thickness adjustment of
48:22 lungs, uh something to do with of the muscles, potentially maybe may
48:28 affected in the in that condition. . So an anatomically what's happening that
48:36 the image to move past. Um was it? The uh the
48:43 the wrong, the wrong focus of lens which it could be too thick
48:47 too thin. And so you adjust by uh giving people glosses that will
48:55 , make it thicker or make it . OK. So for uh the
49:00 one for is that like um is attracting too much or is it too
49:09 that's making the image go pass the ? OK. Uh Again, I'm
49:15 so certain you can answer those questions , that based on whether it's
49:22 too fat or too thin. If look here, obviously, thicker lens
49:29 you focus on the near objects. um it may not be the actual
49:38 of the lenses again, related to ligaments that control the thickness of the
49:44 and it may just control it in direction more than the other making it
49:50 or, or contra or, or making it thinner. So,
49:57 so When we look at stuff, see them in 2D but like I'm
50:03 so interested there. So if we something for too long, if we
50:07 at something either starts to be blurry it starts to look a different shape
50:12 it originally did. Um Yeah, don't know how to answer that.
50:29 You know, eye perception and eye could be related to other conditions.
50:38 problems could be related to blood pressure changes in blood pressure. It changes
50:44 ocular pressure, which is changes the how sharp the image occurs and may
50:50 to do with specific signaling in the surface. It can be so many
50:57 things and I I don't know what the exact symptom is. So
51:04 very hard to answer something like Um People have migraines, they will
51:11 a loss or partial loss of visual . Uh Hopefully, that's not that
51:17 you're tired, you have fatigue, very, becoming difficult for you to
51:24 . Your eyes are kind of almost going cross eyed because you've just been
51:28 too much at the books or the and you're all very different. So
51:33 yeah, can be different things. Well, it could be chemically driven
51:39 be uh because of your physical state lack of sleep or something like
51:46 you know, hopefully nothing serious. . So we also have a um
51:52 field of view from one eye who cover 100 and 50 degrees from
51:59 from one eye is looking at 100 50 degrees if you put a pencil
52:05 very close to your eye, one that can occupy most of my visual
52:11 that can occupy all of my visual can occupy half of it. You
52:16 occupy 1/5 of it just further I know the size of the object
52:24 then know how far away it And so if you know, for
52:28 , the distance to the moon, moon will be about half a degree
52:35 visual angle, 100 and 50 degrees visual angle. So be half a
52:40 with one eye at the at the . And you know the distance of
52:44 moon, that moon will excite neurons approximately 100 and 40 micrometers of
52:55 And this retina, the moon is the retina here, if there was
53:03 star over here or a planet then it would excite the record at
53:11 different point. So that there's a in space that is represented by activation
53:20 a space or point in the You learn that this is called uh
53:27 by point representation or retina topic map the retina has a map of the
53:36 world in different parts of the retina at different portions of this visual angle
53:43 in visual uh field. So important about the retinal circuit is photoreceptors are
53:50 only light sensitive cells. Ganglion cells the only output from the retina.
53:57 the light gets processed by that circuit , bipolar cells. The gang
54:04 the only cells that produce action potential the retinal gang cells and the ganglion
54:09 will form the optic nerve cranial nerve . So you have raw photo receptors
54:20 this is the outer nuclear level where nuclei of photoreceptors are the raw photoreceptors
54:26 the cone photoreceptors you have outer plexiform . This is the layer where there's
54:32 made between photoreceptors, bipolar cells and cells you have in internuclear layer in
54:39 retina which will contain the Somas of cells, horizontal cells and the nuclei
54:45 the bipolar cells. There's an inner layer which is the synapses between amari
54:54 and ganglion cells. And then the cell layer where you have the cell
55:00 the nuclei of the ganglion rectal gang that will project their axons into the
55:09 . So once again, the other around you have gang in inner inner
55:14 layer, outer plexiform, outer nuclear , photoreceptor, outer segments. And
55:20 is where you have the pigmented Ok. So the difference is between
55:26 cone and rod photoreceptors is you can that there's a big difference in the
55:34 segments, in particular anatomically between the photoreceptors where the rod photo receptors have
55:41 free floating discs that have their own . So there are these membranous disks
55:47 are free floating in this outer segment rapper receptors because of that are loaded
55:54 uh photosensitive molecules that are very sensitive they're responsible for night or dark vision
56:02 photoreceptors instead have these imaginations in the membrane, but they don't have as
56:11 of the surface area and they don't this free floating discs like rod photoreceptors
56:22 . So the difference, big difference the inner segments, synoptic terminals are
56:27 but the outer segments of free floating versus the folding uh of the outer
56:35 membrane uh are very, very different the rod versus cone photoreceptor. So
56:43 are high sensitivity to light specialized in vision. More photo pigment is cat
56:51 on those uh uh photosensitive molecules are on the rods and they can capture
56:58 light. There are high amplification Single photon detections, single photon can
57:04 detected by these photoreceptors. They're So they have low temporal resolution,
57:12 response, long integration time and they're sensitive to scattered light rod system is
57:20 acuity. So there are not many present in the povia and they have
57:25 convergent retinal pathways. They're also which means that there's one type of
57:32 pigment and rod just uh photoreceptors. best way to do to,
57:38 to to describe them is when you in the movie theater that's dark.
57:44 first you don't see anything but then or two seconds later, you actually
57:49 discerning more detail, but you're not in the dark, seeing as much
57:55 , you may be seeing lighter versus or gray scale representation unless the light
58:01 on or the light flicker and it the color but in the dark.
58:07 this is rod system, in the , you have cones that are lower
58:13 , but they're specialized for day So when you want to read something
58:19 and it's very small print, you do two things. One thing is
58:24 gonna try to bring it closer to so you can see it better.
58:27 two, very likely you're gonna turn a lighter uh flashlight or a light
58:34 of some sort to, to see you're looking at, candle light,
58:39 where it is, but you're gonna able to see it better. So
58:42 is the cone system that has less pigment, lower amplification, high temporal
58:49 . So fast response, very short time, most sensitive to direct axial
58:55 of light, it's a high acuity system. That means that there's a
59:00 of cones that are concentrated and are in the phobia. They have dispersed
59:06 pathways and they're chromatic. So there three types of cones each with a
59:12 distinct pigment that is most sensitive to different part of the visible light
59:22 Uh For example, we look at distance across the retina. And if
59:27 look in the central retina in the cones are here in blue. The
59:32 regions of the central retina are dominated cones and the peripheral regions are dominated
59:41 raw photoreceptor. So that means that central phobia regions are where we have
59:47 highest security vision and we need direct rays of light for the highest resolution
59:53 in the periphery, we have more the uh ninth vision uh or the
60:00 but receptors that are expressed there. is an illustration of the phobia where
60:07 actually have a anatomical kind of a little crater created and it allows to
60:15 all of these other cellular components in of it, retinal gang cells and
60:20 cells. And for the light to of be collected into the S cup
60:25 the phobias for the race to be here so that they can most effectively
60:31 the cones. And these other cells not going to be in a way
60:37 these direct axle rays of light. a specialized anatomical feature here in the
60:44 and the phobia. As far as color perception goes, we have blue
60:52 and red photo receptors or the cone . So The blue, if you
61:04 a blue color, if you're wearing blue shirt, I see blue color
61:11 is about 440 nm. So when light reflects off the blue shirt,
61:18 about 440 nanometers or so. And me to perceive blue color, I
61:25 only uh have, I only have activate blue cones to see blue color
61:33 I wanted to see green color. there is a green chair, Green
61:41 activate green colour will activate 31% of cones, Uh uh sorry of red
61:51 and 67% of green cones And 36% blue cones. So that wavelength will
62:02 perceived by all three sub types of cone photoreceptors, yellow Will activate 83%
62:15 and 83% green in order to perceive light. So there is no yellow
62:23 . So how do we see So if you were given uh an
62:30 palate And you were given three blue, green and red, you
62:38 could make yellow, you could mix colors to make yellow, you can
62:45 the colors to make other different Black will contain all of the cone
62:52 to a certain extent. This is color mixing. OK. So you
62:57 this uh blue overlapping with red, with green, you're getting white,
63:03 with green, you're getting uh green with blue, you're getting turquoise
63:11 with blue, you're getting uh violet colors. So that means that different
63:18 that we're seeing will to a different activate the different proportions of blue,
63:26 green or the red cones. And you're asked about color blindness, there
63:33 uh different kind of kinds of color , but sometimes it's a genetic component
63:39 there's no expression of one subtype of . And if you're missing one of
63:45 color colors, one of these color , your color mixing is not the
63:52 and your color perception is different. are famous artists that are uh color
63:58 or partially color blind. OK. you could be completely not perceiving color
64:04 some rare cases or you could be blind where you're not perceiving a certain
64:11 uh like red cones are missing, example, and everything for you appears
64:16 blue and green. So your whole is, is is blue and green
64:21 you perceive objects differently. They are artists that are color blind and when
64:26 paint, it looks very strange, they are very interesting paintings because their
64:32 of color in the outside world, we consider, you know, how
64:36 , green trees are supposed to look blue water, uh you know,
64:40 sunset is has different uh perception and in, in their visual systems.
64:49 . So that's enough information before spring , we're gonna end here today.
64:54 luck tomorrow on the quiz and I see you all after spring break.
65:00 ? If you have a question, welcome to come and ask
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