Neuro 31 - Retina

Front 1

how many layers does the cornea have?

Back 1

the cornea is a 5-layer membrane

Front 2

in order for you to be able to see what parts of your eye need to be clear? (3)

Back 2

the cornea, the lens, the fluid of the aqueous humor need to be clear

Front 3

what is a cataract?

Back 3

a clouding of the lens

Front 4

where can you divide the eye from anterior / posterior and what type of errors are seen in the anterior eye?

Back 4

from the lens anterior is the front of the eye; issues here may cause refractive errors

Front 5

what’s the light-sensitive part of your vision?

Back 5

the retina is the light-sensitive seeing part of your eye; it forms all images that are transmitted to the brain

Front 6

what’s the fovea?

Back 6

the fovea is the center of the macula

Front 7

tell me more about the fovea. what’s its reflex? what’s contained there?

Back 7

The fovea, in a healthy eye, has a pinpoint light reflex called the Foveal Light Reflex. This region has the highest density of photoreceptors in the retina, and has the highest visual acuity. It is the thinnest part of the retina, measuring 250microns. The retinal ganglion cells are pushed off to the side to allow for maximum visual acuity.

Front 8

what’s the macula?

Back 8

The macula (macula lutea which is latin for yellow spot) is the center of vision. When you look at something, you are placing that image on your fovea, which is the center of the macula.

Front 9

what makes the fluid in your eye?

Back 9

the ciliary body makes the fluid

Front 10

what’s glaucoma?

Back 10

when your ciliary body makes too much fluid or is damaged -> glaucoma

Front 11

how are images projected onto the retina?

Back 11

upside-down; the brain and the corpus callosum upright the images

Front 12

label the layers of the retina

Back 12

Front 13

there are actually __ separate layers but ___ total

Back 13

there are 7 layers but 10 total

Front 14

what layer forms the optic nerve?

Back 14

the ganglionic cell layers form the optic nerve fibers that project to the brain

Front 15

where in the retina may patients may have wrinkles?

Back 15

on the membrana limitans (limiting membrane)

Front 16

why do you need to dilate your patient’s eyes?

Back 16

because the retina covers the back of the eye and you need dilation to be able to get a good view

Front 17

where do you have a blind spot?

Back 17

there’s a blind spot at the disc / optic nerve -> no cones and rods there; the only thing there is the optic nerve.

Front 18

what forms the optic nerve (Cranial Nerve II)? what’s its general course?

Back 18

formed by the axons of the retinal ganglion cells. This bundle of axons “punches through” the sclera and exits the back of the eye on its way to the brain. There are no photoreceptors on the optic nerve itself, which creates a “blind spot”.

Front 19

where is the optic nerve located? in relation to the fovea?

Back 19

It is located nasally and is approximately 3 millimeters from the fovea.

Front 20

contrast the inner vs. outer part of your eye

Back 20

Inner part -> closest to the vitreous cavity (hollow of the eye) vs. outer part -> closest to the eye wall (choroid, sclera).

Front 21

what do you see on the outer part of your eye?

Back 21

can see your sclera (which is white and forms the outside of the eye) but NOT your choroid, which is the inner layer underneath the retina

Front 22

describe what you see and what you don’t see when you look at the back of the eye

Back 22

it looks red; the retina is microns in size but CLEAR like cellophane laying atop a layer that is reddish brown called the choroid. The color is from the choroidal circulation behind the retina and the pigmented epithelial layer

Front 23

The layers of the retina are all optically ____

Back 23

The layers of the retina are all optically clear (transparent).

Front 24

What does the peripheral retina detect?

Back 24

The peripheral retina detects light and motion, but no detail. Visual acuity drops off rapidly as you move away from the macula.

Front 25

Back 25

Front 26

list the 7 retinal layers

Back 26

Photoreceptor Layer (Prc) (deep) 2. Outer nuclear layer (ONL) 3. Outer plexiform layer (OPL) 4. Inner nuclear layer (INL) 5. Inner plexiform layer (IPL) 6. Retinal ganglion cell layer (RGL) 7. Nerve fiber layer (NFL-in this diagram its called the optic fiber layer, OFL)

Front 27

mnemonic

Back 27

Phonopin Ipreg NFL ;-)

Front 28

name the layers

Back 28

nerve fiber layer

ganglion cell layer

inner plexiform layer

inner nuclear layer

outer nuclear layer

retinal pigemented layer

choroid plexus

Front 29

what’s the course of the ganglion cell layer?

Back 29

it traverses the top part of the retina underneath the inner limiting membrane, goes to the optic disc, forming the optic nerve

Front 30

what’s the #1 cause of blindness in the U.S.?

Back 30

macular degeneration (of the age-related type) is the leading cause of blindness in the U.S. -> damage to the pigmented epithelium, which “feeds” the retina

Front 31

which three layers contain cell bodies?

Back 31

retinal ganglion cell (RGC) layer, inner nuclear layer (INL), and outer nuclear layer ONL

Front 32

what does the outermost layer contain?

Back 32

the photoreceptors outer segments lie in the Photoreceptor layer (Prc).

Front 33

what does the outer nuclear layer contain?

Back 33

the cell bodies of the photoreceptors.

Front 34

what does the Inner nuclear layer (INL) contain?

Back 34

nuclei from the biopolar, horizontal and amacrine cells*

Front 35

what does the Retinal ganglion cell layer (RGL) contain?

Back 35

nuclei / cell bodies from the ganglion cells that ultimately send their axons to the Optic nerve (via the Nerve fiber layer).

Front 36

in what layers are the intraretinal connections?

Back 36

The outer and inner plexiform layers contain intraretinal connections.

Front 37

in the outer plexiform layer, what communicates with what?

Back 37

photoreceptors talk to horizontal and bipolar cells

Front 38

what connections do you find in the inner plexiform layer?

Back 38

Connections between inner nuclear cells (bipolar, horizontal, amacrine) and retinal ganglion cells.

Front 39

The ____ ____ layer contains RGC ____ that converge to form the optic nerve.

Back 39

The nerve fiber layer (NFL) contains RGC axons that converge to form the optic nerve

Front 40

messages enter the eye through what and are processed by what?

Back 40

through the retina, are processed by the rods and cones

Front 41

photoreceptors refers to ____ and ____. their main function is _____.

Back 41

photoreceptors are rods and cones whose main function is phototransduction.

Front 42

what are horizontal cells? where are their cell bodies? NT? function?

Back 42

Horizontal cells are the laterally interconnecting neurons with their cell bodies in the inner nuclear layer. They are GABAergic and play a role in regulating the input from multiple photoreceptor cells.

Front 43

what are amacrine cells? NT? location? interacting with ___ and ___?

Back 43

Amacrine cells are also GABAergic (or glycinergic) inhibitory interneurons. Their dendritic arbors are in the inner plexiform layer interacting with both bipolar cells and ganglion cells.

Front 44

What’s the synaptic input of bipolar cells?

Back 44

Bipolar cells receive synaptic input from only rods or cones (not both, thus they are classified as rod bipolars or cone bipolars

Front 45

what’s the only cell type of the retina to project their axons outside the retina?

Back 45

Ganglion cells are the only ones that project their axons outside the retina through the optic nerve.

Front 46

what cell type do high pressures inside the eye (glaucoma) most commonly damage?

Back 46

the retinal ganglion cells, which are also connecting cells

Front 47

what’s the relation of the blood vessels to the retina?

Back 47

blood vessels are inside the retina.

Front 48

can you see the retina? why or why not?

Back 48

you can’t see the retina because it’s transparent, cellophane clear; you may be able to see a hole or damage

Front 49

what the function of the macula?

Back 49

the center of the vision is the macula, see the freckle on somebody’s nose or color; patients may have great vision if the center of the retina and the fovea look good despite other problems

Front 50

what do you call retinas with holes and tears in them?

Back 50

retinal detachment. fluid from the vitreous or “gel” can get up underneath the retina and separate the retina from the choroid and pigmented epithelium. without your retina, you can’t see.

Front 51

how is your vision affected if the top of your retina is detached?

Back 51

superior retinal detachment -> inferior field defect

Front 52

the dilated exam is key for diagnosing what 3 common conditions?

Back 52

glaucoma, optic nerve disease or retinal detachment; when the field of vision starts to narrow and there’s a defect. can check visual fields.

Front 53

the optic nerve is just a ____ of impulses to the brain

Back 53

the optic nerve is just a CARRIER of impulses to the brain. just fibers

Front 54

where is the highest concentration of cones in your eye?

Back 54

the fovea has the highest concentration of cones; “they see the freckle on somebody’s nose” and important for color; the macula is your friend

Front 55

what cells are the dark knights? where is their concentration highest?

Back 55

rods are the dark knights, higher in the periphery

Front 56

what’s the hub of vision in your eye?

Back 56

the center of the macula in the retina is the hub of vision; the highest concentration of cones and the highest metabolic rate`

Front 57

what’s the most common eye procedure?

Back 57

injections to the eye -> treatment for macular degeneration, more common than cataract surgery now

Front 58

what’s the center of the macula?

Back 58

The fovea is the center of the macula**, the most sensitive part of the eye, “sacrosanct,”

Front 59

what’s the center of the fovea?

Back 59

The foveola (foveolar umbo) is the center of the fovea

Front 60

“it does behoove you to know the layers of the retina”

Back 60

Front 61

what layer forms the optic nerve?

Back 61

ganglion cell layer (GCL) forms optic nerve

Front 62

what technique allows you to image the layers of the retina?

Back 62

layers of OCT optical coherence tomography layers, microns in size allows you to see layers of the retina

Front 63

what layer looks like it has bubbles on optical coherence tomography (OCT)?

Back 63

the choroid looks like it has bubbles

Front 64

where is there very high blood flow in the eye?

Back 64

the choroid, which feeds the pigmented epithelium, which feeds the retina; cannot be fixed

Front 65

name the layers

Back 65

Front 66

where do you want your rods and cones to be?

Back 66

the rods and cones need all the blood flow they can get! near the choroid plexus

Front 67

where does light hit?

Back 67

light comes straight in and hits the foveal umbo so you can process it

Front 68

what does the retinal pigmented epithelium do?

Back 68

nourishes the retina by allowing the choroid to push nutrients through it

Front 69

contrast the cell types involved for nighttime vs. daytime vision

Back 69

nighttime vision -> rods (can detect a single photon) and daylight vision -> cones; though rods have much more activity

Front 70

contrast rods and cones with number, sensitivity and reaction time

Back 70

CONES are not as sensitive to photons as rods, but they react more quickly. Rods are much more numerous ~120 million vs. 6 million

Front 71

where does light pass through first?

Back 71

light first passes through the inner limiting membrane

Front 72

when do you need to have your sharpest vision? what gives you that ability?

Back 72

when they light is off otherwise how can you walk in the dark!? rods give you the ability to see in the dark

Front 73

at what wavelength do you get the maximal response of rods?

Back 73

Maximal response of rods to 510nm (starlight) (peripheral vision best)

Front 74

what do rods use for phototransduction?

Back 74

use retinal and opsin protein (rhodopsin)

Front 75

what’s rhodopsin?

Back 75

A thermolabile protein that is sensitive to red light and is found in the external segments of the rods of the retina.

Front 76

where in the retina are rods absent?

Back 76

absent in the fovea

Front 77

describe the unique structure of the outer segment of rods

Back 77

plasma membrane like flattened floating sacs (DISCS); 1000/sacs per outer segment;

Front 78

how much rhodopsin is there per sac in a rod?

Back 78

1 million rhodopsin molecules per sac (a LOT of molecules in the sac). “you need better, stronger, faster vision in the dark”

Front 79

what’s retinal?

Back 79

a photochemical, the aldehyde form of vitamin A, used by both rods and cones. “a light-absorobing chromophore”

Front 80

what do cones use? to detect what?

Back 80

you use retinal and 3 different cone opsins (photopsins); the 3 different cone opsins are sensitive to blue (443nm), green (535nm), and red (570nm) wavelengths. The are primarily used for daytime (photopic), high acuity and color vision.

Front 81

what are the 3 photoreceptor components

Back 81

1. Outer segments-phototransduction cascade, 2. Inner segments-Cell protein synthesis (Golgi apparatus and endoplasmic reticulum) and metabolic machinery (mitochondria) 3. Synaptic terminal

Front 82

what’s the color detection of rods vs. cones

Back 82

the rods may not have any red/green/blues just light and dark

Front 83

what’s the structure of cones?

Back 83

very similar to rods, discs i.e. evaginations of outer segment plasma membrane; high acuity and color vision

Front 84

a person with three types of cones is called a ____? If less than that?

Back 84

Three cone -> trichromat; vs. dichromat; monochromat

Front 85

what’s the most common human genetic disorder affecting the eyes?

Back 85

Mutations in red or green cone opsins (located on the X chromosome) are the most common human genetic disorder (~5%); “loss of red, green or blue or combination of two!”

Front 86

disease in internal medicine is a ____ in opthamology?

Back 86

dystrophy -> abnormality e.g. in cone

Front 87

describe 3 important components of rods and cones. what are they and what happens there?

Back 87

1)Outer Segment - where photons are captured and phototransduction cascade begins; 2) Inner Segment - cell protein synthesis (Golgi apparatus and endoplasmic reticulum) and metabolic machinery (mitochondria); 3) Synaptic Terminal - The release of excitatory neurotransmitter-Glutamate* to bipolar and horizontal cells, which starts the biochemical cascade

Front 88

what’s phototransduction?

Back 88

the conversion of photons (elementary particles of light) into an electrical signal that can be interpreted by the nervous system; required to see

Front 89

where does phototransduction occur?

Back 89

occurs within the photoreceptors outer segments (in the photoreceptor layer);

Front 90

what does phototransduction depend on?

Back 90

the activation of outer segment proteins called opsins. required for vision

Front 91

what binds what in phototransduction?

Back 91

Opsin binds retinal.

Front 92

what happens on the molecular level for vision to occur?

Back 92

when retinal absorbs light, it induces a change in retinal from a cis isomer to an all-trans isomer* Opsin releases retinal and becomes activated. This initiates the phototransduction cascade.

Front 93

what happens with the stimulus in sensory neurons for other senses (generally)?

Back 93

a stimulus activates a receptor which causes a cell membrane to depolarize, leading to an action potential, which leads to neurotransmitter release

Front 94

Photoreceptors do not have ____ ____

Back 94

action potentials (all or none stimulation)

Front 95

what causes transmitter release in rods and cones?

Back 95

light activation causes a graded change in membrane potential and a corresponding change in the rate of transmitter release onto postsynaptic neurons

Front 96

Photoreceptors ___polarize instead of ___polarize

Back 96

Photoreceptors hyperpolarize

Front 97

Back 97

Front 98

Back 98

Front 99

what molecule does light activate?

Back 99

light stimulation of rhodopsin leads to activation of a G-protein, transducin

Front 100

Retinal is converted from what to what?

Back 100

11,cis retinal to all-transretinal (active form)

Front 101

Activated rhodopsin leads to a series of biochemical events that lead to an overall decrease in what? and what’s the consequence?

Back 101

cGMP and therefore cGMP gated cationic channels on the photoreceptor cell membrane close

Front 102

how do photoreceptor cells hyperpolarize? what happens to NT release?

Back 102

Closed cationic channels cause a HYPERPOLARIZATION of the photoreceptor cell and a relative decrease in the release of Glutamate in the synapse. When the photoreceptor is hyperpolarized, it releases LESS glutamate.

Front 103

the phototransduction cascade allows for what?

Back 103

the amplification* of signal such that 1 activated rhodopsin molecule can lead to 1,000,000 conversion of cGMP to GMP.

Front 104

what are opsins?

Back 104

outer segment proteins, which when bound to light-absorbing chromophore (retinal) are called rhodopsins

Front 105

how are the retinal ganglion cells classified?

Back 105

those showing linear spatial summation (parvocellular, P or midget ganglion cells) and those that do not show linear summation (magnocellular, M or parasol retinal ganglion cells)

Front 106

what are the LGN layers?

Back 106

has magnocellular (1, 2) and parvocellular (3,4,5,6) layers

Front 107

where in the LGN do M cells of the retina project?

Back 107

to the magnocellular layers in the LGN (contra eye to layer 1, ipsi eye to layer 2)

Front 108

where in the LGN do P cells of the retina project?

Back 108

to parvocellularlayers (ipsi 3, 5, contra 4, 6)

Front 109

describe theMagnocellular “pathway” i.e. 1) type of neurons, what they detect/code and how this information goes to the corticies

Back 109

has large, rapidly conducting neurons that mediate visual perception, especially coding of movement and edges as opposed to fine detail. Through the optic radiations this information feeds to the visual cortex and to the parietal association cortex,the dorsal “where” stream.

Front 110

what type are the Parvocellular “pathway” cells? fct? where does it go?

Back 110

are color-sensitive, have greater spatial resolution and discriminate fine details, optic radiations carry this information to the visual cortex) and from there it mostly goes to the temporal association areas, the ventral “what”pathway.