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BMB Test 2 > B7.030 Visual System I > Flashcards

B7.030 Visual System I Flashcards

1
Q

anterior chamber of the eye

A

anterior to the pupil
cornea + fluid compartment
location where fluid exits

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2
Q

posterior chamber of the eye

A

between lens and pupil

location where fluid forms

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3
Q

result of fluid accumulation

A

increased intraocular pressure

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4
Q

causes of fluid accumulation

A

overproduction

clogging of drainage

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5
Q

sphincter muscle

A

closes pupil

under parasympathetic control

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6
Q

radial muscle

A

opens pupil

under sympathetic control

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7
Q

where does visual signal processing begin

A

the retina

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8
Q

photoreceptors

A

transduce photons into neuronal activity
final layer of cells in back of the eye
light passes through all other cells first

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9
Q

fovea

A

triangular break in the ganglion and bipolar cell layers so that light has a more direct path to photoreceptors
concentration of cones at this point
aids in visual acuity

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10
Q

cell layers of the retina

A 
inner: ganglion
inner plexiform layer
middle: bipolar
outer plexiform layer
outer: photoreceptors
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11
Q

function of ganglion cells

A

axons form the optic nerve (CN II) which travels to the thalamus

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12
Q

where are light rays refracted

A

cornea (static)

lens (dynamic)

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13
Q

why are light rays refracted

A

to be more specifically focused on the retina

bent more when objects are closer

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14
Q

how does the shape of the lens change when bending light

A

rounded when bending light, flat when not

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15
Q

result of errors in light refraction

A

images not focused on the retina

reduced visual acuity

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16
Q

hyperopic

A

far sighted
light converges behind retina
larger patch of photoreceptors activated than is necessary

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17
Q

myopic

A

near sighted

light converges in front of retina

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18
Q

astigmatism

A

two focal points of light convergence

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19
Q

2 causes of light refraction errors

A

funky eyeball shape

inability of lens to change shape adequately

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20
Q

presbyopia

A

lens hardened with age, unable to change shape

image focused behind retina

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21
Q

how to correct presbyopia

A

artificially thicken the lens (glasses, contacts)

refractive lens exchange

22
Q

describe how a map of the external environment is created on the retina

A

light from a given location in space will stimulate photoreceptors in a specific location in the retina
location in space that stimulates a given photoreceptor is its receptive field

23
Q

why are images on the retina upside down

A

path that light travels to reach the retina

24
Q

binocular vision

A

both eyes can focus on the same point in space

25
Q

nasal retina

A

temporal visual field

26
Q

temporal retina

A

nasal visual field

27
Q

where is the left half of the visual world processed

A

right optic tract/ LGN/ visual cortex

28
Q

where is the right half of the visual world processed

A

left optic tract/ LGN/ visual cortex

29
Q

what happens in the optic chiasm

A

fibers from the nasal retina (temporal visual field) decussate in order to reach the contralateral side of the brain

30
Q

what is rhodopsin and how does it impact vision

A

molecules embedded in photoreceptor outer segment membrane disks
composed of retinal and opsin
absorbs photons on light and isomerizes, creating the active form

31
Q

metarhodopsin II

A

activated rhodopsin
unstable
triggers next step in visual transduction pathway
eventually recycled by pigment epithelium at the back of the eye

32
Q

how is signal transduced in the photoreceptor

A

activation of rhodopsin triggers a g protein coupled pathway
pathway results in closure of Na+ channels on the outer cell membrane
membrane hyperpolarizes when light hits the retina

33
Q

glutamate release in the photoreceptors

A

occurs with no light
depolarizing current is present
aka when light is present, glutamate release is reduced

34
Q

2 types of photoreceptors

A

rods

cones

35
Q

rod system

A

operates in dim light, can detect a single photon
many rods, many bipolars, one ganglion cell (low acuity)
sacrifices acuity for sensitivity
one type of opsin (monochromatic)
found in periphery of retina

36
Q

cone system

A

operates in bright light (higher threshold for activation)
few cones, one bipolar cell, one ganglion cell
maximizes acuity
found in high density in fovea
different opsins sensitive to different wavelengths of light (color vision)

37
Q

retinal pigment epithelium

A

absorbs extra photons of light
appears dark on histo
supplies blood to photoreceptors

38
Q

embryologic development of the retinal layers

A 
invagination of the optic vesicle results in 2 layers coming into apposition (pigment epithelium and neural retina)
may separate (detached retina)
39
Q

blood supply to the retina

A

inner retinal layers are supplied by branches of the central retinal artery

  • blood vessels obstruct light path to the retina
  • hemorrhage and hyperplasia can impair visual acuity, result in visual field deficits
40
Q

why do we have conjugate eye movements

A

so that an object of interest is focused on the fovea of the retina

41
Q

3 cells in retina

A

photoreceptors
bipolar cells
ganglion cells

42
Q

photoreceptors

A

specialized sensory cells

transduce light into transmitter release

43
Q

bipolar cells

A

receive input from photoreceptors
transfer to ganglion cells
no action potential

44
Q

ganglion cell

A

output cells of the retina

axons form the optic nerve headed for LGN

45
Q

neurotransmitter release in retina

A

amount of neurotransmitter released is proportional to amount of light activating the retinal pigment

dark: cells are depolarized, so more neurotransmitter release
light: cells become hyperpolarized, so less neurotransmitter release

46
Q

what is the LGN

A

nucleus in the thalamus
contains a map of contralateral visual field from the optic tract
laminated structure w 6 layers

47
Q

where do fibers travel once they leave the LGN

A

separate into 2 bundles to reach primary visual cortex

  • parietal lobe fibers = inferior visual field
  • temporal lobe fibers (Meyer’s loop) = superior visual field
48
Q

cortical representation of the fovea

A

large section

located at occipital pole

49
Q

cortical representation of the peripheral regions

A

represented more anteriorly

50
Q

upper bank of sulcus

A

inferior region of visual space

51
Q

lower bank of sulcus

A

superior region of visual space

BMB Test 2 (22 decks)

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