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L32 - visual pathways Flashcards

1
Q

optic radiations

A

fibres which relay information between the thalamus to the primary visual cortex

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2
Q

location of primary visual cortex

A

occipital lobe

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3
Q

origin of optic nerve

A

retina
travels to optic chiasma
travels along optic tracts
reaches lateral geniculate body in the thalamus

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4
Q

visual area of the thalamus

A

lateral geniculate body

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5
Q

cornea

A

transparent layer

area od refraction

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6
Q

layers of the ye

A

conea and sclera
choroid
retina

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7
Q

optic disk

A

blind spot

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8
Q

fovea

A

highest visual acuity (only cones)

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9
Q

where does the optic nerve exit the eye

A

optic disk

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10
Q

sclera

A

white of the eye

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11
Q

choroid

A

vascular middle layer

nourishes the cornea and retina

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12
Q

iris

A
  • pigmented
  • vascular
  • middle layer
  • muscles of the iris control the amount of light entering the eye by determining the diameter of the pupil
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13
Q

ciliary body

A

controls the shape of the lens by pulling on the suspensory ligaments

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14
Q

lens

A

biconvex, avascular structure

light passes through after passing through the pupil

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15
Q

how does the shape of the lens change

A

ciliary body pulls on the suspensory ligamnts

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16
Q

inner layer of the eye

A

retina

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17
Q

what is the retina an extension of

A

diencephalon

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18
Q

layers of the retina

A

neuronal and non-neuronal layer

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19
Q

neuronal layer of the retina

A

ganglion cell axons form the optic nerve

  • photoreceptors
  • bipolar cells
  • ganglion cells
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20
Q

non-neuronal layer of the retina

A

pigmented epithelium

  • sits against choroid
  • light absorbing
  • provides nutrients and capillaries to photoreceptors
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21
Q

bipolar neurones

A

connect photoreceptors to the ganglion cells

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22
Q

ganglion cells

A

give of an axon which becomes the ottos nerve

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23
Q

why is the optic disk a blind spot

A

contains no photoreceptors

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24
Q

interneurones connection photoreceptors, bipolar and ganglion cells

A

horizontal neurones

amacrine neurones

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25
Q

horizontal neurone location

A

level of photoreceptor and bipolar cells

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26
Q

amacrine neurone location

A

level of bipolar cells and ganglionic cells

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27
Q

role of interneurones in the retina

A

modulate transmission

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28
Q

energy change in retina

A

light energy is transferred to electrical energy

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29
Q

types of photoreceptor

A

rods

cones

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30
Q

which photoreceptor is more common

A

rods

20x more common

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31
Q

rods

A
  • sensitive to light
  • vision in dim light
  • high level of convergence
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32
Q

cones

A
  • colour vision
  • high visual acuity
  • lower level of convergence
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33
Q

how does papilloedema occur

A
  • optic nerve has meninges surrounding it to the eyeball
  • increase in CSF (in subarachnoid space) can swell the optic nerve
  • increase in pressure compresses the central retinal vein
  • prevents venous drainage from the eye
34
Q

symptoms of papilloedema

A

headaches
drowsiness
blurred vision
vomiting

35
Q

calcarine sulcus

A

primary visual cortex lies above and below this

36
Q

where does the information from the upper vision field travel

A

lower bank of calcarine sulcus

37
Q

where does information from the lower visual field travel

A

upper bank of the calcarine sulcus

38
Q

where does information from the left half of the visual field travel

A

right hemisphere

39
Q

where does information from the right of the visual field travel

A

left hemisphere

40
Q

how does the 3rd order neurone travel in the visual pathway

A

optic radiations

41
Q

1st order neurones

A

bipolar cells

42
Q

2nd order neurones

A

ganglion cells

43
Q

where do bipolar cells travel from and to

A

photoreceptors to ganglion cells

44
Q

where do ganglion cells travel to

A

to lateral geniculate body in thalamus

45
Q

images from visual field onto retinal fields

A

upside down and mirror reversed

46
Q

fibres travelling in the visual pathway

A

nasal fibres

temporal fibres

47
Q

where do temporal fibres originate

A

laterally (further from nose)

48
Q

where for nasal fibres originate

A

medially (closer to nose)

49
Q

which fibres cross the optic chiasma

A

nasal fibres

50
Q

optic radiations - types

A 
Meyer's loop (inferior)
Superior trajectory (superior)
51
Q

where does the upper left quadrant of the visual field reach on left eye

A
  • nasal fibres travels down on RHS
  • crosses optic chiasma
  • travels down optic tract to tract the LGN
  • optic radiations carry this info to the lower bank of the right calcarine sulcus
52
Q

where does the upper left quadrant of the visual field reach on right eye

A
  • temporal fibres travel down on RHS
  • does not cross the optic chiasma
  • travels down optic tract to tract the LGN
  • optic radiations carry this info to the lower bank of the right calcarine sulcus
53
Q

which trajectory carries lower visual field fibres and to where?

A

superior trajectory carries lower visual field fibres to the upper bank of the calcarine sulcus

54
Q

which trajectory carries upper visual field fibres and to where?

A

Meyer’s loop / inferior trajectory carries upper visual field fibres to the lower bank

55
Q

location of information from the macula in the primary visual cortex

A

posteriorly (towards tip of occipital lobe)

56
Q

location of information from the peripheral fields in the primary visual cortex

A

anteriorly

57
Q

scotoma

A

localised patch of blindness

58
Q

anopia

A

loss of one or more quadrants of the visual field

59
Q

hemianopia

A

half of the visual field is lost

60
Q

quadrantanopia

A

quarter of the visual field is lost

61
Q

homonymous

A

visual field losses are similar for both sides

62
Q

heteronymous

A

visual field losses are different on each side

63
Q

what visual defect is the patient likely to have if they have a pituitary tumour impinging on the optic chiasma?

A

Bitemporal hemianopia

64
Q

bitemporal hemianopia

A

RHS of vision on left eye is gone and LHS of vision on right eye is gone

65
Q

where is the lesion in monocular blindness

A

optic nerve

66
Q

where is the lesion in bitemporal hemianopia

A

optic chiasma - interrups nasal fibres

67
Q

where is the lesion in homonymous hemianopia

A

optic tract

68
Q

pupillary light reflect

A

ability of both pupils to respond (constrict or dilate) defence on the level of light the retina recieves

69
Q

which CN does the pupillary light reflex use

A

oculomotor (CN3)

optic (CN2)

70
Q

what % of neurones do not travel to the LGN - where do they go?

A

10% travel to the pretectal area

71
Q

Edinger-Westphal nucleus

A

oculomotor nerve nucleus by the pretectal area

72
Q

how does info travel from the pretectal area to reach the sphincter papillae muscle

A

ciliary ganglion

73
Q

pen is shone into subjects right eye: normal

A

both pupils constrict

74
Q

pen is shone into subjects right eye: CN3 lesion

A

left eye will not constrict

  • loss of consensual pupillary light reflex
  • info from light is reaching CNS however CN3 is not intact on one side
75
Q

pen is shone into subjects right eye: CN2 lesion

A

neither eye will constrict

  • loss of direct pupillary reflex
  • no light has reached CNS
76
Q

accommodation reflex

A

A series of changes that occur when the gaze is transferred from a distant to near object

77
Q

ciliary muscles in accommodation reflex

A

contract

78
Q

what do ciliary muscles do when they contract

A
  • lens becomes thicker and more rounded

- allow for refraction / bending of light rays to reach the retina

79
Q

sphincter pupillae in accommodation reflex

A

constrict

80
Q

medial rectus muscle in accommodation reflex

A

contract

- ocular convergence

81
Q

afferents in accommodation reflex

A

Carry visual input to visual cortex then to visual association nerve

  • Optic nerve and tract
  • LGN to visual cortex
82
Q

efferents in accommodation reflex

A

run within CN3

  • Parasympathetic to sphincter pupillae & ciliary muscles
  • Motor to medial rectus

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