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CM - Control > L10 - The visual pathway > Flashcards

L10 - The visual pathway Flashcards

1
Q

what is referred to as the human blind spot?

A

optic disk - no photoreceptors - any light received in this area won’t be seen

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2
Q

what area of the eye has the highest visual acuity?

A

fovea

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3
Q

what is the retina made up of?

A
  • neural layer - optic nerve - optic disk (blind spot) - macula (fovea)
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4
Q

what is the cornea?

A

thick, transparent, avascular, major area of refraction

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5
Q

what is the sclera

A

“white of the eye” - covers most of the ocular surface - continuous with the cornea - insertion point for muscles that move the eyeball

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6
Q

what is the middle (vascular) layer of the eye made up of?

A
  • choroid - iris - ciliary body
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7
Q

what does the choroid do?

A

Nourishes the cornea and retina

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8
Q

what does the iris do?

A

Muscles of the iris control the amount of light entering the eye by controlling the diameter of the pupil

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9
Q

what does the ciliary body of the eye do?

A

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

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10
Q

the retina is an extension of which brain structure?

A

diencephalon

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11
Q

the retina can be divided into a non-neuronal and a neuronal layer, describe each

A

The non-neuronal layer consists of pigmented epithelium. Sits against the choroid and is light absorbing. Neural layer (Photoreceptors, bipolar cells, ganglion cells). Ganglion cell axons form the optic nerve.

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12
Q

what different cell types make up the retina?

A

pigmented epithelium (contain melanin to absorb light) rods cones 1o bipolar cells 2o ganglion cells

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13
Q

which cell types make up the non-neuronal layer of the retina?

A

pigmented epithelium - contains melanin which. absorbs light; provides nutrients to photoreceptors

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14
Q

which cell types of the retina are photoreceptors?

A

rods and cones

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15
Q

what do the 1o bipolar cells of the retina do?

A

link photoreceptors to Ganglion cells

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16
Q

the 1o bipolar cells of the retina are surrounded by 2 different types of interneuron - what are they and what do they do?

A

amacrine interneuon: - modulate activity of ganglion cells horizontal interneuron: - modulate transmission

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17
Q

what cell types of the retina form the optic nerve

A

axons of the 2o ganglion cells

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18
Q

what cell types make up the neuronal layer of the retina?

A

cones rods amarcine interneurone horizontal interneurone 1o bipolar cells 2o ganglion cells

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19
Q

what is papilloedema?

A

• A swelling of the optic disk • The optic nerve is surrounded by the meninges • Increases in CSF pressure can swell the optic nerve • Increase in pressure compresses the central retinal vein preventing venous drainage from the eye

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20
Q

what are symptoms of papilloedema?

A

head-aches, drowsiness, blurred vision and vomiting

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21
Q

you will find the primary visual cortex surrounding which sulcus?

A

calcarine

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22
Q

describe the 3o neurone chain from photoreceptor to cortex?

A
  • photoreceptor synapse with bipolar cells (retina) - 1o bipolar cells synapse with 2o ganglion cells (also in retina) - 2o ganglion cell axons fuse to form optic nerve and leave optic disk to LGN in thalamus - 3o thalamocortical neurons travel in optic radiation from thalamus to cerebral cortex
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23
Q

in the 3 neurone chain from photoreceptor to cortex, where is the 3o neuron?

A

optic radiation (passes from lateral geniculate nucleus in thalamus to primary visual cortex)

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24
Q

in the 3 neurone chain from photoreceptor to cortex, which neuron forms the optic nerve?

A

axons of 2o ganglion

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25
Q

the visual pathway is Retinotopically organized, where does the left half of the visual field project?

A

Left half of visual field goes to right hemisphere

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26
Q

the visual pathway is Retinotopically organized, where does the right half of the visual field project?

A

Right half of visual field goes to left hemisphere

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27
Q

the visual pathway is Retinotopically organized, where does the upper half of the visual field project?

A

Upper visual field goes to lower bank of calcarine sulcus

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28
Q

the visual pathway is Retinotopically organized, where does the lower half of the visual field project?

A

Lower visual field goes to upper bank of calcarine sulcus

29
Q

the visual pathway is Retinotopically organized, where does the centre of visual axis (macula) project?

A

occipital lobe

30
Q

some fibres of the visual pathway cross at the optic chiasma, which ones are they?

A

nasal fibres cross temporals don’t

31
Q

which nucleus in the thalamus does visual information get passed too?

A

Lateral geniculate nucleus (LGN)

32
Q

what type of fibres does the superior trajectory of the visual pathway carry?

A

lower visual field fibres

33
Q

what type of fibres does the inferior trajectory (Meyer’s loop) of the visual pathway carry?

A

upper visual field fibres

34
Q

which visual field gets projected to the upper bank of the calcarine sulcus?

A

lower visual field

35
Q

which visual field gets projected to the lower bank of the calcarine sulcus?

A

upper visual field

36
Q

what is a scotoma?

A

localised patch of blinds

37
Q

what is anopia?

A

refers to the loss of one or more quadrants of the visual field

38
Q

what is hemianopia?

A

half of the visual field is lost

39
Q

what is quadrantanopia?

A

quarter of the visual field is lost

40
Q

what is meant by homonymous with reference to visual pathway damage?

A

visual field losses are similar for both sides

41
Q

what is meant by heteronymous with reference to visual pathway damage?

A

visual field losses are on different sides

42
Q

where would a lesion lie if there was monocular blindness in the left eye?

A

lesion in left optic nerve

43
Q

where would a lesion lie if there was monocular blindness in the right eye?

A

lesion in right optic nerve

44
Q

where would a lesion lie if there was bitemporal hemianopia?

A

lesion of the optic chiasma

45
Q

where would a lesion lie if there was homonymous hemianopia that resulted in the loss of right sided eyesight?

A

lesion in left optic tract

46
Q

what is scotoma due to?

A
  • lesion of macula - usually related to age (macular degeneration)
47
Q

a lesion in the macula would lead to what?

A

scotoma

48
Q

a lesion in the macula would lead to what?

A

scotoma

49
Q

a lesion in the left optic nerve would lead to what?

A

monocular blindness in left eye

50
Q

a lesion of the optic chasm would lead to what?

A

bitemporal hemianopia loss of temporal vision

51
Q

a lesion in the left optic tract would result in what?

A

loss of vision from the right visual field

52
Q

what is the pupillary light reflex?

A

Is the ability of both pupils to respond (constrict or dilate) dependant on the level of light the retina receives

53
Q

what two nerves does the pupillary light reflex test?

A

optic (CNII) oculomotor (CNIII)

54
Q

what two nerves does the pupillary light reflex test?

A

optic (CNII) oculomotor (CNIII)

55
Q

with reference to the pupillary light reflex, what is a consensual response?

A

the pupil of the eye without the light constricts

56
Q

with reference to the pupillary light reflex, what is a direct response?

A

the eye with. the light in constricts

57
Q

how would a lesion in CNIII present with a pupillary light reflex test?

A

loss of consensual reflex

58
Q

how would a lesion in CNII present with a pupillary light reflex test?

A

loss of direct pupillary light reflex

59
Q

with reference to the pupillary light reflex, what do both pupils constricting indicate?

A

CNII and CNII intact

60
Q

with reference to the pupillary light reflex, what does loss of the consensual reflex indicate?

A

CNIII lesion

61
Q

to the pupillary light reflex, what does loss of the direct reflex indicate?

A

CNII lesion

62
Q

explain the accommodation reflex pathway

A

• Afferent fibres carrying visual input to visual cortex - Optic nerve and tract - LGN to visual cortex • Then fibres pass to CN III nuclei in midbrain • Efferent fibres – all run within CNIII - Parasmpathetic to spincter pupillae & ciliary muscles - Motor to medial rectus

63
Q

with reference to the accommodation reflex of the eye, which muscles are responsible for accommodation/the lens becoming more rounded?

A

ciliary muscles

64
Q

with reference to the accommodation reflex of the eye, which muscles are responsible for the pupil constricting?

A

sphincter pupillae

65
Q

with reference to the accommodation reflex of the eye, which muscles are responsible for the ocular convergence?

A

medial rectus

66
Q

the retina is made up of rods and cones, which ones are expressed at the macula?

A

cones

67
Q

what are features of rod cells?

A

• 20x more common • Sensitive to light • Vision in dimlight • High level of convergence

68
Q

what are features of cone cells?

A

• Colour vision • High visual acuity • Lower level of convergence • At the macula, one cone to one ganglion cell

69
Q

with reference to rods and cones, which ones are responsible for colour vision?

A

cones

CM - Control (20 decks)

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