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Neuroanatomy > Visual Pathways > Flashcards

Visual Pathways Flashcards

1
Q

how many rods are there

A

130 million

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2
Q

what type of vision do rods provide

A
  • black and white
  • dim
  • peripheral
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3
Q

three components of rods

A
  • inner
  • outer (700 discs, contains rhadapsin)
  • rod fibre (nucleus)
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4
Q

what does rhadapsin do

A

inhibits glutamate which is continuously secreted in darkness

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5
Q

what type of vision do cones provide

A
  • colour
  • bright light
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6
Q

how do cones work

A

3 types - each contain a different pigment to allow for the absorption of red, green and blue light

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7
Q

2 components of cones

A
  • inner
  • outer (pigment-bearing discs)
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8
Q

midget cells

A
  • small dendritic arbors
  • small slow moving nuclei
  • not sensitive to low contrast
  • colour
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9
Q

parasol cells

A
  • large dendritic arbors
  • large fast moving nuclei
  • not sensitive to low contrast
  • colour
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10
Q

name 3 association neurons

A
  • amacrine cells
  • horizontal cells
  • interplexiform cells
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11
Q

amacrine cells function

A

inhibitory and exitatory

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12
Q

horizontal cells function

A

inhibitory

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13
Q

interplexiform cells functon

A

feedback between amacrine and horizontal cells

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14
Q

muller glial cells function

A

support

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15
Q

pathway to visual cortex

A

optic nerve → optic chiasm (hypothalamus) - visual fields cross → lateral geniculate nucleus of the thalamus

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16
Q

name the four portions of the optic nerve

A
  • intraocular portion
  • intraorbital portion
  • intracanalicular portion
  • intracranial portion
17
Q

where is the optic tract and chiasm found

A

superior to the sella turcica and therefore the pituitary gland which it contains

18
Q

what is the optic tract and chiasm susceptible to

A

secondary pituitary disorders

19
Q

what is the pulvinar nucleus

A

Most fibres travel from the chiasm after splitting to lateral geniculate nucleus but 10% travel to superior colliculus and pulvinar nucleus and from here to the primary visual cortex

20
Q

where is the pulvinar nucleus found

A
  • thalamus - largest thalamic nucleus (25% of thalamus size)
  • medial and dorsal to lateral geniculate nucleus
21
Q

what is the lateral geniculate nucleus

A

6 layered structure:
4 parvocellular layers
2 magnocellular layers

22
Q

what do the parvocellular layers receive input from

lateral geniculate nucleus

A

midget ganglion cells

23
Q

what do the magnocellular layers recive input from

A

parasol cells

24
Q

what are optic radiations

A

geniculocalcarine fibres

25
Q

optic radations pathways

A
  • exit dorsally from the lateral geniculate nucleus, then spread into two major bundles (superior and inferior)
  • The dorsal and central bundles travel in parietal lobe to the visual cortex
  • The ventral group (meyer’s loop) of fibres curves in an anteroinferior direction into the anterior pole of the temporal lobe
26
Q

information processed in primary visual cortex

A
  • static vs moving objects
  • pattern recognition
27
Q

where are the second visual cortices found

A
  • occipital lobe
  • parietal lobe
  • temporal lobe
28
Q

information processes in secondary visual cortices

A
  • object recognition
  • colour perception
  • depth
  • motion
29
Q

two types of visual defects due to interruptions of the pathway at the retina

A
  • retinal deachment
  • colour vision deficiency
30
Q

explain retinal detachment

A
  • due to blow to the eye or spontaneously
  • fluid accumulation
  • can lead to blindness
31
Q

explain colour vision deficiency

A
  • dichromatic vision: one opsin not produced
  • monochromatic vision: 2 opsins not produced
32
Q

four visual defects due to interruptions of the pathway at the optic pathway

A
  • monocular blindness
  • bitemporal hemianopia
  • homonymous hemianopia
  • lesions of primary visual cortex
33
Q

explain monocular blindness

A
  • lesion at optic nerve
  • stroke (ophthalmic artery)
  • migraine (transient)
  • multiple sclerosis (bilateral)
34
Q

explaim bitemporal hemianopia

A
  • optic nerve compresson
  • pituitary tumour
  • information from temporal visual fields falls on nasal retina
  • vision is missing in outer half of both left and right visual field
35
Q

homonymous hemianopia

A
  • posterior cerebral artery stroke
  • lesion in optic chiasm
  • vertical midline loss
36
Q

lesiond of primary visual cortex

A
  • scotoma
  • hole in visual field

Neuroanatomy (23 decks)

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