L15: The visual system Flashcards
1
Q
the path an image takes from the eye is
A
- optic nerve
- past the optic chiasm into the
- optic tract,
- to the lateral geniculate nucleus
- to the primary visual cortex in the back of the brain
2
Q
what is the thalamic relay centre in the brain for images
A
geniculate nuclei
3
Q
where in the brain does everything from the left visual field of both eyes go
A
right hemisphere
4
Q
where do the fibres become purely one visual field
A
after the optic chiasm in the optic tract
5
Q
if there is a lesion in the optic nerve on the right side what happens
A
loss information from the right eye only
6
Q
homonymous defect =
A
when the information in a single visual field in both eyes is affected
7
Q
what is damaged in a homonymous defect
A
optic tract
8
Q
what can you get if only a part of optic radiation is damaged
A
quadrantanopia
9
Q
what is macular sparing
A
very centre of visual field is the only preserved vision
10
Q
why does macular sparing happen
A
central eye is highly innervated and has a good blood supply so less likely to be damaged
11
Q
what happens when the optic chiasm is damaged
A
heterogeneous hemianopia
12
Q
what is heterogeneous hemianopia
A
loss of vision in opposite hemifields in each eye
13
Q
2 parts of outermost layer of eye
A
- cornea
- sclera
14
Q
sclera=
A
white of eye
15
Q
cornea=
A
clear bit at the front
16
Q
3 continous layers of the vascular layer
A
- iris
- ciliary body
- choroid
17
Q
choroid=
A
network of blood vessels
18
Q
neural layer of the eye=
A
retina
19
Q
2 humours of eye
A
aqueous humour
vitreous humour
20
Q
aqueous humour 2 parts =
A
anterior chamber
posterior chamber
21
Q
where is the anterior chamber
A
just inside the cornea
22
Q
where is the posterior chamber
A
between the lens and the iris
23
Q
2 blood supplies in the eye
A
- the choroid
- retinal blood vessels
24
Q
fovea=
A
region of highest resolution vision, highest density of neurons
25
what is the fovea good at
fine detail and high sensitivity
26
conjugate eye movement=
eyes move in the same direction
27
4 types of conjugate eye movement
- vestibulo-ocular
- optokinetic -saccade
- smooth pursuit
28
1 type of disconjugate eye movement
-vergence
29
saccade=
directs eyes towards visual target
30
name 6 extraocular muscles
- Superior oblique
- inferior oblique
- superior rectus
- medial rectus
- lateral rectus
- inferior rectus
31
2 muscles on top of one another
- levator palpebrae superioris
| - superior rectus
32
which muscle is on a kinda hook
superior oblique
33
which muscles elevate the eye
- superior rectus
| - inferior oblique
34
which muscles depress the eye
- inferior rectus
| - superior rectus
35
what adducts the eye
medial rectus
36
what abducts the eye
lateral rectus
37
what muscles move the top of the eye towards the nose
superior oblique
| superior rectus
38
what muscles move the top of eye away from the nose
inferior rectus
| inferior oblique
39
cranial nerve innervation of medial rectus, superior rectus and inferior oblique
oculomotor (3)
40
cranial nerve innervation of superior oblique
4- trochlear nerve
41
cranial nerve innervation of lateral rectus
6-abducens
42
final common pathway of all eye movements
brainstem nuclei
43
which is the most sensitive part of the body with the most nerve endings
cornea
44
what connects the lens to the ciliary body
zonules
45
what allows you to change pupil size
muscles in the iris
46
miosis=
pupil constriction
47
miosis nervous control=
parasympathetic
48
what is active in miosis
iris sphincter
49
mydriasis=
pupil dilation
50
what is active in mydriasis
iris dilator
51
what nervous controls mydriasis
sympathetic
52
what did david bowie have
Anisocoria - different levels of pupil dilation
53
accommodation=
the process of focusing an image with the lense
54
what looking at a distant object what shape is the lense
flat
55
looking at distant objects what position are the eyes in
diverge
56
in near objects what do the eyes do
converge
57
nervous control of the accommodation reflex-=
parasympathetic
58
3 factors of the pupil accommodation reflex
- pupil constriction
- lens accommodation
- convergence of the eye
59
what is the most important neural structure in controlling the accommodation reflex
Edinger-westphal nucleus (in brainstem)
60
what ganglion do neural impulses to the eye travel in
ciliary ganglion
61
most common cause of blindness
cataracts
62
cataracts=
opacification of the lens caused by compaction and protein deposition
63
name 5 risk factors for cataracts
```
ageing
trauma
diabetes
smoking
genetic
```
64
treatment for cataracts
lens removed under local anaesthetic and replaced with artificial lens
65
5 risk factors for glaucoma
- raised intraocular pressure
- high BP
- long corticosteroid use
- severe myopia
- eye injury
66
2 types of glaucoma
- primary open-angle glaucoma
| - acute angle-closure glaucoma
67
cause of primary open-angle glaucoma
trabecular meshwork clogged
68
which glaucoma is acute onset
acute-angle-closure
69
cause of acute angle closure glaucoma
iris bows, closes anterior chamber angle and blocks drainage
70
symptom of primary open-angle glaucoma
gradual vision loss (peripheral to central)
71
symptoms of acute angle-closure glaucoma
sudden vision loss/ blurring; red eye; severe eye/ head pain; nausea/ vomiting
72
3 tests for glaucoma
- tonometry
- fundus photography
- visual perimetry
73
what does tonometry measure
intraocular pressure
74
what does fundus photography look at
optic nerve
75
visual perimetry=
measure visual fields
76
glaucoma treatment (5)
- beta blockers
- alpha2-adrenoceptor agonist
- carbonic anhydrase inhibitors
- prostaglandin analogues
- miotics (muscarinic agonists)
77
what produces aqueous humour
ciliary processes
78
where does the aqueous humour travel
passes from the posterior chamber behind the iris through the pupil and into the anterior chamber
79
what drains the aqueous humour
trabecular meshwork
80
anterior chamber angle=
the angle between the cornea and the iris
81
once the aqueous is through the trabecular meshwork where does it drain
schlemm's canal
82
what blood supply supports the outer retina
choroid
83
what blood supply supports the inner retina
retinal vasculature
84
only part of the eye without retinal vasculature=
fovea
85
outermost layer of the retina=
photoreceptors (rods and cones)
86
middle layer of the retina =
- bipolar cells
| - amacrine and horizontal cells
87
what do bipolar cells do
pass information from the receptors into the ganglion cells
88
what do amacrine and horizontal cells do
communication horizontally across the retina
89
what is spread away more in the fovea
the first 2 layers (ganglion and bipolar cells)
90
what photoreceptors are presents in the very centre of the retina
only cones
91
what are cones good at
high resolution vision
92
photoreceptors in the peripheral retina=
more rods
93
where are both rods and cones fatter
peripheral
94
scotopic photoreceptors=
rods
95
scotopic=
night time vision (very sensitive to light)
96
photopic=
cones
97
photopic=
```
daytime vision (less sensitive)
-higher resolution
```
98
3 types of cones
red cones
green cones
blue cones
99
red/green colour blindness is passed down
recessively on X chromosome
100
what do protanopes lack
red cones
101
what do deuteranopes lack
green cones
102
what do tritanopes lack
blue cones (NOT X-linked)
103
2 layers of the lateral geniculate nucleus=
magnocellular
104
magnocellular=
large cells, light/dark greyscale, low resolution
105
4 layers of the lateral geniculate nucleus=
parvocellular
106
parvocellular=
small cells, higher resolution, colour
107
where is the primary visual cortex
back of the brain
108
where are the central visual fields processed in the brain
very back of the brain
109
where are the peripheral visual fields processed
more anteriorly in the visual cortex
110
where is the brain specialises in colour
ventral surface V4
111
where in the brain is sensitive to motion
V5 lateral brain
112
sense found in
parahippocampal place area
113
faces found in
fusiform face area
114
objects found in
lateral occipital cortex
