Special Senses - Vision Flashcards
1
Q
describe the transmission of light through the pathways
A
- visual field stimulus (light/light patterns)
- peripheral NS (eye)
- CN for eye movement (3, 4, 6)
- optic N
- optic tract
- lateral geniculate body of thalamus
- primary visual cortex (17)
- visual association area (18)
- frontal eye fields (8)
2
Q
what is the name of the pathway associated with light/vision
A
retinogeniculocalcarine pathway
3
Q
what are the 3 functions of the visual system
A
- sight for recognition and location of objects
- provide information to be used in postural and limb control
- eye movement control
4
Q
what structures make up the peripheral visual system
A
the eyeball itself
- pupil, retina, iris, lens, cornea, ciliary body, vitreous humor, macula, sclera, choroid, retina
5
Q
clear covering over the colored iris, major light focusing structure
A
cornea
6
Q
whites of the eyes; filled with blood vessels
A
sclera
7
Q
mucous membrane lining of the eyelid - houses blood vessels
A
conjunctiva
8
Q
tear ducts, lacrimal gland keep eye clean and protect from disease
A
lacrimal system
9
Q
colored part of the eye; divides internal space into anterior and posterior chambers
A
iris
10
Q
perforation in center of iris; controls how much light comes in
A
pupil
11
Q
what two muscles determine how much light comes into the eye by controlling the pupil
A
dilator and sphincter muscles
12
Q
constricts pupil in bright ligth
A
sphincter muscle
13
Q
dilates pupil in dark
A
dilator muscle
14
Q
what innervates sphincter muscle
A
ANS branch of CN 3
15
Q
what innervates dilator muscle
A
ANS branch of CN 5
16
Q
deepest layer of the iris and accommodates for near/far vision
A
lens
17
Q
immediately behind iris, contains blood vessels that produce aqueous humor
A
ciliary body
18
Q
fills the anterior chamber to provide metabolic support for the lens and creates intraocular pressure
A
aqueous humor
19
Q
if intraocular pressure becomes too high, what can it lead to
A
glaucoma –> damages the optic N
20
Q
gel-like material in front of the retina; maintain shape of globe
A
vitreous humor
21
Q
lens adopts different shapes in order to focus the light entering the eye via ciliary muscles
A
accomodation
22
Q
center 1cm diameter of retina; degenerates with aging process decreasing visual acuity
A
macula
23
Q
central 1.5 mm-diametr center of macula
A
fovea
24
Q
what does the fovea only contain
A
cones
25
circular elevated region where optic N exits the eye
optic disk
26
has no rods or cones
blind spot in optic disk
27
the retina is a 10 layered peripheral receptor that is stimulated by what
photons (light energy)
28
what are the 3 major cells types in the retina and what do they do
- rods: located in periphery of retina (scotopic - low level illumination, limited resolution, insensitive to color) --> dark
- cones: located in center of each retina (photopic - high level illumination, sharp vision, sensitive to color bands of light via cone pigments (blue, green, red)
- ganglion cells: second order neurons (output cells) that are axons that form optic N
29
sharp vision
vision acuity
30
what colors are cone pigments sensitive to
blue, green red
31
the retina converts light into neuronal signals via what
G-proteins
32
____ and _____ retinas from each eye become axons that merge together as they exit the back of the eye as the optic N
nasal and temporal retinas
33
what is the optic N made of
nasal (medial) and temporal (lateral) axons of ganglion cells (2nd order neurons) in retina that merge to form a bundle of 1 million fibers as it pierces the back of the eye
34
is the optic N CNS or PNS
CNS - myelinated by oligodendrocytes
35
what does the optic N travel through and where does it cross
- optical canal
- optic chiasm
36
what does the optic N become after crossing at chiasm
optic tract
37
where does the optic tract synapse
lateral geniculate body of thalamus (3rd order neurons)
38
after synapsing in thalamus, where does information go
primary visual cortex (17)
39
portion of space that can be viewed by the retina when the eye is fixated straight ahead without eye/head movement
visual field
40
which retina (nasal or temporal) crosses at optic chiasm
nasal
41
are optic N and optic tracts PNS or CNS
CNS
42
from the lateral geniculate nucleus to occipital lobe
calcarine pathway
43
he overlapping of the central portion of the visual fields from each eye create a superimposed single impage
binocular vision
44
where is R visual field information sent to
L occipital lobe
45
what info is carried on nasal retinas
carry ipsilateral temporal field info
46
what info is carried on temporal retinas
contralateral nasal field info
47
what do optic tracts carry
contralateral nasal and temporal fiber information
48
what does damage to the optic N cause
loss of vision in one whole eye
49
what does damage to optic chiasm lead to
bitemporal heminopsia
50
what does damage to optic tract lead to
homonymous heminopsia (see, no see, see, no see)
51
describe R visual field
- L half or R retina (nasal)
- L half of L retina (temporal)
52
laminar arrangement of lateral geniculate body of thalamus
- magnocellular layer: large neurons in layers 1 and 2 that receive information from type M ganglion cells in retina
- paravocellular layer: small neurons in layers 3-6 that receive info from type P ganglion cells
53
what laminar layers of lateral geniculate receive info from contralateral eye
1, 4, 6
54
what laminar layers of lateral geniculate receive info from ipsilateral eye
2, 3, 5
55
is made up of projection fibers carrying information from the superior visual fields and terminate on primary visual cortex below calcarine sulcus
Meyer's loop
56
information from the inferior visual fields terminates on the primary visual cortex ____ the calcarine sulcus
above
57
______ injuries will result in visual field deficits due to path of Meyer's loop around 4th ventricle
temporal lobe
58
what lobes are visual cortices found
occipital lobe
59
area 17 and other name
primary visual cortex
striate cortex I
60
where is visual acuity located in primary visual cortex
most posterior and over greatest area of cortex
61
where is peripheral vision located in primary visual cortex
rostrally - assures accurate foveal vision for survival
62
what does primary visual cortex do
distinguishes intensity of light vs dark (not color), shape, size, location and movement of objects
63
visual association area numbers
18-21
64
what does visual association area do
analyzes colors and motion, fixation of objects in central vision; gives meaning to visual information
65
what can occur if damage to visual association area
visual agnosia --> cannot recognize or associate significance of what is seen; loss of eye coordination and loss of visually guided hand activities
66
involved in circadian rhythms of day-night cycle
suprachiasmic nucleus of hypothalamus
67
connects eyes and ears --> turning to look at a sound
superior colliculus of midbrain
68
reflexive responses of pupils; orientation of the eyes and head in coordination with auditory stimuli (coordination with tectospinal tract); projects information to posterior parietal cortex and visual association areas
pretectal area of midbrain
69
coordination of eye movement requires synthesis of information from
- head movements (vestibular)
- visual objects (vision)
- eye movement and position (proprioception)
- selection of visual target (brainstem and cortex)
70
eye remains abducted and down due to weakness in med/inf oblqiue; eyelid droop (ptosis) due to weakness of levator palpebrae superioris; pupil remains dilated; diploplia
CN 3 palsy
71
eye add but elevates due to weakness in superior oblique; will have difficulty going downstairs and reading; diploplia
CN 4 palsy
72
eye does not abd due to lateral rectus weakness, diploplia
CN 6 palsy
73
what are the 2 objectives of eye movement
- keep eyes stable head movement so environment doesn't bounce (gaze stabilization or visual fixation) --> VOR and optokinetic nystagmus
- directing gaze at visual targets
74
normal response when things are moving around you, making you think you are moving when you aren't
optokinetic nystagmus
75
MLF is a bundle of axons connecting vestibular nuclei in the brainstem and cerebellum with
- CN nuclei 3, 4, 6
- CN nuclei 11
- superior colliculus
76
what CN are CNS
optic and olfactory
77
both eyes move in the same direction
conjugate vision
78
fast eye movement to switch gaze from one object to another (eyes switch from person entering room while reading a book)
saccades
79
what regulates saccades
superior colliclus
80
eye movement follows a moving object like a person walking down sidewalk
smooth pursuit
81
eyes move either toward or away from midliine together (near to far vision); Involves cilliary muscles, medial recti and pupillary constriction to increase the curvature and refractive power of the lens
accomodation-convergence reflex
82
eyes move away from midlien
accomodation
83
eyes move toward midline
convergence
84
what is the normal distance before image doubles/blurs as it moves toward tip of nose
8-10 inches
85
what two reflexes stabilize gaze
- vestibulo-ocular reflex (VOR)
- optokinetic reflex
86
- stabilizes visual images during movement of the head
- elicited by head rotation, flexion or extension
Info from semicircular canal → vestibular nuclei → CN 3 and 6
- results in movement of eyes opposite direction of head movement
Vestibulo-occular reflex
87
- adjusts eye position during slow head movement
- elicited by moving the stimulus
- allows eyes to follow the objects in the visual field - eyes move from edge of visual field followed by a saccade
- influences perception of movement - stopped car with moving bus next to it
optokinetic reflex
88
physiological/normal nystagmus
- Normal VOR reflexive response at end range positions of the eyes
- Quick saccadic movement back to midline
- Can elicit by quick rotation of the head, temp stimulation of the inner ear or optokinetic stimulation
89
pathological nystagmus can be caused by
CN VIII injury, injury to the vestibular apparatus in the inner ear, CNS lesions to the cerebellum or vestibular nuclei in brainstem
90
mediates the size of the pupil to adjust amount of light projected to the retina
pupillary light reflex
91
what structures are needed for pupillary light reflex
- ganglia cells of retina
- CN 2 and 3
- pretectal region in midbrain
- edinger-westphal nucleus
- cilliary ganglia
- sphincter muscles of the eye
92
what type of response is pupillary reflex
parasympathetic
93
cortical blindness occurs due to lesion where
- prechiasmic retina or optic N
- primary visual cortex due to thrombus or embolus in PCA, TBI, MS or anoxic pre/perinatal event
94
has no awareness of visual info; may have blind spot; can perceive light and dark if retina is intact; eye can still move through full ROM; pupillary light reflex remains intact
cortical blindness
95
damage to center of optic chiasm to nasal half of each retina; loss of info from both temporal field (no peripheral vision)
bitemporal hemianopsia/heteronymous hemianopsia
96
what is common cause of bitemporal hemianopsia
pituitary adenoma
97
lesion in pathway after the chiasm in optic tract, optic radiations or primary visual cortex; results in 1/2 of each visual field; if deficits is incomplete will only have 1/4 loss of visual field; may have macular sparing
homonymous hemianopsia
98
double vision
diplopia
99
inability to maintain stable vision when head is moving
gaze palsy
100
involuntary oscillating movement of the eyes
nystagmus
101
swelling of papilla of the retina as a result of increased ICP
papilledema
102
inability to attach meaning to what is seen
- Damage to occipital lobe
visual agnosia
103
inability to discriminate hue - not color blindness - a type of agnosia
achromatopsia
104
inability to recognize a familiar face
prospagnosia
105
inflammatory disorder - may lead to deymyelination often associated with MS
optic neuritis
106
papilledma - what is, what does it indicate, caused by
- optic disc swelling
- elevated ICP
- TBI, stroke, epidural/subdural hemorrhage
- enlargement of blindspot
- detected with opthalmoscope
107
ptosis is the drooping of the eyelid due to poor innervation to what muscle and by what CN
- levator palpebrae superioris
- CN 3
108
shrinking of visual field from the periphery due to build up of aqueous humor that increased the fluid pressure inside the eye
glaucoma
109
what can glaucoma lead to
damage the retina, damage optic N and lead to blindness
110
loss of transparency of the lens and can easily be repaired surgically
cataracts
111
causes of cataracts
Genetic, exposure to UV light, infrared or microwave radiation, secondary to diseases like DM, eye injury or trauma
112
- disease of the retina that damages the central region (fovea) where vision is the sharpest
- loss of detail vision, face recognition, and reading
macular degeneration
