Cranial Nerves - Visual Flashcards
1
Q
What anatomical structure produces the “blind spot”?
A
optic disk
2
Q
Where does the optic nerve exit?
A
optic disk
3
Q
What contains the central fovea (pit)?
A
macula lutea
4
Q
What are the three cell layers of retina?
A
a) pigment cell layer
b) layer of rods and cones
c) ganglion cell layer
5
Q
What layer of the retina is derived from choroid, attaches the retina to the eyeball, and absorbs stray light?
A
pigment cell layer
6
Q
What cell layer contains light receptors?
A
layer of rods and cones
7
Q
What cell layer contains myelinated axons that form the optic nerve?
A
ganglion cell layer
8
Q
What type of light receptors is located at the periphery of the retina and are for low light vision and perception of movement?
A
Rods
9
Q
What type of light receptors are concentrated in the central retina?
A
Cones
10
Q
What is termed the area of maximum visual acuity, color and brightness discrimination?
A
fovea
11
Q
The fovea contains ONLY what kind of receptor?
A
cones
12
Q
In the normal eye, an inverted image of the object is focused on the retina. What is this termed?
A
Refraction
13
Q
What four structures of the eye refract light?
A
- cornea
- aqueous humor
- lens
- vitreous humor
14
Q
Where in the eye is the image inverted?
A
lens
15
Q
Function of the lens?
A
to change the refractive power
16
Q
Changes in refractive power are accomplished by changing what?
A
the shape of the lens (rounder for close viewing, flatter for distant viewing)
17
Q
The change in refractive power which allows the viewing of near objects is called what?
A
accommodation
18
Q
To view a near object, the lens must increase its refractive power by becoming more convex or concave?
A
convex (rounder)
19
Q
At rest, the lens is held in what shape?
A
flat shape
20
Q
What connects the lens to the ciliary muscle?
A
suspensory fibers
21
Q
To accommodate for near vision, the ciliary muscle does what to reduce the tension on the suspensory fibers?
A
contracts
22
Q
Contraction of the ciliary muscle is controlled by what?
A
parasympathetic nerve fibers
23
Q
What is the refractive abnormality in which the image of the an object is focused on the retinal surface?
A
emmetropia
24
Q
What refractive abnormality refers to the focal point falling behind the retinal surface?
A
hypermetropia (far-sightedness)
25
What refractive abnormality refers to the focal point falling in front of the retina?
myopia (near-sightedness)
26
What refractive abnormality refers to the loss of lens elasticity noted with age?
presbyopia
27
What if known as a corrective prescription that includes a part of the lens correcting vision for distance and a part correcting for near vision?
bifocals
28
What are the two types of photoreceptors?
rods and cones
29
Which photoreceptor has a low excitation threshold, poor acuity, and used in dim conditions?
rods
30
Which photoreceptor has a high excitation threshold, high acuity, and used in high light conditions?
cones
31
The ability to distinguish color is due to the presence of what three separate cone populations, each of which is maximally sensitive to a different wavelength of light?
blue, green, and red
32
The perception of other colors is due to what?
the relative excitation of the different populations of cones
33
What results from the absence of one or more of the cone populations?
color blindness
34
Generator potentials originating in receptors are transmitted to what kind of cell?
bipolar cells
35
Once transmitted to bipolar cells, generator potentials are then altered by what?
other cells in the retina
36
Neural coding of visual signals can be visualized as what two separate systems?
- vertical system
| - horizontal system
37
How do signals pass within the vertical system?
signals pass from receptors to bipolar cells to ganglion cells
38
How do signals pass within the horizontal system?
horizontal and amacrine cells provide lateral interactions (lateral inhibition) between the different vertical system components
39
What cells are the final stage of retinal processing?
ganglion cells
40
Ganglion cells transmit information to what?
subcortical visual centers in the brain
41
Axons of ganglion cells form what cranial nerve?
optic nerve
42
What is defined as the area in visual space (or the corresponding area of retinal surface) which, upon illumination, influences the signaling of that neuron?
Receptive Field (of a ganglion cell)
43
Ganglion cells have been subdivided on the basis of what?
on the basis of their response duration or morphology?
44
Cells that respond as long as the stimulus remains within the receptive field are termed?
"sustained" ganglion cells
45
Cells that respond only when the light is turned on or off are termed?
"transient" ganglion cells
46
Sustained and transient ganglion cells roughly correspond to what?
p-cells and m-cells
47
P-cells refer to what?
small ganglion cells
48
M-cells refer to what?
large ganglion cells
49
M-cells are primarily concerned with what?
with signaling changes in the scene being viewed including movement, and changes in light and dark contrast and with basic form analysis
50
P-cells provide information about what?
about fine detail (high resolution analysis of image) and color
51
What is defined as the part of space that is being viewed?
visual field
52
Each half of the brain receives information only from the same or opposite hemifield?
opposite (contralateral)
53
Images of the visual world are composed of information from the two eyes (binocular) which are merged to form a single image. This is termed what?
homonymity
54
What is the term for corresponding halves - both eyes viewing the same or corresponding visual field (the right eye views the right half of the visual field and the left eye also views the corresponding right half of the visual field)?
homonymous
55
The right primary visual cortex (area 17) is perceiving what half of the visual field?
left (contralateral homonymous perception)
56
The visual pathway organization is such that everything caudal to the optic chiasm is carrying only what kind of sensation?
only contralateral homonymous sensation
57
What is defined as a loss of visual perception?
anopia
58
What is defined as a loss of visual perception of half of the entire visual field?
hemianopia
59
What is the term for different halves - each individual eye viewing different visual fields (left viewing left and right viewing right)?
heteronymous
60
When each eye is only able to see the ipsilateral temporal visual field and not the nasal visual fields, the deficit would be classified as what?
Binasal Heteronymous Hemianopia (aka Binasal Hemianopia)
61
Optic nerve fibers from the temporal retina (nasal visual hemifield) course caudally along the lateral edge of the optic nerve, optic chiasm, and optic tract to what nucleus?
ipsilateral lateral geniculate nucleus (L.G.N.)
62
Fibers from the nasal retina (temoral visual field) course caudally along the medial edge of the optic nerve and then cross where?
optic chiasm
63
After crossing at the chiasm, fibers from the nasal retina course along the medial edge of the optic tract to what nucleus?
contralateral lateral geniculate nucleus (L.G.N.)
64
Fibers from the upper retina (inferior or lower visual hemifield) course caudally along what edge of the optic nerve, optic tract, and chiasm?
dorsal edge
65
Fibers from the lower retina (superior or upper visual hemifield) course caudally along what edge of this retinogeniculate pathway?
ventral edge
66
Retinogeniculate fibers carrying information from the more peripheral visual fields are located more superficially or internally within the optic nerve, tract, and chiasm?
superficially
67
Retinogeniculate fibers carrying information from the central (fovea) visual fields are located more superficially or internally within the optic nerve, tract, and chiasm?
internally
68
After the optic nerve fibers pass through the chiasm, they continue as what?
optic tract
69
The optic tract then ends primarily in what nucleus?
80% of optic tract ends in LGN
70
The remaining 20% of the optic tract terminates where?
in the midbrain in or near the superior colliculus
71
That 20% of the optic tract reaches the midbrain via what?
the brachium of the superior collculus (BSC)
72
After the optic tract synapses in the LGN, it proceeds to what? by way of what?
thalamocortical axons proceed to primary visual cortex (area 17, calcarine cortex) by way of visual radiations (geniculocalcarine radiations, optic radiations)
73
The thalamocortical axons coming from the LGN are carrying what information to the primary visual cortex?
visuotopic information (carried to precise regions of the primary visual cortex)
74
Geniculocalcarine fibers that are carrying visuotopic information from the upper halves of both retinae (lower visual hemifields) course directly backward around the lateral ventricle, as part of the internal capsule to reach what?
the superior bank of the calcarine fissure - cuneus
75
Geniculocalcarine fibers that are carrying visuotopic information from the lower halves of the retinae (upper visual hemifields) course forward toward the tip of the temporal horn of the lateral ventricle, then loop inferiorly then caudally in the temporal lobe to reach what?
the inferior bank of the calcarine fissure - lingual gyrus
76
This long loop of geniculocalcarine fibers is called what?
Meyer's Loop
77
Damage to Meyer's Loop separately from the other geniculocalcarine fibers results in what?
contralateral upper homonymous Quandrantanopia (contralateral upper quarter field)
78
The retinotopic organization of the primary visual cortex contains an orderly map of what? Which is received from what?
the contralateral visual field, which is received from neurons of the LGN
79
The map is arranged so that the central visual field is represented in what part of the occipital lobe?
the most posterior part of the occipital lobe
80
The macula is represented where?
at the occipital pole
81
The peripheral visual fields are represented where?
in a rostral direction along the calcarine fissure (cuneus and lingual gyrus) - the more anterior portions of the calcarine sulcus
82
What artery supplies blood to the cuneus and lingual gyrus?
posterior cerebral artery
83
The lateral geniculate nucleus is located where?
located at the termination of the optic tracts (retinocengiculate fibers) in the thalamus
84
How many layers is the LGN composed of?
6 layers in the human
85
Each LGN contains a representation of what?
the contalateral visual hemifield
86
The 6 layers of the LGN are divided into what two groups?
- magnocellular layers
| - parvocellular layers
87
Cells in the magnocellular layers are involved in what?
in the perception of dark and light contrast (M-cells, correspond to information from transient ganglion cells that are activated by rods)
88
Cells in the parvocellular layers process what kind of information?
process fine spatial and color information (P-cells, correspond to information fro sustained ganglion cells that are activated by cones)
89
The retino-collicular fibers travel through what to terminate where?
travel through the brachium of the superior colliculus to terminate in the superior colliculus
90
After the retino-collicular fibers synapse int eh superior colliculus, post-synaptic fibers project where?
project to the prestriate visual areas that surround primary visual cortex (areas 18 and 19)
91
A small bundle of fibers branches off of the retino-collicular fibers where and then terminate where?
branch off in the brachium of the superior colliculus and terminates in the nuclei of the pretectal area just rostral to the superior colliculus
92
This branch off of fibers is the efferent or afferent limb of the pupillary light reflex? function?
afferent limb of the pupillary light reflex that adjusts pupil diameter specific to amount of light entering the eye
93
Connections to the oculomotor complex result in what?
constriction of the pupil
94
Descending connections to T1, T2 intermediolateral cell column control what?
dilation of the pupil
95
Quadrant defects illustrate a lesion where?
often first clue to some pathology in "silent" areas of cortex, especially temporal lobe cortex
96
Macular sparing is a pathology due to what defects?
visual field defects which include everything except macular field (central vision)
97
Macular spring occurs when what is destroyed?
when the entire ipsilateral visual cortex is destroyed except for the occipital pole
98
Axons arising from post-synaptic cells in the subcortical visual nuclei ascend through what to synapse where?
ascend through the optic radiations to synapse with cells in the visual cortex
99
What are the two primary area of the cortex that respond to visual stimulation?
- primary visual (striate) cortex - area 17
| - secondary and tertiary visual (prestriate) cortex - area 18 and 19
100
The foveal representation occupies a large or small portion of the cortical tissue?
LARGE portion
101
After reaching the primary visual cortex and then areas 18 and 19, visual information is then distributed through what three areas?
- areas in the temporal lobe
- areas in the posterior parietal lobe
- parieto-temporal lobe junction
102
Why is visual information distributed to the areas in the temporal lobe?
for object recognition
103
Why is visual information distributed to the areas in the posterior parietal lobe?
for perception of motion, rotation, and depth
104
Why is visual information distributed to the parieto-temporal lobe junction?
for perception of color and to a lesser extent motion, rotation, and depth
105
These three general regions are extensively interconnected to allow us to perceive what?
visual space (depth and movement) along with object specificity (color and form) within the visual space
106
The information derived from p-cells of LGN is responsible for what?
relaying information on form and color of objects to the temporal lobe regions (P pathway)
107
The information derived from m-cells of LGN is responsible for what?
relaying information concerning gross form and motion to parietal lobe areas (M pathway)
108
A lesion to area 17 (primary visual cortex) results in what?
contralateral visual field deficits (visual field cut)
109
If the lesion involves all of area 17 bilaterally, what is the result?
the subject will appear blind
110
If area 17 is lesioned bilaterally, will you still have collicular function?
YES; some limited visual capabilities are demonstrable, such as the pupillary light reflex
111
Prestriate (Extrstriate) Cortex (areas 18 and 19) called the visual association cortex, receives projections from what three sources?
- ipsilateral primary visual cortex
- ipsilateral superior colliculus
- contralateral prestriate cortex
112
Lesions to the prestriate cortex cause deficits in what?
discriminating between objects or patterns
113
Posterior half of the middle and inferior temporal gyri receives projections from where?
prestriate cortex and superior colliculus
114
Cells in the prestriate cortex and superior colliculus have very large or small receptive fields?
large receptive fields
115
Those same cells are responsive to stimuli from both hemifields or just one?
BOTH (because the receptive fields of these cells may extend across midline)
116
The prestriate cortex receives projections from which hemisphere?
contralateral
117
The first level of the visual system includes what?
visual stimuli from both hemispheres are merged to form a single image
118
Bilateral lesions of the prestriate cortex cause difficulty in what?
in identifying the salient features of objects or patterns that distinguish them
119
What parts of the cortex are involved in form and color recognition? A part of it is also involved in movement (translational movement)
posterior part of the temporal lobe and its junction with the inferior parietal lobe (area V5, P pathway)
120
Anterior half of the middle and inferior temporal gyri, brodmann's areas 20 and 21, receives projections from where?
from the posterior half of these gyri (P pathway)
121
Lesions of brodmann's areas 20 and 21 result in what?
greatly impaired in the ability to recognize a previously seen pattern or object
122
Brodmann's areas 20 and 21 function in what?
function in "memorizing" a visual pattern (object recognition)
123
Posterior parietal lobe (area V3, Brodmann's area 7) receives projections from where?
visual association areas (M pathway)
124
Brodmann's area 7 is involved in the ability to do what?
to identify rotational and directional movements; also involved in the ability to identify visual spatial orientation, or position of body in space (depth perception)
125
Calcarine sulcus is referred to as what?
the primary visual cortex
126
Ganglia cells from the temporal side of the retina do not cross and stay ipsilateral to synapse where?
LGN
127
Ganglia cells from the nasal side of the retina crosses the midline at the chiasm and travels contralateral to synapse where?
LGN
128
Does the nasal retina of the same side as the visual field and temporal retina of opposite side of visual field receive the same information?
YES
129
Before axons reach LGN, they send a branch where?
into the midbrain at the level of the superior colliculus (rostral midbrain)
130
Visual pathway?
visual field impacts both retinas --> ganglia cells send axons which form the optic nerve --> some cross midline at the chiasm/ some continue ipsilateral to the superior colliculus --> those that cross form optic tract --> synapse at LGN --> optic radiations (axons from LGN) synapse in the primary visual cortex (calcarine sulcus)
131
Some fibers of the optic tract will bypass the LGN and end where?
superior colliculus
132
Meyer's loop only carries axons to what?
lingual gyrus
133
Meyer's loop only represents what?
the contralateral upper quarter field
134
Caudal vision lies where?
central vision
135
Acute vision lies where?
outside central vision
136
Anything behind the chiasm is what kind of deficit?
hemifield contralateral visual field deficit (the cortex is only concerned with the contralateral visual field)
