Block 2 Exam: Vision Flashcards
1
Q
Wavelength vs. Amplitude
A
Wavelength determines the color of light; amplitude processed as intensity of light.
2
Q
Long waves=
Medium waves=
Short Waves=
A
Red (560nm)
Green (530nm)
Blue (430nm)
3
Q
Convex Lens
A
Bring waves together into focal point, whereas concave lens scatters light
4
Q
Focal Length=
Diopter=
A
distance from lens to point
1/focal length; reciprocal of focal length
5
Q
____ shortens focal length, ____ lengths focal length
A
Convex shortens
Concave lengthens
6
Q
What fluid nourished cornea?
A
Aqueous humor & tear film which is continuously replenished
7
Q
What has the highest refractive power in the eye?
A
Cornea 42 diopters (anything you see 2.4cm behind)
8
Q
What refracts light, and can change shape to where you want to focus and enhance vision focus?
A
lens
9
Q
Where is the aqueous humor?
A
between cornea and lens
10
Q
Where is vitreous chamber?
A
behind the lens
11
Q
Not draining ______ can cause a glycoma if blocked due to pressure.
A
Canal of Schlemn
12
Q
Point where light can directly hit photoreceptors
A
Fovea
13
Q
Blindspot due to lack of photoreceptors, where axons exit the eye
A
Optic disc
14
Q
Axons of retinal ganglion
A
optic nerve
15
Q
What attaches the lens to ciliary fibers and contracts/relaxes lens to alter shape?
A
Ciliary muscles.
16
Q
____ is where photoreceptors are, and where light is transduced from light –> electrical energy.
A
Retina
17
Q
The only cells that send AP to thalamus in vision.
A
Ganglion
18
Q
Accommodation
A
changing the shape of the lens in response to distance of object
19
Q
Lens ____ for distance vision; ___ for close vision.
A
Flattened. Rounded
20
Q
State in which the lens is flat and light rays are focused on retina. (6+ meters away, little effort)
A
Emmetropia
21
Q
_____ pulls on lens, connected to ciliary muscles
A
Zonulas
22
Q
When Ciliary muscles relaxed
A
Zonulas tight, lens flat
23
Q
When ciliary muscles contracted
A
Zonulas slacken, lens round
24
Q
Pupil ____ increases depth of focus
A
constriction
25
Loss of accommodation (with age, around 45)
presbyopia
26
Misshapen cornea
Astigmatism
27
Farsightedness is called____. List what it involves and how it is corrected.
Hyperopia. Focal point behind retina.
Corrected with convex lens
28
Nearsightedness is called____. List what it involves and how it is corrected.
Myopia. Focal point in front of retina.
Corrected with Concave lens.
29
The fact that light passes through ganglion, bipolar and photoreceptor layers is called ___.
Laminar organization
30
Epithelium
Protects the photoreceptors and plays an important role in processing of rhodopsin, which transduces light into electrical energy. Also important for providing nutrients and oxygen and blood supply.
31
Blind spot
Optic disk, no photoreceptors
32
What has highest acuity vision and why?
Fovea, ganglion/bipolar pushed aside. Gets light directly.
33
Convergence:
____ photoreceptors: 1 bipolar neuron.
_____ bipolar: 1 ganglion cell.
Exceptions?
15-45 photoreceptors: 1 bipolar
multiple bipolar: 1 ganglion cell
Exception: 1:1 in fovea of receptors to bipolar
34
____ mostly in periphery, ___ mostly in fovea
Rods
Cones
35
Photoreceptors (Rods)__________ in response to light.
hyperpolarize
36
What do horizontal cells do?
Horizontal cells mediate light on center/surround.
Also release GABA on photoreceptor terminals
37
ON bipolar cells
Invagination
Inhibited by glutamate which closes cGMP-gated Na+ channels. RESPONDS TO GLUTAMATE BY HYPERPOLARIZING.
Light-on: depolarizes by removing inhibition that occurs due to hyperpolarization.
38
OFF bipolar Cells
Flat bipolars
Excited by glutamate via kainate receptors
Inhibited by light, really removal of tonic excitation.
39
Bipolar cells: Direct pathway
bipolar cell is depolarized, so the photoreceptor is hyperpolarized
40
Bipolar cells: indirect pathway
The bipolar cell is hyperpolarized, so the horizontal cell is hyperpolarized, and so is the photoreceptors in the surround.
Indirect important when difference in luminance in surround contributes to light adaption.
41
Light on center:
____ center cone
On-center bipolar ______
Off-center bipolar______
Hyperpolarizes center cone
On-center bipolar depolarized
Off-center bipolar hyperpolarized
42
If light in center, ganglion fire AP if they are
On-center ganglion cells
43
Where do ganglion cells send info?
Lateral geniculate nucleus
44
M-Type Ganglion Cells
Magnocellular, Large, 5%
Large receptive fields, axons highly myelinated, rapid AP conduction
Sensitive to low contrast stimuli, changes in light
45
P-type Ganglion Cells (parvocellular)
90%, wavelength sensitive (medium/long), get info from cones
46
Non-M/P Ganglion Cells
Strongly activated by short wavelength (blue)
47
Ganglion cells are activated by light contrast.
Off-center optimal?
On-center optimal?
Off-center=dark center, light surround.
On-center=light center, dark surround
48
The idea that wavelength are perceived in combination (red vs. green, blue vs. yellow) is
Color Opponency
49
Yellow vs. Blue
Blue: S+ (L- M-)
Yellow: S- (L+ M+)
50
Pathway: Photoreceptors --> Ganglion --> _______, crosses in _____.
Then goes on to optic tract to the ___________ part of the thalamus --> visual cortex.
From thalamus back. do we see ipsilateral, or contralateral?
Photo --> Gang --> optic nerves, cross in optic chaism.
Lateral geniculate nucleus of thalamus
Contralateral
51
Where do most visual projects end up?
Around calcarine sulcus in cuneus area on medial side of occipital lobe.
52
4 main targets of the visual system and their respective functions.
1. Lateral Geniculate nucleus of thalamus (perception)
2. Hypothalamic suprachiasmatic nucleus (circadian rhythms)
3. Tectum (pupil, lens reflects, accommodation, ciliary reflexive)
4. Superior colliculus in midbrain (eye/head movement)
53
Superficial Layer of Superior Colliculus
Two parts:
1. Stratum Griesum superficial SGS
2. Stratum opticum SO
input directly from retina ganglion cells and visual cortex (map of stimuli)
54
Deep layer of superior colliculus
Excitatory input form multimodal sensory cortical and basal ganglia inputs.
Inhibitory input form substantia nigra (map that organizes activity and stimulus selection)
Also somato/auditory input and motor output to brainstem gaze centers
Stratum griesum (Grey) intermediate SGI
55
What does the center portion of binocular vision do?
Depth perception
56
LGN Cells:
Contralateral (different side) info is found in layers __, __, & ___.
Ipsilateral (same side) info found in layers __, __, & __.
Parvocellular cells are in layers ___-___.
Magnocellular cells are in layers ___-___.
Contralateral: 1, 4, 6
Ipsilateral: 2, 3, 5
P-type: 3-6
M-type: 1-2
57
Where do some surprising excitatory inputs in LGN come from?
Primary visual cortex
Brainstem reticular system- involved in alertness/attentiveness, modulate LGN response to visual stimuli
58
The idea that neighboring cells in retina send projections to neighboring places in their target structures is called...
Retinotopy
59
Optic radiations project to
Meyer's loop, genicular calcarine projections from geniculate to calcarine sulcus. (RETINOTOPY)
60
Where is the upper left visual field on the calcarine sulcus?
The lower banks and the lower visual field is on the upper bank (it's inverted)
61
What layer is main output for LGN (V1 neurons)?
Layer 4
62
Motion Pathway
| for these, remember what LGN layers it could actually go to
Magnocellular
Contra/Ipsila Retina ---> LGN (layer 1: contra, layer 2: ipsil) --> 4C-alpha in Striate complex --> converge in 4B layer.
binocular simple and complex, orientation and direction selective- OBJECT MOTION AND GUIDANCE OF MOTOR ACTIONS
63
Shape Pathway
Parvocelllular/interblob
Contra/Ipsila Retina --> LGN (contra 4/6, ipsil 3/5) --> 4C-beta --> Blobs in layers 2/3, converge at interblob
NOT DRIECTION SELCTIVE, but ORIENTATION SELECTIVE (simple or complex), small receptive fields, analysis of small object shape.
64
Color Pathway
Non-M/P
Contra/Ipsil retina --> Koniocellular layers ventral to LGN layers (contra 1&4, ipsil 2&3) ---> Synapses in blobs 2&3.
Blobs: Monocular, lack orientation specificiaty- analysis of object color. Each geniculate receives info about contralateral visual field.
65
4C-alpha layer of visual cortex is
Color insensitive (monocular), used in motion pathway
66
4C-beta layer of visual cortex is
Sensitive to color and wavelength of light. (used in shape pathway)
67
4B layer of visual cortex receives input from ___ eyes, and has a small _________ ____-____ receptive fields.
Both eyes
small center-surround receptive field
68
If you put radioactive proline in an eye, you see alternative columns. Monocular neurons in layer ____ are grouped in columns and get input from alternating eyes. This is called...
Layer 4C
Ocular dominance columns
69
In layers 2, 3, 5, and 6: cytochrome oxidase blobs show that blobs are in rows within ocular dominance column and receive direct inputs from _____________________.
koniocellular regions of LGN and layer 4C.
70
Interblobs, unlike regular blobs have what 3 qualities?
1. Orientation Selectivity
2. Direction Selective
3. Binocularity (info from both eyes)
71
Orientation selectivity
functions for analysis of an object SHAPE (orientation column). used by most cells in V1 outsides 4C (except Blobs). Respond best to bars of light at very specific angles.
72
Direction Selectivity
Functions for analysis of object MOTION. Mostly layer 4B, probably 2/3 too. Best when light bar is moving perpendicular to the optimal orientation in one direction but not the other.
73
Dorsal Streaming Pathway in Cortical Processing
Perception of motion, control of action
spatial cognition – WHERE pathway
Parietal cortex – visual-spatial and integration of bimodal information
MAGNOCELLULAR
74
Ventral Steaming Pathway in Cortical Processing
Faces, objects, & shapes recognition, perception of world –
WHAT pathway
Blobs/interblobs --> V2 which receives projections from blobs/interblobs and which is anatomically organized to define the projects to dorsal/ventral stream.
75
Dorsal Processing:
| MT & MST
MT:
1. Layer V5 receives input form V3/V2 as well as cells in layer 4B of striate.
2. Large receptive fields and direction selection (motion response, Magnocellular)
MST: LINEAR motion, radial motion, circular motion, navigation, directing eye movements (attention) and motion perception)
76
Ventral Processing steps:
| V4 & IT (inferior temporal)
V4: input from blob and interblob regions- orientation and color selective - shape and color perception.
Inferior Temporal: cells respond specifically to specific objects (facial fusiform area) visual perception/memory- strongly to faces. Cells for recognition of specific people? Possible but could occur downstream.
77
What is it called when V4 area is damaged resulting in complete loss of color vision?
Achromatopsia
