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Neurophysiology > Vision > Flashcards

Vision Flashcards

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1
Q

Optical component of the eyes

A

Cornea, aqueous humor, vitreous humor, lens

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2
Q

Neural component of the eyes

A

Rods, cones, bipolar cells, ganglion cells

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3
Q

Function of the optical component of the eyes

A

Focus images on the photoreceptors

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4
Q

Function of the neural component of the eyes

A

Transforms images that reach the photoreceptors into neural discharges which are transmitted to the brain

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5
Q

Primary refractive media of the eye

A

Cornea

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6
Q

Color of the cornea

A

Transparent to allow the light pass through

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7
Q

Why is the cornea transparent

A

Uniform structure, avascularity, deturgescence (stroma of the cornea is kept dehydrated to maintain clarity and transparency)

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8
Q

Metabolism of the cornea

A

Glucose, aerobic (30% glycolysis, 65%PPP)

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9
Q

Two parts of the conjunctiva

A

Palpebral: behind the eyelid (check color; pale = anemia)
Bulbar: covers the sclera

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10
Q

Fibrous outer layer of the eye consisting of collagen

A

Sclera

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11
Q

Fine elastic tissue covering the outer anterior sclera

A

Episclera

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12
Q

Nourishment of sclera

A

From blood vessels of episclera

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13
Q

Parts of the uveal tract

A

Iris, ciliary body, choroid

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14
Q

Central opening of the iris

A

Pupil

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15
Q

Function of the pupil

A

Controls amount of light entering the eye

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16
Q

Pupillary response to bright light

A

CN III; sphincter pupillae; miosis (constricted)

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17
Q

Pupillary response to dark light

A

Sympathetic; dilator pupillae; mydriasis (dilated)

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18
Q

Two zones of the ciliary body

A

Pars plicata: corrugated anterior zone

Pars plana: flattened posterior zone

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19
Q

Function of the ciliary body

A

Controls conformation and focus of the lens through the suspensatory ligaments; produces aqueous humor

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20
Q

Posterior part of the uveal tract, located between the sclera and the retina

A

Choroid

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21
Q

Function of the choroid

A

Supplies blood to the outer portion of the retina

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22
Q

Blood supply of the inner part of the retina

A

Retinal arteries

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23
Q

Blood supply of the outer part of the retina

A

Choroid

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24
Q

Biconvex, avascular, clear structure of the eye

A

Lens

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25
Components of the lens
65% water, 35% proteins and minerals
26
Parts of the lens
Capsule: semipermeable to water and e- Lens nucleus Cortex
27
Metabolism of the lens
Glucose, aerobic metab (85% glycolysis, 10% PPP, 5% TCA)
28
Structural integrity of the lenses are due to
Na-K ATPase, glutathione reductase, protein synthesis
29
Junction of the peripheral cornea and root of the iris
Anterior chamber angle
30
Function of the anterior chamber angle
Contains a trabecular meshwork that resorbs aqueous humor
31
Function of the intraocular fluid
Maintain pressure in eyeball to keep it distended
32
Parts of the intraocular fluid
Aqueous and vitreous humor
33
Isoosmotic fluid lies in front of the lens
Aqueous humor
34
Function of the aqueous humor
Nourishment to cornea and lens; | Removes end-products of metab
35
Aqueous humor pathway
Ciliary process > posterior chamber > pupil > anterior chamber > canal of schlemm
36
Posterior chamber vs posterior segment of the eye ball
Posterior chamber = behind the iris | Posterior segment = behind the lens
37
Posterior to the lens; occupies the posterior segment
Vitreous humor
38
Clear, avascular body with 2/3 volume is of the weight
Vitreous humor
39
Components of the vitreous humor
1% collagen and hyaluronic acid
40
What makes the vitreous humor gel-like
1% collagen and hyaluronic acid = gel like due to its ability to bind large amounts of water
41
Refractive interfaces of the lens system
Between air and anterior cornea; Between posterior cornea and aqueous humor; Between aqueous humor and anterior lens; Between posterior ens and vitreous humor
42
Total optical power of the eye
60 diopters - cornea = 40 - lens = 20
43
Convex vs concave lens
``` Convex = focuses light rays into a single focal point; Concave = diverges light rays ```
44
Refractive power is defined as
Ability to bend light so the image will be focused on the retina
45
Cloudy/opaque areas in the lens obscuring light transmission
Cataracts
46
Pathophysio of cataracts
Loss of osmolariy and change in solubility of lens proteins --> high light scatter
47
Treatment for cataract
Removal of lens nucleus and replacing it with artificial plastic lens
48
Senile vs Diabetic cataract
Senile: age related; changes in architechtural arrangement of lens crytalline due to breakdown of proteins Diabetic: increased osmolarity of lens due to aldose reductase and polyol (aldose) dehydrogenase
49
Myopia
Nearsightedness; Light rays coming from distant objects are focused in front of the retina due to (1) longer eyeballs (2) steeply curved cornea (3) higher refractive power; Use biconcave lenses to diverge rays to lessen refractive power
50
Hyperopia
Farsightedness; Light rays are not bent by lens to focus by the time they reach the retina due to (1) short eyeball (2) flatly-curved cornea (3) weak lens system; Corrected by biconvex lens to bend light more; Accommodation by ciliary muscles to strengthen lens
51
Astigmatism
Disparity in corneal curvature between the axes; Cornea is more of an oblong; Visual image in one plane to focus at different distance from that of the plane at right angles; Trial and error spherical lens that corrects the focus of one of the planes
52
Presbyopia
Lens stiffens which decreases the ability to change shape; | Power of accommodation decreases with age
53
Diseases which the intraocular pressure become too high due to accumulation of aqueous humor
Glaucoma
54
Pathophysio of glaucoma
Accumulation of aqueous humor, IOP rises, posterior pressure increases, axons of optic nerve are compressed
55
Most common cause of irreversible blindness
Glaucoma
56
Most common cause of reversible blindness
Cataract
57
Treatment for glaucoma
Surgery
58
Wide/open angle glaucoma
Aqueous humor has complete physical access to the trabecular meshwork; Increased IOP is due to an increased resistance to aqueous outflow
59
Narrow/closed angle glaucoma
Peripheral zone of iris adheres to trabecular meshwork; physical impediment to egress of aqueous humor (drainage obstruction); fluid cannot reach the trabecular meshwork
60
Parts of the retina seen on fundoscopy
Optic nerve: physiologic blind spot Macula lutea: 3mm yellowish pigmentation due to xanthophylls Fovea: center of macula Foveola: most central and thinnest part of retina (cones only)
61
Metab of retina
Anaerobic glycolysis; | NADH reduces pyruvate to lactate, increasing lactate dehydrogenase
62
Fuel for lactate dehydrogenase of retina
NADH or NADPH
63
Function of rods vs cones
Rods: function at low light; monochromic night vision Cones: function at higher light levels; high acuity color daylight vision
64
Photoreceptors mostly found in the fovea centralis
Cones
65
Photoreceptors mostly found in the eyes except the fovea centralis
Rods (20:1)
66
Function of rhodopsin
Absorption at 500nm; | With 7 transmembrane helices with 11-cis-retinal
67
Pathway of light
Rods and cones > bipolar cells > ganglion cells > optic nerve
68
Provide inhibitory feedback to photoreceptors
Horizontal cells
69
3 types of ganglion cells
Magnocellular 5%: movement, location, depth; largest; respond to rapid changes in visual images Parvocellular 55%: color, form, texture; small visual fields; accurate localization and fine details; receive from >=1 cone W cells 40%: directional movement; small with large diffused receptive fields; receive from crude rod
70
Types of fibers of the optic nerve
Visual 80%: synapse in LGB on neurons whose axons terminate in the visual cortex Pupillary 20%: bypass geniculate body en route to pretectal area
71
T/F: optic sheath is continuous with the meninges
T
72
Neurotransmitter for phototransduction
glutamate
73
Phototransduction in the dark
Photorec not activated by light > all-cis retinal maintained > no activation of transducin > no activation of phosphodiesterase > no conversion of cGMP > Na channels are open > Na influx > depolarization > release neurotransmitter > synapse is inhibitory to the next bipolar cell
74
Visual field for temporal side
Lateral; | Projected to the nasal side of retina
75
Visual field for nasal side
Medial; | Projected to the temporal side of the retina
76
Crosses the optic chiasm
Nasal side
77
L optic tract
L temporal + R nasal
78
R optic tract
R temporal + L nasal
79
What is affected in loss of peripheral vision?
Both nasal sides
80
Affected in tunnel vision
Lesion/s in the optic chiasm
81
Pathway of visual signal
retinas > optic nerves >  optic chiasm > opposite optic trac >t  lateral geniculate body >  optic radiation > visual cortex/calcarine fissure of the occipital lobe
82
Accommodation
Ability of the lens to refocus divergent rays of light on the retina
83
Contraction of the muscles of ciliary body
Diameter of ciliary body is decreased; zonules relax > less pull on the lens > lens assumes spherical shape (more convex) > light is bent > see near objects
84
No contraction of the muscles of ciliary body
Diameter of ciliary body is increased; zonules taut > lenses taut > lenses flattened (less convex) > focus more on far objects
85
Types of ciliary muscles
Meridional fibers | Circular fibers
86
Innervation of ciliary muscles
CN III
87
Wviewing near objects, eyes [converge/diverge] at the center
converge
88
Light entering constricted pupil
More focused, more depth
89
Light entering dilated pupil
More scattered, less depth of focus
90
Responsible for pupillary constriction
Pupillary sphincter muscle
91
Depth of focus is [directly/inversely] proportional to pupillary diameter
Inversely
92
Moving parallax
Images of close-by objects move rapidly across the retinas, while the images of distant objects remain almost completely stationary
93
Stereopsis
Images on the two retinas are different rom each other; | For the perception of depth
94
Types of cones
Blue: 420nm Green: 535nm Red: 565nm
95
Young-Helmholtz Trichromatic (3-color) Theory
Variations in color are accounted for by differential stimulation of the blue, green, or red cones
96
Color blindness
Inability to distinguish colors; | Photore are present but aa are changed = change in absorption spectra = abnormal color vision
97
Protanopia
Red-Green color blindness; Lack either red or green cone Cannot distinguish green, yellow, orange, red; X linked recessive
98
Macula and fovea arise from
Temporal side
99
Origin of blood vessels entering the eye
Optic disc = physiological blindspot

Neurophysiology (2 decks)

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