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Neurophysiology > Vision > Flashcards

Vision Flashcards

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
Q

Components of the lens

A

65% water, 35% proteins and minerals

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26
Q

Parts of the lens

A

Capsule: semipermeable to water and e-
Lens nucleus
Cortex

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27
Q

Metabolism of the lens

A

Glucose, aerobic metab (85% glycolysis, 10% PPP, 5% TCA)

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28
Q

Structural integrity of the lenses are due to

A

Na-K ATPase, glutathione reductase, protein synthesis

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29
Q

Junction of the peripheral cornea and root of the iris

A

Anterior chamber angle

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30
Q

Function of the anterior chamber angle

A

Contains a trabecular meshwork that resorbs aqueous humor

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31
Q

Function of the intraocular fluid

A

Maintain pressure in eyeball to keep it distended

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32
Q

Parts of the intraocular fluid

A

Aqueous and vitreous humor

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33
Q

Isoosmotic fluid lies in front of the lens

A

Aqueous humor

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34
Q

Function of the aqueous humor

A

Nourishment to cornea and lens;

Removes end-products of metab

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35
Q

Aqueous humor pathway

A

Ciliary process > posterior chamber > pupil > anterior chamber > canal of schlemm

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36
Q

Posterior chamber vs posterior segment of the eye ball

A

Posterior chamber = behind the iris

Posterior segment = behind the lens

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37
Q

Posterior to the lens; occupies the posterior segment

A

Vitreous humor

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38
Q

Clear, avascular body with 2/3 volume is of the weight

A

Vitreous humor

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39
Q

Components of the vitreous humor

A

1% collagen and hyaluronic acid

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40
Q

What makes the vitreous humor gel-like

A

1% collagen and hyaluronic acid = gel like due to its ability to bind large amounts of water

41
Q

Refractive interfaces of the lens system

A

Between air and anterior cornea;
Between posterior cornea and aqueous humor;
Between aqueous humor and anterior lens;
Between posterior ens and vitreous humor

42
Q

Total optical power of the eye

A

60 diopters

  • cornea = 40
  • lens = 20
43
Q

Convex vs concave lens

A 
Convex = focuses light rays into a single focal point;
Concave = diverges light rays
44
Q

Refractive power is defined as

A

Ability to bend light so the image will be focused on the retina

45
Q

Cloudy/opaque areas in the lens obscuring light transmission

A

Cataracts

46
Q

Pathophysio of cataracts

A

Loss of osmolariy and change in solubility of lens proteins –> high light scatter

47
Q

Treatment for cataract

A

Removal of lens nucleus and replacing it with artificial plastic lens

48
Q

Senile vs Diabetic cataract

A

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
Q

Myopia

A

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
Q

Hyperopia

A

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
Q

Astigmatism

A

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
Q

Presbyopia

A

Lens stiffens which decreases the ability to change shape;

Power of accommodation decreases with age

53
Q

Diseases which the intraocular pressure become too high due to accumulation of aqueous humor

A

Glaucoma

54
Q

Pathophysio of glaucoma

A

Accumulation of aqueous humor, IOP rises, posterior pressure increases, axons of optic nerve are compressed

55
Q

Most common cause of irreversible blindness

A

Glaucoma

56
Q

Most common cause of reversible blindness

A

Cataract

57
Q

Treatment for glaucoma

A

Surgery

58
Q

Wide/open angle glaucoma

A

Aqueous humor has complete physical access to the trabecular meshwork;
Increased IOP is due to an increased resistance to aqueous outflow

59
Q

Narrow/closed angle glaucoma

A

Peripheral zone of iris adheres to trabecular meshwork; physical impediment to egress of aqueous humor (drainage obstruction); fluid cannot reach the trabecular meshwork

60
Q

Parts of the retina seen on fundoscopy

A

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
Q

Metab of retina

A

Anaerobic glycolysis;

NADH reduces pyruvate to lactate, increasing lactate dehydrogenase

62
Q

Fuel for lactate dehydrogenase of retina

A

NADH or NADPH

63
Q

Function of rods vs cones

A

Rods: function at low light; monochromic night vision
Cones: function at higher light levels; high acuity color daylight vision

64
Q

Photoreceptors mostly found in the fovea centralis

A

Cones

65
Q

Photoreceptors mostly found in the eyes except the fovea centralis

A

Rods (20:1)

66
Q

Function of rhodopsin

A

Absorption at 500nm;

With 7 transmembrane helices with 11-cis-retinal

67
Q

Pathway of light

A

Rods and cones > bipolar cells > ganglion cells > optic nerve

68
Q

Provide inhibitory feedback to photoreceptors

A

Horizontal cells

69
Q

3 types of ganglion cells

A

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
Q

Types of fibers of the optic nerve

A

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
Q

T/F: optic sheath is continuous with the meninges

A

T

72
Q

Neurotransmitter for phototransduction

A

glutamate

73
Q

Phototransduction in the dark

A

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
Q

Visual field for temporal side

A

Lateral;

Projected to the nasal side of retina

75
Q

Visual field for nasal side

A

Medial;

Projected to the temporal side of the retina

76
Q

Crosses the optic chiasm

A

Nasal side

77
Q

L optic tract

A

L temporal + R nasal

78
Q

R optic tract

A

R temporal + L nasal

79
Q

What is affected in loss of peripheral vision?

A

Both nasal sides

80
Q

Affected in tunnel vision

A

Lesion/s in the optic chiasm

81
Q

Pathway of visual signal

A

retinas > optic nerves >  optic chiasm > opposite optic trac >t  lateral geniculate body >  optic radiation > visual cortex/calcarine fissure of the occipital lobe

82
Q

Accommodation

A

Ability of the lens to refocus divergent rays of light on the retina

83
Q

Contraction of the muscles of ciliary body

A

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
Q

No contraction of the muscles of ciliary body

A

Diameter of ciliary body is increased; zonules taut > lenses taut > lenses flattened (less convex) > focus more on far objects

85
Q

Types of ciliary muscles

A

Meridional fibers

Circular fibers

86
Q

Innervation of ciliary muscles

A

CN III

87
Q

Wviewing near objects, eyes [converge/diverge] at the center

A

converge

88
Q

Light entering constricted pupil

A

More focused, more depth

89
Q

Light entering dilated pupil

A

More scattered, less depth of focus

90
Q

Responsible for pupillary constriction

A

Pupillary sphincter muscle

91
Q

Depth of focus is [directly/inversely] proportional to pupillary diameter

A

Inversely

92
Q

Moving parallax

A

Images of close-by objects move rapidly across the retinas, while the images of distant objects remain almost completely stationary

93
Q

Stereopsis

A

Images on the two retinas are different rom each other;

For the perception of depth

94
Q

Types of cones

A

Blue: 420nm
Green: 535nm
Red: 565nm

95
Q

Young-Helmholtz Trichromatic (3-color) Theory

A

Variations in color are accounted for by differential stimulation of the blue, green, or red cones

96
Q

Color blindness

A

Inability to distinguish colors;

Photore are present but aa are changed = change in absorption spectra = abnormal color vision

97
Q

Protanopia

A

Red-Green color blindness;
Lack either red or green cone
Cannot distinguish green, yellow, orange, red;
X linked recessive

98
Q

Macula and fovea arise from

A

Temporal side

99
Q

Origin of blood vessels entering the eye

A

Optic disc = physiological blindspot

Neurophysiology (2 decks)

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