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Physiology Exam 6 > Vision > Flashcards

Vision Flashcards

1
Q

Mammalian chromophore

A

Retinal

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2
Q

____-retinal is transformed by light to _____-retinal

A

11-cis-retinal → all-trans-retinal

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3
Q

Focal power is measured in?

A

Diopter (Dpt)

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4
Q

How to calculate Dpt

A

Dpt = 1 / focal distance (me)

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5
Q

Focal power depends on?

A
  1. Lens shape
  2. Difference between refractive indices of lens and medium
  3. Wavelengh
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6
Q

Additive colors

A

RGB → adds to white

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7
Q

Subtractive colors

A

CYMK → subtracts to black

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8
Q

3 transparent tissues of eye

A
  1. Fovea centralis
  2. Area centralis
  3. Macula lutea
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9
Q

Fovea centralis

A

Pit-like structure in central viewing area with highest concentration of photoreceptors cells

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10
Q

Fovea centralis is found in what species?

A

Humans, monkeys and birds

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11
Q

Area centralis

A

Flat area in central viewing area with higher concentration of photorecptor cells

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12
Q

Mucla lutea

A

Central area of human retina where photoreceptors store yellow pigments which absorb blue lights

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13
Q

Anableps

A

Adaptation for terrestrial and aquatic vision

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14
Q

Anableps underwater vs. above water

A

Underwater: lens provides main refraction

Above water: cornea

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15
Q

Emmetropia

A

Normal vision for far objects → relaxed ciliary m. flattens lens (zonular fibers under tension)

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16
Q

Accomodation

A

Normal or compromised vision for near objects → contracted ciliary m. round lens (zonular fibers relaxed)

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17
Q

Presbyopia

A

Stiff lens from aging → reduced accommodation

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18
Q

Hyperopia

A

Far-sighted → bulbus is too short

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19
Q

Myopia

A

Near-sighted → bulbus is too long

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20
Q

Astigmatism

A

Round like football instead of baseball

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21
Q

Corneal epithelium

A

Barrier between tear fluid and stroma

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22
Q

Corneal endothelium

A

Barrier between stroma and aqueous humor

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23
Q

Layers of corneal epithelium

A

Multi-layered

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24
Q

Layers of corneal endothelium

A

Single layered

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25
Q

Corneal epithelium regeneration

A

7 days

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26
Q

Corneal endothelium regeneration

A

Does not regenerate → stretches to maintain barrier

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27
Q

What is necessary to maintain transparency of stroma?

A

Active ion transport

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28
Q

Corneal epithelium is densely innervated with?

A

Sensory n. fibers

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29
Q

Swelling of the corneal _______ leads to loss of transparency and clouding of cornea

A

Corneal endothelium

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30
Q

Largest avascular organ in body

A

Lens

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31
Q

Cells in lens

A

Have no organelles (fiber cells)

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32
Q

Circulatory system in lens is driven by?

A

Na current generated by Na/K ATPase and followed by fluid flux

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33
Q

Water channels in lens which allow fluid to follow Na curent

A

AQP1, AQP0

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34
Q

Aqueous humor is secreted by?

A

Ciliary epithelium

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35
Q

Aqueous humor exists eye via?

A

Trabecular meshwork and Schlemm’s canal

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36
Q

What maintains bulb inflation?

And at what pressure?

A

Aqueous humor homeostasis as 15 mmHg

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37
Q

What is glaucoma?

A

Retinal damage due to elevated intraocular pressure

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38
Q

Glaucoma is commonly caused by?

A

Blockage of efflux pathway

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39
Q

What is posterior vitreous detachment?

A

With age the vitreous body liquefies and detaches from retina

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40
Q

Cones and rods are located in what layer?

A

Photoreceptor layer

41
Q

Choroid capillary layer aka?

A

Tapetum lucidum

42
Q

Bruch’s membrane is located between?

A

Pigmented epithelium and choroid capillary layer

43
Q

Outer limiting membrane is located between?

A

Outer nuclear and photoreceptor layers

44
Q

Leading cause of blindness

A

Macular degeneration

45
Q

What causes macular degeneration?

A

Loss of RPE (retinal pigmented epithelium) function

46
Q

Functions of RPE

A
  1. Phagocytosis of rods and cones
  2. Visual circle (conversion of retinal)
  3. Viamin A storage
47
Q

Is all RPE pigmented?

A

Nope

48
Q

Function of tapetum lucidum

A

Reflects light back into retina

49
Q

Tapetum cellosum

A

Densely packed zinc-cysteins (dog, cat, ferret)

50
Q

Tapetum fibrosum

A

Extracellular densely packed collagen fibers (equine, cow, sheep)

51
Q

Nocturnal animals have a high density of rods/cones

A

Rods

52
Q

2 retinal photo-pigments

A
  1. Retinal

2. Opsins

53
Q

Opsin is an?

A

Apoprotein

54
Q

Each photo-receptor cell expresses how many types of opsin?

A

Only 1

55
Q

Opsins are what type of receptors?

A

G-protein-coupled

56
Q

Opsins determine?

A

Spectral sensitivity

57
Q

Rhodopsin is in what cell?

A

Rods

58
Q

Opsins are in what cells?

A

Cones

59
Q

Melanopsin is in what cell?

A

ipRGC (intrinsic photo-sensitive retinal ganglion cells)

60
Q

Roles of melanopsin

A
  1. Circadian rhythm
  2. Alertness
  3. Pupillary light reflex
61
Q

Melanopsin has what effect on melatonin?

A

Suppresses melatonin production

62
Q

Pupillary light reflex examines the integrity of?

A
  1. Retina
  2. Ipsilateral optic n.
  3. Both oculomotor nn.
63
Q

Mydriasis

A

Relaxation of iris (sympathetic n.)

Atropine → mAchR antagonist

64
Q

Miosis

A

Constriction of iris (parasympathetic)

Pilocarpine → mAchR agonist

65
Q

ipRG receives light and stimulates what n.?

A

CN II (optic)

66
Q

CN II (optic) sends signal to?

A

Pretecta nucleus which also communicates with other side (to stimulate reflex in both eyes)

67
Q

Pretecta nucleus sends signal to?

A

CN III (oculomotor n.)

68
Q

Oculomotor n. sends signal to?

A

Ciliary ganglia

69
Q

What innervates pupillary constrictor m.?

A

Ciliary ganglia

70
Q

Photopic vision

A

In daylight → mainly cones

71
Q

Scotopic vision

A

In night → mainly rods

72
Q

Rods are ___x more sensitive than cones

A

100x

73
Q

Purkinje effect

A

Wavelength shift → rods don’t see red

74
Q

Outer segment of rods and cones

A

Modified cilium with disks

75
Q

Rods/cones have multiple types of photo sensors

A

Cones → color!

76
Q

Rods/cones have low visual acuity

A

Rods

77
Q

Depolarization leads to?

A

Enhanced glutamate release

78
Q

Hyperpolarization leads to?

A

Reduced glutamate release

79
Q

Guanylyl cyclase generates?

A

cGMP

80
Q

cGMP activates?

A

CNGC

81
Q

CNGC

A

Cyclic-nucleotide gated cation channel

Non-selective cation channel which also conducts Ca

82
Q

Darkness leads to…?

A

Depolarization

83
Q

Light leads to…?

A

Hyperpolarization

84
Q

Light activates?

A

Retinal bound to rhodopsin or opsin receptor

85
Q

How does light cause closure of CNGC channel?

A

Activated receptor activates transducin → activates PDE → breaks down cGMP

86
Q

Transducin

A

Retina specific G-protein

87
Q

Do rods and cones generate APs?

A

No

88
Q

NCKX

A

4 Na/Ca, K exchanger

89
Q

Feedback mechanism of light/dark

A

Cytosolic [Ca] drops when CNGC is closed due to NCKS → stimulates GC to generate cGMP

90
Q

What is univariance?

A

Rods and cones respond to light with hyperpolarization, regarldess of wavelength

91
Q

Magnitude of hyperpolarization depends on?

A

Spectral sensitivity of cell and intensity of light stimulus

92
Q

____ cells are first cells to code light changes by changing AP frequency

A

Ganglion cells

93
Q

OFF-ganglion has higher AP frequency leading to depolarization when?

A

Dark

94
Q

ON-ganglion has higher AP frequency leading to depolarization when?

A

Light

95
Q

How do rods, cones and bipolar cells code light?

A

Graded voltage levels and graded Nt release

96
Q

ON-bipolar cell

A

Sign conversion

Dark: hyperpolarize (when you’re hyper at night you get it on)

Light: depolarizes

97
Q

OFF-bipolar cell

A

Sign conformity

Dark: depolarize

Light: hyperpolarize

98
Q

ON and OFF ganglion cells detect?

A

Contrasts in luminosity

Physiology Exam 6 (7 decks)

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