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KMK > Ocular Physiology > Flashcards

Ocular Physiology Flashcards

1
Q

What purpose does the abundant sarcoplasmic reticulum (SR) in EOMs serve?

A

Allows greater access to Ca, promoting muscle contraction

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2
Q

What is the approximate number of muscle fibers in an EOM motor unit?

A

10 muscle fibers per motor unit

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3
Q

Why is it important that EOMs have very small motor units?

A

Allows for small, precise, accurate movements

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4
Q

What two ocular conditions can Botox be used to treat?

A

Strabismus

Blepharospasm

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5
Q

What is the MOA of Botox?

A

Inhibits release of ACh at the neuromuscular junction

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6
Q

What is the purpose of aqueous?

A

Maintain the shape of the anterior chamber
Helps transmit light to the retina
Provides nutrients and oxygen
Moves waste products from the anterior portion of the eye

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7
Q

Why is carbonic anhydrase important in aqueous production?

A

Aids in production if bicarbonate, which causes an ion gradient

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8
Q

What is the mathematical relationship between liquid content of the vitreous and age?

A

Linear - as age increases, the amount of liquid in the vitreous increases linearly

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9
Q

What is the relative charge inside an axon?

A

Negative

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10
Q

Directing a pt to look left with both eyes would be what classification of eye movement?

A

Levoversion

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11
Q

What is one unique characteristic of vortex veins?

A

They don’t contain valves

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12
Q

Which layers of the cornea prefer lipophilic substances?

A

Epithelium

Endothelium

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13
Q

Which layer of the cornea is hydrophilic?

A

Stroma

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14
Q

When an ophthalmic drug contacts the tear film, the pH of the tears favors what?

A

Alteration of the drug to a more non-ionized state

-non-ionized = lipid soluble

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15
Q

TBUT occurs as a result of what?

A

Migration of lipid into contact with mucous

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16
Q

Parasympathetic innervation is the primary stimulus for increased production and secretion of all of the different layers of the tear film except:?

A

Lipid secretion - lipids are secreted via blinking

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17
Q

Which nerve is responsible for reflex tearing?

A

VII

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18
Q

What does the main lacrimal gland contribute to?

A

Emotional tears

Reflex tears

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19
Q

What is the nutrient supply for the cornea?

A

Aqueous humor

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20
Q

What is the main oxygen supply for the open eye?

A

Tear film

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21
Q

What is the main oxygen supply for the closed eye?

A

Palpebral conj - anterior cornea

Aqueous - posterior cornea

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22
Q

Tear drainage occurs by what mechanism?

A

Contraction of two muscles; one widens the lacrimal sac, and the other acts on the canaliculi to pump tears into the widened sac - stimulated by blinking

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23
Q

What portions of the orbicularis oculi are used in forced closure of the lid?

A

Both orbital and palpebral portions

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24
Q

Which nerve is responsible for reflex blinking?

A

CN V

-CN VII actually executes the blink

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25
Q

What areas form the blood retinal barrier?

A

Tight junctions in the wall of retinal vessels
Tight junctions between RPE cells
-NOTHING in the choroid contributes to the blood/retinal barriers

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26
Q

Where is the majority of the blood found within the eye?

A

Long and short posterior ciliary arteries

-Choroid has the majority of the blood flow

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27
Q

What does the long posterior ciliary artery supply?

A

Anterior choroid

Contributes to the major arterial circle of the iris

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28
Q

What does the short posterior ciliary artery supply?

A

Posterior choroid

Forms circle of Zinn (provides blood for the surface of the optic disc)

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29
Q

The majority of in the eye is in the choroid. Where is the majority of oxygen in the eye?

A

Retinal arteries

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30
Q

Stimulation of sympathetic receptors can cause what IOP response?

A

Both increase or decrease, depending on which receptors are acted upon
A2 - decrease (decreases blood in MACI)
B1/B2 - increase (increases aqueous production)

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31
Q

Sympathetic stimulation of uveal vessels leads to what change?

A

Vasoconstriction

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32
Q

Which vasculature of the eye doesn’t respond to sympathetic stimulation? Why?

A

Retina - it autoregulates

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33
Q

What does perfusion pressure refer to?

A

The pressure difference between arteries and veins of a particular tissue

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34
Q

Which is good for the lens: glutathion or calcium?

A

Glutathion

-“Ca is crappy for the lens”

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35
Q

Are crystallins soluble or insoluble?

A

Soluble lens proteins

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36
Q

What does alpha crystallin do for the lens?

A

Molecular chaperone, reducing cataract formation

37
Q

What does the gradient lens allow for in regards to aberration?

A

Reduces spherical aberration in the periphery

38
Q

Which fibers does a Pancoast tumor affect?

A

Preganglionic sympathetic fibers

39
Q

Where does the sympathetic nervous system synapse in the way to the eye?

A

Superior cervical ganglion

40
Q

Where does the ocular sympathetic system start, and where it its first synapse?

A

Hypothalamus

Center of budge

41
Q

Pupillary constriction in response to the location of a near stimulus begins where?

A

FEF

-Goes on to Edinger Westphal, to ciliary ganglion

42
Q

What is the pathway of pupil constriction due to light?

A

FEF

-goes to pretectal nucleus, to EW to ciliary ganglion

43
Q

Argyll Robertson Pupil results from disruption in what tract?

A

Tectotegmental tract that connects the pretectal to the EW nucleus

44
Q

Patients with Argyll Robertson Pupil will constrict to which stimulus: Near, light?

A

Near

-Poor constriction to light

45
Q

Uveitis is a breakdown of what?

A

Blood aqueous barrier

46
Q

Aqueous production relies almost entirely on what type of secretion?

A

Active secretion

47
Q

Why might a neck tie increase IOP?

A

Increase in venous pressure, which decreases the outflow via TM

48
Q

Uveitis, blood acidosis, and plasma hyperosmolality may cause what change to IOP?

A

Decrease

49
Q

How does isosorbide decreas IOP?

A

Increases plasma osmolarity

-high concentration of ions draws water out

50
Q

Tonometry on a thick cornea may be under or overestimated?

A

Overestimated

51
Q

Tonometry on a thin cornea may be uner or overestimated?

A

Underestimated

52
Q

Which layer of the cornea thickens with age?

A

Descemet’s

53
Q

Which layer of the cornea shows decreased cell count with age?

A

Endothelium

54
Q

What is the first corneal response mounted to an abrasion?

A

Inhibition of basal cell mitosis

-followed by migration

55
Q

The epithelium can help combat edema by pumping what ion where?

A

Cl- into the tears (water follows)

56
Q

What helps to ensure that collagen fibrils are regularly spaced in the cornea to maintain transparency?

A

GAGs

57
Q

Corneal deturgescence is the primary responsibility of what layer of the cornea?

A

Endothelium

58
Q

What is corneal deturgescence?

A

Dehydration of the corneal stroma

59
Q

The corneal stroma is what percent water?

A

78%

60
Q

What type of potentials do amacrine and ganglion cells create?

A

Action potentials

61
Q

What type of potentials do horizontal, bipolar, and PRs generate?

A

Graded potentials

62
Q

Which cells of the retina use excitatory neurotransmitters?

A

PRs
Bipolar cells
Ganglion cells

63
Q

Which cells of the retina use inhibitory neurotransmitters?

A

Amacrine cells

Horizontal cells

64
Q

What are the inhibitory neurotransmitters used by amacrine and horizontal cells?

A

GABA

Glycine

65
Q

What is the excitatory neurotransmitter used by PRs, bipolar cells, and ganglion cells?

A

Glutamate

66
Q

Stimulation of the PRs results in what?

A

Hyperpolarization

67
Q

Phototransduction in the outer segment leads to what occurrences?

A

Hyperpolarization
Generation of graded potentials
Decrease in glutamate release from PRs

68
Q

What is one of the main differences between rod spherules and cone pedicles?

A

Opsin component

-Rhodpsin vs Iodopsin

69
Q

Where is collagen concentration the highest in the vitreous?

A

Vitreous base

70
Q

Where is collagen concentration the lowest in the vitreous?

A

Center

71
Q

What causes the A wave of an ERG?

A

PRs

72
Q

What causes the B wave of an ERG?

A

Bipolar and mueller cells

73
Q

What causes the C wave of an ERG?

A

RPE

74
Q

What should the normal Arden ratio in an EOG be?

A

Greater than 1.8

- less tan 1.65 is very abnormal

75
Q

Where do simple and complex cells first appear along the visual pathway?

A

Primary visual cortex (V1)

76
Q

What are simple cells programmed to specialize in?

A

Objects with a particular orientation

77
Q

What are complex cells programmed to specialize in?

A

Objects with a particular orientation, moving in a specific direction

78
Q

Which is the first place in the visual pathway to combine monocular input for binocular processing?

A

V1 - primary visual cortex

79
Q

Name 4 common causes of retinal artery occlusions.

A

Hollenhorst plaque
Calcification from heart valves
Giant cell arteritis
Sickle cell anemia

80
Q

Artery occlusions cause the retina to turn what color?

A

White

81
Q

Emboli cause what type of vessel occlusion?

A

Arterial occlusions

82
Q

Which is generally larger, Hollenhorst plaques, or calcific plaques?

A

Calcific

83
Q

Hollenhorst plaques are a build-up of what?

A

Cholesterol

84
Q

Thrombi cause what type of vessel occlusion?

A

Vein occlusions

85
Q

What causes a vein occlusion?

A

Artery compresses a vein, causing the thrombus formation

86
Q

What is the largest risk factor for diabetic retinopathy?

A

Duration of DM

87
Q

What is the most common reason for legal blindness in a diabetic?

A

Macular edema

88
Q

What are the 3 series of rules for diabetic retinopathy?

A

4-2-1 rule
High risk characteristics
Definition of CSME

89
Q

What are the layers of the tear film, and what structures secrete those layers?

A

Mucin - goblet cells
Aqueous - Main lacrimal gland/glands of Krause and Wolfring
Meibum - meibomian glands/Zeis and Moll

KMK (8 decks)

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