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Neuro B3 - WLB > Week 3 - Fitzakerely (Vision) > Flashcards

Week 3 - Fitzakerely (Vision) Flashcards

1
Q

What kind of neurotransmitters are involved in striated muscle eyelid movements?

A

ACh –> nicotinic

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2
Q

What kind of neurotransmitters are involved in smooth muscle eyelid movements?

A

Norepinephrine –> alpha-1 adrenergic

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3
Q

Other than spontaneous tear production, reflexive tear production, and tear production as a response to emotional stimuli, how is tear production partially regulated?

A

Parasympathetic Nervous System

ACh –> muscarinic

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4
Q

What are the two fundamental protective mechanisms for the eye?

A
  1. Blinking
  2. Tear production
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5
Q

What is the term used to describe an overflow of tears that is due to overproduction or blocked drainage?

A

Epiphora

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6
Q

What two parts of the eye focus light on the retina?

A

Cornia & Lens

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7
Q

What do you call an eye that is refracting normally?

A

Emmetropic

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8
Q

Is the refractive power greater in the cornea or the lens?

A

Cornea

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9
Q

What is accomodation?

A

focusing power of the lens can be adjusted to allow near vision

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10
Q

What two muscles of the eyelid are striated?

A

Orbicularis oculi (OO)

&

Levator palpebrae superioris (LPS)

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11
Q

What is the smooth muscle of the eyelid?

A

Superior tarsal muscle (ST)

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12
Q

What types of muscles are activated/inactivated when they eyelid is “maintaining ocular opening”?

A

Tonic activation of LPS and ST

Inactivation of OO

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13
Q

What types of muscles are activated/inactivated when they eyelid is performing “gentle opening/closing”?

A

Activation/Inactivation of LPS

Inactivation of OO

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14
Q

What types of muscles are activated/inactivated when they eyelid is “adjusting to changes in globe position”?

A

Activation/Inactivation of LPS

Inactivation of OO

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15
Q

What types of muscles are activated/inactivated when they eyelid is “blinking/firm closure of they eyes”?

A

OO Activation

Inhibition of LPS

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16
Q

Spontaneous blinking originates in premotor brainstem structures that are highly influence by what type of activity?

A

Dopaminergic

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17
Q

Which is faster: blink reflex or spontaneous blinking?

A

blink reflex

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18
Q

Where are lipids secreted from in tear production?

A

Oil glands in the eyelids

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19
Q

What kind of fluid does the lacrimal gland secrete?

A

Aqueous-based solution

(contains lysozyme and other enzymes that provide protection against infection)

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20
Q

What does the conjunctiva secrete in tear production?

A

Mucous

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21
Q

Does basal tear production increase or decrease with age?

A

Decrease

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22
Q

What kind of stimulation produces epiphora?

A

Parasympathetic

(increase lacrimal gland activity or facilitates closure of the lacrimal duct passage)

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23
Q

What system mediates epiphora due to strong emotional responses?

A

Limbic system (hypothalamus)

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24
Q

What happens to the image as light passes through the cornea and the lens?

A
  1. inverted and reversed
  2. refracted
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25
Q

Objects in the left visual field are detected by cells in what two retinal fields?

A

Left nasal retina & Right temporal retina

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26
Q

What one significant modification occurs in the topographic mag established in the retina?

A

Information from the nasal regions of the retinas cross in the optic chiasm.

This ensures that info from the left visual field is processed in the right visual cortex!

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27
Q

What is the refractive power of the eye in diopters?

A

+59 to +75D

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28
Q

What is the refractive power of the cornea?

A

+44D

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29
Q

In hyperopia (far-sightedness), images are focused where?

A

Behind the retina, because the axial length of the eye is less than the focal length

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30
Q

Hyperopia (far-sightedness) can be caused by axial hyperopia. What is this?

A

eyeball is too short

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31
Q

Hyperopia (far-sightedness) can be caused by refractive hyperopia. What is this?

A

refractive power of the eye is abnormall weak

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32
Q

How is hyerpopia (far-sightedness) corrected?

A

Convex lenses

(positive diopters)

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33
Q

In myopia (near-sightedness), images are focused where?

A

in front of the retina

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34
Q

How is myopia (near-sightedness) corrected?

A

Concave lenses

(negative diopters)

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35
Q

What is astigmatism?

A

curvature of the cornea or lens is not equal in all meridians, causing unequal refraction and making a portion of the image out of focus

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36
Q

Age, hysical trauma, radiation, or high glucose concentration in aqueous humor of diabetic patients can all cause what to happen resulting in cataracts?

A

Opacity of the lens

37
Q

Blurred vision with reduced malleability causes what symptoms in presbyopia?

A

Decrease in the accommodative power of the lens

(condition similar to hyperopia)

38
Q

What shape is the lens when focusing light on the retina from a distant source?

A

relatively flat

39
Q

What shape is the lens when focusing light from a a near source onto the retina?

A

stronger (rounder)

40
Q

Stimulation of what causes the lens to flatten?

A

Sympathetic nerves (ß2 receptors)

  • causes relaxation of the ciliary muscle
  • see distant sources
41
Q

Stimulation of what causes the lens to become more rounded?

A

Parasympathetic ciliary ganglion neurons

(via CN III, muscarininc receptors)

-contraction of ciliary muscle –> relaxes the circular fibers

42
Q

What regulates the amount of light entering the eye to keep it within the dynamic range of the photoreceptors?

A

Iris sphinter

43
Q

Myadriasis results from reflex activation of sympathetic fibers that stimulate the dilator pupillae muscles via what mechanism?

A

Alpha-1 receptor

44
Q

The pupillary light reflex causes contraction of what muscles via muscarinic receptor activation?

A

Sphincter pupillae muscles

45
Q

What is the afferent and efferent pathway in miosis (pupillary constriction)?

A

Afferent: Optic Nerve (CN II)

Efferent: stimulation of parasympathetic fibers in Oculomotor Nerve (CN III) –> contraction of the sphincter pupillae muscles

46
Q

What type of glaucoma is most common?

A

Open angle glaucoma (slowly developing problem)

47
Q

What causes open angle glaucoma?

A

Increase in aqueous humor production

OR

Blockage of outflow

48
Q

The loss of vision in glaucoma is cased by what?

A

Compression of the:

  • cornea: edema –> decreased transparency (“halo effect”)
  • retina: damages photoreceptors
  • optic nerve: neural conduction compromised
  • arterial supply: causes necrosis
49
Q

What cells secrete aqueous humor?

A

Ciliary epithelium

50
Q

How does the sympathetic nervous system affect aqueous humor formation (inflow)?

A
  1. Epinephrine –> stimulate ß2 receptors –> increase [cAMP] –> INCREASES FLOW
  2. Norepinephrine –> stimulate alpha-2 receptors –> decrease [cAMP] –> REDUCES PRODUCTION
51
Q

What does ciliary epithelium secrete in order to increase aqueous humor volume via osmosis?

A

Cl-

(carbonic anhydrase –> HCO3- –> Cl- secretion)

52
Q

What are the two mechanisms of aqueous humor drainage (outflow)?

A
  1. Canal of Schlemm (1°) - contraction of the sphincter pupillae
  2. Uveoscleral outflow - reabsorption of aqueous humor through the ciliary muscle (facilitated by prostaglandins)
53
Q

What two things are used to treat glaucoma by working to increase outflow?

A
  • Cholinergic agonists
  • Prostaglandins
55
Q

The outer layer of the retina has what primary cells?

A

Photoreceptors - rods & cones

56
Q

The middle layer of the retina has what type of cells that receive input from the rods or cones and generate graded potentials?

A

Bipolar cells

57
Q

The inner layer of the retina has what type of cells that generate action potentials and whose axons form the optic nerve?

A

Ganglion cells

58
Q

What is the frequency of light perceived as when detected by photoreceptors?

59
Q

What is the intensity of light perceived as by photoreceptors?

A

brightness

60
Q

Light represents what kind of energy with properties of both particles (photons) and waves?

A

Electromagnetic

61
Q

What is the wavelength of visible light that humans can see?

62
Q

What kind of photoreceptors can detect light as dim as 1 photon?

A

Dark-adapted photoreceptors (RODS)

63
Q

What type of photoreceptor is responsible for scotopic vision, has a single pigment type, is more photopigment, high sensitivity, lower temporal resolution, and poor spatial resolution???

64
Q

What type of photoreceptor is responsible for photopic vision, has three pigment types, less photopigment, lower sensitivity, high temporal resolution, and good spatial resolution?

65
Q

Which type of vision/photoreceptor is better for discrimination of surfaces and movement under bright light conditions?

A

Photopic Vision - Cones

66
Q

What are the three types of cones and their corresponding wavelengths?

A

Blue - short

Green - medium

Red - long

67
Q

What does “acuity” in the visual system refer to?

A

The ability to discriminate fine details of the visual scene.

68
Q

What clinical tool is used to assess spatial acuity?

A

Snellen eye charts

(Low acuity = 20/200, High acuity = 20/15)

69
Q

Critical fusion frequency is where a flashing light appears to be continuous rather than repetitive, which is related to what type of visual acuity?

A

Temporal Acuity

70
Q

What type of acuity is described as the ability to distinguish differences in the wavelength of the stimuli (e.g. cone excitation in red rooms)?

A

Spectral Acuity

71
Q

In rods, what does the activation of rhodopsin ultimately lead to?

A

Closure of cyclic nucleotide (cGMP) gated Na+ channels and hyperpolarization of the photoreceptor.

72
Q

What is the resting potential of a rod photoreceptor?

A

about -40 mV

73
Q

What is the current called that occurs in the absence of light when cGMP-dependent Na+ channels are open and the membrane is depolariezed?

A

“Dark” current

74
Q

What kind of channels contained in rods tend to stabilize the membrane potential at about -70 mV?

A

Potassium “leak” channels

(reversal potential for K+ ~-70mV)

75
Q

During hyperpolarization of the photoreceptor membrane, are K+ channels open or closed?

A

Still open!

77
Q

What is the result of hyperpolarization of the photoreceptor membrane?

A

Decrease in the release of excitatory neurotransmitter

78
Q

What cells gradually lose their ability to respond to light in Retinitis pigmentosa?

A

photoreceptors

79
Q

What is the first and second symptoms of Retinitis pigmentosa?

A

1st = night blindness

2nd = tunnel vision

80
Q

Retinopathy is a non-inflammatory damage to the retina (especially the macula), that often results from what?

A

Blocked blood supply

81
Q

What are the first symptoms of vitamin A deficiency?

A
  • Night blindness (due to loss of 11-cis-retinol)
  • dry skin/hair
  • broken fingernails
  • decreased ability to fight infections
82
Q

All visual pigments consist of an opsin combined with what chromophore?

A

11-cis-retinal

83
Q

Can 11-cis-retinal be synthesized by humans?

A

No!

-must be converted from Vitamin A

84
Q

The visual cycle consisting of the bleaching and recycling of retinoids between the photoreceptors and the retinal pigment epithelium (RPE) is present in which type of photoreceptor?

A

Rods

(cones use Muller’s cells - glia - for storage of photopigments)

85
Q

Age-related macular degeneration (AMD) begins with the appearance of yellow deposits in the macula between the RPE and the choroid called what?

A

Drusen

(thought to be cholesterol deposits)

86
Q

What happens in “dry” advanced AMD?

A

Atrophy of the RPE followed by loss of photoreceptors

87
Q

What causes “wet” advanced AMD?

A

abnormal growth of blood vessels in the choroid in response to tissue damage

(leads to irreversible leaking and scarring damage)

88
Q

What kind of vision loss is characteristic of “wet” advanced AMD?

A

Loss of central vision

(expands to include the entire retina)

89
Q

What is currently being used to treat macular degeneration?

A

anti-VEGF antibodies

Neuro B3 - WLB (11 decks)

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