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Neuro 2 > Visual system > Flashcards

Visual system Flashcards

1
Q

What are the 3 layers of the eye?

A

-Sclera
-Choroid
-Retina

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2
Q

What is the characteristics of the sclera?

A

-Hard and opaque
-Protective outer coat
-High water content

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3
Q

What is the characteristics of the choroid?

A

Pigmented and vascular

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4
Q

What is the characteristics of the retina?

A

-Neurosensory tissue

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5
Q

What is the uvea?

A

-Vascular coat of eyeball
-It between the sclera and retina

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6
Q

What are the 3 parts of the uvea?

A
  • Iris
  • Ciliary body
  • Choroid
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7
Q

What is the retina responsible for?

A

Responsible for capturing the light rays

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8
Q

What does the optic nerve do?

A

Transmits electrical impulses from retina to the brain

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9
Q

Where is the optic nerve found?

A

Connects to the back of the eye near the macula

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10
Q

What is the visible portion of the optic nerve called?

A

Optic disc

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11
Q

What is the macula?

A

-Small, highly sensitive part of retina responsible for detailed central vision

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12
Q

Where is the macula found?

A

Roughly in the centre of the retina

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13
Q

What is the centre of the macula called?

A

Fovea

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14
Q

Where is the blind spot?

A

Where the optic nerve meets the eye (optic disc)

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15
Q

Why is there a blind spot?

A

There are no high sensitive cells at that spot

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16
Q

What does central vision control?

A

-Detail day vision
-Colour vision
Fovea has the greatest concentration of cone receptors

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17
Q

What does peripheral vision control?

A

-Movement
-Night vision

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18
Q

How is central vision assessed?

A

Visual acuity assessment

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19
Q

How is peripheral vision assessed?

A

Visual field assessment

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20
Q

When would you get poor visual acuity?

A

Loss of foveal vision

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21
Q

What are the 4 layers of the retina?

A
  1. Retinal pigment epithelium
  2. Outer layer
  3. Middle layer
  4. Inner layer
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22
Q

What is the function of the retinal pigment epithelium?

A

Involved in transporting nutrients from choroid to retina and metabolites from retina to choroid

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23
Q

What does the outer layer of the retina contain and do?

A

-Photoreceptors (first order neuron)
-Detection of light

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24
Q

What does the middle layer of the retina contain and do?

A

-Bipolar cells (second order neuron)
-Local signal processing to improve contrast sensitivity

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25
Q

What does the inner layer of the retina contain and do?

A

-Retinal ganglion cells (third order neuron)
-Transmission of signals from the eye to the brain

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26
Q

What do the retinal ganglion cells converge to form?

A

Optic nerve

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27
Q

What are the 2 main classes of photoreceptors?

A

-Rods
-Cones

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28
Q

Are rods or cones more sensitive to light?

A

Rods

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29
Q

Do rods or cones have a faster response to light?

A

Cones

30
Q

What are rods responsible for?

A

Night vision

31
Q

What are cones responsible for?

A

-Day light fine vision
-Colour vision

32
Q

What do convex lenses do?

A

-Converging lense
-Takes light rays and brings them to a point

33
Q

What do concave lenses do?

A

-Diverging lens
-Takes light rays and spreads them outward

34
Q

What is emmetropia?

A

Parallel light falls on the retina

35
Q

What is ametropia?

A

-Mismatch between axial length and refractive power
-Parallel light rays do not fall on the retina

36
Q

What is myopia?

A

-Near sightedness
-Rays converge at a focal point anterior to retina

37
Q

What are the causes of myopia?

A

-Excessive globe length (common)
-Excessive refractive power

38
Q

What are the symptoms of myopia?

A

-Blurred distance vision
-Headache

39
Q

What is hyperopia?

A

Far sightedness

40
Q

What is hyperopia?

A

Parallel rays converge at a focal point posterior to the retina

41
Q

What are the causes of hyperopia?

A

-Excessive short globe (common)
-Insufficient refractive power

42
Q

What are the symptoms of hyperopia?

A

-Blurred near vision
-Asthenopic symptoms: eye pain, headache in frontal region, burning sensation in eyes

43
Q

What is the near response triad?

A

Adaptation for near vision

44
Q

How does the near response triad work?

A
  1. Pupillary miosis (sphincter pupillae)= increase depth of field
  2. Convergence through medial recti contracting to align both eyes to object
  3. Accommodation where circular ciliary muscles contract to increase refractive power of lens
45
Q

What is presbyopia?

A

Naturally occurring loss of accommodation (focus on near objects) due to ageing

46
Q

How is presbyopia corrected?

A

With reading glasses

47
Q

What is the visual pathway?

A
  1. Eye takes in light
  2. Impulse sent through optic nerve
  3. Optic nerve reaches optic chasm where 53% decussate
  4. Ganglion nerve fibres continue through optic tract
  5. Travel to lateral geniculate nucleus (relay centre in thalamus)
  6. Relays with optic radiation (4th order neuron)
  7. Carried to the primary visual cortex in occipital lobe
  8. Relays to extra striate cortex for higher visual processing
48
Q

What fibres originate from the nasal retina?

A

Crossed fibres

49
Q

What crossed fibres responsible for?

A

Temporal visual field

50
Q

What fibres originate from the temporal retina?

A

Uncrossed fibres

51
Q

What are uncrossed fibres responsible for?

A

Nasal visual field

52
Q

What do lesions anterior to the optic chiasm affect?

A

Visual field in one eye only

53
Q

What do lesions posterior to the optic chiasm affect?

A

Visual field in both eyes

54
Q

What does a lesion at optic chiasm cause?

A

Bitemporal hemianopia

55
Q

What is bitemporal hemianopia?

A

Loss of temporal visual fields

56
Q

What can a lesion posterior to the optic chiasm cause?

A

-Right sided lesion= left homonymous hemianopia in both eyes
-Left sided lesions= right homonymous hemianopia to both eyes

57
Q

How do we get homonymous hemianopia with macula sparing?

A

Primary visual cortex damage usually due to stroke

58
Q

How does the macula get spared in a stroke to the primary visual cortex?

A

Macula receives dual blood supply form posterior cerebral arteries from both sides

59
Q

How does the afferent pathway of the pupillary reflex work?

A
  1. Some of optic nerve exits at posterior third of optic tract
  2. Synapses at brainstem pretectal nucleus
  3. Each pathway from each eye synapses Edinger Westphal nuclei on both sides of brainstem
60
Q

How does the efferent pathway of the pupillary reflex pathway work?

A
  1. Occulomotor nerve efferent comes from Edinger Westphal nucleus
  2. Synapses at ciliary ganglion with the short posterior ciliary nerve
  3. Short posterior ciliary nerve synapses with pupillary sphincter
61
Q

How would right afferent defects present?

A

-No pupil constriction in both eyes when right eye is stimulated with light
-Normal pupil constriction in both eyes when left eye is stimulated with light

62
Q

How would right efferent defects present?

A

-No right pupil constriction whether right or left eye is stimulated with light
-Left pupil constriction in both direct or consensual constriction

63
Q

What test is used to test for relative afferent pupillary defects?

A

Swinging torch test

64
Q

What is the function of the superior rectus muscle?

A

Moves the eye up

65
Q

What is the function of the inferior rectus muscle?

A

Moves the eye down

66
Q

What is the function of the lateral rectus?

A

-Attaches on the temporal side of the eye
-Moves the eye towards the outside of the head

67
Q

What is the function of the medial rectus?

A

-Attached to the nasal side of the eye
-Moves eye toward the middle of the head

68
Q

What is the function of the superior oblique muscle?

A

-Attached high on the temporal side of the eye and passes under the superior oblique
-Moves eye down and out
-Travels through the trochlea

69
Q

What is the function of the inferior oblique muscle?

A

-Attached low on the nasal side of the eye
-Passes over the inferior rectus
-Moves eye up and out

70
Q

What muscles are innervated by the occulomotor nerve?

A

-Superior rectus
-Levator palpebrae superioris
-Inferior rectus
-Medial rectus
-Inferior rectus

71
Q

What muscle is innervated by the trochlear nerve?

A

Superior oblique

72
Q

What muscle is innervated by the abducens nerve?

A

Lateral rectus

Neuro 2 (10 decks)

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