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Neuro 2 > Cranial Nerve III, IV, and VI > Flashcards

Cranial Nerve III, IV, and VI Flashcards

1
Q

What happens to the eyes as you lateral flex head

A

The eyes rotate

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2
Q

what cranial nerves control eye muscles involved in movment

A

Oculomotor III
Trochlear IV
Abducens VI

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3
Q

What is the most common symptom of damage to these nerves

A

Double vision

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4
Q

What nerve constricts the pupil

A

Oculomotor

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5
Q

How many intrinsic ocular muscles are there

A

3

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6
Q

How many extraocular muscles are there

A

6

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7
Q

What is the only cranial nerve to exit the brainstem dorsally

A

Trochlear

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8
Q

What component of the oculomotor nerve innervates the iris sphincter and ciliary muscle

A

Parasympathetic component

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9
Q

What does the iris sphincter do

A

Contracts to constrict the pupil

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10
Q

What does the ciliary muscle contracting do to the lens

A

Causes the lens to become convex or fat

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11
Q

What does the ciliary muscle control

A

Accommodation of the lens

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12
Q

What is the radial pupillary dilator muscle innervated by

A

The ascending cervical sympathetic system

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13
Q

What does the radial pupillary dilator do

A

Dilates pupil

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14
Q

What does the ciliary muscle relaxing do to the lens

A

Causes the lens to flatten out

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15
Q

When viewing a distant object what does the lens look like

A

The lens is flat to allow the light to bend to the retina

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16
Q

When viewing a near object what does the lens look like

A

The lens is convex or fat to allow the light to be bent even more to hit the retina

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17
Q

How is light coming from far objects oriented

A

Parallel

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18
Q

How is light coming from near objects oriented

A

Straight but diverging lines

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19
Q

What are the 3 antagonistic pairs of extraocular muscles

A
  1. Lateral and medial recti
  2. Superior and inferior recti
  3. Superior and inferior obliques
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20
Q

What 3 axes does movement occur in

A

Horizontal, vertical, and torsional

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21
Q

What is torsional movement

A

Twisting movements that bring the top of the eye toward the nose or away from the nose

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22
Q

What extraocular muscles does the oculomotor nerve control (4)

A
  1. Medial rectus
  2. Inferior rectus
  3. Superior rectus
  4. Inferior oblique
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23
Q

What extraocular muscle does the trochlear nerve control

A

Superior oblique

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24
Q

What extraocular muscle does the abducens nerve control

A

Lateral rectus

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25
Q

Where is the oculomotor nucleus

A

In the midbrain at the level of the mesencephalic reticular formation (superior colliculus and red nucleus)

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26
Q

Where is the trochlear nucleus

A

Slightly caudal to the oculomotor nucleus

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27
Q

Where is the abducens nucleus

A

In the pons at the level of the paramedian pontine reticular formation, adjacent to the fasciculus of the facial nerve

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28
Q

Where is the oculomotor nerve at risk of damage

A

When it travels between the superior cerebellar artery and in posterior cerebral artery

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29
Q

Why is the oculomotor nerve at risk of damage passing through these vessels

A

If hemorrhage occurs the nerve can become compressed

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30
Q

What nuclei travel within the oculomotor nucleus (4)

A
  1. Dorsal nucleus (inferior rectus)
  2. Intermediate nucleus (inferior oblique)
  3. Medial nuclei
  4. Ventral nucleus (medial rectus)
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31
Q

What are the 2 nuclei that are part of the oculomotor nuclear complex but aren’t within the oculomotor nucleus

A
  1. Edinger-Westphal nucleus (parasympathetics)

2. Central caudal nucleus (levator palpebrae superioris)

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32
Q

What are the characteristic deficits of CN III damage (3)

A
  1. Impairment of eye movements
  2. Drooping of eyelids (ptosis)
  3. Pupillary dilation
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33
Q

What is effected when there is impairment of eye movements

A

Extraocular muscles

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34
Q

What is effected when there is drooping of the eyelids

A

Levator palpebrae superioris

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35
Q

What is effected when there is pupillary dilation

A

Iris sphincter muscle

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36
Q

What side deficits occur due to trochlear nuclei lesions

A

Contralateral

37
Q

What does the abducens nucleus and fibers of the facial nerve form

A

The facial colliculus on the floor of the 4th ventricle

38
Q

Where do fascicles of CN VI travel and exit the brain stem

A

Ventrally at the pontomedullary junction

39
Q

True or False:

Once the abducens nerve exits the brain stem it travels a long distance to the lateral rectus

A

True

40
Q

What muscles control left and right motions of the eye

A

Lateral and medial recti

41
Q

What muscles control up and down motions of the eye

A

Superior and inferior recti and obliques

42
Q

What is the primary position of the eye

A

Straight ahead, body and head erect

43
Q

What are the 4 secondary positions of the eye

A
  1. Adducted
  2. Abducted
  3. Elevated
  4. Depressed
44
Q

What are the 4 tertiary positions of the eye

A
  1. Gaze up right
  2. Gaze up left
  3. Gaze down right
  4. Gaze down left
45
Q

What is intorsion

A

Top of the eye rotating towards the nose (counter clockwise)

46
Q

What is extorsion

A

Top of the eye rotating away from the nose (clockwise)

47
Q

What are the primary, secondary, and tertiary motions of the inferior rectus

A

Primary: Depression
Secondary: Extorsion
Tertiary: Adduction

48
Q

What are the primary, secondary, and tertiary motions of the superior rectus

A

Primary: Elevation
Secondary: Intorsion
Tertiary: Adduction

49
Q

What are the primary, secondary, and tertiary motions of the superior oblique

A

Primary: Intorsion
Secondary: Depression
Tertiary: Abduction

50
Q

What are the primary, secondary, and tertiary motions of the inferior oblique

A

Primary: Extorsion
Secondary: Elevation
Tertiary: Abduction

51
Q

True or False:

Both eyes must move together

A

True

52
Q

True or False:

Muscles in both eyes are paired or yoked

A

True

53
Q

What does the muscles being paired or yoked cause

A

They both get similar stimulatory signals from the brain

54
Q

Whose law is both yoked muscles get similar stimulatory signals from the brain

A

Herring’s Law

55
Q

True or False:

Muscles in one eye are in antagonist pairs

A

True

56
Q

Whose law is when one of a pair contracts the other must relax

A

Sherrington’s Law

57
Q

What is supraduction also called

A

Elevation

58
Q

What is infraduction also called

A

Depression

59
Q

What is incycloduction also called

A

Incyclotorsion or intorsion

60
Q

What is excycloduction also called

A

Excyclotorsion or extorsion

61
Q

What are version movements

A

Movement of both eyes in the same direction

62
Q

What are the 6 version movements

A
  1. Dextroversion
  2. Levoversion
  3. Supraversion
  4. Infraversion
  5. Dextrocycloversion
  6. Levocycloversion
63
Q

What is dextroversion

A

Movement of both eyes to the right

64
Q

What is levoversion

A

Movement of both eyes to the left

65
Q

What is supraversion

A

Movement of both eyes upward

66
Q

What is infraversion

A

Movement of both eyes downward

67
Q

What is dextrocycloversion

A

Rotation of both upper cornea to the right

68
Q

What is levocycloversion

A

Rotation of both upper cornea to the left

69
Q

What are vergence movements

A

Movement of both eyes in opposite directions

70
Q

What are the 2 vergence movements

A
  1. Convergence

2. Divergence

71
Q

What is convergence

A

Adduction of both eyes towards midline

72
Q

What is divergence

A

Abduction of both eyes back to the primary position

73
Q

What muscles cause dextroversion and levoversion

A

Lateral and medial recti

74
Q

What muscles cause supraversion

A

Superior rectus and inferior oblique

75
Q

What muscles cause infraversion

A

Inferior rectus and superior oblique

76
Q

What muscles cause dextrocycloversion

A

Inferior oblique and inferior rectus of the right eye and superior oblique and superior rectus of the left eye

77
Q

What muscles cause levocycloversion

A

Superior oblique and superior rectus of the right eye and inferior oblique and inferior rectus of the left eye

78
Q

What does complete lesion to CN III cause (5)

A
  1. Ptosis
  2. External strabismus (exotropia or lazy eye)
  3. Pupilo-dilation
  4. Loss of accommodation and light reflex (constriction)
  5. Diplopia (double vision)
79
Q

What causes the pupilo-dilation with complete lesion to CN III

A

Paralysis of pupillary sphincter

80
Q

What occurs with trochlear nerve palsy (2)

A
  1. Hypertropia

2. Extorsion

81
Q

What is hypertropia

A

Misalignment of the eyes superiorly (lazy eye)

82
Q

How can the hypertropia be compensated for

A

Tucking the chin and looking up slightly

83
Q

How can the extorsion be compensated for

A

Tilting the head away from the affected eye to the opposite shoulder

84
Q

True or False:

People with trochlear nerve palsy have difficulty descending stairs

A

True

85
Q

What does the abducens nerve send an interneuron to for innervation purposes

A

The contralateral medial rectus

86
Q

What does lesion to CN VI cause

A

Patient cannot turn ipsilateral eye laterally

87
Q

What deformity can be seen in a patient with CN VI damage

A

Internal strabismus

88
Q

Why does internal strabismus occur with CN VI damage

A

Because the lateral rectus is paralyzed and does not oppose the action of the medial rectus

89
Q

What pathway does the abducens nerve send information to the contralateral medial rectus

A

Medial Longitudinal Fasciculus pathway

Neuro 2 (20 decks)

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