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Neuroanatomy > Chapter 30: Eye Muscles > Flashcards

Chapter 30: Eye Muscles Flashcards

1
Q

Most of the time, a person’s eyes rove back and forth across the field of view. Each movement is called a saccade. Since a horizontal movement must be lateral to the left or lateral to the right, the nucleus that programs _____ saccades is called the nucleus of lateral gaze.

A
  • Horizontal
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2
Q

Since lateral movement of the eyeball is carried out by the _____ nucleus, the nucleus of lateral gaze must project to the _____ nucleus.

A
  • Abducens

- Abducens

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3
Q

Horizontal saccades are programmed by the nucleus of _____ and executed by the _____ nucleus.

A
  • Lateral gaze

- Abducens

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4
Q

Both the nucleus of lateral gaze and the abducens nucleus are in the tegmentum of the _____ just rostral (superior) to the medulla.

A
  • Pons
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5
Q

The abducens nucleus lies just dorsal (posterior) to the reticular formation, but the nucleus of lateral gaze lies next to the ventrolateral (anterolateral) corner of the medial longitudinal fasciculus near the midline of the reticular formation of the _____.

A
  • Pons
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6
Q

The nucleus of lateral gaze is in the paramedian part of the _____ of the _____ anteromedial to the _____ nucleus which it controls.

A
  • Reticular formation
  • Pons
  • Abducens
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7
Q

Due to its paramedian position in the pons, the nucleus of lateral gaze is often called the nucleus of the _____ pontine _____ formation.

A
  • Paramedian

- Reticular

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8
Q

Saccadic movements in the horizontal plane are programmed by the nucleus of _____ which is also called the nucleus of the _____ formation.

A
  • Lateral gaze

- Paramedian pontine reticular

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9
Q

Since the lateral rectus muscle is attached to the lateral side of the eyeball, it abducts the pupil. Thus the lateral rectus muscle is innervated by the _____ nucleus and _____ nerve.

A
  • Abducens

- Abducens

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10
Q

The medial rectus muscle _____ the pupil.

A
  • Adducts
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11
Q

Gaze to the right requires contraction of the right _____ muscle and contraction of the left _____ muscle.

A
  • Lateral rectus

- Medial rectus

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12
Q

When some neurons in the abducens nucleus stimulate the right lateral rectus muscle, other neurons in the abducens nucleus stimulate neurons in the _____ nucleus that control the left _____ muscle.

A
  • Oculomotor

- Medial rectus

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13
Q

The neurons in the abducens nucleus that stimulate the right lateral rectus muscle and the neurons that stimulate the oculomotor neurons for the medial rectus muscle are both stimulated by fibers from the _____ formation.

A
  • Paramedian pontine reticular formation
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14
Q

The messages from the abducens nucleus to the _____ oculomotor nucleus travel in the contralateral medial longitudinal fasciculus (MLF).

A
  • Contralateral
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15
Q

The medial longitudinal fasciculus is black in sections stained with silver or iron because it is heavily _____.

A
  • Myelinated
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16
Q

Eye movements are normally well coordinated because messages between the neurons controlling extraocular muscles are conducted by the heavily myelinated _____.

A
  • Medial longitudinal fasciculus
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17
Q

If the medial longitudinal fasciculus is infarcted between the abducens nucleus and the oculomotor nucleus, the _____ will not contract when the contralateral lateral rectus contracts.

A
  • Medial rectus
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18
Q

Although the medial rectus is not paralyzed when the eyes need to converge on an object in front of them, the medial rectus seems _____ when lateral gaze is attempted away from the side of the injured medial longitudinal fasciculus.

A
  • Paralyzed
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19
Q

The fact that the medial rectus on the side of the injury cannot look away from the injury shows that the axons from the abducens nucleus to the oculomotor nucleus cross over next to the _____ nucleus.

A
  • Abducens
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20
Q

Because the apparent paralysis is due to an injury between two nuclei, it is called _____ ophthalmoplegia.

A
  • Internuclear
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21
Q

Internuclear ophthalmoplegia is unilateral if one _____ is damaged and _____ if both _____ are damaged.

A
  • Medial longitudinal fasciculus
  • Bilateral
  • Medial longitudinal fasciculi
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22
Q

If the left eye can converge but cannot look to the right when the right eye looks to the right, the patient has _____ due to a lesion in the _____ medial longitudinal fasciculus.

A
  • Internuclear ophthalmoplegia

- Left (ipsilateral)

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23
Q

The affected eye of a patient with unilateral internuclear ophthalmoplegia cannot look
_____ the side of the lesion.

A
  • Away from (contralateral to)
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24
Q

Bilateral internuclear ophthalmoplegia is more likely due to multiple sclerosis than to a stroke because the blood supply of the brain is usually _____.

A
  • Separate
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25
Q
  1. Since the superior rectus is attached to the superior surface of the eyeball, it turns the pupil _____.
A
  • Upward
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26
Q

Since the inferior rectus is attached to the inferior surface of the eyeball, it turns the pupil _____.

A
  • Downward
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27
Q

Vertical saccades must be executed primarily by the _____

and _____ muscles.

A
  • Superior rectus

- Inferior rectus

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28
Q

The superior rectus and inferior rectus muscles receive their innervation from the _____ nucleus via _____.

A
  • Oculomotor

- III (the oculomotor nerve)

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29
Q

The rostral interstitial nucleus of the medial longitudinal fasciculus programs vertical saccades by stimulating neurons in the _____ nucleus.

A
  • Oculomotor
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30
Q

Strangely, only the muscle contractions of a vertical saccade are programmed by the rostral interstitial nucleus of the _____.

A
  • Medial longitudinal fasciculus
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31
Q

The _____ nucleus of the medial longitudinal fasciculus seems to be purely stimulatory.

A
  • Rostral interstitial
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32
Q

The _____ nucleus of the medial longitudinal fasciculus is at the _____ end of the _____ fasciculus.

A
  • Rostral interstitial
  • Rostral
  • Medial longitudinal
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33
Q

Vertical saccades would be impossible if the neurons controlling opposing muscles were not _____ by neurons in the interstitial nucleus of Cajal.

A
  • Inhibited
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34
Q

The interstitial nucleus of Cajal must receive projections from the _____ nucleus of the _____ in order to be able to inhibit the right neurons at the right time.

A
  • Rostral interstitial

- Medial longitudinal fasciculus

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35
Q

The rostral interstitial nucleus of the medial longitudinal fasciculus projects to the _____ nucleus and to the _____ nucleus of _____.

A
  • Oculomotor
  • Interstitial
  • Cajal
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36
Q

When the rostral interstitial nucleus of the medial longitudinal fasciculus stimulates lower motor neurons for the superior rectus, the lower motor neurons for the inferior rectus are inhibited by the _____ nucleus of _____.

A
  • Interstitial

- Cajal

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37
Q

Since the vertical saccades are consensual, half of the projections of the rostral interstitial nucleus of the medial longitudinal fasciculus and the interstitial of Cajal must _____.

A
  • Cross
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38
Q

Since the rostral interstitial nucleus of the medial longitudinal fasciculus and the interstitial of Cajal are next to the posterior end of the diencephalon, their fibers cross in the _____ commissure (of the diencephalon).

A
  • Posterior
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39
Q

If vertical saccades of the eyes are independent instead of consensual, one should suspect damage to the _____.

A
  • Posterior commisssure
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40
Q

Brodmann’s area 8, the frontal eye field, controls the end points of horizontal saccades through crossed projections to the _____.

A
  • Paramedial pontine reticular formation (nucleus of lateral gaze)
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41
Q

Damage to one frontal eye field will cause horizontal saccades toward the _____ side to stop in the midline.

A
  • Opposite (contralateral)
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42
Q

Horizontal saccades return to normal few days after injury to the _____ because the superior colliculus takes over its tasks.

A
  • Frontal eye field
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43
Q

The frontal eye field controls vertical saccades via projections to the ipsilateral _____ of the _____ and the _____ nucleus of _____.

A
  • Rostral interstitial nucleus
  • Medial longitudinal fasciculus
  • Interstitial
  • Cajal
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44
Q

Damage to one frontal eye field has no effect on vertical saccades because the projections of the _____ nucleus of the _____ and the _____ partially _____ in the _____.

A
  • Rostral interstitial
  • Medial longitudinal fasciculus
  • Interstitial nucleus of cajal
  • Cross
  • Posterior commissure
45
Q

The eyes naturally move in a direction _____ to head movements in order to keep the same object in the center of the retina. These eye movements are called nystagmus.

A
  • Opposite (contralateral)
46
Q

The speed of _____ matches the speed of head movements because the vestibular nuclei project directly to the oculomotor, trochlear, and abducens nuclei.

47
Q

The movement of the eyes counter to the direction of head movement is the slow component of _____.

48
Q

When the slow component of nystagmus reaches the end of the eyes’ range of movement the eyes snap back to the center of their range of movement. This return is the fast component of _____.

49
Q

The _____ component of nystagmus is opposite to the direction in which the head is turning, but the _____ component of nystagmus is in the same direction as the turning of the head.

A
  • Slow

- Fast

50
Q

Nystagmus is said to “beat” in the direction of the turning of the head, which is the direction of the _____ component of _____.

A
  • Fast

- Nystagmus

51
Q

Thus, when the head turns to the right, nystagmus beats to the _____.

52
Q

The fast component of a right-beating nystagmus is to the _____, and the slow component of a right-beating nystagmus is to the _____.

A
  • Right

- Left

53
Q

Thus, turning to the left produces a _____ nystagmus, and turning to the right produces a _____ nystagmus.

A
  • Left-beating

- Right-beating

54
Q

Normal nystagmus is unusual in that it involves only 2 synapses: one between the fibers coming from the vestibular ganglion and a neuron in a vestibular nucleus and one between the fibers from the vestibular nucleus and the lower motor neuron in the _____, _____, or _____ nucleus.

A
  • Oculomotor
  • Trochlear
  • Abducens
55
Q

Although a lower motor neuron actually stimulates the extraocular muscle, a neuron in a _____ nucleus controls nystagmus.

A
  • Vestibular
56
Q

The _____ field can stop both saccadic movement and nystagmus via its projections to the contralateral nucleus prepositus in the upper medulla.

A
  • Frontal eye
57
Q

The projections of the frontal eye field to the _____ make it possible to stare at an object in the contralateral visual field.

A
  • Nucleus prepositus
58
Q

Damage to one frontal eye field or one corticobulbar tract makes it impossible to stare at an object in the _____ visual field.

A
  • Contralateral (opposite)
59
Q

The ability to fix one’s gaze on an object depends on the projections of the frontal eye field to the _____.

A
  • Nucleus propositus
60
Q

The nucleus prepositus stops _____ via bilateral projections to the rostral interstitial nucleus of the medial longitudinal fasciculus, the interstitial nucleus of Cajal, and the nucleus of lateral gaze.

A
  • Saccades (nystagmus/eye movements)
61
Q

Despite its bilateral projections to the _____ of the _____, the _____ of _____, and the nucleus of _____, each nucleus prepositus only stops nystagmus toward its own side.

A
  • Rostral interstitial nucleus
  • Medial longitudinal fasciculus
  • Interstitial nucleus
  • Cajal
  • Lateral gaze
62
Q

Damage to the left nucleus prepositus causes left-beating _____, even when the head is stationary.

63
Q

Damage to the right nucleus prepositus causes _____.

A
  • Right-beating nystagmus
64
Q

Tracking a moving object with the eyes is automatically programmed by neurons in the superior colliculus. The superior colliculus does not project directly to the oculomotor, trochlear, and abducens nuclei. The superior colliculus projects to the contralateral _____ nucleus of the _____ , _____ nucleus of _____, and nucleus
of _____ which control the oculomotor, trochlear, and abducens nuclei.

A
  • Rostral interstitial
  • Medial longitudinal fasciculus
  • Interstitial
  • Cajal
  • Lateral gaze
65
Q

The parietal association cortex in Brodmann’s area 7 sends information about the position and velocity of the object being tracked to the _____ colliculus.

66
Q

Since the tracking message will cross at a lower level, each area _____ projects to the ipsilateral _____.

A
  • 7

- Superior colliculus

67
Q

The left area 7 and the left superior colliculus are aware of only the _____ visual field.

68
Q

The left superior colliculus projects to the _____ nucleus of _____ which controls horizontal tracking in the _____ visual field.

A
  • Right
  • Lateral gaze
  • Right
69
Q

A lesion in one superior colliculus will disable tracking of an object in the _____ visual field.

A
  • Contralateral (opposite)
70
Q

The frontal eye fields can override the automatic tracking directed by the _____.

A
  • Superior colliculus
71
Q

Immediately after damage to the superior colliculus, unassisted voluntary tracking directed by the frontal eye fields in area _____ is poor.

72
Q

In a few days the frontal eye fields learn to _____ moving objects well.

A
  • Track (follow)
73
Q

Lesions confined to the superior colliculus are difficult to diagnose because the role of the superior colliculi can be taken over by the _____.

A
  • Frontal eye field
74
Q

Because both the superior colliculus and the frontal eye field rely on the _____ cortex for information about the object being tracked, damage to the _____ cortex makes it impossible to track an object in the contralateral visual field.

A
  • Parietal association

- Parietal association

75
Q

The parietal association cortex is Brodmann’s area _____.

76
Q

Damage to the superior colliculi alone is noticeable only for a few _____ after the injury.

77
Q

Constriction of the pupil in _____ light is called the pupillary reflex.

78
Q

The _____ of the _____ in bright light depends on the response of the pretectal nuclei to input from the brachium of the inferior colliculus.

A
  • Constriction (narrowing)

- Pupil

79
Q

The pretectal nuclei are in the rostral (superior) edge of the _____ of the upper midbrain.

80
Q

The pretectal nuclei direct the _____ reflex.

A
  • Pupillary (light)
81
Q

The rostral edge of the midbrain tectum is the rostral edges of the _____.

A
  • Superior colliculi
82
Q

Since the pretectal nuclei are in the edges of the superior colliculi, extensive damage to the superior colliculi is liable to interfere with the _____ reflex.

83
Q

The pupillary reflex is consensual because the projections of the pretectal nuclei are partially _____.

84
Q

Half of the projections of each pretectal nucleus cross in the _____ along with the projections of the interstitial nucleus of Cajal.

A
  • Posterior commissure
85
Q

If the pupillary reflex is not consensual, the _____ has probably been damaged.

A
  • Posterior commissure
86
Q

Intracranial pressure can push the pineal gland down on the _____ hard enough to abolish the consensuality of the pupillary reflex.

A
  • Posterior commissure
87
Q

Since half of the projections of each pretectal nucleus cross in the _____, damage to one pretectal nucleus may have no observable effect.

A
  • Posterior commissure
88
Q

If both pretectal nuclei are damaged, the _____ reflex will be abolished.

89
Q

The pupillary reflex depends on the projections of the _____ nucleus reaching preganglionic parasympathetic neurons in the Edinger-Westfall nucleus (or accessory oculomotor nucleus).

90
Q

The Edinger-Westphal nucleus contains the _____ neurons for the intraocular muscles.

A
  • Preganglionic parasympathetic
91
Q

The oculomotor nucleus extends through most of the _____, but the Edinger-Westphal nucleus is present only at a level just rostral (superior) to the height of the superior colliculus.

A
  • Upper midbrain
92
Q

The Edinger-Westphal nuclei are a pair of tiny parasympathetic nuclei located between the oculomotor nuclei at a level just rostral to the height of the _____.

A
  • Superior colliculus
93
Q

Because the neurons in the _____ nucleus are only parasympathetic, the _____ can only constrict the pupil.

A
  • Edinger-Westphal

- Edinger-Westphal nucleus

94
Q

The preganglionic parasympathetic neurons stimulate constriction of the pupils in response to input from the _____ in response to light or from the visual association cortex in response to converging the eyes on an object close to them.

A
  • Pretectal nucleus
95
Q

The _____ of the pupils in response to the convergence of the eyes is called the accomodation reflex.

A
  • Constriction (narrowing)
96
Q

The pupillary reflex depends on input to the Edinger-Westphal nuclei from the _____ nucleus, but the accomodation reflex depends input from the _____.

A
  • Pretectal

- Visual association cortex

97
Q

Argyll-Robertson’s pupil, in which the accomodation reflex is present and the pupillary reflex is absent is due to damage to the pathway from the _____ nucleus to the _____ nucleus.

A
  • Pretectal

- Edinger-Westphal

98
Q

Damage to the projections of the pretectal nucleus to the Edinger-Westphal nucleus by tertiary syphilis or diabetes results in _____ pupil.

A
  • Argyll-Robertson’s
99
Q

A.R.P. can stand for Argyll-Robertson’s pupil or _____ present.

A
  • Accommodation reflex
100
Q

PRA (ARP backwards) can stand for _____.

A
  • Pupillary reflex abset
101
Q

The preganglionic parasympathetic fibers that control the iris travel from the _____ nucleus to the ciliary ganglion in the oculomotor nerve.

A
  • Edinger-Westphal
102
Q

Damage to the oculomotor nerve (e.g., Weber’s syndrome) will abolish both the _____ reflex and the _____ reflex.

A
  • Pupillary

- Accommodation

103
Q

The preganglionic _____ fibers to the ciliary ganglion travel in the _____ nerve.

A
  • Parasympathetic

- Oculomotor

104
Q

The _____ fibers in the oculomotor nerve synapse on neurons in the ciliary ganglion whose axons are the postganglionic fibers to the iris.

A
  • Preganglionic parasympathetic
105
Q

The postganglionic parasympathetic fibers to the iris are the axons of neurons in the _____.

A
  • Ciliary ganglion
106
Q

Damage to the ciliary ganglion or to the _____ parasympathetic fibers from the ciliary ganglion to the iris will impair both the pupillary reflex and the accomodation reflex.

A
  • Postganglionic
107
Q

Damage to the _____ fibers from the _____ ganglion to the iris abolishes the pupillary reflex and slows down the accomodation reflex. This condition is called Adie’s pupil.

A
  • Postganglionic parasympathetic

- Ciliary ganglion

108
Q

The syndrome in which the pupillary reflex is absent and the accomodation reflex is slow is _____ pupil. _____ pupil is due to damage to the postganglionic fibers from the _____ ganglion to the iris.

A
  • Adie’s
  • Adie’s
  • Ciliary

Neuroanatomy (21 decks)

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