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Neuroanatomy > Ch 30 Eye Muscles > Flashcards

Ch 30 Eye Muscles Flashcards

1
Q

horizontal saccades (saccadic movements in the horizontal plane) are programed by the

A

nucleus of lateral gaze

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2
Q

the horizontal saccades are carried out by the

A

abducens nucleus, after it receives information from the nucleus of lateral gaze

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3
Q

the nucleus of lateral gaze and the abducens nucleus are in the

A

tegmentum of the pons

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4
Q

another name for the nucleus of lateral gaze is the __

A

nucleus of paramedian pontine, because of its paramedian position in the pons

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5
Q

the lateral rectus

A

attaches to the lateral side of the eyeball and abducts the pupil
is innervated by the abducens nucleus

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6
Q

the tegmentum of the pons

A

superior (rostrad) to the medulla

contains the abducens nucleus and the nucleus of lateral gaze

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7
Q

the medial rectus

A

adducts the eye ball

innervates by the oculomotor nucleus

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8
Q

messages from the abducens nucleus travel to the contralateral oculomotor nucleus via the

A

contralateral medial longitudinal fascicles (MLF)

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9
Q

the median longitudinal fasciculus is heavily myelinated in order to

A

well coordinate eye movement messages

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10
Q

internuclear ophthalmoplegia

A
  • damage to the medial longitudinal fasciculus
  • cannot look AWAY from the site of injury
    (left MLF injured then left eye cannot look to the right)
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11
Q

superior rectus muscle

A
  • attaches to the top of the eye
  • eye moves upward
  • innervation by CN III, oculomotor nerve
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12
Q

inferior rectus muscle

A
  • attaches tot he bottom of the eye
  • eye moves downward
  • oculomotor nucleus via CN III
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13
Q

rostral interstitial nucleus of medial longitudinal fasciculus

A
  • programs vertical saccades
  • stimulates the neurons in the oculomotor nucleus
  • purely stimulatory
  • stimulates lower motor neurons
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14
Q

interstitial nucleus of Cajal

A

inhibition of opposing muscles in the vertical saccades
receives projections from the interstitial nucleus of the MLF to inhibit correct neurons at the proper time
- inhibits lower motor neurons

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15
Q

rostral interstitial nucleus and the interstitial nucleus of cajal cross in the

A

posterior commissure of diencephalon

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16
Q

Brodmans Area 8

A
  • the frontal eye field

- controls end point of horizontal saccades through crossed projections to the paramedian poutine reticular formation

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17
Q

damage to one frontal eye field

A
  • horizontal saccades towards the opposite side to stop in the midline of the eye (can’t look away from the injury)
  • has no effect on vertical saccades (because of the crossing in the posterior commissure)
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18
Q

a few days after damage to the frontal eye field

A

the superior colliculous takes over its tasks.

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19
Q

nystagmus

A
  • eyes typically move in the opposite direction of the head movement to keep the object at the center of the retina
  • speed matches speed of head movement
  • vestibular nuclei
  • “beat” in the direction of the turning head (fast component)
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20
Q

vestibular nuclei

A

projects directly to the oculomotor, trochlear, and abducens nuclei

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21
Q

slow component of nystagmus

A

eyes move opposite to head direction

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22
Q

fast component of nystagmus

A

the eyes snap back to the center after reaching the end of their range of motion
same direction as head movement

23
Q

when the head turns to the right

A

right beating nystagmus
fast component to the right
slow component to the left
(opposite for left)

24
Q

synapses of nystagmus

A

disynaptic

1: between the vestibular ganglion and a neuron in a vestibular nucleus
1: between the fibers of the vestibular nucleus and the lower motor neuron in oculomotor, trochlear, and abducens nucleus

25
Q

control of nystagmus

A

controlled by the vestibular nucleus

the muscles are carried out by lower motor neurons

26
Q

nucleus prepositus

A
  • ability to fix ones gaze on an object
  • stops saccades via bilateral projection to the rostral interstitial nucleus of the MLF, nucleus of cajal, and nucleus lateral gaze
  • stops nystagmus toward its own side
27
Q

damage to the right nucleus prepositus causes

A

right beating nystagmus when the head is stationary (eye turns with the head)

28
Q

superior colliciulus

A
  • tracking a moving object with the eyes
  • does not project directly to the oculomotor, trochlear, and abducens nuclei
  • projects to CONTRAlateral rostral interstitial nucleus, nucleus of cajal, and nucleus lateral gaze
29
Q

parietal association cortex in brodmens area 7

A
  • send information about position and velocity of the OBJECT being tracked to the superior colliculus
  • projects to the opposite side because is crosses at a lower level
  • left area 7 and left superior colliculus are aware of the right visual field
30
Q

superior colliculus projection

A
  • projects to opposite nucleus of lateral gaze to control horizontal tracking of that visual field. (L. SC projects too R. lateral gaze to control horizontal tracking in R. visual field)
  • lesion would causes issues in the opposite visual field
  • automatic tracking can be overridden by the frontal eye fields (this makes diagnosing a SC lesion hard because the frontal eye field takes over after a few days, at first is weak but then improves)
  • extensive damage can also effect pupillary reflex because of the location of the pretectal nucleus
31
Q

damage to parietal association cortex (brodman area 7)

A
  • impossible to track objects in the opposite visual field

- frontal eye field and superior colliculus rely on it for info on objects being tracked

32
Q

pupillary reflex

A
  • constriction of the pupil in response to light
  • response of pretectal nuclei to input from the brachium of the inferior colliculus
  • consensual because projections cross in the posterior commissure with interstitial nucleus of Cajal (not consensual- damage is likely due to the posterior commissure)
  • pretectal nucleus projections must reach preganglionic parasympathetics in accessory oculomotor (Edinger Westphal Nucleus)
33
Q

pretectal nuclei

A
  • response to the input from brachium of the inferior colliculus
  • in the rostral (superior) edge of the tectum of the upper midbrain
  • in the edges of the superior colliculus
  • directs pupillary reflex to light (contraction of pupil)
  • half the projections of each cross in the posterior commissure
  • damage is argyll-robertsons pupil
34
Q

intracranial pressure

A

can push the pineal gland down on the posterior commissure causing non consentual pupillary reflex

35
Q

pupillary reflex will be abolished if

A

both pretectal nuclei are damaged

36
Q

edinger westphal nucleus

A
  • contains preganglionic parasympathetics for intraocular muscles
  • located between the oculomotor nuclei
  • accesory oculomotor
  • pretectal nucleus project here for pupillary reflex
  • rostral to superior colliculus
  • can only constrict the pupil because its only parasympathetic
37
Q

steps of pupillary reflex

A
  1. converging of the eyes on an object
  2. light or visual association cortex
  3. input from the pretectal nucleus (received from the brachium of the inferior colliculus)
  4. presynaptic parasympathetics in edinger westphal stimulate constriction of the pupil
38
Q

accommodation reflex

A
  • constriction of the pupils in response to convergence of the eyes
  • depends on input from the visual association cortex
39
Q

argyll-robertson pupil

A

accommodation reflex is present, pupillary reflex is absent

  • damage of the projections from the pretectal nucleus to the edinger-westphal nucleus
  • can be caused by tertiary syphilis or diabetes
40
Q

Weber syndrome

A
  • damage to the oculomotor nerve

- abolish accommodation and pupillary reflex

41
Q

iris control

A

preganganglionic parasympathetics from the edinger westphal nucleus travel to the ciliary ganglion in the oculomotor nerve

42
Q

ciliary ganglion

A
  • postganglionic parasympathetics fibers to the iris

- damage to ciliary ganglion impairs pupillary reflex and accommodation reflex

43
Q

preganglionic parasympathetics

A

oculomotor nerve and accessory oculomotor (edigner westphal)

44
Q

Adie’s pupil

A
  • pupillary reflex absent
  • accommodation reflex slow
  • damage to the postganglionic fibers from the ciliary ganglion to the iris
45
Q

oculomotor nerve contains

A
  • axons of lower motor neurons in the oculomotor nucleus

- axons of preganglions parasympathetic neurons in the edinger-westphal nucleus (accessory oculomotor nucleus)

46
Q

sympathetic input

A
  • dialates pupils

- controlled by superior cervical ganglion

47
Q

superior cervical ganglion

A
  • controls iris via postganglionic sympathetic fibers
  • release norepinephrine
  • dilates pupil
48
Q

constriction of the pupil

A

ciliary ganglion release acetylcholine to the iris

parasympathetics

49
Q

homatoropine

A

acetylcholine receptor blockers

dilate the pupil (because ACH constricts, so blocks ach means pupils dilate)

50
Q

superior oblique muscle

A

controlled by the opposite side trochlear nucleus

51
Q

staring

A

programmed by nucleus prepositus in the upper medulla

52
Q

automatic tracking of a moving object on the right is programmed by

A

left superior colliculus

53
Q

voluntary tracking of a moving object is programmed by

A

frontal eye field

54
Q

injury to the medial longitudinal fasciculus causes

A

internuclear ophthalmoplegia, medial rectus on the same side fails to contract .

Neuroanatomy (19 decks)

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