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SP15 Neuroanatomy - Dr. Pierson > Lecture 7 - Cranial Nerves III, IV, VI > Flashcards

Lecture 7 - Cranial Nerves III, IV, VI Flashcards

1
Q

Sensory and motor nuclei are separated in the brainstem by the _____ _____.

A

sulcus limitans

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2
Q

Cranial nerve nuclei are often _____ in the brainstem.

A

discontinuous

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3
Q

The oculomotor nerve (CN III) has a sympathetic _______ nuclei and the parasympathetic _____-______ nucleus. The trochlear nerve (CN IV) has the _______ nucleus, and the abducens nerve (CN VI) has the ______ nucleus.

A
  • oculomotor
  • Edinger-Westphal
  • trochlear
  • abducens
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4
Q

The superior rectus ______ the eye, while the inferior rectus ______ the eye.

A
  • elevates

- depresses

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5
Q

The lateral rectus ______ the eye, while the medial rectus _______ the eye.

A
  • abducts

- adducts

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6
Q

The superior oblique causes ______ ______, while the inferior oblique causes ______ ______.

A
  • internal rotation (intorsion)

- external rotation (extorsion)

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7
Q

Which 4 cranial nerves innervate the eye/surrounding muscles?

A
  • optic (CN II)
  • oculomotor (CN III)
  • trochlear (CN IV)
  • abducens (CN VI)
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8
Q

The oculomotor nerve (CN III) is easily seen in XS of the _____ ______. The trochlear nerve (CN IV) is easily seen in XS of the ______ _______. The abducens nerve is easily seen in XS of the ______ ______.

A
  • rostral midbrain
  • caudal midbrain
  • caudal pons
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9
Q

The Edinger-Westphal nucleus starts in the ______ ______, and supplies the preganglionic fibers to the ______ ganglion. Postganglionic fibers laterally wrap around the eye to innervate the ______ sphincter and the ______ muscle.

A
  • rostral midbrain
  • ciliary
  • pupillary
  • ciliary
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10
Q

The oculomotor nucleus supplies the voluntary _____ of the eye. It goes _____ and _____ to the eye.

A
  • muscles
  • superior
  • inferior
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11
Q

The ____ ____ _____ muscle of elevation for the eyelid is innervated [bilaterally/contralaterally] by the oculomotor nerve (CN III). The _____ _____ muscle, which elevates the eye, is innerated [bilaterally/contralaterally].

A
  • levator palpebrae superioris
  • bilaterally
  • superior rectus
  • contralaterally
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12
Q

The oculomotor nucleus supplies the medial rectus, inferior rectus, and inferior oblique [bilaterally/ipsilaterally]. The Edinger-Westphal nucleus innervates the ciliary ganglia [bilaterally/ipsilaterally].

A
  • ipsilaterally

- ipsilaterally

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13
Q

Within the brainstem, the oculomotor and Edinger-Westphal nuclei are very close, so a lesion affects ______ motor outputs. Lesions outside the brainstem affect the eyes _______, because the fibers for each eye are separate.

A
  • both

- ipsilaterally (only same side affected)

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14
Q

Outside the brainstem, an oculomotor lesion causing ipsilateral deviation of an eye is called _____ _____. Deviation is lateral, because the medial rectus is weakened; eyes can’t be moved ______.

A
  • lateral strabismus

- medially

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15
Q

4 internal muscles weakened by oculomotor nucleus/nerve injury.

A
  • medial rectus
  • superior rectus
  • inferior rectus
  • inferior oblique
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16
Q

An oculomotor nerve injury causing double vision is called _______. Ipsilateral levator palpebrae superioris weakness is called ______. If the pupil does not dilate on one side in response to light, it is called ______.

A
  • diplopia
  • ptosis
  • mydriasis
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17
Q

The trochlear nucleus is in the periaqueductal gray (PAG), posterolateral to the ______ ______ _______.

A

medial longitudinal fasciculus

18
Q

The trochlear nerve is unique of the cranial nerves, because it is the only one to entirely originate from a _______ nucleus, and is the only nerve on the ______ brainstem surface.

A
  • contralateral

- dorsal

19
Q

The trochlear nerve innervates the _____ ______ muscle. Trochlear fibers leave the nucleus and turn caudally in PAG, arch dorsally to _______, then leave the brainstem in the _____ - _____ junction

A
  • superior oblique
  • decussate
  • midbrain - pons
20
Q

Trochlear lesions have less noticeable deficits, since only the ______ _____ muscle is affected, moving the eyes down and laterally. The result of lesions here is ______.

A
  • superior oblique

- diplopia (double vision)

21
Q

Due to the long, inferior intracranial course of the ______ nerve, it is susceptible to increased intracranial pressure.

A

abducens

22
Q

The abducens innervates the [contralateral/ipsilateral] _____ _____ muscle, which ______ the eye.

A
  • ipsilateral
  • lateral rectus
  • abducts (ABDUCens - ABDUCt)
23
Q

The abducens nucleus is located in the floor of the ___ ventricle in the _____ ____.

A
  • 4th

- caudal pons

24
Q

Located medial to the abducens nucleus are the _____ ____ _____ and motor fibers of the ______ nerve.

A
  • medial longitudinal fasciculus (MLF)

- facial (CN VII)

25
Q

Fibers of the trochlear nerve wrap around the internal _____ of the facial nerve (CN VII). This part and the trochlear nucleus form the ______ ______. The nucleus contains motor neurons and internuclear neurons that ascend up the ______ ______ ______.

A
  • genu
  • facial colliculus
  • medial longitudinal fasciculus
26
Q

Injury to the abducens nerves causes ipsilateral _____ ______ and ______ _______ paralysis.

A
  • medial strabismus

- lateral gaze

27
Q

The medial longitudinal fasciculus is located on the _____ aspect of the brainstem.

A

posterior

28
Q

If the abducens nucleus is injured, the ipsilateral eye will not ______ past midposition, and the contralateral eye will not ______ past midposition.

A
  • abduct

- adduct

29
Q

Both eyes work together for lateral gaze. The ipsilateral eye requires the ______ rectus, while the contralateral eye requires the ______ rectus to contract simultaneously.

A
  • lateral

- medial

30
Q

The medial longitudinal fasciculus (MLF) allows coordination of _____ and _____ movement. The MLF interconnects cranial nerves ___, ___, and ___ to allow this.

A
  • head
  • eye
  • CN III
  • CN IV
  • CN VI
31
Q

Damage to the MLF causes “paralysis of the eye due to damage between the nuclei” called _______ ________.

A

internuclear ophthalmoplegia

32
Q

MLF damage removes excitatory input to ipsilateral _____ nucleus. Consequently, the eye ipsilateral to the lesion fails to move past midposition during _____ ____. Both ______ nuclei are intact, so lateral movements of both eyes are intact.

A
  • oculomotor
  • horizontal gaze
  • abducens
33
Q

The pupillary light reflex involves 4 sets of neurons:

  1. ______ _____: retinal ganglion to pretectal nuclei
  2. Pretectal nuclei to ______-_____ nuclei via the posterior commissure
  3. Preganglionic parasympathetic into _______ nerve, synapse in ciliary ganglion
  4. Postganglionic fibers in short ciliary nerves enter iris and supply the ______ __ ______
A
  • afferent limb
  • Edinger-Westphal
  • oculomotor
  • sphincter of pupillae
34
Q

Changes in optical power by the eye by modifying curvature of the lens in response to objects at varying distances is called ________.

A

accommodation

35
Q

At _____, the lens is flattened by tension on its capsule from the suspensory ligament. For _____ vision, the ciliary muscles contract, relaxing the lens suspensory ligaments. This causes the lens to _______ bulge.

A
  • rest
  • near
  • passively
36
Q

When the pupillary sphincter contracts, _____ light enters the lens of the eye. As muscle tone changes through accommodation, closer objects cause the eyes to move together as the object nears the face, a process called ________.

A
  • less

- convergence

37
Q

The process of receiving a visual stimulus and responding to it with ocular muscles is as follows:

  1. Receive signal from ________ and direct it to ipsilateral fibers of midbrain and pons
  2. Receive signals in preganglionic fibers of first _____ ventral nerve root. These then ascend the sympathetic chain to the _____ _______ ganglion.
  3. Postganglionic fibers ascend with the ______ _____ arteries
  4. Join cranial nerve ____, enter _____ nerves
A
  1. hypothalamus
  2. thoracic; superior cervical
  3. internal carotid
  4. VI (abducens); ciliary
38
Q

The eyes move as pairs. This is called _____ movement, of which there are 3 types:

  1. _______: eyes move from between targets with high speed motions called saccades
  2. _______: eyes follow a moving target through space
  3. _______: eyes stay on target of interest while the head moves. This movement involves the vestibular system, and is called the ________ reflex
A
  • conjugate
  • scanning
  • tracking
  • compensation
  • vestibulocular
39
Q

Scanning involves ______ ______ in the reticular formation. There are 4 of these, which have the movements, “left, right, up, down.”

1 & 2. _______ ______: paramedian pontine reticular formation (PPRF), each pulls eye to its own side

  1. _______ ______: midbrain, rostral interstitial nuclei of the MLF (riMLF)
  2. _______ ______: in midbrain, next to upward center
A
  • gaze centers
  • horizontal saccades
  • upward saccades
  • downward saccades
40
Q

Saccade (rapid scanning eye movement) to the Left:

  1. RIGHT eye field activates ______ paramedian pontine reticular formation (PPRF)
  2. PPRF then activates adjacent _______ neurons
  3. PPRF also signal MLF to activate the ______ nerve that supplies the medial rectus

Result: simultaneous contraction from BOTH rectus muscles (due to 2 dif cranial nerves used) results in saccade to the left

A
  1. left
  2. abducens (CN VI)
  3. oculomotor (CN III)

SP15 Neuroanatomy - Dr. Pierson (10 decks)

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