Lecture 7 - Cranial Nerves III, IV, VI Flashcards
Sensory and motor nuclei are separated in the brainstem by the _____ _____.
sulcus limitans
Cranial nerve nuclei are often _____ in the brainstem.
discontinuous
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.
- oculomotor
- Edinger-Westphal
- trochlear
- abducens
The superior rectus ______ the eye, while the inferior rectus ______ the eye.
- elevates
- depresses
The lateral rectus ______ the eye, while the medial rectus _______ the eye.
- abducts
- adducts
The superior oblique causes ______ ______, while the inferior oblique causes ______ ______.
- internal rotation (intorsion)
- external rotation (extorsion)
Which 4 cranial nerves innervate the eye/surrounding muscles?
- optic (CN II)
- oculomotor (CN III)
- trochlear (CN IV)
- abducens (CN VI)
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 ______ ______.
- rostral midbrain
- caudal midbrain
- caudal pons
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.
- rostral midbrain
- ciliary
- pupillary
- ciliary
The oculomotor nucleus supplies the voluntary _____ of the eye. It goes _____ and _____ to the eye.
- muscles
- superior
- inferior
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].
- levator palpebrae superioris
- bilaterally
- superior rectus
- contralaterally
The oculomotor nucleus supplies the medial rectus, inferior rectus, and inferior oblique [bilaterally/ipsilaterally]. The Edinger-Westphal nucleus innervates the ciliary ganglia [bilaterally/ipsilaterally].
- ipsilaterally
- ipsilaterally
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.
- both
- ipsilaterally (only same side affected)
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 ______.
- lateral strabismus
- medially
4 internal muscles weakened by oculomotor nucleus/nerve injury.
- medial rectus
- superior rectus
- inferior rectus
- inferior oblique
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 ______.
- diplopia
- ptosis
- mydriasis
The trochlear nucleus is in the periaqueductal gray (PAG), posterolateral to the ______ ______ _______.
medial longitudinal fasciculus
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.
- contralateral
- dorsal
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
- superior oblique
- decussate
- midbrain - pons
Trochlear lesions have less noticeable deficits, since only the ______ _____ muscle is affected, moving the eyes down and laterally. The result of lesions here is ______.
- superior oblique
- diplopia (double vision)
Due to the long, inferior intracranial course of the ______ nerve, it is susceptible to increased intracranial pressure.
abducens
The abducens innervates the [contralateral/ipsilateral] _____ _____ muscle, which ______ the eye.
- ipsilateral
- lateral rectus
- abducts (ABDUCens - ABDUCt)
The abducens nucleus is located in the floor of the ___ ventricle in the _____ ____.
- 4th
- caudal pons
Located medial to the abducens nucleus are the _____ ____ _____ and motor fibers of the ______ nerve.
- medial longitudinal fasciculus (MLF)
- facial (CN VII)
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 ______ ______ ______.
- genu
- facial colliculus
- medial longitudinal fasciculus
Injury to the abducens nerves causes ipsilateral _____ ______ and ______ _______ paralysis.
- medial strabismus
- lateral gaze
The medial longitudinal fasciculus is located on the _____ aspect of the brainstem.
posterior
If the abducens nucleus is injured, the ipsilateral eye will not ______ past midposition, and the contralateral eye will not ______ past midposition.
- abduct
- adduct
Both eyes work together for lateral gaze. The ipsilateral eye requires the ______ rectus, while the contralateral eye requires the ______ rectus to contract simultaneously.
- lateral
- medial
The medial longitudinal fasciculus (MLF) allows coordination of _____ and _____ movement. The MLF interconnects cranial nerves ___, ___, and ___ to allow this.
- head
- eye
- CN III
- CN IV
- CN VI
Damage to the MLF causes “paralysis of the eye due to damage between the nuclei” called _______ ________.
internuclear ophthalmoplegia
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.
- oculomotor
- horizontal gaze
- abducens
The pupillary light reflex involves 4 sets of neurons:
- ______ _____: retinal ganglion to pretectal nuclei
- Pretectal nuclei to ______-_____ nuclei via the posterior commissure
- Preganglionic parasympathetic into _______ nerve, synapse in ciliary ganglion
- Postganglionic fibers in short ciliary nerves enter iris and supply the ______ __ ______
- afferent limb
- Edinger-Westphal
- oculomotor
- sphincter of pupillae
Changes in optical power by the eye by modifying curvature of the lens in response to objects at varying distances is called ________.
accommodation
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.
- rest
- near
- passively
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 ________.
- less
- convergence
The process of receiving a visual stimulus and responding to it with ocular muscles is as follows:
- Receive signal from ________ and direct it to ipsilateral fibers of midbrain and pons
- Receive signals in preganglionic fibers of first _____ ventral nerve root. These then ascend the sympathetic chain to the _____ _______ ganglion.
- Postganglionic fibers ascend with the ______ _____ arteries
- Join cranial nerve ____, enter _____ nerves
- hypothalamus
- thoracic; superior cervical
- internal carotid
- VI (abducens); ciliary
The eyes move as pairs. This is called _____ movement, of which there are 3 types:
- _______: eyes move from between targets with high speed motions called saccades
- _______: eyes follow a moving target through space
- _______: eyes stay on target of interest while the head moves. This movement involves the vestibular system, and is called the ________ reflex
- conjugate
- scanning
- tracking
- compensation
- vestibulocular
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
- _______ ______: midbrain, rostral interstitial nuclei of the MLF (riMLF)
- _______ ______: in midbrain, next to upward center
- gaze centers
- horizontal saccades
- upward saccades
- downward saccades
Saccade (rapid scanning eye movement) to the Left:
- RIGHT eye field activates ______ paramedian pontine reticular formation (PPRF)
- PPRF then activates adjacent _______ neurons
- 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
- left
- abducens (CN VI)
- oculomotor (CN III)
