Cranial Nerve VII Facial nerve and Cranial nerve III Flashcards
Where does Cranial nerve VII emerge?
from brainstem at ventrolateral aspect of caudal pons near pontomedullary junction.
nervus intermedius
smaller root of CN VII between root of CN VII and CN VIII contains GSA SA GVE GVA
Large motor root of CN VII
SVE function
Which fossa does CN VII emerge from?
posterior cranial fossa via the internal acoustic meatus same as CN VIII
Where does CN VII go after leaving through internal acoustic meatus?
it courses through temporal bone, then exits via stylomastoid foramen
Functions of facial nerve: SVE
Muscles of facial expression (and a few others)
Functions of Facial nerve: GVE
General visceral efferents, parasympathetic inneration of lacrimal nasal palatine upper pharynx submandibular and sublingual glands
Functions of facial nerve: GSA
General somatic afferents take in sensory info from portion of external ear
Functions of facial nerve SA
Somatic afferents bring in taste info from anterior 2/3 of tongue and palate
Fuctions of facial nerve: GVA
Recurrent fiber path that follows GVE fibers
Where is the facial motor nucleus?
Pons
Describe flow of info from corticobulbar fibers from motor cortex to innervation of facial muscles
Motor cortex -> facial motor nucleus (pons contralateral some ipsilateral) -> stylomastoid foramen -> facial muscles
What would be associated with damage to RIGHT corticobulbar damage to upper motor neurons of CN VII?
Selective weakness of LEFT lower facial muscles.
What would be associated with damage to right facial nerve?
Weakness in RIGHT upper and lower facial muscles
Function of Orbicularis oculi?
closes the eye
Describe blink reflex
CN-V fibers (GSA) carry pain info from cornea to CNS (spinal trigeminal nucleus) CN VII fibers (SVE) close the eye, blink is bilateral, spinal trigeminal fibers relay through recticular formation to bilateral facial motor nuclei
Which Cranial nerves innervate skeletal muscle that control eye movements?
Oculomotor, Trochlear, Abducens
Where do cranial nerves III, IV, and VI emerge from?
Superior orbital fissure (just like cranial nerve V) which is in the sphenoid bone by the way
Which extraocular eye muscles does CN III innervate? (4)
Superior rectus, inferior rectus, medial rectus, inferior oblique
Which extraocular eye muscle does CN IV innervate
superior oblique
Which extraocular eye muscle does CN VI innervate?
Lateral rectus
What is adduction?
movement towards midline
What is abduction?
movement away from midline
What is internal/medial rotation/ intorsion
12 o clock position moves towards nose
What is external/lateral rotation/ extortion
12 oclock position moves away from the nose
Visual axis v orbital axis
visual axis is set off from orbital axis by about 23 degrees
Superior oblique (isolated)
Abducts, depresses and medially rotates eyeball. Attaches to posterior and superior to horizontal axis. Passes medial to vertical axis and attaches to superior aspect of globe, so it abducts
Inferior oblique (isolated)
Abducts elevates and laterally rotates eyeball. attaches posterior and inferior to horizontal axis, depresses posterior aspect of globe so it elevates the eye. Passes medial to vertical axis and attaches to posterior inferior aspect of globe, so it abducts the eye.
Superior rectus (isolated)
Elevates adducts and rotates eyeball medially. Passes medial to vertical axis and attaches to anterior aspect of globe, so it adducts the eye.
Inferior rectus (isolated)
depresses, adducts and rotates eyeball medially. passes medial to vertical axis and attaches to anterior aspect of globe so it adducts eye.
Medial rectus (isolated)
adducts eyeball
lateral rectus
Abducts eyeball
Intorsion of globe
muscles with medial pull above visual axis intort/medially rotate globe, so superior oblique and superior rectus
Extorsion of globe
muscles with medial pull below visual axis extort/laterally rotate globe, so inferior oblique and inferior rectus
when eye is fully adducted which muscles move it up and down?
Superior and inferior oblique, they are in parallel at this point and can be pure elevators and depressors.
When eye is fully abducted which muscles move it up and down?
superior and inferior rectus
Where is CN III nucleus?
in rostral midbrain at level of superior colliculus
Besides the 4 extraocular eye muscles what other efferent effects does CN III have?
GSE for levator palpebrae superioris muscle which elevates superior eyelid. and parasympathetic fibers GVE that pass to constrictor muscle of pupil
Are connections from oculomotor nucleus to inferior rectus, medial rectus, and inferior oblique contralateral or ipsilateral?
they are ipsilateral and leave as the oculomotor nerve through the superior orbital fissure
What do neurons on contralateral oculomotor project to?
to contralateral superior rectus muscles
From which oculomotor nuclei is the levator palpebrai superioris muscle innervated?
from bilateral oculomotor nuclei
Where do GVE fibers that eventually innervate ciliary muscles and sphincter pupillae come from and what is their path
They come from Edinger westphal nucleus, these are preganglionic sympathetic fibers that synapse on ciliary ganglion which then become postganglionic fibers and the innervate the ciliary muscles and pupil sphincter
