Flashcards in Exam #2: Cranial Nerves IV Deck (50):
List the five functional components of the facial nerve (CN VII).
What is the SVE component of the facial nerve?
Brachimotor innervation (motor) to the muscles of facial expression
What are the muscles of facial expression that are innervated by the facial nerve (CN VII)?
Posterior belly of digastric
What is the SVA function of the facial nerve (CN VII)?
Taste from the anterior 2/3 of the tongue
What is the GVE function of the facial nerve (CN VII)?
PNS to the:
- Sublingual glands
What is the GSA function of the facial nerve (CN VII)?
General sensation from the skin:
- Posterior to the ear
- External auditory meatus
What is the GVA function of the facial nerve (CN VII)?
Visceral sensation from the:
- Nasal cavity
- Soft palate
- Adjacent pharyngeal wall
Where does the facial nerve emerge from the brain?
Ventrally at the Cerebello-pontine angle--which is lateral to the abducens
What are the two roots of the facial nerve?
1) Facial nerve proper i.e. motor branch
2) Nervus intermedius
What specifically does the "Facial Nerve Proper" consist of?
Axons whose cell bodies originate from the facial nucleus
What is the function of the "Nervus Intermedius?"
- SVA, GSA, & GVA from neurons originating in the geniculate nucleus
- GVE from the superior salivary nucleus
Where does the facial nerve initially pass through as it leaves the brain? What nerve accompanies it?
The facial nerves passes through the internal acoustic meatus w/ vestibulocochlear nerve to enter the facial canal
Where is the internal acoustic meatus?
Petrous portion of the temporal bone in the skull
What is the swelling of the facial nerve in the facial canal?
Geniculate ganglion, which is the ONLY sensory ganglion of the facial nerve
What is the name of the sensory ganglion associated with the facial nerve?
What are the names of the two PNS ganglia associated with the facial nerve?
1) Pterygopalatine ganglion
2) Submandibular ganglion
What does the Pterygopalatine ganglion consist of?
Cell bodies of post-synaptic PNS neurons terminating in the:
1) Lacrimal gland
2) Nasal mucous membrane
3) Minor salivary gland
*****Note that b/c of this the Pterygopalatine ganglion is also referred to as the "hay fever ganglion."
What are the functions of the Pterygopalatine ganglion?
1) Lacrimal gland= tear formation
2) Nasal mucous membrane= nasal secretions
3) Minor salivary gland= salivary secretion
What does the Submandibular ganglion consist of?
Cell bodies of post-synaptic PNS neurons terminating in the:
1) Submandibular gland
2) Sublingual gland
What is the function of the Submandibular ganglion?
Submandibular gland & sublingual gland are BOTH involved in salivation
What is the chorda tympani?
- Nerve that carries taste sensation from the anterior 2/3 of the tongue
- Joins the facial nerve (cranial nerve VII) inside the facial canal
What is the nerve to the stapedius?
- Part of the facial nerve that innervates the stapedius m.
- Functions to dampen loud noises
What happens when the stapedius is paralyzed?
Through what foramen does the facial nerve exit the skull?
What are the three nuclei associated with the facial nerve?
2) Superior salivary
What does the facial nucleus contain?
Cell bodies of motor neurons (LMNs)
What does the superior salivatory nucleus contain?
Cell bodies of pre-synaptic PNS neurons that synapse with the:
1) Pterygopalatine ganglia
2) Submandibular ganglia
What does the solitary nucleus contain?
This is the nucleus that receives the central processes of taste fibers from the tongue
What is crocodile/ aligator tear syndrome?
Lesion in the facial nerve proximal to the geniculate ganglion
- Pre-ganglionic axons regenerate but make a wrong turn
- Axons that should go to the submandibular gland via the chorda tympani
- However, instead they join the greater petrosal nerve & go to t he pterygopalatine ganglion
****When the person starts eating, instead of producing saliva, the person produces tears on the affected side of the face
What are the two tracts associated with the facial nerve?
1) Solitary Tract
2) Spinal Tract of V
What is the Solitary Tract?
This is the tract that carries taste sensation from the anterior 2/3 of the tongue to the thalamus & hypothalamus
*****This tract mediates visceral responses (I.E VOMITING) to unpleasant stimuli.
What is the Spinal Tract of V?
*****The facial nerve does NOT have a pain nucleus
- Instead it relays nociception from the facial nerve to the spinal tract of V (Trigeminal nerve)
What is the only cranial nerve to have a pain nucleus?
CN V (Trigeminal)
What is the difference between the innervation of the upper & lower halves of the facial nucleus?
Upper= bilateral corticonuclear projections
Lower= contralateral corticonuclear projections ONLY
What is the pyramidal system? What type of smile is generated by the pyramidal system?
Conscious, voluntary control of facial movement that results in an "imitation smile."
What structures do corticonuclear fibers pass through as they descend to the facial nucleus?
What happens when there is a UMN lesion at the level of the genu?
What is the alternate pathway to the facial nucleus?
This is a pathway distinct from the pyramidal system that goes from:
1) Frontal lobe & basal ganglia
2) Reticular formation
3) Facial nucleus
5) Muscles of facial expression
What type of smile is produced by the alternate pathway to the facial nucleus?
A patient s/p CVA with asymmetric smile has a symmetric smile in response to the sight of his granddaughter. What pathways is responsible for this?
CVA caused damage to the pyramidal system but the "Alternate pathway" is intact
Outline the corneal blink reflex.
Afferent fibers = ophthalmic division of CN V (V.1)
Efferent fibers= CN VII-->orbicularis oculi
What is the difference between the direct & concensual pathway?
Direct= blink reflex in stimulated eye
Consensual= blinck reflex in unstimulated eye
What happens when there is a lesion of V.1 in the blink reflex?
Stimulation of affected eye= no blink in either eye
Unaffected eye= bilateral blinking of BOTH eyes
What happens when there is a lesion of CN VII in the blink reflex?
Affected= blink in opposite eye ONLY
Unaffected= blink in ONLY the stimulated eye
How does the pupillary light reflex compare to the corneal light reflex?
- Afferent= optic
- Efferent= CN III
*****However, other general concepts (esp. in regards to lesions) remain the same
Describe the typical presentation of Bell's Palsy.
Complete facial paralysis on the side of the face IPSILATERAL.
Is Bell's Palsy an upper or lower motor neuron lesion?
How does the presentation of Bell's Palsy change if the lesion is in the facial canal vs. distal to the facial canal?
In the facial canal=
- Dry eye
- Pain behind the ear
- Diminished taste sensation
Distal= paralysis ONLY
Match the branches of the facial nerve that are effected to the symptoms of: dry eye, hyperacusis, pain behind the ear, & diminished taste sensation seen in Bell's Palsy w/ lesion in the facial canal.
- Dry eye= petrosal
- Hyperacusis= nerve to stapedius
- Pain behind the ear= posterior auricular (geniculate ganglion)
- Diminished taste sensation= chorda tympani