Cranial Nerves Part 2 Flashcards
1
Q
What are the locations of cranial nerves VII-XII?
A
See lecture notes
2
Q
Where is the facial nerve (VII)?
A
- The facial nerve emerges from the pons, and passes through the internal acoustic meatus.
- The facial nerve runs through the petrous temporal bone and exits the skull via the stylomastoid foramen
3
Q
Where does the facial nerve emerge from and run through?
A
- Facial nerve does not come out of internal acoustic meatus (this is your earhole)
- Actually does a right angle turn and travels inferiorly to emerge out of base of temporal bone
- The facial nerve emerges from the pons, and passes through the internal acoustic meatus.
- The facial nerve runs through the petrous temporal bone and exits the skull via the stylomastoid foramen
4
Q
What are the branches and functions of the facial nerve?
A
- The facial nerve has many functions and a number of branches:
o Chordae tympani (parasympathetic and special sensory)
o Greater petrosal (parasympathetic)
o Motor root
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical - Greater petrosal nerve splits from the rest of the facial nerve within the temporal bone and runs superiorly to innervate the lacrimal gland (just lateral to eyelid/top left in picture) with parasympathetic fibres.
- Chordae tympani splits from the rest of the facial nerve within the temporal bone and runs into the infratemporal fossa to run towards the tongue and provide the anterior 2/3 with special sensory fibres. On its way it also provides the sublingual and submandibular glands with parasympathetic fibres
See notes for pictures
5
Q
What are the branches of the motor portion of the facial nerve?
A
- The motor portion of the facial nerve runs out of the stylomastoid foramen and splits into 5 branches which collectively innervate the muscles of facial expression. o Temporal o Zygomatic o Buccal o Marginal mandibular o Cervical
6
Q
What are the muscles of facial expression?
A
- Orbicular oris and buccinator muscles are not muscles of mastication but do help to keep food in the mood
- Orbicularis occuli muscle closes the eyes (with levator palpebrae superioris opens eye)
- Frontalis muscle raises the eyebrows – linked to occipitalis muscle at back of head via an aponeurosis of the scalp
7
Q
What are the two types of facial nerve palsy?
A
- 2 causes:
o Bell’s Palsy (idiopathic/no known cause but fairly common and often resolves itself)
o Stroke - Major difference in how these pathologies present
- In Bell’s Palsy, lesion is in lower motor neuron to the facial nerve so causes total paralysis of facial muscles on affected side of face
- In strokes, lesion is in upper motor neuron to the facial nerve so lower motor neuron is still innervated and upper half of face retains movement (forehead sparing)
8
Q
Where is the glossopharyngeal nerve (IX)
A
- The glossopharyngeal nerve emerges from the lateral surface of the medulla oblongata with the vagus nerve, they both exit the skull via the jugular foramen
- The glossopharyngeal nerve has general sensory and motor fibres as well as parasympathetic and special sensory fibres. (essentially all the possible types of fibres it could have)
o It provides the posterior 1/3 of the tongue with special sensory and general sensory supply.
o It provides the parotid gland with parasympathetic supply.
o The Glossopharyngeal nerve provides general sensory fibres to the carotid body and sinus which provide information about blood pressure and oxygen saturation respectively.
o It provides the pharynx with general sensory supply, and one muscle of the pharynx, stylopharyngeus (runs from styloid to pharynx) with motor supply.
9
Q
Where is the vagus nerve (X) and what does it do?
A
- The glossopharyngeal nerve emerges from the lateral surface of the medulla oblongata with the vagus nerve, they both exit the skull via the jugular foramen.
- The Vagus nerve contains general motor, sensory and parasympathetic fibres.
- The Vagus nerve provides the soft palate, pharynx and oesophagus with motor supply
- The hard palate is composed of the maxilla and palatine bones, posterior to this is the soft palate, this is composed of muscles covered by mucous membrane.
- The soft palate elevates during swallowing to prevent food entering the nasal cavity.
- The muscles of the soft palate are innervated by the Vagus nerve.
- The Vagus nerve provides the larynx with general sensory and motor supply.
- The vagus nerve is the major parasympathetic nerve of the body.
See lecture notes for pictures
10
Q
Where is the spinal accessory nerve (XI) and what does it do?
A
- The spinal accessory emerges from the first 5-6 cervical segments and then runs superiorly through the foramen magnum then leaves the skull via the jugular foramen.
- It contains motor fibres.
- Innervates:
o Sternocleidomastoid (if both of these contract then you nod your head)
o Trapezius - Spinal accessory nerve runs through the middle between these muscles
11
Q
Where is the hypoglossal nerve (XII) and what does it do?
A
- The hypoglossal nerve emerges from the anterior aspect of the medulla oblongata and runs through the hypoglossal canal.
- It contains motor fibres.
- Innervates the genioglossus muscle in the tongue
- Can test the nerve by asking patient to stick their tongue out
- If they have a lesion in the hypoglossal nerve on one side or the other, then their tongue will point to one side when they stick it out
o For a hypoglossal nerve lesion, the tongue will point towards the lesion (e.g. palsy of left hypoglossal nerve means tongue will point to the left
o If they have a vagus nerve injury, then the opposite is true for the uvula (e.g. palsy of left vagus nerve means uvula will deviate to the right)
12
Q
What provides sympathetic innervation to the head and neck? What happens when these are disrupted?
A
- Sympathetic innervation to the head and neck does not come from cranial nerves but from the thoracic region of the spinal cord.
- The sympathetic fibres travel into the head with the ICA.
- Disruption to the ascending sympathetic nerves causes Horner’s syndrome.
o Constricted pupil
o Anhydrosis
o Partial ptosis
