Cranial Nerves Flashcards
Corneal reflex
How?
Afferent limb
Efferent limb
Approach from the side of their eye and touch the cornea
Ophthalmic division of the trigeminal nerve
Facial nerve - orbicularis oculi contracts
If sense of FLAVOUR is lost, what nerve is most likely damaged?
CN I - Olfactory
Name the 2 muscles that open the eye
Levator palpebrae superioris muscle
Superior tarsal muscle
What nerve innervates the superior tarsal muscle?
Sympathetic nerve
What nerve innervates the levator palpebrae superioris muscle?
Parasympathetic fibres of the oculomotor nerve CN III
Describe a lower motor neurone lesion of the facial nerve and give an example of this condition
You will have ipsilateral paralysis of all of the muscles of facial expression (so there is NO forehead sparing)
Bell’s palsy
A patient has paralysis of only their lower half of their face.
Is this a UMN lesion or a LMN lesion?
Is the lesion of the contralateral or ipsilateral neurones?
Give possible sites of this lesion.
Why is the lower half of the face only affected?
UMN lesion
Contralateral
Primary motor cortex or corticobulbar tracts
Due to the upper half of the face having bilateral innervation so is unaffected by unilateral UMN lesions
What innervates the temporomandibular joint?
And where does this nerve branch off from?
Auriculotemporal nerve (mandibular branch of trigeminal nerve)
Discuss the route of olfactory nerve fibres from the roof of the nasal cavity
Go up through the cribriform plate (of the the ethmoid bone) -> olfactory bulb -> olfactory tract -> temporal lobe
Describe the route of the oculomotor nerve from the midbrain
Midbrain -> lateral wall of cavernous sinus -> superior orbital fissure -> muscles in eye orbit
Which cranial nerve has the longest intracranial route and why?
Trochlear nerve CN IV because it emerges from the dorsal aspect of the brainstem, rather than the ventral side, like the rest of the cranial nerves
What nerves and vein exit via the superior orbital fissure?
Oculomotor nerve Trochlear nerve Ophthalmic nerve Abducens nerve Superior ophthalmic vein
Describe the route of the maxillary nerve from the trigeminal ganglion
Foramen rotundum -> pterygopalatine fossa
Describe the route of the mandibular nerve from the trigeminal ganglion
Foramen ovale -> infratemporal fossa
What nerve enters the bony canal of the mandible then exits through the mental foramen as the mental nerve?
Inferior alveolar nerve
What is the motor function of the glossopharyngeal nerve?
Motor innervation to stylopharyngeus muscle (aid swallowing)
What is the autonomic function of the glossopharyngeal nerve?
Parasympathetic innervation to the parotid gland
What nerve receives general sensation from middle ear and inner tympanic membrane?
Glossopharyngeal nerve
What does the vagus nerve have general sensation to?
Lower pharynx
Whole larynx
External ear
Tympanic membrane
What does the vagus nerve have motor innervation to?
MUSCLES OF:
Pharynx
Larynx
Soft palate
What are the parasympathetic functions associated with the vagus nerve?
Innervation of:
Heart’s:
1. SAN and AVN (↓HR)
Smooth muscle in:
- GI tract (including oesophagus)
- Resp tract (including trachea)
Mucosal glands in:
- Pharynx
- Larynx
- Resp tract
- GI tract
Describe the mechanism behind a carotid sinus massage to correct supra-ventricular tachycardia.
Massaging the carotid sinus, which is innervated by CN IX, stimulates the glossopharyngeal nerve (afferent limb) to send impulses to the vagus nerve (efferent limb). Parasympathetic fibres of the vagus nerve send more impulses to the SAN and AVN, signalling a reduction in impulses released from the SAN and AVN so HR ↓
