Cranial nerves Flashcards
Type(s) of information (modality) from the olfactory nerve?
SVA (special visceral afferent)
Visceral because the sense of smell is from epithelia where things are dissolved in solution)
Where are the olfactory receptors located?
Around the superior nasal conchae
What path does the olfactory nerve follow from the receptors?
- Receptors at superior nasal conchae
- Olfactory bulb (through cribriform plate of the ethmoid bone)
- Mostly through the lateral olfactory stria
- To the primary olfactory area and the uncus
Why is there a strong emotional response to many olfactory stimuli?
Due to the connections of the olfactory pathways strong association with the limbic system, more specifically the amygdala (emotion) and the hippocampus (memory)
What type(s) of information (modality) is carried by the optic nerve?
SSA - Special Somatic afferent
Fibres from which field of eye remain uncrossed and which cross at the optic chiasm?
Fibres from the Nasal field cross
Fibres rom the Temporal field do not and join with Nasal field fibres to form the optic tract.
What is the path that the optic nerve follows from the receptors in the retina?
Ganglionic layer of cells in retina
The optic nerve
The optic chiasm (nasal fibres cross)
The optic tract
The Lateral Geniculate Nucleus of the Thalamus
Genicular-calcarine tract
Only 80% of fibres from the optic tract terminate at the LGN in the thalamus, where do the other 20% go, what are they involved in?
The other 20% travel to the edinger westphal nucleus at the level of the superior colliculus, where they are involved in visual reflexes like the accommodation reflex, and pupillary light reflex.
What type(s) of information (modality) is carried by the occulomotor nerve?
GSE and GVE
General Somatic Efferent as it carries motor innervation to some of the extra-oscular muscles
GVE as it also has parasympathetic fibres that travel to the ciliary ganglion in the orbit
Where is the oculomotor nerve nucleus?
The periaqueductal grey matter of the midbrain (surrounding the central aqueduct at the level of the superior colliculus
What nerve innervates the muscle that lifts the eyelid and what muscle is this?
The oculomotor nerve and it is called levator palpabrae superioris.
What extrinsic muscles of the eye does the occulomotor nerve innervate?
Superior rectus
Medial Rectus
Inferior Rectus
Inferior oblique
What divisions are there of the occulomotor nerve?
Superior branch
Inferior branch
Ciliary ganglion?
What is the type of information (modality that travels in the trochlear nerve?
GSE - General somatic efferent
Innervates one extra-occular muscle
Where is the trochlear nerve nucleus located and what direction do the nerve fibres leave?
In the midbrain at the level of the inferior colliculus, the fibres pass out the dorsum of the brainstem (the only nerve to do this)
What extra-occular muscle does the trochlear nerve innervate?
Superior oblique
What is the course the trochlear nerve takes from the brainstem to the orbit?
emerges from dorsal surface of the midbrain and runs along the tentorium cerebelli, it travels through the cavernous sinus and then out the superior orbital fissure.
Constriction of the superior oblique muscle causes the pupil to move in what way?
Downwardly and laterally
What are the type(s) of information relayed by the trigeminal nerve? Why?
SVE and GSA
GSA due to the general sensory innervation of the face by the three divisions
SVE as the mandibular division innervates the muscles of mastication which are derived from the pharyngeal arches and therefore it is SVE not GSA
What is the principle sensory nucleus of the trigeminal nerve?
The afferents of the trigeminal nerve from the trigeminal ganglion terminate here
What type of fibres from the trigeminal nerve do not synapse in the trigeminal ganglion?
Fibres carrying proprioception.
What are the three branches of the opthalmic nerve?
Lacrimal, Frontal, nasociliary
Where is the anatomical location of the lacrimal and frontal branches of V1?
Lacrimal runs along lateral rectus
Frontal runs along Levator Palpabrae Superioris
What is the course of the nasociliary branch of V1?
Enters between lateral rectus and the occulomotor nerve, it then courses along the medial wall of the orbit and enters the ethmoidal foramen
What are the two divisions of the maxillary nerve?
The middle meningeal nerve and the infraorbital nerve.
What is the course the maxillary nerve follows once it leaves the brainstem (pons)?
Leaves the cranium via foramen rotundum,
It then passes through the cavernous sinus
and through the pterygopalatine fossa to enter the orbit via the infraorbital fissure
here it becomes known as the infraorbital nerve and enters the infraorbital canal
Where does the mandibular nerve exit the cranium and what are the two main divisions?
Exits via foramen ovale and divides into the inferior alveolar nerve and the lingual nerve.
What route does the lingual nerve take once it branches from the mandibular nerve (V3)?
Descends across the lateral pterygoid muscle and is joined by the chorda tympani (CNVII)
Passes over the superior pharyngeal constrictor and styloglossus muscle
Then lies between the Styloglossus and Submandibular gland
Travels to the tip of the tongue
What route does the inferior alveolar nerve take once it branches from the mandibular nerve (V3)?
Descends along with but lateral to the lingual nerve,
Enters the mandibular foramen
Enters the face via the mental foramen to serve the skin of the lower face/lip and mandibular teeth.
What is the sensory function of the opthalmic nerve?
Sensory innervation to:
The bulb of eye Conjunctiva of eye Lacrimal gland Nasal cavity Skin of forehead and nose Mucous membranes of paranasal air sinuses
What is the parasympathetic function of the lacrimal nerve, where does it receive these Psymp fibres?
The parasympathetic fibres from the pterygopalatine ganglion transmitted to the lacrimal gland via a branch of V2 give secretomotor function to the lacrimal gland.
What is the significance of long and short ciliary nerves?
Long Ciliary nerves extend from the nasociliary nerve and contain sensory and motor function, sympathetic fibres cause pupillary dilatation, short ciliary nerves come from the ciliary ganglia and are entirely sensory and carry parasympathetic fibres from the superior cervical ganglion.
Areas of the face covered by the maxillary nerve? (some is okay)
Skin on the side of the nose Cheek Skin of lower eyelid and conjunctiva Upper lip Naso-pharynx maxillary sinus dura in middle cranial fossa skin over anterior temple
What division of the trigeminal nerve carries both motor and sensory fibres?
Mandibular
What is the sensory innervation of the mandibular nerve?
Cheek Lower lip ear External acoustic meatus (ear canal) Anterior two thirds of tongue Mandibular teeth
What are the muscles of mastication and what nerve are they innervated by specifically?
Temporalis
Masseter
Lateral and medial pterygoid.
Innervated by the mandibular nerve.
What type of information (modality) is relayed by the abducent nerve?
GSE - innervates one extra-occular muscle
What nerves travel in the cavernous sinus?
Occulomotor
Trochlear
Opthalmic
Abducent
Aneurysm of what artery in the cavernous sinus can make the abducent nerve vulnerable to compression?
The internal carotid artery
What route does the abducent nerve takes once it leaves the brainstem?
The nucleus is located at the floor of the fourth ventricle
Emerges at the border between the midbrain and the pons
Passes superiorly and anteriorly to pierce the dura and runs close to the internal carotid artery in the cavernous sinus
It passes through the superior orbital fissure to reach the orbit
What is the Medial Longitudinal Fasciculus (MLF)?
It is a tract of nerve fibres (or nerve) that travels between the abducent nucleus and the contralateral occulomotor nerve nucleus and co-ordinates the smooth flowing movements of the eye (lateral conjugate gaze), co-ordinading the lateral and medial rectus muscles to do so.
Where does the major input for the MLF come from and where does it then travel to co-ordinate lateral conjugate gaze?
the input comes from the contralateral frontal eye field, and is located in the general motor cortex, it then travels to the PPRF…
What does the PPRF do for lateral conjugate gaze?
The PPRF then submits fibres to the ipsilateral CNVI nucleus (lateral rectus) and the contralateral CNIII nucleus (medial rectus)
A lesion of the MLF is usually caused by what? What does this cause?
Usually caused by MS
This then causes an inability to generate smooth gaze movements and adduct and nystagmus
What types of information (modalities) are relayed by the facial nerve?
GVE - due to parasympathetic innervation to glands
SVE - due to innervation of muscles of facial expression (2nd pharyngeal arch)
GSA - sensory to areas around the ear
GVA - sensory to viscera such as the soft palate and pharynx
SVA - Taste sensation to anterior 2/3rds of tongue
What type of nucleus is the facial nerve nucleus and how is it divided?
It is a motor nucleus only and is divided into a small part that innervates the upper facial muscles and a larger part that innervates the lower facial muscles
What route does the facial nerve nuclei take to leave the pons and how does it work with the sensory fibres of the facial nerve?
The Facial nerve loops around the abducent nerve and leaves the caudal pons, emerging with the nervus intermedius (sensory component of the facial nerve)
What are the two divisions (roots) of the facial nerve that leave the pons?
The nervus intermedius (Sensory)
The motor root
Once the facial nerve has left the pons what route does it’s two roots take?
Both roots travel together as the facial nerve when they emerge at the gap between the pons and inferior cerebellar peduncle
They exit the cranium via the internal acoustic meatus and then course along the petrous part of the temporal bone in the facial canal
They eventually fuse and become the facial nerve
What nerve passes through the parotid gland but does not innervate it?
Facial nerve
The motor branch of the facial nerve passes through what foramen to innervate the muscles of facial expression?
The stylomastoid foramen
What is the area where the two roots of the facial nerve fuse called?
The geniculate ganglion
The preganglionic and special sensory fibres of the facial nerve leave the skull before the motor branch exits via the petrotympanic fissure what is this nerve called and what does it fuse with? What parasympathetic ganglion does it go onto supply?
Called the chorda tympani, it fuses with the lingual nerve and it goes on to supply the submandibular ganglion
The greater petrosal nerve leaves what ganglion from the facial nerve to go to what parasympathetic ganglion?
Leaves the geniculate ganglion to go to the pterygopalatine ganglion
What does the pterygopalatine ganglion supply?
The Lacrimal gland, nasal mucosa and pharyngeal/palatine glands.
What are the branches of the facial nerve that leave the stylomastoid foramen to supply the muscles of facial expression?
What’s the mnemonic?
Temporal Zygomatic Buccal Mandibular Cervical
To Zanzibar By Motor Car
Apart from the muscles of facial expression what muscles does the facial nerve supply?
Posterior belly of digastric
Stylohyoid
Stapedius
What are the functions of the chorda tympani nerve?
Will go to supply the submandibular ganglion and the special sensory fibres will supply taste to the anterior two thirds of the tongue.
Why would a lesion involving corticobulbar fibres produce paralysis only on the contralateral lower side of the face?
Because the lower side receives contralateral input only and the upper receives bilateral
What type of information (modality) does the vestibulocochlear nerve receive?
SSA - special sensory afferent
What is an acoustic neuroma?
Where does it almost always originate from?
What symptoms does it cause?
Benign schwann cell tumour
Vestibular nerve
Progressive deafness, dizziness and facial weakness
What is the vestibular-spinal tract?
The extra-pyramidal tract that runs from the vestibular apparatus to synapse on lower motor neurones of some skeletal muscle to maintain balance and posture.
From the middle ear what rout does the vestibular and cochlear nerves take to reach the brainstem?
The Cochlear and Vestibular nerves fuse to become one and leave through the external acoustic meatus, these pass through the subarachnoid space and join the brainstem at the cerebellar pontine angle
From the brainstem where do fibres of the cochlear nerve relay auditory information to?
Enter the brainstem at the cerebellar-pontine angle and then go on to to synapse at the ventral or dorsal cochlear nuclei
Auditory information is eventually relayed through the thalamus bilaterally to the primary auditory areas in the cerebral cortex
Wernicke’s area is located where?
Auditory association cortex
What modalities are carried by the glossopharyngeal nerve?
Both Motor and sensory:
GVE - parasympathetic to parotid gland
SVE - Innervates stylopharyngeus (from 3rd arch)
GSA - General sensory from around the ear,
GVA - general sensation to posterior one third of the tongue, and carotid sinus
SVA - Taste to posterior 1/3rd of tongue
Route of glossopharyngeal nerve once leaving the brainstem?
leaves as small rootlets lateral to the olives of the medulla
Exits via the jugular foramen close to the vagus nerve and eventually contributes the the pharyngeal plexus.
What one muscle does the glossopharyngeal nerve innervate?
Stylopharyngeus
What is the branch of the glossopharyngeal nerve that innervates the upper portion of the face (ear, parotid gland)?
tympanic nerve
What nerve innervates the carotid sinus?
Glossopharyngeal nerve
What modalities does the vagus nerve carry?
Both (boobs)
GVE - smooth muscle and glands of digestive tract
SVE - muscles of 4th and 6th pharyngeal arches
SVA - base of tongue and larynx
GSA - ear and external acoustic meatus
GVA - mucous membranes
Where do the vagus nerve’s rootlets emerge from the brainstem?
emerge behind (rostral) to the glossopharyngeal rootlets, between olive and inferior cerebral peduncle
What nerve roots join the vagus nerve proximal to the inferior ganglion (sensory)
Spinal accessory
Branches of the vagus nerve in the neck?
Pharyngeal
Superior laryngeal
Superior cardiac
Recurrent laryngeal nerve
What two divisions of the superior laryngeal nerve are there?
Internal (superior)
External (posterior)
The pharyngeal plexus supplies all the muscles of what 4 things?
Soft palate (apart from one), Larynx, Pharynx, Upper oesophagus
What nerve innervates tensor veli palatini, the only muscle of the soft palate not innervated by the vagus?
The trigeminal nerve (mandibular)
What does the recurrent laryngeal nerve innervate?
Intrinsic muscles of the larynx (except cricothyroid)
Modality of the spinal accessory nerve?
SVE - joins vagus to supply muscles of the 4th and 6th pharyngeal arches.
sternocleidomastoid and trapezius are also supplied by it.
What is the nucleus ambiguus?
Long nucleus that distributes fibres via the Vagus, Glossopharyngeal and spinal accessory nerves.
What are the two roots of the spinal accessory nerve?
The Cranial and spinal (C1-5) root
Where does the cranial root of the spinal accessory nerve emerge?
Lateral aspect of the medulla near the vagus roots
Where do the spinal roots of the accessory nerve emerge and how do they join the cranial roots?
Emerge C1-5 and proceed up through the jugular foramen to join cranial root
Route of the spinal accessory nerve as it leaves the jugular foramen?
Descends along the internal carotid, posterior to the stylohyoid and digastric to supply the sternocleidomastoid
Then passes through the posterior triangle to innervate the trapezius muscle
Modality that the hypoglossal nerve transmits?
GSA - Innervation to most skeletal muscles of the tongue
Where is the hypoglossal nerve nucleus?
Between the dorsal motor nucleus of the vagus nerve and the medulla
Journey of the hypoglossal nerve after it exits the brainstem?
Arises as rootlets between the pyramids and the olives
Runs lateral to lingual and inferior alveolar branches of the mandibular nerve
exits the cranium through the hypoglossal canal and is joined by a branch of c1 and 2
Runs superficial to the external carotid and then deep to digastric (anterior belly) and styloglossus to reach the tongue
What muscle of the tongue does the hypoglossal nerve not innervate? What is it innervated by?
Palatoglossus (vagus)
What are the extrinsic muscles of the tongue?
Hyoglossus
Styloglossus
Palatoglossus (vagus)
Genioglossus
If the upper motor neurones of the hypoglossal nerve were interrupted in the corticobulbar tract what would this result in?
Deviation of the tongue to the paralysed side (not bilateral in the hypoglossal nerve)
