W1: Cranial nerves Flashcards
Order
Olfactory Optic OculomotorTrochlear Trigeminal Abducens Facial Vestibulocochlear GlossopharyngealVagus Accessory Hypoglossal
Mnemonic for sensory, motor or both
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Which cranial nerves are not organised in the brainstem?
CN1 and CN2 → originate in the forebrain
What is a cranial nerve nucleus?
A collection of neurons in the brainstem that is associated with one or more cranial nerves
What does the sulcus limitans do?
Separates the cranial nerve motor nuclei (medial) from sensory nuclei (lateral)
Which cranial nerves are found laterally in the brainstem?
Sensory
Which cranial nerves are found medially in the brainstem?
Motor
What are the sensory cranial nerve nuclei?
Trigeminal sensory nucleus Vestibular nucleus and cochlear nucleus Nucleus solitarius
Describe the trigeminal sensory nucleus?
- large → runs the length of the brainstem - carry general sensory information (touch, pressure, pain, temperature) from the head enter through the trigeminal nerve
Describe the vestibular and cochlear nuclei
- termination of fibres conveying the special senses of motion/positional sense and hearing - from the vestibulocochlear nerve
What terminates in the nucleus solitarius?
visceral afferents, including taste fibres
What three groups can motor cranial nerve nuclei be divided into?
- nuclei of the somatic efferent cell column (near the midline)- nuclei of the branchiomotor cell column (furthest out)- nuclei of the parasympathetic cell column
What are the nuclei of the somatic efferent cell column?
- Oculomotor nucleus - Trochlear nucleus - Abducens nucleus - Hypoglossal nucleus
What are the nuclei of the branchiomotor cell column?
Trigeminal motor nucleus Facial motor nucleus Nucleus ambiguus
What are the nuclei of the parasympathetic cell column?
- Edinger-Westphal nucleus - Superior and inferior salivary nuclei- Dorsal motor nucleus of the vagus
Draw the nuclei
OneNote - under anatomy
Describe the oculomotor nucleus
Efferents run in the oculomotor nerve to innervate the EXTRAOCULAR MUSCLES (levator palpebrae, superioris muscle, superior rectus, inferior rectus, medial rectus and inferior oblique) except the superior oblique and the lateral rectus
Describe the trochlear nucleus
fibres leave in the trochlear nerve and innervate the superior oblique muscle of the eye
Describe the abducens nucleus
efferent run in the abducens nerve and innervate the lateral rectus muscle
Describe the hypoglossal nucleus
innervates the intrinsic and extrinsic muscles of the tongue via the hypoglossal nerve
What does the branchiomotor cell column innervate?
Striated muscles derived from the embryonic branchial (pharyngeal) arches
Describe the trigeminal motor nucleus
supplies fibres to the trigeminal nerve and innervates muscles of mastication, tensor tympani etc
Describe the facial motor nucleus
innervates the muscles of facial expression and the stapedius muscle via the facial nerve
Describe the nucleus ambiguus
Motor fibres to the glossopharyngeal, vagus and cranial part of the accessory nerve to innervate muscles of the pharynx and larynx
What do the nuclei of the parasympathetic cell column consist of?
Preganglionic parasympathetic neurones that send axons into the III, VII, IX and X cranial nerves
Describe the Edinger-Westphal nucleus
leave the brainstem in the oculomotor nerve and pass to the ciliary ganglion in the orbit, within which they synapse, from here, postganglionic fibres innervate the sphincter pupillae and ciliary muscles within the eye
Describe the superior and inferior salivary nuclei
Superior → supplies preganglionic fibres to the facial nerve
Inferior → glossopharyngeal nerve
Describe the dorsal motor nucleus of the vagus
fibres leave in the vagus nerve and are widely distributed to thoracic and abdominal viscera §
Foramen associated with olfactory nerve
Cribiform plate
Foramen associated with optic nerve
Optic canal
Foramen associated with oculomotor
Superior orbital fissure
Foramen associated with trochlear
Superior orbital fissure
Foramen associated with trigeminal
Superior orbital fissure (opthalmic)Foramen rotundum (maxillary)Foramen ovale (mandibular)
Foramen associated with abducens
Superior orbital fissure
Foramen associated with facial
Internal auditory meatus
Foramen associated with vestibulocochlear
Internal auditory meatus
Foramen associated with glossopharyngeal
Jugular foramen
Foramen associated with vagus
Jugular foramen
Foramen associated with accessory
Jugular foramen
Foramen associated with hypoglossal
Hypoglossal canal
Describe the path of the olfactory nerve
olfactory receptors in nasal epithelium/mucosa → axons penetrate cribiform plate → olfactory bulb → olfactory tract → this can split into lateral stria (carries axons to the primary olfactory cortex, located within the uncus of the temporal lobe) and the medial stria (carries axons across the medial plane of the anterior commissure, where they meet the olfactory bulb of the opposite side)
What do the fila olfactoria synapse with in the olfactory bulb and what do they form?
synapse with mitral cells to form synaptic glomeruli
Describe the optic nerve
optic nerve leaves the orbit via the optic canal → optic chiasm (partial decussation) → lateral geniculate nucleus (relay to visual cortex), pretectal nucleus (reflexive eye movements), suprachiasmatic nucleus (sleep-wake)- will cover optic nerve in more detail in vision module
What nerves are involved in control of eye movement?
- oculomotor (III)- trochlear (IV)- abducens (VI)
Tests for oculomotor, trochlear and abducens nerves
Examine pupillary reflexes and eye movements
Describe path of oculomotor nerve
oculomotor nucleus → leaves the cranial cavity via the superior orbital fissure → divides into superior (superior rectus and levator palpabrae superioris) and inferior (inferior rectus, medial rectus and inferior oblique + preganglion to ciliary ganglion)
Describe the functions of the muscles the oculomotor nerve innervates
Superior rectus → elevates the eyeball
Levator palpabrae superioris → raises the upper eyelid
Inferior rectus → depresses the eyeball
Medial rectus → adducts the eyeball (or medially rotates it)
Inferior oblique → elevates, abducts and laterally rotates the eyeball
Describe the parasympathetic inneravion in the oculomotor nerve
Originates in the Edinger-Westphal nucleus - sphincter pupillae → constricts the pupil- ciliary muscles → contracts, causes lens to become more spherical (more for short-range vision) → this is the accomodation reflex
Which branch of the oculomotor nerve do the pre-ganglionic parasympathetic fibres travel in? Where do they synpase?
InferiorIn the ciliary ganglion (behind the orbit)
What happens following damage to cranial nerve III
- DOWNWARD and LATERAL deviation of the eye due to unopposed action of the lateral rectus and superior oblique - DILATED PUPIL- loss of levator palpebrae causes drooping of eyelid → ptosis
At what level of the brainstem is the oculomotor nucleus?
Level of superior colliculus
Mnemonic for cranial nerves controlling eye movement
LR6 (lateral rectus - VI)SO4 (superior oblique - IV)ATR3 (all the rest - III)
Describe pathway of trochlear nerve
arises in trochlear nucleus of brain → decussate → lateral wall of cavernous sinus (along with oculomotor nerve, abducens nerve, the ophthalmic and maxillary branches of the trigeminal and internal carotid) → enters orbit through superior orbital fissure → innervates superior oblique
Damage to trochlear nerve
DIPLOPIA WHEN LOOKING DOWNWARD AND MEDIALLY
eyeball deviates upward and slightly inward
pts have trouble w stairs and tilt head away from affected side
At what level of the midbrain is the trochlear nucleus?
At the level of the inferior colliculus
Which is the only cranial nerve to emerge from the dorsal aspect of the brainstem?
Trochlear
3 functions of superior oblique
- internal rotation (intorsion)- depression- laterally rotates
What can the peripheral aspect of the trigeminal ganglion give rise to?
3 divisions:1) ophthalmic (V1)2) maxillary (V2) 3) mandibular (V3)
What are the three nuclei that the trigeminal sensory nucleus can be divided into?
- nucleus of the spinal tract of the trigeminal - principal sensory nucleus- mesencephalic nucleus
Which division of the trigeminal nerve pass through the lateral wall of the cavernous sinus?
V1 and V2
Discuss path of V1
superior orbital fissure → gives off 3 branches → nasociliary, lacrimal, frontal
What does the lacrimal branch do?
- runs outside the annulus of Zinn on the temple (LATERAL SIDE) side of the superior orbital fissure → pierces through the lacrimal gland & gives off a branch to supply the SKIN of the superior palpebrae and underlying CONJUCTIVA
What does the frontal branch do?
- Runs through the superior orbital fissure outside the annulus of Zinn, medial to the lacrimal nerveBranches- supra-trochlear nerve - supplies conjuctiva and skin of palpebrae (same as lacrimal) & SKIN OF FOREHEAD- supra-orbital - conjuctiva and skin of palpebrae (again) & skin of the forehead & TOP OF THE HEAD
What does the nasociliary branch do?
runs between the superior and inferior branch of the oculomotor nerve inside of the annulus of ZinnBranches1. short ciliary nerves & long ciliary nerves (cornea)2. posterior and anterior ethmoidal nerves (the sinus)3. anterior ethmoidal branches further and supplies the nose 4. infero-trochlear nerve → medial upper eyelid & lacrimal sac & lacrimal caruncleJUST REMEMBER LACRIMAL
What are the 3 nerves that run through the superior orbital fissure but outside the annulus of Zinn?
Lacrimal Frontal Trochlear LIVER FAILURE TEST
Where does V2 go through after the cavernous sinus?
Foramen rotundum (although there is a branch before it enters - DURAL BRANCH - that supplies the dura mater)
Describe V2 innervation after entering the foramen rotundum
- Infraorbital nerve → maxilla and upper lip
- Zygomatic nerve (temple, cheek)These move through inferior orbital fissure
- Alveolar nerve (hard palate, molars)
- Palatine → nasal cavity and palate
Where does V3 move though in the skull?
Foramen ovale
Describe sensory part of V3
- external ear & temple region
Describe motor part of V3
- Muscles of mastication 2. Through mandibular foramen → lower teeth (sensory), skin of the chin (sensory), muscles surrounding hyoid bone (these are motor)3. lingual nerve → ANTERIOR 2/3 OF TONGUE (SENSORY)
Describe termination of thermoceptive and nocicpetive fibres of the trigeminal nerve?
terminate in the spinal nucleus → second order axons project to the contralateral thalamus
Where do proprioceptive axons for spindles and golgi organs in the muscles of mastication terminate?
in the mesencephalic trigeminal nucleus
What is sensory trigeminal innervation responsible for?
toothacheheadache migraine trigeminal neuralgia
How is trigeminal sensory innervation tested?
integrity and symmetry of pain and light tough from all three areas of the face
How is trigeminal motor innervation tested?
jaw opening against resistance, and examining for symmetry and strength
What does the abducens nerve innervate?
Lateral rectus (motor)
Describe path of abducens nerve
abducens nucleus in the pons → moves in Dorello’s canal → IN THE CAVITY OF THE cavernous sinus → superior orbital fissure → lateral rectus
What does the lateral rectus do?
Abduct the eyeball (rotate gaze away from the midline)
Damage to cranial nerve 6
medial deviation of the eye due to unopposed action of the medial rectus
Test for abducens nerve
Examine pupillary reflexes and eye movements
What pharyngeal arch is the facial nerve associated with?
2nd
Describe broadly what the different divisions of the facial nerve do? Describe their pathways
Motor: muscles of facial expression, digastric, stylohyphoid and stapedius Originates in facial motor nucleus → goes around and behind CNVI (facial colliculus) → internal acoustic meatus → facial canal (branch from stapedius) → gives off branches:- temporal → forehead + eyebrow + eye- zygomatic → eye + cheek - buccal → mouth- marginal mandibular → chin- cervical → neck
Sensory: small area around the concha of the auricle & internal acoustic meatus- ear area → geniculate ganglion → internal acoutic meatus → spinal nucleus of trigeminal systemSpecial sensory: TASTE sensation to anterior 2/3 of the tongue (VIA CHORDA TYMPANI)Taste buds → petrotympanic fissure → posterior and anterior cannaliculi → facial canal → internal coustic meatus → NTS
Parasympathetic: supplies many of the glands of the head and neck, including:- submandibular and sublingual salivary glands (VIA CHORDA TYMPANI AND SUBMANDIBULAR GANGLION)- nasal, palatine and pharyngeal mucus glands -lacrimal glands (VIA PTERYGOPALATINE GANGLIA) Superior salivary nucelus → internal acoustic meatus → facial canal → petrotypanic fissure → submandibular & sublingual gland (submandibular ganglion) - sensory so opposite directionAlso → through hiatus → foramen lacerum → pterygopalatine fossa → pterygopalatine ganglion → inferior orbital fissure → lacrimal gland + nasal glands + palatine)
Origins of motor facial nerve
Facial motor nucleus
Origins of parasympathetic facial nerve
Superior salivatory nucleus
Origins of sensory facial nerve component
NTS
Evaluating facial nerve lesions
observing the action of facial muscles [closing eyelids, puffing cheeks, symmetry of motions] - facial muscles are differently affected by peripheral and central nerve lesions • Lower face paralysis indicates a central lesion • Entire face paralysis - peripheral nerve lesion
What may lesions of the facial nerve lead to?
Bell’s palsy → loss of control of facial muscles on one side of face Can have hyperacusis
Describe hyperacusis
The loss of stapedius control can occur due to facial nerve palsies and leads to increased sensitivity to certain sound frequencies (may become too painful or loud)
Describe nerves supplying the pharyngeal arches
1 - trigeminal2 - facial 3 - glossopharyngeal4 - vagus6 - vagus
What is the chorda tympani?
chord that moves from the posterior to the anterior wall of the tympanic cavity - consists of sensory (taste) and parasympathetic (glands) facial nerve
Where does the vestibulocochlear originate?
- vestibular = vestibular nuclei complex-cochlear - central and dorsal cochlear nucleithese combine in the pons to form the vestibulocochlear nerve
Pathway of vestibular nerve
hair cells → internal acoustic meatus → vestibular nucleus in the medulla (composed of superior, inferior, lateral, medial) → four destinations:1. lateral vestibular nucleus (some from medial) → lateral vestibulospinal tract2. inferior cerebellar peduncle - flocculonodular lobe → fastigial nucleus (can also return fibres to the vestibular nuclei)3. Medial vestibular nucleus → nuclei of abducens → connections with contralateral oculomotor and trochlear → coordination of eye and head movements (this is the medial longitudinal fasciculus)4. to thalamus VPM → internal capsule → cortex
Describe pathway of cochlear nerve
organ of corti → spiral gangia → internal acoustic meatus → dorsal and ventral cochlear nuclei 1. dorsal nuclei → contralateral nucleus of lateral lemniscus 2. ventroposterior nucleus → carry on upwards3. anterovental nucleus → superior olivary nucleusThese all form a tract called the LATERAL LEMNISCUS → inferior colliculus → medial geniculate nucleus (ears are lateral so nucleus is medial) → superior temporal gyrus
Describe acoustic neuromas
Most common tumours of ear - grow in the auditory canal due to Schwann cells - loss of hearing and diequilibrium
Tests for vestibulocochlear nerve
audiometry, use of tuning fork to distinguish sensorineural andconductive hearing loss
Tests for vestibular function
caloric or rotational tests; nystagmus
Draw the effects of oculomotor, trochlear and abducens lesions on the eyes
OneNote
Summarise the functions of the glossopharyngeal nerve and pathways
Sensory: Innervates the oropharynx, carotid body and sinus, posterior 1/3 of the tongue, middle ear cavity and Eustachian tube→ spinal nucleus of the trigeminal nerve (middle ear)→ posterior 1/3 of tounge, oropharynx, baroreceptors and chemoreceptors (carotid sinus+body) → jugular foramen → NTS & dorsal nucleus of vagus
Special sensory: Provides taste sensation to the posterior 1/3 of the tonguePoster tongue → jugular foramen → NTS
Parasympathetic: Provides parasympathetic innervation to the parotid gland.Inferior salivatory nucleus → jugular foramen → through the tympanic cavity → haitus of lesser petrosal nerve → foramen ovale → parotid gland
Motor: Innervates the stylopharyngeus muscle of the pharynx
Nucleus ambiguus → jugular foramen → stylopharyngeus (pulls pharynx upwards)
Test for cranial nerve IX and X
Gag reflex - afferents are carried by the glossopharangeal nerve, with the motor efferents by the vagus
Functions and pathway of vagus nerve
Sensory: Innervates the skin of the external acoustic meatus and the internal surfaces of the laryngopharynx and larynx. → jugular foramen → spinal nucleus of the trigeminal nerve Provides visceral sensation to the heart and abdominal viscera.
Special Sensory: Provides taste sensation to the epiglottis and root of the tongue.→ jugular foramen → NTS
Motor: Provides motor innervation to the majority of the muscles of the pharynx, soft palate and larynx.→ nucleus ambiguus → pharyngeal constrictors & speech production w/ larynx
Parasympathetic: Innervates the smooth muscle of the trachea, bronchi and gastro-intestinal tract and regulates heart rhythm.
Which nerve supplies the laryngeal muscles which control the vocal folds?
Recurrent laryngeal nerve
Describe lesions of vagus nerve
Lesions centrally, or unilateral peripheral lesions tend to produce minimal effects due to the bilateral innervation of PS viscera
What does the accessory nerve innervated?
Sternocleidomastoid and trapezius muscles
Describe path of accessory nerve
Cranial part leaves nucleus ambiguus → jugular foramen → combines with the vagus nerve → pharyngeal constrictors Spinal part = originates from C1-5/6 spinal roots → foramen magnum → jugular foramen → descends along the internal carotid → reaches sternocleidomastoid (also gets innervation straight from C2 and C3)Trapezius gets branches from C3 and C4
Tests for accessory
Actions of sternomastoid and trapezius muscles
What are the actions of sternocleidomastoid and trapezius muscles?
trapezius = elevates scapula sternocleidomastoid = rotation of head to contralateral side and flexion of the neck
What is the function of the hypoglossal nerve?
Innervation of all extrinsic and intrinsic muscles of the tongue (apart from palatoglossus which is CN X)
Discuss path of hypoglossal
hypoglossal nucleus → hypoglossal canal → crosses external carotids → mves towards the tongue
Lesion of hypoglossal
lesions of the primary motor cortex/internal capsule leads to ipsilateral tongue weaknesses where protrusion is associated with deviation to the weak side
Which cranial nerves have parasympathetic components? What do they do
oculomotor III - pupil constriction
facial VII - salivary and lacrimal glands
GP IX - salivary glands
vagus X - viscera
