Cranial Nerves Flashcards
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CN I - Olfactory
CN II - Optic
CN III - Oculomotor
CN IV - Trochlear
CN V - Trigeminal
CN VI - Abducent
CN VII - Facial
CN VIII - Vestibulocochlear
CN IX - Glosspharyngeal
CN X - Vagus
CN XI - Accessory
CN XII - Hypoglossal
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CN I - Sensory (Olfactory)
CN II - Sensory (Optic)
CN III - Motor (Oculomotor)
CN IV - Motor (Trochlear)
CN V - Both (Trigeminal)
CN VI - Motor (Abducent)
CN VII - Both (Facial)
CN VIII - Sensory (Vesitbulocochlear)
CN IX - Both (Glossopharyngeal)
CN X - Both (Vagus)
CN XI - Motor (Accessory)
CN XII - Motor (Hypoglossal)
Gross anatomy photo of CNs
Sensory & Motor CN nuclei
Define olfactory bulb
Bundles of olfactory nerve fibres pass through cribriform plate of ethmoid bone
Where do olfactory tracts run
In olfactory sulcus
Olfactory tracts extend from olfactory bulb
What does the olfactory sulcus divide into
Medial and lateral olfactory striae
What happens if there is unilateral olfactory loss (anosmia)
Patient is often unaware of loss as contralateral olfaction can compensate
What does the optic nerve (CN II) do
What is its path
Optic nerve fibres obtain info from photoreceptors in retina
Optic nerve accesses optic cavity via optic canal
- unites with opposite optic nerve forming optic chiasm
- optic tract to lateral geniculate nuclei of thalamus
Where does the vestibulocochlear nerve (CN VIII) exit
Exits brainstem at PONTOMEDULLARY junction (at cerebellopontine angle)
Function of vestibulocochlear nerve (CN VIII)
Vestibular - maintain balance (vertigo)
Cochlear - conducts nerve impulses concerned with sound from organ of Corti in cochlea
Where do the olfactory, optic, facial and vestibulocochlear nerves exit the cranial cavity
Olfactory - foramina of cribriform plate
Optic - optic canal
Facial & vestibulocochlear - internal auditory meatus
Openings in the cranium
What happens as the auditory pathways enter the brainstem
Info crosses at multiple levels
What is common about the oculomotor (CN III), trochlear (CN IV) and abducent (CN VI) nerves
Travel in same part of the brain to innervate the muscles of the eye
In what direction do CN XI and XII travel
Towards the neck
Where does the oculomotor nerve arise
Describe its path
Where does it exit the cranium
Emerges on anterior surface of the brainstem - between pons and midbrain, in INTERPEDUNCULAR FOSSA
Usually passes between posterior cerebral artery and superior cerebellar artery
Exits skull via superior orbital fissure
Differentiate between the 2 nuclei of the oculomotor nerve (CN III)
Main oculomotor nucleus - supplies most of the extrinsic muscles of the eye
Accessory PS nucleus (Adenger-Westphal nucleus) - ciliary ganglion for pupillary light reflex
Name the foramen in the cranium that the oculomotor nerve passes through
Superior orbital fissure
Describe the path of the trochlear nerve (CN IV)
What is noteworthy about this nerve
What does it innervateM
Most fragile of the cranial nerves
Emerges from posterior surface of midbrain, from inferior caliculi
Passes through the superior orbital fissure
Innervates the superior oblique muscle of the eye
Describe the path of the abducent nerve
What does it innervate
What foramen of the cranium does it pass through
Emerges in groove between lower pons and medulla
Enters orbit through superior orbital fissure
Supplies lateral rectus muscle of eyeball
What do the occulomotr, trochlear, ophthalmic and abducent nerves have in common
All traverse the cavernous sinus to exit skull via superior orbital fissure
Specific function of trochlear nerve
Turns eye downwards and laterally
Specific function of abducent nerve
Abducts the eye laterally in horizontal direction
Specific function of oculomotor nerve
All other eye movement (aside from abduction, downward and laterally movement)
What is different about nerves in the medulla region
Emerge as a series of rootlets
Describe the location of the cranial part of the accessory nerve
Posterior to olive
Nerve joins spinal root
Roots exit through jugular foramen
What is the separation of the roots of accessory nerve
CRANIAL
Innervates larynx and pharynx
SPINAL
innervates neck muscles
Sternomastoid function
Turns head to opposite side
Trapezius function
Elevation of shoulder
What does the hypoglossal nerve supply
Where does it emerge
Through what foramen does it leave the skull
Supplies muscle of tongue
Emerges as a set of rootlets in groove between pyramid and olive
Leaves skull through the hypoglossal canal
Pathway for neurons of hypoglossal nerve
Hence what would a lesion result in
Upper motor neurons for tongue movement arise from tongue region of primary motor cortex - corticobulbar pathway
Decussation before they reach the hypoglossal nuclei
Lesion in primary motor cortex/internal capsule results in contralateral tongue weakness
Name the 4 nerves with motor and sensory functions
Trigeminal (CN V)
Facial (CN VII)
Glossopharyngeal (CN IX)
Vagus (CN X)
Describe the path of the trigeminal (V) nerve - largest CN
Leaves anterior aspect of the pons as a small motor root and large sensory root
What does the sensory root of the trigeminal nerve form
Where is it located
Sensory root expands to form trigeminal ganglion in Meckel’s Cave
Name the nerves that arise from the trigeminal ganglion
Opthalmic (V1)
Maxillary (V2)
Mandibular (V3)
What does the motor root of the trigeminal nerve supply
The muscles of mastication
What passes through the foramen spinosum
Middle meningeal artery
What 4 nerves pass through the superior orbital fissure and name if they are motor or sensory in function
Occulomotor - motor
Trochlear - motor
Ophthalmic - sensory
Abducent - motor
Trigeminal neuralgia
Shooting pains across the cheek
Where does the facial nerve (VII) travel
What muscles does it supply
Emerges from the anterior surface of brain between pons and medulla
Supplies muscles of facial expression
Describe the sensory innervation of the facial nerve
What ganglion is associated with it
Sensation of taste from anterior 2/3rds of tongue
Geniculate ganglion
Describe the PS innervation of the facial nerve
What ganglions are associated with it
Innervation to lacrimal glands and sublingual/submandibular glands
Pterygopalatine ganglion
Submandibular ganglion
Name the 5 branches of the facial nerve
Temporal
Zygomatic
Buccal
Mandibular
Cervical
Exits of the facial nerve
Cranial cavity via Internal Acoustic Meatus
Skull to reach muscles of facial expression via stylomastoid foramen
What is Bell’s Palsy
Unilateral facial weakness
Also affects tear production on the same side
Describe the path of the glosspharyngeal nerve
What muscle does it innervate
Emerges just below pontomedullary junction, below CN VIII
Innervates stylopharyngeus muscle in the neck
Describe the sensory innervation of the glossopharyngeal nerve
Sensations of taste - posterior 1/3 of the tongue
Describe the PS innervation of the glossopharyngeal nerve
Name the ganglion
PS innervation of parotid gland
Otic ganglion
What nerve innervates the anterior 2/3rds of the tongue
Facial nerve
Where does the glossopharyngeal nerve exit the skull
through the jugular foramen
Describe the path of the vagus nerve
Emerges as a series of rootlets in groove posterior to olive, just below CN IX
Describe the motor innervation of the vagus nerve
To pharynx
Larynx
Upper oesophageal muscles (gag reflex)
Describe the sensory innervation of the vagus nerve
Heart
Lungs
Larynx
Pharynx
GI
Describe the parasympathetic innervation of the vagus nerve
Heart
Lungs
GI
Overview of nerves passing through the various foramina of the skull
Summary of need to know info for CNs
Optic nerve passing beneath dura
What lies inferior to optic chiasm
Internal carotid arteries
Roof of pituitary fossa
How do optic nerves travel from the retina (medial side) into the optic chiasm
How does it differ with the lateral side
Nerves travel on SAME SIDE of optic chiasm when coming from the lateral side of the retina
Origin of oculomotor
Between cerebral peduncles
Origin of trochlear
Back of midbrain
Origin of abducent
Below the pons
Superior orbital fissure transmits
Oculomotor
Trochlear
Abducent
Where does the oculomotor pierce through the dura
Near the posterior clinoid process
Relationship between oculomotor, trochlear and abducent
Division of oculomotor nerve
Lower branch below optic nerve
Controls size of pupil and shape of lens
What muscle does the trochlear nerve supply
Superior oblieque muscle
Origin of trigeminal nerve
Openings for nerves associated with trigeminal nerve
Ophthalmic - superior orbital fissure
Maxillary - foramen rotundum
Mandibular - foramen ovale
Divisions of ophthalmic nerve
Frontal nerve -> cutaneous branches to forehead
Lacrimal nerve
Nasociliary nerve -> 1+ ethmoidal nerves, but also sensation to eyeball
Infratrochlear nerve (cutaneous)
Origin of facial & vestibulocochlear nerves
Just below pons
Vestibulocochlear nerve as it passes from its origin
Origin of 9th, 10th and 11th nerves
Lateral aspect of medulla
Where do filaments of spinal accessory nerve emerge from
C1-C5
