Cranial Nerves Flashcards by Michelle Doody

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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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Some Say Money Matters, But My Brother Says Big Brains Matter Most

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)

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Gross anatomy photo of CNs

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Sensory & Motor CN nuclei

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Define olfactory bulb

Bundles of olfactory nerve fibres pass through cribriform plate of ethmoid bone

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Where do olfactory tracts run

In olfactory sulcus

Olfactory tracts extend from olfactory bulb

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What does the olfactory sulcus divide into

Medial and lateral olfactory striae

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What happens if there is unilateral olfactory loss (anosmia)

Patient is often unaware of loss as contralateral olfaction can compensate

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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

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Where does the vestibulocochlear nerve (CN VIII) exit

Exits brainstem at PONTOMEDULLARY junction (at cerebellopontine angle)

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Function of vestibulocochlear nerve (CN VIII)

Vestibular - maintain balance (vertigo)

Cochlear - conducts nerve impulses concerned with sound from organ of Corti in cochlea

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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

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Openings in the cranium

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What happens as the auditory pathways enter the brainstem

Info crosses at multiple levels

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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

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In what direction do CN XI and XII travel

Towards the neck

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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

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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

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Name the foramen in the cranium that the oculomotor nerve passes through

Superior orbital fissure

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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

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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

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What do the occulomotr, trochlear, ophthalmic and abducent nerves have in common

All traverse the cavernous sinus to exit skull via superior orbital fissure

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Specific function of trochlear nerve

Turns eye downwards and laterally

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Specific function of abducent nerve

Abducts the eye laterally in horizontal direction

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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