Cranial Nerves Anatomy

How many pairs of cranial nerves are there?

12

Where do the first two pairs of cranial nerves attach?

The forebrain

Where do cranial nerve pairs 3-12 attach?

The brainstem

What is the function of the olfactory nerve (CN I)?

Sense of smell

What clinical condition is associated with loss of smell?

Anosmia

What is the function of the optic nerve (CN II)?

Vision

Where do optic fibers partially cross?

At the optic chiasm

What muscles are innervated by the oculomotor nerve (CN III)?

Superior, inferior, medial rectus, and inferior oblique

What autonomic functions does the oculomotor nerve control?

Pupil constriction and lens accommodation

Which muscle does the trochlear nerve (CN IV) innervate?

Superior oblique

What movement does the superior oblique muscle control?

Downward and lateral movement of the eyeball

What are the three divisions of the trigeminal nerve (CN V)?

Ophthalmic (V1), Maxillary (V2), Mandibular (V3)

What is the function of the mandibular division (V3)?

Controls mastication

What muscle is innervated by the abducens nerve (CN VI)?

Lateral rectus

What are the functions of the facial nerve (CN VII)?

Facial expression, taste anterior 2/3 of tongue, salivary glands

What condition is associated with facial nerve dysfunction?

Bell's palsy

What are the two branches of the vestibulocochlear nerve (CN VIII)?

Vestibular (equilibrium) and cochlear (hearing)

What is the function of the glossopharyngeal nerve (CN IX)?

Taste posterior 1/3 tongue, swallowing, gag reflex

What is a clinical test for CN IX function?

Swallowing and gag reflex

What is the function of the vagus nerve (CN X)?

Parasympathetic control of heart, lungs, digestive tract

What muscles are innervated by the accessory nerve (CN XI)?

Trapezius and sternocleidomastoid

What is the function of the hypoglossal nerve (CN XII)?

Tongue movements for speech and swallowing

What is a common mnemonic for cranial nerve names?

Oh, Oh, Oh, To Touch And Feel Very Green Vegetables, AH

What is a common mnemonic for cranial nerve function (sensory/motor)?

Some Say Marry Money But My Brother Says Big Brains Matter More

CN I

olfactory nerve

CN II

optic nerve

CN III

oculomotor nerve

CN IV

trochlear nerve

CN V

trigeminal nerve

CN VI

abducens

CN VII

facial nerve

CN VIII

vestibulocochlear nerve

CN IX

glossopharyngeal nerve

CN X

vagus nerve

CN XI

spinal accessory nerve

CN XII

hypoglossal nerve

Which cranial nerves are purely sensory?

I, II, VIII

Which cranial nerves are purely motor?

III, IV, VI, XI, XII

Which cranial nerves are both sensory and motor?

V, VII, IX, X

olfactory nerve

sense of smell

uncus

smell and taste center

clinical test of olfactory nerve

ask patient to identify an odor

optic nerve

vision; not a true nerve but an extension of the brain - ensheathed in all three meningeal layers

clinical vision test

snellen eye chart

oculomotor nerve

eyeball movement, pupillary constriction, and lens accommodation (focusing)

what muscles does the oculomotor nerve control?

superior rectus, inferior rectus, medial rectus, inferior oblique

trochlear nerve

movement of the superior oblique muscle (cheater's muscle)

which cranial nerve is the smallest

trochlear nerve

trigeminal nerve

sensory to the face, controls muscles of mastication, and corneal (blink) reflex

Which muscles of mastication are controlled by the trigeminal nerve?

temporalis, masseter, medial pterygoid, lateral pterygoid

What is the largest cranial nerve?

trigeminal nerve

What are the three divisions of the trigeminal nerve?

opthalmic, maxillary, mandibular

What is the function of the opthalmic division of the trigeminal nerve?

sensations from the forehead, eyelids, and nose

What is the function of the maxillary division of the trigeminal nerve?

sensations from lower eyelid, upper lip, and cheek

What is the function of the mandibular division of the trigeminal nerve?

controls mastication

abducens

innervates the lateral rectus muscle of the eye which moves the eyeball laterally; associated with lazy eye

What does the facial nerve control?

Muscles of facial expression

What motor control does the facial nerve provide?

Motor control to the posterior belly of digastric and stylohyoid

Which salivary glands are controlled by the facial nerve?

Lacrimal, submandibular, and sublingual salivary glands

What type of taste does the facial nerve control?

Taste of the anterior 2/3 of the tongue

What disorder is associated with the facial nerve?

Bell's palsy

What are the branches of the facial nerve?

temporal, zygomatic, buccal, mandibular, cervical

vestibulocochlear nerve

hearing and balance

glossopharyngeal nerve

innervates posterior 1/3 of the tongue (bitter taste) and pharynx, responsible for swallowing and gag reflex

vagus nerve

'the wanderer' - innervates digestive organs, heart and other areas

What is the only cranial nerve to extend below the head and neck?

vagus nerve

spinal accessory nerve

innervates trapezius and sternocleidomastoid muscle

Clinical test of spinal accessory nerve

ask patient to shrug shoulders against resistance

hypoglossal nerve

tongue movements: swallowing and speech

Clinical test for hypoglossal nerve

have patient hold tongue against cheek and apply resistance from outside of cheek