CN I — name, modality and function?

Olfactory nerve. Purely sensory: it carries the sense of smell from the olfactory epithelium of the nasal cavity.

CN II — name, modality and function?

Optic nerve. Purely sensory: it carries visual information from the retina to the brain.

CN III — name, modality and function?

Oculomotor nerve. Motor: it supplies the superior, inferior and medial rectus and the inferior oblique, raises the eyelid via levator palpebrae superioris, and carries parasympathetic fibers that constrict the pupil and drive accommodation.

CN IV — name, modality and function?

Trochlear nerve. Motor: it supplies only the superior oblique muscle, which intorts, depresses and abducts the eye. Its depressing action is strongest when the eye is already adducted, which is why a fourth nerve palsy shows up on looking down and in.

CN V — name, modality and function?

Trigeminal nerve. Both: sensation from the face, scalp, cornea and anterior tongue through its ophthalmic, maxillary and mandibular divisions, plus motor supply to the muscles of mastication through V3.

CN VI — name, modality and function?

Abducens nerve. Motor: it supplies only the lateral rectus, the muscle that abducts the eye.

CN VII — name, modality and function?

Facial nerve. Both: motor to the muscles of facial expression, taste from the anterior two-thirds of the tongue, and parasympathetic supply to the lacrimal, submandibular and sublingual glands.

CN VIII — name, modality and function?

Vestibulocochlear nerve. Purely sensory: hearing through its cochlear division and balance and head position through its vestibular division.

CN IX — name, modality and function?

Glossopharyngeal nerve. Both: taste and sensation from the posterior third of the tongue and from the pharynx, motor supply to stylopharyngeus, parasympathetic supply to the parotid gland, and input from the carotid body and carotid sinus.

CN X — name, modality and function?

Vagus nerve. Both: parasympathetic supply to the heart, lungs and abdominal viscera, motor supply to most muscles of the pharynx and larynx, and sensation from the pharynx, larynx and viscera.

CN XI — name, modality and function?

Accessory nerve. Motor: it supplies the sternocleidomastoid and the trapezius, so it turns the head and shrugs the shoulders.

CN XII — name, modality and function?

Hypoglossal nerve. Motor: it supplies the intrinsic and extrinsic muscles of the tongue, with the exception of palatoglossus.

Which cranial nerves are purely sensory, which purely motor, and which are both?

Purely sensory: I, II and VIII. Purely motor: III, IV, VI, XI and XII. Both sensory and motor: V, VII, IX and X. The mnemonic is 'Some Say Marry Money But My Brother Says Big Brains Matter Most'.

Which cranial nerve emerges from the dorsal surface of the brainstem?

The trochlear nerve (CN IV). It is the only cranial nerve to exit dorsally, and its fibers cross so that each nerve supplies the superior oblique on the opposite side.

Which nerves form the afferent and efferent limbs of the pupillary light reflex?

The optic nerve (CN II) is the afferent limb carrying the light signal, and the oculomotor nerve (CN III) is the efferent limb that constricts the pupil.

Which nerves form the afferent and efferent limbs of the corneal reflex?

The afferent limb is the ophthalmic division of the trigeminal nerve (V1), and the efferent limb is the facial nerve (CN VII), which closes the eye through orbicularis oculi.

Which nerves form the afferent and efferent limbs of the gag reflex?

The glossopharyngeal nerve (CN IX) is the afferent limb and the vagus nerve (CN X) is the efferent limb.

What are the eye findings in a complete oculomotor (CN III) palsy?

The eye rests down and out because the unopposed lateral rectus and superior oblique dominate, the eyelid droops (ptosis), and a compressive lesion also leaves the pupil dilated and poorly reactive to light.

How does an abducens (CN VI) palsy present?

The affected eye cannot abduct past the midline, producing horizontal double vision that is worst when the patient looks toward the affected side.

How does a trochlear (CN IV) palsy present?

Vertical double vision that is worst on looking down and inward, such as when reading or walking down stairs. Patients often tilt the head away from the affected side to compensate.

How does a lower motor neuron facial (CN VII) lesion differ from an upper motor neuron one?

A lower motor neuron lesion such as Bell palsy weakens the whole half of the face, forehead included. An upper motor neuron lesion, as in a stroke, spares the forehead, because the upper face receives input from both hemispheres.

Which way does the tongue deviate in a hypoglossal (CN XII) lower motor neuron lesion?

Toward the side of the lesion. The intact genioglossus on the healthy side pushes the tongue across, so the protruded tongue points at the damaged nerve.

Which way does the uvula deviate in a vagus (CN X) lesion?

Away from the side of the lesion. The working side of the soft palate pulls the uvula toward itself when the patient says 'ahh'.

Which cranial nerves pass through the superior orbital fissure?

CN III, CN IV, CN V1 and CN VI — the three nerves that move the eye plus the ophthalmic division of the trigeminal.

Which foramen does each division of the trigeminal nerve use?

V1 the superior orbital fissure, V2 the foramen rotundum, V3 the foramen ovale — standing for Standing Room Only.

Which cranial nerves exit through the jugular foramen?

CN IX, CN X and CN XI — glossopharyngeal, vagus and accessory.

Which skull openings do CN I, II, VII, VIII and XII pass through?

CN I the cribriform plate; CN II the optic canal; CN VII and CN VIII the internal acoustic meatus; CN XII the hypoglossal canal.

What is the mnemonic for the 12 cranial nerves in order?

A widely used one is 'Oh Oh Oh To Touch And Feel Very Good Velvet, Such Heaven' for the names: olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal. Pair it with 'Some Say Marry Money But My Brother Says Big Brains Matter Most' for whether each is sensory, motor or both.

Which cranial nerves are both sensory and motor?

Four of them: V (trigeminal), VII (facial), IX (glossopharyngeal) and X (vagus). Nerves I, II and VIII are purely sensory, and III, IV, VI, XI and XII are purely motor.

What is the fastest way to memorize the cranial nerves?

Anchor the order with a mnemonic, then attach modality and function to each number, since the mnemonic alone only gives you the list of names. Cram can build these cards from your own anatomy notes with AI and schedule spaced reviews so the twelve stay separate in memory.

27 free flashcards

Cranial Nerves flashcards

This deck covers all twelve cranial nerves one at a time: the Roman numeral, the name, whether the nerve is sensory, motor or both, and what it actually does. It then adds the two classic mnemonics, the skull openings each nerve passes through, and clinical cards on how the nerves are tested — the pupillary light, corneal and gag reflexes, and the deviation patterns seen in third, fourth, sixth, seventh, tenth and twelfth nerve lesions.

Cranial nerves get tested two ways: straight identification (which nerve supplies the lateral rectus?) and applied reasoning (a patient's tongue deviates to the left — which nerve?). The sensory/motor/both classification is the single most missed detail, because the pattern is irregular and cannot be guessed from a nerve's name. Locking number, name, modality and function together is what makes the clinical questions answerable in seconds.

The deck

How to study this deck

Use both classic mnemonics together, not one alone: 'Oh Oh Oh To Touch And Feel Very Good Velvet, Such Heaven' gives the names in order, and 'Some Say Marry Money But My Brother Says Big Brains Matter Most' gives the modality (S = sensory, M = motor, B = both) for the same twelve positions.
Drill the four mixed nerves as their own set — V, VII, IX and X are the only ones that are both sensory and motor. Knowing that everything else is purely one or the other cuts the classification problem roughly in half.
Rehearse the deviation rules out loud with the direction attached: the tongue deviates toward the side of a twelfth nerve lesion, while the uvula deviates away from the side of a tenth nerve lesion. Saying 'toward' and 'away' aloud is what stops the two blurring together.

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