Cranial Nerves

Vocabulary flashcards covering the names, numbers, origins, passageways, functions, innervations, and clinical conditions for all 12 cranial nerves as presented in the lecture.

Olfactory Nerve (CN I)

A purely sensory cranial nerve that originates in the olfactory receptor cells of the nasal mucosa, passes through the cribriform plate of the ethmoid bone, synapses in the olfactory bulb, and carries afferent impulses for the sense of smell.

Anosmia

A condition characterized by partial or total loss of smell, often resulting from a fracture of the ethmoid bone or lesions of the olfactory nerve fibers.

Optic Nerve (CN II)

A purely sensory cranial nerve arising from the retina of the eye that passes through the optic canal, forms the optic chiasma, and transmits afferent impulses for vision to the visual cortex of the occipital lobe.

Papilledema

Swelling of the optic disc, the site where the optic nerve leaves the eyeball, which can be detected during clinical examination using an ophthalmoscope.

Anopsias

Visual field defects caused by damage to the visual pathway beyond the optic chiasma.

Oculomotor Nerve (CN III)

A motor cranial nerve exiting the midbrain via the superior orbital fissure that supplies somatic motor fibers to four extrinsic eye muscles and levator palpebrae superioris, as well as parasympathetic fibers to the sphincter pupillae and ciliary muscle.

External Strabismus

A condition resulting from oculomotor nerve paralysis where the affected eye rotates laterally at rest because the actions of the extrinsic eye muscles not served by CN III are unopposed.

Trochlear Nerve (CN IV)

A motor cranial nerve emerging from the dorsal midbrain that passes through the superior orbital fissure to innervate the superior oblique muscle of the eye.

Trigeminal Nerve (CN V)

The largest cranial nerve, emerging from the pons, which serves as the chief general sensory nerve for the face and supplies motor fibers via its mandibular division to the muscles of mastication.

Ophthalmic Division ($V_1$)

The sensory division of the trigeminal nerve that passes through the superior orbital fissure to convey sensory impulses from the skin of the anterior scalp, upper eyelid, nose, nasal cavity mucosa, cornea, and lacrimal gland.

Maxillary Division ($V_2$)

The sensory division of the trigeminal nerve that passes through the foramen rotundum to convey impulses from the nasal cavity mucosa, palate, upper teeth, skin of the cheek, upper lip, and lower eyelid.

Mandibular Division ($V_3$)

The division of the trigeminal nerve passing through the foramen ovale that provides sensory input from the anterior tongue, lower teeth, chin, and scalp, and supplies motor fibers to the muscles of mastication.

Tic Douloureux

Also known as trigeminal neuralgia; an agonizing condition caused by inflammation or pressure on the trigeminal nerve root, characterized by severe stabbing facial pain provoked by sensory stimuli.

Abducens Nerve (CN VI)

A motor cranial nerve leaving the inferior pons and passing through the superior orbital fissure to supply somatic motor fibers to the lateral rectus muscle of the eye.

Internal Strabismus

A clinical condition resulting from abducens nerve paralysis where the affected eyeball rotates medially at rest because the lateral rectus muscle cannot abduct the eye.

Facial Nerve (CN VII)

A mixed cranial nerve entering the temporal bone via the internal acoustic meatus and exiting through the stylomastoid foramen; it innervates muscles of facial expression, provides parasympathetic output to lacrimal and salivary glands, and conveys taste from the anterior two-thirds of the tongue.

Bell's Palsy

A rapid-onset paralysis of the facial muscles on the affected side accompanied by partial loss of taste, commonly caused by herpes simplex I viral inflammation of the facial nerve.

Vestibulocochlear Nerve (CN VIII)

A sensory cranial nerve passing through the internal acoustic meatus that comprises a vestibular division for the sense of equilibrium and a cochlear division for the sense of hearing.

Glossopharyngeal Nerve (CN IX)

A mixed cranial nerve passing through the jugular foramen that innervates the stylopharyngeus muscle, provides parasympathetic innervation to the parotid gland via the otic ganglion, and carries taste and general sensation from the posterior third of the tongue and pharynx.

Vagus Nerve (CN X)

A mixed cranial nerve exiting through the jugular foramen that extends into the thorax and abdomen, providing parasympathetic fibers to the heart, lungs, and visceral organs, as well as somatic motor fibers to pharyngeal and laryngeal muscles.

Accessory Nerve (CN XI)

A motor cranial nerve formed by cranial roots from the medulla and spinal roots ($C_1$-$C_5$) entering via foramen magnum and exiting via jugular foramen to supply motor innervations to the sternocleidomastoid and trapezius muscles.

Hypoglossal Nerve (CN XII)

A motor cranial nerve arising from the medulla and exiting via the hypoglossal canal to supply the intrinsic and extrinsic muscles of the tongue for speech, manipulation of food, and swallowing.