Cranial nerves — table
The twelve cranial nerves: course, branches and functions. 12 entries.
Cranial nerves 12
| Cranial nerve | Course & exit | Branches | Function |
|---|---|---|---|
| CN I — Olfactory nerve (CN I) | Olfactory epithelium (superior nasal concha, upper septum and roof), then fila olfactoria through the cribriform plate, wrapped by meninges, then the olfactory bulb (mitral and tufted cells).… | — | Olfaction (detection and discrimination of odorants); Contributes most of the perception of flavour; Olfactory–limbic links for emotion, memory, feeding and reproductive behaviour |
| CN II — Optic nerve (CN II) | Retinal ganglion cells → optic disc → lamina cribrosa → intraorbital nerve (inside the muscle cone; the central retinal artery enters it about 1 cm behind the globe) → optic canal (with the ophthalmic artery) → optic chiasm… | — | Conveys visual information from the retina to the lateral geniculate nucleus and visual cortex; Afferent limb of the pupillary light reflex (to the pretectal nuclei); Afferent limb of the accommodation (near) reflex |
| CN III — Oculomotor nerve (CN III) | Oculomotor and Edinger–Westphal nuclei (periaqueductal midbrain, superior colliculus level) → fascicles through the tegmentum and red nucleus → interpeduncular fossa → subarachnoid space between the PCA and SCA, lateral to the… | Superior division: superior rectus and levator palpebrae superioris. Inferior division: medial rectus, inferior rectus, inferior oblique, and the parasympathetic (motor) root to the ciliary ganglion.… | Elevation (superior rectus, inferior oblique), depression (inferior rectus) and adduction (medial rectus) of the eye; Elevation of the upper eyelid (levator palpebrae superioris);… |
| CN IV — Trochlear nerve (CN IV) | Nucleus (caudal midbrain) → dorsal decussation in the superior medullary velum → emerges below the inferior colliculus → winds around the lateral midbrain → between the PCA and SCA → along the free tentorial edge → lateral wall… | — | Depression of the adducted eye (looking down and in); Intorsion of the eye; Assists abduction |
| CN V — Trigeminal nerve (CN V) | — | V1 (ophthalmic), through the superior orbital fissure, divides into lacrimal, frontal (supraorbital and supratrochlear) and nasociliary nerves: • Nasociliary gives long ciliary nerves to the cornea, the infratrochlear and… | General sensation (touch, pain, temperature, proprioception) of the face, scalp, eye, nasal and oral cavities, teeth and dura; Mastication (muscles of the 1st pharyngeal arch); Tensing the tympanic membrane and the soft palate |
| CN VI — Abducens nerve (CN VI) | Nucleus (dorsal pons, beneath the facial colliculus) → emerges at the pontomedullary junction → ascends in the prepontine cistern along the clivus → pierces the dura and angles over the petrous apex (Dorello's canal) → runs… | — | Abduction of the eye (lateral rectus); Via abducens interneurons and the MLF, coordinates conjugate horizontal gaze |
| CN VII — Facial nerve (CN VII) | Pontomedullary junction → internal acoustic meatus (with VIII and the labyrinthine artery) → facial canal: labyrinthine segment → geniculate ganglion → tympanic segment (medial wall of the middle ear) → mastoid segment →… | In the facial canal: • Greater petrosal nerve, from the geniculate ganglion. It joins the deep petrosal nerve to form the nerve of the pterygoid canal (Vidian nerve), which runs to the pterygopalatine ganglion.… | Facial expression, eye closure and blink (orbicularis oculi), lip seal and the buccinator role in chewing; Dampening of loud sounds (stapedius reflex); Taste from the anterior 2/3 of the tongue |
| CN VIII — Vestibulocochlear nerve (CN VIII) | Spiral and vestibular ganglia → internal acoustic meatus (posterior to the facial nerve; cochlear part anteroinferior) → crosses the cerebellopontine angle cistern → enters the brainstem at the pontomedullary junction → cochlear… | — | Hearing (sound transduced by cochlear hair cells); Detection of head rotation (semicircular canals) and of linear acceleration and gravity (utricle, saccule);… |
| CN IX — Glossopharyngeal nerve (CN IX) | Medulla → jugular foramen (anterior part) → superior and inferior (petrosal) ganglia → descends between the ICA and IJV → winds around the posterior border of stylopharyngeus → passes between the superior and middle constrictors… | - Tympanic nerve: tympanic plexus, then lesser petrosal nerve, then otic ganglion, then the parotid gland via the auriculotemporal nerve. • Carotid sinus nerve.… | Taste and general sensation from the posterior third of the tongue; Sensation from the oropharynx, tonsils, middle ear and auditory tube;… |
| CN X — Vagus nerve (CN X) | Postolivary sulcus → jugular foramen (superior and inferior ganglia) → carotid sheath → root of the neck. On the right it passes anterior to the subclavian artery (giving the right RLN);… | - Auricular branch (Arnold nerve): skin of the external acoustic meatus and the back of the auricle. • Pharyngeal branch: the motor part of the pharyngeal plexus.… | Swallowing (pharyngeal phase) and elevation of the soft palate; Phonation and protection of the airway (laryngeal muscles; cough reflex); Slowing of the heart rate (parasympathetic to the SA/AV nodes, M2 receptors) |
| CN XI — Accessory nerve (CN XI) | Spinal accessory nucleus (C1–C5/6) → rootlets ascend in the subarachnoid space → foramen magnum → posterior cranial fossa → jugular foramen → descends posterolateral to the IJV → deep to and through sternocleidomastoid → emerges… | — | Rotation of the head to the opposite side and flexion of the neck (SCM); Elevation, retraction and upward rotation of the scapula (trapezius), essential for raising the arm above the head |
| CN XII — Hypoglossal nerve (CN XII) | Hypoglossal nucleus → preolivary sulcus → hypoglossal canal → carotid sheath region (medial to the IJV) → loops anteriorly around the origin of the occipital artery (sternocleidomastoid branch) → crosses lateral to the ICA, ECA… | — | Protrusion (genioglossus), retraction and depression (hyoglossus, styloglossus) of the tongue; Shaping the tongue for articulation of speech; Moving food during chewing and initiating the oral phase of swallowing |