Function: (1) sensation to face

(2) motor innervation to muscles of mastication

Nuclei: (3 sensory + 1 motor nucleus)

1. mesencephalic nucleus: proprioception extends to level of inferior colliculus
   

   Cranial Nerves

   # Name Nuclei Function I Olfactory Anterior olfactory nucleus Transmits sense of smell; Located in olfactory foramina of ethmoid II Optic Lateral geniculate nucleus Transmits visual information to brain; Located in optic canal III Oculomotor Oculomotor nucleus, Edinger-Westphal nucleus Innervates levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique; Located in superior orbital fissure IV Trochlear Trochlear nucleus Innervates superior oblique muscle; Located in superior orbital fissure V Trigeminal Principal sensory trigeminal nucl., Spinal trigeminal nucleus, Mesencephalic trigeminal nucl., Trigeminal motor nucleus Receives sensation from face and innervates muscles of mastication; Located in superior orbital fissure (ophthalmic branch), foramen rotundum (maxillary branch), and foramen ovale (mandibular branch) VI Abducens Abducens nucleus Innervates lateral rectus; Located in superior orbital fissure VII Facial Facial nucleus, Solitary nucleus, Superior salivary nucleus Provides motor innervation to muscles of facial expression and stapedius, receives special sense of taste from anterior ⅔ of tongue, and provides secretomotor innervation to salivary glands (except parotid) and lacrimal gland; Located and runs through internal acoustic canal to facial canal and exits at stylomastoid foramen VIII Vestibulocochlear ( vestibular + statoacustic n.) Vestibular nucleus, Cochlear nucleus. Senses sound, rotation and gravity; Located in internal acoustic canal IX Glossopharyngeal Nucleus ambiguus, Inferior salivary nucleus, Solitary nucleus Receives taste from posterior ⅓ of tongue, provides secretomotor innervation to parotid gland, and provides motor innervation to stylopharyngeus (essential for tactile, pain, and thermal sensation). Sensation is relayed to opposite thalamus and some hypothalamic nuclei. Located in jugular foramen X Vagus Nucleus ambiguus, Dorsal motor vagal nucleus, Solitary nucleus Supplies branchiomotor innervation to most laryngeal and pharyngeal muscles; provides parasympathetic fibers to nearly all thoracic and abdominal viscera down to the splenic flexure; and receives special sense of taste from epiglottis. Major function: controls muscles for voice and resonance and soft palate. Located in jugular foramen XI Accessory Nucleus ambiguus, Spinal accessory nucleus Controls muscles of neck and overlaps with functions of vagus; Located in jugular foramen XII Hypoglossal Hypoglossal nucleus Provides motor innervation to muscles of tongue and other glossal muscles. Important for swallowing (bolus formation) and speech articulation. Located in hypoglossal canal mnemonic: On Old Olympus Towering Tops A Finn And German Viewed Some Hops

   
   
2. main sensory nucleus: tactile sensation
3. motor nucleus: motor innervation
4. spinal nucleus: pain + temperature sensation extends to level of 2^nd cervical vertebra

Location: tegmentum of lateral pons, along anterolateral aspect of 4^th ventricle

Segments:

1. cisternal portion exits lateral pons traversing prepontine cistern before passing underneath the tentorium to enter the middle cranial fossa at the petrous apex
2. preganglionic portion passes through porus trigeminus (= opening in dura) into the Meckel cave (trigeminal cistern), where it synapses with trigeminal (= gasserian / semilunar) ganglion
   Meckel cave: CSF-filled subarachnoid space formed by dura mater + leptomeninges at the most anteromedial portion of petrous pyramid
   Gasserian ganglion: contains cell bodies of sensory fibers except those for proprioception
3. postganglionic portion → trifurcation

Trifurcation into 3 principal branches:

1. Ophthalmic nerve (V₁)
   Course: travels within lateral cavernous sinus inferior to cranial nerve IV and superior to V₂
   Exit: superior orbital fissure
   Supply: sensory innervation of scalp, forehead, nose, globe
   Division: lacrimal, frontal, nasociliary nn.
   • mediates afferent aspect of corneal reflex
   
   
2. Maxillary nerve (V₂)
   Course: travels within lateral cavernous sinus inferior to V₁
   Exit: through foramen rotundum into pterygopalatine fossa
   Supply: sensory innervation of middle third of face, upper teeth
   Main trunk: infraorbital nerve
3. Mandibular nerve (V₃)
   Course: NOT through cavernous sinus
   Exit: from Meckel cave through foramen ovale into masticator space
   Supply:
   1. sensory innervation of lower third of face, tongue, floor of mouth, jaw
   2. motor innervation of muscles of mastication (masseter, temporalis, medial + lateral pterygoid), mylohyoid m., anterior belly of digastric m., tensor tympani m., tensor veli palatini m.

Exits from Meckel cave: