Cranial Nerves - Axons Enter and Exit

Olfactory (CN I)

axons travel from the nasal mucosa through the cribriform plate and synapse on neurons in olfactory bulb (neurons send axons to olfactory cortex in temporal lobe)

Optic (CN II)

enter skull via optic canal (1/2 of axons cross at optic chiasm - axons continue as the optic tract to the thalamus and synapse in lateral geniculate nucleus)

-LGN axons project to primary visual cortex (in occipital lobe) at the calcarine fissure

Oculomotor (CN III)

-axons come from midbrain and exit through superior orbital fissure

-innervates: medial rectus, superior rectus, inferior rectus, inferior oblique, and levator palpebrae

Trochlear (CN IV)

-axons come from midbrain

-ONLY CN to emerge from posterior brainstem

-axons go through superior orbital fissure

-innervates: superior oblique

Trigeminal (CN V)

-emerges from pons

-relay in the thalamus then project to the somatosensory

-V1: ophthalmic (enters: superior orbital fissure)

-V2: maxillary (enters: foramen rotundum)

-V3: mandibular (leave and enter: foramen ovale)

Abducens (CN VI)

-axons originate in pons

-exit through superior orbital fissure

-targets lateral rectus

Facial (CN VII)

-sensory: taste sensation ant. 2/3 (enter: internal acoustic meatus)

-motor exit through stylomastoid foramen (innervates: 2 suprahyoid muscles and stapedius muscle)

Vestibulocochlear (CN VIII)

-axons enter through internal acoustic meatus

-synapse in medial geniculate nucleus (of thalamus) then project to primary auditory cortex

Glossopharyngeal (CN IX)

-carries general sensory and taste info. to posterior 1/3 of tongue and pharynx

-carries motor info to stylopharyngeus

-axons enter and exit through jugular foramen

Vagus (X)

-sensory info carries from neck, thorax, abdomen, and pelvis

-motor axons target muscles of palate, pharynx, tongue, and larynx

-axons enter and exit through jugular foramen

Spinal Accessory (CN XI)

-enter through foramen magnum and exit through jugular foramen

-innervates: sternocleidomastoid and trapezius

Hypoglossal (CN XII)

-exit: hypoglossal canal

-innervates: muscles to tongue