Olfactory Nerve

(smell)

• arise from the olfactory receptor
• pass through the cribriform plate of the ethmoid bone
• fibers synapse in olfactory bulbs
• pathway terminates in the primary olfactory cortex
• purely sensory (olfactory) function

II - Optic Nerve

(vision)

• arise from retinas
• pass through the optic canals, converge and partially cross over at the optic chiasma
• optic tracts continue to the thalamus, where they synapse
• optic radiation fibers run to the occipital (visual) cortex
• purely sensory (visual) function

III - Oculomotor nerves

(eyelid and eyeball movement)

• fibers extend from the ventral midbrain through the superior orbital fissures to the extrinsic eye muscles
• functions in raising eyelid, directing the eyeball, constricting the iris (parasympathetic) and controlling lens shape

IV - Trochlear nerves

(innervates superior oblique; turns eye downward and laterally) 

• fibers from the dorsal midbrain enter the orbits via the superior orbital fissures to innervate the superior oblique muscle
• primarily a motor nerve that directs the eyeball

V - Trigeminal Nerve

(chewing; face & mouth touch & pain)

• largest cranial nerves; fibers extend from pons to face
• 3 divisions:

1. opthalamic (v1) passes through the superior orbital fissure
2. maxillary (v2) passes through the foramen rotundum
3. mandibular (v3) passes through the foramen ovale

• convey sensory impulses from various areas of the face (v1) and (v2) and supplies motor fibers (v3) for mastication

VI - Abducens Nerve

(turns eye laterally)

• fibers from the inferior pons enter the orbits via the superior orbital fissures
• primarily a motor, innervating the lateral rectus muscle

VII - facial nerve

(controls facial expression; secretion of tears; saliva taste)

• fibers from the pons travel through the internal acoustic meatus and emerge through the stylomastoid formina to the lateral aspect of the face
• chief motor nerve of the face w/ 5 major branches
• motor functions include facial expression, parasympathetic impulses to lacrimal and salivary glands
• sensory function (taste) from the anterior 2/3 of the tongue

VIII - Vestibulochlear nerve

(hearing; equilibrium senstation)

• afferent fibers from the hearing receptors (cochlear division) and equlibrium receptors (vestibular division) pass from the inner ear through the internal acoustic meatuses, and enter the brain stem at the pons-medulla border
• mostly sensory function; small motor component for adjustment of sensitivity of receptors

IX - Glossopharangeal nerves

(taste; senses carotid BP)

• fibers from the medulla leave the skull via the jugular foramen and run to the throat
• motor functions - innervate part of the tongue and pharynx for swallowing, and provide parasympathric fibers to th parotid salivary glands
• senory functions - fibers conduct taste and general sensory impulses from the pharynx and posterior tongue, and impulses from the carotid chemoreceptors and baroreceptors

X - Vagus nerve

(senses aortic BP; slows HR; stimulates digestive organs; taste)

• extend into the abdomen
• the only cranial nerve that extends beyond the head and neck region
• fibers from the medulla exit the skull via jugular foramen
• most motor fibers are parasympathetic fibers that help regulate the activities of the heart, lungs, and abdominal viscera
• sensory fibers carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors, and taste buds of posterior tongue and pharynx

XI - Accessory (spinal) nerves

(controls trapezius & sternocleidomastoid; controls swallowing movement)

• formed from ventral rootlets from the C1-C5 region of the spinal cord (not the brain)
• rootlets pass into the cranium via each foramen magnum
• accessory nerves exit the skull via the jugular foramina to innervate the trapezius and sternocleidomastoid muscles

XII - Hypoglossal nerve

(controls tongue movement)

• fibers from the medulla exit the skull via the hypoglossal canal
• innervate extrinsic and intrinsic muscles of the tongue that contribute to swallowing and speech