Module 27: Cranial Nerve Review

Neural modality

Type of info carried in a nerve, includes general somatic sensory, general somatic motor, general visceral sensory, general visceral motor, and special sensory

General somatic sensory

Sense of touch, proprioception, pain and temperature

General somatic motor

Conscious motor innervation of skeletal muscles

General visceral sensory

Unconscious sensation from visceral structures

General visceral motor

Unconscious motor innervation to cardiac or smooth muscle and glands

Special sensory

Vision, audition, taste, vestibulation, smell

Cranial nerves

Primarily responsible for the sensory and motor functions of the head and neck, twelve total, CN I is associated with telencephalon, CN II associated with diencephalon, CN III-XII originate from brainstem, oculomotor, facial, glossopharyngeal, and vagus associated with the parasympathetic division, superior cervical ganglia associated with the sympathetic division

Olfactory Nerve

CN I. Modality: special sensory - olfaction

Passageway: cribriform plate foramina of ethmoid bone

Synapses in the olfactory bulbs and is the only short nerve traveling from the olfactory mucosa through cribriform plate foramina to olfactory bulb.

Optic nerve

CN II. Modality: special sensory - vision

Passageway: optic canal

Technically a tract of the brain that is covered in meninges, but isn’t the optic tract until after nasal fibers cross into the optic chiasm

Oculomotor nerve

CN III. Modality: somatic motor - 4/6 extrinsic eye muscles, superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae superioris; visceral motor - sphincter pupillae and ciliary muscle

Passageway: superior orbital fissure

Preganglionic fibers synapse in ciliary ganglion and travel to the sphincter pupillae in the iris and ciliary muscle

Trochlear nerve

CN IV. Modality: somatic motor - superior oblique

Passageway: superior orbital fissure

Tendon of superior oblique travels through trochlea at superior medial aspect of the orbit

Trigeminal nerve

CN V. Modality: somatic motor - four muscles of mastication, myelohyoid, anterior belly of digastric, tensor tympani, tensor veli palatani (mandibular division); somatic sensory - sense of touch, temperature, proprioception, pain from the face

Passageway: superior orbital fissure for the ophthalmic division

Split into three divisions, ophthalmic, maxillary, mandibular. Sensory axons enter cranium and synapse at trigeminal ganglion

Ophthalmic division of the trigeminal nerve

CN V1. Modality: somatic sensory - cornea, nose, forehead, anterior scalp

Passageway: superior orbital fissure

Maxillary division of the trigeminal nerve

CN V2. Modality: somatic sensory - nasal mucosa, palate, gums, cheek

Mandibular division of the trigeminal nerve

CN V3. Modality: somatic motor - tensor vali palatini; somatic sensory - anterior 2/3 tongue, meninges, skin of the chin, lower jaw, lower teeth, part of the ear

Abducens nerve

CN VI. Modality: somatic motor - innervates lateral rectus

Passageway: superior orbital fissure

Facial nerve

CN VII. Modality: special sensory - taste from anterior 2/3 of the tongue; visceral motor - innervates and promotes secretion from lacrimal, sublingual, and submandibular glands of the head and neck; visceral sensory - monitoring secretion from the glands; somatic sensory - sense of touch from small area behind the hear; somatic motor - posterior belly of the digastric, stylohyoid, stapedius, muscles of facial expression except levator palpebrae superioris

Passageway: enters through internal acoustic meatus, branch that innervates facial muscles exits the skull and enters the face via the stylomastoid foramen

Some preganglionic parasympathetic fibers synapse in the pterygopalatine ganglion. Postganglionic fibers leave to travel to lacrimal gland and other gland scattered in mucosa of nasal and oral cavities, palate, and pharynx

Some preganglionic parasympathetic fibers synapse in the submandibular ganglion. Postganglionic fibers leaving this ganglion travel to the submandibular and sublingual salivary glands

Vestibulocochlear nerve

CN VIII. Modality: special sensory - cochlear branch is audition, vestibular branch is equilibrium and balance

Passageway: internal acoustic meatus

Glossopharyngeal nerve

CN IX. Modality: special sensory - taste from posterior 1/3 of the tongue; somatic sensory - sense of touch, temperature, pain from the pharynx; visceral motor - innervates and promotes secretion from parotid gland; visceral sensory - monitors secretion from parotid gland, monitors oxygen and carbon dioxide levels in the blood via carotid bodies; somatic motor - stylopharyngeus muscle

Passageway: jugular foramen

Preganglionic parasympathetic fibers synapse in the otic ganglion, then postganglionic fibers travel to the parotid gland

Carotid bodies are located at the point where common carotid artery branches into internal and external carotid arteries

Vagus nerve

CN X. Modality: special sensory - taste from base of the tongue, epiglottis, upper pharynx; visceral motor - innervates heart, pharynx, larynx, trachea, lungs, midgut, and hindgut organs; visceral sensory - monitors contraction of smooth and cardiac muscle and secretion from glands in the organs; somatic sensory - sense of touch, pain, and temperature from external acoustic meatus, eardrum, laryngopharynx, larynx; somatic motor - muscles of the pharynx, muscles of the larynx and palate

Passageway: jugular foramen

Recurrent laryngeal nerve branches in the thorax, where the left loops under the arch of the aorta and returns to the neck to innervate laryngeal muscles

Accessory nerve

CN XI. Modality: somatic motor - trapezius and sternocleidomastoid

Passageway: jugular foramen

Sometimes called the spinal accessory nerve

Hypoglossal nerve

CN XII. Modality: somatic motor - intrinsic and extrinsic muscles of the tongue

Passageway: hypoglossal canal