Exam 3: Cranial Nerves

What are the symptoms of Bell's Palsy?

SVA component affected: 1. Loss of taste in anterior 2/3 of tongue. SVE component affected: 2. Mouth may droop and inability to close affected eye. 3. Paralysis of stapedius muscle = hyperacusis (sounds are abnormally loud). GVE component affected: 4. Impairment of secretion.

Where does CN XI (spinal accessory nerve) arise from? What muscles does it innervate? What nerve fiber type is this?

1. Arises from ventral horn of spinal cord (cervical). 2. SVE- Trapezoid and stermastoid muscles.

Which CN is only sensory?

1. CN I - Olfactory nerve. 2. CN II - Optic nerve. 3. CN VIII - Vestibulocochlear nerve.

What are the [3] CN responsible for eye movement?

1. CN III (oculomotor) 2. CN IV (trochlear) 3. CN VI (abducens)

Which CN regulates the size and shape of the lens in the eye? What reflexes are associated?

1. CN III (oculomotor). 2. Pupillary reflex and accommodation reflex.

Which CN have GVA fibers? What sensations are conveyed by these fibers?

1. CN IX (glossopharyngeal) and CN X (vagus). 2. Convey signals associated with changes in blood pressure.

Name Function: CN VII (Facial nerve) - General somatic sensory (GSA).

Sensation from a small region near the external auditory meatus

Name Function: CN IX (Glossopharyngeal nerve) - General somatic sensory (GSA).

Sensation from middle ear, region near the external auditory meatus, pharynx, and posterior one-third of tongue

Name Function: CN X (Vagus nerve) - general somatic sensor (GSA).

Sensation from pharynx, meninges, and a small region near the external auditory meatus

Name Function: CN IX (Glossopharyngeal nerve) - general visceral sensory (GVA).

Chemo-receptors and baroreceptors of carotid body

Name Function: CN X (Vagus nerve) - general visceral sensory (GVA).

Chemoreceptors and baroreceptors of the aortic arch.

Name Function: CN V (Trigeminal nerve) - General somatic sensory (GSA).

Sensations of touch, pain, temperature, joint position, and vibration for the face, mouth, anterior two-thirds of tongue, nasal sinuses, and meninges

Name Function: CN I (Olfactory nerve) - special somatic sensory (SSA).

Olfaction (smell).

Some cranial nerves have both afferent and efferent fibers. What type of information is conveyed by these two different fiber types?

1. Afferent fibers (GSA, GVA, SSA, SVA) carry sensory information from skeletal muscle, organs, and peripheral receptors (i.e. mechanoreceptors or chemoreceptors) of specialized senses (i.e. hearing, vision, taste, and touch). 2. Efferent fibers (GSE, SVE, GVE) carry motor information to skeletal muscle, smooth muscle and organs.

How are GVA fibers of CN IX (glossopharyngeal) related to GVA fibers of CN X (vagus)?

1. CN IX GVA fibers synapse on solitary nucleus in lower medulla which synapses with dorsal motor nucleus of CN X & nucleus ambiguus. 2. Allows activation of reflex mechanism that stimulates vagal slowing of the heart rate after receiving visceral sensory signals from receptors of carotid sinus (CN IX) and aortic arch (CN X).

Medial/internal strabismus of eye and horizontal diplopia is the result of damage to which CN involved in eye movement? Would this be a general rule, UMN exception, or LMN exception? Which eye would be affected?

1. CN VI (abducens) is damaged, causing paresis of lateral rectus which cannot oppose actions of medial rectus. Diplopia (double vision) is due to inability for both eyes to focus on the same object. 2. General rule of UMN lesion. 3. Contralateral eye.

Which CN involved forms the facial colliculus? What other CN involved in eye movement does it course around?

1. CN VII (facial) 2. CN VI (abducens)

How are GSA fibers of CN VII (facial) related to trigeminal system of CN V?

1. CN VII (facial) GSA cell bodies of geniculate ganglion enter CNS via intermediate nerve and synapse on neurons of spinal trigeminal nucleus. 2. Thus cutaneous sensation originating from CN VII is transmitted to thalamus/cerebral cortex via trigeminal system.

Which CN does not emerge from the brain? Where does it emerge from?

1. CN XI Accessory 2. Spinal cord

Where does the nucleus of CN XII originate? Where does this nerve exit out of the brainstem?

1. CN XII (hypoglossal nerve) originates from hypoglossal nucleus in the dorsomedial lower medulla. 2. CN XII exits the medulla between the pyramids and inferior olivary nucleus.

What is the normal function of CN XII? What happens if there is an UMN lesion? LMN lesion?

1. Controls the shape and position of the tongue. 2. UMN Lesion exception: Tongue deviates to the opposite side of the lesion (contralateral). 3. LMN Lesion general rule: Tongue deviates to the same side of the lesion (ipsilateral).

How are GSA fibers of CN X (vagus) related to trigeminal system of CN V?

1. Cutaneous receptors for pain & temp, pressure & tactile stimuli located in back of ear and external auditory canal have cell bodies in jugular ganglion. 2. Neurons in jugular ganglion project to medulla & terminate on spinal trigeminal nucleus to be conveyed to the thalamus/cerebral cortex.

What occurs if there is damage to CN III? What eye muscles would not be affected?

1. Drooping of ispilateral eye lid (ptosis), dilation of ipsilateral pupil, lateral strabismus, diplopia if eye is raised, oculomotor opthalmoplegia, Weber's syndrome. 2. Superior oblique (CN IV) and lateral rectus (CN VI).

Which nucleus pair projects parasympathetic fibers to the ciliary ganglion to make up the GVE component of CN III?

1. Edinger-Westphal nucleus.

What type of movements are performed by the levator palpebrae superior muscle? Which nerve innervates it?

1. Elevates the upper eyelid. 2. CN III (oculomotor).

Describe the course of fibers of CN XI that innervate the trapezius muscle and sternocleidomastoid muscle?

1. Fibers for sternocleidomastoid descend ipsilaterally to spinal accessory nucleus. 2. Fibers for trapezius muscle cross midline of the medulla decussation to synapse on contralateral nucleus.

Which type of nerve fiber has cell bodies outside of the CNS and convey sensations of pain/temp, conscious/non-conscious propioception, touch and pressure? Where are the nuclei that they synapse on? Which CN have these nerve fiber types?

1. GSA - general somatic afferent. 2. Brainstem. 3. CN V (trigeminal), CN VII (facial) CN IX (glossopharyngeal), CN X (vagus).

What is the sensory and motor component of CN V (trigeminal)? What are the targets of these fibers?

1. GSA - provides most of the somatosensory inputs (pain/temp, touch, & pressure) of the head to the CNS. 2. SVE - provides motor innervation to skeletal muscles of mastication.

Which sensory component of CN X synapses on CN V? What occurs if there is a lesion of this fiber?

1. GSA fibers conveying info from receptors of pain & temp, pressure and tactile stimuli. 2. Disruption/Alteration of cough reflex, swallowing, vomiting, mucous secretions of GI/respiratory tracts, regulation of respiration, & cardiovascular functions.

Which type of nerve fiber innervates skeletal muscles derived from occipital somites? Where are their cell bodies located? Which CN have these nerve fiber types?

1. GSE - general somatic efferent. 2. Brainstem. 3. CN III (oculomotor), CN IV (trochlear), CN VI (abducen), CN XII (hypoglossal). * Hint: External eye muscles and tongue are of occipital somite origin.

What are the [3] sensory components of CN X (vagus)? What type of information is conveyed by these fibers?

1. GVA (travels with GVE) - provides response reflexes, i.e. baroreceptor reflex (aortic arch) that results in lowering high bp. 2. SVA - respiratory functions and taste. 3. GSA - pain, temperature, pressure and tactile stimuli.

Which type of nerve fiber has cell bodies in the serous lining or muscle players of the viscera and convey thirst, hunger, non-specific visceral pain, and general unpleasant feelings? How are CN involved?

1. GVA - general visceral afferent. 2. CN are not directly involved with fibers linked to these sensations but are related via reflex mechanisms of CN IX & CN X (i.e. vomiting, coughing, increased GI secretions etc)

What are the [3] sensory components of CN IX (glossopharyngeal)? What type of information is conveyed by these fibers? Where in the brainstem do they transmit info to?

1. GVA - transmits info from carotid sinus baroreceptors to solitary nucleus in medulla. 2. SVA - (chemoreceptors) transmits changes in blood gases (CO2 & O2) & pH sensed by carotid body; transmits taste from posterior 3rd of tongue to medulla. 3. GSA - transmits somatosensory inputs from back of ear to medulla.

Which type of nerve fiber innervate smooth muscle and glands via pre-ganglionic parasympathetic fibers? Where are their cell bodies located? Which CN have these nerve fiber types?

1. GVE - general somatic efferent. 2. Brainstem and spinal cord (lateral horn). 3. CN III (oculomotor), CN VII (facial), CN IX (glossopharyngeal), and CN X (vagus).

How are GSA fibers of CN IX (glossopharyngeal) related to trigeminal system of CN V?

1. Glossopharyngeal GSA afferents from tympanic membrane & skin of external ear synapse on spinal trigeminal (CN V) nucleus in medulla. 2. Somatosensory input is thus conveyed to cerebral cortex/thalamus via trigeminal tract.

Why does a lesion to CN III lead to Weber's Syndrome? What additional symptoms are present as a result?

1. If lesion is in midbrain, fibers of corticospinal tract contained within crus cerebri are also affected. 2. Patient displays symptoms of both CN III palsy and UMN paralysis of contralateral limbs.

What type of movements are performed by the following eye muscles? Which nerves innervate them? 1. Medial rectus muscle. 2. Lateral rectus muscle.

1. Medial rectus muscle (CN III) -moves eye medially; adduction. 2. Lateral rectus muscle (CN VI) -moves eye laterally; abduction.

What are the [3] main sensory nuclei in the pons that 1st order GSA fibers of CN V synapse on? What information do they convey?

1. Mesencephalic nucleus - unconscious propioception. 2. Chief sensory nucleus - conscious propioception (discriminative touch & simple touch), pressure & tactile sensation. 3. Spinal nucleus & tract - pain and temperature.

What two CN enter CNS at the level of forebrain and do not have sensory nuclei in the brainstem?

1. Olfactory (CN I) 2. Optic (CN II)

What is unique about CN IV (trochlear)? Where are the cell bodies located?`

1. Only nerve that exits dorsally and crosses. 2. Below PAG at the level of the inferior colliculus in the midbrain.

What are the [3] sensory divisions of CN V (trigeminal)? Where do they distribute fibers to?

1. Opthalamic division - Forehead, cornea, upper eyelid, dorsal surface of nose, & mucous membranes of nasal & frontal sinuses. 2. Maxillary division - lateral surface of nose, upper teeth, hard palate of upper cheek, & mucous membranes. 3. Mandibular division: Lower jaw, lower teeth, chin, parts of posterior cheek, temple, external ear, anterior 2/3 of tongue, & floor of mouth.

What occurs if there is damage to the SVE component of CN V (trigeminal)? Which division of CN V is affected?Does this follow general rule, UMN exception, or LMN exception?

1. Paralysis of muscles of mastication; leads to deviation of jaw to affected (ipsilateral) side. 2. Mandibular branch. 3. Follows general rule (LMN).

What occurs as a result of damage to CN IV (trochlear)? Would this be a general rule, UMN exception, or LMN exception? Which eye would be affected?

1. Paresis of superior oblique leads to outward rotation of eye due to no longer being able to oppose inferior oblique muscle. (Difficult to look 2. Vertical diplopia/difficulty walking down stairs due to difficulty moving eye downward and inward (medial). 3. LMN exception. 4. Contralateral eye affected.

Which type of nerve fiber has cell bodies outside of the CNS and convey info to the brain from highly specialized somatic receptors? Which CN have these nerve fiber types?

1. SSA - special sensory afferent. 2. CN I (olefactory), CN II (optic), CN VIII (vestibulocochlear).

What are the [2] sensory components of CN VII (facial)? Where are their cell bodies located? What type of information is conveyed by these fibers?

1. SVA - convey taste from anterior 2/3 of tongue. 2. GSA - cutaneous sensation from back ear and external meatus. 3. Soma are in the geniculate ganglion.

Which type of nerve fiber has cell bodies outside of the CNS and convey info to the brain from highly specialized chemoreceptors? Which CN have these nerve fiber types?

1. SVA - special visceral afferent (involved in taste). 2. CN VII (facial), CN IX (glossopharyngeal), and CN X (vagus).

What are the [2] motor components of CN VII (facial)? What nuclei are involved? What are the targets of their fibers?

1. SVE - Originates in facial motor nucleus in tegmentum lower pons and fibers project and divide into branches to supply the muscles of facial expression. 2. GVE - orginates in superior salivatory nucleus in reticular formation of lower pons and projects parasympathetic pre-ganglionic fibers to (2) types of ganglion to innervate glands of lacrimation, mucous and salivation in nasal and oral cavities.

What are the actions of the motor components of CN X?

1. SVE - contract pharynx and larynx. 2. GVE : -Bronchioconstriction - Speeding of peristalsis - Slowing of cardiac cycle -Increase in secretions of bronchi, stomach, pancreas and intestines.

What are the actions of the motor components of CN IX?

1. SVE - contracts stylopharyngeus muscle which innervates upper part of pharynx during speech & swallowing. 2. GVE - stimulates parotid gland to release saliva.

What are the [2] motor components of CN X (vagus)? What nuclei are involved? What are the targets of their fibers?

1. SVE - originates in nucleus ambiguus (caudal half) and projects to larynx & pharynx muscles. 2. GVE - originates in dorsal motor nucleus and projects pre-ganglionic parasympathetic fibers to viscera (smooth muscle) & glands.

What are the [2] motor components of CN IX (glossopharyngeal)? What nuclei are involved? What are the targets of their fibers?

1. SVE - originates in nucleus ambiguus (rostral half) and projects to stylopharyngeus muscle. 2. GVE - originates in inferior salivatory nucleus and projects pre-ganglionic parasympathetic fibers to parotid gland.

What area of the brain is involved when there is a supranuclear lesion (superior to a nucleus) causing tongue paralysis?

Area 4; primary motor cortex (lateral pre-central gyrus)

Which type of nerve fiber innervates skeletal muscle derived from mesenchyme of branchial arches? Where are their cell bodies located? Which CN have these nerve fiber types?

1. SVE - special visceral efferent (Identical to GSE). 2. Brainstem or spinal cord. 3. CN V (trigeminal), CN VII (facial), CN IX (glossopharyngeal), CN X (vagus) and CN XI (spinal accessory).

What type of muscles are innervated by CN III?

1. Skeletal muscle (GSE) - all extraocular muscles except superior oblique & lateral rectus muscle. 2. Smooth muscle (GVE) - pre-ganglionic paraysympathetic innervation to ciliary ganglion which innervate the pulpillary constrictor and ciliary muscles.

How is taste information transmitted to the cerebral cortex?

1. Solitary nucleus in the medulla receives inputs from: CN VII (anterior 2/3 of tongue), CN IX (posterior 1/3 of tongue), & CN X (epiglottis). 2. Solitary nucleus projects axons to VPM of thalamus. 3. Then VPM to lateral parts of post-central gyrus (primary somatosensory cortex or Area 3,1,2).

What type of movements are performed by the following eye muscles? Which nerves innervate them? 1. Superior oblique muscle. 2. Inferior oblique muscle.

1. Superior oblique (CN IV) - rotates eye downward when in medial position; internal rotation/intorsion. 2. Inferior oblique (CN III) - rotates eye upward when in medial position; external rotation/extorsion.

What type of movements are performed by the following eye muscles? Which nerves innervate them? 1. Superior rectus muscle. 2. Inferior rectus muscle.

1. Superior rectus muscle (CN III) - move eye upward. 2. Inferior rectus muscle (CN III) - move eye downward.

What are the common causes of damage to the opthalmic division of CN V? What symptoms are associated?

1. Tic Douloureaux (trigeminal neuralgia) - leads to severe pain in the area of distribution. 2. Opthalamic (herpes) zoster or shingles - associated with viral infection; leads to painful ulceration on cornea which can cause blindness.

What occurs if there is damage to the SVE motor component of CN VII? Does this follow general rule, UMN exception or LMN exception?

1. UMN lesion exception: contralateral lower half of face is paralyzed. 2. LMN lesion general rule: Paralysis of all muscles of face on ipsilateral side (including inability to wrinkle forehead).

What occurs if there is damage to the SVE motor component of CN IX? Does this follow general rule, UMN exception or LMN exception?

1. Weakness in muscle of pharynx and impared reflex dependent muscles (i.e. gag, uvular, and palatal reflexes). 2. General rule.

What type of reflex occurs from the innervation of the pupillary constrictor and ciliary muscles?

Accommodation reflex- action of the eye in response to focusing on a near object and then looking at a distant object (vice versa).

At what level do most cranial nerves (CN) exit the CNS?

Brainstem.

During a routine examination, a physician attempted to elicit a gag reflex response in a patient by stroking posterior pharynx with cotton tipped probe. This reflex is initiated primarily by activating the sensory endings of: a. CN IV. b. CN VII. c. CN IX. d. CN XI. e. CN XII.

C. CN IX Explanation: The afferent limb of the gag reflex involves GSA fibers of CN IX that enter the brainstem and make synapse with SVE fibers of CN X, which innervates the efferent limb of the gag reflex (pharyngeal muscles).

A 34-yr old man is hit in the head with a heavy object and was taken to the emergency room. He was given an MRI scan, and 36 hrs later, regained consciousness. Several days later, the patient reported difficulty in following a moving object presented within his visual field & also felt little to no sensation in his forehead after a mild pin prick administered to that region. The MRI provided evidence that the head injury most likely caused damage to: a. Peripheral fibers of the facial nerve. b. Central processes of the trigeminal nerve. c. Nerve fibers in the superior orbital fissure. d. Ventral half of the midbrain. e. Processes passing thru the jugular foramen.

C. Nerve fibers in the superior orbital fissure. Explanation: CN III, IV, VI, and opthalmic branch of CN V exit through the superior orbital fissure. Damage to this fissure would affect functions of these cranial nerves. CN III, IV, & VI - loss in ability to move eyes, such as in following a moving object. Opthalmic branch of CN V - loss of pain & temperature sensation to forehead.

Which CN are associated with mostly/only motor function?

CN III (occulomotor), IV (trochlear), VI (abducens), XI (Accessory spinal), XII (hypoglossal).

Which CN have both sensory and motor components?

CN V (trigeminal), VII (facial), IX (glossopharyngeal), X (vagus).

Which CN involved in eye movement is most susceptible to damage when there is high intercranial pressure caused by a posterior fossa tumor with hydrocephalus?

CN VI - due to its course ventral to the pons towards the cavernous sinus.

Which cranial nerves carry taste information?

CN VII (Facial), CN IX (Glossopharyngeal) and CN X (Vagus).

Of the (3) CN that only have sensory function, which have nuclei in the brainstem?

CN VIII has cochlear and vestibular nuclei in the brainstem.

What occurs if there is damage to the GSA component of CN V of the opthalmic division?

Corneal reflex will be lost.

A 60-yr old man was admitted to local hospital after c/o difficulty in swallowing and his voice becoming increasingly hoarse, and at times, little to no voice could be produced. Patient was given a neurologic/general medical examination and MRI. The examinations revealed deviations of the uvula to one side and significant reduction of gastric fluids. The MRI revealed the presence of a growing tumor, whose location is in the: a. Ventromedial medulla. b. Dorsolateral pons. c. Internal acoustic meatus. d. Jugular foramen. e. Hypoglossal canal.

D. Jugular foramen. Explanation: Jugular foramen contains fibers of CN IX & X. CN X (SVE) - innervates intrinsic muscles of larynx; results in loss of speech and affects swallowing (producing hoarseness). CN X (GVE) - reduction in gastric secretions.

A patient displays ipsilateral medial gaze paralysis coupled with contralateral hemiplegia. The lesion located in the: a. Medulla. b. Caudal pons. c. Rostral pons. d. Midbrain. e. Diencephalon.

D. Midbrain. Explanation: Medial gaze is governed by CN III, which passes close to crus cerebri en route to exiting the brain. Lesion affects fiber of CN III and descending fibers of corticospinal tract within crus cerebri. This lesion would produce paralysis of the limbs on contralateral side of body in addition to ipsilateral CN III palsy = Weber's syndrome.

In lateral gaze paralysis, both eyes are conjugatively directed to the side opposite the lesion. The most likely site of the lesion: a. CN III. b. MLF - medial longitudinal fasciculus. c. CN IV. d. Pontine gaze center. e. CN VI.

D. Pontine gaze center. Explanation: Pontine gaze center projects axons to ipsilateral CN VI (for lateral gaze) & contralateral CN III (for medial gaze). Conjugate lateral gaze requires activation of CN VI on one side & CN III on opposite side, which controlled by the pontine gaze center. Lesion at this site will produce conjugate gaze to the side opposite of the lesion due to unopposed action of the pontine gaze center on the intact side.

Name Function: CN VIII (Vestibulocochlear nerve) - Special somatic sensory (SSA).

Hearing and vestibular sensation

Name Function: CN XII (Hypoglossal nerve) - somatic motor (GVE).

Intrinsic muscles of the tongue

What type of movement is performed by the muscles innervated by CN XI?

Ipsilateral trapezius muscle and contralateral sternocleidomastoid muscle contract to tip the head up to observe an object in your hand.

Name Function: CN VI (Abducens nerve) - somatic motor (GSE).

Lateral rectus muscle; causes abduction of the eye

What occurs if there is a lesion in the nucleus ambiguus or SVE fibers of CN X? Does this lesion follow general rule, UMN exception, or LMN exception?

Lesion follows general rule: 1. Paralysis of pharynx and larynx. 2. Uvula is deviated to the normal side, hoarseness and difficulty in swallowing. 3. Asphyxia (oxygen deficiency) & Loss of voice if bilateral lesion.

Name Function: CN III (Oculomotor nerve) - somatic motor (GSE).

Levator palpebrae superior, and all extraocular muscles, except for superior oblique and lateral rectus

What occurs if there is bilateral damage to the sensory component of CN IX?

Loss of taste and sensation from posterior 1/3 of tongue

Bell's Palsy is the most common cause of ______ lesion where CN VII (facial) is affected as it transverses facial canal in petrous temporal bone.

Lower motor neuron (LMN).

Which sensory nucleus of CN V is involved in the jaw-jerk reflex?

Mesencephalic -unconconscious propioception from muscle spindle receptors in mandibular branch of CN V.

Name Function: CN VII (Facial nerve) - branchial motor (SVE).

Muscles of facial expression, stapedius muscle, and part of digastric muscle

Explain why the muscles of the forehead are not affected by an UMN lesion?

Muscles of forehead are innervated bilaterally (general rule) and are thus partially spared unless there is a bilateral lesion.

Name Function: CN V (Trigeminal nerve) - Branchial motor (SVE).

Muscles of mastication and tensor tympani muscle

Name Function: CN X (Vagus nerve) - parasympathetic (GVE).

Parasympathetics to heart, lungs, and digestive tract down to the splenic flexure

Name Function: CN VII (Facial nerve) - Parasympathetic (GVE).

Parasympathetics to lacrimal glands, and to submaxillary, submandibular, and all other salivary glands except parotid

Name Function: CN IX (Glossopharyngeal nerve) - Parasymphathetic (GVE).

Parasympathetics to parotid gland

Name Function: CN III (Oculomotor nerve) - parasympathetic general visceral efferent (GVE).

Parasympathetics to pupil constrictor and ciliary muscles for near vision

Name Function: CN X (Vagus nerve) - branchial motor (SVE).

Pharyngeal muscles (swallowing) and laryngeal muscles (voice box)

What type of muscles are innervated by CN VI?

Skeletal muscle (GSE) - lateral rectus muscle.

What type of muscles are innervated by CN IV?

Skeletal muscle (GSE) - superior oblique muscle.

Name Function: CN XI (Spinal accessory nerve) - branchial motor (SVE).

Sternomastoid and upper part of trapezius muscle

Name Function: CN IX (Glossopharyngeal nerve) - Branchial motor (SVE).

Stylopharyngeus muscle

Name Function: CN IV (Trochlear nerve) - somatic motor (GSE).

Superior oblique muscle; causes depression and intorsion of the eye

Name Function: CN VII (Facial nerve) - Special visceral sensory (SVA).

Taste from anterior two-thirds of tongue

Name Function: CN X (Vagus nerve) - special visceral sensory (SVA).

Taste from epiglottis and pharynx

Name Function: CN IX (Glossopharyngeal nerve) - special visceral sensory (SVA).

Taste from posterior one-third of tongue

Cell bodies of GSA fibers of CN V are lcoated in the _____ ganglion.

Trigeminal ganglion.

When CN IV (trochlear) is affected, patients compensate ____ diplopia by tilting their head so that the image from the normal eye aligns with the affected eye.

Vertical diplopia

Name Function: CN II (Optic nerve) - special somatic sensory (SSA).

Vision