Cranial Nerves PDF

Cranial nerves I – Olfactory II – Optic III – Oculomotor IV – Trochlear V – Trigeminal VI – Abducent VII – Facial VIII – Vestibulocochlear IX – Glossopharyngeal X – Vagus XI – Acc...

Cranial nerves I – Olfactory II – Optic III – Oculomotor IV – Trochlear V – Trigeminal VI – Abducent VII – Facial VIII – Vestibulocochlear IX – Glossopharyngeal X – Vagus XI – Accessory XII – Hypoglossal  Composition of cranial nerves Components found in nerves to other parts of the body GSA General somatic afferent: cutaneous, joints, and muscle sense GVA General visceral afferent: sense from internal organs GSE General somatic efferent: motor to voluntary muscle (somites) GVE General visceral efferent: smooth muscle and glands. All these components are also found in cranial nerves Special components only found in cranial nerves SSA special somatic afferent and SVA special visceral afferent Special senses: smell, taste, vision, hearing, and balance SVE special visceral efferent: voluntary motor to pharyngeal arch muscle.  Cranial nerve nuclei Somatic efferent nuclei supply General visceral efferent nuclei skeletal muscle that is derived The nuclei in this column give (embriologically) from origin to preganglionic fibres somites. They are as follows: that end in peripheral ganglia. 1. The oculomotor nucleus is Postganglionic fibres arising in situated in the midbrain these ganglia supply smooth (upper part, at the level of the muscle or glands. superior colliculus). The nuclei of the two sides form a single These neurons, preganglionic complex that lies in the and postganglionic, form part of central grey matter, ventral to the parasympathetic nervous the aqueduct. system. The nuclei of this group: 2. The trochlear nucleus is 1. The Edinger-Westphal nucleus situated in the midbrain lies in the midbrain (lower part, at the level of the 2. The salivatory nuclei (superior inferior colliculus). The and inferior) lie in the pons nucleus lies ventral to the (dorsal part) just above its aqueduct in the central grey junction with the medulla. matter.  Cranial nerve nuclei 3. The abducent nucleus is 3. The dorsal nucleus of the situated in the lower part vagus lies in the medulla. of the pons. It lies in the Special visceral efferent grey matter lining the floor nuclei of the fourth ventricle, These nuclei supply skeletal near the midline. muscle derived from 4. The hypoglossal nucleus branchial arch mesoderm. lies in the medulla. 1. Motor nucleus of the It is an elongated column trigeminal nerve lies in the extending into both the upper part of the pons, in its open and closed parts of dorsal part. the medulla. Its upper 2. The nucleus of the facial part lies deep to the nerve lies in the lower part hypoglossal triangle in the of the pons floor of the fourth ventricle. 3. The nucleus ambiguus lies in the medulla.  Cranial nerve nuclei General somatic afferent General and special visceral nuclei is represented by the afferent nuclei sensory nuclei of the 1. Both these columns are trigeminal nerve: represented by the nucleus of the solitary tract, present 1. The main sensory nucleus in the medull. lies in the upper part of the 2. Like other cranial nerve pons, lateral to the motor nuclei in the medulla, the nucleus of the nerve. cells of this nucleus form an 2. The spinal nucleus extends elongated column from the main nucleus down extending into both the into the medulla. In addition open and closed parts of to fibres of the trigeminal the medulla. nerve, it also receives 3. The nucleus of the solitary general somatic sensations tract receives fibres carried by the facial, carrying general visceral sensations through the glossopharyngeal and vagus vagus and nerves. glossopharyngeal nerves.  Cranial nerve nuclei 3. The mesencephalic 4. Fibres of taste (special nucleus of the visceral afferent) trigeminal nerve carried by the facial, extends from the upper glossopharyngeal and end of the main sensory vagus nerves end in the nucleus into the upper part of the midbrain. nucleus. This part also Special somatic known as the gustatory afferent nuclei nucleus. These are the cochlear and vestibular nuclei.  Cranial nerves CN having longest intraosseous Facial nerve course CN having longest extracranial Vagus nerve course 1. Thinnest and most slender Trochlear cranial nerve 2. Only one to originate from the dorsal surface 3. Longest intracranial course 1. Thickest and largest cranial Trigeminal nerve 2. Largest branch of trigeminal is mandibular nerve  Cranial nerves Arnold nerve Auricular branch of vagus (alderman nerve) Jacobson nerve Tympanic branch of glossopharyngeal nerve Criminal nerve of Grassi Branch of right posterior vagus that passes to left behind oesophagus ending in gastric cardia. It is cut in highly selective vagotomy to avoid recurrent peptic ulceration Nerve of Wrisberg Sensory component of facial nerve which carries taste sensation from anterior 2/3 of tongue Vidian nerve Nerve of pterygoid canal Nerve of Latarjet Branch of anterior gastric nerve and supplies the pylorus. It is left intact in highly selective vagotomy so that the function of gastric emptying remains intact.  First cranial nerve The olfactory cells (16-20 million) are bipolar neurons. They lie in the olfactory part of the nasal mucosa. The olfactory nerves, about 20 in number, represent central processes of the olfactory cells. They pass through the cribriform plate of ethmoid and make synaptic glomeruli with cells of olfactory bulb. Cells in olfactory bulb give off fibres that form olfactory tract and reach the primary olfactory areas. These are located in the primary olfactory cortex which includes the anterior perforated substance, periamygdaloid and prepiriform area. Third neuron located in the primary olfactory cortex which includes the anterior perforated substance, and several small masses of grey matter around it. Fibres arising in the primary olfactory cortex go to the secondary olfactory cortex located in the uncus and anterior part of the parahippocampal gyrus. The fibres reach the cerebral cortex without synapsing in any of the thalamic nuclei.  Second cranial nerve Optic nerve, constituted by the axons of ganglion cells in retina, project from the nasal hemiretina to the contralateral lateral geniculate body and from the temporal hemiretina to the ipsilateral geniculate body. Optic nerve axons are covered by a membrane continuous with the dura and leave the orbit by passing through the optic canal. Optic chiasma contains decussating fibers from the two nasal hemiretinas and non-crossing fibers from the two temporal hemiretinas. Optic tract contains fibres from the ipsilateral temporal hemiretina and the contralateral nasal hemiretina. It projects to the ipsilateral lateral geniculate body, pretectal nuclei, and superior colliculus. Third cranial nerve Oculomotor nerve. It is distributed to the extraocular as well as the Third cranial nerve intraocular muscles. Since it is a somatic motor nerve, it is in series with the IV, VI, and XII cranial nerves, and also with the ventral root of spinal nerves. Functional components 1. General somatic efferent, for muscles of eyeball which help in its movements 2. General visceral efferent or parasympathetic, for contraction of pupil and accommodation. 3. General somatic afferent column carries proprioceptive fibres from the extraocular muscles to mesencephalic nucleus of V.  Nucleus The oculomotor nucleus is situated in the ventromedial part of central grey matter of midbrain at the level of superior colliculus. Ventrolaterally, it is closely related to the medial longitudinal bundle. The nucleus is connected: To the pyramidal tracts of both sides which form the supranuclear pathway of the nerve. To the pretectal nuclei of both sides for the light reflex To the fourth, sixth and eight nerve nuclei by medial longitudinal bundle for coordination of the eye movements. To the tectobulbar tract for visuoprotective reflexes. 1. In the intraneural course, the fibres arise from the nucleus Course and and pass ventrally through distribution the tegmentum, red nucleus and substantia nigra. 2. At the base of the brain, the nerve is attached to the oculomotor sulcus on the medial side of the crus cerebri. 3. The nerve passes between the superior cerebellar and posterior cerebral arteries, and runs forwards in the interpeduncular cistern, on the lateral side of posterior communicating artery to reach the cavernous sinus. 4. The nerve enter the cavernous sinus by Course and piercing the posterior distribution part of its roof on the lateral side of the posterior clinoid process. It descends to the lateral wall of the sinus where it lies above the trochlear nerve. In the anterior part of the sinus, the nerve divides into upper and lower divisions. 5. The two divisions of the Course and nerve enter the orbit distribution through the middle part of the superior orbital fissure. In the fissure, the nasociliary nerve lies in between the two divisions while the abducent nerve lies inferolateral to them. 6. In the orbit, the smaller upper division ascends on the lateral side of optic nerve, and supplies the contralateral superior rectus and part of the levator palpebrae superior. The larger, lower, division divides into three branches for the insilateral medial rectus, the ipsilateral inferior rectus and the Course and ipsilateral inferior oblique. The nerve to the inferior oblique is the longest of distribution these. It gives off the parasympathetic root to the ciliary ganglion and then supplies the inferior oblique muscle. Forth cranial nerve Trochlear nerve supplies only Forth cranial the superior oblique muscle of the eyeball. It is the only nerve cranial nerve which emerges on the dorsal aspect of the brain stem. Functional components 1. General somatic efferent, for lateral movements of the eyeball. 2. The general somatic afferent, for proprioceptive impulses from the muscle to the mesencephalic nucleus of V nerve. The trochlear nucleus is situated in the ventromedial part of the central grey matter of midbrain at the level of inferior coliculus.  Course and distribution 1. In its intraneural course, the nerve runs dorsally round the central grey matter to reach the upper part of the superior or anterior medullary velum where it decussates with opposite nerve to emerge on the opposite side. 2. Surface attachment. Trochlear nerve is attached to the superior medullary velum one on each side of the frenulum veli just below the inferior colliculus. It is the only cranial nerve which emerges on the dorsal aspect of the brain stem. 3. The nerve winds round the superior cerebellar peduncle and the cerebral peduncle just above the pons. It passes between the posterior cerebral and superior cerebellar arteries to appear ventrally between the temporal lobe and upper border of pons.  Course and distribution 4. The nerve enters the cavernous sinus by piercing the posterior corner of its roof. Next it runs forwards in the lateral wall of cavernous sinus between the oculomotor and ophthalmic nerves. In the anterior part of sinus, it crosses over the oculomotor nerve. Course and 5. Trochlear nerve enters the orbit distribution through the lateral part of the superior orbital fissure. 6. In the orbit, it passes medially, above the origin of Trochlear levator palpebrae nerve superioris and ends by supplying the contralateral superior oblique muscle on its orbital sirface. Forth cranial nerve Sixth cranial nerve This is the sixth cranial nerve. It is made up of fibres that arise Abducent nerve in the abducent nucleus and supply the lateral rectus muscle of the eyeball. The abducent nucleus is located in the lower part of the pons, in relation to the upper part of the floor of the fourth ventricle. The position of the nucleus in relation to the floor of the fourth ventricles is indicated by an elevation called the facial colliculus. Arising from this nucleus the fibres of the nerve pass through the substance of the pons and emerge on the surface of the brainstem at the lower border of the pons cranial to the pyramid. The nerve then runs upwards, forwards and laterally. Abducent nerve It pierces the dura lateral to the dorsum sellae of the sphenoid bone. It then runs upwards to reach the upper border of the petrous temporal bone and bends round it to enter the middle cranial fossa. The nerve now comes to lie within the cavernous sinus, where it is closely related to the internal carotid artery. The nerve is first lateral to the artery and then inferolateral to it. At the anterior end of the cavernous sinus Abducent the nerve passes nerve through the superior orbital fissure to enter the orbit.  Abducent nerve The nerve ends by supplying the lateral rectus muscle. The fibres of the abducent nerve are classified as somatic efferent.  Fifth cranial nerve Trigeminal nerve has one motor and three sensory nuclei. The motor nucleus is located in pons and send the motor fibers by mandibular nerve. Sensory nuclei: 1. Mesencephalic nucleus: this nucleus extends in the midbrain. It receives proprioceptive impulses from muscle of mustication, temporomandibular joint and teeth. 2. Principle sensory nucleus of V nerve: fibres carrying touch and pressure relay in this nucleus. 3. Spinal nucleus of V nerve: fibres conveying pain and temperature sensation from most of the face area.  Fifth cranial nerve Trigeminal (semilunar) ganglion consists of cell bodies of sensory fibers that distribute along three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3). It creates an impression at the apex of the petrous portion of the temporal bone in the middle cranial fossa and is located in a pouch between two layers of dura (Meckel cave). Trigemin al ganglion  Fifth cranial nerve Ophthalmic division is sensory innervates the area above the upper eyelids and dorsum of the nose. Exits skull through superior orbital fissure. Branches Subdivisions Region Frontal nerve Supratrochlear Upper eyelid, conjunctiva, lower part of forehead Supraorbital Frontal sinus, upper eyelid, forehead Nasociliary nerve Posterior ethmoidal Sphenoidal sinus, posterior ethmoidal sinus Anterior ethmoidal Middle, anterior ethmoidal sinus Long ciliary Sensory to eyeball Infratrochlear Eyelids, lacrimal sac Branch to ciliary ganglion  Fifth cranial nerve Maxillary nerve (sensory) is constituted by axon given by cell bodies in the trigeminal ganglion, pass through the lateral wall of the cavernous sinus and next the foramen rotundum to enter the pterygopalatine fossa. Region Branches In the middle cranial fossa Meningeal branch In the pterygopalatine Ganglionic branches fossa Posterior superior alveolar Zygomatic nerve In the infraorbital canal Middle superior alveolar Anterior superior alveolar On the face Palpebral branch Nasal branch Labial branch  Fifth cranial nerve Mandibular nerve is given at trigeminal ganglion at the floor of the middle cranial fossa and passes through the foramen ovale to enter the infratemporal region. It provides sensory innervation to the lower teeth and gum and to the lower part of the face below the lower lip and mouth. It supplies 8 muscles developing in first pharyngeal arch. Branches of the Branches from Branches from main trunk anterior division posterior division 1.Nerve spinosus 1.Masseteric 1.Auriculotemporal (meningeal branch) 2.Lateral pterygoid nerve: a) Auricular b) Superior temporal c) To TMJ d) To parotid gland 2.Lingval 2.Nerve to medial 3.Deep temporal pterygoid: 3.Inferior alveolar : 4.Buccal a) Tensor veli palatini a) Mylohyoid b) Tensor tympani b) Anterior belly of c) Medial ptrygoid digastric Fifth cranial nerve  Seventh cranial nerve Facial nerve is the nerve of the second branchial arch. Facial nerve has two parts: motor to facial expression muscles and nervus intermedius. The fibers arise from the motor nucleus of facial nerve, loop around the abducent nucleus, raising facial colliculus, exit the brainstem at the ponto-medullary junction. Next the fibers enter the internal auditory meatus, pass through the facial canal in the middle ear cavity, give a branch to stapedius muscle, exit the skull through the stylomastoid foramen. The nerve fibers innervate stylohyoid muscle, posterior belly of the digastric muscle, auricular muscle and enter the parotid gland to give rise to 5 terminal branches (temporal, zygomatic, buccal, marginal mandibular, cervical) to supply muscles of facial expression. Seventh cranial nerve  Seventh cranial nerve Nervus intermedius (nerve of Wrisberg) carries fibers for taste, salivation, lacrimation, and general sensation (from the external ear). It has two nucleus: superior salivatory nucleus and nucleus tractus solitarius. Superior salivatory nucleus contains the cell bodies of parasympathetic axonswithing the nervus intermedius. These secretomotor fibers reach the geniculate ganglion, pass through it without synapse and carry preganglionic parasympathetic secretory fibers to glands by two pathways: 1. Lacrimal pathway- secretomotor fibers pass through the nervus intermedius and greater petrosal nerve to the pterygopalatine ganglion. 2. Submandibular pathway - secretomotor fibers pass through the nervus intermedius and chorda tympani to the submandibular ganglion to innervate the submandibular and sublingual glands.  Seventh cranial nerve Greater petrosal nerve is a branch of the facial nerve that arises distal to the geniculate ganglion, inside the facial canal in middle ear cavity. It enters the middle cranial fossa through the hiatus for greater petrosal nerve. It proceeds towards the foramen lacerum, where it joins the deep petrosal nerve to form the Vidian nerveof the pterygoid canal, which passes through the pterigoid canal to reach the pterygopalatine ganglion. Postganglionic parasympathetic fibers from pterygopalatine ganglion supply lacrimal gland and the mucosal glands of the nose, palate, and pharynx. Vidian nerve is formed by union of greater petrosal nerve with deep petrosal nerve. This nerve is formed at the floor of foramen lacerum and runs anteriorly in pterigoid canal to reach the pterygopalatine ganglion. Chorda tympani nerve is given in the middle ear cavity it carries secretomotor fibers for submandibular and sublingual glands and taste sansations from anterior 2/3 of the tongue towards the geniculate ganglion and next run in facial nerve to reach the nucleus tractus solitarius. Seventh cranial nerve  Eighth cranial nerve The vestibulocochlear nerve is the eighth paired cranial nerve. It is comprised of two parts – vestibular fibres and cochlear fibres. Both have a purely sensory function. The vestibular and cochlear portions of the vestibulocochlear nerve are functionally discrete, and so originate from different nuclei in the brain: Vestibular component – arises from the vestibular nuclei complex in the pons and medulla. Cochlear component – arises from the ventral and dorsal cochlear nuclei, situated in the inferior cerebellar peduncle. Both sets of fibres combine in the pons to form the vestibulocochlear nerve. The nerve emerges from the brain at the cerebellopontine angle and exits the cranium via the internal acoustic meatus of the temporal bone. Within the distal aspect of the internal acoustic meatus, the vestibulocochlear nerve splits, forming the vestibular nerve and the cochlear nerve. The vestibular nerve innervates the vestibular system of the inner ear, which is responsible for detecting balance. The cochlear nerve travels to cochlea of the inner ear, forming the spiral ganglia which serve the sense of hearing.  Eighth cranial nerve The vestibulocochlear nerve is unusual in that it primarily consists of bipolar neurones. It is responsible for the special senses of hearing (via the cochlear nerve), and balance (via the vestibular nerve). Hearing The cochlea detects the magnitude and frequency of sound waves. The inner hair cells of the organ of Corti activate ion channels in response to vibrations of the basilar membrane. Action potentials travel from the spiral ganglia, which house the cell bodies of neurones of the cochlear nerve. The magnitude of the sound determines how much the membrane vibrates and thereby how often action potentials are triggered. Louder sounds cause the basilar membrane to vibrate more, resulting in action potentials being transmitted from the spiral ganglia more often, and vice versa. The frequency of the sound is coded by the position of the activated inner hair cells along the basilar membrane.  Eighth cranial nerve Equilibrium (Balance) The vestibular apparatus senses changes in the position of the head in relation to gravity. The vestibular hair cells are located in the otolith organs (the utricule and saccule), where they detect linear movements of the head, as well as in the three semicircular canals, where they detect rotational movements of the head. The cell bodies of the vestibular nerve are located in the vestibular ganglion which is housed in the outer part of the internal acoustic meatus. Information about the position of the head is used to coordinate balance and the vestibulo-ocular reflex. The vestibulo- ocular reflex (also called the oculocephalic reflex) allows images on the retina to be stabilised when the head is turning by moving the eyes in the opposite direction. It can be demonstrated by holding one finger still at a comfortable distance in front of you and twisting your head from side to side whilst staying focused on the finger.  Ninth cranial nerve Glossopharyngeal nerve belongs to the third branchial arch.  Ninth cranial nerve Glossopharyngeal nerve exit the cranial cavity through the jugular foramen, gives the following branches: 1. The tympanic nerve contributes to the tympanic plexus on the medial wall of the middle ear with sympathetic fibers from the internal carotid plexus. Its secretomotor axons continue beyond the tympanic plexus as the lesser petrosal nerve in the floor of the middle cranial fossa, which leaves through the foramen ovale to bring preganglionic parasympathetic fibers to the otic ganglion. Postganglionic parasympathetic fibers leave the otic ganglion to innervate the parotid gland. 2. The carotid branch supplies the carotid sinus and the carotid body. 3. The pharyngeal branches 4. The muscular branch supplies the stylopharyngeus muscle. 5. The tonsillar branch 6. The lingual branch carry taste and general sensations from the posterior 1/3 of the tongue including the circumvallate papillae. Ninth cranial nerve  Tenth cranial nerve Vagus nerve has the largest distribution in the body and contributes about 75% to the parasympathetic system. Nuclei : 1. Nucleus ambiguus 2. Dorsal nucleus of vagus (parasympathetic): it is a mixed nucleus, being both motor (visceromotor and secretomotor) and sensory (viscerosensory) 3. Nucleus of tractus solitarius (gustatory) 4. Nucleus of spinal tract of trigeminal  Tenth cranial nerve In the jugular foramen, the superior ganglion gives off: Meningeal and Auricular branches The ganglion also gives off communicating branches to the glossopharyngeal and cranial root of accessory nerves and to the superior cervical sympathetic ganglion.  Tenth cranial nerve In the neck, the vagus nerve passes into the carotid sheath, travelling inferiorly with the internal jugular vein and common carotid artery. At the base of the neck, the right and left nerves have differing pathways: The right vagus nerve passes anterior to the subclavian artery and posterior to the sternoclavicular joint, entering the thorax. The left vagus nerve passes inferiorly between the left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering the thorax. Several branches arise in the neck: Pharyngeal branches – Provides motor innervation to the majority of the muscles of the pharynx and soft palate. Superior laryngeal nerve – Splits into internal and external branches. The external laryngeal nerve innervates the cricothyroid muscle of the larynx. The internal laryngeal provides sensory innervation to the laryngopharynx and superior part of the larynx. Recurrent laryngeal nerve (right side only) – Hooks underneath the right subclavian artery, then ascends towards to the larynx. It innervates the majority of the intrinsic muscles of the larynx. Carotid branch supply the carotid body and carotid sinus.  Tenth cranial nerve In the thorax, the right vagus nerve forms the posterior vagal trunk, and the left forms the anterior vagal trunk. Branches from the vagal trunks contribute to the formation of the oesophageal plexus, which innervates the smooth muscle of the oesophagus. Two other branches arise in the thorax: Left recurrent laryngeal nerve – it hooks under the arch of the aorta, ascending to innervate the majority of the intrinsic muscles of the larynx. Cardiac branches – these innervate regulate heart rate and provide visceral sensation to the organ. The vagal trunks enter the abdomen via the oesophageal hiatus, an opening in the diaphragm. In the Abdomen In the abdomen, the vagal trunks terminate by dividing into branches that supply the oesophagus, stomach and the small and large bowel (up to the splenic flexure). Tenth cranial nerve  Eleventh cranial nerve Accessory nerve has two parts: cranial and spinal. Cranial root arise from the medulla oblongata below the roots of the vagus. Spinal roots arises from spinal cord C1- C5, form a trunk that ascends in the vertebral canal, enter foramen magnum and join the cranial part. Both pass through the jugular foramen, cranial accessory fibers join the vagus nerve to innervate the muscles of palate, pharynx and larynx. The spinal accessory nerve supplies sternocleidomastoid muscle, lies on levator scapulae in the posterior cervical triangle, then reach and supply trapezius.  Twelfth cranial nerve The hypoglossal nerve is the twelfth paired cranial nerve. Its name is derived from ancient Greek, ‘hypo‘ meaning under, and ‘glossal‘ meaning tongue. The nerve has a purely somatic motor function, innervating the majority of the muscles of the tongue. The hypoglossal nerve arises from the hypoglossal nucleus in the medulla oblongata of the brainstem. It then passes laterally across the posterior cranial fossa, within the subarachnoid space. The nerve exits the cranium via the hypoglossal canal. Now extracranial, the nerve receives a branch of the cervical plexus that conducts fibres from C1/C2 spinal nerve roots. These fibres do not combine with the hypoglossal nerve – they merely travel within its sheath. It then passes inferiorly to the angle of the mandible, crossing the internal and external carotid arteries, and moving in an anterior direction to enter the tongue.  Twelfth cranial nerve The hypoglossal nerve is responsible for motor innervation of the vast majority of the muscles of the tongue (except for palatoglossus). These muscles can be subdivided into two groups: 1) Extrinsic muscles Genioglossus (makes up the bulk of the tongue) Hyoglossus Styloglossus Palatoglossus (innervated by vagus nerve) 2) Intrinsic muscles Superior longitudinal Inferior longitudinal Transverse Vertical Together, these muscles are responsible for all movements of the tongue.  Twelfth cranial nerve Role of the C1/C2 Roots The C1/C2 roots that travel with the hypoglossal nerve also have a motor function. They branch off to innervate the geniohyoid (elevates the hyoid bone) and thyrohyoid (depresses the hyoid bone) muscles. Another branch containing C1/C2 fibres descends to supply the ansa cervicalis – a loop of nerves that is part of the cervical plexus. From the ansa cervicalis, nerves arise to innervate the omohyoid, sternohyoid and sternthyroid muscles. These muscles all act to depress the hyoid bone.  Qustion 1. The vagus nerve is associated with the derivatives of which pharyngeal arch? a) 1st b)2nd c) 3rd d)4th  Question 2. Which branch of the vagus nerve does not arise in the neck? a) Pharyngeal branches b)Auricular branches c) Superior laryngeal nerve d)Recurrent laryngeal nerve  Question 3. What is the main function of the recurrent laryngeal nerve? a) Motor innervation to the intrinsic muscles of the larynx b)Sensory innervation to the posterior part of the external auditory canal c) Motor innervation to the muscles of the pharynx d)Parasympathetic innervation to  Question 4. Through which structures do the spinal accessory nerve enter and exit the cranium respectively? a) Foramen magnum and foramen ovale b)Foramen magnum and jugular foramen c) Jugular foramen and foramen magnum d)Foramen magnum and foramen  Question 5. Which of the following is an extracranial branch of the facial nerve? a) Nerve to stapedius b)Greater petrosal nerve c) Chorda tympani d)Buccal nerve  Question 6. At which point along the course of the facial nerve are the terminal motor branches released? a) Within the facial canal b)At the stylomoastoid foramen c) At the geniculate ganglion d)Within the parotid gland  Question 7. What is the function of the hypoglossal nerve? a) Somatic sensory b)Visceral sensory c) Visceral motor d)Somatic motor  Question 8. What extrinsic tongue muscle is not innervated by the hypoglossal nerve? a) Genioglossus b)Hypoglossus c) Palatoglossus d)Styloglossus