PNS Exam 2 Material

Cranial nerve VIII (Vestibulocochlear Nerve) carries what information?

Purely sensory!

CN VIII = 2 nerves that NEVER mix (vestibular and cochlear nerves)

Where does the vestibular nerve terminate?

Vestibular nuclear complex

What are the 4 parts of the vestibular nuclear complex? Which part receives most information?

(1) Superior (Bechterew)

(2) Medial (Schwalbe)

(3) Lateral (Dieter)

(4) Inferior

Medial receives most information

Where do we find the cell bodies of fibers carried in the vestibular nerve?

Vestibular ganglion

Located in the internal acoustic meatus

What are the two parts of the vestibular ganglion?

(1) Superior part

(2) Inferior part

Where do we find the cell bodies of fibers carried in the cochlear nerve?

Spiral ganglion

Located within the cochlea

What are the 2 cochlear nuclei?

Anterior and posterior cochlear nuclei

The cochlear nerve is made up of what type of neurons?

Bipolar neurons

What is the "hearing receptor"?

Spiral organ (Organ of Corti)

Where do dendrites of the bipolar neurons of the cochlear nerve extend?

Dendrites (peripheral processes) extend from the spiral organ (organ of Corti) and carry information to the spiral ganglion

Where do axons from the spiral ganglion travel (terminate)?

Axons carry information in the cochlear nerve to terminate in the two cochlear nuclei

Where are the cochlear nuclei located?

Posterior, superior medulla oblongata, lateral to the vestibular nuclei

Where do axons travel from the cochlear nuclei? (3 steps)

(1) Axons cross to the other side of the brainstem

(2) Synapse in the trapezoid nuclei OR superior olivary nucleus

(3) Axons form the lateral lemniscus

Won't test because tested in CNS but reminder: lateral lemniscus carries auditory information to the medial geniculate body (thalamus) and then info goes to the temporal lobe

Where do dendrites from the vestibular ganglion extend?

Dendrites extend to 3 inner ear structures:

(1) saccule

(2) utricle

(3) semicircular canals

Where do axons from the vestibular ganglion travel?

Carry information to the vestibular nuclei

Where is the vestibular nuclei located?

Medulla oblongata on the floor of the rhomboid fossa

Which nucleus does most vestibular nerve fibers terminate at?

Medial Vestibular Nucleus (Schwalbe)

Some fibers from the vestibular nerve do not synapse at the vestibular nuclei. Where do these fibers go?

Travel directly to the cerebellum by way of the inferior cerebellar peduncle

What is the apparent origin of the vestibulocochlear nerve?

Cerebellopontine angle (recess)

Where does the vestibulocochlear nerve travel after it exits the CNS?

Travels in the posterior cranial fossa to the internal acoustic meatus (enters the internal acoustic meatus with the facial nerve)

The cochlear nerve carries how many fibers?

About 30-40,000 fibers

Where does the cochlear nerve travel once it enters the internal acoustic meatus?

Travels along the internal acoustic meatus inferior to the facial nerve

Leaves the temporal bone and reaches the spiral ganglion of the cochlea

The vestibular nerve carries how many fibers?

About 20,000 fibers

What happens to the vestibular nerve as it approaches the ear?

Divides into superior and inferior branches

Superior branch = larger

The inferior branch of the vestibular nerve carries approximately how many fibers?

About 8,000 fibers

What nerves make up the inferior branch of the vestibular nerve?

(1) Saccular Nerve

(2) Posterior Ampullary Nerve

What does the saccular nerve supply?

Saccule

What does the posterior ampullary nerve supply?

Posterior ampullary crest

The superior branch of the vestibular nerve carries approximately how many fibers?

About 12,000 fibers

What nerves make up the superior branch of the vestibular nerve?

(1) Lateral Ampullary Nerve

(2) Anterior Ampullary Nerve

What does the lateral ampullary nerve supply?

Lateral semicircular canal

What does the anterior ampullary nerve supply?

Anterior semicircular canal

What is the utricle supplied by?

2 Branches:

(1) a branch from the lateral ampullary nerve

(2) a branch directly off the superior branch of the vestibular nerve

Where does Voit's nerve branch off of? What does it supply?

Branch off the superior branch of the vestibular nerve

Supplies the saccule

What is an acoustic neuroma/vestibular schwannoma? (What is the slight difference between the two?

Tumor of CN VIII

Name difference is due to the patient's initial symptoms:

— acoustic neuroma = hearing problems

— vestibular schwannoma = equilibrium problems

What is tinnitus? This is commonly the first sign of what disease?

Ringing of the ears

Commonly the first sign of Meniere's disease (vertigo, tinnitus, and hearing loss)

When can we use cochlear implants? When are they not useful?

Used for sensory/neural issues

NOT useful for conductive hearing loss

What is Vestibular disease? How is this different from cervicogenic vertigo? How do you test which one?

Equilibrium problems (vertigo) due to issue with vestibular nerve

Cervicogeneic vertigo = issues with cervical spine instead

To test: hold head still and turn body in a spinning chair

CN IX (glossopharyngeal nerve) carries what type of information?

(1) Motor

(2) Sensory

(3) Autonomic (parasympathetic)

What muscle(s) does the glossopharyngeal nerve supply?

Stylopharyngeus muscle

Where are the cell bodies of motor fibers (LMNs) in the glossopharyngeal nerve?

Superior part of the nucleus ambiguus

Preganglionic parasympathetic fibers carried in the glossopharyngeal nerve originate where?

Inferior salivary nucleus

Where do sensory fibers in the glossopharyngeal nerve terminate?

(1) Solitary nucleus (taste in the superior part)

(2) Spinal nucleus of trigeminal (pain anf temperature)

What are the two peripheral ganglia associated with the glossopharyngeal nerve?

Superior ganglion (smaller) and inferior ganglion (also called petrosal ganglion)

What areas does the glossopharyngeal nerve supply general sensory for?

(1) Nasopharynx

(2) Oropharynx

(3) Posterior 1/3 of the tongue

(4) Uvula

(5) Palatine tonsils

(6) Tympanic cavity (NOT hearing sensory — pain = middle ear infections)

Glossopharyngeal neurons carrying general sensory have their cell bodies where? Where do these fibers terminate?

Inferior ganglion

Terminate in the spinal nucleus of the trigeminal (pain and temperature)

The glossopharyngeal nerve carries taste information from where? Where do these neurons have their cell bodies? Where do they terminate?

Posterior 1/3 of the tongue (behind the sulcus terminalis)

Cell bodies in the inferior ganglion

Terminate in the superior part of the solitary nucleus

Some fibers from the inferior ganglion of the glossopharyngeal nerve synapse in the lower part of the solitary nucleus. What do these fibers carry?

Visceral afferent information from the carotid sinus and carotid body

The nucleus ambiguus contributes LMNs to which 3 cranial nerves?

C.N. IX, X, and XI

Preganglionic parasympathetic axons carried by the glossopharyngeal nerve originate where? Where do they synapse?

Originate: inferior salivary nucleus

Synapse in the otic ganglion

Where do postganglionic parasympathetic fibers from the otic ganglion travel and supply?

Fibers follow the auriculotemporal nerve

Supplies:

(1) Parotid gland

(2) Buccal glands

(3) Inferior labial glands

What is the apparent origin of the glossopharyngeal nerve?

Superior, lateral aspect of the medulla oblongata

Where does the glossopharyngeal nerve exit the skull?

Jugular foramen

Where are the superior and inferior ganglia located?

Superior = inside the cranium

Inferior = beyond the jugular foramen, outside the cranium

The tympanic nerve arises from which ganglion?

Inferior ganglion

What information does the tympanic nerve carry?

(1) Preganglionic parasympathetic fibers (end in the otic ganglion)

(2) Sensory fibers

Where does the tympanic nerve travel? What fibers does it gain here?

Fibers are carried through the tympanic canaliculus into the tympanic cavity

In the tympanic cavity, it receives postganglionic sympathetic fibers from the superior cervical ganglion to form the tympanic plexus

The Tympanic Plexus carries somatosensory information from which structures?

(1) Tympanic cavity

(2) Pharyngotympanic tube (Eustachian tube)

(3) mastoid air cells

Carries primarily pain and temperature

Preganglionic parasympathetic fibers pass through the tympanic plexus and form what nerve? Where does it travel?

Lesser petrosal nerve

Travels through the lesser petrosal canal to the otic ganglion

Where does the carotid branch join the glossopharyngeal nerve? What information does it carry?

Ascends from below and enters the nerve at the inferior ganglion

Carries afferent information from chemoreceptors in the carotid body and baroreceptors in the carotid sinus

What do pharyngeal branches of the glossopharyngeal nerve supply?

Sensory information from the mucosa of the pharynx

What do fibers of the pharyngeal branches of the glossopharyngeal nerve combine with? What does this form?

Combine with some vagal branches to form the pharyngeal plexus

What does the muscular branch of the glossopharyngeal nerve supply?

Stylopharyngeus muscle

Action: elevate larynx and pharynx

Tonsilar branches of the Glossopharyngeal nerve supply what?

Sensory information from:

(1) palatine tonsils

(2) Oral mucosa

Lingual branches of the glossopharyngeal nerve supply what?

General sensory and taste from the posterior 1/3 of the tongue (behind the sulcus terminalis)

What is the longest and most important parasympathetic cranial nerve?

C.N. X (Vagus nerve)

What type of information does the vagus nerve carry?

Mixed:

— motor

— parasympathetic

— sensory (including some taste)

Motor fibers in the vagus nerve originate from where?

Nucleus ambiguus

Where do preganglionic fibers in the vagus nerve originate from? Where does this receive information from?

Posterior (dorsal) nucleus of the vagus

Receives information directly from the hypothalamus and the carotid sinus

Where does somatic sensory information carried in the vagus nerve terminate?

Spinal nucleus of trigeminal

Where does taste and viscerosensory information carried in the vagus terminate?

Nucleus of the solitary tract (solitary nucleus)

What two peripheral ganglia are associated with the vagus nerve?

Superior (jugular) and inferior (nodose) ganglia

Note: NOT the same as glossopharyngeal superior and inferior ganglia

Somatic sensory fibers in the vagus nerve has their cell bodies where? Where do they carry information to?

Superior ganglion

Synapse in the spinal nucleus of the trigeminal nerve

Somatic sensory information in the vagus nerve is carried from where?

(1) dura (infratentorial/posterior fossa)

(2) auricle

(3) external auditory canal

(4) lateral tympanic membrane

(5) mucosa of the oropharynx and laryngopharynx

The vagus nerve carries taste from where?

Epiglottis

Vagus fibers carrying taste have their cell bodies where? Where do they carry information to?

Cell bodies in the inferior ganglion

Synapse in the superior part of the solitary nucleus

Where do fibers carrying visceral sensory information have their cell bodies? Where do they synapse?

Cell bodies in the inferior ganglion

Synapse in the inferior part of the solitary nucleus

Where does the vagus nerve carry visceral sensory information from?

(1) larynx

(2) laryngopharynx

(3) viscera in the thoracic and abdominal cavities

(4) pressure receptors in the aortic arch

(5) chemoreceptors in the para-aortic body

What is the apparent origin of the vagus nerve?

Lateral aspect of the medulla oblongata as a series of rootlets

These rootlets combine to form a trunk before it exits the skull

Before the vagus exits the skull, what branch does it give off?

Meningeal branch

What does the meningeal branch of the vagus nerve supply?

Dura of the posterior cranial fossa

The jugular foramen is compartmentalized by what structure?

Fibrous septum

The vagus and accessory nerves travel where relative to the fibrous septum of the jugular foramen? Where does the glossopharyngeal nerve travel?

Vagus and accessory nerve = anterior to the fibrous septum

Glossopharyngeal nerve = posterior to the fibrous septum

The vagus nerve shares a meningeal sheath with which nerve?

Accessory nerve

Where is the superior ganglion located? Inferior ganglion?

Superior Ganglion = Jugular foramen

Inferior Ganglion = inferior to the jugular foramen (outside the cranial vault)

Which branch is given off the vagus nerve at the superior ganglion? Where does it travel?

Auricular branch

Travels through the mastoid canaliculus and the tympanomastoid fissure to reach the external auditory meatus

What does the auricular branch supply?

Sensory information from the meatus and a small portion of the auricle

Where does the vagus nerve travel once it leaves the jugular foramen?*

Travels inferiorly within the carotid sheath between the internal carotid artery and the internal jugular vein

It will travel between the internal jugular vein and common carotid artery inferior to the carotid bifurcation

What branches does the vagus nerve give off in the neck?

(1) Pharyngeal Branch

(2) Branches to the Carotid Artery

(3) Superior Laryngeal Branch

(4) Recurrent Laryngeal Nerve

(5) Superior and Inferior Cardiac Branches

When does the pharyngeal branch come off the vagus nerve?

At the level of the inferior ganglion

What does the pharyngeal branch combine with to form the pharyngeal plexus?

Glossopharyngeal nerve and sympathetic fibers from the sympathetic trunk

Vagal fibers in the pharyngeal plexus supply what?

Motor supply to:

(1) pharyngeal constrictor muscle

(2) levator veli palatine muscle

What other branches of the vagus nerve are given off at the inferior ganglion?

Branches to the carotid artery

What do branches to the carotid artery supply?

Visceral sensory information from chemoreceptors in the carotid body

Where does the vagus nerve give off the superior laryngeal nerve?

Given off just inferior to the inferior ganglion

The superior laryngeal nerve gives off what two branches?

(1) External Laryngeal Nerve

(2) Internal Laryngeal Nerve

What does the external laryngeal nerve supply?

Motor supply to the cricothyroid muscle

What does the internal laryngeal nerve supply?

Sensory from the laryngeal mucosa as far inferior as the vocal folds

What does the recurrent laryngeal nerve supply?

Motor fibers to all the muscles of the larynx EXCEPT the cricothyroid

Muscles: thyroarytenoid, posterior cricoarytenoid, lateral cricoarytenoid, and arytenoid muscles

Sensory from the larynx inferior to the vocal folds

Where dose the recurrent laryngeal nerve on the LEFT side come off the vagus nerve? Where does it pass?

Comes off after the vagus nerve passes in front of the aortic arch

Then passes under the aortic arch and ascends to become the inferior laryngeal nerve