Cranial nerves 8-12 Flashcards
What is the function and pathway of the vestibulocochlear nerve?
- CN VIII; this nerve leaves the cranial vault through the internal acoustic meatus side by side with the facial nerve. But once in the petrous portion of the temporal bone it takes an alternate route and terminates within the inner ear. (Purely sensory nerve).
- A truly sensory nerve that is a combination of two separate branches.
- -The cochlear nerve receives sensory input from the cochlea convey the special sense of sound.
- -The vestibular branch receives sensory information from the vestibular apparatus composed of the auto lifts and semicircular canals which conveys information related to balance in equilibrium.
What happens if you damage the cochlear branch or damage the vestibular branch of the vestibulocochlear nerve?
- Damage to cochlear will affect hearing
- Damage to the vestibular branch would result in feelings of vertigo which is a medical term to describe the error in perception in which stationary objects are perceived as to be in motion.
What symptoms are carried over with vertigo?
- associated with dizziness, nausea and a phenomenon known as nystagmus (reflexive movement of the eyes back & forth due to rapid coordinated contractions and relaxations between the medial and lateral rectus muscles).
- Nystagmus help when a person is spinning horizontally it helps the eyes fixate on stationary objects in a person’s surroundings to help maintain orientation. So it’s natural only when a person is spinning around.
What is the pathway and function of the glossopharyngeal nerve?
- The first of the three cranial branches exiting the cranial vault through the jugular foramen
- A bulge right as the nerve exits the jugular foramen indicates the existence of the petrous ganglion and just before the nerve exits the foramen you find the superior ganglion; They both contain cell bodies for sensory function coming back from Naso and oropharynx.
- as CN IX descends it wraps itself around the internal carotid artery which makes it medial to the vessel inferior to the styloid process
- It keeps descending on the lateral surface of the stylopharyngeus muscle providing a brachial motor function to the stylopharyngeus m (only muscle innervated by CN IX).
Describe the relationship between the three nerves exiting the jugular foramen?
-bunch of communicating branches between them as we
What forms the pharyngeal plexus?
- The CN IX nerve branches and many of its fibers combine with CNX fibers remaining in posterior pharynx and forming the pharyngeal plexus.
- CNX would provide motor innervation while the CN IX would recieve general sensory of this region
What is the pathway of the branches of CN IX that passes through superior and middle pharyngeal constrictor muscles?
=They pass through these muscles to reach the mucosa of Naso and oropharynx
- The lingual branch terminates in the mucosa of the oropharynx and posterior 1/3 of the tongue. THis provides general sensory and special sense of taste back to brain stem.
- This contrasts with the anterior 2/3 of the tongue where the trigeminal nerve provided general sensory for that region and the facial nerve for taste
=Tonsillar branches from as well in that region and passes to the palatine tonsils innervating the mucosa in the inferior nasopharynx
=Finally there is also the nerve to the carotid sinus which remains with the wall of the carotid sinus and receives information regarding chemo and baro reception from carotid body in this region
Describe the path from the glossopharyngeal nerve to the parotid gland with the ins and outs
- Preganglionic fibers originate in the brain stem (inferior Salvatori nucleus) merge with other components of glossopharyngeal nerve fibers and exits through the jugular foramen.
- Then they course into tympanic nerve (general sensory fibers) and pass through the tympanic plexus and form the lesser petrosal nerve.
- They preganglionic fibers then pass through foramen ovale to enter otic ganglion and synapse with postganglionic fibers
- Postganglionic fibers pass from the otic ganglion into the auricular temporal nerve and finally pass through parotid glands via short communicating branches
- In conclusion, the parasympathetic fibers of CN IX produce salivation within the parotid gland only.
What does damage to CN IX results in?
- would affect salivation from parotid glands
- other symptoms inclide altered sensation towards the back of the mouth (taste of posterior 1/3)
What is the pathway and function of vagus? emphasis on the neck region
- Along with CN IX it exits through the jugular foramen down in the carotid sheath between the internal carotid artery and inter jugular vein.
- AS CNX descends it goes posteriorly to the carotid artery
What are the two ganglia associated with the vagus nerve?
- Jugular ganglion which includes fibers related to general sensation from meningeal and auricular branch that arises before CNX Exits jugular foramen.
- The inferior (Nodosum) ganglion contain cell bodies that signal to visceral afferent sensations.
What is the first branch of the vagus nerve in the neck?
- The pharyngeal branch; it emerges off the vagus nerve just past the inferior ganglion and branches extensively and blends with middle constrictor muscle (Vagus contribution to pharyngeal plexus).
- The vagus contribution of the pharyngeal plexus provides motor innervation to all muscles of pharynx except for the stylopharyngeus (only muscle motor innervated by glossopharyngeal).
What is the function and pathway of the second branch of CNX in the neck; the laryngeal nerve;
- The laryngeal branch divides into two additional branches; The external and internal laryngeal branches
- External branch contributes to the pharyngeal plexus but also sends a deep branch to the cricothyroid muscles.
- The internal branch is sensory; supplies mucosal superior to the true vocal folds;
- Then there are the recurrent laryngeal branches; they terminate within the larynx responsible for motor innervation to the remainder of the muscles in the larynx. damage to either side will lead to hemiparalysis to vocal folds on the corresponding sides.
What is the pathway and function of accessory nerve?
- third and final cranial nerve emerging from jugular foramen; as it emerges it immediately migrate laterally anterior to the internal jugular.
- Innervates the trapezius and sternocleidomastoid
What are the causes of jugular foramen syndrome?
-Variety of symptoms caused by compression of structures within the jugular foramen
-Most common causes are tumors in the neck or inferior cranial vault but can also be caused by trauma, infection and bone disease.
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