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Cranial Nerves z
Introduction to the Cranial Nerves
| Question | Answer |
|---|---|
| Name the 12 pairs of cranial nerves | olfactory, optic, occulomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal |
| CNI exits from the ____ | Telencephalon |
| CN II exits from the ____ | Diencephalon |
| CN III exits from the ____ | brainstem (midbrain) |
| CN IV exits from the ____ | brainstem (midbrain) |
| CN V exits from the ____ | brainstem (pons) |
| CN VI exits from the ____ | brainstem (pons) |
| CN VII exits from the ____ | brainstem (pons) |
| CN VIII exits from the ____ | brainstem (pons) |
| CN IX exits from the ____ | brainstem (medulla oblongata) |
| CN X exits from the ____ | brainstem (medulla oblongata) |
| CN XI exits from the ____ | brainstem (medulla oblongata) |
| CN XII exits from the ____ | brainstem (medulla oblongata) |
| Which nerves carry preganglionic parasympathetic fibers? | CN III , VII, IX and X |
| What nerves carry general sensory neurons (pseudounipolar neurons)? | CN V, VII, IX, and X |
| Which nerves carry taste neurons? | CN VII, IX, and X (also pseudounipolar neurons) |
| What are the branchiomeric cranial nerves? (definition and list) | Innervate structures derived from branchial arches: CN V (branchial arch 1), VII (b.a. 2), IX (b.a. 3), X (b.a. 4-6), and XI (b.a. beyond 6?) |
| What does the term: "branchial motor fibers" mean? | Equivalent of somatic motor fibers, except that they are fibers in cranial nerves instead of spinal nerves (functionally same as other skeletal muscles) |
| * * What fibers carry the parasympathetics of the Occulomotor nerve (CNIII)? What postganglionic neuron do they synapse with? What structures do they target? | Parasympathetic root of ciliary ganglion (pre)-->ciliary ganglion (post)-->ciliary muscle and sphincter of the pupil |
| * * What fibers carry the parasympathetics of the facial nerve (CNVII)? What postganglionic neuron do they synapse with? What structures do they target? | Greater petrosal nerve (pre)-->pterygopalatine ganglion(post)-->lacrimal, nasal, and palatine glands; chorda tympani (pre)-->submandibular ganglion (post)-->submandibular, sublingual, and lingual glands |
| * * What fibers carry the parasympathetics of the Glossopharyngeal nerve (CNIX)? What postganglionic neuron do they synapse with? What structures do they target? | Lesser petrosal nerve (pre)-->otic ganglion (post)-->parotid gland |
| What sense is associated with CN I? Where does the nerve sit? Where are the sensory neurons located? | Olfaction (smell); sensory nerves in olfactory mucosa on superior nasal septum and mucosa-->axons pass through cribiform plate of the ethmoid and end in olfactory bulb of the forebrain (has special sensory fibers for smell) |
| * What vessel does the CN II travel along with? What foramen do they go through? What sense is associated with CN II? | Optic nerve travels with opthalmic artery through the optic canal; special sensory fibers for sight |
| * What types of fibers are carried by the occulomotor? | Somatic motor and parasympathetic |
| Where does the oculomotor emerge from? | From ventral aspect of the midbrain and proceeds along lateral wall of the cavernous sinus; enters orbit through superior orbital fissure where it divides |
| What are the two divisions of the oculomotor nerve? | Superior division: levator palpebrae superioris muscle, superior rectus eye muscle. Inferior division: medial rectus eye muscle, inferior rectus eye muscle, inferior oblique eye muscle |
| The preganglionic parasympathetic fibers of the oculomotor travel with the ____ division and depart from it as the parasymathetic ____ of the ____ ganglion. | inferior, root, ciliary |
| Describe the path of the trochlear nerve: what openings does it pass through? What other nerves does it pass by? What does it supply? | Emerges from the dorsal aspect of the midbrain; passes through the lateral wall of the cavernous sinus and enters the orbit through the superior orbital fissure (alongside CN III, V1, and VI); superior oblique eye muscle |
| What does CN VI supply? Where does it pass through? What other structure is it closely associated with prior to entering orbital cavity? | Lateral rectus eye muscle; through cavernous sinus in the company of the internal carotid artery and enters the orbit through the superior orbital fissure |
| What are the two divisions of CN VIII? What are they involved in (sensory wise)? | Vestibular: conveys information about balance and equilibrium. Cochlear: conveys sensory information related to hearing. |
| What opening does CNVIII enter alongside the facial nerve? | internal acoustic meatus |
| What types of fibers are carried by the CN IX? | Sensory and motor, preganglionic parasympathetics |
| Where does CN IX emerge from the brain? | From the medulla oblongata from a groove called the post olivary sulcus |
| Where are the sensory ganglia located for CN IX? What type of special neurons are located here? | Located in jugular foramen; pseudounipolar neurons |
| Where does CN IX emerge from the skull? What other nerve(s) does it exit with? | Via the jugular foramen along with Vagus nerve (CN X) and accessory nerve (CN XI) |
| What nerves exit via the jugular foramen? | CN IX, X, and XI |
| What are the (5) major branches of the CN IX? | Tympanic branch, carotid nerve, motor branch to the stylopharyngeus muscle, pharyngeal and tonsilar branches, and lingual branch |
| What branch does CN IX give off right at the jugular foramen? Where does it go into? | Tympanic branch; into tympanic cavity |
| What branch of the glosspharyngeal has ALL of the preganglionic parasympathetic fibers? | The tympanic branch (it also has all of the sensory fibers of the tympanic cavity) |
| The tympanic nerve plus postganglionic sympathetic fibers from the superior cervical ganglion and a twig from from the facial nerve form what plexus? Where is this? | The tympanic plexus; The tympanic cavity |
| The preganglionic parasympathetic fibers within this plexus then coverge on what nerve? Describe the path of this nerve. | Lesser petrosal nerve; passes out of the petrous portion of the temporal bone in the hiatus of the lesser petrossal nerve; exits skull through foramen ovale; enters infratemporal fossa; synapses with postganglionic parasympathetic neurons (otic ganglion) |
| What nerve does the lesser petrossal nerve pass through the hiatus of the lesser petrosal nerve? | Greater petrossal nerve |
| Where do the postganglionic parasympathetic fibers of the tympanic branch eventually enervate? | The parotid gland |
| What structure does the carotid nerve eventually enervate? | The sensory fibers from baroreceptors (pressure) in the carotid sinus and chemoreceptors in the carotid body |
| What is the only muscle innervated by the glosspharyngeal nerve? What nerve branch supplies it? | The motor branch to the stylopharyngeus muscle |
| What branches of CN IX are responsible for general sensation from the mucous membrane of much of the pharynx and the palatine tonsils? | Pharyngeal and tonsilar branches |
| * What does the lingual branch of CN IX do? | General sensation to the posterior 1/3 of tongue, taste fibers for posterior 1/3 of tongue |
| How can you assess a lession to the CN IX? | Test taste on posterior 1/3 of tongue. Can also be tested by stroking posterior 1/3 of tongue (for gag reflex), though lack of reflex might be also due to loss of CN X (motor fibers); referred pain in middle ear from tonsilar region is also common |
| What types of fibers are carried by the vagus nerve? | Mixed sensory, motor, and preganglionic parasympathetics |
| Where does it emerge from in the brain? | Post-olivary sulcus; leaves skull through jugular foramen with glossopharyngeal and accessory nerves |
| Where do the sensory fibers of the vagus nerve originate from? | Its pseudounipolar neurons are located in the superior and inferior ganglia, which are located in the jugular foramen |
| What are the major branches of the vagus nerve? | Meningeal, auricular, pharyngeal, carotid, aortic, superior laryngeal, recurrent laryngeal, vagal branches for viscera |
| What is the function of the meningeal branch of the vagus nerve? | Sensory to the dura mater in the posterior cranial fossa (actually consists of sensory branches of the upper cervical nerves which hitchhike on the vagus); supplies most of the meninges |
| What is the function of the auricular branch of the vagus nerve? Why is it important? | Supplies the external auditory meatus and the external surface to the tympanic membrane; important because irritation may cause cough reflex or nausea |
| * What is the function of the pharyngeal branch? | Contains motor and sensory fibers; it is the main motor to the pharynx; contributes to the pharyngeal plexus |
| What nerves contribute to the pharyngeal plexus? | Pharyngeal branch of CN X, postganglionic parasympathetics from superior cervical ganglion, and the pharyngeal branch of CN IX |
| What is the only muscle of the pharynx CN X does not supply? What is the only muscle of the palate that CN X does not supply? | Stylopharyngeus (CN IX) and tensor of the palate (V3) |
| What does the carotid branch of the CN X do? | Carries sensory fibers from baroreceptors in the carotid sinus and chemoreceptors in the carotid body |
| What does the aortic branch of CN X do? | Carries sensory fibers from aortic baroreceptors (pressure) in the aortic arch and chemoreceptors in the aortic body (adjacent to the aortic arch) |
| What are the two branches of the superior laryngeal branch? | Internal laryngeal branch (sensory) and the external laryngeal branch (motor) |
| What membrane is pierced by the internal laryngeal nerve? What does it supply? | Pierces thyrohyoid membrane to supply internal lining of the larynx as far as the vocal cords; also provides some taste and sensory fibers to the epiglottis; also supplies valleculae of tongue |
| * What muscles does the external laryngeal nerve supply? | The cricothyroid, the cricopharyngeus portion of the inferior constrictor; the rest of the muscles are supplied by the recurrent laryngeal nerve |
| What two vessels does the vagus nerve proceed with in the neck? What structure contains these three structures? | Internal carotid artery and internal jugular vein; in carotid sheath |
| Describe the path of the vagus nerve once it passes the root of the neck | Left: passes in front of arch of aorta; left laryngeal nerve arches below+behind aorta to left of lig. arteriosum and ascends between the trachea and esophagus. Right r.l. nerve originates below the beginning of the subclavian artery |
| What muscles does the recurrent laryngeal nerve supply? | Motor fibers to ALL muscles in larynx EXCEPT cricothyroid muscle and sensory fibers to the trachea and larynx below the level of the vocal cords |
| Describe (briefly) the fiber composition of the vagal branches below the recurrent laryngeal nerves | Carry preganglionic parasympathetics and visceral sensory fibers for the thoracic viscera and abdominal organs (including foregut and midgut derivatives) |
| What symptoms are associated with the vagus nerve? How do you test? | increased pulse, constant nausea, decreased rate of respiration, sensation of suffocation, hoarse low voice. May have difficulty swallowing. Test with gag reflex, faulty mov. of uvula, paralyzed vocal cord; can't survive bilateral destruction of nerve |
| Where does CN XI emerge from? | From sides of the upper three or four cervical segments of the spinal cord between the dorsal and ventral rootlets of respective spinal nerves |
| Where does it exit from? | Ascends through foramen magmum and exits skull through jugular foramen along with glossopharyngeal and vagus nerves |
| What two muscles are enervated by the accessory nerve? How does a lesion to the accessory nerve typically present? | Sternocleidomastoid and the trapezius; weakness in turning head to the opposite side as well as sagging of the shoulder |
| What types of fibers are carried by the hypoglossal? | Pure motor nerve |
| Where does the hypoglossal nerve emerge from in the brain? How does it leave the skull? | From medulla oblongata from the pre-olivary sulcus in line with ventral roots of spinal nerves; leaves through hypoglossal canal |
| What muscles are supplied by the hypoglossal nerve? | Supplies all of the intrinsic and extrinsic muscles of the tongue with the exception of the palatoglossus, which is supplied by the vagus nerve |
| How does a lesion to the hypoglossal nerve present? | Results in paralysis and atrophy of the intrinsic muscles of the tongue. When potruded, tongue turns to the side of the lesion (due to unopposed action of the genioglossus muscle from unaffected side). Touch, pressure, temp, and taste UNAFFECTED. |
| What nerve branches compose the tympanic plexus? | Preganglionic Parasympathetic and sensory fibers from tympanic branch of CN IX; twig from facial nerve CN VII; postganglionic sympathetic fibers from the superior cervical ganglion |
Created by:
karkis77
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