Cranial Nerves Flashcards
Which cranial nerves do not originate on the brain stem?
CN I and CN II
Which cranial nerve originates on the dorsum of the brainstem?
CNIV
Where are the cell bodies of sensory fibers located?
Ganglia outside the brain
Where are the cell bodies of motor fibers located?
Nuclei within the brain
CNI
Olfactory Nerve. SENSORY. Cell bodies located in olfactory mucosa (covering the superior nasal concha and superior part of nasal septum). Axons pass through cribiform plate on their way to the brain
CNII
Optic Nerve. SENSORY. Fibers of optic nerve arise from the retina (not the brain). Orbital portion of nerve ~5cm long. From each eyeball, optic nerve passes posteriorly to the apex of the orbit to exit via the optic foramen. Right and left optic nerves meet at the optic chiasm(a) and some portions decussate (cross over). After the optic chiasm(a), mixed crossed fibers leave the chiasm(a) to terminate in the brain
Optic Chiasm
Location of crossing over of some optic nerves. Medial optic nerves decussate; lateral optic nerves do not.
Optic Tracts
After optic chiasm, nerve FIBERS are mixed crossed and uncrossed. Goes on to synapse at Lateral Genticulate Nuclei
Lateral Genticulate Body
Location of optic tract synapse in brain
CNIII
Oculomotor Nerve. MOTOR. Originates on the VENTRAL surface of the brainstem, pierces the dura, enters the cavernous sinus. Enters orbit via superior orbital fissure. Provides motor fibers to ALL extraocular muscles EXCEPT lateral rectus (CNVI) and superior oblique (CNIV). Also carries presynaptic parasympathetic fibers to cilliary ganglion (for intrinsic eyeball muscle) and proprioception fibers to eyeball muscles. Damage to the nerve results in ptosis (drooping of the upper eye lid), and dilation of pupils
CNIV
Trochlear Nerve. MOTOR. Most slender, very small, yet has the longest intracranial course. Originates from the DORSUM of the brain stem, eventually penetrates the dura and enters the cavernous sinus. From cavernous sinus, passes through the superior orbital fissure to enter the orbit via superior orbital fissure. Supplies only one muscle: Superior oblique of the orbit. Damage to this nerve results in double vision when patient looks downward and outward
Which muscle is supplied by the trochlear nerve?
Suprior Oblique muscle
CNV
Trigeminal Nerve. Sensory and Motor (What a bastard). Nerve of the first pharyngeal arch. Provides sensory innervation to the head; motor innervation to the muscles of mastication and a few other muscles. Emerges from the pons by a sensory and a motor root. Synapses onto semilunar ganglia.
Muscles not controlled by CNIII
Lateral Rectus (CNVI) and Superior Oblique (CNIV)
Semilunar Ganglion
AKA Trigeminal ganglion. contains cell bodies of the sensory root fibers. The ganglion forms a shallow groove on the anteromedial side of the petrous part of the temporal bone, known as the trigeminal impression
Divisions of CNV
Opthalmic (Sensory), Maxillary (Sensory), Mandibular (Mixed)
CNV1
Opthalmic division of CNV. Smallest division of CNV. Passes through the cavernous sinus. Divides into branches that enter the orbit via the superior orbital fissure and supply the orbit and part of the face with sensory information.
CNV2
Maxillary division of CNV. Enters cavernous sinus while still inside the skull. Exits skull via the foramen rotundum. Gives off major branches: Zygomatic, palatine, nasal, infraorbital
Zygomatic Nerve
Branch of CNV2. Supplies skin over the zygomatic bone and skin between (including) the lower eyelid and upper lid
Palatine (Greater and Lesser) nerve
Branch of CNV2. Supply the soft and hard palate
Nasal (sphenopalatine, nasopalatine) Nerve
Branch of CNV2. Supply the mucosa of the nose
Infraorbital Nerve
Exits through the infraorbital foramen to supply the skin between (including) lower eyelid and upper lip
CNV3
Mandibular division of CNV. Sensory and motor. Exits skull through foramen ovale to enter infratemporal fossa. Includes motor root of CNV. Branches: motor branches to muscles of mastication, buccal (long buccal), auriculotemporal, lingual, inferior alveolar
Motor branches of CNV3
Innvervate muscles of mastication. Efferent nerves for the medial pterygoid, tensor tympani, and tensor veli palatini muscles.
Buccal (Long Buccal) nerve
Branch of CNV3. Sensory to buccal mucosa and adjacent gingiva
Auriculotemporal Nerve
Branch of CNV3. Encircle the middle meningeal artery. Passes through the parotid gland, to ascend into the scalp anterior to the ear. Sensory to the TMJ, external acoustic meatus, skin of temple and scalp. Contains postganglionic parasympathetic fibers for the parotid gland.
Lingual Nerve
Branch of CNV3. Sensory to anterior 2/3 of the tongue. Enters floor of mouth. Carries taste fibers from anterior 2/3 of tongue and parasympathetic fibers to oral glands.
Inferior alveolar nerve
Branch of CNV3. Motor fibers leave before the nerve enters the mandibular foramen as the mylohyoid nerve. Enters mandibular foramen and courses through the mandibular canal. In the canal gives sensory branches to the mandibular teeth. Its mental branch emerges from the mental foramen as the mental nerve
Mylohyoid nerve
Branch of CNV3. Branches off of inferior alveolar before it enters the mandibular foramen, innervates the mylohyoid.
Mental Nerve
Branch of CNV3. Terminal portion of inferior alveolar nerve. Emerges from mental foramen to innervate skin over mental area.
CNVI
Abducens nerve, MOTOR. Leaves the brain and traverses the cavernous sinus before passing through the superior orbital fissure to enter the orbit. Supplies only one muscle: Lateral rectus muscle. Damage to this nerve causes pupils that cannot move laterally beyond the midpoint.
CNVII
Facial nerve, MOTOR AND SENSORY (Mixed). Accompanies CNVIII into the internal acoustic meatus. At distal end of the meatus CN VII enters the facial canal; while in the facial canal, gives off branches: Branch to stapedius muscle, chorda tympani, greater petrosal nerve. Leaves facial canal to exits at the stylomastoid foramen. Distal to the stylomastoid foramen CN VII gives off branches: Branches to posterior belly of digastric and stylomastoid muscles, and branches to muscles of facial expression: (temporal, zygomatic, buccal, mandibular, and cervical)
Branches to Stapedius muscle
Branch of CNVII while still in facial canal. Supplies motor innervation to the stapedius muscle
Chorda Tympani
Supplies taste to the anterior 2/3rds of the tongue. Originates at tongue/taste buds, joins lingual nerve of CNV3. Acts as an onramp to meet up with CNVII..
Greater Petrosal Nerve
Branch of CNVII given off while in facial canal. Contains preganglionic parasympathetic fibers to the pterygopalatine ganglion. The postganglionic fibers go supply the lacrimal gland
Branches to Posterior belly of digastric and stylohyoid muscles
Branches of CNVII given off after exiting the facial canal. Supply motor innervation to the stylohyoid and digastric muscles.
Temporal nerve
Branch of CN VII. proceeds superiorly slightly anterior to the ear
Zygomatic Nerve (CNVII)
Branch of CN VII. courses towards the corner of the eye
Buccal Nerve (CNVII)
Branch of CN VII. motor to the muscles over the cheek area
Mandibular Nerve (CNVII)
Branch of CN VII. proceeds inferomedially across the mandible
Cervical Nerve (CNVII)
Branch of CN VII. courses below the mandible to supply the platysma
Taste fibers of CN VII
Taste fibers (special sensation) from anterior 2/3 of tongue and from the palate
CNVIII
Vestibulocochlear nerve. SENSORY. consists of two parts - the cochlear and vestibular portions which differ in their peripheral distribution, central connections and function. leaves the brainstem with CN VII and courses with this nerve through the internal acoustic meatus. Divides into two parts: cochlear division (nerve of hearing) and vistibular division (nerve of equilibrium)
Cochlear division responsibility?
Nerve of hearing
Vestibular division responsibility?
Nerve of equilibrium
CNIX
Glossopharyngeal Nerve. MIXED MOTOR AND SENSORY. Nerve of the 3rd pharyngeal arch. Leaves the brain stem (along with X and XI). This nerve also contains presynaptic parasympathetic fibers destined for the otic ganglion. Leaves the cranium via jugular foramen. supplies a motor branch to the stylopharyngeus muscle and then joins the CN X and XI and postganglionic sympathetic fibers to form the pharyngeal plexus. Terminal branches go to the posterior third of tongue, including the circumvallate papillae, for special taste and general sensation. Provides a small branch to the carotid sinus – nerve to carotid sinus
Pharyngeal Plexus
Network of fibers innervating palate, larynx, and pharynx. Contains motor and sesnory fibers from CNIX and CNX, as well as superior cervical ganglion sympathetic fibers.
Carotid branch of CNIX
Innervates carotid sinus. Runs downward anterior to the internal carotid artery. Communicates with vagus nerve. Communicates information from baroreceptors at the sinus
CNX
Vagus Nerve. MIXED MOTOR AND SENSORY. Nerve of the 4th pharyngeal arch. Longest CN, has the most extensive course/distribution of any CN. Exits the skull via jugular foramen. Provides following branches in the neck: pharyngeal plexus (along with CNIX) and soft palate, superior laryngeal plexus, recurrent laryngeal nerves, cardiac branches, branch to carotid sinus
Superior Laryngeal Nerve
Branch of vagus nerve. Has an external and internal branch. Supplies motor innervation to cricothyroid; function is interrelated with recurrent laryngeal nerve w/r/t vocal cords. Damage causes subtle vocal defects
Recurrent Laryngeal Nerve
Supplies intrinsic muscles of the larynx with the exception of the cricothyroid (innervated by the superior laryngeal nerve)
Cardiac Branches
Branches given off of the vagus nerve to the heart
Carotid Sinus Branch of CNX
Meets with CNIX branch to carotid sinus
Where does the left vagus nerve enter the thorax?
Anterior to the arch of the aorta
Where does the right vagus nerve enter the thorax?
Over the subclavian artery
CNXI
Spinal accessory nerve. MOTOR NERVE, innervates SCM and trapezius muscles. formed by both cranial and spinal components. Cranial portion leaves the lateral side of the brain stem and unites with the spinal part to pass through the jugular foramen. Distal to the foramen the cranial part separates from the spinal part and joins the vagus to contribute to the pharyngeal plexus. The spinal portion originates from C1 to C5 spinal levels. It enters the cranium through the foramen magnum to join the cranial portion. After exiting the skull it separates from the cranial part and proceeds towards the posterior triangle. While crossing the posterior triangle it is joined by branches from the 2nd, 3rd and 4th cervical nerves.
CNXII
Hypoglossal. MOTOR NERVE. CN XII leaves the brain stem slightly medial to CN IX, X and XI and exits through the hypoglossal canal. Courses between the internal carotid artery and the internal jugular vein in the neck and loops around the occipital artery to enter the oral cavity. Supplies motor branches to the intrinsic and extrinsic muscles of the tongue. Lesions of this nerve cause the protruded tongue to deviate TOWARD THE SIDE OF THE LESION
