Cranial Nerves Flashcards
What are special sensory fibers?
carry information to the brain about smell, vision, taste, hearing or balance
What are Somatic (general) sensory fibers?
touch, pain, temp, pressure, vibration and proprioception
Visceral sensory fibers carry information about?
distension and pain from viscera, blood vessels etc
Branchial motor fibers innervate?
skeletal muscles derived from branchial arches
Somatic motor fibers innervate?
skeletal muscles derived from somites
Visceral motor fibers innervates?
smooth muscle, cardiac muscle and glands
Name the sensory ganglia of CNs?
trigeminal ganglion (V), geniculate ganglion (VII) spiral and vestibular ganglia (VIII), Superior and inferior ganglia of (IX) Superior and inferior ganglia of (X)
Define sensory ganglion:
swellings along the course of a cranial nerve that contain cell bodies of sensory neurons
no synapses
pseudopolar neurons collect information from head and neck and sends it to the sensory ganglion -> brainstem
Define Parasympathetic ganglia
visceral motor ganglia
all parasympathetic
preganglionic fibers synapse with postganglionic parasympathetic neurons, then they innervate smooth muscle, cardiac muscle, glands
What are the Parasympathetic ganglia of CNs?
ciliary ganglion (III), submandibular and pterygopalatine ganglia (VII), otic ganglion (IX), intramural (terminal) ganglion (X)
CN 1 Name Ganglia Fiber type Route
Olfactory nerve
no ganglia
SS - smell
Route: cribiform plate of ethmoid bone to olfactory bulb of anterior cranial fossa and synapses with secondary sensory neurons in the olfactory tract
CN 2 Name Ganglia Fiber type Route
optic nerve
no ganglia
SS - vision (and reflexes)
Route: exits through optic canal to optic chiasm, Fibers decussate such that nasal fibers from the contalateral eye and temporal fibers from the ipsilateral eye unite as the optic tract and extend to the brain.
Note: CN II is an actual extension of the brain
CN 3 Name Ganglia Fiber type Route
Occulomotor Nerve
SM
VM - parasympathetic root of ciliary ganglion
Route: brainsteim->exits middle crainal fossa via superior orbital fissue,then splits to inferior and superior divisions
What do the different divisions of the SM fibers of CN III innervate?
Superior: levator palpebrae superiororis muscles and superior rectus muscle
Inferior: medial rectus m. inferior rectus and inferior oblique m.
:describe parasympathetics of III
Presynaptic parasympathetics from preganglionic parasympathetic neurons in the brainstem follow the inferior division of CN III and depart as the parasympathetic root of the ciliary ganglion. Here they synapse with postganglionic parasympathetic neurons whose fibers reach the eye via short ciliary nerves and innervate smooth muscle fibers of the constrictor pupillae (to constrict the pupil) and ciliary muscle (to thicken the lens)
CN 4 Name Ganglia Fiber type Route Innervation
Trochlear Nerve:
no ganglia
SM
Route: arise from neurons in the brainstem. ->exits the middle cranial fossa via the superior orbital fissure and enters the bony orbit
Innervates: superior oblique muscle of the eye.
CN 5 Name Ganglia Fiber type Route
Trigeminal Nerve:
1 sensory ganglion, the trigeminal
GS, BM fibers.
Route: trifurcates:
V1: ophthalmic (CN V1) nerve which exits the middle cranial fossa via the superior orbital fissure
V2 Maxillary nerve (CN V2) that passes through the foramen rotundum,
V3: mandibular nerve (CN V3) that traverses the foramen ovale.
CN 6 Name Ganglia Fiber type Route Innervation:
Abducens Nerve:
no ganglia
SM fibers from brainstem.
Route: exits the middle cranial fossa via the superior orbital fissure and enters the bony
orbit
Innervates: lateral rectus muscle of the eye.
CN 7 Name Ganglia Fiber type Route Innervation:
Facial Nerve:
two motor ganglia: pterygopalatine and submandibular
one sensory ganglion: the geniculate.
Fibers: Motor root carries: BM (Nervous intermedius carries: VM (preganglionic parasympathetics), GS and SS (10 branches).
Route: brainstem as a motor root and a mixed-function root (nervous intermedius), both exit the posterior cranial fossa via the internal acoustic
meatus (motor root is superior to the nervous intermedius). -> facial canal, a tunnel in the petrous temporal bone, and unite -> geniculate ganglion and produces the greater petrosal nerve ->
then passes posterior to the middle ear where it produces the stapedius nerve and chorda tympani. Next, it sends a branch to the auricular nerve (branch of CN X) and then exits the stylomastoid foramen where it sequentially produces
the posterior auricular nerve and stylohyoid nerve and then passes through the parotid gland. It terminates by dividing into temporal, zygomatic, buccal, (marginal) mandibular and cervical nerves.
Name origin/route of greater petrosal nerve/what does it do?
What kind of fibers is it?
CN VII: Brainstem as a motor root and a mixed-function root (nervous intermedius), both exit the posterior cranial fossa via the internal acoustic
meatus (motor root is superior to the nervous intermedius). -> facial canal, a tunnel in the petrous temporal bone, and unite -> geniculate ganglion and produces the greater petrosal nerve -> presynaptic fibers crosses the floor of the middle cranial fossa, enters the pterygoid canal and join sympathetic fibers -> reaches the pterygopalatine ganglion in the pterygopalatine fossa. Then presynaptic fibers synapse with postsynaptic neurons.
Postsynaptic fibers hitchhike on branches of CN V to innervate the lacrimal gland and glands of the paranasal sinuses, nasal cavity, hard and soft palates and associate gingival. Cause gland secretion.
Visceral Motor (parasympathetic) fibers. Special Sensory fibers: Palatine fibers follow the palatine nerves (branches of CN V), pterygopalatine ganglion, nerve of the pterygoid canal and greater petrosal nerve to the geniculate ganglion. Central processes follow the nervous intermedius to the brainstem.
Name origin/route of corda tympani/what does it do?
Route: brainstem as a motor root and a mixed-function root (nervous intermedius), both exit the posterior cranial fossa via the internal acoustic
meatus (motor root is superior to the nervous intermedius). -> facial canal, a tunnel in the petrous temporal bone, and unite -> geniculate ganglion and produces the greater petrosal nerve ->
then passes posterior to the middle ear where it produces the stapedius nerve and chorda tympani. Crosses the tympanic cavity, joins the lingual nerve (branch of CN V) to the submandibular
ganglion where presynaptic fibers synapse with postsynaptic neurons. Postsynaptic fibers follow blood vessels to innervate submandibular and
sublingual salivary glands and minor salivary glands in the floor of the mouth and adjacent gingiva.
Cause gland secretion.
Also has SS fibers: 2/3 taste for anterior of the tongue and soft palate
.
What does the branchial motor fibers of CN VII do?
Form the motor root of the facial nerve.
Routes:
Follow facial nerve and form the stapedius nerve that innervates this muscle
Follow the auricular nerve that innervates posterior auricular and occipitalis muscles.
Follow the stylohoid nerve to innervate stylohyoid and posterior belly of the digastric muscles. Follow temporal, zygomatic, buccal, marginal mandibular and cervical branches to innervate
the many muscles of facial expression.
What does the somatic sensory fibers of CN VII do? (Don’t get this)
Peripheral processes of somatic sensory neurons in the geniculate ganglion innervate the external ear. Fibers follow the auricular nerve (branch of CN X) and then the facial nerve to the geniculate ganglion. Central processes follow the nervous intermedius to the brainstem.
What does the SS fibers of CN VII do/what are the routes?
Special Sensory: Peripheral processes of special sensory neurons in the geniculate ganglion innervate taste buds in the anterior 2/3 of the tongue and the soft palate via two different routes. Tongue fibers follow the lingual nerve (branch of CN V) and chorda tympani to the geniculate ganglion. Palatine
fibers follow the palatine nerves (branches of CN V), pterygopalatine ganglion, nerve of the pterygoid canal and greater petrosal nerve to the geniculate ganglion. Central processes follow the nervous intermedius to the brainstem.
CN 8 Name Ganglia Fiber type Route Innervation:
Vestibulocochlear Nerve: Th
two sensory ganglia, the vestibular and cochlear
Fibers: Special sensory
Route: two divisions, vestibular and cochlear
Nerve rises in the brainstem, exits the posterior cranial fossa via the internal acoustic meatus (inferior to nervous intermedius of CN VII) and traverses the petrous temporal bone where it divides and distributes to membranous structures of the inner ear.
Describe the vestibular divison of CN VIII:
For balance.
Formed of central processes from special sensory neurons within the vestibular ganglion. Peripheral processes innervate the inner ear and detect position and movement of the head relating to balance (see Ear Lecture). Central processes form the vestibular division that joins the cochlear division to form CN VIII.
Describe the cochlear divison of CN VIII:
For hearing:
Formed of central processes from special sensory neurons located in the spiral ganglion of the cochlea. Peripheral processes innervate the spiral organ (of Corti) of the inner ear and perceive sound waves relating to hearing (see Ear Lecture). Central processes form the cochlear to CN VIII.
CN 9 Name Ganglia/locations Fiber type Route Innervation:
Glossopharyngeal Nerve:
Ganglia: one motor ganglion, Sensory: otic, superior and inferior sensory ganglia.
Fibers: BM, VM, VS, GS, SS; 7 branches.
Otic ganglion is the site of synapse between presynaptic parasympathetic fibers and postsynaptic parasympathetic neurons; it lies deeply in the infratemporal fossa.
Sensory ganglia house neurons whose peripheral processes detect general, visceral and special sensations. Superior sensory ganglion lies in the jugular foramen and the inferior ganglion just below.
CN IX arises from the brainstem and exits the posterior cranial fossa via the jugular foramen and anterior to CN X. Near or in the jugular foramen, it gives off the tympanic nerve and a branch to the auricular nerve (branch of CN X). Then produces stylopharyngeus, pharyngeal, tonsillar, lingual and carotid nerves.
