Cranial Nerves: Olfactory, Optic, Oculomotor, Trochlear, Abducent, Vestibulocochlear, Glossopharyngeal, Accessory, and Hypoglossal Flashcards
What is the first cranial nerve?
the olfactory nerve
The olfactory nerve is made up of what fibers? (non specific)
sensory
Where does the olfactory nerve arise from?
the olfactory epithelial cells lining the olfactory mucosa that cover the ethmoturbinates and the caudal aspect of the walls of the septum
What nerves take the same route of the olfactory nerve?
the terminal nerve and the accessory olfactory nerve
What process does the the accessory olfactory nerve take part in?
the phlemen response
What is the accessory olfactory nerve also known as?
the vomeronasal nerve
Where does the olfactory nerve terminate at?
the olfactory bulb
What does the olfactory nerve pass through to get to its termination point?
the cribriform plate
True or False: the olfactory nerve can be seen with the naked eye
False: it is microscopic
What is the second cranial nerve?
the optic nerve
The optic nerve is made up of what type of fibers (specific and non specific)?
sensory - SSA
What is the origin of the optic nerve?
the retinal ganglion
What does the optic nerve pass through to get the cranial cavity?
the sclera and the optic canal
Where is the optic canal located?
within the presphenoid bone
In the dog, what do about 75% of the axons cross over for the optic nerve?
they cross over to the opposite side a the optic chiasma and course further as optic tracts on the lateral aspect of the diencephalon part of the brain
What is the third cranial nerve?
the oculomotor nerve
The oculomotor nerve is made up of what type of fibers (non specific)?
motor
What part of the oculomotor nerve supplies the extrinsic muscles of the eyeball?
a ventral motor root (containing GSE fibers)
What does the oculomotor nerve carry to the ocular smooth muscles?
parasympathetic general visceral efferent
Where are the neurons of the oculomotor nerve located?
in the oculomotor nuclei in the mesencephalon, ventrolateral to the mesencephalon
Through what does the oculomotor nerve exit the cranial cavity?
the orbital fissure
What are the two branches of the oculomotor nerve?
a small dorsal branch and a large ventral branch
What does the dorsal branch of the oculomotor nerve supply?
the dorsal rectus and the levator palpebrae superioris muscles
Where does the ventral branch of the oculomotor nerve course?
ventral lateral to the optic nerve
What does the ventral branch of the oculomotor nerve supply?
the medial rectus, ventral rectus, and ventral obliques
What does the ventral branch of the oculomotor nerve contain?
ciliary ganglion
What do the ciliary ganglion of the oculomotor nerve supply?
the ciliary muscle and the sphincter muscle of the iris
What is ptosis?
when the levator palpebrae superioris muscle is not able to elevate the upper eyelid and creates a droopy eyelid looking appearance
What is the fourth cranial nerve?
the trochlear nerve
The trochlear nerve is made up of what type of fibers (non specific)?
motor
What does the trochlear nerve supply?
motor innervation to the dorsal oblique muscle of the contralateral side
What do axons on the left side of the brain stem supply?
the muscle of the eyeball on the right side
Where is the nucleus of the trochlear nerve located?
it surrounds the mesencephalic aqueduct but is caudal to the oculomotor nucleus
Through what does the trochlear nerve go through to exit the cranial cavity?
the orbital fissure
What are the special features of the trochlear nerve (3 things)?
- it is the only cranial nerve that arises from the dorsal aspect of the brainstem
- it is the only nerve that supplies to the muscle of the opposite side
- it is the smallest cranial nerve and only supplies one muscle
What is the sixth cranial nerve?
the abducent nerve
The abducent nerve has what type of fibers (nonspecific)?
motor
What does the abducent nerve supply?
motor fibers to the lateral rectus and retractor bulbi muscles of the eyeball
Where are the neurons of the abducent nerve located?
in the abducent nucleus in the medulla oblongata close to the trapezoid body
What is the course of the abducent nerve before it exits the cranial cavity?
they cross the reticular foramen and emerges through the trapezoid, lateral to the pyramid, and courses rostrally adjacent to the stalk of the pituitary gland
The abducent nerve exits the cranial cavity through what?
the orbital fissure
When does the abducent nerve innervate its target muscles?
after it enters the periorbita
What is the only nerve that does not exit the cranial cavity?
the vestibulocochlear nerve
What is the eighth cranial nerve?
the vestibulocochlear nerve
What are the roots of the vestibulocochlear nerve?
vestibular and cochlear root
Where are the neurons for the vestibular root of the vestibulocochlear nerve located?
in the vestibular ganglion within the petrous part of the temporal bone
What do the axons of the vestibular root of the vestibulocochlear nerve innervate?
the hair cells in the cristae ampullare and macula utriculi and sacculi of the membranous labyrinth
Where is the cochlear root of the vestibulocochlear nerve located?
in the spiral ganglion within the osseous modiolus of the cochlea
What part of the neurons of the chochlear root of the vestibulocochlear nerve synapse with what?
the dendritic processes of the neurons synapse with the hair cells of the spiral organ and the cochlear duct
What impulses does the cochlear root of the vestibulocochlear nerve transmit?
impulses perceived as sound
Along with never leaving the skull, what else does the vestibulocochlear nerve not leave?
the petrous part of the temporal bone via the internal acoustic meatus
Where does the vesstibular root of the vestibulocochlear nerve terminate?
in the vestibular nucleus
Where does the cochlear root of the vestibulocochlear nerve terminate?
in the trochlear nucleus
What is the ninth cranial nerve?
the glossopharyngeal nerve
The glossopharyngeal nerve has what type of nerve fibers (specific)?
GVA, SVA, GSE, and GVE fibers
What do the GVA fibers of the glossopharyngeal nerve innervate?
the caudal 1/3 of the tongue, pharyngeal mucosa, and the carotid sinus
What do the SVA fibers of the glossopharyngeal nerve innervate?
the taste buds in the foliate and vallate papillae in the caudal 1/3 of the tongue
Where do the GSE fibers of the glossopharyngeal nerve originate from?
the nucleus ambiguous
Where do the GVE fibers of the glossopharyngeal nerve originate from?
the neurons located in the parasympathetic nucleus of the glossopharyngeal nerve
Where does the glossopharyngeal nerve emerge from?
caudal to the vestibulocohlear nerve
The glossopharyngeal nerve exits the cranial cavity through what?
the jugular foramen in the tympanooccipital fissure
What else exits in the same place that the glossopharyngeal nerve exits?
the vagus and accessory nerves
What does the glossopharyngeal nerve give off once it exits the cranial cavity?
the tympanic nerve
What type of fibers does the tympanic nerve of the glossopharyngeal nerve have?
GVE
What type of axons does the tympanic nerve of the glossopharyngeal nerve contain?
preganglionic parasympathetic axons
The tympanic nerve enters the _____ _____ and forms the _____ _____.
tympanic cavity, tympanic plexus
What arises from the tympanic plexus?
the minor petrosal nerve
What does the minor petrosal nerve form?
the neurons in the otic ganglion
Where is the otic ganglion located?
adjacent to the oval foramen
What type of axons are in the otic ganglion?
postganglionic axons
What do the postganglionic axons of the otic ganglion supply?
it joins the auriculotemporal nerve and supplies the GSE to the parotid and zygomatic salivary glands
Before giving off its terminal branches, where does the glossopharyngeal course?
medial to the cranial cervical sympathetic ganglion
What are the five terminal branches of the glossopharyngeal nerve?
branch to the carotid sinus, sylopharyngeal branch, tonsillar branch, lingual branch, pharyngeal branch
What is contained in the branch to the carotid sinus of the glossopharyngeal?
it contains baroreceptors in the wall of the carotid bulb and chemoreceptors in the carotid body
What type of fibers does the stylopharyngeal branch carry?
GSE fibers
What does the stylopharyngeal branch of the glossopharyngeal nerve supply?
the stylopharyngeus mussle and other pharyngeal muscles along the vagus nerve
What does the tonsillar branch of the glossopharyngeal nerve supply?
the palatine tonsil
What direction does the lingual branch of the glossopharyngeal nerve course?
rostroventrally
What does the lingual branch of the glossopharyngeal nerve supply?
the tongue mucosa, the taste buds in the vallate and foliate papillae, and the gland in the submucosa of the tongue
What kind of fibers does the lingual branch of the glossopharyngeal nerve carry to the caudal 1/3 of the tongue mucosa and where are they located?
GVA - in the sensory ganglia where it passes between the jugular foramen and tympanooccipital fissure
What kind or fibers does the lingual branch of the glossopharyngeal nerve carry to the tastebuds in the vallate and foliate papillae?
SVA
What type of fibers does the lingual branch of the glossopharyngeal nerve carry to the submucosa of the tongue?
GVE fibers
What is the course of the pharyngeal nerve of the glossopharyngeal nerve?
it joins the pharyngeal branches from the vagus to form the pharyngeal plexus
What does the pharyngeal plexus receive branches from aside from the glossopharyngeal nerve?
hypoglossal nerve, postganglionic sympathetic axons from the cranial cervical ganglion
What do the branches derived from the pharyngeal plexus supply and what type of fibers do they carry?
pharyngeal muscles (GSE), pharyngeal mucosa (GSA), and glands in the pharyngeal mucosa
What fibers are in charge of the gag reflex?
the GSA and GSE fibers (but not all of them)
How do the pharyngeal muscles function during the gag reflex?
they all contract simultaneously to constrict the laryngopharynx
How dooes the hyoglossus, genioglossus, and geniohyoideus function during the gag reflex?
they pull the hyoid bone and tongue rostrally
What is the eleventh cranial nerve?
the accessory nerve
The accessory nerve is innervated by what type of fibers (non specific)?
motor
What are the roots of the accessory nerve?
the cranial root and the spinal root
Where is the nucleus of the cranial root of the accessory nerve located?
in the medulla oblongata
Where are the neurons of the spinal root of the accessory nerve located?
in the cervical spinal cord segments from C1-C7
For the spinal root, where does each spinal root emerge from the spinal cord?
laterally from the spinal cord, midway between the dorsal and ventral roots of the cervical spinal nerves
How do the spinal roots become part of the accessory nerve?
they join together to form the spinal root
How does the spinal root of the accessory nerve enter the cranial cavity?
the foramen magnum
What does the spinal root of the accessory nerve do once it enters the cranial cavity?
it joins the cranial root of the accessory nerve
What is the accessory nerve attached to and where?
the medulla very close to the roots of the glossopharyngeal nerve and the vagus nerves
What does the accessory nerve leave the cranial cavity through?
the tympanooccipital fissure
Once the accessory nerve exits the cranial cavity, what does it do?
it divides into the dorsal and ventral branch
What is the course of the dorsal branch of the accessory nerve?
courses caudally in the neck ventral and then dorsal to the transverse processes of the cervical vertebrae
What does the dorsal branch of the acccessory nerve innervate?
the trapezius, cleidocervicalis, cleidomastoideus, and omotransversarius
What does the ventral branch of the accessory nerve innervate?
the cranial part of the sternocephalicus adn the cleidomastoideus in some dogs
What is the twelfth cranial nerve?
the hypoglossal nerve
Thy hypoglossal nerve is innervated by what type of fibers (non specific and specific)?
motor - GSE
What does the hypoglossal nerve innervate?
the intrinsic and extrinsic muscles of the tongue
Where are the neurons of the hypoglossal nerve located?
in the midline in the floor of the fourth ventricle of the medulla
Where do the roots of the hypoglossal nerve emerge?
from the medulla oblongata lateral to the pyramid on the ventral surface of the medulla
What does the hypoglossal nerve exit through to leave the cranial cavity?
the hypoglossal canal
How does the hypoglossal nerve course?
ventrorostrally lateral to the external carotid artery
What happens when the hypoglossal nerve courses ventral to the external carotid artery?
it gives off two communicating branches
What does the first communicating branches of the hypoglossal nerve go to?
to the cervical nerve to form the cervical loop
After giving of the communicating branches what is the course of the hypoglossal nerve?
it courses ventrally and rostrally, and passes medial to the mandibular salivary gland and cranially it lies close to the lingual artery where it enters the tongue
Why does injury to the hypoglossal nerve cause?
paralysis to the tongue
What is strabismus?
injury to the oculomotor, trochlear, and abducent nerves that cause a deviated eye
What causes lateral strabismus?
injury to the oculomotor nerve
What is lateral strabismus?
when the muscles cannot pull the eyeball medially and dorsally
What causes medial strabismus?
injury to the abducent nerve
What is medial strabismus?
when the muscles of the eye cannot pull the eye latery
What does injury to the trochlear nerve cause?
the dorsal oblique is not functional do it cannot rotate the eyeball in the other direction
What is ptosis?
when the levator palpebrae superioris muscle is not able to elevate the upper eyelid
What nerve is involved in ptosis?
the oculomotor nerve
