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