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