Cranial Nerves Flashcards
,What are the 3 major cranial nerves serving special sense organ?
I- olfactor
II- Optic
VIII - Vestibulocochlear
They develop in part from epidermal neurogenic placodes
are not parts of other cranial sensory-motor nerve

What are the 4 somatic motor nerves that move the eye and tongue?
III - Oculomotor (exits from venral midbrain)
IV - Trochlear (exits dorsally and decussates)
VI - Abducens (emerges caudal to VII)
XII - Hypoglossal
- have no affiliated sensory ganglia, thus they have only efferent components
- sensory fibers in the peripheral parts of these nerves are “hitch-hikers” from nearby mixed nerves
- are more (XII, VI, III) or less (IV) comparable to ventral roots of spinal nerves

What are the 4 mixed branchial nerves that move and sense jaws, face, pharynx, and larynx?
V - trigeminal
VII - Facial
IX - Glossopharyngeal
X - Vagus
This nerve is the only special motor nerve that is cranial only in a roundabout way and innervates the sternocleidomastoid and trapezius muscle
XI - Spinal Accessory
What is the Otic Placode?
auditory and vestibular sensory haircells and ganglion cells
Involves Cranial nerve VIII
What is the Optic Placode?
Lens
Involces CN II
WHat is the olfactory placode?
Central Projecting sensory cells
This structure is located at the diencephalon wall. What is it and what does it contain?
This is the Optic Vesicle
contain sensory cells and ganglion cells
What does CN I (Olfactory Nerve) consist of?
consists of the central-projecting axons of bipolar olfactory sensory neurons (= olfactory receptor cells) situated in the olfactory epithelium.
The axons collect as fine bundles that traverse the olfactory foramina in the cribriform plate of the ethmoid bone to reach the olfactory bulbswhere they synapse on second order olfactory neurons.

This “Cranial Nerve” is actually a CNS tract, not peripheral nerve and covered by meningies. Located in the nasal cavity?
CN I (Olfactory)
It is covered with dura, arachnoids, and pia mater

Patient comes in reporting that he has difficulty smelling after doing some drugs. What is one possible diagnosis that can be considered?
Anosmia (loss of sense of smell)
This occurs when there is Damage to the olfactory sensory epithelium or disruption of the fibers at the cribiformplate
To exam the function of CN I you will expose the patient to test odorants
What is the path of the Optic nerve (CN II)
begin at the retina and extend to the optic chiasma, where approximately half of the optic fibers cross to the other side. The fibers continue as the optic tracts and most of them terminate by synapsing in the lateral geniculate nuclei of the thalamus.

What is different about the Optic nerve compared to some other cranial nerves?
The retina and optic nerves arise from the walls of the embryonic diencephalon. Accordingly, the optic nerves are brain tracts, not peripheral nerves.
Most of the axons that make up the optic nerve come from where? axons of retinal ganglion cells.
axons of retinal ganglion cells.

This nerve is actually made of two nerves. It enters the brain at the pontomedullary junction, just dorsal to the root of the VIIth nerve.
CN: VIII
(Vestibulocochlear Nerve)

The VIIIth nerve fibers pass peripherally to into the _____, accompanied by the VIIth nerve, via the __________.
Temporal bone
Internal Acoustic meatus

What does the cochlear nerve (portion of CN VIII) comprise of?
afferent axonal processes of cells in the spiral ganglion which innervate the auditory haircells of the spiral organ(Organ of Corti)
as well as,
efferent axons of central neurons located in the superior olivary/periolivarynuclei that form the olivocochlear bundle

The Vestibular nerve (part of CN VIII) comprises of?
afferentaxonal processes of cells in the vestibular ganglion (Scarpa’s)which innervate:
vestibular hair cells of the ampullae of the semicircular canals, sensing angular acceleration
vestibular hair cells of the maculae of the saccular and utricular otoliths, sensing linear acceleration
as well as,
efferent axons of central neurons located in two vestibular efferent nuclei

Where do the afferent fibers of the cochlear nerve project?
project to the lowest order brainstem auditory centers, the dorsal and ventral cochlear nuclei

The vestibular nerve afferent fibers project to where?
to the vestibular nuclei (superior, medial, lateral and descending) and to the vestibulocerebellum

The vestibular nuclei connect to what other structures besides the Vestibular nerve afferetn fibers?
connect with brainstem, spinal and cerebellar centers involved in postural and gaze control (among others)
MLF and Vestibulospinal tracts are what?
Major central vestibular pathways
They lead to extrocular and cervical motor nuclie controlling eye and head movements
How do you test Vestibular function?
Routine auditory test (done with a tuning fork)
or
asking the patient to walk a straight line
or
observing eye movements during introduction of cool or warm water into the external ear canal.
What is the Caloric Test?
Observing eye movement during introduction of cool/warm water.
induces alternating eye movements (Nystagmus) by generating convection in the endolymph of the horizontal semicircular canal. The caloric vestibulo-ocular reflex is especially useful in testing brainstem function in comatose patients.








































