Cranial Nerves 4 - Herring Flashcards
Only composed of special sensory fibers for vision
CN II
1st order cell bodies for vision of CN II = ____________ of the inner layer of the eyeball
Retinal ganglion cells
Right and left optic nerves unite in the cranial cavity to form the
optic chiasm
Some central processes of CN II, cross to the other side (decussate); others do not = this forms the ___________
optic tracts
Optic tracts of CN II continue to 2nd-order cell
bodies in the ___________ of
the thalamus (primary pathway) and SYNAPSE here as well
lateral geniculate nucleus
Axons from the 2nd order cell bodies of CN II project to the _________ which is for getting visual stimulus back to the occipital lobe
occipital cortex
Lesions of CN II present with a __________ of visual field defects
RANGE
We can have complete blindness from one or both eyes
Loss of only a portion of
the visual field in each eye
* Due to the mix of
some fibers crossing
and others not
crossing at the optic
chiasm
Each cranial nerve reflex will have a ________ limb & a _________ limb
sensory ; motor
For the most part, 2nd order sensory neurons of CN II project to the __________ limb
motor
Regarding pupillary light reflex, sensory CN II senses
light
Regarding pupillary light reflex, CN III is _______ and sends parasympathetic to the _________ muscle
motor ; constrictor pupillae muscle
What is the smallest cranial nerve
CN IV
Where are the somatic motor LMNs of CN IV located
trochlear nucleus
Axons of LMNs of CN IV decussate within the
brainstem
Axons of LMNs of CN IV decussate within the brainstem then exit on its ___________ surface which is the ONLY CN TO DO SO
dorsal
Axons from the right trochlear nucleus form the ______ trochlear nerve
left
What muscle is the peripheral target of CN IV
superior oblique muscle
Regarding a lesion of CN IV, someone would be unable to look ________ when the pupil (eye) is adducted
down
Results in diplopia when both eyes (pupils) are looking down in the medial position (going
down stairs, reading)
CN IV nerve lesion =
ipsilateral pupil presentation
CN IV - Trochlear nucleus lesion =
contralateral pupil presentation
Where are the LMNs of CN VI
Abducens nucleus
What muscle is the peripheral target of CN VI
lateral rectus muscle
Lesion of CN VI
Unable to ABDUCT the eye during clinical (“H-pattern”) testing
Results in diplopia when looking toward the affected side
regarding a lesion to CN VI or left abducens nucleus, when a patient is asked to look to the left, what happens?
The patient’s left eye stays straight and the patient’s right eye looks left (double vision)
regarding a lesion to CN VI or left abducens nucleus, when a patient is asked to look to the right, what happens?
both eyes look to the right (normal vision) because it’s the left lateral rectus muscle that is damaged which is not used when looking to the right
What is the primary cranial nerve for somatic motor innervation to the extra-ocular muscles & levator palpebrae superioris
Except lateral rectus muscle (CN VI) and superior oblique (CN IV)
CN III
CN III has ____________
fibers to 2 of the 3 intrinsic
muscles of the eye
Preganglionic parasympathetic
Regarding somatic motor for CN III, where are the LMNs
oculomotor nucleus
axons of LMNs of CN III form the _______ nerve
oculomotor nerve
Where are the preGPS cell bodies of CN III located
Edinger-Westphal (accessory
oculomotor) nucleus
Where are the postganglionic parasympathetic cell
bodies of CN III located
Ciliary ganglion
Postganglionic parasympathetic fibers
(axons) of CN III hitch a ride on a branch of CN V, which branch?
V1
What are the 4 peripheral targets of CN III
Extraocular muscules
Levator palpebrae superioris
Sphincter pupillae
ciliary muscles (lens)
Lesion to CN III - the eye (pupil) has what 3 symptoms in the anatomical position (when patient attempts to look straight ahead):
Dilated pupil
Ptosis (droopiness) of upper eyelid
Pupil is directed “down & out” (resulting in diplopia)
** this is because we have lost 4 of the 6 muscles **
What is the primary cranial nerve for somatic sensory (pain, temperature, proprioception, & touch) innervation from the head
CN V
CN V is somatic motor to what 2 muscles
muscles of mastication
pharyngeal arch 1 muscles
Regarding somatic sensory for CN V, the 1st order cell bodies for touch, pain, & temp are located in the
trigeminal ganglion
The peripheral processes of CN V form 3 divisions, what are they
CN V1
CN V2
CN V3
Which branch of CN V is somatic motor
CN V3 (mandibular)
Central processes forming the trigeminal nerve project to different nuclei (2nd order cell bodies) - what are they?
Main / chief / principal nucleus
Spinal trigeminal nucleus
Discriminative touch of CN V goes to what nucleus
Main / chief / principal nucleus
Pain and temperature for CN V goes to what nucleus
Spinal trigeminal nucleus
For CN V, 2nd order cell bodies primarily send their axons to 3rd order cell bodies located in the
VPM of the thalamus
For CN V, 3rd order cell bodies project to the inferolateral portion of the
postcentral gyrus
For CN V, where are the 1st order cell bodies for proprioception
Mesencephalic nucleus
For somatic motor of CN V, where are the UMNs located
Cell bodies located in the precentral gyrus
For CN V somatic motor, UMNs axons project BILATERALLY through the _________ tract
corticonuclear / corticobulbar
The somatic motor LMNs of CN V are located in what nucleus
trigeminal motor nucleus
The axons of LMNs of CN V contribute to CN V and follow what branch of CN V
mandibular (CN V3)
What are the sensory from (pain, temp, touch) peripheral targets of CN V1
Skin at & superior to the eyes
Eyeball (including cornea)
** basically skin of the forehead and eyeball **
Lesion of CN V1 =
Decreased (or abnormal) sensations of pain, temperature, & touch from area of distribution
** lose sensory from forehead and eyeball **
Peripheral targets of V3 = Sensory (pain, temp, touch) from
Skin along the region of the mandible
Anterior 2/3rd tongue
External ear
Peripheral targets of V3 = Somatic motor to what 2 muscles
muscles of mastication
pharyngeal arch 1 muscles
CN V3 passes through _________ to reach __________ ganglion
foramen ovale
trigeminal
Sensory lesion to CN V3
Decreased (or abnormal) sensations of pain, temperature, & touch from area of distribution
** mandible and anterior 2/3 tongue **
Motor lesion to CN V3
Deviation of mandible to side of the lesion during mouth opening
** lose motor to ipsilateral muscles of mastication **
Sensory corneal reflex is from what CN
V1 (somatic sensory from eyeball)
** this is to close eyelid/blink **
Motor corneal reflex is from what CN
CN VII (somatic motor to orbicularis oculi & visceral motor parasympathetic to lacrimal gland for tear production)
Signs & Symptoms of impacted CN V1 & CN V2 from Cavernous Sinus Thrombosis
sensory deficits for forehead, eyeball, and cheek
Regarding Sympathetic Pathway to the Head - where are the preganglionic sympathetic cell
bodies
T1 - T4
Regarding Sympathetic Pathway to the Head - where are the postganglionic sympathetic cell bodies
Superior Cervical Ganglion
Postganglionic sympathetic fibers from the superior cervical ganglion form
cephalic arterial rami
After postGS fibers form cephalic arterial rami, they reach their target organs by forming a plexuses, but to now get to the EYE, they follow what artery
ophthalmic artery
If we lost sympathetics in the head, what would we see
Flushed face due to vasodilation as we have lost VASOCONSTRICTION from the smooth muscle of arteries
No more sweating because we have lost innervation to our sweat glands
Dry mouth because we have lost innervation to our salivary glands
Constricted pupil because we have lost innervation to the dilator pupillae muscle
Ptosis because we have lost innervation the superior tarsal muscle BUT we still have the levator palpebrae muscle so it’s only slight ptosis
Signs/symptoms of Oculosympathetic Palsy / Horner’s Syndrome
Slight ptosis of the upper eyelid
Constricted pupil
Vasodilation
Decreased sweating
Central processes of what cell bodies form CN II (optic nerve)
retinal ganglion cells
if sensory CN II is damaged, we will have no ____________
constriction
if right side motor CN III is damaged, what will we see
nothing will happen on the right side but we will have the expected response on the left side
what can we expect to see if we accidentally impair CN II during a dental injection
temporary complete or partial blindness
the axons of the right abducens nucleus forms the _____ abducens nerve
right
if you damage CN III as it travels between the brainstem and superior orbital fissure, you damage what 2 fibers?
preGPS fibers
somatic motor fibers
Cavernous Sinus Thrombosis can impact what CNs?
3, 4, 6, V1 and V2
What 3 signs/symptoms can you expect to see with cavernous sinus thrombosis
Fixed pupil (can’t move because we lost all the nerves innervating the muscles to move the eye)
Pupil unresponsive to light changes (due to loss of both parasympathetic innervation (CN III) and sympathetic innervation (traveling on ICA)
Ptosis of the upper eyelid (because lost innervation to it)
What signs/symptoms can we expect to see from a misplaced dental injection to CN III?
Ptosis of upper eyelid (because we lost innervation to levator palpebrae superioris)
Pupil in down and out position at rest (because we lost innervation to 4 out of the 6 muscles)
Can’t do H pattern
Proprioception of CN V goes to what nucleus
Mesencephalic nucleus
