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Puder Cranial Nerves #1
Terms in this set (31)
Cranial Nerve I; name and function
Olfactory nerve; relays odorant information from olfactory epithelium to pyriform cortex
It is special sensory
Pathway of CNI
Axons of cell bodies project through the cribriform plate to synapse on the olfactory bulbs (cell bodies of second neuron) whose axons (olfactory tracts) will bifurcate and synapse in the pyriform (pear shaped) area of the inferior temporal lobe
What does CNI synapse on?
Olfactory bulb and tract <--- this is not CNI, it is the second neuron in the olfactory pathway
This neuron goes into the temporal lobe's pyriform cortex
Skull fracture and anosmia
An anteroposterior skull fracture parallel to the superior saggital suture can tear olfactory axons in the cribriform plate resulting in ipsilateral loss of smell = anosmia
Frontal lobe tumors or meningiomas on the floor of the anterior cranial fossa can interfere with the transmission of _______ info.
Damage to the primary cortical olfactory area in the temporal lobe from tumors or seizures can result in ________.
olfactory hallucinations (phantom smells)
CNII; name and function
Optic nerve; part of the visual system which transduces light energy into visual info
CNII cell bodies (ganglion cells) receive info from rods and cones of bipolar neurons that transduce light energy
The cell body projects its axons out of the eye as the optic nerve --> optic chiasm --> optic tract to synapse onto the lateral geniculate nucleus of the thalamus --> visual cortex in occipital lobe
CNII is the second nerve in the pathway
Optic nerve on gross brain
these are all of the axons of CNII
Damage to CNII; what side does blindness occur on?
Significance of CNIII, IV and VI
They are all cranial nerves that are lower motor neurons as well as cranial nerves
CNIII; name and function
Oculomotor nerve; innervates 4 of the 6 eye muscles necessary for eye movement (ipsilaterally) and the superior eyelid muscle (levator palpebrae superioris)
It also has a parasympathetic visceral motor component which innervates intrinsic ocular muscles necessary for pupillary constriction
CNIII pathway; find the Oculomotor nerve on the slide
Mickey Mouse, so we're in the midbrain
The two eyes means that we're in the upper slice
is the oculomotor nucleus
Result of losing function of CNIII
Paralysis of 4 of the 6 ipsilateral eye muscles
Causes ipsilateral eye to be in a downward, abducted position resulting in
strabismus and diplopia
Ptosis also present (loss of innervation to eyelid muscle)
Where is the visceral motor (parasympathetic) component of CNIII located? And what happens if there is a lesion here?
Small group of cell bodies called the
contain the visceral motor (parasympathetic) component of CN III. It is located near the occulomotor nucleus - but too small to be seen on midbrain section. These axons project out to the pupillary constrictor and ciliary muscles of the ipsilateral eye causing pupillary constriction and accomodation. A lesion to Edinger-Westphal and nerve results in --->
dilated pupil and loss of accomodation
CNIV; name and function
Trochlear nerve; innervates the superior oblique muscle of the eye
Action of superior oblique muscle is inward rotation and downward movement of the eye (the eye movement used when trying to walk down a set of steps)
CNIV pathway; find the trochlear nucleus on the slide
; lower slice of midbrain; ipsilateral lesion of CN IV --> eye up and outward!
Cranial Nerves are always __________ (ipsilateral/contralateral)?
This means that a lesion in the CN always affects the ipsilateral side of whatever the CN is innervating
What symptoms would a lesion of CN IV exhibit?
Lower motor neuron symptoms of
outward rotation of eye
weakness of downward gaze
If you see a person with their head tilted to the side, what cranial nerve may they have damaged?
A patient will tilt their head to the unaffected side to correct diplopia
CN V; what are the three major divisions?
CN V1; ophthalmic
CN V2; maxillary
CN V3; mandibular
What is the distribution of the two modalities of the trigeminal nerve?
General sensory (V1, V2, V3)
Branchial Motor (V3)
What is tic doloureaux?
another name for Trigeminal neuralgia --> episodes of lacinating, severe pain of unknown etiology
Symptoms of motor lesions of the trigeminal nerve?
LMN lesion to muscles of mastication; characterized by paralysis, atrophy of muscles, and decreased strength of bite
ID Spinal Trigeminal Tract and Nucleus; what's its function? (verbatim Puder question from lecture)
Relaying pain and temp sensation from the ipsilateral face
ID Principal Sensory Nucleus; what's its function? (verbatim Puder question from lecture)
Relaying touch and vibratory sense sensation from the ipsilateral face
Function/Location of Trigeminal Motor Nucleus
(Recall that this is from CNV3)
Innervate muscles of mastication on the ipsilateral side
Dysfunction; flaccid paralysis of muscle of mastication/loss of bite
This is a lower motor neuron
Mesencephalic nucleus function
Proprioceptive info from muscle spindles in mastication muscles (so you don't bite your tongue)
Located near the 4th ventricle
CNVI; name and function
Abducens; innervates lateral rectus muscle of the eye
Laterally rotates/abducts the eye
Where is the CNVI on the slide?
Medial/internal strabismus (eye misalignment), diplopia (double vision); what type of lesion?
Lesion to CN VI --> lower motor neuron symptoms
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