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75 Cards in this Set
- Front
- Back
True or false: Cranial nerves are inside the CNS.
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False: outside
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Where is the origin of the cranial nerves?
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brainstem (in CNS, but axons are outside)
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How many cranial nerves are there?
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12
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UMN are located where AND carry info where?
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-located in CNS (never leave it)
-carry info into brain (stop at brainstem) |
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Where do LMN originate at AND what do they innervate?
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-originate at the brainstem
-innervate muscle |
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What is another name for LMN?
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alpha motoneurons
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What are the 3 classes of neurons AND where are they located?
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-multipolar (motor and interneurons)
-bipolar (only found in ear and eye) -unipolar (all sensory neurons are unipolar) |
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True or false: Alpha motoneurons (LMN) are large and can be up to a meter long in humans.
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True
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Are alpha motoneurons myelinated?
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Yes
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What do alpha motoneurons terminate as? They are always what? AND what do they release?
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-terminate as motor endplate
-always excitatory (cause muscle to contract) -release only Acetylocholine (Ach) (NT that causes the muscle to contract) |
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What forms connections between muscles and CNS (motor cortex)?
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lower motor neurons
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True or false: All motor Cranial Nerves are lower motor neurons.
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True
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What is the final common pathway?
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alpha motoneurons and their axons are the only connection between the CNS and muscle
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Where do most of the cranial nerves originate?
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in the brainstem (10 of the 12 do)
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What do the motor nuclei receive impulses from?
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cortex through the corticobulbar tract
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Where are motor nuclei located?
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in the brainstem
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Where are the cell bodies for afferent connections of cranial nerves located?
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-outside of the brainstem in ganglia
-in a sensory organ such as the ear or the eye |
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Name the cranial nerves.
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I. Olfactory
II. Optic III. Oculomotor IV. Trochlear V. Trigeminal VI. Abducens VII. Facial VIII. Vestibulocochlear IX. Glossopharyngeal X. Vagus XI. Accessory XII. Hypoglossal |
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Which 2 cranial nerves do not originate in the brainstem?
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I. Olfactory
II. Optic |
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Which is the largest cranial nerve?
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V. Trigeminal
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What are the major functions of cranial nerve III?
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-occulomotor
-eyelid and eyeball movement -maintaining an open eyelid, precise movement of the eyes for visual tracking and fixation on an object, constriction of the pupil, adjustment of the pupil to light -motor nerve for vision |
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What is the major function of cranial nerve IV?
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-trochlear
-motor nerve for vision -innervates superior oblique turns eye downward and laterally |
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What is the major function of cranial nerve VI?
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-Abducens
-motor nerve for vision -turns eye laterally |
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What type of nerve is cranial nerve V?
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mixed (anterior- motor, posterior- sensory)
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What are the major functions of cranial nerve V?
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-sensory for face and head
-motor for muscles of mastication and speech |
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What are the 3 divisions of cranial nerve V?
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(trigeminal)
-opthalamic (sensory) -maxillary (sensory) -mandibular (mixed) |
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What type of innervation does cranial nerve V receive from the motor cortex?
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(trigeminal)
receives bilateral innervation |
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True or false: All cranial nerves receive bilateral innervation.
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False - Hypoglossal?
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What are the muscles of mastication that cranial nerve V has motor pathways to?
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-masseter (elevates jaw)
-temporalis (elevates jaw) -anterior belly of the digastric (lowers jaw) -medial and lateral pterygoid (protrusion of jaw) -mylohyoid (lowers jaw and elevates tongue and floor of oral cavity) -tensor veli palatini (tenses soft palate) -tensor tympani (tenses tympanic membrane) |
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Where does cranial nerve V provide sensation (touch and pressure) to?
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-face and scalp
-mucous membrane in oral cavity -anterior 2/3 of tongue, and teeth |
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Sensory neurons have cell bodies in the trigeminal ganglion and project centrally to the....
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-mesencephalic nucleus
-principle sensory nucleus (pontine trigeminal nucleus) -spinal nucleus (nucleus of spinal tract) |
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Injury to sensory branches of the trigeminal nerve will result in?
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numbness in face (fractures of facial bones may sever sensory branches)
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What is Trigeminal neuralgia?
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-aka tic douloureux - means painful tic
-a facial pain syndrome -severe pain of unknown origin -onset of pain is rapid in response to only mild stimuli -usually develops in individuals over 50 years old and the most common facial pain syndrome in this age group -incidence of 4/100,000 |
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What would happen if there were an UMN lesion of the trigeminal nerve?
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slight spasticity, but ability to chew only mildly affected because of bilateral innervation
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What would happen if there were an LMN lesion of the trigeminal nerve?
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-mandible will deviate toward the affected side due to unopposed pull of lateral pterygoid
-ipsilateral flaccidity or paralysis and atrophy |
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Is the facial nerve motor, sensory, or mixed?
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mixed
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What type of innervation does the facial nerve have?
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bilateral and contralateral (exception to the rule)
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What 3 nuclei of the facial nerve originate from the lower pons? AND what do they innervate?
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-motor (face)
-nucleus of the tractus solitarius -parasympathetic (superior salvitory nucleus) |
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True or false: The tractus solitarius is shared by other cranial nerves.
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True
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What does the parasympathetic nuclei of the facial nerve supply?
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glands
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What does the tractus solitarius of the facial nerve provide?
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taste
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What are the motor pathways of CN VII?
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-efferent fibers from the cortex project via the corticobulbar tract to the ipsilateral and contralateral motor nuclei in the pons
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Explain the bilateral and contralateral features of CN VII.
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fibers that project to:
-forehead are bilateral -lower facial muscles are contralateral |
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If CNs VI and VII are not functioning, where is the lesion?
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within the pons
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If CNs VII and VIII are not functioning, where is the lesion?
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in the region of internal acoustic meatus
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What function does CN VII provide to the tongue?
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taste for the anterior 2/3 portion
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What CNs provide taste to the nucleus solitarius?
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-facial
-vagus -glossopharyngeal |
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Where does the super salivatory nucleus receive input from?
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hypothalamus
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For salivation, food stimulates tactile, pressure, and taste receptors, which transmit signals where?
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to the salivatory nuclei in the medulla and pons
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What stimulates salivation?
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-tactile, pressure, and taste receptors
-odor -sight -thought of food |
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What does an UMN lesion of CN VII cause?
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loss of voluntary control of only lower muscles of facial expression contralateral innervation
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What does a LMN lesion of CN VII cause?
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all muscles supplied by nerve are paralyzed ipsilaterally
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Describe Bells Palsy.
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-LMN paralysis of muscle of one side of face
-no known etiology (thought to be viral or immune deficiency) -usually resolves spontaneously in 3-4 weeks) |
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Is CN VIII sensory, motor, or mixed? AND what type of innervation does it supply?
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-sensory (hearing and balance)
-bilateral |
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Is CN IX sensory, motor, or mixed? AND what type of innervation does it supply?
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-mixed
-bilateral |
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Where does the motor branch of the glossopharyngeal CN pass thru? AND what is the function of this motor branch?
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-nucleus ambiguous:
-- only to stylopharygeus (elevates larynx and pharynx; dialates pharynx to permit the passage of large bolus) |
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Where does the sensory branch of CN IX pass thru?
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nucleus solitarious (specialized nucleus for taste)
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What does the sensory branch of CN IX do?
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-provides sensation to palate, pharynx, and tongue
-touch and taste from posterior 1/3 of tongue -afferent component of gag relex (CN X is the efferent part) |
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What does damage to IX CN cause?
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absence of gag reflex
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What are possible causes of a LMN lesion?
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-brain stem stroke
-spinal injury -surgery -viral infection on cranial nerve (e.g., Bells Palsy) -bacterial infection |
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If the tongue deviates to the left due to an UMN lesion in the facial CN, which motor strip is affected?
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right side
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Is Vagus CN ("The Wanderer") sensory, motor, or mixed? AND what type of innervation does it provide?
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-mixed
-bilateral innervation |
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What 3 nuclei located in the medulla are associated with CN X? AND tell whether they are motor or sensory.
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-nucleus ambiguus (motor)
-dorsal nucleus (motor) -nucleus solitarius (sensory) |
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What 3 branches are there of the nucleus ambiguus (a nuclei of the vagus nerve)?
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-pharyngeal branch
-laryngeal branch -superior laryngeal branch |
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Describe the dorsal nucleus branch of CN X.
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-motor
-parasympathetic: involuntary muscles of bronchi, esophagus, heart, stomach, small intestine and most of large intestine |
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Describe the nucleus solitarius branch of CN X.
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mediates larynx, pharynx, thorax, and abdomen
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Describe how the nucleus ambiguus relates to CN X.
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-central connections: descending input is bilateral from corticobulbar fibers
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What are the 3 major motor branches of the nucleus ambiguus for the Vagus CN?
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-pharyngeal
-superior laryngeal nerve -recurrent laryngeal nerve |
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What are the 2 branches of the superior laryngeal nerve branch of the nucleus ambiguus of the vagus CN? AND tell whether they are sensory or motor.
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-internal branch: sensory
-external branch: motor (innervates one muscle--cricothyroid-->pitch) |
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Describe the pharyngeal branch of the nucleus ambiguus of the vagus CN.
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innervates:
-all muscles of the pharynx except stylopharyngeus (CN IX) -all muscles of the palate except tensor veli palatini (CN V3) |
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Describe the recurrent laryngeal nerve branch of the nucleus ambiguus of the vagus CN.
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-motor to intrinsic muscles of larynx
-sensory to regions below vocal folds |
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What are the 2 sensory pathways of CN X?
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-internal superior laryngeal
-recurrent laryngeal nerve |
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What areas does CN X provide sensory to?
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-larynx
-pharynx -thorax -abdomen |
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Describe the internal superior laryngeal sensory branch of CN X.
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-general sensation (pain, touch, temp): mucosa in pharynx; laryngeal region above vocal fold
-sensory fibers project to the nucleus solitarius innervating taste buds overlying epiglottis |
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Describe the recurrent laryngeal nerve sensory branch of CN X.
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general sensation (pain, touch, temp): laryngeal region at vocal folds and below
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