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156 Cards in this Set
- Front
- Back
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What is the effect of a CN I lesion?
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anosmia (loss of smell)
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What are the most common causes of anosmia?
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sinusitis and URI, head trauma, orbitofrontal tumors (rare)
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What does the oculomotor nerve innervate?
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levator palpebrae superioris, medial rectus, superior rectus, inferior rectus, and inferior oblique muscles
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What are the 4 effects of a CN II lesion?
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ptosis (eyelid drooping), outward deviation of the eye, large and nonreactive pupil, diplopia
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What is unique about the trochlear nerve?
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only nerve to exit the brainstem dorsally
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What does CN IV innervate?
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contralateral superior oblique m (decussates in midbrain)
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What are the effects of a CN IV lesion?
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diplopia, especially in attempting downward gaze when the eye is adducted
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What is unique about CN VI?
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it is has the longest intracranial couse of all the cranial nerves
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What does CN VI innervate?
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lateral rectus muscle
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What is the effect of a CN VI lesion?
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diplopia, on attempted abduction of the affected eye
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If both pupils constrict when light is shined on the right eye, but neither constricts when light is shined on the left eye, what is the problem?
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left optic nerve lesion
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What is miosis?
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constriction of the pupil
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What is mydriasis?
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dilation of the pupil
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If the left pupil constricts when light is shined in either eye, while the right pupil fails to constrict when light is shined in either eye, what is the problem?
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right CN III lesion
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What is a relative afferent pupillary defect?
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when both pupils initially constrict, however when light is moved to the affected eye, dilation occurs due to the relatively reduced afferent input from an optic nerve lesion.
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What is the near reflex?
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when viewing a nearby object it causes the eyes to constrict the pupils, accommodate the lens, and converge the eyes
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What is the dissociation of the light and near reflex?
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when the pupils constrict in the near reflex, but the light reflex is absent. Due to the selective disruption of the pupillary light reflex pathway at the superior colliculus or pretectal area
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What are some of the causes of a light-near reflex dissociation?
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Neurosyphilis (argyll robertson pupil); parinaud's syndrome (pineal tumor compressing the dorsal midbrain)
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What are the symptoms of Horner's syndrome?
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miosis (pupillary constriction); anhidrosis (lack of sweating); mild ptosis (paralysis of superior tarsal m.); enopthalmos
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What are the usual causes of the Horner's syndrome?
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lateral medullary infarct (Wallenberg's syndrome, 1st order neuron); Apical lung tumor (2nd order neuron); neck trauma (3rd order neuron)
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What is nystagmus?
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repetitive, oscillatory jerky eye movements
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What are the causes of nystagmus?
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imbalance of vestibular or brainstem control of eye movements, from lesions or drug toxicity affecting vestibular system, brainstem, or cerebellum
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What is monocular diplopia and its cause?
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seeing double vision with one eye closed, caused by an ocular disorder or psychiatric disorder, not neurological
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What is binocular diplopia and its cause?
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seeing double with both eyes open and seeing normally with either eye closed; caused by lesions of the brainstem, CN III, IV, VI; cerebellum or extraocular muscles
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What is internuclear opthalmoplegia?
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MLF syndrome, inability of the adducting eye on the side of the MLF lesion to pass the midline and nystagmus of the contralateral eye during abduction, convergence is intact
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What are the most common causes of internuclear opthalmoplegia?
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multiple sclerosis in younger patients and ischemic infarction in older patients
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What are the symptoms of bilateral upper motor neuron lesion of CN V?
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bilateral weakness of muscles of mastication with hyperactive jaw jerk reflex
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What are the symptoms of a unilateral UMN lesion of CN V?
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the jaw does not deviate with an UMN lesion because the muscles of mastication bave bilateral cortical control
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What are the symptoms of a LMN lesion of CN V?
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atrophy of the masseter muscle on the side of the lesion causing deviation of the jaw towards that side
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What is superior orbital fissure syndrome?
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sensory loss of opthalmic division of CN V plus paresis of CN III, CN IV, CN VI; a lesion of the cavernous sinus can also cause similar symptoms
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What are the symptoms of trigeminal neuralgia?
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episodic, lightning jabs of pain usually in maxillary or mandibular division of CN V, with no abnormalities of CN V with clinical exam.
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What are the causes of trigeminal neuralgia?
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compression of the trigeminal nerve due to a tortuous blood vessel (in the elderly); lesion from multiple sclerosis when CN V enters the pons (in younger pts)
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What are the treatments for trigeminal neuralgia?
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anticonvulsants; repositioning of blood vessels surgically or destruction of a nerve branch
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What are the symptoms of an UMN facial nerve lesion?
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if the lesion involves the motor cortex or its corticobulbar tract, this would cause only paralysis of the lower 2/3 of the contralateral face bc the upper 1/3 of the face is controlled by both the ipsilateral and contralateral motor cortex
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What are the symptoms of a LMN facial nerve lesion?
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paralysis of the entire ipsilateral half of the face, if the lesion is within the petrous bone above the stylomastoid foramen then there would also be a loss of taste to the anterior 2/3 of the tongue and hyperacusis with paralysis of stapedius m.
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What are the symptoms of a lesion in the cerebellopontine angle of posterior fossa?
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this acoustic neuroma would cause ipsilateral facial paralysis, loss of taste, deafness, and tinnitus
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What are the symptoms of a pontine lesion near CN VII nucleus?
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ipsilateral facial paralysis, ipsilateral weakness of lateral gaze due to involvement of the PPRF and adjacent CN VI
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What is Bell's palsy and its treatment?
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sudden nontraumatic periperal CN VII palsy and possibly hyperacousis (paralysis of stapedius m.) due to inflammation of CN VII within the petrous bone from possible viral infection; some pts benefit from corticosteroid treatment most fully recover.
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What is the result of a CN IX and CN X lesion?
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impaired speech and swallowing, decreased gag reflex, hoarseness, LMN lesion causes ipsilateral drooping of palatal arch at rest (uvula points to normal side)
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What is the result of a CN XI lesion?
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weakness of ipsilateral sternocleidomastoid and trapezius m. making it difficult to shrug the shoulder or rotate the head to the opposite side
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What is the result of an UMN CN XII lesion?
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may not cause weakness or deviation because ipsilateral and contralateral motor cortex control the hypoglossal nucleus, however in some the UMN is controlled mainly by the contralateral cortex and would cause the tongue to deviate away from the involved hemisphere
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What is the result of a LMN CN XII lesion?
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weakness of the ipsilateral half of tongue and deviation of the tongue toward the side of the lesion; atrophy, fasciculation and fibrillations are apparent
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What are causes of deficits in one or more cranial nerves?
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polyneuropathies (DM, Guillain-Barre); tumors, fractures, infection and inflammation of meninges
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In a crossed brainstem syndrome what are the symptoms in the body and face?
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ipsilateral CN deficit; contralateral limb weakness of UMN type (corticospinal tract); pain and pin sensory loss on ipsilateral face (trigeminal tract) and contralateral body (spinothalamic)
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What is medial midbrain syndrome (Weber syndrome)?
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ipsilateral CN III lesion and contralateral hemiplegia (cerebral peduncle involved) due to occlusion of a branch of the posterior cerebral artery
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What is the cause of lateral medullary syndrome (Wallenberg syndrome)?
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occlusion of the vertebral or posterior inferior cerebellar artery (PICA)
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What are the signs and symptoms of
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vertigo, nystagmus, nausea and vomiting (vestibular nuclei); ipsilateral dysmetria, clumsiness (inferior cerebellar peduncle); ipsilateral horner's (hypothalamic autonomic tract); ipsilateral palate (CN IX) and vocal cord (CN X) paralysis (nucleus ambiguus); impaired pin and temp sense on ipsilateral face (spinal trigeminal), and contralateral body (spinothalamic)
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What is the location of the cerebellar vermis?
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a midline zone of the cerebellum which is most clearly observe on the inferior surface of the cerebellum
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What are the longitudinal zones of the cerebellum?
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vermis, paravermal zone, and lateral hemispheres
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What separates the anterior from the posterior cerebellar lobe?
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the primary fissure
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What separates the posterior lobe from the flocculonodular lobe?
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posterolateral fissure
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What is the anterior cerebellar lobe?
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What is the posterior cerebellar lobe?
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What is the flocculonodular lobe?
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What is a folium?
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one of the many undulating ridges of tissue within the cerebellum
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What are mossy fibers?
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cerebellar afferents except climbing fibers, noradrenergic and serotonergic fibers, include spinocerebellar, pontocerebellar, reticulocerebellar, and vestibulocerebellar projections; terminate as large rosettes in contact with granule cells
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What are climbing fibers?
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arise exclusively from the inferior olivary complex, terminate in purkinje cell dendrites
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What runs in the inferior cerebellar peduncle?
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primarily afferent pathways: dorsal and ventral spinocerebellar tracts, cuneocerebellar tract, tigeminocerebellar tract, olivocerebellar tract, and reticulocerebellar fibers; juxtarestiform body contains interconnections btw the cerebellum and vestibular nuclei
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What runs in the superior cerebellar peduncle?
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primarily efferent fibers which decussate in the midbrain forming the rubrospinal tract, parvocellular red nucleus ventral latearl thalamic nucleus; some afferents from the ventral spinocerebellar tract, raphe nuclei, and locus cereleus;
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What runs in the middle cerebellar peduncle?
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pontocerebellar afferents from pontine gray and project as mossy fibers to the contralateral cerebellar cortex
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What are the deep cerebellar nuclei?
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fastigal (medial), globose, emboliform, dentate (lateral)
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What three arteries supply the cerebellum on each side?
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posterior inferior cerebellar artery, anterior inferior cerebellar artery, superior cerebellar artery
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What is the function of the vestibulocerebellum?
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involved in the maintenance of equilibrium and coordination of eye movements, closely related to the vestibular system
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What is the function of the spinocerebellum?
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concerned with regulating and coordinating muscle tone
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What is the function of the neocerebellum?
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involved in planning and coordinating somatic motor movements, both stereotyped and nonstereotyped; receives cortical inputs via the pontine nuclei
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What are the cardinal features of cerebellar disorders?
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ipsilateral signs with lateralized lesions, all clinical deficits are motor, gradual but definite recovery in time, somatotopic deficits with lateral lesions affecting limbs and medial lesions affecting the trunk, considerable severity if the superior cerebellar peduncle or deep cerebellar nuclei are involved
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What are the three functional divisions of the cerebellum?
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vestibulocerebellum (flocculonodular lobe); spinocerebellum (vermal and paravermal zones); neocerebellum (lateral hemispheres)
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To what nucleus/nuclei does the vestibulocerebellum division of the cerebellum project?
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fastigal nucleus
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To what nucleus/nuclei does the spinocerebellum division of the cerebellum project?
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globose and emboliform nuclei
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To what nucleus/nuclei does the neocerebellum division of the cerebellum project?
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dentate nucleus
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What are the three histological layers of the cerebellar cortex?
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granule cell layer (innermost); Purkinje layer (middle); molecular layer (outer)
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What neurons lie within the granule cell layer of the cerebellar cortex?
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parallel fibers
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What neurons lie within the purkinje cell layer of the cerebellar cortex?
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purkinje neurons
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What lies within the molecular layer of the cerebellar cortex?
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axons of parallel fibers and dendrites of the purkinje cells
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What is the purkinje cell to climbing fiber ratio?
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each purkinje cell only receives a synapse from one climbing fiber; however the climibing fiber can go to several purkinje cell
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Are purkinje cells release excitatory or inhibitory NTs?
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inbibitory, GABA-ergic of the deep cerebellar nuclei and vestibular nuclei
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What are basket or stellate cells?
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cells in the molecular layer of the cerebellum which receive granule cell inputs and powerfully inhibit purkinje cells at their axon hillock
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What are golgi cells?
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interneurons within the granule layer of the cerebellum which inhibit granule cells by inhibiting the mossy cell inputs
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Since purkinje cells, the only efferents from the cerebellar cortex are inhibitory, what fibers provide excitatory inputs to the deep cerebellar and vestibular nuclei?
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axon collaterals of mossy fibers (spinocerebellar) and climbing fibers
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What is the origin of the dorsal spinocerebellar tract and what information does it relay?
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dorsal nucleus of Clarke; afferent information from muscle spindles from the lower region
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What other tract is the dorsal spinocerebellar tract equivalent to?
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cuneocerebellar tract
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What is the origin of the cuneocerebellar tract and what information does it relay?
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lateral cuneate nucleus; afferent info from muscle spindles from the upper region
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What is the origin of the ventral spinocerebellar tract and what information does it relay?
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dorsal horn and intermediate gray; relays feedback info about spinal cord activity as it changes in response to descending motor pathways
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What is the origin of the trigeminocerebellar tract and what information does it relay?
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spinal trigeminal nucleus; afferent info from muscle spindles from the head
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What is the origin of the olivocerebellar fibers and what information does it relay?
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inferior olivary complex; acts as an integrating center that relays powerful excitatory climbing fibers to all areas of cerebellar cortex and involved in learning and timing of movements
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What is the origin of the reticulocerebellar fibers and what information does it relay?
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paramedian and lateral reticular nuclei; receives afferents from motor cortex, red nucleus, vestibular nuclei, and spinal cord
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What efferents travel in the inferior cerebellar peduncle?
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all associated with vestibulocerebellum are involved in adjusting muscle tone, coordinating equilibrium, and control of motor/eye movements to vestibular stimuli
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What is the origin of the efferents which run in the superior cerebellar peduncle?
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dentate nucleus (parvocellular red nucleus and ventral lateral thalamic nucleus); emboliform and globose nuclei (magnocellular red nucleus and crossed rubrospinal tract)
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Are the ascending limb efferent from the superior cerebellar peduncle involved with control of flexor or extensor muscle tone?
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flexor
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What is ataxia?
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clumsy intermittent movement, which may have components of several symptoms
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What is dysmetria?
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when a patient undershoots or overshoots when trying to touch a mark
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What is dysdiadochokinesia?
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inability to perform rapidly alternating movements such as supinating and pronating the forearm and hand
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What is decomposition of movement?
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phases of complex movements separated into individual breakdance or puppetlike movements
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What is intention tremor?
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characteristic tremor that becomes most pronounced at the end of a movement by is not present at rest
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What is the corpus cerebelli?
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the entire cerebellum other than the flocculonodular lobe; term used in reference to lesions that may be near the midline or in the lateral hemisphere
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What are the symptoms of flocculonodular syndrome?
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associated with medulloblastomas, a childhood tumor of the roof of the fourth ventricle and extending into the posterior vermis, unsteady broad stumbing gait, dizziness and nystagmus, hydrocephalous, and papilledema of optic disc
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What is outward current across a cell membrane?
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positive charges moving to the extracellular space or negative charges moving into the cell
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What K+ channels are responsible for the membrane resting potential?
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inward rectifiers in nerve cells
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How does one calculate the nernst potential for K?
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Vk = -61mV x log [K]i/[K]o
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What K+ channels are responsible for the repolarization of the cell membrane after an AP?
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delay rectifiers
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Does increasing Cl- permeability increase or decrease neuronal excitability?
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decrease
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What is the space length constant?
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(Rm/Ri)^1/2
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What are two reasons why an action potential cannot propagate backwards?
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Na+ channels are inactivated in the region behind the propagation front; K+ channels are highly activated in the region behind the propagation front
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Loss of myelin is associated with an increase or decrease in the Rm and a increase or decrease in the space length constant?
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decrease; decrease
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Does an AP travel faster in a large diameter or small diameter fiber?
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large diameter - less intracellular resistance
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Which neurons, large or small, have larger exicitatory potentials (EPSPs)? Is this expected?
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Smaller motorneurons so they fire the first Aps (the Size principle). This is contrary to the expected greater electrical excitability of larger neurons, however in the body it is affected by many complex physiological conditions.
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Since a single EPSP is usually not sufficient to trigger an AP in a neuron what are two ways for the AP to be triggered?
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Spatial summation (two EPSP at distinct locations at the same time); temporal summation (two EPSP at the same site in rapid succession)
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What is presynaptic inhibition?
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when an inhibitory presynaptic axon sends a collateral axon to synapse on a parallel excitatory presynaptic axon and releases a distinct NT to depolarize the excitatory neuron an prevent its NT from being released
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What is the most frequently used neurotransmitter in the CNS? Is it inhibitory or exitatory?
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Glutamate; excitatory
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What is the most common inhibitory neurotransmitters in the CNS?
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GABA and glycine - activate Cl- channels or GABAb does K+ channels
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What does the black widow spider toxin- alpha latrotoxin do?
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promotes fusion of synaptic vesicles into the synapse and excessive release of NT causes severe muscle spasms
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What toxins block nicotinic receptors?
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curare, snake toxins, hexamethonium
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What drugs block muscarinic receptors?
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atropine
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How is norepinephrine produced?
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from dopamine via dopamine beta-hydroxylase
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How is epinephrine produced?
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from norepinephrine via methyl-transferase
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What ganglion, effector organ, and effect does the edinger-westphal nucleus (III) have?
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ciliary ganglion; ciliary m, sphincter pupillae m.; accomodation and pupillary constriction
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What ganglion, effector organ, and effect does the lacrimal nucleus (VII) have?
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sphenopalatine ganglion; lacrimal gland; tears
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What ganglion, effector organ, and effect does the superior salivatory nucleus (VII) have?
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submandibular ganglion; submandibular and sublingual glands; thin, copious saliva
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What ganglion, effector organ, and effect does the inferior salivatory nucleus (IX) have?
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otic ganglion; parotid gland; thin, copious saliva
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What ganglion, effector organ, and effect does the dorsal motor nucleus (X) have?
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no named ganglion; stomach and small intestine; increased secretion and mobility
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What ganglion, effector organ, and effect does the nucleus ambiguus (X) have?
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intracardiac and pulmonary ganglia; heart and lungs; decreased HR, some decreased contractile force
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What ganglion, effector organ, and effect does the intermedial spinal gray of S2-S4 have?
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vesicular ganglia in myenteric plexus of colon and in walls of organs; descending colon, rectum and genitourinary system; contraction of bladder, colon, rectum, and penile erection
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What is the intracelluar signal and some of the basic targets and effects of the alpha-1 adrenergic receptor?
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increases IP3, DAG and Ca2+; vasoconstriction, constriction of iris, GI sphincters, piloerection, uterus, seminal vesicles; inhibits myenteric plexus, activates apocrine sweat glands, increases liver glucose production
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What is the intracelluar signal and some of the basic targets and effects of the alpha-2 adrenergic receptor?
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decreased cAMP; inhibits sympathetic nerve terminal release of norepinephrine
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What is the intracelluar signal and some of the basic targets and effects of the beta-1 adrenergic receptor?
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increased cAMP; increases HR and force of contraction (CO); renin release to increase BP; breakdown of fat cells increasing fatty acid levels
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What is the intracelluar signal and some of the basic targets and effects of the beta-2 adrenergic receptor?
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increased cAMP; relaxes skeletal m. blood vessels, brochiole muscles, uterine muscles, GI smooth m. and bladder detrusor m.
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What is the intracelluar signal and some of the basic targets and effects of the M1 muscarinic receptor?
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increased IP3, DAG, Ca2+; activates myenteric plexus
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What is the intracelluar signal and some of the basic targets and effects of the M2 muscarinic receptor?
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opens K channel; decrease HR and contraction also can decrease cAMP and Ca2+; to inhibit norepi release from sympathetic nerves
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What is the intracelluar signal and some of the basic targets and effects of the M3 muscarinic receptor?
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increased IP3, DAG, Ca2+; pupillary constriction and accommodation, constriction of brochiolar m., GI smooth m., uterine m. and bladder; relaxes vascular m.; stimulates GI secretion eccrine sweat glands, tears, salivary, pancreas and bile
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What are the preganglionic spinal level of the sympathetic superior cervical ganglion and what organs does it innervate?
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C8-T1 to T2; tarsal m., iris m., salivary glands
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What are the preganglionic spinal level of the sympathetic middle cervical and stellate ganglion and what organs does it innervate?
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T1 to T5; lungs, heart
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What are the preganglionic spinal level of the sympathetic celiac ganglion and what organs does it innervate?
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T6 to T10; stomach, small intestine, spleen, liver and pancreas
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What are the preganglionic spinal level of the sympathetic superior and inferior mesenteric ganglion and what organs does it innervate?
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T8 to L2; colon
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What are the preganglionic spinal level of the sympathetic inferior mesenteric and hypogastric plexus ganglion and what organs does it innervate?
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T11 to L2; urinary bladder and ureter
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What are the preganglionic spinal level of the sympathetic superior and middle cervical ganglion and what organs does it innervate?
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C8 to T3; head, neck sweat glands and blood vessels
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What are the preganglionic spinal level of the sympathetic stellate ganglion and T2-T5 paravertebral ganglion and what organs does it innervate?
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C8 to T5; glands and blood vessles of upper limb and chest
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What are the preganglionic spinal level of the sympathetic T6 to L2 paravertebral ganglion and what organs does it innervate?
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T6 to L2; sweat glands and blood vessels of lower chest and abdomen
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What are the preganglionic spinal level of the sympathetic L1 to S4 paravertebral ganglion and what organs does it innervate?
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T10 to L2; sweat glands and blood vessels of lower extremities
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What is the ratio between preganglionic and postganglionic cells?
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from 1:2 to 1:100 this results in a huge amount of divergence and widespread diffuse response
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What are the two types of terminal postganglionic cell NT release?
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varicosities; fiber bundle nerve terminal
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Besides acetylcholine what are three additional NT released from the parasympathetic nervous system?
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ATP (innervates smooth m. in bladder); Vasoactive intestinal peptide (VIP) innervates glands and blood vessels in the gut; Nitric Oxide (NO) promotes vasodilation in the cardio, urogenital, respiratory, and GI systems (relaxing sphincters)
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How is the adrenal gland innervated by the sympathetics?
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pre-ganglionic fibers do not synapse in either paravertebral or prevertebral ganglia and reach chromaffin cells (modified post-ganglionic cells) of the adrenal medulla and releases epinephrine
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Besides NE what are three additional NT released from the sympathetic nervous system?
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acetylcholine (used with cholinergic M3 to innervate eccrine sweat glands); Neuropeptide Y (mediates vasoconstriction); ATP (increases speeod of vasculature contraction in conjunction with NE)
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Where can autonomic afferents synapse?
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in a spinal reflex (elicits a ipsilateral response); in a supraspinal reflex (elicits a bilateral response)
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What is the function of the reticular formation?
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a coordinating system/pattern generator: eye movements, chewing, swallowing, micturition, respiratory control, cardio control, sleeping/wake
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What is the median reticular formation?
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a column of serotonergic neurons (raphe nuclei)
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What is the paramedian reticular formation?
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the efferent zone; located in medulla (ventral reticular nucleus, gigantocellular reticular nucleus); pons (caudal pontine nucleus and PPRF) and midbrain (mesenchepalic)
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What is the lateral or parvocellular reticular formation?
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afferent zone; extends from the medulla to pons
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What are the aminiergic neurons of the reticular formation?
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serotonergic (brainstem midline); dopaminergic (ventral tegmental nuclei of midbrain); noradrenergic (locus ceruleus of pons); epi-secreting (minor in medulla)
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Where are the cholinergic neurons of the reticular formation found?
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pedunculopontine nucleus
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What is the Ascending reticular activating system (ARAS)?
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plays a role in level of alertness, sleep-wake rhythms and alerting rxns
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What are the efferent projections of the reticular formation into the spinal cord?
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via the pontine and medullary reticulospinal tracts, descend bilaterally, without somatotopy
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What are the efferent projections of the reticular formation into the brainstem?
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via the reticulobulblar fibers within the central tegmental tract
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What is the raphe nuclei?
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origin of the serotonergic projections of the reticular formation
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What is the locus ceruleus?
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origin of the noradrenergic projections of the reticular formation
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What is the periaqueductal gray (PAG)?
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region around cerebral aqueduct in midbrain which has an excitatory projection to the magnus raphe nucleus (role in pain perception) which results in analgesia
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