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93 Cards in this Set
- Front
- Back
how does the cerebellum exert influence |
through connections to motor systems of the cortex and brainstem; does NOT have direct connections with LMNs |
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what do the inferior vermis and flocculonodular lobes regulate |
balance and eye movements through interactions with the vestibular circuitry |
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more lateral cerebellar regions control |
lateral motor systems |
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large regions of most of the lateral cerebellar hemispheres are important in |
motor planning |
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what do cerebellar lesions generally cause |
ataxia - characterisitc type of irregular uncoordinated movement |
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how can cerebellar lesions be localized |
1) ataxia is ipsilateral to side of cerebellar lesion 2) midline lesions of cerebellar vermis/flocculonodular lobes mainly cause unsteady gait (truncal) and eye movement abnormalities (along with vertigo, nausea, vomiting) 3) lesions lateral to cerebellar vermis mainly cause ataxia of limbs |
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what other fxns do cerebellar pathways participate in |
speech articulation, respiratory movements, motor learning, and possibly certain higher-order cognitive processes |
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what attaches the cerebellum to the brainstem |
cerebellar peduncles - 3 white matter tracts |
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what connections does the flocculonodular lobe have |
vestibular nuclei connections |
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most inferior portion of the cerebellar vermis |
nodulus |
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folia |
small ridges running from medial to lateral on the surface of the ccrebellum (gyri) |
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what does the superior cerebellar peduncle carry |
mainly outputs from the cerebellum |
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what do the middle and inferior cerebellar peduncles carry |
inputs to the cerebellum |
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where does the superior cerebellar peduncle descutate |
midbrain at level of the inferior colliculi (brachium conjunctivum) |
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alternative name for middle cerebellar peduncle |
brachium pontis |
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alternative name for the inferior cerebellar peduncle |
restiform body meaning 'rope-like body' |
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what lobes are important in control of proximal and trunck muscles and in vestibulo-ocular control respectively |
vermis and flocculonodular lobes |
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what part of the cerebellum is mainly involved in control of more distal appendicular muscles in the arms and legs |
intermediate part of cerebellar hemisphere |
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what part of the cerebellum is involved in planning the motor program for extremities |
lateral part |
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where are outputs relayed from in the cerebellum |
deep cerebellar nuclei and vestibular nuclei |
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what are the deep cerebellar nuclei (roof nuclei) |
dentate, emboliform, globose, fastigial (Don't Eat Greasy Foods) |
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where does the dentate nucleus receive projections from |
lateral cerebellar hemispheres |
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interposed nuclei and inputs |
emboliform and globuse nuclei; receive input from intermediate part of cerebellar hemispheres |
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where do fastigial nuclei recive input from |
vermis, and small input from flocculonodular lobe |
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where do most fibers leaving the inferior vermis and flocculi project to |
vestibular nuclei |
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three layers of cerebellar cortex |
granule cell layer, purkinje cell layer, and molecular layer |
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what is in the molecular layer |
inmyelinated granule cell axons, purkinje cell dendrites, and several types of interneurons |
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two primary kinds of synaptic inputs to the cerebellum |
1) mossy fibers 2) climbing fibers |
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mossy fibers |
ascend through cerebellar white matter to form excitatory synapses onto dendrites of the granule cells |
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where do granule cells send axons to |
into molecular layer, bifurcate forming parallel fibers that run parallel to the folia and form excitatory synaptic connections with numerous Pukinje cells |
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what carries all output from the cerebellar cortex |
axons of purkinje cells into cerebellar white matter |
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what kind of synapses do purkinje cells form |
inhibitory synapses onto deep cerebellar nuclei and vestibular nuclei, which then convey outputs from cerebellum to other regions through excitatory synapses |
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climbing fibers |
arise exclusively from neurons in the contralateral inferior olivary nucleus; they wrap around the cell body and proximal dendritic tree of purkinje cells forming powerfully excitatory synapses |
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inhibitory interneurons |
basket cells and stellate cells in the molecular layer |
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what are basket and stellate cells excited by |
inputs from granule cell parallel fibers |
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where do basket and stellate cells project to |
travel rostral to caudal perpendicular to parallel fibers to cause lateral inhibition of adjacent purkinje cells |
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where do stellate cells terminate |
purkinje cell dendrites |
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where do basket cells terminate |
form strong inhibitory basketlike connections on purkinje cells |
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golgi cells |
in granule cell layer, recive excitatory inputs from granule cell parallel fibers in molecular layer and provide feedback inhibition onto granule cell dendrites |
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cerebellar glomerulus |
small clearings amoung granule cells; contain axons and dendrites encapsulated in a glial sheath |
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two types of inputs in glomeruli |
large mossy fiber axon terminals and golgi cell axon terminals, which form synapses onto one type of postsynaptic cell (granules cell dendrites) |
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simple way to remember excitatory and inhibitory processes of cerebellar cortex |
axons projecting upward are excitatory (mossy, climbing, granule cell parallel fibers) and axons projecting downward are inhibitory (purkinje, stellate, basket, and goli cells) |
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where does the dentate nucleus project to and where does it decussate |
superior cerebellar peduncle, decussates in the midbrain to reach the contralateral ventral lateral nucleus (VL) of the thalamus |
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large rostral parvocellular division of the red nucleus |
involved in cerebellar circuitry and projects to the inferior olive; dentate nucleus projects here |
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magnocellular division of the red nucleus |
gives rise to the rubrospinal tract |
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where do the interposed nuclei project to |
superior cerebellar peduncle to contralateral VL - influences lateral corticospinal tract; also project to contralateral magnocellular division of red nucleus |
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how do the cerebellar vermis an flocculonodular lobes affect proximal trunk movements and vestibulo-ocular control |
connections to medial motor pathways (anterior corticospinal, reticulospinal, vestibulospinal, and tectospinal for trunk and medial longitundinal fasciculus for eyes) |
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what projects to the fastigial nucleus |
inferior vermis and flocculonodular have small projections here (mostly to vestibular nuclei) |
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where do outputs from fastigial nucleus go |
pathways running along with superior cerebellar peduncle and inferior cerebellar peduncles (called uncinate fasciculus and juxtarestiform body) |
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juxtarestiform body |
lying on lateral wall of 4th ventricle; carries fibers both ways btwn vestibular nuclei and cerebellum |
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what are reciprical connections btwn cerebellum and and vestibular nuclei important for |
equilibrium and balance |
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where do inputs to the cerebellum come from |
1) virtually all areas of cerebral cortex 2) multiple sensory modalities (vestibular, visual, auditory, somatosensory) 3) brainstem nuclei 4) spinal cord |
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what are celebellar inputs carried by |
mossy fibers, except those from the inferior olivary nucleus which is via climbing fibers |
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major source of input to cerebellum and where do they come from |
corticopontine fibers; primary sensory and motor cortices and visual cortex make the largest comtributions |
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where do corticopontine fibers synapse |
in pontine nuclei, then cross midline to enter contralateral middle cerebral peduncle and give rise to mossy fibers |
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4 tracts from spinal cords that go to cerebellum |
dorsal and ventral spinocerebellar tracts for lower extremities and cuneocerebellar and rostral spinocerebellar tracts for upper extremities and neck |
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2 kinds of feedback info from spinocerebellar tracts |
1) afferent info about limb movements by dorsal and cuneocerebellar tracts 2) info about spinal cord interneurons by ventral and rostral spinocerebellar tracts |
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where does the dorsal spinocerebellar tract ascend |
near surface of spinal cord just lateral to lateral corticospinal tract |
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where do fibers of the dorsal spinocerebellar tract come from |
large, myelinated axons of primary sensory neurons carrying proprioception, touch, and P sense enter dorsal roots and ascend in gracile fasciculus, rather than continuing some synapse in nucleus dorsalis of clark to ascend ipsilaterally in dorsal spinocerebellar tract |
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what do the fibers in the dorsal spinocerebellar tract give rise to |
mossy fibers that travel in ipsilateral cerebellar cortex via inferior cerebellar peduncle |
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upper-extremity equivalent of the dorsal spinocerebellar tract |
cuneocerebellar tract |
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what do the dorsal and cuneocerebellar tracts allow the cerebellum to control |
provide rapid feedback to allow fine adjustments of movement to be made |
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where does the ventral spinocerebellar tract arise |
neurons along the outer edge of the central gray matter called spinal border cells and from scattered neurons in the spinal cord intermediate zone |
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where do fibers of the ventral spinocerebellar tract ascend |
cross over in ventral commisure of spinal cord to ascend in ventral spinocerebellar tract ventral to the dorsal spinocerebellar tract and peripheral to the anterolateral systems |
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how do the ventral spinocerebellar tract fibers get to the cerebellum |
majority join superior cerebellar peduncle and cross a second time to reach ipsilateral side of where pathway began |
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where does the rostral spinocerebellar tract enter the cerebellum |
via inferior and superior cerebellar peduncles |
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how do fibers from the inferior olivary nuclear complex enter cerebellum |
cross the medulla to enter contralateral cerebellum; form major portion of inferior cerebellar peduncle and terminate as climbing fibers |
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the lateral reticular nucleus project via the inferior cerebellar peduncle and gives rise to |
mossy fibers |
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what provides a neuromodulatory role in the cerebellum |
noradrenergic inputs from locus ceruleus and serotonergic inputs from the raphe nuclei; not via climbing or mossy fibers! |
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blood supply to cerebellum |
PICA, AICA, and SCA |
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where does PICA generally arise |
from verebral artery |
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where does AICA generally arise |
from lower basilar just below the PCA |
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what does PICA supply |
lateral medulla, most of the inferior half of the cerebellum, and inferior vermis |
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What does AICA supply |
inferior lateral pons, middle cerebellar peduncle, strip of ventral cerebellum btwn PICA and SCA including flocculus |
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What does SCA supply |
upper lateral pons, superior cerebellar peduncle, most superior half of cerebellar hemisphere including deep cerebellar nuclei and superior vermis |
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what do patients with cerebellar infarcts present with |
vertigo, nausea and vomiting, horizontal nystagmus, limb ataxia, unsteady gait, headache; along with affected regions of pons or medulla |
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what can cause ataxia without cerebellum involvment |
cerebellar peduncles via infarction of lateral medulla or pons |
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what infarcts tend to affect only the cerebellum and spare the brainstem |
SCA infarcts |
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what infarcts can lead to swellin gof cerebellum and compression of the 4th ventricle |
PICA and SCA |
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fatal gastroenteritis |
cerebral hemorrhage with only symptoms of nausea and vomiting |
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lesions around the cerebellar vermis affect |
medial motor systems - wide base and unsteady, drunk-like gait |
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what can hydrocephalus involve that resembles cerebellar ataxia |
damage to frontopontine pathways; lesions of the prefrontal cortex can cause same affect |
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ataxia-hemiparesis |
syndrome often caused by lacunar infarcts; combination of unilateral UMN signs and ataxia usually affecting the same side (contralateral to lesion) |
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what lesions can cause ataxia-hemiparesis |
corona radiata, internal capsule or pons that involve both corticospinal and corticopontine fibers; also frontal, parietal, or sensorimotor cortex, or midbrain lesions involving fibers of superior cerebellar peduncle or red nucleus |
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sensory ataxia |
posterior-column-medial lemniscal pathway disrupted resulting in loss of position sense; worse when eyes closed |
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when is head tilt seen in cerebellar lesions |
extending to the anterior medullary velum which may affect trochlear nerves |
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dysmetria |
abnormal under or overshoot during movements toward a target |
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dysrhythmia |
abnormal rhythm and timing of movements |
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myoclonus |
sudden, rapid-movement disorder |
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postural tremor |
apply P to patient outstretch arm and release is abnormal; large0amplitude in cerebellar lesions |
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titubation |
pecular tremor of the trunk or head; can occur with midline cerebellar lesions |
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gaze paretic type of nystagmus |
slow phases toward primary position and fast phases occur back to target; can change directions in cerebellar lesions |
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scanning or explosive speech |
irregular fluctuations in both rate and volume |