Cerebellum Flashcards
what do lesions to the cerebellum do
cuase decomposition of movements into their indiv components which then become uncoordinated (ataxia)
- motor deficts but not paralysis bc cerebellum modulates motor activity
- NO SENSORY DEFICITS
what lobes do the primary fissure separate
what lobes do the posterolateral fissure separate
anterior lobe and post lobe
posterior lobe and flocculonodular lobe
whats the only lateral cerebellar peduncle?
MCP
comes off the lateral pons
why can you not see the nodules from the ventral aspect but you can see the flocculus
bc the nodulus is off the vermis and it’s midline and it is INside
-nodulus would be the very last little nub of vermis sitting INSDIE the 4th vetnricle
what is it called when the tonsils hang below the level of the foramen magnum
arnold chiari malformation
what are folia
the tiny folds (gyri) over the cerebellar cortex
where is the deep cerebellar nuclei embedded in
embedded deep w/in the white matter
-but is gray matter “nuclei”
is the medullary portion gray or white matter
white matter
what do each of the 3 layers of the cerebellar cortex contain
- molecular layer: most external w/ axons (of granule cells) and dendrites (of purkinje cells)
2: purkinje layer: indiv cell bodies of purkinje cells lined up in a row - granule layer: most internal layer of the cerebellar cortex
are purkinje cells exhibitory or inhibitory? what neurotransmitter do they use
inhibitory
GABA
what nt do granule cells use
glutamate
how do inputs enter the cerebellum?
as mossy fibers or climbing fibers
incoming mossy fibers provide _____ input directly onto _____Cells
excitary input directly onto granule cells in the granule layer
wehre do climbing fibers come from and wehre do they enter
-what kind of contact do these make on purkinje cells
come from the inf olive and enter the cerebellum via the inf cerebellar peduncle
-each climbing fiber makes a massive, strong excitatory contact onto one or a small number of purkinje cells
purkinje cells send their axons down, out of the cerebellar cortex to synapse on what
- a deep cerebellar nucleus (DCN) embedded deep w.in the cerebellar white matter or
- a vestibular nucleus in the brainstem
what does a strong activation of a purkinje cell cause
a decreased activation of its target
why is the output of the cerebellar cortex inhibitory
bc the only ecll leaving the cerebellar cortex is the purkinje cell, which is inhibitory
what is the sole efferent neuron of the cerebellar cortex
purkinje cell
wht are the 4 pairs of DCN -deep cerebellar nuclei
medial to lateral: fastigial globose emboliform dentate
wehre do the interposed and fastigial nuclei receive inputs from
vermis and paravermis areas (spinocerebellum)
wehre does the dentate nuclei receive input from
cerebellar hemispheres (cerebrocerebellum)
in most cases, the fibers of the DCN leave the cerebellum through..
the superior cerebellar peduncle (SCP)
what are the 3 functional areas that the cerebellum is divided into
- spinocerebellum=vermis and intermediate zone
- cerebrocerebellum=hemispheres
- vestibulocerebellum=flocculonodular complex
what is the spinocerebellum’s function
- important for control of body muscularature for gait and posture (output)
- coordinate w/ spinal cord (input)
what is cerebrocerebellum’s function
- importnat for planning movements (output)
- coordinates w/ cerebral cortex (input)
what is the vestibulo-cerebellum’s function
- importnat for balance, posture, and eye movements (output)
- coordinates w/ inner ear (input)
the cerebellum has _____ impact on motor activity by impacting the ______;
indirect
UMNs
there is no direct impact on the LMNs
what does dysfucntion of the spinocerebellum do
vermal outputs: results in gait and truncal ataxia
paravermal: appendicular ataxia
what are the inputs to the spinocerebellum via
via the dorsal spinocerebellar tract and the cuneocerebellar tract
where do mossy fibers synapse at
granuel cells
what do cerebellar lesions cause
ipsi clinical deficits
proprioceptive input info from the right arm/leg =>____ spinocerebellum => ____ thalamus => ____ motor cortex ==> ____ sided body msucles
right spinocerebellum
left thalamuc
left motor cortex
right sided body muscles
what does damage to the spinocerebellum cause
ataxia of stance and gait
decreased muscle tone (hypotonia)
where is the cerebrocerebellum located
lateral hemispheres
what are the inputs and outputs of the cerebrocerebellum
receives input from the cerebral cortex (motor cortex) and sends outputs back to the cerebral cortex via VA/L thalamus
what is the cerebrocerebellum mostly concerned w/
coordinating distal musculature
ex reaching and grasping
what does a lesion at the cerebrocerebellum give
ataxia
the pontocerebellars enter the cerebellum via the MCP as ________ and synpase on the granule cells
mossy fibers and synpase on the granule cells of the cerebrocerebellar cortex
where will the fibers of the cerebrocerebellum go
many of these fibers will rise to VA/VL thalamus (which will then project to cortex)
1/3 will rise to the red nucleus
what is the path of the cerebrocerebellum fibers
- pontocerebellars enter the cerebellum via the MCP as mossy fibers and synpase on the granule cells of the cerebrocerebellar cortex
- granuel cell axons go up the molecular layer
- bifurcate in a T shaped fashion and synapse on Purkinje dendritic tree
- purkinje cell then sends its efferent inhibitory axon down to synapse on dentate nucleus
- fibers exit cerebellum and re-enter the brainstem through a cerebellar peduncle on ramp (SCP)
- fibers of SCP decussate at lvl of caudal midbrain
- fibers rise to VA/VL thalamus but 1/3 go to red nucleus
what happens when there is a lesion to the cerebrocerebellum
loss of coordinated muscle activity
- ataxia
- dysmetria
- scanning speech
- dysdiadochokinesia
- nystagmus
- rebound phenomenon
where can inputs to the vestibulocerebellum come from
- from the vestibular labyrinth (hair cells in the otolish organs-utricle, saccule, or semicircular canals)
- from vestibular nuclei (located in the lateral recess of the floor of the 4th ventricle)
if you are a purkinje cell are you’re in the flocculonodular lobe (vestibulocerebellum) where do you synpase on
vestibular nuclei (not in the cerebellum but in the brainstem)
- act as surrogates for the DCN
- vest nuclei receive info directly from purkinje cells
what does the MLF connect
connected all the EOM nuclei (3, 4, 6)
clinically, what happens whn there is a lesion to the cerebellum midline?
what happens when there is damage to the latral hemispheres?
midline ataxia from lesions to cerebellum midline
appendicular ataxia from damage to the lateral hems
what happens in midline ataxia
lead to functinal deficit w/in the vestibulocerebellum or spinocerebellum
-instability of people as they sit, stand, walk
what are the hallmarks of hemispheric cerebellar disease
- ipsi, appendicular
- ataxia of movements of extremities: dysmetria (abnormalility of hitting their target), intention tremor, dysdiadochokinesia (incoordination of rapid alternating movemtn)
- ataxia of speech
