Cerebellum Flashcards
disorders to the cerebellum results in ?
general- in comparison to cerebrum
disruption of normal movement - NOT abolishment
these disruptions are in stark contrast to the paralysis caused by damage to the cerebral cortex
what are the 4 common manifestations of lesions to the cerebellum?
1- hypotonia (related to “pendular reflexes”)
2- an inability to stand or walk
- atasia
- abasia
3- ataxia (abnormal execution of multi-jointed voluntary movements)
4- intension tremor (action tremor) and terminal tremor
what is atasia?
loss of the ability to maintain a steady limb or body posture
what is abasia?
loss of the ability to maintain upright stance against gravity
what are the pendular reflexes?
tap knee with hammer, should get a stretch reflex
if there is a lesion in the cerebellum, reflex would continue – going back and forth before your knee relaxed
what are the general functions of the cerebellum?
Regulates- force and timing of motor activities
Helps with the range and direction of motor movements
Allows for the rapid progression from one movement to the next
Sequencing of motor movements
Agonist-antagonist interplay (synergy)
Help with planning of movements
Helps with the maintenance of upright posture
Motor Learning
Subconscious movement
appears to function as a comparator- compensates for errors (internal and external feedback) in movements
*changed by experience- thus plays a role in learning motor tasks
cerebellum controls the controller in a feedforward manner.. what does this mean?
corrects for all the errors as the messages are being sent down- makes the corrections BEFORE the LMNs get it
feedback is after the action has already happened
dynamic- changes by experience
(doesn’t connect directly to LMNs- sends its coordination inputs to the control centers- vestibular nuclei, etc.)
what are the 3 functional divisions?
1- vestibulo cerebellum
2- spinocerebellum
3- cortico cerebellum
what lobe controls the vestibulo cerebellum division?
where does it receive projections from?
flocculonodular lobe
“archicerebellum” (oldest part of the structure phylogenetically) (fishO)
flocculonodular lobe receives many projections from the vestibular nuclei
what are the functions of the vestibulo cerebellum division?
coordinate head and eye movement
body equilibrium- help with the maintenance of balance
what are the afferent components of the vestibulo cerebellum system?
vestibular system
vestibular apparatus
visual centers- superior colliculus, lateral geniculate and striate cortex
what are the efferent components of the vestibulo cerebellum system?
vestibular nuclei- responsible for maintaining posture
reticular formation
what lobe controls the spinocerebellum function division?
what is the corresponding nucleus?
the anterior lobe (vermal portion) and the intermediate areas of the hemispheres
“paleocerebellem” second oldest part phylogenetically (reptiles)
nucleus=
fastigial- to medial descending systems
interposed- to lateral descending systems
what are the functions of the spinocerebellum division?
controls medial and lateral components of the descending motor system and thus plays a role in the EXECUTION ongoing limb movements
regulates muscle tone
(axons come from SC (all the dorsal, ventral, rostral, cuneo, reticular cerebellar tracts)
what is the somatotopical arrangement for the spinocerebellum division?
vermis= eyes and trunk
lateral to vermis= axial musculature
what are the afferent components of the spinocerebellum division?
vermis- visual, hearing, vestibular
hemispheric- spinocerebellar and reticulocerebellar tracts
what are the efferent components of the spinocerebellum division?
BS motor nuclei (red nucleus, RF, etc)
what lobe controls the corticocerebellum functional division?
what is the corresponding nucleus?
posterior lobe
“pontocerebellum”
“neocerebellum”
largest
nucleus- dentate nucleus- to motor and premotor cortices
what are the functions of the corticocerebellum division?
planning and (cortex-initiation of movements)
learning and storage
precision in the control and rapid movements and fine dexterity
concerned with preparation of movement
what are the afferent components of the corticocerebellum division?
pontocerebellar
pontine nuclei directly associated
what are the efferent components of the corticocerebellum division?
dentothalamic fibers (cerebellothalamocortical fibers)
explain the motor loop through the lateral cerebellum:
???
pontine nuclei
-axons from layer V pyramidal cells in the sensorimotor cortex form massive projections to the pons
corticopontocerebellar projection
-20x larger than pyramidal tract
function -execution of planned, voluntary, multipoint movements
what are the cerebellar outputs?
fastigial nucleus to medial descending systems
interposed nucleus to lateral descending systems
BOTH –> motor execution
dentate nucleus to motor and premotor cortices –> motor planning
vestibular nuclei –> balance and eye movements
what are the cerebellar inputs?
corticopontine inputs
spinal and trigeminal inputs
visual and auditory inputs
vestiular inputs
what is the circuitry of the vestibulo cerebellum?
from the flocculonodular lobe descends through the superior cerebellar peduncle to the vestibular nucleus to the MLF and descends the medial vestibulospinal tracts
afferents:
vestibular receptors –> vestibular nucleus up the inferior cerebellar peduncle to the flocculonodular lobe
what is the circuitry of the spino cerebellar division?
controlling and stabilizing axial and proximal musculature
coordinates movements of distal extremities via the red nucleus
more for execution of movement
what is the circuitry of the corticocerebellar division?
these systems come from the cortex, they are the largest
project down to the pons to pontine nuclei then refers info to pontine cerebellar
neocerebellum (ahead of time) motor nucleus monitors what is going on (activity goes on before movement is initiated
cerebral cortex–> ponto system –> pons to hemispheres to dentate –> cerebral cortex –> out foraminal tracts
Cortex asks cerebellum, ‘this is my intention, how do I do it?’, cerebellum makes prediction of best way of doing something under environmental factors, sends info back to cortex, initiates movement
what are the results of a vestibulo cerebellum disorder?
decreased equilibrium
ataxic gait- upright posture
wide base of support
less of a problem in a gravity eliminated environment
pathological nystagmus
-romberg
what are the results of a spinocerebellum disorder?
hypotonia- primarily decrease is in gamma MN drive
titubation- staggering in trying to walk -vermis and intermediate zones ataxia of axial and proximal muslces -gravity=unrelated -usually worse on LE
balance problems due to inability to coordinate
what are the results of a corticocerebrellum disorder?
delays in initiation and termination of movement
intention tremor (increases toward the ends of movements)
disorders in the temporal coordination of movements involving multiple joints
disorders in the spatial coordination of hand and finger ms
dysmetria- errors in range and force of movements (overshoot and undershoot)
timing is off
ataxia
dysdiadochokinesia- can’t rapidly alternate between movements
decomposition of movement (multi joints)- not bracing proximal joints against forces
normal rhythm and flow of movement is decreased
-slurred speech and broken syllables
dysarthria- due to vermis control of facial muscles
lesions of inferior olive complex:
precise function unknown
usually associated with pyramidal tracts- therefore over shadowed
olivocerebellar degeneration-exception disorder begins about 40-50 olive atrophies and results in: -contralat progressive ataxia of extremities -intention tremor -dysarthria may develop -motor learning??
what are other functions of the cerebellum?
cognitive computation independent of motor execution (timing of serial events)
lesions of lateral cerebellum caused inability to learn a word-association task
limbic system
- affective changes occur during cerebellar lesions:
- anxiety, aggression, hyper spontaneous disinhibited behavior, etc- disorders of emotional control
