Cerebellum Flashcards
What is the middle of the cerebellum called?
The vermis
What are the lateral masses of the cerebellum called?
The hemispheres
From what structures embryologically does the cerebellum develop from?
The alar plates of the neurotube
What type of disorders result from damage to the cerebellum?
Disruption of normal movement
How are lesions to the cerebellum and cerebral cortex different in terms of symptoms?
Movements are disrupted, not abolished
What are the 4 symptoms caused by a lesion to the cerebellum?
- Hypotonia
- Inability to walk or stand
- Ataxia
- Intension tremor and terminal tremor
What is loss of the ability to maintain a steady limb or body posture?
Astasia
What is loss of the ability to maintain an upright stance against gravity?
Abasia
What is ataxia?
Abnormal execution of multi-joint voluntary movements
What are intension tremors?
Begin to shake when beginning movements
What are terminal tremors?
Shaking at ends of movements
Does the cerebellum connect to lower motor neurons?
No, it synapses on centers that control LMN such as cortex, vestibular nuclei, reticular formation, etc…
What does the cerebellum regulate?
The force and timing of motor activities
What type of learning is the cerebellum involved in?
Motor learning
What level of consciousness does the cerebellum function at?
Subconcious
How does the cerebellum help muscle interplay?
Smooths interaction between agonists and antagonists
What type of posture does the cerebellum help to maintain? What system does it work in conjunction with in maintaining this type of posture?
- Upright posture
- Vestibular system
How does the cerebellum regulate movements and posture?
Adjusts output of major descending systems of the brain
Describe how the cerebellum adjusts movements in a feedforward manner?
- Compares movement intention with performance
- Integrates current state of motor system with the internally generated commands to PREDICT future state
How can the cerebellum be changed?
- Experience
- Practice makes perfect
What are the 3 functional divisions of the cerebellum?
- Archicerebellum/ vestibulocerebellum
- Paleocerebellum/ Spinocerebellum
- Corticocerebellum/ Pontocerebellum/ Neocerebellum
What is the function of the vestibulocerebellum?
- Coordinates head and eye movement
- Coordinates equilibrium of the body/ maintains balance
What are the 5 afferents of the vestibulocerebellum?
- Vestibular system
- Vestibular apparatus
- Superior colliculus
- Lateral geniculate
- Striate cortex
What are the 2 efferents of the vestibulocerebellum?
- Vestibular nuclei
- Reticular formation
What is the oldest functional division of the cerebellum phylogenetically?
- Vestibulocerebellum
What type of animals did the vestibulocerebellum originally develop in? What is the implication for its function?
- Water dwelling animals
- All that was required was an upright posture
What structures make up the paleocerebellum/ spinocerebellum?
- Vermis
- Intermediate areas of hemispheres
What are the 2 functions of the paleo/spinocerebellum?
- Execution of ongoing limb movements
- Regulation of muscle tone
What portions of the descending motor system are controlled by the paleo/ spinocerebellum?
- Medial and lateral components
How is the cerebellum somatotopically arranged?
Vermis (proximal and axial musculature)
Hemispheres (spinocerebellar and reticulocerebellar tracts)
What afferent information is processed in the vermis of the paleo/ spinocerebellum?
- Visual
- Hearing
- Vestibular
What afferent tracts are processed in the hemispheres of the paleo/ spinocerebellum?
- Spinocerebellar
- Reticulocerebellar
What are the efferent fibers of the paleo/ spinocerebellum?
- Brain stem motor nucleus such as red nucleus or reticular formation
What are the 3 functions of the cortico/ponto/neocerebellum?
- Planning/ PREPARATION and initiation of movements
- Learning and storage
- Precision in control of rapid movements and fine dexterity
What is the afferent tract of the cortico/ ponto/ neocerebellum?
Pontocerebellar tract
What is the efferent tract of the cortico/ ponto/ neocerebellum?
- Dentothalamic fibers (cerebellothalamocortical fibers)
What is the function of the motor loop through the lateral cerebellum?
- Execution of planned, voluntary, multijoint movements
What tract makes up the projection from the pons to the cerebellum that is involved in the motor loop through the lateral cerebellum?
Corticopontocerebellar
How many times larger is the corticopontocerebellar tract than the pyradmidal tract?
20 times
What two cerebellar nuclei are involved in motor execution?
- Fastigial nucleus
- Interposed nucleus
In what structure are the fastigial and interposed nuclei found?
The vermis of the cerebellum
What cerebellar nucleus is involved in motor planning?
Dentate nucleus
Which cerebellar nucleus is related to motor execution of the medial descending musculature?
Fastigial nucleus
Which cerebellar nucleus is related to motor execution of the lateral descending musculature?
Interposed nucleus.
What nuclei are responsible for coordination of balance and eye movements?
Vestibular nuclei
Which portion of the cerebellum receives input from the vestibular system?
The vestibulocerebellum, and the vermis
Which portion of the cerebellum receives input from spinal and trigeminal inputs?
- Spinocerebellum (medial portion/ intermediate hemisphere)
Which portion of the cerebellum receives input from the visual and auditory systems?
Middle of vermis
Which portion of the cerebellum receives input from the corticopontine systems?
- Lateral hemispheres
What is the lobe on the inferior aspect of the cerebellum?
- Flocculonodular lobe
What descending musculature does the vestibulocerebellar cerebellum innervate?
Medial/ proximal/ axial
What is the overall pathway from afferent to efferent output through the spinocerebellar pathway?
- Spinal cord afferents to spinocerebellum
- Vestigial nucleus to controlling areas
- Ventral medial system activated for proximal and axial musculature (????) (slide 13)
Describe the corticocerebellar pathway from the cerebral hemispheres back to the motor cortex.
- Corticopontine tracts project to the internal capsule
- Cortico pontine continue through the inferior the inferior colliculus to pontine nuclei in the mid pons
- Pontine nuclei in the mid pons project to the cerebellum through the middle cerebellar peduncle/ pontocerebellar projection
- Pontocerebellar projections synapse on the posterior lobe complex of the lateral the contralateral cerebellum
- Cerebellar nuclei project through superior cerebellar peduncle
- Cross at decussation of superior cerebellar peduncle
- Project to the ventral lateral nucleus of the thalamus (???)
- Project to the motor cortex
(This is all guesswork from the picture)
What are the 2 excitatory fibers to the purkinje cells in the cerebellar cortex?
- Mossy fibers
- Climbing fibers
From what do the mossy fibers originate from?
- Spinal cord
- Pontine nuclei
- Vestibular ganglia and nuclei
- Reticular formation nuclei
What cell do mossy fibers synapse on?
Granule cells and directly on deep cerebellar nuclei
What is the name of the fiber of the granule cell that rulls along the moelcular layer of the cortex?
Parallel fiber
What do parallel fibers of granule cells synapse on?
- Purkinje cells
- Basket cells
- Stellate cells
- Golgi cells
What type of neurotransmitter is released by basket, stellate, and golgi cells? What is its effect?
- GABA
- Inhibitory effect
What are Purkinje cells?
Output cells from the cerebellar cortex
From where do climbing fibers originate?
Exclusively the inferior olivary nucleus
What do climbing fibers synapse on?
- Dendrites of purkinje cells
- Collateral to deep cerebellar nuclei
What neurotransmitter is released by climbing fibers? What is the effect?
- Glutamate or aspartate
- Excitatory response
What neurotransmitter is released by Purkinje cells? What structures does this affect?
- GABA
Inhibits deep cerebellar nuclei
What structures do efferent fibers of the deep cerebellar nuclei project to?
- Inferior olive
- Reticular formation
- Vestibular nuclei
- Red nucleus
- Thalamus
What does the recurrent collateral from the deep cerebellar nuclei project to?
Granule cells in granular layer.
What is the ratio of climbing fibers to purkinje cells?
1:1
What portion of the cerebellum processes forward models of motor command?
Neocerebellum
Describe the forward model of motor command.
- Cerebellum receives copy of efferent motor commands from the cortex through the corticopontocerebellar tract (mossy fibers) to granule cells, which send collateral to cerebellar nuclei, which generate predictions
- The cerebellar nuclei send signals to the inferior olive to generate an error signal to update plastic microcircuits
- Excitatory connections send expected outcome information to the primary motor cortex
What is the function of the forward model of motor command?
- Increases time and accuracy of simple motor tasks
- Contributes to proper execution of complex motor tasks (comprehension and awareness of sequences over time)
See slide 17 for homunculus
See slide 17 for homunculus
What 2 structures process information from the sensory association cortex to plan and program movement for the premotor cortex?
- Basal ganglia
- Cerebro-cerebellum
(There are also direct connections from the sensory association cortex)
What structures have an influence on the output of the motor cortex?
- Spino-cerebellum
- Pre-motor cortex
Describe the interplay between the motor cortex and spino-cerebellum.
- Motor cortex sends collaterals to spinocerebellum, which is also receiving feedback from the body
- The spinocerebellum sends back efferents to the motor cortex
Which part of the cerebellum is the most commonly injured?
- The vestibulo cerebellum
What are symptoms of a vestibulo cerebellum lesion?
- Ataxia of gait and/ or upright posture
- Wide base of support
- Pathological nystagmus
What type of environment causes some of the effects of a vestibulo cerebellum lesion to be lessened?
Gravity eliminated environment
What are symptoms of a spinocerebellum lesion?
- Hypotonia throughout th ebody
- Titubation (staggering when trying to walk)
What causes the hypotonia associated with a spinocerebellar lesion?
- Decrease in gamma motor neuron drive
What causes the titubation associated with a spinocerebellar lesion?
- Ataxia of axial and proximal muscles
What portions of the cerebellum are typically damaged when titubation is present?
Vermis and intermediate zones
How does gravity affect titubation?
It doesn’t
Is titubation usually worse in upper or lower extremities?
LE
What is the overall effect of lesions to the corticocerebellum?
- Delays in initiation and termination of movements
- Disordered temporal and spatial coordination of multiple joints
What type of tremor may occur in a corticocerebellar lesion?
Intention tremor
What is dysdiadochokinesia? (caused by corticocerebellar lesion)
- Inability to perform quick alternating movements
What is decomposition of movement? (caused by corticocerebellar lesion)
- Not bracing proximal joints
How is speech affected by corticocerebellar lesions?
- Rhythm and flow of movement causes slurred speech and broken syllables
- Dysarthria due to vermis control of facial muscle loss
What is dysmetria? (caused by corticocerebellar lesion)
- Errors in range and force of movements
- Overshooting and undershooting
What is dyssynergia? (caused by corticocerebellar lesion)
- Break down of symmetry across multiple joints during movement
