Cerebellum Flashcards
What is the role of the cerebellum?
To compare intended movements with those that actually occur - minimise the difference between intended and actual movements
Where is the cerebellum located?
Sits caudal to the cerebral hemispheres and dorsal to the pons and medulla oblongata
Describe the structure of the cerebellum
Highly folded cortex of grey matter plus deep nuclei
It has white matter forming branching tracts - arbor vitae (tree of life)
What lies immediately ventral to the cerebellum?
The 4th ventricle
What is the function of the pons?
Act as a bridge between the spinal cord, cerebellum and cerebrum
What is the function of the medulla oblongata?
Act as the neural mass responsible for involuntary movement e.g. breathing
Name the 3 lobes of the cerebellum
Anterior
Posterior
Flocculonodular
What is the function of the central vermis of the cerebellum?
Receives information from the trunk and the proximal limbs
Where does the intermediate zone receive information from?
The distal limbs
What are the peduncles?
3 stalks of white matter which communicate the deep cerebellar nuclei with other CNS structures
They contribute to the structures forming the roof of the 4th ventricle
The caudal cerebellar peduncles carry what type of fibres and what type of information?
Afferent fibres carrying sensory information from vestibular organs and proprioceptors to the cerebellum
The middle cerebellar peduncles carry what type of fibres and what type of information?
Afferent fibres which bring information about intended movements - brings sensory fibres in from the spinal cord
The rostral cerebellar peduncles carry what type of fibres and what type of information?
Efferent fibres which decussate and run from the cerebellum to the thalamus and midbrain
What are the 3 layers of grey matter?
- Granule layer
- Purkinje layer
- Molecular layer
Which layer of grey matter contains dendrites and axons?
Molecular layer
Which layer of grey matter contains dendrites of one particular nerve fibre?
Granule layer
What are the two main sets of afferent axons synapsing on the deep nuclei and cortex of the cerebellum?
Mossy fibres
Climbing fibres
How do deep nuclei increase motor function?
They have their excitatory output to the upper motor neurone tracts
What are upper motor neurones?
Tracts that go from the brainstem, down the spinal cord to synapse with LMNs to pass on information to enable limb movement
What are the 3 nerve fibre types in the cerebellum?
Purkinje
Mossy
Climbing
Cerebellar function is crucial for which aspects of movement?
Balance, coordination and refinement
How does the cerebellum achieve its function?
Constant comparison of information from the motor planning centres with input from vestibular and proprioceptive sensory organs - what was intended vs what happened
Where are corrective signals from the cerebellum sent to?
Via the thalamus to the brain stem upper motor nuclei
What is the function of the vestibulocerebellum/flocculonodular lobe?
Coordinates balance and eye movements in response to input from vestibular and visual systems
What is the function of the spinocerebellum/vermis?
Coordinates muscle tone and movement
What is the function of the cerebrocerebellar/lateral cerebellar hemispheres?
Coordinates planning of limb movements
How is the cerebellum different in animals with a large tail?
The cerebellar vermis has a well-developed lobule at the rostral end called the lingula
How is the cerebellum different in precocial and altricial animals?
Precocial - near-fully developed cerebellum at birth
Altricial - cerebellar development continues for weeks after birth
What is ataxia?
Inability of the vestibulo and spinocerebellum to coordinate balance and movement of the axial skeleton - uncoordinated gait and balance
Loss of input from the cerebellar cortex leads to?
Reduced inhibition of UMN function causing hypermetria and increased muscle tone
