Week 8 - cerebellum Flashcards
What is the cerebellum?
prominent hindbrain structure - one of the most recognisable regions of the brain due to its shape and location
What are folia?
gyro formations of the cerebellum
What is the function of the cerebellum?
- detects differences in motor error
- aids motor cortex in producing accurate and smooth movements by modulating and refining motor cortex commands using feedback form proprioceptors and other sensory organs
- involved in sensorimotor coordination
name the three lobes the cerebellum can be anatomically divided into
- anterior lobe
- posterior lobe
- flocculonodular lobe
Does the cerebellum initiate movement?
no - detects differences in motor error between an intended movement and the actual movement
is the cerebellum of a cow longer than of a human?
yes
What are the major components of the cerebellum?
- cerebelar cortex
- deeper cerebellar nuclei
- cerebellar peduncles
Subdivide the cerebellar cortex into its three functional zones based on differences in their sources of input
- cerebrocerebellum
- spinocerebellum
- vestibulocerebellum
What does the cerebrocerebellum comprise?
most lateral cerebellar hemisphere
largest subdivision
What does the spinocerebellum comprise of?
- comprises anterior lobe and vermis
- occupies median and paramedic zone of cerebellar hemispheres
What does the vestibulocerebellum comprise of?
- caudal inferior lobes include
- flocculus and nodulus
From what areas does the cerebrocerebellum receive its inputs?
indirectly from the cerebral cortex
What is the function of the cerebrocerebellum?
regulating highly skilled movements initiated by the motor cortex eg. speech, voluntary movement of arms and hands, hand eye coordination
From what areas does the spinocerebellum receive its inputs?
directly form the spinal cord
What is the function of the spinocerebellum?
regulation of muscle tone and movement of distal muscles eg. arm and legs
From what areas does the vestibulocerebellum receive its inputs?
from vestibular nuclei in brainstem and processes vestibular information
What is the function of the vestibulocerebellum?
regulation of the vestibule-ocular reflex - ensure stability of gaze, and movements maintaining posture and balance of the head and body
name the three deep cerebellar nuclei
- dentate, interposed, fastigial nucleus
Where are all in/out puts to the cerebellar cortex relayed to?
- doesn’t have ires input form or output to rest of brain, all in/outputs relayed through deep cerebellar nuclei
name the three cerebellar peduncles
superior, middle, inferior
what is the function of the cerebellar peduncles?
make connections between the cerebellum and other parts of the nervous system
What does the superior cerebellar peduncle comprise?
output fires projecting form deep cerebellar nuclei to midbrain structures (eg. primary motor cortex)
What does the middle cerebellar peduncle comprise?
comprises input fibres projecting to the cerebellum largely from base of the pons
What does the inferior cerebellar peduncle comprise?
comprises input fibres projecting to the cerebellum from the spinal cord and vestibular nuclei
From what three regions does the cerebellum receive projections?
cerebral cortex
sensory pathways (spinal cord)
Brian stem
Where do projections form the cerebral cortex go to in the cerebellum?
- largest input
- cortical input going to cerebrocerebellum
Do cortical axons project directly into the cerebellum?
no - synapse on nucleus in pons (pontine nucleus) located on same side of brainstem as hemisphere of origin
axons of pontine are transverse pontine fibres, cross midline and enter cerebellum via middle cerebellar peduncle
How do sensory pathways project to the cerebellum?
- vestibular axons from 8th CN and axons form vestibular nuclei in medulla project to vesibulocerebellum
- relay neurons in dorsal nucleus of Clarke in spinal coord + external cuneate nucleus of caudal medulla send their axons to spino-cerebellum
How does the brainstem project to the cerebellum?
- receives modulatory input form inferior olivary nucleus in brainstem from structures such as cerebral cortex and red nucleus
- olivo-cerebellar axons exit medially form inferior live and enter cerebellum via inferior cerebral peduncle
explain output projections form the cerebellum to the cortical motor systems
- from dentate nucleus and interposed nucleus -> relay in VL thalamus complex -> project to motor cortex
what do lower motor neurons in medial ventral from contribute to?
control of axial and proximal limb musculature
name the three layers of the cerebellar cortex
- molecular layer
- Purkinje cell layer
- granule cell layer
Describe the molecular layer of the cerebellum
contains apical dendrites of Purkinje cells, m parallel fibres form granule cells, basket cells and stellate cells
Describe the Purkinje cell layer of the cerebellum
comprises middle layer of cerebellar cortex and contains Purkinje cell body
describe the granule cell layer of the cerebellum
contains granule cell bodies
What is the ultimate destination of afferent pathways to cerebellar cortex?
Purkinje cells
Is input from cerebral cortex to Purkinje cells direct or indirect?
indirect
What are mossy fibres?
axons form pontine nuclei and most other sources of cerebellar input from brainstem and spinal cord
Where do mossy fibres synapse?
on neurons in deeper cerebellar nuclei and on granule cells in granule cell layer
What do granule cells give rise to?
parallel fibres that ascend to the molecular layer of the cerebellar Cortex
How is the molecular layer of the cerebellum structured?
- parallel fibres fork to form T-shaped branches that form excitatory synapses with the dendritic spines of Purkinje cells
What do Purkinje cells do?
- receive direct modulatory input form climbing fires which arise in inferior olivary nucleus
- modulate effectiveness of parallel fibre connections
- project to deep cerebellar nuclei
What modulates inhibitory activity of Purkinje cells?
inputs form basket cells and stellate cells
What is motor error correction?
- mediated by climbing fires that ascend form inferior olive to contact dendrites of Purkinje cells
- climbing fibres modify efficacy of parallel fibre - Purkinje cell connection, producing long term changes in cerebellar output - motor learning
