Cerebellum Flashcards
Function of cerebellum
To detect motor error between intended movement and actual movement and reduce this error
How does cerebellum influence movement
By modifying activity of UMNs (like BG)
Grey matter structures in cerebellum
Cerebellar cortex: input
Deep nuclei: input and output
Parts of cerebellum
Cerebrocerebellum: regulation of highly skilled movements. Planning of complex sequences of movements
Spinocerebellum: lat part movements of distal muscles. Med part movement of proximal muscles. Regulates eye movements
Vestibulocerebellum: gets input from vestibular nucli. Regulation of movements underlying posture and VOR reflex
Connections to cerebellum
To other parts of the nervous system via the superior, middle and inferior cerebellar peduncles
Superior peduncle
Almost entirely afferent from deep cerebllar nuclei.
Axons project to superior colliculi, after relaying in thalamus, primary motor and premotor
Middle cerebellar peduncle
Afferent from pontine nuclei which receives info from wide range of cerebral cortex areas and superior colliculi
Inferior cerebllear peduncle
Multiple afferent and efferents
Afferent from vestibular nuclei
Efferent to vestibular nuclei and reticular formation
Cerebellar modulatory input
From inferior olive and locus ceruleus in brainstem
Nuclei participate in learning and memory functions seved by cerebellar activity
Where does cerebellar cortex project to
Deep cerebellar nuclei
And vestibular complex
Major deep nuclei on each hemisphere
- dentate nucleus (cerebrocerebellum)
- two interposed nuclei: globose and emboliform (spinocerebellum)
- fastigial nucleus (spinocerebellum)
- vestibular nuclei (vestibulocerebellum)
Dentate nucleus
Gets afferent from cerebrocerebellum
Efferents destined for premotor and cortices of frontal lobe
Planning voliational movements
Dentate nucleus pathway
- fibres exit via superior cerebellar peduncle
- first relayed in ventral nuclear complex of thalamus
- cross midline and ascend contralateral hemisphere
Gives out fibres to red nucleus which projects to inferior olive. Feedback mechanism
Fastigial nuclei
Project from spinocerebellum
Project via inferior cerebellar peduncle
Goes to reticular formation and vestibular complex
Governs axial and proximal limb musculature
Interposed nuclei
Project via superior cerebellar peduncle
To thalamic circuits that interact with motor regions of frontal lobe for voliational movements
Also project to contralateral superior colliculus
Vestibular nuclei
Via inferior peduncle
Termonate in nuclei of vestibular complex
Movements of head, eyes, neck for linear accell
Afferents from pontine nuclei
1
Pontine nuclei get afferent fibres from cortex and relay to contralateral cerebellar cortex
Axons from pontine nuclei are MOSSY fibres
These synapse on neurones in deep cerebellar nuclei and on granule cells in granule layer of cerebellar cortex
Afferents from pontine nucle2
Granule cells give rise to parallel fibres that ascend to molecular layer of cerebllar cotex
Parallel fibres bifurcate in molecular layer. Relay onto dendritic spines of purkinje fibres
Afferents from pontine nuclei
3 purkinjes
Purkinje cell bodies in purkinje layer
Also get modulatory inputs from climbing fibres (come from inf olive) that synapse onto their shafts
Purkinjes project to deep cerebellar nuclei
Are GABAergic so oversall output of cerebellar cortex is inhibitory
2 stages of cerebellar processing
EXCITATORY LOOP
INHIBTIROY LOOP
Excitatory loop
Mossy fibres and climbing fibres drive activation of deep cerebellar nuclei
Inhibitory loop
Inhibitory purkinje fibres modulate activity of deep nuclei by responding to excitatory signals of parallel fibres to generate inhibitory output
Cerebellar damage
Persistent errors of movement on ipsilateral side
Alcohol on cerebellum
Degen of ant portion of cerebellar cortex
Affects spinocerebellum, affecting movement of lower limbs
Wide staggering gait
Damage to vestibulocerebellum
Impaired ability to stand up and maintain direction of gaze
Eyes cant fixate - nystagmus
