L22 - Cerebellum Flashcards
Function of Cerebellum?
Sensorimotor integration:
regulatory influence on muscular activity»_space; coordination and control of movements
also contributes to cognitive processes
Divide the anatomical lobes of the cerebellum?
Anterior, Posterior, Flocculonodular lobes (from Nodulus and Folcculus nodes)
10 lobes in total
Connection between cerebellum and brainstem?
Superior, Middle, Inferior cerebellar peduncle
Superior = output
Middle and inferior = input
Divide the cerebellum into saggital zones, function of these zones and nuclei that resides in each zone.
1) Medial zone (vermal cortex) = Fastigial nucleus
2) Intermediate zone (intermediate cortex) = globose nucleus, emboliform nucleus, Interposed nuclei
3) Lateral zone (hemispheri cortex) = Dentate nucleus
1 + 2 = Spinocerebellum
3 = Cerebrocerebellum
Vestibulocerebellum = flocculonodular lobe
List 5 cells types in cerebellum.
- Purkinje cells
- Golgi, Stellate, Basket cells
- Granule cells
Function of Purkinje cells in cerebellum?
Receive direct and indirect input from climbing fibers and mossy fibers
Only cortical output neuron (GABAnergic)
Project to mainly inhibit subcortical/ deep cerebellar nuclei + some end in vestibular nuclei
Function of the lateral zone of cerebellum?
Contains 2 dentate nuclei:
For projection through superior cerebellar peduncle to thalamus to motor/ pre-motor cortex for motor planning
Function of the vermal cortex of cerebellum?
Vermal cortex = medial zone
Contains 2 fastigial nuclei:
Project through superior cerebellar peduncle to:
1) Medial descending pathway for motor execution
2) Vestibular nuclei for balance and eye movement
List the inhibitory interneurons in the cerebellum? Function?
Basket, Golgi, Stellate cells
Regulatory interneurons (GABA neurotransmitter = inhibitory) of Purkinje cells
Describe the excitatory input to the cerebellum and the cells involved?
Two inputs reach the cerebellar cortex via excitatory fibers:
1) Direct pathway: Climbing fibers from inferior olive (visual, audio, vestibular signals)»_space; Inferior cerebellar peduncle
» Deep cerebellar nuclei and directly to Purkinje cells
2) Indirect pathway:
Mossy fibers from spinal cord/ brainstem (visual, audio, vestibular)»_space; Inferior cerebellar peduncle»_space; Granule cells fibers»_space; Parallel fibers at the top of cerebellar cortex»_space; Purkinje cell dendritic trees
Describe the 2 modes of signal spread in the parallel fibers at the top of cerebellar cortex?
1) 1-dimensional spread: focal mossy inputs excite on-beam P cells + inhibit subcortical, brainstem cells
2) 2-dimensional spread: focal mossy inputs excite on-beam basket cells, stellate cells
» transverse fibers spread inhibition to neighboring off-beam P-cells
» dis-inhibit neighboring subcortical, brainstem cells (more excited)
Where do signals from the subcortical cerebellar nuclei end up?
a. first to thalamus: then to the cerebral cortex
b. brainstem nuclei (e.g. red nucleus, vestibular nuclei and reticular formation).
List the 3 cerebellar functional units? **
- Spinocerebellum
- Cerebrocerebellum
- Vestibulocerebellum
Function of the Vestibulocerebellum?
a) Control of vestibulospinal reflex (postural movements via the axial motor system).
b) Coordination of vestibulo-ocular reflex.
Input and output of vestibulocerebellum?
Input: vestibular nucleus, spinal cord, reticular formation
Processing: Vermal cerebellum + Vestibulocerebellum
Output:
1) Vermal cerebellum»_space; lateral vestibulospinal tract
2) Vestibulocerebellum»_space; reticulospinal tract
Function of the Spinocerebellum? What tracts are involved
ERROR-DETECTOR:
COMPARING the command signals (intended action) originated from the cerebral cortex [cortico-ponto-cerebellar circuit]
with updated feedback from actual execution of the motor action [spinocerebellar tract]
> > correct mistakes during the course of movements
Divide the spinocerebellum into 2 zones and their respective function?
Error-detection and update from spinocerebellar tract
a) Medial corticonuclear zone - Control both postural and voluntary movements of axial and proximal body parts
b) Intermediate corticonuclear zone - Coordinate voluntary movements of distal body parts by executing moment-to-moment course corrections
Describe how the medial corticonuclear zone of the spinocerebellum exerts control? (3 tracts: 2 descending, 1 ascending))
Origin: Vermis (fastigial nucleus), send fibers to:
i) descending vestibulospinal tract
ii) Descending reticulospinal tract (can loop back to vermis via spinocerebellar pathway or mossy fibers)
iii) ascending thalamocortical projection, acting on medial descending motor system»_space; proximal and truncal muscles
Describe how the Intermediate corticonuclear zone of the spinocerebellum exerts control? (2 pathways)
Error detection and moment-to-moment control
1) Direct: via Rubrospinal tract»_space; spinal cord
2) Indirect: via thalamocortical projections»_space; corticospinal tract of lateral descending motor system
Which saggital zone makes of the cerebrocerebellum?
lateral corticonuclear zone
Function of cerebrocerebellum?
1) Converts movement designs from association cortex [cerebro-cerebellar tract] to movement programs
> > > sent to premotor cortex (area 6) for subsequent execution of goal-directed* voluntary movements* (i.e. voluntary oculomotor control)
2) Non-motor cognition
Sequence of pathway through the cerebrocerebellum?
Association cortex
» Pontine relay nuclei»_space; Mossy fibers»_space; Dentate nuclei»_space; thalamus»_space; pre- motor cortex»_space; corticospinal tract in spinal cord
or directly from dentate nucleus to rubrospinal tract in spinal cord
List 4 pathological manifestations of cerebellar lesion?
Ataxia
Intention tremor
Hypotonus
Nystagmus
Define the mechanism of ataxia caused by cerebellar lesion? How to test?
Errors in rate, range, force, direction of voluntary movements
due to Decomposition of movement and Asynergia (out of sync/ smoothness)
Tests:
1) Finger to nose test
2) Tandem steps test (unsteady gait)
3) Scanning, slurred speech
