cerebellum Flashcards
What are the functional subdivison of the cerebellum and what they do (4)
- Cerebrocerebellum: motor planning, execution of skilled and complex spatio-temporal sequences (speech)
- Vestibulocerebellum (flocculonodular): posture, equilibrium, balance, eye movements
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——control of ongoing movement— - Spinocerebellum: gross limb movement - distal musculature
- Vermis - eye movements, trunk muscles, proximal muscles
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What would be more affected in an anterior lobe lesion?
Lower limb or upper limb
Lower limb because its somatic distribution is completely contained in the anterior lobe
The upper limb is only partially in the anterior lobe.
(upside down sex doll)
“don’t eat greasy food”
Deep cerebellar nuclei @ lvl of pons.
Lateral to medial
-Dentate (receives output from lateral hemisphere of cerebellum)
======(interposed nuclei)=======
- Emboliform
- Globosus
- —–receives intermediate hemisphere—
-Fastigial (receives vermis)
Describe the superior cerebellar peduncle (mostly outputs - motor learning, planning and cognition
PATHWAY 1: the double cross
- starts in the dentate nucleus
- (deep cerebellar nuclei always send info to contralateral side): in a climb to midbrain’s red nucleus, the superior cerebral peduncles decussate first
- Parvocellular red nucleus
- Inferior olivary nucleus
- Olivocerebellar fibers to return to the dentate nucleus (travels in the inferior cerebral peduncle)
PATHWAY 2: direct
- Dentate nucleus
- no synapse in red nucleus
- synapse in ventral lateral nucleus
- goes to motor and association cortex
Guillain Mollaret Triangle
- Dentate nucleus > superior cerebellar peduncle
- Red nucleus > (central tegmental tract)
- Inferior olivary nucleus > (inferior cerebellar peduncle) back
Describe the output from the intermediate zone of cerebellum
PATHWAY 1———
- Interposed nuclei
- Superior cerebellar peduncle
- Magnocellular red nucleus
- Fibers cross immediately in midbrain and travels down as rubrospinal tract
PATHWAY 2
- Interposed nuclei
- Superior cerebellar peduncle
- skips red nucleus, synapses in ventral lateral nucleus
4.
Describe the largest input to cerebellum pathway Cortico-ponto-cerebellar tract
Frontal/parietal cortex > pontine nuclei > middle cerebellar peduncle (CONTRALATERAL) > cerebellar cortex/deep nuclei
So you can see how from there the circuit goes to red nucleus to execute the results of planning but also goes back up into the VL > cortex to report back to the same region that sent the input!
Dorsal spinocerebellar tract and ventral spinocerebellars (leg proprioception)
DRG conveying proprioception > Nucleus dorsalis of Clark > travels superiorly > through inferior cerebellar peduncle > IPSILATERAL SIDE of cerebellum
ALSO: ventral spinocerebellar tract (SUPER WEIRD)
there is a track that also starts from nucleus dorsalis of Clark > decussation > inferior cerebellar peduncle > superior cerebellar peduncle > decussates AGAIN > ipsilateral side of cerebellum (same area)
Cuneocerebellar tract
Relays upper body proprioception
- info from dorsal root ganglio
- synapses in external cuneate nucleus in the medulla (so travels with DCMLS for a bit)
- Inferior cerebellar peduncle
- Cerebellum
** unconscious proprioception always ends up on the ipsilateral cerebellum
Describe the microscopic structure of the cerebellum
The cerebellum features folia
each folia has a core of white matter covered superficially by gray matter
The cortex can be divided into 3 layers
Molecular - outer, stellate cells, basket cells
Purkinje - middle
Granular - inner, granule cells, golgi cells
Describe the major cell types of the cerebellum
Purkinje cells are the only cells providing outflow information to the cerebellar nuclei.
All other neurons are just there to shut off or turn on Purkinje
Granules are the only ones that release glutamate and are excitatory for Purkinje cells
- Cerebellar output in INHIBITORY
- Cerebellar input is excitatory
Mossy Fibers
Climbing fibers
Mossy fibers from pontine nuclei, CN 8, spinal cord are EXCITATORY for granule cells
Climbing fibers from the contralateral inferior olivary nucleus are also EXCITATORY,
they have unique structure, they come up and only innervate on Purkinje cell, wraps around the trident.
THis promotes changes in the cerebellar output (promotes motor learning)
What is dysdiadochokinesis:
reduced ability to perform alternating movement such as pronation and supination of the forearm, at a moderately quick pace
Anterior lobe syndrome (particularly vermis)
Presents with general ataxia, gait ataxia, legs more affected than arms, broad based, staggering gait
Causes:
- toxin ingestion (sensitive to ethanol)
- thiamine (B1) Wernicke-Korsakoff) - memory impairment, confusion, gait ataxia, oculomotor disorders, nystagmus
Describe the output from the vermis and flocculonodular lobe
The cerebellum receives input from the cerebellar cortex
Deep cerebellar nuclei (fastigial) - synapse on superior colliculus, reticular formation, vestibular nuclei - which then descend the spinal cord
Tectospinal tract
Vestibulospinal tract
