General Information

• Size has increased with phylogeny--with need for control in skilled responses
• Functions as a correlation center with sensory and motor outflow
• Stimulation--no conscious sensation nor overt movements
• Correlates the muscle-tendon--vestibular message, as well as tactile, visual and auditory; computes most effective muscle effort required, then relays to:
  • Motor cortex (via ventral thalamic nucleus)
  • Motor-neuron pool

Functions

Damage produces dysmetria and asynergia

• Dysmetria--results from loss of proprioceptive input

• Asynergia--motor deficit--loss of involuntary motor responses
  • Injury to internal nuclei--more severe effects
  • Injury to efferent tracts--most severe effects

• Diagnosis of cerebellar injury is good but treatment is not employed

Cerebellar Peduncles

Superior cerebellar peduncle

• Afferent: Ventral cerebellar path
• Efferents:
  • Fastigo-bulbar--to inferior cerebellar peduncle
  • Brachium conjunctivium--to red nucleus from dentate; motor cortex via thalamus

Middle cerebellar peduncle

• Afferent only: Crossed fibers from pontine nucleus relay cortical and extrapyramidal information to brachium pontis

Inferior cerebellar peduncle

• Afferents
  • Vestibulo-cerebellar path (juxarestiform)
  • Dorsal spinocerebellar path (restiform)
  • Olivary nucleus: ventral internal arcuate fibers to restiform body

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Cerebellar Cortex

Nuclei

• Dentate
• Fastigial
• Globose
• Emboliform

• Afferent fibers (mossy fibers) synapse in granular layer on dendrites of granule cells
• Granule cells project to outermost (molecular layer) and branch in parallel with felia
• Granule cell axons synapse with many Purkinje cells whose dendritic fields are at right angles with the granule cells
  • Cell bodies of Purkinje cells form a second layer of cerebellum
  • Collaterals from Purkinje cells (climbing fibers) return to molecular layer and synapse with other Purkinje cell dendrites
  • Basket cells
• All Purkinje axons synapse with cell bodies in cerebellar nuclei

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Formal divisions

1. Archicerebellum--prefish & fish (smallest)
   • Flocculi -- vestibular correlation center
   • Nodule
   • Connections:
     • Vestibular to juxtarestiform body;
     • Fastigial nuclei to fastibulobulbar tract to vestibular nucleus and Reticular formation.
   • Lesions lead to vestibular symptoms

2. Paleocerebellum (intermediate in size)
   • Anterior lobe: connects spinocerebellar tract
   • Dominant system in quadrupeds
   • Receives olivary and cerebropontine connect

3. Neocerebellum--develops w/ skilled movements
   • Middle lobes--largest
   • Olivary and cerebral control only
   • Olivary nucleus: relays extrapyramidal system

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Afferents and Efferents

Afferents

1. Vestibulo-cerebellar path
   • 8th--juxtarestiform body--posterior lobe

2. Spinocerebellar paths (few cross)
   • Ventral spinocerebellar tract (older path)
   • Dorsal spinocerebellar tract
     • Synapse at Nucleus Dorsalis of Clarke; enters restiform body

3. Olivocerebellar tract--relays both spinal and extrapyramidal contributions
   • Olivary nucleus - cross as ventral internal arcuate fibers and enter restiform body; mainly to middle lobe

4. Cortico-pontocerebellar tract
   • Arises from motor areas (not projection)
   • Corona radiata

Efferents

• Fastiobular--from fastigial nucleus
• Brachium conjunctivium--from dentate nucleus to red nucleus, thalamus, globus pallidus
• Motor neuron pool via rubrospinal and reticulospinal tracts
• Others influence motor systems at cortical level via thalamus and in basal ganglia

Terms to Know