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The Cerebellum

The Cerebellum. Position. Lies above and behind the medulla and pons and occupies posterior cranial fossa Its surface is high convoluted, forming folds or folia, being oriented transversely. Cerebellum. External features.

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The Cerebellum

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  1. The Cerebellum

  2. Position • Lies above and behind the medulla and pons and occupies posterior cranial fossa • Its surface is high convoluted, forming folds or folia, being oriented transversely Cerebellum

  3. External features Consists of twocerebellarhemisphere united in the midline by the vermis

  4. External features Three peduncles • Inferior cerebellar peduncle －connect with medulla and with spinal cord, contain both afferent and efferent fibers • Middle cerebellar peduncle －connect with pons, contain afferent fibers • Superior cerebellar peduncle －connect with midbrain, contain mostly efferent fibers

  5. External features • Tonsil of cerebellumtwo elevated masses on inferior surface of hemispheral portion just nearby foramen magnum

  6. Lobes • Two deep fissures • Primary fissure • Uvulonodular fissure • Three lobs • Flocculonodular lobe • Anterior • Posterior lobe

  7. Lobes Anterior lobe corpus of cerebellar Primary fissure Posterior lobe Flocculonodular lobe Posterolateral fissure

  8. Internal structures Gray matter • Cerebellar cortex • Cerebellar nuclei • Dentate nucleus • Fastigial nucleus • Emboliform nucleus • Globose nucleus White matter

  9. Internal structures Fastigial nucleus Cerebellar cortex Globose nucleus Dentate nucleus Emboliform nucleus medullary center

  10. Deep Nuclei 1. fastigial nucleus 2. globose nucleus 3. emboliform nucleus 4. dentate nucleus

  11. Three functional divisions • Vestibulocerebellum • Archicerebellum • Flocculonodular lobe • Spinocerebellum • Paleocerebellum • Vermis and intermediate zone • Cerebrocerebellum • Neocerebellum • Lateral zone Intermediate zone Vermis Lateral zone Flocculonodular lobe

  12. Spinocerebellum: Vermis Intermediate hem. Spinocerebellum (Vermis + Intermed. Hem) Cerebrocerebellum: Lateral hem. Control of limbs and trunk Cerebrocerebellum (Lateral hemisphere) Planning of movement+ Vermis Vestibulo-cerebellum (Floculo-nodular lobe) Intermediate hem. Lateral hem. Control of eye & head movements Balance Floculo-nodular lobe Cerebellar divisions IVth vent

  13. Connections and function of cerebellum Vestibulocerebellum • Connections • Afferents: receive input from vestibular nuclei and inner ear. • Efferents: projects to the vestibular nucleus → vestibulospinal → motor neurons of anterior horn • Function: involved in eye movements and maintain balance

  14. Connections and function of cerebellum Spinocerebellum • Connnection • Afferents: receive somatic sensory information via spinocerebellar tracts

  15. Efferents: • Fastigeal reticular and fastigial vestibular pathways: Vermis projects to the fastigial nucleus → vestibular nuclei and reticular formation → vestibulospinal tract and reticulospinal tract → motor neurons of anterior horn • Intermediate zone projects to the interposed nuclei • Globose- emboliform-rubral pathway: Contralateral red nucleus → rubrospinal tract →motor neurons of anterior horn • Function: play an important role in control of muscle tone and coordination of muscle movement on the same side of the body

  16. Connections and function of cerebellum Cerebrocerebellum • Connection • Afferents: receives input from the cerebral cortex via a relay in pontine nuclei(corticopontocerebellar pathway) • Efferents: (dentothalamic pathway): dentate nucleus → contralateral thalamus → primary motor cortex → corticospinal tract → motor neurons of anterior horn • Function: participates in planning movements

  17. summary • Cerebellar efferent fibers: • Globose-emboliform-rubral pathway • Dentothalamic pathway • Fastigial reticular pathway • Fastigial vestibular pathway

  18. summary • Cerebellar afferent fibers: • Afferent fibers from cerebral cortex: corticopontocerebellar pathway. • Afferent fibers from spinal cord: Anterior and posterior spinocerebellar tracts • Afferent fibers from vestibular nerve

  19. Pyramidal Tract and Associated Circuits upper motor neuron UMN Cerebellum BASAL GANGLIA pyramidal tract lower motor neuron UMN

  20. CerebellumFunction Maintenance of Equilibrium - balance, posture, eye movement Coordination of movement of walking and posture maintenance - posture, gait Adjustment of Muscle Tone Motor Learning – Motor Skills

  21. Balance

  22. Motor Skill Pablo Casals

  23. CerebellumClinical Syndromes 1-Ataxia: incoordination of movement - decomposition of movement - tremor - past-pointing 2- dysdiadochokinesia 3-Hypotonia, Nystagmus 4- dysarthria

  24. Posture Gait – Ataxia

  25. a b c Cerebellar Ataxia Ataxic gait and position: Left cerebellar tumor a. Sways to the right in standing position b. Steady on the right leg c. Unsteady on the left leg d. ataxic gait d

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