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Cerebellum

Cerebellum. STRUCTURAL 1. Major Components 2. Microscopic View FUNCTIONAL 3. Cerebellar Pathways 4. Clinical Correlations. Cerebellum General Description. Structural

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Cerebellum

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  1. Cerebellum STRUCTURAL 1. Major Components 2. Microscopic View FUNCTIONAL 3. Cerebellar Pathways 4. Clinical Correlations

  2. CerebellumGeneral Description Structural A bilaterally symmetrical structure in the posterior cranial fossa attached to the brain stem by means of three cerebellar peduncles Functional Functions in execution of a wide variety of movements, maintaining fine control and coordination of simple and complex movements

  3. 1.Major Components

  4. Cerebellum

  5. Major Components Cerebellar Hemispheres

  6. FOLIA =folia(leaves) Major Components

  7. Cerebellar Peduncles Major Components

  8. Superior Peduncle Major Components Efferent Projections superior peduncle

  9. Middle Peduncle Major Components Afferent Projections middle peduncle pons

  10. Inferior Peduncle Major Components Afferent & efferent Projections inferior peduncle

  11. Deep Cerebellar Nuclei Major Components

  12. Superior view Anatomic Divisions Anterior Lobe Primary fissure

  13. Inferior view Anatomic Divisions Vermis Flocculus Tonsils

  14. Anatomic Sub Divisions tonsil

  15. Functional Divisions Vestibulocerebellum (Archicerebellum) regulates balance and reflex eye movements

  16. Functional Divisions Spinocerebellum (Paleocerebellum) Adjusting ongoing movements and controlling muscle tone

  17. Functional Divisions Cerebrocerebellum (Neocerebellum) Planning and initiation of skilled movements

  18. 2.Microscopic View

  19. cerebellar cortex (gray matter) arbor vitae (white matter)

  20. Cerebellar Cortex 3 layers 1) Molecular 2) Purkinje 3) Granule 5 cell types Purkinje ([-], EFF) Granule ([+], target of Mossy) Stellate ([-], inhibit nearby Purkinje) Basket ([-], inhibit distant Purkinje) Golgi ([-], inhibit Granule) 2 fibers Mossy fiber ([+], 1ry AFF from cortex, brianstem, spinal cord) 2. Climbing fiber ([+], AFF, from inferior olive

  21. OUTPUT [-] Inhibitory projections via deep cerebellar nuclei - Purkinje Cells INDIRECT TARGETS (via deep cerebellar nuclei): -motor cortex -brainstem DIRECT TARGET -vestibular nuclei direct projections to vestibular nuclei

  22. INPUT [+] Excitatory - Mossy fibers - Climbing fibers Corticobulbar projections Mossy fibers Climbing fibers

  23. Summary ANATOMICALLY– three lobes: anterior, posterior, and flocculonodular FUNCTIONALLY– vestibulo-, spino-, and cerebrocerebellum CEREBELLAR CIRCUITS INPUT – to cerebellar cortex via mossy and climbing fibers to excite Purkinje OUTPUT – from cerebellar cortex (Purkinje cells) which 1) INDIRECTLY project to motor cortex and brainstem via deep cerebellar nuclei and 2) DIRECTLY to inferior olive

  24. 3.CerebellarPathways

  25. Vestibullocerebellum Function: tells cerebellum about the state of body equilibrium AFFERENTS via inferior peduncle from: vestibular apparatus vestibular nuclei via middle peduncle from: primary visual cortex superior colliculus Function: -influences vestibulospinal tracts that control postural muscles (to maintain equilibrium) -influences vestibulo-ocular reflex EFFERENTS via inferior peduncle to: vestibular nuclei

  26. Spinocerebellum Function: tells cerebellum about the state of your muscles (proprioception) AFFERENTS via inferior peduncle from: spinal cord Function: -influences lateral muscles (paramedian zone) -influences axial muscles (vermis) EFFERENTS Two sets from VERMIS and PARAMEDIAN zone with somatotopic organization

  27. Somatotopic Organization

  28. Spinocerebellum VERMIS Function: -influences corticobulbar tracts that control facial/tongue muscles -influences vestibulospinal, reticulospinal and ventral corticospinal tracts that control axial muscles EFFERENTS via superior peduncle and fastigial nucleus to: vestibular nuclei reticular formation motor cortex

  29. Spinocerebellum PARAMEDIAN ZONE Function: -effeinfluences rubrospinal, lateral corticospinal tracts that control limb muscles EFFERENTS via superior peduncle and interposed nuclei to: red nucleus motor cortex

  30. Cerebrocerebellum Function: tells cerebellum what the cortex is doing or planning to do AFFERENTS via pontine nuclei (corticopontine tract) via middle peduncle: cerebral cortex Function: -influences corticospinal and corticobulbar tracts to regulate complex movements -influences cerebellum for motor learning EFFERENTS via superior peduncle and dentate nucleus to: motor cortex (via thalamus) red nucleus

  31. Motor learning feedback loop

  32. Summary The cerebellum displays IPSILATERAL control (i.e., controls movement on the same side of the body, since all pathways project ipsilaterally, bilaterally or double cross) The superior cerebellar peduncle is the primary OUTPUT pathway from the deep cerebellar nuclei The middle cerebellar peduncle is an INPUT pathway from the cerebral cortex The inferior cerebellar peduncle provides input from the spinal cord, brainstem and inferior olive AND output to the brainstem

  33. 4.ClinicalCorrelations

  34. Ataxia: Loss of coordination Errors initiating and terminating movements dysmetria: errors in gauging distance and direction of a target causing overshoot/undershoot (overshoot of a target is called past-pointing)

  35. Intention (action) tremor Repeated overshoot and undershoot usually at the end of the movement

  36. Ataxia: Loss of coordination Dysdiadochokinesia: errors in timing of muscle contractions of rapid alternating movements

  37. Gait Ataxia

  38. Truncal Ataxia

  39. Cerebellar Damage • physical trauma • interruption of blood supply (superior cerebellar a., AICA, PICA) • alcoholism (affects Purkinje cells in anterior lobe) • cancer(degeneration of Purkinje cells) *Unilateral lesions produce ipsilateral symptoms

  40. Vestibulocerebellar lesions • Postural Pathways • VOR affected • Sx • truncal ataxia • nystagmus

  41. Vestibullocerebellum Function: tells cerebellum about the state of body equilibrium AFFERENTS via inferior peduncle from: vestibular apparatus vestibular nuclei via middle peduncle from: primary visual cortex superior colliculus Function: -influences vestibulospinal tracts that control postural muscles (to maintain equilibrium) -influences vestibulo-ocular reflex EFFERENTS via inferior peduncle to: vestibular nuclei

  42. Spinocerebellar lesions • (A) MIDLINE(@ axial/facial muscles) • Sx • truncal ataxia, dysarthria • (B) LATERAL(@ limb muscles) • Sx • gait ataxia, dysmetria, intention tremors • (C) ANT LOBE(@ leg muscles) • Sx • gait ataxia • Affects muscle tone

  43. Spinocerebellum Function: tells cerebellum about the state of your muscles (proprioception) AFFERENTS via inferior peduncle from: spinal cord Function: -influences lateral muscles (paramedian zone) -influences axial muscles (vermis) EFFERENTS Two sets from VERMIS and PARAMEDIAN zone with somatotopic organization

  44. Spinocerebellum VERMIS Function: -influences corticobulbar tracts that control facial/tongue muscles -influences vestibulospinal, reticulospinal and ventral corticospinal tracts that control axial muscles EFFERENTS via superior peduncle and fastigial nucleus to: vestibular nuclei reticular formation motor cortex

  45. Spinocerebellum PARAMEDIAN ZONE Function: -effeinfluences rubrospinal, lateral corticospinal tracts that control limb muscles EFFERENTS via superior peduncle and interposed nuclei to: red nucleus motor cortex

  46. Cerebrocerebellar lesions • Skilled movement of distal muscles (e.g., typing, speech) • Sx • dysmetria, intention tremor, dysdiadochokinesis, dysarthria

  47. Cerebrocerebellum Function: tells cerebellum what the cortex is doing or planning to do AFFERENTS via pontine nuclei (corticopontine tract) via middle peduncle: cerebral cortex Function: -influences corticospinal and corticobulbar tracts to regulate complex movements -influences cerebellum for motor learning EFFERENTS via superior peduncle and dentate nucleus to: motor cortex (via thalamus) red nucleus

  48. References

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