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Cerebellum I

Cerebellum I. Introduction ​- Basic circuit is a loop between cerebral cortex, basal ganglia/cerebellum, and thalamus, with modulating input at second item ​- Anterior, posterior, flocculonodular lobes, ​primary and posterolateral fissures ​- Vermis , paravermis , lateral hemispheres. .

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Cerebellum I

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  1. Cerebellum I

  2. Introduction ​- Basic circuit is a loop between cerebral cortex, basal ganglia/cerebellum, and thalamus, with modulating input at second item ​- Anterior, posterior, flocculonodular lobes, ​primary and posterolateral fissures ​- Vermis, paravermis, lateral hemispheres.

  3. I. VESTIBULOCEREBELLUM ​- Vestibulocerebellum = flocculonodular lobe ​- Input: vestibular nuclei and Scarpa’s (vestibular) ganglion ​- Output: vestibular nuclei to control head/eye movements (e.g VOR) ​- Clinical signs: impaired vestibular function, poor eye control, nystagmus.

  4. II. SPINOCEREBELLUM ​- Spinocerebellum = vermis + paravermis ​- Vermisfastigial nucleus, paravermis interposed nuclei ​- Input ​- Clarke’s nucleus (via dorsal spinocerebellar tract) and lateral cuneate nucleus (via cuneocerebellar tract) provide ipsilateral muscle spindle

  5. ​- Ventral spinocerebellar tract (deep tendon receptors). ​- Reticular formations via spinal input ​- Output ​- Vermisfastigial nucleus pontine reticular formation for extensor a

  6. ​- Paravermis interposed nuclei  red nucleus, VL thalamus for motor function ​- Clinical signs ​- Cerebellarhypotonia: reduced muscle tone due to reduced deep nuclei activity ​- Dysmetria: failure to make seamless coordination, muscle overshoots.

  7. III. PONTOCEREBELLUM ​- Pontocerebellum = lateral hemispheres ​- Input: cerebral cortex via contralateralpontine nuclei ​- Output: dentate nucleus  VL thalamus for motor planning and medial thalamus for working memory ​- Clinical signs: decomposition of movement into a series of individual acts separated by stops.

  8. IV. Cerebellar circuitry ​- Mossy fibers: various origins  granule cells; excites many PCs via parallel fibers ​- Climbing fibers: inferior olive  Purkinje cells; powerful excitation ​- Purkinje cells: planar in stacks, input from many MFs and single CF, output to deep nuclei.

  9. ​- Basket and stellate cells inhibit Purkinje cells whereas golgi cells inhibit granule cells ​- Spacing of PCs allows for precisely timed actions in response to rich, complex input ​- Circuitry is responsible for learning by practice.

  10. V. Cerebellar Peduncles ​A) Inferior peduncle ​- Input from dorsal spinocerebellar tract, cuneocerebellar tract, olivocerebellar afferents ​- Some efferents to vestibular nuclei, but mostly input.

  11. B) Middle peduncle ​- Input from pons to pontocerebellum ​C) Superior peduncle ​- Output to red nuclei and VL thalamus (latter is input to primary motor cortex) ​- Input from ventral spinocerebellar tract (minor). 

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