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CEREBELLUM Gross Morphology Tentorium cerebelli Falx cerebelli Anatomical Plan I Left and right hemispheres: Anterior and posterior lobe: Subconscious movements of skeletal muscles Flocculonodular nodes: Concerned with equilibrium Vermis Anatomical Divisions Cerebellar cortex: Gyri = Folia Myelinated medulla: Arbor vitae Cerebellar Peduncles Inferior (restiform bodies): Connects to medulla Middle (brachium pontis): Connects to pons Superior (brachium conjunctivum): Connects to midbrain and thalamus Nuclei Intracerebellar (paired): Dentate Emboliform Globose Fastigial Pontine nuclei (pons): Inferior olivary nuclei (medulla) Plan II: Flocculonodular Lobes Archicerebellum Vestibulocerebellum Flocculi separated by nodulus Functions: Regulation of muscle tone Maintenance of equilibrium (axial musculature) Regulation of head/eye movements Plan II: Anterior Lobe Paleocerebellum Functions: Receives proprioceptive information Regulates muscle tone Plan II: Posterior Lobe Neocerebellum Cerebrocerebellum Functions: Receives cerebral input via pons Involved in muscle movement Involved in planning and coordination Anatomical Plan III Medial (vermal) zone: Fastigial nucleus Part of spinocerebellum Paramedian (paravermal) zone: Globose and emboliform nuclei Part of spinocerebellum Lateral (hemispheric) zone: Dentate nucleus Equivalent to neocerebellum (cerebrocerebellum) Afferent: Mossy Fibers Via inferior cerebellar peduncles: Dorsal spinocerebellar Reticulocerebellar Via superior cerebellar peduncles: Ventral spinocerebellar Via middle cerebellar peduncles: Pontocerebellar Afferent: Climbing Fibers Climbing fibers arise from inferior olivary nuclei Efferent Tracts All efferent fibers from cortex are from Purkinje cells: Purkinje cells project to intracerebellar nuclei. Efferent Tracts Via inferior cerebellar peduncles: To vestibular nuclei: Cerebellovestibular: From flocculonodular lobe = (vestibulocerebellum) From fastigial nucleus To lateral vestibular nucleus: Cerebellovestibular From anterior vermis (spinocerebellum) Efferent Tracts Via inferior cerebellar peduncles: To reticular formations in pons and medulla: Cerebelloreticular tract: From fastigial nucleus Efferent Tracts Via superior cerebellar peduncles: To red nucleus (nucleus ruber): Cerebellorubral tract: From dentate, emboliform, and globose nuclei To ventral anterior and ventral lateral thalamic nuclei: Cerebellothalamic tracts: From dentate, emboliform, and globose nuclei Efferent Tracts Thalamocortical tracts: To motor cortex Through internal capsule Corticopontine tracts: To pontine nuclei Functions Skeletal muscle coordination Maintain equilibrium and posture Synergic control of muscle activity Kinetic memory? Cerebellar Cortex: Layers Molecular layer (outer) Granular layer (middle) Purkinje layer (deeper) Cerebellar Cortex: Cell Types Stellate cells Basket cells Granular cells Golgi cells Purkinje cells Cerebellar Cortex Organization Climbing and mossy fibers convey excitatory input from spinal cord and brainstem to deep cerebellar nuclei and cortex. Cerebellar Cortex Organization Climbing fibers originate from inferior olivary nuclei and are excitatory to deep cerebellar nuclei and Purkinje cells. Cerebellar Cortex Organization Mossy fibers originate from spinal cord and other parts of the brain and are excitatory to granular cells. Granular Cells Granular cells receive input from mossy fibers: Excitatory input. Collaterals from mossy fibers also to intracerebellar nuclei. Granular cells project into molecular layer and give off left/right axon collaterals. Granular Cells Granular cells are excitatory. Synapse with: Stellate, Golgi, basket, and Purkinje cells Other Cortical Cells Stellate cells synapse with dendritic tree of Purkinje cells (inhibitory). Basket cells synapse with axon hillock of Purkinje cell (inhibitory). Golgi cells synapse with cell bodies of granular cells (inhibitory). Purkinje cells synapse with intracerebellar nuclei (inhibitory). Cerebellar Cortex Climbing fibers from inferior olivary nuclei: Synapse with intracerebellar nuclei: Axon collaterals Excitatory Synapse with dendritic tree of Purkinje cells: Excitatory Excitatory burst “cleans” Purkinje cells Cerebellar Cortex Only efferents from cerebellar cortex are Purkinje cell axons. All efferents from cerebellum are from intracerebellar nuclei. Cerebellar Cortex Noradrenergic projections from locus ceruleus. Serotoninergic projections from raphe nuclei.