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.
