Purkinje Cells Climbing Fibers

Blood Supply: 1. Superior Cerebellar 2. Posterior Cerebellar 3. Anterior Inferior Cerebellar External Features: Convolutions forming Folia 1. Anterior lobe- in front of primary fissure 2. Posterior Lobe- behind primary fissure 3. Flocculonodular lobe- Nodule + Flocculi a. Vestibulocerebellum: control of equilibrium, Eye movements VOR) 4. Longitudinal Subdivisions: a. Midline: Vermis- Spinocerebellum: control of axial / proximal limb movement b. Intermediate Zone- Spinocerebellum : control of distal limb movement c. Lateral Zone: Cerebrocerebellum: planning and initiation of movement Internal Structure of Cerebellar Cortex: Purkinje cells: inhibitory, major out put neurons of cerebellar cortexDeep Cerebellar N GABAnergic *Granule cells: excitatoryExcite purkinje Glutamatergic Golgi cells: inhibitoryInhibit Granule Cells GABAnergic Basket cells: inhibitoryPurkinje GABAnergic Stellate cells: inhibitoryPurkinje GABAnergic Afferent Cells: Climbing Fiber: Excitatory 1:1 purkinje Mossy Fiber: Inhibit Granule cells 1. Molecular Layer: Dendrites of Purkinje Cells Parallel fibers from axons of granule cells (excitatory) Climbing fibers from inveriof olivary nucleus (excitatory) Stellate Cells: inhibit purkinje (superficial) Basket Cells: inhibit purkinje (deep) 2. Purkinje Layer: Purkinje Cells (inhibitory GABA) 3. Granular Layer Granule Cells (excitatory)

Golgi cells (inhibitory) Mossy Fiber (excitatory): glomeruli Deep Cerebellar Nuclei: Major output neurons of cerebellum: Excitatory – Receive collaterals from extrinsic afferents to the cerebellar cortex – Receive input from cerebellar cortex – Constitute the major output neurons of the cerebellum 1) Dentate- largest most lateral 2) Emboliform- part of interposed nuclei 3) Globose – part of interposed nuclei 4) Fastigial Nucleus- most media

Synaptic Circuits: Climbing Fibers + Purkinje Fibers – Deep Cerebellar Fibers Mossy Fibers + Granule Cells + Parallel Fibers + Purkinje Cells – Deep Cerebellar Fibers Inhibitory Neurons: Basket Cells and Stellate Cells in molecular Layer Golgi Cells in the Granule Cell Layer Major Afferents: 1.Vestibular nuclei Vestibulocerebellum (from ipsilateral vest. Labrynth + vest nuclei)

2. Inferior Cerebellar Peduncle (restiform body) Spinal Cord Spinocerebellum - Dorsal spinocerebellar Tract (from ipsilateral spinal cord and lower medulla) - Cuneocerebellar tract (from ipsilateral spinal cord and lower medulla) - Oliveocerebellar tract (from contralateral inferior olivary nucleus)

3. Superior Cerebella Peduncle (brachium conjunctivum) Spinal cord Spinocerebellum -Ventral spinocerebellar tract (from contralateral spinal cord; projects to contralateral spinocerebellum)

4. Middle Cerebellar Peduncle (brachium pontis) CortexCerebrocerebellum:

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Cortico-ponto-cerebellar tractcerebrocerebellum (from contralateral cortex, via pontine nuclei to cerebrocerebellum

5. Monoaminergic fibers from the brainstem: – Serotonergic Fibers from raphe nuclei – Noradrenergic fibers from the locus ceruleus

MAJOR EFFERENTS: 1) Flocculonodular Lobe Vestibular Nuclei (reciprocal connections) – Controls eye movement and body equilibrium while stabdine/moving

2) Cerebellar Cortex Deep Cerebellar NucleiSuperior Cerebellar Peduncle (brachium conjunctivum) 1. Vermis fastigial nucleus (medial)Brain Stem regions Medial Descending Systems Proximal M. Vermisfastigial nucleusthalamusmotor/premotor cortex

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Axial and proximal motor control; controls the ongoing execution of

movement 2. Intermediate ZonesInterposed nucleus (emboliform/globose)brainstem regions (red nucleus)lateral descending systems distal limb muscles Intermediate ZonesInterposed Nucleus(emboliform/globose)Thalamusmotor and premotor cortexvia corticospinal tractdistal limb muscles ○ Distal motor control; controls ongoing exectution of movement

3. Lateral Zone dentate nucleus(lateral) red nucleus thalamus motor/premotor cortex corticospinal tractspinal cordcorticopontine tractback to lateral zone (cerebrocerebellum) ○ Initiation, planning and timing of voluntary movements

General Functional Significance of Cerebellum: 1. Control of balance and eye movement (vestibule-ocular reflex) 2. Regulates movement and posture indirectly by modulating the output of the major descending motor systems 3. Compares intention with actual movement and compensates for errors in movement a. Corticopontocerebellar Tract- plans for movement from motor/premotor b. Ventral Spinocerebellar Tract- monitors integration of descending/peripheral info of movement in spinal cord c. Dorsal Spinocerebellar Tract- receives feedback info from sensory periphery d. Dentatorubrothothalamic tract- projects to motor centers that send fibers to Spinal cord to adjust output of motor system Dysfunctions of the Cerebellum: -Lesions cause disruption of coordinated limb and eye movements, impairs balance and reduced muscle tone. - Cerebellar lesions typically cause ipsilateral motor signs - Major Signs: Ataxia- uncoordinated movements Hypotonia – low tone Intentional tremor-tremor during movements Dysdiadochokinesia- irregular pattern of alternating movements (supination/pronation) Dysmetria – overshoot/undershoot distances grasping for objects Nystagmus- Hyperactive/Hypoactive *Damage to Cerebellum can Impare motor learning*