LAB #10: CEREBELLUM

In order to function in coordinating precise timing and sequencing of movements, the cerebellum must process information from many sources before sending “corrections” to upper motor neuron systems. Input comes to the cerebellum via the inferior cerebellar peduncle from:      vestibular receptors      body surface & muscle receptors      the inferior olive Input comes to the cerebellum via the middle cerebellar peduncle from:      widespread areas of cerebral cortex      (after a synapse in pontine nuclei) Outflow from the cerebellum reaches upper motor neuron systems via the superior cerebellar peduncle for:      -cerebral cortex, especially SMA      (after a synapse in the thalamus)      -the red nucleus Outflow from the cerebellum to brainstem upper motor neurons that regulate proximal muscles (vestibular nuclei, reticular nuclei) travels through the inferior peduncle.

OVERVIEW OF INTRINSIC CONNECTIONS OF THE CEREBELLUM   Axons that enter the cerebellum as climbing fibers (from inferior olivary nuclei) or mossy fibers (all other input) terminate in:       cerebellar cortex       deep nuclei of cerebellum Impulse transmission through the cerebellar cortex includes:       - termination of climbing fibers on Purkinje cell dendrites & deep cerebellar nuclei;       - termination of mossy fibers on granule cells & deep nuclei;           - ascent of granule cell axons as parallel fibers in molecular layer;      - termination of parallel fibers on Purkinje cells;      - descent of Purkinje cell axons to deep cerebellar nuclei

Haines 2-31 1) vestibulocerebellum = flocculonodular lobe -> balance & eye movement; 2) spinocerebellum = vermis (medial zone) + intermediate hemisphere (zone) ->   adjustments for smooth movement of proximal (vermis) and distal (intermediate   cortex) limb movement; 3) cerebrocerebellum = lateral hemisphere (zone) -> motor planning

Haines 2-33

Haines 2-30

Haines 5-15 Deep cerebellar nuclei Fastigial nucleus Interposed nuclei Dentate nucleus Cerebellar cortex Cerebellar white mater

Blackboard 4 Cerebellar cortex Cerebellar white matter Molecular Layer Granular layer White Matter Cerebellar white matter

Blackboard 5 molecular layer Purkinje layer granule layer

Haines 5-11 Olivocerebellar fibers – cerebrocerebellum receives fibers from contralalteal ION Vestibular Nuclei Inf Cerebellar peduncle Reticular Form inferior cerebellar peduncle . This fiber system contains important input to the cerebellum, from: vestibular nuclei - send fibers to the vestibulocerebellar cortex and fastigial nuclei (with axons from the vestibular nerve) deep (especially muscle- muscle spindles) and body surface receptors traveling from the spinal cord and brainstem (just know they enter cerebellum mainly via the inferior peduncle) inferior olivary nuclei - receive input from the cerebral cortex, reticular formation, red nucleus -send climbing fibers to the contralateral cerebellum olivocerebellar fibers - identify as they cross the midline and enter the inferior cerebellar peduncle The inferior cerebellar peduncle also brings fibers from the cerebellum to: vestibular nuclei : -receive fibers from the fastigial nucleus and cortex of the vestibulocerebellum -influences lower motor neurons via the vestibulospinal tracts and vestibulo-ocular paths reticular formation - receives fibers from the fastigial nucleus -influences lower motor neurons via reticulospinal tracts Inf Olivary Nucleus Midrostral Medulla Level

Haines 5-12 Olivocerebellar fibers Vestibular Nuclei Inf Cerebellar peduncle Inf Olivary Nucleus Rostral Medulla Level

Haines 5-25 Corticopontine fibers Rostral Midbrain Level Corticospinal basis pedunculi (crus cerebri)of midbrain - contains: corticopontine fibers - medial 2/5 and lateral 2/5 of peduncle corticospinal & corticobulbar fibers - middle 1/5 of peduncle (note that these fiber tracts are degenerated on the right side) Corticospinal Fibers Corticobulbar fibers Rostral Midbrain Level

Haines 5-18 Middle Cerebellar Peduncle Pontine Nuclei identify a major input system to the cerebellum via the middle cerebellar peduncle: pontine nuclei - pale regions in base of pons - receive corticopontine fibers (synapse) - send mossy fibers to contralateral cerebellar cortex pontocerebellar fibers - cross midline from pontine nuclei middle cerebellar peduncle - contains pontocerebellar fibers Pontine Nuclei Pontocerebellar fibers Rostral Pons Level

Haines 5-19 Rostral Pons Level Sup. Cerebellar peduncle superior cerebellar peduncle - contains exiting fibers from interposed & dentate nuclei of the cerebellum en route to the red nucleus (cerebellorubral fibers) and to the thalamus (cerebellothalamic fibers) Rostral Pons Level

Haines 5-20 Rostral Pons Level Sup. Cerebellar peduncle Trace the superior cerebellar peduncle rostrally toward the midbrain , noting that it becomes covered laterally with another fiber bundle (lateral lemniscus) and that it is moving toward the midline to cross. Rostral Pons Level

Sup. Cerebellar peduncle decussation Haines 5-22 Sup. Cerebellar peduncle decussation Pons/midbrain jctn Level

Sup. Cerebellar peduncle decussation Haines 5-23 Sup. Cerebellar peduncle decussation Caudal Midbrain Level

Haines 5-25 Cerebellothalamic fibers Red Nucleus Red Nucleus red nucleus - receives cerebellorubral fibers from contralateral cerebellum - magnocellular part receives fibers from interposed nuclei and forms rubrospinal tract cerebellothalamic fibers - fibers from the dentate and interposed nuclei that travel lateral to the red nucleus - are en route to ventral lateral nucleus (VL) of thalamus Rostral Midbrain Level

Haines 5-26 Rostral Midbrain Level

Haines 5-32 thalamus Realize that the cerebellothalamic fibers travel mainly to the ventral lateral (VL) nucleus of the thalamus (HAINES ATLAS AND IMAGE BANK: IMAGE). From the thalamus, fibers ascend in the internal capsule to reach the primary motor and premotor cortex (review on half brain if necessary).