BMS2-15 Cerebellum Dr Aylin AKTAR.pdf

Cerebellum Dr. A. Aktar Cerebellum – Functions • Correction during movement • Precision & accuracy • Motor learning • Reflex modification • Regulates voluntary movement & posture (balance & muscle tone)- indirectly by adjusting output of major descending systems of brain • Lesions of the cereb...

Cerebellum Dr. A. Aktar Cerebellum – Functions • Correction during movement • Precision & accuracy • Motor learning • Reflex modification • Regulates voluntary movement & posture (balance & muscle tone)- indirectly by adjusting output of major descending systems of brain • Lesions of the cerebellum: Disrupted coordination of eye & limb movements Impaired balance Decreased muscle tone Simone Biles, above in Stuttgart, Germany, October 2019, completes a twisting double tuck dismount The most decorated gymnast in world championship history, with a total of 32 Olympic and World Championship medals Cerebellum – Basic Structure • • • • • • • At back of brain, immediately inferior to occipital & temporal lobes Within posterior cranial fossa Separated from cerebral lobes by the tentorium cerebelli, a tough layer of dura mater About 1/10th weight of cerebrum Contains > neurons than entire CNS Separated from pons & medulla by 4th ventricle Joined to brainstem by 3 (paired) peduncles • Superficial cortex - tightly folded • Core: Underneath cortex. White matter 4 deep cerebellar nuclei embedded in white matter Cerebellum – Infratentorial Localization • . Cerebellum – Infratentorial Localization • . Cerebellum – External Features • 2 laterally located hemispheres • Connected in midline by the vermis, a narrow midline area Cerebellum – Anatomical Parts Cerebellum – Anatomical Parts Anterior lobe Posterior lobe Flocculonodular lobe Cerebellar Zones • Vermis: In midline of cerebellum • Intermediate Zone: . Either side of vermis • Lateral hemispheres: Lateral to the intermediate zone • No difference in gross structure btwn the lateral hemispheres & intermediate zones Cerebellum – Functional Areas (3) 1) Cerebrocerebellum : • Largest division. Formed by the lateral hemispheres • Involved in planning movements & motor learning • Regulates coordination of muscle activation & important in visually guided movements Cerebellum – Functional Division 2) Spinocerebellum: • Comprised of vermis & intermediate zone • Regulates body movements by allowing for error correction • Receives proprioceptive information Cerebellum – Functional Division 3) Vestibulocerebellum • Involved in controlling balance & ocular reflexes • Receives inputs from vestibular system Cerebellum – Somatotropic Localization Cerebellar Peduncles • 3 pairs • Connect w/brain stem Middle c. p.: Largest & most lateral Cerebellar Peduncles Cerebellum – Peduncles . Anterior Surface of Cerebellum Cerebellum – Anterior View • . Cerebellum – Peduncles Superior cerebellar peduncles • White matter connecting cerebellum to midbrain Cerebellum – Peduncles Middle cerebellar peduncles • Largest peduncle. Connects to pons • Composed entirely of incoming pontocerebellar fibers – which in turn come from cerebral cortex • Connects contralateral pontine nuclei to cerebellar cortex • Carries input from contralateral cerebral cortex Cerebellum – Peduncles Inferior cerebellar peduncles • Incoming fibers from medulla oblongata Cerebellum – Layers Cortex has 3 layers Cerebellum – Layers Cortex - grey matter Cortex – Grey matter Core – White matter Core – White matter Deep Cerebellar Nuclei 4 cerebellar nuclei embedded in white matter: Dentate, emboliform, globose, fastigi nuclei Deep Cerebellar Nuclei Coronal Section Cerebellum – Basic Circuits Input (afferents): From cerebral cortex → Pons → Majority terminates in cerebellar cortex → axons of cortical purkinje cells → deep cerebellar nuclei → cerebellar efferents → various circuitry • Thalamus → motor cortex • Brain stem nuclei • Reticular system nuclei Cerebellum – Folia and Fissures I Tree of Life • Arbor vitae Cerebellum – Vasculature 3 paired arteries: • Superior cerebellar artery (SCA) from basilar a. • Anterior inferior cerebellar artery (AICA) from basilar a. • Posterior inferior cerebellar artery (PICA) from vertebral a. Cerebellum – Vasculature 3 paired arteries: • Superior cerebellar artery (SCA) • Anterior inferior cerebellar artery (AICA) • Posterior inferior cerebellar artery (PICA)