Cerebellum Functional Anatomy Functions Disorders 19 January 2022

Cerebellum Functional Anatomy Functions Disorders 19 January 2022 Cerebellum 1

Neural centres for control of movements Motor cortex Basal ganglia cerebellum Brain Stem Spinal Cord 19 January 2022 Skeletal muscles Cerebellum 2

Cerebellum 19 January 2022 Cerebellum 3

Cerebellum n n n Associated with all aspects of control of movements Its removal produces no deficits in emotional or intellectual functions Causes profound disturbances in production of coordinated movements 19 January 2022 Cerebellum 4

Cerebellum n Functions in controlling of timing of • Duration and strength of movements • Motor activities n n Rapid progression from one movement to next Helps to control the interplay • Between agonist and antagonist muscles 19 January 2022 Cerebellum 5

Cerebellum n Human cerebellum consists • Two lateral hemispheres • On either side of vermis n Corpus cerebella • Anterior & posterior lobes n Flocculonodular lobe • Phylogenetically the oldest part n 19 January 2022 Archiecerebellum Cerebellum 6

Cerebellum n Anterior lobe and part of mid portion of posterior lobe • Paleocerebellum n 90% of posterior lobe • Recent • Highly developed in primate • Neocerebellum 19 January 2022 Cerebellum 7

Cerebellum Anterior lobe Primary fissure Posterior lobe Flocculonodular lobe 19 January 2022 Cerebellum 8

Cerebellum n n Longitudinal functional division Vermis: • Control muscles of axial body, the neck, shoulders, hips • Responsible for balance • Regulation of axial and postural muscles n Intermediate zone • Control of muscles of distal portions of upper and lower limbs 19 January 2022 Cerebellum 9

Cerebellum n Lateral zone • Planning of sequential movements • Timing of motor activities • Coordination of motor activities 19 January 2022 Cerebellum 10

Vermis Anterior Lobe Intermediate lobe Lateral Lobe Primary Fissure Post. Lobe Flocculanodular Lobe Longitudinal Division of cerebellum 19 January 2022 Cerebellum 11

Cerebella Inputs n n From spinal cord Spinal cerebella tract • Dorsal SCT n From muscle spindle, Golgi tendon organs, joint receptors, skin • Appraise cerebellum of n n n 19 January 2022 Muscle contraction Degree of tension on muscle tendons Position and rate of movements of parts of body Cerebellum 12

Cerebella Afferents Spino-cerebella tracts Vent. Spin. C. T Dorsal S. C. T Muscles, joints Receptors 19 January 2022 Cerebellum 13

Cerebella Afferents n Ventral SCT • Excited by signals arriving in spinal cord from CST & RUST • Provide information to cerebellum n 19 January 2022 About the arrival of motor signals at spinal cord Cerebellum 14

Cerebella Afferents n From cerebral cortex • cortico-cerebella pathway Motor cortex pons cerebellum • Mossy fibers n Motor cortex inferior olive cerebellum • Climbing fibers n 19 January 2022 Cerebellum 15

Cortico-cerebella pathways Motor cortex Ponto cerebella (mossy fibres) BG Pons Cerebella cortex RF Inferior Olive Olivo cerebella (Climbing fibres 19 January 2022 Cerebellum From/To spinal cord 16

Cerebella Inputs n From Vestibular apparatus • Vestibular nerve Vestibular nucleus Flocculonodular lobe • Signals from eyes n Important for maintenance of • Equilibrium and balance 19 January 2022 Cerebellum 17

Premotor area Vestibular Input Occipital lobe (Eye movement) Superior Colliculus Eye Pons Olivary nucleus Vestibular Nerve Vestibular Nucleus 19 January 2022 Cerebellum Flocculo nodular lobe 18

Cerebellum Inputs n Motor signals from cortex to spinal cord • Sent to cerebellum via collateral • Cerebellum receives Copy of motor instructions for n Voluntary movements to muscles n 19 January 2022 Cerebellum 19

Cerebellum Inputs n Cerebellum also receives • Information about actual performance n n From proprioceptors, joint receptors Cerebellum compares • Instructions with performance • Corrects any discrepancies 19 January 2022 Cerebellum 20

Motor cortex BG RF Cerebellum Vestibular apparatus Movements executed by muscles Spinal Cord 19 January 2022 Cerebellum 21

Cerebella Efferent Cerebella cortex Cerebral cortex Midbrain Nuclei, reticular formation DCN Deep Cerebella Nuclei: Dentate, Interpositus, Fastigial 19 January 2022 Spinal cord Cerebellum 22

Output from Vermis Fastigial nucleus Reticular Formation Lateral vestibular nucleus (Deiters) VEST 19 January 2022 REST Cerebellum 23

Out put from Intermediate lobe Motor Cortex Ventral Lateral/ Anterior Thalamus BG Intralaminar nucleus Intermediate zone Red Nucleus Interpostus Nucleus CST 19 January 2022 Cerebellum RUST 24

Out put from Lateral Cerebella zone Motor Cortex Ventral Lateral/ Anterior Thalamus Lateral zone Red Nucleus Dentate Nucleus RUST 19 January 2022 Cerebellum CST 25

Cerebella Cells n Purkinje cells • Big with extensive networks of dendrites • Receive excitatory signals from n n Climbing fibers Granular cells via parallel fibers • Glutamate • Receive inhibitory signals from n Basket cells (GABA) • Axons form the only output from cerebella cortex n 19 January 2022 GABA Cerebellum 26

Cerebella Cells n Granule cells • Receive inputs from n Mossy fibers • Send signals to n n n Purkinje, Golgi, basket cells Glutamate Golgi cells • Stimulated by granule cells via parallel fibers • They inhibit the granule cells 19 January 2022 Cerebellum 27

Cerebella (Cells) n Basket cells • Molecular layer • Stimulated by parallel fibers • Inhibition of Purkinje cells (GABA) 19 January 2022 Cerebellum 28

Molecular layer + + + BC Deep cerebella Nuclei layer 19 January 2022 Climbing fibers Purkinje Cell layer Granular Cell layer + PC GC + - + Gran. Cell + + DCN Cerebellum Mossy fibres 29

Summary n Cerebella system • Consists of cerebellum, efferent and afferent connections n n Is essential for execution of smooth coordinated movement Does not exert its effects directly on the muscles • Efferent connections are to neurons of pyramidal and extra pyramidal system n 19 January 2022 Effects are mediated through these systems Cerebellum 30

Cerebella System n Information passing down the pyramidal system to the muscles • Is sent via collateral to the cerebellum • Cerebellum receives a copy of instructions for voluntary mov. Sent to muscles n Cerebellum also receives information about the actual performance • From proprioceptor, joint receptors, skin 19 January 2022 Cerebellum 31

Cerebella System n Cerebellum compares • Instructions with performance • Any discrepancy is corrected n n Via efferent pathways to motor system Chief characteristics of damage to cerebella system • Lack of precession in voluntary movement 19 January 2022 Cerebellum 32

Motor cortex BG RF cerebellum Vestibular apparatus Movements executed by muscles Spinal Cord 19 January 2022 Cerebellum 33

Disorders of Cerebellum n Lesion of one cerebella hemisphere • Leads to dysfunction of limbs on the same side n Midline cerebella structure lesion • Disturbances of equilibrium in upright posture • Ataxia of stance and gait Broad based gait n Tendency to fall to either side n Difficult in stopping suddenly or turning n 19 January 2022 Cerebellum 34

Disorders of Cerebellum n More laterally placed cerebella lesions • Voluntary movement disturbances • Cerebella ataxia 19 January 2022 Cerebellum 35

Cerebella Ataxia n Disturbances of voluntary movements • Un coordinated or clumsiness • Movements are badly damped Slow to start n Slow to stop n • Sequences of movements are disjointed Decomposition of movements n Ataxia is not made worse by closure of eyes n 19 January 2022 Cerebellum 36

Manifestations n Dysdiadochokinesia • Inability to make repeated movements n Dysmetria • Inability to execute correct range of voluntary movements with precision • Past pointing 19 January 2022 Cerebellum 37

Manifestations n Intentional tremors • Coarse irregular tremors as limb approaches target • Badly damped movements • Oscillate around target n Pendular knee jerks • Rebound phenomenon 19 January 2022 Cerebellum 38

Manifestations n Dysarthria • Speech disorders n Nystagmus • Eye movements poorly damped • Oscillate around target n Hypotonia 19 January 2022 Cerebellum 39