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Cerebellar Architecture in Relation to its function (final) friday part 1.pptx
- 1. Cerebellar Architecture in Relationto its function SPEAKER:DR.VIDYA PANDA MODERATOR:DR.PRANATI NANDA
- 2. SCHEMA • ANATOMICAL SUBDIVISIONS •FUNCTIONAL DIVISION. • CEREBELLAR CORTEX ARCHITECTURE • DEEP NUCLEI OF CEREBELLUM • SOMATOSENSORY PROJECTIONS • AFFERENT AND EFFERENT CONNECTIONS • CIRCUITS WITHIN THE CEREBELLUM. • CEREBELLUM FUNCTIONS • CEREBELLAR LESIONS AND TESTS.
- 3. Major anatomical subdivisionsof the cerebellum.
- 4. THE CEREBELLAR PEDUNCLECONNECTIONS
- 6. Role of FunctionalParts
- 7.
- 9. Internal Organisation ofCerebellar Hemisphere Deep Nuclei of cerebellum
- 10. SOMATOSENSORY PROJECTION AREASIN THE CEREBELLUM
- 11. AFFERENT TRACTS TRANSMITS PONTOCEREBELLARIMPULSES FROM MOTOR AND OTHER PARTS OF CEREBRAL CORTEX VIA PONTINE NUCLEI DORSAL SPINOCEREBELLAR PROPRIOCEPTIVE AND EXTEROCEPTIVE IMPULSES FROM BODY. VENTRAL SPINOCEREBELLAR PROPRIOCEPTIVE AND EXTEROCEPTIVE IMPULSES FROM BODY CUNEOCEREBELLAR PROPRIOCEPTIVE IMPULSES ESPECIALLY FROM HEAD AND NECK. OLIVOCEREBELLAR PROPRIOCEPTIVE INPUT FROM WHOLE BODY VIA RELAY IN INFERIOR OLIVE TECTOCEREBELLUM AUDITORY AND VISUAL IMPULSES VIA INFERIOR AND SUPERIOR COLLICULI VESTIBULOCEREBELLAR VESTIBULAR IMPULSES FROM LABYRINTHS,DIRECT AND VIA VESTIBULAR NUCLEI. PRINCIPAL AFFERENTS OF CEREBELLUM
- 12.
- 13. Neural circuit ofthe functional unit of cerebellum.
- 14. Functions of Cerebellumin overall motor controll Vestibulocerebellum:To control equilibrium and postural movements. Spinocerebellum: 1.Function of cerebellum to prevent overshoot and to damp movements. 2.Cerebellar control of ballistic movements. Cerebrocerebellum: 1.Planning of sequential movements. 2.Timing function for sequential movements.
- 15. Connection & functionof the Vestibulocerebellum Floculonodular Lobe Vermis FASTIGIAL NUCLEUS VESTIBULAR NUCLEUS Vestibular Organ lower motor neuron LMN ARCHICEREBELLUM vestibulospinal tract MLF
- 16. Archicerebellum • Floculonodular lobe-Vestibulocerebelum • Function: • Maintenance of equilibrium • Suppress Vestibulo Ocular Reflex • Muscle tone in relation to head posture • Animal ablation • Disorder of equilibrium • Positional nystagmus • Human: Meduloblastoma • Trunkal ataxia • Vestibular nystagmus (fast component towards the side of lesion) • Positional nystagmus does not fatigue • Vertigo January 3, 2025
- 17. FUNCTIONS OF SPINOCEREBELLUM.
- 18. Main Connections ofthe Paleocerebellum RED NUCLEUS NUCLEUS INTERPOSITUS ANTERIOR LOBE PARAVERMAL ZONE PALEOCEREBELLUM Inferior Olivary Nucleus Lower motor neuron SPINAL CORD Rubro spinal tract spinocerebellar tract
- 19. CONTROL OF BALLISTICMOVEMENT • Three major changes occur in these ballistic movements when the cerebellum is removed: • 1) The movements are slow to develop and do not have the extra onset surge that the cerebellum usually provides. • 2: The force developed is weak; 3:The movements are slow to turn off,usually allowing the movement to go beyond the intended mark. Therefore in absence of cerebellar circuit the motor cortex has to think extra hard to turn ballistic movements on and off.Thus the automatism of ballistic movements is lost.
- 20. Paleo-cerebellum • Anterior lobe+ Vermis • Afferent: • Spinocerebellar tract • Spino-> olivo->cerebellar • Spino -> reticulo -> cerebellar • Efferent • Fastigio -> vestibulo -> spinal • Fastigio -> Reticulo -> Spinal • Function • Tone control • Posture of axial muscle • Equilibrium and locomotion • Animal ablation • Increased lengthening and shortening • Increased tendon reflex • Exaggerated postural reflex (positive supporting reflex) • Human • Alcoholic degeneration • Cerebellar degeneration • Gait ataxia • Rarely mild hypotonia, dysmetria and dysarthria January 3, 2025
- 21. Connections and functionsof the Neocerebellum CEREBRAL CORTEX THALAMUS Pontine Nucleus Lower motor neuron LMN DENTATE NUCLEUS POSTERIOR LOBE CEREBELLAR HEMISPHERE NEOCEREBELLUM Pyramidal tract L R
- 22. Neocerebellum • Ablation inDog and Cat. • Inconstant result. • Monkey ablation • Hypotonia • Clumsiness of ipsilateral limb • Dentate nucleus ablation -> more enduring effect intention tremor January 3, 2025
- 23. CEREBELLUM AND MOTORLEARNING • The cerebellum is concerned with learned adjustments that make coordination easier when a given task is performed over and over. • As a motor task is learned, activity in the brain shifts from the prefrontal areas to parietal and motor cortex and the cerebellum. The basis of learning in the cerebellum is probably the input via the olivary nuclei. Climbing fibre activation produces a large complex spike in the Purkinje cell and this spike produces long term modification of the pattern of mossy fibre input to that particular Purkinje cell. It’s activity is increased when a new movement is being learned and selective lesions of the olivary complex abolish the ability to produce long term adjustments in certain motor responses.
- 24. CEREBELLAR DISORDERS • Dyssynergia:Disruption of the normal smooth control of movement provided by gradual contraction of synergic muscle and relaxation of their antagonist. • Rebound phenomenon (abnormal check reflex):This results due to inability to put on brake(suddenly stop) of ongoing movement. • Decomposition of movement • Scanning speech • Cogwheel eye movment
- 25. Dysmetria Inabilityof the sensorimotor apparatus to measure distance in the course of movement Hypometria and hypermetria of the limb and eye Tremor : Postural and intention Ataxia of gait: falling towards the side of lesion Nystagmus:
- 26. TESTS TO DEMONSTRATETHE DYSFUNCTIONS.
- 27.
Editor's Notes
- #3 The cortex is convoluted into many folia. Three major transverse divisions (lobes) are recognized— The anterior lobe is most rostral, posterior lobe and flocculo-nodular lobe more caudally. These lobes are divided by the primary fissure and the posterolateral fissure, respectively. Larsell described 10 lobules (subdivisions of the lobes) that can be recognized in all animals. Lobules I-V are within anterior lobe, lobules VI-IX are in posterior lobe and lobule X comprises the floccular-nodular lobe. Anatomical division- : the anterior lobe (rostral to the "primary fissure"), the posterior lobe (dorsal to the "primary fissure") and the flocculonodular lobe, The first two can be further divided in a midline cerebellar vermis and lateral cerebellar hemispheres.
- #4 The cerebellum lies dorsal to the brainstem in the posterior fossa. The superior peduncle to the midbrain.The middle cerebellar peduncle to the pons.The inferior cerebellar peduncle to the medulla.
- #5 The floculonodualr lobe:related to vestibular apparatus also called vestibulocerebellum.It is concerned with control of body,posture,equilibrium and maintaining visual fixation.vestibulo-ocular reflex. The entire anterior lobe and parts of posterior lobe that receive information from spinal cord are called spinocerebellum.It is concerned with axial and limb muscles and postural reflexes. The remaining part of the posterior lobe receives information from cerebral cortex and pons and thus called neocerebellum.It is concerned with skilled voluntary movements.
- #7 THE CEREBELLAR CORTEX AN OUTER MOLECULAR LAYER. A MIDDLE PURKINJEE CELL LAYER INNER GRANULE CELL LAYER MOLECULAR LAYER:NERVE ENDINGS Dendrites of the purkinjee cells Axons of the granule cells and the Afferent fibres from inferior olivary nucleus which ascend into this layer as the climbing fibres and form synapses with the dendrites of purkinjee cells. 2.The nerve cells are of two types: Star shaped stellate cells more superficial in location Deep located basket cells .these cells possess a relative sparse dendritic tree which receives input from parallel fibres. Purkinjee cell layer:It is only one cell thick consisting only large flask shaped purkinjee cell,biggest neuron in the body.Their axons form the only output of the whole cerebellar cortex which passes to form synaptic connection in the deep cerebellar nuclei. Granule cell layer:granule and golgi cells.Each cell axon ascends to the outer molecular layer and then bifurcates to form a “t”.The two branches of the “t” run along the long axis of the folium and are called parallel fibres.They make excitatory synaptic contact with dendrites of many Purkinje cells,golgi cells, basket cell and stellate cell.
- #8 Two types of afferent fibres enter the cerebellum-mossy fibres and climbing fibres. CLIMBING FIBRES:These fibres arise mainly from cells of inferior olivary nucleus.Their activity is increased when a new movement is being learned.They establish one to one connections with the Purkinje cell dendrites and excite it to discharge. Mossy fibres:They are axons of spinocerebellar,vestibulocerebellar,reticulocerebellar,cuneocerebellar,corticopontocerebellar tracts.Each mossy fibre makes synaptic connection with many granule cell.They are excitatory to dendrites of all the fibres.They exert a weak excitatory effect on many Purkinje cells via parallel fibres of granule cell.Therefore the sequence- Mossy fibre-granule cell-parallel fiber-Purkinje cell provide excitation of purkinjee cell.
- #10 The anterior area encloses the entire anterior lobe and lobulus simplex.The body representation is an ipsilateral projection and is inverted,axial body surface is represented medially and the extremities laterally. The posterior area is located primarily in the paramedian lobule.The body representation is a bilateral projection ,less defined and is erect.
- #11 The cerebral cortex is by far the source of the largest input to the cerebellum, and the major destination of this input is the cerebrocerebellum. These cortical axons do not project directly into the cerebellum. Rather, they synapse on neurons in the ipsilateral pontine nuclei (i.e., on the same side of the brainstem as their hemisphere of origin). These pontine nuclei receive input from a wide variety of sources, including almost all areas of the cerebral cortex and the superior colliculus. The axons of the cells in the pontine nuclei, called transverse pontine fibers (or pontocerebellar fibers), cross the midline and enter the contralateral cerebellum via the middle cerebellar peduncle. This massive, crossed projection of transverse pontine fibers into the cerebellum via the middle cerebellar peduncle is the means by which signals originating in one cerebral hemisphere are sent to neural circuits in the opposite cerebellar hemisphere.
- #12 A pathway originates in the midline structures of cerebellum(the vermis) and then passes through the fastigial nuclei into the medullary and pontine regions of brain stem.This circuit functions in close association with the equilibrium apparatus and vestibular nuclei to control equilibrium. A pathway that originates in intermediate zone of cerebellar hemisphere 2;interposed nucleus to ventrolateral and ventro anterior nuclei of thalamus and then to cerebral cortex.This complex circuit mainly helps coordinate the reciprocal contractions of agonist and antagonist muscles in the peripheral portions of limbs, hands fingers and thumbs. A pathway that begins in the cerebellar cortex of the lateral zone of cerebellar hemisphere and then passes to dentate nucleus and then to contralateral thalamus and then to cerebral cortex.Plays an important role in helping coordinate sequential motor activities initiated by cerebral cortex. ;
- #13 1.The output of granule cell (whose axons form parallel fibres) is always excitatory.They specially make synaptic connections with dendrites of purkinjee cell,basket cell and stellate cell. The output of the purkinjee cell ,golgi cell and basket cell is always inhibitory. The basket cells and the stellate cells are excited by the granule cells via the parallel fibres and their output inhibits purkinjee cells discharge. The golgi cells are excited by the collaterals from the climbing fibres,purkinjee cells and parallel fibres,and they inhibit transmission from mossy fibers to the granule cells. The Purkinjee fiber output is inhibitory to deep cerebellar nuclei.These nuclei also receive excitatory input via collaterals from mossy fibers,climbing fibers and also other excitatory inputs.However ,the ultimate impulse coming out of the deep cerebellar nuclei is always excitatory.
- #17 To prevent overshoot and to damp movement:All movements are pendular.When an arm is moved,momentum develops and the momentum must be overcome before the movement can be stopped.Because of momentum, all pendular movements have a tendency to overshoot.Overshooting occurs in a person whose cerebellum has been destroyed.If the cerebellum is intact,appropriate learned ,subconscious signals stop the movement precisely at the intended point, thereby preventing overshoot and tremor.This activity is the basic characteristic of damping system.
- #19 Timing function for sequential movement:Lateral zone of cerebellum is to provide timing for succeeding movement.Lesions in this lateral zones cause complex movements(eg; those required for writing ,running or even talking ) to become incoordinate and lacking ability to progress in orderly sequence from one movement to next.Such cerebellar lesions are said to cause failure of smooth progression of movements.
- #21 Since each cerebellar hemisphere is concerned with the ipsilateral side of the body, this pathway crosses the midline & reach the opposite hemisphere (1st crossing). The motor cortex in each hemisphere governs the contralateral musculature (Through crossing of Pyramidal tract), Hence muscles of same side receives, information from the ipsilateral cerebellar hemisphere. For this reason, the dentate axons that exit the cerebellum via the superior cerebellar peduncle cross the midline at the decussation of the superior cerebellar peduncle in the caudal midbrain, and then ascend to the contralateral thalamus.
- #24 REBOUND PHENOMENON:If the patient is asked to flex his limb against resistance and then asked to stop immediately by withdrawing the resistance,he cannot stop instead arm moves with a wide arc.This is called rebound phenomenon.
- #25 NYSTAGMUS:Tremor of the eyeballs which occurs when the patient attempts to fix his eyes on an object.It consists of a slow to and fro movement on looking to the affected side due to hypotonia,and a rapid to and fro movement on looking to the opposite side.
- #26 FINGER NOSE TEST:The patient is asked to place the index finger of his extended arm over his nose with eyes closed. ADIADOCHOKINESIS:The patient is unable to carry out rapidly alternate and passive movement eg: supination and pronation of forearm.This is because they cannot start or stop movements quickly or easily and their motions are slow and irreregular. HEEL KNEE TEST:The patient lies in the lying down position.He is asked to touch his knee by the opposite heel then moving the heel along the tibia downwards. GAIT:The patient walks awkwardly in a clumsy manner with feet well apart.They have such difficulty maintaining balance that their gait appears drunken, called drunken gait.