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Y2 s2 locomotion coordination 2013

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Y2 s2 locomotion coordination 2013

  1. 1. Coordination of movementand CerebellumProf. Vajira WeerasingheProfessor of PhysiologyFaculty of MedicineUniversity of PeradeniyaY2S2 Locomotion module
  2. 2. Objectives1. Discuss the role of the cerebellum on motorcoordination2. Explain giving examples how coordination isaffected in neurological disease
  3. 3. Role of cerebellum on motorcoordination
  4. 4. Introduction• the cerebellum and basalganglia are large collections ofnuclei that modify movement ona minute-to-minute basis• these regions have markedsimilarities between them in theoverall pattern of theirconnections with the cerebralcortex- both receive information fromthe motor cortex- both send information back tocortex via the thalamus
  5. 5. Introduction• the cerebellum sends excitatoryoutput to the motor cortex, whilethe basal ganglia sendsinhibitory output• the balance between these twosystems allows for smooth,coordinated movement- a disturbance in either systemwill manifest itself as amovement disorder
  6. 6. Functional significance ofcerebellum• Functions outside conscious awareness• Involved in coordinating motor activities and learningnew motor skills• Particularly involved in adjusting activities to meet newconditions• May also be involved in other types of learning and inemotional reactivity
  7. 7. structure• Cerebellum is divided into 3 lobes by 2transverse fissures– anterior lobe– posterior lobe– flocculonodular lobe
  8. 8. • Anterior cerebellum and part of posteriorcerebellum– receives information from the spinal cord• Rest of the posterior cerebellum– receives information from the cortex• Flocculonodular lobe– involved in controlling the balance throughvestibular apparatus
  9. 9. • lateral zone– this is concerned with overall planning ofsequence and timing• intermediate zone– control muscles of upper and lower limbsdistally• vermis– controls muscles of axial body, neck, hip
  10. 10. Inputs• corticopontocerebellar• from motor and premotor cortex (also sensory cortex)• these tracts supplies the contralateral cerebellar cortex• olivocerebellar• from inferior olive– excited by fibres from» motor cx» basal ganglia» reticular formation» spinal cord
  11. 11. Inputs (cont’d)• vestibulocerebellar• to the flocculonodular lobe• reticulocerebellar• to the vermis• spinocerebellar tracts– dorsal spinocerebellar tracts• from muscle spindle, prorpioceptive mechanoreceptor (feedbackinformation)– ventral spinocerebellar tarcts• from anterior horn cell– excited by motor signals arriving through descending tracts (efferencecopy)
  12. 12. Outputs• through deep cerebellar nuclei: dentate,fastigial, interpositus– 1. vermis -> fastigial nucleus -> medulla, pons– 2. intermediate zone-> nucleus interpositus-> thalamus -> cortex-> basal ganglia-> red nucleus-> reticular formation– 3. lateral zone -> dentate nucleus-> thalamus -> cortex
  13. 13. Neuronal circuitry of the cerebellum• Main cortical cells in cerebellum are known asPurkinje Cells (large cells)• There are about 30 million such cells• These cells constitute a unit which repeatsalong the cerebellar cortex
  14. 14. • Somatotopic representation of the body ispresent in cerebellar cortex although it is not asclear as cerebral cortex
  15. 15. Topographical representationvermisintermediatezone
  16. 16. Functional unit of the cerebellarcortex• a Purkinje cell• a deep nuclear cell• inputs• output from the deep nuclear cell
  17. 17. Purkinje cellInputfrom InferioroliveInputfrom otherafferentsClimbingfibreMossy fibreGranule cellsDeep nuclearcellOutputexcitationexcitationinhibition
  18. 18. • Even at rest, Purkinje cells & deep nuclear cellsdischarge at 40-80 Hz• afferents excite the deep nuclear cells• Purkinje cells inhibit the deep nuclear cells
  19. 19. Functions of cerebellum• planning of movements• timing & sequencing of movements• control of rapid movements such as walkingand running• calculates when does a movement shouldbegin and stop
  20. 20. Overview of motor systemhierarchy1. Motor areas in the cerebral cortex
  21. 21. Overview of motor systemhierarchy1. Motor areas in the cerebral cortex2. Brainstem
  22. 22. Overview of motor systemhierarchy1. Motor areas in the cerebral cortex2. Brainstem3. Spinal cordmotor circuitsrhythmic movements reflexes voluntary movements
  23. 23. Overview of motor systemhierarchy1. Motor areas in the cerebral cortex2. Brainstem3. Spinal cordmotor circuitsrhythmic movements reflexes voluntary movements
  24. 24. Overview of motor systemhierarchy1. Motor areas in the cerebral cortex2. Brainstem3. Spinal cordmotor circuitsrhythmic movements reflexes voluntary movementsCerebellum Basal ganglia
  25. 25. Overview of motor systemhierarchy1. Motor areas in the cerebral cortex2. Brainstem3. Spinal cordmotor circuitsrhythmic movements reflexes voluntary movementsCerebellum Basal gangliaThalamus
  26. 26. ‘Error correction’• cerebellum receives two types of information– intended plan of movement• direct information from the motor cortex– what actual movements result• feedback from periphery– these two are compared: an error is calculated– corrective output signals goes to• motor cortex via thalamus• brain stem nuclei and then down to the anterior horn cellthrough extrapyramidal tracts
  27. 27. • ‘Prevention of overshoot’– Soon after a movement has been initiated– cerebellum send signals to stop themovement at the intended point (otherwiseovershooting occurs)• Ballistic movements– movements are so rapid it is difficult to decideon feedback– a high-velocity musculoskeletal movement,such as a tennis serve or boxing punch,requiring reciprocal coordination of agonisticand antagonistic muscles– rapid movements of the body, eg. fingermovements during typing, rapid eyemovements (saccadic eye movements)
  28. 28. planning of movements• mainly performed by lateral zones• sequencing & timing– lateral zones communicate with premotor areas, sensorycortex & basal ganglia to receive the plan– next sequential movement is planned– predicting the timings of each movement• compared to the cerebrum, which works entirely on acontralateral basis, the cerebellum works ipsilaterally
  29. 29. Motor learning• the cerebellum is also partly responsible forlearning motor skills, such as riding a bicycle- any movement “corrections” are stored as part ofa motor memory in the synaptic inputs to thePurkinje cell- research studies indicate that cerebellum is apattern learning machine- cellular basis for cerebellum-dependent motorlearning is know to be a type of long-termdepression (LTD) of the Purkinje cell synapses
  30. 30. Neurotransmitters• Excitatory: glutamate» (Climbing, mossy, parallel fibres)• Inhibitory: GABA» (Purkinje cell)• Serotonin and Norepinephrine are also knownto be involved
  31. 31. Cerebellar disorders• Examples– Cerebellar stroke– Hereditary spinocerebellar ataxia– Alcoholic cerebellar degeneration
  32. 32. features of cerebellar disorders• ataxia– incoordination of movements– difficulty in regulating the force, range, direction,velocity and rhythm of movements– It is a general term and may be manifested in anynumber of specific clinical signs, depending on theextent and locus of involvement– limb movements, gait, speech, and eye movementsmay be affected
  33. 33. features of cerebellar disorders• ataxic gait• broad based gait• leaning towards side of the lesion• dysmetria• cannot plan movements• abnormal finger nose test• past pointing & overshoot• cannot stop at the intended point and thus overshootresults
  34. 34. features of cerebellar disorders• decomposition of movements• movements are not smooth• decomposed into sub-movements• intentional tremor• at rest: no tremor• when some action is performed: tremor starts
  35. 35. features of cerebellar disorders• dysdiadochokinesis• unable to perform rapidly alternating movements• dysarthria• slurring of speech• scanning speech• nystagmus• oscillatory movements of the eye
  36. 36. features of cerebellar disorders• hypotonia– reduction in tone• particularly in pure cerebellar disease• due to lack of excitatory influence on gamma motorneurons by cerebellum• pendular jerks• legs keep swinging after a tap• rebound• increased range of movement with lack of normal recoil tooriginal position
  37. 37. features of cerebellar disorders• titubation• head tremor• truncal ataxia• patients with disease of the vermis and flocculonodularlobe will be unable to stand at all as they will have truncalataxia
  38. 38. Cerebellar degeneration
  39. 39. Spino Cerebellar Ataxia (SCA)• Hereditary• May be autosomal dominant or recessive• About 50 types of spinocerebellar ataxia present• Some types can be pure cerebellar• Ataxia results from variable degeneration of neuronsin the cerebellar cortex, brain stem, spinocerebellartracts and their afferent/efferent connections
  40. 40. Case history 1
  41. 41. Alcoholic Cerebellar Degeneration• Estimated overall prevalence of alcohol dependence is0.5–3% of the population in Europe or USA• Central and peripheral nervous systems are the twoprincipal targets• Chronic alcohol ingestion can impair the function andmorphology of many brain structures particularlycerebellum
  42. 42. Alcoholic Cerebellar Degeneration• Both acute and chronic ingestion of alcohol result incerebellar dysfunction• Main complaint in patients presenting alcohol-inducedcerebellar dysfunction is difficulty in standing andwalking
  43. 43. Case history 2
  44. 44. Clinical examination of cerebellarfunctions• Gait (broad-based)• Muscle power (normal)• Muscle tone (hypotonia)• Finger-nose test (abnormal)• Heel-knee-shin test (abnormal)• Rapid alternating movements (abnormal)• Speech (dysarthria)• Eye movements (nystagmus)• Reflexes (pendular)• Rebound phenomenon
  45. 45. • ROMBERG TEST IS NOT A SIGN OFCEREBELLAR DISEASE– It is a sign of a disturbance of proprioception, eitherfrom neuropathy or posterior column disease– Patient does not know where their joint is in spaceand so uses their eyes– In the dark or with eyes closed they have problems
  46. 46. • Videodemonstrations• Videodemonstrations• Videodemonstrations

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