Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Motor system3 cerebellum


Published on

  • Be the first to comment

Motor system3 cerebellum

  1. 1. cerebellum <ul><li>centre of motor coordination </li></ul><ul><li>cerebellar disorders cause </li></ul><ul><ul><li>incoordination or ataxia </li></ul></ul>
  2. 6. structure <ul><li>Cerebellum is divided into 3 lobes by 2 transverse fissures </li></ul><ul><ul><li>anterior lobe </li></ul></ul><ul><ul><li>posterior lobe </li></ul></ul><ul><ul><li>flocculonodular lobe </li></ul></ul>
  3. 8. structure <ul><ul><li>anterior lobe (paleocerebellum) </li></ul></ul><ul><ul><li>large posterior lobe (neocerebellum) </li></ul></ul><ul><ul><li>flocculonodular lobe (archicerebellum is the oldest lobe) </li></ul></ul>
  4. 9. <ul><li>Anterior cerebellum and part of posterior cerebellum </li></ul><ul><ul><li>receives information from the spinal cord </li></ul></ul><ul><li>Rest of the posterior cerebellum </li></ul><ul><ul><li>receives information from the cortex </li></ul></ul><ul><li>Flocculonodular lobe </li></ul><ul><ul><li>involved in controlling the balance through vestibular apparatus </li></ul></ul>
  5. 10. <ul><li>Functionally cerebellum is divided into 3 areas medial to lateral </li></ul><ul><ul><li>lateral zone </li></ul></ul><ul><ul><li>intermediate zone </li></ul></ul><ul><ul><li>vermis </li></ul></ul>
  6. 12. <ul><li>lateral zone </li></ul><ul><ul><li>this is concerned with overall planning of sequence and timing </li></ul></ul><ul><li>intermediate zone </li></ul><ul><ul><li>control muscles of upper and lower limbs distally </li></ul></ul><ul><li>vermis </li></ul><ul><ul><li>controls muscles of axial body, neck, hip </li></ul></ul>
  7. 13. Inputs <ul><li>corticopontocerebellar </li></ul><ul><ul><ul><li>from motor and premotor cortex (also sensory cortex) </li></ul></ul></ul><ul><ul><ul><li>these tracts supplies the contralateral cerebellar cortex </li></ul></ul></ul><ul><li>olivocerebellar </li></ul><ul><ul><ul><li>from inferior olive </li></ul></ul></ul><ul><ul><ul><ul><li>excited by fibres from </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>motor cx </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>basal ganglia </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>reticular formation </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>spinal cord </li></ul></ul></ul></ul></ul>
  8. 14. Inputs (cont’d) <ul><li>vestibulocerebellar </li></ul><ul><ul><ul><li>to the flocculonodular lobe </li></ul></ul></ul><ul><li>reticulocerebellar </li></ul><ul><ul><ul><li>to the vermis </li></ul></ul></ul><ul><li>spinocerebellar tracts </li></ul><ul><ul><li>dorsal spinocerebellar tracts </li></ul></ul><ul><ul><ul><li>from muscle spindle, prorpioceptive mechanoreceptor (feedback information) </li></ul></ul></ul><ul><ul><li>ventral spinocerebellar tarcts </li></ul></ul><ul><ul><ul><li>from anterior horn cell </li></ul></ul></ul><ul><ul><ul><ul><li>excited by motor signals arriving through descending tracts (efference copy) </li></ul></ul></ul></ul>
  9. 15. Outputs <ul><li>through deep cerebellar nuclei: dentate, fastigial, interpositus </li></ul><ul><ul><li>1. vermis -> fastigial nucleus -> medulla, pons </li></ul></ul><ul><ul><li>2. intermediate zone -> nucleus interpositus -> thalamus -> cortex -> basal ganglia -> red nucleus -> reticular formation </li></ul></ul><ul><ul><li>3. lateral zone -> dentate nucleus -> thalamus -> cortex </li></ul></ul>
  10. 16. Outputs <ul><li>Functions </li></ul><ul><ul><li>1. vermis -> fastigial nucleus -> medulla, pons </li></ul></ul><ul><ul><li>control balance and equilibrium with the vestibular pathways </li></ul></ul>
  11. 17. Outputs <ul><li>Functions </li></ul><ul><ul><li>2. intermediate zone -> nucleus interpositus -> thalamus -> cortex -> basal ganglia -> red nucleus -> reticular formation </li></ul></ul><ul><ul><li>coordinate reciprocal contractions of agonist & antagonist muscles in limbs </li></ul></ul>
  12. 18. Outputs <ul><li>Functions </li></ul><ul><ul><li>3. lateral zone -> dentate nucleus -> thalamus -> cortex </li></ul></ul><ul><ul><li>coordinate sequential motor activities initiated by the cerebral cortex </li></ul></ul>
  13. 19. Neuronal circuitry of the cerebellum <ul><li>Main cortical cells in cerebellum are known as Purkinje Cells (large cells). </li></ul><ul><li>There are about 30 million such cells. </li></ul><ul><li>These cells constitute a unit which repeats along the cerebellar cortex. </li></ul>
  14. 23. <ul><li>Somatotopic representation of the body is present in cerebellar cortex although it is not as clear as cerebral cortex. </li></ul>
  15. 24. Topographical representation vermis intermediate zone
  16. 25. Functional unit of the cerebellar cortex <ul><li>a Purkinje cell </li></ul><ul><li>a deep nuclear cell </li></ul><ul><li>inputs </li></ul><ul><li>output from the deep nuclear cell </li></ul>
  17. 26. Purkinje cell Input from Inferior olive Input from other afferents Climbing fibre Mossy fibre Granule cells Deep nuclear cell Output excitation excitation inhibition
  18. 27. Output Inputs Inputs
  19. 28. <ul><li>Purkinje cells & deep nuclear cells fire continuously </li></ul><ul><li>afferents excite the deep nuclear cells </li></ul><ul><li>Purkinje cells inhibit the deep nuclear cells </li></ul>
  20. 29. Functions of cerebellum <ul><li>planning of movements </li></ul><ul><li>timing & sequencing of movements </li></ul><ul><li>particularly during rapid movments such as during walking, running </li></ul><ul><li>from the peripheral feedback & motor cortical impulses, cerebellum calculates when does a movement should begin and stop </li></ul>
  21. 30. Motor Cortex Thalamus Cerebellum Muscles brain stem nuclei proprioceptive tactile feedback
  22. 31. <ul><li>‘ Error correction’ </li></ul><ul><li>cerebellum receives two types of information </li></ul><ul><ul><li>intended plan of movement </li></ul></ul><ul><ul><ul><li>direct information from the motor cortex </li></ul></ul></ul><ul><ul><li>what actual movements result </li></ul></ul><ul><ul><ul><li>feedback from periphery </li></ul></ul></ul><ul><ul><li>these two are compared: an error is calculated </li></ul></ul><ul><ul><li>corrective output signals goes to </li></ul></ul><ul><ul><ul><li>motor cortex via thalamus </li></ul></ul></ul><ul><ul><ul><li>brain stem nuclei and then down to the anterior horn cell through extrapyramidal tracts </li></ul></ul></ul>
  23. 32. <ul><li>‘ Prevention of overshoot’ </li></ul><ul><ul><li>Soon after a movement has been initiated </li></ul></ul><ul><ul><li>cerebellum send signals to stop the movement at the intended point (otherwise overshooting occurs) </li></ul></ul><ul><li>Ballistic movements </li></ul><ul><ul><li>rapid movements of the body, eg. finger movements during typing, rapid eye movements (saccadic eye movements) </li></ul></ul><ul><ul><li>movements are so rapid it is difficult to decide on feedback </li></ul></ul><ul><ul><li>therefore the movement is preplanned </li></ul></ul>
  24. 33. planning of movements <ul><li>mainly performed by lateral zones </li></ul><ul><li>sequencing & timing </li></ul><ul><ul><li>lateral zones communicate with premotor areas, sensory cortex & basal ganglia to receive the plan </li></ul></ul><ul><ul><li>next sequential movement is planned </li></ul></ul><ul><ul><li>predicting the timings of each movement </li></ul></ul>
  25. 34. features of cerebellar disorders <ul><li>ataxia </li></ul><ul><ul><li>incoordination of movements </li></ul></ul><ul><ul><li>ataxic gait </li></ul></ul><ul><ul><ul><li>broad based gait </li></ul></ul></ul><ul><ul><ul><li>leaning towards side of the lesion </li></ul></ul></ul><ul><li>dysmetria </li></ul><ul><ul><li>cannot plan movements </li></ul></ul><ul><li>past pointing & overshoot </li></ul><ul><li>decomposition of movements </li></ul><ul><li>intentional tremor </li></ul>
  26. 35. features of cerebellar disorders <ul><li>dysdiadochokinesis </li></ul><ul><ul><li>unable to perform rapidly alternating movements </li></ul></ul><ul><li>dysarthria </li></ul><ul><ul><li>slurring of speech </li></ul></ul><ul><li>nystagmus </li></ul><ul><ul><li>oscillatory movements of the eye </li></ul></ul>
  27. 36. features of cerebellar disorders <ul><li>hypotonia </li></ul><ul><ul><li>reduction in tone </li></ul></ul><ul><ul><ul><li>due to excitatory influence on gamma motor neurons by cerebellum (through vestibulospinal tracts) </li></ul></ul></ul><ul><li>decreased reflexes </li></ul><ul><li>head tremor </li></ul><ul><li>head tilt </li></ul>