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Y2 s2 locomotion seminar coordination 2011
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Y2 s2 locomotion seminar coordination 2011

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  • I am currently studying the nuero component of my medical training - the connections between structures (functional anatomy) are multiple and constantly relaying back and forth, any tips on learning the KEY pathways and functions?
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  • 1. Staff Seminar on Coordination of movement Prof. Vajira Weerasinghe Dept of Physiology Prof. Nimal Senanayake Dept of Medicine Y2S2 Locomotion module
  • 2. Objectives
    • Discuss the role of the cerebellum on motor coordination
    • Explain giving examples how coordination is affected in neurological disease
  • 3. Role of cerebellum on motor coordination
  • 4. Introduction
    • the cerebellum and basal ganglia are large collections of nuclei that modify movement on a minute-to-minute basis
    • these regions have marked similarities between them in the overall pattern of their connections with the cerebral cortex
    • both receive information from the motor cortex
    • both send information back to cortex via the thalamus
  • 5. Introduction
    • the cerebellum sends excitatory output to the motor cortex, while the basal ganglia sends inhibitory output
    • the balance between these two systems allows for smooth, coordinated movement
    • - a disturbance in either system will manifest itself as a movement disorder
  • 6.  
  • 7. structure
    • Cerebellum is divided into 3 lobes by 2 transverse fissures
      • anterior lobe
      • posterior lobe
      • flocculonodular lobe
  • 8.  
  • 9.
    • Anterior cerebellum and part of posterior cerebellum
      • receives information from the spinal cord
    • Rest of the posterior cerebellum
      • receives information from the cortex
    • Flocculonodular lobe
      • involved in controlling the balance through vestibular apparatus
  • 10.  
  • 11.
    • lateral zone
      • this is concerned with overall planning of sequence and timing
    • intermediate zone
      • control muscles of upper and lower limbs distally
    • vermis
      • controls muscles of axial body, neck, hip
  • 12. 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
  • 13. Inputs (cont’d)
    • vestibulocerebellar
        • to the flocculonodular lobe
    • reticulocerebellar
        • to the vermis
    • spinocerebellar tracts
      • dorsal spinocerebellar tracts
        • from muscle spindle, prorpioceptive mechanoreceptor (feedback information)
      • ventral spinocerebellar tarcts
        • from anterior horn cell
          • excited by motor signals arriving through descending tracts (efference copy)
  • 14. 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
  • 15.  
  • 16.  
  • 17. Neuronal circuitry of the cerebellum
    • Main cortical cells in cerebellum are known as Purkinje Cells (large cells).
    • There are about 30 million such cells.
    • These cells constitute a unit which repeats along the cerebellar cortex.
  • 18.  
  • 19.  
  • 20.  
  • 21.
    • Somatotopic representation of the body is present in cerebellar cortex although it is not as clear as cerebral cortex.
  • 22. Topographical representation vermis intermediate zone
  • 23. Functional unit of the cerebellar cortex
    • a Purkinje cell
    • a deep nuclear cell
    • inputs
    • output from the deep nuclear cell
  • 24. Purkinje cell Input from Inferior olive Input from other afferents Climbing fibre Mossy fibre Granule cells Deep nuclear cell Output excitation excitation inhibition
  • 25.
    • Even at rest, Purkinje cells & deep nuclear cells discharge at 40-80 Hz
    • afferents excite the deep nuclear cells
    • Purkinje cells inhibit the deep nuclear cells
    • GABA is involved as the neurotransmitter
  • 26. Functions of cerebellum
    • planning of movements
    • timing & sequencing of movements
    • particularly during rapid movments such as during walking, running
    • from the peripheral feedback & motor cortical impulses, cerebellum calculates when does a movement should begin and stop
  • 27. Overview of motor system hierarchy 1. Motor areas in the cerebral cortex
  • 28. Overview of motor system hierarchy 1. Motor areas in the cerebral cortex 2. Brainstem
  • 29. Overview of motor system hierarchy 1. Motor areas in the cerebral cortex 2. Brainstem 3. Spinal cord motor circuits rhythmic movements reflexes voluntary movements
  • 30. Overview of motor system hierarchy 1. Motor areas in the cerebral cortex 2. Brainstem 3. Spinal cord motor circuits rhythmic movements reflexes voluntary movements
  • 31. Overview of motor system hierarchy 1. Motor areas in the cerebral cortex 2. Brainstem 3. Spinal cord motor circuits rhythmic movements reflexes voluntary movements Cerebellum Basal ganglia
  • 32. Overview of motor system hierarchy 1. Motor areas in the cerebral cortex 2. Brainstem 3. Spinal cord motor circuits rhythmic movements reflexes voluntary movements Cerebellum Basal ganglia Thalamus
  • 33.
    • ‘ 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 cell through extrapyramidal tracts
  • 34.
    • ‘ Prevention of overshoot’
      • Soon after a movement has been initiated
      • cerebellum send signals to stop the movement at the intended point (otherwise overshooting occurs)
    • Ballistic movements
      • movements are so rapid it is difficult to decide on feedback
      • a high-velocity musculoskeletal movement, such as a tennis serve or boxing punch, requiring reciprocal coordination of agonistic and antagonistic muscles
      • rapid movements of the body, eg. finger movements during typing, rapid eye movements (saccadic eye movements)
      • therefore the movement is preplanned
  • 35. planning of movements
    • mainly performed by lateral zones
    • sequencing & timing
      • lateral zones communicate with premotor areas, sensory cortex & 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 a contralateral basis , the cerebellum works ipsilaterally
  • 36. Motor learning
    • the cerebellum is also partly responsible for learning motor skills , such as riding a bicycle
    • any movement “corrections” are stored as part of a motor memory in the synaptic inputs to the Purkinje cell
    • research studies indicate that cerebellum is a pattern learning machine
    • cellular basis for cerebellum-dependent motor learning is know to be a type of long-term depression (LTD) of the Purkinje cell synapses