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Understanding Movement Disorders: Anatomy and Physiology Overview

Explore the intricate motor systems that control locomotion, posture, and work, monitoring muscle activity through proprioceptive receptors and feedback mechanisms, while delving into causes, motor disorders, and pathways affecting movement. Gain insight into the basal ganglia, Parkinson's and Huntington's diseases, and the involvement of the cerebellum in motor functions.

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Understanding Movement Disorders: Anatomy and Physiology Overview

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  1. CHAPTER VMovement disorders Part I: Anatomy and physiology of motor system

  2. Motor systems • Motor systems are complex and include sophisticated control systems the purpose of which is to serve locomotion, posture and work.

  3. Several feedback systems monitor muscle activity The length of muscles and the strength of contractions are monitored by: • Input from proprioceptive receptors in muscles, joints and tendons • Local feedback from motor nerves (Renshaw inhibition)

  4. Posture Monitored by • proprioceptors, • vestibular system • vision

  5. Causes of movement disorders • More or less anatomically specific neural degeneration • Injuries (trauma, strokes, surgery, etc) • Chemicals (alcohol, drugs) • Inflammations and infections (viral) • Tumors • Genetic • Neural plasticity • Genetic • Idiopathic

  6. Motor disorders • Lack of function • Inadequate function • Hyperactivity

  7. Disorders of motor systems • Hypokinesia • Hyperkinesia • Spasticity • Ataxia • Gait and balance disturbances

  8. Two different descending motor pathways: • Lateral system • Fine movements • Medial system • Posture etc.

  9. Lateral system

  10. Medial system

  11. Motor pathways The motoneurons (alpha motoneurons) are the final common pathways

  12. The alpha-motoneurons (common final pathway) receive many inputs Some arefacilitating and some are inhibitory

  13. Motor pathways

  14. Somatotopic organization of the motor cortex

  15. Two motoneurons receiving input from cortical cells

  16. Terminations of the corticospinal tract projections of sensory pathways Motor areas Sensory areas

  17. Renshaw inhibition Fibers of the corticospinal tract terminate on motoneurons or interneurons

  18. Extensive processing of motor command occurs in the spinal cord (and brainstem) Spinal reflexes play an important role in all motor functions Some functions such as walking is programmed in the spinal cord

  19. Monosynaptic stretch reflex

  20. Hoffman reflex

  21. Reflexes are modulated from supraspinal sources

  22. Reciprocal spinal reflex

  23. Descending vestibular pathways

  24. Medial system Posture and automatic functions

  25. Tendon reflex

  26. Flexor reflex

  27. Convergence of excitatory inputs Convergence of inhibitory and excitatory inputs

  28. Input to propriospinal neurons of the forelimb of the cat

  29. Magnetic stimulation of motor cortex in an awake individual From Rosler Fig 2B

  30. Input to an Ia inhibitory interneuron

  31. Input to an Ib (inhibitory) interneuron

  32. BASAL GANGLIA Extrapyramidal system Pyramidal system

  33. Two descending motor tracts The alpha-motoneuron is the final common pathway

  34. Anatomical localization motor pathways

  35. Basal ganglia

  36. Parkinson’s disease

  37. Huntington’s disease

  38. Direct and indirect pathways

  39. Basal ganglia connect to supplementary motor areas and primary motor cortex SMA: Supplementary motor area STN: Subthalamic nucleus

  40. Involvement of the cerebellum

  41. Involvement of the cerebellum and pontine nuclei

  42. Overview of motor pathways

  43. ANATOMICAL LOCATIONS OF THE BASAL GANGLIA

  44. Middle cerebral artery

  45. BASAL GANGLIA

  46. ANATOMICAL LOCATION OF THE CAUDATE NUCLEUS

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