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2217 – Motor system Somatic – striated muscle Autonomic – smooth muscle, cardiac muscle, glands

2217 – Motor system Somatic – striated muscle Autonomic – smooth muscle, cardiac muscle, glands Upper and lower motor neurons (final common path) Segmental (reflexes) and suprasegmental control Pyramidal vs ‘extrapyramidal’ systems. Reflexes. Descending Pathways. Pyramidal system

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2217 – Motor system Somatic – striated muscle Autonomic – smooth muscle, cardiac muscle, glands

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  1. 2217 – Motor system Somatic – striated muscle Autonomic – smooth muscle, cardiac muscle, glands Upper and lower motor neurons (final common path) Segmental (reflexes) and suprasegmental control Pyramidal vs ‘extrapyramidal’ systems

  2. Reflexes

  3. Descending Pathways • Pyramidal system • Extrapyramidal system • basal ganglia, thalamus • red nucleus • subthalamic nuclei • substantia nigra • reticular formation • vestibulo-spinal? • tecto-spinal? • cerebellum?

  4. Pyramidal Tracts Pyramidal cells in the primary motor cortex A major tract in primates Mainly for fine motor control Homunculus in primary motor cortex

  5. From cortex (only about 50% from primary motor cortex) Passes through the posterior limb of the internal capsule in somatotopic order Passes through cerebral peduncles Sends branches off to bulbar nuclei (both ipsi and contra) At pyramids 85% cross midline 50-55% end in cervical cord 5-10% direct on motor neurons Damage effects not as bad as might be expected from its size cortico-bulbar cortico-spinal

  6. Extrapyramidal pathways Tectospinal Rubrospinal Reticulospinal Vestibulospinal

  7. Extra-pyramidal tracts • Tegmento-spinal(7) • Rubro-spinal(8) • Medial long. Fasc.(10) • Tecto-spinal(9) • Reticulo-spinal(6,5) • Vestibulo-spinal(4)

  8. The basal ganglia

  9. Basal Ganglia

  10. “Striatum” Caudate Putamen Globus pallidus Basal ganglia = caudate nucleus and lenticular (lentiform) nucleus Lenticular nucleus = Globus pallidus + putamen

  11. Kandel et al

  12. Basal ganglia problems • Involuntary movement at rest • Hypokinesia • A “mask” like face • Rigidity • Typical of Parkinson’s disease • Treated by L-Dopa • Experimentally by fetal grafts (stem cell grafts ??) • Globus pallidus, subthalmic nucleus lesions

  13. Cerebellum

  14. CEREBELLUM

  15. Cerebellar Movement Disorders • Dysmetria - over-reaching (test by touching your nose) DISTANCE • Disdiadochokinesia - disjointed movement, poor timing (touch fingers in order) TIMING • Dyssynergia - disjointed force (touch examiner’s finger) FORCE • Ataxia - poor coordination (all the above) • Clonus - contraction in response to stretch • Paresis - weakness, partial paralysis

  16. Movement deficits associated with large cerebellar lesions Disruption of spatial accuracy and temporal coordination of movements

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