Motor system4 basal ganglia undergraduates

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Motor system4 basal ganglia undergraduates

  1. 1. Basal ganglia <ul><li>These are a set of deep nuclei located in and around the basal part of the brain that are involved in motor control, action selection, and some forms of learning </li></ul>
  2. 2. Basal ganglia <ul><li>Caudate nucleus </li></ul><ul><li>Putamen </li></ul><ul><li>Globus pallidus </li></ul><ul><ul><li>(internal and external) </li></ul></ul><ul><li>Subthalamic nuclei </li></ul><ul><li>Substantia nigra </li></ul><ul><ul><ul><ul><ul><li>International Basal Ganglia Society </li></ul></ul></ul></ul></ul>
  3. 3. (Ref. Guyton)
  4. 4. thalamus globus pallidus putamen caudate
  5. 6. basal ganglia <ul><li>caudate nucleus </li></ul><ul><li>putamen </li></ul><ul><li>globus pallidus </li></ul><ul><li>subthalamic nuclei </li></ul><ul><li>substantia nigra </li></ul>corpus striatum lentiform nucleus
  6. 7. <ul><li>Interconnecting circuitry through these nuclei </li></ul><ul><li>These circuits start from the cortex and ends in the cortex </li></ul><ul><li>These circuits are very complex </li></ul><ul><li>Their effect is excitatory or inhibitory on motor functions (depending on the neurotransmitter involved) </li></ul><ul><li>They also have a role in cognitive functions. </li></ul>
  7. 8. PUTAMEN CIRCUIT <ul><li>Starts from premotor Cx, SMA & 1° sensory area. </li></ul><ul><li>Then goes to putamen (striatum) </li></ul><ul><li>Then to globus pallidus </li></ul><ul><li>Then to thalamus </li></ul><ul><li>Return to 1° motor Cx </li></ul>
  8. 9. Cortex Putamen globus pallidus Thalamus
  9. 10. PUTAMEN CIRCUIT <ul><li>This circuit functions to control complex patterns of movement in association with the motor Cx </li></ul><ul><li>eg. </li></ul><ul><ul><li>writing letters of alphabet, </li></ul></ul><ul><ul><li>cutting papers with scissors, </li></ul></ul><ul><ul><li>hammering nails, </li></ul></ul><ul><ul><li>passing a football, </li></ul></ul><ul><ul><li>vocalisation </li></ul></ul>
  10. 11. CAUDATE CIRCUIT <ul><li>Starts from all parts of the Cx: frontal, parietal, occpital, temporal. and association Cx </li></ul><ul><li>Then to caudate nucleus </li></ul><ul><li>Then to globus pallidus </li></ul><ul><li>Then to thalamus </li></ul><ul><li>Finally to Premotor Cx, SMA </li></ul>
  11. 12. Cortex Caudate globus pallidus Thalamus
  12. 13. CAUDATE CIRCUIT <ul><li>This circuit functions in the cognitive control of movement. </li></ul>
  13. 16. <ul><li>Some of these circuits are excitatory and some inhibitory </li></ul><ul><li>This depends on the neurotransmitter involved. </li></ul><ul><li>Inhibitory : dopamine and GABA </li></ul><ul><li>Excitatory : Ach </li></ul><ul><li>Others : glutamate (from cortical projections) enkephalin etc </li></ul>
  14. 17. <ul><li>Following pathways are known: </li></ul><ul><li>Dopamine pathway from substantia nigra to caudate nucleus and putamen </li></ul><ul><li>GABA pathway from caudate and putamen to globus pallidus and substantia nigra </li></ul><ul><li>Ach pathway in the caudate and putamen </li></ul>
  15. 18. Cortex Putamen globus pallidus Caudate Substantia nigra Subthalamic nucleus Reticular formation Dopamine Thalamus Reticular formation glutamate GABA Interneurons: Ach striatum GABA + + Thalamus
  16. 20. Functions of Basal Ganglia <ul><li>Motor control </li></ul><ul><li>Learning </li></ul><ul><li>Sensorimotor integration </li></ul><ul><li>Reward </li></ul><ul><li>Cognition </li></ul>
  17. 23. Cortico–Basal Ganglia Motor Loop <ul><li>Basal ganglia receives information from cerebral cortex (frontal, prefronal and parietal) </li></ul><ul><li>Complex mechanisms occur inside basal ganglia </li></ul><ul><li>Output goes to the thalamus </li></ul><ul><li>From the thalamus to the frontal cortex (premotor and supplementary motor areas) </li></ul>Basal ganglia inhibit muscle tone
  18. 24. Basal Ganglia disorders <ul><li>Parkinsonism </li></ul><ul><li>Athetosis </li></ul><ul><li>Chorea </li></ul><ul><li>Hemiballismus </li></ul><ul><ul><ul><li>Basal ganglia disorders are also called extrapyramidal disorders </li></ul></ul></ul>
  19. 25. Parkinsonism <ul><li>due to destruction of dopamine secreting pathways from substantia nigra to caudate and putamen. </li></ul><ul><ul><li>also called “paralysis agitans” or “shaking palsy” </li></ul></ul><ul><ul><li>first described by Dr. James Parkinson in 1817. </li></ul></ul><ul><li>In the west, it affects 1% of individuals after 60 yrs </li></ul><ul><li>Classical Clinical features: </li></ul><ul><li>Tremor, resting </li></ul><ul><li>Rigidity of all the muscles </li></ul><ul><li>Akinesia (bradykinesia): very slow movements </li></ul><ul><li>Postural instability </li></ul>
  20. 26. <ul><ul><li>expressionless face </li></ul></ul><ul><ul><li>flexed posture </li></ul></ul><ul><ul><li>soft, rapid, indistinct speech </li></ul></ul><ul><ul><li>slow to start walking </li></ul></ul><ul><ul><li>rapid, small steps, tendency to run </li></ul></ul><ul><ul><li>reduced arm swinging </li></ul></ul><ul><ul><li>impaired balance on turning </li></ul></ul><ul><ul><li>resting tremor (3-5 Hz) (pill-rolling tremor) </li></ul></ul><ul><ul><ul><li>diminishes on action </li></ul></ul></ul><ul><ul><li>cogwheel rigidity </li></ul></ul><ul><ul><li>lead pipe rigidity </li></ul></ul><ul><ul><li>impaired fine movements </li></ul></ul><ul><ul><li>impaired repetitive movements </li></ul></ul>
  21. 29. other areas
  22. 30. Cortex Putamen globus pallidus Caudate Substantia nigra Subthalamic nucleus Reticular formation Dopamine Thalamus Reticular formation glutamate GABA Interneurons: Ach striatum GABA + + Thalamus
  23. 32. Parkinsonism <ul><li>this could be caused by </li></ul><ul><ul><li>idiopathic causes (no definite cause) </li></ul></ul><ul><ul><li>drugs </li></ul></ul><ul><ul><li>toxins </li></ul></ul><ul><ul><li>MPTP (1 methyl 4 phenyl tetrahydropyridine) </li></ul></ul><ul><ul><ul><li>experimentally induced parkinsonism </li></ul></ul></ul><ul><ul><li>associated with other disorders </li></ul></ul>
  24. 33. Parkinsonism <ul><li>Treatment is to </li></ul><ul><ul><li>increase dopamine content by giving dopaminergic drugs </li></ul></ul><ul><ul><ul><li>Ldopa </li></ul></ul></ul><ul><ul><li>decrease Ach activity by giving anticholinergic drugs </li></ul></ul>
  25. 34. Chorea <ul><li>Lesions in the caudate nucleus </li></ul><ul><li>jerky movements of the hand, face and other parts </li></ul><ul><li>patient is unable to control them </li></ul><ul><li>may get worse with anxiety </li></ul><ul><li>disappears in sleep </li></ul>video
  26. 36. Athetosis <ul><li>Lesions in putamen </li></ul><ul><li>spontaneous slow writhing movements (twisting movements) of fingers, hands, toes, feet. </li></ul>
  27. 37. Hemiballismus <ul><li>Lesions in subthalamus </li></ul><ul><li>violent, flailing movements of arm & leg on one side of the body </li></ul>

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