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Motor system4 basal ganglia undergraduates

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  • 1. Basal ganglia
    • 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
  • 2. Basal ganglia
    • Caudate nucleus
    • Putamen
    • Globus pallidus
      • (internal and external)
    • Subthalamic nuclei
    • Substantia nigra
            • International Basal Ganglia Society
  • 3. (Ref. Guyton)
  • 4. thalamus globus pallidus putamen caudate
  • 5.  
  • 6. basal ganglia
    • caudate nucleus
    • putamen
    • globus pallidus
    • subthalamic nuclei
    • substantia nigra
    corpus striatum lentiform nucleus
  • 7.
    • Interconnecting circuitry through these nuclei
    • These circuits start from the cortex and ends in the cortex
    • These circuits are very complex
    • Their effect is excitatory or inhibitory on motor functions (depending on the neurotransmitter involved)
    • They also have a role in cognitive functions.
  • 8. PUTAMEN CIRCUIT
    • Starts from premotor Cx, SMA & 1° sensory area.
    • Then goes to putamen (striatum)
    • Then to globus pallidus
    • Then to thalamus
    • Return to 1° motor Cx
  • 9. Cortex Putamen globus pallidus Thalamus
  • 10. PUTAMEN CIRCUIT
    • This circuit functions to control complex patterns of movement in association with the motor Cx
    • eg.
      • writing letters of alphabet,
      • cutting papers with scissors,
      • hammering nails,
      • passing a football,
      • vocalisation
  • 11. CAUDATE CIRCUIT
    • Starts from all parts of the Cx: frontal, parietal, occpital, temporal. and association Cx
    • Then to caudate nucleus
    • Then to globus pallidus
    • Then to thalamus
    • Finally to Premotor Cx, SMA
  • 12. Cortex Caudate globus pallidus Thalamus
  • 13. CAUDATE CIRCUIT
    • This circuit functions in the cognitive control of movement.
  • 14.  
  • 15.  
  • 16.
    • Some of these circuits are excitatory and some inhibitory
    • This depends on the neurotransmitter involved.
    • Inhibitory : dopamine and GABA
    • Excitatory : Ach
    • Others : glutamate (from cortical projections) enkephalin etc
  • 17.
    • Following pathways are known:
    • Dopamine pathway from substantia nigra to caudate nucleus and putamen
    • GABA pathway from caudate and putamen to globus pallidus and substantia nigra
    • Ach pathway in the caudate and putamen
  • 18. Cortex Putamen globus pallidus Caudate Substantia nigra Subthalamic nucleus Reticular formation Dopamine Thalamus Reticular formation glutamate GABA Interneurons: Ach striatum GABA + + Thalamus
  • 19.  
  • 20. Functions of Basal Ganglia
    • Motor control
    • Learning
    • Sensorimotor integration
    • Reward
    • Cognition
  • 21.  
  • 22.  
  • 23. Cortico–Basal Ganglia Motor Loop
    • Basal ganglia receives information from cerebral cortex (frontal, prefronal and parietal)
    • Complex mechanisms occur inside basal ganglia
    • Output goes to the thalamus
    • From the thalamus to the frontal cortex (premotor and supplementary motor areas)
    Basal ganglia inhibit muscle tone
  • 24. Basal Ganglia disorders
    • Parkinsonism
    • Athetosis
    • Chorea
    • Hemiballismus
        • Basal ganglia disorders are also called extrapyramidal disorders
  • 25. Parkinsonism
    • due to destruction of dopamine secreting pathways from substantia nigra to caudate and putamen.
      • also called “paralysis agitans” or “shaking palsy”
      • first described by Dr. James Parkinson in 1817.
    • In the west, it affects 1% of individuals after 60 yrs
    • Classical Clinical features:
    • Tremor, resting
    • Rigidity of all the muscles
    • Akinesia (bradykinesia): very slow movements
    • Postural instability
  • 26.
      • expressionless face
      • flexed posture
      • soft, rapid, indistinct speech
      • slow to start walking
      • rapid, small steps, tendency to run
      • reduced arm swinging
      • impaired balance on turning
      • resting tremor (3-5 Hz) (pill-rolling tremor)
        • diminishes on action
      • cogwheel rigidity
      • lead pipe rigidity
      • impaired fine movements
      • impaired repetitive movements
  • 27.  
  • 28.  
  • 29. other areas
  • 30. Cortex Putamen globus pallidus Caudate Substantia nigra Subthalamic nucleus Reticular formation Dopamine Thalamus Reticular formation glutamate GABA Interneurons: Ach striatum GABA + + Thalamus
  • 31.  
  • 32. Parkinsonism
    • this could be caused by
      • idiopathic causes (no definite cause)
      • drugs
      • toxins
      • MPTP (1 methyl 4 phenyl tetrahydropyridine)
        • experimentally induced parkinsonism
      • associated with other disorders
  • 33. Parkinsonism
    • Treatment is to
      • increase dopamine content by giving dopaminergic drugs
        • Ldopa
      • decrease Ach activity by giving anticholinergic drugs
  • 34. Chorea
    • Lesions in the caudate nucleus
    • jerky movements of the hand, face and other parts
    • patient is unable to control them
    • may get worse with anxiety
    • disappears in sleep
    video
  • 35.  
  • 36. Athetosis
    • Lesions in putamen
    • spontaneous slow writhing movements (twisting movements) of fingers, hands, toes, feet.
  • 37. Hemiballismus
    • Lesions in subthalamus
    • violent, flailing movements of arm & leg on one side of the body