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Sensory and Motor Systems (. (Cultaneous Senses: sensitivity to skin touch…

- - - - Lateral
        
        independent limb movement
        
        hand and finger
        
        includes dorsolateral corticospinal tract, dorsolateral corticorubrospinal tract
      - Ventromedial
        
        automatic movements, coordinated movements involved in posture, locomotion
        
        ventromedial corticospinal tract, ventromedial cortico-brainstem spinal tract
- - - - 1.) Frontal, parietal, and temporal cortex project to the striatum (caudate and putamen)
        
        ) Striatum projects to the globus pallidus (GP)
        
        3.) GP projects to VA/VL nuclei of the thalamus
        4.) VA/VL -> motor cortex
        Basal ganglia is “informed” of planned movements and can influence these movements via this loop
    - - M1
        
        Striatum (D1 receptors)
        
        Substantia Nigra (DA)
        
        Globus Pallidus (GP
        
        Thalamus: VA/VL
        
        M1
    - - Outputs: 3 cortical areas in the Thalamus
        
        Thalamic Nucleus: VA/VL
        
        M1
        
        Supplementary motor cortex
        
        Premotor cortex
  - - - 2 cerebellar hemispheres and 4 deep cerebellar nuclei
      - Structure
        
        Flocculonodular lobe: caudal end; postural reflexes
        ◦ Damage: Disturbances in posture and balance
        
        Vermis: intermediate zone; influences automatic behaviors & posture
        ◦ Damage: deficits in movements produced by the rubrospinal tract
        
        Lateral Zone; Control of independent skilled movements: calculates closely timed sequences of muscular contractions -> rapid skilled movements
        -Damage: weakness of movements, impaired timing
        
        Cerebellar cortex: control of arms and legs
      - Outputs: to every major motor structure in the brain
        
        damage = jerky movements
      - Parkinson's Disease
        
        Characterized by:
        
        muscular rigidity
        
        slowed movements
        
        resting tremor
        
        posture instability
        
        Cause by:
        
        SN DA neurons dying
        -DA input to the striatum (via the SN) facilitates movements
        -Lack of DA inputs -> increase in inhibitory output of the GPi (less inhibition of the inhibitor); there's too much inhibition of the motor cortex
        
        Additional Causes
        
        Toxins:
        -exposure to pesticides and herbicides
        -MPTP
        
        Autosomal recessive juvenile parkinsonism:
        -Mutation in Parkin Gene
        -Toxin accumultes in SN cells (express this gene)
        
        Treatments
        
        Pharmacotherapy
        -L-DOPA: eventually stops working b/c not enough SN DA neurons in increase DA output
        -DA Agonist
        
        Lesion Therapies
        
        Pallidotomies
        -Destruction of GPi
        -reduces rigidity and improves movement
        -PET studies show motor cortex activity pre-surgery is decreased; the activity increases to normal levels post-surgery
        
        Fetal Tissue Treatments
        
        Transplant fetal SN cells to the patient’s SN
        
        hard to do though, 90% cells die; good results when successful