Motor (Descending) Tracts

Motor (Descending) Tracts

1. Corticospinal Tract

   • Voluntary movement
     • Pain withdrawal response
       • Tested by reflexes and muscle strength
   • UMN starts in Primary motor cortex and descends to...
     • ...Pyramids in Medulla
       • Split into anterior fibres (5-25%) remain ipsilateral
         • Decussate in the spinal cord before synapsing with LMNs
           • LMNs in ANTERIOR HORN OF S.C
           • Runs to T6
       • Split into lateral fibres (75-95%) and decussate!
         • Directly synapse with LMNs in the grey matter
           • Runs length of cord

2. Tectospinal Tract

   • Conveys fibres which orientate head and neck during eye movements
   • Eye
     • Input from to Superior Colliculus (midbrain)
       • DECUSSATION in Dorsal Tegmental Decussation
         • Descends through brainstem
           • Synapses with LMN (interneuron) in the anterior horn of the S.C
             • Upper cervical cord
           • Close to the medial longitudinal fasiculus

3. Reticulospinal Tract

   • Co- ordinates muscle group activation for orientation of body towards/ away from stimulus
   • MEDIAL
     • Pons (Pontine reticular fibres)
       • Remains ipsilateral, descending through brainstem
         • Reaches the Medial Reticulospinal tract in Ant Funiculus
           • Synapses with LMN in anterior horn of S.C
   • LATERAL
     • Medulla (Medulla reticular fibres)
       • fibres remain ipsilateral as they descend through brain stem
         • Fibres reach the Lateral Reticulospinal tract in Ant Funiculus
           • Synapses with LMN!
       • fibres DECUSSATE and descend through brain stem
         • fibres reach the Lateral Reticulospinal tract and synapse with LMN in Ant. horn
   • First tract to be discovered!

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