Motor Neurone Pathways

Summary

  • Control of the motor pathway
    • Cerebellum
    • Basal Ganglia
  • The motor pathway
  • The motor (descending) tracts
    • Pyramidal:
      • Corticospinal
      • Corticobulbar
    • Extra-pyramidal:
      • Rubrospinal
      • Tectospinal
      • Vestibulospinal
      • Reticulospinal
      • Olivospinal

Control of the motor pathway

  • Several important components in the brain are involved in the motor pathway
    • Cerebral cortex – contains the primary motor cortex from where conscious control of movement is derived
    • Cerebellum – receives and integrates proprioceptive input. Also important for coordinating repeated movements 
    • Basal Ganglia plays a key role in preventing excessive movement via projections to the cortex and reticular formation
      • Corpus striatum
        • Caudate nucleus
        • Putamen
        • Globus pallidus
      • Red nucleus
      • Substantia nigra
    • Thalamus (VPL)
    • Inferior olivary nucleus
    • Vestibular nuclei
    • Reticular formation
  • There is a complex interplay in the different components involved in motor function
    • Different areas contribute to different tracts (and hence different movements)
A VERY simplified diagram showing the input pattern into the descending pathways.

The Motor Pathway

Neurones in motor pathway

  1. Primary neurone (the UMN)
    • Cell body in cerebral cortex or brainstem nuclei
    • Control
  1. Secondary neurone (interneurone)
    • Not always present
    • Located in spinal cord
    • Short neurone synapsing with tertiary neurone
  1. Tertiary neurone (the LMN)
    • Aka Lower motor neurone
    • Innervates skeletal muscle in spinal nerve
    • Cell body in brainstem/ventral horn

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