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)

The Motor Pathway

Neurones in motor pathway

1. Primary neurone (the UMN)
   • Cell body in cerebral cortex or brainstem nuclei
   • Control

2. Secondary neurone (interneurone)
   • Not always present
   • Located in spinal cord
   • Short neurone synapsing with tertiary neurone

3. Tertiary neurone (the LMN)
   • Aka Lower motor neurone
   • Innervates skeletal muscle in spinal nerve
   • Cell body in brainstem/ventral horn