Extrapyramidal Systems


Pathways originate from subcortical motor centres such as:
  • Corpus striatum
  • Anterior thalamus
  • Subthalamic nucleus
  • Red nucleus
  • Substantia nigra
  • Tectum
  • Vestibular nuclei
  • Reticular formation
  • Cerebellum

These centres project to each other and to the cerebral cortex directly or indirectly and then some of them project to lower motor neurons.

 


Lower motor neuron as an integrator

  • Lower motor neurons constitute final common pathway to muscles
  • It integrates signals from pyramidal, extra-pyramidal and spinal systems then directs them to the muscles

The corticoreticulospinal system  
   

Components

  • Cortico-reticular
  • Reticulo-spinal

Course

  • Parallel to cortico-spinal

Function

  • Control of voluntary motor activity
  • Modulation of segmental and postural reflexes
  • Regulation of muscle tone.