Cortical & brainstem Control

• Where is the motor cortex located in the brain?

  Anterior to the central cortical sulcus
• What are the divisions of the motor cortex?

  • Primary motor cortex
  • Premotor area
  • Supplementary motor area
• What is the primary function of the primary motor cortex?

  Planning and initiation of voluntary movements
• How does the primary motor cortex control muscle activity?

  It controls the opposite side of the body
• What information does the premotor area receive?

  Information from supplementary motor area and primary motor cortex
• What is the role of the premotor area in movement?

  It sets posture at the beginning of movement
• What does the supplementary motor area control?

  Higher motor functions and bimanual tasks
• What happens if there is a lesion in the supplementary motor area?

  Difficulty in performing complex motor activities
• What are descending pathways?

  Fibers passing downward influencing spinal cord neurons
• How are descending motor pathways classified?

  • Pyramidal tracts
  • Extrapyramidal tracts
• What are pyramidal tracts associated with?

  Descending tracts passing through the medulla pyramid
• What are extrapyramidal tracts?

  Descending pathways not passing through the medulla pyramid
• What are the two systems of descending pathways?

  • Lateral system
  • Medial system
• What do lateral system pathways regulate?

  Skilled voluntary movements
• What are the components of the medial system pathways?

  Reticulospinal, vestibulospinal, tectospinal, anterior corticospinal tracts
• What is the primary function of the lateral corticospinal tract?

  Control of skilled voluntary activities
• What percentage of corticospinal fibers are in the lateral corticospinal tract?

  About 80%
• What is the role of the anterior corticospinal tract?

  Control of posture
• Where do the fibers of the corticospinal tract originate?

  From the primary motor cortex
• What is the course of the corticospinal tract fibers?

  They converge through the internal capsule
• What happens to 80% of the corticospinal fibers after passing through the pyramid?

  They decussate and descend in the lateral funiculus
• How do lateral corticospinal fibers connect to motor neurons?

  They have monosynaptic connections with anterior horn cells
• What is the termination point for the fibers of the ventral corticospinal tract?

  On interneurons in the same side of the spinal cord
• What is the main function of the motor cortex?

  Initiation, planning, and control of movement
• What is the effect of a lesion in the lateral corticospinal tract?

  Impairment of skilled voluntary activities
• What is the effect of a lesion in the anterior corticospinal tract?

  Inability to maintain posture while walking
• Where does the rubrospinal tract originate?

  From the red nucleus in the midbrain
• What is the course of the rubrospinal tract?

  Fibers cross over and descend in the spinal cord
• What does the rubrospinal tract control?

  Skilled voluntary movements
• Where does the pontine reticulospinal tract originate?

  From nucleus reticularis pontis-oralis and pontis-caudalis
• What is the function of the pontine reticulospinal tract?

  Excites motor neurons of proximal extensor muscles
• Where does the medullary reticulospinal tract originate?

  From nucleus gigantocellularis in the medulla
• What is the main function of the medullary reticulospinal tract?

  Inhibits activities of motor neurons innervating extensors
• Where does the lateral vestibulospinal tract originate?

  From the lateral vestibular nucleus
• What is the function of the lateral vestibulospinal tract?

  Excites motor neurons for proximal extensor muscles
• Where does the medial vestibulospinal tract originate?

  From the medial vestibular nucleus
• What does the medial vestibulospinal tract control?

  Body posture and head position
• Where does the tectospinal tract originate?

  From the tectum or superior colliculus
• What is the function of the tectospinal tract?

  Regulates contralateral head movement in response to visual stimuli
• What are the key terms related to the motor cortex and its pathways?

  • Motor cortex
  • Primary motor cortex
  • Premotor area
  • Supplementary motor area
  • Pyramidal tracts
  • Extrapyramidal tracts
  • Lateral system
  • Medial system