Motor Pathways Lecture Notes

Introduction

• Focus on motor pathways in the brain.
• Emphasis on motor cortex and somatosensory cortex.
  • Motor Cortex: Controls motor movement.
  • Somatosensory Cortex: Controls sensation.

Brain Structure

• Cortex Composition:
  • Outer gray matter: Location of synapses.
  • Inner white matter: Contains myelinated axons.
• Body representation in motor cortex includes hands, face, legs.

Motor Pathways Overview

• Two main pathways:
  • Lateral Pathway: Responsible for voluntary movements.
  • Anteriomedial Pathway: Focus on axial muscles for posture and balance.

Lateral Pathway

• Tracks Involved:
  1. Lateral Corticospinal Tract: Controls distal muscles (e.g., forearm).
  2. Anterior Corticospinal Tract: Controls proximal muscles (e.g., arm).
  3. Rubrospinal Tract: Voluntary control of big muscles.
• Key Structures:
  • Midbrain
  • Pons
  • Medulla
  • Spinal cord

Corticospinal Tract Details

• Lateral Corticospinal Tract:
  • Pathway: Motor cortex → thalamus → midbrain → medulla → lateral corticospinal tract → ventral horn of spinal cord → skeletal muscle.
  • Upper Motor Neuron: From motor cortex.
  • Lower Motor Neuron: From ventral horn, targets distal muscles.
• Anterior Corticospinal Tract: Similar pathway, targets proximal muscles.

Rubrospinal Tract

• Begins in the midbrain's red nucleus.
• Crosses over, descends via medulla, synapses in rubrospinal tract.
• Can help recover function if corticospinal tract is damaged.

Anteromedial Pathway

• Functions: Control of axial muscles for posture and balance.
• Tracks:
  1. Tectospinal Tract
  2. Vestibulospinal Tract (medial and lateral): Head balance and turning.
  3. Reticulospinal Tract: Originates from medulla or pons, controls axial muscles.

Additional Notes

• Contralateral Control: Left brain controls right side of the body and vice versa.
• Cerebellum's Role: Coordinates motor pathways, contributes to balance and posture.
• Tectospinal Tract Function: Responsible for orientation response in the environment.

Conclusion

• Importance of understanding motor pathways for voluntary control.
• Corticospinal tract highlighted as crucial for voluntary movement control.