Motor Pathways Lecture Notes

Introduction

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• Video Context: Focus on motor pathways. Recommended to watch introductory videos on descending and ascending tracts and sensory motor pathways.

Brain Cortexes

• Motor Cortex: Located in front of the central gyrus, controls motor movements.
• Somatosensory Cortex: Located at the back, associated with sensation.

Motor Cortex Structure

• Composed of outer gray matter with synapses and inner white matter with myelinated axons.
• Contains areas that represent specific body regions (e.g., hands, face, legs).
• Motor signals originate here to control specific body parts.

Motor Pathways

Types of Motor Pathways

• Lateral Pathway: Responsible for voluntary movements.
  • Lateral Corticospinal Tract: Controls distal muscles (e.g., forearm).
  • Anterior Corticospinal Tract: Controls proximal muscles (e.g., arm), not part of the lateral pathway.
  • Rubrospinal Tract: Voluntary control of large muscles.

Key Structures

• Midbrain, Pons, Medulla: Important structures the motor pathways pass through.
• Spinal Cord: Contains designated tracts for lateral and anterior pathways.

Corticospinal Tract

• Pathway for hand movement: Originates from motor cortex, passes through thalamus, midbrain, medulla, and synapses in the spinal cord.
• Upper Motor Neuron: First neuron from cortex to spinal cord.
• Lower Motor Neuron: Second neuron targeting skeletal muscles.

Rubrospinal Tract

• Originates from the red nucleus in the midbrain.
• Critical for voluntary control of major muscles.
• Can compensate for corticospinal lesions.

Anterior Medial Pathways

• Control axial muscles (spine, rib muscles) for posture and balance.
• Vestibulospinal Tract: Maintains head balance and turning.
• Reticulospinal Tract: Posture and balance; includes medullary and pontine tracts.
• Tectospinal Tract: Orientation response in the environment.

Important Concepts

• Contralateral Control: Left brain controls right body side and vice versa.
• Lesions: Corticospinal lesions cause paralysis on the opposite side.

Conclusion

• Motor pathways are crucial for voluntary and involuntary muscle control.
• Corticospinal Tract: Most important for voluntary control.

Additional Information

• Coordination and Balance: Cerebellum interconnects with motor pathways for these functions.

Summary

• Divided into lateral and anterior medial pathways.
• Importance of understanding voluntary control and compensatory mechanisms.

Note: This summary covers the main points of motor pathways including the structure, function, and significance of various tracts involved in both voluntary and involuntary movements.