Physiology · Central Nervous System

Pyramidal motor pathway

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Definition

  • The pyramidal tract (corticospinal tract, upper motor neuron) is the descending motor pathway whose fibres pass through the pyramid of the medulla; the three terms are interchangeable.

Classification of Descending Pathways

  • Clinical split: pyramidal (through the medullary pyramid) vs extrapyramidal (bypass it).
    • Physiologically inappropriate, since most anterior corticospinal fibres themselves bypass the pyramid.
  • Physiological split:
    • Lateral system: lateral CST + rubrospinal; to distal limb muscles; skilled movement.
    • Medial system: reticulospinal, vestibulospinal, tectospinal + anterior CST; to proximal/axial muscles; posture.

Origin, Course and Termination

Corticospinal Crossing