Lecture Notes: Rubrospinal Tract

Introduction

• Continuation of the series on descending tracts.
• Focus on the rubrospinal tract in this lecture.

Origin of the Rubrospinal Tract

• Begins at the red nucleus, located in the midbrain.
• Related structures:
  • Midbrain, pons, medulla, spinal cord, cerebral cortex, cerebellum.

Functions of the Red Nucleus

• Involved in the activation of flexor muscles.
• Believed to supply upper limb flexors.
• Research indicates maintaining lower limb flexors through unclear mechanisms.

Stimulation of the Red Nucleus

• Cerebral Cortex:
  • Contributes fibers (cortical rubral fibers) for stimulation.
  • Involving the primary motor cortex, premotor cortex, and supplementary motor area.
• Cerebellum:
  • Through deep cerebellar nuclei: globose and emboliform nuclei.
  • Provides unconscious proprioceptive information.

Pathway

• Decussation:
  • Occurs in the midbrain at the ventral tegmental decussation.
  • Fibers cross over to the contralateral side.
• Descent:
  • Descends into the lateral white column of the spinal cord.
  • Aids the lateral corticospinal tract.

Termination and Function

• Affects alpha and gamma motor neurons in the anterior grey horn.
  • Alpha Neurons: Affect extrafusal muscle fibers.
  • Gamma Neurons: Maintain tension on muscle spindles.
• Influences flexor muscles, especially in the upper limbs.
• Recent findings suggest a regulatory role in lower limb flexors.

Summary

• The rubrospinal tract is important for stimulating upper limb flexors and potentially regulating lower limb flexors.
• Main stimulation derived from the cerebellum and cortical rubral fibers.
• Crosses in the midbrain and descends with the lateral corticospinal tract.

Next Topic

• The next lecture will discuss the medullary reticulospinal tract.
• To be followed by a comprehensive review of the descending tracts.

Note: This note summarizes key points from the lecture on the rubrospinal tract, covering origin, pathway, function, and related research findings. Use this guide to review the basic concepts discussed in class.