Spinal Pathway Series: Dorsal Column Medial Lemniscus Pathway

Introduction

• Second tutorial in spinal pathway series.
• Focus on Dorsal Column Medial Lemniscus Pathway.
• Dorsal Column also known as Posterior Column.
• Conveys fine touch and proprioception.

Nerve Endings that Sense Fine Touch

• Four types:
  • Meissner Corpuscles
  • Pacinian Corpuscles
  • Ruffini Endings
  • Merkel Endings

Pathway Overview

Neurons and Their Cell Bodies

• Nerve Endings: Present in the Upper and Lower Limbs.
• Cell Bodies: Located in the Dorsal Root Ganglion.
• Neurons are pseudo-unipolar (axon runs in two directions).

Path from Body to Spinal Cord

• Neurons project from body to spinal cord.
• Dorsal Column: Composed of Cuneate and Gracile Fasciculi.
  • Gracile Fasciculus: Axons from lower limb.
  • Cuneate Fasciculus: Axons from upper limb.
• Axons enter spinal cord at different levels: Lower limb more caudal, Upper limb more rostral.

Ascending Pathway in the Brain Stem

• Brain Stem Components: Thalamus, Midbrain, Pons, Medulla Oblongata.
• Nuclei in Medulla:
  • Cuneate Nucleus
  • Gracile Nucleus
  • Cuneate and Gracile Fasciculi project to their respective nuclei.
• Decussation: Axons cross over to the other side of the brain stem, known as Internal Arcuate Fibers.
• Medial Lemniscus: Continuation of fibers through the brain stem.

Thalamic and Cortical Projections

• Ventral Posterolateral Nucleus of the Thalamus: Receives synapse from medial lemniscus.
• Post Central Gyrus in Cortex: Primary sensory area receiving projections from the thalamus.

Summary of Neurons in Pathway

• First Neuron: In the dorsal root ganglion.
• Second Neuron: In the Cuneate or Gracile Nucleus.
• Third Neuron: In the Ventral Posterolateral Nucleus of the Thalamus.

Conclusion

• Tutorial completed on Dorsal Column Medial Lemniscus Pathway.
• Next tutorial will cover the Spinothalamic Tract.

Additional Information

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