The Dorsal ColumnMedial Lemniscal System

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The Dorsal Column-Medial Lemniscal System
"I do not feel obliged to believe that the same
God who has endowed us with sense, reason, and
intellect has intended us to forgo their use." -
Galileo Galilei
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Introduction

• The dorsal column-medial lemniscus system conveys
  somatic discriminative sensory information from
  touch, vibration, and joint position receptors
• Throughout the system, the fibers are arranged
  somatitopically in relation to their entry into
  the CNS
• The cell bodies reside in the dorsal root and
  trigeminal ganglia

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Synapsing in the cord
Gracile

• The fibers from the lower
• limbs synapse on the
• Gracile Nucleus.
• Those from the upper
• limbs synpase on the
• Cuneate Nucleus.

Cuneate
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From below the belt (and above it)

• The fibers from
• the leg, trunk, and
• arm ascend
• ipsilaterally as
• the dorsal columns

C1
C8
L5
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The great cross over

• Axons leaving the
• dorsal column
• nuclei cross as
• arcuate fibers and
• Ascend as the
• contralateral
• medial lemniscus.

Medulla
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What about the face?

• At the level of the
• brainstem, primary
• sensory axons from
• the face synapse
• in the principle
• trigeminal nucleus
• and cross to join
• the contralateral
• medial lemniscus.

Midbrain Pons
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Up, up , and away!

• The medial lemniscus
• ascends to the ventral
• posterior thalamic
• nucleus
• Lateral Division (VPL) - Leg, Trunk, and Arm
• Medial Division (VPM) - Face

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Top Floor - Cortex

• From the VPL and the
• VPM of the thalamus,
• the fibers extend
• to the primary sensory
• cortex

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Primary Sensory Cortex

• Sensory information from the dorsal
  column-lemniscal
• system eventually terminates on the postcentral
  gyrus
• of the brain.

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The Homunculus!
Shoulder, arms, abdomen
Legs, feet, ankles
Hand (large thumb)
The arrangement of fibers correlates to their
entry into the spinal cord.
Face
Tongue
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And now for the movie.