The Dorsal Column-Medial Lemniscal System

1. 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

2. 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

3. 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

4. From below the belt (and above it) The fibers from the leg, trunk, and arm ascend ipsilaterally as the dorsal columns C1 C8 L5

5. The great cross over Axons leaving the dorsal column nuclei cross as arcuate fibers and Ascend as the contralateral medial lemniscus. Medulla

6. 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

7. 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

8. Top Floor - Cortex From the VPL and the VPM of the thalamus, the fibers extend to the primary sensory cortex

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

10. 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

11. And now for the movie….