Transcript The Dorsal Column-Medial Lemniscal System

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
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
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
From below the belt (and above it)
The fibers from
the leg, trunk, and
arm ascend
ipsilaterally as
the dorsal columns
C1
C8
L5
The great cross over
Axons leaving the
dorsal column
nuclei cross as
arcuate fibers and
Ascend as the
contralateral
medial lemniscus.
Medulla
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
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
Top Floor - Cortex
From the VPL and the
VPM of the thalamus,
the fibers extend
to the primary sensory
cortex
Primary Sensory Cortex
Sensory information from the dorsal column-lemniscal
system eventually terminates on the postcentral gyrus
of the brain.
The Homunculus!
The arrangement of
fibers correlates to
their entry into the
spinal cord.
Tongue
Face
Hand
(large thumb)
Shoulder,
arms,
abdomen
Legs,
feet,
ankles
And now for the movie….
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