The Anterolateral System

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The Anterolateral System

• Pain and Temperature Transmision

"If you are distressed by anything external, the
pain is not due to the thing itself, but to your
estimate of it and this you have the power to
revoke at any moment. -Marcus Aurelius
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OUCH!!!

• The Anterolateral System is an ascending pathway
  conveying pain and temperature sensation.
• Cell bodies of the primary sensory neurons
  reside in the dorsal root ganglia and the
  trigeminal complex.
• This pathway receives input from thermoreceptors,
  nociceptors, and mechanoreceptors.

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Getting into the Spinal Cord

• Primary axons synapse in Rexed layers I-IV of the
  dorsal horn
• Secondary axons cross in the anterior white
  column to form the anterolateral tract.

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Sensation from the face

• Pain and temperature sensation from the face are
  conveyed from fibers in the spinal trigeminal
  complex.
• These fibers cross in the brain stem and join the
  anterolateral tract.

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Connections in the brain stem

• ALT axons distribute to the reticular formation,
  central gray substance, and finally the
  intralaminar and posterior thalamus
• The neospinothalamic tract distributes
  somatotopically in the ventral posterior
  thalamus
• VPL - Leg, Trunk, Arms
• VPM - Face

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To the 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 ALS eventually
terminates on the postcentral gyrus of the brain.
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The Homunculus!
Shoulder, arms, abdomen
Hand (large thumb)
Face
The arrangement of fibers correlates to their
entry into the spinal cord.
Legs, feet, ankles
Tongue
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And Now for the Movie..