The Anterolateral System

Pain and Temperature Transmision

• 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.

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.

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.

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

To the Cortex

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

Primary Sensory Cortex

Sensory information from the ALS eventually terminates on

the postcentral gyrus of the brain.

The Homunculus!

The arrangement of fibers correlates totheir entry into the spinal cord. Legs,

feet,ankles

Shoulder,arms, abdomen

Hand(large thumb)

Face

Tongue

And Now for the Movie…..

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