Anterolateral System

Synonyms

ALS; Spinothalamic tract

Definition

One of two ascending pathways in the spinal cord that carry conscious sensory information from the upper and lower extremities, trunk, and posterior portion of the head to the brain (the other being the lemniscal system).

Current Knowledge

Of the two ascending somatosensory pathways (the other being the posterior columns or lemniscal system) the anterolateral system (ALS) is the more primitive and polysynaptic and is primarily responsible for the sensations of pain, temperature, and crude (“less well defined”) or simple touch. Input into the ALS is derived from both specialized cutaneous receptors and free nerve endings in the skin. These sensory impulses then travel centrally (toward the cord) in the peripheral nerves. Just outside the cord, the peripheral nerves bifurcate into the dorsal and ventral nerve roots. The dorsal roots, which carry sensory information, then synapse in the gray matter of the cord (dorsal horns) on the same side in...