Spinothalamic tract
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The spinothalamic tract is the sensory pathway in the body that transmits pain, temperature, itch and crude touch. These types of sensation cross over to the other side of the body at the spinal cord, not in the brainstem like the posterior column-medial lemniscus pathway and corticospinal tract.
The name spinothalamic tells us sensation runs up the spinal cord to the thalamus, this is true but misleading, as all sensory pathways synapse at the thalamus.
There are two main parts of the spinothalamic tract (STT). The lateral spinothalamic tract transmits pain and temperature, the anterior (or ventral in animals) spinothalamic tract transmits touch.
The types of sensory information trasmitted via the STT are described as affective sensation. This means that the sensation is accompanied by a compulsion to act. For instance an itch is accompanied by a need to scratch, and a painful stimulus makes us want to withdraw from the pain.
Path of sensation
Unipolar neurons (those with only one long process) in the dorsal root ganglion have axons that lead from the skin, into the dorsal spinal cord where they synapse with secondary neurons in the marginal nucleus. These secondary neurons are called tract cells.
The axons of the tract cells cross over to the other side of the spinal cord via the white commissure, and to the ventrolateral corner of the spinal cord. The axons travel up the length of the spinal cord into the brainstem.
Travelling up the brainstem, the tract moves dorsally, as the neurons ultimately synapse with the thalamus.