The pathway begins in the posteromarginal nucleus and in the proprius nucleus and has an extensive area of origin in the intermediate gray matter of the spinal cord.
The pathway ends at different levels in formatio reticularis , including the nucleus solitarius (tractus spinosolitarius) and the two parabracialis nuclei (tractus spinoparabrachialis). Here, the pain signals through connections to the circulatory and respiratory centers can reflexively trigger an increase in blood pressure, increased heart rate and faster breathing.
The pain signalling into the formatio reticularis contributes to its ability to activate, "wake up", higher levels in the brain, e.g. the thalamus and limbic system with the amygdala.