Which tract carries the sensation of pain and temperature?

• A. Spinothalamic tract
• B. Posterior column
• C. Spinothalamic tract and posterior column
• D. Proprioception

Answer: (A)

Pain and temperature travel through the spinothalamic tract, which is part of the anterolateral system. In this pathway, first-order neurons from the skin enter the spinal cord and synapse in the dorsal horn. The second-order neurons then cross to the opposite side of the spinal cord and ascend in the spinothalamic tract to the thalamus, where they relay to the somatosensory cortex via third-order neurons. This contralateral ascent explains why a unilateral spinal lesion often causes loss of pain and temperature on the opposite side.

The posterior column, by contrast, carries fine touch, vibration, and proprioception, not pain or temperature, so it does not convey these sensations. Proprioception is specifically linked to the dorsal columns and related pathways, not to pain and temperature. While other pathways exist for pain signals reaching brainstem and other areas, the principal tract encoding conscious pain and temperature is the spinothalamic tract.