Which tract transmits pain and temperature sensations?

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

Answer: (B)

Pain and temperature signals travel in the spinothalamic tract, part of the anterolateral system. After entering the spinal cord, these fibers synapse in the dorsal horn and cross to the opposite side almost immediately via the ventral white commissure. They then ascend contralaterally in the spinothalamic tract to the thalamus and onward to the somatosensory cortex. This early crossing explains why a unilateral lesion often produces contralateral loss of pain and temperature below the lesion level. The posterior column–medial lemniscus pathway handles fine touch, vibration, and proprioception and stays on the ipsilateral side before crossing in the medulla. Proprioception is specifically a dorsal-column function, not pain and temperature. Hence, the tract that transmits pain and temperature sensations is the spinothalamic tract.