Second-order neurons leaving lamina I or lamina V cross to which tract?

Second-order neurons leaving lamina I or lamina V cross to which tract?

• A. Anterior corticospinal tract
• B. Ipsilateral dorsal column
• C. Contralateral lateral spinothalamic tract
• D. Ipsilateral spinothalamic tract

Answer: (C)

Second-order neurons in lamina I and lamina V of the dorsal horn receive nociceptive input and cross to the opposite side of the spinal cord, then ascend in the contralateral spinothalamic tract (the lateral spinothalamic tract) to the thalamus and onward to the cortex. This crossing at the level of the anterior white commissure explains why pain and temperature are felt on the opposite side of the body. The dorsal column pathway, by contrast, carries fine touch and proprioception and remains ipsilateral until it crosses higher up in the brainstem, not in the spinal cord. The anterior corticospinal tract is a motor pathway and not part of the pain transmission route.

Second-order neurons in lamina I and lamina V of the dorsal horn receive nociceptive input and cross to the opposite side of the spinal cord, then ascend in the contralateral spinothalamic tract (the lateral spinothalamic tract) to the thalamus and onward to the cortex. This crossing at the level of the anterior white commissure explains why pain and temperature are felt on the opposite side of the body. The dorsal column pathway, by contrast, carries fine touch and proprioception and remains ipsilateral until it crosses higher up in the brainstem, not in the spinal cord. The anterior corticospinal tract is a motor pathway and not part of the pain transmission route.