Final answer:
Sensory nerves travel to the thalamus via the spinothalamic tract, which primarily transmits pain and temperature information and decussates at the level of entry, then ascends contralaterally to the brain for processing.
Step-by-step explanation:
How do sensory nerves travel to the thalamus to relay sensory information and allow modulation of sympathetic output? The sensory nerves ascend through the spinothalamic tract to relay this information. The spinothalamic tract and dorsal column-medial lemniscus pathway are two major pathways that bring sensory information to the brain. The spinothalamic pathway primarily conveys pain and temperature and decussates at the level of entry, then ascends contralaterally. In contrast, the dorsal column system, which conveys fine touch, vibration, and proprioceptive information, decussates in the medulla and then ascends. Testing these stimuli can provide information on whether these pathways are functioning properly and help to distinguish which pathway may be damaged in certain conditions.