Pain signals from A-delta and C-fibers travel to specific areas of the brain, influencing the experience of pain. The reticular formation in the brain stem plays a crucial role in processing these signals and affects functions like sleep-wake cycles and circadian rhythm. When C-fibers are stimulated, they arouse the central nervous system, making it challenging to fall back asleep after experiencing pain, as they signal the brain to stay awake due to the perceived pain.