system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does caffeine stop working on the brain/not make people feel awake anymore after adaption but still trigger physical side effects like shaky hands?
gpt
Caffeine works by blocking the detectors that your brain uses to figure out if you are tired.  If they get block too often, your brain decides the detectors are not working and simply grows more until their are more detectors than the caffeine can block.  This means you can still feel tired now, but that doesn't stop anything else the chemical may do.