system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If Caffeine just blocks adenosine in the brain from making you feel sleepy, how is it a stimulant for the central nervous system?
gpt
well caffeine antagonises the adenosine receptors. Adenosine being a neurotransmitter that in increased quantities when you get fatigued over the course of a day. By stopping the action of adenosine you essentially prevent its depressive action thus creating a stimulating effect.