system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If caffeine works by blocking the receptors that make you feel tired, why does too much caffeine cause you to feel "wired"?

Shouldn't you just max out at feeling perfectly alert/rested?
gpt
Because caffeine has multiple effects on multiple systems. Blocking tiredness is just one of them. It is also a central nervous system stimulant that raises heart rate etc. It's this effect that can take you to being "wired" above your baseline alertness level.