The 'caffeine crash' occurs when accumulated adenosine signals sleepiness after caffeine is metabolized.

“Unfortunate things happen. And that's what we call the caffeine crash. Which is caffeine has a half life and it's metabolized and.”

“its ability to offset the sleepiness system, if you will, this adenosine system, and to control our schedules in that way to essentially take a withdrawal against the bank that is adenosine and then pay that back later in the form of getting sleepy later as opposed to when we want to be alert”

“the the adenosine is still building up and then at some point the caffeine wors off and therefore not only do you go back to the same level of Denine of adenosine that you did 2 hours ago it's that plus the additional 2 hours of adenosine that has been building up and what you experience is something called a caffeine crash”

“And this is why when that caffeine wears off, adenosine will bind to that receptor sometimes with even greater what we call affinity. And you feel the crash, you feel especially tired.”