adenosine
A natural substance in the brain that helps to regulate sleep and is thought to add to the need for sleep when we stay awake for longer than usual. Caffeine works by blocking the places in the brain where adenosine acts.
Where it comes up
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01
How long does caffeine stay in your system?
How long caffeine stays in your body, why an afternoon coffee keeps some people up, and how it can thin deep sleep even if you fall asleep fine.
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02
Why am I wide awake at bedtime?
Wide awake at bedtime after a long day? Why the body clock pushes alertness in the evening, how naps and caffeine add to it, and what helps tonight.
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03
What makes us feel sleepy?
Why sleepiness builds the longer you're awake, how the body clock puts it off, and why caffeine, naps and sleeping in work the way they do.