science museum

Caffeine

When you drink a cup of coffee, the drug it contains - caffeine - takes effect within minutes. It then blocks chemical signals in your brain, stopping you from feeling sleepy. In moderate doses caffeine also improves mental ability - reaction times, memory and reasoning skills. It takes your body 3-5 hours to break down caffeine, which is why coffee at bedtime may stop you sleeping.

The drug caffeine stops you from feeling sleepy.
The drug caffeine stops you from feeling sleepy.
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