The following is an excerpt taken from a post at Lifehacker. The full article can be read
here.
Caffeine Doesn't Actually Get You Wired
Right off the bat, it's worth stating again: the human brain, and caffeine, are nowhere near totally understood and easily explained by modern science. That said, there is a consensus on how a compound found all over nature, caffeine, affects the mind.
Every moment that you're awake, the neurons in your brain are firing away. As those neurons fire, they produce adenosine as a byproduct, but adenosine is far from excrement. Your nervous system is actively monitoring adenosine levels through [Sleepy Parts]. Normally, when adenosine levels reach a certain point in the [sleepy parts of your] brain and spinal cord, your body will start nudging you toward sleep, or at least taking it easy. There are actually a few different [Sleepy Parts] throughout the body, but the one caffeine seems to interact with most directly is the A1 [Sleepy Part]. More on that later.
Enter caffeine. It occurs in all kinds of plants, and chemical relatives of caffeine are found in your own body. But taken in substantial amounts—the semi-standard 100mg that comes from a strong eight-ounce coffee, for instance—it functions as a supremely talented adenosine impersonator. It heads right for the [Sleepy Parts] in your system and, because of its similarities to adenosine, it's accepted by your body as the real thing and gets into the receptors.
