One more reason to get a good night’s sleep | Jeff Iliff

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Sleep. It's something we spend about a third of out lives doing, but do any of us really understand what it's all about?

Two thousand years ago, Galen, one of the most prominent medical researchers of the ancient world, proposed that while we're awake, our brain's motive force, its juice, would flow out to all the other parts of the body, animating them but leaving the brain all dried up, and he thought that when we sleep, all this moisture that filled the rest of the body would come rushing back, rehydrating the brain and refreshing the mind.

Now, that sounds completely ridiculous to us now, but Galen was simply trying to explain something about sleep that we all deal with every day. See, we all know based on our own experience that when you sleep, it clears your mind, and when you don't sleep, it leaves your mind murky. But while we know a great deal more about sleep now than when Galen was around, we still haven't understood why it is that sleep, of all of our activities, has this incredible restorative function for the mind. So today I want to tell you about some recent research that may shed new light on this question. We've found that sleep may actually be a kind of elegant design solution to some of the brain's most basic needs, a unique way that the brain meets the high demands and the narrow margins that set it apart from all the other organs of the body. So almost all the biology that we observe can be thought of as a series of problems and their corresponding solutions, and the firs problem that every organ must solve is a continuous supply of nutrients to fuel all those cells of the body. In the brain, that is especially critical; this intense electrical activity uses up a quarter of the body's entire energy supply, even though the brain accounts for only about two percent of the body's mass. So the circulatory system solves the nutrient delivery problem by sending blood vessels to supply nutrients and oxygen to every corner of our body.