Why is lying down and resting with your eyes closed but awake not as restful as actually sleeping?
In: 1
Sleeping is about more than just resting your body. It’s more about resting and “cleaning” your brain.
If we only needed to recover physically, then we probably would have never evolved to sleep. Why spend hours being unconscious when this renders you (almost entirely) unable to detect and respond to predators and other dangers? For physical recovery, it would be enough to just lie still and maybe lower your metabolism a bit, while remaining aware of your surroundings.
So, the fact that we go unconscious *must* have to do something with the brain needing to be “powered off”, or at least in a much less active state. It’s a bit like how you sometimes have to reboot your computer in order to install an update. There are certain things that are hard (or impossible) to do while the machine is in operation.
One leading theory right now is that the brain produces chemical waste products while awake that can only be properly cleaned up in sleep mode. An analogy that is often used is that you can’t clean your house (or at least not very well) while you’re hosting a party. You have to wait until the guests have left to really clean properly. In addition, we also know that sleep plays an important role in learning and the storage of memories, suggesting that perhaps the “rewiring” of the connections between brain cells (i.e. forming new *synapses*, getting rid of existing ones, or merely altering their efficacies) that is required for both of these things is something that primarily happens during sleep.
One thing that is certain is that there is a chemical called *adenosine* that slowly builds up in your brain while you are awake, and this is the chemical that makes you feel sleepy. This chemical is only cleared up during sleep, so if you don’t sleep (or not enough) then the remaining adenosine will keep you feeling tired. (As an aside, the way caffeine makes you feel less tired is that it blocks the sleepy-making effect of adenosine, without actually getting rid of the adenosine itself. Once the caffeine has run its course, you feel the full brunt of the built-up adenosine again.)
However, I’m not sure (and perhaps we simply don’t know yet) whether adenosine builds up anyway as a result of some other brain process, and is only co-opted by the brain as a way to monitor when it is time to go to sleep (a bit like if you used the number of empty beer bottles as a measure of when to send your guests away because it’s time to clean the house), or if adenosine actually has no other function and is deliberately produced only as a way to keep track of how long you’ve been awake (like if you drew a tally mark on your hand for every ten minutes that your party went on).
Latest Answers