I have a sneaking suspicion that would be like pumping oxygen directly into the blood and then trying to hold your breath - even though you technically don't need to breathe, millions of years of evolutionary tricks will make sure you do. Try telling your brain that it does not need to sleep after 72 hours just because you have cleared up the toxins
Actually, this would work. But O2 isn't the problem, the CO2 is. You'll need a process to filter the CO2 out of your blood, as that's what causes your body's breathing reflex to occur. If you could filter the CO2 from the blood stream, while also providing O2, you would literally not need to breath.
"like pumping oxygen directly into the blood and then trying to hold your breath - even though you technically don't need to breathe"
It's not that simple. You need to get gases in and OUT. You also need more than O2. You need to clear CO2 as well as lactic acid and other biproducts. Some CO in the mix greatly assists exchange. Simply bubbling 02 into your blood is going to kill you with a blood clot. And, RBC's actually curl up into a cylinder shape in your pulmonary capillaries to maximize gas transfer, unlike when they're flying around your circulatory system. Pick up a physio textbook, they're a fun read.
Probably not. If a lot of energy is being used in the clean up process, then the need for sleep is most likely driven by the physical advantages of sleep, not the advantage of using less energy or similar.
Note this quote: "Cells in the brain, probably the glial cells which keep nerve cells alive, shrink during sleep. This increases the size of the interstitial space, the gaps between brain tissue, allowing more fluid to be pumped in and wash the toxins away."
Neurons are powerful cells that are so active that they cannot even keep themselves healthy. The glial cells are there to help. If the glial cells are shrinking and (presumably) partially shutting down in order to efficiently clean out the brain, then sleep is an efficient engineering solution -- you are trading off having a super-active brain for ~16 hours at the cost of a less effective brain for ~8 hours.
There may be less efficient solutions that allow for 24 hours semi-wakefulness, we might be able to tune the total activity of the brain down for continuous operation, but being in a groggy half-asleep state all day is probably not what you were hoping for.
It's an interesting choice from an evolutionary standpoint: At the time homo sapiens evolved, we presumably had saber-tooth tigers, tyrannosaurus rexes, abonimable snowmen (or whatever :) prowling the bushes around the place we slept.
If you were all alone, wouldn't it be a better survival trait to be groggy 24h/day than to be fully alert 16h/day and dead to the world the remaining 8h?
I've heard that there are species of fish (and possibly birds) that are awake around the clock; they deal by sleeping one brain hemisphere at a time, which leaves enough active brain to avoid obstacles and predators.
If humans never took that evolutionary road, does it mean that we are genetically disposed to social groups, i.e. "someone else is watching your back while you sleep"?
> I've heard that there are species of fish (and possibly birds) that are awake around the clock; they deal by sleeping one brain hemisphere at a time, which leaves enough active brain to avoid obstacles and predators.
Whales are known to do this; I imagine it makes breathing much less difficult.
We'd need some chemical that can cross blood brain barrier, get into the cells and refactor most harmful subtances that build up there. Not an easy task.
