Probably a very stupid question but I can’t wrap my head around it. For instance if someone had head trauma, why can they not wake up after a few days or so? What is it that keeps them unconscious for such a duration of time with nothing to wake them?
Edit: i’m confused why this got so many upvotes but thanks😁
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There’s a part of the brain called the “reticular activating system” (RAS), which is located in the brainstem. There are a bunch of connections from it all throughout the rest of the brain. Although this is a simplification, basically this system being turned “on” makes us conscious, and it being turned “off” makes us unconscious. How to define consciousness is really, really hard and almost more philosophy than science, but one way to understand it is to think about whether or not we are able to perceive and react to our environment.
We naturally go through cycles of this system turning on and off as we sleep and wake up. However, if this system gets hurt from a stroke, physical brain damage or swelling, or some kind of toxins causing the nerve cells to not work well, it will make you unconscious–even if most of the rest of the brain is in decent shape! Of course, big damage to the rest of the brain can also cause a coma, but usually it has to be *really* big damage to both the left and right halves of the brain to cause that if the RAS isn’t touched by itself.
A coma that lasts for a long time is usually a pretty bad sign in terms of predicting if someone will recover. Although there are a lot of different factors, if someone is in a coma for more than 3 days their chances of recovery are usually less than 1 in 10. If someone is in a coma for more than 2 weeks, the odds of recovering are more like 1 in 50.
Some people may have enough healing of the rest of their brain so that some basic functions like the sleeping/waking cycle, opening their eyes, and some spontaneous movements start to come back, but they will remain completely not able to respond to anything in their environment and its believed they have no actual consciousness/thought–this is called a “persistent vegetative state.”
The opposite to this is if the connections between the brain and the rest of the body get destroyed but the RAS doesn’t get hurt. This is called a “locked-in” syndrome, and results in being completely conscious but unable to move any part of your body except your eyes.
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