Eli5: Why do we need to sleep so much, what happens in the body when asleep that cannot happen while normal resting or relaxing? Or is it just for the brain?
In: Biology
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The truth is nobody knows. The most common hypothesis is that that time is used by your brain to “tidy up” , to process experiences, learned things, thoughts, etc.
Like a lot of others mentioned, while you sleep your body goes into recovery mode. Specifically, a lot of toxins that are created as a byproduct during the day are removed. However, it’s more than just that. Sleep is also heavily involved in memory consolidation. During sleep, your brain decides which memories to store for the long term and filters out “useless memories.” Additionally, a lot of different hormones are released while you are sleeping which for some reason the body doesn’t release while awake. I think there’s a growth factor hormone or something but I don’t remember the details.
There are a lot of different functions that occur while you sleep and we are just figuring them out. But I would say the main functions are clearing waste and consolidating memories.
This isn’t very ELI5, but during a normal sleep cycle, our brain shrinks, allowing for the cerebrospinal fluid in the brain to be “flushed” and we get new csf. People that don’t get enough sleep, really do have a “cloudy” brain. This is called the glymphatic system and there’s a red talk about it. We also have time for muscles and everything to repair
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Consolidation of memories, learnings and brain chemical reset.
This cannot happen live so has to go online, like any server during maintenance.
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We simply do not know. We do know what happens when you don’t sleep though. Moodiness, fatigue, weaker willpower, lack of concentration, hallucinations and even death. Thus most hypothesises are based on what gets affected when you don’t sleep.
Not an expert, but here are some things I haven’t seen mentioned:
a) our brains are big, relative to our body, more than most mammals.
b) we have evolved to not need shorter sleep. Most animals are light sleepers because of their environment. Most commonly, most wild animals are light sleepers and sleep in smaller intervals because they remain alert for predators. There are less common sleep patterns like dolphins, who need to stay awake to go up for air so they sleep one half of their brain at a time.
c) ultimately, we don’t know and the field of sleep is still a huge mystery.
Most other people have gone into memories and brain cleaning stuff, so I’ll ignore that.
Sleep is when repair happens. Nicks and cuts in your skin are repaired, damaged muscles are rebuilt. Your body also converts vitamin D into seratonin and the seratonin into testosterone during sleep. These chemicals are used for a lot of daily function and a lack of them is linked to things like depression.
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