I don't understand sleep.

Before, I naively thought it was related to some kind of 'energy' or 'wakefulness' resource that gets depleted as time goes by without rest.

But that's not it, higher activity levels don't make you sleep sooner, they might make you more fatigued and it might correlate with sooner sleep onset but the relation is not 1:1, more activity doesn't equate to earlier sleep, in fact many times it might do the oposite.

Even plants follow some regular pattern of higher and lower activity levels, but seems more related to the environment and resources available.

Maybe we sleep because of the day-night cycle? we adapted to live in daylight, so by specializing we focus our biological resources, and during the night what we do is sleep to limit the consumption of those resources (metabolic rate slows down during sleep) because doing anything else is not useful, we are not adapted for being nocturnal.

So basically sleep is like some kind of instinctual behavior, sleep is induced by the body, the body actively makes us sleep. But then, why do perform so poorly if we don't sleep? a consequence of our adaptations to that day-night pattern? If sleep is only an induced physiological behavior, Why if we stay awake a lot we risk our health? is this dependence on sleep an accident then?

My question is this. If we consider sleep as a behavior actively induced by the body, akin to an instinct, rather than the depletion of a physiological resource (I think this is true), why does insufficient sleep result in adverse health effects, such as those observed in conditions like fatal familial insomnia?

  • $\begingroup$ Stack Exchange is for specific questions and specific answers; can you narrow your post to one specific question about sleep? $\endgroup$
    – Bryan Krause
    Commented Feb 10 at 17:11
  • $\begingroup$ Why are the two options "depletion of a resource" and "learned behavior"? Clearly sleep is not learned. $\endgroup$
    – Bryan Krause
    Commented Feb 10 at 17:33
  • $\begingroup$ Yes, I imagined someone might misunderstand that part. I never said sleep is learned, but seems similar, like an instinct, but probably doesn't fit the definition. I think the question is if a biological system requires intrinsically periods of less activity (not only regular sleep) to maintain proper functioning indefinitely. We have the confounding factor of the sun periodic effects, which caused even fruit flies to have an internal 24h clock, and this relates to the existence of sleep. If life evolved in a place with no periodic effects and constant resources, would sleep exist? $\endgroup$
    – gabriel
    Commented Feb 10 at 19:05
  • $\begingroup$ "Learned" and "instinct" are opposites, so yes it's quite weird to use one to describe the other. $\endgroup$
    – Bryan Krause
    Commented Feb 10 at 19:15
  • 1
    $\begingroup$ Do existing Q&A like biology.stackexchange.com/questions/324/… answer your question? If not, can you clarify why not and what your specific question is? $\endgroup$
    – Bryan Krause
    Commented Feb 10 at 20:45


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