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Mystery of sleep

  1. Sep 22, 2016 #1
    Why we sleep is said to be one of the greatest unsolved mysteries of science. Haven't they cracked it yet? is there any animal or even living system that doesn't sleep?
     
  2. jcsd
  3. Sep 22, 2016 #2

    Drakkith

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    Despite extensive research, we aren't entirely sure on all the functions of sleep nor on why sleep is necessary for these functions. The brain is an incredibly complex biological system, even in creatures as simple as insects. Add to that all the different ways the brain interacts with the body and the difficulty of probing things at the microscopic scale and you quickly run into enormous hurdles. Simply figuring out how a single cell works has taken decades and decades of research, and we still don't know all the details. How do you observe all the different chemical and physical changes going on in a cell without killing it? How do you observe the interactions of neurons with other neurons without being able to directly observe the propagation every electrical impulse and chemical change throughout the entire network of neurons? And then you have to take into account the fact that there are multiple neurotransmitters, hormones, inhibitory signals, excitation signals, and countless other things all happening at the same time. And you can't simply dissect a creature to figure these things out, as a dead brain does none of the above, so you have very little to observe.

    Not sure. Try this article: https://en.wikipedia.org/wiki/Sleep_(non-human)
     
  4. Sep 22, 2016 #3
    Even the tiny 1mm C. elegans sleeps...

    http://www.med.upenn.edu/apps/faculty/index.php/g306/c424/p13610

    I assume the C. elegans has a brain. Are their living systems without any brains.. do they also sleep?
     
  5. Sep 22, 2016 #4

    Drakkith

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    There are certainly organisms without brains, but these are typically unicellular organisms. I don't know if they can sleep or not. The concept of sleep gets a little fuzzy at this level. If a bacterium goes dormant, is it sleeping?
     
  6. Sep 22, 2016 #5

    Ygggdrasil

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    Brains are specific to animals, but not all animals have brains. Jellyfish, for example, lack brains (though they do have nervous systems), and jellyfish have been reported to sleep (http://www.abc.net.au/news/2004-12-16/sleeping-habits-of-deadly-jellyfish-revealed/603852).

    Plants and fungi are examples of multicellular organisms lacking a brain and nervous system. However, these organisms operate on circadian rhythms and their physiology changes between day and night (this is especially true for plant due to photosynthesis). Even unicellular photosynthetic organisms show circadian behaviors. Should we count these circadian behaviors as "sleep" even though they likely serve very different purposes?
     
    Last edited: Sep 22, 2016
  7. Sep 22, 2016 #6

    jim mcnamara

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    Single-celled organisms like Euglena have diurnal cycles - periods of the 24 hour day when they are active and periods of inactivity. Planktonic oragnisms rise and sink in the oceans similarly, in a daily rhythm.

    Sleep for humans is part of the same thing - a response to an environmental cyclic period. A lot of modern humans have altered night into day with artificial light, so our sleep habits are not like our ancestors. Sleep is a safe way to avoid periods of the daily light/dark cycle where humans are at a disadvantage.

    A possible explanation of why humans sleep at night:
    A long time ago, some investigators used a sound recording in an experiment. The recording was lions and hyenas fighting over a kill. (I think) It was part of a soundtrack for a National Geographic film. Anyway, they played the sounds to volunteers under different circumstances, mostly different light levels. In complete darkness the response of the volunteers was universally extreme unease. Why? - because on a dark night humans out in the open are/were completely helpless against large predators. We are apparently hardwired that way. So humans on the savanahs slept during times of the day when we were easy prey - up in trees. We do not have the kind of night vision large cats have, for example. Now we worry about street gangs and muggers....

    And no, I am not going to try to find the reference for this one. I am not even sure where to start. Someone else may know.

    Circadian is a synonym for diurnal. See the drawing at the start of this: https://en.wikipedia.org/wiki/Circadian_rhythm
     
  8. Sep 22, 2016 #7
    Have we fully mastered the cell.. or understood each of the function down to microdetails? Maybe cells themselves need rest? But then heart cells continue to beat without rest (is this true).. so can't we say sleep benefit each individual cell?
     
  9. Sep 22, 2016 #8

    jim mcnamara

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    Your definition of sleep and mine are not the same. Human sleep is a functional change in brain activity, like most mammals. Single cells do not have brains, and do not sleep. What you are doing is ascribing characteristics to something that is not fit to have those characteristics. It is a kind of logical fallacy that we use in telling stories. Why? Can you see?
    Look up anthropomorphism:
    https://en.wikipedia.org/wiki/Anthropomorphism

    If you want to think that way, do so. Just don't believe everything you think.

    An example: automobiles have a personality. Personality applies primarily to humans. Cars are inanimate.
     
  10. Sep 22, 2016 #9

    Drakkith

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    Nope. Though we do know a great deal about how a cell functions.

    That depends on what you mean by "rest". Cells may enter periods of reduced activity, but it would be hard to call this "sleep".

    Again, this depends on what you mean by "sleep" and "rest". Sleep is rarely talked about when studying the behavior of unicellular organisms, even in ones that go dormant for long periods of time. Heart cells rest between each beat, but what does rest mean in this context? It means that they are recovering from the previous contraction, building up ATP and doing other cellular functions while waiting for the next action potential from the sinoatrial node to cause it to contract. So even at rest the cell is still performing many cellular functions. The same is true for essentially every cell in your body. They only differ in that the exact processes going on inside them can be different.

    I really wouldn't use the term "sleep" when discussing anything without at least a basic nervous system.
     
  11. Sep 22, 2016 #10
    The most accessible or significant are the rats experiment in which they died within 2 weeks when they lack sleep. Has any others replicated this?

    I saw this in the shared page above https://en.wikipedia.org/wiki/Sleep_(non-human)
    1. Jump up ^ Guidelines for the Care and Use of Mammals in Neuroscience and Behavioral Research. Institute for Laboratory Animal Research (ILAR), National Research Council. The National Academies Press. 2003. p. 121. ISBN 978-0-309-08903-6. Sleep deprivation of over 7 days with the disk-over-water system results in the development of ulcerative skin lesions, hyperphagia, loss of body mass, hypothermia, and eventually septicemia and death in rats (Everson, 1995; Rechtschaffen et al., 1983).
     
  12. Sep 22, 2016 #11

    Fervent Freyja

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    True. A good article on the topic and loaded with citations:
    Yes, many people have died trying to go without sleep, a world record holder went 11 days without sleeping: https://en.wikipedia.org/wiki/Randy_Gardner_(record_holder)
     
  13. Sep 23, 2016 #12
    Could sleeping occur because the earth has night and day cycle and somehow evolution integrate this into the system? Can this be refuted? In a planet with two suns where there is no night. Perhaps there is no need for sleep?

    The Jellyfish has no nervous system and no brain yet it still sleeps. What would happen if it didn't sleep. Can't we design living system that doesn't require sleep? If you replace all the neurons or cells with corresponding electronic circuitry.. would there still be the requirement of sleep?
     
  14. Sep 23, 2016 #13

    Evo

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    You only have to look at our own world.
    https://en.wikipedia.org/wiki/Midnight_sun
     
  15. Sep 24, 2016 #14

    jim mcnamara

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    Please provide a reference for:
    Thanks.
     
  16. Sep 24, 2016 #15
    I read it in message #5 that jellyfish has no brain yet sleep.. but I think I read it wrong that they didn't have nervous system. Googling states they do.

    http://neurodojo.blogspot.com/2009/05/jellyfish-nervous-system-myth-busted.html

    "It is not true that jellyfish have no central nervous systems. They have an unusual nervous system, because jellyfish are not bilaterally symmetrical – that is, they don’t have a left side and a right side. So while most invertebrates have a chain of ganglia lying down the middle of the body, with one very large one at the front end (the brain), jellyfish don’t.

    Instead, jellyfish have a ring nervous system, located along the margin of the bell. There is definitely a concentration of neurons in that location (although it contains relatively few neurons compared to other animals). Plus, those neurons do serve as an active relay and processing station for sensory and motor activity. Those are two of the main things that central nervous systems do, so there seems to be no good reason to deny that jellyfish have a central nervous system."

    Does jellyfish have memories?
     
  17. Sep 24, 2016 #16
    The fruit fly or Drosophila melanogaster DNA has been completely sequenced in 2000 and their brain still being mapped.. for example this just in last week https://www.technologyreview.com/s/602398/first-3-d-map-of-a-fruit-flys-brain-network/

    In the following the fruit fly is said to shed some light on mystery of sleep
    http://www.scientificamerican.com/article/fruit-flies-reveal-sleep/
    http://www.nbcnews.com/id/14945525/...y-study-sheds-light-human-sleep/#.V-b9B5D_pjo
    https://www.psychologytoday.com/blo...eep-and-long-term-memory-maybe-s-why-we-sleep

    Sleeping seems to have more to do with memory consolidation and some brain housekeeping. So why is this not accepted as the final answer?

    Also I can't find knock out fruit fly or experiments where they are not made to sleep for days.. do they also die like the rats? What changes in their body if they are prevented from sleeping continuously?
     
  18. Sep 24, 2016 #17

    Fervent Freyja

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    In this case, finding correlations doesn't rule out other possible variables involved or result in a conclusion regarding the total function of sleep. The most it does is allow us to state with certainty that a few more variables are involved with sleep and suggests further experimentation should be done. Also, this is not the only study finding correlations between sleep and memory, there are many more. Memory consolidation is most definitely not the only function or purpose of sleep- many studies have found other processes are involved that are unrelated to memory, but essential for health or survival.
     
  19. Sep 25, 2016 #18
    When I lack sleep. I get colds and upper respiraratory infection more easily. But isn't it that our immune cells travel in the body by Brownian motion.. so what do you think is the effect of lack of sleep on the immune system really? Does it mean the immune cells have to sleep too and they get weaker if they lack sleep?
     
  20. Sep 25, 2016 #19

    Fervent Freyja

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    Lack of sleep is undoubtedly shown to be correlated with lower immune function, for many reasons. However, it doesn't mean that cells are lacking 'sleep'. Brownian motion doesn't describe motion/signaling in cellular processes.
     
  21. Oct 1, 2016 #20

    BillTre

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    I think, if they died, they would die like flies!

    Immune cells move through the circulation. At various places they can leave the circulation and infiltrate into tissues or specific organs. These movements are not random.
     
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