What is Sleep: Definition and 163 Discussions

Sleep is a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and inhibition of nearly all voluntary muscles during rapid eye movement (REM) sleep, and reduced interactions with surroundings. It is distinguished from wakefulness by a decreased ability to react to stimuli, but more reactive than a coma or disorders of consciousness, with sleep displaying different, active brain patterns.
Sleep occurs in repeating periods, in which the body alternates between two distinct modes: REM sleep and non-REM sleep. Although REM stands for "rapid eye movement", this mode of sleep has many other aspects, including virtual paralysis of the body. A well-known feature of sleep is the dream, an experience typically recounted in narrative form, which resembles waking life while in progress, but which usually can later be distinguished as fantasy. During sleep, most of the body's systems are in an anabolic state, helping to restore the immune, nervous, skeletal, and muscular systems; these are vital processes that maintain mood, memory, and cognitive function, and play a large role in the function of the endocrine and immune systems. The internal circadian clock promotes sleep daily at night. The diverse purposes and mechanisms of sleep are the subject of substantial ongoing research. Sleep is a highly conserved behavior across animal evolution.Humans may suffer from various sleep disorders, including dyssomnias such as insomnia, hypersomnia, narcolepsy, and sleep apnea; parasomnias such as sleepwalking and rapid eye movement sleep behavior disorder; bruxism; and circadian rhythm sleep disorders. The use of artificial light has substantially altered humanity's sleep patterns.

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  1. J

    Medical Can't sleep, thinking too much.

    Wondering if anyone could enlighten me as to why I can lay in bed in hours, trying unsuccessfully to sleep, while my brain is going on a roller coaster of thoughts. It doesn't happen every night, but it is frustrating since I never remember what I was thinking about in the morning.
  2. H

    Medical How does the body know how much to sleep?

    My question is suppose we go to sleep without setting an alarm and intending to get up only when we wake up. How does the body know that it needs X hours of sleep at night. Is our subconsciousness monitoring our stress levels and when it has determined that our stress level is sufficiently low...
  3. R

    Medical Why Do We Sleep? Exploring the Science and Theories Behind Our Need for Rest

    What is you best guess or has science already solved it?
  4. N

    Why Isn't My Computer's Sleep Mode Working Properly?

    Ok, so a few mos ago some you computer whizzes said low power or sleep was ok way to leave my computer at night ... Those buttons worked as prescribed, got a yellow lamp atop my tower... Then after a few mos the white color lamp atop the tower remained on...still does, does not change to...
  5. B

    How can I stop my chronic sleep deprivation?

    Hi guys I am having a tough time fighting what I think is chronic sleep deprivation. It is 2:39am as I write this, and I cannot fall myself to sleep, and yet when I am in school, or reading on the weekend afternoons, I will have hell trying to keep myself awake. My eating pattern is unusual, I...
  6. Evo

    Mayim Bialik's Son May Sleep in Her Bed Until He's 7 Years Old

    Sorry, An eight year old boy still breastfeeding? A 12 year old sleeping with their parents? While they're having sex? http://www.andersoncooper.com/2012/05/21/photos-inside-time-magazines-are-you-mom-enough-issue/...
  7. T

    Medical Detecting Early Signs of Sleep: What to Look For?

    Hi PF, I need some help. I'm studying to be an electrical engineer and I'm trying to make a cheap, non-invasive device that can detect when a person is starting to fall asleep. The device should be able to work on any person and perform a task before they can fall asleep. *Can anyone tell me...
  8. R

    Burst Sleep Mode in Embedded C: Cooling & Interrupts

    Hi, I am correcting a Embedded C code which requires Burst sleep mode. This sleep period is purely depend on the user input cool time and this is really to coll the machine. I thought of using Sleep function for this user input time but is it able to respond to other interrupts in this...
  9. R

    Managing Continuous Operation of Flame Machine with Sleep Function

    Hi, I am correcting a C code which was written for a flame machine. My desire is to give a burst cool time when the machine working continuously. In deep, user could have the facility to enter the flame time and cool time before a continuous operation. So, i exactly want to off the...
  10. E

    I want to sleep with my Professor

    Shes really hot is it ok? I know its unethical for professors to pursue students but what if i pursue her? Anybody else have this problem?
  11. N

    RAM and sleep: how do they work?

    I have two questions with which I'd appreciate some help: (1) What are the pros and cons of leaving my home PC in SLEEP mode instead of "SHUT DOWN" (shut off)... I tend to leavge it in sleep mode for portions of the day and wonder if I should bother shutting it off for the night. (2) I...
  12. F

    Getting enough sleep everyday or practicing every day?

    Just assume, for the sake of argument that staying on top of your ordinary responsibilities consumes most of your entire day, e.g. you rarely have breaks or time to yourself. I think many of us have been there before. You notice your grades are slipping and you want to improve them. You...
  13. T

    Why Are Rails and Pull Down Resistors Essential in Digital Circuits?

    Homework Statement 8. Describe why rails are used in building a digital logic circuit. 9. Describe why a pull down resistor is needed for a switch in a digital circuit. Homework Equations 8. I've found nothing on rails. 9. A resistor with one end connected to a LOW voltage level...
  14. W

    Any Tips for a Restless Night's Sleep?

    A good nights sleep is something I always look forward to. It really is the best part of the day. Alas, tonight I have not slept so well. And, I will have to plough through the day. Any good remedies for a bad nights sleep?
  15. A

    How do you get yourslef to sleep easily even thought u are awake

    some times I am kept awake till like 1am, oops sry spelling error.
  16. E

    Attempting a polyphasic sleep pattern

    Polywhatawhosea? Polyphasic sleeping is when u break up your sleep into smaller sections throughout the day. You condition your body to naturally hit REM sleep right when u fall asleep so you get the restorative qualities of REM sleep yet you sleep only a fraction of what you would with one core...
  17. T

    How Do rand, srand, and sleep Functions Work in C Programming?

    in C how can one use rand,srand and sleep functions... also what type of random numbers are generated by rand & srand.? thanks
  18. C

    Medical Do you dream constantly? Does dreamless sleep even exist?

    Do you dream constantly? Does "dreamless sleep" even exist? We know that... We can dream in all 5 stages of sleep (not just REM) We move around very often throughout the night (all in nREM since you're paralyzed in REM) Memories are sorted out constantly in all stages of sleep. And if you...
  19. W

    Medical Uberman Sleep Schedule: Myth or Reality?

    I wasn't quite sure whether to put this here or is skepticism and debunking. Anyway here goes. I was reading the other day about this different way of sleeping that allows one to sleep just two hours a day. It is called the Uberman sleep schedule. Basically, one sleeps every 3-4 hours for 20-30...
  20. S

    Medical What are the Effects and Timeline of Sleep Deprivation?

    As I was lying awake staring at the ceiling last night, I wondered what the effects of sleep deprivation were. Would you experience decreased coordination, memory loss, ect? A timeline would be useful, i.e. Day 1-lalalalala, like that. I have heard that the CIA once used sleep deprivation as a...
  21. R

    The Mystery of Sleep: Exploring the Purpose and Importance of Rest

    One of biology biggest mysteries is why do we sleep. In spite of decades of research. Scientists still haven't figured out the secret of sleep. If you are aware of the arguments and research. You would know that anabolism can occur even while being still... so why do living things have to...
  22. R

    Medical Sleep, How little is too little

    I was just wondering how much sleep you actually need to stay alive and healthy. I sleep very little, 6 hours on a good and normally more like 4 hours. The thing is however I feel totally fine and no matter what I do I can't sleep any more, I was talking to my cousin about this and he says...
  23. C

    Medical Unconscious Memory during Sleep: Is Everything Remembered When You Wake Up?

    OK so people told me that you are partly conscious/on a low level of consciousness when you sleep. They also told me that you perceive everything around you when you sleep, but don't think about it. Now, when you sleep your memory doesn't work on as high of a level as when you're awake. If it...
  24. T

    How much sleep do you need in school?

    Hi all, just out of curiosity, how much sleep did you get in school (high school, college etc.)? I'm a high school student from Singapore, and I average under 6 hours of sleep per day. But in my school, I get more sleep than probably about 80% of the student population. I know some who get...
  25. A

    Medical The Science of Sleep: Understanding What Happens When We Drift Off

    OK I have a few questions about sleep. What do you feel when you sleep? I read somewhere that being asleep is different from being dead or under anaesthesia so what do you feel? Like do you perceive passage of time or something. I read somewhere that you do and it sort of makes sense since when...
  26. A

    Subliminal Learning While You Sleep & Other Inventive Learning Methods

    Hi, I'm Andrew, a 2nd year Physics undergrad studying for my end of year exams. Currently I'm looking into new, perhaps unconventional ways of learning. I have used conventional techniques to date, just reading, writing and doing problems to learn, and I have done quite well in all of my exams...
  27. A

    Question about sleep and consciousness

    OK, if you=consciousness and consciousness=awareness does it mean you die when you sleep since you're not aware? And when you wake up it isn't you because it's a new awareness? Also since there are tiny temporal gaps between when you receive brain waves does it mean that you die many times in...
  28. D

    Do we swallow insects and spiders in our sleep?

    Is it true that we swallow insects and spiders when we're sleeping?
  29. L

    The more you sleep, the more you feel tired?

    I am an ordinary high school studnet and I sleep about ten hours a day while many of my friends in my home country sleep about three-four hours a day. It looks like I sleep more than the average, where I have heard that an abverage person sleeps 8 hours a day, but I always feel tired. Also, I...
  30. C

    Medical I heard there is a disease where you don't sleep

    Does anyone know what I'm talking about? I heard some people have a disorder where they can never go to sleep even if they try. I think I heard it can happen after some trauma. My question is, how do I catch this disease?
  31. wolram

    How Long Can You Go Without Sleep?

    Due to my illness i have not slept for 72 hours, i have had some cat naps of 10 mins or so, my question is how long could a body keep this up.
  32. K

    Medical Sleep Paralysis: My Terrifying Experience

    Has anyone had sleep paralysis before? I experienced my first instance of sleep paralysis last night and it's extremely odd. My eyes were completely open and I heard the voice of my brother, and the noise of my other brother running downstairs, this was all accompanied by zippers opening and...
  33. Z

    How to function with sleep deprivation

    Hello PFers, My exams are approaching and I need to put in more studyhours. I can't getup without having a sound sleep of atleast 8 hours. I tried many things - kept the alarm far away so that I have to walk a few steps to turn it off, put the A.C. on a timer etc but failed. I don't care if...
  34. O

    Polyphasic Sleep (Uberman) to boost GPA

    Hey guys, Description of Sleep Schedule I'm not sure if you have heard of the "Uberman sleep schedule" before but it consists of sleeping in 30 minute nap periods every 4 hours so that you can stay up consistently 24/7. I'm not sure if there are long-term detrimental effects but I am...
  35. Simfish

    What do professors feel about students who sleep overnight in their department?

    It's a pretty common topic at phdcomics. :p But anyways, what do they feel about them? Do they consider it a positive thing or a negative thing? Certain administrators HATE this (well, certain people who hate "weird" people would hate this, or I guess, people who are obsessed with keeping their...
  36. Dembadon

    What is the quickest way to format and copy a quote in a programming language?

    ...so forgive the stupid game: What would be the most efficient way to reproduce the following without using keyboard shortcuts for formatting, or any variant of a quote + copy-paste method? Do you know how long this took?
  37. S

    Medical Only 5-6.5 hours of sleep is ideal?

    I knew that this amount of sleep (or less) seemed to work for some people. However the general view was that most people needed 7-8 hours of quality sleep for good health. This follow up study in women seems to refute this. The researchers followed over 400 women over 14 years with minimal loss...
  38. jtbell

    Not going to get much sleep tonight

    My wife, who teaches German at the same college where I teach, organized an excursion for dinner tonight at a German restaurant in another town about a 45-minute drive away, including about 15 students and some faculty and staff. We all drove down there in several cars. After dinner, a...
  39. J

    Do animals' also become unconscious during their sleep like humans?

    Hi I'm not a biology or science student. So, please keep your replies in plain and straight language so you could be understood. Thanks. Do animals and birds also become unconscious during their deep sleep like humans? Among humans the extent to which one is absorbed in one's sleep varies...
  40. N

    Medical Does Sleeping in Total Darkness Aid in Detoxification?

    I remember hearing somewhere that the body undergoes a series of detoxification phases as you sleep. The body can only perform this process when you are asleep so getting 7-9 hours of sleep is not enough; it's when you get the sleep that's also important. However, I tried using Google to...
  41. G

    Where do lymphocytes sleep, and other naive questions

    Ok, I will never post another biology question to yahoo answers. I'm watching Carl Sagan's Cosmos for the billionth and billionth time, and suddenly something other than stars got my attention: lymphocytes. I watched them destroying bacteria and I wondered: do they just destroy the bacteria...
  42. R

    If sleep were not required, but just optional, would you ever sleep?

    If sleep were not required, but just optional (you didn't get tired), would you ever sleep? I can say that I'd sleep much less often, if ever.
  43. D

    Medical Sleep / REM Sleep and homeostasis

    Physiology texts indicate that an animal deprived of sleep will face homeostasis disturbances, for example they can loose weight despite an increased caloric intake, and they will eventually die. An animal deprived of REM sleep for several sleeping sessions in a row will show increased REM...
  44. L

    Please help me or I may not be able to sleep tonight tonight

    I was just reading this article on the WSJ online entitled "Man vs. God". Well surprise, surprise I'm a Christian and happen to understand enough about physics to be a computer Engineering major. My question is, is there proof of the non-existence of "God". i.e is it right to say there is no...
  45. P

    Sleep and Academic Success: How Many Hours Do You Really Need?

    I was curious to see the sleeping patterns of some the intelligent people here at PF. I get 5-6 hrs per night on average. Considering the consensus of a "good night's rest" is 8 hrs, I am worried that my 6 hrs a night might be negatively influencing my studies. What is your sleeping average...
  46. R

    Medical Delayed Sleep Phase Syndrome - Will Power, or better see a specialist?

    I slept at 5:30 p.m. today, woke up at 12 midnight because I slept 1.5 hours yesterday night. I think the only reason why I slept for 6 hours is the melatonin. I took another dose of it at 1 p.m. but I'm still here typing at 2:30 a.m. so chances are I won't feel sleepy until 10:00 a.m. AND...
  47. W

    Medical Reading in Sleep: Exploring the Mysterious Phenomenon

    Sometimes, usually early in the morning when I'm half awake/half asleep I dream of reading out of a book. The words appear very clearly and the image remains fixed, and I read from left to right, just like with a real book. Sometimes the words do not exist, it's gibberish, sometimes its fully in...
  48. R

    Medical I thought it was 2 weeks to get adjusted to less sleep?

    I've been trying to get used to 5 to 8 hours of sleep, 6.5 hours per day on average for a month now. There are still some days where I just want to sleep in, and if I do sleep in I'll oversleep for 12 hours. Here is the thing, I can easily run on less than 7 hours of sleep, but when I wake up I...
  49. L

    Why Do Animals Sleep? Research & Advances

    I've always been curious about the answer to this question. Can anyone point me to some research regarding this subject matter? Have we made any advances on finding out the answer to this question? I am assuming that it would be pretty inefficient, and toiling on the body and brain to be active...
  50. Greg Bernhardt

    Do Sleep Machines Emit Delta Waves?

    Anyone use sleep machines? My father is asking one for xmas. Are they really just cd players or is there more to it? For example this Brookstone one I am looking at has claims of delta wave technology. Is that bunk?
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