Why do we sleep?

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  • #26
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If this topic has been exhausted I have a question about why we sleep 7-8 hours. Humans existed for 10s of thousands of years before they controlled fire and the environment is very dark from 1/2 hour after sunset to 1/2 before sunrise. Why isn't our sleep period closer to 11 hours? What did humans do for those 3 hours every night without light?
 
  • #27
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Because we have yet to understand all the processes that occur wrt to the human circadian rhythm. Once we have a good enough understanding of that and of similar animals we will probably be able to formulate solid ideas of how it evolved.

Where did you get "DNA programming" from?

What I meant was it was a a biological organism requirements... and since all organisms are controlled by DNA.. then it was an appropriate term.

Anyway. I read that the smaller an animal is.. such as rats, the longer they sleep.. for example.. rats sleep 15 hours a day while dogs and cats sleep more than 8 hours... while elephants sleep only 4 hours.. I read there a direct correlation between the need for sleeps and size of animals.. something to do with metabolism.. the bigger an animal, the smaller its metabolism... so less sleep.. but what has sleep got to do with mitochondria of the entire organism.. not just the brain? unless for those who believes it benefits the brain only, please explain the above observations like correlations of size of animals and sleeping requirements.
 
  • #28
Drakkith
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If this topic has been exhausted I have a question about why we sleep 7-8 hours. Humans existed for 10s of thousands of years before they controlled fire and the environment is very dark from 1/2 hour after sunset to 1/2 before sunrise. Why isn't our sleep period closer to 11 hours? What did humans do for those 3 hours every night without light?

If I'm not mistaken I think the recommended sleep length is more like 8-9 hours. That would fit more in line with the 13-14 hours per day that you have light.
 
  • #30
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What I meant was it was a a biological organism requirements... and since all organisms are controlled by DNA.. then it was an appropriate term.

Anyway. I read that the smaller an animal is.. such as rats, the longer they sleep.. for example.. rats sleep 15 hours a day while dogs and cats sleep more than 8 hours... while elephants sleep only 4 hours.. I read there a direct correlation between the need for sleeps and size of animals.. something to do with metabolism.. the bigger an animal, the smaller its metabolism... so less sleep.. but what has sleep got to do with mitochondria of the entire organism.. not just the brain? unless for those who believes it benefits the brain only, please explain the above observations like correlations of size of animals and sleeping requirements.


Is that really true? Felines come in a wide variety of sizes and all of them sleep as much as they can.

A lot of doctors now say that people should sleep 9 hours a day instead of 8, and that's around how long Sloths spend sleeping!

I found this on wikipedia:


Comparative average sleep periods for various mammals (in captivity) over 24 hours

horses - 2.9 hours
elephants – 3+ hours
cows - 4.0 hours
giraffes - 4.5 hours
humans - 8.0 hours
rabbits - 8.4 hours
chimpanzees - 9.7 hours
red foxes - 9.8 hours
dogs - 10.1 hours
house mice - 12.5 hours
cats - 12.5 hours
lions - 13.5 hours
platypuses - 14 hours
chipmunks - 15 hours
giant armadillos - 18.1 hours
little brown bats - 19.9 hours


I think this kind of disproves what you said. Lions are bigger than cats but sleep more, rabbits are smaller than humans but sleep about the same amount, elephants and horses are completely different sizes but sleep around the same amount of time. (just a little terminology note: if it was right I don't think it would be a "direct correlation" because it would be a negative correlation. (One variable goes up, one goes down))

Wikipedia suggests it has more to do with the eating habits of the animal than its size, as well as the amount of predation it has to worry about. If you're on the top of the food chain you can sleep more. If you have to eat almost all day to get enough food to survive you can't sleep much. I guess usually being big means having to eat more, but not if you're predator.


http://en.wikipedia.org/wiki/Sleep_(non-human)#Sleep_in_different_species < loooooooooove that cat
 
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  • #31
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I am insomniac... i have to take ambien (zolpidem), a sleeping pill.. just to sleep and I only sleep 4 hours a day. When I sleep 2 hours.. I can feel my body heating up in the day.. that is why I think part of the reason for sleep is to either add heat to the body or to make the ATP synthesis more efficient in the entire body.. not just the brain. But why and how exactly? That is the question.
 
  • #32
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They said in the Berkeley lecture that a lot of insomniacs actually technically get 8 hours of sleep a night, though they're obviously not aware of it and usually exhausted anyway.

They didn't give any details of the experiment. I wonder what they actually meant, maybe the brain takes quick 10 second opportunities to slip into REM.

There was a radio DJ who used to hold the record for the longest period of time spent without sleep (he did it on purpose), something like 10 days, I forget, in the end he was hallucinating and he thought the doctors were trying to kill him. When they tested his brain they found even though he seemed to be awake the readouts were identical to those of a sleeping person. So it seems even though he was conscious in most senses the brain was somehow getting the types of sleep it needed. Maybe the brains of insomniacs do something similar?

I don't know nothing 'bout no ATP synthesis
 
  • #33
Drakkith
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I am insomniac... i have to take ambien (zolpidem), a sleeping pill.. just to sleep and I only sleep 4 hours a day. When I sleep 2 hours.. I can feel my body heating up in the day.. that is why I think part of the reason for sleep is to either add heat to the body or to make the ATP synthesis more efficient in the entire body.. not just the brain. But why and how exactly? That is the question.

I don't think this is true. I think that your temperature regulation is slightly off due to lack of sleep or something similar.
 
  • #34
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I don't think this is true. I think that your temperature regulation is slightly off due to lack of sleep or something similar.

I wonder if anyone else encounters this. When I lack sleep or too tired. I can feel my testicles getting hot. I think the explanation is the blood in the legs flow faster that is why there is feeling of heat to the body. Now why does the blood in the body flow faster? It's because there may be lack of heat in the cells for lack of sleep. So the body compensates by making more blood flow. Also isn't mitochrondrial processes of ATP synthesis partly contribute to the body ambient heat, first agree with this portion and why not if not?
 
  • #35
Pythagorean
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The body doesn't actually need sleep, it's the brain that needs it. And yet the brain is very active when we sleep.

Oops, I didn't catch this, didn't see anybody else comment on it yet. This isn't true. The body needs sleep. In fact, rats, when forced to stay up, developed open sores that would not heal and their hair started falling out. Even in humans, a significant portion of wound healing depends on sleep.

Of course, the brain has important house-keeping during sleep cycles, too. There is a large amount of transcription and cellular trafficking that occurs when light cues disappear, particularly pertaining to proteins like fabp7 and psd9, important forming and regulating synaptic junctions.
 
  • #36
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Oops, I didn't catch this, didn't see anybody else comment on it yet. This isn't true. The body needs sleep. In fact, rats, when forced to stay up, developed open sores that would not heal and their hair started falling out. Even in humans, a significant portion of wound healing depends on sleep.

Of course, the brain has important house-keeping during sleep cycles, too. There is a large amount of transcription and cellular trafficking that occurs when light cues disappear, particularly pertaining to proteins like fabp7 and psd9, important forming and regulating synaptic junctions.

I read that in those rats forced to stay awake.. they just died weeks later. They didn't do any autopsies. But are there other studies where the cause were established? There we can know exactly what parts are affected and why.
 
  • #37
Pythagorean
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Those rats that died... died with sores and hair loss.

http://ukpmc.ac.uk/abstract/MED/2928622/reload=0;jsessionid=yOqr99pk3yuHZZRGGfbk.20

And another study cites the above journal to investigate REM sleep deprivation in particular.

Sleep deprivation is widely regarded as a stressor and has been shown to have significant effects on host defences. Severely sleep-deprived rats develop lesions on their paws and tails, suggesting possible deficits in the healing process. The purpose of this study was to assess the impact of rapid eye-movement (REM) sleep deprivation (RSD) on wound healing in a rat model. Male dark-hooded Long-Evans rats, 2–4 months old, were subjected to dorsal application of two sterile punch biopsies, each 3.5 mm in size. Biopsies were performed either immediately before or immediately after 5 days of sleep deprivation. Wound healing in REM sleep-deprived animals was compared with home cage control and yoked control animals. RSD did not produce differences in the rate of healing, regardless of the timing of the biopsy punch. RSD does not appear to have significant effects on wound healing and thus appears to act differently from other types of stressors on wound healing.

Effects of sleep deprivation on wound healing
L. MOSTAGHIMI, W. H. OBERMEYER, B. BALLAMUDI, D. MARTINEZ–GONZALEZ, R. M. BENCA
Journal of Sleep Research
Volume 14, Issue 3, pages 213–219, September 2005

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2869.2005.00455.x/abstract
 
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  • #38
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Those rats that died... died with sores and hair loss.

But that's not the cause of their death. Sores and hair loss are just external features. What is the internal cause?

http://ukpmc.ac.uk/abstract/MED/2928622/reload=0;jsessionid=yOqr99pk3yuHZZRGGfbk.20

And another study cites the above journal to investigate REM sleep deprivation in particular.



Effects of sleep deprivation on wound healing
L. MOSTAGHIMI, W. H. OBERMEYER, B. BALLAMUDI, D. MARTINEZ–GONZALEZ, R. M. BENCA
Journal of Sleep Research
Volume 14, Issue 3, pages 213–219, September 2005

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2869.2005.00455.x/abstract


So you mean only Non-REM Sleep Deprivation can affect wound healing?
 
  • #39
Pythagorean
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But that's not the cause of their death. Sores and hair loss are just external features. What is the internal cause?

Nobody claimed that; all I said was that the rest of your body needs sleep too, not just your brain.

Nobody knows the exact cause of death; probably because there's multiple failures that happen. You're essentially skipping an important book-keeping phase in a self-organized system.

So you mean only Non-REM Sleep Deprivation can affect wound healing?

No, I just said sleep deprivation in general.

This one study shows that REM sleep deprivation alone doesn't seem to account for it (based on their methods and interpretations). It's an important distinction between that and the statement you've made above. In fact, it's become a problem in the literature lately with null-hypothesis rejection tests that people confuse negative statements with the opposite of their positive statements. You can read more about that here:

http://au.academia.edu/JesperWSchne...al_significance_tests_in_research_assessments
 
  • #40
279
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Is that really true? Felines come in a wide variety of sizes and all of them sleep as much as they can.

A lot of doctors now say that people should sleep 9 hours a day instead of 8, and that's around how long Sloths spend sleeping!

I found this on wikipedia:


Comparative average sleep periods for various mammals (in captivity) over 24 hours

horses - 2.9 hours
elephants – 3+ hours
cows - 4.0 hours
giraffes - 4.5 hours
humans - 8.0 hours
rabbits - 8.4 hours
chimpanzees - 9.7 hours
red foxes - 9.8 hours
dogs - 10.1 hours
house mice - 12.5 hours
cats - 12.5 hours
lions - 13.5 hours
platypuses - 14 hours
chipmunks - 15 hours
giant armadillos - 18.1 hours
little brown bats - 19.9 hours

Do you have listings for the numbers of hours of sleeps of insects?

Can you name one living thing that doesn't require sleep?

I think this kind of disproves what you said. Lions are bigger than cats but sleep more, rabbits are smaller than humans but sleep about the same amount, elephants and horses are completely different sizes but sleep around the same amount of time. (just a little terminology note: if it was right I don't think it would be a "direct correlation" because it would be a negative correlation. (One variable goes up, one goes down))

Wikipedia suggests it has more to do with the eating habits of the animal than its size, as well as the amount of predation it has to worry about. If you're on the top of the food chain you can sleep more. If you have to eat almost all day to get enough food to survive you can't sleep much. I guess usually being big means having to eat more, but not if you're predator.


http://en.wikipedia.org/wiki/Sleep_(non-human)#Sleep_in_different_species < loooooooooove that cat
 
  • #41
Ryan_m_b
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Do you have listings for the numbers of hours of sleeps of insects?

Can you name one living thing that doesn't require sleep?
It's unclear if insects sleep, they definitely exhibit sleep like behaviour (I.e daily periods of inactivity) but we've got no real way of knowing how similar this phenomenon is to sleep in other classes of organism.

As for naming organisms that don't sleep: plants fungus and microorganisms. They have circadian cycles but done actually sleep.
 
  • #42
Monique
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Fruit flies sleep, the definition is 5 minutes of inactivity. Caffeine will reduce their sleep. During the time they sleep they'll exhibit resistance to activity when they're stimulated, similar to our sleep. Also, by forcing flies to stay awake they will actually accumulate sleep-debt, when they're given the chance to sleep they'll sleep for longer and deeper. Fruit flies are used as a model to study sleep, for example: http://www.ncbi.nlm.nih.gov/pubmed/18591491
 
  • #43
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Oops, I didn't catch this, didn't see anybody else comment on it yet. This isn't true. The body needs sleep. In fact, rats, when forced to stay up, developed open sores that would not heal and their hair started falling out. Even in humans, a significant portion of wound healing depends on sleep.
.



Were those rats the same rats that were kept awake by being forced to stay standing on a ledge and if they relaxed they would fall off the ledge and into some water and have to climb up again?

What about rats that could rest but not sleep? Wouldn't they heal the same? Is it really specifically sleep that the body needs or just periods of rest?
 
  • #44
Pythagorean
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Were those rats the same rats that were kept awake by being forced to stay standing on a ledge and if they relaxed they would fall off the ledge and into some water and have to climb up again?

What about rats that could rest but not sleep? Wouldn't they heal the same? Is it really specifically sleep that the body needs or just periods of rest?

I'm not sure. All the literature says "sleep deprivation".

Gilliland et al., 1989; Kushida et al., 1989 are the two major studies. If you want to pursue your question in the literature, you can find all works citing these studies with Google Scholar and look at the methodologies section of these studies themselves.
 
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  • #45
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Hi, I noticed I lose weight when I lack sleep. Is it possible the higgs were involved? How do you discount this possibility?

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." - Sir Arthur Conan Doyle
 
  • #47
Drakkith
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Hi, I noticed I lose weight when I lack sleep. Is it possible the higgs were involved? How do you discount this possibility?

Absolutely not.

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." - Sir Arthur Conan Doyle

If this is the quote you want for all your posts you can put it in it's own place in the options menu or something in the control panel. That way you don't need to put it in every time and people won't quote it when replying.
 
  • #48
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It is said that the human brain is the most complex object in the universe. This means biological system are more complex and efficient or compact than any machine. Since biological system needs sleep. Does this mean any Artificial Intelligence (A.I.) machines in the future need to sleep too? If not.. how can it be.. biological beings exceeds any machines.. for example.. you can't create a bacteria or virus out of nano machines because living system already use atom scales in the molecular parts. Since machines need to follow the living as model. Then future machine A.I. need sleep too?
 
  • #49
Drakkith
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It is said that the human brain is the most complex object in the universe.

There is no real "meaning" in what you have said here. What is your criteria for judging the complexity of an object? One could argue that since we are all part of the Milky Way galaxy, which is easily classified as an "object", that the Milky Way is the most complex object in the universe.

This means biological system are more complex and efficient or compact than any machine.

I don't agree. MANY features of living creatures are horribly inefficient, large, or likewise worse off than equivalent mechanical devices. My CCD camera for my telescope is far more capable of detecting light than my eye is, and has equal resolution over the entire chip, unlike the retina of the eye. The muscles in your body are much less efficient than a hydraulic system that is not only capable of meeting the same standards as our one of our limbs, but easily surpasses it in terms of strength and doesn't NEED to be as complicated to perform the same actions. (Complexity doesn't mean something is better)

On the flip side there are plenty of biological components that we cannot replicate yet to be as reliable or perform the same functions in the same environments. Hence why we can't just stick new hearts and lungs into people anytime we want.

The point is that it isn't that one or the other is better or worse. They are simply different.

Since biological system needs sleep. Does this mean any Artificial Intelligence (A.I.) machines in the future need to sleep too?

We don't know. I don't see why it would be though. Remember that the human body is not just a program that runs within a computer like an AI is. The body requires rest to repair and regenerate itself, along with whatever neurological stuff it may need to do in the brain. An AI is just a program without a physical body that it needs to repair. (Though you could give it one if technology was sufficiently advanced I suppose)

If not.. how can it be.. biological beings exceeds any machines.. for example.. you can't create a bacteria or virus out of nano machines because living system already use atom scales in the molecular parts. Since machines need to follow the living as model. Then future machine A.I. need sleep too?

Since when are machines required to follow living creatures as a model? Have you ever seen an animal with a transmission and wheels? How about the inner workings of a generator such as electromagnets?
 
  • #50
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Well , I read something about evolution .
I can say sleep came to existence in most organisms while evolving .
When the first rudimentary photosensitive tissue developed , we can say sleep also developed in the same era (Not the same day , as evolution is a long process) .
And it is known , most if not all organisms , show some sort of light sensitivity.
The living world acquired this new tool and slowly slowly started becoming dependent on it.
Earth receives light half of the time , and there is a relation between no light and sleeping , the organisms were so dependent on light that they had to find out a way to skip the night (NOTE: this is all in terms of evolution and selectivity no one is deciding here who gets what ) . And slowly this form of hibernation or lack of physical activity became sleep as we know now. In this course some organisms developed better photoreceptors than the others , but sleep was still in their genes .Using survival of the fittest theorem I imagine these organism found that hunting (searching for food) at night was more profitable than in the day . Since these organisms could outperform many in the nighttime, they are what we call nocturnal beings . They sleep aswell , but not in the time frame of other organisms generally .
 

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