Interesting!

Every child might tend to think that it would be a waste of time to sleep for one third of our lives, 8 hours per day...

Nevetheless, in medical terms, it is a real necessity. That our brain should enter soothing regeneration phase, that permits dreams, and guarantees best functioning during active phases. It is a neurologic demand. Also our muscles rest and our metabolic rhythm relaxes, thus allowing better performance after rest.

Tell that to your children. It is not waste, It is a necessary vital investment.

Interesting!

Every child might tend to think that it would be a waste of time to sleep for one third of our lives, 8 hours per day...

Nevetheless, in medical terms, it is a real necessity. That our brain should enter soothing regeneration phase, that permits dreams, and guarantees best functioning during active phases. It is a neurologic demand. Also our muscles rest and our metabolic rhythm relaxes, thus allowing better performance after rest.

Tell that to your children. It is not waste, It is a necessary vital investment.

It really is about what we do when we are awake! Do we waste much of the 2/3 of our lives? some people achieved a life time at a young age when compared with others three times their age.

Interesting question!

We tend to think of sleep as a time when the mind and body shut down. But this is not the case; sleep is an active period in which a lot of important processing, restoration, and strengthening occurs. Exactly how this happens and why our bodies are programmed for such a long period of slumber is still somewhat of a mystery. But scientists do understand some of sleep's critical functions, and the reasons we need it for optimal health and wellbeing.

One of the vital roles of sleep is to help us solidify and consolidate memories. As we go about our day, our brains take in an incredible amount of information. Rather than being directly logged and recorded, however, these facts and experiences first need to be processed and stored; and many of these steps happen while we sleep. Overnight, bits and pieces of information are transferred from more tentative, short-term memory to stronger, long-term memory—a process called "consolidation." Researchers have also shown that after people sleep, they tend to retain information and perform better on memory tasks. Our bodies all require long periods of sleep in order to restore and rejuvenate, to grow muscle, repair tissue, and synthesize hormones.

https://sleepfoundation.org/excessivesleepiness/content/why-do-we-need-sleep

Sleep is a period of internal rest that eventually gives us strength to work again. It is never a waste of time.

This is a very important and profound question. On the one hand, the answer is trivial. We sleep because in order to work effectively, our brain should periodically rest. On the other hand, it is non-trivial to discover the mechanism by which the brain provides itself with such an opportunity to rest. Let’s try, on the basis of general physical considerations and our common sense, to find out this mechanism. It is obvious that when the brain is awake, it is that part of our body in which some of the physicochemical processes specific to the brain are most intensively flowing. Conversely, when we sleep, these processes take place in a much less intensive regime. Without going into the specific details of these processes, one can say with a sufficient degree of certainty that these processes are somehow associated with molecular quantum transitions. The physical cause of molecular quantum transitions is associated with a certain, recently discovered, unique property of an electron that binds atoms to molecules. This property consists in provoking by a light electron of chaos in the vibrational motion of very heavy nuclei “for the purpose” to control their motion in the processes of molecular quantum transitions. This chaos is called dozy chaos. One of the constituent elements of dozy chaos is a dozy-chaos radiation. It represents some weak electromagnetic radiation, which is produced by the electric fields existing in the molecule for a short time of the molecular quantum transition. Since the waking brain is associated with a colossal number of molecular quantum transitions, it is that part of the body in which the dozy-chaos radiation is mainly concentrated. Accordingly, in the sleeping brain, the concentration of dozy-chaos radiation must be much less than that is present in the waking brain. During sleep, the electromagnetic dozy-chaos radiation can not leave the brain into the outer space, because otherwise, in order to wake up, it would always require some external source of this radiation. There is obviously no such source in nature. Consequently, when we fall asleep, the dozy-chaos radiation largely moves from the brain to other parts of the body, and when we wake up, it returns to the brain. It is such a periodic motion of weak dozy-chaos radiation, which is of an electromagnetic nature, throughout the body during the day and night, from the brain and back, provides an effective rest and work of the brain. This is the physical nature of sleep. See also DOI: 10.1007/978-3-642-33914-1_6 and DOI: 10.13140/RG.2.2.22417.12647.

Interesting! thanks so much Vladimir

Our solid state drive (brain) needs time to run "cleandisk" and "defrag." And this down time is used productively by the rest of the body, to heal tissues and kill off bugs, and to grow for young ones, more effectively than it can do when fully awake.

The main purpose of sleep is "housekeeping" for the brain, however.

Sleep is needed "to clean out the brain":

Haydon notes that "More recent studies indicate that the astrocyte plays pivotal, sleep-dependent roles in ‘cleaning the brain’ during sleep. This work indicates that a glymphatic pathway that critically relies on astrocytic aquaporin 4, is able to flush solutes from the brain and that deficits in this pathway may contribute to Alzheimer’s disease."

Reference/sites:

Article Astrocytes and the modulation of sleep

Dennis

Dennis Mazur

As per Noble laureate in literature Rabindranath Tagore,

"Rest is a part of work; as eye lids are the parts of eyes".

[Translation may be incomplete].

So, we can say --

Sleep is a part of our work schedule, as eye lids are the parts of eyes!

Happy New Year!

Greetings to all RG members and non-members.

Sleep is necessary for both living and non living (i.e. shot down of systems). This is basically to maintain balance, allow or bring physical systems to zero efficiency to enable re- organization/re- juvenation of energy for subsequent productions..

In a short period of time, sleep is more important than nutrition ingestion. In the mouse experiment, when completely blocking sleep, it dies about 1, 2 weeks, but this is shorter than when no food is given.

Until 1900, people's original sleep cycle was a general rhythm that took 4-5 hours of sleep after the sun went down and a second sleep during the day. There are studies that point out that insomnia is occurring due to the system that came to be actively carried out in the 20th century, the adverse effect of the eight hour labor regime.

PAS de mie caline, pas de Alice ça glisse, Frankie Vincent n’ira pas tjrs au même pays de merveilles, sensa .... tionnelle, cette musique de merde, ma ça fait bouger les fesses et ça plait aux ainés ceppi di minchia franco frances'

Dear @Ahmad, there are some same or related questions about sleeping. Good answers and resources were placed there.

https://www.researchgate.net/post/Why_do_we_sleep2

https://www.researchgate.net/post/Why_do_we_sleep

Our bodies are the most sophisticated machines on the planet. The body needs time to repair and refresh itself for it to function better for all humans. The only natural maintenance process designed for it is SLEEP.

Dickson Adom

Why Do We Sleep?

By:

Sleep is one of our most basic human needs. We spend about a third of our lives doing it and there are serious health consequences to sleep deprivation. It’s safe to say that sleep is as necessary as food and water, but why do we all spend so many hours doing it?

Scientists simply aren’t sure why. Sleep researcher William Dement, who co-discovered REM sleep and is often described as the father of sleep medicine, told National Geographic that, “as far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy.”

As lying unconscious for an extended period of time made our ancestors vulnerable to attacks, researchers suggest that there must be some advantages to outweigh this considerable risk. The biggest hurdle to understanding why we sleep was that the brain activity that occurs during sleep was largely hidden from researchers. New methods, though still somewhat in their infancy, are helping researchers to better understand the purpose of sleep.

In a 2000 study, published in Brain Research, researchers Terrence Sejnowski and Alain Destexhe, added to the growing evidence that sleep allows us to “consolidate” our memories. Consolidation is the important process whereby short-term memory is converted into long-term memory. Sejnowski and Destexhe found that when we sleep, our brain consolidates the information that we’ve learnt in a day by opening calcium-mediated biochemical pathways in pyramidal neurons. Researchers suggest that this process and the necessary “network reorganization” take time and need to occur when normal processes such as sensory processing aren’t happening. “This may ultimately be the primary reason why we need to sleep,” researchers note.

Some researchers suggest that the benefits of memory consolidation don’t outweigh the risks of sleeping. They instead point to other theories. Researchers from the University of Rochester argue that sleep may provide the brain with an important opportunity to take out the trash. In a 2013 study, published in the journal Science, researchers found that cerebral spinal fluid is pushed around the brain to clear waste chemicals that are produced as part of a cell’s natural activity. This method of waste removal, known as the glymphatic system, mainly occurs when we sleep.

"You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can't really do both at the same time," lead researcher Dr Maiken Nedergaard told the BBC.

Another theory suggests that the reason why we sleep is down to energy demands. In a 2008 study, published in PLOS Biology, Emmanuel Mignot says that this theory is firmly grounded in natural selection. As animal performance and prey availability peak at different times during the day, sleep could have been selected for to save energy. Mignot suggests that there are some flaws in this theory because it does not explain the selection for REM sleep, which in most species results in an increase in energy expenditure.

There are of course limitations to all the main theories put forward to explain the mystery of why we sleep, but an improvement in technology and a renewed interest in this question might mean a definitive answer won’t remain elusive for long. For now though, why don’t we all go and sleep on it?

Cited from:http://www.iflscience.com/health-and-medicine/why-do-we-sleep/

I found this quite interesting:

Research Physical nature of sleep

Complementing the very interesting answer given by Dr Maria Bettencourt Pires,

Our organism produces a hormone, necessary to a better functioning of our body mainly while in the deepest phase of the sleep, it is called growth hormone (GH). It is important because this hormone is used in our body to stimulates the anabolic process, as the cellular growth or skeletal muscles hypertrophy, for example.

More information can be found in a classical book of medical physiology called GUYTON & HALL - Medical Physiology.

Dear Maria,

Many thanks for your appreciation. I think that the ideas in my article should be combined with those facts that are known in biochemistry and medicine.

Best regards,

Vladimir

when i fell tared my mad tell mt take arest so i go to sleep

we sleep in order to replenish neurotransmitters. These are chemical substances that are used for communication between neurons. They get used up more when we are awake. During sleep, less are used than are produced and thus the reserve for use the following day is created

Researchers identify genetic mutations that influence sleep.

Sleep is ubiquitous across the animal kingdom yet little is known about the mechanisms that regulate it. A new Nature study has identified two genetic mutations that influence the type and amount of sleep experienced by mice. Hiromasa Funato, University of Tsukuba, and colleagues made this discovery by examining the sleep patterns of more than 8,000 mice with randomly generated genetic mutations.

Sleep has two different states; non-rapid-eye-movement sleep (NREM sleep or deep sleep) and rapid-eye-movement sleep (REM sleep or dream sleep). The first mutation identified in the study, which affected the Sik3gene, increased the amount of NREM sleep. This means that the total time spent awake was reduced and the inherent need for sleep was increased.

The second mutation affected the Nalcn gene and reduced the total amount and length of REM sleep. The authors believe this to be a result of the REM-sleep-inhibiting neurons becoming more excitable.

https://www.researchgate.net/blog/post/waking-up-to-the-mechanisms-of-sleep

There are a few things we literally cannot live without. Oxygen is one. Another is food and water. And then there is sleep: forcibly keep an animal awake for long enough and you will kill it. The same almost certainly applies to humans.

This fact alone tells us that sleep must be doing something pretty important. But despite decades of intense scientific study there still is no consensus on exactly what that something is.

Researchers have found that sleep is beneficial to humans in many ways: it helps us process memories, and keeps our social and emotional lives on track. Yet we still do not really know how, why or even exactly when sleep.

At first glance, sleep really should not exist. It makes very little sense for animals to deliberately lose consciousness, sometimes for hours on end every single day.

“The cost of losing consciousness to survival is astronomical,” says Matthew Walker at the University of California in Berkeley. Whatever functions sleep performs, they must be so fundamentally important that they far outweigh the obvious vulnerability associated with being asleep.

This means we can confidently reject one of the simplest theories of sleep: that we drift off simply because we have nothing better to do.

This could be described as the indolence theory of sleep. Once an animal has eaten, seen off any rivals and exhausted any potential mating opportunities, it effectively has an empty schedule. With no urgent business to attend to, losing consciousness kills time for a few hours.

It is a fun idea, but considering that a sleeping animal is significantly more likely to be caught and eaten than a waking animal, this hypothesis makes “zero sense”, says Walker.

We might as well cross another theory of sleep off the list, too.

Some researchers have suggested that sleep is a good way to save valuable energy, given that mammalian core body temperatures often drop during some stages of sleep.

Does a housefly sleep? How about an earthworm?

However, Walker and many other sleep researchers are not convinced. Crunching the numbers makes it clear that sleep does not serve this purpose.

“The amount of energy humans save by falling asleep, versus simply lying on the couch, is about what you find in a slice of brown bread,” he says. “Losing consciousness just isn’t worth saving 120 calories.”

But what is sleep for, if these ideas are out? Before we can really think about answering that question, it would be helpful to address something more fundamental: who sleeps?

We have no problem recognising that humans sleep. Most people can tell that pet cats and dogs sleep too.

But we might feel less confident about identifying when, or even if, a pet goldfish sleeps. And when it comes to smaller or more distantly related animals we would be even less sure. Does a housefly sleep? How about an earthworm?

Sleep now appears to be an almost universal feature of animal life

There is now an emerging consensus on the behavioural features that define sleep, and these features can be used to look for sleep in simple animals, says Ravi Allada at Northwestern University in Evanston, Illinois.

There are three main elements. First and foremost, sleep renders an animal quiet and still: muscles are not very active during sleep.

Second, sleep makes animals slower to respond. For instance, if you make a loud noise near a sleeping animal, it will react more slowly than an awake animal.

And finally, we can recognise sleep because it keeps animals from getting tired. If you keep an animal up all night, it will compensate the next day by sleeping for longer than it normally would. This is sometimes called “sleep rebound”.

Using these criteria, there is growing confidence that even relatively simple animals like fruit flies and microscopic nematode worms do in fact sleep. “There are now lots of publications on these model systems,” says:

“I believe that the behavioural features used to characterise sleep are quite reliable for identifying this behaviour in animals… and to differentiate sleep from a simple rest,” says Paul-Antoine Libourel at the Lyon Neuroscience Research Center in France.

According to Libourel, sleep now appears to be an almost universal feature of animal life. “This suggests that sleep is fundamental for the survival of species. Natural selection did not suppress it.”

In fact, natural selection did the exact opposite: it built on the concept of sleep, adding in new stages and new functions. At some point in prehistory, the most famous of all stages of sleep appeared: rapid eye movement (REM) sleep.

“If there’s a new kid on the block it’s REM sleep,” says Walker. “Non-REM sleep was the original form.”

The origins of REM sleep particularly bother researchers like Libourel.

We know that humans possess REM sleep. It seems pretty clear that almost all other mammals do so too, even very “primitive” egg-laying mammals like the duck-billed platypus. This means we can be reasonably confident that it was present in some of the first mammals that walked the Earth, about 220 million years ago.

The proto-mammals began spending the hours of daylight asleep below ground in dark burrows

As it happens, dinosaurs first appeared on Earth around this time too. Many of them disappeared about 65 million years ago, but one group of dinosaurs lives on: we call them birds. And birds, like mammals, have REM sleep.

Perhaps REM sleep emerged in some distant common ancestor of mammals and the bird-dinosaurs, says Libourel, or perhaps it originated independently in the two groups. But either way, why did REM sleep appear?

Some researchers think there is no functional explanation, and that REM sleep is just a byproduct of other evolutionary changes. For instance, according to Ruben Rial at the University of the Balearic Islands in Majorca, Spain, it is probably significant that both mammals and birds are warm-blooded.

Rial and his colleagues suggest that the appearance of warm-blooded animals triggered a complicated chain of causes and consequences, which ultimately saw proto-mammals adopt a nocturnal existence – quite unlike their daytime-active reptilian ancestors.

The proto-mammals began spending the hours of daylight asleep below ground in dark burrows, which offered protection both from predators and from intense sunlight that would damage their sensitive night-adapted.

“However, they conserved most of the neural mechanisms that controlled their ancient behavioural output,” says Rial.

Reptiles go through two main behavioural phases each day: a passive phase in which they lie still and bask to warm up their bodies, and an active phase in which they forage, protect themselves from predators, socialise or breed.

Rial says that some of the more “primitive” regions of the proto-mammals’ brains continued to follow these ancient patterns of activity, even as more “advanced” brain regions made sure that any reptilian-like mental activity was not converted into actual behaviours.

This means we can see non-REM sleep as a direct descendant of reptilian basking, and REM sleep as an inherited form of reptilian daytime activity. “However, this activity was enclosed within a paralysed body,” he says. “This was the origin of REM and dreams.”

This might sound more like a story than a provable hypothesis, but some established facts do support the idea.

For instance, there is good evidence that the earliest mammals were nocturnal – and this nocturnal bottleneck did influence behaviour.

Sleep – and in particular REM sleep – helps recalibrate emotional functions in the brain

We also know that our brains are remarkably active during REM sleep: so active, in fact, that an REM brain looks like the brain of an animal, like a reptile, that is fully awake. For this reason, REM sleep is sometimes called “active sleep” or even “paradoxical sleep”.

Even so, other researchers do not share the view that REM sleep is a mere side-effect of broader evolutionary change.

Walker, for one, is convinced that REM sleep has a real and important function. “We’ve done a lot of work that suggests sleep – and in particular REM sleep – helps recalibrate emotional functions in the brain,” he says.

Think back to your childhood, says Walker. If you try to recall the strongest earliest memories you have, almost all of them will be memories of an emotional event: perhaps a particularly exciting birthday, or the frightening experience of being separated from your parents on your first day at school.

“What’s striking now, though, is that you can recall these are memories of an emotional event but they are no longer themselves emotional. They do not elicit the same visceral reaction,” he says.

We have REM sleep to thank for the change, says Walker. It carries out a very important function: allowing us to remember and learn from important experiences, without being crippled by the emotional baggage that they originally carried.

“REM sleep provides overnight therapy,” says Walker. “[It helps] the brain perform an elegant trick of divorcing the emotional bitter rind from the information-rich orange.”

This hypothesis even offers an explanation for distressing conditions like post-traumatic stress disorder (PTSD).

People with PTSD often experience emotionally overwhelming flashbacks.

“A soldier with PTSD walks into a carpark and hears a car backfire. Not only do they have a flashback to a combat situation, but they have an emotional reaction: their heart races, their palms sweat,” says Walker. “It tells us that the brain has not separated the emotion from the memory.”

It was the people who had experienced the longest, most miserable dreams that gained clinical resolution from their depression

Walker points out that repetitive nightmares are a hallmark of PTSD. He says we can interpret this as the brain offering up a highly emotional memory so that REM sleep can peel away the emotion.

But, for some reason, REM fails to do so. The memory remains emotional. So the next night the brain tries again, with the same result, and so on.

Even the vivid dreams we experience during REM sleep appear to be adaptive, and part of this process. We know as much from the seminal work of Chicago-based sleep researcher Rosalind Cartwright in the 1980s and 1990s.

Cartwright studied the dream habits of people who were showing signs of depression, as a consequence of bitter divorces.

After a year, it was the people who had experienced the longest, most miserable dreams that gained clinical resolution from their depression. Paradoxically, the test subjects whose dreams were more like those of people without depression remained depressed.

It was a staggering finding, says Walker.

We spend about 25% of our sleep in an REM state, whereas for most other primates the figure is just 5-10%

Previously it had seemed plausible that dreams were just a curious side-effect of sleep: rather like the way an incandescent lightbulb gives out heat as a consequence of its primary light-giving function. “But if that were really true, Rosalind Cartwright’s results would make no sense whatsoever,” says Walker.

Taken together, these findings suggest to Walker that REM sleep evolved in birds and mammals because both groups are cognitively and socially advanced. They use sleep, and dreams, to help make sense of their waking world. “I think the warm-blooded connection is a little bit of a red herring,” he says.

This could explain why human sleep is so unusual. A study published at the end of 2015 found that we spend about 25% of our sleep in an REM state, whereas for most other primates the figure is just 5-10%. This makes sense if you consider how much more complicated our social interactions are, says Walker.

We may be closing in on understanding why mammals and birds evolved REM sleep. But what about non-REM sleep, which evolved first and is seen in many more animals?

Sleep must have originated for a reason. Whatever that reason is, it must be related to some biological feature, or features, shared by all animals that sleep: not just mammals and birds.

Over time, a sea of neurotransmitter molecules can build up in the synapse

Robert Cantor at Dartmouth College in Hanover, New Hampshire thinks he has identified that common feature: a relatively complex brain and nervous system. Specifically, a complex brain through which signals are transmitted by molecules called neurotransmitters.

There are small junctions called synapses between nerve cells. When one cell has a message to pass to its neighbour, it often sends it in chemical form as a swarm of neurotransmitter molecules, which latch onto receptors on the receiving cell.

“This molecular process is common to all organisms that sleep,” says Cantor. “It exists in the vast majority of synapses in nervous systems, regardless of complexity.”

Over time, a sea of neurotransmitter molecules can build up in the synapse, interfering with its ability to function properly. What is needed is a process to flush away those molecules. That process happens most efficiently when we sleep, he says.

Cantor had been toying with this idea for some time when, in 2012, it received a significant boost. Neuroscientists discovered a previously unrecognised network of vessels in the brain that flush out the fluids between brain cells: the “glymphatic system”. A year later it emerged that the glymphatic system is most active during sleep.

Evolution has a tendency to repurpose things

“I’ve read quite a bit about the glymphatic system over the past few years,” says Cantor. “What has struck me as rather surprising is that, to my knowledge, nobody has systematically analysed exactly what solutes are present in the fluid that is washed out.”

He suspects that neurotransmitters are particularly abundant in the fluid. If that is true, it offers an explanation for the origin of sleep: flushing out neurotransmitters is so important to the nervous system that, in order to get it done, animals began to sleep – despite the disadvantages that come with losing consciousness.

Sleep almost certainly does play a part in this sort of brain-cleaning activity, says Walker. But we cannot be sure that this was the single factor that triggered the origin of sleep.

The trouble is that sleep might have evolved first, and then the brain and nervous system harnessed the opportunity it provides to flush out unwanted molecules from the brain.

Sleep impacts every major system in the body.

This is a common problem that evolutionary biologists face when trying to work out why particular features first evolved: evolution has a tendency to repurpose things.

For instance, breathing is very important for bringing in oxygen and removing carbon dioxide, but it is also now crucial for human speech and singing. “Nobody would affirm that the [respiratory] system [originally] served to allow the production of words,” says Rial.

Pinpointing the driving factor, or factors, that led to the origination of sleep is going to be a challenge because sleep has so many beneficial effects.

Sleep impacts every major system in the body. Cut down on sleep and it is not just your brain that struggles: the reproductive, metabolic, cardiovascular, thermoregulatory and immune systems all suffer too, says Walker. In principle, the evolution of sleep could have been driven by the benefits it brings to any one of these systems.

Sleep is a state we enter to fix the systems that are put under stress when we are awake

“We used to ask the question; ‘Does sleep do any good, or serve any function?’” says Walker. “Now we’ve been forced to upend the question and ask if there is anything that isn’t improved by sleep, or impaired by sleep deprivation. And currently the answer is ‘no’.”

Fortunately, Earth is still home to living representatives of some of the earliest groups of animals: things like jellyfish, which may show a primitive form of sleep. It is probably by studying these more "primitive" animals that we will figure out what originally drove the appearance of sleep, says Allada.

Even single-celled organisms, at least those that live for longer than 24 hours, might hold clues. “They show stages of what we would call passive and active cellular activity,” says Walker. “That could be seen as a precursor of sleep.”

By Colin Barras