Human beings spend, on average, one-third of our lives asleep. That is a significant amount of time and so, it must be implied, that sleep is a very important practice for organisms.
In fact, every organism on the planet appears to sleep to some degree. Rats and dolphins do it, even fruit flies and micro-organisms!
Sleep must, therefore, be a vital part of survival on our planet. If you don't believe such a claim, see how long you could last without it.
But what happens when you travel to the land of nod? Why is it important? Where do we go?
Here we'll attempt to address some of these fundamental questions on sleep.
What do your brain and body do when you are sleeping?
The sleep process is one of the most widely studied phenomena in our lives. While a lot is still unknown, and probably always will be, scientists have been able to decipher at least some of the basic biomechanical processes that occur.
What has been gleaned, according to sites like The National Sleep Foundation, is that when we sleep, a distinctive pattern of brain activity occurs. Technically called sleep architecture, our brains follow a pattern of REM (rapid eye movement) and NREM (non-rapid eye movement) phases.
This sequence generally follows a series of 90-minute cycles throughout a typical night's sleep.
NREM is by far the largest component of sleep cycles constituting around 75% a night. This phase can further be subdivided into 1 of 4 stages.
N1, or stage 1, is the phase between being awake and falling asleep. It is the lightest form of sleep.
N2, or stage 2, is when sleep really begins. Subjects begin to become disengaged from their surroundings, heart rates become regular, and body temperatures tend to drop.
It's for this reason that it is usually advised to sleep in a cool room to help you fall to sleep quicker.
N3, or stages 3 and 4, is the deepest and most restorative phase. Blood pressure drops, breathing slows, muscles relax and blood flow increases to them. During this phase, most tissue damage repair occurs and hormones are released, like the human growth hormone.
REM is the smallest component of sleep. It makes up the remaining 25% or so. It first occurs after about 90 minutes of falling asleep and recurs roughly every 90 minutes.
This phase tends to get longer as sleep progresses throughout the night. REM sleep tends to combine increased energy provision to the brain and body and so, this is generally when dreams occur.
As the name suggests, your eyes dart back and forth and your body is usually immobile and relaxed. Your muscles are, in effect, disabled.
Another common hormone, cortisol, also tends to dip at bedtime and gradually increases until morning.
Where does consciousness go when we sleep?
Consciousness is generally defined as "the state of being aware of and responsive to one's surroundings" - Oxford English dictionary. When we sleep, you move in and out of your connection to the outside world.
According to sites like socratic.org, while asleep an individual moves in and out of consciousness. But the level to which this occurs varies widely from person to person.
"When you are asleep you leave your conscious state and move into a subconscious state as evidenced by your inability to participate in an intelligent conversation. Some people can respond to inquiries during sleep, but the conversation is nonsensical.
Other sleepers will not respond at all to noises or conversation because they are in a deep sleep closer to the unconscious level, or they have been conditioned not to respond even if the conversation is perceived.
Then there are sleepers who are almost still conscious when they sleep and are able to respond almost instantly to any sound or conversation they hear." - socratic.org,
You can, at any point, be roused from sleep by loud noises or other stimuli - depending on the stage of sleep you are in of course. From this perspective, consciousness is with you all the time so it doesn't really 'go' anywhere.
Rather, it is simply temporarily suppressed during sleep - depending on the person and occasion.
What happens to your body when we sleep at night?
Further to what we touched on above, various processes occur while you are asleep. Although you are consciously detached from the world (depending on the stage of sleep) your body still needs to be kept alive.
So, although reduced, your body continues to respire and conduct other basic processes to keep your organs alive and well. Waste is processed and your heart continues to pump blood around the body.
During sleep, your body is far from at rest, per se.
"Trillions of neurons light up. The endocrine system kicks into overdrive. The bloodstream is flooded with a potent cocktail of critically vital hormones," - Scientific American.
For your brain, the sleep process appears to be vitally important. Some believe, according to The Independent, that sleep provides a "safe place" of sorts to practice dealing with situations and emotions.
It is, in a sense, a kind of simulation space for your mind and a process necessary for organizing experiences and saving memories. It may also be a time when your brain rids itself of unwanted feeling and emotions - a kind of defragmentation process.
Your brain also spends time asleep doing some spring cleaning.
Throughout the day your brain "is spending its day building up adenosine, a molecule leftover from cell activity. As adenosine builds up, we feel sleepy.
Part of the reason caffeine keeps us awake is that it blocks the actions of adenosine. So, the molecule continues to build up until we give in and fall asleep.
Then, the brain can do a little house cleaning, get rid of the extra adenosine and you wake up feeling alert again." - Grunge.com.
There are also some other studies that suggest sleeping helps to deal with pain (emotional and physical). Researchers at the University of Berkeley, for example, recently discovered that sleep deprivation is linked with higher pain sensitivity.
Their study discovered that the neural mechanism that detects, evaluates and responds to pain are disrupted if you don't get a good night's sleep. This, in their view, indicates that sleep is vitally important in improving a person's ability to cope with pain.
As interesting as this is, ultimately, scientists are not entirely sure why we sleep exactly.
Many theories abound for its development with theories ranging from protecting us at night from predators (i.e. you're not moving around) to energy conservation in a resource-limited environment.
While we may never find out definitively in the future, it is clear that the sleep process is a time when your body can repair and consolidate after the rigors of the day preceding it. For younger humans, it is also a time that is important for them to physically grow and develop.
Ultimately sleep evolved for a reason so make sure you get a good's night sleep regularly. You will feel the benefits in no time.