1 sheep, 2 sheep, 3 sheep, 4 - Here’s why we sleep and much more

A warm bath, ensuring all of our sheep are accounted for, some steaming cocoa, relaxing music, or maybe an orgasm. There are many ways to help us reunite with Mr. Sandman every night - some scientifically proven, others old wives' tales that might just work since we’ve made them our evening habits and rituals. Do you have a specific sleep schedule? Are you a morning person, or do you love the dark and quiet company of the night? Could you, once settled in your comfy cover fort, sleep till kingdom come, or does your own body wake you up? Do you think you get enough sleep, or are you constantly dragging around like the zombie extra from The Walking Dead? Why is sleep important, and can you override this need with coffee? Is it even possible to live without sleep, and would chronic lack of sleep implode you physically, mentally, and emotionally? 

The brain and sleep

This wet few pounds of mass between our ears is the height of evolutionary development and the control room of our body. No aspect of our physical or emotional function escapes brain domination. It is constantly busy processing massive amounts of information you’re not consciously aware of (not to go bonkers from the overwhelm), such as the details of the environment, the position of our body, sounds, smells, and textures, and keeping us alive by sustaining breathing and heartbeat. The brain is also constantly rearranging information and making new connections, making us react properly to our physical and social surroundings while regulating body temperature, hormones, mood, coordinating muscle movement… Although accounting for only around 2% of body mass, the brain uses a disproportionately large amount of metabolic energy, around 20%. This percentage is pretty much a constant while you sleep, problem-solve, or do nothing, as there are so many things going on as background programs that are crucial for life and have been removed from conscious control, so we can’t mess with it.
 

Such a busy organ needs its “time off (not really, as deep sleep is showtime for the brain and barely distinguishable from an awakened state by the energy consumed).” We can think of sleep as a master deep clean, regeneration, defragmenting, cleanup, and reordering of the brain, crucial to maintaining normal function. This is why we sacrifice one-third of our life to the “golden chain that ties health and our bodies together,” as Thomas Dekker characterized sleep, or to “the most moronic fraternity in the world, with the heaviest dues and the crudest rituals” as Vladimir Nabokov chose to view it. Therefore, whether you look forward to your soft and warm bed or roll your eyes at this daily waste of time, there is no escaping it. Sleep is the most fundamental biological need, and sleep hygiene is something you should get serious about as you age. Just to hammer the point home, sleep deprivation is likely to kill us faster than food deprivation. We (unfortunately) can’t store restfulness the way we can calories (also, unfortunately). Be happy you don’t need 18 hours as an opossum does. They really spend most of their time playing possum.

Why do we get tired?

Why do we even feel tired after not sleeping for about 16 Hrs? What happens in our brains when we start to feel that drowsy lack of concentration and motivation to do anything other than close our eyes? Well, there is this part of the hypothalamus (a brain structure deep in the temporal lobe) that acts as a timer and secretes melatonin and cortisol, which are responsible for making us want to go to sleep and waking us up in the morning, respectively. Cortisol has gotten a bad rep as a hormone that surges during stress, but it has a much more vital daily function of snatching us from deep sleep and making us feel awake and alert as the morning comes. Unfortunately, cortisol is also negatively associated with insulin sensitivity, and a chronically elevated level (as is stress, can increase insulin resistance). Basically, we should get a jolt of cortisol to wake up, and then it steadily drops, ending in its lowest valley as we prepare for bed. Melatonin is cortisol’s polar opposite and a lot of people take melatonin for sleep. Does supplementing melatonin work is not the issue now, as we would ideally create all of our necessary chemicals for a healthy sleep cycle ourselves.  Anyway, melatonin will signal to our body that we are pooped and that we need to get some shuteye.

Your chirpy and delightful self will turn into a narcoleptic maniac because of a chemical called adenosine. It is a byproduct of ATP (adenosine triphosphate), the molecule of metabolic energy in our bodies. When this energy gets used up all day long for the brain’s various doo-dahs, once the ATP is burned, adenosine is a leftover, just as you would get some leftover ash by burning firewood. Adenosine starts to build up, and it connects to specific receptors, signaling the body it is time to shut down. The more it builds up, the more tired you’ll feel. 
 

How does caffeine work?

Would you call yourself a coffee addict, and when was the last time you’ve tried to go without for any substantial amount of time? If you’ve noticed some addictive withdrawal behaviors, if you stray too far from your last caffeine hit, you’re not alone. The debate on caffeine addiction is still out, with some saying you cannot get truly addicted to caffeine because it doesn’t stimulate the brain's reward centers as highly addictive drugs do. Others say that blocking the adenosine from sitting in its natural receptor (the accumulation of which makes us tired) stimulates dopamine, which would have otherwise been suppressed by this adenosine. So do we just really, really, really like our coffee, or are we addicted? Maybe it’s a little bit of both, and maybe we’re more addicted to the sugar in caffeinated drinks than the caffeine itself.  

Also, one small but very important detail to know: Coffee doesn’t actually wake you up but kind of tricks you into not feeling tired, and what a marvelous trick indeed. It blocks the adenosine receptors and doesn’t allow your brain to realize how tired it really is. Its full effects kick in about half an hour after your delicious cup of java, and they stay relatively active for the next 6 hours. If you don’t refill your cup in the meantime, after six hours, you will have experienced the all-too-familiar energy crash.

Sleep cycles

People used to be convinced that when we are asleep, our brain is sleeping and resting too. We were not yet able to peek into the mysteries of the sleeping brain at the beginning of the 20th century, but at about halfway through, the EEG machine enabled us to open the black box. In 1953, scientist Nathaniel Kleitman and his student Eugene Aserinsky from the University of Chicago were the first to suspect that there is more to sleep than just powering down. They determined that sleep is composed of multiple sleep stages by monitoring the periods in which the subjects could move their eyes although asleep and the period in which the eyes remained still. Their research started the exploration of sleep that continues to this day.

The sleep stage in which the eyes jerkily move around is called the “Rapid Eye Movement” phase or, as it is more commonly known, the REM phase, while the eyes are still or moving slowly in NREM or non-REM sleep. Although both are necessary, they are very different, and some of the information might surprise you. Not only is the brain not completely inactive when asleep, but at a certain point, it even displays a higher level of activity than in an awake state.

How are REM and NREM sleep different?

It seems that REM and NREM each play their own role and that we need to experience both each night to feel well-rested, and we’ll go through about 5 stages of each sleep cycle that lasts between 90-120 minutes. In NREM sleep, the neurons located in the brain stem stop firing completely, while those in the cerebral cortex only reduce their activity. But the NREM phase does something interesting. While doing their job in an awake state, the neurons will fire one by one, but in NREM, the adjacent neurons will fire simultaneously. Paradoxically, the body will consume less energy, but the voltage of the brain waves will be of a higher frequency.

There is a small group of neurons that induces NREM sleep, and there is no definite proof as to what triggers their activation, but heat seems to be one of them. How to fall asleep fast? A hot shower will initially warm you up and be followed by a large thermal dump, cooling down the body's core temperature for a deep, restful slumber and a proper beauty sleep (it is true, your skin will look better if you have high-quality sleep and you will age slower). The NREM phase is not without dreams, as it was first considered, but they are only not as vivid, and we don’t remember them after waking up.

The REM sleep is a bit different. Firstly, the neurons fire one by one as they would when you are up and about, so their combined voltage is lower than that of a brain in the NREM phase. The consumption of energy is also equal to a waking body that is not doing any heavy physical work, and the neurons in the forebrain and the brain stem are equally or even more active than they are during waking hours. At this stage, the dreams will be very vivid, and if you wake the person up during REM sleep, they will, in most cases, be able to recall the dream. The motor system that usually controls the muscles is also active, so a person can twitch or move a bit. The brain sends out neurotransmitters that block the signals sent to the muscle tissue, yet they seem not to affect those muscles responsible for eye movement.

As Jerome M. Siegel explains in “Why We Sleep,”  there are always exceptions, but the general rule seems to be that larger organisms need less sleep than smaller ones. There is a good reason behind it. The smaller the animal, the faster its metabolic rate. The faster the metabolic rate, the more energy gets burned and leaves more adenine behind, and it also generates more of the dangerous molecules called free radicals. They will bring mayhem to the system by mutating, damaging, or destroying cells.

NREM sleep is especially vital for these organisms because the slower metabolic rate will allow for the damage to be fixed. This is also true for humans, but we are still faced with the problem of REM sleep and why it is so physiologically important that it resembles a waking state. Two immensely important researchers might shed some light on this conundrum in 1973. Dennis McGinty and Ronald Harper of U.C.L.A. studied three neurotransmitters called monoamines (serotonin, histamine, and norepinephrine). During a waking state, the cells producing these monoamines never stop firing, but they cease completely once we enter REM sleep. This phenomenon has been explained 15 years later by Michael Rogawski, who in 1988, found that by the constant release of monoamines, their receptors lose sensitivity and become less responsive. The cessation of their release during REM sleep will allow the receptors to recuperate and gain full sensitivity again.

What is the purpose of sleep?

So now we know all of this. But we are still uncertain as to why we sleep in general. What is its purpose? Humans and animals all sleep or display some sort of sleep-like behavior. One of the evolutionary reasons might be that your body is tired at night because it wants to force you to lie down and keep still so as to be less visible to predators and to conserve energy. This hypothesis doesn’t seem to be viable. If it were true, it would mean that the animals higher in the food chain would sleep less because there are no predators for them to hide from, but it isn’t so. Lions sleep or nap up to 15 hours a day. When it comes to conserving energy, it also doesn’t seem like the best explanation because energy savings during sleep are negligible, and that is only in NREM phase. In contrast, the energy consumption during REM sleep resembles that of a waking state, as we’ve mentioned in the sleep cycles segment.

Restoration might seem like a much better reason because, in addition to reabsorbing the adenine buildup, the same genes necessary to repair the sustained cell damage are only active during sleep. Damaged cells get replaced by new ones, and the growth hormone is released in larger quantities. Still, brain processing and memory consolidation seem like the most legitimate explanation for why our bodies so desperately need sleep.

The brain becomes a sort of trash can during the day. It is constantly active and absorbs large quantities of information whether you like it or not. It gets cluttered by unnecessary junk and needs to get regular maintenance to keep functioning at optimal levels. While you are awake, your brain works in medium-range brainwaves, but while asleep, the waves are of high and low frequency only. This means that the brain is choosing which connections to strengthen, that is, which information can be useful and keeps it and which to get rid of as junk.

Why do we dream?

We agree that our brain is an amazing “machine” with a lot of things we still have to figure out, but one of the most amazing and puzzling additional features of sleeping is - dreams. Intertwined in myths, legends, and ancient cultures as a conduit to subconscious information or other realms, dreams have entered legitimate scientific scrutiny through the work of psychoanalyst Sigmund Freud, at the beginning of the 20th century. He was interested in what that talking cat, hedgehog juggler late for work, semi-flooded room, or planting dandelions in a hotel lobby with your first crush had to say about the unconscious thoughts and emotions that get processed while we sleep.

No matter if you remember them or not, we all dream and they are important for the proper functioning of our brain while awake. Although Freud interpreted dreams as symbolic manifestations of hidden desires in 1899, they are more than that. Dreams are also a way in which the brain trains itself, and dreaming serves multiple purposes, such as choosing which events of the day might be worth keeping. Through dreams, the brain searches for connections between seemingly unrelated events deals with the emotions that the conscious brain is not ready to handle, and prepares you to face another day better than you were the day before.

We dream both in REM and NREM but the dreams serve different purposes. In NREM, there are boring dreams about everyday activities that will reinforce your already existing views or will practice existing skills. REM sleep activates the gray matter that has been inactive during NREM, and dreams are much more exciting and vivid. REM cycle dreams might put you in a dangerous or unusual situation with strong emotional responses.

Here, we might face something that our waking mind is blocking and prepare ourselves to react to a situation in reality. Therefore, conquering that castle or calming a rowdy crowd might be about a difficult business meeting tomorrow, or a dream about flying might just be working through an emotion of relief and a burden being lifted. Put simply, REM sleep keeps us sane, and it is common to find an array of psychological disorders in those who, for any reason, can’t achieve REM sleep. We usually lose all self-consciousness while we dream. Still, sometimes the dorsolateral prefrontal cortex gets switched back on, and we might experience the rare and elusive lucid dream that allows us agency, a dream that we can control and direct, rather than being just passengers in our own mind.

The effects of the lack of sleep

It is all fine and dandy if we get our solid seven or eight hours (more for teenagers). Yet, life will throw curve balls, and there will be times when we can’t sleep due to internal or external circumstances. What happens to the brain if you have counted all the sheep and still can’t sleep? You might think that staying awake for 24+ hours is very doable and that you would not feel it that much, but the brain begs to differ. If it doesn’t get enough rest, even just for a day, the amygdala goes into overdrive and shuts down your prefrontal cortex. The prefrontal cortex is the most evolved part of the brain responsible for logic and reasoning. If incapacitated (as it is when you’re solidly drunk), all the information gets rerouted directly to the most primitive part of the brain, locus coerulens, and our reactions are raw and uncensored (ergo the shame reward at the bottom of bottles the next morning once the prefrontal cortex is back online).

This sleep deprivation suppressing of the frontal cortex is also the reason why tired people seem irritable and moody. Don’t judge them; they can’t help themselves when they are on primitive autopilot.  If you continue to stay awake and test your limits, you are in for a real mudslide. Memory and speech control are the next to go, as they are not crucially important. After that, general paranoia and even hallucinations set in. Longer periods of disrupted sleep will crash your immune system and make it 50% more vulnerable to viruses and bacteria. Have you ever noticed getting sick soon after a period of sleepless nights? This is why. If you’re going to indulge, make sure it’s worth it because most of the things are not. When a brain is tired, and you still won’t let it sleep, it will find alternative ways to feel better. What we are talking about are quick shots of energy. Congratulations, you’ve got intense cravings and no frontal cortex to say no. The brain will try to find any kind of stimulation, be it junk food full of carbs and sugar, alcohol, drugs, or superhuman amounts of caffeine. But no matter how hyped you get on all these substances, nothing can substitute a good sound sleep.

Just keep in mind that sleepy drivers are as lethal and dangerous as drunk drivers. You may think you are too busy to sleep and there is too much to see, to learn, to do… but you don’t have sole ownership of all the problems in this world, and very few things can’t wait till tomorrow. There is no use in punishing your body this way. So get off the internet, turn off your phone, make your room dark and relatively cold, turn the caffeine madness down a notch, and give yourself a break from time to time. We wish you sweet dreams. In the words of Jim Butcher: “Sleep is God. Go worship.”