Sleep State Switching – How Do We Fall Asleep?

Wonder how do we exactly fall asleep? Think of your brain as an electrical system, which has ongoing circuits that can switch off or on, to induce sleep or wakefulness. The transitional phase between these two conditions is called sleep state switching – also known as the flip-flop switch model. In this model, the neurons switch off or on to prevent arousal or sleep, to keep you asleep or to keep you alert during the periods of wakefulness.

If you are struggling to fall asleep at night, then you probably have enough time to think about many things, starting from personal problems such as ex-partners to what to cook tomorrow and how to pass an exam. But did you ever wondered how do we fall asleep? What happens in those few seconds when we switch off and enter the world of dreams? And how is it possible that we are barely aware of it? Sleeping peacefully or staying wide awake depends mainly on the way a few small areas in our brain tend to function, but a lot of other factors can impact the stability of that well-established system, causing us to be sleepy or awake at inappropriate times. 

Out of 24-hours we have at our disposal, we usually spend 16 hours awake, and sleep for the rest eight hours. It’s very interesting that only a small number of brain cells is in charge of that, so, today we will see what science has to say about it, and how exactly our brain falls asleep.

The Flip-Flop Switch

With many scientific achievements and discoveries over the past century, scientists were able to find out how exactly our brain falls asleep and to understand better how the entire process which controls our circadian rhythm functions. We can think about our brain as an electrical system, which has ongoing circuits that can switch off or on, to induce sleep or wakefulness. The transitional phase between these two conditions is called sleep state switching; one way to explain it is known as the flip-flop switch model. In this model, the neurons switch off or on to prevent arousal or sleep, and to keep you asleep once you fall into it, or to keep you alert during the periods of wakefulness. 

For the majority of people who do not have any sleep-related problems or disorders, switch model is useful in regulating their sleep pattern, which is in accordant to their social obligations and daily functioning. In other words, this is what keeps us awake in situations where it is not appropriate to fall asleep, for instance, at a business meeting or in a restaurant. Patients who are diagnosed with narcolepsy or other sleep disorders have a problem with the way this switch functions. Since it does not switch properly, it gives them the ability to fall asleep anywhere and anytime, no rules, even when they would rather be awake.

How Does it Work?

Sometimes, falling asleep can turn into a real struggle, and it can last for hours, but the essential part of transitioning from wake to sleep phase lasts only a few seconds while getting to that point can take much longer. The ability to stay asleep or awake for a stable period of time is an outcome of mutual inhibition of two different groups of neurons. Wakefulness and sleep are two different states, and we cannot be both at the same time, even though only a few seconds is between them, they inhibit one another. That is why experts agreed to use the term flip-flop switch, which is otherwise used in electronics to describe the circuit with two stable states, but flip-flops do not have transitional stages, they are either on or off, which is basically how scientists understand our sleep and wake stages work.

The neurons which participate in the switching process are located deep in our brain; one of them is orexin. Orexin or hypocretin is in charge of regulating the arousal, wakefulness, and appetite, lack of in the brain can cause cataplexy, which is a type of narcolepsy. The human brain contains around 10-20.000 of neurons which produce orexin, and most of them are located in the lateral hypothalamus and perifornical area. Hypothalamus is a part of the brain in charge of different functions related to endocrine and nervous systems. Some of the duties of the hypothalamus that are related to the nervous system include control of circadian rhythm, inner clock and sleep-wake cycle,  body temperature, hunger and thirst, emotional response, etc.

Now, let us go back to the core of things, orexin keeps us awake until the switch occurs and triggers the ventrolateral preoptic nucleus in our brain to start producing GABA and galanin neurotransmitters. Galanin is present in the brain, spinal cord, and gut, and it is involved in a few different functions, including sleep regulation. GABA is a neurotransmitter related to mood, and a lot of people take GABA supplements to enhance their sleep and mood. These two can calm the brain and prepare it for the state of sleep by blocking orexin, which use to keep us awake. By doing so, they reversed the cycle, or switched it, and induced sleep.

When talking about these things, we should make some things clear; neurons are the cells which are a part of the nervous system, to communicate with other cells they need to use neurotransmitters, which can pass their information to other cells like a carrier. Neurotransmitters are chemical compounds which tell neurons what to do, so in the spirit of today’s topic, if a group of sleep cells gets a message to stop their activity, they will stop, and the brain will also understand that message and start promoting wakefulness because those cells are now taking over, while the sleep cells are inhibited.

The model of sleep state switching can also be used to explain how we go from one stage of sleep to another. Some of the researchers claim that the switch occurs in the mesopontine tegmental area, which is located near the center of the brain. Right there, the neurons are regulating the switch between REM and NREM. In this case, while we are already sleeping, on both “sides,” we have neurons which produce the GABA neurotransmitter, but the switch in charge of triggering REM also has some glutamatergic neurons.

The flip-flop switch model is just a mechanism of how the switch happens, but by practicing some healthy habits, we can enhance the work of it, as well as our inner circadian clock.

What If The Flip-Flop Does Not Work Correctly?

Having a disbalance in your flip-flop switch is usually a sign of some other sleep-related disorders that follow destabilization of the switching process. For example, when the person is in the prolonged state of arousal, certain chemicals will start piling up in the brain and move the balance to the state of sleep, but chemicals are not the only ones in charge of triggering neurons. A lot of things around us, such as light, stress, or sound, can speed up or delay our sleep onset, but also some other conditions such as homeostatic sleep drive or circadian rhythm. 

Here are some of the disorders that go hand in hand with changes in the flip-flop switch.

  • Narcolepsy. As we mentioned it, this is by far the most common condition which can be related to inconsistency of the switch model, and to the lack of orexin, which promotes wakefulness. People suffering from this condition usually experience excessive sleepiness, which hinders their normal daily activities, and it is often followed by vivid hallucinations, seconds before falling asleep.


  • Cataplexy. This is a condition which strikes around 70% of people suffering from narcolepsy, there are no cases of cataplexy without narcolepsy, so they always go together. Cataplexy refers to sudden and temporary episodes during which a person is in a state of paralysis. The person is fully aware and conscious, but her muscles are weakened, and this condition is usually triggered by some strong, happy emotions, such as laughter, or happiness. This condition occurs when autoimmune destruction of neurons which produce orexin in the hypothalamus occurs, but it is still a mystery why only positive emotions can trigger it, and not the negative ones.


  • Hypnagogic hallucinations. Hypnagogia refers to intense, dream-like hallucinations which occur right when we start falling asleep. So as the person is still somewhat aware of what is going on, he/she can have the feeling that someone else is inside of the room, to smell or to hear something, etc. This mental phenomenon can also include lucid thoughts, dreams, or sleep paralysis, which is a separate sleep disorder.


  • Sleep paralysis. This is a type of muscle paralysis similar to cataplexy, but it does not stop once the person awakes, and in some cases, it can be followed by hallucinations. Sleep paralysis can occur either when the person is waking up or falling asleep, and the person is conscious and aware of the situation, but unable to speak or move any parts of the body. These episodes of brief paralysis usually last no longer than a few minutes, although, to the person going through it, it may seem like it lasts a whole eternity. There are no rules when it comes to liability, it can strike healthy people, those diagnosed with narcolepsy, and it can also run in families as a genetic predisposition. It is triggered by sleep deprivation, stress, or irregular sleep patterns.

How to Ensure Proper Work of Flip-Flop Switch Pattern

After we have seen what the consequences of irregular flip-flop switches can be, let us see now what we can do to prevent that from happening, and secure a healthier sleep routine that will enhance the quality of our life. These tips are all common sense advice, and the things we know we should practice, but somehow we always tend to avoid them, even though they are a part of sleep hygiene. Establishing healthy sleep hygiene sounds general and well-known, but a lot of people are not aware of what that means. Sleep hygiene implies a number of different habits and practices which should be followed on a daily basis to secure proper sleep quality and alertness during the daytime.

  • The right amount of sleep. We all need to sleep, but not all of us need the same amount of rest every night. For example, babies and children sleep far more than adults. Eight hours of sleep are considered an optimal and recommended amount of shut-eye for an average adult person, but we all know people who run on less or more hours, depending on how it works best for them. The crucial thing is to understand what your body needs, and to get enough rest. Sleeping significantly less or more than eight hours is usually a sign of some sleep disorder.


  • Sleep patterns. Once you know how much sleep you need, you will benefit even more from going to bed and waking up at the same time every day. You do not have to be very precise, but maintaining some type of a schedule will improve your sleep, and after only a few days of adjusting to it, your body will naturally be prepared for rest at the desirable time.


  • Avoid stimulants. Among different types of sleep stimulants, caffeine is probably the one that most people consume daily, and that is why it is so dangerous for our flip-flop switch because it can cause orexin disorders. Being moderate is the main thing when it comes to usage of stimulants such as caffeine, nicotine or alcohol, and their use should be avoided during the evening, even alcohol, which is known as a sleep inducer. If you drink it before bedtime, you will probably fall asleep faster, but it is also more likely that you will wake up during the night as the body starts processing alcohol.


  • Light physical activity. Not only exercising is good for your physical shape and health, but it will also help with your sleep habits because no matter how light or short exercises you are practicing, it is still going to exhaust your body and induce sleepiness. It is recommended to avoid exercising right before bedtime, but since this is not the same for everyone, we suggest trying different times, and finding out what is the right time for you.


  • Food. In the past, food was considered just a basic need for survival, but today there is a whole science around it, and we now know what should we eat if we do not want our stomach to wake us up in the middle of the night. All foods that are fatty, fried, spicy, or carbonated drinks, can cause issues with digestion and sleep, especially when they are taken late at night. 


  • Exposure to natural light. It is underrated, but crucial since the daylight has an essential role in our sleep-wake cycle. Being exposed to sunlight during the day, and to the darkness at night helps to maintain our inner clock in balance, and keep our sleep-wake cycle away from any potential disorders.


  • Bed equipment. This stands for basically anything that is a part of your bed, starting from the mattress. The right mattress is essential for sleep, since if it is uncomfortable, it can mess up your sleep, and the same goes for pillows. Today a wide selection of materials and compositions is available, so that everyone can find something that fits their needs and terms of comfort. Comfortable sheets, appealing patterns, and designs, or whatever makes you feel good, the overall impression should be pleasant to you, since it should represent your oasis.

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