There was a point where you slept. When you were a newborn, you slept 16 hours per day. After a day of playing as a child, you fell into a heavy, restful sleep. After a random relaxing day, you fell asleep happy. You didn’t need an understanding of sleep, because it just happened. 

But maybe those things haven’t happened in a while, and it’s like your body and mind somehow forgot to sleep. However, just as you don’t forget other basic human functions like getting hungry or breathing, you never truly forget how to sleep. Now, you have to strip away all the additional layers that have made sleep difficult. 

The first layer is understanding sleep and the processes that go on to make sleep possible. Understand that yes, there are anxious thoughts, behaviours, beliefs, and emotions that make it very difficult to get sleep. But your biology also plays a vital role too.

Learning about sleep will help you realise that it’s not completely up to you and your thoughts. You can let your very own biology help you.

The Five Stages of Sleep

grey cat sleeping atop white bed sheets

We go through five different stages of sleep throughout the night. And we experience them in a sequential order multiple times per night. These stages serve different functions to supporting sleep and feeling rested:

Stage 1

This is when you are ‘drifting off’. Your heart rate slows, your muscles relax, and it can almost feel meditative1. The purpose of this stage is to put you into a state of relaxation that prepares you for the next stage of sleep. 

If you’ve ever experienced a hypnic jerk where you jerk yourself awake, this is the stage in which it happens. And to put icing on the shit cake that is insomnia, it happens more frequently when sleep deprived2. There’s no conclusive reason for hypnic jerks. But one theory is that we are just fancy monkeys in shoes – it’s a primitive response to keep us from falling out of a tree.

Stage 2

A deeper sleep than stage 1, but still a light stage of sleep. The purpose of this stage is to restore your energy that you’ve expended during the day. 

Interestingly, if insomniacs wake up during stage 2 sleep, they are far more likely to report that they were actually awake when they were in fact sleeping3.

Stages 3 and Stage 4

This is what we know as deep sleep or ‘slow wave sleep’. Our brains have the least amount of activity going on here. Some studies have even shown that 100 decibel noises can’t wake some people at this stage4. Stages 3 and 4 are the most important stage of sleep to feel rested and to feel renewed physical and mental energy the following day.

Stage 5

Known as rapid eye movement (REM) sleep. As the name states, this stage is characterized by rapid eye movements, and it’s also when we dream. If you were to get a brain scan during this stage, the brain waves resemble the brain waves you’d see during waking hours5. Our understanding of REM sleep is to process and store information (including emotional information) into memory. If you’re an insomniac, you probably don’t remember a lot of your dreams because your brain is too busy trying to catch up on deep sleep when you finally do fall asleep.

Sleep Cycles

Our understanding of sleep as adults is that we typically have 90 minute (give or take) sleep cycles. This means we go through stages 1-5 of sleep several times per night when we sleep a full night. For example, in a seven and a half hour night, we will have five sleep cycles.

And guess what? It’s perfectly normal to wake briefly after a sleep cycle, and in lighter stages of sleep. We typically don’t remember these wakings. But during an average healthy sleep, we wake up about 2-4 times throughout the night6.

This means that the person who sleeps fine, and feels rested has actually woken up several times per night. So if you’re the type to get stressed about waking up in the middle of night, just remember this is normal and it’s part of our biology.

These wakings only start to affect us when it starts happening for more than a few minutes, at least three times per night. 

Interestingly, our deep sleep periods are longer at the beginning of the night and our stage 5 only lasts a few minutes. As the night wears on, the pattern reverses. We spend less time in deep sleep and more time dreaming. This is why you might notice that you remember dreams from the morning a lot better. It’s because your REM stage is now longer7.

This is also why our sleep grows lighter and we are more prone to waking up as the night progresses. So sleep maintenance insomniacs…this is part of the reason why you are the way you are. 

Understanding Sleep: Your 24 Hour Clock

a white neon light clock with no numbers and black hands pointing at the 1:20 position. This image in on the article understanding sleep.

Barring a disorder like circadian rhythm disorder, your brain runs on a 24-hour clock. This clock regulates your day by releasing melatonin 8

⮞ Starting in the later evening between 9pm and midnight, our melatonin levels rise. It reduces our body temperature which signals to your body that it’s time for sleep. For most of us, this block of time would be the ideal time to go to bed.

⮞ Between roughly midnight and 3am is when melatonin levels are at their highest. If you are still awake at this time, you will feel drowsy. It’s difficult to focus your attention on any one thing. Once early morning hits, between 3am and 6am, your melatonin levels gradually start to fall.

⮞ Sometime between 6am and 9am is when your body stops producing melatonin. This of course is also when the sun happens to rise in most parts of the world. This helps to reduce melatonin concentration in your body. It’s your natural signal that it’s time to be alert and start the day.

⮞ The later morning between 9am and noon is when we are typically at our most alert, since now the melatonin is cleared out and we are producing cortisol. While cortisol is known as the ‘stress hormone’, it does much more than that, including the regulation of the ‘wake’ part of your sleep/wake cycle9. It also regulates your blood pressure, blood sugar, and metabolism for when we are primarily awake and eating. It also manages how your body uses the food you eat, and fights inflammation.

⮞ For the rest of the day until around 9pm our cortisol levels start to drop (hence why many people become groggy around 3pm). The cycle starts again.

Prior Wakefulness and Sleep DriveA Key Understanding to Sleep

When it comes to sleep, your daily functioning can be classified into two systems:

  • Your wake system, which promotes alertness, is up and running for roughly 16 hours per day. 
  • Your sleep system that promotes, you guessed it, sleep, lasts for roughly 8 hours per day.

These two cycles occur because of the neurotransmitters being released by the brain. During your wake cycle, neurotransmitters called norepinephrine, histamine, and serotonin are being released. These help keep you awake10

But then there’s an interplay where adenosine, which is the sleep neurotransmitter, builds up during the day and slows down the ‘wake’ neurotransmitters. 

The longer the wake system is “on” (i.e., the more time you are awake), the greater the internal drive is for sleep. This is because adenosine has more time to build up in your body. Plus, the more active you are during the day, the greater your sleep drive will be at night. Activity signals your body to produce the sleepy adenosine neurotransmitter.