By Luke Langlois, Blogger and AP Psychology Student

It is truly a miracle that most humans enjoy sleeping. After all, we do spend one-third of our lives sleeping. And, we all have a general idea of what we get from sleeping. Sleeping gives humans the energy to carry out our day. Sleeping somehow cures humans of short-term illnesses or some sort of stress. To our conscious minds, sleeping is like a small time machine. But, contrary to what we might perceive, a LOT goes on while we’re sleeping. Coincidentally, there is a whole unit in AP Psychology about sleep and consciousness, so, why not share this knowledge? Today, I present to you a bit about what goes on in your head during your deep sleeps.

The Stages of Sleep

Scientists have defined five different stages that humans progress through during sleep.

Stage 1 – A light sleep: Stage 1 of the sleep cycle is, as might be expected, the stage where one is in the “lightest” sleep. You’re not awake, but you’re not completely asleep. It is best described as the stage of drifting off to sleep. Sudden noises or disruptions will easily bring you back to a completely conscious state. Individuals will sometimes feel as if they are physically falling during this stage. Additionally, individuals sometimes have what is called a “hypnic jerk” during this stage, where they may experience abrupt muscle spasms and jump back awake. This stage lasts about 5-10 minutes.

Stage 2 – Preparing for a deeper sleep: This is a fairly short stage that is part of the transition into a deeper sleep. During this transition, the individual’s brain waves continue to slow down, with some specific bursts of activity which are known as “sleep spindles.” During this stage, the body’s temperature slightly decreases, and the heart rate gradually lowers. This is a generally uneventful stage and serves mainly as the “sleeping housekeeping” for the body. This stage lasts about twenty minutes.

Stage 3 –  Transitioning into a deeper sleep: This is where an individual begins to transition into a much deeper sleep. After this stage, it becomes very difficult to awaken an individual. Slow brain waves known as “delta” waves emerge in this stage. Brain activity here is quite low. This stage lasts about 5-10 minutes. Be aware that some sources will not recognize this period as its own separate stage, and will instead group it in with the next stage, calling it all “Stage 3.”

Stage 4 – Deep Sleep, but without REM: Stage 4 is sometimes referred to as “delta sleep” because of the continuation of the delta brain waves during this stage. It is quite difficult to awaken someone from this sleep, and it will take some additional effort. There is no dreaming during Stage 4, but some well-known sleep events occur here, like sleepwalking. This stage is the most “restorative” stage for the body, and lasts for about 30 minutes.

Stage 5 – REM!: REM sleep, also known as the “Rapid-Eye Movement” stage is the most active stage for the brain, even if it is the deepest stage of sleep. During this stage, the body experiences increased eye movement, an increased breathing rate, and increased brain activity. Dreaming is most prevalent in this stage and rarely occurs in other stages. While these systems become more active, the voluntary muscle systems are paralyzed. The brain releases a paralyzing chemical that, theoretically, prevents the body from acting out its dreams. The length of this stage varies, depending on how long an individual sleeps.  

So, now that you’ve got a general look at the stages of sleep, there are some things that should be mentioned. First, one sleep cycle does not equal the total amount of time that one spends sleeping. One will go through multiple sleep cycles in the typical 8-hour sleep. Secondly, this is not a completely linear 1-5 sequence. When an individual first falls asleep, they only progress from Stage 1 to Stage 4. After Stage 4 is reached, the brain goes backwards. It goes into Stage 3, then 2, and then falls into the REM stage. One sleep cycle lasts about 90 minutes. I will send off this post with something practical for the nappers in the audience. A 90-minute nap is going to provide you with the best “refresh,” as you have been able to go through one whole sleep cycle. But, this is not to say that shorter naps aren’t as effective. No matter what, sleep on!

Editor: Makena Behnke