Sleep is very important to one’s body despite how it is usually associated with lethargic actions. Most full-time workers hardly get enough sleep and consume large amounts of caffeine to keep themselves up. However, times have changed as students pull up all-nighters to work and study for their college work, resorting to the same sleep routine as those of full-time workers. This culture has been normalised to the point that some even consider 3 am to be the ‘new midnight’.
To put it into simple words, ‘sleep’ is the same as consuming food to keep us working throughout the day and maintain the normal functioning of the body. Thus, sleep is one of the most important activities for a healthy body because during sleep your body takes time to grow bones, repair muscles, manage hormones and sort memories.
Four stages of sleep
When you close your eyes to get some sleep, your brain goes through 4 stages. Where stages 1, 2 and 3 are considered non-rapid eye movement (NREM) sleep, which is also known as quiet sleep.
While stage 4 is considered rapid eye movement (REM) sleep which is also known as active sleep or paradoxical sleep. The stages have their own function which is required in maintaining our brain’s cognition.
With every successive REM stage, there is an increase in the duration and depth of each sleep cycle as it repeats itself every night. Moreover, some stages of this sleep cycle are also in association with physical repairs that are required for keeping the body in a healthy state and also to get ready for the following day.
State of your brain as you enter sleep
To conduct such tests regarding sleep, non-invasive tests are used for recording the activity in the brain. With the use of an electroencephalogram (EEG), scientists and researchers are able to see how the brain functions and how it engages in various mental activities as the person enters sleep or in sleep.
Beta waves are small and fast brain waves that notify that the brain is active and engaged. They are produced during the earliest stages of sleep when you are still awake and alert.
Once it begins to relax, it lights up along with alpha waves. In this transition stage into a deep sleep, you may experience strange and vivid sensations known as hypnagogic hallucinations. Examples may include sensations of falling from a tall building or a cliff.
Stage 1 of NREM
As it is the beginning stage, it is the transitioning between wakefulness and sleep during the first sleep cycle. The most common occurrences of an example for this stage has to be those times when you awaken someone only for them to reply back that they weren’t sleeping at all.
During this transitioning stage of sleep:
Your brain will be slower than it was when you were awake.
Your heartbeat rate, breathing and eye movements will also slow down.
Your body relaxes and you might experience your muscles twitching.
Stage 1 lasts for around 5 to 10 minutes which is only for a brief period. During this period, theta waves at high amplitude are produced which slows brain waves mostly occurring in the frontal lobe of your brain.
Stage 2 of NREM
The duration of stage 2 is about 20 minutes per cycle and approximately 50% of the total sleep cycle is spent here, according to the American Sleep Foundation.
During stage 2:
Less aware of your surroundings.
Your body temperature will decrease.
Your eyes stop moving.
Your breathing and heartbeat rate become more normal compared to stage 1.
Sleep Spindles are bursts of rapid and rhythmic brain wave activity produced by the brain. These sleep spindles are thought to be a feature that is responsible for gathering, processing and filtering new memories which had been acquired the previous day.
At the same time, your body starts to prepare for the next stages i.e. stage 3 NREM and REM sleep.
Stage 3 of NREM
Delta waves which are slow brain waves start to emerge during this stage. Thus, due to the emergence of delta waves, stage 3 of NREM is also referred to as delta sleep. This stage is a period of deep sleep where any sort of auditory disturbance or activities might fail to wake the person who is in a deep sleeping state. Getting enough of this stage of sleep can make you feel active and fresh the following day.
During stage 3:
Your muscles are relaxed.
Your breathing slows down and your blood pressure drops.
You peacefully progress into a state of deep sleep.
Moreover, it is at this stage of sleep where your body starts doing physical repairs while your brain consolidates declarative memories. Declarative memories include those types of factual knowledge such as general knowledge, or personal experiences, and other things you have learned during your journey.
REM Sleep (Stage 4)
The most intriguing part about stage 4 is the way your brain’s activity closely resembles its activity during active hours – when awake. Your brain is constantly aroused with mental activities during this stage.
However, despite the uncanny resemblance of brain activity, your body is temporarily paralysed which prevents you from acting out your dreams. Stage 4 begins approximately 90 minutes after falling asleep.
During REM sleep:
Your brain activity lights up.
Your body is immobilised and relaxed.
Your breathing is faster and irregular than before.
Your eye movements increase.
You dream.
Just like the previous stage (Stage 3), memory consolidation occurs but it is thought that during REM sleep emotions and emotional memories are stored and processed. Additionally, your brain also makes use of this period to permanently fix information in your memory, therefore, making this stage an important period for learning.
To conclude the four processes
Your brain is active and very busy while you are asleep. It’s busy organising, forming and storing information and memories. Thus, not getting enough sleep can decrease your metabolism.
