Are you interested to know what are the stages of sleep?
You may already be aware that you are not sleeping continuously the whole night in a comatose position. You probably remember the time just before you fell asleep and after that you have no memory of what happened, except if you woke up at some time in the middle of the night.
You go through the following four stages during sleep
Stage one - AWAKE STATE
Stage two - REM SLEEP
Stage three - LIGHT SLEEP
Stage four - DEEP SLEEP
Slow wave sleep, also called deep sleep, is an important stage in the sleep cycle that enables proper brain function and memory. While most adults are aware that they should aim for between 7 and 9 hours of sleep each night, the science of sleep is quite complex.
It is now discovered that we sleep in cycles of 90 mins where we go through the 4 stages or sometimes just 2 or 3 stages.
A healthy adult will get 5 or 6 cycles of sleep per night
There may be some ways to get both better sleep and more deep sleep each night, allowing a person to wake up feeling more rested and refreshed.
Stage one - Awake State
This is the state just before you fall asleep. This is the shortest stage and lasts less than 2% of your total sleep time. This is a transition period during which the body and brain shift from a state of wakefulness to one of sleep. This period is relatively short, lasting only a few minutes, and the sleep is fairly light. People may wake up from this stage of sleep more easily than from other stages.
During this stage, the body starts to slow its rhythms down. The heart rate and breathing rate slow down, and the eyes begin to relax. The muscles also relax but may occasionally twitch.
The brain unwinds along with the body. The brain waves start slowing down as brain activity and sensory stimulation decrease.
Stage two - REM SLEEP
In the first sleep cycle, this REM sleep is extremely short or sometimes nonexistent. But after the first cycle of sleep, the body goes into REM sleep for much longer.
During this stage of sleep, the eyes dart back and forth behind the closed eyelids. This state is closer to the wakeful state than the other stages of sleep. In REM sleep, the brain waves start to resemble the brain waves of the wakeful state. The heartbeat and breathing rate speed up.
The REM stage is also when most dreaming occurs. The brain temporarily paralyzes the arms and legs to prevent the body from acting out these dreams.
Stage three - LIGHT SLEEP
The third stage of sleep is another lighter stage of sleep that occurs as the body starts transitioning to deeper sleep. As the National Institute of Neurological Disorders and Stroke note, humans spend most of their time during the sleep cycle in this stage of sleep.
In the body, the heart rate and breathing rate slow down even more. The muscles relax further, and eye movements stop. The body temperature also goes down.
Although the brain waves slow down further, this stage also includes small bursts of electrical signals in the brain.
Stage four - DEEP SLEEP
Deep sleep or slow-wave sleep is the fourth stage of sleep. Although the body completes a few cycles throughout the night, this stage occurs in longer periods during the first part of the night.
In the body, the heart rate and breathing rate are at their lowest during this part of the sleep cycle. The muscles and eyes are also very relaxed, and the brain waves become even slower. This is when delta waves sleep occurs
It may be very difficult to wake someone from this stage of sleep, which is when sleep disorders, such as sleepwalking, occur.
Deep sleep requirements
While a person needs all the stages of sleep, deep sleep is especially important for brain health and function. Deep sleep helps the brain create and store new memories and improves its ability to collect and recall information.
This stage of sleep also helps the brain rest and recover from a day of thinking, allowing it to replenish energy in the form of glucose for the next day.
Deep sleep also plays a role in keeping the hormones balanced. The pituitary gland secretes human growth hormone during this stage, which helps tissues in the body grow and regenerate cells.
Importantly, a person has to get enough deep sleep for these functions to take place. The amount of deep sleep that a person has will relate to how much overall sleep they get. Sleeping 7 to 9 hours is the recommendation for most adults, which will usually give the body plenty of time in the deeper states of sleep.
If the body does not get enough deep sleep one day, it will compensate the next time it can get sleep by quickly moving through the cycles to reach the deepest levels of sleep faster and stay there longer.
Read more about how much Deep Sleep is required in https://www.ignatiusraphael.com/post/deep-sleep-what-is-it-how-much-is-required