What happens while you are sleeping?

When we sleep well, we wake up feeling refreshed and alert for our daily activities. Sleep affects the way we look, feel and perform on a daily basis and can have a major impact on our overall quality of life.

1.How important sleep is for each of us Each of us spends about a third of our lives (about 25 years) on sleep. Sleep is as important to life as food or water. Despite extensive research, scientists still don't fully understand what happens while we're asleep. Feeling sleepy is the driving force that urges each person to go to sleep.
However, by different reasons such as sleep disorders in children, in the elderly or sleep disorders in pregnant women or excessive use of stimulants, this motivational source can be completely annihilated.
Scientists used to think that humans were physically and mentally inactive during sleep. But up until now they had known that this was not true. All night, our body and brain have to do quite a lot of work related to human health.
This activity is expressed through the stages of sleep and can be divided into 2 main stages: non-rapid eye movement (NREM) and rapid eye movement (REM) stages.
Non-Rapid Eye Movement (NREM) Phase: This is the period when the body spends most of its time resting. During this stage, your brain becomes less responsive to the outside world and harder to wake up. Your thinking and most bodily functions slow down. You spend about midnight sleeping normally. Most of our sleep (about 70 to 80 percent) is a non-rapid eye movement phase, characterized by brainwaves that occur in bursts during the NREM phase of sleep with slow, fast wavelengths that do not even. This is the stage when the body enters the deepest sleep. Without this stage, the ability to form memories, thinking as well as the connections between parts of the brain will be severely impaired. NREM is important for transferring short-term memories into long-term storage. Deep sleep is also the time when the body releases the highest levels of growth hormone, which is important for the regeneration and repair of cells in the body.
Rapid eye movement (REM) phase : In this stage your eyes swing back and forth behind your eyelids. Your dreams appear most during this stage. Your pulse, body temperature, breathing rate, and blood pressure rise to daytime levels. Your sympathetic nervous system, which helps with automatic responses like fight or movement. However, your body remains almost completely still.

The purpose of the REM phase is not really clear and the effects of REM sleep deprivation are less severe than those of NREM sleep deprivation. This stage can be considered as the period in which most vivid and emotional dreams occur compared to the NREM stage in which only dreams tend to be realistic, based on concepts and definitions developed from prior to.
Many scientists think that rapid eye movement sleep allows our brains a safe place to practice processing situations or emotions that we rarely encounter in our daily lives. During REM sleep, our muscles are temporarily paralyzed, preventing the expression of these emotions to avoid endangering the body itself. Some scientists believe that REM sleep is the body's way of releasing unwanted memories or negative emotions. However, no matter which interpretation is correct, in fact REM is still the place that provides us with emotional dreams. You typically go through all of these sleep stages 3 to 5 times a night. The first REM period can be just a few minutes, but it gets longer with each new cycle, up to about half an hour. Other way. And if you lose REM sleep for any reason, your body will try to make it back up the next night. Scientists are uncertain about the purpose of this.
Some of the prominent changes when the body is sleeping are:
Body temperature Your body temperature drops a few degrees before you go to sleep and is at its lowest about 2 hours before you wake up. During REM sleep, your brain will even turn off your body thermometer. That being hot or cold in the bedroom affects you more. In general, a cool room helps you sleep better. Light activities like exercising when you wake up raise your temperature and keep you awake.

Breath Your breath changes a lot when you wake up. But when you fall into a deep sleep, you breathe slower and more regularly. Then, as you enter the REM phase, your breathing will be faster and more variable.

Heart Rate Deep sleep, NREM lowers your heart rate and blood pressure, giving your heart and blood vessels a chance to rest and recover. But during REM, these rates rebound or fluctuate.
Brain Activity When you close your eyes and begin drifting into NREM sleep, your brain cells settle down from their daytime activity levels and begin to follow a more regular, rhythmic pattern.
But when you start dreaming, your brain cells are active and random. In fact, during REM sleep, brain activity is similar to when you wake up.
Dreams Dreams are still a mystery. It's not clear what causes them or what the purpose of the dream is. Dreams are very common during REM, especially when dreaming is very intuitive, but you can also dream during other sleep stages. Nocturnal terrors - when people appear to be awake and cry out in fear or panic - occur during a deeper state of sleep.
Time to Repair During deep sleep, your body works to repair muscles, organs and other cells. Chemicals that boost your immune system start circulating in your bloodstream. Spending time in deep sleep helps you stay younger and healthier when you don't get enough sleep.
Clearing up the body That's what scientists think happens during the REM phase. This activity helps your brain clarify information without needing and discarding. People with REM deficiency in particular - compared to other sleep stages lose this advantage.
Hormonal symphony Your body makes more hormones while you sleep. For example, levels of growth hormone increase, and cortisol . Additionally, a lack of sleep can mess with levels of hormones that control hunger — leptin and ghrelin — and that can change how much you eat and cause you to gain weight.

In addition, changes in the body during sleep were also seen across the 5 stages of sleep distinguished by changes in brain activity by EEG. The first stage begins with the baby falling asleep as the body gradually loses consciousness and gently enters sleep.
Then there are two stages of deep sleep, brain activity begins to slow down, breathing rate, heart rate, body temperature drop. Eventually the brain resumes activity and the body enters rapid eye movement sleep. This cycle occurs many times throughout the night, and each time the duration of REM sleep becomes longer.
Five specific sleep stages include:
Stage 1: Lasts from 1 to 7 minutes. During this stage the eyelids begin to droop and the sleepy muscles pull in more and more intensely. The brain activity measured on the EEG begins to slow down, the cortical waves are higher and sharper. As the sleep cycle repeats, the body enters this phase in a semi-awake state. Stage 2: This phase usually lasts between 10 and 25 minutes. Marked by a noticeable slowdown in brain activity and the body falling into a light sleep. On the EEG screen, this stage is characterized by a slowing down of brain waves along with an increase in their size. Brain waves also appear with irregular strength and weakness. When the body is in stage 2 of sleep, the eyes will stop moving but you can still wake up easily. Stage 3: Usually lasts about 20 to 40 minutes. At the start of stage 3, the brain waves stop indicating that the body has entered moderate sleep. This is the money to enter a deep sleep. On EEG, brain waves are slower and produce delta waves with waves of irregular intensity. When entering stage 3 of sleep, the body will have a hard time waking up. Stage 4: This phase usually lasts between 20 and 40 minutes. There is some debate as to whether stage 3 and stage 4 are really separate or should they be counted only as one stage of sleep because of their similarity. Stage 4 is the deepest stage of sleep and during this stage it is extremely difficult for the body to wake up. The EEG shows slow, high waves called delta waves. In addition, muscles in this stage are also maximally relaxed, breathing becomes slow and rhythmic, snoring may appear. Stage 5: Usually lasts about 10 to 60 minutes. After the body enters a state of deep sleep, the brain begins to function again and what appears on the EEG is no different from when it is awake. This is around the time most dreams start to happen. Muscles are temporarily paralyzed and your eyes start to roll back and forth. That is why this stage is also known as the rapid eye movement (REM) phase.

Scientists used to think that both physical and mental activities of people would completely stop when they slept. However, that was no longer accurate when the EEG appeared. They have partly answered the question many people have as to what happens while they are asleep. Throughout the night, the body and brain actually continue to work and these are all jobs that have a big impact on health.
There are 2 main types of sleep: rapid eye movement (REM) sleep and slow eye movement (NREM) sleep. Each stage of the brain has different mechanisms to regulate the activity of the body.

Article reference source: webmd.com, independent.co.uk