What happens while we sleep

Previously scientists used to believe that as people drifted off to sleep, their brains and bodies would go into “shutdown” mode allowing are body to recover from the previous day.What researchers have since learned: Sleep is a whole lot more complicated, and it’s a much more active state than you might think. In fact, while you’re getting your zzz’s, your brain goes through various patterns of activity.

Sleep cycle contains two parts- NREM (NoN REM cycle) plus a REM cycle. Your brain first enters four different stages of NREM sleep and then goes through REM. The cycle repeat themselves until you wake up.

Find out what goes on each stage step by step below

Stage one:

This is lightest sleep stage. The introduction to sleep is relatively brief, lasting up to seven minutes. Here, you are in light stage sleep, which means that you’re somewhat alert and can be easily woken. It’s during this stage of sleep that people often indulge in brief “catnaps.” Here you may feel like you’re falling or have sudden muscle twitches (also known as “hypnic jerks”).

Stage Two:

During this second stage, your heart rate slows, your muscles contract and relax, and your body temperature decreases as you prepare to go into deep sleep.

Stages Three & Four:

This stage is the beginning of deep sleep, as the brain begins producing slower delta waves. You won’t experience any eye movement or muscle activity. At this point, it becomes a little harder for you to be awakened, because your body becomes less responsive to outside stimuli. You move into an even deeper, more restorative stage of sleep next. It’s most difficult to wake up during this stage. This is when the body repairs muscles and tissues, stimulates growth and development, boosts immune function, and builds up energy for the next day.

When you wake up someone from these two stages they are often confused and disoriented because they need to adjust. These two stages are so deep that some children wet their beds, sleep walk or even experience night terrors.

Rapid Eye Movement (REM) Sleep:

You generally enter REM sleep about 90 minutes after initially falling asleep, and each REM stage can last up to an hour. An average adult has five to six REM cycles each night. During this final phase of sleep, your brain becomes more active. This is when most dreaming occurs, your eyes jerk quickly in different directions (hence, the name!), heart rate and blood pressure increase, and breathing becomes fast, irregular, and shallow. REM sleep plays an important role in learning and memory function.


A full cycle takes around 90 to 110 minutes. The first cycle is usually shorter with deep sleep taking the lion’s share and the REM stage being shorter. As the night progresses, the deep sleep phase becomes shorter while the REM phase increases. As we approach the end of our sleep, it is mainly split between stages 1, 2 and the REM stages.

  • On average, light sleep will take up about 50 to 60 percent or more of your night. Whether you get more or less light sleep isn’t really going to affect how you feel too much, because it’s just whatever time is left that’s not spent in deep sleep or REM.
  • Deep sleep, on the other hand is likely to take up 10 to 25 percent (depending on your age) of your sleep.
  • Too little, on the other hand, and sleep becomes unrefreshing. The two main things that can lead to less deep sleep is age—people naturally get less as they get older—and anything that interferes with your sleep, like pain, illness, medical problems, sleep apnea, and other sleep disorders. They can keep you out of deep sleep artificially, which makes your sleep a little more shallow.Also, shift work. Your body wants to get into deep sleep at night, and it wants to avoid deep sleep during the day, So you have a natural delay of how long it will take you to get into it.
  • Lastly, REM makes up about 20 to 25 percent of your nightly sleep and mostly takes place in the second half of the night.

If you cut your sleep short, most of what you’re cutting out is REM. And too little REM sleep can leave you feeling groggy, less able to focus, and might lead to memory problems. That’s why it’s important to get enough rest after learning something new or before taking an exam. Many medications can also block REM. Most antidepressants can cut REM sleep by half.

Consistently getting too much REM could also create problems. If you go too much over 25 percent of REM, it might cause too much brain activation, which can leave you angry and irritable and can even potentially exacerbate depression and anxiety.

The amount of time you spend in each stage also depends on your age.

“Sleep is that golden chain that ties health and our bodies together”-Thomas Dekker

16 responses to “What happens while we sleep”

  1. I fell asleep while reading this blog….🤣🤣 But you keep on writing more informative blogs. Good job ” Smriti Singh “. 👍

    Liked by 1 person

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