4 stages of sleep (NREM and REM sleep cycles)


When you sleep, your brain goes through four stages of sleep.

  • Stages 1 to 3 are what is considered a dream no rapid eye movement (NREM), also known as a restful sleep.
  • Stage 4 is sleeping with rapid eye movement (BDG), also known as active sleep or paradoxical dream.

Each has a unique function and role in maintaining the overall cognitive activity of your brain. Some stages also involve physical repairs that maintain your health and prepare you for the next day.

The entire sleep cycle is repeated several times per night with each subsequent stage of REM sleep increasing in Duration and depth of sleep.

This article covers the basics of the sleep cycle, what happens when each stage of sleep occurs, and what can affect your ability to pass these stages correctly.

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Entrance to the Dream

Widely used electroencephalogram (EEG). a noninvasive test that records brain activity, scientists can see how the brain participates in a variety of mental activities as a person falls asleep and falls asleep.

During the early stages of sleep, you are still relatively awake and alert. At this time, the brain produces so-called beta waves, small, fast brain waves that mean the brain is active and busy.

When the brain begins to relax and slow down, it lights up with alpha waves. During this transition to deep sleep, you may experience strange and vivid sensations known as hypnagogic hallucinations.

Common examples of this phenomenon include the feeling of falling or hearing someone call you by name.

There are also myoclonic pull; if you have ever shuddered suddenly, apparently for no reason, then you have experienced it.

No 5 stages of sleep?

Sleep used to be divided into five different stages, but this was modified by the American Academy of Sleep Medicine (AASM) in 2007.

Stage 1

The first stage of the sleep cycle is the transition period between wakefulness and sleep.

If you wake someone at this stage, you may report that you haven’t actually slept.

During the first stage of sleep:

  • Your brain slows down
  • Your heart rate, eye movements, and breathing slow down along with this
  • Your body relaxes and your muscles can contract

This short sleep period lasts between five and 10 minutes. At this time, the brain is still quite active and produces high amplitude Theta waves, which are slow brain waves that originate mainly in the frontal lobe of the brain.

Stage 2

According to The American Sleep Foundation, people spend about 50% of their total sleep time during NREM stage 2, which lasts about 20 minutes per cycle.

During the second stage of sleep:

  • You become less aware of your environment
  • Your body temperature drops
  • Your eye movements stop
  • Your breathing and heartbeat become more regular

The brain also begins to produce bursts of rapid, rhythmic brain wave activity, known as sleep spindles. They are thought to be a function of memory consolidation, when your brain collects, processes, and filters the new memories you acquired the day before.

As this happens, your body slows down in preparation for stage 3 of NREM sleep and REM sleep, the stages of deep sleep in which the brain and body recover, recover and restart the next day.

Stage 3

Deep, slow brain waves, known as Delta waves, begin to appear during sleep in stage 3 of the NREM stage, which is also called Delta sleep. This is a period of deep sleep in which any noise or activity in the environment may not wake the sleeping person.

Getting enough sleep on stage 3 of NREM allows you to feel rested the next day.

During NREM stage 3 sleep:

  • Your muscles are completely relaxed
  • Your blood pressure drops and your breathing decreases
  • You immerse yourself in your deepest sleep

It is during this stage of deep sleep that your body begins its physical recovery.

Meanwhile, your brain consolidates declarative memories, such as general knowledge, facts or statistics, personal experiences, and other things you’ve learned.

Fast sleep

As your brain is excited by mental activity during REM sleep, the fourth stage of sleep, your voluntary muscles become immobilized.

It is at this stage that your brain activity is closest to your activity during waking hours. However, his body is temporarily paralyzed, which is a good thing, since it prevents him from fulfilling his dreams.

Fast sleep begins about 90 minutes after falling asleep. At this hour:

  • Your brain lights up with activity
  • Your body is relaxed and immobilized
  • Your breathing is fast and irregular
  • Your eyes move quickly
  • Dream

As in stage 3, memory consolidation also occurs during REM sleep. However, fast sleep is believed to be when emotions and emotional memories are processed and persist.

Your brain also uses this time to anchor information in memory, making it an important step in learning.

Ongoing repair work

During deep sleep (stage 3 and REM), your cells are repaired and repaired, and hormones are released to stimulate bone and muscle growth. Your body also uses deep sleep to strengthen your immunity so you can fight disease and infection.

Sequence of sleep stages

It is important to understand that sleep does not go through all four stages in a perfect sequence.

When you have a full night of continuous sleep, the stages develop as follows:

  1. The dream begins with the NREM stage 1 dream.
  2. NREM stage 1 moves on to NREM stage 2.
  3. NREM stage 2 is followed by NREM stage 3.
  4. Then NREM stage 2 is repeated.
  5. Finally, you’re in a REM dream state.

Once BDG sleep ends, the body usually returns to stage 2 BDG before starting the cycle again.

The time spent at each stage changes throughout the night as the cycle repeats (about four to five times in total).

Dream architecture it refers to the exact cycles and stages that a person experiences at night. A sleep specialist can show you this information in what is known as a hypnogram, a graph obtained with an EEG.

What Could Disrupt Your Cycle

Interrupted sleep is a term used to describe a sleep that is not continuous throughout the night. When this happens, your sleep cycle may be disrupted. The unfinished stage of sleep can be interrupted and the cycle can be repeated before it is completed.

There are a number of problems that can disrupt your sleep cycles. Depending on which of them is in the game, this can happen from time to time or chronically.

Some factors that are associated with intermittent sleep and therefore can affect your sleep stages include:

  • Advanced age: Sleeping naturally becomes easier and it’s easier to wake you up.
  • Nocturia: Often wakes up with the urge to urinate
  • Sleep disorders, include obstructive apnea in sleep (breathing that stops and begins during sleep) and restless legs syndrome (strong feeling of needing to move legs)
  • Pain: Difficulty falling asleep or falling asleep due to acute or chronic pain conditions, such as fibromyalgia.
  • Mood disorders. such as depression and bipolar disorder
  • Other health conditions including disease Alzheimer’s disease Parkinson, obesity, heart disease and asthma
  • Lifestyle habits: Little / no exercise, cigarette smoking, excessive caffeine consumption, excessive alcohol consumption

Whenever you have trouble falling asleep or sleeping at night, it affects your sleep cycle.


As your body goes through all four stages of the sleep cycle, it goes through various biological processes that affect your temperature, your breathing, your cells, and your muscles.

All this time, your brain is busy forming, organizing, and storing memories.

Over time, getting enough sleep and cycling in four stages as you should can cause health problems and difficulties with the following:

  • Training and concentration
  • Be creative
  • Sound decision-making
  • Troubleshooting
  • Evoking memories or information
  • Control over your emotions or behavior

A Few Words From Get Meds Info

It is important not only to get seven to nine hours of sleep per night, but also to provide continuous, quality sleep that allows your body to benefit from each of these four stages.

If you experience any of the following, make an appointment with your health care provider, as you may not get enough sleep as you need:

  • Have trouble falling asleep or falling asleep at least three nights a week
  • You wake up regularly feeling anxious
  • Your daytime activities are affected by fatigue or mental activity
  • You often need to take a nap to get through the day
  • A sleepmate told him that he snores or drowns when he sleeps
  • Lack of sleep affects your mental well-being
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