Stages of sleep

sleep stages

What are the different stages of sleep?

Although you may think that there are nights when you don’t dream, your brain can go through 6 stages of sleep in which we produce mental images.

We go through different stages of sleep while we sleep at night.

Sleep is a physiological process. Your body constantly needs to replenish its depleted energies during the day, as well as to perform some internal actions for body to function proper.

However, this process goes through various stages, which are vital for a quality sleep without distractions, that allows the body to rest completely.

Sometimes the sleep stages can be affected by factors outside the body, such as:

  • Cigarette consumption
  • Excessive consumption of coffee
  • Alcoholism
  • Anxiety
  • Stress

How to recognize a body that is entering a stage of sleep?

By keeping the eyes closed, electrical oscillations can be clear on the electroencephalogram (EEG) at an alpha rhythm of 8-13 per second.

After few minutes changes are highlighted, which are associated with each of the stages of sleep, according to the brain activity.

Stage 1

  • It belongs to the stage of light sleep. It is a state of brief drowsiness, where the brain enters and leaves sleep. This is the stage where you can wake up very easily.
  • In stage 1, the eyes have rapid movements, this process is known as REM (rapid eye movements) while the muscles are relaxing.
  • The person is able to perceive auditory and sensorial stimuli, being little or no rested at all, because it is a minimum rest stage. In addition, this stage contains sudden muscle contractions.

That is why we can sometimes feel the sensation of suffering a sudden drop: it is the perception of entering the depth of stage 1, to pass in a few minutes to stage 2 of the dream.

Stage 2

  • In the second phase of sleep, a pattern is identified in which eye movements stop, while dynamic brain waves are declining, leaving only a single activity of rapid brain waves.
  • The brain activity known as sleep spindles appears on the EEG. In addition to the slow waves, they represent the moment when body temperature, heart rate and respiratory rate begin to decrease progressively.
  • At this stage, the nervous system blocks the sensory stimuli, so it is almost impossible to receive information from outside.
  • Thus, this phase becomes a part of sleep repair, although in minimal proportions.

Stage3

  • At this stage of sleep the person begins to have waves of brain dynamics much slower than in the previous phase.
  • They are called delta waves, which are interspersed with fast, but smaller waves.
  • It is a part of deep sleep in which the person usually stays for 2 or 3 minutes without eye movements, (non-REM sleep) being difficult to wake up.
  • Blockage of sensory stimuli is intensified. If the person wakes up at this stage, he will feel disoriented and confused.
  • In this period, there are no imaging dreams, blood pressure decreases and growth hormone is increasing.

Stage 4

  • It is a stage guided almost exclusively by delta waves. It’s intense deep sleep, and in this phase it’s much harder to wake people up.
  • There is no activity of eye movements or muscle tone. Usually, in this sleep phase, children often wet the bed, walk asleep or experience night terrors.
  • This happens within the stages of very slow sleep, usually lasts about 20 minutes and dreams do not occur.
  • However, it’s the step that helps us to know if sleep has been restorative or not.

How many cycles of sleep stages occur in one night?

People usually sleep varying between non-REM sleep and REM sleep in periods ranging from 70 to 100 minutes.

REM sleep can last from 5 to 30 minutes, and the rest belongs to non-REM.

Both cycles are usually repeated every half hour at night, and we can achieve between 4 and 6 cycles of REM sleep.

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