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Stages of Sleep

  • You cycle through these four stages every 90 to 110 minutes

  • The stages can be distinguished by electrical changes in your brain, which can be measured by an electroencephalogram (EEG)

stage 1

  • Up to 7 minutes

  • “Drowsy” period

  • You are easily awoken and brain is still very active.

  • EEG electrical activity starts to slow down.

stage 2

  • Light sleep​

  • Eyes stop moving.

  • Body becomes disengages with its surroundings.

  • Body temperature drops.

  • Breathing and heart rate are regular.

  • You are still awoken easily.

  • Waves on the EEG increase in size, and there are short 1-2 second bursts called "sleep spindles." 

An EEG

stage 3

  • Slow wave sleep​

  • Deepest sleep

  • Blood pressure drops.

  • Breathing becomes slower.

  • Muscles are relaxed.

  • Blood supply to muscles increases.

  • Tissue grows and is repaired.

  • Energy is restored.

  • Hormones, such as growth hormone, are released.

As the night progresses, you spend less time in Stage 3 and more time in REM!

rem (stage 4)

  • ​25% of the night!

  • ​Eyes dart back and forth.

  • Brain starts to perk up.

  • Muscles are temporarily paralyzed ; body becomes immobile and relaxed.

  • Electrical activity starts to resemble the brain when it is awake.

Most dreams occur during this stage!

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