Stages of Non-rapid Eye Movement (NREM) and Rapid Eye Movement (REM) Sleep

Sleep Cycles

4-6 lasting approx 90 minutes each, alter in length and time throughout the night. 4 Distinct Stages: 3 NREM stages, 1 REM stage

Stage 1/NREM 1: Characteristics

• Sleep State: Transitional period between wakefulness and sleep

• Heart Rate: Decreases

• Eye Movement: Eyes slow rolling movement, once asleep stop moving

• Muscle Tension: Relax

Stage 1/NREM 1: Length of Stage

1-7 Minutes, if uninterrupted quickly move to NREM 2, minimal time is spent

Stage 2/NREM 2: Characteristics

• Sleep State: Light NREM sleep

• Heart Rate: Decreases

• Eye Movement: Stops

• Muscle Tension: Relax, occasional twitch

Stage 2/NREM 2: Length

10-25 Minutes, increases in length with each stage repetition

Stage 3/NREM 3: Characteristics

• Sleep State: Deep NREM sleep

• Heart Rate: Decreases

• Eye Movement: Minimal

• Muscle Tension: Most relaxed

Stage 3/NREM 3: Length

20-40 Minutes for first few in sleep cycles, then reduce in length

Stage 4/REM : Characteristics

• Sleep State: Dreams occur

• Heart Rate: Increases to match rate of wakefulness but varies depending on dream content

• Eye Movement: Rapid, visual info not transmitted to brain

• Muscle Tension: Temporarily paralysed (atonia) except for muscles involved in breathing and eye muscles

Stage 4/REM : Length

10-60 Minutes, increases over night ranging from few minutes to one hour