Sleep-Wake Cycle

Question 1

Duration

Answer 1

Three stages of NREM, one REM stage

Approximately 4-6 sleep cycles per night

Approximately 90 minutes per sleep cycle

Question 2

NREM1

Answer 2

Transitional period between wakefulness and sleep

1-7 minutes

Heart rate decreased, muscles relaxed

Eye movement slowed, stops when asleep

If uninterrupted, moves to NREM2

Question 3

NREM2

Answer 3

Light nonREM sleep

Eye movement sleeps, muscles continue to sleep (occasional twitches)

20-40 minutes

Heart rate starts to slow

Repeated 10-25 minutes, increasing in length with every repetition

Question 4

NREM3

Answer 4

Deep nonREM sleep

Minimal eye movement

Muscles at most relaxed

20-40 minutes

Heart rate continues to decrease

Question 5

REM

Answer 5

Rapid eye movement, visual information not transmitted to brain

Temporarily paralysed (atonia) except for eye and breathing muscles

10-60 minutes

Heart rate increases to match rate when awake, varies with dream content