8.3 Discuss the phases and stages of sleep cycle

Normal sleep involves two phases:

nonrapideye movement (NREM) sleep and rapid eye movement (REM) sleep

REM

sleep is the phase at the end of each sleep cycle.

NREM

sleeper progresses through 4 stages during a typical 90-minute sleep cycle.

Lighter sleep is

characteristic of stages 1 and 2, during which a person is more easily aroused.

Stage 2: NREM

Stage lasts 10 to 20 minutes, it is a period of sound sleep, relaxation progresses, body functions continue to slow, Arousal remains relatively easy

Stage 3: NREM

Stage lasts 14 to 30 minutes, It is the deepest stage of sleep, If sleep loss has occured, sleeper spends considerable portion of night in this stage, Vital signs are significantly lower than wakin hours, SLeepwalking and enuresis (bedwetting) sometimes occur

Stages of sleep cycle- Pre sleep

Gradually developing sleepiness-- 10 to 30 minutes,, difficulty falling asleep--it lasts an hour or more.

Once asleep

person usually passes through 4 or five complete sleep cycles per night-- each consisting of 4 stages of NREM sleep and a period of REM sleep--Each cycle lasts approximately 90 to 100 minutes.

Stage 1: NREM

Stage lasts a few minutes, It includes lightest level of sleep, Decreased physiological activity begins with greadual fall in vital signs and metabolism, sensory stimuli such as noise easily arouses person, awakened, person feels as though daydreaming has occured.

REM Sleep

Stage usually begins about 90 minutes after sleep has begun, duration increases with each sleep cycle and averages 20 minutes, Vivid, full full-color dreaming occurs; less vivid dreaming occurs in other stages, Stage is typified by rapidly moving eyes, fluctuating heart and respiratory rates, increased or fluctuating blood pressure, loss of skeletal muscle tone and increase of gastric secretions, It is very difficult to arouse sleeper.

Deeper Sleep

Stages 3 & 4 involve a deeper sleep, called slow-wave sleep.

Deep Sleep

The quality of sleep from stage I through stage 4 becomes increasingly deep.