SLEEP!

Importance of Sleep1. Sleep Protects: Sleeping in the

darkness when predators loomed about kept our ancestors out of harm’s way.

2. Sleep Recuperates: Sleep helps restore and repair brain tissue.

3. Sleep Helps Remembering: Sleep restores and rebuilds our fading memories.

4. Sleep and Growth: During sleep, the pituitary gland releases growth hormone. Older people release less of this hormone and sleep less.

The Beginnings of Sleep (sometimes known as Stage 0)o you are actually still relatively awake (although

sometimes drowsy)o brain produces small and fast beta waveso You may experience hypnagogic hallucinations (examples:

feeling like you are falling or hearing someone call your name)

o Another very common event during this period is known as a myoclonic jerk (aka “sleep start” – when you wake up startled)

Stage 1• beginning of the sleep cycle• relatively light stage of sleep• brain produces high amplitude theta waves, which are very

slow brain waves. • lasts between 5-10 minutes

Stage 2 brain begins to produce bursts of rapid, rhythmic brain wave

activity known as sleep spindles

lasts for approximately 20 minutes

body temperature starts to decrease and heart rate begins to slow

Stage 3• deep, slow brain waves (delta waves) begin to emerge

during

• transitional period between light sleep and a very deep sleep.

Stage 4

o sometimes referred to as delta sleep

o deep sleep that lasts for approximately 30 minutes

o bed-wetting and sleepwalking are most likely to occur at the end of stage 4 sleep.

Stage 5 (REM Stage)

REM = rapid eye movement

REM sleep is characterized by:

eye movement

increased respiration rate

increased brain activity.

voluntary muscles become paralyzed.

The Sequence of Sleep Stages

o Sleep begins in stage 1 and progresses into stages 2, 3 and 4.

o After stage 4 sleep, stage 3 and then stage 2 sleep are repeated before entering REM sleep.

o Once REM sleep is over, the body usually returns to stage 2 sleep.

o Sleep cycles through these stages approximately four or five times throughout the night.

o On average, we enter the REM stage approximately 90 minutes after falling asleep.

o The first cycle of REM sleep might last only a short amount of time, but each REM cycle becomes longer. REM sleep can last up to an hour as sleep progresses.