Sleep architecture

Sleep:

    EEG shows, sleep is a dynamic behavior, not a passive activity.

    Neuroendocrinological structures and chemicals responsible for sleep regulation are:

• Sleep promoting neurons in anterior hypothalamus acts through cerebral cortex with neurotransmitters. 
• Sleep promoting hormone Melatonin produced in the pineal gland.

Sleep stages:

1. NREM sleep:

    No rapid eye movement.

    Restorative sleep, bodily recovery and growth

    Boosts immune system

    As you age, less NREM sleep

    N3 for insightful thinking and creativity.

2. REM sleep:

    Rapid eye movement.

    Essential to cognitive functions like memory, learning, creativity & vivid dreams.

    Deprived of REM sleep shortens life span.

    REM declines with growing age.

Sleep cycle:

    A hypnogram based on brain waves shows:

    1. 4-6 sleep cycles in a night.

    2. Each cycle last 90 minutes on average.

    3. Each cycle with 4 sleep stages;

Stage 1  NREM  N1       wake-sleep transition state                           1-5 mins          

Stage 2  NREM  N2       most of NREM sleep occurs in this stage   10-60 mins      

Stage 3  NREM  N3       slow wave-, delta-, deep sleep                     20-40 mins     

Stage 4   REM   REM    active sleep                                                    10-60 mins     

               N1, N2, N3 amounts 75%, while REM amounts 25% of all sleep.

Some other terms used, less often:

1. Core sleep: Slow wave sleep, mainly N2 and Deep sleep N3.
2. Optional sleep: rest of the sleep is grouped as Optional.