Causes of Fatigue Slideshow Pictures Take the Sleep Quiz! Foods That Help or Harm Your Sleep Slideshow Pictures

Synonyms and Keywords

sleep understanding the basics, stages of sleep, stage I, stage II, stage III, stage IV, delta waves, delta activity, non-rapid eye movement, NREM, rapid eye movement, REM, light sleep, deep sleep, circadian rhythms, melatonin, biological clock, hypothalamus, neurons, nerve cells, brain activity during sleep, pineal gland, prolactin, testosterone, growth hormone, sleep rhythm, neurotransmitters, sleep deprivation, lack of sleep, sleep cycles, sleep time, amount of sleep needed, jet lag, insomnia, sleep hygiene, sleepwalking