Sleep Sounds - Calming melodies & nature (Android Application)
SLEEP The timing and progression of the sleep cycle and the total amount of nightly sleep required for optimal health varies from infancy to adulthood, depending on developmental stage and temperament . Children, particularly infants, require the most sleep during a 24-hour period. The natural sleep-wake cycle, governed by an internal "biological clock," tends toward a 25-hour day. It is affected by the relative balance of light and darkness in the environment. As darkness approaches, the hormone melatonin is secreted by the pineal gland and signals the brain that it is time to sleep. Non-REM deep sleep Sleep begins in stage one of the sleep phase known as NREM, or non-rapid eye movement, sleep. NREM sleep has four stages: light sleep, deeper sleep, and two stages of deepest sleep. Stage one is the "drifting off" period of light sleep in th