- published: 22 Jun 2014
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Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than being in hibernation or a coma. Sleep is a heightened anabolic state, accentuating the growth and rejuvenation of the immune, nervous, skeletal and muscular systems. It is observed in all mammals, all birds, and many reptiles, amphibians, and fish.
The purposes and mechanisms of sleep are only partially clear and are the subject of intense research. Sleep is often thought to help conserve energy, but decreases metabolism only about 5–10%. Hibernating animals need to sleep despite the hypometabolism seen in hibernation, and must return from hypothermia to euthermia in order to sleep, making sleeping "energetically expensive."
In mammals and birds, sleep is divided into two broad types: rapid eye movement (REM) and non-rapid eye movement (NREM or non-REM) sleep. Each type has a distinct set of associated physiological, neurological, and psychological features. The American Academy of Sleep Medicine (AASM) further divides NREM into three stages: N1, N2, and N3, the last of which is also called delta sleep or slow-wave sleep (SWS).
Robert Sylvester Kelly (born January 8, 1967), better known by his stage name R. Kelly, is an American singer-songwriter and record producer. Often referred to as the King of R&B, Kelly is recognized as one of the most successful R&B artists of all-time. A native of Chicago, Kelly began performing during the late 1980s and debuted in 1992 with the group Public Announcement. In 1993, Kelly went solo with the album 12 Play. He is known for a collection of major hit singles including "Bump n' Grind", "Your Body's Callin'", "I Believe I Can Fly", "Gotham City", "Ignition (Remix)", "If I Could Turn Back the Hands of Time", "The World's Greatest", "I'm a Flirt", and the hip-hopera "Trapped in the Closet". In 1998, Kelly won three Grammy Awards for "I Believe I Can Fly".
Kelly has written, produced, and remixed songs for many artists including The Winans, The Isley Brothers, Charlie Wilson, Quincy Jones, K-Ci & JoJo, Aaliyah, Janet Jackson, Whitney Houston, Toni Braxton, Michael Jackson, Hi-Five, Nivea, Ciara, Mary J. Blige, Luther Vandross, Gerald LeVert, Raheem DeVaughn, Ruben Studdard, Jaheim, Kelly Price, Tamia, Maxwell, Celine Dion, Britney Spears, Usher, B2K, Twista, Tyrese, Jennifer Lopez, Trey Songz, and others in the U.S. and abroad.