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Rheum from a cat's eyes. Rheum (/ r uː m /; from Greek: ῥεῦμα rheuma 'a flowing, rheum') is a thin mucus naturally discharged from the eyes, nose, or mouth, often during sleep (contrast with mucopurulent discharge). [1] [2] [3] Rheum dries and gathers as a crust in the corners of the eyes or the mouth, on the eyelids, or under the nose. [3]
Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals (including humans) and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. The core body and brain temperatures increase during REM sleep and skin ...
Non-rapid eye movement sleep is known for its beneficial effect on memory consolidation, especially for declarative memory (while procedural memory improvement is more associated with REM-sleep), [26] even if establishing a clear-cut distinction between stages' influence on type of learning may not be possible.
Sleep is divided into two broad types: non-rapid eye movement (non-REM or NREM) sleep and rapid eye movement (REM) sleep. Non-REM and REM sleep are so different that physiologists identify them as distinct behavioral states. Non-REM sleep occurs first and after a transitional period is called slow-wave sleep or deep sleep.
A young house sparrow (Passer domesticus) exhibits unihemispheric slow-wave sleep. Unihemispheric slow-wave sleep (USWS) is sleep where one half of the brain rests while the other half remains alert. This is in contrast to normal sleep where both eyes are shut and both halves of the brain show unconsciousness.
RBD is a sleep disorder characterized by the loss of normal skeletal muscle atonia during REM sleep and is associated with prominent motor activity and vivid dreaming. [6] [2] These dreams often involve screaming, shouting, laughing, crying, arm flailing, kicking, punching, choking, and jumping out of bed.
Sleep onset is the transition from wakefulness into sleep. Sleep onset usually transits into non-rapid eye movement sleep (NREM sleep) but under certain circumstances (e.g. narcolepsy ) it is possible to transit from wakefulness directly into rapid eye movement sleep (REM sleep).
Although their eyes are open, their expression is dim and glazed over. [8] This may last from 30 seconds to 30 minutes. [6] Sleepwalking occurs during slow-wave sleep (N3) of non-rapid eye movement sleep (NREM sleep) cycles. It typically occurs within the first third of the night when slow-wave sleep is most prominent. [8]