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The Oxford English Dictionary's definition of Ultradian specifies that it refers to cycles with a period shorter than a day but longer than an hour. [1] The descriptive term ultradian is used in sleep research in reference to the 90–120 minute cycling of the sleep stages during human sleep. [2]
The sleep cycle is an oscillation between the slow-wave and REM (paradoxical) phases of sleep. It is sometimes called the ultradian sleep cycle, sleep–dream cycle, or REM-NREM cycle, to distinguish it from the circadian alternation between sleep and wakefulness. In humans, this cycle takes 70 to 110 minutes (90 ± 20 minutes). [1]
Known as slow-wave sleep or stage 3 non-REM sleep, this is the deepest stage of sleep and the hardest to wake up from. Brain activity slows down, muscles and bones strengthen, hormones regulate ...
The basic rest–activity cycle (BRAC) is a physiological arousal mechanism in humans proposed by Nathaniel Kleitman, [1] hypothesized to occur during both sleep and wakefulness. Empirically, it is an ultradian rhythm of approximately 90 minutes (80–120 minutes [ 2 ] ) characterized by different levels of excitement and rest.
Dynastic cycle (traditional Chinese: 朝代循環; simplified Chinese: 朝代循环; pinyin: Cháodài Xúnhuán) is an important political theory in Chinese history. According to this theory, each dynasty of China rises to a political, cultural, and economic peak and then, because of moral corruption, declines, loses the Mandate of Heaven ...
A circadian rhythm (/ s ər ˈ k eɪ d i ə n /), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours.Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrained by the environment).
Zooming out from the dynastic cycle but maintaining focus on power dynamics, the following general periodization, based on the most powerful groups and the ways that power is used, has been proposed for Chinese history: [37]: 45 The aristocratic settlement state (to c. 550 BCE)
Slow-wave sleep (SWS), often referred to as deep sleep, is the third stage of non-rapid eye movement sleep (NREM), where electroencephalography activity is characterised by slow delta waves. [2] Slow-wave sleep usually lasts between 70 and 90 minutes, taking place during the first hours of the night. [3]