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In contrast, circadian rhythms complete one cycle daily, while infradian rhythms such as the menstrual cycle have periods longer than a day. 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]
Empirically, it is an ultradian rhythm of approximately 90 minutes (80–120 minutes [2]) characterized by different levels of excitement and rest. The cycle is mediated by the human biological clock .
Kleitman and others following have referred to this rhythm as the basic rest–activity cycle, of which the "sleep cycle" would be a manifestation. [ 14 ] [ 19 ] A difficulty for this theory is the fact that a long non-REM phase almost always precedes REM, regardless of when in the cycle a person falls asleep.
"The word 'siesta' comes from the Latin 'sexta,' meaning the sixth hour after someone wakes up," says Dr. Dylan Petkus, MD, MPH, a sleep researcher with Optimal Circadian Health. For example, he ...
A zeitgeber (/ ˈ (t) s aɪ t ɡ eɪ b ər, ˈ z aɪ t-/ (T)SYTE-gay-bər, ZYTE-, German: [ˈtsaɪtˌɡeːbɐ]) is any external or environmental cue that entrains or synchronizes an organism's biological rhythms, usually naturally occurring and serving to entrain to the Earth's 24-hour light/dark and 12-month cycles.
Overview, including some physiological parameters, of the human circadian rhythm ("biological clock"). Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. [1] These cycles are known as biological rhythms.
The oldest quantitative laws in psychology are Weber's law, which states that the smallest noticeable difference in stimulus intensity is proportional to the intensity of the reference; and Fechner's law, which quantifies the relationship between the intensity of the physical stimulus and its perceptual counterpart (e.g., testing how much ...
Ultradian rhythms, which are cycles shorter than 24 hours, such as the 90-minute REM cycle, the 4-hour nasal cycle, or the 3-hour cycle of growth hormone production. Tidal rhythms, commonly observed in marine life, which follow the roughly 12.4-hour transition from high to low tide and back. Lunar rhythms, which follow the lunar month (29.5 ...