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Circarhythms
Published in Sue Binkley, Biological Clocks, 2020
The occurrence of REM sleep has been mainly documented in mammals. Something akin to REM sleep has been observed in birds, and its occurrence in lizards and other lower vertebrates is questionable. The reason we are discussing REM sleep here is that it has an ultradian rhythm; in the human it recurs through the night in cycles that are 70–90 minutes long.
Astrocytes and Infra-Low Frequencies
Published in Hanno W. Kirk, Restoring the Brain, 2020
In healthy individuals, ultradian rhythms are reasonably phase-locked to the circadian rhythm, so that of the number of cycles of peaks and troughs within a 24-hour cycle is approximates an integer (10 or 12 as opposed to 13.6 or 8.38 cycles per day). The number of ultradian cycles per person typically ranges from 8 to 15 per day. As stated above, this activity falls into the infra-low frequency range. A frequency of 1 mHz corresponds to a 17-minute ultradian rhythm; 0.18 mHz to a 90-minute cycle; and 0.14 mHz to 2 hours, the general range of our Basic-Rest-Activity-Cycle (BRAC), i.e. how we tend to rest and work in near-two-hour increments.59,60
Chronic Posttraumatic Disorders of Consciousness
Published in Rolland S. Parker, Concussive Brain Trauma, 2016
Symptoms: Disruption of social patterns (i.e., connection between events or between particular responses and outcomes) may remove the social cues to which circadian rhythms are attuned (Healy & Williams, 1988). In women, an approximately 90-min ultradian rhythm is present, with larger bursts of gonadotropin secretion occurring during sleep than during the day (Reichlin, 1998). There can be a delayed sleep phase syndrome (DSPS) with chronic inability to fall asleep.
Circadian and ultradian rhythms in normal mice and in a mouse model of Huntington’s disease
Published in Chronobiology International, 2022
Christopher G. Griffis, Janki Mistry, Kendall Islam, Tamara Cutler, Christopher S. Colwell, Alan Garfinkel
The general phenomenon of an ultradian rhythm that is modulated into a “nighttime phase” in which it is expressed and a “daytime phase” in which it is quiescent, (or vice versa), may be common in circadian physiology. Consider, for example, the expression of estradiol in a healthy 27-year-old female (Licinio et al. 1998). Here, there is a clear high-amplitude 1-hr rhythm in the daytime which is absent at night (Supplemental Figure S2). Previous work has also informally supported the notion of ultradian rhythm modulation by the circadian rhythm: for example, in an investigation of ultradian rhythmicity of several physiological parameters in Q175 mice, including heart rate, CBT, and locomotor activity, Smarr and colleagues concluded that “ultradian rhythm amplitude is modulated by time of day” (2019).
Role of glucocorticoid negative feedback in the regulation of HPA axis pulsatility
Published in Stress, 2018
Julia K Gjerstad, Stafford L Lightman, Francesca Spiga
Rapid changes in CORT secretion are not only observed after stress, but also occur in basal (non-stressed) conditions throughout the 24-h cycle. In basal conditions, the pattern of CORT release is highly dynamic, with a circadian rhythm characterized by high levels of secretion prior to the active phase (night in the rat and day in humans) and low levels during the inactive phase (Carnes et al., 1988a; Watts et al., 2004). CORT secretion is also characterized by an ultradian rhythm, a high frequency pulsatile secretion, with variable amplitude through the 24-h cycle. Pulses of CORT with higher amplitude occur immediately prior to and during the active phase, so that the circadian changes of CORT are actually due to changes in the amplitude of CORT pulses during the 24-h cycle (Jasper & Engeland, 1991; Windle et al., 1998). The ultradian rhythm of CORT in the rat was first observed using intra-adrenal microdialysis technique (Jasper & Engeland, 1991). Since then, the use of an automated blood sampling systems has allowed researchers to study how the CORT ultradian rhythm changes in physiological and pathological conditions in the rat (Clark et al., 1986; Windle et al., 1998). Further, ultradian rhythm of CORT has been observed in human and other several mammals (Fulkerson, 1978; Henley et al., 2009; Holaday et al., 1977; Lewis et al., 2005). Similarly, pulsatile secretion of ACTH has also been observed in humans (Henley et al., 2009), sheep (Apostolakis et al., 1992) and in the rat (Carnes et al., 1986, 1988b). Importantly, both in human and in the rat, dynamic changes in CORT are preceded by similar fluctuations in ACTH concentration in the plasma (Henley et al., 2009; Jasper & Engeland, 1991). Due to the difficulty of measuring CRH concentration in the median eminence, as a result of the very stressful surgery needed for portal blood sampling in the rat and the low sensitivity of CRH assays, only a few studies have shed light on the pattern of CRH secretion in vivo. Nevertheless, pulsatile CRH secretion in the median eminence has been observed in free-moving rats (Ixart et al., 1991, 1994). Furthermore, episodic CRH has been shown in sheep (Engler et al., 1990).