Why and How Do We Model Circadian Rhythms?

Beersma, Domien

doi:10.1177/0748730405277388

Cited by 26 publications

(25 citation statements)

References 41 publications

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“…The simplifications are at the same time advantageous and disadvantageous. They are advantageous because they help to understand major principles of regulation, and they are disadvantageous because other major principles may be overlooked [24]. A shortcoming of the two-process model of sleep regulation, for instance, is that it is deterministic .…”

Section: Model Limitationsmentioning

confidence: 99%

Circadian control of the sleep–wake cycle

Beersma

Gordijn

2007

Physiology & Behavior

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It is beyond doubt that the timing of sleep is under control of the circadian pacemaker. Humans are a diurnal species; they sleep mostly at night, and they do so at approximately 24-h intervals. If they do not adhere to this general pattern, for instance when working night shifts or when travelling across time zones, they experience the stubborn influence of their circadian clock.In recent years much has been discovered about the organisation of the circadian clock. New photoreceptor cells in the retina have been found to influence the input to the clock, and much of the molecular machinery of the clock has been unravelled. It is now known that the circadian rhythm of sleep and wakefulness is only loosely coupled to the circadian rhythm of the pacemaker. New theories have been proposed for the functions of sleep and the sites at which those functions are executed. In spite of this rapid increase in knowledge of the circadian clock and of sleep regulatory processes, much remains to be discovered concerning the precise interaction between the biological clock and sleep timing. This is particularly unfortunate in view of the 24-h demands of our society for 7 days a week. Too little is known about the negative consequences of the societal pressures on well-being and performance.

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Section: Model Limitationsmentioning

confidence: 99%

Circadian control of the sleep–wake cycle

Beersma

Gordijn

2007

Physiology & Behavior

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“…Not all of them focus on the light perception and the light reactions. We, therefore, do not mention all models here but refer to some papers (Beersma 2005;Ruoff and Rensing 2004;Leloup and Goldbeter 1999;Forger et al 1999;Lakin-Thomas and Johnson 1999;Jewett et al 1999a, b;Leloup and Goldbeter 1998;Deacon and Arendt 1996;Goldbeter 1995;Diez-Noguera 1994).…”

Section: Single and Multi-oscillator Modelsmentioning

confidence: 97%

“…Many models of the circadian clockwork have been published, emphasizing different aspects of the oscillating system (Dalchau 2012;Beersma 2005) and different approaches such as used in systems biology (Hogenesch and Ueda 2011;Yamada and Forger 2010;Ukai and Ueda 2010;Hubbard et al 2009). For the history see Tyson et al (2008) and Roenneberg et al (2008).…”

Section: ( )mentioning

confidence: 99%

How Light Resets Circadian Clocks

2014

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The daily revolutions of the earth around its axis are responsible for day and night and its annual orbit around the sun for the seasons with their fluctuations in day length. Most organisms have adapted to these diurnal and annual cycles. The strategies and mechanisms used are quite delicate and complicated.It came as a surprise that photosynthesis and many other processes are, however, additionally controlled by internal clocks. Thus, photosynthesis fluctuates not only during the daily light-dark cycle (=LD; see the List of Abbreviations and http://www.circadian.org/dictionary.html) but also when the plants are kept under LL and constant temperature (Hennessey and Field 1991). However, the period length (period for short) of this rhythmic event then deviates from exactly 24 h and is therefore called circadian (from Latin circa, about, and dies, day). If in the absence of LD and temperature cycles other 24 h time cues (also called zeitgeber, German for time giver) would control the rhythm, it should show an exact 24 h rhythm. This is not the case, demonstrating the endogenous nature of a clock that is locked to light signals (see Fig. 18.1). Spectrum of RhythmsEndogenous rhythms of organisms are not only tuned to the daily cycle of 24 h. The range of rhythms found in organisms covers ultradian (with periods of several hours to very short ones), circadian, and annual (with periods of about a year) rhythms. Other rhythms such as tidal, 14-day, and monthly ones cope with influences of the moon on the earth, mainly on the water movements of the oceans, and they are therefore found in organisms at the coasts and in the sea. Annual rhythms interact with the day-length changes during the year (see below). There are furthermore rhythms with periods covering several years. The following discussion of a "biological clock" is restricted to circadian rhythms. Even they are often not just composed of one clock type but form a "circadian system" consisting of two or more clocks with different prop- Function of Circadian ClocksThe term "clock" usually implies a time-measuring device or function. For instance, the day length (or night length) can be determined by an organism. Since day length is a function of the time of the year (long days in summer, short days in winter), it can be used to time certain events such as flowering or tuber formation of a plant or breeding of birds and mammals during the most appropriate season. These processes are denoted photoperiodism (see Chap. 19).However, a clock can also be used to set a certain temporal order. For instance, the circadian control of our sleepwake cycle ensures that we rise in the morning and fall asleep in the evening at a preferred time. Food intake and digestion are likewise controlled by this clock and gated to certain times of the day (Silver et al. 2011;Duguay and Cermakian 2009;Forsgren 1935). The circadian clock will time these events also under constant conditions. Furthermore, circadian clocks can serve as alarm clocks.

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“…Moreover, when spatial relations between SCN neurons are maintained in explants, the variability between cells was much reduced, indicating that oscillations in individual neurons were being synchronized to those in others (Herzog et al 2004). (For a discussion of computational modeling of such synchronization, see Beersma 2005). Recent studies point to vasoactive intestinal polypeptide (VIP) as a major agent for establishing synchrony, although GABA and gap junctions may also be involved (Vansteensel et al 2008).…”

Section: The Upward Path Ii: Network Between Cells and Between Organsmentioning

confidence: 99%

The Downs and Ups of Mechanistic Research: Circadian Rhythm Research as an Exemplar

Bechtel

2010

Erkenn

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In the context of mechanistic explanation, reductionistic research pursues a decomposition of complex systems into their component parts and operations. Using research on the mechanisms responsible for circadian rhythms, I consider both the gains that have been made by discovering genes and proteins that figure in these intracellular oscillators and also highlight the increasingly recognized need to understand higher-level integration, both between cells in the central oscillator and between the central and peripheral oscillators. This history illustrates a common need to complement reductionistic inquiry with investigations at higher-levels. Unlike most other accounts of reduction, the mechanistic framework accommodates this complementary relationship between reductionistic and systems approaches.

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Why and How Do We Model Circadian Rhythms?

Cited by 26 publications

References 41 publications

Circadian control of the sleep–wake cycle

Circadian control of the sleep–wake cycle

How Light Resets Circadian Clocks

The Downs and Ups of Mechanistic Research: Circadian Rhythm Research as an Exemplar

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