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Introduction
Published in Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe, Visual and Non-Visual Effects of Light, 2020
Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe
The circadian rhythm of human physiological functions is controlled by two clusters of neurons called the suprachiasmatic nuclei (SCN), which are located at the base of the hypothalamus in close proximity to the intersection of the optic nerves (hence the name). Information on the alternation of day and night reaches the SCN via a visual tract through photosensitive retinal ganglion cells. In response to light, melanopsin is activated and information is transmitted, thanks to which SCN cells begin “measuring” the next day. In the suprachiasmatic nucleus, the path to sympathetic centers in the thoracic spinal cord begins. From here, further fibers exit into the pineal gland, which secretes melatonin. The lack of light is a signal for the pineal gland to produce this hormone, and thus prepares the human body for the sleep phase. In contrast, the presence of bright white light or monochromatic light with specific wavelengths in the range between 420 and 550 nm inhibits the secretion of this hormone and puts the body in a state of readiness (wakefulness). It has been proven that light with a length perceived as blue (between 450 and 490 nm) is most responsible for the direct non-visual effect.
Contributing Factors of Accident Occurrence
Published in Koji Fukuoka, Safer Seas, 2019
Circadian mechanism is a daily cycle of alertness and sleep and works as an internal body clock, regulating circadian rhythms. Internal body clock is regulated by the superchiasmatic nucleus (SCN), a small cluster of nerve cells near hypothalamus in the brain. Information of light and darkness from the eyes are conveyed through the Retinohypothalamic tract to the SCN, which synchronizes our body’s rhythms to a 24-hour cycle (Moore-Ede 1993).
Neuroscience of Sleep and Circadian Rhythms
Published in Gerald Matthews, Paula A. Desmond, Catherine Neubauer, P.A. Hancock, The Handbook of Operator Fatigue, 2017
Siobhan Banks, Melinda L. Jackson, Hans P.A. Van Dongen
The circadian system is composed of a central “clock,” or circadian pacemaker, which is located in the suprachiasmatic nuclei (SCN) of the hypothalamus in the brain, and peripheral clocks distributed across the body and brain. Other important components include photoreceptors and visual pathways (e.g., retinohypothalamic tract; RHT); and output pathways such as the pineal gland. The SCN is synchronized (“entrained”) to a 24-hour cycle by external Zeitgebers (time cues), the most salient of which is light (Wever, 1989).
Zearalenone perturbs the circadian clock and inhibits testosterone synthesis in mouse Leydig cells
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Lijia Zhao, Yaoyao Xiao, Cuimei Li, Jing Zhang, Yaojia Zhang, Meina Wu, Tiantian Ma, Luda Yang, Xiaoyu Wang, Haizhen Jiang, Qian Li, Hongcong Zhao, Yiqun Wang, Aihua Wang, Yaping Jin, Huatao Chen
The circadian clock system exists in nearly all organs, tissues, and cells (Dibner, Schibler, and Albrecht 2010). Various physiological functions and behaviors exhibit robust circadian rhythms driven by an endogenous circadian clock, including the sleep/wake cycle, feeding, body temperature, blood pressure, and release of endocrine hormones (Ye et al. 2011). In mammals, the circadian clock is composed of a core pacemaker in the suprachiasmatic nucleus (SCN) of the hypothalamus and various oscillators in peripheral tissues. The SCN controls the oscillators in peripheral tissues through humoral and neuronal cues in a hierarchical manner (Dibner, Schibler, and Albrecht 2010; Silver et al. 1996). The molecular oscillator of the circadian clocks consists of interlocked transcriptional-translational feedback loops involving the genes Bmal1, Clock, Pers (Per1/2/3), and Crys (Cry1/2) which are required to generate endogenous circadian oscillations (Buhr and Takahashi 2013). The BMAL1/CLOCK heterodimer increases the transcription of the Per and Cry genes by binding to an E-box element, resulting in generation of circadian rhythms. Subsequently, the accumulated PER and CRY proteins translocate into the nucleus where they inhibit BMAL1/CLOCK activities. Several other essential proteins, including the orphan nuclear receptors ROR, REV-ERBs, and DBP, make up an auxiliary feedback loop that enhances these circadian oscillators to be more robust.
Developing a fatigue questionnaire for Chinese civil aviation pilots
Published in International Journal of Occupational Safety and Ergonomics, 2020
Jing Dai, Min Luo, Wendong Hu, Jin Ma, Zhihong Wen
Flight fatigue is closely related to several factors. First is the circadian rhythm phase. Circadian rhythms are generated by a molecular oscillator composed of a set of clock genes that act in a cell-autonomous way and are present in all cell types. These clocks are coordinated by a master clock in the neurons of the suprachiasmatic nucleus (SCN), which is located in the anterior hypothalamus [23]. One feature of circadian clocks is that they are light sensitive. This sensitivity to light creates problems for crewmembers who have to sleep out of step with the day/night cycle, or who have to fly across time zones and experience sudden shifts in the day/night cycle [2]. If pilots’ periodic circadian rhythm was damaged (such as staying up late), the pilots might suffer acute fatigue, and this would decrease the pilots’ operational capability and the vigilance level of flight security. Furthermore, circadian rhythm disorders for a long time can cause various health problems (such as gastrointestinal disease).
Restricting short-wavelength light in the evening to improve sleep in recreational athletes – A pilot study
Published in European Journal of Sport Science, 2019
Melanie Knufinke, Lennart Fittkau-Koch, Els I. S. Møst, Michiel A. J. Kompier, Arne Nieuwenhuys
Sleep and wakefulness are regulated by two distinct process: a homeostatic process (Process S) that depicts increasing sleep pressure following sustained wakefulness, and a circadian process (Process C)(Borbely, 1982), which is regulated by the circadian system and requires periodic light–dark exposure for stable entrainment to the geographical day (Czeisler et al., 1986; Duffy & Wright, 2005). Specifically, information on environmental light is received by photoreceptors in the retina and, via non-image forming intrinsically photoreceptive retinal ganglion cells (ipRGC) (Brainard et al., 2001; Thapan, Arendt, & Skene, 2001), directly transmitted to the suprachiasmatic nucleus (SCN), the site of the circadian ‘master clock’. The SCN, in turn, sends information on circadian time to, for example, the pineal gland where melatonin is secreted in the evening, or suppressed in case of evening-light exposure (Brainard et al., 2001). Hence, the timing of light exposure is crucial: daytime light exposure facilitates the process of waking up and staying alert during the early day, while in the evening, the absence of light facilitates sleepiness.