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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. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος, and biology, which pertains to the study, or science, of life. The related terms chronomics and chronome have been used in some cases to describe either the molecular mechanisms involved in chronobiological phenomena or the more quantitative aspects of chronobiology, particularly where comparison of cycles between organisms is required.
Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is the delaying of a person's circadian rhythm compared to those of societal norms. The disorder affects the timing of biological rhythms including sleep, peak period of alertness, core body temperature, and hormonal cycles.
The suprachiasmatic nucleus or nuclei (SCN) is a small region of the brain in the hypothalamus, situated directly above the optic chiasm. The SCN is the principal circadian pacemaker in mammals, responsible for generating circadian rhythms. Reception of light inputs from photosensitive retinal ganglion cells allow the SCN to coordinate the subordinate cellular clocks of the body and entrain to the environment. The neuronal and hormonal activities it generates regulate many different body functions in an approximately 24-hour cycle.
A zeitgeber 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.
A chronotype is the behavioral manifestation of underlying circadian rhythm's myriad of physical processes. A person's chronotype is the propensity for the individual to sleep at a particular time during a 24-hour period. Eveningness and morningness are the two extremes with most individuals having some flexibility in the timing of their sleep period. However, across development there are changes in the propensity of the sleep period with pre-pubescent children preferring an advanced sleep period, adolescents preferring a delayed sleep period and many elderly preferring an advanced sleep period.
Jürgen Walther Ludwig Aschoff was a German physician, biologist and behavioral physiologist. Together with Erwin Bünning and Colin Pittendrigh, he is considered to be a co-founder of the field of chronobiology.
Bacterial circadian rhythms, like other circadian rhythms, are endogenous "biological clocks" that have the following three characteristics: (a) in constant conditions they oscillate with a period that is close to, but not exactly, 24 hours in duration, (b) this "free-running" rhythm is temperature compensated, and (c) the rhythm will entrain to an appropriate environmental cycle.
Chronobiology International is a peer-reviewed scientific journal that covers all aspects of biological and medical rhythm research, chronotherapeutics, and chronoprevention of risks. It is the official journal of the International Society for Chronobiology, the American Association for Medical Chronobiology and Chronotherapeutics, and the Society for Light Treatment and Biological Rhythms. According to the Journal Citation Reports, the journal has a current impact factor of 2.562 (2018).
The morningness–eveningness questionnaire (MEQ) is a self-assessment questionnaire developed by researchers James A. Horne and Olov Östberg in 1976. Its main purpose is to measure whether a person's circadian rhythm produces peak alertness in the morning, in the evening, or in between. The original study showed that the subjective time of peak alertness correlates with the time of peak body temperature; morning types have an earlier temperature peak than evening types, with intermediate types having temperature peaks between the morning and evening chronotype groups. The MEQ is widely used in psychological and medical research and has been professionally cited more than 4,000 times.
Till Roenneberg is a professor of chronobiology at the Institute of Medical Psychology at Ludwig-Maximilian University (LMU) in Munich, Germany. Roenneberg, in collaboration with Martha Merrow, explores the impact of light on human circadian rhythms, focusing on aspects such as chronotypes and social jet lag in relation to health benefits.
Michael Warren Young is an American biologist and geneticist. He has dedicated over three decades to research studying genetically controlled patterns of sleep and wakefulness within Drosophila melanogaster.
Takao Kondo was a Japanese biologist and professor of biological science at Nagoya University in Nagoya, Japan. He is best known for reconstituting the circadian clock in vitro.
Carl Hirschie Johnson is an American-born biologist who researches the chronobiology of different organisms, most notably the bacterial circadian rhythms of cyanobacteria. Johnson completed his undergraduate degree in Honors Liberal Arts at the University of Texas at Austin, and later earned his PhD in biology from Stanford University, where he began his research under the mentorship of Dr. Colin Pittendrigh. Currently, Johnson is the Stevenson Professor of Biological Sciences at Vanderbilt University.
The Society for Research on Biological Rhythms (SRBR) is an international chronobiological research society with three key goals:
- to promote the advancement and dissemination of basic and applied research in all aspects of biological rhythms.
- to enhance the education and training of students and researchers in the field.
- to foster interdisciplinary communication and an international exchange of ideas.
Martha Merrow is an American chronobiologist. She currently chairs the Institute of Medical Psychology at the Ludwig Maximilian University of Munich. Her career focuses primarily on investigating the molecular and genetic mechanisms of the circadian clock. Since joining the Ludwig Maximilian University in 1996, Merrow has investigated molecular and genetic mechanisms of the circadian clock as well as daily human behavior and medical psychology.
A circannual cycle is a biological process that occurs in living creatures over the period of approximately one year. This cycle was first discovered by Ebo Gwinner and Canadian biologist Ted Pengelley. It is classified as an Infradian rhythm, which is biological process with a period longer than that of a circadian rhythm, less than one cycle per 24 hours. These processes continue even in artificial environments in which seasonal cues have been removed by scientists. The term circannual is Latin, circa meaning approximately and annual relating to one year. Chronobiology is the field of biology pertaining to periodic rhythms that occur in living organisms in response to external stimuli such as photoperiod.
Hajime Tei is a Japanese neuroscientist specializing in the study of chronobiology. He currently serves as a professor at the Kanazawa University Graduate School of Natural Science & Technology. He is most notable for his contributions to the discovery of the mammalian period genes, which he discovered alongside Yoshiyuki Sakaki and Hitoshi Okamura.
Ken-Ichi Honma is a Japanese chronobiologist who researches the biological mechanisms underlying circadian rhythms. After graduating from Hokkaido University School of Medicine, he practiced clinical psychiatry before beginning his research. His recent research efforts are centered around photic and non-photic entrainment, the structure of circadian clocks, and the ontogeny of circadian clocks. He often collaborates with his wife, Sato Honma, in work involving the mammalian suprachiasmatic nucleus (SCN), its components, and associated topics.
Chronodisruption is a concept in the field of circadian biology that refers to the disturbance or alteration of the body's natural biological rhythms, particularly the sleep-wake cycle, due to various environmental factors. The human body is synchronized to a 24-hour light-dark cycle, which is essential for maintaining optimal health and well-being. However, modern lifestyles, which involve exposure to artificial light, irregular sleep schedules, and shift work, can disrupt this natural rhythm, leading to a range of adverse physiological outcomes. Chronodisruption has been linked to a variety of health issues, including neurodegenerative diseases, diabetes, mood disorders, and cancer. Such disruptors can lead to dysregulation of hormones and neurotransmitters, though research continues to fully understand the physiological implications of chronodisruption. Indeed, research in chronobiology is rapidly advancing, with an increasing focus on understanding the underlying mechanisms of chronodisruption and developing strategies to prevent or mitigate its adverse effects. This includes the development of pharmacological interventions, as well as lifestyle modifications such as optimizing one's sleeping environment and timing of meals and physical activity.
References
- ↑ "Michael H. Smolensky". utexas.edu. Retrieved December 27, 2017.
- ↑ "Bios" (PDF). nih.gov. Retrieved December 27, 2017.
- ↑ "New Drugs Are Precisely Timed To Match Body's Biological Clock". The New York Times . March 6, 1996. Retrieved December 27, 2017.
- ↑ Francesco Portaluppi, Michael H. Smolensky, Yvan Touitou. Ethics and methods for biological rhythm research on animals and human beings. The Journal of Biological and Medical Rhythm Research Volume 27, 2010 - Issue 9-10 1911-1929
- ↑ "Michael Smolensky" . Retrieved December 27, 2017.
- ↑ "Smolensky, Michael H." worldcat.org. Retrieved December 27, 2017.
- ↑ AE, Reinberg (December 28, 2017). "Do night and around-the-clock firefighters' shift schedules induce deviation in tau from 24 hours of systolic and diastolic blood pressure circadian rhythms?". Chronobiology International. 34 (8): 1158–1174. doi:10.1080/07420528.2017.1343833. PMID 28920706. S2CID 1490115.
- ↑ Y, Touitou (December 28, 2017). "Twenty-four-hour pattern in French firemen of lag time response to out-of-hospital cardiac arrest and work-related injury". Indian Journal of Experimental Biology. 52 (5): 420–4. PMID 24851404.
- ↑ M, Riedel (December 1, 2003). "24-hour pattern of work-related injury risk of French firemen: Nocturnal peak time". Chronobiology International. 28 (8): 697–705. doi:10.3109/07420528.2011.603170. PMID 21929300. S2CID 33014574.
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