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Encyclopedia > Chronobiology

Chronobiology is a field of science that examines periodic (cyclic) phenomena in living organisms. These cycles are known as biological rhythms. "Chrono" pertains to time and "biology" 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. Part of a scientific laboratory at the University of Cologne. ... Look up time in Wiktionary, the free dictionary. ... Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: βίος, bio, life; and λόγος, logos, knowledge), also referred to as the biological sciences, is the study of living organisms utilizing the scientific method. ... For other uses, see Life (disambiguation). ...

Contents

Description

The variations of the duration of biological activity in living organisms occur for many essential biological processes. These occur (a) in animals (eating, sleeping, mating, hibernating, migration, cellular regeneration, etc), and (b) in plants (leaf movements, photosynthetic reactions, etc.). The most important rhythm in chronobiology is the circadian rhythm, a roughly 24 hour cycle shown by physiological processes in plants and animals. (The term circadian comes from the Latin circa, meaning "around" and dies, "day", meaning literally, "around a day."). This and other many other important cycles are also studied, including: The leaf is the primary site of photosynthesis in plants. ... A circadian rhythm is a roughly-24-hour cycle in the physiological processes of living beings, including plants, animals, fungi and cyanobacteria. ... For other uses, see Latin (disambiguation). ...

  • Infradian rhythms, which are long-term cycles, such as the annual migration or reproduction cycles found in certain animals or the human menstrual cycle.
  • Ultradian rhythms, which are short cycles, such as the 90-minute REM cycle, the 4-hour nasal cycle, or the 3-hour cycle of growth hormone production. They have periods of less than 24 hours.
  • Tidal rhythms, commonly observed in marine life, which follow the (roughly) 12-hour transition from high to low tide and back.

An infradian rhythm is a biological rhythm with a period longer than 24 hours. ... Menstrual cycle The menstrual cycle is a recurring cycle of physiological changes that occurs in the females of several mammals, including human beings and apes. ... Ultradians are the regular recurrence in cycles of less than 24 hours from one stated point to another, as certain biologic activities which occur at such intervals, regardless of conditions of illumination. ... Rapid eye movement (REM) sleep is the normal stage of sleep characterized by rapid movements of the eyes. ... The nasal cycle is the rhythmic, alternating side-to-side fluctuation in nasal airflow. ... Growth hormone (GH) or somatotropin (STH) is a protein hormone which stimulates growth and cell reproduction in humans and other animals. ...

History

Franz Halberg of the University of Minnesota is widely considered the "father of chronobiology". Franz Halberg is a scientist and the founder of modern chronobiology. ... This article is about the oldest and largest campus of the University of Minnesota. ...


A circadian cycle was initially discovered, in the 1700s, in the movement of plant leaves by the French scientist Jean-Jacques d'Ortous de Mairan. For a description of circadian rhythms in plants by de Mairan, Linnaeus, and Darwin see [1]. In 1751 Swedish botanist and naturalist Carolus Linnaeus designed a floral clock using certain diurnal species of flowering plants. By arranging the selected species in a circular pattern, he designed a clock that indicated the time of day by observing which flowers were open and which ones were closed. For example, he discovered that the hawk's beard plant, opened its flowers at 6:30 am, whereas another species, the hawkbit, did not open its flowers until 7 am. More recently, light therapy and melatonin administration have been explored by Dr. Alfred J. Lewy (OHSU) and other researchers as a means to reset abnormal animal and human circadian rhythms. Jean-Jacques dOrtous de Mairan (November 26, 1678 – February 20, 1771) was a French geophysicist. ... Botany is the scientific study of plant life. ... -1... Carl Linnaeus, Latinized as Carolus Linnaeus, also known after his ennoblement as  , (May 23, 1707[1] – January 10, 1778), was a Swedish botanist, physician and zoologist[2] who laid the foundations for the modern scheme of nomenclature. ... A floral clock or flower clock may be one of two things: A large decorative clock set into a flower bed in a park or other public recreation area, the most famous being in Geneva, Switzerland, and the largest in the world being in Tehran, Iran; A flower bed divided... Diurnal may mean: in biology, a diurnal animal is an animal that is active in the daytime. ... Classes Magnoliopsida - Dicots Liliopsida - Monocots The flowering plants or angiosperms are the most widespread group of land plants. ... Hawkbit is a flower which resembles Dandelion. ... Bright light therapy is a common treatment for seasonal affective disorder. ... Melatonin, 5-methoxy-N-acetyltryptamine, is a hormone found in all living creatures from algae[1] to humans, at levels that vary in a diurnal cycle. ... Oregon Health and Science University is the present-day (2003) name for a university that can trace its roots back to the 1860s. ...


More recent research by William Rowe in the UK has discovered another colour/light clock called Chromo[2] that helps the body understand what time it is based on a very simple colour and time standard. The theory allows you to control your circadian rhythm by using colour to release different hormones in your body, the two main ones being seratonin and melatonin. Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesised in serotonergic neurons in the central nervous system and enterochromaffin cells in the gastrointestinal tract. ... Melatonin, 5-methoxy-N-acetyltryptamine, is a hormone found in all living creatures from algae[1] to humans, at levels that vary in a diurnal cycle. ...


In the second half of 20th century, substantial contributions and formalizations have been made by Europeans such as J├╝rgen Aschoff and Colin Pittendrigh, who pursued different but complementary views on the phenomenon of entrainment of the circadian system by light (parametric, continuous, tonic, gradual vs. nonparametric, discrete, phasic, instantaneous, respectively; see this historical article). (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999... In chronobiology, entrainment of a circadian system is the alignment of its own period and phase to the period and phase of an external rhythm, which in this context is called zeitgeber. ...


Other fields

Related to, but not part of, chronobiology is the unsubstantiated theory of biorhythms. These are said to describe a set of cyclic variations in human behaviour. The basis of this theory are physiological and emotional cycles. This article or section is in need of attention from an expert on the subject. ...


Chronobiology is a truly interdisciplinary interacting field of investigation. Jetlag is one of the medical conditions in which Chronobiology research is deeply involved, having also interaction in many other medical fields as sleep disorders, endocrinology, geriatrics, sports medicine, space medicine and more. Jet lag (or jet-lag) is a physical condition caused by crossing multiple time zones during flight. ... Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones. ... Geriatrics is the branch of medicine that focuses on health promotion and the prevention and treatment of disease and disability in later life. ... This article or section is in need of attention from an expert on the subject. ... Space medicine is the practice of medicine on astronauts in outer space. ...


Research publications

  • Hastings, Michael, "The brain, circadian rhythms, and clock genes". Clinical review. BMJ 1998;317:1704-1707 19 December.
  • U.S. Congress, Office of Technology Assessment, "Biological Rhythms: Implications for the Worker". U.S. Government Printing Office, September 1991. Washington, DC. OTA-BA-463. NTIS PB92-117589
  • Ashikari, M., Higuchi, S., Ishikawa, F., and Tsunetsugu, Y., "Interdisciplinary Symposium on 'Human Beings and Environments': Approaches from Biological Anthropology, Social Anthropology and Developmental Psychology". Sunday, 25th August, 2002
  • "Biorhythm experiment management plan", NASA, Ames Research Center. Moffett Field, 1983.
  • "Biological Rhythms and Human Adaptation to the Environment". US Army Medical Research and Materiel Command (AMRMC), US Army Research Institute of Environmental Medicine.
  • Ebert, D., K.P. Ebmeier, T. Rechlin, and W.P. Kaschka, "Biological Rhythms and Behavior", Advances in Biological Psychiatry. ISSN 0378-7354

External articles


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