Chronobiology
Encyclopedia
Chronobiology is a field of biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
that examines periodic (cyclic) phenomena in living organisms and their adaptation to solar
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
- and lunar
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος (chrónos, meaning "time"), and biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, which pertains to the study, or science, of life
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...
. 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.
Chronobiological studies include but are not limited to comparative anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
, physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
, genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
, molecular biology
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
and behavior
Behavior
Behavior or behaviour refers to the actions and mannerisms made by organisms, systems, or artificial entities in conjunction with its environment, which includes the other systems or organisms around as well as the physical environment...
of organisms within biological rhythms mechanics. Other aspects include development, reproduction, ecology and evolution.
Description
The variations of the timing and 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.), (b) in plants (leaf movements, photosynthetic reactions, etc.), and in microbial organisms such as fungi and protozoa. They have even been found in bacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, especially among the cyanobacteria (aka blue-green algae, see bacterial circadian rhythms
Bacterial circadian rhythms
Bacterial circadian rhythms, like other circadian rhythms, are endogenous "biological clocks" that have the following three characteristics: in constant conditions Bacterial circadian rhythms, like other circadian rhythms, are endogenous "biological clocks" that have the following three...
). The most important rhythm in chronobiology is the circadian rhythm
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
, a roughly 24-hour cycle shown by physiological processes in all these organisms. The term circadian comes from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
circa, meaning "around" and dies, "day", meaning "approximately a day."
The circadian rhythm can further be broken down into routine cycles during the 24-hour day:
- Diurnal, which describes organisms active during daytime
- Nocturnal, which describes organisms active in the night
- CrepuscularCrepuscularCrepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
, which describes animals primarily active during the dawn and dusk hours (ex: white-tailed deer, some bats)
Many other important cycles are also studied, including:
- Infradian rhythmInfradian rhythmAn infradian rhythm is a rhythm with a period longer than the period of a circadian rhythm, i.e. with a frequency less than one cycle in 28 hours, such as menstruation, breeding, tidal or seasonal rhythms...
s, which are cycles longer than a day, such as the annual migration or reproduction cycles found in certain animals or the human menstrual cycleMenstrual cycleThe menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purpose of sexual reproduction. This article focuses on the human menstrual cycle....
. - Ultradian rhythms, which are cycles shorter than 24 hours, such as the 90-minute REM cycle, the 4-hour nasal cycleNasal cycleThe nasal cycle is the alternating congestion and decongestion of the nasal cavities in humans. It is a physiological congestion of the nasal concha due to selective activation of one half of the autonomic nervous system by the hypothalamus. It should not be confused with pathological nasal...
, or the 3-hour cycle of growth hormoneGrowth hormoneGrowth hormone is a peptide hormone that stimulates growth, cell reproduction and regeneration in humans and other animals. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of the anterior...
production. - Tidal rhythmsTideTides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
, commonly observed in marine life, which follow the roughly 12-hour transition from high to low tide and back. - Gene oscillations – some genes are expressedGene expressionGene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
more during certain hours of the day than during other hours.
Within each cycle, the time period during which the process is more active is called the acrophase. When the process is less active, the cycle is in its bathyphase or trough phase. The particular moment of highest activity is the peak or maximum; the lowest point is the nadir. How high (or low) the process gets is measured by the amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
.
History
A circadian cycle was first observed in the 18th century in the movement of plant leaves by the French scientist Jean-Jacques d'Ortous de MairanJean-Jacques d'Ortous de Mairan
Jean-Jacques d'Ortous de Mairan , a French geophysicist, astronomer and most notably, chronobiologist, was born in the town of Béziers on November 26, 1678...
(for a description of circadian rhythms in plants by de Mairan, Linnaeus, and Darwin see this page). In 1751 Swedish botanist and naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Carolus Linnaeus
Carolus Linnaeus
Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
(Carl von Linné) designed a floral clock
Floral clock
A floral clock or flower clock is a large decorative clock set into a flower bed in a park or other public recreation area.The floral clock was a form of carpet bedding set onto an operational clock-face, invented in 1903 by John McHattie of Edinburgh Parks in Princes Street Gardens, Edinburgh and...
using certain species of flowering plant
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
s. By arranging the selected species in a circular pattern, he designed a clock that indicated the time of day by the flowers that were open at each given hour. For example, among members of the daisy family, he used the hawk's beard
Crepis
Crepis, commonly known in some parts of the world as hawksbeard or hawk's-beard , is a genus of about 200 annual and perennial flowering plants of the family Asteraceae superficially resembling the dandelion, the most conspicuous difference being that Crepis usually has branching...
plant which opened its flowers at 6:30 am and the hawkbit
Hawkbit
Hawkbits are dandelion-like flowers in the family Asteraceae . Their English name derives from the mediæval belief that hawks ate the plant to improve their eyesight...
which did not open its flowers until 7 am.
The 1960 symposium at Cold Spring Harbor Laboratory
Cold Spring Harbor Laboratory
The Cold Spring Harbor Laboratory is a private, non-profit institution with research programs focusing on cancer, neurobiology, plant genetics, genomics and bioinformatics. The Laboratory has a broad educational mission, including the recently established Watson School of Biological Sciences. It...
laid the groundwork for the field of chronobiology.
It was also in 1960 that Patricia DeCoursey invented the phase response curve
Phase response curve
A phase response curve illustrates the transient change in the cycle period of an oscillation induced by a perturbation as a function of the phase at which it is received...
, one of the major tools used in the field since.
Franz Halberg
Franz Halberg
Franz Halberg is a scientist and one of the founders of modern chronobiology. He first began his experiments in the 1940s and later founded the Chronobiology Laboratories at the University of Minnesota...
of the University of Minnesota
University of Minnesota
The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...
, who coined the word circadian, is widely considered the "father of American chronobiology." However, it was Colin Pittendrigh
Colin Pittendrigh
Colin Pittendrigh was a US-American biologist of English parentage. He is a co-founder of modern chronobiology along with Jürgen Aschoff and Erwin Bünning.-Life:...
and not Halberg who was elected to lead the Society for Research in Biological Rhythms in the 1970s. Halberg wanted more emphasis on the human and medical issues while Pittendrigh had his background more in evolution and ecology. With Pittendrigh as leader, the Society members did basic research on all types of organisms, plants as well as animals. More recently it has been difficult to get funding for such research on any other organisms than mice, rats, humans and fruit flies
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
.
Recent developments
More recently, light therapyLight therapy
Light therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, usually controlled with various devices...
and melatonin
Melatonin
Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...
administration have been explored by Dr. Alfred J. Lewy
Alfred J. Lewy
Alfred J. Lewy, graduated from University of Chicago, in 1973 after studying Psychiatry, Pharmacology and Ophthalmology. He is a full professor and Vice-Chair of the department of Psychiatry at OHSU, Oregon Health & Science University, and holds an MD and PhD...
(OHSU), Dr. Josephine Arendt (University of Surrey
University of Surrey
The University of Surrey is a university located within the county town of Guildford, Surrey in the South East of England. It received its charter on 9 September 1966, and was previously situated near Battersea Park in south-west London. The institution was known as Battersea College of Technology...
, UK) and other researchers as a means to reset animal and human circadian rhythms. Humans can be morning people or evening people; these variations are called chronotype
Chronotype
Chronotype is an attribute of animals, including human beings, reflecting at what time of the day their physical functions are active, change or reach a certain level...
s for which there are various assessment tools and biological markers.
In the second half of 20th century, substantial contributions and formalizations have been made by Europeans such as Jürgen Aschoff
Jürgen Aschoff
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.-Life:...
and Colin Pittendrigh, who pursued different but complementary views on the phenomenon of entrainment
Entrainment (chronobiology)
Entrainment, within the study of chronobiology, occurs when rhythmic physiological or behavioral events match their period and phase to that of an environmental oscillation. A common example is the entrainment of circadian rhythms to the daily light–dark cycle, which ultimately is determined by...
of the circadian system by light (parametric, continuous, tonic, gradual vs. nonparametric, discrete, phasic, instantaneous, respectively; see this historical article, subscription required).
There is also a food-entrainable biological clock, which is not confined to the suprachiasmatic nucleus. The location of this clock has been disputed. Working with mice, however, Fuller et al. concluded that the food-entrainable clock seems to be located in the dorsomedial hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
. During restricted feeding, it takes over control of such functions as activity timing, increasing the chances of the animal successfully locating food resources.
Other fields
Chronobiology is an interdisciplinary field of investigation. It interacts with medical and other research fields such as sleep medicineSleep medicine
Sleep medicine is a medical specialty or subspecialty devoted to the diagnosis and therapy of sleep disturbances and disorders. From the middle of the 20th century, research has provided increasing knowledge and answered many questions about sleep-wake functioning. The rapidly evolving field has...
, endocrinology
Endocrinology
Endocrinology is a branch of biology and medicine dealing with the endocrine system, its diseases, and its specific secretions called hormones, the integration of developmental events such as proliferation, growth, and differentiation and the coordination of...
, geriatrics
Geriatrics
Geriatrics is a sub-specialty of internal medicine and family medicine that focuses on health care of elderly people. It aims to promote health by preventing and treating diseases and disabilities in older adults. There is no set age at which patients may be under the care of a geriatrician, or...
, sports medicine
Sports medicine
Sports medicine is a branch of medicine that deals with physical fitness, treatment and prevention of injuries related to sports and exercise...
, space medicine
Space medicine
Space medicine is the practice of medicine on astronauts in outer space whereas astronautical hygiene is the application of science and technology to the prevention or control of exposure to the hazards that may cause astronaut ill health. Both these sciences work together to ensure that...
and photoperiodism
Photoperiodism
Photoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals.Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of the light and dark periods...
.
The notion of biorhythm
Biorhythm
Biorhythm is an attempt to predict various aspects of a person's life through simple mathematical cycles. Most scientists believe that the idea has no more predictive power than raw chance, and consider the concept an example of pseudoscience.-Beliefs:...
s, a classic example of pseudoscience, which attempts to describe a set of cyclic variations in human behavior based on physiological and emotional cycles, is not a part of chronobiology.
See also
- Bacterial circadian rhythmsBacterial circadian rhythmsBacterial circadian rhythms, like other circadian rhythms, are endogenous "biological clocks" that have the following three characteristics: in constant conditions Bacterial circadian rhythms, like other circadian rhythms, are endogenous "biological clocks" that have the following three...
- CircaseptanCircaseptanA circaseptan rhythm is a cycle consisting of 7 days in which many biological processes of life resolve.-References:* Halberg F et al. 1965: "Spectral resolution of low-frequency, small-amplitude rhythms in excreted 17-ketosteroid: probable androgen-induced circaseptan desynchronization". Acta...
, 7-day biological cycle - Sense of time
- Suprachiasmatic nucleusSuprachiasmatic nucleusThe suprachiasmatic nucleus or nuclei, abbreviated SCN, is a tiny region on the brain's midline, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms...
- Alexander ChizhevskyAlexander ChizhevskyAlexander Chizhevsky was a Soviet-era interdisciplinary scientist, a biophysicist who founded “heliobiology” and “aero-ionization”...
- Michel SiffreMichel SiffreMichel Siffre is a French underground explorer, adventurer and scientist. He was born January 3, 1939 in Nice, where he spent his childhood. At just 10 years of age he explored the Imperial Cave Park, and discovered a passion for caving....
Further reading
- 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, 25 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
- Horne, J.A. (Jim) & Östberg, Olov (1976). A Self-Assessment Questionnaire to determine Morningness-Eveningness in Human Circadian Rhythms. International Journal of Chronobiology, 4, 97–110.
- Roenneberg, Till, Cologne (2010). Wie wir ticken – Die Bedeutung der Chronobiologie für unser Leben, Dumont, ISBN 978-3832195205.
External articles
- Halberg Chronobiology Laboratory at the University of MinnesotaUniversity of MinnesotaThe University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...
, founded by Franz HalbergFranz HalbergFranz Halberg is a scientist and one of the founders of modern chronobiology. He first began his experiments in the 1940s and later founded the Chronobiology Laboratories at the University of Minnesota...
, the "Father of Chronobiology" - The University of VirginiaUniversity of VirginiaThe University of Virginia is a public research university located in Charlottesville, Virginia, United States, founded by Thomas Jefferson...
offers an online tutorial on chronobiology. - See the Science Museum of VirginiaScience Museum of VirginiaThe Science Museum of Virginia is a science museum located in Richmond, Virginia.-History:In 1906, the Virginia General Assembly approved funds for the construction of a simple "exhibits center" to display mineral and timber exhibits being assembled for the Jamestown Exposition of 1907. After the...
publication Can plants tell time? - The University of Manchester has an informative Biological Clock Web Site
- S Ertel's analysis of Chizhevsky's work