{"id":1924,"date":"2023-02-13T14:11:16","date_gmt":"2023-02-13T14:11:16","guid":{"rendered":"https:\/\/integrativa.pt\/?p=1924"},"modified":"2026-02-02T12:37:52","modified_gmt":"2026-02-02T12:37:52","slug":"biorhythms-follow-the-biological-clock","status":"publish","type":"post","link":"https:\/\/integrativa.pt\/en\/biorritmo-seguir-o-relogio-biologico\/","title":{"rendered":"Biorhythms: following the biological clock"},"content":{"rendered":"
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Living beings have internal time regulation mechanisms that organise multiple physiological functions. These systems are largely synchronised with the natural rhythms of planet Earth, such as the alternation of day and night and the succession of seasons.<\/p>\n

The study of these mechanisms, known as chronobiology, has become increasingly important in the field of health. In 2017, this area gained particular prominence with the award of the Nobel Prize for Medicine to Jeffrey C. Hall, Michael Rosbash and Michael W. Young, for their contribution to understanding the molecular mechanisms involved in regulating circadian rhythm. As Michael Rosbash said after the prize was announced, even before the Earth's atmosphere had its current composition, the cycle of light and darkness already had an influence on the beginning of life on the planet.<\/p>\n

Chronobiology studies cell rhythms, hormonal cycles and the relationship between sleep and wakefulness. As the human being is a multi-cellular organism, made up of multiple interdependent systems, it is necessary for organs and functions to be coordinated in time. Without this organisation, processes such as hunger, sleep or metabolic activity would tend to occur less efficiently.<\/p>\n\n\t\t<\/div>\n\t<\/div>\n<\/div><\/div><\/div><\/div>

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Logan, R.W., McClung, C.A. Rhythms of life: circadian disruption and brain disorders across the lifespan. Nat Rev Neurosci<\/em> 20, <\/strong>49-65 (2019). https:\/\/doi.org\/10.1038\/s41583-018-0088-y<\/h6>\n\n\t\t<\/div>\n\t<\/div>\n<\/div><\/div><\/div>
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Volobuev, A., and P. Romanchuk. \u201cGenetics and Epigenetics of Sleep and Dreams.\u201d Bulletin of Science and Practice<\/i>, vol. 6, no. 7, July 2020, pp. 176-217.\u00a0DOI.org (Crossref)<\/i>, https:\/\/doi.org\/10.33619\/2414-2948\/56\/21.<\/h6>\n\n\t\t<\/div>\n\t<\/div>\n<\/div><\/div><\/div><\/div>
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The central biological clock<\/h4>\n

The central biological clock corresponds anatomically to the suprachiasmatic nucleus, a small cluster of neurons located in the hypothalamus. This nucleus acts as a synchronisation centre, integrating environmental signals and helping to coordinate the body's internal rhythms.<\/p>\n

The suprachiasmatic nucleus receives information about light intensity from specific cells in the retina, the photoreceptor ganglion cells. This functional link helps explain the importance of light exposure in regulating biological rhythms.<\/p>\n

Circadian rhythm and biological regulation<\/h4>\n

The circadian rhythm participates in the regulation of numerous biological processes and is significantly influenced by the cycle of light and darkness. Sunlight acts as one of the main environmental signals associated with states of alertness and rest. In general, greater exposure to light is associated with greater activation, while reduced luminosity favours states of less activity and rest.<\/p>\n

To transmit this information to the body, the central nervous system uses hormonal mediators such as cortisol and melatonin, as well as catecholamines such as adrenaline and noradrenaline. These substances take part in the temporal signalling that guides awakening, physical and mental activity and preparation for sleep.<\/p>\n

During the day, for example, the digestive system tends to increase enzyme production in line with the usual meal times, while the endocrine system adjusts hormone release to the body's energy needs.<\/p>\n

Clinical expressions of circadian rhythm<\/h4>\n

Circadian rhythms contribute to understanding various phenomena observed in clinical and epidemiological practice. Spontaneous births occur more frequently during the night and early morning, a phenomenon associated with the hormonal release characteristic of this period. From an evolutionary point of view, this organisation may have reduced the vulnerability of both mother and newborn.<\/p>\n

On the other hand, cardiovascular events such as myocardial infarction or stroke have a higher incidence in the morning. This pattern is related to variations in blood pressure throughout the night, which tends to reach lower values in the early hours of the morning and progressively increase as the body wakes up and becomes more upright.<\/p>\n

People with chronic pain often report greater intensity of symptoms on waking, which may be associated with lower nocturnal production of cortisol, an anti-inflammatory hormone.<\/p>\n

A widely recognised example of a circadian rhythm mismatch is the jet lag<\/em>, resulting from the abrupt change of time zone.<\/p>\n

Zeitgebers<\/em>external regulators of biorhythms<\/h4>\n

Although the biological clock functions autonomously, it needs external stimuli to maintain its synchronisation. These stimuli are called Zeitgebers,<\/em> a German term meaning \u201ctime givers\u201d.<\/p>\n

Among the main Zeitgebers<\/em> The following stand out:<\/p>\n