biological clock

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1. pertaining to biology.
2. a medicinal preparation made from living organisms and their products, such as a serum or vaccine.
biological clock the physiologic mechanism that governs the rhythmic occurrence of certain biochemical, physiologic, and behavioral phenomena in living organisms. See also biological rhythms.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

biological clock

1. An internal mechanism in organisms that controls the periodicity of various functions or activities, such as metabolic changes, sleep cycles, or photosynthesis.
a. The time period during which a person who desires to have a biological child, especially a woman approaching the decline of reproductive capability, is still able to do so.
b. The capacity to be fertile, especially in such a woman: She was eager to have a child before her biological clock stopped working.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
Physiology An organism’s internal timer that sets biological rhythms—e.g., metabolism, sleep-wake cycles, and photosynthesis
Vox populi As currently used, that which ticks away the time left for a woman to have babies, ideally before age 40
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

biological clock


internal clock

an internal mechanism (as yet poorly understood) by which many plants and animals keep a sense of time, making possible a rhythmic pattern of behavour. Many organisms have such ‘clocks’ producing activity cycles of approximately 24 hours (CIRCADIAN RHYTHMS) which, however, can be affected by external influences that ‘set’ the clock (entrainment). An individual's clock can be re-entrained if placed in a new time zone, but after rapid, long-distance travel the process can take several cycles, creating ‘jet-lag’ until internal and external rhythms are synchronized. Biological clocks affect not only whole organism activities (e.g. sleeping) but also cellular patterns of activity (e.g. varying METABOLIC RATES). See also DIURNAL RHYTHM.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Biological clock

A synonym for the body's circadian rhythm, the natural biological variations that occur over the course of a day.
Mentioned in: Cluster Headache
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Our wellbeing is affected when there is a temporary mismatch between our external environment and this internal biological clock, for example when we travel across several time zones and experience 'jet lag.' There are also indications that chronic misalignment between our lifestyle and the rhythm dictated by our inner timekeeper is associated with increased risk for various diseases," the foundation stated.
A woman's biological clock begins ticking once she is 27 years of age and she experiences a good decline in the number of eggs by the age of 30.
Since humans are fundamentally diurnal creatures, staying awake at night can significantly disrupt all of the body's internal biological clocks. These disruptions are far from harmless: over the long term, they can lead to a high incidence of various health problems, such as metabolic or cardiovascular problems or even certain types of cancer.
YOUR biological clock may have a role to play in your metabolism and chances of developing diabetes, scientists reported in a new study released on Sunday.
They cover the human biological clock from genes to chronotherapy, photosensitivity as a disregarded attribute to analyze photo-periodic clocks, respiration rhythm and quality of sleep in the total wellness and development of a child, circadian sleep-wake rhythms in pre-term infants, interactions between the circadian and the immune systems as a framework for understanding disease, the spider monkey Ateles geoffroyi as a case study in the chronoecology of neotropical primates, the role of clocks and chaos in a biodynamic approach to cancer, and experimental findings and analytical properties of a klepsydraic model of internal time presentation.
This biological clock or body clock however, does not measure time in minutes.
It adds further evidence for the role of the biological clock in autism.'
Viewing male sexual health in terms of a biological clock is a new way of approaching the issue.
Experts at fatigue management consultancy Awake based the formula around circadian rhythms, the 24 hour biological clocks that determine our sleeping and waking cycles.
As humans explore beyond their earthly environments, their biological clocks will be severely disoriented.
Modern 24-hour society is exacting a heavy toll in health problems by causing people to ignore their biological clocks, an expert said yesterday.
It is most often used by shift workers, jet-lagged travelers and those with Seasonal Affective Disorder to help re-set biological clocks. However, melatonin may inhibit a woman's ovulation by disturbing hormone levels, and large doses can have undesirable side effects, such as daytime fatigue.

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