biological clock(redirected from Biological clocks)
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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.
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.
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.
internal clockan 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
A synonym for the body's circadian rhythm, the natural biological variations that occur over the course of a day.
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Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.