Chronobiology: Human circadian pacemaker and circadian rhythms

Desynchronization of human circadian rhythms.

In man as well as in animals, diurnal rhythms are based on endogenous, periodic processes which can be considered self-sustained oscillations in a technical sense2). Evidence for this is given by the observation that, underconstant conditions, the rhythm continues a) undamped and b) with a frequency which deviates from that of the earth's rotation6). It is this deviation of the free-running 'ci...

Circadian rhythms.

1997 marks the 25th anniversary of the discovery of the master circadian pacemaker in mammals in the hypothalamic suprachiasmatic nucleus. Remarkable progress has been made over the last 25 years in elucidating the physiological mechanisms involved in the entrainment, generation and expression of circadian rhythms at the cellular and systems levels. The recent discovery and cloning of the first...

Circadian rhythms.

Circadian rhythms are a ubiquitous adaptation of eukaryotic organisms to the most reliable and predictable of environmental changes, the daily cycles of light and temperature. Prominent daily rhythms in behavior, physiology, hormone levels and biochemistry (including gene expression) are not merely responses to these environmental cycles, however, but embody the organism's ability to keep and t...

Ultradian Rhythms Underlying the Dynamics of the Circadian Pacemaker

Circadian rhythms and reproduction.

There is a growing recognition that the circadian timing system, in particular recently discovered clock genes, plays a major role in a wide range of physiological systems. Microarray studies, for example, have shown that the expression of hundreds of genes changes many fold in the suprachiasmatic nucleus, liver heart and kidney. In this review, we discuss the role of circadian rhythmicity in t...