diurnal rhythm

Also found in: Dictionary, Thesaurus, Encyclopedia.


1. Pertaining to the daylight hours; opposite of nocturnal.
2. Repeating once each 24 hours, for example, a diurnal variation or a diurnal rhythm. Compare: circadian.
[L. diurnus, of the day]
Farlex Partner Medical Dictionary © Farlex 2012

circadian rhythm

The diurnal cadence which, in humans (without cyclical cues provided by natural light), is 24.1–24.2 hours (older data had put this figure at 25.4 hours). Photoperiodic information from the eyes synchronises the circadian pacemaker with the light-dark cycle; circadian rhythm affects drug metabolism (e.g., antacids, halothane), serum levels of various substances (in particular adrenocortical hormones) that are routinely measured to detect and monitor disease, physiologic activities (e.g., blood pressure, myocardial blood flow and oxygen demand), psychosomatic disease and sleep cycles, cell division, haematopoiesis and natural killer cell activity.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

diurnal rhythm

a pattern of activity based upon a 24-hour cycle, in which there are regular light and dark periods. See also CIRCADIAN RHYTHM.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
Diurnal rhythm of cardiac troponin: consequences for the diagnosis of acute myocardial infarction.
When clinicians see patients with AD who are having psychotic and other symptoms (e.g., delusions, hallucinations, and disturbances in diurnal rhythm), they should check prescribed medications, physical illnesses, and mental stress because these factors can affect the cholinergic system and thereby contribute to psychosis.
IC placed in the uterotubal junction was successfully to measure intrauterine temperature and detected diurnal rhythm. Fluctuation of uterine temperature was rather stable compared to rectal and vaginal temperature, and showed a luteal phase hyperthermia.
Performance measures show marked practice effects that may mask the true nature, if any, of a diurnal rhythm, and although various methods can be used to balance for practice effects, such approaches assume that different participants exhibit similar time of day and practice trends (Folkard, 1984).
Heart rate normally varies according to a diurnal rhythm under autonomic control; in atrial fibrillation the diurnal fluctuations in heart rate are greater.
Nelson, "Timing of light pulses and photoperiod on the diurnal rhythm of hippocampal neuronal morphology of Siberian hamsters," Neuroscience, vol.
The ideal time for sampling is at the nadir in the diurnal rhythm, typically close to midnight, which is impractical for outpatient blood sampling.
(1996) Diurnal rhythm of the muscular performance of elbow flexors during isometric contractions.
A diurnal rhythm of stimulatory input to the hypothalamo-pituitary-adrenal system as revealed by timed intrahypothalamic administration of the vasopressin V1 antagonist.
Conversely, the term "diurnal rhythm" refers to patterns of activity or behavior that follow day-night cycles, such as the breakfast-lunch-dinner schedule.
Dafny, "Acute and chronic psychostimulant treatment modulates the diurnal rhythm activity pattern of WKY female adolescent rats," Journal of Neural Transmission, vol.