di·ur·nal

(dī-ŭr'năl),

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.

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

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References in periodicals archive

Diurnal rhythm of cardiac troponin: consequences for the diagnosis of acute myocardial infarction.

Biological Variation of Creatinine, Cystatin C, and eGFR over 24 Hours

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.

Novedoso termometro intracorporal ubicado en la union uterotubarica para medir la temperatura uterina bovina. Nota tecnica

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).

Diurnal variations in the mood and performance of highly practised young women living under strictly controlled conditions

Heart rate normally varies according to a diurnal rhythm under autonomic control; in atrial fibrillation the diurnal fluctuations in heart rate are greater.

Xamoterol improves the control of chronic atrial fibrillation in elderly patients

Nelson, "Timing of light pulses and photoperiod on the diurnal rhythm of hippocampal neuronal morphology of Siberian hamsters," Neuroscience, vol.

Photoperiod-Induced Neuroplasticity in the Circadian System

The ideal time for sampling is at the nadir in the diurnal rhythm, typically close to midnight, which is impractical for outpatient blood sampling.

Steroid Profiling for Adrenocortical Disorders: A Pathway for Omics-Based Diagnostics

(1996) Diurnal rhythm of the muscular performance of elbow flexors during isometric contractions.

Time-of-day effects on EMG parameters during the Wingate test in boys

A diurnal rhythm of stimulatory input to the hypothalamo-pituitary-adrenal system as revealed by timed intrahypothalamic administration of the vasopressin V1 antagonist.

Role of Neuromedin S in Plasma Testosterone and Cortisol Concentrations in Male Adult Rhesus Monkey (Macaca mulatta)

Conversely, the term "diurnal rhythm" refers to patterns of activity or behavior that follow day-night cycles, such as the breakfast-lunch-dinner schedule.

CHRONOBIOLOGICAL REGULATION OF ALCOHOL INTAKE

Unlike troponin T, troponin I has no diurnal rhythm.

Twenty-Four-Hour Biological Variation Profiles of Cardiac Troponin I in Individuals with or without Chronic Kidney Disease

Dafny, "Acute and chronic psychostimulant treatment modulates the diurnal rhythm activity pattern of WKY female adolescent rats," Journal of Neural Transmission, vol.

Neural Mechanisms of Circadian Regulation of Natural and Drug Reward