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1. An instrument other than a watch for measuring or indicating time, especially a mechanical or electronic device having a numbered dial and moving hands or a digital display.
2. A biological clock.
v. clocked, clocking, clocks
To register or record with a mechanical device: clocked the winds at 60 miles per hour.

clock′er n.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


A gene on chromosome 4q12 that encodes a ubiquitously expressed human homolog of the mouse clock gene, which forms a heterodimer with ARNTL and activates E-box element transcription of several circadian clock proteins (e.g., PER1 and PER2). CLOCK is highly expressed in the suprachiasmatic nucleus.

Molecular pathology
CLOCK-ARNTL double mutations in the PAS domains result in syngernistic desensitisation to high levels of CRY on repression of CLOCK-ARNTL transcriptional activity of PER1, disrupting circadian rhythmicity.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


A device for measuring time.

biological clock

1. An internal system in organisms that influences behavior in a rhythmic manner. Functions such as growth, feeding, secretion of hormones, the rate of drug action, the wake-sleep cycle, the menstrual cycle, and reproduction coincide with certain external events such as day and night, the tides, and the seasons. Biological clocks appear to be set by environmental conditions in some animals, but if these animals are isolated from their environment they continue to function according to the usual rhythm. A gradual change in environment does produce a gradual change in the timing of the biological clock. See: circadian; maladaptation to night work; zeitgeber
2. A colloquial term for the decrease in fertility that accompanies aging, particularly as women approach the age of 35.
Medical Dictionary, © 2009 Farlex and Partners

Patient discussion about clock

Q. How do you wake up in the morning if your narcolepsy is so severe you can't hear the alarm clock, phone ring? biggest problem is sleep paralysis, can't wake up. Late for work, everything, life is suffering because of severity. Have tried ritalin, natural supplements, hypnosis therapy, Provigal, antidepressants, nothing seems to work. Employer thinks it's an excuse, friends are irritated, I'm at my wits end. Life is spent sleeping more than awake.

A. Narcolepsy cannot yet be cured. But EDS and cataplexy, the most disabling symptoms of the disorder, can be controlled in most patients with drug treatment. Often the treatment regimen is modified as symptoms change. For decades, doctors have used central nervous system stimulants-amphetamines such as methylphenidate, dextroamphetamine, methamphetamine, and pemoline-to alleviate EDS and reduce the incidence of sleep attacks. For most patients these medications are generally quite effective at reducing daytime drowsiness and improving levels of alertness. However, they are associated with a wide array of undesirable side effects so their use must be carefully monitored. Common side effects include irritability and nervousness, shakiness, disturbances in heart rhythm, stomach upset, nighttime sleep disruption, and anorexia. For full article: Hope this helps.

More discussions about clock
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References in periodicals archive ?
(2018) published a study reporting on the transcript sequences for most of the core circadian clock genes in the limpet Cellana rota.
Acuna-Fernandez et al., "Melatonin, clock genes and mitochondria in sepsis," Cellular and Molecular Life Sciences, vol.
Paul et al., "GSK3 activity regulates rhythms in hippocampal clock gene expression and synaptic plasticity," Hippocampus, vol.
It is inherited in autosomal dominant mode, caused by circadian cycle irregularity as circadian clock genes are key players in its development.
In conclusion, our results showed that the 3111T/C variant of CLOCK gene was closely related to the occurrence of motor fluctuation and sleep disorders in a northeastern Chinese population.
In mammals, circadian rhythm is controlled by hypothalamic suprachiasmatic nucleus (SCN), and regulated by a transcriptional feedback loop with clock genes, such as circadian locomotor cycle kaput ( Clock ), Brain and muscle Arnt-like protein-1 ( Bmal1 ), Period ( Per ), Cryptochrome ( Cry ), Reverse erythroblastosis virus ( Rev-erb ), Retinoic acid receptor-related orphan receptor ( Rora ) genes, and their corresponding proteins.[sup][7] Clock and Bmal1 are two critical transcriptional activators, which stimulate the expression of Per and Cry at the beginning of the day.
Recent DNA microarray analysis of islets derived from Tg mice at 4 weeks of age showed that the mRNA levels of E-box-driven clock genes were markedly reduced in the islets of Tg mice (Table 1) [52], indicating malfunction of the molecular clock in the islets of Tg mice.
An amplified product of 1597 bp was obtained in strains isolated from north facing slopes while 1598 bp product was amplified in strains isolated from south facing slope for frequency clock gene. Point mutations on nucleotide 115 T(A), 947 G(T), and 948 T(G) position were observed in S2 and S3 strains, when aligned against reference sequence of S.
There is a link between clock gene expression and sleep-related processes; however the underlying regions supporting sleep homeostasis have received relatively limited focus.
According to the National Sleep Foundation, the human body consists of circadian clock genes, or simply known as an internal body clock, which regulates the way the body works each day.
Ogasawara et al., "A circadian clock gene, REV-ERB[alpha], modulates the inflammatory function of macrophages through the negative regulation of Ccl2 expression," Journal of Immunology, vol.