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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.

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References in periodicals archive ?
Specifically, neutrality of DNA sequence changes favors their use as tools in phylogeny estimation, both because it lowers the probability of convergent and parallel changes, and also because it makes local clocklike evolution more probable.
One striking recent discovery is 'neutral evolution': the persistent, perhaps clocklike, replacement of genes by variants which seem to be their phenotypic equivalents.
This clocklike regularity lured Allan Lindh and other USGS seismologists here, to see if they could predict Parkfield's next temblor.
These segments, however, are untitled, except for an enigmatic, clocklike logo of the title in various poses at the beginning of several segments.
The quail provide the link between the artwork and the familiar natural world and allow the poet to imagine that world itself in terms of design: "the quail / over the snow // on our back field run free and clocklike, briefly safe." Art makes that moment of "safety" more enduring.
" In Lithuania;' Christopher Simpson writes in Blowback, "municipal killing squads employing Lithuanian Nazi collaborators eliminated 46,692 Jews in fewer than three months, according to their own reports, mainly by combining clocklike liquidation of 500 Jews per day in the capital city of Vilnius with mobile cleanup' sweeps through the surrounding countryside."
Finally everyone would drift off to sleep, oblivious, except for me, of the far-off rumble of the nighty B-52 strike, which with clocklike regularity came just before 3:30 a.m.
There, he had used radio waves to probe the secrets of pulsars, the spinning, magnetized neutron stars that emit bursts of radiation with clocklike regularity.
Even though the X-ray and spectral events recur with clocklike regularity, no two cycles are exactly the same.
The water continued to drip with clocklike regularity.
The difference in log-likelihood values between the two trees was nonsignificant (G = 21.2, 14 df, P [greater than] 0.096), supporting the assumption of clocklike sequence evolution in this group of closely related haplotypes.
Without any complicating factors, pulsar signals would arrive with clocklike regularity, like lighthouse beams.