The Body Clock

Circadian rhythms are internally generated, thus the outputs of the circadian system are not reactions to changes in posture or environment but come from within the individual (p. 11). As well as being endogenous they are also persistent and self-sustaining, meaning that the cycle of wakefulness and sleep continues in the absence of external cues. 

The most important characteristic of the human circadian system for the shiftworker is that much of it is resistant to abrupt changes in schedule. This means that the circadian rhythm will continue to cycle in a way that is not adapted to current working patterns for some time, possibly weeks or even months. Note that circadian rhythms never fully adapt, even in cases where the operator is working on a permanent night shift The practical effect of this is that the operator s circadian rhythm can be caUing for sleep when 

FIGURE 9.1 Circadian rhythm as measured by body temperature. (Data from Monk, T.H. and Embrey, D.E., in Night and Shiftwork Biological and Social Aspects, A. Reinberg, Ed., Pergamon Press, Oxford, U.K., 1981, pp. 473-480. With permission.) 

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Smokensky, Michael, and Lynne Lamberg. The Body Clock Guide to Better Health. New York Henry Holt Company, Inc., 2000. 

Sometimes drivers think they can beat the body clock to drive those extra few miles. Relate the following information to your drivers, stressing that NHTSA says they won t keep them awake while driving ... 

Ramelteon (Rozerem). Recently approved by the FDA for treatment of insomnia in the US, ramelteon acts via a completely novel mechanism of action, that is, stimulating so-called melatonin Ti and T2 receptors in the brain s suprachiasmatic nucleus (SCN). The SCN is regarded as the body s master clock that regulates the sleep-wake cycle and other circadian rhythms. The effects of ramelteon in some respects mimic those of melatonin. Ramelteon, in clinical trials, administered at bedtime doses of 8 mg, outperformed placebo with respect to several indices of sleep disturbance (see Table 9.4). 

Although a substantial body of evidence indicates that the functions of DBT and SGG depend on PER and TIM phosphorylation respectively, these may not be the only substrates in the Drosophila clock. For example, in mammals it was recently found that casein kinase 1 phosphorylates CRY and BMALl (the orthologue of CYC) in addition to PER (see below) (Eide et al 2002). 

Jet lag, a disturbance of the sleep-wake cycle, occurs when there is a disparity between the external time and the traveler s endogenous circadian clock (internal time). The internal time regulates not only daily sleep rhythms but also body temperature and many metabolic systems. The synchronization of the circadian clock relies on light as the most potent "zeitgeber" (time giver). 

Anthroposophists also take a unique approach to medicine. The body, they say, has three poles — cool, warm, and balancing. Illness arises from a disharmony of these poles, and we can restore the harmony with a variety of animal, mineral, and plant substances. We must take the time of day and planet constellations into consideration as we prepare these remedies, and we must never work on them between noon and three o clock in the afternoon because this is the least alive time of day. Anthroposophists frown upon vaccinations, but they approve of color therapy and a mistletoe preparation invented by Steiner. Sauerkraut they regard as a special food we require it for the health of our digestive tracts. 

The visual sense provided additional surprises. Virtually every item in range of my vision was transformed. The alarm clock was a work of art from a Cellini studio. Alice s gaudy jewelry was on loan from the Empress Josephine. The faces of my companions radiated light. Auras shone about their bodies. For just a moment I felt an inexpressible kinship with them. 

Potentized homeopathic medicines have preferential action on sides of the body some are more effective on one side than on the other. This differential effect of the medicines with respect to laterality can be traced to functional asymmetry of the human brain. The brain can asymmetrically modulate nurochemical, neuroendocrine and immune reactivity. Potentized drugs are very often selected on the basis of time modalities of symptoms of a disease. The time modalities of the drug action can be correlated with the internal clock or biological rhythms of organisms which are disturbed in diseased conditions. Melatonin, secreted in the brain, has marked influence on the circadian rhythms. 

The Doctor thrust his hands into his pockets and attempted a shrug, despite the cold creeping into his bones. Well, I m a connoisseur of fine art myself I can understand your passion. But, close to where, if you don t mind my asking I can t quite make out our location and there s a shortage of identifiable landmarks. And as for fixing our temporal position, well, my body clock is usually as accurate a timepiece as - ... 

Buys RM, Van Eden CG, Goncharuk VD, Kalsbeek A (2003) The biological clock tunes the organs of the body timing by hormones and the autonomic nervous system. J Endocrinol 177 17-26... 

The time of falling asleep is determined by three factors, which in normal sleepers occur at bedtime. These are (a) circadian rhythm, i.e. the body s natural clock in the hypothalamus triggers the rest/ sleep part of the sleep-wake cycle, (b) tiredness, i.e. time since last sleep, usually about 16 hours and (c) lowered mental and physical arousal. If one of these processes is disrupted then sleep initiation is difficult, and it is these three factors that are addressed by a standard sleep hygiene program (see below). Early in the course of insomnia rigorous adherence to sleep hygiene principles alone may restore the premorbid sleep pattern but in some patients the circadian process is less stable and they are less susceptible to these measures. 

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