Circadian Rhythms

Recent experiments (4) have shown that there are no significant age or gender-related differences in thermal environment preference when all other factors such as weight of clothing and activity level are the same. Whereas people often accept thermal environments outside of their comfort range, there is no evidence that they adapt to these other conditions. Their environmental preference does not change. Similarly there is no evidence that there is any seasonal or circadian rhythm influence on a person s thermal preference. 

Melatonin [73-31-4] C 2H N202 (31) has marked effects on circadian rhythm (11). Novel ligands for melatonin receptors such as (32) (12), C2yH2gN202, have affinities in the range of 10 Af, and have potential use as therapeutic agents in the treatment of the sleep disorders associated with jet lag. Such agents may also be usehil in the treatment of seasonal affective disorder (SAD), the depression associated with the winter months. Histamine (see Histamine and histamine antagonists), adenosine (see Nucleic acids), and neuropeptides such as corticotropin-like intermediate lobe peptide (CLIP) and vasoactive intestinal polypeptide (VIP) have also been reported to have sedative—hypnotic activities (7). 

Melatonin. Melatonin (A/-acetyl-5-metlioxytryptaniine) [73-31-4] C 2H gN2O2(250) is secreted from the pineal gland and retina during dark periods of the vertebrate circadian rhythm (65). Melatonin regulates biological rhythms and neuroendocrine function and is formed from serotonin (5-HT). 

There are two concerns about the effects of shift rotation and night work disruption of "circadian rhythms" and sociological costs, that is, effects on the worker s family life. 

The practical implications of this experiment are that when evaluating the effects of shift work due to circadian effects, the type of task being carried out by the worker must be taken into account. For example, skill-based tasks would be expected to exhibit the performance changes characteristic of low memory load tasks, whereas performance variations in knowledge-based tasks would be expected to follow the pattern of high memory load tasks. Performance on rule-based tasks may depend on the degree of frequency of use of the rules, which in turn may determine the memory load. If these results were confirmed by further process plant studies, it would have implications for when different types of operation (involving different levels of memory load) should be scheduled to reduce circadian rhythm effects and minimize errors. 

Studies by Smith et al. (1982), Folkard et al. (1979), and Colquhoim et al. (1969), have investigated the disruption of circadian rhythms caused by having to be awake and work at imusual hours and by having to sleep during daytime. With respect to the sociological effects, studies by Kasl (1974) and Kahn (1974) concluded that fixed afternoon and night shifts lead to lower levels of social satisfaction because it becomes difficult to participate in family activities. 

Monk, T. H., Embrey, D. E. (1981). A Field Study of Circadian Rhythms in Actual and Interpolated Task Performance. In A. Reinberg, N. Vieux, P. Andlauer (Eds.), Night and Shift Work Biological and Social Aspects. Oxford, UK Pergamon Press. 

T No A PKA Brain (neuron), adrenal (medulla) Neurotransmission, synaptic plasticity, LTP, memory,circadian rhythm... 

Circadian Rhythms. Figure 1 Mammalian circadian system is organized as a hierarchy of multiple clocks thatfunction to synchronize timing of internal processes between each other and with the environment. See details in the text. 

Bell-Pedersen D, Cassone VM, Earnest DJ et al (2005) Circadian rhythms from multiple oscillators lessons from diverse organisms. Nat Rev Genet 6(7) 544-556... 

Hypothalamus-pituitary-adrenal (HPA) Axis Circadian Rhythms Appetite Control Orexins... 

Saper CB, Scammell TE, Lu J (2005) Hypothalamic regulation of sleep and circadian rhythms. Nature 437 1257-1263... 

Autocatalysis can cause sustained oscillations in batch systems. This idea originally met with skepticism. Some chemists believed that sustained oscillations would violate the second law of thermodynamics, but this is not true. Oscillating batch systems certainly exist, although they must have some external energy source or else the oscillations will eventually subside. An important example of an oscillating system is the circadian rhythm in animals. A simple model of a chemical oscillator, called the Lotka-Volterra reaction, has the assumed mechanism ... 

---