Researchers know that living organisms, including humans, have an internal biological clock. This predictable change in the light environment allows organisms to predict and adapt their activity-rest rhythms and physiology to specific needs. hours of the day-night cycle. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get an original essay Despite the fact that the body's circadian system acts independently of external signals, but as mentioned, environmental conditions, such as light, temperature and food, reset the biological clock through several pathways. Environmental temperature cycles reset the biological clock via cellular heat shock signaling and humoral/neural pathways. Food availability is also a powerful driver of time and drives peripheral clocks via nutrient-sensing pathways and hormonal pathways. The superchiasmatic nucleus (SCN) of the brain's hypothalamus is synchronized by light/dark cycles and organized by peripheral clocks. The SCN circadian clock is driven by external signals and coordinates the peripheral clock by sending signals to peripheral tissues such as the liver, skeletal muscle, adipose tissue and pancreas, through hormones and neurotransmitters. Three fundamental processes underlie the regulation of sleep: first, the control of biological mechanisms is a homeostatic process mediating the increase in the tendency to sleep during wakefulness and its dissipation during sleep; Another control mechanism is an Ultradian process occurring during the sleep episode and represented by the alternation of the two fundamental sleep states, non-REM sleep and REM sleep. And a third mechanism controls a circadian process, a clock-like mechanism that is fundamentally independent of previous sleep and wakefulness and which determines the alternation of periods with high and low sleep propensity. The circadian clock drives many outcomes, including sleep/wake and metabolic cycles. as well as hormonal changes. Proper alignment between light, the circadian clock, and production behaviors produces temporal order in organisms essential for survival. The circadian clock allocates sleep to a particular time in the day-night cycle, while a homeostatic mechanism tracks the need for sleep. Sleep and behavioral activity have an important effect on the levels of many hormones (e.g., melatonin, growth hormone). Although sleep occurs in one part of the circadian cycle, the timing of minimum body temperature and maximum melatonin concentration should occur toward the end of the sleep period [6, 7]. Core temperature typically reaches its minimum around 4:30-5:00 a.m. in human adults, and melatonin (normally completely absent during daylight hours) usually begins to be produced around 8:00-9:00 p.m. at night and stops around 7:00 a.m. :00-8:00 in the morning. The tendency for deepest sleepiness occurs in the middle of the night, around 2:00-3:00 a.m., accompanied by a shorter, less profound period of sleepiness approximately twelve hours later, around 2:00-3:00 p.m. (fig1). .Melatonin is not necessary for sleep in humans. For example, patients who have had their pineal gland removed for medical reasons often experience little disruption in their sleep-wake cycle [10]. Nevertheless, several studies have examined the ability of exogenous melatonin to promotesleep in humans, with often contradictory results. The melatonin system plays a well-established role in regulating the circadian clock and the rhythms it controls. In preclinical studies, melatonin has shown great promise for the treatment of insomnia or circadian rhythm sleep disorders (CRSD). However, the physicochemical and pharmacokinetic properties of melatonin have slowed the realization of this potential. The development of selective melatonin agonists with improved properties has improved the prospects for manipulating the melatonin system to treat patients with various sleep disorders. Nocturnal light exposure has been shown to affect the expression of specific genes in the SCN called clock genes, such as period (per). The level of perexpression in SCN cells determines the phase of the circadian clock. Thus, exposure to bright light in the evening causes a phase delay in the circadian clock, whereas similar exposure late at night causes a phase advance. Since the SCN clock controls pineal melatonin release, such phase shifts will manifest as changes in the timing of melatonin secretion. Indeed, the level of circulating melatonin is one of the most reliable measures of the phase of the circadian clock in humans. The circadian clock allocates sleep to occur at a particular time in the day-night cycle, while a homeostatic mechanism tracks the need for sleep. This homeostatic drive builds up during periods of wakefulness and decreases with sleep. The combination of the circadian mechanism and the homeostatic sleep drive determines sleep duration. It was assumed for many years that light influences sleep only secondarily, through changes in circadian photoentrainment. However, several studies have demonstrated that light directly affects both sleep onset and sleep homeostatic drive. Thus, the circadian clock and sleep may interact closely to allow organisms to adapt to their environment. This interaction can be used to explain why changes in the light environment, such as those associated with shift work, shortened days in winter, and transmeridian travel, are associated with general changes in health, including poor health. mental health such as seasonal affective disorder, depression. , and cognitive dysfunction. The effects of light on the circadian system have been studied extensively, with an emphasis on how changes in the light environment lead to changes in circadian rhythms which, in turn, influence sleep and contribute to alterations in mood and cognitive functions. Circadian genes may play an important role in controlling several biological processes, including DNA repair, oxidative stress, maintenance of genomic stability, cell proliferation, and apoptosis. Therefore, they can have a significant impact on the carcinogenic process. Impairment of circadian disorders, cardiovascular disease, obesity, glucose intolerance, alcohol abuse and cancer. It has been widely observed that there is a molecular feedback loop for specific clock genes that act as positive and negative regulators of the biological clock. Furthermore, circadian gene expression in humans is reported to be similar to that observed in rodent peripheral tissues, although tissue-specific clock gene expression patterns have also been observed. Daily variationsof clock gene expression associated with different rhythmicity and maximum or minimum expression in various peripheral tissues of the human body are strongest for peripheral blood leukocytes, probably due to the presence of diverse populations cells in this tissue. However, subpopulations of blood leukocytes may be useful for the study of human circadian rhythms, because circadian genes are expressed, with the peak level occurring during the usual period of activity. The DSM-V defines sleep-wake rhythm disorder as follows: A persistent or recurrent disorder. pattern of sleep disruption due primarily to an alteration of the circadian system or a misalignment between the endogenous circadian rhythm and the sleep-wake schedule required by the physical environment or an individual's social or work schedule. The International Classification of Diseases (ICD-10-CM, 2014) lists 6 subtypes of sleep disorders related to the circadian rhythm: delayed sleep phase type, free running type, advanced sleep phase type, wake-wake type irregular sleep, type of shift work, jet lag. kind. Sleep disturbances lead to excessive sleepiness or insomnia, or both. Sleep disorders cause clinically significant distress or impairment in social, occupational, and other important areas of functioning. Researchers know that living organisms, including humans, have an internal biological clock, that this predictable change in light environment allows organisms to predict and adapt their activity-rest rhythms and physiology at specific times. of the day-night cycle. Despite the fact that the body's circadian system acts independently of external cues, as mentioned, environmental conditions, such as light, temperature, and food, reset the biological clock through multiple pathways. Environmental temperature cycles reset the biological clock via cellular heat shock signaling and humoral/neural pathways. Food availability is also a powerful time giver and entrains peripheral clocks via nutrient-sensing and hormonal pathways. The superchiasmatic nucleus (SCN) of the hypothalamus of the brain is synchronized by light/dark cycles and is thus organized by peripheral clocks. The SCN circadian clock is driven by external signals and coordinates the peripheral clock by sending signals to peripheral tissues such as the liver, skeletal muscle, adipose tissue and pancreas, through hormones and neurotransmitters. Three fundamental processes underlie the regulation of sleep: first, the control of biological mechanisms is a homeostatic process mediating the increase in the tendency to sleep during wakefulness and its dissipation during sleep; Another control mechanism is an Ultradian process occurring during the sleep episode and represented by the alternation of the two fundamental sleep states, non-REM sleep and REM sleep. And a third mechanism controls a circadian process, a clock-like mechanism that is fundamentally independent of previous sleep and wakefulness and which determines the alternation of periods with high and low sleep propensity. The circadian clock drives many outcomes, including sleep/wake and metabolic cycles. as well as hormonal changes. Proper alignment between light, the circadian clock, and production behaviors produces temporal order in organisms essential for survival. The circadian clock allocates sleep to a particular time in the day-night cycle, while,.