Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "Criteria

To be called circadian, a biological rhythm must meet these four general criteria:
The rhythms repeat once a day (they have a 24-hour period). In order to keep track of the time of day, a clock must be at the same point at the same time each day, i.e. repeat every 24 hours.
The rhythms persist in the absence of external cues (endogenous). The rhythm persists in constant conditions with a period of about 24 hours. The rationale for this criterion is to distinguish circadian rhythms from simple responses to daily external cues."

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "sleepiness increases and decreases with a period of approximately 24 hours.[5] In 1918, J.S. Szymanski showed that animals are capable of maintaining 24-hour activity patterns in the absence of external cues such as light and changes in temperature.[6] Ron Konopka and Seymour Benzer isolated the first clock mutant in Drosophila in the early 1970s and mapped the "period" gene, the first discovered genetic component of a circadian clock.[7] Joseph Takahashi discovered the first mammalian 'clock gene' (CLOCK) using mice in 1994.[8][9]
The term "circadian" was coined by Franz Halberg in the late 1950s.[10]
[edit]Criteria

To be called circadian, a biological rhythm must meet these four general criteria:"

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Circadian Genes, Rhythms and the Biology of Mood Disorders

Circadian Genes, Rhythms and the Biology of Mood Disorders: "The molecular clock
The primary molecular clock is located in the suprachiasmatic nucleus (SCN) in the hypothalamus, and consists of a transcriptional feedback loop which cycles over the course of approximately twenty-four hours in the absence of environmental input (Reppert and Weaver, 2001; Ko and Takahashi, 2006). The major transcriptional activator consists of a dimer between the Circadian Locomotor Output Cycles Kaput Protein (CLOCK) and Brain and Muscle ARNT-like Protein 1 (BMAL1, also known as ARNTL or MOP3). This complex binds to E-box sequences in the promoters of"
 genes including the Period (Per) and Cryptochrome (Cry) genes. The PER and CRY proteins are translated in the cytoplasm, and are phosphorylated by Casein Kinase I ε and δ (CK1) and Glycogen Synthase Kinase 3β (GSK3β)
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Circadian Genes, Rhythms and the Biology of Mood Disorders

Circadian Genes, Rhythms and the Biology of Mood Disorders: "Indeed some of the major hallmarks of diseases like major depressive disorder (MDD) and bipolar disorder (BPD) are abnormal sleep/wake, appetite, and social rhythms (Boivin, 2000; Bunney and Bunney, 2000; Lenox et al., 2002; Grandin et al., 2006). Depression symptoms are also diurnal with the most severe symptoms occurring typically in the morning (Rusting and Larsen, 1998), and depression is more prevalent in areas of the world that receive little sunlight for extended periods of time (Booker et al., 1991). In addition, one of the most common mood disorders, affecting some 2–5% of the population in temperate climates, is seasonal affective disorder (SAD), a syndrome where depressive symptoms occur only in the winter months when there are shorter days and a later dawn (Lam and Levitan, 2000; Magnusson and Boivin, 2003). Thus, it has long been hypothesized that abnormalities in the molecular clock underlie the development of these disorders. "

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Circadian Genes, Rhythms and the Biology of Mood Disorders

Circadian Genes, Rhythms and the Biology of Mood Disorders: "abnormalities in circadian rhythms may underlie the development of mood disorders such as bipolar disorder, major depression and seasonal affective disorder. Furthermore, some of the treatments that are currently employed to treat mood disorders are thought to act by shifting or “resetting” the circadian clock, including total sleep deprivation and bright light therapy. There is also reason to suspect that many of the mood stabilizers and antidepressants used to treat these disorders may derive at least some of their therapeutic efficacy by affecting the circadian clock. Recent genetic, molecular and behavioral studies implicate individual genes that make up the clock in mood regulation. "

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Circadian rhythm sleep disorder - causes, DSM, functioning, effects, therapy, adults, examples, person

Circadian rhythm sleep disorder - causes, DSM, functioning, effects, therapy, adults, examples, person: "The Fourth Edition Text Revision of the Diagnostic and Statistical Manual of Mental Disorders ( DSM-IVTR , a handbook used by mental health professionals to diagnose mental disorders) defines circadian rhythm sleep disorder as one of several primary sleep disorders . Within the category of primary sleep disorders, it is classified as one of the dyssomnias, characterized by irregularities in an individual's quality, timing, and amount of sleep. In earlier versions of the DSM , the disorder is called sleep-wake schedule disorder.

Description

Circadian rhythm sleep disorder involves an alteration of an individual's circadian system or a mismatch between a person's natural, or endogenous, circadian system and the external, or exogenous, demands placed on it. It can lead to insomnia at certain times of the day or excessive sleepiness throughout the day. The insomnia or excessive sleepiness results in impaired functioning in social, occupational, or other environments."

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The Pineal Gland

The Pineal Gland: "elevating melatonin synthesis in the pinealocytes (Ganguly et al., 2001; Schomerus and Korf 2005). Recent studies have also shown that the removal of the SCN results in a daytime increase in Aa-nat mRNA levels, suggesting that the presence of an inhibitory SCN output contributs to the control of pineal melatonin rhythm (Kalsbeek et al., 2000). It has also been suggested that the GABA-ergic output of the SCN terminals on to the pre-autonomic PVN neurons may be the daytime inhibitory signal contributing to the morning decline of melatonin synthesis (Kalsbeek et al., 2000).

Another important factor in the regulation of the melatonin level is represented by light. Light is the dominant environmental factor that regulates melatonin biosynthesis in vertebrates, and regardless of whether a species is diurnal/nocturnal or exhibits crepuscular activity, pineal melatonin levels are high during the dark phase of a natural or imposed illumination cycle (Reiter, 1991; Arendt, 1999)."

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