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Sleep associated with a high frequency of phasic activities, particularly muscle twitches, dominate the daily life of altricial mammals and human neonates. “Active sleep” is the term that has been used to describe these behavioral phenomena in the neonatal rat, cat and rabbit in comparison to the sleep state without phasic activities, which is called “quiet sleep”.1
Organisms exhibit cyclic variations in a variety of essential functions, including the sleep-wake cycle, hormonal regulation, and reproduction. A primary environmental signal regulating these functions is the daily alternation of darkness and light exerted by the rotation of the earth. Superimposed upon the daily light-dark cycle is a seasonal influence that modifies the relative durations of day...
Biological rhythms and the biological clocks that control them are fundamental properties of most living organisms, ranging from several forms of bacteria to multicellular plants and animals. These properties share many formal and biochemical properties, and affect all aspects of physiological function, ranging from control of transcription to metabolism to cell cycle to behavior. Because these rhythms...
As the Earth rotates on its axis, it presents two well-defined environments, the day and the night. As the Earth's rotation axis is tilted, the relative length of day and night changes systematically along the year. As an evolutionary consequence, living creatures have responded to these two geophysical environments by developing predictive mechanisms to adapt themselves successfully. This is the...
The development of the concept of homeostasis began in the mid 19th century, when Claude Bernard (1813–1878) claimed that ‘la fixeté du milieu interieur' is essential for higher organisms to survive in an ever changing environment. “Standing or staying the same” is the literal meaning of the term homeostasis, which was introduced later by Walter B. Cannon (1871-1945) and derived from the Greek words...
Melatonin, the principal hormone secreted by the pineal gland, influences the function of diverse neuroendocrine and other systems in mammals. This indoleamine hormone is also involved in maintaining brain homeostasis, entraining biological rhythms and coordinating reproductive function to changes in photoperiod in seasonal breeders.1,2 Other studies indicate a potentially important immunomodulatory...
Serotonin was first isolated from serum by Rapport et al. 1,2 and was subsequently found to be present in the brain and to function as a neurotransmitter. 3–5 Over the course of the last 50 years there has been an explosion of knowledge of the serotonergic system. The relatively recent development of selective serotonin reuptake inhibitors (SSRIs) and their effectiveness in treating a vast array of...
Neurons in the brain regulate different functions of the body through the release of a variety of chemicals, the neurotransmitters. These neurotransmitters and neurochemicals may be broadly divided into two main classes. The small-molecule neurotransmitters such as acetylcholine, biogenic amines, amino acids viz. gamma aminobutyric acid (GABA), glycine, glutamate and also several neuroactive peptides...
Hormones can modulate and be modulated by sleep. This close relationship has been recognised for many decades. Sleep deprivation is an adverse condition that can alter the functioning of the neuroendocrine system, inasmuch as concentrations of hormones involved in anabolic processes, such as growth hormone (GH) are reduced, whilst levels of hormones involved in anabolic processes, such as glucocorticoids...
We spend almost one-third of our life sleeping, yet very little is understood as to why we need sleep or how do we sleep. The extrinsic and intrinsic controlling mechanisms of sleep have fascinated scientists for generations and many different theories, networks and endogenous compounds have been proposed. Although various substances are labeled 'sleep-inducing substances' for example, delta sleep...
An exciting recent development in sleep research was the discovery of the importance for vigilance state control and narcolepsy-cataplexy of neurons containing orexin (also known as hypocretin) neuropeptides. Narcolepsycataplexy is a chronic, debilitating sleep disorder that is characterized by excessive daytime sleepiness, manifested as attacks of daytime somnolence at inappropriate times. 1–3 Narcoleptics...
Circadian rhythms are endogenously generated rhythms with a period length of about 24-hrs. Evidence gathered over the past decade indicates that the circadian timing system develops prenatally and the suprachiasmatic nuclei, the site of a circadian clock, is present by mid-gestation in primates. Recent evidence also shows that the circadian system of primate infants is responsive to light at very...
Smith Magenis syndrome (SMS), is a rare genetic disease emblematic of neurodevelopmental disorder. Clinical features include mild dysmorphism, short stature, developmental delay and abnormal behavior. Severe sleep disturbances and maladaptive daytime behavior were linked to abnormal circadian rhythm of melatonin. SMS is the demonstration of biological basis for sleep disorder in a genetic disease...
Normal circadian rhythms are synchronized to a regular 24 hr environmental light/dark (L/D) cycle. Both suprachiasmatic nucleus (SCN) and melatonin are essential for this adaptation. Desynchronization of circadian rhythms as occurs in chronobiological disorders result in severe disturbances of sleep. The Circadian rhythm sleep Disorders (CRSDs) include delayed sleep phase syndrome (DSPS), Non 24 hr...
Sleep, a state marked by lessened consciousness, lessened movement of the skeletal muscles, and slowed-down metabolism, has an essential restorative function and an important role in memory consolidation. Sleep is an orchestrated neurochemical process involving sleep promoting and arousal centers in the brain. Sleep propensity depends on the amount of sleep deprivation and on the circadian clock phase...
In the majority of totally blind individuals, the biological clock is no longer synchronized, or entrained, by the light/dark cycle. Despite exposure to regular social cues, meal times and sleep/wake schedules, the circadian phase (timing) of biological events in these individuals continues to drift to a progressively later (or, rarely, earlier) hour. As a result, these individuals suffer from periodic...
In normal individuals living on a day-oriented schedule, it is hypothesized that a harmonious relationship between homeostatic and circadian processes serves to promote uninterrupted bouts of 8 hours of sleep and 16 hours of wakefulness per day.l.2
There is increasing evidence that headache disorders have many connections with melatonin secretion and pineal function. I will overview in this chapter the putative role of melatonin in the pathophysiology and treatment of headache disorders.
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