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Orexin (/ ɒ ˈ r ɛ k s ɪ n /), also known as hypocretin, is a neuropeptide that regulates arousal, wakefulness, and appetite. It exists in the forms of orexin-A and orexin-B.The most common form of narcolepsy, type 1, in which the individual experiences brief losses of muscle tone ("drop attacks" or cataplexy), is caused by a lack of orexin in the brain due to destruction of the cells that ...
Wakefulness is a daily recurring brain state and state of consciousness in which an individual is conscious and engages in coherent cognitive and behavioral responses to the external world. Being awake is the opposite of being asleep , in which most external inputs to the brain are excluded from neural processing.
Orexins strongly excite various brain nuclei to affect an organism's wakefulness by affecting their dopamine, norepinephrine, histamine and acetylcholine systems. These systems work together to stabilize the organism's sleep cycles. Once made, the orexin peptides can bind to the orexin receptor; which is a G protein-coupled receptor. This ...
Orexin neurons in the posterior lateral hypothalamus potentiate neurons in the ascending arousal system and help stabilize the brain in the waking state (and consolidated wakefulness, which builds up homeostatic sleep drive, helps stabilize the brain during later sleep). The loss of orexin neurons in the disorder narcolepsy destabilizes the ...
Through the diverse outputs of the orexin system, the orexin neurons in the lateral hypothalamus mediate an array of functions. Two of the most commonly noted functions of orexin peptides in the lateral hypothalamus are the promotion of feeding behavior and arousal (i.e., wakefulness). [3] [6] More generally, the orexinergic neural projections ...
Orexin, otherwise known as hypocretin, is a neuropeptide that acts within the brain to regulate appetite and wakefulness as well as a number of other cognitive and physiological processes. Loss of these orexin-producing neurons causes narcolepsy and most individuals with narcolepsy have a reduced number of these neurons in their brains.
Rapid eye movement sleep ( REM sleep or REMS) is a unique phase of sleep in mammals (including humans) and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream vividly. The REM phase is also known as paradoxical sleep ( PS) and sometimes ...
Hypocretin regulates sleep and states of arousal. Hypocretin deficiency is further associated with decreased levels of histamine and epinephrine, chemicals important in promoting wakefulness, arousal and alertness. Diagnosis. The diagnosis of narcolepsy and cataplexy is usually made by symptom presentation.