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Circadian rhythms have been documented for centuries. For example, French astronomer Jean-Jacques d’Ortous de Mairan noted the periodic 24-hour movement of Mimosa plant leaves as early as 1729. However, science has only recently begun to uncover the cellular mechanisms responsible for driving observed circadian rhythms.
A circadian rhythm (/ s ər ˈ k eɪ d i ə n /), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours.Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrained by the environment).
The Rev-Erb proteins are members of the nuclear receptor (NR) superfamily of intracellular transcription factors and key regulatory components of the circadian clock. There are two forms of the receptor, Rev-Erb alpha and Rev-Erb beta, which are each encoded by a separate gene (NR1D1 and NR1D2, respectively). [1] [2]
The SCN is then able to influence the sleep wake cycle, acting as the "apex of a hierarchy" that governs physiological timing functions. [2] "Rest and sleep are the best example of self-organized operations within neuronal circuits". [1] A-riot-of-rhythms-neuronal-and-glial-circadian-oscillators-in-the-mediobasal-hypothalamus-1756-6606-2-28-S3
In the brain, NPAS2 functions as a generator and maintainer of mammalian circadian rhythms. More specifically, NPAS2 is an activator of transcription and translation of core clock and clock-controlled genes through its role in a negative feedback loop in the suprachiasmatic nucleus (SCN), the brain region responsible for the control of ...
The SCN of the hypothalamus contains an endogenous pacemaker that regulates circadian rhythms. [4] The zeitgeber found to have the most profound effect on the SCN is light, which is the form of stimulation of which conversion is needed for it to be processed by the brain. Neurotransmitters that travel the RHT are responsible for delivering this ...
The production of speech is a highly complex motor task that involves approximately 100 orofacial, laryngeal, pharyngeal, and respiratory muscles. [2] [3] Precise and expeditious timing of these muscles is essential for the production of temporally complex speech sounds, which are characterized by transitions as short as 10 ms between frequency bands [4] and an average speaking rate of ...
The circadian oscillators in eukaryotes that have been studied function using a negative feedback loop in which proteins inhibit their own transcription in a cycle that takes approximately 24 hours. This is known as a transcription-translation-derived oscillator (TTO).(2) Without a nucleus, prokaryotic cells must have a different mechanism of ...