Sleep-Wake Regulation Of Sleep Essay

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Sleeping is a natural part of our daily life. It is a behavior that is displayed every day and is necessary for us to function. To be able to rest efficiently an animal, be it a human or another mammal, needs to fall asleep in a matter of seconds or minutes; but since a sleeping animals are more vulnerable to predation, it also needs to wake easily in case of threat. Those requirements show how well regulated the sleep-wake regulation has to be.
Historically, sleep studies have been done by a combination of electroencephalography (EEG) and electromyography (EMG), the signals obtained allowed to define three sleep/wake stages(REF). The first one is displayed by awake animal, the EEG show a high frequency activity (beta waves) and the EMG signal is high, reflecting the motor activity of the animal. The second and third stages are present in sleeping animals, called respectively non-rapid eye movement sleep (NREM sleep) and rapid eye movement sleep (REM sleep). They are characterized by a slow EEG activity (delta waves) during the NREM sleep and a high frequency activity (theta waves) coupled with a
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Arousal is obtained by an inhibition of the sleep-promoting structures and promotion of the cortex activity. It is an active process mediated by the upper brainstem neurons in the pedunculopontine nucleus (PPT), laterodorsal tegmental nucleus (LDT), locus coeruleus(LC), tuberomammillary nucleus (TMN) and ventral periaqueductal gray (vPAG). In a perfect mirror image, sleep is regulated by an inhibition of the ascending arousal fibers and of the cortex activity. It is mediated by the ventrolateral (VLPO) and median (MnPO) preoptic nuclei. This reciprocal inhibition is called a flip-flop switch and is regulated on several levels allowing a refined control of the animal sleeping

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