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Sleep can follow a physiological or behavioral definition. In the physiological sense, sleep is a state characterized by reversible unconsciousness, special brainwave patterns, sporadic eye movement, loss of muscle tone (possibly with some exceptions; see below regarding the sleep of birds and of aquatic mammals), and a compensatory increase following deprivation of the state, this last known ...
In cats, the sleep cycle lasts about 30 minutes, though it is about 12 minutes in rats and up to 120 minutes in elephants (In this regard, the ontogeny of the sleep cycle appears proportionate with metabolic processes, which vary in proportion with organism size. However, shorter sleep cycles detected in some elephants complicate this theory).
Desert kangaroo rats are denizens of desert areas with sandy soil; vegetation is typically sparse and consists of creosote bush, a variety of grasses, and cacti. [8] Desert kangaroo rats live in burrow systems under slight mounds of soil 6-9m across; [8] they sleep in a den, which is sealed off at extreme temperatures, during the day. [4]
In response to long periods of hunger, its metabolic rate can be reduced by up to 25 percent. [15] The naked mole-rat survives for at least 5 hours in air that contains only 5% oxygen; it does not show any significant signs of distress and continues normal activity. It can live in an atmosphere of 80% CO 2 and 20% oxygen. In zero-oxygen ...
They do this in part by lowering their metabolic rate, which reduces the loss of water through their skin and respiratory system. Evaporation through the skin is the major route of loss. [12] Merriam's kangaroo rats obtain enough water from the metabolic oxidation of the seeds they eat to survive and do not need to drink water at all. [11]
[10]: §9.1–2 263–282 (PGO waves have long been measured directly in cats but not in humans because of constraints on experimentation; however, comparable effects have been observed in humans during "phasic" events which occur during REM sleep, and the existence of similar PGO waves is thus inferred.) [15] These waves occur in clusters ...
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An even lighter type of sleep has been seen in rats that have been kept awake for long periods of time. In a process known as local sleep, specific localized brain regions went into periods of short (~80 ms) but frequent (~40/min) NREM-like states. Despite the on-and-off periods where neurons shut off, the rats appeared to be awake, although ...