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The circadian rhythm provides a person with a signal for when to sleep and when to wake up. [43] If circadian rhythm and sleep-wake cycle are misaligned, this might lead to negative affect and emotional instability. [44] It has been found that emotions vary depending on the circadian rhythm and the duration of how long one was awake. [45]
The "Preservation and Protection" theory holds that sleep serves an adaptive function. It protects the animal during that portion of the 24-hour day in which being awake, and hence roaming around, would place the individual at greatest risk. [115] Organisms do not require 24 hours to feed themselves and meet other necessities.
Changes in daily routines place stress on the body's maintenance of sleep-wake cycles, appetite, energy, and alertness, [8] all of which are affected during mood episodes. For example, depressive symptoms include disturbed sleep patterns (sleeping too much or difficulty falling asleep), changes in appetite, fatigue, and slowed movement or ...
The electrical activity seen on an EEG represents brain waves. The amplitude of EEG waves at a particular frequency corresponds to various points in the sleep-wake cycle, such as being asleep, being awake, or falling asleep. [18] Alpha, beta, theta, gamma, and delta waves are all seen in the different stages of sleep.
After sustained periods of sleep, both the speed and synchronicity of the neurons firing are shown to decrease. [5] Another effect of wakefulness is the reduction of glycogen held in the astrocytes, which supply energy to the neurons. Studies have shown that one of sleep's underlying functions is to replenish this glycogen energy source. [6]
The bunker experiment was a scientific experiment that began in 1966 to test whether humans, like other species, have an intrinsic circadian clock. [1] It was started by Jürgen Aschoff and Rütger Wever of the Max Planck Institute for Behavioral Physiology and later taken over by Jürgen Zulley.
The cognitive shuffle is based on Beaudoin’s somnolent information processing theory. [5] [13] The somnolent information processing theory postulates the existence of a sleep onset control system that evolved to ensure that falling asleep tends to happen when it is evolutionarily opportune (safe, timely) to fall asleep. [14]
The basic rest–activity cycle (BRAC) is a physiological arousal mechanism in humans proposed by Nathaniel Kleitman, [1] hypothesized to occur during both sleep and wakefulness. Empirically, it is an ultradian rhythm of approximately 90 minutes (80–120 minutes [ 2 ] ) characterized by different levels of excitement and rest.