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Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001.

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Neuroscience. 2nd edition.

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Physiological Changes in Sleep States

A variety of physiological changes take place during the different stages of sleep (see Figure 28.6). Periods of non-REM sleep are characterized by decreases in muscle tone, heart rate, breathing, blood pressure, and metabolic rate. All these parameters reach their lowest values during slow-wave sleep. In non-REM sleep, body movements are reduced compared to wakefulness, although it is common to change sleeping position (tossing and turning). Periods of REM sleep, in contrast, are characterized by increases in blood pressure, heart rate, and metabolism to levels almost as high as those found in the awake state. In addition, REM sleep, as the name implies, is characterized by rapid, rolling eye movements, paralysis of large muscles, and the twitching of fingers and toes. Penile erection also occurs during REM sleep, a fact that is clinically important in determining whether a complaint of impotence has a physiological or psychological basis. Interestingly, REM sleep is found only in mammals (and juvenile birds)

Despite the similar EEG recordings obtained in REM sleep and wakefulness, the two conditions are clearly not equivalent brain states. Unlike wakefulness, REM sleep is characterized by dreaming, visual hallucinations, increased emotion, lack of self-reflection, and a lack of volitional control. Since most muscles are inactive during REM sleep, the motor responses to dreams are relatively minor (sleepwalking actually occurs during non-REM sleep and is not accompanied or motivated by dreams). This relative paralysis arises from increased activity in GABAergic neurons in the pontine reticular formation that contact lower motor neuron circuitry in the spinal cord. Similarly, activity of descending inhibitory projections from the pons to the dorsal column nuclei causes a diminished response to somatic sensory stimuli during REM sleep. Taken together, these observations have led to the aphorism that non-REM sleep is characterized by an inactive brain in an active body, whereas REM sleep is characterized by an active brain in an inactive body.

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By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.

Copyright © 2001, Sinauer Associates, Inc.
Bookshelf ID: NBK10916

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