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Article: Sleep
- Article from:
- Gale Encyclopedia of Children's Health: Infancy throughAdolescence
- Author:
CopyrightCOPYRIGHT 2006 Thomson Gale. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Sleep
Definition
Sleep is a biological imperative critical to the maintenance of mental and physical health. It is a state of lessened consciousness and decreased physical activity during which the organism slows down and repairs itself. The sleep cycle involves two distinct phases that alternate cyclically from light sleep to deep then deeper and deepest sleep throughout the sleep period. There are two main phases of sleep.
Description
The timing and progression of the sleep cycle and the total amount of nightly sleep required for optimal
health varies from ...
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