The Sleep–Wakefulness Cycle

  • Fernando Reinoso-SuárezEmail author
  • Isabel de Andrés
  • Miguel Garzón
Part of the Advances in Anatomy, Embryology and Cell Biology book series (ADVSANAT, volume 208)


Wakefulness (W) is necessary for a thoughtful and precise knowledge of things, allowing us to recognize our essential attributes and the changes that we experience in ourselves. We spend about two-thirds of our life in W. This state is circadian and homeostatically regulated and precisely meshed with sleep into the sleep–wakefulness cycle (SWC). Sleep is also a necessary, active, periodic, and diverse condition. Although five different stages have been described for sleep in man, most experimental studies have curtailed them into two sleeping stages: Slow wave sleep (SWS), also called non-REM sleep (NREM sleep); and rapid eye movement sleep (REM sleep or paradoxical sleep). Together with W, these three phases constitute the SWC. The hypothalamic suprachiasmatic nucleus is the pacemaker for SWC circadian rhythmicity. Photic retinal stimulation by light modulates suprachiasmatic nucleus activity through the retino-hypothalamic pathway, tuning the SWC to a circadian rhythm with a nocturnal sleep time in adult humans.


  1. Berger H (1929) Über das electroenkephalogram des Menschen. Arch Psychiat Nervenkr 87:527–570CrossRefGoogle Scholar
  2. Rechtschaffen A, Kales A (1968) A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects. University of California, Brain Information Service/Brain Research Institute, Los Angeles, CAGoogle Scholar
  3. Ursin R, Sterman MB (1981) A manual for standardized scoring of sleep and waking states in the adult cat. University of California Brain Information Service, Los AngelesGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Fernando Reinoso-Suárez
    • 1
    Email author
  • Isabel de Andrés
    • 1
  • Miguel Garzón
    • 1
  1. 1.Departamento de Anatomía Histología y NeurocienciaUniversidad Autónoma de MadridMadridSpain

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