WHAT IS SLEEP?

摘要

Strictly speaking, the term "sleep" only applies to animals with complex nervous systems. Nevertheless it is possible to identify sleep-like states in invertebrates that allow us define sleep more broadly. These include cycles of rest and activity, a stereotypical body position, lack of responsiveness and compensatory rest after sleep deprivation. Insects in particular have a state very similar to sleep, as do scorpions and some crustaceans.Even microorganisms, which lack a nervous system, have daily cycles of activity and inactivity driven by internal body clocks known as circadian clocks.