Usingizi

Usingizi (kwa Kiingereza "sleep") ni hali ya binadamu na wanyama kupumzika kwa mwili na akili. 

Usingizi hutokea wakati mapigo ya moyo na upumuaji hupungua kwa ngazi zao za chini. Misuli yako inatulia na inaweza kuwa vigumu kukuamsha. Huwa hujitambui wala hujitawali sawasawa.

Tanbihi

 Vyanzo 

 Parmeggiani, Pier Luigi, & Ricardo A. Velluti, eds. (2005). The Physiologic Nature of Sleep. London: Imperial College Press. .
 Parmeggiani, Pier Luigi (2011). Systemic Homeostasis and Poikilostasis in Sleep: Is REM Sleep a Physiological Paradox? London: Imperial College Press. 
 Turek, Fred W. & Phyllis C. Zee, eds. (1999). Regulation of Sleep and Circadian Rhythms. New York: Marcel Dekker, Inc. 

Viungo vya nje

 Rethinking Sleep, David K. Randall, New York Times, September 2012
How to Sleep, James Hamblin, The Atlantic, January 2017

Jamii:Biolojia
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