( ( Sleep-wake patterns ) ( ( are ( governed ( by ( ( ( circadian rhythms ) , ) ( which ( usually ( ( ( ( ( ( run ( on ( 25-hour cycles ) ) ) ( with ( ( two ( natural ( daily ( peak times ) ) ) ) ( for sleeping ) ) ) ) , ) ( at night ) ) and ) ( ( at mid-day ) ( , ( the ( traditional ( siesta time ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Sleep-wake) (NNS patterns)) (VP (VBP are) (VP (VBN governed) (PP (IN by) (NP (NP (NN circadian) (NNS rhythms)) (, ,) (SBAR (WHNP (WDT which)) (S (ADVP (RB usually)) (VP (VP (VBN run) (PP (IN on) (NP (JJ 25-hour) (NNS cycles))) (PP (IN with) (NP (NP (CD two) (JJ natural) (JJ daily) (NN peak) (NNS times)) (PP (IN for) (NP (NN sleeping))))) (, ,) (PP (IN at) (NP (NN night)))) (CC and) (VP (PP (IN at) (NP (NN mid-day))) (, ,) (NP (DT the) (JJ traditional) (NN siesta) (NN time)))))))))) (. .)))
Sleep-wake patterns are governed by circadian rhythms, which usually run on 25-hour cycles with two natural daily peak times for sleeping, at night and at mid-day, the traditional siesta time.
(ROOT (S (NP (NN Circadian) (NNS rhythms)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (NP (JJ daily) (NNS cycles)) (PP (IN of) (NP (NN behavior)))))) (, ,) (PP (IN like) (NP (DT the) (JJ sleep-wake) (NN cycle)))) (. .)))