Yin Qiao e Yang Qiao - awake or sleeping

The Ling Shu (Spiritual Pivot) states:

 “When the taiyang (bladder)

channel enters the brain it is divided into the Yin Motility (yin qiao mai) and the Yang Motility (yang qiao mai); it is here that the yin and yang meet; yang enters the yin and yin moves outwards to the

yang, meeting at the inner corner of the eye. When the

yang is abundant, the eyes are staring open; when the yinis abundant, the eyes will be closed shut” 

 “[When] defensive qi does not enter into the yin it will frequently

remain at the yang. [When] it remains at the yang then

yang qi will be full, [when] yang qi is full, the Yang

Motility vessel [will become] abundant, [when] it does

not enter the yin, then yin qi will become deficient and

therefore the eyes will not close”