Covered in 6.5:

-Energetic dualities exist in the body
-Ida is the lunar, feminine, Yin, meditative channel
-Pingala is the solar, heated, Yang, masculine channel
-These energies criss-cross on sushumna nadi like a double helix
-The chakras reside at the points on the spine where they intersect
-Ida represents the sympathetic nervous system
-Pingala represents the parasympathetic nervous system
-Yoga balances these energetic channels, and in turn balances the nervous system
-A healthy person switches from left to right nostril dominance every 80 minutes or so
-When the left nostril is predominant so is our parasympathetic nervous system; more blood flows to the right hemisphere of the brain
-When the right nostril is predominant so is our sympathetic nervous system; more blood flows to the left hemisphere of the brain
-Overview of breathing exercises to hack the nervous system
-Chandra Bhedana: Inhaling through the left nostril and exhaling through the right; moves energy into the left nostril (stimulates parasympathetic nervous system); calms you down
-Surya Bhedana: Inhaling through the right nostril and exhaling through the left; moves energy into right nostril (stimulates sympathetic nervous system); wakes you up
-Nadi Shodhana: Alternate nostril breathing to bring energy back into Sushumna Nadi (central, energetic highway of the spine)
-Padadhirasana: Arms crossed; hands under armpits
-How all this is relevant to bringing people out of Savasana