A sense of calm and connectedness
The brain interprets the long slow breath out as a sign that everything is okay and responds by holding off on the adrenaline, and slowing down other functions, such as your heart rate, bringing you a sense of calm and connectedness.
Your breath between surges
Wonderful. So this is your breath between surges making sure that when the surge comes, it is greeted by a relaxed and confident mind and a relaxed and confident body.