[–] totes_magotes [S] 0 points 2 points (+2|-0) ago 

The vagus nerve runs from the brain to several areas of the body. It modulates the parasympathetic nervous system, which controls heart rate and lung function, among other processes.

Diaphragmatic breathing stimulates the vagus nerve and the parasympathetic nerve system, reversing the affects of the sympathetic nerve system (fight or flight).