What's up about these nerves - Vagus & Phrenic?
The Phrenic and Vagus nerve are often mentioned in conjunction with breathing exercises- and respiration contexts with different important purposes.
The course of the phrenic and vagus nerves are similar: they both start in the neck, run downward in the mediastinum and pass through the diaphragm in your belly.
The phrenic nerve is one of the most important nerves in the body thanks to its role in respiration. It's a mixed nerve, consisting of motor, sensory, and sympathetic nerve fibers. The left phrenic nerve controls the left side of the diaphragm, and the right phrenic nerve controls the right side.
Picture source: Science Direct
The vagus nerve(s) are actually more than 80 000 nerve fibres that constitute the main nerves of our parasympathetic nervous system (rest and digest).
It controls our body functions such as digestion, heart rate and immune system.
Picture source Kai Health
Summary
You can't consciously control these two nerves, but you can affect them by breathing - inhaling and exhaling using the diaphragm. By doing so at different rates and volumes also helps lowering and increasing your Carbon Dioxide levels and , in the end, all kinds of stress.