[2] These afferents synapse with the visceral motor nucleus of the vagus nerve, located in the reticular formation of the brain stem.
The efferent portion is carried by the vagus nerve from the cardiovascular center of the medulla to the heart, of which increased stimulation leads to decreased output of the sinoatrial node.
This reflex has been seen to occur during many pan facial trauma surgeries due to stimulation of any of the three branches of trigeminal nerve.
[5] The reflex can be blocked by intravenous injection of an anti-muscarinic acetylcholine (ACh) antagonist, such as atropine or glycopyrrolate.
A commonly-used technique in the field of brainspotting called "vergence" deliberately triggers this reflex in order to calm patients.