Final answer:
The Valsalva maneuver involves the sensitivity of the vagus nerve, which is responsible for autonomic functions, including cardiovascular regulation and the gag reflex.
Step-by-step explanation:
The Valsalva maneuver is a technique that affects intrathoracic pressure and influences the cardiovascular system. The sensitivity of the vagus nerve (cranial nerve X) is utilized during this maneuver, as it plays a role in autonomic functions of the thoracic and upper abdominal cavities, affecting heart rate and blood pressure. The vagus nerve is tested through its motor control functions during the gag reflex, highlighting its role in visceral regulation. Additionally, preganglionic parasympathetic fibers, which are found in the vagus nerve, contribute to the autonomic regulation of the body, participating in various reflexive actions and bodily controls.