Final answer:
Quiet breathing is managed by the respiratory centers in the brainstem, which regulate the contraction of the diaphragm and external intercostal muscles. These centers monitor blood pH and CO2 levels to adjust breathing rate. Nasal breathing is preferred for its air conditioning benefits.
Step-by-step explanation:
The physiologic events associated with controlling quiet breathing involve a series of processes that occur primarily without conscious control. Quiet breathing, or eupnea, is the type of breathing that happens at rest and involves the contraction of the diaphragm and the external intercostal muscles to facilitate air movement into and out of the lungs.
Unconscious breathing is controlled by the respiratory centers in the medulla and pons of the brainstem, which monitor blood pH and carbon dioxide levels. These centers adjust the breathing rate as needed to maintain blood gas and pH within a narrow optimum range. The pneumotaxic center in the pons can also modulate the rate of breathing.
Nasal breathing is often considered superior to mouth breathing because it filters, warms, and moistens incoming air more effectively. During quiet breathing, the diaphragm contracts, moving downward to create a vacuum that draws air into the lungs (inhalation), and relaxes during exhalation, allowing air to be expelled from the lungs.