Considering the role of the chemoreceptor in the regulation of the respiration rate, the most important stimulus that induces changes in ventilation is:
a. partial pressure of oxygen (PO2) in venous blood.
b. partial pressure of oxygen (PO2) in systemic capillaries.
c. partial pressure of carbon dioxide (PCO2) in arterial blood.
d. partial pressure of oxygen (PO2) in pulmonary capillaries.

The correct answer is c. partial pressure of carbon dioxide (PCO2) in arterial blood.

Explanation:

Ventilation is a term generally used to designate the movement of air in and out of the lungs, that is, alveolar ventilation is the volume of air that reaches the alveoli in one minute and participates in gas exchange. Carbon dioxide partial pressure (PCO2) consists of analyzing the amount of dissolved carbon dioxide in the blood, just like with pO2. Normal results range from 35mmHg to 45mmHg. If the level is low it may indicate respiratory alkalosis; if the level is high it may indicate respiratory acidosis. It can only be analyzed in arterial blood.