Question

Fill in the blanks with increase, decrease, no change.

Continued breathing through the re-breathing bag leads to a(n) __________ in alveolar [PCO2] which then leads to a(n) ________ in blood arterial [PCO2] and a(n) __________ in brain ECF [PCO2]. The change in blood arterial [PCO2] leads to a(n) __________ in arterial H+ concentration. The change in brain ECF [PCO2] leads to a(n) __________ in brain ECF [H+]. This change in arterial [H+] and brain ECF [H+] leads to a(n) __________ firing rate of the peripheral and central chemoreceptors. This leads to a(n) __________ in the contractions of the respiratory muscles which causes a(n) __________ in the rate and depth of ventilation The re-breathing apparatus is disconnected and the subject breathes normally for 2 min. This leads to a leads to a(n) __________ in blood arterial [PCO2]. This will cause a(n) __________ in the firing rate of the peripheral and central chemoreceptors. This leads to a(n) __________ in the contractions of the respiratory muscles which causes a(n) __________ in the rate and depth of ventilation.

The re-breathing apparatus is disconnected and the subject breathes normally for 2 min. This leads to a ______ in blood arterial [PCO2]. This will cause a ______ in the firing rate of the peripheral and central chemoreceptors. This leads to a ______ in the contractions of the respiratory muscles which causes a ______ n the rate and depth of ventilation.

Answer 1

Continued breathing through the re-breathing bag leads to an increase in alveolar [PCO2] which then leads to an increase in blood arterial [PCO2] and an increase in brain ECF [PCO2]. The change in blood arterial [PCO2] leads to an increase in arterial H+ concentration. The change in brain ECF [PCO2] leads to an increase in brain ECF [H+]. This change in arterial [H+] and brain ECF [H+] leads to an increased firing rate of the peripheral and central chemoreceptors. This leads to an increase in the contractions of the respiratory muscles which causes an increase in the rate and depth of ventilation.

The re-breathing apparatus is disconnected and the subject breathes normally for 2 min. This leads to a leads to a decrease in blood arterial [PCO2]. This will cause a decrease in the firing rate of the peripheral and central chemoreceptors. This leads to a decrease in the contractions of the respiratory muscles which causes a decrease in the rate and depth of ventilation.

(Rebreathing bags retain 1/3rd of the exhaled air by the patient, which has a higher concentration of CO2. This extra CO2 present in the bag will be inhaled by the patient and will increase alveolar CO2 concentration. This leads to an increase in arterial and ECF CO2 concentrations. The following changes occur as described. When the bag is disconnected, the patient breathes normal air, which has a much less concentration of CO2. Thus the previous changes come back to normal, and ventilation rate reduces.)