Q: A patient is breathing air at sea level (760 mm Hg) with 21% oxygen. What is the partial pressure of oxygen ($$P_{O_2$}) in $$this air? Use the formula $$P_{gas} = \%gas \times P_{total}.$$

$$P_{O_2$} = 0.21 \times 760 = 160 mm Hg$$

Q: A sealed vessel contains a gas mixture of 50% oxygen, 10% carbon dioxide, and 40% nitrogen at a total pressure of 5 atmospheres. What is the partial pressure of carbon dioxide ($$P_{CO_2$}$$)?

$$P_{CO_2$} = 0.10 \times 5 = 0.5$$ atm

Q: Which equation correctly represents the reaction catalyzed by carbonic anhydrase in erythrocytes?

$$CO_2 + H_2O$$ \xrightleftharpoons[\text{carbonic anhydrase}]{} H_2CO_3$$

Question 1

Which of the following best describes the three layers of the respiratory membrane where gas exchange occurs in the lungs?

Accepted Answer

Type I alveolar cells, endothelial cells, and capillary basement membrane

Question 2

A patient is breathing air at sea level (760 mm Hg) with 21% oxygen. What is the partial pressure of oxygen ($$P_{O_2$}) in $$this air? Use the formula $$P_{gas} = \%gas 	imes P_{total}.$$

Accepted Answer

$$P_{O_2$} = 0.21 	imes 760 = 160 mm Hg$$

Question 3

Which of the following statements about the movement of gases during gas exchange is correct?

Accepted Answer

Oxygen moves from alveoli to blood at the same rate it is consumed by cells.

Question 4

A sealed vessel contains a gas mixture of 50% oxygen, 10% carbon dioxide, and 40% nitrogen at a total pressure of 5 atmospheres. What is the partial pressure of carbon dioxide ($$P_{CO_2$}$$)?

Accepted Answer

$$P_{CO_2$} = 0.10 	imes 5 = 0.5$$ atm

Question 5

Which equation correctly represents the reaction catalyzed by carbonic anhydrase in erythrocytes?

Accepted Answer

$$CO_2 + H_2O$$ \xrightleftharpoons[	ext{carbonic anhydrase}]{} H_2CO_3$$

Question 6

Which of the following best explains why oxygen is primarily transported in the blood bound to hemoglobin rather than dissolved in plasma?

Accepted Answer

Oxygen is not very soluble in plasma, so 98.5% is transported by hemoglobin.

Question 7

Which nerve is responsible for stimulating the diaphragm during inspiration?

Accepted Answer

Phrenic nerve

Question 8

Which of the following is the main function of peripheral chemoreceptors in the regulation of breathing?

Accepted Answer

They respond mainly to changes in blood pH.

Question 9

A person is exposed to high levels of carbon dioxide. Which of the following best describes the response of central chemoreceptors?

Accepted Answer

They respond indirectly to increased CO2 via decreased pH in the cerebrospinal fluid.

Question 10

Which of the following best describes the effect of acidosis on the central nervous system?

Accepted Answer

Acidosis (pH \u003c 7.35) causes CNS depression.

Question 11

Which of the following is the most important reason for the tight regulation of blood pH?

Accepted Answer

Small changes in pH can alter protein activity and disrupt physiological processes.

Question 12

Which of the following best describes the movement of gases according to their partial pressures?

Accepted Answer

Each gas diffuses down its own partial pressure gradient, independent of other gases.

Question 13

During quiet breathing, which muscles are primarily responsible for inspiration?

Accepted Answer

Diaphragm and external intercostal muscles

Question 14

Which of the following is the correct respiratory quotient (RQ) at rest, given that cells consume 250 mL O2 and produce 200 mL CO2?

Accepted Answer

$$RQ = \frac{200}{250} = 0.8$$

Question 15

Which of the following best describes how most carbon dioxide is transported in the blood?

Accepted Answer

As bicarbonate ions dissolved in plasma

Question 16

Which region of the brainstem is primarily responsible for integrating respiratory information and generating the breathing rhythm?

Accepted Answer

Medulla oblongata

Question 17

Which of the following is a direct effect of alkalosis (blood pH \u003e 7.45) on the central nervous system?

Accepted Answer

CNS over-excitation

Question 18

Which of the following is NOT a peripheral input to the respiratory centers?

Accepted Answer

Cerebellar neurons

Question 19

A patient has a blood pH of 7.30. Which condition does this indicate, and what is a likely physiological effect?

Accepted Answer

Acidosis; CNS depression

Question 20

Which of the following best describes the role of hemoglobin in carbon dioxide transport?

Accepted Answer

Hemoglobin binds CO2 to form carbaminohemoglobin, transporting 5–8% of CO2.

Gas Exchange and Regulation of Breathing: The Respiratory System

Study Guide - Practice Questions

Study Guide - Flashcards