Question 1

Alveolar partial pressures do not fluctuate to any extent between inspiration and expiration.

Accepted Answer

This is because the alveoli are constantly exchanging gases with the capillaries and maintaining a relatively constant partial pressure of oxygen and carbon dioxide.

Question 2

The partial pressure of nitrogen in the atmosphere is greater than the partial pressure of oxygen in the atmosphere.

Accepted Answer

This is because nitrogen makes up a greater percentage of the atmosphere (about 78%) compared to oxygen (about 21%). Therefore, nitrogen exerts a greater partial pressure.

Question 3

O₂ is much more soluble in blood than CO₂ is.

Accepted Answer

The answer of O₂ is much more soluble in blood...

Question 4

The tidal volume is the sum of the vital capacity,expiratory reserve volume,and inspiratory reserve volume.

Accepted Answer

Tidal volume is a separate measure of the amount of air breathed in and out during normal breathing, and is not the sum of other lung volumes.

Question 5

Alveolar PO₂ is higher following inspiration than following expiration.

Accepted Answer

The answer of Alveolar PO₂ is higher following inspiration than...

Question 6

In the plateau region of the Hb-O₂ curve,a large decrease in PO₂ results in a small decrease in Hb saturation,whereas in the steep portion of the curve,a small decrease in PO₂ results in a large decrease in percent Hb saturation.

Accepted Answer

This statement is correct. The plateau region of the Hb-O₂ curve represents the saturation of Hb at high PO₂ levels, where additional increases in PO₂ have little effect on Hb saturation. In this region, there is a large reserve of oxygen bound to Hb that can be released to tissues with even small decreases in PO₂. In contrast, the steep portion of the curve represents the saturation of Hb at lower PO₂ levels, where even small decreases in PO₂ can cause large reductions in Hb saturation, leading to decreased oxygen delivery to tissues.

Question 7

At the systemic capillaries,the PO₂ is in the range of the steep portion of the O₂-Hb curve.

Accepted Answer

At systemic capillaries, the partial pressure of oxygen (PO₂) is in the range of the steep portion of the oxygen-hemoglobin (O₂-Hb) dissociation curve. This means that a small decrease in PO₂ results in a significant release of oxygen from hemoglobin, allowing for efficient oxygen delivery to the tissues.

Question 8

During hyperventilation,arterial PCO₂ levels decrease because CO₂ is blown off more rapidly than it is being produced in the tissues.

Accepted Answer

During hyperventilation, the rate of breathing increases, leading to an increased rate of removal of CO₂ from the body. This results in a decrease in arterial PCO₂ levels.

Question 9

A molecule of nitrogen exerts more pressure than a molecule of oxygen because nitrogen is a larger molecule.

Accepted Answer

The size of the molecule does not determine the pressure it exerts. Pressure is determined by the number of molecules and their kinetic energy. Both nitrogen and oxygen have the same number of molecules in a given volume and at a given temperature, so they exert the same pressure.

Question 10

O₂ moves from the alveoli to the blood by active transport.

Accepted Answer

O₂ moves by diffusion from areas of high concentration to areas of low concentration. Therefore, it does not require active transport.

Question 11

The combination of Hb and CO₂ is known as carbaminohaemoglobin.

Accepted Answer

This is true. When carbon dioxide (CO₂) binds to haemoglobin (Hb) in the blood, the compound formed is called carbaminohaemoglobin.

Question 12

Systemic arterial PO₂ is greater than tissue PO₂.

Accepted Answer

Systemic arterial PO₂ is the oxygen concentration in the blood leaving the heart and circulating through the arteries, which is typically higher than the oxygen concentration in the tissues. This allows for oxygen to diffuse from the blood into the tissues and supply cellular respiration.

Question 13

During external respiration,the PCO₂ is greater in the blood of the pulmonary capillaries than in the alveoli.

Accepted Answer

During external respiration, carbon dioxide diffuses from the blood in the pulmonary capillaries, where its partial pressure (PCO₂) is higher, into the alveoli, where its partial pressure is lower, facilitating its exhalation from the body.

Question 14

Systemic arterial PCO₂ is less than tissue PCO₂.

Accepted Answer

Systemic arterial PCO₂ is typically around 40 mmHg, while tissue PCO₂ is typically around 46-48 mmHg. This is due to the fact that some CO₂ is produced as a byproduct of cellular metabolism and diffuses out of cells into the interstitial fluid, increasing the local partial pressure of CO₂ in tissues. This drives CO₂ diffusion from tissues into the bloodstream, resulting in a lower arterial PCO₂.

Question 15

The most important factor that determines the extent to which haemoglobin is saturated with oxygen is the blood PO₂.

Accepted Answer

The partial pressure of oxygen (PO₂) in the blood is the most important factor that determines the extent to which haemoglobin is saturated with oxygen.

Question 16

During external respiration,the PO₂ is greater in the alveoli than in the blood of the pulmonary capillaries.

Accepted Answer

During external respiration, oxygen diffuses from the higher PO₂ in the alveoli into the lower PO₂ in the pulmonary capillaries to be carried to the rest of the body.

Question 17

Increased acidity at the tissue cells stimulates increased dissociation of oxyhaemoglobin.

Accepted Answer

Increased acidity, or decreased pH, can cause the Bohr effect which stimulates the release of oxygen from oxyhaemoglobin at the tissue cells. This is often seen in tissues with high metabolic rates, where increased carbon dioxide production leads to increased acidity.

Question 18

The quantity of O₂ that will diffuse between the alveolar air and pulmonary blood depends solely on the partial pressure gradients that exist between the alveoli and blood.

Accepted Answer

The answer of The quantity of O₂ that will diffuse...

Question 19

Carbonic anhydrase catalyzes the formation of the oxyhaemoglobin.

Accepted Answer

Carbonic anhydrase catalyzes the reversible conversion of carbon dioxide and water to carbonic acid, which dissociates to form bicarbonate and hydrogen ions. It does not catalyze the formation of oxyhaemoglobin.

Question 20

The partial pressure of a gas in blood depends on the amount that is physically dissolved and not on the total content of the gas present in the blood.

Accepted Answer

The partial pressure of a gas in blood is determined by the amount that is physically dissolved in the blood, which depends on factors such as the solubility of the gas in the blood, the partial pressure of the gas in the surrounding environment, and the temperature. The total content of the gas present in the blood, including that which is dissolved and that which is bound to hemoglobin, can also affect the overall oxygen-carrying capacity of the blood, but it does not directly determine the partial pressure of the gas.

Quiz 11: The Respiratory System