Question 1

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

Accepted Answer

Hyperventilation results in a rapid elimination of CO₂ from the lungs, leading to a decrease in arterial PCO₂ levels. This occurs because CO₂ is being eliminated from the body more rapidly than it is being produced in the tissues.

Question 2

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

Accepted Answer

The partial pressure of nitrogen in the atmosphere is approximately 78% while the partial pressure of oxygen is approximately 21%. Therefore, the partial pressure of nitrogen is greater.

Question 3

Alveolar PO₂ is higher following inspiration than following expiration.

Accepted Answer

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

Question 4

Systemic arterial PO₂ is greater than tissue PO₂.

Accepted Answer

Systemic arterial blood carries oxygen from the lungs to the tissues of the body. When it reaches the tissues, the oxygen diffuses out of the blood and into the cells where it is used for cellular respiration. Because of this process, the systemic arterial PO₂ (partial pressure of oxygen in arterial blood) is initially greater than the tissue PO₂ (partial pressure of oxygen in the tissues). As the oxygen diffuses into the tissues, the tissue PO₂ increases and the arterial PO₂ decreases.

Question 5

The peripheral chemoreceptors are not activated during carbon monoxide poisoning despite the fact that the total O₂ content in the blood can become lethally low.

Accepted Answer

Peripheral chemoreceptors, which are primarily sensitive to the partial pressure of oxygen (PaO2) in arterial blood rather than the total oxygen content, are not activated during carbon monoxide poisoning because carbon monoxide does not significantly affect PaO2. Instead, carbon monoxide binds to hemoglobin with much greater affinity than oxygen, reducing the blood's capacity to transport oxygen without altering the PaO2 that the chemoreceptors detect.

Question 6

The respiratory centre is located in the cerebral cortex.

Accepted Answer

The respiratory centre is actually located in the medulla oblongata, which is part of the brainstem.

Question 7

Systemic arterial PCO₂ is less than tissue PCO₂.

Accepted Answer

Systemic arterial PCO₂ is lower than tissue PCO₂ because tissues produce CO₂ as a byproduct of metabolism, increasing its concentration in tissue compared to arterial blood.

Question 8

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

Accepted Answer

At the systemic capillaries, where oxygen is being offloaded to the tissues, the PO₂ is generally in the range of the steep portion of the O₂-Hb curve, meaning that even small decreases in PO₂ will result in large decreases in the amount of oxygen bound to hemoglobin. This allows for efficient oxygen delivery to the tissues.

Question 9

The combination of Hb and CO₂ is known as carbamino haemoglobin.

Accepted Answer

This is true. When carbon dioxide binds to the amino groups on the globin portion of hemoglobin, it forms carbamino hemoglobin.

Question 10

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

Accepted Answer

When the tissue cells become more acidic, there is an increased dissociation of oxyhemoglobin. This is known as the Bohr effect, which is an important physiological mechanism that helps to deliver oxygen to the tissues where it is needed. As the acidity increases, the affinity between the haemoglobin molecule and the oxygen molecule decreases, allowing the oxygen to be released more easily. This process ensures that the tissues receive the oxygen they need, even when they are under stress or working hard.

Question 11

Administering O₂ to patients with severe chronic lung disease will not depress their drive to breathe.

Accepted Answer

Administering O₂ to patients with severe chronic lung disease can actually suppress their drive to breathe. These patients rely on low levels of oxygen in their blood to stimulate their breathing, so supplemental oxygen may reduce this hypoxic drive and lead to respiratory depression. Close monitoring and adjustments to oxygen therapy are necessary to prevent this from occurring.

Question 12

Arterial PO₂ remains normal or may even increase slightly during exercise, despite the fact that O₂ consumption by the tissues is greatly increased.

Accepted Answer

During exercise, the increase in cardiac output and blood flow results in the maintenance or slight increase in arterial PO₂, allowing for adequate oxygen delivery to the tissues despite increased oxygen consumption. This is achieved through various mechanisms such as increased ventilation, capillary recruitment, and oxygen diffusion.

Question 13

Carbonic anhydrase catalyzes the formation of the oxyhaemoglobin.

Accepted Answer

Carbonic anhydrase catalyzes the reaction between carbon dioxide and water to form carbonic acid, which can then dissociate into bicarbonate ions and hydrogen ions. It does not catalyze the formation of oxyhaemoglobin.

Question 14

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

Accepted Answer

Tidal volume is the volume of air that is inhaled or exhaled during normal breathing without conscious effort. It is not the sum of vital capacity, expiratory reserve volume, and inspiratory reserve volume, which are all separate pulmonary volumes.

Question 15

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 the blood.

Accepted Answer

Other factors such as the surface area of the alveoli, the thickness of the alveolar-capillary membrane, and the solubility of oxygen in blood also play significant roles in the diffusion process.

Question 16

O₂ is much more soluble in blood than CO₂ is.

Accepted Answer

CO₂ is about 20 times more soluble in blood than O₂, which is why CO₂ is more efficiently transported from the tissues to the lungs for exhalation.

Question 17

In the plateau region of the O₂-Hb 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 true. The plateau region of the O₂-Hb curve represents the saturation of Hb with O₂ at high PO₂ levels. Since Hb is already almost fully saturated at these high PO₂ levels, a large decrease in PO₂ will only cause a small decrease in percent Hb saturation. In contrast, the steep portion of the curve represents the saturation of Hb with O₂ at low PO₂ levels, where small changes in PO₂ can significantly affect the percent Hb saturation.

Question 18

Respiration is reflexively inhibited by alkalosis caused by a reduction in concentration of non-carbon dioxide-generated H⁺, the result of which is accumulation of H⁺-generating carbon dioxide to restore the acid-base balance toward normal.

Accepted Answer

The statement is true. When the blood becomes alkaline (alkalosis), respiration is inhibited reflexively. This is because alkalosis reduces the concentration of non-carbon dioxide-generated hydrogen ions (H⁺) in the blood, which is compensated by the accumulation of H⁺-generating carbon dioxide. This restores the normal acid-base balance in the blood. The respiratory center in the brainstem senses these changes in the blood pH and adjusts the breathing rate and depth accordingly to regulate the carbon dioxide concentration and maintain acid-base balance.

Question 19

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

Accepted Answer

The oxygen saturation of haemoglobin is primarily determined by the partial pressure of oxygen in the blood (blood PO₂). This relationship is described by the oxygen-haemoglobin dissociation curve, which shows how haemoglobin binds and releases oxygen in response to changes in PO₂. Other factors, such as blood pH and temperature, can also affect the affinity of haemoglobin for oxygen, but these are secondary to the influence of PO₂.

Question 20

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

Accepted Answer

The size of the molecule does not determine the pressure it exerts. The pressure exerted by a gas is determined by its number of molecules and their average kinetic energy. Nitrogen and oxygen gas have similar molecular weights and sizes, so their pressures are typically similar under the same conditions.

Quiz 12: The Respiratory System