NCLEX : Gas Exchange

Study concepts, example questions & explanations for NCLEX

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Example Questions

Example Question #1 : Gas Exchange

Which of the following structures is the site of gas exchange in the lung?

Possible Answers:

The bronchiole

The pleura

The bronchus

The alveolus

Correct answer:

The alveolus

Explanation:

Gas exchange in the lung occurs exclusively in the alveoli, the tiny grape-like clusters of sacks at the terminus of the bronchioles of the lung. The gas contained in the larger structures of the lung - the trachea, bronchi, and bronchioles, is termed "dead space" as it does not participate in gas exchange.

Example Question #2 : Gas Exchange

Which of the following is the main trigger for the impulse to breathe?

Possible Answers:

High blood carbon dioxide

Low blood oxygen

Dilation of the bronchioles

Constriction of the bronchioles

Correct answer:

High blood carbon dioxide

Explanation:

The main trigger for the impulse to breathe is high carbon dioxide (decreased blood pH). In response to a decrease in blood pH, the medullary respiratory center triggers the diaphragm and the external intercostal muscles to increase breathing rate.

Example Question #3 : Gas Exchange

Myoglobin can bind with __________ molecule(s) of oxygen, while hemoglobin can bind with __________ molecule(s) of oxygen.

Possible Answers:

two . . . four

three . . . four

one . . . two

one . . . four

Correct answer:

one . . . four

Explanation:

Myoglobin, an oxygen-binding protein in the muscle tissue, can bind with one molecule of oxygen. Hemoglobin, the main oxygen-binding metalloprotein in red blood cells, can bind four molecules of oxygen. 

Example Question #4 : Gas Exchange

Hyperventilation results in which of the following?

Possible Answers:

Respiratory alkalosis

Ketoacidosis

Metabolic acidosis

Respiratory acidosis

Correct answer:

Respiratory alkalosis

Explanation:

While hyperventilation or tachypnea may be triggered by various forms of acidosis, they will not cause a decrease in blood pH, but rather push the blood into a more alkaline state. This occurs due to loss of carbon dioxide during respiration, followed by a compensatory decrease in bicarbonate ions. The result is in an elevation in the pH of the blood. This condition is known as respiratory alkalosis.

Example Question #5 : Gas Exchange

What does the term "partial pressure" describe?

Possible Answers:

The pressure of a gas at  above sea level

The difference between the gas pressure at a particular altitude and sea level

The pressure of an overall gas mixture during transition (adding a new gas)

The pressure contributed by a single gas in a gas mixture

Correct answer:

The pressure contributed by a single gas in a gas mixture

Explanation:

Many gases, such as room air, are composed of several gasses (in the case of room air, primarily nitrogen, oxygen, and several trace gasses). Partial pressure is the amount of pressure that each gas contributes. To find the total pressure of a gas mixture, one would find the sum of all partial pressures of each individual gas. 

Example Question #6 : Gas Exchange

How do oxygen and carbon dioxide cross the capillary epithelium and alveolar cell membranes during gas exchange?

Possible Answers:

Simple diffusion

Osmotic exchange

 pump

 transporter

Correct answer:

Simple diffusion

Explanation:

Gas exchange in the alveoli occurs by the process of simple diffusion. The blood that enters the lung capillaries is relatively low in oxygen and high in , in comparison to the room air that is drawn into the alveoli during respiration. The separation between the capillaries and the alveolar epithelium is thin enough that these gasses can exchange across their pressure gradients by the process of simple diffusion.

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