NCLEX : Gas Exchange
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Example Questions
Example Question #21 : Respiratory System
Which of the following structures is the site of gas exchange in the lung?
The alveolus
The bronchus
The bronchiole
The pleura
The alveolus
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 #1 : Gas Exchange
Which of the following is the main trigger for the impulse to breathe?
Low blood oxygen
Constriction of the bronchioles
High blood carbon dioxide
Dilation of the bronchioles
High blood carbon dioxide
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 #2 : Gas Exchange
Myoglobin can bind with __________ molecule(s) of oxygen, while hemoglobin can bind with __________ molecule(s) of oxygen.
one . . . two
one . . . four
three . . . four
two . . . four
one . . . four
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 #3 : Gas Exchange
Hyperventilation results in which of the following?
Respiratory acidosis
Respiratory alkalosis
Ketoacidosis
Metabolic acidosis
Respiratory alkalosis
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 #2 : Gas Exchange
What does the term "partial pressure" describe?
The pressure of an overall gas mixture during transition (adding a new gas)
The pressure of a gas at 
The difference between the gas pressure at a particular altitude and sea level
The pressure contributed by a single gas in a gas mixture
The pressure contributed by a single gas in a gas mixture
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 #2 : Gas Exchange
How do oxygen and carbon dioxide cross the capillary epithelium and alveolar cell membranes during gas exchange?
Simple diffusion
Osmotic exchange
Simple diffusion
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 
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