Q: A climber reaches the summit of Mount Everest, where the atmospheric pressure is 250 mm Hg. If the fractional concentration of oxygen in air remains 21%, what is the partial pressure of oxygen ($$P_{O_2$}) at $$the summit?

$$P_{O_2$} = 0.21 \times 250 = 52.5 mm Hg$$

Q: Which of the following equations correctly calculates the partial pressure of carbon dioxide ($$P_{CO_2$}) in $$dry air at sea level?

$$P_{CO_2$} = 0.0003 \times 760 = 0.23 mm Hg$$

Question 1

A climber reaches the summit of Mount Everest, where the atmospheric pressure is 250 mm Hg. If the fractional concentration of oxygen in air remains 21%, what is the partial pressure of oxygen ($$P_{O_2$}) at $$the summit?

Accepted Answer

$$P_{O_2$} = 0.21 	imes 250 = 52.5 mm Hg$$

Question 2

According to Dalton's Law, which equation correctly represents the total pressure of a gas mixture?

Accepted Answer

$$P_{total} = P_1$ + P_2$ + P_3$ + \ldots + P_n$$

Question 3

A patient with pulmonary edema has fluid accumulation in the alveoli. Which of the following best describes the effect on gas exchange?

Accepted Answer

Increased diffusion distance, leading to decreased $$P_{O_2$} in $$arterial blood

Question 4

Which of the following factors does NOT directly affect the solubility of a gas in a liquid in the human body?

Accepted Answer

Temperature (because it does not change much in humans)

Question 5

If alveolar ventilation decreases in a region of the lung, what is the local response in the pulmonary arterioles?

Accepted Answer

Vasoconstriction to divert blood to better-ventilated areas

Question 6

Which of the following equations correctly calculates the partial pressure of carbon dioxide ($$P_{CO_2$}) in $$dry air at sea level?

Accepted Answer

$$P_{CO_2$} = 0.0003 	imes 760 = 0.23 mm Hg$$

Question 7

A patient is experiencing hypoventilation due to CNS depression. Which of the following changes would you expect in their arterial blood gases?

Accepted Answer

Decreased $$P_{O_2$}$$ and increased $$P_{CO_2$}$$

Question 8

Which of the following best explains why oxygen diffuses from blood to cells in systemic circulation?

Accepted Answer

The partial pressure of oxygen in systemic arteries ($$P_{O_2$}) is $$higher than in cells

Question 9

Which of the following shifts the hemoglobin-oxygen dissociation curve to the right, promoting oxygen unloading in tissues?

Accepted Answer

Increased temperature, decreased pH, and increased $$P_{CO_2$}$$

Question 10

A scuba diver ascends rapidly from deep water. Which physiological principle explains the formation of nitrogen bubbles in the blood?

Accepted Answer

Decreased pressure reduces gas solubility, causing dissolved nitrogen to come out of solution

Question 11

Which of the following is the main form in which carbon dioxide is transported in the blood?

Accepted Answer

As bicarbonate ion ($$HCO_3$$^-$$) in plasma

Question 12

What is the role of carbonic anhydrase in red blood cells?

Accepted Answer

It catalyzes the conversion of $$CO_2$$ and $$H_2O to$$ $$H^+$$ and $$HCO_3$$^-$$

Question 13

Which of the following would increase the affinity of hemoglobin for oxygen?

Accepted Answer

Decreased temperature and increased pH

Question 14

A patient is exposed to carbon monoxide (CO). What is the effect on oxygen transport?

Accepted Answer

CO binds to hemoglobin with higher affinity than $$O_2$$, preventing oxygen binding

Question 15

Which of the following best describes the Bohr effect?

Accepted Answer

A decrease in pH (increase in $$H^+) $$reduces hemoglobin's affinity for oxygen, promoting oxygen unloading

Question 16

Which of the following is true regarding the matching of ventilation and perfusion in the lungs?

Accepted Answer

Blood is diverted away from under-ventilated regions to better-ventilated regions

Question 17

If the partial pressure of oxygen in arterial blood is 100 mm Hg and hemoglobin is 98.5% saturated, what is the partial pressure of oxygen in mixed venous blood where hemoglobin is 75% saturated?

Accepted Answer

$$P_{O_2$} = 40 mm Hg$$

Question 18

Which of the following is a direct result of increased metabolic activity in tissues?

Accepted Answer

Increased $$CO_2$$ production, leading to increased oxygen unloading from hemoglobin

Question 19

Which of the following equations represents the conversion of carbon dioxide and water to bicarbonate and hydrogen ions in red blood cells?

Accepted Answer

$$CO_2 + H_2O$$ \rightleftharpoons H^+ + $$HCO_3$$^-$$

Chapter 18: Gas Exchange and Transport: Human Physiology

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