Question

A mountain climber ascends to an altitude where the partial pressure of oxygen in the atmosphere is very low.

a. What happens to the climber’s ventilation rate?

b. Which chemoreceptor (oxygen or carbon dioxide/pH) would cause this change in ventilation rate at high altitude? Your answer should reflect that you know the stimuli for change in ventilation rate under different conditions

c. What happens to plasma concentrations of carbon dioxide after a period of time hyperventilation?

d. What happens to plasma pH after a period of time at high altitude? Your answer should reflect that you understand the relationship between CO2 levels and pH.

e. What happens to levels of erythropoietin in the blood after a period of time at high elevations? Your answer should include the stimulus for the release of EPO

f. How does a low concentration of oxygen in the alveoli affect the state of contraction of pulmonary arterioles?

g. Explain why pulmonary edema is a symptom of altitude sickness. Your answer should demonstrate your understanding of fluid exchanges at the capillary level

Answer 1

Answer

a. At higher altitudes, the ventilation rate of the climber’s increases leading to decrease in the partial pressure of oxygen. This is due to the decreased availability of atmospheric oxygen, as the body is unable to synthesize enough ATP in the cells.

b. The main stimulus of ventilation above the sea level is carbon dioxide. The chemoreceptors will detect the levels of the CO₂ in the blood by monitoring the H+ ions concentration in blood.

c. After a time period of hyperventilation, the concentration of carbon dioxide reduces since the body eliminates more carbon dioxide than it can produce.

d. After a period of time at higher altitude, the pH levels decrease leading to increased H⁺ ions concertation in the blood. This results in increased PCO2 levels.

e. After a period of time at higher altitude, due to decreased oxygen levels, hypoxia will occur. This will result in increased erythropoietin levels which eventually increase the synthesis of hemoglobin and RBC.

f. The low concentration of oxygen results in lung hypoxia. The lung hypoxia will cause the pulmonary arterioles to become vasoconstricted, which will result in an excessive increase in the pulmonary arterial pressure and failure of the right side of the heart.

g. Pulmonary edema occurs due to vasoconstriction of pulmonary arterioles and increased pulmonary arterial pressure. In this condition, the plasma and red blood cells accumulate in the lungs as a result of hypobaric hypoxia.