Question

Which two of the following changes (a to d) usually tend to occur in plain dwellers when they move to higher altitudes ( \(3500 \mathrm{~m}\) or more) (i) Increase in red blood cell size (ii) Increase in red blood cell production (iii) Increase in breathing rate (iv) Increase in thrombocyte count (a) Both (iii) and (iv) (b) Both (i) and (iv) (c) Both (iii) and (i) (d) Both (ii) and (iii)

Short answer

The correct answer is (d) Both (ii) Increase in red blood cell production and (iii) Increase in breathing rate.

Step-by-step solution

Review Concepts

In high-altitude environments, the amount of oxygen available to the human body is reduced. In response to this, the body undergoes several physiologic adaptations.

Analyzing each option

(i) Increase in red blood cell size: This does not usually occur upon high altitude exposure. It's the number not the size of the red blood cells that adjusts to promote oxygen transport. \n(ii) Increase in red blood cell production: This indeed occurs in response to high altitude. With less oxygen available, the body produces more red blood cells to facilitate oxygen transport. \n(iii) Increase in breathing rate: Breathing rate does indeed increase at high altitudes as a short-term response to get more oxygen. \n(iv) Increase in thrombocyte count: Changes in thrombocyte or platelet count are not a typical response to high-altitude exposure.

Choosing the right answer

Based on the above analysis, both (ii) and (iii) are usually expected changes at high altitude. Hence, option (d) which includes both (ii) and (iii) is the correct answer.