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

(d) Both (ii) and (iii)

Step-by-step solution

Understand the changes in the body at high altitude

The most relevant changes when moving to higher altitudes are related to how our body adapts to lower oxygen levels. To compensate for reduced oxygen, the body increases red blood cell production and the breathing rate rises in order to absorb more oxygen from the air.

Match the changes to the correct options

Looking at the options a to d, we analyze which ones are aligned with the major physiological alterations in our body when we experience high altitude conditions. The ones that match the explanation given in Step 1 are: (ii) Increase in red blood cell production and (iii) Increase in breathing rate.

Choose the correct option

The correct option is the one that includes both (ii) Increase in red blood cell production and (iii) Increase in breathing rate. Thus, the correct answer is (d) Both (ii) and (iii).

Key concepts

Red Blood Cell Production

When individuals move to higher altitudes, one crucial physiological adaptation is an increase in red blood cell production. This process is known as erythropoiesis. At high altitudes, oxygen levels in the air are significantly lower than at sea level. To compensate for this lack of oxygen, the body produces more red blood cells, which are responsible for transporting oxygen from the lungs to the rest of the body.
The hormone erythropoietin (EPO) plays a vital role in this process. It is primarily produced in the kidneys and stimulates the production of red blood cells in the bone marrow.

• Increased red blood cells allow for more efficient oxygen delivery to tissues.
• This adaptation is essential for maintaining oxygen supply to muscles and organs under low oxygen conditions.

Without this increase in red blood cell count, people living at high altitudes would experience symptoms of hypoxia much more frequently.

Breathing Rate

Another key adaptation when moving to high altitudes is an increase in the breathing rate. As oxygen levels decrease with altitude, it becomes necessary for the body to adjust its respiratory patterns to take in more oxygen.
The primary way to do this is by increasing the rate and depth of breathing, which helps enhance oxygen uptake in the lungs.

• This adaptation is critical for providing the body with the necessary oxygen to function effectively.
• Initially, faster breathing rates can lead to lower carbon dioxide levels in the blood, which the body gradually adjusts to over time.

By breathing more frequently and deeply, individuals are better able to cope with the reduced oxygen availability that high altitudes present.

Physiological Changes at High Altitudes

High altitudes impose a unique set of challenges on the human body, primarily due to lower oxygen availability. The body undergoes several physiological changes to adapt and ensure survival.
Besides increasing red blood cell production and breathing rate, other adjustments occur, such as a rise in heart rate and changes in energy metabolism.

• The body may also produce more hemoglobin, the protein in red blood cells that carries oxygen.
• Capillary density may increase to improve oxygen delivery to tissues.

These changes demonstrate the body's remarkable ability to adjust to challenging environments, enabling individuals to thrive at high altitudes.

Oxygen Levels

At high altitudes, the partial pressure of oxygen is lower than at sea level. This means that even though the percentage of oxygen in the air remains approximately 21%, there is less oxygen available for the body to use.
This reduced availability can lead to symptoms of acute mountain sickness if the body doesn't adjust efficiently.

• With adaptation, the body can increase its use of oxygen by enhancing lung capacity and altering blood components.
• Oxygen saturation levels may initially drop, but improve as physiological changes occur.

Ultimately, the successful adaptation to lower oxygen levels enables prolonged stay and activity at higher altitudes with minimal adverse effects.

Thrombocyte Count

Though less commonly discussed than red blood cells, thrombocytes (or platelets) play a significant role in the body's response to high altitudes. Thrombocytes help in blood clotting and wound healing.
While some studies suggest that moving to high altitudes could increase thrombocyte count, this adaptation is not as pronounced or immediate as others, like increased red blood cell production or breathing rate.

• Enhanced platelet production can be a response to promote hemostasis in the lower-oxygen environment.
• Variations in thrombocyte count may depend on the duration and extent of high-altitude exposure.

Even though it plays a lesser role than other physiological changes, thrombocyte count adjustments may contribute to overall adaptation.