What chronic adaptation occurs in response to prolonged hypoxia?

• A. Decreased red blood cell production
• B. Increased production of myoglobin
• C. Increased production of erythropoietin (EPO)
• D. Decreased diameter of blood vessels

Answer: (C)

In response to prolonged hypoxia, the body undergoes several adaptive changes to improve oxygen delivery to tissues. One of the primary adaptations is the increased production of erythropoietin (EPO), a hormone produced primarily by the kidneys. EPO stimulates the bone marrow to increase the production of red blood cells (RBCs). The increase in RBC mass enhances the blood's oxygen-carrying capacity, thereby improving oxygen delivery to tissues that may be experiencing low oxygen levels due to chronic hypoxia.

This adaptation is crucial for individuals living at high altitudes or those suffering from chronic respiratory conditions that impair oxygen uptake. In these situations, the body's need for oxygen exceeds the amount that can be provided through normal physiological means, prompting the increase in EPO production.

The other options do not represent suitable adaptations to prolonged hypoxia. For instance, decreased red blood cell production would worsen oxygen transport rather than enhance it. Although increased myoglobin production is important for muscle oxygen storage, it is not as direct a response as the increase in EPO and red blood cell production. Additionally, decreased diameter of blood vessels would lead to increased blood pressure and increased resistance, ultimately making it even more difficult for tissues to receive adequate blood flow and oxygen, which does not