coping with low O2 at higher altitudes

[hacheemaster]

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Another EK question:

At high altitude, water vapor pressure in the lungs remains the same and carbon dioxide pressure falls slightly. Oxygen pressure falls. The body of a person remaining at high altitudes for days, weeks, and even years will acclimatize. All of the following changes assist the body in coping with low oxygen EXCEPT:
A. increased red blood cells
B. decreased vascularity of the tissues
C. increased pulmonary ventilation
D. increased diffusing capacity of the lungs.

I remember from biochemistry that the red blood cells don't increase in number when the body is at a higher altitude, they simply get more efficient at carrying oxygen. Therefore, I thought A was the right answer. The correct answer is B. I did not choose B because I thought it was too vague. What tissues decrease in vascularity? All of them? 50%?

Did my mind simply make up the fact that RBCs increase efficiency not number? I guess when I chose A I reasoned that decreased vascularity of the tissues would mean less demand for oxygen.Therefore, that would be an appropriate mechanism to cope with low oxygen.

 

[Charles_Carmichael]

Another EK question:

At high altitude, water vapor pressure in the lungs remains the same and carbon dioxide pressure falls slightly. Oxygen pressure falls. The body of a person remaining at high altitudes for days, weeks, and even years will acclimatize. All of the following changes assist the body in coping with low oxygen EXCEPT:
A. increased red blood cells
B. decreased vascularity of the tissues
C. increased pulmonary ventilation
D. increased diffusing capacity of the lungs.

I remember from biochemistry that the red blood cells don't increase in number when the body is at a higher altitude, they simply get more efficient at carrying oxygen. Therefore, I thought A was the right answer. The correct answer is B. I did not choose B because I thought it was too vague. What tissues decrease in vascularity? All of them? 50%?

Did my mind simply make up the fact that RBCs increase efficiency not number? I guess when I chose A I reasoned that decreased vascularity of the tissues would mean less demand for oxygen.Therefore, that would be an appropriate mechanism to cope with low oxygen.

When you're in a low O2 situation, your kidneys release erythropoietin. Erythropoietin stimulates RBC synthesis, so you make more RBCs. This increases the blood's capacity to carry oxygen. What you remembered from biochem about increased efficiency is for the short-term...you increase the number of RBCs if you stay at a higher altitude for a longer time (ie. more than a few weeks). Erythropoietin is a hormone and it takes longer for its actions to result in increased RBC numbers.

About the decreased vascularity, think about it like this: if you're already getting low O2 levels (compared to normal) for a muscle, do you want to take away blood vessels that supply it? No, because then, the muscle would get even less O2 when it actually needs more O2. No matter what, taking away blood vessels would decrease the amount of O2 delivered to that particular tissue and this is not what you want when you're at a higher altitude. Hope this helps.

 

[G1SG2]

When you're in a low O2 situation, your kidneys release erythropoietin. Erythropoietin stimulates RBC synthesis, so you make more RBCs. This increases the blood's capacity to carry oxygen. What you remembered from biochem about increased efficiency is for the short-term...you increase the number of RBCs if you stay at a higher altitude for a longer time (ie. more than a few weeks). Erythropoietin is a hormone and it takes longer for its actions to result in increased RBC numbers.

About the decreased vascularity, think about it like this: if you're already getting low O2 levels (compared to normal) for a muscle, do you want to take away blood vessels that supply it? No, because then, the muscle would get even less O2 when it actually needs more O2.

Kaushik, you should write an MCAT Bio review manual! I'd soo buy it (only if you gave me half off, though)

 

[hacheemaster]

thanks!

 

[Charles_Carmichael]

Kaushik, you should write an MCAT Bio review manual! I'd soo buy it (only if you gave me half off, though)

Haha thanks for the compliment! I think I'll put this comment down in my signature; this way you can never change your mind! 😀

If I do make a review (which is never), you'll be the first to know heh.

 

[G1SG2]

Haha thanks for the compliment! I think I'll put this comment down in my signature; this way you can never change your mind! 😀

If I do make a review (which is never), you'll be the first to know heh.

Aww, yay! I feel honored 🙂