Dismiss Notice

Interview Feedback: Visit Interview Feedback to view and submit interview information.

Interviewing Masterclass: Free masterclass on interviewing from SDN and Medical College of Georgia

pulmonary/systemic response to low O2

Discussion in 'MCAT Study Question Q&A' started by muhali3, Jul 24, 2011.

  1. muhali3

    7+ Year Member

    Joined:
    May 6, 2009
    Messages:
    1,787
    Likes Received:
    119
    Status:
    Medical Student
    Why does low O2 trigger vasoconstriction in pulmonary circulation but vasodilation in systemic circulation?
     
  2. CityLights

    7+ Year Member

    Joined:
    Jan 27, 2010
    Messages:
    1,609
    Likes Received:
    75
    My recollection about this from my physiology class is that pulmonary vasoconstriction in the presence of low O2 allows the blood flow to be redirected towards areas of the lungs where better gas exchange may be taking place, so it may lead to a larger total surface area of gas exchange.
     
  3. Charles_Carmichael

    Moderator Emeritus 7+ Year Member

    Joined:
    May 10, 2008
    Messages:
    4,078
    Likes Received:
    39
    Status:
    Non-Student
    CityLights is correct. Pulmonary vasoconstriction reduces blood flow to areas of the lung that aren't well-ventilated and shunts the blood towards areas that are adequately ventilated.

    The vasodilation in the systemic circulation would be an attempt to get more blood per unit time to tissues (there would also be an increased cardiac output & decreased MAP as a result of low arterial pO2, I'd imagine). The way I'm thinking of it, it would be sort of similar to the vasodilatory effect of exercise. Since the muscles require much more oxygen, there's vasodilation, increased CO, etc, to meet the oxygen demand of the muscles (and to carry away CO2 of course).

    At least, that's how I think of it (though I could be wrong in my reasoning). Hope this helps.
     

Share This Page