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    Few questions;
    1. Why does hypocapnia lead to cerebral vasoconstriction?
    2. How can a pulmonary embolism lead to hypotension?
    3. Why is alveolar ventilation high in emphysema and low in chronic bronchitis?

    Thank you!
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    1) The brain is highly adapted to ensure constant oxygen supply. Part of that is dilating to high CO2, and the inverse with low CO2. In terms of exact molecular mechanism of this - i don't know. Google.
    2) A small PE wouldn't. A large PE can block the pulmonary vessels.
    3) Do you know what these conditions are? What do you think?
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    (Original post by nexttime)
    1) The brain is highly adapted to ensure constant oxygen supply. Part of that is dilating to high CO2, and the inverse with low CO2. In terms of exact molecular mechanism of this - i don't know. Google.
    2) A small PE wouldn't. A large PE can block the pulmonary vessels.
    3) Do you know what these conditions are? What do you think?
    1 and 2 - thank you
    3. Yes, I understand that emphysema is a loss in the elasticity of the alveolar walls and as a result you get air trapping since the elastic recoil that helps in expelling air from the lungs during exhalation is reduced whereas chronic bronchitis is inflammation where you get hyperplasia and hypertrophy of mucin glands in the airways - I understand that you get mucus plugs in chronic bronchitis and how that would reduce alveolar ventilation. What I don't understand is in emphysema, surely those pockets of trapped air aren't being ventilated so wouldn't ventilation fall? (At least that's my understanding which may well be incorrect)

    Thanks!
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    (Original post by RR97)
    1 and 2 - thank you
    3. Yes, I understand that emphysema is a loss in the elasticity of the alveolar walls and as a result you get air trapping since the elastic recoil that helps in expelling air from the lungs during exhalation is reduced
    !
    Well yes, but you've missed the other huge component that defines emphysema: loss of alveolar surface area and formation of bullae. Some of these can be massive - easily visible on a chest x-ray. Help?
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    (Original post by nexttime)
    Well yes, but you've missed the other huge component that defines emphysema: loss of alveolar surface area and formation of bullae. Some of these can be massive - easily visible on a chest x-ray. Help?
    Mmm still not sure why you'd get increased alveolar ventilation?
 
 
 
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