4.6 Physiology of the Pulmonary Circulation

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xangxelax
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259040
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4.6 Physiology of the Pulmonary Circulation
Updated:
2014-01-29 18:12:54
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  1. Compare and contrast the systolic and diastolic pressures in the pulmonary and systemic circulations.
    • Systemic: systolic - 120; diastolic - 80
    • Pulmonary: systolic - 25; diastolic - 8
  2. Describe the change in pulmonary vascular resistance with the change in pulmonary arterial pressure.
    • ↑ pulmonary arterial pressure leads to:
    • 1. Pulmonary vascular resistance ↓
    • 2. Pulmonary blood flow ↑
  3. Describe how the pulmonary vasculature uses distension and recruitment to reduce vascular resistance when pressure rises.
    W/ ↑ pulmonary arterial pressure, vessels are distended and more vessels are opened up (recruitment)
  4. Describe the change in pulmonary vascular resistance with changes in lung volume.
    • ↓ Lung Volumes = ↑ resistance b/c extra alveolar vessels are narrowed
    • ↑ Lung Volumes = ↓ resistance b/c capillaries are stretched
  5. Contrast the contributions of the capillaries and the extra-alveolar vessels to pulmonary vascular resistance at different lung volumes.
    • ↓ Lung Volumes = ↑ resistance b/c extra alveolar vessels are narrowed
    • ↑ Lung Volumes = ↑ resistance b/c capillaries are stretched
  6. Describe hypoxic vasoconstriction.
    • Pulmonary vessels constrict when there is low O2 levels in the alveoli
    • Constriction triggered by lower levels of PAO2 not PaO2
    • ↓ O2 → depolarization of vascular smooth muscle, and then Ca2+ entry through voltage-gated Ca2+ channels (additional Ca2+ leads to additional constriction)
    • Inhibition of NO synthase is another mech. leading to reduced vasodilation and more vasoconstriction
  7. Describe the effect of the pulmonary circulation on angiotensin I, angiotensin II, bradykinin, histamine, dopamine, and serotonin.
    • Angiotensin I - Converted to angiotensin II by ACE
    • Angiotensin II - Unaffected
    • Bradykinin - inactivated
    • Histamine - Not affected
    • Dopamine - Not affected
    • Serotonin - removed and stored
  8. Describe how pulmonary edema can develop by loss of fluid from the pulmonary capillaries.
    • Lymphatics in the interstitium remove the fluid but this system can get overwhelmed, at which point the fluid can go into the alveolar space
    • Na/K ATPase works to draw fluid out of the alveolar spaces
  9. Which zone will blood flow best?
    Zone 3 at the bottom of the lung
  10. What are the 2 ways to reduce pulmonary vascular resistance?
    • Distension - make vessels bigger
    • Recruitment - open up more vessels

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