pulmonary circulation

Question 1

is pulmonary circulation high or low resistance

Answer 1

low

Question 2

why does increasing cardiac output not increase MAP and cause pulmonary oedema

Answer 2

arteries distend due to greater compliance, and perfusion to hypoperfused beds towards apex increases

Question 3

what is the effect of increasing ventilation

Answer 3

inspiration compresses alveolar vessels as no cartilage, and during expiration the thorax decreases in volume to pinch the outside of extra-alveolar vessels

Question 4

effect on resistance of alveoli being really full or empty

Answer 4

increases

Question 5

diagram of effect of increasing ventilation on pulmonary vascular resistance

Answer 5

benjis

Question 6

what does hypoxaemia cause in pulmonary circuit vs systemic

Answer 6

in pulmonary causes vasoconstriction

Question 7

how does hypoxaemia cause vasoconstriction in the pulmonary circuit

Answer 7

smooth muscle O2 sensitive K+ channels close, decreasing efflux of K+ and increasing membrane potential until depolarisation, Ca2+ channels open and Ca2+ influx, causing vascular smooth muscle cell contraction

Question 8

why does hypoxaemia cause vasoconstriction in the pulmonary circuit

Answer 8

stops blood flowing through unventilated alveoli to match ventilation and perfusion (prevents blood flowing to less efficient parts of gas exchange if lower O2 there)

Question 9

pulmonary vascular resistance: beneficial effects of hypoxaemia

Answer 9

during foetal development to increase resistance in pulmonary circuit, so increased flow through shunts (first breath increases alveolar PO2 and dilates pulmonary vessels)

Question 10

pulmonary vascular resistance: detrimental effects of hypoxaemia

Answer 10

COPD where reduced alveolar ventilation and air trapping means all lung vessels constrict, causing increased resistance so hypertension, right ventricular hypertrophy and congestive heart failure