Respiration lecture 3 Flashcards
Which system is the low-pressure system?
Pulmonary circulation
Which system is the high pressure system?
Systemic circulation
During its systole, what pressure does the right ventricle develop?
about 25 mmHg
During its systole, what pressure does the left ventricle develop?
about 120 mmHg
What happens to the pressure in the right ventricle when systole ends?
The pressure drops rapidly
During diastole, what pressure does the pulmonary circulation have?
about 8 mmHg
What is the mean pulmonary arterial pressure?
15 mmHg
What is the mean systemic pressure?
100 mmHg
The drop in pressure of the pulmonary circulation is ___ than the drop in pressure of the systemic circulation
much smaller
What is the formula for flow?
Flow = pressure/resistance
Why is there low vascular resistance in the pulmonary circulation?
Because the walls of the blood vessels are thinner
What allows the lungs to accept the whole cardiac output at all times even if the pressure of the pulmonary system is significantly lower than the systemic system?
The low vascular resistance and high compliance of the pulmonary circulation
What resistance does the pulmonary system have?
high or low?
Low resistance
What is the cardiac output of each system?
the same
What kind of blood vessel walls are there in the pulmonary circulation? why?
thin and contain less smooth muscle than comparable vessels in the systemic circulation (offer less resistance)
What happens to pulmonary resistance as pulmonary blood flow increases?
Resistance has to be decreased to allow more flow for the same pressure
What happens during recruitment of closed vessels?
Blood vessels that are closed at rest open to allow more flow at the same pressure
What happens during distention of blood vessels?
The blood vessels that are already open get bigger (dilation) to allow more flow for the same pressure
What are the 2 ways resistance can decrease?
There can be recruitment and/or distension to accommodate the larger flow without increasing the pressure
Which drugs cause contraction of vascular smooth muscle?
Serotonin
Histamine
Norepinephrine
What do serotonin, histamine and norepinephrine do to pulmonary vascular resistance in larger pulmonary arteries?
it increases resistance
Which drugs relax smooth vascular muscle?
acetylcholine
isoproterenol
What does acetylcholine and isoproteranol do to pulmonary vascular resistance?
it decreases resistance
What happens in regions of the lungs that are poorly ventilated? Why?
There is a reflex vasoconstriction
It avoids sending blood to poorly ventilated regions and having poorly oxygenated blood
What produces nitric oxide?
endothelial cells
Which drug relaxes vascular smooth muscle?
nitric oxide
What does nitric oxide lead to?
vasodilation to improve blood flow
What is pulmonary blood flow affected by?
gravity
In the upright position, how does blood flow increase?
in a linear relation, blood flow is higher at the bottom of the lungs and lower at the top of the lungs
Why are the vessels more distended toward the bottom of the lungs?
because gravity increases vascular pressure at the bottom of the lungs
How can the pulmonary capillaries be if alveolar pressure is greater than blood pressure in the capillaries?
compressed
Where is there more blood flow, at the bottom of the lungs or at the top?
bottom
What causes an uneven distribution of blood flow from the top to bottom of the lung
the hydrostatic pressure of the blood
What are the 3 zones of the lungs?
top (zone 1)
middle (zone 2)
bottom (zone 3)
How is the pulmonary arterial pressure vs the alveolar pressure in the top zone of the lungs?
Pa < PA
What happens to the capillaries in the top zone of the lungs?
They are compressed
How is the pulmonary arterial pressure vs the alveolar pressure vs venous pressure in the middle zone?
Pv<PA<Pa
What does the flow depend on in the middle zone of the lungs?
the difference between the alveolar and arterial pressures. If Alveolar pressure is greater there is no more flow
Explain the effect of each pressure in the middle zone
Pv is smaller than PA so the blood vessel is compressed. Pv is not a variable to consider in this case
PA and Pa determine the flow because if Pa > PA, blood will flow but if it changes into PA>Pa, the flow will be completely cut off like in the top portion
How is the pulmonary arterial pressure vs the alveolar pressure vs venous pressure in the bottom zone of the lungs?
Pa>Pv>PA
What does the flow depend on in the bottom zone of the lungs?
The difference in pressure between the arterial and veinous blood, the pressure gradient
What affects the distribution of ventilation?
Gravity
In an upright lung at rest, what happens to the alveoli at the top of the lungs?
They are more open than the bottom ones
During breathing, are the alveoli at the top of the lungs or at the bottom of the lungs opened wider?
Since the top alveoli are already open, they don’t have much more space for “new” air. The bottom alveoli will open more (in comparison to resting state)
Why is there more fresh air at the bottom of the lungs?
A greater change in pressure happens
Ventilation increases slowly from ___ to ___ of the lung but blood flow increases more rapidly.
top
bottom
How is the ventilation-perfusion ratio at the top vs at the bottom?
it is high at the top and much lower at the bottom
What is Fick’s principle?
O2 consumption per minute is equal to the O2 taken up by the blood in the lungs in one minute
