Respiration - Lecture 3 Flashcards
Which system is the low pressure system?
the pulmonary system
Which system is the high pressure system?
the systemic system
During its systole, what pressure does the right ventricle develop?
25 mmHg
During its systole, what pressure does the left ventricle develop?
120 mmHg
What happens to the pressure in the right ventricle when systole ends?
it falls to atmospheric pressure (0)
During diastole, what pressure does the pulmonary circulation have?
8 mmHg
What is the mean pulmonary arterial pressure?
15 mmHg
What is the mean left arterial pressure?
5 mmHg
The drop in pressure of the pulmonary circulation is ___ of the drop in pressure of the systemic circulation
1/10
What is the formula for flow?
flow = pressure/resistance
What does the low vascular resistance in the pulmonary circulation rely on?
the thin walls of the vascular system
What allows the lungs to accept the whole cardiac output at all times?
the low vascular resistance and high compliance of the pulmonary circulation
What kind of resistance does the pulmonary system have?
low resistance
What is the cardiac output of each system?
the same
What kind of blood vessel walls are there in the pulmonary circulation?
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?
it decreases
What happens during recruitment of closed vessels?
more blood vessels open = less resistance = more blood flow
What happens during distention of blood vessels?
the blood vessels perfused may become wider = less resistance
What are the 2 ways resistance can decrease?
recruitment and distention
Which drugs cause contraction of smooth muscle?
serotonin, histamine and norepinephrine
What do serotonin, histamine and norepinephrine do to pulmonary vascular resistance in larger pulmonary arteries?
they increase it
Which drugs relax smooth muscle?
acetylcholine and isoproteranol
What does acetylcholine and isoproteranol do to pulmonary vascular resistance?
they increase it
What happens in regions of the lungs that are poorly oxygenated?
there is a reflex vasoconstriction
What produces nitric oxide?
endothelial cells
Which drug relaxes vascular smooth muscle?
nitric oxide
What does nitric oxide lead to?
vasodilation
What is pulmonary blood flow affected by?
gravity
In the upright position, how does blood flow increase?
linearly from top to bottom of the lungs
Why are the vessels more distended toward the bottom of the lungs?
because gravity increases vascular pressure
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?
the 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, middle, bottom
How is the pulmonary arterial pressure vs the alveolar pressure in the top zone of the lungs?
pulmonary arterial pressure < the alveolar pressure
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?
pulmonary arterial pressure > the alveolar pressure > venous pressure
What does the flow depend on in the middle zone of the lungs?
the difference between arterial and alveolar pressures
How is the pulmonary arterial pressure vs the alveolar pressure vs venous pressure in the bottom zone of the lungs?
pulmonary arterial pressure > venous pressure > alveolar pressure
What does the flow depend on in the bottom zone of the lungs?
the arterio-venous pressure difference
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 opened than the bottom ones
During breathing, are the alveoli at the top of the lungs or at the bottom of the lungs opened wider?
the alveoli from the bottom of the lungs
Why is there more fresh air at the bottom of the lungs?
because that is where the 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 abnormally 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
