Respiratory 5 Flashcards
What exists between alveoli and pulmonary capillaries at all time
Partial pressure gradient for O2 and CO2
What determines the O2 and CO2 diffusion rate between alveoli and capillaries
Gas composition in alveoli
In alveoli what remains relatively constant during quiet respiration assuming perfusion is normal
PO2 and PCO2
What is perfusion
Blood flow
O2 entering alveoli is equal to what
O2 uptake from pulmonary capillaries
What can alter partial pressures of O2 and CO2 and alter diffusion
Alterations in ventilation rate independent of changes in CV system
Ex) hyperventilation or hypoventilation
What can cause hypoventilation
Alcohol, drugs
What happens during hypoventilation
Slow breathing
- increased PCO2, not ventilating as much CO2 out
- decreased PO2 bringing in less O2
What happens during hyperventilation
Breathing rapidly, deeply
- bringing in more O2 than being taken up by capillaries
- O2 builds up in alveoli, alveolar PO2 increases
- exhaling CO2 faster then being brought to pulmonary capillaries, PCO2 decreases
- increased diffusion of O2 and CO2
What must happen so one organ system does not work harder then it needs to
Ventilation and alveolar blood flow (perfusion) must match
What must happen for external respiration
- Bringing O2 from atmosphere into alveoli
- Blood flow must be high enough to pick up available O2
- Matched ventilation/perfusion
What is local regional control to match perfusion and ventilation in lungs?
Gravity
How does gravity affect blood flow in lungs
- blood flow is higher at base of lung and decreases up to apex during rest
- low pressure circuit and right ventricle doesn’t create enough pressure to go against gravity
- pressure of pumping and downward pressure causes perfusion in base
How does gravity affect ventilation
- highest at base and decreases as move up
- entire lung not -3 mmHg, more positive at base
Why is the intrapleural pressure more negative at the apex
Bigger space between the pleura because gravity
What does a more negative intrapleural pressure do to the alveoli at the apex
Partially open and filled with air even at rest and therefore do not take much air during ventilation
What does not innervate the pulmonary arterioles like it does the systemic arterioles
Autonomic innervation
What are the two local controls for smaller areas of the lungs
Pulmonary arterioles influenced by O2
Bronchioles sensitive to CO2
What can affect blood flow in pulmonary arterioles
Decreasing O2 levels around
Decrease causes constriction
Why do the pulmonary arterioles constrict in response to low O2
Increases resistance so blood flow can be diverted to ventilated arterioles that have adequate O2
What causes constriction to low O2 in pulmonary arterioles
O2 sensitive K+ channels close
What affects air flow in bronchioles
Increase CO2 causes dilation, reduces resistance so more CO2 exhaled
Decrease CO2 causes constriction, not over ventilating and no excessive removal of CO2
What happens when one alveoli is blocked and air cannot move in
- at first blood will continue to flow by, from CO2 and CO2 will increase in alveoli and region
- O2 will decrease, no fresh O2 and everything in alveoli picked up
- increase CO2 causes dilation of bronchiole
- decrease O2 will cause arterioles to constrict
- blood will take path of least resistance
What are 3 local control of arterioles and bronchioles
PCO2 increases - bronchioles dilate
PCO2 decreases - bronchioles constrict
PO2 decreases - pulmonary arteries constrict
