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68 Cards in this Set
- Front
- Back
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How does the arterial blood pressure in Pulmonary circulation compare to that in systemic?
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Much LOWER
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What is mean
-aortic pressure -pulmonary pressure |
Aortic = 100 mm Hg
Pulm = 15 mm Hg! |
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How does circulation Resistance compare in the lungs to systemic?
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Lower also
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What cardiac output does the lung circulation recieve?
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RIGHT ventricular output
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Is RV CO any different from LV CO?
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No they should be equal
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When is bloodflow through the lung UNIFORM?
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When supine - laying down
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What happens to bloodflow in the lung when STanding?
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Gravity makes bloodflow NONuniform
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Where is bloodflow lowest/highest when standing?
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Lowest bflow = APEX (top)
Highest bflow = BASE (bottom) |
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Where is VENTILATION lowest/highest in the lungs when standing?
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Lowest airflow = APEX
Highest airflow = BASE Same as for bloodflow |
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Why is bloodflow so low at the top of the lungs?
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Because ALVEOLAR pressure is higher than either arterial or venous pressure so they are compressed
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Why is bloodflow a little bit higher in the middle of the lungs?
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Because now Arterial pressure exceeds alveolar pressure
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Why is bloodflow best in the base of the lungs?
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Because both arterial and venous pressure exceed alveolar
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What is the MAIN REGULATOR of pulmonary bloodflow?
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HYPOXIA
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What does hypoxia DO to pulm bloodflow?
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Causes vasoCONSTRICtion
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Why is it important to remember that hypoxia in the lungs causes vasoconstriction?
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This is COUNTERINTUITIVE and opposite what happens in all other tissues!
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What is the purpose of vasoconstricting pulm vessels in hypoxia?
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To redirect the blood to better perfused areas.
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In what normal physiologic condition is Hypoxic vasoconstriction extremely abundant?
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In the fetus before birth!
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What is the abundance of Hypoxic vasoconstriciton in the fetus called?
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Fetal Pulmonary Vascular Resistance
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What happens to this FPVR at birth?
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The first breath causes a rapid oxygenation of alveoli so the pulm vessels dilate
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So what is the physiologic shunt?
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The normal 2% of bloodflow that somehow squeaks past the lungs
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When is a R-L shunt 50%?
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Some congenital defects like TETRALOGY OF FALLOT
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What does a R->L shunt ALWAYS result in?
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Mixture of venous and arterial blood so a reduced PaO2
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What is more common, a R-L shunt of a L-R shunt?
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L->R shunt by far!
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Why are L-R shunts more common?
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Because the pressure on the left side of the heart is so much greater.
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What is a congenital anomaly in which a L-R shunt might be seen?
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PDA
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Do L-R shunts alter arterial PO2?
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NO; they just increase arterial oxygen in the right heart!
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What is the VQ ratio?
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The ratio of alveolar ventilation to pulmonary bloodflow
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Why is matched V and Q important?
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To achieve ideal exchange of O2 and CO2
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What is the normal VQ ratio?
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80%
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Where is the highest VQ ratio in the lungs? Lowest?
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Highest RATIO = Top
Lowest Ratio = Bottom |
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Why is the VQ ratio higher at the top of the lung than the bottom?
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Because ventilation has less regional variation than bloodflow
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What has more regional variation, PO2 or PCO2?
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Po2
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Where is there more gas exchange in the lungs?
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At the TOP - exchange is HIGHER
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So where is PO2 highest and PCO2 lowest in the lungs?
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At the top!
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What is the result of exchange being lowest at the bottom of the lungs where the VQ ratio is lower?
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Higher PCO2 and Lower PO2
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What happens to the VQ ratio if a piece of steak gets caught in your throat?
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V becomes 0 so VQ=0
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What is a VQ ratio of 0 called?
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A shunt
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What will happen to arterial PO2 and PCO2 in a shunt?
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They will become same as VENOUS levels - 40 mm O2, 46 mm CO2
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What happens to the VQ ratio if a pulmonary embolism blocks bloodflow to the lungs?
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VQ ratio becomes INFINITY
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What is an infinite VQ ratio called?
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DEAD SPACE
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What will happen to gas exchange in the case of Dead space?
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There is no gas exchange bc there is no blood available
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What will the alveolar levels of O2 and CO2 become in dead space?
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Same as atmospheric
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Where does breathing control sensory info get coordinated?
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In the BRAINSTEM
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What does the Brainstem control with output in response to sensory integration?
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-Respiratory muscles
-Breathing cycle |
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What are the 4 centers for breathing control in the brainstem and cortex?
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1. Medullary respiratory center
2. Apneustic center 3. Pneumotaxic center 4. Cerebral cortex |
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Where is the medullary respiratory center located?
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In the RETICULAR FORMATION
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What are the 2 groups of nuclei that make up the medullary respiratory center?
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1. Dorsal
2. Ventral |
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What is the Dorsal group responsible for?
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INSPIRATION/basic rythm for breathing
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What is the Ventral group responsible for?
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Expiration
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Which group is normally used?
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Just the dorsal group - ventral only activates expiration when nonpassive (exercise)
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What does the dorsal group recieve sensory info from?
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The vagus and glossopharyngeal nerves
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What does info is conveyed by:
-vagus -glossopharyngeal |
Vagus = mechanoreceptors from lung and peripheral chemoreceptors
Glossopharyngeal = periph chemos |
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How does the Dorsal resp group of the medullary respiratory center convey OUTPUT? To where?
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Via the PHRENIC nerve
To the DIAPHRAGM |
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Where is the Apneustic center?
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In the LOWER PONS
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What does the Apneustic center do?
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Stimulates Inspiration for a deep, prolonged GASP
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Where is the Pneumotaxic center?
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In the UPPER PONS
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What is the Pneumotaxic center responsible for?
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Inhibition of respiration to regulate inspiratory volume and respiratory RATE
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What are 2 types of chemoreceptors and what do they detect?
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Central and Peripheral
Detect O2, CO2, and H+ |
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Where are Central chemoreceptors located?
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Medulla
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What stimulus to the central medulla chemoreceptors will stimulate breathing?
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Decreased pH (Increased PCO2)
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Why are the medulla chemoreceptors only responsive to acid pH?
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All they detect is acid in CSF, not CO2 directly
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What can detect PO2 or PCO2?
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Peripheral chemoreceptors
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Where are peripheral chemoreceptors located?
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In the Carotid bodies and Aortic arch
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At what arterial PO2 will the peripheral chemoreceptors stimulate breathing?
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Only when it gets all the way down to 60 mm Hg
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What chemoreceptors are more important for detecting increased PCO2 in blood?
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the Central ones more than peripheral
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What chemoreceptors are more important for stimulating a respiratory compensation to metabolic acidosis?
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PERIPHERAL - because H+ can't cross the BBB
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Why does breathing and ventilation increase in exercise?
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We don't really know
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What blood levels DO or DO NOT change during exercise?
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NO change in PaCO2/PaO2
VENOUS CO2 increases |
