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59 Cards in this Set
- Front
- Back
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What 2 Gas laws are important in gas exchange?
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Dalton's: pressure of one gas in a mix is independent of others.
Henry's: Concentration of a gas is limited by its diffusion constant and proportional to its partial pressure. |
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So what is Barometric pressure?
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The total of the individual partial pressures of N2, O2, etc.
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What is Po2 in atmosphere?
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Pbarometric x O2 fraction
760 x .21 = 160 mmHg |
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What is Po2 in lungs?
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(760 - water vapor)x.21= 150
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What does Henry's law mean?
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The conc of gas in a liquid (blood) depends on the partial pressure of it in the air above the liquid.
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What 4 things affect diffusion?
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1. Increasing membrane SA
2. Increasing diff. coefficient. 3. Increasing Conc. gradient 4. Decreasing thickness of memb. |
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What is "Diffusing Capacity"?
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The max amount of gas the lungs can transfer to the blood.
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What 2 things limit Diffusion?
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-Perfusion
-Diffusion |
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How does Perfusion affect gas diffusion from lungs to blood?
Does this occur in normal or diseased states? |
Perfusion is blood flow; when decreased, less blood transfers.
This can occur normally. |
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How does Diffusion affect gas flow from lungs to blood?
In what states is it decreased? |
Well it's obvious. Decrease occurs in diseased states.
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Which limiting factor has more impact on transfer of o2 from lungs into blood?
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PERFUSION (blood flow).
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Why is perfusion more important?
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B/c when blood flows past alveoli, O2 levels btwn the 2 structures EQUILIBRATE. Therefore perfusion is approx equal to diffusion; decreasing perfusion has profound effects on diffusion.
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Why doesn't Diffusion changes alter the amt of O2 transferred to blood?
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Because Diffusion is movement of O2 in both directions - lungs to blood, and blood to lungs. Doubling only doubles both directions of movement.
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What is ONE instance in which o2 transfer to blood IS diffusion limited?
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in Extremely Strenuous exercise: the rate of blood flow is too fast to allow equilibration and O2 doesn't diffuse.
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How does pulmonary hydrostatic pressure compare to systemic?
What is typical value? |
It is mch lower to prevent filtration (would cause edema).
Typical val: 10 mm Hg |
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When does pulmonary filtration and edema occur?
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In left heart failure - backed up blood flow increases Pressure in lung capillaries.
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What is systemic artery MAP?
What is it at the beginning of systemic capillaries? In the right ventricle and pulmonary artery? |
Systemic MAP = 93
At beginning = 20 Right ventric= 15 Pulm capills = 10 |
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What 3 things can regulate pulmonary vascular resistance?
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1. CO cardiac output
2. Autonomic nervous sys. 3. Hypoxia |
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What does exercising do to pulmonary circulation (not truly though)
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1. Incr. Cardiac Output CO
2. Incr. MAP 3. Incr. pulm pressure 4. Causes filtration/edema 5. you die |
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What allows you to exercise without dying? How?
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Decreasing Total Periph Resist.
B/c CO = MAP x TPR; since MAP doesn't change TPR must. |
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What is the major regulator of MAP in the lungs?
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resistance - by changing the number of open capillaries and increasing their radii.
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What are the formal terms for increasing the radii and number of open capillaries?
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Distention and Recruitment.
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What is the effect of Recruitment and Distention?
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Decreased TPR, so that when CO increases MAP doesn't change and you don't get pulmonary edema.
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What are 3 benefits of Recruitm and Distention?
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1. No filtration (edema)
2. Decreased velocity, allows time for equilibration. 3. Increased SA for gas exch. |
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What is the effect of autonomic regulation of lung vasculature resistance?
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not important.
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What can alter lung vasc resistance other than the ANS and TPR?
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Hypoxia.
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If you're matching bl flow to airflow, what will hypoxia do?
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Decrease blood flow.
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What does decreased blood flow do to capillaries?
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decreases - constricts them.
Seems counter to reason, but you DON'T WANT blood to go where there is no O2; it's a waste. |
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What is the effect of high altitude on pulmonary circulation?
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It causes a general vasoconstriction of pulm capillaries. Therefore the heart must work harder.
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don't forget to look at gasexchng in lungs and tissues
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ok
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What are the 2 forms that oxygen is found/transported in blood?
How much of each? |
-Dissolved - 0.3mL in 100mL
-Bound to Hemoglobin - 20.1 mL |
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Why is so little O2 dissolved in blood?
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O2 just dissolves poorly in plasma.
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At a Po2 of 100 mm Hg, how much oxygen is bound to Hb?
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Hemoglobin is saturated, so 20.1 mL of O2 in 100 mL blood.
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What is the Po2?
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Only dissolved oxygen in blood - none of the HbO2 counts.
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For functioning, which form of O2 is more important?
What are 3 reasons for why? |
Dissolved.
1. Its amount determines Po2 2. The tissues only use dissolv. 3. Chemoreceptors only detect dissolved O2. |
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What values of Po2 are important? Where are they seen?
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100: lungs
60: lungs still 40: Tissue 25: Active tissue |
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What perc. of Hb is bound at Po2 of 100?
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100% or close to it.
Po2 100 occurs in lungs where oxygen pressure is 100%. |
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What perc. of Hb is bound at Po2 of 60?
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almost 100% in spite of low O2
Po2 60 occurs in lungs still, but within the plateau - Safety factor/device. |
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What perc. of Hb is bound at Po2 of 40?
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-75% Hb satn.
Po2 40 occurs in TISSUES. As blood flows past tissues, O2 is transferred to tissues in need. |
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What perc. of Hb is bound at Po2 of 25?
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50% Hb satn. Because O2 dissolved diffuses to tissues, more dissoc. from Hb to replace the diffused. STEEP curve.
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Review: At what pressure is Hb
100% saturated almost 100%? 75%? 50%? |
100 and almost 100 = lungs
75 = tissues 50 = active tissues. |
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What major effect (name) influences the Hb diss. curve?
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the BOHR effect.
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What is the bohr effect?
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Co2/H+ can bind Hb and decrease its affinity for oxygen.
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How is the Hb diss curve affected by a
-Shift to the left? -Shift to the right? |
To the left: increases Hb affinity for O2, so more is Hb-bound at any given Po2.
To the right: easier to deliver. |
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75% satn Hb occurs at what Po2?
What if curve shifts to left? To right? |
75% is normally at Po2 of 40.
-If you shift to left, 75% is saturated until 25 Po2. -If shift to right, 75% is shifted only until 60 (in normal conditions 100% would be satd at this Po2!) |
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What causes the oxygen diss curve to shift to the left?
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-decreased DPG
-Decreased CO2, H+, and Temp. |
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What causes the O2 diss curve to shift to the right?
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-Increased DPG
-Increaesd Co2, H+, and Temp. (more acidic - active tissue) |
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What are 4 causes of hypoxia?
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1. Diffusion impairment (due to pulmonary edema)
2. Decreased atm Po2 (due to high altitudes) 3. Anemia 4. Carbon monox poisoning |
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What 2 hypoxia causes are detected by chemoreceptors?
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Impaired diffusion
Decreased atmosph. Po2 |
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So what in general do chemoreceptors detect?
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Decreased O2 PRESSURE in the blood.
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How do anemia and CO poisoning alter blood oxygen levels?
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NOT by changing Po2, but by decreasing O2 CONTENT b/c Hb is unable to deliver it.
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what is carboxyhemoglobin?
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Hb bound to Hb - it has a very high affinity for CO.
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what does Hb get in exchange for O2 delivery?
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CO2.
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In what 3 forms is CO2 transported? How much of each form is found?
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-Dissolved in plasma, 10%
-Bound to protein (Hb), 30% -As Bicarbonate, 60% |
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What enzyme catalyzes formation of Carbonic acid H2CO3, and where is it found?
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Carbonic anhydrase, in RBCs.
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As blood flows past tissues, what is the CO2 transfer process?
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1. Co2 dissolv in tissues diffuses to blood plasma, then into RBCs.
2. In RBCs, some CO2 binds H2O and converts to H2CO3 then dissociates into Hco3- and H+. 3a.HCO3-is exchanged for Cl- into/from plasma. (Cl shift) 3b. H+ binds HbO2- and makes Methemoglobin (HHb) in exch for O2 transfer to tissue. 4. HHb reacts w/ any other CO2 to form CarbaminoHb. |
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Because of transfering HCO3- to the plasma , what do RBCs get loaded w/ as they pass tissues?
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Chloride ions - due to the Cl- shift.
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What and Where is the Haldane effect?
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In the lungs - when O2 binds Hb, less CO2 binds Hb.
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what and where is the Bohr effect?
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In the tissues - increased CO2 and H+ decrease O2 affinity of Hb.
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