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59 Cards in this Set

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  • Back
What 2 Gas laws are important in gas exchange?
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.
So what is Barometric pressure?
The total of the individual partial pressures of N2, O2, etc.
What is Po2 in atmosphere?
Pbarometric x O2 fraction

760 x .21 = 160 mmHg
What is Po2 in lungs?
(760 - water vapor)x.21= 150
What does Henry's law mean?
The conc of gas in a liquid (blood) depends on the partial pressure of it in the air above the liquid.
What 4 things affect diffusion?
1. Increasing membrane SA
2. Increasing diff. coefficient.
3. Increasing Conc. gradient
4. Decreasing thickness of memb.
What is "Diffusing Capacity"?
The max amount of gas the lungs can transfer to the blood.
What 2 things limit Diffusion?
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.
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.
Which limiting factor has more impact on transfer of o2 from lungs into blood?
PERFUSION (blood flow).
Why is perfusion more important?
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.
Why doesn't Diffusion changes alter the amt of O2 transferred to blood?
Because Diffusion is movement of O2 in both directions - lungs to blood, and blood to lungs. Doubling only doubles both directions of movement.
What is ONE instance in which o2 transfer to blood IS diffusion limited?
in Extremely Strenuous exercise: the rate of blood flow is too fast to allow equilibration and O2 doesn't diffuse.
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
When does pulmonary filtration and edema occur?
In left heart failure - backed up blood flow increases Pressure in lung capillaries.
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
What 3 things can regulate pulmonary vascular resistance?
1. CO cardiac output
2. Autonomic nervous sys.
3. Hypoxia
What does exercising do to pulmonary circulation (not truly though)
1. Incr. Cardiac Output CO
2. Incr. MAP
3. Incr. pulm pressure
4. Causes filtration/edema
5. you die
What allows you to exercise without dying? How?
Decreasing Total Periph Resist.

B/c CO = MAP x TPR; since MAP doesn't change TPR must.
What is the major regulator of MAP in the lungs?
resistance - by changing the number of open capillaries and increasing their radii.
What are the formal terms for increasing the radii and number of open capillaries?
Distention and Recruitment.
What is the effect of Recruitment and Distention?
Decreased TPR, so that when CO increases MAP doesn't change and you don't get pulmonary edema.
What are 3 benefits of Recruitm and Distention?
1. No filtration (edema)
2. Decreased velocity, allows time for equilibration.
3. Increased SA for gas exch.
What is the effect of autonomic regulation of lung vasculature resistance?
not important.
What can alter lung vasc resistance other than the ANS and TPR?
If you're matching bl flow to airflow, what will hypoxia do?
Decrease blood flow.
What does decreased blood flow do to capillaries?
decreases - constricts them.
Seems counter to reason, but you DON'T WANT blood to go where there is no O2; it's a waste.
What is the effect of high altitude on pulmonary circulation?
It causes a general vasoconstriction of pulm capillaries. Therefore the heart must work harder.
don't forget to look at gasexchng in lungs and tissues
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
Why is so little O2 dissolved in blood?
O2 just dissolves poorly in plasma.
At a Po2 of 100 mm Hg, how much oxygen is bound to Hb?
Hemoglobin is saturated, so 20.1 mL of O2 in 100 mL blood.
What is the Po2?
Only dissolved oxygen in blood - none of the HbO2 counts.
For functioning, which form of O2 is more important?
What are 3 reasons for why?
1. Its amount determines Po2
2. The tissues only use dissolv.
3. Chemoreceptors only detect dissolved O2.
What values of Po2 are important? Where are they seen?
100: lungs
60: lungs still
40: Tissue
25: Active tissue
What perc. of Hb is bound at Po2 of 100?
100% or close to it.
Po2 100 occurs in lungs where oxygen pressure is 100%.
What perc. of Hb is bound at Po2 of 60?
almost 100% in spite of low O2
Po2 60 occurs in lungs still, but within the plateau - Safety factor/device.
What perc. of Hb is bound at Po2 of 40?
-75% Hb satn.
Po2 40 occurs in TISSUES.
As blood flows past tissues, O2 is transferred to tissues in need.
What perc. of Hb is bound at Po2 of 25?
50% Hb satn. Because O2 dissolved diffuses to tissues, more dissoc. from Hb to replace the diffused. STEEP curve.
Review: At what pressure is Hb
100% saturated
almost 100%?
75%? 50%?
100 and almost 100 = lungs
75 = tissues
50 = active tissues.
What major effect (name) influences the Hb diss. curve?
the BOHR effect.
What is the bohr effect?
Co2/H+ can bind Hb and decrease its affinity for oxygen.
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.
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!)
What causes the oxygen diss curve to shift to the left?
-decreased DPG
-Decreased CO2, H+, and Temp.
What causes the O2 diss curve to shift to the right?
-Increased DPG
-Increaesd Co2, H+, and Temp.
(more acidic - active tissue)
What are 4 causes of hypoxia?
1. Diffusion impairment (due to pulmonary edema)
2. Decreased atm Po2 (due to high altitudes)
3. Anemia
4. Carbon monox poisoning
What 2 hypoxia causes are detected by chemoreceptors?
Impaired diffusion
Decreased atmosph. Po2
So what in general do chemoreceptors detect?
Decreased O2 PRESSURE in the blood.
How do anemia and CO poisoning alter blood oxygen levels?
NOT by changing Po2, but by decreasing O2 CONTENT b/c Hb is unable to deliver it.
what is carboxyhemoglobin?
Hb bound to Hb - it has a very high affinity for CO.
what does Hb get in exchange for O2 delivery?
In what 3 forms is CO2 transported? How much of each form is found?
-Dissolved in plasma, 10%
-Bound to protein (Hb), 30%
-As Bicarbonate, 60%
What enzyme catalyzes formation of Carbonic acid H2CO3, and where is it found?
Carbonic anhydrase, in RBCs.
As blood flows past tissues, what is the CO2 transfer process?
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.
Because of transfering HCO3- to the plasma , what do RBCs get loaded w/ as they pass tissues?
Chloride ions - due to the Cl- shift.
What and Where is the Haldane effect?
In the lungs - when O2 binds Hb, less CO2 binds Hb.
what and where is the Bohr effect?
In the tissues - increased CO2 and H+ decrease O2 affinity of Hb.