PSIO202 Exam 2 Lecture 12-13 Flashcards
In a mixture, what is the pressure of a gas proportional to?
its concentration
What is the partial pressure of a gas?
a function of the total gas pressure, or atmospheric pressure (aka the partial pressure of that gas / atmospheric pressure is a percentage)
What are the typical percentages of oxygen, nitrogen, and CO2?
21%, 79%, 0.04%
What are the partial pressures of oxygen, nitrogen, and CO2 at sea level?
159 mmHg, 593 mmHg, and 0.3 mmHg
How do you calculate the partial pressure of a gas as a given atmospheric pressure?
(percent gas) x (atmospheric pressure) = P gas
How is partial pressure denoted?
P sub gas
Ex: P sub O2
What is the partial pressure of water vapor in the blood?
47 mmHg
What are the partial pressures of O2 and CO2 in the arterial blood? Explain why this might be.
100 and 40
O2 is high because it has not been given to tissues yet, and CO2 is low because it has already been expelled/no more has been taken in from the cells yet.
What are the partial pressures of O2 and CO2 in the venous blood? Explain why this might be.
40 and 45
O2 is low because the oxygen has been given to tissues, and CO2 is slightly higher because it has collected from tissue cells metabolic activity.
What are the partial pressures of O2 and CO2 in the alveolar blood? Explain why this might be.
105 and 40
Oxygen is even higher than arterial because it has JUST been oxygenated, not even a little has been given up yet.
CO2 is the same as arterial because not much is there in the first place, so not much moves out at the alveoli (not much change ever).
Explain the changes in gas concentration as blood moves through the cycle of oxygenation, supplying tissues, and return.
When blood is in the alveoli, the pressure differences are between the atmospheric air and the air in the alveoli. Since the atmospheric air is high in O2 (159 mmHg) and the air in the alveoli is low in O2 (40 since it has all been given to tissues) the O2 moves in and is inhaled. Opposite for CO2, atmospheric is 0.3 while alveolar is 45, so it moves out and is exhaled. This results in a new concentration of PO2 105 and PCO2 40 oxygen up and CO2 down).
When the oxygenated blood gets to the capillaries and tissue, the tissue has less O2 (40) and more CO2 (45) from metabolic activity. Therefore, O2 from blood moves into cells and CO2 from cells moves into blood. Now blood has less O2 (40) and more CO2 (45). It gets transported back to the lungs, where it is oxygenated again as a result of the difference in the blood and atmospheric partial pressures.
When blood first reaches the tissue cells, what is both of their partial pressure of O2 and CO2? What is the movement that occurs?
blood 100 and 40, tissue is 40 and 45
O2 moves into tissue, CO2 moves out of tissue
During inspriation, what volume of fresh air actually enters the lungs? What happens to the rest?
350 mL, other 150 mL fills dead space
How do the AVERAGE alveolar values change during inhalation and exhalation? Why?
not much, because the volume of fresh gas inhales is relatively small compared to the volume which was already there (FRC), 350 mL vs around 2400 mL
When happens to the concentration of O2 and CO2 during inspiration?
O2 increases and CO2 deacreases
What are the relative (high or low, not numbers) concentrations of O2 and CO2 in the expired air?
low O2 and high CO2
What is the Fick method?
most accurate way to measure whole body O2 uptake
O2 consumption = blood flow x tissue oxygen extraction
O2 consumption = cardiac output x (arterial O2 - mixed venous O2)
Same method for CO2 production, but (venous CO2 - arterial CO2)
Where are the best locations to sample arterial and venous partial pressures?
aorta and vena cava
What are the typical values for O2 consumption at rest and max exertion? What are the units?
rest - 250
max exertion - 3500
in mL/min
What are the typical values for CO2 production at rest and max exertion? What are the units?
rest - 200
max exertion - 3800
in mL/min
What is the respiratory quotient? What influences RQ?
CO2 produced per O2 consumed
depends on type of nutrient used by the cell
What is the RQ for pure fat vs. carbohydrates? What does this mean?
pure fat: 0.7, indicates 0.7 CO2 is produced for every O2 used
carbohydrates: 1, indicates that 1 CO2 is produced for every O2 used
What is critical for the binding and release of O2 from hemoglobin?
the PO2
What happens with oxygen and hemoglobin when the alveolar PO2 is really high?
oxygen diffuses into the blood and they bind
What happens with oxygen and hemoglobin when the tissue PO2 is really low?
oxygen is released from hemoglobin and diffuses out of the blood
What is the transit time? explanation in words and value at rest
rate of bloodflow through the pulmonary capillaries
0.8 seconds at rest
How long does it take for oxygen to diffuse into the blood? Why is this a good thing?
0.25 seconds, so it has plenty of time to diffuse within the 0.8 second transit time
How is O2 transported, and what percent each?
dissolved - 2%
bound to hemoglobin - 98%
What does the oxy-hemoglobin dissociation curve represent?
the relationship between the amount of O2 binding to hemoglobin and the PO2
What are the axis of the oxy-hemoglobin dissociation curve?
x - PO2
y - percent saturation of hemoglobin
What is a normal arterial saturation of hemoglobin?
98-99%
What are the three points that we should know from the oxy-hemoglobin dissociation curve?
PO2 of 100 = saturation of almost 100%
40 = 75%
20 = 35%
What three factors influence the position of the oxy-hemoglobin dissociation curve?
pH, PCO2, and temperature
How does pH affect the oxy-hemoglobin dissociation curve?
lower pH/more acidic = shift right, lower saturation at same partial pressure
higher pH/more basic = shift left, higher saturation at same partial pressure
How does CO2 affect the oxy-hemoglobin dissociation curve?
higher CO2, more hydrogen ion, lower pH = shift right, lower saturation at same partial pressure
lower CO2, less hydrogen ions, higher pH = shift left, higher saturation at same partial pressure
How does temperature affect the oxy-hemoglobin dissociation curve?
high temp = shift right a lot, lower saturation at same partial pressure
low temp = shift left a lot, higher saturation at same partial pressure
What is the shift when the pH is low, PCO2 is high, and temperature is high?
Bohr shift (right)
All factors in the Bohr shift casue what to happen? Where is this important, and why?
more oxygen released at any given pressure of O2 (oxygen released)
important at the tissue capillaries because that is where the hemoglobin needs to release oxygen more readily
How many mL of oxygen can a full saturated gram of hemoglobin bind?
1.34 mL
What is the normal gram amount of hemoglobin in males and females?
men - 160 grams per liter
women - 140-150 grams per liter
How can you find O2 concentration from amount of hemoglobin and oxygen per hemoglobin?
O2 conc. = grams hemoglobin per liter x mL O2 per gram hemoglobin
What are anemia and hypoxia? What can cause each?
anemia - low hemoglobin
iron deficiencycy
hypoxia - low O2 (and therefore low hemoglobin SATURATION)
elevation
What can be causes of CO poisoning?
car exhaust, tobacco smoke
How does CO cause poisoning (biologically) and what can treat it?
it competes with oxygen to find to the heme group of hemoglobin, so it can be treated by administering pure O2
What are the ways CO2 is transported, and what percent is each?
dissolved - 7%
hemoglobin - 23%
HCO3- - 70%
What is another term for the CO2 which is transported bound to hemoglobin?
carbamino-hemoglobin
How is CO2 formed into bicarbonate when it is taken from the tissue cells into the blood? AKA internal respiration
CO2 + water (and carbonic anhydrase) create H2CO3 (carbonic acid), which breaks down into a hydrogen ion and HCO3- (bicarbonate)
HCO3- leaves the RBC to travel in the plasma, and Cl- enters to balance the charge
How is CO2 reformed in the blood for relase into the alveoli (and then expiration)? AKA external respiration
O2 binds to the Hb which releases a H+, HCO3- enters to react with that H+ (and carbonic anhydrase) to form H2CO3 (carbonic acid) again. Cl- move out to balance the negative charge of the HCO3- coming in. H2CO3 then breaks down into the water and CO2 which is then released to the alveoli.
Where do the reactions that use/form bicarbonate happen? Where in the blood do the bicarbonate ions travel?
The process happens in the RBC, but the bicarbonate ions travel in the plasma
