Section 10 Flashcards
What are the 4 factors affecting gas exchange?
- Partial pressure gradients
- Diffusion capacity
- Surface area for gas exchange
- Number of red blood cells
In the upright position, blood perfusion is less in the ______ region of the lungs due to gravity and alveoli expansion compressing capillaries resulting in decreased blood flow.
Apical
Perfusion is [increased/decreased] in the base region due to gravity, ______ enlarge compressing the ______ decreasing the size of the ______
Increased; capillaries; alveoli; alveoli
Gravity-dependent lung segments have the most _________.
Blood perfusion
For CO2 to diffuse from the muscle tissue into capillary blood, a ______ must exist.
Pressure Gradient (46mmHg—>40mmHg)
How long does the blood remain in lungs or tissues under resting conditions? during exercise conditions?
.75 s; .3 - .4 s
How do exercise conditions effect equilibration?
Exercise conditions don’t allow enough time for O2 to equilibrate
The volume of gas that diffuses through a membrane each minute for a partial pressure difference of 1 mmHG
Diffusion capacity
Diffusion capacity number size reflects the __________ and _________.
Diffusion distance; surface area
What is the normal diffusion distance for alveolar-capillary diffusion path? what is the max distance? what is the distance in a muscle cell membrane?
1-4 u; 25 u; 1 u
The larger the distance gas molecules must travel, there is [greater/less] diffusion capacity.
less
What do pulmonary diseases that results in scar or fibrous tissue, which replaces normal lung parenchyma, result in?
Thicker alveolar membranes and greater diffusion distances; decrease in diffusion capacity
What increases diffusion capacity?
exercise and training
How does DC increase during exercise?
Capillaries adjacent to alveoli and muscle fibers dilate resulting in an increased surface area for gas exchange
How does DC increase with training?
Capillary density increases around m. fibers in trained, increasing surface area of gas exchange
The greater the surface area for diffusion the [greater/lesser] the gas exchange
Surface area
Why does the number of RBCs affect gas exchange?
the greater the RBCs the greater the amount of O2 can be “picked up” in the lungs and “delivered” to the dissue
At altitude, there is a significant increase in RBCs called ______, which is a normal adaptation to enhance gas exchange
Polycythemia
What is the alveolar partial pressure for CO2? for O2?
40 mmHg; 100 mmHg
What is the tissue partial pressure for CO2? for O2?
46 mmHG; 40 mmHg
Does O2 or CO2 equilibrate faster during gas exchange?
CO2 (more soluble)
What membranes make up the distance that O2 and CO2 need to travel across in order to diffuse?
Alveolar membrane, interstitial fluid, and capillary membrane
Most (60-90%) CO2 is transported in the blood as _____. Some (10-20%) is bound to ____________.
HCO3; the protein part of hemoglobin molecule
Hemoglobin, like albumin is a _________, both of which are very soluble.
Globular protein
What is the major function of the erythrocyte?
Serves as a container for hemoglobin
Hemoglobin is composed of 4 polypeptide chains and 4 prosthetic groups called ______.
Hemes
Myoglobin is located within the muscle cell and also binds O2:
- Only contains one heme group
- Has greater affinity for O2 than does hemoglobin
- Accepts O2 from hemoglobin
- Stores O2 until need for oxidative energy system in the muscle cell
What does P50 represent?
the PO2 needed to saturate Hb or Mb to 50%
As the H+ rises, what happens to the PO2 needed to saturate the Hb to 50%?
PO2 increases
What average volume (mL) of O2 is needed to saturate each gram of Hb in the blood? what is the max?
males = 16 g/100 mL, females = 15 g/100 mL; max = 20.1
Percent saturation of Hb with O2 changes with different conditions in:
- PO2
- pH or [H+]; the Bohr effect
- Temperature
- Location of the blood in the system circulation
- Affinity of Hb for O2
Conditions that increase the P50 [increase/reduce] the affinity that Hb or Mb have for O2 and facilitate the unloading of the O2 to the tissue.
Reduce
What conditions increase the P50?
- Low pH or high [H+]
- Higher temp
- Higher [PCO2]
- Higher [2, 3, DPG]
- Exercise and resting environment of the tissue
Conditions that reduce the P50 [increase/reduce] the affinity that Hb or Mb have for O2 and facilitate the unloading of the O2 to the tissue.
Increase
What conditions decrease the P50?
- High pH or low [H+]
- Lower temp
- Lower [PCO2]
- Lower [2, 3, DPG]
- Lung conditions relative to the tissues
Describes a given partial pressure of O2, the Hb molecule holds more O2 at a higher pH
The Bohr Effect
As described by the Bohr effect, when the pH decreases, Hb affinity for O2 [increases/decreases] and when the pH increases, Hb affinity for O2 [increases/decreases]
decreases; increases
When O2 binds with Hb, it release _____.
2.8 H+
There is more free hydrogen in the ______ and more oxygen in the ______.
Tissue; lungs
Why does O2 have a harder time binding to adult Hb when 2,3 DPG is present?
2,3 DPG reduces the affinity Hb has for oxygen, because it is competing for the same binding site on Hb (wins out over O2)
In the presence of 2,3 DPG, O2 has greater affinity for ______ hemoglobin than _____ hemoglobin.
Fetal; Maternal
Name the relative P50 for Mb, Adult Hb at rest, Adult Hb during exercise, and fetal Hb from biggest to smallest
Adult Hb exercise P50 > Fetal Hb P50 > Adult Hb at rest P50> Mb P50
Represents how much O2 is consumed by the tissues from each 100 mL of blood
Arterial mixed venous oxygen difference (Arterial O2 - Venous O2)
Arterial oxygen in resting conditions is 19.5 mL/ mL blood. Why is it less during exercise? (can be as little 15)
Blood passes lungs more quickly in exercise, not allowing time for full O2 loading
Any PPO2 greater saturation creates a [left/right] shift in the oxyhemoglobin dissociation curve, while at any PPO2 lower saturation O2 creates a [left/right] shift.
Left; right
A left shift in the oxyhemoglobin dissociation curve is created by:
- Greater O2 affinity for Hb (O2 more easily loaded in lungs)
- Increased pH (lungs: pH = 7.7
- Decreased temp
A right shift in the oxyhemoglobin dissociation curve is created by:
- Less O2 affinity for Hb (O2 more easily unloaded in muscle cells)
- decrease in pH, increase in PCO2
- increased temperature
- Muscular exercise
- Increased 2,3 DPG
A right shift in oxyhemoglobin dissociation curve indicates that it takes a [higher/lower] P50 to saturate Hb while a left shift indicates it takes a [higher/lower] P50 to saturate Hb.
Higher; lower
Where is carbonic anhydrase (CA) concentrated?
The red blood cell
