Gas Exchange & Transport Flashcards
What is 2 things affect O2 reaching the alveoli (causes of low alveolar partial pressure of oxygen)
- inspired air has low O2 content (hypoxic environment)
2. Alveolar ventilation is inadequate (hypoventilation)
What can cause hypoventilation? (4)
shallow breathing, decreased lung compliance, incresed airway resistance = asthma, CNS depression from anxiety & epilepsy medications
Alveolar gas exchange is influenced by… (3)?
- O2 reaching the alveoli
- Gas diffudion between alveoli and blood, adequate
- perfusion of alveoli (blood circulation around alveoli)
What Affects diffusion between alveoli and lungs? (2)
- SA
2. Diffusion distance
What affects difusion distance?
- Barrier thickness & amount of fluid (pulmedena)
Diffusion rate is inversly proportional to…
diffusion distance
Diffusion rate is proportional to
SA X barrier permeability X concentration gradient
What happens with emphysema?
Destruction of alveoli so less SA for gas exchange
WHat happens with cystic fibrosis
Thick alveolar membrane which slows gas exchange and loss of compliance so less alveolar ventilation
Pulmonary Edema
fuild build up = increased diffusion distance = decreased PO2
Asthma
COnstriction of bronchioles which decreases alveolar ventilation therefore gas exchange
What is the average carrying capacity of oxygen with RBC
200ml/L of blood
Erythripoises
Process by which the body makes RBC
RBC are
Erythrocytes
The amount of oxygen bound to Hb depends on
Plasma O2 & Amount of Hb
Plasma O2 determines the % saturation of…
Hb
Amount of HB determines the total amount of Hb …
Binding site
Total Hb binding sites is calculated from
Hb content per RBC X # of RBC
What is the carrying capacity of human blood
20 ml/100ml
Why is the O2 equilibrium curve significant? (2)
- Even when PO2 in the blood is 60%, 90% of heme groups are still saturated
- Venous has a PO2 of 40% which = 75% saturation which is a resevoir if metabolism increases or execising muscles
what is P50?
the PO2 at which 50% Hb is satruated with O2
A low PO2 (low P50) means?
high affinity for O2
Which has a higher P50? Myoglobin or Hemoglobin? Why?
Myoglobin. Because it takes only 3% PO2 to reach P50, vs. Hemoglobin which requires 33% PO2
P50 and Affinity are _________ related
Inversely
Therefore, as P50 increases, O2 affinity …
Decreases!!
A decrease in pH means what for acidity?
More acidity
When pH decreases what happens to affinity?
Decreased affinity
A decrese in pH & affinity shifts the curve to the …
right
An increase in pH shifts the curve to the left and increases
affinity
H+ acts as a
allosteric modulator
What is a allosteric modulator
Knocks O2 off to bind to Hb
What is the Bohr Effect?
An adaptation aimed at maximizing the delivery of O2 to the tissues
Where does the Bohr Effect shift to lower Hb-O2 affinity in? vs. Shifting to higher Hb-O2 affinity in?
Lower affinity in systemic tissues because more acidity from CO2 therfore O2 is kicked off
Higher affinity in respiratory organ as there is a lower acidity and O2 can be bound, not knocked off
What is the effect of the PCO2 do to the curve?
Moves it to the right to decrease affinity for oxygen
What is the temperature change effect of the curve?
An increase in temperature shifts the curve to the right to allow for increased offloading of oxygen when exercising (muscles are hot so DUHHH)
What is the 2,3-DPG (organic phosphate) effect on the curve
A higher level of 2,3-DPG shifts the curve to the right, important during pregnancy as it offloads O2 to the featus
Gamma globins have a …
Higher affinity for oxygen
What does a Gamma do
helps take oxygen from maternal blood
What is the effect of FHb to the curve
LEFT! INCREASED AFFINITY fetal Hb sucks up oxygen like no other !!
How is breathing influenced (3)
- neurons in medulla
- CO2 levels = primary stimulus
- Sensory input from chemoreceptors to the medulla to help maintain blood-gas homeostasis
Role of PERIPHERAL Chemoreceptors in ventilation
- Located in corotid and aortic arteries
- Constantly sensing CO2 & O2 Concentrations
- ALways relaying info to brain (tonic contorl to medulla)
- Responds primarily to O2 CHANGES IN BLOOD (opposite of central receptors)
- Signals medulla to increase ventillation if PO2 is low, which means less ATP, so less K+ channels/closed, More positive inside cell therfore the cell depolarizes because potassium can’t leave because no ATP, CG ca2+ open and NT released onto sensory neurons to brain = medulla in increase ventilation
INTRacellular responses to super low O2
Hypoxia-inducible factors are formed to cope with low intracellular O2
- erythropoesis : synthesis of RBC
- synthesis glu transporters
- Synthesis of enzymes of anerobic glycolysis (to speed up ATP production)
- Angiogenisis (new blood vessels)
