Gas Exchange & Transport

Question 1

What is 2 things affect O2 reaching the alveoli (causes of low alveolar partial pressure of oxygen)

Answer 1

1. inspired air has low O2 content (hypoxic environment)

2. Alveolar ventilation is inadequate (hypoventilation)

Question 2

What can cause hypoventilation? (4)

Answer 2

shallow breathing, decreased lung compliance, incresed airway resistance = asthma, CNS depression from anxiety & epilepsy medications

Question 3

Alveolar gas exchange is influenced by… (3)?

Answer 3

1. O2 reaching the alveoli
2. Gas diffudion between alveoli and blood, adequate
3. perfusion of alveoli (blood circulation around alveoli)

Question 4

What Affects diffusion between alveoli and lungs? (2)

Answer 4

1. SA

2. Diffusion distance

Question 5

What affects difusion distance?

Answer 5

1. Barrier thickness & amount of fluid (pulmedena)

Question 6

Diffusion rate is inversly proportional to…

Answer 6

diffusion distance

Question 7

Diffusion rate is proportional to

Answer 7

SA X barrier permeability X concentration gradient

Question 8

What happens with emphysema?

Answer 8

Destruction of alveoli so less SA for gas exchange

Question 9

WHat happens with cystic fibrosis

Answer 9

Thick alveolar membrane which slows gas exchange and loss of compliance so less alveolar ventilation

Question 10

Pulmonary Edema

Answer 10

fuild build up = increased diffusion distance = decreased PO2

Question 11

Asthma

Answer 11

COnstriction of bronchioles which decreases alveolar ventilation therefore gas exchange

Question 12

What is the average carrying capacity of oxygen with RBC

Answer 12

200ml/L of blood

Question 13

Erythripoises

Answer 13

Process by which the body makes RBC

Question 14

RBC are

Answer 14

Erythrocytes

Question 15

The amount of oxygen bound to Hb depends on

Answer 15

Plasma O2 & Amount of Hb

Question 16

Plasma O2 determines the % saturation of…

Answer 16

Hb

Question 17

Amount of HB determines the total amount of Hb …

Answer 17

Binding site

Question 18

Total Hb binding sites is calculated from

Answer 18

Hb content per RBC X # of RBC

Question 19

What is the carrying capacity of human blood

Answer 19

20 ml/100ml

Question 20

Why is the O2 equilibrium curve significant? (2)

Answer 20

1. Even when PO2 in the blood is 60%, 90% of heme groups are still saturated
2. Venous has a PO2 of 40% which = 75% saturation which is a resevoir if metabolism increases or execising muscles

Question 21

what is P50?

Answer 21

the PO2 at which 50% Hb is satruated with O2

Question 22

A low PO2 (low P50) means?

Answer 22

high affinity for O2

Question 23

Which has a higher P50? Myoglobin or Hemoglobin? Why?

Answer 23

Myoglobin. Because it takes only 3% PO2 to reach P50, vs. Hemoglobin which requires 33% PO2

Question 24

P50 and Affinity are _________ related

Answer 24

Inversely

Question 25

Therefore, as P50 increases, O2 affinity …

Answer 25

Decreases!!

Question 26

A decrease in pH means what for acidity?

Answer 26

More acidity

Question 27

When pH decreases what happens to affinity?

Answer 27

Decreased affinity

Question 28

A decrese in pH & affinity shifts the curve to the …

Answer 28

right

Question 29

An increase in pH shifts the curve to the left and increases

Answer 29

affinity

Question 30

H+ acts as a

Answer 30

allosteric modulator

Question 31

What is a allosteric modulator

Answer 31

Knocks O2 off to bind to Hb

Question 32

What is the Bohr Effect?

Answer 32

An adaptation aimed at maximizing the delivery of O2 to the tissues

Question 33

Where does the Bohr Effect shift to lower Hb-O2 affinity in? vs. Shifting to higher Hb-O2 affinity in?

Answer 33

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

Question 34

What is the effect of the PCO2 do to the curve?

Answer 34

Moves it to the right to decrease affinity for oxygen

Question 35

What is the temperature change effect of the curve?

Answer 35

An increase in temperature shifts the curve to the right to allow for increased offloading of oxygen when exercising (muscles are hot so DUHHH)

Question 36

What is the 2,3-DPG (organic phosphate) effect on the curve

Answer 36

A higher level of 2,3-DPG shifts the curve to the right, important during pregnancy as it offloads O2 to the featus

Question 37

Gamma globins have a …

Answer 37

Higher affinity for oxygen

Question 38

What does a Gamma do

Answer 38

helps take oxygen from maternal blood

Question 39

What is the effect of FHb to the curve

Answer 39

LEFT! INCREASED AFFINITY fetal Hb sucks up oxygen like no other !!

Question 40

How is breathing influenced (3)

Answer 40

1. neurons in medulla
2. CO2 levels = primary stimulus
3. Sensory input from chemoreceptors to the medulla to help maintain blood-gas homeostasis

Question 41

Role of PERIPHERAL Chemoreceptors in ventilation

Answer 41

1. Located in corotid and aortic arteries
2. Constantly sensing CO2 & O2 Concentrations
3. ALways relaying info to brain (tonic contorl to medulla)
4. Responds primarily to O2 CHANGES IN BLOOD (opposite of central receptors)
5. 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

Question 42

INTRacellular responses to super low O2

Answer 42

Hypoxia-inducible factors are formed to cope with low intracellular O2

1. erythropoesis : synthesis of RBC
2. synthesis glu transporters
3. Synthesis of enzymes of anerobic glycolysis (to speed up ATP production)
4. Angiogenisis (new blood vessels)