lecture 26

Question 1

what is air composed of?

Answer 1

78% N2,
21% O2,
0.033% CO2

Question 2

Dalton’s Law definition

Answer 2

the total pressure exerted by a mixture of gases is the sum of pressures exerted by all individual gases

Question 3

partial pressure

Answer 3

the pressure exerted by an individual gas

Question 4

total air pressure, Patm= …. (all gases)

Answer 4

Pn2+ Po2 + Pco2

Question 5

in humid air, Patm= … (all gases)

Answer 5

Pn2+ Po2+ Pco2 +Ph2o

Question 6

in dry air Pgas= Patm*…

Answer 6

Patm*% of gas in atmosphere

Question 7

in humid air, Pgas= (Patm…)*…

Answer 7

(Patm-Ph2o)*% gas in atmosphere

Question 8

as alveolar ventilation increases, — increases and — decreases

Answer 8

Po2 increases and Pco2 decreases

Question 9

in the atmosphere, Po2=?

Answer 9

160 mm Hg

Question 10

in the atmosphere, Pco2=?

Answer 10

0.25 mm Hg

Question 11

in the alveoli, Po2=?
(normal quiet breathing)

Answer 11

100 mm Hg

Question 12

in the alveoli, Pco2=?
(normal quiet breathing)

Answer 12

40 mm Hg

Question 13

alveolar partial pressures can vary with..

Answer 13

hypoventilation or hyperventilation

Question 14

match perfusion with ventilation (explain)

Answer 14

perfusion= blood flow through organs and tissues

ventilation= breathing

the rate is matched, v efficient system

100 mm Hg in alveoli= 100 mm Hg in capillary blood

Question 15

if you hypoventilate… (Po2 and Pco2)

Answer 15

v slow brething
Pco2 rises in alveoli
Po2 falls off

Question 16

if you hyperventilate… (Po2 and Pco2)

Answer 16

v fast breathing
Pco2 falls off because you keep expelling it
Po2 rises because you keep pulling in o2

Question 17

How does O2 enter alveoli/circulation?

Answer 17

-at a thin interface
-type I alveolar cells are for exchange
- O2 transported to heart
(98% attached to Hb in RBC, rest dissolved gas in plasma)
- O2 dropped of and used for cell resp.

Question 18

what happens after O2 is used for cell resp. (byproduct?)

Answer 18

• used to create ATP.
• a byproduct of cell resp is CO2
• Co2 is transported as bicarbonate (HCO3-) or dissolved + bound to Hb
• CO2 is dropped in the lungs and expelled

Question 19

What cellular barriers to O2 and CO2 have to diffuse across?

Answer 19

alveolar epithelial cells and capillary endothelial cells
(2 cells, 4 membranes)

-apical and basolateral membranes

Question 20

Fick’s Law

Answer 20

greatest flux= high concentration (partial pressure) gradient

big distance= lower flux
–> diffusion rate proportional to: ADdeltaP/T^2
small change in T (thickness)= really big change in rate

Question 21

rate of diffusion is directly proportional to (3 things)

Answer 21

• surface area (A)
• membrane permeability (D= diffusion constant)
• concentration (partial pressure) gradient

Question 22

rate of diffusion is inversely proportional to

Answer 22

diffusion distance (T)

Question 23

what is T in Fick’s Law?

Answer 23

diffusion distance
- membrane thickness
- interstitial fluid

Question 24

what patterns does air follow in terms of flow between atmosphere and alveoli?

Answer 24

air moves by bulk flow between atmosphere and alveoli

Question 25

diffusion reaches — under normal circumstances

Answer 25

equilibrium

Question 26

in pulmonary circulation, what is alevolar and venous blood Po2 and Pco2?

Answer 26

pulmonary= deoxygenated

Alveolar Po2 > venous blood Po2
Alveolar Pco2 < venous blood Pco2

Question 27

in systemic circulation, what is arterial and tissue Po2 and Pco2?

Answer 27

systemic= oxygenated blood

arterial Po2 > tissue Po2
arterial Pco2 < tissue Pco2

Question 28

3 factors that affect gas exchange

Answer 28

1. gas diffusion between alveoli and blood
2. adequate perfusion of alveoli
3. O2 reaching the alveoli
   –> alveolar ventilation (hypo/hyper, decreased due to mucus)
   –> composition of inspired air (sea level vs. mntn top)

Question 29

perfusion

Answer 29

the process of blood flowing to the alveoli of the lungs through capillaries

Question 30

ineffective gas exchange leads to

Answer 30

low O2 content in blood

hypoxia= not enough O2 to meet body’s needs

Question 31

2 factors that decrease the amount of O2 reaching the alveoli

Answer 31

1. low O2 content in the atmosphere
2. low alveolar ventilation
   - decreased lung compliance (cold, bronchitis…)
   - increased airway resistance
   - CNS depression (drugs, alcohol overdose)

Question 32

lung compliance

Answer 32

how easily they expand to accommodate a new volume
(no “snap back”)

Question 33

conditions that cause hypoxia?

Answer 33

emphysema
asthma
fibrotic lung disease
pulmonary edema

Question 34

emphysema

Answer 34

decreased SA
decreased Po2 (pp gradient)
= lower rate of diffusion, ineficient O2 uptake

Question 35

asthma

Answer 35

=excessive bronchoconstriction
increased resistance
decreased flow

–> less O2 getting in lungs

Question 36

fibrotic lung disease

Answer 36

= scar tissue building up around alveoli
- increased thickness
- decreased Pco2 (pp gradient)
- reduce compliance
–> decrease O2 coming in

Question 37

pulmonary edema

Answer 37

interstitial fluid (buildup of fluid in interstitial space, in between type I and epithelial cells)

–>increased distance (d^2, mild cases greatly affect diffusion)
- seen in heart failure, fluid builds up)