gas exchange

Question 1

composition of the air we breathe

Answer 1

78 percent nitrogen
21 percent oxygen
0.033 percent carbon dioxide

Question 2

dalton’s law

Answer 2

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

the pressure exerted by an individual gas is called the partial pressure of that gas

Question 3

total air pressure equation

Answer 3

Patm = PN2+PO2+PCO2

Question 4

total air pressure equation in humid air

Answer 4

Patm=PN2+PO2+PCO2+PH20

Question 5

total partial pressure in dry air equation

Answer 5

Pgas= Patm x % of gas in atmosphere

Question 6

total partial pressure in humid air equation

Answer 6

Pgas= (Patm-PH2O)x % of gas in atmosphere

Question 7

gas composition in the atmosphere of O2 and CO2

Answer 7

PO2= 160 mm Hg
PCO2= 0.25 mm HG

Question 8

alveolar partial pressures during normal quiet breathing

Answer 8

PO2= 100 mm Hg
PCO2 = 40 mmHg

Question 9

as alveolar ventilation increases alveolar PO2 _______ and PCO2 ______

Answer 9

increases, decreases

Question 10

explain pulmonary gas exchange and transport

Answer 10

1. Oxygen enters the blood at alveolar-capillary interface
2. oxygen is transported in blood dissolved plasma or bound to hemoglobin inside RBCS
3. oxygen diffuses into cells, cellular respiration determines metabolic CO2 production
4. CO2 diffuses out of the cells
5. CO2 is transported, dissolved, bound to hemoglobin or as HCO3-
6. CO2 enters alveoli at alveolar-capillary interface

Question 11

what is the rate of diffusion directly proportional to

Answer 11

concentration (partial pressure) gradient

AxDx (delta Pgas)/ T^2

Question 12

partial pressures in venous blood

Answer 12

O2: 40 mm Hg
CO2: 46 mm Hg

Question 13

partial pressures in arterial blood

Answer 13

O2: 100 mm Hg
CO2: 40m HG

Question 14

partial pressures in cells

Answer 14

O2<= 40 mm Hg
CO2> = 46 mm Hg

Question 15

what is alveolar gas exchange influenced by

Answer 15

oxygen reaching alveoli: composition of inspired air; alveolar ventilation - rate and depth of breathing, airway resistance, lung compliance

gas diffusion between alveoli and blood: SA, diffusion distance - barrier thickness and amount of fluid

adequate perfusion of alveoli

Question 16

factors that decrease the amount of oxygen in the blood

Answer 16

insufficient exchange
hypoxia
low oxygen in the atmosphere
low alveolar ventilation: decreased lung compliance (how easily they can expand), increased air resistance, CNS depression: drugs, alcohol overdose

Question 17

emphysema

Answer 17

affects elastance (lose it)
destruction of alveoli means less SA for gas exchange
oxygen is normal or low (Po2 low)
affects SA and partial pressure gradient in ficks law
ie/ from smoking

Question 18

astma

Answer 18

increased histamine
increased airway resistance, decreases alveolar ventilation
bronchioles constricted
increased resistance, decreased airflow

affects partial pressure gradient

Question 19

fibrotic lung disease

Answer 19

thickened alveolar membrane shows gas exchange. loss of lung compliance may decrease alveolar ventilation

PO2 low

build up of scar tissue around alveoli by particulate irritants ie/ asbestos

affects distance (scar tissue build up) and partial pressure gradient (decreased in compliance)

Question 20

pulmonary edema

Answer 20

fluid in interstitial space increases diffusion distance. Arterial PCO2 may be normal due to higher CO2 solubility in water

increase in interstitial fluid is often a result of heart failure

affects distance in fick’s law

Question 21

name the four pathological conditions that cause hypoxia

Answer 21

emphysema
astma
fibrotic lung disease
pulmonary edema

Question 22

what happens at equilibrium to partial pressures

Answer 22

they are equal

Question 23

what is more soluble O2 or CO2

Answer 23

CO2

Question 23

what happens to concentrations at equilibrium

Answer 23

they are unlikely to be equal

Question 24

Hemoglobin

Answer 24

found in rbs reversibly binds to O2 - unbuckling when o2 is low and loads up when high each hb molecule has the ability to bind to 4 o2 molecules

Question 25

total O2 in blood equation

Answer 25

amount dissolved in plasma + amount bound to hemoglobin

Question 26

Po2 value at the resting cell

Answer 26

40 mm Hg (unloads at tissure)

Question 27

Po2 value at alveoli

Answer 27

100 mm Hg (loads at lungs)

Question 28

why does the O2-Hb dissociation curve plateau

Answer 28

all hemoglobin will all eventually be bound to O2

Question 29

what would happen if oxygen binding to hemoglobin was not cooperative

Answer 29

hemoglobin would just hang onto oxygen curve would be hyperbolic

Question 30

what happens to affinity when pH is low

Answer 30

reduces oxygens carrying capacity of Hb oxygen dissociates more at the tissues

Question 31

what happens when PCO2 is increased

Answer 31

oxygen dissociates more at tissues

Question 32

O2 transport in blood

Answer 32

98 percent bound to hemoglobin - then will transport to cells, HbO2->Hb+O2, oxygen then dissolved in plasma and then used in cellular respiration 2 percent dissolved in tissues - will just stay dissolved in plasma In lungs: PO2 is high, drives oxygen exchange into plasma, high plasma PO2 drives oxygen binding to Hb. forward reaction dominates In tissues: PO2 is low, drives oxygen exchange out of plasma, low plasma PO2 drives O2 release from hemoglobin, reverse rxn dominates

Question 33

CO2 transport in blood

Answer 33

7% dissolved gas in plasma 23% as HbCO2, not binding just hitches a ride, gets transported to the lungs then CO2 diffuses out to the plasma and then alveolus 70% as bicarbonate dissolved in plasma CO2 + H2O <---> H2CO3(carbonic acid) <--->H+ + HCO3- carbonic anhydrase enzyme H+ buffered by Hb in rbcs

Question 34

respiratory acidosis

Answer 34

excess H+ present

Question 35

central chemoreceptors

Answer 35

located in medulla increased activity in response to increase PCO2 resulting in increased rate and depth of respiration

Question 36

peripheral chemoreceptors

Answer 36

located in carotid sinuses and aortic arch increased activity in response to increased PCO2 and H+ concentration or decreased PCO2 afferent signals back to respiratory control center of medulla oblongaae, resulting in increased rate and depth of respiration