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BPK 205 > gas exchange > Flashcards

gas exchange Flashcards

1
Q

composition of the air we breathe

A

78 percent nitrogen
21 percent oxygen
0.033 percent carbon dioxide

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2
Q

dalton’s law

A

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

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3
Q

total air pressure equation

A

Patm = PN2+PO2+PCO2

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4
Q

total air pressure equation in humid air

A

Patm=PN2+PO2+PCO2+PH20

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5
Q

total partial pressure in dry air equation

A

Pgas= Patm x % of gas in atmosphere

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6
Q

total partial pressure in humid air equation

A

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

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7
Q

gas composition in the atmosphere of O2 and CO2

A

PO2= 160 mm Hg
PCO2= 0.25 mm HG

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8
Q

alveolar partial pressures during normal quiet breathing

A

PO2= 100 mm Hg
PCO2 = 40 mmHg

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9
Q

as alveolar ventilation increases alveolar PO2 _______ and PCO2 ______

A

increases, decreases

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10
Q

explain pulmonary gas exchange and transport

A
  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
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11
Q

what is the rate of diffusion directly proportional to

A

concentration (partial pressure) gradient

AxDx (delta Pgas)/ T^2

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12
Q

partial pressures in venous blood

A

O2: 40 mm Hg
CO2: 46 mm Hg

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13
Q

partial pressures in arterial blood

A

O2: 100 mm Hg
CO2: 40m HG

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14
Q

partial pressures in cells

A

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

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15
Q

what is alveolar gas exchange influenced by

A

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

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16
Q

factors that decrease the amount of oxygen in the blood

A

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

17
Q

emphysema

A

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

18
Q

astma

A

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

affects partial pressure gradient

19
Q

fibrotic lung disease

A

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)

20
Q

pulmonary edema

A

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

21
Q

name the four pathological conditions that cause hypoxia

A

emphysema
astma
fibrotic lung disease
pulmonary edema

22
Q

what happens at equilibrium to partial pressures

A

they are equal

23
Q

what is more soluble O2 or CO2

A

CO2

23
Q

what happens to concentrations at equilibrium

A

they are unlikely to be equal

24
Q

Hemoglobin

A

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

25
Q

total O2 in blood equation

A

amount dissolved in plasma + amount bound to hemoglobin

26
Q

Po2 value at the resting cell

A

40 mm Hg (unloads at tissure)

27
Q

Po2 value at alveoli

A

100 mm Hg (loads at lungs)

28
Q

why does the O2-Hb dissociation curve plateau

A

all hemoglobin will all eventually be bound to O2

29
Q

what would happen if oxygen binding to hemoglobin was not cooperative

A

hemoglobin would just hang onto oxygen
curve would be hyperbolic

30
Q

what happens to affinity when pH is low

A

reduces oxygens carrying capacity of Hb

oxygen dissociates more at the tissues

31
Q

what happens when PCO2 is increased

A

oxygen dissociates more at tissues

32
Q

O2 transport in blood

A

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

33
Q

CO2 transport in blood

A

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

34
Q

respiratory acidosis

A

excess H+ present

35
Q

central chemoreceptors

A

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

36
Q

peripheral chemoreceptors

A

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

BPK 205 (14 decks)

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