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Physiology for Pharmacy > Lecture 4: Gas Exchange > Flashcards

Lecture 4: Gas Exchange Flashcards

1
Q

what is pulmonary gas exchange?

A

diffusion of O2 from alveolar air into pulmonary blood

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2
Q

CO2 moves from ____ to ___

A

pulmonary blood to alveolar air

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3
Q

gases difuse down their ___ gradients

A

partial pressure

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4
Q

what is systemic has exchange?

A

excahnge of O2 and Co2 between systemic capillaries and tissue cells

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5
Q

the exchange of O2 and CO2 occurs via ___ diffusion

A

passive

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6
Q

passive diffusion is governed by what 3 laws?

A

dalton, henry, Fick

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7
Q

what is Dalton’s law?

A

the pressure exerted by each gas in a mixture is independent of the pressure exerted by other gases becasue the molecules are so far apart

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8
Q

the pressure of each individiual gas is its ___ pressure

A

partial

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9
Q

the total pressure of the mix of gases is the sum of ____

A

all the partial pressures

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10
Q

what is atmospheric pressure?

A

760mmHg

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11
Q

what is the partial pressure of humidified air? why is it lower than the atmospheric pressure?

A

500mmHg; because the partial pressure of water has to be subtracted

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12
Q

____ law states that the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of the gas in which the liquid is in equilibrium

A

Henry’s

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13
Q

what will happen to the difusion rate as long as Po2 in gas phase is higher than the Po2 in liquid?

A

there will be a net difusion of O2 into liquid

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14
Q

the concetration of a gas is equal to the ___ and ___ of the gas

A

pressure and solubility

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15
Q

the more soluble a gas, the ____ its concentration will be at any given pressure

A

greater

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16
Q

transfer of gases across cell membranes and capillary walls occurs by diffusion, described by _____’s law

A

Fick

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17
Q

Fick’s Law depends on what variables?

A

surface area, diffusion coeficient, partial pressure difference, thickness of membrane

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18
Q

what are 3 important parameters for efficient gas exchange in the lungs?

A
  1. partial pressure difference
  2. large surface area
  3. disatnce needs to be small
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19
Q

what is the driving force of efficient gas exchange according to Fick’s Law?

A

partial pressure difference

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20
Q

the diffusion coeficient for CO2 is ~ ____x greater than for O2

A

20

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21
Q

when diffusion is decreased, is hypoxia or hypercapnia likely to happen first?

A

hypoxia

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22
Q

the rate of O2 diffusing out of the alveoli is great enough that complete ____ is reached well before the blood reaches the end of the alveolar-capillary exchange unit

A

equilibrium

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23
Q

if there is an abnormal alveolar diffusion barrier, this will impair diffusion and ____ will not be reached

A

equilibrium

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24
Q

give 2 examples of conditions that impair alveolar diffusion, preventing equilibrium being reached

A

fibrosis and pulmonary edema

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25
Q

when an alveolar-diffusion barrier such as fibrosis is present it is almost impossible to reach equilibrium when the barometric pressure ____

A

drops

26
Q

what are the 2 main parts of hemoglobin?

A
  1. globin

2. heme

27
Q

what is the structure of globin?

A

protein made of 4 polypeptide chains

28
Q

what is contained in the heme? what is its function>

A

Fe, carries O2

29
Q

how many O2 can be bound to 1 hemoglobin?

A

4

30
Q

O2 is not very soluble in water, and therefore also not in our blood, what is used to allow its transport in the body?

A

hemoglobin

31
Q

as Po2 increases, more O2 associates with ___

A

hemoglobin

32
Q

the oxygen-hemoglobin dissociation curve has what shape?

A

sigmoidal

33
Q

the oxygen hemoglobin dissociation curve is an example of ____ cooperativity

A

positive

34
Q

between 60-100mmHg the O2 hemoglobin curve hits a plateau. The hemoglobin is ___% saturated with O2. whay does this plateau exist?

A

90; safety feature, plateau allows pO2 to drop significantly before the effects are truly felt by hemoglobin

35
Q

the binding of O2 to hemoglobin is both ___ and fully ___

A

rapid; reversible

36
Q

what is P50 on the o2 hem curve?

A

Po2 where Hb is 50% saturated by O2

37
Q

changes in P50 reflect changes in hb’s ____ for O2

A

affinity

38
Q

an increase in P50 means a ____ in Hbs affinity for O2 and vice versa

A

decrease

39
Q

the binding of the first O2 to Hb causes a ____ that makes it easier for the second O2 to bind and so on

A

conformational change

40
Q

a lower pH causes the affinity of Hb for O2 to ____

A

decrease

41
Q

a high blood Co2 causes the affinity of Hb for O2 to ___

A

decrease

42
Q

high temperature causes the affinity of Hb for O2 to ___

A

decrease

43
Q

addition of BPG/DPG causes the affinity of Hb for O2 to ___

A

decrease

44
Q

the affinity of Hb is often decreased by _____ hydrogen ionproduction

A

increased

45
Q

CO prevents the binding of ___ to ____

A

O2 to Hb

46
Q

CO has a ____x more affinity for Hb than O2

A

250

47
Q

cigarette smokers and those who live close to traffic polution have up to __% of their Hb bound to CO. What is the normal % of Hb boud to CO?

A

10; 1

48
Q

CO poisoning causes the O2 Hb curve to shift in what direction?

A

left

49
Q

CO poisoning _____ the affinity of HB for O2. what is the effect of this?

A

increases; Hb holds onto it and doesnt let it do its job

50
Q

in what 3 ways is CO2 carried in the blood?

A
  1. dissolved
  2. bound to carbamino compounds
  3. in the form of bicarbonate
51
Q

the majority of CO2 is carried in the blood in what form ?

A

bicarbonate ions

52
Q

the enzyme used to make CO2 and H2o into carbonic acid is ____ and is only found in the _____

A

carbonic anhydrase; RBC (not plasma!)

53
Q

as blood picks up more Co2, the bicarbonate ions accumulate inside ____

A

RBC

54
Q

how can bicarbonate exit the RBC?

A

by exchanging for Cl (chloride shift)

55
Q

the ratio of sodium bicarbonate to carbonic acid is ___ . what is this vital to?

A

20 to 1 ; acid base balance

56
Q

as long as the ration remains at 20:1, the pH will remain at

A

7.4

57
Q

there is a balance between HCo3- governed by ___ and PCO2 governed by ___

A

renal excretion; ventilation

58
Q

if a person is hypoventilating or has a lung disease that prevents normal elimination of CO2, there is a ___ in arterial PCO2 and ___ in arterial H+ concentration. This is called respiratory ___

A

increase; increase; acidosis

59
Q

if a person is hyperventilating, there is a ___ in arterial CO2 and a ____ in arterial [h+]. This is called respiratory ___

A

decrease; decrease; alkalosis

60
Q

H+ in the RBC is buffered by ___

A

deoxyhemoglobin

Physiology for Pharmacy (39 decks)

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