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MSAP > Week 4 - Physiology > Flashcards

Week 4 - Physiology Flashcards

1
Q

Pulmonary mechanics is similar to

A

heart mechanics - gas flow instead of blood flow

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2
Q

Respiration is used to primarily control

A

CO2 - because it’s super important to control blood pH

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3
Q

define Gauge Scale

A

Any scale of measurement the has an arbitrary 0 other than the absolute

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4
Q

True or False - If something measures twice as much on a gauge scale, then it is twice as much

A

False - because zero on a gauge scale is not absolute zero

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5
Q

what are the two gauge scales used in pulmonary physiology?

A

mmHg and cmH2O

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6
Q

What is defined as 0 on the two gauge scales used in pulmonary physiology

A

atmospheric pressure = 0

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7
Q

A negative pressure indicates what?

A

that the pressure is less than atmospheric

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8
Q

Define the following pressures: PB, PA, PP

A

PB - bariatric (atmospheric) pressure… always 0, it’s the arbitrary defined 0 of the gauge scale
PA - pressure in the alveoli. Is also 0 because it is connected to PB
PP - Pressure of the pleural space

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9
Q

The pariaetal and plural membrane lubricate the lungs for what purpose?

A

to allow the membranes to easily slide along the lungs as the lungs are constantly expanding and contracting

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10
Q

What is the typical pressure in the PP (pleural space) and why

A

-5cmH2O, because the lungs and thorax are both elastic structures trying to pull away from the pleural space, thus decreasing pressure

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11
Q

What happens to each pressure as muscles expand the thoracic space

A

1) thoracic cavity increases in size, causing pleural space to expand
2) PP changes from -5 cmH2O to -10 cmH2O
3) PT increases from 5 to 10, causing slight negative in alveoli as they expand
4) air from outside flows from 0 to the slight negative in the alveoli, filling lungs with air.

Exhaling is the exact same order of steps, but opposite direction of movement and pressures

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12
Q

What formula is used to determine the pressure differential across the alveolar wall (PT)

A

PT=PA-PP

ie, at rest Pa=0 PP=-5 -> 0-(-5)=5

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13
Q

What drives inspiration and expiration?

A

PP

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14
Q

define lung compliance ( C )

A

C=ΔV/ΔP
V=volume
P=pressure

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15
Q

A normal graph of the relationship between pressure and volume in the longs described in terms of compliance follows what slope?

A

low compliance -> high compliance -> low compliance

low slope -> steep slope -> low slope

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16
Q

With Fibrosis, what would you expect to happen to the lung compliance curve

A

lower compliance

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17
Q

In a high compliance lung you need (more/less) pressure to reach the same volume as a normal compliance lung.

A

less

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18
Q

Emphysema is associated with what kind of lung compliance

A

high compliance

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19
Q

Rank the following in order of most to least pressure needed to achieve the same lung volume: normal compliance, low compliance, high compliance

A

low compliance -> normal -> high compliance

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20
Q

What are the partial pressures of gases in the atmosphere?

A

PO2=160mmHg

PCO2= 0 (used to define the partial pressure gauge scale)

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21
Q

Assuming constant ventilation of the alveoli, what are the gas partial pressures in the alveoli?

A 
P02 = 100 mmHg
PCO2 = 40 mmHg
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22
Q

True or false, given constant breathing, the partial gas pressures in arterial blood are the same is in the alveoli

A

True

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23
Q

what are the partial pressures of gasses in venous blood

A 
PO2 = 40 mmHg
PCO2 = 45 mmHg
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24
Q

What three things drive the rate of gas flow?

A
  • partial pressure differential
  • surface area
  • diffusion distance
25
Q

What determines the direction of the flow of gases

A

gas partial pressure differentials (higher pressure to lower pressure)

26
Q

True or false, concentration of gases affects the direction in which a gas will diffuse

A

false

27
Q

Increasing the rate of ventilation has what effect on the gas partial pressures in the alveolus?

A

PO2 increases

PCO2 decreases

28
Q

Decreasing the rate of ventilation has what effect on the gas partial pressures in the alveolus?

A

PO2 decreases

PCO2 increases

29
Q

What controls the gas partial pressures in the alveolus

A

the rate of ventilation/breathing

30
Q

Define Henry’s Law

A

the amount of gas in a solution is equal to it’s partial pressure of the gas outside the solution times it’s solubility.

31
Q

Which gas has higher solubility, CO2 or O2?

A

CO2

O2 is only 0.003 mLO2/dLblood/mmHg

32
Q

Why is hemoglobin so important?

A

Blood can only carry 0.3mL O2 per dL of blood, however the body needs 200mL O2 per minute…

33
Q

what is the storage capacity of hemoglobin?

A

1 g of Hb can store 1.36mL O2

34
Q

How much Hb does a typical young male have? How much O2 total is in his blood?

A

15 g Hb per dL blood

  1. 36mL O2/gHb x 15gHb/dL blood = 20.4mL O2/dL blood
  2. 4+0.3 (from plasma)=20.7mL O2/dL blood
35
Q

Why is CO2 so important?

A

CO2+H2O H+ + HCO3-

controlling the level of CO2 is the main method of controlling blood pH

36
Q

Explain how bicarbonate ends up in the plasma

A

CO2 forms H+ and HCO3+ when dissolved in water, however red blood cells use carbonicanhydrase to rapidly dissociate all CO2, and then the cells expel only CO3+. At the lungs it is reformed, but during transport red blood cells insure CO2 is carried as CO3+ in the blood

37
Q

Controlling ventilation controls CO2 levels which in turn controls ____

A

blood pH

38
Q

Increased ventilation results in acidosis/alkalosis

A

alkalosis

39
Q

Decreased ventilation results in acidosis/alkalosis

A

acidosis

40
Q

What is the importance of increased H+ production resulting from breakdown of CO2?

A

H+ is used to dissociate/release O2 from hemoglobin allowing O2 to be distributed to cells

41
Q

Why is such a high partial pressure of O2 in the lungs important?

A

As PO2 increases the saturation of O2 binding sites that are used up rapidly increases, thus maximizing the O2 content of the blood.

42
Q

What factors decrease O2 affinity for Hb (right shift in Hb Dissociation Curve)

A

decrease in pH
increase in temperature
increase in CO2

43
Q

What is another name for a right shift in the Hb Dissociation Curve as a result of CO2, and why is this concept important?

A

Bohr effect.
The increase in the presence of CO2 helps drive the release of O2 from Hb, allowing it to be released to tissues and cells.

44
Q

Describe the differences in the values for the formula Q=ΔP/R in systemic vs pulmonary

A 
pulminary:
Q=5
ΔP=25-5=20
therefor R=4
Systemic:
Q=5
ΔP=100-0=100
therefore R=20
45
Q

Why is low resistance in pulmonary circulation important?

A

low resistance allows lower driving pressure to maintain flow of blood equal to systemic circulation, thus helping prevent edema in the lungs.

46
Q

Which organ is the only organ to receive close to 100% of cardiac output (in fact, it’s often rounded to 100%)?

A

the lungs, which is why it is a prime location to modify the blood as with harmones, and very important for angiotensin/renin system.

47
Q

Where are receptors located to detect the presence of O2, and what are they called?

A

in the carotid and aortic arch. they are called peripheral chemoreceptors

48
Q

At what PO2 do the O2 receptors signal the brain to increase ventilation?

A

> 60 mmHg of O2

49
Q

what gas does the body monitor to determine minute to minute breathing rate

A

CO2

50
Q

True of False: As with O2, the body has direct receptors for detecting the presence of CO2

A

False

51
Q

How does the body determine CO2 levels?

A

Central Chemoreceptors: detect H+ in CSF

52
Q

What allows measure of H+ in CSF to be an accurate measure of CO2

A

The blood brain barrier. It does not allow H+ to cross, but does allow CO2 to cross, which can then dissociate to H+ and CO3- on the other side

53
Q

CO2 in the blood is loosely/tightly regulated at 40mmHg

A

very tightly, it is one of the only substance your body tightly regulates and will almost always be seen right at 40mmHg

54
Q

Why is CO2 preferred for regulation over O2

A

O2 is rarely ever a limiting factor

55
Q

Besides O2, what else does Peripheral Chemoreceptors detect?

A

Significantly high levels of arterial H+ (metabolic acidosis)

56
Q

What happens in Emphysema?

A

breakdown of alveolar walls

  • decrease surface area
  • decrease cross sectional area (increases resistance)
  • increase in lung compliance due to loss of elasticity from loss of structure
57
Q

The increased resistance in pulmonary circulation results in what for the heart, and what for the lungs?

A

increase work/load on the heart, resulting in heart problems

increase filtration in the lungs resulting in edema

58
Q

In emphysema is is easy/difficult to inspire and easy/difficult to expire

A

easy inspire/difficult expire

59
Q

Is emphysema a restrictive or obstructive disease?

A

obstructive - the destruction of alveolar walls results in less pull keeping airways open, so airways become floppy and prone to collapse (obstruction)

MSAP (6 decks)

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