Lecture 23 - Respiratory Physiology #2

Question 1

What is the amount of air breathed in and out during one normal breath (one normal respiratory cycle)

Answer 1

Tidal volume (VT)

Question 2

what is the volume of air that remains in the lungs after a complete and forceful expiration?

Answer 2

Residual Volume (RV)

Question 3

What is the amount of air that you can inspire beyond what you breathe in during a normal breath?

Answer 3

inspiratory reserve volume

Question 4

what is the amount of air you can expire beyond what you breathe out during a normal breath?

Answer 4

expiratory reserve volume

Question 5

what is the maximum amount of air that can be inspired after the maximum amount of air has been expired (the most that you can breathe in and out with minimal effort)

Answer 5

vital capacity

Question 6

vital capacity + residual volume = ?

Answer 6

total lung capacity

Question 7

residual volume + expiratory reserve volume = ?

Answer 7

functional residual capacity

Question 8

the amount of air in the lung after a normal expiration is known as:

Answer 8

the functional residual capacity. it is the lung volume that occurs when the chest wall and lung are in equilibrium

Question 9

T or F: energy is used during breathing

Answer 9

True! Energy is needed to overcome both contractile forces of the lungs, and the resistance to airflow found in the respiratory system

Question 10

what is compliance?

Answer 10

It is a measure of distensibility of the lung, and is determined by measuring the change in lung volume as a result of a change in pressure

Question 11

in the mid-range of pressure, compliance is:

Answer 11

high, as the change in volume is large for a given change in pressure

Question 12

at high pressures (for example, at the end of inspiration) compliance is:

Answer 12

low, as the lungs are less distensible

Question 13

the term describing the attractive forces between atoms/molecules is called:

Answer 13

surface tension

Question 14

alveolar surface tension can be calculated by what equation?

Answer 14

P = 2T/r, where:
P is the pressure inside the alveolus
T is the tension on the inner surface
r is the internal radius of the alveolus

Question 15

When the radius of an alveolus is small, you need ____ pressure to overcome the surface tension in order to expand the alveolus

Answer 15

MORE.

Question 16

the substance that reduces the number of water molecules that can attract each other, and therefore reduces the work required to breathe, is called:

Answer 16

surfactant

Question 17

pulmonary surfactant is synthesized by:

Answer 17

type II alveolar epithelial cells (secretory cells)

Question 18

what is the percentage of lipid to protein in pulmonary surfactant?

Answer 18

70% lipid
30% protein

Question 19

at the end of expiration, the alveolus is what size? How does this effect the surfactant?

Answer 19

the alveolus is at its smallest size (r is low), and therefore the surfactant becomes more concentrated on the surface. this greatly reduces the surface tension (T)

Question 20

what are two functions of surfactant at the end of expiration?

Answer 20

1. it counteracts the effects of the small radius, so that the pressure at the start of inspiration is not too high to open
2. it reduces the surface tension, which stabilizese the alveolus so that when it is small, the lung doesn’t collapse

Question 21

at the end of inspiration, what size is the alveolus? What, in turn, happens to the surface tension?

Answer 21

alveolus is at its largest size. as a result, surfactant spreads out and becomes less concentrated, and surface tension (T) increases.

Question 22

How does increased surface tension aid in the end of inspiration?

Answer 22

It assists the elastin and collagen fibers by creating an upper limit to the expansion of the lungs, while also providing some recoil so that expiration can be a passive process

Question 23

what is the equation for airway resistance?

Answer 23

8nl/(pi)r^4,

where:
n = viscosity of the fluid
l = length of tube
r = radius of the tube

Question 24

what has the greatest effect on the resistance to air flow?

Answer 24

airway diameter. this is because radius is to the power of four in the denominator of poisuilles law, meaning that if the radius is halved, the force must increase by 16x to maintain constant flow

Question 25

The largest resistance to airflow occurs at which branches?

Answer 25

Branches 4 and 5. This is due to the turbulence as the branches first divide

Question 26

Why does airway resistance go down if the radius of the airways gets progressively smaller?

Answer 26

while the diameter of each individual tube gets smaller and smaller with each bifarcation, the total diameter of all the airways increases exponentially

Question 27

Which has lower resistance to airflow: the respiratory zone, or the conducting zone?

Answer 27

the respiratory zone, which makes it easier to breathe

Question 28

What are the three gas laws?

Answer 28

Volume = constant / Pressure

Volume = constant x temperature

dissolved amount of a gas = pressure x solubility coefficient

Question 29

the pressure exerted by a specific gas when it is in a mixture of gases is known as:

Answer 29

partial pressure

Question 30

which law states that the pressure exerted by one gas is independent of the pressure exerted by other gases, and that the sum of all individual gas pressures is equal to the total gas pressure?

Answer 30

Daltons Law

Question 31

how do you calculate partial pressure (P) of a gas?

Answer 31

fractional concentration (%) of the gas x the total gas pressure

Question 32

What are the notations for arterial, venous, and alveolar pressures of a gas?

Answer 32

Pa = arterial pressure

Pv = venous pressure

PA = alveolar pressure

Question 33

True or False: if compartment A has a higher partial pressure of oxygen than compartment B, but the total gas pressure of A is lower than B, oxygen will move against its concentration gradient so that the total gas pressures of A and B reach equilibrium

Answer 33

False. regardless of the total pressure of a gas mixture, individual gases diffuse in response to their own gradients (from areas of high partial pressure to areas of low partial pressure)

Question 34

Diffusion across a membrane follows what law?

Answer 34

Fick’s law:

Vgas = A x D x (P1 -P2)/T, where:

A = surface area of the membrane
D = the diffusion coefficient for the gas
P1 and P2 = partial pressures on each side of the membrane
T = thickness of the membrane

Question 35

How can the PO2 be so high as a driving force, while PCO2 remains low?

Answer 35

CO2 is soluble in water, while O2 is not as soluble.

Question 36

For optimal gas exchange, surface area should be:

Answer 36

large

Question 37

For optimal gas exchange, the diffusion coefficient should be:

Answer 37

fast

Question 38

For optimal gas exchange, the difference between the two partial pressures should be:

Answer 38

large

Question 39

For optimal gas exchange, the thickness of the membrane between the two partial pressures should be:

Answer 39

thin