Respiration 2 movement of air

Question 1

What does the distensibility of the lungs mean (measure of elasticity)?

Answer 1

The ease with which the lungs and thorax expand during pressure changes

Question 2

How do you measure distensibility?

Answer 2

Change in volume / change in pressure

Question 3

What is the effect on inspiration and expiration when there’s a high or low compliance?

Answer 3

• low compliance = more work required to inspire
• high compliance = often involves more difficulty expiring (loss of elastic recoil)

Question 4

What is the ‘anatomical’ component of elastic recoil in the lungs?

Answer 4

Elastic nature of the cells + extracellular matrix

Question 5

What is the elastic recoil in the lung due to?

Answer 5

Surface tension generated at the air-fluid interface

Question 6

What results in surface tension?

Answer 6

Differences in forces on water molecules at air/water interfaces

Question 7

How are the forces balanced in a gas bubble?

Answer 7

Balance between the pressure exerted by the gas + the surface tension at the gas/water border

Question 8

What is the equation that describes the balance of forces in a gas bubble?

Answer 8

• Laplace’s equation
• P = 2T / r

Question 9

Is surface tension constant or not?

Answer 9

Constant

Question 10

How does the volume of the air sacs in the lungs differ?

Answer 10

Pressure in larger sacs < smaller sacs

Question 11

How does air flow between the alveoli?

Answer 11

• from smaller to larger alveoli
• leads to their collapse

Question 12

How do smaller alveoli overcome collapsing?

Answer 12

Production of surfactant

Question 13

What produces surfactant?

Answer 13

• type II pneumocytes
• composed of a number of lipids + proteins

Question 14

What are the functions of surfactant and how does it do it?

Answer 14

-prevent alveolar collapse - decrease surface tension
-alveolar size regulation - spread of surfactant slows rate of inflation
-increases compliance - lungs can inflate more easily
-prevents oedema - reduces fluid entering alveoli

Question 15

What is anatomical dead space?

Answer 15

Volume of conducting airways

Question 16

What is physiological dead space?

Answer 16

Volume of lungs not participating in gas exchange

Question 17

What is vital capacity?

Answer 17

-fullest inhale followed by fullest exhale, then it’s the volume remaining in the lungs
-from highest peak to next trough

Question 18

What is FEV1?

Answer 18

-forced expiratory volume in 1 second
-amount that’s forcibly exhaled in 1 second

Question 19

What is inspiratory reserve volume?

Answer 19

-breathe in normally, then breath in without breathing out
-from peak of regular breathing to peak of max inhale (highest peak)

Question 20

What is expiratory reserve volume?

Answer 20

-breathe out normally, then breathe out again without breathing in
-from trough of regular breathing to trough of max exhale

Question 21

What is tidal volume on a graph?

Answer 21

From peak to trough of regular breathing

Question 22

What is residual volume on a graph?

Answer 22

From trough of max exhale to 0

Question 23

What is total lung capacity on a graph?

Answer 23

From 0 to peak of max inhale

Question 24

What is inspiratory capacity on a graph?

Answer 24

From trough of regular exhale to peak of max inhale

Question 25

What is functional residual capacity on a graph?

Answer 25

From 0 to trough of regular exhale

Question 26

What is the flow of air into or out of the lungs proportional and inversely proportional to?

Answer 26

-proportional to pressure gradient
-inversely proportional to resistance

Question 27

How do you calculate the flow of air into or out of the lungs?

Answer 27

change in pressure / resistance

Question 28

What law determines the impact of resistance on flow?

Answer 28

Poiseuille’s law

Question 29

What is airway resistance proportional or inversely proportional to?

Answer 29

-proportional to gas viscosity + tube length
-inversely proportional to the 4th power of the radius

Question 30

How do you calculate the airway resistance?

Answer 30

(8 / pi) x [(gas viscosity x length) / r^4]

Question 31

What do small changes in airway diameter have a big impact on?

Answer 31

Resistance + so flow rate

Question 32

How do you calculate total resistance when resistance is in series + parallel?

Answer 32

-in series: Rt = R1 + R2 + R3 + …
-in parallel: 1/Rt = 1/R1 + 1/R2 + 1/R3 + …

Question 33

What factors impact on airway resistance?

Answer 33

-airway diameter
-increased mucus secretion - reduce airway diameter
- oedema - increased fluid retention in lung tissue causes swelling + narrowing of airways
-airway collapse - narrows airway

Question 34

What controls bronchial smooth muscle?

Answer 34

-autonomic nervous system
-humoral factors

Question 35

How does the autonomic nervous system control the bronchial smooth muscle?

Answer 35

-parasympathetic - ACh released from vagus, acts on muscarinic receptors leading to constriction
-sympathetic - release of norepinephrine from nerves - weak agonist leads to dilation

Question 36

How do humoral factors control the bronchial smooth muscle?

Answer 36

-epinephrine circulating in blood - better agonist leads to dilation
-histamine - released during inflammatory processes + leads to constriction