Physiology 1 + 2

Question 1

4 steps of respiration?

Answer 1

Ventilation = mechanical process of moving gas in and out of the lungs

Gas exchange between alveoli + blood = exchange of O2 and CO2 between air in alveoli + blood in pulmonary capillaries

Gas transport in blood = binding and transport of O2 and CO2 in circulating blood

Gas exchange at tissue level = exchange of O2 and CO2 between the blood in the systemic capillaries and the body cells

Question 2

Lung movements?

Answer 2

Inspiration = active process

Resting expiration = passive

Question 3

Opposing forces acting on the lungs?

Answer 3

Question 4

how do lungs adhere to the chest wall?

Answer 4

Transmural pressure gradient - sub-atmospheric intrapleural pressure (intrathoracic) creates transmural pressure gradient

Intrapleural fluid cohesiveness - water molecules in intrapleural fluid resist being pulled apart (so pleural membranes stick together)

Question 5

3 pressures in ventilation

Answer 5

…

Question 6

pneumothorax?

effect on lung forces?

Answer 6

pneumothorax = air in the pleural space

abolishes transmural pressure gradient –> lung collapse

Question 7

Boyle’s law?

Answer 7

As volume of gas increases, pressure exerted by the gas decreases

i.e. before inspiration, intra-alveolar pressure is equivalent to atmospheric pressure
inspiration makes intra-alveolar pressure fall and become less than atmospheric

Question 8

changes in intra-alveolar and intra-pleural pressures during respiratory cycle?

Answer 8

Question 9

inspiration active or passive?

Muscles?

Answer 9

active

diaphragm - increases vertically

external interocostal muscles - lift ribs and move out sternum “bucket handle mechanism”

Question 10

expiration active or passive?

describe process

Answer 10

normally passive

chest wall + lungs recoil due to elastic properties
Lung recoil = intra-alveolar pressure rises
Because air molecules become contained in smaller volume (Boyle’s Law)
Air then leaves lungs down pressure gradient

Question 11

what causes lungs to recoil during expiration?

Answer 11

1 - elastic connective tissue in lungs

2 - alveolar surface tension (most important)

Question 12

what is alveolar surface tension?

Answer 12

attraction between water molecules –> produces force which resists stretching of the lungs

if alveoli were lined wit water alone (no surfactant) the alveoli would collapse

Question 13

what reduces alveolar surface tension?

Answer 13

surfactant

Question 14

which alveoli have higher tendency to collapse?

what is surfactant?

Answer 14

smaller alveoli (according to Law of LaPlace)

surfactant is mix of lipids + proteins secreted by type II alveoli

Question 15

respiratory distress syndrome of the new born caused by?

Answer 15

developing foetal lungs unable to synthesise surfactant until late in pregnancy

premature babies may not have enough pulmonary surfactant

Question 16

other than surfactant, what is another factor that keeps alveoli open?

Answer 16

Alveolar interdependence

if one alveolus collapses –> surrounding alveoli are stretched and then recoil, expanding the collapsed alveolus to open it

Question 17

Major inspiratory muscles?
Accessory muscles of inspiration?
Muscles of active expiration?

Answer 17

Major = diaphragm + external intercostal

Accessory = SCM, scalenus + pectoral

Active expiration = abdominal muscles + internal intercostal

Question 18

What lung capacities can be measured with spirometry?

Answer 18

Tidal volume, inspiratory reserve volume, expiratory reserve volume, inspiratory capacity + vital capacity

cannot be measured = functional residual capacity + total lung capacity

Question 19

Lung volumes?

Answer 19

Question 20

Lung capacities?

Answer 20

Question 21

Total lung capacity?

Sum?

Answer 21

Maximum volume of air the lungs can hold at end of maximum inspiration

TLC = vital capacity + residual volume
average value approx 5.7L (4.5 + 1.2) but varies between individuals

Question 22

Residual volume increases when?

Answer 22

Residual volume increases when the elastic recoil of the lungs is lost e.g. in emphysema

Question 23

Volume time curve allows you to determine?

Answer 23

Forced Vital Capacity (FVC): maximum volume that can be forcibly
Expelled from the lungs following a maximum inspiration

Forced Expiratory Volume in one second (FEV1): volume of air that can be expired during the first second of expiration in an FVC (Forced Vital Capacity) determination

Question 24

FEV1/FVC ratio normal?
Asthma?
COPD?
Obstructive?

Answer 24

Normal = >75%
Asthma = <75%, reversible in response to bronchodilator
COPD = <70% post-bronchodilator

Obstructive = >75%

Question 25

Answer 25

…

Question 26

Primary determinant of airway resistance?

What controls this?

Answer 26

Radius of airway

Parasympathetic = bronchoconstriction
Sympathetic = bronchodilator

Question 27

Intrapleural pressure inspiration?

Expiration?

Answer 27

Inspiration = falls
Expiration = rises

Question 28

Dynamic airway compression?

When is it worst?

Answer 28

Dynamic airway compression makes active expiration to be more difficult in patients with airway obstruction

Causes no problems in normal people

Problem becomes worse if the patient also have decreased elastic recoil of lungs (e.g. a patient with emphysema and obstructed airway caused by COPD)

Question 29

Peak flow meter function?
Used for?
How is it measured?
Value?

Answer 29

Gives estimate of peak flow rate (assesses airway function)

Useful in asthma or COPD

Measured by short-sharp blow into peak flow meter - best of 3 attempts taken

Peak flow rate varies with age + height

Question 30

Pulmonary compliance?

Answer 30

During inspiration, lungs are stretched
Compliance = measure of effort that goes into stretching the lungs

The less compliant lungs are, the more work is required to produce given degree of inflation

Question 31

Pulmonary compliance decreased by?
What does this cause?

Spirometry?

Answer 31

Pulmonary compliance decreased by = pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant

Decreased pulmonary compliance means greater change in pressure is needed to produce a given change in volume - this causes shortness of breath especially on exertion

Decreased pulmonary compliance may cause a restrictive pattern of lung volumes in spirometry

Question 32

Increased pulmonary compliance occurs when?
Leads to?
What factor affects compliance?

Answer 32

Compliance may become abnormally increased if the elastic recoil of the lungs is lost i.e. emphysema

Patients have to work harder to get the air out of the lungs – hyperinflation of lungs

Compliance increases with increasing age

Question 33

Situations where work of breathing is increased?

Answer 33

When pulmonary compliance is decreased

When airway resistance is increased

When elastic recoil is decreased

When there is a need for increased ventilation