resp physiology

Question 1

what is internal respiration

Answer 1

the intracellular mechanism which consumes O2 and produces CO2

Question 2

what is external respiration

Answer 2

sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of our body

Question 3

4 steps of external respiration

Answer 3

ventilation
gas exchange
gas transport in blood
gas exchange

Question 4

what is ventilation

Answer 4

the mechanical process of moving air between the atmosphere and alveolar sacs

Question 5

what are the forces keeping the alveoli open

Answer 5

• transmural pressure gradient
• pulmonary surfactant
• alveolar interdependence

Question 6

what are the elastic forces promoting alveolar collapse

Answer 6

• elastic recoil of lungs and chest wall
• alveolar surface tension

Question 7

describe intra-alveolar pressure and atmospheric pressure

Answer 7

they are the same

• however the intra-pleural pressure is slightly less

Question 8

what is something that can abolish transmural pressure gradient

Answer 8

a pneumothorax

• this is due to how Air enters the pleural space from outside or from the lungs

Question 9

The intra-alveolar pressure must become less than atmospheric pressure for air to flow into the lungs during inspiration. How is this achieved?

Answer 9

the lungs expand during inspiration and this makes the intra-alveolar pressure fall and become less that atmospheric

• this is explained by Boyles law (as the volume of a gas increases the pressure decreases)

Question 10

major inspiratory muscle

Answer 10

diaphragm
external intercostal muscle

Question 11

expiratory muscles

Answer 11

Abdominal muscles and
internal intercostal muscles

Question 12

What causes the lungs to recoil during expiration?

Answer 12

Elastic connective tissue in the lungs
alveolar surface tension

Question 13

describe alveolar surface tension

Answer 13

Attraction between water molecules at liquid air interface

In the alveoli this produces a force which resists the stretching of the lungs

If the alveoli were lined with water alone the surface tension would be too strong so the alveoli would collapse

It lowers alveolar surface tension by interspersing between the water molecules lining the alveoli

Question 14

accessory muscles of inspiration

Answer 14

Sternocleidomastoid, scalenus, pectoral

Question 15

tidal volume

Answer 15

Volume of air entering or leaving lungs during a single breath

Question 16

inspiratory reserve volume

Answer 16

Extra volume of air that can be maximally inspired over and above the typical resting tidal volume

Question 17

expiratory reserve volume

Answer 17

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume

Question 18

residual volume

Answer 18

Minimum volume of air remaining in the lungs even after a maximal expiration

Question 19

inspiratory capacity

Answer 19

Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + TV)

Question 20

functional residual capacity

Answer 20

Volume of air in lungs at end of normal passive expiration (FRC = ERV + RV)

Question 21

total lung capacity

Answer 21

Total volume of air the lungs can hold
(TLC = VC + RV)

Question 22

vital capacity

Answer 22

Maximum volume of air that can be moved out during a single breath following a maximal inspiration (VC = IRV + TV + ERV)

Question 23

what is the Primary determinant of airway resistance

Answer 23

the radius of the conducting airway

Question 24

Parasympathetic stimulation causes

Answer 24

bronchoconstriction

Question 25

Sympathetic stimulation causes

Answer 25

bronchodilatation

Question 26

what is compliance

Answer 26

a measure of effort that has to go into stretching or distending the lungs

• change in lung volume per unit change in transmural pressure gradient across the lung wall (i.e difference between intra-alveolar and intrapleural pressure)
• The less compliant the lungs are, the more work is required to produce a given degree of inflation

Question 27

decreased compliance may cause

Answer 27

a restrive pattern

Question 28

when may compliance be abnormally increases

Answer 28

if the elastic recoil of the lungs is lost

eg emphysema

Question 29

pulmonary ventilation =

Answer 29

tidal volume x resp rate

Question 30

why is alveolar ventilation less that pulmonary ventilation

Answer 30

due to anatomical dead space

• this is where there is good perfusion but poor ventilation

Question 31

Alveolar Ventilation =

Answer 31

(Tidal Volume – Dead Space) x Respiratory Rate

Question 32

what does the transfer of gases between the body and atmosphere depend on

Answer 32

ventilation and perfusion

Question 33

alveolar dead space =

Answer 33

Ventilated alveoli which are not adequately perfused with blood

Question 34

the physiological dead space =

Answer 34

the anatomical dead space + the alveolar dead space

Question 35

factors affecting the rate of gas exchange across alveolar membrane

Answer 35

• Partial Pressure Gradient of O2 and CO2
• Diffusion Coefficient for O2 and CO2
• Surface Area of Alveolar Membrane
• Thickness of Alveolar Membrane

Question 36

what is the partial pressure of a gas

Answer 36

The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature.

Question 37

the diffusion coefficient for CO2 is

Answer 37

20x more than for O2

Question 38

what do Type I alveolar cells do

Answer 38

line the alveoli