Respiratory System and Mechanics of Breathing II

Question 1

PTotal =

Answer 1

Pelastic + Presistive = V/C + V(dot)R

Question 2

Pulmonary Resistance (R)
Composed of:

Answer 2

• frictional resistance of lung & chest wall tissue (~20%)
• airways resistance (~80%)

Question 3

The movement of fluid (i.e. air) flowing through a rigid,

smooth bore tube is governed by

Answer 3

Poiseuille’s Law:

Question 4

The total airway resistance to flow is the sum of all

Answer 4

the
resistances of the nose and mouth (a substantial portion
of the total) and of the 23 generations of the
tracheobronchial tree.

Question 5

• Airway resistance is from the friction between

Answer 5

gas

molecules and between gas molecules and the walls.

Question 6

• Airway resistance is important (~80%) and makes the

sliding of

Answer 6

lung tissue over each other (viscous tissue

resistance, ~20%) a minor issue.

Question 7

Turbulent flow requires a much greater

Answer 7

driving pressure

Question 8

• Doubling the length (l) of

the airways doubles the

Answer 8

airway resistance.

Question 9

• But halving the radius (r)

increases the resistance by

Answer 9

sixteen-fold.

Question 10

Poiseuille’s Law

Answer 10

• Gives the relationship for laminar flow in a cylindrical tube.
• It states that the rate of flow is due to the difference in pressure (DP) between the two ends:
• i.e. Flow is proportional to DP.

Question 11

Intermediate sized

airways contribute

Answer 11

most

of the total resistance.

Question 12

• Total cross-sectional

area increases towards

Answer 12

the periphery, whereas
total airflow is
constant.

Question 13

• Flow is therefore more

laminar in the

Answer 13

small

airways.

Question 14

Flow is:
• effort dependent at
• effort independent at

Answer 14

high lung volumes.

low lung volumes.

Question 15

Work is proportional to ΔP x ΔV
The work of inspiration consists of three different
fractions:

Answer 15

(i) compliance work, or elastic work i.e. that required
to expand the lungs against elastic forces (recoil).
(ii) tissue resistance work, i.e. that required to
overcome the viscosity of the lung and chest wall
structures.
(iii) airway resistance work, i.e. that required to move
air through the airways into the lungs.

Question 16

0AECD0 Insp. work done overcoming

Answer 16

elastic forces.

Question 17

ABCEA Insp. work done overcoming

Answer 17

viscous (airway + tissue) resistance.

Question 18

AECFA Work done on expiration to overcome

Answer 18

airway (+ tissue) resistance.

Question 19

Emphysema

Answer 19

destruction of lung tissue
around alveoli makes them
collapse on expiration. creating larger air spaces instead of many small ones.

Question 20

Bronchitis

Answer 20

Increased mucous buildup in

the airways.

Question 21

Obstructive disease

e.g.

Answer 21

Resistive work greatly increased (ABCEA) insp
COPD (i.e. emphysema and bronchitis.)
Obstruct airways, resulting in increased work of breathing especially during
expiration.

Question 22

Restrictive disease

e.g.

Answer 22

Elastic work increased (0AECD0)
fibrosis, pulmonary congestion.
Restrict lung expansion, resulting in a decreased lung volume, an
increased work of breathing, and inadequate ventilation and/or oxygenation.

Question 23

The Work of Breathing
Rapid shallow breathing ¯
• Slow deep breathing ¯

Answer 23

decr elastic work but ­­incr frictional (viscous) work.
decr frictional work but ­­incr elastic
work.

Question 24

During INCREASED ventilation to levels of ~50 L min-1:

Total cost of breathing =

Answer 24

total VO2 - resting VO2

Question 25

Control of breathing must:
• Establish -
• Match -

Answer 25

the automatic rhythm for contraction of
respiratory muscles (rate and volume).
rhythm to metabolic demands, varying
mechanical conditions, & episodic non-ventilatory
behaviours (talking, eating etc).

Question 26

Respiratory control is an example of a

______________ system

Answer 26

“negative feedback”

Question 27

Control of Breathing

Reflexes from:

Answer 27

Lungs
Airways
CV system
Muscles & joints
Skin
Arterial
chemoreceptors
Central
chemoreceptors

Question 28

• PaCO2 normally _____

controlled.

Answer 28

tightly

Question 29

______chemoreceptors provide most of stimulus with
contribution from __________
chemoreceptors more rapid

Answer 29

Central

peripheral

Question 30

Response magnified when PaO2 is

Answer 30

lowered.

Question 31

With Exercise:
Increases in:
Whereas ____ remains normal until
very high exercise level.

Answer 31

VT, fR,VE

PaO2

Question 32

Neural control of ventilation
3 resp control areas:
All located in?

Answer 32

1. Rhythmicity Area
2. Apeunistic Area
3. Pneumotaxic Area
   BRAINSTEM

Question 33

1. Rhythmicity Area
   Where?
   Inspiratory cells stimulate:
   Expiratory cells stimulate:

Answer 33

The rhythmicity Area:
medulla oblongata brainstem
Inspiratory and expiratory portions.
Inspiratory- stimulate phrenic and intercostall nerves. Expiratory cells stimlate lower spinal and intercostal nerves

Question 34

2. Apeunistic Area
   Where?
   stimulates ?

Answer 34

pons of Brain stem

stimulates inspiratory cells of rhythmicity area and promotes insp.

Question 35

3. Pneumotaxic Area
   Where?
   stimulates ?

Answer 35

Upper Pons

Inhibitory effect of apneustic area and inhibts insp. During excercise promotes exp

Question 36

3 Mechanisms that control of ventilation

Answer 36

Nervous
Voluntary
Chemical

Question 37

Voluntry control of ventilation
where?
what?

Answer 37

cerebral cortex
limited control
can incr of decr rate and tidal vol.
singing excercise etc

Question 38

Central chemoreceptors
where
how

Answer 38

medulla oblaongata brain stem
activated by changes in chemical composition of cerebral spinofluid
Directly stimulate rhythymicity centre

Question 39

peripheral chemoreceptors
where
how

Answer 39

Aortic arch and carotid arteries

changes in CO2 and PH and O2 in blood

Question 40

Two types of propriocepters

Answer 40

joint propriocepters

stretch receptors

Question 41

joint propriocepters

Answer 41

stimulated by movement of limbs

excite resp centre to incr rate and depth of breath

Question 42

stretch receptors

Answer 42

mechanoreceptors sense stretch/ tension in bronchi. Inhibit insp ( Hering Breur Inflation Reflex)