Unit VII (38-43) - Respiration

Question 2

What factors cause lung elasticity? Which are most significant?

Answer 2

Tissue elastic forces - 1/3
Fluid-air surface tension forces - 2/3

Question 3

What cells secrete surfactant?

Answer 3

Type II alveolar epithelial cells

Question 4

What is surfactant’s function?

Answer 4

Reduces surface tension of water

Question 5

How does alveolar size affect the pressure caused by surface tension?

Answer 5

Smaller size = greater effect

Question 6

Draw and label a typical spirogram

Answer 6

pg495

Question 7

Describe the innervation of the bronchial tree

Answer 7

SNS
- very little direct innervation
- exposed to systemic Ep/NEp
- NEp has greatest effect on betam receptors => bronchodilation
PNS
- nerve fibres from vagus
secrete acetylcholine => bronchoconstriction

Question 8

How does bronchoconstriction occur in allergic reactions?

Answer 8

Histamine and slow reactive substance of anaphylaxis released by mast cells

Question 9

How is the pulmonary circulation divided?

Answer 9

High pressure low flow - trachea, bronchial tree, supporting tissue of lung
Low pressure high flow - alveolar capillaries

Question 10

How is left atrial pressure estimated?

Answer 10

Measuring pulmonary wedge pressure

Question 11

What is the response in the lung vasculature to alveolar oxygen decreasing <70% normal?

Answer 11

Vasoconstriction

Question 12

What are the 3 zones of pulmonary blood flow?

Answer 12

Zone 1 - no blood flow during all portions of cardiac cycle. Only occurs under abnormal conditions ie breathing against positive pressure or low pulmonary systolic pressure
Zone 2 - intermittent blood flow only during peak pulmonary artery pressure
Zone 3 - continuous blood flow

Question 13

What is Henry’s law?

Answer 13

Partial pressure = concentration/solubility

Question 14

How does the solubility of O2 and CO2 compare?

Answer 14

CO2 >20x more soluble than O2

Question 15

What factors can cause the haemoglobin dissociation curve to shift to the right?

Answer 15

Increased CO2
Increased temperature
Increased BPG
Increased H+ ions

Question 16

How does shifting the haemoglobin dissociation curve to the right affect dynamics?

Answer 16

Enhances release of O2

Question 17

How is CO2 carried in the blood?

Answer 17

As dissolved CO2 (7%), carbaminohaemoglobin, plasma proteins and bicarbonate (70%)

Question 18

What is the chloride shift?

Answer 18

Cl- content of venous blood greater than arterial
After CO2 is converted to H2CO3 and HCO3 in the red blood cell, HCO3 diffuses out in exchange for Cl- via HCO3-Cl exchnager

Question 19

What is the Haldane effect?

Answer 19

As O2 binds hgb, Co2 displaced from blood
O2+hgb stronger acid than unbound hgb
- Acidic hgb less likely to combine with CO2
- Acidic hgb more likely to donate H+ to bind HCO3- and produce CO2

Question 20

Where is the respiratory centre located?

Answer 20

Medulla oblongata and pons

Question 21

How is the respiratory centre organised?

Answer 21

Dorsal respiratory group - inspiration
Ventral respiratory group - expiration
Pneumotaxic centre - rate and depth of breathing

Question 22

What does the formal respiratory group of neurons control? Where are its neurons located? Where do they receive input from?

Answer 22

Inspiration and respiratory rhythm
Nucleus of the tracts solitarius
Sensory termination of the vagal and glossopharyngeal nerves
Input from peripheral chemoreceptors, baroreceptors, receptors in liver, pancreas and GIT and lungs

Question 23

What is the function of the pneumotaxic centre?

Answer 23

Transmits signals to inspiratory area to limit inspiration and increase breathing rate
Controls switch off point of inspiratory ‘ramp’

Question 24

What limits inspiration to prevent lung overinflation?

Answer 24

Hering-breuer inflation reflex
Stretch receptors in lung transmit signals via vagus into dorsal respirator group when overstretched - terminated inspiratory ramp

Question 25

What is the function of the ventral respiratory group?

Answer 25

Provide extra respiratory drive during periods of need for greater respiration
Activated when signals from DRG spill over
Contribute to inspiration and expiration
Recruit abdominal muscles during heavy respiration

Question 26

What causes direct chemical control of respiration? Describe how it works

Answer 26

H+ and HCO3
Chemosensitive area - highly sensitive to H/HCO3 changes

Question 27

How does oxygen impact chemical control of respiration?

Answer 27

No major direct effect
Stimulates peripheral chemoreceptors in carotid and aortic bodies - when oxygen concentration falls, chemoreceptors stimulated
Aortic bodies contain glomus cells - O2-sensitive K channels - inactivated when O2 falls markedly - opens Ca channels - stimulate DRG

Question 28

What has the most potent effect on the chemo sensitive area?

Answer 28

Most sensitive to H+
However, has little direct effect as doesn’t cross BBB
Instead CO2 crosses and dissociates into H+/HCO3

Question 29

How does altered CO2 affect respiration chronically and acutely?

Answer 29

Great acute effect
Attenuated chronic effect - renal readjustment
- HCO3- diffuses across BBB more slowly