Mechanics of Breathing

Question 1

The pressure exerted by a gas is inversely proportional to what?

Answer 1

to its volume

Question 2

Total pressure of a gas mix is the sum of what?

Answer 2

the pressures of the individual gases

Question 3

Volume occupied by a gas is directly related to what?

Answer 3

Its absolute temperature

Question 4

The amount of gas dissolved in a liquid is determined by what?

Answer 4

the pressure of the gas and it’s solubility

Question 5

How much pleural fluid is there in total?

Answer 5

10-20ml

Question 6

What is pleurisy?

Answer 6

Inflammation of the pleura

Question 7

Relative to atmospheric pressure, intraparietal pressure is always what?

Answer 7

Negative

Question 8

How does expiration function at rest?

Answer 8

Passive

Question 9

Which muscles are used for forceful expiration?

Answer 9

Internal intercostal

Abdominal muscles

Question 10

Which muscles are used for forceful inspiration?

Answer 10

Sternocleidomastoids
Scalenes
External Intercostals
Diaphragm

Question 11

What shape is the diaphragm at rest?

Answer 11

Domed

Question 12

In which direction do the ribs and sternum move for inspiration

Answer 12

Upwards and outwards

Question 13

What is asthma?

Answer 13

Over-reactive constriction of bronchial smooth muscle

Question 14

How does asthma affect breathing?

Answer 14

Increased resistance

Expiration more difficult

Question 15

What is Intra-thoracic pressure? Is it positive or negative?

Answer 15

Pressure inside the thoracic cavity (alveoli)

Positive or negative relative to Patmos

Question 16

What is transpulmonary pressure? Positive or negative?

Answer 16

Difference between alveolar pressure and intra-pleural pressure. Always positive in health.

Question 17

What force in the lungs aids in expiration?

Answer 17

Elastic recoil of lung tissue

Question 18

What is the major determining factor in airway resistance?

Answer 18

Radius

Question 19

Why does air flow into the lung when the volume is increased?

Answer 19

Alveolar pressure is negative relative to atmospheric pressure

Question 20

Innervation for breathing supplied by what?

Answer 20

Phrenic nerve to diaphragm

Intercostal nerves

Question 21

Where are the respiratory centres located? (above C3-5)

Answer 21

Pons and Medulla

Question 22

The Dorsal Respiratory Group controls what muscles?

Answer 22

Primarily Inspiratory muscles

Question 23

The Ventral Respiratory group controls what?

Answer 23

Expiratory, some inspiratory (tongue, pharynx, larynx)

Question 24

What factors effect ventilation rate?

Answer 24

Emotion
Mechano-sensory reflex (stretch reflex)
Chemoreceptors
Voluntary action

Question 25

What is the most significant factor in controlling ventilation rate?

Answer 25

Chemoreceptor input

Question 26

Where are the Central chemoreceptors located?

Answer 26

Medulla

Question 27

What do the central chemoreceptors detect?

Answer 27

[H+] in the CSF around brain (driven by levels of CO2)

Question 28

What causes a reflexive inhibition in ventilatory rate?

Answer 28

Reduced CSF [H+]

Question 29

How do H+ levels increase in the CSF?

Answer 29

Dissociation of Carbonic acid to H+ and HCO3-

Question 30

Where are the peripheral chemoreceptors located?

Answer 30

Carotic and Aortic bodies

Question 31

What do the peripheral chemoreceptors detect?

Answer 31

Changes in arterial PO2 and [H+]

Question 32

What causes stimulation of the ventilation rate by the peripheral chemoreceptors?

Answer 32

Significant changes in arterial PO2

Question 33

How are changes in plasma pH detected?

Answer 33

Peripheral chemoreceptors

Question 34

Is high PCO2 or low PO2 more uncomfortable?

Answer 34

High PCO2

Question 35

When is respiration inhibited?

Answer 35

Swallowing

Question 36

What follows swallowing? Why?

Answer 36

Swallowing is followed by expiration to expel food particles

Question 37

Which common drugs depress the respiratory centre?

Answer 37

Barbiturates

Opioids

Question 38

What effect do gaseous anaesthetics have on respiration?

Answer 38

Increased Rate

Decreased Tidal volume