Lecture 31. Breathing and Ventilation

Question 1

What are the three phases of rhythmic breathing?

Answer 1

Inspiration - Active: Initiated by activation of the nerves to the inspiratory muscles
Post-Inspiration - Active: Recruitment of post-inspiratory muscles
Expiration - Passive: Inspiratory muscles relax and lungs recoil
– Active: activation of expiratory muscles

Question 2

What do inspiratory muscles do?

Answer 2

Contract to draw air into the lungs and create normal breathing

Question 3

What is the most important inspiratory muscle?

Answer 3

Diaphragm
Asymmetrically innervated
70% of your Tidal volume

Question 4

What do post-inspiratory muscles do?

Answer 4

Slow diaphragm recoil and coordinate orofacial movement

Question 5

When do expiratory muscles become active?

Answer 5

In times of high demand to increase tidal volume

Question 6

What does contraction of the tongue support?

Answer 6

Supports the airway and reduces resistance during inspiration and expiration

Question 7

What three types of plural membrane make up the thorax?

Answer 7

Costal parietal pleura
Mediastinal parietal pleura
Diaphragmatic parietal pleura

Question 8

What is the visceral pleura?

Answer 8

A thin layer of epithelium covering each lung

Question 9

What is the parietal pleura?

Answer 9

Lines inner surface of the walls of the thorax

Question 10

What is the pleural cavity?

Answer 10

Maintains a partial vacuum which helps keep the lungs
expanded

Question 11

What is the intrapleural fluid?

Answer 11

Allows pleurae to slide over one another

Question 12

What generates pressure within the pleura?

Answer 12

Differential set points of muscles and lungs

Question 13

What is the transpulmonary pressure (Pₜₚ)?

Answer 13

Difference in pressure between the inside and outside of the lungs within the thorax

Question 14

What is the intrapleural pressure (Pᵢₚ)?

Answer 14

The pressure outside the lungs in the thorax

Question 15

What is the alveoli pressure (Palv)?

Answer 15

The pressure inside the lungs is the air pressure inside the alveoli pressure

Question 16

What keeps the lungs inflated?

Answer 16

Palv > Pip

Question 17

What causes pneumothorax (collapsed lung)?

Answer 17

Air in the plural cavity

Question 18

What is Boyle’s law?

Answer 18

Predicts that if the volume inside the lungs is
changed, pressure inside the lungs will also change

Question 19

What generates air movement in the lung?

Answer 19

Alveolar pressure

Question 20

What alters trans-pulmonary pressure to draw air into the lungs?

Answer 20

Inspiratory muscle contractions

Question 21

What alters trans-pulmonary pressure to push air out of the lungs?

Answer 21

Expiratory muscle contractions

Question 22

What is the exchange of gases in alveoli and tissues dependent on?

Answer 22

Partial pressures O₂ and CO₂

Question 23

What is Dalton’s Law?

Answer 23

In a mixture of gases, the pressure exerted by each gas (the partial pressure) is the pressure that the gas would exert if it were the only gas in the volume occupied by the mixture

Question 24

What determines atmospheric pressure?

Answer 24

Patm = PN₂ + PO₂ + PCO₂ + PH₂O = 760 mm Hg

Question 25

What is anatomical dead space?

Answer 25

Volume of gas within the conducting airways
Increases PCO₂ in the alveoli

Question 26

What is physiological dead space?

Answer 26

Volume of gas not involved in gas exchange
The two are almost equal in healthy lungs

Question 27

When does net diffusion of a gas occur?

Answer 27

From a region where its partial pressure is high to a region where it is low

Question 28

How is oxygen in the blood primarily transported?

Answer 28

On haemoglobin

Question 29

What is the Bohr effect?

Answer 29

Carbon dioxide (CO₂) shifts the haemoglobin saturation curve to the right causing O₂ to dissociate from haemoglobin

Question 30

How is CO₂ predominantly transported in the blood?

Answer 30

As bicarbonate ion

Question 31

When does carbon monoxide poisoning occur?

Answer 31

Haemoglobin has an affinity for CO that is 210 times greater than its affinity for O₂, preventing the unloading of O₂ onto tissues