Drive - physiology

Question 1

What is meant by the term minute volume?

Answer 1

The volume air inspired/expired in a minute

Question 2

What is the approximate minute volume?

Answer 2

5L/ min

Question 3

What is interpleural pressure?

Answer 3

The pressure in the pleural space

Question 4

What is alveolar pressure

Answer 4

Air pressure in the pulmonary alveoli

Question 5

Where does the phrenic nerve arise from?

Answer 5

C3, C4 and C5

Question 6

What is inspiration initiated by?

Answer 6

Neurally induced contraction of the diaphragm and the external intercostal muscles located between the ribs

Question 7

What is the most important inspiratory muscle that acts during normal quiet breathing?

Answer 7

Diaphragm

Question 8

When stimulated to contract what is the movement of the diaphragm?

Answer 8

Downwards

Question 9

When stimulated to contract what is the movement of the external intercostal muscles?

Answer 9

Upwards and outwards

Question 10

What happens to the intrapleural pressure and transpulmonary pressure when the thoracic volume increase?

Answer 10

Intrapleural pressure = decreases

Transpulmonary pressure = increases

Question 11

What happens (during inspiration) when transpulmonary pressure becomes more positive? (and why)

Answer 11

The lungs expand because transpulmonary pressure > elastic recoil.

Question 12

What effect does lung expansion have on alveolar pressure?

Answer 12

Becomes more negative

Question 13

What occurs when alveolar pressure becomes more negative?

Answer 13

Inwards airflow

Question 14

What occurs to the muscles of the diaphragm and external intercostal muscles during (passive) expiration? and what does this cause?

Answer 14

They relax resulting in a decreasing thoracic volume

Question 15

What allows the lungs and chest walls to passively collapse?

Answer 15

Elastic recoil

(as muscle relaxation causes increased intrapleural pressure which decreases transpulmonary pressure to below that of the elastic recoil force)

Question 16

What causes alveolar pressure to increase?

Answer 16

Air temporarily compressed

Question 17

What does increased alveolar pressure cause?

Answer 17

Outwards airflow

Question 18

What additionally to the process of passive expiration occurs during forced expiration?

Answer 18

The internal intercostal muscles also contract (as do the abdominal muscles)

Question 19

What does the contraction of the internal intercostal muscles cause?

Answer 19

The ribs to move downwards and inwards (actively decreasing thoracic volume)

Question 20

What does contraction of the abdominal muscles result in?

Answer 20

Forcing the relaxed diaphragm moving further up - decreases thoracic volume

Question 21

In what lung structure is the greatest resistance and why is this?

Answer 21

Trachea as it has a much smaller surface area than (combined) the bronchi do.