6.7 The mechanism of breathing

Question 1

Calculation for pulmonary ventilation?

Answer 1

tidal volume x ventilation rate

Question 2

What is tidal volume?

Answer 2

The volume of air exhaled or inhaled in one breath

Question 3

What is ventilation rate?

Answer 3

The number of breaths taken in one minute

Question 4

Explain the process of exhalation (expiration).

Answer 4

The diaphragm relaxes and curves upwards.
The internal intercostal muscles between the ribs relax.
This causes the rib cage to move down and inwards.
As a result the volume of the thoracic cavity decreases.
Pressure within the thoracic cavity increases.
Atmospheric pressure is less than that of the thoracic cavity and air is forced from the lungs.

Question 5

Explain the process of inhalation (inspiration).

Answer 5

The diaphragm contracts and flattens.
The external intercostal muscles between the ribs contract.
This causes the rib cage to up and outwards.
As a result the volume of the thoracic cavity increases.
Pressure within the thoracic cavity decreases.
Atmospheric pressure is greater than that of the thoracic cavity and air is forced into the lungs.

Question 6

is breathing in an active or passive process?

Answer 6

active, it uses energy

Question 7

is breathing out an active or passive process?

Answer 7

largely passive, does not require much energy

Question 8

how does gas move?

Answer 8

gases move from a region where their pressure is higher to a region where their pressure is lower

Question 9

during normal quiet breathing, what is the cause of air being forced from the lungs?

Answer 9

the recoil of the elastic tissue in the lungs is the main cause of air being forced out.
only under more strenuous conditions such as exercise do the various muscles play a major part.

Question 10

What is the purpose of ventilation?

Answer 10

To maintain diffusion of gases across the alveolar epithelium, air is constantly moved in and out of the lungs.

Question 11

outline the movement of the diaphragm muscle in inhalation?

Answer 11

The diaphragm muscle contracts, it flattens, increasing the volume of the thorax

Question 12

outline the movement of the diaphragm muscle in exhalation?

Answer 12

the diaphragm muscle relaxes, it arches upwards, reducing the volume of the thorax

Question 13

What cavity is involved in gas exchange in the lungs?

Answer 13

thorax/thoracic cavity

Question 14

state the equation for pulmonary ventilation rate

Answer 14

tidal volume x breathing rate