Mechanics of breathing

Question 1

What muscles contract during inspiration at rest? And what effect does this have?

Answer 1

• external intercostal muscles
• diaphragm
• The volume of the thoracic cavity increases, pulmonary pressures are lower than atmospheric, so air rushes in.

Question 2

What muscles contract during inspiration during exercise? And what effect does this have?

Answer 2

• external intercostal muscles
• diaphragm
• scalenes
• pectoralis minor
• sternocleidomastoid
• Contract to create bigger volume, so more air rushes in.

Question 3

What muscles relax during expiration during rest? And what effect does this have?

Answer 3

• external intercostal muscles
• diaphragm
• There is a decrease in lung volume, increase in pulmonary pressure, therefore air is forced out from high to low.

Question 4

What muscles relax during expiration during exercise and which extra muscles contract? And what effect does this have?

Answer 4

• external intercostal muscles relax
• diaphragm relaxes
• internal intercostal muscles contract
• rectus abdominis contracts
• air is forced out more rapidly.

Question 5

What does the respiratory control centre (RCC) control and where is it located?

Answer 5

• The RCC controls how we breathe

- Located in the Medulla Oblongata

Question 6

What is the Inspiratory Centre (IC) responsible for?

Answer 6

Responsible for normal breathing of inspiration & expiration (12-15 breaths/min)

Question 7

What does the inspiratory centre (IC) control during exercise? And what is the effect of this?

Answer 7

• Increases the stimulation of diaphragm & external intercostals
• Stimulates additional inspiratory muscles (sternocleidomastoid, pectoralis minor) with increase force of contraction & therefore deeper inspiration

Question 8

What does the expiratory centre (EC) control during exercise? And what is the effect of this?

Answer 8

• Stimulates expiratory muscles internal intercostals & rectus abdominis causing forced expiration