Breathing

Question 1

Muscles involved in quiet inspiration

Answer 1

diaphragm mainly - decreases, intrapleural and alveolar pressures, raises abdominal pressure
external intercostal muscles - elevate the ribcage
scalene muscles - insert into first two ribs, move the sternum upwards and forwards

Question 2

Muscles involved in forced inspiration

Answer 2

accessory inspiratory muscles help - 
•	scalene muscles 
•	sternomastoids 
•	serratus anterior 
along with the usual diaphragm, external interscostals, scalene muscles

Question 3

Muscles involved in quiet expiration

Answer 3

none, it’s all elastic recoil of chest wall and alveoli

Question 4

Muscles involved in forced expiration

Answer 4

When ventilation exceeds ~40 L/min, there is activation of expiratory muscles:
• abdominal muscles, including the obliques (speeds up recoil of the diaphragm by raising intra-abdominal pressure)
• internal intercostals (accessory muscles) help to compress the rib cage, which reduces volume of the thoracic cavity

Question 5

Which nerves innervate the diaphragm

Answer 5

phrenic coming off at “C3,4,5 keeps the diaphragm alive”

Question 6

What mediates neural control of ventilation?

Answer 6

chemoreceptors