Inspiration & Expiration

Question 1

What 2 muscles are used for inspiration?

Answer 1

• Diaphragm
• External intercostals

Question 2

What are the accessory muscles of inspiration?

Answer 2

• Sternocleidomastoid
• Scalene (anterior, middle and posterior)
• Serratus anterior
• Serratus posterior
• Pectoralis major
• Pectoralis minor
• Trapezius
• Latissimus dorsi

Question 3

What the muscles are used for forced expiration?

Answer 3

• Abdominals
• Rectus abdominis
• External oblique
• Internal oblique
• Transversus abdominis

Question 4

Describe how relaxed inspiration takes place.

Answer 4

• Controlled by impulses from the respiratory centre in the brainstem
• Nerve stimulation causes contraction of the diaphragm and outer intercostals (expands thoracic cage and lungs)
• Expansion creates lower pressure (relative to outside the body)
• Air rushes in

Question 5

Describe how the abdominal muscles cause forced expiration.

Answer 5

Abdominal muscles contract, causing the abdominal contents to push up against the diaphragm - reducing the vertical diameter of the thorax

Question 6

What muscles produce inspiration?

Answer 6

• Diaphragm
• External intercostals

Question 7

What muscles produce forced expiration?

Answer 7

• Internal intercostals
• Rectus abdominis
• Transversus abdominis
• Internal + external obliques

Question 8

Is expiration an active or passive process?

Answer 8

Mostly passive, but can be active too

Question 9

Is inspiration an active or passive process?

Answer 9

Active (requiring energy)

Question 10

Accessory muscles of inspiration can assist what (2) things?

Answer 10

• Deep inspiration
• During episodes of respiratory distress

Question 11

What can the use of accessory muscle of inspiration suggest?

Answer 11

A sign of respiratory distress

Question 12

How does forced expiration occur?

Answer 12

• Contraction of the abdominal muscles: causes the abdominal contents to push up against the diaphragm (reduces the vertical diameter of the thorax)
• Contraction of the internal intercostals: depress the ribs and decrease space in the thorax

Question 13

Why are accessory muscles of respiration special?

Answer 13

• Composed of fatigue resistant muscle fibres (Type 1)
• Controlled by both voluntary + involuntary mechanisms

Question 14

What triggers the inspiratory centre?

Answer 14

• Chemoreceptors which can detect changes in CO2, O2 and H+ in the blood
  CO2 + H2O <–> H2CO3 <–> H+ + HCO3-
• Peripheral chemoreceptors in the aortic arch (via vagus nerve) and carotid bodies (via glossopharangyl nerve)
• Central chemoreceptors near the medulla
• Muscle spindles and golgi tendon organs in respiratory muscles (provide input re: muscle length and force)