Inspiration & Expiration Flashcards
What 2 muscles are used for inspiration?
- Diaphragm
- External intercostals
What are the accessory muscles of inspiration?
- Sternocleidomastoid
- Scalene (anterior, middle and posterior)
- Serratus anterior
- Serratus posterior
- Pectoralis major
- Pectoralis minor
- Trapezius
- Latissimus dorsi
What the muscles are used for forced expiration?
- Abdominals
- Rectus abdominis
- External oblique
- Internal oblique
- Transversus abdominis
Describe how relaxed inspiration takes place.
- 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
Describe how the abdominal muscles cause forced expiration.
Abdominal muscles contract, causing the abdominal contents to push up against the diaphragm - reducing the vertical diameter of the thorax
What muscles produce inspiration?
- Diaphragm
- External intercostals
What muscles produce forced expiration?
- Internal intercostals
- Rectus abdominis
- Transversus abdominis
- Internal + external obliques
Is expiration an active or passive process?
Mostly passive, but can be active too
Is inspiration an active or passive process?
Active (requiring energy)
Accessory muscles of inspiration can assist what (2) things?
- Deep inspiration
- During episodes of respiratory distress
What can the use of accessory muscle of inspiration suggest?
A sign of respiratory distress
How does forced expiration occur?
- 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
Why are accessory muscles of respiration special?
- Composed of fatigue resistant muscle fibres (Type 1)
- Controlled by both voluntary + involuntary mechanisms
