Skeletal Muscles Involved in Breathing

• What causes breathing in humans?

  Changing the volume of the thoracic cavity
• What is the principal muscle of inspiration?

  Diaphragm
• How does diaphragm contraction affect the thoracic cavity?

  It moves downward, increasing cavity volume
• What happens to the pressure in the thoracic cavity during inspiration?

  It lowers
• What occurs when the thoracic cavity volume increases?

  Air moves into the lungs
• How is expiration generally characterized?

  It is generally passive
• Which muscles contract to increase thoracic cavity volume besides the diaphragm?

  External intercostals, scalene, sternocleidomastoid
• What happens to the thoracic cavity volume during expiration?

  It returns to normal
• What causes air to move out of the lungs during expiration?

  Raising pressure in the thoracic cavity
• What are the factors impacting muscle contraction during breathing?

  Elastic recoil, compliance, work of breathing
• What is the work of breathing?

  The effort required for lung expansion and contraction
• How is inspiration characterized in terms of process?

  It is an active process
• What stimulates the process of inspiration?

  Chemical receptors
• What characterizes expiration in terms of lung mechanics?

  It depends on elastic recoil of the lungs
• Why is it important to consider how hard a client is working during breathing?

  It indicates their respiratory effort and efficiency