Respiratory system

• Inspiration at rest muscles used:

  • diaphragm
  • external intercostal muscles
• Expiration at rest muscles used:

  • diaphragm
  • external intercostal muscles
• Movement during inspiration at rest: ribs move up and out, diaphragm flattens
• Movement during expiration at rest: ribs move down and in, diaphragm moves into a dome
• Volume of air during inspiration at rest = increase
• Volume of air in lungs during expiration at rest = decreases
• Pressure in lungs during inspiration at rest = decreases
• Pressure in lungs during expiration at rest = increases
• Muscles used during inspiration while exercising:

  • Diaphragm
  • External intercostals
  • pectoralis minor
  • sternocleidonastoid

  (all contract with more force than during rest)
• Muscles used during expiration while exercising:

  • rectus abdominals
  • internal intercostal muscles
• Movement during inspiration while exercising: ribs move up and out further than at rest
• Movement during expiration while exercising: ribs moving down and in faster + with more force than at rest
• Volume of air in lungs during inspiration while exercising = increases more than at rest
• Volume of air in lungs during expiration while exercising = decrease quicker than at rest
• Pressure of air in lungs during inspiration while exercising = decreases more than at rest
• Pressure of air in lungs during expiration while exercising = increases further + faster than at rest
• Regulation of breathing: altering breathing frequency and depth to maintain the appropriate levels of oxygen and carbon dioxide
• There are two centres within the RCC (Respiratory control centre):

  • The inspiration centre stimulates inspiratory muscles to contract at rest + during exercise
  • The expiratory centre is inactive at rest, but will stimulate additional expiratory muscles to contract during exercise
• Signal from RCC travels down a nerve to cause muscle contraction at rest to inspire:

  • phrenic nerve causes diaphragm contraction
  • intercostal nerve causes external intercostals to contract
• No muscles are stimulated to contract during expiration at rest, air is passively forced out
• During exercise as well as the diaphragm and external intercostal muscles the sternocleidomastoid and pectoralis minor also contract to cause inspiration
• Barorecepters detect increase in air pressure in lungs during exercise causing internal intercostals and rectus abdomini to be stimulated and contract to cause expiration