gas exchange in animals

• Which of the two is an energy using process? Inspiration or expiration?

  Inspiration
• Describe the process of inspiration

  • Diaphragm contracts, flattening and lowering
  • External intercostal muscle contracts
  • Ribs rise up and out
  • Volume of thorax increases
  • Pressure is reduced (lower than atmospheric pressure) so air is drawn in through pressure gradient
• Describe the process of expiration

  • External intercostal muscles relax
  • Diaphragm relaxes, moving up and in
  • Pressure in the thorax increases to greater than atmospheric pressure
  • So air moves out of the lungs
  • volume in the thorax decreases
• What two muscles contract under forced expiration?

  • Internal intercostal muscles- pulling the ribs down hard and fast
  • Abdominal muscles- forcing the diaphragm up to increase pressure in the lungs rapidly
• true or false? Forced expiration is an energy using process

  TRUE