Inspiration (inhalation)

• what type of process is breathing?

  active process
• why is breathing an active process?

  as muscle contraction requires energy
• how does the process of inspiration work?

  1. external intercostal muscles contract
  2. ribs are pulled upwards and outwards
  3. at the same time, the diaphragm muscles contract so the diaphragm flattens
  4. outer pleural membrane is attached to the thoracic cavity wall so its pulled up and out with the ribs, and the lower part is pulled down with the diaphragm-the inner membranes follows and so lungs expand, increasing volume inside the alveoli
  5. this reduces pressure in the lungs
  6. atmospheric air pressure is now greater than the pressure in the lungs, so air is forced into the lungs
• what does it mean that the internal intercostal muscles are antagonistic to the external intercostal muscles?

  the internal intercostal muscles relax when the external intercostal muscles contract in inspiration, and vice versa on expiration