Biology- Breathing

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Breathing In (inhalation/inspiration)

1. Nervous impulses travel from the Medulla Oblongata...

2. to the external intercostal muscles and diaphragm.

3. The external intercostal muscles contract pulling the ribs upwards and outwards.

4. The diaphragm contracts (flattens).

5. The volume inside the lungs is increased.

6. The pressure inside the lungs is decreased compared with the pressure outside the body.

7. Air rushes in and the lungs inflate.

Breathing out (exhalation/expiration)

1. No nervous impulses travel from the medulla oblongata to the intercostal muscles and diaphragm.

2. External intercostal muscles relax pulling the ribs inwards and downwards.

3.The diaphragm relaxes (dome shaped).

4.The volume inside the lungs is decreased.

5.The pressure inside the lungs is decreased compared with the pressure outside the body.

6.Air rushes out and the lungs inflate.

More impulses from the medulla oblongata cause faster breaths in.

The internal intercostal muscles only contract when a forceful breath out is needed.

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