The mechanism of breathing

Question 1

2 Phases of breathing/ventilation

Answer 1

Inspiration (inhalation)
Expiration (Exhalation)

Question 2

Muscles that change the pressure within the lungs

Answer 2

The diaphragm
The internal intercostal muscles
The external intercostal muscles

Question 3

Process of inspiration

Answer 3

Active process
+The external intercostal muscles contract while the internal muscles retract.
+Due to this, the ribs are pulled upwards and outwards. This increases the V of the thorax
+The diaphragm muscles contract, which flatten it and increases the V of the thorax
+The increased V results in the decrease in air pressure.
+Atmospheric pressure is now greater than the pulmonary pressure, so air is drawn in.

Question 4

Process of expiration

Answer 4

Passive process
+The internal IC muscles contract, the external muscles relax.
+The ribs move downwards and inwards, decreasing the volume of the thorax.
+The diaphragm muscles relax and is pushed up against the contents of the abdomen and the volume is decreased.
+The decreased volume of the thorax increases the pressure of the lungs
+ The pulmonary pressure is greater than atmospheric pressure, so air is forced out.