2.2 Inspiration and expiration

Question 1

What does breathing refer to?

Answer 1

The movement of air in and out of the lungs.

Question 2

What does inspiration mean?

Answer 2

Breathing in

Question 3

What does expiration mean?

Answer 3

Breathing out

Question 4

What is most air?

Answer 4

Nitrogen- we do not need it or use it, passes harmlessly in and out of our lungs.

Question 5

Role of intercostal muscles

Answer 5

Brain sends nerve messages to external intercostal muscles and the diaphragm.
Contraction of the external muscles causes rib cage to swing up and out. Nerve impulses to the diaphragm make it contract and flatten, pressing on digestive organs below.
Movement of the rib cage and diaphragm means the lungs have to follow which makes the lungs stretch, opening the microscopic alveoli. Increases the internal volume of the lungs, which means the pressure of the air in lungs decreases below that of the atmosphere so air rushes into the lungs, inflating the alveoli. This is inspiration.

Question 6

Role of diaphragm

Answer 6

To carry out expiration the brain stops sending nerve messages to the ribs and the diaphragm and so they stop contracting.
Diaphragm recoils upwards into its domed position, gravity causes rib cage to drop back and downwards. Decreases the volume of the lungs, air pressure in the lungs increases above the pressure of atmospheric air which means air is forced out.
If air needs to be forced out more quickly, for example coughing, the internal intercostal muscles contract to pull the rib cage back down with more force.

Question 7

Role of pleural membranes

Answer 7

Crucial to the lungs inflating and deflating as well as preventing friction as the lungs move. If the space between the membranes in punctured, the lung on that side will inflate.