Respiration Questions

How inspiration and expiration work: 

Inspiration:

The intercostal muscles and the diaphragm contract to begin inspiration.
Process: 

the intercostal muscles contract -> ribs elevate -> increase dimension of thoracic cavity -> air pressure in lungs is lowered -> air moves into lungs

contraction of diaphragm -> diaphragm moves down -> dimension of thoracic cavity increases -> air pressure in lungs lower -> air moves into lungs

Expiration:
intercostal muscles and diaphragm relax -> diaphragm & ribs relax -> volume of thoracic cavity decreases -> pressure in lungs increase -> air is exhaled

Inflate and Deflate?  

Inflation:

Caused when your chest moves up (contraction of thoracic cavity). Your lungs inflate with oxygen when you breath causing them to expand therefore expanding your lungs/chest.

Deflation:
Caused when your diaphragm and intercostal muscles relax. 

What part of the process requires a "muscle contraction" of the diaphragm?

Inhalation!