In the expiration condition,the diaphragm becomes

State the sequence of events for inspiration (breathing in).
$I$ - Increase in lung volume
$II$ - Decrease in intrapulmonary pressure
$III$ - Contraction of respiratory muscles
$IV$ - Increase in thoracic volume
$V$ - Air rushes into the lungs

Guard cell movement furnishes an example of

The lungs do not collapse during breathing and some air always remains in the lungs which can never be expelled because:

An increase in pulmonary volume decreases the intra-pulmonary pressure to less than the atmospheric pressure,which forces the air from outside to move into the lungs. This process is known as:

Expiration occurs only when.....