Question

upward and downward movement of diaphragm occurs consecutively

Answer 1

In the process of exhalation and inhalation, diaphragm plays a important role
During Inspiration, diaphragm becomes flat making the air enter into our lungs
and during exhalation, diaphgram relaxes and comes back to it's dome shape
As we inhale and exhale continuously, the movement of diaphgram is also consecutive

Answer 2

1) simultaneous rising up of ribs and lowering of diaphragm causes decrease in pressure on lungs

2) due to this, air moves into the lungs through nose.

3) when ribs return to their original position and diaphragm rises up, pressure on the lung increases.

4) due to this air moves out from it through nose. therefore upward and downward movement of diaphragm occurs consecutively.