Which muscles help us to increase the strength of inspiration and expiration?

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because

Lung ventilation movements are due to

Explain the process of inspiration under normal conditions.

Select the correct events that occur during inspiration.
$(a)$ Contraction of diaphragm
$(b)$ Contraction of external inter-costal muscles
$(c)$ Pulmonary volume decreases
$(d)$ Intra pulmonary pressure increases

Name the important parts involved in creating a pressure gradient between the lungs and the atmosphere during normal respiration.