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Solution


Q.

Inspiration is initiated by
 a) Extension of the diaphragm        b)    Contraction of the diaphragm
 c) Extension of the lungs                d)    Contraction of the lungs
1 A
2 B
3 C
4 D

Ans.

(b) Inspiration is initiated by the contraction of diaphragm, which increases the volume of thoracic chamber in the antero-posterior axis. The contraction of the external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of thoracic chamber in the dorso-ventral axis. The overall increase in the thoracic volume causes a similar increase in the pulmonary volume