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

AA
BB
CC
DD

A.

(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

 



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