MCQ
Inspiration is initiated by
  • A
    Relaxation of the diaphragm
  • Contraction of the diaphragm
  • C
    Relaxation of the intercostal muscles
  • D
    Contraction of the lungs

Answer

Correct option: B.
Contraction of the diaphragm
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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