Question

Which of the following sequences is correct to initiate inspiration?
(i) The contraction of external intercostal muscles raises the ribs and sternum
(ii) Volume of thorax increases in the dorso-ventral axis
(iii) Intrapulmonary pressure decreases
(iv) Diaphragm contraction
(v) Air rushes into lungs
(vi) Volume of thorax increases in the anterior-posterior axis

• A. $(i), (ii), (iv), (v), (iii), (vi)$
• B. $(i), (ii), (iii), (iv), (vi), (v)$
• C. $(i), (ii), (iv), (vi), (iii), (v)$
• D. $(vi), (v), (i), (ii), (iii), (iv)$

Answer 1

Answer: (C)

The correct sequence of events in the initiation of respiration is:
(i) The contraction of external intercostal muscles raises the ribs and sternum
(ii) The volume of thorax increases in the dorsoventral axis
(iv) Diaphragm contraction
(vi) The volume of thorax increases in the anterior-posterior axis
(iii) Intrapulmonary pressure decreases
(v) Air rushes into lungs
So, the correct answer is '(i),(ii),(iv),(vi),(iii),(v)'.