Breathing and Exchange of Gases Question 1
1. Select the correct events that occur during inspiration.
[2020]
(i) Contraction of diaphragm
(ii) Contraction of external inter-costal muscles
(iii) Pulmonary volume decreases
(iv) Intra pulmonary pressure increases
(a) (iii) and (iv)
(b) (i), (ii) and (iv)
(c) Only (iv)
(d) (i) and (ii)
Show Answer
Answer : d
Hints & Solution
(d) Inspiration is initiated by the contraction of diaphragm, which increases the volume of thoracic chamber in the anterio-posterior axis. The contraction of external inter-coastal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorso-ventral axis. Inspiratory Reserve Volume (IRV): Additional volume of air, a person can inspire by a forcible inspiration. This averages $2500 mL$ to $3000 mL$.
