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 $3000 mL$.