Question

Which one of the following process does not occur during inspiration in humans?

• A. contraction of internal intercostal muscles
• B. contraction of phrenic muscles
• C. an overall increase in the volume of the thoracic chamber
• D. the intra-pulmonary pressure decreases than atm. pressure

Answer 1

Answer: (A)

During inspiration, contraction of the external intercostal muscles between ribs and phrenic muscles of diaphragm occurs. Due to this, the volume of thoracic chamber increases from all sides and this also increases the pulmonary volume and therefore decreases pulmonary pressure than atmospheric pressure.