Question

Select the correct events that occur during inspiration.
(a) Contraction of diaphragm 
(b) Contraction of external inter - costal muscles 
(c) Pulmonary volume decreases 
(d) Intra pulmonary pressure increases

• A. (a) and (b)
• B. (c) and (d)
• C. (a), (b) and (d)
• D. only (d)

Answer 1

The Correct Option is A

The question focuses on the physiological changes in the body during the process of inspiration, which is part of the breathing cycle. Here's the explanation:

1. Contraction of Diaphragm (a): During inspiration, the diaphragm, a dome-shaped muscle at the base of the lungs, contracts and flattens. This contraction increases the vertical diameter of the thoracic cavity, leading to a decrease in intrapulmonary pressure and allowing air to flow into the lungs from the atmosphere.
2. Contraction of External Inter-costal Muscles (b): These muscles are positioned between the ribs. When they contract during inspiration, they elevate the ribs and expand the chest cavity, further contributing to the decrease in intrapulmonary pressure and assisting in drawing air into the lungs.
3. Pulmonary Volume Decreases (c): This statement is incorrect during inspiration. Instead, during inspiration, the pulmonary volume actually increases as the thoracic cavity expands, resulting in a lower intrapulmonary pressure that facilitates air inflow.
4. Intra Pulmonary Pressure Increases (d): This statement is incorrect. Intra pulmonary pressure decreases during inspiration, as the increased volume of the thoracic cavity creates a pressure gradient that causes air to move into the lungs.

The correct events during inspiration are the contraction of the diaphragm and the external inter-costal muscles, which are listed in options (a) and (b). Thus, the correct answer is:

(a) and (b)

In summary, inspiration is facilitated by increasing the thoracic and pulmonary volume through muscle contractions, which creates a pressure gradient allowing air to enter the lungs. Incorrect statements about decreasing volume or increasing pressure during inspiration can be ruled out based on the physiological mechanics of breathing.