Question

When the respiratory diaphragm contracts, it flattens, lowering the floor of the thoracic cavity. At the same time, the intercostal muscles pull the ribs up and out. The active forces of the muscle groups cause a(n) __________ (increase/decrease) in thoracic volume. Given the relationship between pressure and volume, this would cause pressure within the lungs to __________ (increase/decrease)

Answer 1

The contraction of the respiratory diaphragm and intercostal muscles during inhalation increases thoracic volume and decreases pressure in the lungs, causing air to enter.

Step-by-step explanation:

When the respiratory diaphragm contracts, it flattens, leading to an increase in thoracic volume. Concurrently, the intercostal muscles pull the ribs up and out. Owing to Boyle's Law, which posits an inverse relationship between pressure and volume, this increase in thoracic volume leads to a decrease in pressure within the lungs as compared to the external atmosphere. As a result, air is drawn into the lungs.

Answer 2

1. Increase

2. Decrease

Step-by-step explanation:

During inspiration, diaphragm contracts and lowers down. There is a simultaneous contraction of external intercostal muscles and movement of rib-cage upward and outward. All these events lead to an increase in the volume of the thoracic cavity. Increase in volume of the thoracic cavity results in expansion of lungs and lowering down the air pressure within alveoli of lungs.