True about inspiration, the intrapleural pressure becomes
**Core Concept**
During inspiration, the diaphragm and other respiratory muscles contract, increasing the volume of the thoracic cavity. This increase in volume creates a partial vacuum, drawing air into the lungs. The intrapleural pressure, which is the pressure within the pleural space surrounding the lungs, becomes more negative to facilitate this process.
**Why the Correct Answer is Right**
As the diaphragm descends and the rib cage expands, the volume of the thoracic cavity increases. This increase in volume is met by a decrease in intrapleural pressure, making it more negative relative to atmospheric pressure. The more negative intrapleural pressure creates a pressure gradient that draws air into the lungs through the openings of the airways. The decrease in intrapleural pressure is also facilitated by the elastic recoil of the lungs, which helps to expand the lungs and increase their volume during inspiration.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the intrapleural pressure does not become positive during inspiration. A positive intrapleural pressure would actually push air out of the lungs, rather than drawing it in.
**Option B:** This option is incorrect because the intrapleural pressure does not remain unchanged during inspiration. The contraction of the diaphragm and other respiratory muscles creates a change in intrapleural pressure that facilitates the drawing of air into the lungs.
**Clinical Pearl / High-Yield Fact**
The intrapleural pressure becomes more negative during inspiration to facilitate the drawing of air into the lungs. This is a critical concept to understand in respiratory physiology, as it helps to explain how the lungs expand and contract during breathing.
**Correct Answer:** C.