Question

Inspiration occurs when the pressure within the lungs is

• A. Less than the atmospheric pressure
• B. Greater than the atmospheric pressure
• C. Equal to the atmospheric pressure
  
• D. None of the above
  

Answer 1

The correct option is A

Less than the atmospheric pressure

The correct option is A.

Explanation of the correct option:

1. When the pressure inside the lungs is less than the atmospheric pressure, inspiration happens, and when the pressure inside the lungs is more than the atmospheric pressure, expiration occurs.
2. The air travels into and out of the lungs due to the pressure gradient between the lungs and the atmosphere.
3. When the pressure inside the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, or when there is a negative pressure in the lungs in relation to the atmospheric pressure, inspiration occurs.

Explanation of the incorrect option:

Option B:

Expiration happens when the alveolar pressure exceeds the ambient pressure, and air flows out of the alveoli.

Option C:

There will be no air movement into or out of the lungs if the air pressure is equal.

Final Answer: Inspiration occurs when the pressure within the lungs is less than the atmospheric pressure.