Neet Solved Paper 2015 Question 59
Question: When you hold your breath which of the following gas changes in blood would first lead to the urge to breathe?
Options:
A) Falling $ O _2 $ concentration
B) Rising $ CO _2 $ concentration
C) Falling $ CO _2 $ concentration
D) Rising $ CO _2 $ and falling $ O _2 $ concentration
Show Answer
Answer:
Correct Answer: B
Solution:
- When we hold our breath, $ CO _2 $ concentration rises and accumulates in blood and lungs, triggering impulses from respiratory centre part of brain. The body has the ability to detect rising $ CO _2 $ levels and send signals to take a breath, so as to compensate the lowering levels of $ CO _2 $ in blood and lungs. Gases diffuse from air to blood passively, i.e. from high concentration to low. When lungs become concentrated with same $ CO _2 $ as in blood, it no longer leaves blood and keep rising till next breath. As one breathes in $ CO _2 $ diffuses out of lungs and oxygen is taken in. Thus neutralizing the acidity caused by high $ CO _2 $ levels.
