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When you hold your breath, which of the following gas changes in blood would first lead to the urge to breathe?

  • Falling O2 concentration

  • Rising CO2¬†concentration

  • Falling CO2 concentration

  • Rising CO2 and falling O2 concentration

Answer

B.

Rising CO2 concentration

When we hold our breath, CO2 concentration rises and accumulates in blood and lungs, triggering impulses from respiratory centre part of brain. The body has the ability to detect rising CO2 levels and send signals to take a breath, so as to compensate the lowering levels of O2 in blood and lungs. Gases diffuse from air to blood passively, i.e. from high concentration to low.
When lungs become concentrated with same CO2 as in blood, it no longer leaves blood and keep rising till next birth. As one breathes in CO2 diffuse out of lungs and oxygen is taken in. Thus, neutralising the acidity by high CO2 levels.

When we hold our breath, CO2 concentration rises and accumulates in blood and lungs, triggering impulses from respiratory centre part of brain. The body has the ability to detect rising CO2 levels and send signals to take a breath, so as to compensate the lowering levels of O2 in blood and lungs. Gases diffuse from air to blood passively, i.e. from high concentration to low.
When lungs become concentrated with same CO2 as in blood, it no longer leaves blood and keep rising till next birth. As one breathes in CO2 diffuse out of lungs and oxygen is taken in. Thus, neutralising the acidity by high CO2 levels.