Which of the following is not a stimulus for breathing?

Question

A. Rising blood pressure
B. Arterial pH resulting from CO2 retention
C. Rising Carbon Dioxide Levels
D. Arterial PO2 below 60 mm Hg

Answer 1

It's A.

There are chemoreceptors in the brain that detect three things in blood related to breathing

1. Carbon Dioxide levels in blood
2. H+ ion concentration (pH)
3. Oxygen levels in blood.

It is normally only the CO2 levels that govern breathing. But hypoxia (low O2) will trump all the other stimuli, meaning regardless of what pH is or CO2 levels are, if you're low on O2 you want to breath, and badly. However, most of the time your O2 levels are way above what's needed, and so just by venilating away your CO2 you're getting enough O2. But an arterial pO2 level of below 60 is low enough to kick in your hypoxic drive to breath.

The only one on the list that has absolutely nothing to do with breathing, is blood pressure.

Answer 2

Actually D is correct. The body has no mechanism to detect PO2 levels but CO2 Levels stimulate breathing both ways. Of you blow off too much CO2 and your blood pH rises you will breathe more deeply and probably blow off even more CO2 This is what is know as hyperventilating. So B is also a cause of increased breathing although you typed the answer wrong. or you got C wrong as they are the same thing. Or they are both dorky answers to try to fool you as D is probably the only correct answer.
However A may also be correct because rising blood pressure usually does not affect breathing unless it kills you.

Answer 3

I would say A since when my BP goes up my breathing is not stimulated to go up.

Answer 4

A