During physical exercise, the breathing rate increases. Is it positive or negative feedback in regulating the breathing rate.

This is an example of negative feedback. In this case,
during physical exercise, there is a greater output of carbon dioxide by the cells. The
high levels of carbon dioxide in the blood plasma coupled with a lower ph cause
chemoreceptors in the medulla oblongata to stimulate the medullary respiratory center to
send impulses to the respiratory muscles to increase the breathing rate. This will cause
excess carbon dioxide to be removed and eventually, the oxygen levels will rise. Carbon
dioxide levels and ph will go back to normal once again.