An increase in the amount of carbon dioxide in the blood stimulates the respiratory center of the brain. As a result, impulses are sent from the(1) medulla to the diaphragm, increasing the rate of breathing(2) cerebrum to the chest muscles, decreasing the rate of breathing(3) medulla to the trachea, causing it to constrict(4) cerebrum to the alveoli, causing them to activelytransport oxygen

Basically involuntary respiration is controlled by the Respiration centers in the brain Stem. They are group of respiratory neurons ; the dorsal and ventral respiratory groups located in the medulla oblongata , and the pontine respiratory group located in the Pons varolii.

The primary function of this center is for creation and maintenance of respiration rhythms and adjustment of the sequences to fluctuation in body homeostatic balance .

In order to regulate respiration rate and its depth, it collects its input signals from chemoreceptors ( cells that generate biological signals from chemical substances), mechanoreceptors( receptors which relay external physical stimuli of touch, and pressure to internal stimulus by regulation of gated ion channels), the hypothalamus and the cerebral cortex. The fluctuation in the levels of plasma C02, oxygen, and blood pH, stimulated the input progression.

Therefore an elevated C02 blood levels, marked by low pH send input signals to the respiratory centers in the medulla.The latter sends signals to the respiratory muscles (and the diaphragm,) to initiate mechanism of rapid breathing to exhaled more C02 so that the acidity of the blood is reduced..