Mechanisms for regulating ventilation and pulse rates.

Ventilation rate is controlled by the medulla and the pons in the brain stem. The activity of this centre is stimulated by peripheral chemoreceptors, which are located in the aorta and carotid arteries.
Chemoreceptors are specialised nerve cells that monitor the pH of blood. They measure the pH of blood by detecting hydrogen ion concentration, the higher the concentration the more acidic the blood. Chemoreceptors also monitor carbon dioxide levels in the blood. It is carbon dioxide that influences the amount of hydrogen ions in the blood.
When levels of carbon dioxide and hydrogen ions become high the chemoreceptors stimulate the respiratory centres to speed up so that the excess carbon dioxide and hydrogen can be removed from the blood.

The pulse rate is regulated by by the sino-atrial node. This specialised group of cells are responsible for generating the electrical impulses that makes the heart contract.
Like ventilation rate pulse rate can be affected by chemoreceptors. An increased ventilation rate usually goes hand in hand with increased pulse rate. This is because the blood needs to travel faster in order to get to the lungs so that carbon dioxide can be exhaled. An increase in ventilation rate will stimulate the SA node to increase its rate of fire thus increasing the pulse rate.

References:
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