The medulla oblongata is the primary respiratory control center. Its main function is to control the rate or speed of involuntary respiration. The apneustic center sends signals for inspiration for long and deep breaths. It controls the intensity of breathing and is inhibited by the stretch receptors of the pulmonary muscles at maximum depth of inspiration, or by signals from the pneumotaxic center. It increases tidal volume.The pnuemotaxic center sends signals to inhibit inspiration that allows it to finely control the respiratory rate. Its signals limit the activity of the phrenic nerve and inhibits the signals of the apneustic center. It decreases tidal volume.The apneustic and pneumotaxic centers work against each other together to control the respiratory rate.