pons

The pons sits just above the medulla, a bulging bridge of nerve fibers in the brainstem. If the medulla is the metronome that sets the beat, the pons is the editor that smooths the phrasing, especially the timing of when one breath ends and the next begins.

Its main respiratory hub is the pontine respiratory group, sometimes called the pneumotaxic center, in the upper pons. It helps limit the length of inspiration and shape the orderly switch from breathing in to breathing out, keeping the rhythm even rather than gasping or prolonged. A lower pontine area historically called the apneustic center is thought to influence the depth and duration of inspiration.

In practice the pons modulates rather than creates the rhythm: the medulla can sustain a basic pattern on its own, but without normal pontine input breathing tends to become irregular. Damage at different brainstem levels produces characteristic abnormal breathing patterns that neurologists use to help localize injury.