Role of the vestibular system in regulating respiratory muscle activity during movement.

1. Changes in posture can affect the resting length of the diaphragm, which is corrected through increases in both diaphragm and abdominal muscle activity. Furthermore, postural alterations can diminish airway patency, which must be compensated for through increases in firing of particular upper airway muscles. 2. Recent evidence has shown that the vestibular system participates in adjusting the activity of both upper airway muscles and respiratory pump muscles during movement and changes in body position. 3. Vestibulo-respiratory responses do not appear to be mediated through the brainstem respiratory groups; labyrinthine influences on respiratory pump muscles may be relayed through neurons in the medial medullary reticular formation, which have recently been demonstrated to provide inputs to both abdominal and diaphragm motoneurons. 4. Three regions of the cerebellum that receive vestibular inputs, the fastigial nucleus, the nodulus/uvula and the anterior lobe, also influence respiratory muscle activity, although the physiological role of cerebellar regulation of respiratory activity is yet to be determined. 5. It is practical for the vestibular system to participate in the control of respiration, to provide for rapid adjustments in ventilation such that the oxygen demands of the body are continually matched during movement and exercise.