Neurophysiology: Neuroanatomy

The neuroanatomy that supports the act of normal breathing consists of a central neural network of inspiratory and expiratory neurons that project to spinal and brainstem motor nuclei that ultimately innervate the respiratory muscles (diaphragm, intercostals, abdominal, and upper airway). This central neural network receives afferent feedback from sensors that monitor the mechanical effectiveness of lung expansion (mechanoreceptors) and the adequacy of arterial oxygen and carbon dioxide levels (chemoreceptors). The integrated respiratory neural drive is adjusted to accomplish a wide range of reflex activities, from sleep to exercise, as well as voluntary maneuvers such as vocalization or breath holding. The optimization of respiration to meet these various demands is accomplished by the respiratory neural control system, which initiates a respiratory rhythm (central pattern generator located within the brainstem) that is modulated by afferent information from the sensors and other higher brain centers into an integrated neural output to respiratory muscles. A number of clinical disorders produce abnormal breathing patterns. The causes of the neuropathology can be disease linked or genetic. The abnormal pattern that is produced depends on the location of the defect within the respiratory network and can result in failure to breathe or altered breathing patterns.