26.20 : Neural Control of Respiration

The neural regulation of respiration is a meticulously coordinated process primarily controlled by the respiratory centers located within the brainstem. These centers, composed of specialized neurons, transmit nerve impulses that control the contraction and relaxation of our respiratory muscles.

Respiratory Centers in the Brainstem

Two primary areas comprise the respiratory center: the medullary respiratory center in the medulla oblongata and the pontine respiratory group in the pons. The medullary respiratory center further subdivides into the dorsal respiratory group (DRG) and the ventral respiratory group (VRG).

Medullary Respiratory Center

Dorsal respiratory group (DRG): During normal quiet breathing, the DRG neurons transmit impulses to the diaphragm and external intercostal muscles via the phrenic and intercostal nerves, respectively. The impulses are released in bursts, starting weakly and escalating in strength for about two seconds, then gradually decreases. This results in muscle contraction and inhalation. In the absence of DRG activity, the diaphragm and external intercostals relax, allowing passive recoil of the lungs and thoracic wall.

Ventral Respiratory Group (VRG): The VRG houses a cluster of neurons known as the pre-Bötzinger complex, integral to generating the breathing rhythm. The VRG provides input to the DRG, dictating the rate at which DRG neurons fire action potentials. The VRG becomes particularly active during forceful breathing, such as during exercise or playing wind instruments, where it controls both forceful inhalation and exhalation.

Pontine Respiratory Group (PRG)

The pontine respiratory group (PRG) is another crucial component of the respiratory center. It transmits impulses to the VRG of the medulla, modifying and fine-tuning the breathing rhythms produced by the VRG during certain activities like vocalization, sleep, and exercise.