Brain Control of Breathing: Medullary & Pontine Centers, Chemoreceptors & Voluntary Override

Breathing is generated by a distributed brainstem network with cortical modulation.

Medullary Centers

• Dorsal Respiratory Group (DRG): Inspiratory rhythm generator (NTS). Integrates peripheral chemoreceptor input.
• Ventral Respiratory Group (VRG): PreBötzinger complex (rhythm), Bötzinger (expiratory), nucleus ambiguus (laryngeal), retroambiguus (expiratory muscles).

Pontine Modulation

• Pneumotaxic Center (Upper Pons): Limits inspiration → ↑ rate, prevents overinflation.
• Apneustic Center (Lower Pons): Promotes inspiration; lesion → apneusis (prolonged gasping inspiration).

Chemoreceptor Drive

• Central (Medulla): CSF pH (CO₂/H⁺) — 80% drive.
• Peripheral (Carotid/Aortic Bodies): PaO₂ <60 mmHg, ↑PaCO₂, ↓pH — hypoxic drive.

Voluntary Control

Motor cortex → corticospinal → respiratory muscles. Breath-hold, speech, singing. Limited by "breakpoint" (CO₂/H⁺).

Clinical Relevance

• Ondine's Curse (CCHS): PHOX2B mutation → loss of automatic breathing.
• Opioid overdose: μ-receptor suppression of preBötC.