Regulation of ventilation

CNS regulation
Ventilation is regulated by several groups of neurons in the brainstem:


 * Medullary respiratory center (in reticular formation)
 * Dorsal respiratory group: inspiration and breathing rate
 * Ventral respiratory group: active expiration and inspiration
 * Pneumotaxic center (in upper pons): regulates length of inhalation via inhibition.

Several chemoreceptors and mechanoreceptors are important in providing sensory input to regulatory groups in the CNS.

Central

 * In medulla
 * Sensitive to pH changes of CSF (due primarily to pCO2 change, also acidosis)
 * Activation leads to hyperventilation within 20-30 s

Peripheral

 * Carotid and aortic bodies
 * Sensitive to
 * decreases in pO2 < 10-13 kPa (baroreceptors)
 * increases in pCO2 (baroreceptors)
 * decreases in pH (chemoceptors)
 * heat (thermoreceptors)
 * stimulation leads to hyperventilation

Mechanoreceptors

 * Lung stretch receptors (in smooth muscle of airways): decrease respiratory rate – Hering-Breuer reflex
 * Irritant receptors (between airway epithelial cells): stimulated by noxious particles
 * Juxtacapillary receptors (in alveolar walls by capillaries): stimulated by engorgement of capillaries, leading to tachypnea
 * Joint and muscle receptors: activated to stimulate early breathing during exercise

Defensive respiratory responses to irritants
''look at slides to look for description. you have defense like hair. here though you havee to know receptors and pathways. it improves your grade this way.''

Cough

 * 1) Irritation of lower airway receptors
 * 2) small inspiration followed by forced expiration against closed glottis
 * 3) pressures in thorax and abdomen build up
 * 4) glottis is forced open
 * 5) air rushes out, loosens mucus and foreign particles

Sneeze

 * 1) Irritation of nasal receptors
 * 2) deep inspiration
 * 3) pressures in thorax and abdomen rise, but pharynx constricts
 * 4) air is forced through nose and mouth, facial and nasal muscles also constrict
 * 5) air rushes out, loosens mucus and foreign particles