KEY POINTS

1. Respiration is regulated to meet the metabolic demands for delivery of oxygen and removal of carbon dioxide.

Central Control of Respiration

1. Respiratory rhythmicity originates in the medulla and is modified by higher brain centers and inputs from peripheral receptors.

Pulmonary and Airway Receptors

1. Pulmonary stretch receptors, irritant receptors, and juxtacapillary receptors can influence the rhythm of breathing.

2. Muscle spindle stretch receptors monitor the effort exerted by respiratory muscles.

Chemoreceptors

1. Hypoxia, acidosis, and hypercapnia are all potent stimuli for ventilation.

2. Peripheral chemoreceptors are the only receptors monitoring blood oxygen levels.

3. The ventilatory response to carbon dioxide is mediated through a medullary chemoreceptor.

4. Ascent to high altitude is accompanied by a decrease in inspired oxygen tension and consequently by hypoxemia, which leads to an increase in ventilation.

5. During exercise, ventilation must increase because the tissues demand more oxygen and produce more carbon dioxide.