Breathing, Demystified

New model clarifies how respiration is regulated

Breathing seems like a no-brainer, but from birth on, two pacemakers in the brain work in tandem to regulate this vital function and provide backup during respiratory distress.

Credit: Donna Coveney/MIT

The pacemakers are networks of neurons, near each other in the brain stem, that perform complementary tasks. One, dominant from infancy through childhood, is more closely associated with exhalation, but it also sends signals to activate the other, which is associated with inhalation. In adulthood, the second pacemaker takes over, but if extreme physical exertion or distress causes a drop in blood oxygen, it signals the other to activate--an event that might sound like a gasp. Mountain climbers and astronauts rely on this respiratory backup system to survive.

Scientists had previously identified the neural pacemakers, but they had debated which plays the bigger role. Chi-Sang Poon, a principal research scientist in the Harvard-MIT Division of Health Sciences and Technology, and his colleagues resolved the controversy by showing that the two coöperate through what they call a "handshake." They described how the pacemakers interact in a recent paper published online in the Proceedings of the National Academy of Sciences.

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An electrical engineer by training, Poon heads a lab at MIT that includes graduate students in computer science, physics, and chemical, mechanical, electrical, and aeronautical/astronautical engineering. He and his team are now developing a comprehensive model of the entire respiratory control system. Medical applications of their work could include the study of pacemaker abnormalities that may be associated with crib death, as well as with sleep apnea in premature babies and the elderly.

Ultimately, Poon and his colleagues see their work as a model for developing new biomechanical systems. "Understanding the mechanism of how vital functions are regulated may inspire novel control systems--paradigms that could be used in robots or fighter jets," he says.