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Control of Breathing

By Dillon Lim - Medicine Student @ Brasenose College, Oxford


N.B. We use breathing, ventilation and respiration interchangeably here; respiration is definitely not the cellular respiration used to produce ATP!

Breathing is controlled by complex neural networks within the more primitive brain. The activity of these neurons controls the rate of ventilation based on signals coming from receptors in the brain, near blood vessels, and in the respiratory vessels themselves. These include chemoreceptors, which are sensitive to blood pH and gas concentrations, as well as mechanoreceptors, which detect stretch in pulmonary and respiratory tissues.

The basal rate of ventilation is around 12 breaths a minute. This control is conducted by specific areas of the pons and medulla in the brain. Neurons here often display consistent changes in their firing activity at different stages of the respiratory cycle (breathing in and out) and are therefore described as “respiratory-related”. The control of breathing is an incredibly complex activity for the brain to handle. A “central pattern generator” needs to be able to coordinate inputs from the rest of the body about its metabolic status and the concentrations of O­2/CO2 in the blood, as well as be able to adjust breathing patterns to deal with things like speaking, eating and swallowing. It has been suggested it is possible that multiple such pattern generators exist which take over in different situations, but one structure that almost certainly plays a key role is called the pre-Bötzinger complex, which has many respiratory-related neurons.

Experimentally ablating it leads to loss of breathing rhythm and a decrease in the amplitude of breathing. Working out all the neural circuits and centres involved here requires more work.

Chemoreception (detection of chemical signals) to regulate breathing takes place both peripherally and centrally. Peripheral chemoreceptors are located at aortic and carotid bodies (i.e., small structures at the aorta and at the carotid arte