Q: Is there a nerve responsible for carrying signals regarding CO2/02 needed and to be expelled by the body? And how are these signals conveyed? Is there a specific part of the brain dealing with such signals? Also when a deep breath is needed and taken in, there is a feeling of satisfaction, how does the body immediately know that enough O2 has been supplied?

A:The regulation of breathing is under the control of a respiratory centre in the medulla of the brain. Signals come to it from chemoreceptors in the carotid body glomus glands in the neck: these special cells sense the partial pressure of oxygen in the blood. If these receptors are removed or damaged by carotid artery surgery, sensitivity to low concentrations of oxygen are lost. Several autonomic nerves are involved, as is the cerebrum. Thus, emotional or intellectual states can affect the appreciation of oxygen changes in the blood, and can influence the subjective awareness of breathlessness. Various people, including athletes on the one hand and chronic lung disease patients on the other, may have different sensations from the average.