Negative-feedback control systems Negative-feedback control systems. A: General scheme of a negative-feedback control system. B: How the respiratory control system works as a negative-feedback control system. Note that the central chemoreceptors also act as sensors for the respiratory control system, with the and pH of the cerebrospinal fluid the regulated variables that feed back to the sensors. Source: Chapter 9. Control of Breathing, Pulmonary Physiology, 8e Citation: Levitzky MG. Pulmonary Physiology, 8e; 2013 Available at: http://accessmedicine.mhmedical.com/DownloadImage.aspx?image=/data/books/levi8/levi8_c009f007.png&sec=42514426&BookID=575&ChapterSecID=42512987&imagename= Accessed: October 24, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved