Three main components contribute to dyspnoea: afferent signals, efferent signals, and central information processing. The central processing in the brain compares the afferent and efferent signals and dyspnoea results when a mismatch occurs between the two, such as when the need for ventilation (afferent signalling) is not being met by physical breathing (efferent signalling). The afferent receptors allow the brain to assess whether the efferent or motor commands to the ventilatory muscles are effective, meeting the required demands of airway pressure, air flow, and/or lung movement. When these respond inappropriately to the command, the intensity of the dyspnoea increases.