The Bainbridge response is often ignored. Atrial baroceptors signal an increase in central venous pressure and thus of preload to the heart. Nerve activity travels to the brain and release the sinus atrial node from vagal inhibition. This response can be abolished by atropine. It was shown that the Bainbridge response remains preserved in an isolated heart preparation so neural influences form only part of the response.
In the model the Bainbridge response helps to maintain constant the blood distribution between arterial and venous phase. A larger preload to the heart normally occurs when metabolic activity is increased lowering the resistance in the cerebral and/or systemic circulation by the metabolic response. Chemical and mechanical factors run in parallel: cardiovascular regulation is at the same time based on humoral (pCO2 and/of pH) and on mechanical factors (pressure and volume).
In the above graph the scenarios "CO2 retention" followed by "hyperventilation" were selected twice: the first time without and then with the Bainbridge response active. Note how the changes in pCO2 (orange) result in changes in blood pressure (red) because of the CNS ischemic response but not in heart rate (blue). Once the Bainbridge response is turned on (at time axis = 75), HR changes with central venous pressure and dampens the changes in arterial blood pressure.