It is detected by stretch receptors in the wall of the right atrium, the afferent limb is via the vagus nerve, it is regulated by a center in the medulla oblongata of the brain,[1] and the efferent limb involves reduced vagal activity and increased sympathetic nervous system outflow.
[3] The Bainbridge reflex may also contribute to respiratory sinus arrhythmia as intrathoracic pressure decreases during inspiration causing increased venous return.
[5] The reflex was originally demonstrated by Bainbridge in 1915 who observed an increase in heart rate following infusion of blood or saline into the jugular vein of anaesthetized dogs.
[13] The Bainbridge reflex is the predominant,[16][17] but not the only mechanism mediating increases in heart rate in response to increased atrial stretch: stretching of the pacemaker cells of the sinoatrial node has a direct positive chronotropic effect on the rate of the sinoatrial node.
[18] This local response involves stretch-activated ion channels, as was demonstrated by stretching single isolated pacemaker cells while recording their cellular electrical activity.