Accelerans nerve forms a part of the sympathetic branch of the autonomic nervous system, and its function is to release noradrenaline at its endings on the heart. The heart beats according to a rhythm set up by the sinus-atrial node or pacemaker, which is located on the right atrium of the heart. It is acted on by the nervous system, as well as hormones in the blood, and venous return: the amount of blood being returned to the heart. The two nerves acting on the heart are the vagus nerve, which slows heart rate down by emitting acetylcholine, and the accelerans nerve which speeds it up by emitting noradrenaline.[1][2] This results in an increased blood flow, preparing the body for a sudden increase in activity.[3][4][5] These nerve fibres are part of the autonomic nervous system, part of the 'fight or flight' system.
Right where the sinus-atrial node is, the negative charge of the interior of the fibres of heart muscles breaks down spontaneously the cells in the pacemaker about 70 minutes each time.[6] As a result of this, a small current sweeps over the atria, which then reaches the insulating connective tissue between the atria and ventricles. When the current reaches this part, the atrio-ventricular node picks it up, thus creating the rhythm of the heartbeats through the rate and strength of each palpitation which is controlled by the accelerans nerve.[2][4]