<P> While heart rhythm is regulated entirely by the sinoatrial node under normal conditions , heart rate is regulated by sympathetic and parasympathetic input to the sinoatrial node . The accelerans nerve provides sympathetic input to the heart by releasing norepinephrine onto the cells of the sinoatrial node ( SA node ) , and the vagus nerve provides parasympathetic input to the heart by releasing acetylcholine onto sinoatrial node cells . Therefore , stimulation of the accelerans nerve increases heart rate , while stimulation of the vagus nerve decreases it . </P>
<P> While heart rhythm is regulated entirely by the sinoatrial node under normal conditions , heart rate is regulated by sympathetic and parasympathetic input to the sinoatrial node . The accelerans nerve provides sympathetic input to the heart by releasing norepinephrine onto the cells of the sinoatrial node ( SA node ) , and the vagus nerve provides parasympathetic input to the heart by releasing acetylcholine onto sinoatrial node cells . Therefore , stimulation of the accelerans nerve increases heart rate , while stimulation of the vagus nerve decreases it . </P>
which part of the heart normally controls the heart rate
which part of the heart normally controls the heart rate
the sinoatrial node
the sinoatrial node