Which of the following is NOT a function of the sinoatrial node?

The sinoatrial (SA) node, often referred to as the natural pacemaker of the heart, primarily functions by initiating heartbeats and regulating heart rate. It generates electrical impulses that cause the heart to contract, thus playing a crucial role in establishing the rhythm of the heartbeat.

While the SA node does conduct electrical impulses to the atria and coordinates the timing of heart contractions, it does not maintain venous pressure. Maintaining venous pressure is a function of the venous system and is influenced by various factors, including blood volume, venous return, and the tone of the smooth muscle in the veins. The circulatory system relies on the overall function of the cardiovascular system, but the SA node itself is not involved in directly regulating venous pressure. Therefore, the correct choice highlights its role distinctly separate from other vital functions in circulation.