Sinoatrial node Ca into the cell), and the activation of potassium channels, which allows the flow of K out of the cell, making the membrane potential more negative. Heart rate depends on the rate at which the sinoatrial node produces action potentials. At rest, heart rate is between 60 and 100 beats per minute. This is a result of the activity of two sets of nerves, one acting to slow down action potential production (these are parasympathetic nerves) and the other acting to speed up action potential production (sympathetic nerves). The sympathetic nerves begin in the thoracic region of the spinal cord
Sinoatrial node it has arisen from the circumflex artery, which is a branch of the left coronary artery. Finally, the SA node artery commonly passes behind the superior vena cava, before reaching the SA node; however in some instances it passes in front. Despite these many differences, there doesn’t appear to be any advantage to how many sinoatrial nodal arteries an individual has, or where they originate There are no large veins that drain blood away from the SA node. Instead, smaller venules drain the blood directly into the right atrium. The main role of a sinoatrial node cell is to initiate