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
Node (circuits) Node (circuits) In electrical engineering, a node is any point on a circuit where the terminals of two or more circuit elements meet. In circuit diagrams, connections are ideal wires with zero resistance, so a node may consist of the entire section of wire between elements, not just a single point. According to Ohm's law, "V = IR", the voltage across any two points of a node with negligible resistance is showing that the voltage at every point of a node is the same. However, there are some notable exceptions where the voltage difference is large enough to become significant: