<P> If the SA node does not function, or the impulse generated in the SA node is blocked before it travels down the electrical conduction system, a group of cells further down the heart will become its pacemaker . </P> <P> The sinoatrial node was first discovered by a young medical student, Martin Flack, in the heart of a mole, whilst his mentor, Sir Arthur Keith, was on a bicycle ride with his wife . They made the discovery in a makeshift laboratory set up in a picturesque farmhouse in Kent, England, called Mann's Place . Their discovery was published in 1907 . </P> <Ul> <Li> <P> Heart; conduction system (SA node labeled 1) </P> </Li> <Li> <P> Schematic representation of the atrioventricular bundle </P> </Li> </Ul> <Li> <P> Heart; conduction system (SA node labeled 1) </P> </Li>

Where does the sinoatrial node send an impulse after it initiates the electrical signal