Describe the initiation and conduction of electrical signals through the heart.

For the heart to pump efficiently the control of contraction of its atrium and ventricles needs to be coordinated. Electrical signal starts at the sinoatrial (SA) node, also known as the pacemaker node. The SA node produces action potentials that spread across the atria of the heart causing them to contract. From the atria the signal carries onto the atrioventricular (AV) node in the interventricular septum. Here the impulses pause and slow allowing the atria to fully contract and empty. Signal continues into the Bundle of His, this structure carries the impulses from the AV node to the purkinje fibers in the ventricles. These are located in the ventricle walls and spread the impulses through the ventricles forcing them to contract.