The electrical impulse that initiates the heartbeat typically originates from the?

The electrical impulse that initiates the heartbeat originates from the SA node, also known as the sinoatrial node. The SA node is located in the right atrium and serves as the primary pacemaker of the heart. It generates electrical signals that spread throughout the atria, causing them to contract and pump blood into the ventricles. This action sets the rhythm of the heartbeat and influences the heart rate.

The other structures mentioned play important roles in the conduction system of the heart but are not responsible for initiating the heartbeat. The AV node, for instance, acts as a gatekeeper that receives impulses from the atria and transmits them to the ventricles, ensuring proper timing between atrial and ventricular contractions. The Bundle of His and Purkinje fibers are part of the conduction pathway that helps distribute the impulse rapidly through the ventricles but do not initiate the heartbeat. Therefore, the SA node's role as the primary pacemaker makes it the correct answer.