The two structures that directly receive an electrical impulse from the sinoatrial (SA) node are:

1. Right atrium: The SA node is located in the right atrium, and the impulse spreads directly through the atrial muscle tissue.

2. Internodal pathways: These are specialized conduction pathways that connect the SA node to the atrioventricular (AV) node. They facilitate the rapid and efficient transmission of the electrical impulse from the SA node to the AV node.