What is the normal pacemaker of the heart?

SA node in R atrium: The internal pacemaker of the heart is called the sino-atrial (sa) node and is located in the upper part of the right atrium by the right auricle. It is inherently active in that it doesn't need the brain to operate - just to regulate it. The sa node then directs its signals to the av node to the bundle of his to the purkinje fiber system. This regulates the contraction of all 4 chambers.

The sinus node: The sinus node is a group of specialized pacemaker cells that is located in the upper right atrium. These cells react to circulating chemicals, such as adrenaline, and there are nerve connections from the brain that modify the heart rate in response to the body's needs.