Final answer:
The sinoatrial (SA) node is the cardiac pacemaker responsible for initiating the heart's rhythm.
Explanation:
The sinoatrial (SA) node located in the upper wall of the right atrium is known as the cardiac pacemaker of the heart. It initiates the normal rhythm of the heart by creating an action potential that leads to atrial contraction.
Learn more about cardiac pacemaker here:
https://brainly.com/question/42972171
