The volume of blood circulated by a human heart over a lifetime would fill more than a trio of oil supertankers. The contraction of the heart muscle constantly regulates this flow in the form of a pulse, measured in heartbeats per minute. The right atrium, which is one of four heart chambers, contains the sinus node, which acts as the pacemaker for the heart. The body's nervous system, neurotransmitters, and hormones regulate the sinus node. In addition, exercise, physical activity and emotional and physical stress also affect heart rate. yes I know this is more than 1 way lol