What does the term "pace maker of the heart" refer to?

The term "pacemaker of the heart" refers to the SA (sinoatrial) node, which is located in the right atrium. The SA node is crucial for initiating the electrical impulses that stimulate heartbeats. It effectively establishes the heart's rhythm and rate by generating electrical signals that cause the heart muscles to contract and pump blood throughout the body.

As the primary pacemaker, the SA node responds to various physiological needs and can modify the heart rate with influences from the autonomic nervous system. This adaptability is vital for maintaining homeostasis, particularly during activities such as exercise or periods of rest.