Final answer:
Cardiac contractility is the ability of cardiac muscle to shorten in response to an electrical stimulus due to the heart's autorhythmic nature. An electrocardiogram can illustrate the electrical activity during a heart contraction. The SA node and other conductive cells help regulate the pace and coordination of these contractions.
Step-by-step explanation:
The ability of cardiac cells to shorten and cause cardiac muscle contraction in response to an electrical stimulus is known as contractility. This refers to the muscle's ability to contract forcibly during the contraction phase. The heart's rhythmic contractions occur thanks to the property of autorhythmicity, where pacemaker cells within the heart spontaneously generate electrical impulses without needing signals from the nervous or endocrine systems. These impulses then propagate across the heart via a depolarization wave, coordinating the contraction of the heart muscle and thus pumping blood throughout the body. It is this process that allows the heart to function as a unit—a functional syncytium. The electrical activity of the heart can be monitored with an electrocardiogram (ECG), which illustrates the depolarization waves that correspond to atrial and ventricular contraction. Noteworthy, different parts of the heart such as the sinoatrial (SA) node, atrioventricular (AV) node, and Purkinje fibers play a pivotal role in this autorythmic process, ensuring the heart beats at a regular pace and pumps blood effectively.