What are the pacemakers of the heart?

Question

In my test earlier, there were 4 blanks, I only know the SA node as a pacemaker... thanks

Answer 1

Cardiac pacemaker, a group of cells within the heart that together initiate contractions and set the pace of beating.

Artificial pacemaker, a device implanted to provide proper heart rhythm when the body's natural pacemaker does not function properly

The contractions of the heart are controlled by electrical impulses, these fire at a rate which controls the beat of the heart.

The cells that create these rhythmical impulses are called pacemaker cells, and they directly control the heart rate. Artificial devices also called pacemakers can be used after damage to the body's intrinsic conduction system to produce these impulses synthetically.

Although all of the heart's cells possess the ability to generate these electrical impulses (or action potentials), a specialised portion of the heart, called the sinoatrial node, is responsible for the whole heart's beat.

The sinoatrial node (SA node) is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava. These cells are modified cardiac myocytes. They possess some contractile filaments, though they only contract relatively weakly.

Cells in the SA node will spontaneously depolarize, resulting in contraction, approximately 100 times per minute. This native rate is constantly modified by the activity of sympathetic and parasympathetic nerve fibers, so that the average resting cardiac rate in adult humans is about 60 beats per minute. Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the primary pacemaker.

If the SA node doesn't function, or the impulse generated in the SA node is blocked before it travels down the electrical conduction system, a group of cells further down the heart will become the heart's pacemaker, this is known as an ectopic pacemaker. These cells form the atrioventricular node (AV node), which is an area between the atria and ventricles, within the atrial septum.

The cells of the AV node normally discharge at about 40-60 beats per minute, and are called the secondary pacemaker.