Editing Cardiac pacemaker (section)

{{short description|Network of cells that facilitate rhythmic heart contraction}}
{{about|the natural pacemaker in the heart|the medical device that simulates the function|Artificial cardiac pacemaker}}
{{More citations needed|date=December 2009}}

[[image:ConductionsystemoftheheartwithouttheHeart-en.svg|right|thumb|350px|Image showing the cardiac pacemaker or [[SA node]], the primary pacemaker within the [[electrical conduction system of the heart]]]]

The '''cardiac pacemaker''' is the [[heart]]'s natural rhythm generator. It employs pacemaker [[Cell (biology)|cells]] that produce electrical impulses, known as [[Cardiac action potential|cardiac action potentials]], which control the rate of contraction of the [[cardiac muscle]], that is, the [[heart rate]]. In most humans, these cells are concentrated in the [[sinoatrial (SA) node]], the primary pacemaker, which regulates the heart’s [[sinus rhythm]].

Sometimes a secondary pacemaker sets the pace, if the SA node is damaged or if the [[electrical conduction system of the heart]] has problems. [[Cardiac arrhythmia]]s can cause [[heart block]], in which the contractions lose their rhythm. In humans, and sometimes in other animals, a mechanical device called an [[artificial pacemaker]] (or simply "pacemaker") may be used after damage to the body's intrinsic conduction system to produce these impulses synthetically.