Editing Muscle cell (section)

====Cardiac muscle contraction====
{{See also|Bowditch effect}}
Specialized [[cardiomyocytes]] in the [[sinoatrial node]] generate electrical impulses that control the [[heart]] rate.  These electrical impulses coordinate contraction throughout the remaining heart muscle via the [[electrical conduction system of the heart]].  Sinoatrial node activity is modulated, in turn, by nerve fibers of both the [[Sympathetic nervous system|sympathetic]] and [[Parasympathetic nervous system|parasympathetic]] nervous systems.  These systems act to increase and decrease, respectively, the rate of production of electrical impulses by the sinoatrial node.