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Heart rate is the number of times the heart beats per minute. This is normally determined by the electrical activity of the Sino-Atrial node. The autonomic nervous system controls the rate of discharge of the S-A node.

Heart rate is determined by four factors:

  1. Intrinsic rate: The natural rate of discharge of cardiac tissue in the absence of other factors.
  2. Sympathetic activity: Increases heart rate.
  3. Parasympathetic activity: Decreases heart rate.
  4. Pharmacologic: Increases or decreases heart rate depending on the drug.