how is the cardiac cycle initiated ? how is the heart rate or the number of...

how is the cardiac cycle initiated ? how is the heart rate or the number of cardiac cyles per minute modulated?

Expert Solution

The cardiac electric activity that triggers Cardiac cycle originates in a specialized cardiac conduction system and spreads via this system to all parts of the myocardium. The structures that make up the conduction system are the Sinoatrial node (SA node), the internodal atrial pathways, the atrioventricular node (AV node), the bundle of His and its branches, and the Purkinje system.

The Cardiac Cycle consists of mainly three phases The Atrial Systole, Ventricular Systole, and Ventricular Diastole.

The normal human heart, each beat originates in the SA node. The heart beats about 70-80 times a minute at rest. The rate is slowed (bradycardia) during sleep and accelerated (tachycardia) by, exercise, fever, and many other stimuli.

The Heart rate is modulated by either Vagal stimulation Which causes Bradycardia( decreased HR), or Sympathetic or Adrenergic stimulation which causes Tachycardia( increased HR).

Sydney Mullin answered 1 year ago

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