Download The Heartbeat

The Heartbeat
• What Two Types of Cardiac Cells are Needed
for the Heartbeat?
• Contractile cells
• Provide the pumping action
• Cells of the conducting system
• Generate and spread the action
potential
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Heartbeat
• What is the Conducting System?
• Starts and spreads electrical impulses in heart
• Two types of cells
• Nodal cells
• Pacemaker cells
• Reach threshold first
• Set heart rate
• Conducting cells
• Distributes stimuli to myocardium
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Heartbeat
• What is the Conducting System? (cont’d)
• Heart is self-exciting
• Pacemaker cells establish heart rate
• Normal pacemaker is sinoatrial (SA) node
• Impulse spreads from SA node:
• Across atria
• To atrioventricular (AV) node
• To AV bundle and bundle branches
• Via Purkinje fibers to ventricles
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Heartbeat
• What is the Electrocardiogram (ECG or EKG)?
• A recording of the electrical activity of the
heart
• Three main components
• P wave
• Atrial depolarization
• QRS complex
• Ventricular depolarization
• T wave
• Ventricular repolarization
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings