1. The Electrical Conduction System
Advanced Cardiac Care in the Streets Understanding EKGs Ray Taylor Valencia Community College
The Electrical Conduction System

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3. The Electrical Conduction System
Objectives
1. Identify the location and function of the following:
SA Node
Internodal pathways
Bachmann’s Bundle
AV Node
Bundle of His
AV Junction
Bundle Branches
Purkinje Network

4. The Electrical Conduction System
Objectives
2. Relate the normal path of an impulse traveling through the heart’s electrical conduction system

5. Cardiac Conduction System
Components
Sinoatrial Node
Internodal Atrial Pathways
Bachman’s Bundle
Atrioventricular Node
Atrioventricular Junction
Bundle of His
Left and Right Bundle Branches
Purkinje Fibers

6. The SA Node
The Sinoatrial [SA] Node is located in the upper posterior portion of the right atrial wall of the heart
Junction of RA and SVC
“primary pacemaker” of the heart
Firing rate = 60 to 100 beats per min.
Depolarization and Myocardial contraction occurs after impulse leaves SA Node

7. Internodal Pathways
The Internodal pathways receive the electrical impulse as it exits the SA Node.
Anterior, posterior, and middle pathways
Pathways distribute impulse throughout atria
Transmit impulse from SA Node to AV Node

8. Bachmann’s Bundle
Bachmann’s Bundle - a group of interatrial fibers contained in left atrium
A subdivision of anterior internodal tract
Conducts electrical activity from the SA Node to the left atrium

9. The AV Node
The Atrioventricular (AV) Node - located on floor of right atrium above tricuspid valve
Electrical activity delayed seconds
Allows for more complete filling of ventricles
Only pathway for atrial electrical impulses to reach ventricles
“Gate-Keeper to the ventricles

10. The AV Junction The AV Junction is where SA Node joins Bundle of His
SA Node fails or slows below normal, AV junctional tissues initiate electrical activity
Secondary (escape) Pacemaker
Discharges at intrinsic firing rate 40 – 60 beats per minute

11. The Bundle of His
Bundle of His - conduction pathway that leads out of AV node
Lies at top of interventricular septum
Referred to as the “common bundle”
Makes electrical connection between atria and ventricles
Ability to self-initiate electrical activity at intrinsic firing rate of 40 to 60 beats per min.

12. Bundle Branches Bundle of His divides into two main Bundle Branches
1. Right Bundle Branch
Long and thin
Extends to apex of right ventricle
2. Left Bundle Branch
Anterior and posterior fascicles
Conduct electrical activity from Bundle of His to Purkinje Network

13. Purkinje’s Network
Purkinje’s Network - fibers that spread throughout the ventricles
Carries impulses directly to ventricular muscle cells
Intrinsic firing rate of 20 to 40 beats per min.

14. Summary of Conduction System
SA node
Internodal pathways and Bachman’s bundle
AV Node
His Bundle
Bundle Branches
Purkinje Network

15. Summary of Discharge Rates
Sinoatrial Node
Primary pacemaker with fastest intrinsic discharge rate
60 – 100 beats per minute
AV Junction
Secondary pacemaker
40 – 60 beats per minute
Purkinje Fibers
20 – 40 beats per minute

16. Thank you!