Lecture Notes: Electrical Anatomy and Physiology of the Heart

Introduction

• Objective: Understanding the heart's electrical conduction system, role in generating/transmitting impulses, coordinated heart contractions, and significance of conduction pathway.
• Key Terms: Concepts related to heart’s electrical system; pause and know meanings.

Heart's Electrical System

• Purpose: Acts as internal wiring ensuring correct timing and sequence for heart contraction.
• Role: Ensures synchronized contraction of atria (upper chambers) and ventricles (lower chambers).
• Impact: Efficient blood flow and circulation; dysfunction leads to arrhythmias.

Components of the Electrical Conduction System

SA Node (Sinoatrial Node)

• Location: Upper right atrium.
• Function: Initiates impulses, natural pacemaker of the heart.
• Rate: 60-100 impulses per minute.
• Influence: Autonomic nervous system affects impulse rate (sympathetic increases, parasympathetic decreases).

AV Node (Atrioventricular Node)

• Location: Junction between atria and ventricles.
• Function: Delays impulses, ensuring atria contract before ventricles (atrial kick).
• Backup Role: Can act as pacemaker (40-60 bpm) if SA node fails.

Bundle of His

• Location: Top of interventricular septum.
• Function: Transmits impulses from AV node to bundle branches.
• Importance: Ensures synchronized ventricular contraction.
• Issues: Malfunction can cause bundle branch blocks.

Right and Left Bundle Branches

• Location: Interventricular septum.
• Function: Conduct impulses to respective ventricles.
• Role: Ensures simultaneous ventricular contraction for optimal cardiac output.
• Issues: Blockages cause asynchronous contractions.

Purkinje Fibers

• Location: Ventricular walls.
• Function: Distribute impulses rapidly for synchronized ventricular contraction.
• Importance: Maintains effective pumping of blood.

Physiology of Conduction

Depolarization

• Process: Electrical activation and contraction of cardiac cells via ion exchange (Na+, Ca2+ in; K+ out).

Repolarization

• Process: Restores cells to resting state (K+ in; Na+, Ca2+ out).

Sequence of Conduction

1. SA Node: Initiates impulse.
2. AV Node: Delays impulse.
3. Bundle of His: Transmits impulse.
4. Bundle Branches: Conduct to ventricles.
5. Purkinje Fibers: Facilitate ventricular contraction.

Clinical Significance

• ECG Interpretation: Understanding the conduction system assists in identifying arrhythmias and other cardiac anomalies.
• Cardiac Monitoring: Essential for real-time heart rhythm/rate observation and detecting deviations.
• Treatment Decisions: Recognizing pathway abnormalities guides interventions (e.g., pacemaker placement).

Recap

• Key Concepts: Importance of synchronized heart contractions and the role of conduction components.
• Clinical Application: Knowledge crucial for ECG interpretation, monitoring, and managing cardiac conditions.

Conclusion

• Apply knowledge in clinical practice to improve patient outcomes and manage heart conditions effectively.