Electrocardiogram (EKG/ECG) Lecture Notes

Introduction

• Speaker: Leslie Samuel from Interactive Biology
• Topic: Understanding the electrocardiogram (EKG or ECG)
• Purpose: To explain how to read an EKG and understand its components.

What is an EKG?

• An EKG records the electrical activity of the heart.
• Used to detect irregularities in heart function.
• Recorded using skin electrodes placed on different parts of the body.
• Results in a graph with distinct components.

Heartbeat Signal Generation (Brief Review)

• SA Node: Starts the signal in the right atrium.
• Signal Pathway:
  • SA node → Atria (contraction)
  • Signal reaches AV node.
  • Signal travels via bundle fibers to Purkinje fibers → Ventricles (contraction).

EKG Components

• P-Wave:

  • Represents atrial depolarization.
  • Occurs when the SA node signal spreads to atrial muscle cells.
  • Atrial depolarization leads to contraction.

• QRS Complex:

  • Represents ventricular depolarization.
  • Larger than the P-wave due to larger muscle mass of ventricles compared to atria.
  • Ventricles are responsible for pumping blood throughout the body.

• T-Wave:

  • Represents ventricular repolarization.
  • Follows the depolarization and leads to relaxation.

Additional Insights

• Atrial Repolarization:
  • Occurs but is not visible on the EKG.
  • Overshadowed by the larger QRS complex during ventricular depolarization.

Conclusion

• The EKG consists of the P-wave (atrial depolarization), QRS complex (ventricular depolarization), and T-wave (ventricular repolarization).
• Understanding these components helps interpret the electrical activity and function of the heart.
• Further learning: Understanding how electrical signals result in heart contraction (suggested next video by Leslie Samuel).