Cardiac Cycle Lecture Notes

Introduction

• Lecturer: Leslie Samuel
• Focus: Simplifying the cardiac cycle
• Objective: Understand the cardiac cycle by the end of the lecture

Cardiac Cycle Overview

• Definition: The sequence of events in a heartbeat from start to finish.
• Key Components: Atria, Ventricles, Heart Valves

Blood Flow Through the Heart

• Left Side: Blood returns from the lungs.
• Right Side: Blood returns from the body.
• Atria Function: Contract to push blood into the ventricles.
• Ventricles Function: Contract to push blood out of the heart.

Electrocardiogram (ECG)

• Purpose: Shows electrical signals of the heart

P Wave

• Function: Depolarization of the atria
• Effect: Atria contract (Atrial Systole)
• Result: Increase in atrial pressure and ventricular volume as blood flows into ventricles.

QRS Complex

• Function: Depolarization of the ventricles
• Effect: Ventricular contraction (Ventricular Systole)
• Result: Increase in ventricular pressure

Isovolumetric Contraction

• Definition: Volume remains constant as ventricles contract
• Process: Both atrioventricular and semilunar valves are closed, leading to an increase in ventricular pressure

Ejection Phase

• Trigger: Semilunar valve opens when ventricular pressure exceeds aortic pressure (~80 mmHg)
• Result: Blood is ejected from the ventricles, reducing ventricular volume

T Wave

• Function: Ventricular repolarization
• Effect: Ventricular relaxation and pressure decrease

Isovolumetric Relaxation

• Process: Ventricles relax with closed valves, decreasing pressure
• Outcome: Atrioventricular valve opens once ventricular pressure is below atrial pressure

Phonocardiogram (Heart Sounds)

• First Sound (Lub): Closure of atrioventricular valves (Occurs during QRS complex)
• Second Sound (Dub): Closure of semilunar valves (Occurs after T wave)

Conclusion

• Summary: Recap of the cardiac cycle from ECG perspective

• Encouragement: Review the material to solidify understanding

• Presenter: Leslie Samuel from Interactive Biology

• Reminder: Understanding the cardiac cycle can be fun and engaging!