Cardiac Cycle Lecture Notes

Introduction

• Heart Sounds: Lub dub, lub dub - representation of the heart's action.
• Cardiac Cycle: Consists of systole (contraction) and diastole (relaxation).

Phases of the Cardiac Cycle

1. Atrial Systole

• Atria Contract: Initiated by the P wave on the EKG.
• Atrial Depolarization: Key to atrial contraction.
• Increased Atrial Pressure: Results in blood flow into ventricles.

2. QRS Complex

• Ventricular Depolarization: Leads to ventricular contraction.
• Increased Ventricular Pressure: Compressed blood during isovolumetric contraction.
• Valve Action: Blood exits when valves open due to high pressure.

3. T Wave

• Ventricular Repolarization: Ventricles relax.
• Isovolumetric Relaxation: Pressure decreases, ventricles in relaxation phase.
• AV Valves Open: Passive filling of ventricles, cycle repeats.

Heart Sounds and Valves

• Sound "Lub": Closing of AV valves.
• Sound "Dub": Closing of semilunar valves.

Definitions

• Systole: Contraction phase of the heart.
• Diastole: Relaxation phase of the heart.
• Cardiac Cycle: Full process of heart's contraction and relaxation.

Additional Resources

• Guide for Deeper Understanding: Available at thecardiaccycle.com.

Presenter

• Leslie Samuel: From Interactive Biology, aiming to make biology fun.

• Ending with a musical repetition to emphasize the rhythmic nature of the cardiac cycle.