Heart Lecture 2 Narration

Cardiac Action Potential00:00:02

The lecture explains cardiac action potentials, highlighting the unique plateau phase caused by the influx of calcium ions, which helps prevent fatigue. It emphasizes a resting membrane potential of -90mV and describes the phases of depolarization and repolarization.

Electrical Activity and the EKG00:06:27

An overview of the EKG/ECG machine and its function in recording the electrical activity of the heart. The P-wave corresponds to atrial depolarization, the QRS complex represents ventricular depolarization, and the T-wave represents ventricular repolarization.

Segments and Intervals00:09:23

Clarification of EKG terminology: intervals (such as PQ and QT) encompass waves and segments, while segments (PQ and ST) are the flat lines between waves, representing periods where contraction is occurring without electrical deflection.

The Cardiac Cycle00:13:20

A detailed walk-through of the cardiac cycle, which typically lasts 800 milliseconds. It explains how electrical signals trigger mechanical contraction (systole) and relaxation (diastole), including valve mechanics (AV and semilunar valves) and pressure-driven blood flow.