ECG Electrophysiology Basics 1

Question 1

What ions are primarily responsible for the cardiac action potential?

Accepted Answer

Sodium, potassium, and calcium

Answer

The cardiac action potential involves sodium influx (depolarization), calcium influx (plateau phase), and potassium efflux (repolarization), each contributing to different phases.

Question 2

What is the refractory period of cardiac cells?

Accepted Answer

The time during which cells cannot be re-stimulated to contract

Answer

The refractory period is when cardiac cells are unresponsive to new electrical stimuli, preventing tetanic contraction and ensuring the heart has time to fill between beats.

Question 3

What is automaticity in cardiac electrophysiology?

Accepted Answer

The ability of certain cardiac cells to generate their own electrical impulses

Answer

Automaticity is the ability of specialized cardiac cells (SA node, AV node, Purkinje fibers) to spontaneously depolarize and generate electrical impulses without external stimulation.

Question 4

What is the difference between depolarization and repolarization?

Accepted Answer

Depolarization is electrical activation; repolarization is electrical recovery

Answer

Depolarization is the process where cardiac cells become electrically activated (less negative), triggering contraction. Repolarization is the recovery process returning cells to their resting state.

Question 5

What is the intrinsic rate of the AV node when it acts as the pacemaker?

Accepted Answer

40-60 beats per minute

Answer

The AV node has an intrinsic firing rate of 40-60 bpm, slower than the SA node (60-100 bpm). It serves as a backup pacemaker if the SA node fails.

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ECG Electrophysiology Basics 1