CRAT Cardiac Anatomy and Physiology 3

Question 1

The PR interval on the ECG reflects conduction through which structures?

Accepted Answer

Atria, AV node, and bundle of His

Answer

The PR interval encompasses atrial depolarization (P wave) plus the conduction delay through the AV node and bundle of His before ventricular activation begins.

Question 2

Which cells in the heart have the property of automaticity, meaning they can spontaneously depolarize?

Accepted Answer

Pacemaker cells in the SA node, AV node, and His-Purkinje system

Answer

Automaticity — the ability to spontaneously depolarize — is possessed by pacemaker cells throughout the conduction system, with the SA node having the highest rate.

Question 3

In the normal cardiac conduction sequence, what is the correct order of activation?

Accepted Answer

SA node → atria → AV node → bundle of His → bundle branches → Purkinje fibers → ventricles

Answer

Normal conduction proceeds from the SA node through the atria, pauses at the AV node, then travels via the His-Purkinje system to activate the ventricles.

Question 4

Depolarization of cardiac muscle cells occurs primarily due to rapid influx of which ion?

Accepted Answer

Sodium (Na+)

Answer

Phase 0 of the cardiac action potential in non-pacemaker cells is characterized by rapid sodium influx through fast sodium channels, causing the steep upstroke of depolarization.

Question 5

Which layer of the heart is responsible for the electrical-to-mechanical coupling that produces contraction?

Accepted Answer

Myocardium

Answer

The myocardium (middle muscular layer) is where electrical depolarization triggers calcium release and actin-myosin cross-bridge formation, producing mechanical contraction.

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT Cardiac Anatomy and Physiology 3