CRAT Cardiac Anatomy and Physiology 2

Question 1

Which structure is the primary pacemaker of the heart under normal conditions?

Accepted Answer

Sinoatrial (SA) node

Answer

The SA node in the right atrium is the dominant pacemaker, firing at 60-100 bpm due to its fastest intrinsic automaticity.

Question 2

What is the intrinsic firing rate of the AV node if it serves as the escape pacemaker?

Accepted Answer

40-60 bpm

Answer

The AV junction has an intrinsic escape rate of 40-60 bpm, slower than the SA node but faster than ventricular escape rhythms.

Question 3

During ventricular depolarization, which ECG component is produced?

Accepted Answer

QRS complex

Answer

The QRS complex represents ventricular depolarization — the electrical activation that spreads through the ventricular myocardium triggering contraction.

Question 4

The refractory period of the AV node serves which primary function?

Accepted Answer

Limiting ventricular rate during rapid atrial arrhythmias

Answer

The AV node's inherent delay and refractory period act as a gatekeeper, preventing excessively rapid atrial rates from being conducted to the ventricles at dangerous speeds.

Question 5

Which coronary artery most commonly supplies the SA node?

Accepted Answer

Right coronary artery (RCA)

Answer

In approximately 60% of individuals, the SA node is perfused by the right coronary artery, which is why inferior MI (RCA territory) often causes sinus bradycardia or AV block.

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT Cardiac Anatomy and Physiology 2