CRAT Arrhythmia Recognition, Anatomy, and Physiology 2

Question 1

The cardiac action potential plateau phase (Phase 2) is maintained primarily by which ion current?

Accepted Answer

Slow inward calcium current (ICa-L)

Answer

Rapid sodium influx

Answer

Rapid potassium efflux

Answer

Chloride influx

Question 2

Which ECG finding is expected during the absolute refractory period of the cardiac cycle?

Accepted Answer

No cardiac stimulus can produce a new action potential — corresponds to the QRS complex through early T wave

Answer

Any stimulus can produce fibrillation

Answer

The SA node is firing rapidly

Answer

P waves are produced by atrial repolarization

Question 3

Which ion primarily responsible for Phase 3 (rapid repolarization) of the ventricular action potential?

Accepted Answer

Potassium efflux through IKr and IKs channels

Answer

Sodium influx

Answer

Calcium influx

Answer

Chloride efflux

Question 4

Automaticity in pacemaker cells is generated by which mechanism?

Accepted Answer

Spontaneous slow diastolic depolarization (Phase 4) driven by the If funny current

Answer

Rapid sodium channel opening during rest

Answer

Passive potassium influx

Answer

Calcium pump activity

Question 5

A reentrant arrhythmia requires which three conditions to be established and maintained?

Accepted Answer

A closed circuit pathway, unidirectional block in one limb, and slow conduction in the other limb allowing recovery

Answer

Two SA nodes and an accessory pathway

Answer

Complete AV block and ventricular escape rhythm

Answer

Three P waves for each QRS complex

Question 6

The atrioventricular node (AV node) is located in which part of the heart?

Accepted Answer

Posteroinferior right atrium at the junction with the interventricular septum (Koch's triangle)

Answer

High right atrium near the superior vena cava

Answer

Left ventricular free wall

Answer

Interventricular septum at the cardiac apex