CRAT Arrhythmia Recognition, Anatomy, and Physiology 3

Question 1

Triggered activity as a mechanism of arrhythmia is caused by which electrophysiological phenomenon?

Accepted Answer

Afterdepolarizations (early or delayed) that reach threshold and trigger additional action potentials

Answer

Reentrant circuits in the AV node

Answer

Complete failure of sodium channel function

Answer

Vagal suppression of pacemaker cells

Question 2

The gap junctions in cardiac muscle (intercalated discs) serve which primary electrical function?

Accepted Answer

Allowing direct electrical coupling between adjacent cells for rapid propagation of action potentials

Answer

Storing calcium for contraction

Answer

Providing structural support to prevent cell rupture

Answer

Producing the QRS complex

Question 3

Which anatomical structure separates the atrial and ventricular conduction systems, making the AV node the only normal electrical connection between them?

Accepted Answer

The fibrous cardiac skeleton (annulus fibrosus)

Answer

The interventricular septum

Answer

The pericardium

Answer

The coronary sulcus

Question 4

The His-Purkinje system conducts at a significantly faster velocity than the AV node. What is the approximate conduction velocity in Purkinje fibers?

Accepted Answer

2-4 m/sec (up to 4 m/sec)

Answer

0.02-0.05 m/sec (as in AV node)

Answer

0.3-0.5 m/sec

Answer

10 m/sec

Question 5

In the autonomic nervous system, vagal (parasympathetic) stimulation affects the heart primarily through which neurotransmitter and receptor?

Accepted Answer

Acetylcholine acting on M2 muscarinic receptors in the SA and AV nodes

Answer

Norepinephrine acting on beta-1 receptors

Answer

Epinephrine acting on alpha-1 receptors

Answer

Dopamine acting on D1 receptors

Question 6

Which concept explains why the SA node normally suppresses potential pacemaker activity in the AV node and His-Purkinje system?

Accepted Answer

Overdrive suppression — faster pacemakers suppress slower ones by repeatedly resetting their Phase 4 depolarization

Answer

The SA node releases a chemical that inhibits lower pacemakers

Answer

The AV node has no automaticity

Answer

Retrograde conduction blocks all lower pacemakers