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

Triggered activity results from afterdepolarizations — oscillations in membrane potential that occur during (early afterdepolarizations, EADs) or after (delayed afterdepolarizations, DADs) repolarization and can trigger additional action potentials.

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

Gap junctions (connexins) in intercalated discs create low-resistance electrical connections between cardiac cells, allowing action potentials to propagate rapidly from cell to cell — making the heart function as an electrical syncytium.

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 fibrous cardiac skeleton electrically insulates the atria from the ventricles, making the AV node and bundle of His the only normal pathway for electrical conduction — accessory pathways in WPW breach this insulation.

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

Purkinje fibers conduct action potentials at 2-4 m/sec — among the fastest conduction velocities in the heart — enabling nearly simultaneous activation of both ventricles for synchronous contraction.

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

Parasympathetic (vagal) fibers release acetylcholine, which binds M2 muscarinic receptors on SA and AV nodal cells, slowing the heart rate and prolonging AV nodal conduction via potassium channel activation.

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT - Certified Rhythm Analysis Technician Practice Test

CRAT Arrhythmia Recognition, Anatomy, and Physiology 3