Quiz: Cardiac Electrical Physiology and Arrhythmias — 10 Fragen

1. What is the conduction pathway in the heart?

A. The physical anatomical route of the electrical wiring within the heart tissue.

B. The pathway through which blood flows during cardiac contraction.

C. The sequence of electrical activation that ensures coordinated contraction of the heart muscle.

D. The sequence of mechanical events leading to heart muscle contraction.

Answer: (C)

Erklärung

The conduction pathway is the sequence of electrical activation in the heart that ensures coordinated contraction, starting from the SA node and passing through atria, AV node, bundle of His, bundle branches, and Purkinje fibers.

2. Which structure acts as the heart's natural pacemaker and initiates electrical impulses?

A. Atrial Conduction System

B. SA Node

C. AV Node

D. Purkinje Fibers

Answer: (B)

Erklärung

The SA Node, or sinoatrial node, is the primary pacemaker of the heart, setting the rhythm by initiating electrical impulses. The other options play roles in conduction but do not originate the impulse.

3. During which ionic movement does Phase 0 of the cardiac action potential primarily occur?

A. Efflux of potassium ions through delayed rectifier channels

B. Efflux of chloride ions through chloride channels

C. Influx of calcium ions through L-type calcium channels

D. Influx of sodium ions through fast sodium channels

Answer: (D)

Erklärung

Phase 0 of the cardiac action potential is characterized by a rapid influx of sodium ions through fast sodium channels, leading to depolarisation. This is the primary ionic event during this phase, making it the correct answer. The other options refer to ionic movements that occur during different phases: calcium influx during Phase 2 (plateau), potassium efflux during Phase 3 (repolarisation), and chloride channels are not the main contributors to Phase 0.

4. What is the primary function of the AV node in cardiac conduction?

A. Fire electrical impulses rapidly to ventricles

B. Delay conduction to allow atrial contraction

C. Generate pacemaker activity

D. Distribute impulses to the Purkinje fibers

Answer: (B)

Erklärung

The AV node delays the electrical impulses from the atria to the ventricles, ensuring atrial contraction occurs prior to ventricular contraction for efficient cardiac function.

5. What is the primary role of refractory periods in cardiac electrophysiology?

A. To initiate action potentials in cardiac cells

B. To coordinate atrial and ventricular contractions

C. To prevent re-entry circuits and abnormal rhythms

D. To generate the heart's pacemaker activity

Answer: (C)

Erklärung

Refractory periods serve to prevent re-entry circuits and abnormal rhythms by ensuring that cardiac cells cannot be re-excited immediately after depolarisation, thus maintaining a coordinated and rhythmic heartbeat.

6. Which phase of the cardiac action potential is characterized by rapid Na⁺ influx?

A. Phase 0: Depolarisation

B. Phase 2: Plateau

C. Phase 3: Repolarisation

D. Phase 4: Resting potential

Answer: (A)

Erklärung

Phase 0 involves rapid Na⁺ entry through fast sodium channels, causing rapid depolarisation of the cardiac cell membrane.

7. How do the conduction speeds vary across the cardiac conduction pathway?

A. Slow in the His-Purkinje system and fast in the atria

B. Fast in atria and ventricles, slow in AV node

C. Slow in atria, very slow in AV node, very fast in His-Purkinje system

D. Constant throughout the pathway

Answer: (C)

Erklärung

The conduction speed is slow in the atria, very slow at the AV node to allow filling, and very fast in the His-Purkinje system for synchronised ventricular contraction.

8. What is the significance of the AV delay in cardiac conduction?

A. Prevents atrial contraction

B. Allows ventricles to fill after atrial contraction

C. Initiates ventricular depolarisation

D. Speeds up overall conduction velocity

Answer: (B)

Erklärung

The AV delay permits the atria to contract and empty blood into the ventricles before the ventricles contract, optimizing cardiac efficiency.

9. Which ion movement sustains the plateau phase during the cardiac action potential?

A. Na⁺ influx

B. K⁺ efflux

C. Ca²⁺ influx

D. Cl⁻ influx

Answer: (C)

Erklärung

The plateau phase is mainly maintained by the influx of Ca²⁺ via L-type calcium channels, balancing K⁺ efflux and prolonging depolarisation.

10. Which structure rapidly distributes impulses throughout the ventricles, causing synchronized contraction?

A. SA Node

B. Bundle of His

C. Purkinje fibers

D. Atrial myocardium

Answer: (C)

Erklärung

Purkinje fibers form a network that rapidly conducts electrical impulses, ensuring the ventricles contract in a coordinated manner for effective pumping.