Cardiac Syncytium and Arrhythmias Quiz
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Questions and Answers

What is the primary function of gap junctions in the cardiac syncytium?

  • To enable synchronized contraction of cardiac cells (correct)
  • To increase the strength of contraction
  • To promote vascular smooth muscle contraction
  • To prevent electrical signals from passing between cells

Which ion is primarily responsible for the rapid depolarization in phase 0 of the cardiac myocyte action potential?

  • Chloride (Cl)
  • Calcium (Ca)
  • Potassium (K)
  • Sodium (Na) (correct)

What occurs during phase 2 (plateau) of the cardiac myocyte action potential?

  • Rapid depolarization
  • Influx of sodium ions
  • Repolarization via potassium channels
  • Simultaneous entry of calcium and efflux of potassium (correct)

Which channels are responsible for pacemaker depolarization in the cardiac nodal action potential?

<p>Leak currents of sodium and potassium (A)</p> Signup and view all the answers

What characterizes an ectopic beat?

<p>It is initiated by myocytes outside the normal conduction pathway (C)</p> Signup and view all the answers

What describes a common cause of tachycardia associated with after-polarization?

<p>High [Ca]i triggers trains of action potentials (D)</p> Signup and view all the answers

What is the mechanism of re-entry in arrhythmias?

<p>A circulating impulse re-excites previously active tissue (B)</p> Signup and view all the answers

Which feature is characteristic of Wolfe-Parkinson-White (WPW) syndrome?

<p>Shortened PR interval due to retrograde conduction (B)</p> Signup and view all the answers

Flashcards

What do gap junctions in the heart do?

Gap junctions allow rapid and direct flow of electrical signals between cardiac cells, ensuring that they contract in a synchronized manner, crucial for an efficient heartbeat.

What is the main ion responsible for the rapid depolarisation in phase 0?

During phase 0, the rapid rise in membrane potential is largely due to the sudden influx of sodium ions (Na+) into the cardiac myocyte.

Describe the ionic movement during phase 2 of the cardiac action potential.

Phase 2, the plateau, is a balancing act - calcium ions entering the cell are counteracted by potassium ions leaving. This delayed repolarization allows for a sustained contraction.

What is the primary mechanism for pacemaker depolarization?

The pacemaker potential is a slow, spontaneous depolarization in the heart's pacemaker cells due to special leak currents allowing sodium and potassium to move into the cell.

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What is an ectopic beat?

An ectopic beat is an abnormal heartbeat that originates from a location outside the sinoatrial (SA) node, the heart's natural pacemaker.

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How does after-polarisation cause tachycardia?

Tachycardia due to after-polarisation is often caused by high intracellular calcium levels ([Ca]i), which can trigger a series of action potentials in a rapid succession, leading to a fast heart rate.

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Explain the mechanism of re-entry arrhythmias.

Re-entry arrhythmias occur when an electrical impulse travels around a loop in the heart, repeatedly re-exciting tissues causing an irregular heartbeat.

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What is a key feature of Wolfe-Parkinson-Write (WPW) syndrome?

Wolfe-Parkinson-White (WPW) syndrome is characterized by a shortened PR interval, due to an additional pathway that allows electrical signals to bypass the AV node.

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Study Notes

Cardiac Syncytium and Action Potential

  • Gap junctions in cardiac syncytium increase the strength of contraction and enable synchronized contraction of cardiac cells
  • The rapid depolarization in the cardiac myocyte action potential phase 0 is primarily due to sodium (Na+) ions
  • Phase 2 (plateau) of the cardiac myocyte action potential involves simultaneous entry of calcium (Ca2+) and efflux of potassium (K+)
  • Pacemaker depolarization in cardiac nodal action potentials is caused by leak currents of sodium and potassium.

Ectopic Beats and Arrhythmias

  • Ectopic beats originate outside the normal conduction pathway
  • Early afterdepolarization (EAD) can lead to prolonged depolarisation and ventricular arrhythmias like Torsades de Pointes
  • EAD is often linked to high intracellular calcium levels
  • Re-entry in arrhythmias occurs when a circulating impulse re-excites previously active tissue
  • Wolff-Parkinson-White (WPW) syndrome is characterized by a shortened PR interval.

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Description

Test your knowledge on cardiac syncytium and action potential, examining how synchronized contractions occur in heart cells. Additionally, explore ectopic beats and arrhythmias, understanding their origins and implications in cardiac health. This quiz covers important concepts related to cardiac physiology and pathophysiology.

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