ECG Electrophysiology Basics 1 — Questions and Answers
Question 1: What ions are primarily responsible for the cardiac action potential?
- Sodium, potassium, and calcium (Correct answer)
- Only sodium and potassium
- Iron and magnesium
- Chloride and phosphate
Correct answer: Sodium, potassium, and calcium
The cardiac action potential involves sodium influx (depolarization), calcium influx (plateau phase), and potassium efflux (repolarization), each contributing to different phases.
Question 2: What is the refractory period of cardiac cells?
- The time during which cells cannot be re-stimulated to contract (Correct answer)
- The resting period between heartbeats
- The time it takes for blood to fill the chambers
- The duration of the T wave
Correct answer: The time during which cells cannot be re-stimulated to contract
The refractory period is when cardiac cells are unresponsive to new electrical stimuli, preventing tetanic contraction and ensuring the heart has time to fill between beats.
Question 3: What is automaticity in cardiac electrophysiology?
- The ability of certain cardiac cells to generate their own electrical impulses (Correct answer)
- The automatic recording feature of ECG machines
- The heart's response to exercise
- The regulation of blood pressure
Correct answer: The ability of certain cardiac cells to generate their own electrical impulses
Automaticity is the ability of specialized cardiac cells (SA node, AV node, Purkinje fibers) to spontaneously depolarize and generate electrical impulses without external stimulation.
Question 4: What is the difference between depolarization and repolarization?
- Depolarization is electrical activation; repolarization is electrical recovery (Correct answer)
- They are the same process
- Depolarization occurs only in atria
- Repolarization occurs only in ventricles
Correct answer: Depolarization is electrical activation; repolarization is electrical recovery
Depolarization is the process where cardiac cells become electrically activated (less negative), triggering contraction. Repolarization is the recovery process returning cells to their resting state.
Question 5: What is the intrinsic rate of the AV node when it acts as the pacemaker?
- 40-60 beats per minute (Correct answer)
- 60-100 beats per minute
- 20-40 beats per minute
- 100-150 beats per minute
Correct answer: 40-60 beats per minute
The AV node has an intrinsic firing rate of 40-60 bpm, slower than the SA node (60-100 bpm). It serves as a backup pacemaker if the SA node fails.
Question 6: What is conductivity in cardiac tissue?
- The ability to transmit electrical impulses from cell to cell (Correct answer)
- The ability to contract
- The ability to respond to stimuli
- The ability to return to resting state
Correct answer: The ability to transmit electrical impulses from cell to cell
Conductivity is the ability of cardiac cells to transmit electrical impulses to adjacent cells through gap junctions, ensuring coordinated contraction throughout the heart.
ECG Electrophysiology Basics 1
What ions are primarily responsible for the cardiac action potential?