Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

18. The Heart

Electrocardiogram (ECG)

Anatomy & Physiology

18. The Heart

Electrocardiogram (ECG)

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Multiple Choice

The QRS wave of an ECG represents which event in the cardiac cycle?

Atrial repolarization

Ventricular depolarization

Ventricular repolarization

Atrial depolarization

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Verified step by step guidance

Step 1: Begin by understanding the components of an ECG (electrocardiogram). An ECG is a graphical representation of the electrical activity of the heart during the cardiac cycle. It consists of several waves: P wave, QRS complex, and T wave.

Step 2: Recall the physiological events associated with each wave. The P wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization. Atrial repolarization occurs but is typically masked by the QRS complex.

Step 3: Focus on the QRS complex. Ventricular depolarization is the electrical event that triggers the contraction of the ventricles, which is crucial for pumping blood to the lungs and the rest of the body.

Step 4: Eliminate the incorrect options based on the definitions. Atrial depolarization corresponds to the P wave, ventricular repolarization corresponds to the T wave, and atrial repolarization is not distinctly visible because it is obscured by the QRS complex.

Step 5: Conclude that the QRS wave of an ECG represents ventricular depolarization, as this is the electrical activity associated with the contraction of the ventricles.