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

During which part of the ECG are the atria repolarizing?

T wave

U wave

P wave

QRS complex

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Verified step by step guidance

Understand the components of an ECG: An electrocardiogram (ECG) is a test that records the electrical activity of the heart. It consists of several waves: P wave, QRS complex, T wave, and sometimes a U wave.

Identify the function of each wave: The P wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization. The U wave is not always present and its origin is not well understood.

Focus on atrial repolarization: Atrial repolarization is the process by which the atria return to their resting state after depolarization.

Consider the timing of atrial repolarization: Atrial repolarization occurs during the QRS complex. However, it is not visible on the ECG because it is masked by the larger electrical activity of the ventricles depolarizing.

Conclude that the QRS complex is the part of the ECG where atrial repolarization occurs, even though it is not directly visible due to the dominance of ventricular depolarization signals.