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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2:53 minutes

Problem 5

Textbook Question

More than one choice may apply.
Atrial repolarization coincides in time with the
a. P wave
b. T wave
c. QRS wave
d. P-Q interval

Verified step by step guidance

Understand the concept of atrial repolarization: Atrial repolarization is the process by which the atria return to their resting electrical state after depolarization. This occurs after the atria have contracted and is typically masked by other electrical events in the heart.

Review the components of an electrocardiogram (ECG): The P wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization. The P-Q interval is the time between the start of atrial depolarization and the start of ventricular depolarization.

Recognize that atrial repolarization is not directly visible on an ECG: Atrial repolarization coincides with the QRS complex, which represents ventricular depolarization. The electrical activity of atrial repolarization is overshadowed by the larger electrical signal of the QRS complex.

Eliminate incorrect options: The P wave represents atrial depolarization, not repolarization. The T wave represents ventricular repolarization, not atrial repolarization. The P-Q interval is a time measurement and does not directly represent atrial repolarization.

Conclude that atrial repolarization coincides with the QRS wave: This is because the electrical activity of atrial repolarization occurs simultaneously with ventricular depolarization, which is represented by the QRS complex.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atrial Repolarization

Atrial repolarization refers to the process by which the atria of the heart recover from depolarization after contraction. This electrical event is not typically visible on an electrocardiogram (ECG) as a distinct wave, but it occurs during the QRS complex, which represents ventricular depolarization.

Electrocardiogram (ECG) Waves

An electrocardiogram (ECG) displays the electrical activity of the heart through various waves: the P wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization. Understanding these waves is crucial for interpreting cardiac function and identifying abnormalities.

QRS Complex

The QRS complex is a key component of the ECG that reflects the rapid depolarization of the ventricles. It typically masks the atrial repolarization, which occurs simultaneously, making it important to recognize that while atrial repolarization happens during this time, it is not represented as a separate wave on the ECG.