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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Problem 12

Textbook Question

Explain what each of the following terms represents on an electrocardiogram (ECG).
a. P wave
b. QRS complex
c. T wave
d. P-R interval
e. S-T segment

Verified step by step guidance

The P wave on an electrocardiogram (ECG) represents atrial depolarization, which is the electrical activity that triggers the contraction of the atria. This occurs as the sinoatrial (SA) node sends an electrical impulse through the atria.

The QRS complex represents ventricular depolarization, which is the electrical activity that triggers the contraction of the ventricles. It is a rapid and large deflection due to the greater muscle mass of the ventricles compared to the atria.

The T wave represents ventricular repolarization, which is the process of the ventricles recovering electrically after contraction. This allows the ventricles to prepare for the next cycle of depolarization and contraction.

The P-R interval is the time from the beginning of the P wave to the start of the QRS complex. It represents the period during which the electrical impulse travels from the atria to the ventricles via the atrioventricular (AV) node, bundle of His, and Purkinje fibers.

The S-T segment is the flat portion of the ECG between the end of the QRS complex and the beginning of the T wave. It represents the period when the ventricles are fully depolarized and contracting, before they begin repolarization.

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Key Concepts

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

P Wave

The P wave on an electrocardiogram (ECG) represents atrial depolarization, which is the electrical activity that triggers the contraction of the atria. It is the first deflection in the ECG tracing and indicates the beginning of the cardiac cycle, reflecting the heart's preparation for pumping blood into the ventricles.

QRS Complex

The QRS complex signifies ventricular depolarization, which is the rapid electrical activation of the ventricles leading to their contraction. This complex is typically the most prominent feature on an ECG, consisting of three distinct waves (Q, R, and S) and is crucial for assessing the heart's rhythm and function.

T Wave

The T wave represents ventricular repolarization, the process by which the ventricles recover and prepare for the next heartbeat. It follows the QRS complex and is essential for understanding the heart's electrical recovery phase, indicating the heart's readiness for the next cycle of contraction.