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

Electrical Conduction System of the Heart

Anatomy & Physiology

18. The Heart

Electrical Conduction System of the Heart

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Multiple Choice

What is happening in the heart as the semilunar valves are closing?

The atria are relaxing and the semilunar valves are opening.

The atria are contracting and filling the ventricles with blood.

The ventricles are relaxing and the atrioventricular valves are opening.

The ventricles are contracting and ejecting blood into the arteries.

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Verified step by step guidance

Understand the function of the semilunar valves: These valves are located between the ventricles and the major arteries (aorta and pulmonary artery). They prevent backflow of blood into the ventricles after contraction.

Identify the cardiac cycle phase: The semilunar valves close at the end of ventricular systole, which is when the ventricles have finished contracting and are beginning to relax.

Recognize the role of the atrioventricular (AV) valves: As the ventricles relax, the pressure within them drops, causing the AV valves (tricuspid and mitral) to open, allowing blood to flow from the atria into the ventricles.

Differentiate between systole and diastole: During systole, the ventricles contract and eject blood, causing the semilunar valves to open. During diastole, the ventricles relax, leading to the closure of the semilunar valves and opening of the AV valves.

Conclude the sequence of events: As the semilunar valves close, the ventricles are in the early phase of diastole, relaxing and preparing to fill with blood from the atria through the open AV valves.