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

Cardiac Cycle

Anatomy & Physiology

18. The Heart

Cardiac Cycle

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Multiple Choice

During which phase of the cardiac cycle are all four heart valves open?

Ventricular systole

Isovolumetric relaxation

Isovolumetric contraction

There is no phase when all four valves are open

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Verified step by step guidance

Understand the structure and function of the heart valves: The heart has four valves—tricuspid, pulmonary, mitral, and aortic—that ensure unidirectional blood flow through the heart chambers and into the circulatory system.

Learn the phases of the cardiac cycle: The cardiac cycle consists of systole (contraction) and diastole (relaxation). Key subphases include ventricular systole, isovolumetric contraction, isovolumetric relaxation, and ventricular filling.

Analyze the role of heart valves during each phase: During ventricular systole, the semilunar valves (aortic and pulmonary) are open, while the atrioventricular valves (tricuspid and mitral) are closed to prevent backflow. During isovolumetric contraction and relaxation, all valves are closed to maintain pressure gradients.

Recognize why all four valves cannot be open simultaneously: The opening of valves is tightly regulated to prevent backflow and ensure efficient blood movement. If all valves were open, blood would flow backward, disrupting circulation.

Conclude that there is no phase in the cardiac cycle where all four valves are open: This is a physiological impossibility due to the heart's design and function, ensuring proper blood flow and pressure regulation.