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

At what point during the cardiac cycle does the atrioventricular (AV) valve close?

At the beginning of ventricular systole

During atrial systole

During ventricular diastole

At the end of ventricular systole

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Verified step by step guidance

Understand the cardiac cycle phases: The cardiac cycle consists of atrial systole, ventricular systole, and diastole. Each phase involves specific actions of the heart chambers and valves.

Identify the role of the atrioventricular (AV) valves: The AV valves, which include the mitral and tricuspid valves, prevent backflow of blood from the ventricles to the atria.

Determine when the AV valves close: The AV valves close to prevent backflow when the ventricles contract, marking the beginning of ventricular systole.

Analyze the options: During atrial systole, the atria contract, pushing blood into the ventricles, so the AV valves are open. During ventricular diastole, the ventricles relax and fill with blood, so the AV valves are open. At the end of ventricular systole, the ventricles finish contracting, and the semilunar valves close.

Conclude that the AV valves close at the beginning of ventricular systole, as this is when the ventricles contract and the pressure causes the AV valves to shut.