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

The shutting of the semilunar valves occurs during which phase of the cardiac cycle?

Atrial systole

Isovolumetric relaxation

Isovolumetric contraction

Ventricular ejection

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Verified step by step guidance

Understand the cardiac cycle: The cardiac cycle consists of several phases, including atrial systole, isovolumetric contraction, ventricular ejection, and isovolumetric relaxation.

Identify the role of semilunar valves: The semilunar valves (aortic and pulmonary valves) prevent backflow of blood from the arteries into the ventricles.

Determine when semilunar valves close: The semilunar valves close when the pressure in the ventricles falls below the pressure in the arteries, which occurs after ventricular ejection.

Recognize the phase following ventricular ejection: After the blood is ejected from the ventricles, the heart enters the isovolumetric relaxation phase, where the ventricles relax and the semilunar valves close.

Conclude the phase associated with semilunar valve closure: The closing of the semilunar valves marks the beginning of isovolumetric relaxation, as the ventricles prepare to fill with blood again.