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

Which factor accounts for the movement of the heart valves during the cardiac cycle?

Electrical impulses from the sinoatrial node

Contraction of the heart valves themselves

Differences in blood pressure across the valves

Hormonal stimulation from the adrenal glands

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Verified step by step guidance

Understand the role of heart valves in the cardiac cycle: Heart valves ensure unidirectional blood flow through the heart chambers by opening and closing in response to pressure changes.

Identify the primary mechanism for valve movement: Heart valves do not contract themselves; instead, their movement is passive and driven by differences in blood pressure across the valves during the cardiac cycle.

Relate pressure differences to the phases of the cardiac cycle: During systole (ventricular contraction), pressure in the ventricles rises, forcing the atrioventricular valves (tricuspid and mitral) to close and the semilunar valves (pulmonary and aortic) to open. During diastole (ventricular relaxation), pressure in the ventricles falls, allowing the atrioventricular valves to open and the semilunar valves to close.

Clarify why other options are incorrect: Electrical impulses from the sinoatrial node initiate contraction of the heart muscle but do not directly move the valves. Hormonal stimulation from the adrenal glands influences heart rate and contractility but does not control valve movement.

Conclude that the correct factor is differences in blood pressure across the valves, as this is the direct mechanism responsible for their movement during the cardiac cycle.