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 Heart2h 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

You are listening to the heart through a stethoscope. When you hear the first heart sound, which of the following options correctly matches the structure to the pressure change that would be most responsible for producing that sound?

Ventricles: pressure increasing.

Aorta: pressure decreasing.

Ventricles: pressure decreasing.

Atria: pressure increasing.

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Verified step by step guidance

Understand the cardiac cycle: The heart sounds are associated with the closing of heart valves. The first heart sound, 'lub,' is primarily due to the closure of the atrioventricular (AV) valves (mitral and tricuspid valves) at the beginning of ventricular systole.

Identify the phase of the cardiac cycle: The first heart sound occurs at the start of ventricular systole, when the ventricles contract. This contraction increases the pressure within the ventricles.

Relate pressure changes to heart sounds: As the ventricles contract, the pressure inside them rises sharply. This increased pressure causes the AV valves to close, producing the first heart sound.

Eliminate incorrect options: The aorta's pressure is not directly responsible for the first heart sound. Similarly, atrial pressure changes are not responsible for this sound, as the atria are in diastole when the first heart sound occurs.

Conclude with the correct match: The first heart sound is most closely associated with the ventricles' pressure increasing as they contract, leading to the closure of the AV valves.