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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5:32 minutes

Problem 20

Textbook Question

Discuss how the Frank-Starling law of the heart helps to explain the influence of venous return on stroke volume.

Verified step by step guidance

Understand the Frank-Starling law of the heart: This principle states that the strength of the heart's contraction is directly proportional to the initial length of the cardiac muscle fibers (preload). In simpler terms, the more the heart muscle is stretched during filling, the stronger the contraction and the greater the stroke volume.

Define venous return: Venous return refers to the amount of blood returning to the heart via the veins. It directly affects the preload, as increased venous return stretches the ventricular walls more during diastole.

Explain the relationship between venous return and preload: When venous return increases, the ventricles fill with more blood, leading to greater stretching of the cardiac muscle fibers. This increased preload enhances the force of contraction according to the Frank-Starling law.

Connect preload to stroke volume: The stronger contraction resulting from increased preload ejects more blood from the ventricles during systole, thereby increasing stroke volume. Stroke volume is the amount of blood pumped out of the heart with each beat.

Summarize the influence: The Frank-Starling law demonstrates that venous return is a critical factor in regulating stroke volume. Higher venous return leads to increased preload, stronger contractions, and ultimately a higher stroke volume, ensuring the heart adapts to varying demands for blood flow.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Frank-Starling Law

The Frank-Starling law states that the strength of the heart's contraction is directly related to the degree of stretch of the cardiac muscle fibers. This means that as more blood fills the heart during diastole, the muscle fibers are stretched, leading to a more forceful contraction during systole. This intrinsic mechanism allows the heart to adjust its output based on the volume of blood returning to it.

Venous Return

Venous return refers to the amount of blood that returns to the heart via the veins. It is a critical factor influencing stroke volume, as increased venous return leads to greater filling of the heart, which in turn enhances the stretch of the cardiac muscle fibers. This relationship is vital for maintaining adequate cardiac output, especially during physical activity when the body requires more oxygen and nutrients.

Stroke Volume

Stroke volume is the amount of blood ejected by the heart with each contraction. It is influenced by several factors, including preload (the initial stretching of the cardiac muscle), afterload (the resistance the heart must overcome to eject blood), and contractility. Understanding stroke volume is essential for assessing cardiac function and the overall efficiency of the heart in pumping blood throughout the body.