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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Problem 4

Textbook Question

More than one choice may apply.
During atrial systole,
a. The atrial pressure exceeds ventricular pressure.
b. 70 percent of ventricular filling occurs.
c. The AV valves are open.
d. Valves prevent backflow into the great veins.

Verified step by step guidance

Step 1: Understand the cardiac cycle phases, focusing on atrial systole, which is the contraction of the atria pushing blood into the ventricles.

Step 2: Analyze option (a): During atrial systole, the atrial pressure must exceed ventricular pressure to allow blood to flow from the atria to the ventricles.

Step 3: Evaluate option (b): Consider when the majority of ventricular filling occurs, noting that most filling happens passively before atrial systole.

Step 4: Assess option (c): During atrial systole, the atrioventricular (AV) valves (tricuspid and mitral) should be open to permit blood flow from the atria to the ventricles.

Step 5: Consider option (d): Determine if valves prevent backflow into the great veins during atrial systole, focusing on the role of the AV valves and the absence of valves at the entry of the great veins.

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Key Concepts

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

Atrial Systole

Atrial systole is the phase of the cardiac cycle where the atria contract, pushing blood into the ventricles. This phase is crucial for ensuring that the ventricles are adequately filled with blood before they contract during ventricular systole. Understanding this phase helps clarify the dynamics of blood flow and pressure changes within the heart.

Pressure Gradients

Pressure gradients are differences in pressure that drive blood flow through the heart and circulatory system. During atrial systole, the pressure in the atria exceeds that in the ventricles, allowing blood to flow into the ventricles. Recognizing how these gradients influence valve function and blood movement is essential for understanding cardiac physiology.

Heart Valves

Heart valves, including the atrioventricular (AV) valves, regulate blood flow direction and prevent backflow. During atrial systole, the AV valves are open, allowing blood to flow from the atria to the ventricles. Understanding the role of these valves is critical for grasping how the heart maintains efficient circulation and prevents regurgitation.