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 6

Textbook Question

More than one choice may apply.
Soon after the onset of ventricular systole, the
a. AV valves close.
b. semilunar valves open.
c. first heart sound is heard.
d. aortic pressure increases.

Verified step by step guidance

Understand the phases of the cardiac cycle: Ventricular systole refers to the contraction of the ventricles, which occurs after the ventricles fill with blood during diastole. This contraction generates pressure within the ventricles.

Analyze the behavior of the AV (atrioventricular) valves: During ventricular systole, the pressure in the ventricles exceeds the pressure in the atria, causing the AV valves (tricuspid and mitral valves) to close. This prevents backflow of blood into the atria.

Examine the semilunar valves: As ventricular pressure continues to rise during systole, it eventually exceeds the pressure in the arteries (aorta and pulmonary artery), causing the semilunar valves (aortic and pulmonary valves) to open, allowing blood to be ejected into the arteries.

Relate the first heart sound to valve closure: The first heart sound (S1) is produced by the closure of the AV valves at the beginning of ventricular systole. This sound is often described as a 'lub' sound.

Consider the effect on aortic pressure: As blood is ejected from the left ventricle into the aorta during systole, the pressure in the aorta increases. This is a direct result of the ventricular contraction and the opening of the aortic semilunar valve.

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Key Concepts

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

Ventricular Systole

Ventricular systole is the phase of the cardiac cycle when the ventricles contract, pumping blood into the aorta and pulmonary artery. This phase is crucial for maintaining blood circulation throughout the body. It begins after the atria have emptied their blood into the ventricles and is marked by a rapid increase in ventricular pressure.

Heart Valves

The heart contains four main valves: the atrioventricular (AV) valves and the semilunar valves. During ventricular systole, the AV valves close to prevent backflow into the atria, while the semilunar valves open to allow blood to flow into the arteries. Understanding the function of these valves is essential for grasping the mechanics of blood flow during the cardiac cycle.

Cardiac Sounds

The first heart sound, often described as 'lub,' occurs when the AV valves close at the beginning of ventricular systole. This sound is an important indicator of heart function and is used in clinical settings to assess cardiac health. The timing of this sound relative to the phases of the cardiac cycle is critical for understanding heart dynamics.

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Master Systole, Diastole, Pressure, & Valves with a bite sized video explanation from Bruce Bryan

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Related Practice

Textbook Question

The sequence of contraction of the heart chambers is:

a. Random

b. Left chambers followed by right chambers

c. Both atria followed by both ventricles

d. Right atrium, right ventricle, left atrium, left ventricle

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Textbook Question

When the semilunar valves are open, which of the following are occurring?

(1) Coronary arteries fill

(2) AV valves are closed

(3) Ventricles are in systole

(4) Ventricles are in diastole

(5) Blood enters the aorta

(6) Blood enters pulmonary arteries

(7) Atria contract

a. 2, 3, 5, 6

b. 1, 2, 3, 7

c. 1, 3, 5, 6

d. 2, 4, 5, 7

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Textbook Question

Mrs. Hamad, a middle-aged woman, is admitted to the coronary care unit with a diagnosis of left ventricular failure resulting from a myocardial infarction. Her chart indicates that she was awakened in the middle of the night by severe chest pain. Her skin is pale and cold, and moist sounds of pulmonary edema are heard over the lower regions of both lungs. Explain how failure of the left ventricle might cause these signs and symptoms.

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Textbook Question

What are the valves in the heart, and what is the function of each?

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Textbook Question

The pericardial cavity is located between:

a. The parietal pericardium and the fibrous pericardium.

b. The fibrous pericardium and the myocardium.

c. The parietal pericardium and the visceral pericardium.

d. The epicardium and the endocardium.

Which of the following statements is true?

a. The tricuspid valve is located between the right atrium and the right ventricle.

b. The mitral valve is located between the pulmonary veins and the left atrium.

c. The pulmonary valve is located between the pulmonary artery and the pulmonary veins.

d. The aortic valve is located between the right ventricle and the aorta.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

The heart consists of two superior ventricles and two inferior atria.

A birth defect called transposition of great vessels results in the pulmonary trunk emanating from the left ventricle and the aorta stemming from the right ventricle.

Which ventricle is thicker-walled, and why?