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 17

Textbook Question

An increase in preload causes a/an in stroke volume in accordance with the law. An increase in afterload causes a/an in stroke volume. An increase in contractility causes a/an in stroke volume.

Verified step by step guidance

Understand the concept of preload: Preload refers to the degree of stretch in the cardiac muscle fibers at the end of diastole, just before contraction. According to the Frank-Starling law, an increase in preload leads to an increase in stroke volume because the stretched muscle fibers generate a stronger contraction.

Understand the concept of afterload: Afterload is the resistance the heart must overcome to eject blood during systole. An increase in afterload typically decreases stroke volume because the heart has to work harder to push blood against the higher resistance.

Understand the concept of contractility: Contractility refers to the intrinsic ability of the cardiac muscle to contract, independent of preload and afterload. An increase in contractility enhances the force of contraction, leading to an increase in stroke volume.

Apply the Frank-Starling law to preload: Recall that the Frank-Starling law explains the relationship between preload and stroke volume. Increased preload stretches the cardiac muscle fibers, resulting in a stronger contraction and increased stroke volume.

Summarize the relationships: Increased preload leads to increased stroke volume (Frank-Starling law), increased afterload leads to decreased stroke volume, and increased contractility leads to increased stroke volume.

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Key Concepts

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

Preload

Preload refers to the initial stretching of the cardiac muscle fibers prior to contraction, which is influenced by the volume of blood returning to the heart. An increase in preload typically leads to an increase in stroke volume, as described by the Frank-Starling law, which states that the heart pumps more effectively when it is filled with more blood.

Afterload

Afterload is the pressure against which the heart must work to eject blood during systole. An increase in afterload can lead to a decrease in stroke volume because the heart has to exert more force to overcome this resistance, which can limit the amount of blood ejected with each heartbeat.

Contractility

Contractility refers to the intrinsic ability of cardiac muscle fibers to contract and generate force. An increase in contractility enhances the heart's ability to pump blood, resulting in an increase in stroke volume. This is often influenced by factors such as sympathetic nervous system activity and certain medications.

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Related Practice

Textbook Question

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

Atrial systole is responsible for ejecting most of the blood into the ventricles during the ventricular filling phase of the cardiac cycle.

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Textbook Question

Which chamber generates the highest pressure during systole?

a. Right atrium

b. Right ventricle

c. Left atrium

d. Left ventricle

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Textbook Question

The first heart sound is called ________ and it is caused by the closing of the ________ valves. It occurs at the beginning of the ________ phase of the cardiac cycle. The second heart sound is called ________ and it is caused by the closing of the ________ valves. It occurs at the beginning of the ________ phase of the cardiac cycle.

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Textbook Question

Cardiac output is equal to:

a. End-diastolic volume minus end-systolic volume.

b. Heart rate multiplied by stroke volume.

c. Stroke volume divided by end-diastolic volume.

d. Heart rate multiplied by preload.

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Textbook Question

Which of the following statements is false?

a. The sympathetic nervous system releases epinephrine and norepinephrine, which are positive chronotropic and inotropic agents.

b. The endocrine system regulates cardiac output through chronotropic and inotropic hormones and through hormones that regulate water balance.

c. The parasympathetic nervous system releases acetylcholine and epinephrine, which are strongly negative inotropic agents.

d. Factors such as electrolyte concentrations, body temperature, and age all affect cardiac output.

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Textbook Question

You are an athletic trainer who is working with someone planning to run a marathon. Your trainee tells you to give him a workout that will make his heart 'beat faster than ever before.' What do you tell him about the effects of too rapid a heart rate?

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Multiple Choice

A doctor puts his stethoscope on a patient's chest over the location of the heart and hears an abnormal swishing sound. Which of the following conditions is the best diagnosis for the patient's condition?

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Textbook Question

More than one choice may apply.

Given a volume of 150 ml at the end of diastole, a volume of 50 ml at the end of systole, and a heart rate of 60 bpm, the cardiac output is

a. 600 ml/min

b. 6 liters/min

c. 1200 ml/min