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Define cardiac cycle, and follow the events of one cycle.
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Ch. 18 The Cardiovascular System: The Heart
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034
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TOC.tableOfContents
- Ch. 1 The Human Body: An Orientation24
- Ch. 2 Chemistry Comes Alive25
- Ch. 3 Cells: The Living Units21
- Ch. 4 Tissue: The Living Fabric20
- Ch. 5 The Integumentary System11
- Ch. 6 Bones and Skeletal Tissues19
- Ch. 7 The Skeleton14
- Ch. 8 Joints7
- Ch. 9 Muscles and Muscle Tissue26
- Ch. 10 The Muscular System26
- Ch. 11 Fundamentals of the Nervous System and Nervous Tissue19
- Ch. 12 The Central Nervous System26
- Ch. 13 The Peripheral Nervous System and Reflex Activity32
- Ch. 14 The Autonomic Nervous System19
- Ch. 15 The Special Senses26
- Ch. 16 The Endocrine System23
- Ch. 17 Blood25
- Ch. 18 The Cardiovascular System: The Heart24
- Ch. 19 The Cardiovascular System: Blood Vessels27
- Ch. 20 The Lymphatic System and Lymphoid Organs and Tissues14
- Ch. 21 The Immune System: Innate and Adaptive Body Defenses27
- Ch. 22 The Respiratory System21
- Ch. 23 The Digestive System31
- Ch. 24 Nutrition, Metabolism, and Energy Balance26
- Ch. 25 The Urinary System26
- Ch. 26 Fluid, Electrolyte, and Acid-Base Balance24
- Ch. 27 The Reproductive System24
- Ch. 28 Pregnancy and Human Development25
- Ch. 29 Heredity11
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Non è quello che usi tu?Cambia libro di testo
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Marieb, Hoehn 11th EditionCh. 18 The Cardiovascular System: The HeartProblema 15
Marieb, Hoehn 11th EditionCh. 18 The Cardiovascular System: The HeartProblema 15Capitolo 18, Problema 15
The activity of the heart depends on intrinsic properties of cardiac muscle and on neural factors. Thus:
a. Vagus nerve stimulation of the heart reduces heart rate
b. Sympathetic nerve stimulation of the heart decreases time available for ventricular filling
c. Sympathetic stimulation of the heart increases its force of contraction
d. All of the above
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Step 1: Understand the role of the vagus nerve in heart function. The vagus nerve is part of the parasympathetic nervous system and generally acts to slow down the heart rate by releasing acetylcholine, which decreases the rate of depolarization in the sinoatrial (SA) node.
Step 2: Consider the effect of sympathetic nerve stimulation on the heart rate and ventricular filling time. Sympathetic stimulation increases heart rate, which reduces the duration of diastole, thereby decreasing the time available for ventricular filling.
Step 3: Analyze how sympathetic stimulation affects the force of contraction. Sympathetic nerves release norepinephrine, which increases calcium availability in cardiac muscle cells, enhancing the force of contraction (positive inotropic effect).
Step 4: Evaluate each statement individually based on the physiological effects described: (a) vagus nerve stimulation reduces heart rate, (b) sympathetic stimulation decreases ventricular filling time, and (c) sympathetic stimulation increases contraction force.
Step 5: Conclude whether all statements are correct by confirming that each aligns with known cardiac physiology, leading to the correct choice among the options.
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Autonomic Nervous System Regulation of the Heart
The autonomic nervous system controls heart activity through two main branches: the parasympathetic (vagus nerve) and sympathetic nerves. The vagus nerve decreases heart rate by releasing acetylcholine, which slows the pacemaker cells. In contrast, sympathetic stimulation increases heart rate and contractility by releasing norepinephrine.
Video consigliato:
1:10
Introduction to the Autonomic Nervous System Example 1
Effect of Sympathetic Stimulation on Heart Rate and Ventricular Filling
Sympathetic stimulation raises heart rate, which shortens the cardiac cycle and reduces the time available for ventricular filling during diastole. This can affect stroke volume but is compensated by increased contractile force to maintain cardiac output.
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6:13Control of Heart Rate
Sympathetic Influence on Cardiac Contractility
Sympathetic nerves increase the force of heart contractions by enhancing calcium influx into cardiac muscle cells. This positive inotropic effect improves stroke volume and overall cardiac output, enabling the heart to pump more blood during stress or exercise.
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9:39Contractile Tissue: Molecular Physiology
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