Textbook Question
Describe some cause(s) of muscle fatigue and define this term clearly.
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Ch. 9 Muscles and Muscle Tissue
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034
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Table of contents
- 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: 9780136874034Not the one you use?Change textbook
Chapter 9, Problem 23
a. Describe the structure of a sarcomere and indicate the relationship of the sarcomere to myofilaments.
b. Explain the sliding filament model of contraction using appropriately labeled diagrams of a relaxed and a contracted sarcomere.
Verified step by step guidance1
Step 1: Describe the sarcomere as the basic functional unit of a muscle fiber, defined as the segment between two Z discs (or Z lines). Explain that it is composed of organized myofilaments: thick filaments made primarily of myosin and thin filaments made primarily of actin.
Step 2: Explain the arrangement of these myofilaments within the sarcomere: thin filaments attach to the Z discs and extend toward the center, while thick filaments are located in the center of the sarcomere overlapping with thin filaments. Mention the presence of the A band (length of thick filaments), I band (region with only thin filaments), H zone (region with only thick filaments), and M line (center of thick filaments).
Step 3: Introduce the sliding filament model by describing how muscle contraction occurs when thin filaments slide past thick filaments, shortening the sarcomere without changing the length of the filaments themselves.
Step 4: For the relaxed sarcomere, describe the wider I bands and H zone, indicating less overlap between thick and thin filaments. For the contracted sarcomere, describe how the I bands and H zone narrow or disappear due to increased overlap, while the A band remains constant in length.
Step 5: Suggest drawing or visualizing two diagrams side by side: one of a relaxed sarcomere showing clear bands and zones, and one of a contracted sarcomere showing shortened distance between Z discs and increased overlap of filaments, labeling the Z discs, A band, I band, H zone, thick and thin filaments to illustrate the sliding filament mechanism.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Structure of a Sarcomere
A sarcomere is the basic contractile unit of striated muscle, defined by Z-discs at each end. It contains organized myofilaments: thick filaments made of myosin and thin filaments made of actin. The arrangement of these filaments creates distinct bands (A, I, H) visible under a microscope, essential for muscle contraction.
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Proteins of the Sarcomere
Myofilaments and Their Role in the Sarcomere
Myofilaments are protein filaments within the sarcomere responsible for contraction. Thick filaments (myosin) have heads that bind to thin filaments (actin) to generate force. The interaction and overlap of these filaments determine the sarcomere’s length and contraction state.
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Sliding Filament Model of Muscle Contraction
The sliding filament model explains muscle contraction as the sliding of thin filaments past thick filaments, shortening the sarcomere without changing filament length. During contraction, actin and myosin filaments slide closer, reducing the I-band and H-zone, which shortens the muscle fiber and generates tension.
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Related Practice
Textbook Question
Explain how a slight (but smooth) contraction differs from a vigorous contraction of the same muscle. Use the concepts of multiple motor unit summation.
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Textbook Question
When a suicide victim was found, the coroner was unable to remove the drug vial clutched in his hand. Explain the reasons for this. If the victim had been discovered three days later, would the coroner have had the same difficulty? Explain.
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Textbook Question
Muscle-relaxing drugs are administered to a patient during major surgery. Which of the two chemicals described next would be a good skeletal muscle relaxant and why?
• Chemical A binds to and blocks ACh receptors of muscle cells.
• Chemical B floods the muscle cells' cytoplasm with Ca²⁺.
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Textbook Question
True or false: Most muscles contain a predominance of one skeletal muscle fiber type. Explain the reasoning behind your choice.
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Textbook Question
Smooth muscle has some unique properties, such as low energy usage, and the ability to maintain contraction over long periods. Tie these properties to the function of smooth muscle in the body.
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