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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Ch. 9 Muscles and Muscle Tissue
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732
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Table of contents
- Ch. 1 The Human Body: An Orientation25
- Ch. 2 Chemistry Comes Alive24
- Ch. 3 Cells: The Living Units24
- Ch. 4 Tissue: The Living Fabric19
- Ch. 5 The Integumentary System12
- Ch. 6 Bones and Skeletal Tissues19
- Ch. 7 The Skeleton14
- Ch. 8 Joints7
- Ch. 9 Muscles and Muscle Tissue26
- Ch. 10 The Muscular System25
- Ch. 11 Fundamentals of the Nervous System and Nervous Tissue23
- Ch. 12 The Central Nervous System25
- Ch. 13 The Peripheral Nervous System and Reflex Activity30
- Ch. 14 The Autonomic Nervous System16
- Ch. 15 The Special Senses26
- Ch. 16 The Endocrine System26
- Ch. 17 Blood27
- Ch. 18 The Cardiovascular System: The Heart25
- Ch. 19 The Cardiovascular System: Blood Vessels27
- Ch. 20 The Lymphatic System and Lymphoid Organs and Tissues16
- 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
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
Chapter 9, Problem 26
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⁺.
Verified step by step guidance1
Step 1: Understand the role of acetylcholine (ACh) in skeletal muscle contraction. ACh is a neurotransmitter that binds to receptors on muscle cells, triggering a series of events that lead to muscle contraction.
Step 2: Analyze Chemical A, which binds to and blocks ACh receptors on muscle cells. Blocking these receptors prevents ACh from initiating muscle contraction, effectively causing muscle relaxation.
Step 3: Analyze Chemical B, which floods the muscle cell cytoplasm with Ca²⁺. Calcium ions inside muscle cells promote contraction by enabling the interaction between actin and myosin filaments.
Step 4: Compare the effects of both chemicals. Since Chemical A prevents the initiation of contraction by blocking ACh receptors, it acts as a muscle relaxant. Chemical B, by increasing intracellular Ca²⁺, would promote contraction rather than relaxation.
Step 5: Conclude that Chemical A would be a good skeletal muscle relaxant because it inhibits the signal for contraction, whereas Chemical B would not relax muscles but instead cause or enhance contraction.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acetylcholine (ACh) Receptors and Neuromuscular Transmission
ACh receptors on muscle cells receive signals from motor neurons to trigger muscle contraction. Blocking these receptors prevents ACh from binding, stopping the signal and causing muscle relaxation. This mechanism is key for drugs that act as muscle relaxants during surgery.
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Steps of Muscle Contraction Example 3
Role of Calcium Ions (Ca²⁺) in Muscle Contraction
Calcium ions inside muscle cells initiate contraction by enabling interaction between actin and myosin filaments. Increasing cytoplasmic Ca²⁺ typically promotes contraction, so flooding muscle cells with Ca²⁺ would enhance, not relax, muscle activity.
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Mechanism of Skeletal Muscle Relaxants in Surgery
Skeletal muscle relaxants used in surgery often work by blocking neuromuscular transmission, either by inhibiting ACh receptors or preventing ACh release. Effective relaxants reduce muscle contractions to facilitate surgical procedures without affecting consciousness.
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Related Practice
Textbook Question
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.
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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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