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Questions and Answers
What is the primary function of skeletal muscle tissue in the body?
Which of the following proteins are myofilaments primarily comprised of?
What percentage of body weight does skeletal muscle tissue constitute?
What term refers to the plasma membrane of muscle cells?
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Which type of muscle tissue is involuntary and found only in the heart?
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How does smooth muscle function in the body?
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Which property of muscle tissue allows it to return to its original shape after stretching?
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What role do sphincter muscles play in the body?
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What connective tissue sheath surrounds the entire skeletal muscle?
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Which connective tissue sheath wraps each individual muscle cell?
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What structure is the functional unit of skeletal muscle tissue?
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Which of the following describes an indirect muscle attachment?
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What is the primary role of the myofibrils in muscle tissue?
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During muscle contraction, the pull is exerted on which of the following?
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What is the characteristic of skeletal muscle fibers regarding their nuclei?
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Which term describes the less movable attachment of a muscle?
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What is the primary role of the titin molecule in the sarcomere?
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Which region of the sarcomere contains only thin filaments?
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What defines the A band in the sarcomere?
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What happens during a concentric contraction?
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What structure surrounds each myofibril and is specialized for calcium ion storage?
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What initiates the sliding filament mechanism during muscle contraction?
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Which of the following statements is true regarding the H zone within the A band?
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What feature distinguishes I bands from A bands?
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Study Notes
Muscle Tissue Overview
- Muscle tissue is responsible for body movement, organ function, and temperature regulation.
- Three types of muscle tissue: skeletal, cardiac, and smooth.
- Skeletal muscles represent nearly half of the body's mass.
- Muscle cells possess distinctive properties: contractility, excitability, extensibility, and elasticity.
Skeletal Muscle
- Composed of skeletal muscle tissue, connective tissues, blood vessels, and nerves.
- Muscle fibers are multinucleated and elongated, formed by the fusion of embryonic cells.
- Myofibrils, the contractile units of skeletal muscle, are long, cylindrical structures within the cytoplasm.
- Myofibrils are composed of repeating segments called sarcomeres, which are the functional units of muscle contraction.
Sarcomere Structure
- Z disc: Defines the boundaries of each sarcomere.
- Thin (actin) filaments: Extend from the Z disc toward the center of the sarcomere.
- Thick (myosin) filaments: Located in the center of the sarcomere, overlapping the inner ends of the thin filaments.
- A band: Encompasses the full length of the thick filament, including the inner ends of thin filaments.
- H zone: Central region of the A band where no thin filaments are present.
- M line: Located in the center of the H zone, containing tiny rods that hold thick filaments together.
- I band: Region containing only thin filaments, part of two adjacent sarcomeres.
Specialized Structures in Muscle Fibers
- Sarcoplasmic reticulum (SR): Specialized smooth endoplasmic reticulum responsible for calcium storage and release.
- T tubules: Deep invaginations of the sarcolemma (plasma membrane) that extend into the muscle fiber.
- Triad: A T tubule flanked by two terminal cisterns of the SR, crucial for muscle excitation-contraction coupling.
Muscle Contraction
- Contractility: Shortening of muscle cells due to the sliding of thin and thick filaments.
- Concentric contraction: Muscle shortens to do work.
- Eccentric contraction: Muscle generates force as it lengthens, acting as a brake against gravity.
- Sliding filament mechanism: Explains concentric contraction where the myosin heads pull thin filaments towards the center of the sarcomere.
- Calcium ions released from the SR initiate the sliding filament mechanism.
- ATP provides energy for the sliding process.
Muscle Attachment
- Origin: The less movable attachment of a muscle.
- Insertion: The more movable attachment of a muscle.
- Direct attachment: Connective tissue fibers are short and directly attach to the bone.
- Indirect attachment: Connective tissue forms a tendon or aponeurosis, which connects to the bone.
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Description
Explore the fascinating world of muscle tissue, including its types, structures, and functions. This quiz covers skeletal muscle composition, the role of myofibrils, and the intricate design of sarcomeres. Test your knowledge on how these components work together to facilitate movement and maintain body functions.
