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Questions and Answers
What is the function of the sarcoplasmic reticulum in muscle cells?
What type of protein is titin classified as?
How are thin filaments structured within skeletal muscle fibers?
What is the role of Z discs in a muscle fiber?
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What distinguishes the I band in a sarcomere?
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Which statement accurately describes the sliding filament mechanism?
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What is the basic functional unit of a muscle fiber?
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How do sodium potassium pumps contribute to muscle cells?
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Study Notes
Muscle Tissue
- Muscle tissue is composed of cells specialized for contraction
- Muscle cells are called myocytes
Muscle Cell Characteristics
- Myocyte cytoplasm is called sarcoplasm
- Myocyte plasma membrane is called sarcolemma
- Sarcoplasmic reticulum (SR) is a modified endoplasmic reticulum
- Forms a web-like network surrounding myofibrils
- Varies in structure in different types of muscle tissue
Skeletal Muscle Organization
- Composed of muscle fibers that are long, cylindrical cells
The Skeletal Muscle Fiber
- Contains multiple nuclei
- Contains myofibrils, which are bundles of protein filaments
Sarcoplasmic Reticulum
- Network of interconnected tubules that run parallel to myofibrils
- Stores and releases calcium ions, crucial for muscle contraction
Structure of the Myofibril
- Contains three types of myofilaments
- Thick filaments: composed of myosin protein
- Thin filaments: composed of actin, tropomyosin, and troponin proteins
- Elastic filaments: composed of the protein titin; stabilizes myofibril structure and resists excessive stretching
Myofilament Arrangement and the Sarcomere
- Myofilaments are arranged into repeating units called sarcomeres
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Sarcomere: functional contractile unit of a muscle fiber.
- Bounded by two Z-discs
- Contains alternating light and dark bands
- Light band (I band) - only contains thin filaments
- Dark band (A band) - contains both thick and thin filaments
- Z discs: located in the center of the I band
- Anchors thin filaments
- Attaches myofibrils to each other
Protein Myofilament Arrangement
- Sarcomere: The region from one Z-disc to the next
- Myosin: located in the center of the sarcomere
- Actin: extends toward the edges of the sarcomere
Sliding Filament Mechanism of Contraction
- Actin and myosin filaments slide past each other, shortening the sarcomere
- The length of the filaments themselves do not change
- The I band and H zone shorten
- The A band remains the same length
Membrane Potential
- Muscle cells like all cells have a resting membrane potential
- The difference in electrical charge across the plasma membrane
- Maintained by sodium potassium pumps
- Pumps three sodium ions out of the cell for every two potassium ions pumped into the cell
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Description
Explore the structure and function of muscle tissue in this quiz. Understand the characteristics of myocytes, the organization of skeletal muscle, and the role of the sarcoplasmic reticulum in muscle contraction. Test your knowledge on myofilaments and their components.
