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Skeletal Muscle Anatomy quiz #1 Flashcards

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Skeletal Muscle Anatomy quiz #1
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  • What protein primarily composes the thick filaments in skeletal muscle sarcomeres?
    The thick filaments in skeletal muscle sarcomeres are primarily composed of the protein myosin.
  • What is the function of the sarcoplasmic reticulum in skeletal muscle fibers?
    The sarcoplasmic reticulum is a membranous structure that surrounds myofibrils and is crucial for releasing calcium during muscle contraction. Its role will be discussed further when covering muscle contraction mechanisms.
  • How are myofibrils related to sarcomeres in skeletal muscle anatomy?
    Myofibrils are long structures composed of repeating units called sarcomeres. Each myofibril extends the length of the muscle fiber and contains many sarcomeres in sequence.
  • What distinguishes a muscle fiber from a muscle fascicle?
    A muscle fiber is a single, long, multinucleated cell, while a muscle fascicle is a bundle of multiple muscle fibers. Muscle fascicles collectively form the skeletal muscle.
  • Why do skeletal muscles appear striated under a microscope?
    The striated appearance is due to the arrangement of sarcomeres, which create alternating dark and light bands. This pattern results from the organization of thick and thin filaments within each sarcomere.
  • What region of the sarcomere contains only thin actin filaments and no thick myosin filaments?
    The I band contains only thin actin microfilaments and does not overlap with thick myosin filaments. It is named for the thin letter 'I' to help remember its composition.
  • What is the role of the M line (or M disc) in the sarcomere?
    The M line is a vertical anchor located in the middle of the sarcomere, specifically in the center of the H zone and A band. It serves as an anchoring point for thick myosin filaments.
  • How do Z discs define the boundaries of a sarcomere?
    Z discs mark both the start and end of a sarcomere, serving as vertical anchors for thin actin filaments. Each sarcomere is defined as the region between two Z discs.
  • What is the composition of the A band in a sarcomere?
    The A band contains the entire length of thick myosin filaments and also includes regions where thin actin filaments overlap with myosin. It is defined by the presence of both filament types.
  • Why are skeletal muscles considered voluntary muscles?
    Skeletal muscles are classified as voluntary because we have conscious control over their contractions, such as moving our biceps. This distinguishes them from involuntary muscle types like cardiac and smooth muscle.