Chapter 10.1-10.2- Muscle Cells

  1. Three Classes of Muscle Tissue:

    • Skeletal muscle tissue

    • Cardiac muscle tissue

    • Smooth muscle tissue

    • Skeletal and cardiac muscle tissues are striated.

    • Skeletal muscle tissue is voluntarily controlled, while cardiac and smooth muscle tissues are involuntarily controlled.

  2. Prefix "Sarco-":

    • The prefix "sarco-" means flesh or muscle.

  3. Organelles Unique to Muscle Cells:

    • Some organelles unique to muscle cells include:

      • Myofibrils

      • Sarcoplasmic reticulum

      • Transverse tubules (T-tubules)

  4. Name of Cell Membrane of Skeletal Muscle Fiber:

    • The cell membrane of a skeletal muscle fiber is called the sarcolemma. It differs from a typical cell membrane in that it has invaginations called transverse tubules (T-tubules) that penetrate into the interior of the muscle fiber.

  5. Components of Skeletal Muscle Fiber Triad:

    • A skeletal muscle fiber triad consists of:

      • Two terminal cisternae of the sarcoplasmic reticulum

      • A T-tubule

  6. Myofibril:

    • A myofibril is a cylindrical organelle found in muscle cells, primarily composed of actin and myosin filaments.

  7. Types of Myofilaments:

    • The three types of myofilaments found in a myofibril are:

      • Thick filaments (composed of myosin)

      • Thin filaments (composed of actin, troponin, and tropomyosin)

      • Elastic filaments (composed of titin)

  8. Differences Between Thick and Thin Filaments:

    • Thick filaments (myosin) are larger and have myosin heads that protrude and interact with thin filaments (actin).

    • Thin filaments (actin) are smaller and have binding sites for myosin heads to attach during muscle contraction.

  9. Sarcomere:

    • A sarcomere is the basic structural and functional unit of a muscle. Its length is determined between two Z-lines.

  10. Arrangement of Myofilaments in a Sarcomere:

    • Thin filaments (actin) are anchored to the Z-lines and extend toward the center of the sarcomere.

    • Thick filaments (myosin) are located in the center of the sarcomere, overlapping with thin filaments.

  11. I-band and A-band:

    • In the I-band, you would find only thin filaments.

    • In the A-band, you would find both thick and thin filaments overlapping.

  12. Name of Alternating Light-Dark Lines:

    • The alternating light-dark-light-dark lines in a skeletal muscle fiber are called striations.

  13. H-zone of a Sarcomere:

    • The H-zone is the region in the center of the sarcomere where only thick filaments are present.

  14. Changes During Muscle Contraction:

    • During muscle contraction:

      • The length of the I-band decreases.

      • The length of the A-band remains constant.

      • The H-zone decreases or disappears as thick and thin filaments slide past each other.