Draw a relaxed and contracted sarcomere (see Textbook, p. 286, Fig. 11.6)

A sarcomere is the basic unit of muscle tissue. In its **relaxed** state, it looks like this: ``` Z |--------------------|====================|--------------------| Z ``` - **Z-line (Z):** Marks the ends. - **I-band:** Light area with only thin filaments. - **A-band:** Dark area with overlapping thick and thin filaments. - **H-zone:** Central part of the A-band with only thick filaments. In the **contracted** state, it looks like this: ``` Z |--------|===============|--------| Z ``` - **I-band:** Reduced due to filament overlap. - **H-zone:** Decreased or disappears. - **A-band:** Remains the same length. **Key Points:** - **Sliding Filament Theory:** Thin and thick filaments slide past each other during contraction. - **Cross-Bridge Formation:** Myosin heads attach to actin, pulling filaments closer. - **Relaxation:** Filaments return to their original positions when the muscle relaxes. These diagrams show how muscle contraction shortens the sarcomere by overlapping the thin and thick filaments.