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Multiple Choice
Which of the following best describes the term 'Z line' in muscle tissue?
A
A protein that stores oxygen in muscle cells
B
A structure that marks the boundary between adjacent sarcomeres in a myofibril
C
The site where a motor neuron communicates with a muscle fiber
D
The region where thick and thin filaments overlap
Verified step by step guidance
1
Understand the context: The term 'Z line' is related to muscle tissue, specifically the microscopic structure of myofibrils within muscle fibers. Myofibrils are composed of repeating units called sarcomeres, which are the functional units of muscle contraction.
Define the Z line: The Z line is a structure within the sarcomere that serves as the boundary between adjacent sarcomeres. It is composed of proteins that anchor the thin filaments (actin) of the sarcomere, providing structural support and alignment.
Eliminate incorrect options: Review the provided choices and eliminate those that do not describe the Z line. For example, 'A protein that stores oxygen in muscle cells' refers to myoglobin, not the Z line. Similarly, 'The site where a motor neuron communicates with a muscle fiber' refers to the neuromuscular junction, and 'The region where thick and thin filaments overlap' refers to the A band within the sarcomere.
Focus on the correct description: The Z line is best described as 'A structure that marks the boundary between adjacent sarcomeres in a myofibril.' This aligns with its role in defining the limits of each sarcomere and anchoring the thin filaments.
Conclude with the importance of the Z line: The Z line plays a critical role in muscle contraction by maintaining the organization of sarcomeres and ensuring efficient force transmission during contraction and relaxation cycles.