The sarcomere is the region of a myofibril between two successive:
Correct answer: C. Z-Line
- A. I-Line
- B. A-Line
- C. Z-Line
- D. M-Line
Explanation
Option C is correct. The sarcomere is the region of a myofibril between two successive Z-lines. A myofibril is a long, thin strand of muscle tissue that is made up of sarcomeres. Sarcomeres are the basic contractile units of muscle tissue. The Z-line is a thin, dark line that marks the boundary of a sarcomere. It is made up of a protein called α-actinin, which helps to anchor the actin filaments in place. I-band: The I-band is the light-colored band in the sarcomere. It contains only actin filaments. A-band: The A-band is the dark-colored band in the sarcomere. It contains both actin and myosin filaments. M-line: The M-line is a thin line in the center of the A-band. It is made up of a protein called myomesin, which helps to stabilize the myosin filaments.
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About Muscle Contraction
Muscle contraction is explained by the sliding filament model, in which myosin heads pull actin filaments within sarcomeres using ATP. The topic covers calcium, troponin, tropomyosin, the neuromuscular junction and relaxation, with attention to how filament length stays almost constant while the sarcomere shortens.
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