Muscle myofibrils contain myosin and actin myofilaments, which are responsible for the contraction and relaxation of muscles. They are not found in the sarcolemma (the muscle cell membrane) or the T-tubules, and while they do contribute to muscle structure, they do not hold muscle cells together. Muscle myofibrils are also responsible for the striated appearance of muscle fibers.

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Muscle Myofibrils

Question 32

Multiple Choice

Muscle myofibrils

A) are found in the sarcolemma.
B) extend from the sarcolemma to the T-tubule.
C) contain myosin and actin myofilaments.
D) hold muscle cells together.
E) do not appear striated.

Correct Answer: