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Chapter 12: Problem 19

In a muscle fiber, a. the sarcolemma is connective tissue holding the myofibrils together. b. the \(\mathrm{T}\) system causes release of \(\mathrm{Ca}^{2+}\) from the sarcoplasmic reticulum. c. both actin and myosin filaments have cross-bridges. d. there is no endoplasmic reticulum. e. All of these are correct.

Short Answer

Expert verified
The correct statement about muscle fibers is: b. the T system causes the release of Ca2+ from the sarcoplasmic reticulum.

Step by step solution

01

Analyzing statement a

The sarcolemma is the cell membrane that surrounds muscle fibers, not a connective tissue that holds the myofibrils together. This statement is incorrect.
02

Analyzing statement b

The T (transverse) system (T-tubules) is a network of tubules that help spread the electrical impulse throughout the muscle fibers, which in turn causes the release of Ca2+ from the sarcoplasmic reticulum. This statement is correct.
03

Analyzing statement c

In myofibrils, actin and myosin filaments create the contractile units of muscle fibers. Myosin filaments have cross-bridges, but actin filaments do not. This statement is incorrect.
04

Analyzing statement d

Muscle fibers have a specialized type of endoplasmic reticulum, called the sarcoplasmic reticulum, which is responsible for the storage and release of Ca2+ ions during muscle contractions. This statement is incorrect.
05

Analyzing statement e

Since not all statements are correct, the statement "All of these are correct" is incorrect.
06

Conclusion

Among the given statements, the correct statement is: b. the T system causes the release of Ca2+ from the sarcoplasmic reticulum.

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Most popular questions from this chapter

Which of the following statements about cross-bridges is false? a. They are composed of myosin. b. They bind to ATP after they detach from actin. c. They contain an ATPase. d. They split ATP before they attach to actin.

When muscles contract, a. sarcomeres increase in length. b. actin breaks down ATP. c. myosin slides past actin. d. the H zone disappears. e. calcium is taken up by the sarcoplasmic reticulum.

Describe the sliding filament model of muscle contraction within a sarcomere. Begin with the nerve impulse and end with the relaxation of the muscle. (pages \(261-63\) )

To increase the force of muscle contraction, a. individual muscle cells have to contract with greater force. b. motor units have to contract with greater force. c. motor units need to be recruited. d. All of these are correct. e. None of these is correct.

Which of these is a direct source of energy for muscle contraction? a. ATP b. creatine phosphate c. lactic acid d. glycogen e. Both a and b are correct.
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