Chapter 10, Problem 2DYKB

The physiologic event that takes place at the plasma membrane of a skeletal muscle fiber is

1. a. release of calcium.
2. b. propagation of an action potential.
3. c. binding of calcium by troponin.
4. d. crossbridge cycling.

Summary Introduction

Introduction:

Skeletal muscles are composed of $\text{40}-\text{50}\text{\%}$ adult body weight. It is primarily attached to the skeleton of the body but also found at the opening of urinal tracts and gastrointestinal tracts.

Answer to Problem 2DYKB

Correct answer:

The propagation of action potential takes place at the plasma membrane of skeletal muscle fiber. Therefore, option b. is correct.

Explanation of Solution

Reason for the correct statement:

Option b. is given as “propagation of an action potential”. The plasma membrane is called as sarcolemma when present in skeletal muscle fiber and T-tubules invade the sarcolemma. Voltage-gated channels are located within the T-tubules and sarcolemma. These channels include both Voltage-gated ${\text{Na}}^{\text{+}}$ channels and Voltage-gated ${\text{K}}^{\text{+}}$ channels which participate in the conduction of action potential. Hence, sarcolemma (plasma membrane) helps in the propagation of action potential.

Hence, option b. is correct.

Reasons for the incorrect statements:

Option a. is given as “release of calcium”.

The physiological event of a release of calcium takes place at sarcoplasmic reticulum. Hence, option a. is incorrect.

Option c. is given as “binding of calcium by troponin”.

The physiological event of binding of calcium by troponin takes place in the sarcomere. Hence, option c. is incorrect.

Option d. is given as “cross-bridge cycling”.

The physiological event of cross-bridge cycling takes place in the sarcomere. Hence, option d. is incorrect.

Hence, options a., c., and d. are incorrect.

Conclusion

Action potential propagates along the length of the plasma membrane of skeletal muscle fiber.