A single contraction of skeletal muscle is most likely to be terminated by which of the following actions?
**Core Concept**
The termination of a single contraction of skeletal muscle is a complex process involving multiple factors, primarily governed by the regulation of calcium ions (Ca2+) and the energy supply. The process involves the coordinated action of various molecules and cellular mechanisms to ensure muscle relaxation and preparation for the next contraction.
**Why the Correct Answer is Right**
The correct answer is **repolarization of the T-tubule membrane**. This process is initiated by the decrease in intracellular calcium levels, which triggers the closure of calcium channels and the subsequent repolarization of the T-tubule membrane. This action is crucial in terminating the contraction and preparing the muscle for relaxation.
* **Option A:** **Inhibition of the release of calcium from the sarcoplasmic reticulum** is incorrect because the release of calcium is essential for muscle contraction, not its termination.
* **Option B:** **Activation of the sodium-potassium pump** is incorrect because while the sodium-potassium pump is important for maintaining the resting membrane potential, it is not directly involved in the termination of a single contraction.
* **Option C:** **Increased activity of the parasympathetic nervous system** is incorrect because the parasympathetic nervous system is primarily involved in promoting relaxation and reducing sympathetic activity, but it is not directly responsible for terminating a single contraction.
**Clinical Pearl / High-Yield Fact**
The termination of a single contraction is a critical process that ensures muscle relaxation and preparation for the next contraction. Understanding the mechanisms involved in this process is essential for managing muscle disorders and developing effective treatment strategies.
**Correct Answer:** C.