Question

Select the correct matching from the following: (a) Plasma membrane of muscle fibres Sarcolemma (b) Cytoplasm of muscle fibres \(-\) Sarcoplasm (c) Endoplasmic reticulum of muscle fibres \(-\) Sarcoplasmic reticulum (d) All the above

Short answer

The correct matchings are: (a) Plasma membrane of muscle fibres \(-\) Sarcolemma (b) Cytoplasm of muscle fibres \(-\) Sarcoplasm (c) Endoplasmic reticulum of muscle fibres \(-\) Sarcoplasmic reticulum. Therefore, option (d) All of the above is also correct.

Step-by-step solution

Identify the relevant terminology

First, understand the unique terminology used in muscle fiber biology. In this case, Sarcolemma is the specialized name for the plasma membrane of muscle fibres, Sarcoplasm is the cytoplasm, and the Sarcoplasmic reticulum refers to the specialized endoplasmic reticulum of muscle fibres.

Match with correct corresponding

Following are the correct matchings: \n\n (a) Plasma membrane of muscle fibres \(-\) Sarcolemma \n (b) Cytoplasm of muscle fibres \(-\) Sarcoplasm \n (c) Endoplasmic reticulum of muscle fibres \(-\) Sarcoplasmic reticulum

Confirm correctness of all options

After matching all options individually, check the last option '(d) All of the above'. Since all previous matchings are correct, so is this option.

Key concepts

Sarcolemma

The sarcolemma is a critical structure in muscle fiber biology. It functions as the plasma membrane that envelopes each muscle cell. This membrane is not just a simple barrier; it has essential roles in the muscle cell's function and overall health. Primarily, the sarcolemma maintains the environment for muscle contraction and regulates the interchange of ions and molecules between the muscle cell and its surroundings.
The sarcolemma is equipped to handle the unique demands of muscle contraction. It houses specialized proteins and ion channels that facilitate the transmission of action potentials. This electrical signal propagates along the sarcolemma, leading to muscle contraction.
Furthermore, the sarcolemma coordinates with T-tubules, invaginations of the membrane that penetrate into the muscle cell. These T-tubules help quickly transmit electrical signals deep into the muscle fiber, ensuring uniform contraction. Therefore, the sarcolemma is vital for both protecting the muscle cells and supporting their complex functioning.

Sarcoplasm

Inside the muscle cell, the sarcoplasm holds the title of the cytoplasm. It's where numerous biochemical processes occur, crucial for muscle activity. Unlike regular cytoplasm, sarcoplasm is rich in glycosomes, which store glycogen, and myoglobin, an oxygen-binding protein.
This abundance of glycogen is essential as it supports energy production during muscle contraction. When muscles work intensely, the stored glycogen in glycosomes is broken down for the necessary fuel. Similarly, myoglobin in the sarcoplasm ensures a steady oxygen supply, meeting the high demands during physical exertion.
Moreover, the sarcoplasm contains numerous mitochondria, the powerhouses of the cell. These structures facilitate the production of ATP, which is vital for contraction and relaxation cycles. All these elements make the sarcoplasm a powerhouse for supplying the energy and resources muscles need to do their job.

Sarcoplasmic Reticulum

The sarcoplasmic reticulum (SR) plays an indispensable role in muscle fiber function, acting as a specialized type of endoplasmic reticulum in muscle cells. Its primary duty is managing and storing calcium ions ( Ca^{2+} ), which are pivotal for muscle contraction.
When a muscle fiber receives a nerve impulse, it leads to the release of Ca^{2+} from the sarcoplasmic reticulum into the sarcoplasm. These calcium ions bind to regulatory proteins on actin filaments, thereby promoting contraction.
After contraction, the muscle must relax. The sarcoplasmic reticulum is responsible for this phase as well. It efficiently pumps Ca^{2+} back from the sarcoplasm into its storage compartments, making the muscle ready for the next cycle of contraction.

• Calcium plays a gatekeeping role, switching muscle fibers between rest and activity.
• The sarcoplasmic reticulum also forms a network that wraps around myofibrils, the components that directly contract.

Therefore, the SR is a crucial component in the regulation of muscle activity, enabling coordinated and effective muscle contractions.