Question

The cell membrane of a muscle ber is called a ________. a. myobril b. sarcolemma c. sarcoplasm d. myolament

Short answer

Answer: The correct term that refers to the cell membrane of a muscle fiber is the sarcolemma. This specialized cell membrane plays a crucial role in regulating ion and nutrient exchange, as well as electrical impulses needed for muscle contraction.

Step-by-step solution

Review the terminologies

Familiarize with the following terms: - Myobril refers to elongated contractile threads found in muscle cells. - Sarcolemma is the fine, transparent tubular sheath that envelops the fibers of muscular tissues. - Sarcoplasm is the cytoplasm of muscle cells. - Myofilament refers to the filaments of myofibrils, constructed from proteins, principally myosin or actin.

Choose the correct term

The cell membrane of a muscle fiber is called the sarcolemma. Therefore, the correct answer is (b) sarcolemma.

Brief explanation

The sarcolemma is the specialized cell membrane surrounding muscle fibers. It plays an essential role in the regulation of ions and nutrient exchange, as well as electrical impulses that are necessary for muscle contraction.

Key concepts

Sarcolemma

The sarcolemma is a crucial component of muscle fibers. It acts as the cell membrane of a muscle fiber and has special features that differentiate it from other cell membranes.
Understanding the sarcolemma is essential in grasping how muscles function. The sarcolemma:

• Encompasses each muscle fiber.
• Serves as a barrier between the interior of the muscle cell and its external environment.
• Is involved in transmitting electrical impulses called action potentials.
• Facilitates the exchange of ions, primarily sodium (\( Na^+ \)) and potassium (\( K^+ \)), which are crucial for muscle contraction.

Moreover, the sarcolemma is responsible for maintaining the stability and structure of muscle fibers, providing them with the necessary support to undergo contractions and relaxations efficiently, which is indispensable for any physical activity.

Myofibrils

Myofibrils are specialized structures within muscle cells that play a central role in muscle contraction.
They are the thread-like fibers that run parallel to one another within the muscle cell, giving muscles their characteristic strength and contractile ability. Key points about myofibrils:

• Myofibrils are made up of repeating units called sarcomeres, which are the functional units of muscle contraction.
• They contain alternating bands of thick (myosin) and thin (actin) filaments, which slide past each other to generate contraction.
• During muscle contraction, the sarcomeres shorten as the actin filaments slide over the myosin filaments.

Each myofibril is surrounded by a network of sarcoplasmic reticulum, a structure that stores calcium ions. When a muscle contracts, calcium ions are released from the sarcoplasmic reticulum, which triggers the sliding filament process, leading to contraction.

Muscle Cell Membranes

Muscle cell membranes are integral in maintaining the function and structure of muscle fibers.
They consist of the sarcolemma and other specialized layers that ensure efficient muscle operation. The main functions of muscle cell membranes include:

• Providing structure and shape to muscle fibers.
• Preserving the balance of ions and nutrients necessary for muscle activity.
• Serving as a gateway for signaling molecules that initiate muscle contractions and responses.

Each muscle cell membrane is uniquely adapted with structures like proteins that act as receptors, transporters, and channels that facilitate the complex processes of excitation and contraction. This specialized equipment allows the muscle to respond rapidly to stimuli, making it possible to perform actions ranging from slight twitches to powerful forceful movements. Overall, the structure and function of muscle cell membranes are vital to the dynamic nature of muscle tissues and their ability to support movement and bodily functions.