muscle skeletal questions

Perimysium

A tissue sample contains a skeletal muscle organ surrounded by a layer of collagen, but the bundles of muscle fibers within it lack their individual collagen envelopes. Which connective tissue layer is missing around the fascicles?

Endomysium

A pathologist examines a cross-section of muscle and identifies a connective tissue layer containing capillaries, nerve fibers, and myosatellite cells directly surrounding a single muscle fiber. Which layer is being viewed?

A drug selectively destroys collagen fibers at the very ends of a muscle where the epimysium, perimysium, and endomysium merge into a broad, flattened sheet. Which specific attachment structure was damaged?

Aponeurosis

A patient suffers a laceration that severs a tendon attaching a muscle to a bone. When the muscle contracts, what change will occur in the movement of the attached bone?

No movement will occur (the muscle pull cannot be transmitted to the bone matrix).

The muscle fibers will fail to grow very large and will remain small and single-nucleated (instead of multinucleated).

A genetic mutation prevents myoblasts from fusing together during embryonic development. What structural abnormality would you expect in the mature muscle cells regarding their size and number of nuclei?

Muscle repair and tissue regeneration.

A chemical treatment destroys myosatellite cells residing in the endomysium. What long-term capability of the skeletal muscle tissue will be impaired following injury?

Sarcolemma

An investigator measures a change in the electrical potential across the cell membrane of a muscle fiber. Which cellular structure is undergoing this electrical change?

Sarcoplasm

A toxin alters the fluid environment containing enzymes, glycogen, and organelle networks inside a muscle fiber. Which compartment of the muscle cell is affected?

To transmit action potentials deep into the muscle fiber so the entire cell contracts simultaneously.

An electron micrograph shows narrow, tubular extensions of the sarcolemma reaching deep into the sarcoplasm. What is the primary function of these passageways during stimulation?

The repeating, organized pattern of myofilaments (thick and thin filaments) arranged into sarcomeres.

A histology slide shows repeating dark and light bands along the entire length of a myofibril. What structural level of organization creates this striated appearance?

Sarcomere

A longitudinal section of a myofibril reveals repeating structural units extending from one Z line to the next Z line. What functional unit of muscle contraction is being observed?

A Band

Under light microscopy, a region of the sarcomere contains the full length of thick filaments, including areas of filament overlap. Which band is being identified?

I Band

A region of a sarcomere contains thin filaments but completely lacks thick filaments. Which band does this region represent?

M Line

A protein strand runs down the center of the H band and connects adjacent thick filaments at the midline. What is this structure called?

H Band

A resting sarcomere shows a central light region within the A band that contains thick filaments but no thin filaments. What is this central area called?

it is functional because it is where thick and thin filaments interact to cause contraction.

A microscopic zone within the A band contains interlocked thick and thin filaments. What is this specific region called, and why is it functional during contraction?

Z Line

• A dark line marks the boundary ends of a sarcomere at the center of each I band. What structural line is this?

F-actin (filamentous actin)

An isolated thin filament contains two twisted strands of globular actin subunits. What specific protein strand forms this structural backbone?

Nebulin

A protein polymer extends along an F-actin strand to hold the globular G-actin subunits in alignment. What is this structural protein?

Tropomyosin

In a resting muscle, a long double-stranded protein sits over the active sites of G-actin. What protein directly blocks myosin binding?