Question

Which of the following statements are correct regarding skeletal muscle?

1. Muscle bundles are held together by collagenous connective tissue layer called fascicle.
2. Sarcoplasmic reticulum of muscle fibre is a store house of calcium ions.
3. Striated appearance of skeletal muscle fibre is due to distribution pattern of actin and myosin proteins.
4. M line is considered as functional unit of contraction called sarcomere.

Choose the most appropriate answer from the options given below:

• A. B and C only
• B. A, C and D only
• C. C and D only
• D. A, B and C only

Answer 1

Answer: (A)

B and C only

Answer 2

B. Sarcoplasmic reticulum of muscle fiber is a storehouse of calcium ions.

• This statement is correct - The sarcoplasmic reticulum is a specialized type of endoplasmic reticulum found in muscle cells. It stores and releases calcium ions, which are crucial for muscle contraction.

C. Striated appearance of skeletal muscle fiber is due to the distribution pattern of actin and myosin proteins.

• This statement is correct - The striated appearance of skeletal muscle fibers is due to the repeating arrangement of actin and myosin filaments, which create alternating dark (A bands) and light (I bands) bands along the length of the muscle fiber.

The other statements are incorrect:

A. Muscle bundles are held together by a collagenous connective tissue layer called fascicle.

• This statement is incorrect - Muscle bundles are actually called fascicles, and they are held together by a collagenous connective tissue layer called perimysium.

D. M line is considered the functional unit of contraction called a sarcomere.

• This statement is incorrect - The sarcomere is the basic functional and structural unit of muscle contraction. The M line is a structural protein that helps stabilize the central region of the sarcomere.

Therefore, the correct option is (A): B and C only