12.1k views
5 votes
Contractile unit of muscle = sarcomere

2. a muscle cell = fiber

3. plasma membrane of the muscle fiber = sarcolemma

4. a long filamentous organelle with a banded appearance found within muscle cells = myofibril

5. actin- or myosin-containing structure = myofilament

6. cord of collagen fibers that attaches a muscle to a bone = tendon

1 Answer

3 votes

Final answer:

A muscle fiber is surrounded by a sarcolemma and contains myofibrils organized into sarcomeres, which house thick myosin and thin actin myofilaments essential for muscle contraction.

Step-by-step explanation:

Skeletal muscle fibers are specialized cells with a key role in body movement. A muscle fiber, also known as a myocyte, is enclosed by a plasma membrane known as the sarcolemma, containing a cytoplasm termed sarcoplasm. Within these fibers, myofibrils run the length of the cell and anchor to the sarcolemma, giving it a striated appearance. Myofibrils are composed of repeat units called sarcomeres, the contractile units of the muscle, which contain the myofilaments actin and myosin.

Myofibrils exhibit a banded pattern due to the organization of these myofilaments. Thick myofilaments consist of myosin while the thin ones are composed of actin, troponin, and tropomyosin. The sarcoplasmic reticulum (SR), a specialized form of endoplasmic reticulum, is involved in the storage, release, and uptake of calcium ions (Ca++), crucial for muscle contraction and relaxation processes.

User Allenwei
by
8.3k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories