Chapter 41, Problem 1MC

Summary Introduction

Introduction:

Muscles are defined as soft tissues that are found in humans and animals. There are three types of muscles found in humans such as skeletal muscle, cardiac muscle, and smooth muscle. It contains filament protein such as actin and myosin that are responsible for the contraction of the muscle. Muscles also help to produce force and motion.

Answer to Problem 1MC

Correct answer:

Structures that range from largest to smallest are muscle, muscle fiber, myofibril, thick and thin filaments. Therefore, option (d) is correct.

Option (d) is given as “muscle, muscle fiber, and myofibril, thick and thin filaments”.

Explanation of Solution

Justify reasons for the correct statement:

Muscle cells are soft tissue and are composed of thick and thick filaments that are attached to each other and form cross-bridge and cause muscle contraction. Muscle fibers are surrounded by a plasma membrane called sarcolemma and they also contain cytoplasm called sarcoplasm. Each muscle fiber contains parallel cylindrical myofibrils and is found in striated muscle. Muscle fibers contain multinucleated cells and these cells combine together to form muscle. Myofibril is surrounded by specialized reticulum called sarcoplasmic reticulum. The thick and thin filaments are myosin and actin. Actin filament contains two accessory proteins such as troponin and tropomyosin.

Hence, option (d) is correct.

Justify reasons for the incorrect statements:

Option (a) is given as “motor unit, muscle, myofibril, muscle fiber, thick and thin filament”.

Motor unit is formed when motor neuron synapses with multiple muscle fibers in a single muscle. It consists of motor neuron and skeletal muscle fibers. Hence, it is a wrong answer.

Option (b) is given as “muscle, muscle cell, myofibril, muscle fiber, actin, and myosin”.

Muscle is a part of the skeletal system which includes all the structures such as muscle cell, myofibril, muscle fiber, and actin and myosin filament. Hence, it is a wrong answer.

Option (c) is given as “muscle cell, thick and thin filaments, sarcomeres, myofibril”.

Muscle cell, thick and thin filaments, sarcomeres and myofibril are the structures that together form a muscle cell. Hence, it is a wrong answer.

Hence, options (a), (b), and (c) are incorrect.

Conclusion

Muscle is a soft tissue, which is made of myofibrils, muscle cells, and fibers, a thick and thin filament such as actin and myosin.