Chapter 34, Problem 1STP

Summary Introduction

Introduction:

Muscle contraction occurs as sarcomeres shorten, when thick and thin filaments get over each other, which are referred to as the sliding filament concept of muscle contraction. ATP offers the power for cross-bridge formation and filament sliding.

Answer to Problem 1STP

Correct answer:

The correct answer is option (A) It contracts.

Explanation of Solution

Explanation/justification for the correct answer:

Option (A) It contracts. When a muscle contracts, the actin is pulled along myosin to the center of the sarcomere until the actin and myosin filaments are fully overlapped. In other words, for a muscle cell to contract, the sarcomere must shorten. So, the correct answer is option A.

Explanation for incorrect answer:

Option (B) It grows. When the actin fibers are pulled to the center of the sarcomeres, it is main reason why skeletal muscle contraction. It does not grow. So, this is an incorrect answer.

Option (C) It relaxes. Skeletal muscle relaxation happens when stimulation of the nerve stops. Calcium is then pumped back into the sarcoplasmic reticulum breaking the connection between actin and myosin. Actin and myosin back to their unbound state causing the muscle to relax.So, this is an incorrect answer.

Option (D) It stretches. Skeletal musclegrows in a transversely isotropic pattern, along the fiber direction in response to passive mechanicalstretch and orthogonal to the fiber direction in response to active mechanical stress. So, this is an incorrect answer.