Chapter 33, Problem 15STP

Summary Introduction

To explain:

The role of actin and myosin in muscle contraction.

Introduction:

The muscular system is one of the vital systems of a body. It is a system of bones and muscles where bones are connected to other bones and also to muscles. The muscular system helps in the movement of body parts and also enables locomotion. It also provides strength, structure and rigidity to the body.

Explanation of Solution

The muscles in our body are made up of muscle fibers called myofibrils. Myofibrils consist of the contractile proteins- actin and myosin. These myofibrils are arranged in a specialized manner which forms a unit of contraction called a sarcomere.

The striations of skeletal muscles are a result of sarcomeres, which run from Z line to Z line. The Z line is the line where the actin filaments attach the myofibril. The place where the actin and myosin bands overlap each other is called the A band. The M line is a line consisting of only myosin filaments.

The motion of contraction of the sarcomere is understood by the sliding filament theory which states that when a nerve signal reaches the muscle, the actin filaments slide towards each other causing the muscles to contract. The myosin remains stationary. The arrangement of the components of a sarcomere causes a muscle to shorten and then relax.

Conclusion

The actin and myosin are key components in muscle contraction and it is the movement of these proteins that allows the muscles to contract and to relax.