Chapter 12, Problem 1aCP

Describe the actions of muscles when they contract, and define the terms agonist and antagonist in muscle action.

Summary Introduction

To review:

The actions of contracted muscles and the definitions of antagonist and agonist involved in muscle action.

Introduction:

The skeletal muscles are composed of muscle fibers and activated by somatic motor neuron that results in the contraction of these muscles leading to their movement. The skeletal muscles are joined to the bones at both ends through tendons (connective tissue). The contraction and relaxation result in different movements of the body.

Explanation of Solution

The skeletal muscle contraction results in various actions or movements that depend upon the type of joints and attachments present within the muscles. Different actions that are seen during the contraction of different muscles are given below:

Agonist- Agonist provides the major force to complete the movement. They are also known as ‘prime movers’of skeletal muscles and cause movement through their own activation.

Antagonist- In antagonist muscles, the contraction is done by the involvement of two muscles such as flexor and extensor whict act on the same muscle (as agonist) causing the opposite action.