Question

What are Antagonistic Muscles? Give one example.

Answer 1

Muscles are a type of soft tissue containing protein filaments of actin and myosin that slides on each other leading to contraction causing changes in length and shape of the muscle. Muscles are present in most animals and they help in locomotion and movements.

Complete answer:
The main function of muscle is to provide movement through muscle contraction. They are attached to bones with the help of tendons and during contraction of muscle, there is pulling off our bones too. However they cannot push, only pull is present. For bringing off a single movement at a joint, one pair of muscle contracts and the other pair of muscles relaxes that bring the body part back to the original position. These muscles which work like this are referred to as Antagonistic pairs.
In this, the pair which contracts are called Agonist and the muscle which relaxes are called antagonists. Antagonistic muscle has opposite actions of the prime mover and they play important roles in muscle function, that is they maintain body position and control rapid movement. For examples include the Triceps which acts as an antagonist for Biceps muscle during Biceps flexion or contraction. Another example includes the Hamstrings acting as Antagonist for Quadriceps during Knee extension.

Note: For the efficient working of antagonistic pairs, the certain muscle acts as a fixator that supports and stabilizes the joint. There is also a muscle that does not pull against the skeleton for movements which involves muscles of facial expression. Their insertion and origin are in the skin, so a group of individual muscles contracts to form a smile.