Group Action of Muscles

Question 1

With reference to the group action of muscles, explain how a muscle contributes to movement, when it is acting as a:
Agonist (Prime Mover)
Give one example for each of the roles above.

Answer 1

A muscle that initiates/carries out/maintains a movement.

Eg: biceps in elbow flexion

Question 2

With reference to the group action of muscles, explain how a muscle contributes to movement, when it is acting as a:
Antagonist
Give one example for each of the roles above.

Answer 2

A muscle which acts in a direction that is opposite to the agonist.
If the agonist is working the antagonist is relaxed due to ‘reciprocal inhibition’
Eg: Triceps in elbow flexion produced by activity in Biceps

Question 3

With reference to the group action of muscles, explain how a muscle contributes to movement, when it is acting as a:
Fixator
Give one example for each of the roles above.

Answer 3

A muscle which contracts to control the position of a bone so it can act as a steady base from which the agonist can contract.
Eg: in elbow flexion rhomboids & trapezius act as fixators of the shoulder girdle

Question 4

With reference to the group action of muscles, explain how a muscle contributes to movement, when it is acting as a:
Synergist
Give one example for each of the roles above.

Answer 4

A muscle which works simultaneously with one or more muscles to produce a combined action to make the prime mover work more efficiently.
It prevents unwanted movement at a joint
It could alter the angle of pull of the prime mover