Naming muscles according to their action Sanjaya Adikari Department of Anatomy Faculty of Medicine Peradeniya

Origin and insertion Origin – Proximal attachment where there is less movement Insertion – Distal attachment where there is greater movement Use the terms, proximal/ distal attachment to avoid confusions

Prime mover & antagonist Prime mover is the muscle that does the desired movement at a joint Antagonist is the muscle that has the action opposite to that of prime mover Eg:- Flexion of the elbow joint Biceps brachii is a prime mover Triceps is the antagonist

Prime mover & antagonist…

Synergist Synergist assists the prime mover by preventing unwanted movements at other joints Eg:- Flexion of the fingers Flexor digitorum profundus and superficialis are the prime movers Extensor muscles of the wrist joint are the synergists

Synergists…

Synergists… Eg:- Supination of the pronated forearm Biceps brachii and spinator are the prime movers Triceps acts as a synergists of biceps to prevent flexion of the elbow joint

Synergists… Eg:- Flexion of the elbow joint Biceps brachii is a prime mover Posterior fibres of deltoid acts as a synergist to prevent extension of the shoulder joint

Fixators Fixators stabilize one attachment of a muscle so that the contraction moves the other end Eg:- Abduction of the shoulder joint Deltoid is the prime mover Levator scapulae, rhomboids and trapezius are fixators

Fixators… Eg:- Abduction of the little finger Abductor digiti minimi is the prime mover Flexor carpi ulnaris acts as a fixator of pisiform bone