Naming muscles according to their action Sanjaya Adikari

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