 This describes a muscle that causes specific movement or possibly several movements to occur through the process of its own contraction  To be effective as a mover in the skeletal system, it must actually cross one or more structures that can move, typically seen where the muscle crosses a joint by way of a tendon.  Examples: 1. Biceps brachii – elbow flexion 2. Triceps brachii – elbow extension

 Classification used to describe a muscle that acts in opposition to the specific movement generated by the agonist.  Responsible for returning a limb, arm or leg, to its initial position.  Important for balance, extending limbs, holding objects aloft, and contracting limbs.  Examples: 1. Flex the knee against resistance: hamstring group (agonist) and the quadricep group (antagonist) 2. Elbow flexion: biceps brachii (agonist) and the triceps brachii (antagonist)

 Kind of muscle that performs or helps performs the same set of joint motion as the agonist.  Also called “neutralizers”, b/c they help cancel out, or neutralize, extra motion from the agonist to make sure that the force generated works w/in the desired plan of motion.  Example: flex your wrist and then make a fist. See how hard it is? Now extend your wrist and make a fist. Easy, right? That is b/c the extensor m. of the wrist act as a synergist in cooperation with the flexor m. of the fingers acting as prime movers, or agonist.

Includes head, neck, back, shoulders, arms, hands, and fingers

 Buccinator : aids in mastification, tenses cheeks in blowing and whistling, and aids in closure of mouth.  Frontalis : wrinkles forehead and fixes galeal aponeurosis, a tough layer of fibrous tissue which covers the upper part of the cranium.  Masseter : elevates mandible ( enables forced closure of mouth)  Orbicularis Oculi : closes eyelids, aids passage and drainage of tears.  Orbicularis Oris : narrows orifice of mouth, purses lips and puckers lip edges.

 Platysma : depresses and wrinkles skin of lower face and mouth; aids in forced depression of mandible.  Sternocleidomastoid : flexes and laterally rotates cervical spine; protracts head when acting together

 Thorax (Chest) Muscles:  Diaphragm: contracts for inspiration and assists in raising intra-abdominal pressure.  Intercostals: fix intercostal spaces during respiration.  Pectoralis Major: b/c of different insertions, clavicular head allows arm flexion and adduction; sternal head allows adduction and medial rotation arm. Also is an accessory for inspiration.  Serratus Anterior: laterally rotates and protracts the scapula.

 Abdomen  External Oblique Abdominus: supports abdomen wall, assists forced expiration, aids in raising intra- abdominal pressure, and w/ muscles of opposite side, abducts and rotates trunk.  Rectus Abdominus: flexes trunk, aids expiration and raises intra-abdominal pressure.

 Back:  Latissimus Dorsi: extends, abducts, and medially rotates arm; costal attachment aids w/ deep inspiration and forced expiration.  Rhomboid Major: retracts scapula; rotates scapula to rest position.  Trapezius: laterally rotates, elevates and retracts scapula; if scapula is fixed, extends and laterally flexes neck.

 Rotator Cuff Muscles:  Supraspinatus: Abducts arm and stabilizes shoulder joint.  Infraspinatus: Laterally rotates arm and stabilizes shoulder joint.  Teres Minor: Laterally rotates arm and stabilizes shoulder joint.  Teres Major: Medially rotates and adducts arm.  Subscapularis: Medially rotates arm and stabilizes shoulder joint.

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 Deltoid: Anterior fibers flex and medially rotates; Middle fibers abducts arm; Posterior fibers extend and laterally rotates arm.  Triceps brachii:  Long Head: Extends the arm at the shoulder and Extends the forarm at the elbow.  Medial Head: Extends the forearm at the elbow.  Lateral Head: Extends the forearm at the elbow.

 Biceps brachii: Supinates the forearm, flexes the elbow, and weakly flexes the shoulder. Lower Arm:  Brachialis: Flexes the elbow.  Coracobrachialis: Flexes and weakly adducts arm.  Brachioradialis: Flexes the arm at the elbow and brings the forearm into midprone, when the hand faces inwards or medially, position.

 Supinator: Supinates forearm; only acts alone when elbow is extended.  Pronator Teres: Pronates forearm and flexes elbow.  Flexor Carpi Radialis: Flexes and abducts wrist.  Flexor Carpi Ulnaris: Flexes and abducts wrist.  Palmaris Longus: Flexes wrist.  Flexor pollicis brevis/longus: Flexes metacarpophalangeal joint of thumb; Flexes distal phalanx of thumb.

 Flexor digiti minimi brevis: Flexes metacarpophalangeal joint of little finger, 5 th phalange.  Extensor indicis: Extends all joints of index finger, 3 rd phalange.  Extensor carpi radialis brevis/longus: Extends and abducts hand at wrist.  Extensor pollicis brevis/longus: Extends metacarpophalangeal joint of thumb; Extends interphalangeal and metacarpophalangeal joints.

 Extensor carpi ulnaris: Extends and adducts hand at wrist.  Extensor digitorum: Extends all joints of fingers, 2 nd - 4 th phalange.  Extensor digiti minimi: Extends all joints of little finger, 5 th phalange.  Adductor pollicis: Adducts carpophalangeal joint of thumb, 1 st phalange.

 Abductor pollicis brevis/longus: Abducts thumb at metacarpophalangeal and carpometacarpal joints; Abducts and extends thumb at carpometacarpal joint.  Abductor digiti minimi: Abducts little finger, 5 th phalange, at metacarpophalangeal joint.