Skeletal Muscles “Muscle Man”

Muscles are arranged as levers to make work easier.

Each muscle has an origin (immovable end) and an insertion (movable end). The muscle can only contract.

Muscles are arranged in pairs - antagonistic muscle pairs to allow continuous movement. ex: biceps brachii flexes forearm triceps brachii extends forearm

The muscle with the main responsibility for movement of a body part is the prime mover or agonist. The opposing muscle is the antagonist. Other muscles that aid in movement are synergists. Synergists that immobilize a bone or joint are fixators.

Muscle names derive from: Location frontalis

Muscle names derive from: Shape deltoid

Muscle names derive from: Size gluteus maximus

Muscle names derive from: direction of fibers external oblique

Muscle names derive from: number of origins biceps brachii

Muscle names derive from: 6. location of origin and/or insertion sternocleidomastoid

Muscle names derive from: action of muscle flexor digitorum

Sometimes several of these are combined. ex: extensor carpi radialis longus

Muscles to learn name (correct spelling), general location, and action. Muscle Name Action of Muscle orbicularis oris pucker mouth orbicularis oculi squint eye frontalis raises eyebrows masseter closes jaw sternocleidomastoid head flexion deltoid abduct / rotates arm pectoralis major adduct arm; flexes arm

Muscles to learn name (correct spelling), general location, and action. Muscle Name Action of Muscle external oblique trunk flexion / rotates rectus abdominis flex / rotates lumbar trapezius raises / rotates scapula latissimus dorsi extend / adduct arm biceps brachii flexes forearm triceps brachii extends forearm flexor digitorum flexes wrist and fingers extensor digitorum extends wrist and fingers

Muscles to learn name (correct spelling), general location, and action. Muscle Name Action of Muscle rectus femoris knee extensor sartorius flexes / laterally rotates thigh gracilis flexes / medially rotates thigh gluteus maximus thigh extensor hamstrings thigh extension; knee flexion gastrocnemius flex foot diaphragm inspiration