Describe the relationship between bones and skeletal muscles in producing body movements.

Muscles act on bones by pulling, never pushing. As a muscle shortens, its insertion (attachment on the movable bone) moves toward its origin (its fixed or immovable point of attachment). Whatever one muscle or muscle group can do, another muscle or group can undo.

Prime mover (agonist)

has the major responsibility for producing a specific movement

antagonist

opposes or reverses a particular movement. When the prime mover is active, antagonist muscles are usually stretched or relaxed.

Synergists

muscles that help the prime mover by either adding extra force to the same movement or reducing undesirable or unnecessary movements that might occur as the prime mover contracts

Fixator

a type of synergist which immobilizes a bone, or a muscle’s origin so that the prime mover has a stable base on which to act

Define the criteria employed in naming skeletal muscles:

• Location
• Shape
• Relative size
• Direction of muscle fibers
• Number of origins
• Location of attachments
• Action

Parallel:

long axis of the fascicles run with the longitudinal axis of the muscle - strap like or fusiform - expanded belly (biceps).

Pennate (feather):

fascicles are short and attached obliquely to a central tendon running the length of the muscle

unipennate

Fascicles insert into only 1 side of the tendon

bipennate

If inserted into the tendon from opposite sides

Convergent:

broad origin - fascicles converge toward a single tendon -essentially triangular (pectoralis major).

Circular:

fascicles arranged in concentric rings. Surround external body openings which they close by contracting sphincters.

sphincters

A circular muscle surrounding an opening; acts as a valve

orbicularis oculi -

zygomaticus -

platysma -

orbicularis oculi -closes eyes, blinking, squinting

zygomaticus - raises lateral corners of mouth (smiling)

platysma - depresses mandible, pulls lower lip back and down

orbicularis oris -

frontalis -

masseter -

orbicularis oris - closes mouth, purses lips (kissing)

frontalis - raises eyebrows, wrinkles skin of forehead

masseter - closes jaw, elevates mandible

sternocleidomastoid -

deltoid -

pectoralis major -

sternocleidomastoid - flexes neck (together); rotates head toward opposite shoulder (individually)

deltoid - prime mover of arm abduction

pectoralis major - arm flexion, adducts and medially rotates arm

rectus abdominis -

trapezius -

latissimus dorsi -

rectus abdominis - flexes vertebral column, fixes and depresses ribs, stabilizes pelvis during walking

trapezius - extends head, retracts scapula, elevates and depresses scapula (shrug shoulders)

latissimus dorsi - prime mover of arm extension; adducts and medially rotates arm

erector spinae -

triceps brachii -

biceps brachii -

erector spinae - extends and abducts vertebral column

triceps brachii -extension of forearm

biceps brachii - flexion of forearm, supination of forearm

flexor carpi radialis -

flexor carpi ulnaris -

flexor digitorum superficialis -

flexor carpi radialis - wrist flexion, abducts hand

flexor carpi ulnaris - wrist flexion, adducts hand

flexor digitorum superficialis - flexes wrist and phalanges of fingers 2-5

flexor pollicis longus -

extensor carpi ulnaris -

carpi radialis longus –

flexor pollicis longus - flexes thumb

extensor carpi ulnaris - extends and adducts wrist extensor

carpi radialis longus – extends and abducts wrist

extensor digitorum -

extensor pollicis longus -

iliopsoas -

extensor digitorum - finger extension

extensor pollicis longus - extends thumb

iliopsoas - flex trunk on thigh, hip flexor

tensor fasciae latae -

sartorius -

rectus femoris -

tensor fasciae latae - flexes, abducts, and medially rotates thigh

sartorius - flexes and laterally rotates thigh (cross-legged sitting)

rectus femoris - extends knee and flexes thigh at hip adductor

longus –

gluteus maximus -

biceps femoris -

longus – adducts, flexes, and medially rotates thigh

gluteus maximus - hip extensor, laterally rotates thigh

biceps femoris - extends thigh, flexes knee, laterally rotates leg

gastrocnemius -

flexor digitorum longus -

flexor hallucis longus -

gastrocnemius - flexion of knee when foot is dorsiflexed

flexor digitorum longus - flexes toes; plantarflexes and inverts foot

flexor hallucis longus - flexes great toe; pushes off when walking

fibularis longus -

tibialis posterior -

tibialis anterior -

fibularis longus - plantarflexes and everts foot

tibialis posterior - inversion and plantarflexion of foot

tibialis anterior - dorsiflexes and inverts foot

extensor digitorum longus -

extensor hallucis longus -

extensor digitorum longus - toe extension; dorsiflexes and everts foot

extensor hallucis longus - extends great toe