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