Unit 2 Kinesiology muscular system

Myofilament

protein unit within a myofibril, a contractile unit

Myofibril

unit of myofilaments, composed of long proteins (acting, myosin)

Sarcolemma

encases muscle belly

Sarcoplasm

Cytoplasm within muscle cells

Sarcomere

a segment of myofilaments in between 2 z-discs

3 components of a muscle contraction

Neurological, chemical, and mechanical

motor unit

functional unit that includes the axon, motor end plates, and muscles fibers activated by the nerve

distal end of muscle

insertion

proximal end of muscle

origin

slow twitch muscles

O2 dependence, slow contraction, produce less tension, high resistance to fatigue, used to maintain posture

fast twitch muscles

no O2 dependence, fast contraction, produce more tension, low resistance to fatigue, used for faster activities

muscle spindle

reports status to CNS, very sensitive to stretch, send stress signals to CNS when over stretched

Hypertrophy

Muscle gain

Atrophy

muscle loss

Fusiform

muscles that have fibers that run in the direction of pull

radiate

muscles that radiate from the tendon

Piraform/Pennate

muscles that run oblique to direction of pull

Bipennate

muscles that run in two directions oblique to the direction of pull

Multipennate

muscles with many different cross sections

Tendon

muscle to bone attachment

Viscoelasticty

property of materials that are both viscous/ elastic

Viscous

plasticity; permanent change

Elastic

can return to original shape

skeletal muscles

create mvmt, resist mvmt, and stabilize; can change their tone and length

eccentric contraction

muscle lengthens

concentric contraction

muscle shortens

isometric contraction

static contraction

Agonist

muscle which contracts to produce the action

Antagonist

muscle contracts to produce opposite action

Prime mover

muscle most effective in producing the action

Assistors

helps prime movers when they can’t do the action alone

Synergists

2+ muscles performing same action

Stabilizers

stabilizing muscles

force couple

two muscles on either side of a joint axis helping maintain or perform an action

active insufficiency

inability of a 2 joint muscle to shorten or contract because it is already contracted

passive insufficiency

inabliity of a 2 joint muscle to perform an action because the muscle is being stretched