Anatomy Concept 3: Muscular System Vocab

insertion

where the muscle is attached to a movable bone

origin

where the muscle is attached to an immovable bone

prime mover (agonist)

muscle most responsible for producing a certain movement

antagonist

muscles that do the reverse of a certain movement

synergist

muscles that help the prime mover

fixator

synergist muscles that immobilize the muscle's origin bone, increasing the effectiveness of the prime mover

myofibril

organelle that makes up most of muscle cells

myofilaments

the contractile proteins, actin and myosin, of muscle cells

sarcomere

the contractile unit of the muscle

muscle fibers

muscle cells

fasicles

bundle of muscle fibers

epimysium

wraps around the outside of the muscle

perimysium

surrounds each fasicle

endomysium

surrounds each muscle fiber

resting membrane potential

the voltage across the cell membrane (usually between -50 and -90 mV)

action potential (ap)

a large change in membrane potential

neuromuscular junction

where the axon terminal of the motor neuron meets the muscle fiber

motor unit

basic functional team for muscle movement (one nerve cell and muscle fibers)

twitch

involuntary contraction of a muscle in response to a single nerve cell (ap)

graded muscle contraction

ability of skeletal muscles to vary the strength of their contractions to match the movement (precise or powerful)

summation

cumulative effect of multiple stimuli to produce a response greater than the effect of one

tetanus (lockjaw)

severe bacterial infection causing painful, uncontrolled muscle spasms and stiffness starting in the jaw but spreading

recruitment

activating more motor units to increase muscle tension and force

threshold stimulus

minimum level of stimulation required to trigger a response

muscle tone

the continuous, passive, partial contraction of muscles, keeping them ready for action

muscle tension

force generated by contracting muscle fibers

muscle fatigue

Inability of a muscle to maintain its strength of contraction or tension

lever

a system of bones moved by muscles around a joint to create motion

fulcrum

pivot (around a joint)

effort

force (moved by muscles)

load

resistance (system of bones)