unit 2-Support and Motion Honors-Concept 3: The Muscular System-Study Guide-Vocab Section

Insertion

Where the muscle is attached to a movable bine

Origin

Where muscle is attached to an immovable object

Prime Mover

A.K.A “Agonists”. muscles most responsible for producing a certain movement

Antagonists

Muscles that oppose or do the reverse of a certain movement. Usually stretched or relaxed when a prime mover is active. Can regulate prime movers by adding resistance. Located on the opposite side of a joint from the prime mover.

Synergist

Muscles that help the prime mover, such as stabilizing across a joint or adding some “oomph”

fixator

synergist muscles that specifically immobilize the muscle’s origin bone to increase the prime mover’s effectiveness. They also help maintain an upright posture.

myofibrils

organelle that makes up most of the muscle cells.

myofilaments

also known as actin and myosin they are thin filaments and run the length of each myofibril.

sarcomeres 

the contractile unit of the muscle and each myofibril is a chain of sarcomeres. Each sarcomere is separated by Z disc (or Z line) borders on each end of the myofibril. the thick filaments contain the contractile protein myosin, and the thin filaments contain the contractile protein actin

muscle fibers

muscle cells

fascicles

muscle fibers (muscle cells) bundle together to form a muscle organ.

Epimysium

wraps around the entire outside of the muscle

Perimysium 

surrounds each fascicle

Endomysium

surrounds each muscle fiber

resting membrane potential

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

Action Potential

A large change in membrane potential that spreads rapidly over long distances within the cell. the movement of ions through ion channels can create this large change. 

Neuromuscular junction 

where the axon terminals of the motor neurons meet the muscle fiber, including the spaces between those fibers (the synaptic cleft)

lever

a rigid bar that moves on a fixed point (the fulcrum) when a force is applied to it

fulcrum

joints attached to bones

effort

the applied force used to move a resistance.

load 

muscle contractions create force that is applied to the insertion bone.