Term | Definition |
acetylcholine | a chemical messenger released from the end of a motor neuron |
actin | protein of which the thin myofilaments are composed |
aerobic respiration | process that breaks down fatty acids for energy when oxygen is present |
anaerobic respiration | process that breaks down glucose for energy when oxygen is not plentiful |
antagonist | muscles that oppose the action of a prime mover |
aponeurosis | flat, broad tendon that attaches a muscle to another muscle or to bone |
ATP | adenosine triphosphate; used for energy in cells to perform various functions, including muscle contractions |
atrophy | decrease in the size of a muscle |
belly | the thick midsection or middle of the muscle |
complete tetanus | condition in which impulses arrive so fast that muscle cannot relax between stimuli and twitches merge into one prolonged contractions |
creatine phosphate | compound stored in muscle that is used for short bursts of high-energy activity |
endomysium | delicate connective tissue covering each muscle fiber |
epimysium | connective tissue covering that surrounds muscles as a whole and binds all muscle fibers together |
fascia | connective tissue surrounding the muscle |
fascicles | bundles of muscle fibers |
hypertrophy | enlargement of a muscle |
incomplete tetanus | condition of rapid muscle contraction with only partial relaxation |
insertion | the end of a muscle that attaches to the more mobile bone |
isometric contraction | contraction in which the tension within a muscle increases while its length remains the same; think plnak exercise |
isotonic contraction | contraction in which the muscle changes length to move a load; think lifting a weight |
motor unit | a neuron and all the muscle fibers it stimulates |
muscle fiber | a skeletal muscle cell |
muscle tone | continuous state of partial muscle contraction that allows for the maintenance of posture |
myofibrils | long protein bundles that fill the sarcoplasm of a muscle fiber |
myofilaments | fine protein fibers that make up a myofibril |
myosin | protein of which the thick myofilaments are composed |
neuromuscular junctions | connection between a motor neuron and a muscle fiber |
origin | the end of a muscle that attaches to the more stationary bone |
perimysium | sheath of connective tissue encasing fascicles |
prime mover | the main muscle triggering a movement |
sarcomere | the unit of contraction of the myofibrils of a muscle |
sarcoplasm | the cytoplasm of a muscle fiber |
synaptic cleft | narrow space between the end of a motor nerve and the muscle fiber |
synergists | muscles that assist in the movement of a bone |
tendon | strong, fibrous cord through which a muscle attaches to a bone |
transverse (T) tubules | tubules that extend across the sarcoplasm and allow electrical impulses to travel deep into the cell |
treppe | phenomenon in which each successive twitch contracts more forcefully than the previous one |
twitch | single, brief contraction |