the muscle system

epimysium

outermost protective layer that surrounds muscles

perimysium

layer that surrounds the fascicle

endomysium

smallest and deepest component that surrounds myofibrils

sarcoplasmic reticulum

stores, releases, and reabsorbs calcium ions

transverse tubules

tiny intersitial fluid-filled pockets that extend into the muscle cell

muscular atrophy

loss of muscle mass when muscles are not stimulated enough

latent period

short delay from when the action potential reaches the muscle until tension can be observed

contraction period

muscle is generating tension

relaxation period

time for the muscle to return to normal length

creatine phosphate

rapidly mobilizable reserve of high-energy phosphates

tetanus (complete)

stimulus frequency is so high that the relaxation phase disappears and contractions become continuous

tetanus (incomplete)

muscle goes through quick cycles of contraction with a short relaxation phase for each

wave summation

muscle fiber is stimulated again before it has relaxed completely