8.2 - Structures of skeletal muscles

what are muscle bundles held together by

connective tissue called perimysium

what are muscles held together by

epimysium that tapers at end to form tendon

what are muscle fibers

muscle cells

what is the structure of a muscle cell

many nuclei

surrounded by plasma membrane sarcolemma

contains cytoplasm called sarcoplasm

what surrounds a myofibril and what does it store

sarcoplasmic reticulum that stores calcium ions

what are the two types of myofilaments

thick - protein myosin

thin - protein actin

why do the myofilaments move

ATP activates nerve impulses that contracts myofibril