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Concept explainers
Indicate which of the following are true.
Chronically shortened muscles will lose sarcomeres in series in order to maintain ideal amounts of myofilament overlap.
Contractile force is proportional to the length of a muscle.
Muscle organ contraction is all or nothing.
Muscle cells are surrounded by an endomysium.
Actin is the thick filament and Z-lines are where the cross-bridges zig-zag to adjacent actin filaments.
Muscles with fewer motor units are weaker, i.e., capable of less force.
A nerve impulse, calcium, and ATP are necessary for muscle contraction.
Tendons attach bones to bones and help to limit the range of motion at joints.
Muscle tissue is very dynamic and will respond to chronic stress by becoming stronger (making more myofilaments), chronic contraction by becoming shorter (losing sarcomeres in series), and stretching by becoming longer (adding sarcomeres in series).
Myofilaments are actually long strands of proteins.
Skeletal muscles contain connective tissue, blood vessels, and nerves. There are three layers of connective tissue: epimysium, perimysium, and endomysium. Skeletal muscle fibers are organized into groups called fascicles. Blood vessels and nerves enter the connective tissue and branch in the cell.
Each muscle is made up of groups of muscle fibers called fascicles surrounded by a connective tissue layer called perimysium. There are multiple units of individual muscle fibers within each fascicle surrounded by endomysium, a connective tissue sheath.
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