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muscles that, when contracting, directly oppose prime movers; relax while prime mover in contracting to produce movement; provide precision and control during contraction of prime movers
muscles that contract at the same time as the prime movers; they facilitate prime mover actions to produce a more efficient movement
network of tubules and sacs found within muscle fibers, stores calcium ions within its sacs
segment of myofibril between two successive Z lines, myofibrils consists of many of these, contractile unit of muscle fibers
triplet of tubules; allows an electrical impulse traveling along a T tubule to stimulate the membranes of adjacent sacs of the sarcoplasmic reticulum
within myofibrils, thick and thin; thin attach to both Z lines of a sarcomere and extend part way toward the center; thick do not attach to the Z lines
a quick jerk of a muscle that is produced as a result of a single, brief threshold stimulus
the staircase phenomenon; gradual, step like increase in the strength of contraction that is seen in a series of twitch contractions that occur 1 second apart
contraction in which the tone or tension within a muscle remains the same but the length of the muscle shortens (same tension)
contraction in which muscle length remains the same while the muscle tension increases (same length)
fulcrum lies between the pull and the load, not abundant in the human body, serve as levers of stability
load lies between the fulcrum and the joint at which the pull is exerted, presence of these levers in the human body is a controversial issue
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